Manually length-adjustable fork for a lifting device, forklift truck provided therewith and method therefor

Abstract

Disclosed is a manually length-adjustable fork for a lifting device such as a forklift truck, a forklift truck provided therewith, and a method therefor. The fork includes a fixed fork part; an adjustable fork part displaceable relative to the fixed fork part and provided from a tubular profile which is for a large part open on the side facing downward during use; and a locking mechanism connected to the fixed fork part and provided with a locking catch, a spring mechanism and a fastener accessible from an underside for manual operation of the locking catch.

Claims

1. A manually length-adjustable fork for a lifting device such as a forklift truck, said fork having a first outer end and along a longitudinal axis in a forward direction therefrom a second outer end, said fork comprising: a fixed fork part; an adjustable fork part displaceable relative to the fixed fork part and provided from a tubular profile which is open on an underside of the profile; and a locking mechanism connected to the fixed fork part, wherein the locking mechanism is provided with: a locking catch for locking the adjustable fork part to the fixed fork part; a spring mechanism operatively connected to the locking catch; and a fastener accessible from the underside of the tubular profile for manual operation of the locking catch from the underside, wherein the fastener is accessible from a forwardly facing side of the locking mechanism and wherein the fastener is attached directly to the locking catch for ease in engaging and disengaging the locking catch wherein the fastener is accessible when the fork is in an elevated position; wherein the locking mechanism further comprises a fixed part provided with a slotted hole such that the fastener is movable in an adjustment direction therein perpendicular to the longitudinal axis during the manual adjustment of the fork.

2. The manually length-adjustable fork as claimed in claim 1, wherein the slotted hole is provided with a clearance in a direction substantially perpendicular to the adjustment direction such that the locking catch is connectable with the adjustable fork part.

3. The manually length-adjustable fork as claimed in claim 2, wherein the slotted hole of the locking mechanism is provided with an additional outward bending compensation clearance in a direction substantially perpendicular to the adjustment direction.

4. The manually length-adjustable fork as claimed in claim 1, wherein the locking catch is provided with a rectangular form.

5. The manually length-adjustable fork as claimed in claim 1, wherein the locking catch is provided with a locking body which extends in the direction of movement of the catch during locking and unlocking.

6. The manually length-adjustable fork as claimed in claim 1, wherein the fastener is provided removably in the locking mechanism.

7. The manually length-adjustable fork as claimed in claim 1, wherein the locking catch is provided on one side of the fork and moves in a direction B laterally to the fork.

8. The manually length-adjustable fork as claimed in claim 1, wherein the adjustable fork part is provided with a handle for displacing the adjustable fork part relative to the fixed fork part.

9. The manually length-adjustable fork as claimed in claim 1, further comprising a secondary locking arranged on the fixed fork part wherein the secondary locking comprises a wear plate.

10. The manually length-adjustable fork as claimed in claim 1, wherein the locking mechanism further comprises a lubricating means.

11. A forklift truck provided with a manually length-adjustable fork as claimed in claim 1.

12. A method for manually lengthening and/or shortening the manually length-adjustable fork as claimed in claim 1, comprising the steps of: providing the manually length-adjustable fork; unlocking the adjustable fork part with the locking mechanism; displacing the adjustable fork part relative to the fixed fork part from a side facing downward of the fork; and locking the adjustable fork part at a desired position with the locking mechanism.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings, in which:

(2) FIG. 1 shows a view of a forklift truck provided with a manually length-adjustable fork according to the invention;

(3) FIG. 2 shows a bottom view of the forks of FIG. 1;

(4) FIG. 3 shows a detail of the locking mechanism of the forks of FIG. 2;

(5) FIGS. 4-6 show an alternative locking mechanism according to the invention;

(6) FIGS. 7-10 show alternative embodiments according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(7) A forklift truck 2 (FIG. 1) is provided with cab 4, frame 6 and a number of wheels 8. Mast construction 12 is provided on front side 10 of forklift truck 2. In the shown embodiment construction 12 is provided with two guides 14 in which or on which fork board 16 is arranged. Two forks 18 according to the invention are arranged on fork board or connecting element 16.

(8) Fork 18 consists of a fixed fork part 20. Fixed fork part 20 is provided at a first outer end 21A with a number of mounting points or mounting elements 22 for mounting on element 16. Via a first part 24 oriented substantially vertically during use and a bend 26 the fixed fork part 20 transposes into a second part 28 which is substantially horizontal during use. In the shown embodiment second fork part 28 connects to the adjustable fork part 30 which is slidable thereover. In the shown embodiment adjustable fork part 30 is provided with a first recess 32 for a mode of use with a lengthened fork, and a second recess 34 for a mode of use with a shortened fork. A plurality of intermediate recesses are optionally possible for the purpose of thereby realizing further adjustable fork lengths. A nose element 35 is situated on the front side, i.e. at the free second outer end 21B of fork 18. Nose element 35 is inserted under the goods to be picked up. The second outer end 21B is forward of the first outer end 21A along a longitudinal axis L.

(9) In the shown embodiment the outer end of fixed fork part 20 is provided with locking mechanism 36 (FIG. 2). Close to locking mechanism 36 a locking plate or wear plate 38 is also arranged on fixed fork part 20 using a number of clamping bushes 40. Wear strip 42 is situated in lengthwise direction of second part 28 of fixed fork part 20. Adjustable fork part 30 is formed from a tubular profile, wherein an open space 44 is provided on the underside. Provided close to nose 35 of adjustable fork part 30 is a recess or handle/handgrip 46 for the purpose of manually sliding adjustable fork part 30 in and/or out. Fork part 30 slides over guide surfaces 48 using bent edge 50. In the shown embodiment edge 50 is provided at the outer end remote from nose 35 with a stop surface 52. In a maximally extended/lengthened position of adjustable fork part 30 the stop 52 comes into contact with locking plate 38. In the shown embodiment locking plate 38 is mounted with clamping bushes 40 on fixed fork part 20. For removal of plate 38 clamping bushes 40 can be struck via continuous holes into fixed fork part 20. Clamping bushes 40 can be struck out of fork 18 again via continuous holes.

(10) Locking mechanism 36 (FIG. 3) comprises a locking block 54 which is fixedly connected to fixed fork part 20. Locking mechanism 36 is further provided with a strip or element 56, which in the shown embodiment is arranged fixedly on block 54 and in which a slotted hole 58 is arranged. Locking pin or operating pin 60 is provided movably in slotted hole 58, wherein pin 60 is secured with screw thread 62 in locking body or locking element 64 which is movable relative to locking block 54. Access to the locking pin 60 is from the underside of the tubular profile and also from the forwardly facing side 36A (FIG. 2) of the locking mechanism 36 when the fork is in an elevated position. Catch 66 protrudes in the locked situation wholly or partially through one of the openings 32, 34 in adjustable fork part 30. In the shown embodiment catch 66 is provided on one side of fork 18.

(11) The upper edge 68 of catch 66 facing upward during use lies against the upper edge of one of the openings 32, 34 when adjustable fork part 30 is loaded. Catch 66 is pressed by spring 70 through one of the openings 32, 34, wherein in the shown embodiment spring 70 is arranged wholly or partially in chamber 72 of element 64 and supports on the other side against the fixedly disposed partition 74 connected to locking block 54.

(12) Element 64 is provided movably in a direction B which is substantially perpendicular to the sliding direction A, also called the adjustment direction, of adjustable fork part 30 relative to fixed fork part 20. In the shown embodiment element 64 is embodied as a round rod, wherein at the outer end locking catch 66 is provided with a square form. Slotted hole 58 is provided with an additional clearance 76 substantially as seen in direction of movement B of pin 60. Owing to the extra clearance 76 pin 60 has additional space in slotted hole 58 so that, preferably in combination with spring 70 provided with an extra stroke, catch 66 can compensate the outward bending of the tubular profile of adjustable fork part 30 and thereby leaves the locking in place.

(13) Slotted hole 58 is also shaped such that there is an additional clearance for pin 60 with which a rotation can be performed in direction C about an axis substantially parallel to direction B. Upper edge 68 of catch 66 can hereby as it were align itself relative to the edge of one of the openings 32, 34 in adjustable fork part 30.

(14) It is possible in the shown embodiment by removing pin 60 to disassemble catch 66 with element 64 in relatively simple manner for the purpose of replacement and/or maintenance. Spring 70 can also be removed here in simple manner from locking mechanism 36.

(15) Providing catch 66 with element 64 as one entity creates a good guiding of a movement of catch 66 with body 64 in locking mechanism 36, thereby avoiding catch 66 being pressed askew.

(16) Catch 66 is preferably made of a high-strength steel whereby, in combination with the rectangular shape of the outer end of catch 66, the surface area can remain relatively limited, and locking mechanism 36 can thereby be applied in relatively thin forks.

(17) During length adjustment of fork 18 pin 60 is displaced in direction B in slotted hole 58 counter to the spring force of spring 70. Catch 66 is here taken out of one of the openings 32, 34 in adjustable fork part 30. In the shown embodiment adjustable fork part 30 can be displaced here via bent edges 50 over guides 48 of fixed fork part 20 by the same user via handle 46 using the other hand. This displacement is continued by the user until catch 66 with element 64 is situated at one of the other openings 32, 34 in adjustable fork part 30. As a result of the action of spring element 64 with catch 66 thereon is pressed wholly or partially into opening 32, 34, whereby a locking of locking mechanism 36 is realized in the new position of fork 18.

(18) When adjustable fork part 30 is loaded, some misalignment of adjustable fork part 30, particularly in the furthest extended position thereof, can occur relative to fixed fork part 20. By providing clearance 76, whereby in this case a small rotation of pin 60 in rotation direction C will occur, upper edge 68 of catch 66 will be aligned with the periphery of opening 32, 34 such that the force is transmitted via a surface and point loads are avoided despite misalignment occurring.

(19) An alternative locking mechanism 80 (FIGS. 4-6) comprises largely the same or similar components as the locking mechanism 36 described and shown above. Alternative locking mechanism 80 is lubricated via connection 82. In the shown embodiment connection 82 is connected via chamber 82 to channel 84 and debouches in lubricator chamber 88 which is provided as recess in locking body 90. Body 90 is also provided with recesses 92. In the shown embodiment pin 94 is provided with stop surface 96. In the shown embodiment passages 98 provide recesses 92 with lubrication.

(20) It will be apparent that diverse measures and components of the shown embodiments are mutually interchangeable or can be applied in similar manner.

(21) An alternative embodiment 100 (FIG. 7) is based on the embodiment shown in FIG. 3. In embodiment 100 however, edge 102 of slotted hole 104 arranged in tube or strip 56 forms a stop for pin 60. In the shown embodiment slotted hole 104 (FIG. 7) therefore takes a smaller form than slotted hole 56 (FIG. 3). Transition 106 from rectangular catch 66 to round element 64 is also moved further inward. In this embodiment transition 106 does not therefore lie in any situation against another surface or element. An advantage hereof is that compensation in direction C is even simpler, since the rotation movement can be performed with even less undesirable resistance.

(22) In a further alternative embodiment 108 (FIG. 8) transition 106 from rectangular catch 66 to round element 64 is moved further inward compared to the embodiment shown in FIG. 3. Also provided on tube or strip 56 is an additional stop in the form of edge 110 against which transition 106 comes to lie in a locked situation. A larger stop surface with tongue or edge or ring 110 can be realized compared to embodiment 100 of FIG. 7.

(23) In yet another alternative embodiment 112 (FIG. 9) the tongue or edge 110 is dispensed with when compared to embodiment 108 shown in FIG. 8. Transition 106 is however again moved inward. A covering 114 is also arranged on the outer side of adjustable fork part 30. Covering 114 can be provided as cover plate arranged with a welded or soldered connection. Alternative connections are also among the possibilities. It is also possible to provide a covering 114 by arranging a kind of indentation or recess at the desired location for catch 66 using a punch in a type of deep-drawing process. It is also possible to mill into the side wall of fork part 30 a recess in which catch 66 is provided in the locked situation. This embodiment has the drawback that the wall thickness of the side wall of fork part 30 is reduced at the position of the recess.

(24) An alternative locking mechanism 116 (FIG. 10) based on mechanism 80 (FIG. 4) can likewise be provided with a covering 118 in similar manner to covering 114 of mechanism 112 of FIG. 9.

(25) An advantage of covering 114, 118 is that no dirt can penetrate. The number of breakdowns and/or contaminants in the mechanism is hereby reduced. A further advantage is that it is possible if desired to dispense with an inclining edge on the outer end of catch 66. A small hole 120 is optionally also arranged in covering 114, 118 for a visual inspection of the locking with catch 66. The foremost surface of catch 66 is further optionally provided here with a different colour or provided in fluorescent or otherwise contrasting manner. Visual inspection of a correct locking is hereby possible. It is also possible to make covering 114, 118 wholly or partially transparent in order to realize a similar effect.

(26) It is the case for all embodiments that the size of catch 66 is not determined by for instance the size of the fingers of a user since operation during adjustment is performed using pin 60. It is thus possible for instance to provide catch 66 with a smaller surface so that breakdowns and/or the danger of penetration of contamination is further reduced.

(27) It is thus expressly possible to interchange measures of the locking mechanism of FIG. 3 with measures of the locking mechanism of FIGS. 4-6. Additionally or alternatively, measures of the different alternative embodiments can for instance be interchanged.

(28) The present invention is by no means limited to the above described preferred embodiments thereof. The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged. Locking mechanism 36 can for instance also be applied to types of lifting device other than forklift truck 2, for instance platform lifts and pallet trucks.