Self-leveling front-end loader having a double boom with a dogleg bend of 105 to 135 degrees including an extension powered by hydraulic cylinders

Abstract

A self-leveling front-end loader for attachment to a tractor. The self-leveling front-end loader includes a support structure configured to be attached to the tractor, and two extendable booms, each boom including a proximal leg, a distal leg, and a self-leveling hydraulic linkage configured to maintain the tilt angle of an accessory, such as a bucket. Each extendable boom has a boom extension hydraulic cylinder for extending the boom by up to 2 to 4 feet, a lift hydraulic cylinder to lift each boom, a self-leveling hydraulic cylinder, and a tilt hydraulic cylinder to tilt the accessory. The extendable booms enhance the capability of the front-end loader to position payload higher and farther than a standard front end loader, while preserving the stability and lifting capacity of the front-end loader. The booms have a traditional dogleg bend of 105 to 135 degrees, providing the two booms a wide range of motion.

Claims

1. A front-end loader for attachment to a tractor or a rubber tired construction backhoe, the front-end loader including hydraulic cylinders, each hydraulic cylinder having a cylinder barrel, a piston rod, a proximal end, and a distal end, the front-end loader comprising: a support structure configured to be attached to the tractor, the support structure having an upper attachment portion and a lower attachment portion; two booms, each boom including: a proximal leg having a pivot end and an extension end, the pivot end being pivotally attached to the upper attachment portion, and a boom extension hydraulic cylinder, having the proximal end attached to the proximal leg, and a distal leg having an extension end and an accessory support end, the extension end of the distal leg being attached to the distal end of the boom extension hydraulic cylinder, the distal leg including an extension shaft that is fixedly attached to the extension end of the distal leg, the extension shaft being slidably supported by a receptacle at the extension end of the proximal leg; a lift hydraulic cylinder having a proximal end and a distal end, the proximal end of the lift hydraulic cylinder pivotally attached to the lower attachment portion of the support structure, and the distal end of the lift hydraulic cylinder being pivotally attached to the extension end of the proximal leg; a tilt hydraulic cylinder having a proximal end and a distal end, the distal end of the tilt hydraulic cylinder being configured to pivotally attach to an implement assembly that is configured to be pivotally attached to the accessory support end of the distal leg; and a self-leveling linkage, including: a self-leveling cylinder, having a proximal end and a distal end, the proximal end of the self-leveling cylinder pivotally attached to the upper attachment portion of the support structure, the self-leveling cylinder being in fluid communication with the boom extension hydraulic cylinder, and the self-leveling cylinder and the boom extension hydraulic cylinder configured in a series hydraulic circuit, and a connecting linkage pivotally attached to the extension end of the distal leg, the connecting linkage pivotally connected to the distal end of the self-leveling cylinder, and the connecting linkage pivotally connected to the proximal end of the tilt hydraulic cylinder, such that a movement of the distal end of the self-leveling cylinder corresponds to a linked movement of the proximal end of the tilt hydraulic cylinder.

2. The front-end loader of claim 1, wherein the distal end of each distal leg of the two booms is configured to attach to an accessory, including at least one of: a bucket, pallet forks, hay forks, bale spears.

3. The front-end loader of claim 1, wherein the receptacle within the extension end of the proximal leg includes wear pads configured to slidably support the extension shaft of the distal leg.

4. The front-end loader of claim 1, wherein the boom extension hydraulic cylinder and the self-leveling cylinder are configured in the series hydraulic circuit such that the boom extension hydraulic cylinder and the self-leveling cylinder each co-extend by a substantially equal distance, and the boom extension hydraulic cylinder and the self-leveling cylinder each co-retract by a substantially equal distance.

5. The front-end loader of claim 1, wherein a cross member is attached to each of the two booms.

6. The front-end loader of claim 1, wherein each boom extension hydraulic cylinder extends a respective boom of the two booms by 2 to 4 feet.

7. The front-end loader of claim 1, wherein each boom extension hydraulic cylinder is configured to extend and retract the two booms AFTER the lift hydraulic cylinder has raised the two booms to a raised position.

8. The front-end loader of claim 1, further including: conventional wheel weights to provide additional counter weight for added stability.

9. The front-end loader of claim 1, wherein the distal leg of each boom extends from the proximal leg of the boom at a 105 to 135 degree angle.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Many additional features and advantages will become apparent to those skilled in the art upon reading the following description, when considered in conjunction with the accompanying drawings, wherein:

(2) FIG. 1A is a side view of the front-end loader showing the accessory support end in a lowered position, the lift hydraulic cylinder in the retracted position, the boom extension hydraulic cylinder in the retracted position, also having the extension shaft of the distal leg fully retracted into the receptacle of the proximal leg of the boom, and having the self-leveling cylinder in the retracted position.

(3) FIG. 1B is a side view of the front-end loader of FIG. 1A, showing the boom extension hydraulic cylinder in the partially extended position, also having the extension shaft of the distal leg partially extended from the receptacle of the proximal leg of the boom, thereby extending the reach of the boom, and having the self-leveling cylinder in the partially extended position.

(4) FIG. 2A is a perspective front and side view of the front-end loader attached to a bucket accessory, showing the front-end loader and the bucket in a lowered position, having each lift hydraulic cylinder in the retracted position, each boom extension hydraulic cylinder in the retracted position, also having the extension shaft of each distal leg fully retracted into the receptacle of the proximal leg of each boom, and having each self-leveling cylinder in the retracted position.

(5) FIG. 2B is a perspective front and side view of the front-end loader and bucket accessory of FIG. 2A, showing each boom extension hydraulic cylinder in the extended position, also having the extension shaft of each distal leg fully extended from the receptacle of the proximal leg of each boom, thereby extending the forward reach of each boom, and having each self-leveling cylinder in the extended position.

(6) FIG. 3 is a perspective front and side view of the front-end loader mounted on a tractor and attached to a bucket accessory, showing the front-end loader and the bucket in the lowered position, having each lift hydraulic cylinder in the retracted position, each boom extension hydraulic cylinder in the retracted position, having the extension shaft of each distal leg fully retracted into the receptacle of the proximal leg of each boom, and having each self-leveling cylinder in the retracted position.

(7) FIG. 4 is a perspective front and side view of the front-end loader mounted on the tractor and attached to a bucket accessory, showing the front-end loader and the bucket in a lowered position, having each lift hydraulic cylinder in the retracted position, each boom extension hydraulic cylinder in the extended position, having the extension shaft of each distal leg fully extended from the receptacle of the proximal leg of each boom, thereby extending the forward reach of each boom, and having each self-leveling cylinder in the extended position.

(8) FIG. 5 is a perspective front and side view of the front-end loader mounted on the tractor and attached to the bucket accessory, showing the front-end loader and the bucket in a raised position, having each lift hydraulic cylinder in the extended position, each boom extension hydraulic cylinder in the retracted position, having the extension shaft of each distal leg fully retracted into the receptacle of the proximal leg of each boom, and having each self-leveling cylinder in the retracted position.

(9) FIG. 6 is a perspective front and side view of the front-end loader mounted on the tractor and attached to the bucket accessory, showing the front-end loader and the bucket in a raised position, having each lift hydraulic cylinder in the extended position, each boom extension hydraulic cylinder in the extended position, having the extension shaft of each distal leg fully extended from the receptacle of the proximal leg of each boom, thereby extending the height and reach of each boom, and having each self-leveling cylinder in the extended position.

(10) FIG. 7A is a side view of the front-end loader attached to the bucket accessory showing the bucket in a lowered position, the lift hydraulic cylinder in the retracted position, the boom extension hydraulic cylinder in the retracted position, also having the extension shaft of the distal leg fully retracted into the receptacle of the proximal leg of the boom, and the self-leveling linkage maintaining the bucket at a level bucket angle.

(11) FIG. 7B is a side view of the front-end loader of FIG. 7A, showing the bucket in a raised position, the lift hydraulic cylinder in the extended position, and the self-leveling linkage maintaining the raised bucket at the same level bucket angle as for the lowered bucket in FIG. 7A.

(12) FIG. 8A is a side view of the front-end loader attached to the bucket accessory showing the bucket in a lowered position, the lift hydraulic cylinder in the retracted position, the boom extension hydraulic cylinder in the extended position, also having the extension shaft of the distal leg partially extended from the receptacle of the proximal leg of the boom, and the self-leveling linkage maintaining the bucket at a level bucket angle.

(13) FIG. 8B is a side view of the front-end loader of FIG. 8A, showing the bucket in a raised position, the lift hydraulic cylinder in the extended position, and the self-leveling linkage maintaining the raised bucket at the same level bucket angle as for the lowered bucket in FIG. 8A.

(14) FIG. 9A is an isometric side view of the proximal leg, showing a proximal leg attachment hole configured to attach to the upper attachment portion of the support structure, a proximal leg attachment pin configured to attach to the proximal end of the boom extension hydraulic cylinder, two lift cylinder attachment holes configured to attach the proximal leg to the distal end of the lift hydraulic cylinder, and hidden lines showing the proximal leg receptacle configured to receive the extension shaft of the distal leg.

(15) FIG. 9B is an isometric side view of the distal leg, showing the extension shaft, a distal leg attachment pin configured to attach to the distal end of the boom extension hydraulic cylinder, two attachment holes configured to attach to the linkage lower attachment of the self-leveling linkage, and two accessory attachment holes configured to attach to an accessory, such as the bucket accessory.

(16) FIG. 10 is an isometric side view of the proximal leg and the distal leg, the proximal leg receptacle receiving and supporting the extension shaft of the distal leg, the extension shaft partially extended from the proximal leg.

(17) FIG. 11A is a cross sectional view of the proximal leg, showing four wear pads configured to slidably support the extension shaft of the distal leg.

(18) FIG. 11B is a isometric view of the distal end of the proximal leg, also showing a hidden line view of a plurality of wear pads lining the proximal leg receptacle.

(19) FIG. 12 is a perspective front and side view of the front-end loader mounted on the tractor and attached to a pallet forks accessory, showing the front-end loader and the pallet forks in a lowered position, having each lift hydraulic cylinder in the retracted position, each boom extension hydraulic cylinder in the retracted position, and the extension shaft of each distal leg fully retracted into the proximal leg receptacle of each boom.

(20) FIG. 13A is a side view of a partially loaded truck and the front-end loader mounted on the tractor, showing the pallet forks accessory in a raised position, although not at an adequate height to place the pallet forks payload upon the truck, also showing the front-end loader having each lift hydraulic cylinder in the extended position, each boom extension hydraulic cylinder in the retracted position, and the extension shaft of each distal leg being fully retracted into the receptacle of the proximal leg of each boom, and having each self-leveling cylinder in the retracted position.

(21) FIG. 13B is a side view of the partially loaded truck and the front-end loader of FIG. 13A, having the pallet forks accessory in the raised position, and showing each boom extension hydraulic cylinder in the extended position, thereby bringing the pallet forks to a sufficient height and reach so as to place the pallet forks payload upon the truck, also showing the extension shaft of each distal leg being fully extended from the receptacle of the proximal leg of each boom, and having each self-leveling cylinder in the extended position.

(22) FIG. 14A is a hydraulic circuit diagram of a hydraulic circuit including a hydraulic reservoir, a hydraulic pump, a hydraulic control valve, and a hydraulic cylinder, showing the hydraulic control valve in the neutral position, and the hydraulic cylinder piston rod in a static position.

(23) FIG. 14B is a hydraulic circuit diagram of the hydraulic circuit of FIG. 14A, showing the hydraulic control valve in the open forward flow position, and the hydraulic cylinder piston rod extending.

(24) FIG. 14C is a hydraulic circuit diagram of the hydraulic circuit of FIG. 14A, showing the hydraulic control valve in the open reverse flow position, and the hydraulic cylinder piston rod retracting.

(25) FIG. 15A is a hydraulic circuit diagram of a hydraulic circuit configured to control two hydraulic cylinders, including the hydraulic reservoir, the hydraulic pump, two hydraulic control valves, and two hydraulic cylinders, showing the upper hydraulic control valve in the open forward flow position and the upper hydraulic cylinder piston rod extending, and also showing the lower hydraulic control valve in the neutral position and the lower hydraulic cylinder piston rod in a static position.

(26) FIG. 15B is a hydraulic circuit diagram of the hydraulic circuit of FIG. 15A, showing the upper hydraulic control valve in the neutral position and the upper hydraulic cylinder piston rod in a static position, and also showing the lower hydraulic control valve in the open forward flow position and the lower hydraulic cylinder piston rod extending.

(27) FIG. 16A is a hydraulic circuit diagram of a series hydraulic circuit, including the hydraulic reservoir, the hydraulic pump, one hydraulic control valve, and having a first hydraulic cylinder and a second hydraulic cylinder configured as a series hydraulic circuit, showing the hydraulic control valve in the open forward flow position and both the first and second upper hydraulic cylinder piston rods extending.

(28) FIG. 16B is a hydraulic circuit diagram of the series hydraulic circuit of FIG. 16A, showing the hydraulic control valve in the open reverse flow position and both the first and second upper hydraulic cylinder piston rods retracting.

(29) FIG. 17 is a top view of the front-end loader 100 attached to a bucket accessory, showing the hydraulic pump, the hydraulic control valve, two booms, and hydraulic hoses, the hydraulic hoses configured for each boom so as to connect the boom extension hydraulic cylinder and the self-leveling cylinder in a series hydraulic circuit.

DETAILED DESCRIPTION

(30) With reference to FIG. 1A, a side view of a front-end loader 100 is shown having an extendable boom 118, the boom 118 including a proximal leg 114 and distal leg 116. The boom 118 is shown having a boom extension hydraulic cylinder 126 in a retracted position, and having a lift hydraulic cylinder 120 in a retracted position, corresponding to the distal leg 116 accessory support end 140 being in a lowered position.

(31) The distal end of the lift hydraulic cylinder 120 is pivotally attached to the distal end of the proximal leg 114 at the distal lift attachment 124. As the lift hydraulic cylinder 120 extends, the proximal leg 114 and the boom 118 are raised, and as the lift hydraulic cylinder 120 retracts, the proximal leg 114 and the boom 118 are lowered.

(32) The front-end loader 100 includes a support structure 102 configured to be mounted on a tractor 302 (shown in FIG. 3). The support structure 102 includes a lower attachment portion 108 that pivotally supports the proximal end of the lift hydraulic cylinder 120 at the proximal lift attachment 122. The support structure 102 also includes an upper attachment portion 110 configured to pivotally support the proximal leg 114 of the boom 118 at the proximal leg pivot 112.

(33) The distal leg 116 of the boom 118 is extendable from the proximal leg 114. In this view, the boom extension hydraulic cylinder 126 is shown in the retracted position, and accordingly the distal leg 116 is in the retracted position with respect to the proximal leg 114. The proximal end of the boom extension hydraulic cylinder 126 is attached to the proximal end of the proximal leg 114 at a proximal extension attachment 128. The distal end of the boom extension hydraulic cylinder 126 is attached to the proximal end of the distal leg 116 at the distal extension attachment 130.

(34) A self-leveling linkage 142 includes a self-leveling cylinder 144 and a linkage connector 150. The linkage connector 150 is configured to attach to: the distal leg 116 at the linkage lower attachment 154, the self-leveling cylinder 144 at the self-leveling distal attachment 152, and the tilt hydraulic cylinder 132 at the proximal tilt attachment 134.

(35) As the boom extension hydraulic cylinder 126 is in the retracted position, the self-leveling cylinder 144 is also in the retracted position. The proximal end of the self-leveling cylinder 144 is attached to a self-leveling proximal attachment 148 of the support structure 102. The distal end of the self-leveling cylinder 144 is attached to the linkage connector 150 at the self-leveling distal attachment 152.

(36) The distal leg 116 includes a tilt hydraulic cylinder 132 which controls the tilt angle of an accessory, such as a bucket 204 (shown in FIG. 2A), the accessory being attached to and supported by the accessory support end 140. The tilt hydraulic cylinder 132 is pivotally attached to the linkage connector 150 by a proximal tilt attachment 134, and also is pivotally attached to the accessory support end 140 by a distal tilt attachment 136.

(37) In this embodiment, the distal leg 116 extends from the proximal leg 114 at a boom legs angle 138 of 105 to 135 degrees.

(38) With reference to FIG. 1B, a side view of a front-end loader 100 is shown having an extendable boom 118, the boom 118 including a proximal leg 114 and distal leg 116. The boom 118 is shown having a boom extension hydraulic cylinder 126 in the partially extended position, and having a lift hydraulic cylinder 120 in a retracted position, corresponding to the distal leg 116 accessory support end 140 being in a lowered position.

(39) The distal end of the lift hydraulic cylinder 120 is pivotally attached to the distal end of the proximal leg 114 at the distal lift attachment 124. As the lift hydraulic cylinder 120 extends, the proximal leg 114 and the boom 118 are raised, and as the lift hydraulic cylinder 120 retracts, the proximal leg 114 and the boom 118 are lowered.

(40) The front-end loader 100 includes a support structure 102 configured to be mounted on a tractor 302 (shown in FIG. 3). The support structure 102 includes a lower attachment portion 108 that pivotally supports the proximal end of the lift hydraulic cylinder 120 at the proximal lift attachment 122. The support structure 102 also includes an upper attachment portion 110 configured to pivotally support the proximal leg 114 of the boom 118 at the proximal leg pivot 112.

(41) The distal leg 116 of the boom 118 is extendable from the proximal leg 114. The distal leg 116 is shown in the partially extended position with respect to the proximal leg 114, corresponding to the boom extension hydraulic cylinder 126 being in the partially extended position, and both the extension shaft 106 and an extension cylinder piston rod 104 also being in partially extended positions.

(42) The proximal end of the boom extension hydraulic cylinder 126 is attached to the proximal end of the proximal leg 114 at a proximal extension attachment 128. The distal end of the boom extension hydraulic cylinder 126 is attached to the proximal end of the distal leg 116 at the distal extension attachment 130.

(43) A self-leveling linkage 142 includes a self-leveling cylinder 144 and a linkage connector 150. The linkage connector 150 is configured to attach to: the distal leg 116 at the linkage lower attachment 154, the self-leveling cylinder 144 at the self-leveling distal attachment 152, and the tilt hydraulic cylinder 132 at the proximal tilt attachment 134.

(44) As the boom extension hydraulic cylinder 126 is in the partially extended position, the self-leveling cylinder 144 is also in the partially extended position. The proximal end of the self-leveling cylinder 144 is attached to a self-leveling proximal attachment 148 of the support structure 102. The distal end of the self-leveling cylinder 144 is attached to the linkage connector 150 at the self-leveling distal attachment 152.

(45) The self-leveling cylinder 144 and the boom extension hydraulic cylinder 126 are integrated and simultaneously work together by extending together and retracting together, to preserve a self-leveling function while the extendable boom 118 is being extended and retracted.

(46) The distal leg 116 includes a tilt hydraulic cylinder 132 which controls the tilt angle of an accessory, such as a bucket 204 (shown in FIG. 2A), the accessory being attached to and supported by the accessory support end 140. The tilt hydraulic cylinder 132 is pivotally attached to the linkage connector 150 by a proximal tilt attachment 134, and also is pivotally attached to the accessory support end 140 by a distal tilt attachment 136.

(47) In this embodiment, the distal leg 116 extends from the proximal leg 114 at a boom legs angle 138 of 105 to 135 degrees.

(48) With reference to FIG. 2A, a perspective front and side view of a front-end loader 100 is shown having an extendable boom 118 (shown in FIG. 1A), the boom 118 including a proximal leg 114 and distal leg 116. A boom extension hydraulic cylinder 126 is in a retracted position, and the self-leveling cylinder 144 is in the retracted position. The self-leveling cylinder 144 and the boom extension hydraulic cylinder 126 are integrated and simultaneously work together, by extending together and retracting together to preserve a self-leveling function while each extendable boom 118 is being extended and retracted.

(49) The lift hydraulic cylinder 120 is in a retracted position, corresponding to the distal leg 116 accessory support end 140 and the bucket 204 being in a lowered position.

(50) The front-end loader 100 includes a support structure 102 configured to be mounted on a tractor 302 (shown in FIG. 3). The support structure 102 pivotally supports the proximal end of the lift hydraulic cylinder 120 at the proximal lift attachment 122. The support structure 102 is also configured to pivotally support the proximal leg 114 of the boom 118 (shown in FIG. 1A) at the proximal leg pivot 112.

(51) The distal end of the lift hydraulic cylinder 120 is pivotally attached to the distal end of the proximal leg 114 at the distal lift attachment 124. The boom 118 is shown in a lowered position; however, as the lift hydraulic cylinder 120 extends, the proximal leg 114 and the boom 118 are raised, and as the lift hydraulic cylinder 120 retracts, the proximal leg 114 and the boom 118 are lowered.

(52) The distal leg 116 of the boom 118 is extendable from the proximal leg 114. The boom extension hydraulic cylinder 126 is shown in the retracted position, and therefore the distal leg 116 is in the retracted position with respect to the proximal leg 114. The proximal end of the boom extension hydraulic cylinder 126 is attached to the proximal end of the proximal leg 114 at a proximal extension attachment 128. The distal end of the boom extension hydraulic cylinder 126 is attached to the proximal end of the distal leg 116 at the distal extension attachment 130.

(53) The distal leg 116 includes a tilt hydraulic cylinder 132 which controls the tilt angle of an accessory, such as the bucket 204, the accessory being attached to and supported by the accessory support end 140. The tilt hydraulic cylinder 132 is pivotally attached to the proximal end of the distal leg 116 by a proximal tilt attachment 134, and also is pivotally attached to the accessory support end 140 by a distal tilt attachment 136 (shown in FIG. 1A).

(54) With reference to FIG. 2B, a perspective front and side view of a front-end loader 100 is shown, having an extendable boom 118 (shown in FIG. 1B), the boom 118 including a proximal leg 114 and distal leg 116. The boom 118 is shown in an extended position, having the boom extension hydraulic cylinder 126, the extension shaft 106, the extension cylinder piston rod 104, and the self-leveling cylinder 144 in extended position.

(55) The self-leveling cylinder 144 and the boom extension hydraulic cylinder 126 are integrated and simultaneously work together, by extending together and retracting together to preserve the self-leveling function while each extendable boom 118 is being extended and retracted.

(56) The lift hydraulic cylinder 120 is in the retracted position corresponding to the distal leg 116 of the boom 118 and the bucket 204 being in a lowered position. The front-end loader 100 includes the support structure 102 configured to be mounted on the tractor 302 (shown in FIG. 3B). The support structure 102 pivotally supports the proximal end of a lift hydraulic cylinder 120 at the proximal lift attachment 122. The support structure 102 is also configured to pivotally support the proximal leg 114 of the boom 118 (shown in FIG. 1B) at the proximal leg pivot 112.

(57) The distal end of the lift hydraulic cylinder 120 is pivotally attached to the distal end of the proximal leg 114 at the distal lift attachment 124. The boom 118 is shown in a lowered position; however, as the lift hydraulic cylinder 120 extends, the proximal leg 114 and the boom 118 are raised, and as the lift hydraulic cylinder 120 retracts, the proximal leg 114 and the boom 118 and the bucket 204 are lowered.

(58) The distal leg 116 of the boom 118 is extendable from the proximal leg 114. The distal leg 116 is shown in the extended position corresponding to the boom extension hydraulic cylinder 126 being in the extended position, and both the extension shaft 106 and an extension cylinder piston rod 104 in extended positions.

(59) The proximal end of the boom extension hydraulic cylinder 126 is attached to the proximal end of the proximal leg 114 at a proximal extension attachment 128. The distal end of the boom extension hydraulic cylinder 126 is attached to the proximal end of the distal leg 116 at the distal extension attachment 130.

(60) The distal leg 116 includes a tilt hydraulic cylinder 132 which controls the tilt angle of an accessory, such as the bucket 204, the accessory being attached to and supported by the accessory support end 140. The tilt hydraulic cylinder 132 is pivotally attached to the proximal end of the distal leg 116 by a proximal tilt attachment 134, and also is pivotally attached to the accessory support end 140 by a distal tilt attachment 136 (shown in FIG. 1A).

(61) With reference to FIG. 3, a perspective front and side view is shown of the front-end loader 100, having the support structure 102 mounted on the tractor 302. The front-end loader 100 includes, as an accessory, the bucket 204. The front-end loader 100 and the bucket 204 are shown in a lowered position, having each lift hydraulic cylinder 120 in the retracted position. Also, each boom 118 (shown in FIG. 1A) is in the retracted position, having each boom extension hydraulic cylinder 126 and each self-leveling cylinder 144 in the retracted position, and having each extension shaft 106 (shown in FIG. 1B) of the distal leg 116 fully retracted into the proximal leg receptacle 908 (shown in FIG. 9A) of the proximal leg 114. Each boom 118 of the two booms is attached to a cross member 202 configured to hold the two booms at a fixed distance apart and to provide structural support for the front-end loader 100.

(62) The tractor 302 includes two rear wheels 304 and two front wheels 306. In this embodiment, the distal leg 116 extends from the proximal leg 114 at a boom legs angle 138 of 105 to 135 degrees (shown in FIG. 1A) to prevent each distal leg 116 from striking against each of the front wheels 306 (or other parts of the tractor 302) when the two booms are in the lowered position.

(63) In some embodiments, the two rear wheels 304 can include conventional wheel weights (not shown) attached to the rear wheels 304 to provide additional counter weight for added stability, and to counter-balance the weight of the front-end loader 100 and the weight of an accessory attached to the accessory support end 140, such as the bucket 204.

(64) In some embodiments, the accessory support end 140 is configured to attach to one of: the bucket 204, pallet forks 1202 (shown in FIG. 12), hay forks (not shown), and bale spears (not shown).

(65) With reference to FIG. 4, a perspective front and side view is shown of the front-end loader 100, having the support structure 102 mounted on the tractor 302. The front-end loader 100 includes, as an accessory, the bucket 204. The front-end loader 100 and the bucket 204 are shown in a lowered position, having each lift hydraulic cylinder 120 in the retracted position. Also, each boom 118 (shown in FIG. 1A) is in the extended position, having each boom extension hydraulic cylinder 126 and each self-leveling cylinder 144 in the extended position, and having the extension shaft 106 of each distal leg 116 fully extended from the proximal leg receptacle 908 (shown in FIG. 9A) of the proximal leg 114.

(66) The extension cylinder piston rod 104 of each boom extension hydraulic cylinder 126 is extended, and the self-leveling cylinder piston rod 146 of each self-leveling cylinder 144 is extended, providing extended reach for the front-end loader 100 bucket 204.

(67) Each boom 118 (shown in FIG. 1A) of the two booms is attached to a cross member 202 configured to hold the two booms at a fixed distance apart and to provide structural support for the front-end loader 100.

(68) The tractor 302 includes two rear wheels 304 and two front wheels 306, and in this embodiment, the distal leg 116 extends from the proximal leg 114 at a boom legs angle 138 of 105 to 135 degrees (shown in FIG. 1A) to prevent each distal leg 116 from striking against the front wheels 306 (or other parts of the tractor 302) when the two booms are in the lowered position.

(69) In some embodiments, the two rear wheels 304 can include conventional wheel weights (not shown) attached to the rear wheels 304 to provide additional counter weight for added stability, and to counter-balance the weight of the front-end loader 100 and the weight of an accessory attached to the accessory support end 140, such as the bucket 204.

(70) In this embodiment, the boom extension hydraulic cylinder 126 extends each boom 118 by 2 to 4 feet.

(71) With reference to FIG. 5, a perspective front and side view is shown of the front-end loader 100, having the support structure 102 mounted on the tractor 302. The front-end loader 100 includes as an accessory the bucket 204. The bucket 204 is in a raised position, having the lift cylinder piston rod 502 of each lift hydraulic cylinder 120 in the extended position, and each proximal leg 114 in the raised position. Each boom extension hydraulic cylinder 126 and each self-leveling cylinder 144 are in the retracted position, and therefore the two booms are retracted (not extended).

(72) With reference to FIG. 6, a perspective front and side view is shown of the front-end loader 100, having the support structure 102 mounted on the tractor 302. The front-end loader 100 includes the bucket 204 accessory shown in a raised position. Each lift cylinder piston rod 502 of each lift hydraulic cylinder 120 in the extended position, and therefore each proximal leg 114 is in the raised position.

(73) To further raise and extend the bucket 204, each boom extension hydraulic cylinder 126 is in the extended position, having each extension shaft 106 of the distal leg 116 fully extended from the proximal leg receptacle 908 (shown in FIG. 9A) of the proximal leg 114 of each boom 118 (shown in FIG. 1A). Also, the extension cylinder piston rod 104 of each boom extension hydraulic cylinder 126 is extended, and the self-leveling cylinder piston rod 146 of each self-leveling cylinder 144 is extended, providing extended reach for the front-end loader 100 bucket 204.

(74) The boom extension hydraulic cylinder 126 and the self-leveling cylinder 144 are configured as a series hydraulic circuit (see FIG. 16A, FIG. 16B, and FIG. 17) such that the boom extension hydraulic cylinder 126 and the self-leveling cylinder 144 each co-extend by a substantially equal distance, and the boom extension hydraulic cylinder 126 and the self-leveling cylinder 144 each co-retract by a substantially equal distance.

(75) In some embodiments, the two rear wheels 304 include conventional wheel weights (not shown) to provide additional counter weight for added stability, and to counter-balance the weight of the front-end loader 100 and the weight of an accessory, such as the bucket 204. These conventional wheel weights added to the two rear wheels 304 can provide an especially important counter-balance when the boom extension hydraulic cylinder 126 of each boom 118 (shown in FIG. 1A) are in the extended position, as shown.

(76) In some embodiments, the boom extension hydraulic cylinder 126 of each boom 118 is configured to extend and retract each boom 118 AFTER the lift hydraulic cylinder 120 has raised each boom 118 (shown in FIG. 1A) to a raised position.

(77) With reference to FIG. 7A, a side view of a front-end loader 100 is shown having an extendable boom 118 (shown in FIG. 1A), including a proximal leg 114 and distal leg 116, and the bucket 204 accessory. The distal leg 116 of the boom 118 is extendable from the proximal leg 114. In this view, the boom extension hydraulic cylinder 126 and the self-leveling cylinder 144 are shown in the retracted position, and therefore the distal leg 116 is in the retracted position with respect to the proximal leg 114.

(78) The lift hydraulic cylinder 120 is in the retracted position, corresponding to the distal leg 116 accessory support end 140 and the attached bucket 204 being in a lowered position.

(79) The bucket tilt angle 702 is shown at a level tilt position.

(80) With reference to FIG. 7B, a side view of a front-end loader 100 and the bucket 204 of FIG. 7A are shown. The lift hydraulic cylinder 120 is in the extended position, corresponding to the distal leg 116 accessory support end 140 and the attached bucket 204 being in the raised position.

(81) The bucket tilt angle 702 can be changed with the tilt hydraulic cylinder 132. The tilt hydraulic cylinder 132 is configured to control the tilt angle of an accessory, such as a bucket 204.

(82) As the lift hydraulic cylinder 120 raises the distal leg 116 and the bucket 204 to the raised position, the self-leveling linkage 142 maintains a constant bucket tilt angle 702. Accordingly, the raised bucket 204 is maintained at the same bucket tilt angle 702 as for the lowered bucket 204 position shown in FIG. 7A.

(83) The bucket tilt angle 702 is shown at a level tilt position. Because the self-leveling linkage 142 maintains a constant bucket tilt angle 702, no matter how high or low the bucket 204 is raised, the bucket tilt angle 702 remains the same. Accordingly, the bucket tilt angle 702 remains invariant.

(84) The boom extension hydraulic cylinder 126 is configured in a series hydraulic circuit (shown in FIG. 16A and FIG. 16B) with the self-leveling cylinder 144, the self-leveling cylinder 144 being included in the self-leveling linkage 142. This series hydraulic circuit integrates the self-leveling hydraulics with the extension hydraulics of the extendable boom 118 (shown in FIG. 1). The self-leveling cylinder 144 and the boom extension hydraulic cylinder 126 are integrated and simultaneously work together to preserve the self-leveling function while the extendable boom 118 is being extended and retracted.

(85) If the bucket tilt angle 702 is adjusted independently by the tilt hydraulic cylinder 132 to a alternative bucket tilt angle 702, such as 30 degrees, and the lift hydraulic cylinder 120 is then extended or retracted to raise or lower the distal leg 116 and the bucket 204 to the raised position or the lowered position, the self-leveling linkage 142 maintains a constant bucket tilt angle 702 at 30 degrees. It does not matter what the bucket tilt angle 702 is, as the distal leg 116 and the bucket 204 are raised and lowered, the self-leveling linkage 142 will maintain the bucket tilt angle 702 at a constant angle, such as 30 degrees. This is why the front-end loader 100 is called self-leveling.

(86) With reference to FIG. 8A, a side view of a front-end loader 100 is shown having an extendable boom 118 (shown in FIG. 1A), including a proximal leg 114 and distal leg 116, and the bucket 204 accessory. The distal leg 116 of the boom 118 is extendable from the proximal leg 114. In this view, the boom extension hydraulic cylinder 126 and the self-leveling cylinder 144 are shown in the extended position, and therefore the distal leg 116 is in the extended position with respect to the proximal leg 114.

(87) The lift hydraulic cylinder 120 is in the retracted position, corresponding to the distal leg 116 accessory support end 140 and the attached bucket 204 being in a lowered position.

(88) The bucket tilt angle 702 is shown in a level tilt position.

(89) With reference to FIG. 8B, a side view of a front-end loader 100 and the bucket 204 of FIG. 8A are shown. The lift hydraulic cylinder 120 is in the extended position, corresponding to the distal leg 116 accessory support end 140 and the attached bucket 204 being in a raised position.

(90) The bucket tilt angle 702 can be changed with the tilt hydraulic cylinder 132. The tilt hydraulic cylinder 132 is configured to control the tilt angle of an accessory, such as a bucket 204.

(91) As the lift hydraulic cylinder 120 raises the distal leg 116 and the bucket 204 to the raised position, the self-leveling linkage 142 maintains a constant bucket tilt angle 702. Accordingly, the raised bucket 204 is maintained at the same bucket tilt angle 702 as for the lowered bucket 204 position shown in FIG. 7A.

(92) The bucket tilt angle 702 is shown at a level tilt position. Because the self-leveling linkage 142 maintains a constant bucket tilt angle 702, no matter how high or low the bucket 204 is raised, the bucket tilt angle 702 remains the same. Accordingly, the bucket tilt angle 702 remains invariant.

(93) The boom extension hydraulic cylinder 126 is configured in a series hydraulic circuit (shown in FIG. 16A and FIG. 16B) with the self-leveling cylinder 144, the self-leveling cylinder 144 being included in the self-leveling linkage 142. This series hydraulic circuit integrates the self-leveling hydraulics with the extension hydraulics of the extendable boom 118 (shown in FIG. 1). The self-leveling cylinder 144 and the boom extension hydraulic cylinder 126 are integrated and simultaneously work together to preserve the self-leveling function while the extendable boom 118 is being extended and retracted.

(94) If the bucket tilt angle 702 is adjusted independently by the tilt hydraulic cylinder 132 to a alternative bucket tilt angle 702, such as 30 degrees, and the lift hydraulic cylinder 120 is then extended or retracted to raise or lower the distal leg 116 and the bucket 204 to the raised position or the lowered position, the self-leveling linkage 142 maintains a constant bucket tilt angle 702 at 30 degrees. It does not matter what the bucket tilt angle 702 is, as the distal leg 116 and the bucket 204 are raised and lowered, the self-leveling linkage 142 will maintain the bucket tilt angle 702 at a constant angle, such as 30 degrees.

(95) With reference to FIG. 9A, an isometric side view is shown of the proximal leg 114, including a proximal leg attachment hole 902 configured to pivotally attach to the proximal leg pivot 112 (shown in FIG. 1A) at the upper attachment portion 110 of the support structure 102 (both shown in FIG. 1A). The proximal leg 114 also includes a proximal leg attachment pin 904 configured to support the proximal end of the boom extension hydraulic cylinder 126 (shown in FIG. 1A).

(96) An extension end 906 of the proximal leg 114 includes a proximal leg receptacle 908 configured to receive and slidably support the extension shaft 106 Of the distal leg 116 (both shown in FIG. 9B), and two lift cylinder attachment holes 910 configured to receive the distal lift attachment 124 at the distal end of the lift hydraulic cylinder 120 (both shown in FIG. 1A).

(97) With reference to FIG. 9B, an isometric side view is shown of the distal leg 116, including a distal leg attachment pin 912 configured to support the distal end of the boom extension hydraulic cylinder 126 (shown in FIG. 1A), two tilt cylinder attachment holes 914 configured to receive the linkage lower attachment 154 of the linkage connector 150 (both shown in FIG. 1A), and accessory attachment holes 916 that are configured to receive and support the accessory support end 140 (shown in FIG. 1A).

(98) With reference to FIG. 10, an isometric side view of the proximal leg 114 and the distal leg 116 is shown, with hidden lines showing the proximal leg receptacle 908 partially receiving and slidably supporting the extension shaft 106 of the distal leg 116.

(99) Included on the proximal leg 114 is the proximal leg attachment hole 902 configured to pivotally attach to the proximal leg pivot 112 (shown in FIG. 1A). In addition, the proximal leg attachment pin 904 is configured to support the proximal end of the boom extension hydraulic cylinder 126 (shown in FIG. 1A). Also, two lift cylinder attachment holes 910 are configured to receive the distal lift attachment 124 at the distal end of the lift hydraulic cylinder 120 (shown in FIG. 1A).

(100) The distal leg 116 includes the distal leg attachment pin 912 configured to support the distal end of the boom extension hydraulic cylinder 126 (shown in FIG. 1A). Two tilt cylinder attachment holes 914 are configured to receive the linkage lower attachment 154 of the linkage connector 150 (both shown in FIG. 1A), and accessory attachment holes 916 are configured to receive and support the accessory support end 140 (shown in FIG. 1A). The accessory support end 140 (shown in FIG. 1A) is configured to provide support for various accessories, such as the bucket 204 (shown in FIG. 1B).

(101) With reference to FIG. 11A, a cross sectional view of the proximal leg 114 is shown, showing four wear pads 1102 that, in this embodiment, are included within the proximal leg receptacle 908 (shown in FIG. 9A) of the proximal leg 114. The wear pads 1102 are configured to slidably support the extension shaft 106 of the distal leg 116 (both shown in FIG. 1B).

(102) With reference to FIG. 11B, an isometric view of the distal end of the proximal leg 114 is shown, also showing a hidden line view of a plurality of wear pads 1104 lining the proximal leg receptacle 908 (shown in FIG. 9A). In this embodiment, the plurality of wear pads 1104 are configured to slidably support the extension shaft 106 of the distal leg 116 (shown in FIG. 9B).

(103) In this embodiment, the extension end 906 of the proximal leg 114 includes the proximal leg receptacle 908 (shown in FIG. 9A) within the proximal leg 114 that includes a plurality of wear pads 1104 to slidably support the extension shaft 106 of the distal leg 116 (both shown in FIG. 9B) to provide a long service life.

(104) With reference to FIG. 12, a perspective front and side view is shown of the front-end loader 100 mounted on the tractor 302, including pallet forks 1202 attached to the accessory support end 140 of the distal leg 116 of the front-end loader 100.

(105) With reference to FIG. 13A, a side view is shown of the tractor 302, including the front-end loader 100 attached to pallet forks 1202. The lift hydraulic cylinder 120 is in the extended position, and the pallet forks 1202 are raised, however since the boom extension hydraulic cylinder 126 and the self-leveling cylinder 144 are in the retracted position, each boom 118 (shown in FIG. 1A) is not extended, and a bale of material 1302 is not raised high enough to be successfully placed on a truck 1304.

(106) With reference to FIG. 13B, a side view is shown of the tractor 302, including the front-end loader 100 attached to pallet forks 1202. The lift hydraulic cylinder 120 is in the extended position, and the pallet forks 1202 are raised. Because the boom extension hydraulic cylinder 126 and the self-leveling cylinder 144 are in the extended position (having the extension cylinder piston rod 104, the self-leveling cylinder piston rod 146, and the extension shaft 106 in the extended position), each boom 118 (shown in FIG. 1A) is extended, and therefore the bale of material 1302 is raised high enough to be successfully placed on the truck 1304.

(107) With reference to FIG. 14A, a hydraulic circuit diagram is shown of a hydraulic circuit configured to control one hydraulic cylinder 1408. A hydraulic reservoir 1402 holds a reservoir of hydraulic fluid that is pumped up to a high pressure on the valve side of a hydraulic pump 1404. A hydraulic control valve 1406 is configured in a neutral position, and the hydraulic fluid is simply returned to the hydraulic reservoir 1402, having performed no work on the hydraulic cylinder 1408. In addition, since the hydraulic control valve 1406 is in a neutral position, there is no hydraulic fluid flow at both a head port 1410 and a rod port 1420 of the hydraulic cylinder 1408, and due to the incompressibility of the hydraulic fluid, the volumes of a head fluid 1412 and a rod fluid 1416 remain constant, and a ram 1414 and a piston rod 1418 maintain a static position.

(108) With reference to FIG. 14B, a hydraulic circuit diagram is shown of a hydraulic circuit configured to control one hydraulic cylinder 1408. The hydraulic reservoir 1402 holds a reservoir of hydraulic fluid that is pumped up to a high pressure on the valve side of the hydraulic pump 1404. The hydraulic control valve 1406 is configured in an open forward flow position, and therefore the high pressure hydraulic fluid flows through the hydraulic control valve 1406 and through the head port 1410 and into the head fluid 1412. Because the head fluid 1412 is at a higher pressure than the rod fluid 1416, the ram 1414 moves to the right, and in doing so expands the volume of the head fluid 1412, and at the same time the piston rod 1418 extends outward from the hydraulic cylinder 1408. Simultaneously, the rod fluid 1416 volume decreases and the rod fluid 1416 passes out of the rod port 1420, the hydraulic fluid returning back through the hydraulic control valve 1406 and returning to the hydraulic reservoir 1402.

(109) With reference to FIG. 14C, a hydraulic circuit diagram is shown of a hydraulic circuit configured to control one hydraulic cylinder 1408. The hydraulic reservoir 1402 holds a reservoir of hydraulic fluid that is pumped up to a high pressure on the valve side of the hydraulic pump 1404. The hydraulic control valve 1406 is configured in an open reverse flow position, and therefore the high pressure hydraulic fluid flows through the hydraulic control valve 1406 and through the rod port 1420 and into the rod fluid 1416. Because the rod fluid 1416 is at a higher pressure than the head fluid 1412, the ram 1414 moves to the left, and in doing so expands the volume of the rod fluid 1416, and at the same time the piston rod 1418 retracts inward into the hydraulic cylinder 1408. Simultaneously, the head fluid 1412 volume decreases and the head fluid 1412 passes out of the head port 1410, the hydraulic fluid returning back through the hydraulic control valve 1406 and returning to the hydraulic reservoir 1402.

(110) With reference to FIG. 15A, a hydraulic circuit diagram is shown of a hydraulic circuit configured to control two hydraulic cylinders, a first hydraulic cylinder 1510 and a second hydraulic cylinder 1512.

(111) The front-end loader 100 of the invention (shown in FIG. 1A) is an example of an application of four hydraulic cylinders: the lift hydraulic cylinder 120, the boom extension hydraulic cylinder 126, the self-leveling cylinder 144, and the tilt hydraulic cylinder 132 (each shown in FIG. 1A). It is understood that the description herein of the basic operation of two hydraulic cylinders can be similarly extended to a hydraulic circuit with more than two hydraulic cylinders, such as are included in the front-end loader 100 of the invention.

(112) A hydraulic reservoir 1502 holds a reservoir of hydraulic fluid that is pumped up to a high pressure by a hydraulic pump 1504.

(113) A first hydraulic control valve 1506 is configured in an open forward flow position, and therefore high pressure hydraulic fluid flows through the first hydraulic control valve 1506 and through a first head port 1514 and into to a first head fluid 1518. Because the first head fluid 1518 is at a higher pressure than a first rod fluid 1522, a first ram 1520 moves to the right, and in doing so expands the volume of the first head fluid 1518, and at the same time a first piston rod 1524 extends outward from the first hydraulic cylinder 1510. Simultaneously, the first rod fluid 1522 volume decreases and the first rod fluid 1522 flows out of a first rod port 1516, the hydraulic fluid returning back through the first hydraulic control valve 1506 and returning to the hydraulic reservoir 1502.

(114) A second hydraulic control valve 1508 is configured in a neutral position, and therefore the hydraulic fluid entering the second hydraulic control valve 1508 is simply returned to the hydraulic reservoir 1502, having performed no work on the second hydraulic cylinder 1512. In addition, since the second hydraulic control valve 1508 is in a neutral position, there is no hydraulic fluid flow at both a second head port 1526 and a second rod port 1528 of the second hydraulic cylinder 1512. Due to the incompressibility of the hydraulic fluid, the volumes of a second head fluid 1530 and a second rod fluid 1534 remain constant, and a second ram 1532 and a second piston rod 1536 maintain a static position.

(115) With reference to FIG. 15B, a hydraulic circuit diagram is shown of a hydraulic circuit configured to control two hydraulic cylinders, the first hydraulic cylinder 1510 and the second hydraulic cylinder 1512. The hydraulic reservoir 1502 holds a reservoir of hydraulic fluid that is pumped up to a high pressure by the hydraulic pump 1504.

(116) The first hydraulic control valve 1506 is configured in a neutral position, and therefore the hydraulic fluid entering the first hydraulic control valve 1506 is simply returned to the hydraulic reservoir 1502, having performed no work on the first hydraulic cylinder 1510. Because the first hydraulic control valve 1506 is in a neutral position, there is no hydraulic fluid flow at both a first head port 1514 and a first rod port 1516 of the first hydraulic cylinder 1510. Due to the incompressibility of the hydraulic fluid, the volumes of a first head fluid 1518 and a first rod fluid 1522 remain constant, and a first ram 1520 and a first piston rod 1524 maintain a static position.

(117) The second hydraulic control valve 1508 is configured in an open forward flow position, and therefore the high pressure hydraulic fluid flows through the second hydraulic control valve 1508 and through a second head port 1526 and into a second head fluid 1530. Because the second head fluid 1530 is at a higher pressure than a second rod fluid 1534, a second ram 1532 moves to the right, and in doing so expands the volume of the second head fluid 1530, and at the same time a second piston rod 1536 extends outward, from the second hydraulic cylinder 1512. Simultaneously, the second rod fluid 1534 volume decreases, and the second rod fluid 1534 flows out of a second rod port 1528, the hydraulic fluid returning back through the second hydraulic control valve 1508 and returning to the hydraulic reservoir 1502.

(118) With reference to FIG. 16B, a hydraulic circuit diagram is shown of a series hydraulic circuit configured to control two hydraulic cylinders, a first hydraulic cylinder 1608 and a second hydraulic cylinder 1610.

(119) A hydraulic reservoir 1604 holds a reservoir of hydraulic fluid that is pumped up to a high pressure by a hydraulic pump 1602.

(120) A hydraulic control valve 1606 is configured in an open forward flow position, and therefore high pressure hydraulic fluid flows through the hydraulic control valve 1606 and through a first head port 1614 and into to a first head fluid 1622. Because the first head fluid 1622 is at a higher pressure than a first head first rod fluid 1616, a first ram 1624 moves to the right, and in doing so expands the volume of the first head fluid 1622, and at the same time a first piston rod 1612 extends outward from the first hydraulic cylinder 1608. Simultaneously, the first rod fluid 1616 volume decreases and the first rod fluid 1616 flows out of a first rod port 1620, the hydraulic fluid flowing into a second head port 1632 of the second hydraulic cylinder 1610.

(121) Simultaneously, hydraulic fluid flows through the second head port 1632 and into to a second head fluid 1634. Because the second head fluid 1634 is at a higher pressure than a first second rod fluid 1630, a second ram 1626 moves to the right, and in doing so expands the volume of the second head fluid 1634, and at the same time a second piston rod 1618 extends outward from the second hydraulic cylinder 1610. Simultaneously, the second rod fluid 1630 volume decreases and the second rod fluid 1630 flows out of a second rod port 1628, the hydraulic fluid flowing returning back through the hydraulic control valve 1606 and returning to the hydraulic reservoir 1604.

(122) Because of the incompressibility of the hydraulic fluid, the total volume of the first rod fluid 1616 and the second head fluid 1634 remain a constant. In addition, the two series hydraulic circuit cylinders, namely the first hydraulic cylinder 1608 and the second hydraulic cylinder 1610, are sized with matching cylinder diameters such that the movement of the first ram 1624 is equal to the movement of the second ram 1626. Accordingly, the movements of the first piston rod 1612 and the second piston rod 1618 are matched so that the extension amounts of the first piston rod 1612 and the second piston rod 1618 extend equally and move in tandem.

(123) The self-leveling cylinder 144 and the boom extension hydraulic cylinder 126 of the front-end loader 100 are configured as a series hydraulic circuit. The series hydraulic circuit integrates the self-leveling hydraulics with the extension hydraulics of each extendable boom 118 (shown in FIG. 1A and FIG. 1B). The self-leveling cylinder 144 and the boom extension hydraulic cylinder 126 (both shown in FIG. 1A) are integrated and simultaneously work together to preserve the self-leveling function while each extendable boom 118 is being extended and retracted.

(124) With reference to FIG. 16B, a hydraulic circuit diagram is shown of a series hydraulic circuit configured to control two hydraulic cylinders, the first hydraulic cylinder 1608 and the second hydraulic cylinder 1610.

(125) The hydraulic reservoir 1604 holds a reservoir of hydraulic fluid that is pumped up to a high pressure by the hydraulic pump 1602.

(126) The hydraulic control valve 1606 is configured in an open reverse flow position, and therefore high pressure hydraulic fluid flows through the hydraulic control valve 1606 and through the second rod port 1628 and into to the second rod fluid 1630. Because the second rod fluid 1630 is at a higher pressure than a first head second head fluid 1634, the second ram 1626 moves to the left, and in doing so expands the volume of the second rod fluid 1630, and at the same time the second piston rod 1618 retracts inward into the second hydraulic cylinder 1610. Simultaneously, the second head fluid 1634 volume decreases and the second head fluid 1634 flows out of the second head port 1632, the hydraulic fluid flowing into the first rod port 1620 of the first hydraulic cylinder 1608.

(127) Simultaneously, hydraulic fluid flows through the first rod port 1620 and into the first rod fluid 1616. Because the first rod fluid 1616 is at a higher pressure than the first head fluid 1622, the first ram 1624 moves to the left, and in doing so expands the volume of the first rod fluid 1616, and at the same time the first piston rod 1612 retracts inward into the first hydraulic cylinder 1608. Simultaneously, the first head fluid 1622 volume decreases and the first head fluid 1622 flows out of the first head port 1614, the hydraulic fluid flowing returning back through the hydraulic control valve 1606 and returning to the hydraulic reservoir 1604.

(128) Because of the incompressibility of the hydraulic fluid, the total volume of the second head fluid 1634 and the first rod fluid 1616 remain a constant. In addition, the two series hydraulic circuit cylinders, namely the first hydraulic cylinder 1608 and the second hydraulic cylinder 1610, are sized with matching cylinder diameters such that the movement of the first ram 1624 is equal to the movement of the second ram 1626. Accordingly, the movements of the first piston rod 1612 and the second piston rod 1618 are matched so that the extension amounts of the first piston rod 1612 and the second piston rod 1618 retract equally and move in tandem.

(129) The self-leveling cylinder 144 and the boom extension hydraulic cylinder 126 of the front-end loader 100 are configured as a series hydraulic circuit. The series hydraulic circuit integrates the self-leveling hydraulics with the extension hydraulics of each extendable boom 118 (shown in FIG. 1A and FIG. 1B). The self-leveling cylinder 144 and the boom extension hydraulic cylinder 126 (both shown in FIG. 1A) are integrated and simultaneously work together to preserve the self-leveling function while each extendable boom 118 is being extended and retracted.

(130) With reference to FIG. 17, a top view of the front-end loader 100 attached to a bucket 204 is shown.

(131) In this embodiment, for each boom 118 (shown in FIG. 1A), the self-leveling cylinder 144 is positioned above the proximal leg 114, and the boom extension hydraulic cylinder 126 is positioned on the outer side of the proximal leg 114.

(132) The distal leg 116 of each boom 118 is extendable from the proximal leg 114. The boom extension hydraulic cylinder 126 and the self-leveling cylinder 144 are shown in retracted positions, and accordingly the distal leg 116 is in the retracted position with respect to the proximal leg 114. Each proximal leg 114 includes the boom extension hydraulic cylinder 126. The proximal end of the boom extension hydraulic cylinder 126 is attached to the proximal end of the proximal leg 114 at the proximal extension attachment 128. The distal end of the boom extension hydraulic cylinder 126 is attached to the proximal end of the distal leg 116 at the distal extension attachment 130.

(133) The proximal end of each self-leveling cylinder 144 is attached to the self-leveling proximal attachment 148, and the distal end of the self-leveling cylinder piston rod 146 of each self-leveling cylinder 144 is attached to the self-leveling distal attachment 152.

(134) The distal leg 116 includes a tilt hydraulic cylinder 132 which controls the tilt angle of an accessory, such as the bucket 204, the accessory being attached to and supported by the accessory support end 140.

(135) For each boom 118 (shown in FIG. 1A), the self-leveling cylinder 144 and the boom extension hydraulic cylinder 126 are configured as a series hydraulic circuit.

(136) The hydraulic reservoir 1604 holds a reservoir of hydraulic fluid that is pumped up to a high pressure by the hydraulic pump 1602. The hydraulic control valve 1606 is configured in one of: an open forward flow position, a open reverse flow position, and a neutral position.

(137) In this embodiment, when the hydraulic control valve 1606 is configured in an open forward flow position, the boom extension hydraulic cylinder 126 and the self-leveling cylinder 144 extend, and each distal leg 116 extends. When the hydraulic control valve 1606 is configured in an open reverse flow position, the boom extension hydraulic cylinder 126 and the self-leveling cylinder 144 retract, and each distal leg 116 retracts. When the hydraulic control valve 1606 is configured in a neutral position, the boom extension hydraulic cylinder 126 and the self-leveling cylinder 144 maintain a static position, and each distal leg 116 maintains a static position.

(138) In this embodiment, a hydraulic head hose 1702 is connected to a self-leveling head port 1708 of each self-leveling cylinder 144, and a hydraulic rod hose 1704 is connected to an extension rod port 1714 of each boom extension hydraulic cylinder 126. For each boom 118, a hydraulic series hose 1706 connects the self-leveling cylinder 144 and the boom extension hydraulic cylinder 126 in a series hydraulic circuit by connecting a self-leveling rod port 1710 of the self-leveling cylinder 144 to an extension head port 1712 of the boom extension hydraulic cylinder 126.

(139) This series hydraulic circuit integrates the self-leveling hydraulics with the extension hydraulics of each extendable boom 118. The self-leveling cylinder 144 and the boom extension hydraulic cylinder 126 are integrated and simultaneously work together, by extending together and retracting together to preserve the self-leveling function while each extendable boom 118 is being extended and retracted.

(140) The boom extension hydraulic cylinder 126 and the self-leveling cylinder 144 are configured in the series hydraulic circuit such that the boom extension hydraulic cylinder 126 and the self-leveling cylinder 144 each co-extend by a substantially equal distance, and the boom extension hydraulic cylinder 126 and the self-leveling cylinder 144 each co-retract by a substantially equal distance.

(141) Other modifications and implementations will occur to those skilled in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the above description is not intended to limit the invention, except as indicated in the following claims.