Truck Mounted Forklift

Abstract

This invention relates to a truck mounted forklift comprising a U-shaped chassis having a pair of side bars bridged by a rear crossbar. There is provided a driver's station, a motive power unit and a lifting mechanism on the chassis. There is further provided a skid steer drive mechanism comprising two driven front wheels and a dolly rear wheel. The dolly rear wheel is rotatably mounted about a vertical axis offset from a central axis of the dolly rear wheel, and there is a releasable locking mechanism to secure the dolly rear wheel in a fixed orientation about the vertical axis. The releasable locking mechanism comprises a hydraulically operated locking pin on the chassis and a locking pin receiver on the dolly rear wheel. The locking pin is operated by way of a locking pin actuator on a driver's console, and there is a locking pin indicator on the console to warn the operator of the locking pin configuration.

Claims

1) A truck mounted forklift comprising a U-shaped chassis having a pair of forwardly projecting side bars bridged by a rear crossbar, a driver's station mounted on the chassis, a motive power unit mounted on the chassis, and a lifting mechanism mounted on the chassis for engagement of a load between the side bars, and in which there is provided a skid steer drive mechanism comprising a pair of driven front wheels, one driven front wheel mounted adjacent the forwardmost end of one of the side bars and the other driven front wheel mounted adjacent the forwardmost end of the other of the side bars, and a dolly rear wheel mounted on the rear crossbar, the dolly rear wheel being rotatably mounted about a vertical axis offset from a central axis of the dolly rear wheel, and in which there is provided a releasable locking mechanism to releasably secure the dolly rear wheel in a fixed orientation about the vertical axis, the releasable locking mechanism comprising a hydraulically operated locking pin mounted on the chassis and a complementary locking pin receiver mounted on the dolly rear wheel.

2) The truck mounted forklift as claimed in claim 1 in which there is provided a sensor on the hydraulically operated locking pin operable to detect when the locking pin is fully engaged in the locking pin receiver, and a locking pin indicator responsive to the sensor, the locking pin indicator being located in the driver's station operable to display whether the locking pin is in either a locked configuration engaging the locking pin receiver or a released configuration free of the locking pin receiver.

3) The truck mounted forklift as claimed in claim 1 in which there is provided a driver console in the driver's station, forward of a driver's seat, and in which there is provided a locking pin actuator switch on the driver console.

4) The truck mounted forklift as claimed in claim 3 in which the locking pin indicator is located on the driver console in the driver's station adjacent to the locking pin actuator switch.

5) The truck mounted forklift as claimed in claim 1 in which there is provided a locking pin actuator switch located outside the driver's station accessible when the truck mounted forklift is mounted on the rear of a carrying vehicle.

6) The truck mounted forklift as claimed in claim 1 in which the locking pin is spring loaded biased towards a locked configuration.

7) The truck mounted forklift as claimed in claim 1 in which the hydraulically operated locking pin is provided with a charge feed to unlock the locking pin.

8) The truck mounted forklift as claimed in claim 7 in which the charge feed is fed from the transmission pump of the truck mounted forklift.

9) The truck mounted forklift as claimed in claim 1 in which the locking pin is chamfered to facilitate insertion of the end of the locking pin into the complementary locking pin receiver.

10) The truck mounted forklift as claimed in claim 1 in which the locking pin receiver comprises a locking plate held in a fixed relationship relative to the dolly rear wheel, the locking plate having a pair of locking pin receiving apertures.

11) The truck mounted forklift as claimed in claim 10 in which the pair of locking pin receiving apertures are located diametrically opposed to each other on the locking plate.

12) The truck mounted forklift as claimed in claim 10 in which the locking pin receiving apertures are located on the locking plate to cause the dolly wheel to be aligned parallel to a longitudinal axis of the truck mounted forklift when the locking pin is engaged in either of the locking pin receiving apertures.

13) The truck mounted forklift as claimed in claim 12 in which the central axis of the dolly rear wheel is forward of the vertical axis when the locking pin is engaged in the first locking pin receiving aperture, and the central axis of the dolly rear wheel is rearward of the vertical axis when the locking pin is engaged in the second locking pin receiving aperture.

14) The truck mounted forklift as claimed in claim 13 in which when the locking pin is engaged in the first locking pin receiving aperture, the dolly rear wheel is stowed under the truck mounted forklift substantially forward of the aft-most point of the truck mounted forklift.

15) The truck mounted forklift as claimed in claim 10 in which the locking plate is configured to promote location of the locking pin in the nearest locking pin receiving aperture when the locking pin is operated and abutting the locking plate.

16) The truck mounted forklift as claimed in claim 15 in which the upper surface of the locking plate surrounding the locking pin receiving aperture is inclined downwardly towards the locking pin receiving aperture.

17) The truck mounted forklift as claimed in claim 15 in which the locking pin tapers towards a tip, and there is provided a channel recessed in the upper surface of the locking plate for receiving the tip of the locking pin, the channel configured so that it widens as it approaches the locking pin receiving aperture.

18) A truck mounted forklift comprising a U-shaped chassis having a pair of forwardly projecting side bars bridged by a rear crossbar, a driver's station mounted on the chassis, a motive power unit mounted on the chassis, and a lifting mechanism mounted on the chassis for engagement of a load between the side bars, and in which there is provided a skid steer drive mechanism comprising a pair of driven front wheels, one driven front wheel mounted adjacent the forwardmost end of one of the side bars and the other driven front wheel mounted adjacent the forwardmost end of the other of the side bars, and a dolly rear wheel mounted on the rear crossbar, the dolly rear wheel being rotatably mounted about a vertical axis offset from a central axis of the dolly rear wheel, and in which there is provided a releasable locking mechanism to releasably secure the dolly rear wheel in a fixed orientation about the vertical axis, the releasable locking mechanism comprising a hydraulically operated locking pin mounted on the chassis and a complementary locking pin receiver mounted on the dolly rear wheel; and in which there is provided a sensor on the hydraulically operated locking pin operable to detect when the locking pin is fully engaged in the locking pin receiver, and a locking pin indicator responsive to the sensor, the locking pin indicator being located in the driver's station operable to display whether the locking pin is in either a locked configuration engaging the locking pin receiver or a released configuration free of the locking pin receiver.

19) The truck mounted forklift as claimed in claim 18 in which there is provided a driver console in the driver's station, forward of a driver's seat, and in which there is provided a locking pin actuator switch on the driver console.

20) A truck mounted forklift comprising a U-shaped chassis having a pair of forwardly projecting side bars bridged by a rear crossbar, a driver's station mounted on the chassis, a motive power unit mounted on the chassis, and a lifting mechanism mounted on the chassis for engagement of a load between the side bars, and in which there is provided a skid steer drive mechanism comprising a pair of driven front wheels, one driven front wheel mounted adjacent the forwardmost end of one of the side bars and the other driven front wheel mounted adjacent the forwardmost end of the other of the side bars, and a dolly rear wheel mounted on the rear crossbar, the dolly rear wheel being rotatably mounted about a vertical axis offset from a central axis of the dolly rear wheel, and in which there is provided a releasable locking mechanism to releasably secure the dolly rear wheel in a fixed orientation about the vertical axis, the releasable locking mechanism comprising a hydraulically operated locking pin mounted on the chassis and a complementary locking pin receiver mounted on the dolly rear wheel; and in which the complementary locking pin receiver comprises a locking plate held in a fixed relationship relative to the dolly rear wheel, the locking plate defining a pair of locking pin receiving apertures; the locking pin receiving apertures being located on the locking plate to cause the dolly wheel to be aligned parallel to a longitudinal axis of the truck mounted forklift when the locking pin is engaged in either of the locking pin receiving apertures; and in which the central axis of the dolly rear wheel is forward of the vertical axis when the locking pin is engaged in the first locking pin receiving aperture, and the central axis of the dolly rear wheel is rearward of the vertical axis when the locking pin is engaged in the second locking pin receiving aperture; and in which when the locking pin is engaged in the first locking pin receiving aperture, the dolly rear wheel is stowed under the truck mounted forklift substantially forward of the aft-most point of the truck mounted forklift.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The invention will now be more clearly understood from the following description of some embodiments thereof given by way of example only with reference to the accompanying drawings, in which:

[0029] FIG. 1 is a perspective view of a truck mounted forklift according to the invention;

[0030] FIG. 2 is a rear perspective view of the truck mounted forklift of FIG. 1;

[0031] FIG. 3 is a side view of the truck mounted forklift of FIG. 1;

[0032] FIG. 4 is a side view of the truck mounted forklift with the dolly rear wheel locked in an operating configuration;

[0033] FIG. 5 is an enlarged view of the dolly rear wheel and a disengaged locking mechanism shown in ghost outline;

[0034] FIGS. 6(a) and 6(b) are views of the hydraulically operated locking pin free of the locking pin receiving aperture;

[0035] FIGS. 7(a) and 7(b) are views of the hydraulically operated locking pin engaged in the locking pin receiving aperture;

[0036] FIG. 8 is a view of the driver's console in the driver's station;

[0037] FIGS. 9(a) to 9(g) inclusive are views of the hydraulically operated locking pin; and

[0038] FIG. 10 is a diagrammatic view of the hydraulic circuit.

DETAILED DESCRIPTION OF THE DRAWINGS

[0039] Referring initially to FIGS. 1 to 4 inclusive, there is shown a truck mounted forklift, indicated generally by the reference numeral 100, comprising a U-shaped chassis 101 having a pair of forwardly projecting side bars 103, 105 bridged by a rear crossbar 107. The truck mounted forklift further comprises a driver's station 109 mounted on the chassis, a motive power unit 111 mounted on the chassis, and a lifting mechanism 113 mounted on the chassis for engagement of a load (not shown) between the side bars. In the embodiment shown, the lifting mechanism 113 is an upright mast 115 having a fork carriage 117 carrying tines 119, 121. The fork carriage 117 is moveable up and down the upright mast 115 in a reciprocal fashion. The reach of the tines 119, 121 may be adjusted using a pantograph linkage so that goods may be picked up and/or transported rearward of the front wheels 123, 125, and picked up and/or put down forward of the front wheels 123, 125.

[0040] The truck mounted forklift incorporates a skid steer drive mechanism comprising a pair of driven front wheels 123, 125, one driven front wheel 123 mounted adjacent the forwardmost end of one of the side bars 103 and the other driven front wheel 125 mounted adjacent the forwardmost end of the other of the side bars 105. Referring specifically to FIG. 2, the skid steer drive mechanism further comprises a dolly rear wheel 127 mounted on the rear crossbar. The dolly rear wheel 127 is rotatably mounted about a vertical axis 129 offset from a central axis 131 of the dolly rear wheel 127.

[0041] As will be described in more detail below, the skid steep mechanism comprises a releasable locking mechanism to releasably secure the dolly rear wheel 127 in a fixed orientation about the vertical axis 129.

[0042] Referring specifically to FIG. 3, the dolly rear wheel 127 is shown in a locked, stowed configuration in which the dolly rear wheel 127 is secured underneath the chassis 101, substantially forward of the rear crossbar 107. It can be seen that in this configuration, the truck mounted forklift 100 is tilted forwards with the dolly rear wheel raised relative to the driven front wheels 123, 125. This is how the truck mounted forklift is configured when mounted on a carrying vehicle (not shown). This is achieved by tilting the upright mast backwards using a tilt cylinder (not shown) when the tines 119, 121 are engaged in fork sockets (not shown) on the carrying vehicle. It will be understood that when the forklift is in this tilted configuration, if unlocked, the dolly rear wheel 127 will have a tendency to rotate about the offset vertical axis (part of the wheel mounting 128 that rotates about the vertical axis is shown in ghost outline angled forwards) to a position where the dolly rear wheel is facing forwards aligned with the longitudinal axis of the truck mounted forklift. In addition to the foregoing, there is shown an operator control console 200 having a control panel thereon (that will be described in more detail with respect to FIG. 8 below), and an operator joystick 300 for steering the truck mounted forklift.

[0043] Referring specifically to FIG. 4, there is shown a view of the forklift with the dolly rear wheel 127 in an alternative locked configuration protruding rearwardly from the truck mounted forklift (the part of the wheel mounting 128 is shown in ghost outline angled rearwards). In this configuration, the truck mounted forklift 100 can be driven in a straight line for a prolonged period of time and can be driven up or down a slope, even at an angle offset to the direction of the slope. It can be seen that the upright mast 115 is still tilted rearwards so that the tines 119, 121 are inclined upwards away from the truck mounted forklift. This is a common configuration for the lifting arrangement when transporting a load on the tines 119, 121.

[0044] Referring now to FIG. 5, there is shown a view of the dolly rear wheel with the releasable locking mechanism shown in ghost outline. The releasable locking mechanism comprises a hydraulically operated locking pin 133 mounted on the chassis, and a pair of complementary locking pin receivers 135, 137 which are formed in a locking plate 139 attached to and forming part of the dolly rear wheel 127. It will be understood that when the locking pin 133 is engaged in the locking pin receiver 137, the dolly rear wheel protrudes outwardly from the rear of the truck mounted forklift. If the dolly rear wheel 127 is rotated through 180° about the vertical axis 129, and the locking pin 133 is engaged in the other locking pin receiver 135, the dolly rear wheel 127 will be stowed underneath the truck mounted forklift.

[0045] Referring now to FIGS. 6(a) and 6(b), there are shown views of the locking pin 133 free of the locking pin receivers 135, 137. As will be described in more detail below, if the locking pin is actuated or if the fluid supply is removed from the hydraulic actuating cylinder, the locking pin 133 will be urged downwards onto the locking plate 139. When the locking pin aligns with one of the locking pin receivers 135, 137 on the locking plate 139, the locking pin will be urged downwards into the locking pin receiver 135, 137, as illustrated in FIGS. 7(a) and 7(b) respectively.

[0046] As can be seen in FIGS. 6(a), 6(b), 7(a) and 7(b), the locking pin 133 is chamfered to facilitate insertion of the end 134 of the locking pin into the complementary locking pin receiver 135, 137. The locking plate 139 may be configured to promote location of the locking pin 133 in the nearest locking pin receiver 135, 137 when the locking pin is operated and abutting the locking plate 139. For example, it is envisaged that the upper surface of the locking plate 139 surrounding the locking pin receiver 135, 137 may be inclined downwardly towards the locking pin receiver 135, 137. Similarly, it is envisaged that the locking pin 133 may taper towards a tip, and there may additionally be provided a channel recessed in the upper surface of the locking plate 139 for receiving the tip of the locking pin 133, the channel configured so that it widens as it approaches the locking pin receiver 135, 137. As the locking pin 133 is urged towards the locking plate, the downward force will act to progress the pin downwardly causing the pin to be inserted further into the channel and the locking plate to rotate 139 until the pin is located into one of the locking pin receivers 135, 137.

[0047] Referring to FIG. 8, there is shown an operator control console 200. The operator control console includes a locking pin actuator switch 201 that allows the operator to selectively lock and unlock the locking mechanism. In addition, there is provided a human machine interface (HMI) 203 which incorporates a locking pin indicator 205 which illustrates to the operator whether or not the locking pin is in a locked, engaged configuration. In this way, the operator will be able to determine at a glance whether or not the locking pin is engaged, and the operator will be able to lock or unlock the locking pin with the mere press of a button on the operator console. The locking pin indicator 205 will be responsive to a sensor (not shown) adjacent to the locking pin that will be able to sense the position of the locking pin and determine whether it is retracted or fully extended out of a locking cylinder (not shown). If the locking pin is fully extended out of the locking cylinder it will be known that the locking pin is fully engaged.

[0048] Referring now to FIGS. 9(a) to 9(g) inclusive, there is shown a locking cylinder, indicated generally by the reference numeral 400, having a locking pin 133 configured in the manner of a piston in the locking cylinder 400 and mounted for reciprocal movement in and out of the locking cylinder 400. A helical spring 401 is provided to urge the locking pin 133 out of the locking cylinder 400 towards a locking pin receiver (not shown). When the truck mounted forklift 100 is started up, hydraulic fluid flows into the transmission circuit (not shown) and a charge flow is provided to the locking cylinder 400 to retract the locking pin 133 into the locking cylinder 400 against the helical spring 401 force. This unlocks the locking mechanism and allows the dolly rear wheel 127 to rotate about the vertical axis 129 for normal truck mounted forklift operation. A magnetic sensor 403 detects a target 405 on the locking pin 133 to determine whether the locking pin is fully extended.

[0049] When it is desired to allow the locking pin 133 to move out of the cylinder and lock the dolly rear wheel in place, the dolly rear wheel 127 is aligned by the operator of the forklift in the desired direction, the hydraulic fluid pressure is removed by the operator pushing the locking pin actuator switch 201, and the helical spring 401 acts to push the locking pin 133 out of the locking cylinder 400 into a locking configuration. Similarly, it will be understood that if the engine is turned off, the hydraulic fluid supply is removed, the locking pin 133 will be pushed out of the locking cylinder 400 into a locking configuration under the helical spring 401 force.

[0050] Reference is made to the dolly rear wheel 127 being aligned by the operator of the forklift in the desired direction. It will be understood that in order to align the dolly rear wheel 127 in an operative configuration as shown in FIG. 4, the operator simply has to drive the truck mounted forklift forward for a short distance. After a short distance, the dolly rear wheel 127 will follow the direction of movement of the truck mounted forklift and will be ready for locking by the locking pin 133 being inserted into the locking pin receiver 137. Similarly, in order to align the dolly rear wheel 127 in a stowed configuration as shown in FIG. 3, the operator simply has to reverse the truck mounted forklift backwards for a short distance. Due to the fact that the dolly rear wheel central axis 131 is mounted about an offset vertical axis 129, the dolly rear wheel 127 will move to a configuration with the dolly rear wheel behind the vertical axis 129 in line with the direction of travel of the truck mounted forklift. Alternatively, it is envisaged that it is possible to align the dolly wheel 127 in a stowed configuration during the truck mounting procedure. When the forklift truck is raised off the ground with no weight on the rear dolly wheel, and with the forklift truck tilted forwards, the rear dolly wheel will have a tendency to rotate about the vertical axis under gravity into the stowed configuration. Once in the desired position, the locking pin 133 is engaged in the locking pin receiver 135.

[0051] Finally, referring to FIG. 10, there is shown a diagrammatic view of the hydraulic circuit, indicated by the reference numeral 500. The hydraulic circuit comprises a transmission circuit 501 which feeds a charge flow to the locking cylinder 400 via the park brake valve circuit 503. In other words, similar to the park brake, when the fluid from the transmission circuit 501 is cut off, the charge flow to the locking cylinder 400 is cut off and the locking cylinder assumes a locked configuration.

[0052] Various modifications could be made without departing from the scope of the invention. For example, it is envisaged that it may be advantageous to have a tilt sensor (one or more tilt switches, one or more accelerometers, or a 3 axis accelerometer for example) that would detect when the forklift was on a slope, and a control system that would automatically apply the locking pin if it detected that the forklift was on a slope. In other words, it may be possible to provide a safety feature that would automatically apply the locking pin if the machine detected a potentially dangerous operating condition. However, care would be necessary to ensure that this did not cause damage to the machine or a more serious safety issue.

[0053] It is envisaged that in addition to the locking pin actuator switch located on the control panel, that it may be advantageous to provide a locking pin actuator switch (as illustrated by reference numeral 132 in FIGS. 1 and 2) located outside the driver's station accessible when the truck mounted forklift is mounted on the rear of a carrying vehicle. In this way, if the locking pin is engaged in the locking pin receiver with the rear wheel located in the incorrect position, the locking pin can be temporarily released to allow the wheel to be realigned without the driver having to climb up into the vehicle.

[0054] Throughout the specification, reference is made to a hydraulically operated locking pin. It is envisaged that an electrically operated locking pin may be provided instead of a hydraulically operated locking pin. For example, an electric motor or a solenoid may be provided to withdraw the locking pin from the locking pin receiver. This may be particularly advantageous on a battery powered truck mounted forklift. Alternatively, it is envisaged that a pneumatically operated locking pin may be provided instead of a hydraulically operated locking pin.

[0055] In this specification the terms “comprise, comprises, comprised and comprising” and the terms “include, includes, included and including” are all deemed interchangeable and should be afforded the widest possible interpretation.

[0056] The invention is not solely limited to the embodiments hereinbefore described but may be varied in both construction and detail within the scope of the appended claims.