Patent Application
20060245866
An industrial pallet truck is utilized to lift and transport loads between locations. The operator of the pallet truck may be required to move loads repeatedly on and off of the pallet truck within a very short period of time, and is often required to move specific inventory from various locations in what is termed “picking.” During this practice, it is desirable that the operator can leave the pallet truck and pick a load while the pallet truck continues to move in the direction of the next load. In this way, the lifting and transporting of loads is most efficient. To avoid inadvertent vehicle travel, pallet trucks have a dead-man mechanism that engage a vehicle brake in the event that the operator leaves the pallet truck and releases the control arm. It is not possible for the operator to continue to hold the control arm in a non-braking position as he leaves the pallet truck and moves to the next pick location, therefore it is desirable to have a coast control system which retards, or overrides the dead-man brake mechanism, to allow the pallet truck to coast. The coast control system typically holds the control arm in a fixed or variable position between vertical and horizontal, such that the vehicle brake does not become engaged, and the pallet truck is allowed to coast to a stop in a controlled manner. Coast control systems are well known in the art, for example whereby a control arm brake is used to prevent the control arm from moving back to a vertical braking position.
Coast control systems known require an actuation mechanism on the pallet truck that places the pallet truck in a low speed travel mode, and activates the coast control device that overrides the dead-man brake. After the coast control system is activated, the operator is able to actuate the traction motor by means of a pick button or throttle, for example, which powers the pallet truck in a low travel speed mode. Such systems are inefficient, in that they require activation of multiple controls in order to actuate the traction motor within the low speed travel mode, or require multiple activations of the same control to accomplish this task. Some existing coast control systems provide for a coast control button on the control arm handle that must be pressed to activate the coast control system, and a separate pick button, or “jog switch”, that must be pressed to actuate the traction motor after the coast control system has been activated. Another related system provides for a coast control button on the control arm control head that first functions as means of selecting the low speed travel mode and activating the coast control system, and then must be pressed subsequently to actuate the traction motor. While both of these systems control the mode of travel and operation of the coast control system, they are not efficient or intuitive. The present invention addresses these and other problems associated with the prior art.
The present invention provides for an improved method and system to control the operability of a motorized vehicle such as an industrial pallet truck. The improved method relates to the simplified and intuitively functional and logical operation of the motorize vehicle in the pick state, or walking state.
The foregoing and other objects, features and advantages of the invention will become more readily apparent from the following detailed description of a preferred embodiment of the invention which proceeds with reference to the accompanying drawings.
A detailed description of the invention will now be provided, making reference to the accompanying figures.
The present invention provides for a pick button 108 that activates a pick state, and thereby activates both a coast control system 109 and a traction motor 110 at the first instance of it being pressed. The pick button 108 may then be repressed as necessary to again actuate the traction motor 110 within a low speed travel mode, with the coast control system 109 continuing to be activated throughout. The advantage of this invention is in the immediate responsiveness of the pallet truck 20 to the operator's desire to both engage the coast control system 109 and actuate the traction motor 110 in order to most efficiently initiate the picking process. The present invention describes a system whereby the pallet truck 20 operates in the low speed travel mode unless the operator takes definite action to activate a high speed travel mode, or a vehicle brake switch 101 (
The steer control handle 13 has two symmetrically located pick buttons 108 and two symmetrically located variable throttles 107. When the operator is on the operator platform 5 or is walking alongside of the pallet truck 20, the operator may activate the pick button 108 or throttle 107 with the same hand that is holding and controlling the steer control handle 13. The pallet truck 20 is accelerated by means of a traction motor 110 that may be operated in either the low speed travel mode or the high speed travel mode. In either low speed or high speed travel modes, the traction motor 110 may be actuated by means of the throttle 107. The rate of acceleration and maximum travel speeds obtained in the low and high speed travel modes are determined according to the current limiting characteristics of the low and high speed travel circuits, respectively. For example, the low speed travel mode provides for a maximum travel speed of approximately 3.5 miles per hour. Activation of the throttle 107 will cause the traction motor 110 to move in the forward or reverse direction in the low speed travel mode depending on the command sent by the throttle 107 to the traction motor 110. In the example pallet truck 20 shown in
With the throttle 107 positioned in the forward or reverse direction, the operator may simultaneously or sequentially press either of the two symmetrically located high speed buttons 4, located on the control panel 12 (
The control panel 12 is further equipped with two symmetrically located auxiliary pick buttons 208, an auxiliary lift button 8 and an auxiliary lower button 9, which function to lift and lower, respectively, the forks 10. Auxiliary pick button 208, auxiliary lift button 8, and auxiliary lower button 9, function the same as pick button 108, lift button 18, and lower button 19, respectively. Where this written description references any of the buttons located on the steer control handle 13, the associated auxiliary button on the control panel 12 will be assumed to provide the same functionality and achieve the same result as if it had instead been pressed by the operator. An alternate embodiment of the invention provides for the auxiliary pick buttons 208 functioning purely to activate the coast control system 109, and not actuate the traction motor 110 on the initial or any subsequent activation of the auxiliary pick buttons 208. In this embodiment, actuation of the traction motor 110 would be accomplished by activating the pick buttons 108 after the coast control system 109 has first been activated.
With the pallet truck 20 in a powered-down state, a pneumatic control arm return spring 31 (
With the pallet truck 20 in a powered-on state, and the control arm 2 lowered to a non-braking position, the pallet truck 20 automatically enters the low speed travel mode. In this mode, the operator may operate the pallet truck 20 when riding on, when walking alongside, or walking behind, the pallet truck 20. If the operator releases the control arm 2, the return spring 31 will cause the control arm 2 to return to a vertical position and activate the vehicle brake switch 101 thereby causing the pallet truck 20 to stop. The coast control system 109 is activated anytime the pallet truck 20 is in the pick state.
The dead man brake mechanism and coast control system 109 is shown in
The coast control system 109 described in this invention provides for retaining the control arm 2 in a fixed position between vertical and horizontal, however other locking mechanisms can be employed, such as a magnetic or friction device, which would hold the control arm 2 in any one of an infinite number of positions between vertical and horizontal.
When the control arm 2 is forced out of the fixed position held by the coast control system 109, the solenoid 35 will cease to apply force to the detent 32, and instead the solenoid return spring 36 will cause the detent 32 to retract through the solenoid holding weldment 38 and away from the control arm stop 34 by means of the movable detent return plate 37 which is attached directly to the detent 32.
With the pallet truck 20 operating in the low speed travel mode, the operator is able to activate the pick state, or walking state, of the pallet truck 20 by activating a pick button 108. The pick button 108, or other type of switch, may be located anywhere on the truck, including the control arm handle 13, the operator platform 5, or on the support bar 7, for example. In the preferred embodiment, the pick state is activated by means of a pick button 108 located on the control arm handle 13. In the pick state, the coast control system 109 of the pallet truck is activated which causes the control arm 2 to remain in a non-braking position, and thereby prevents the vehicle brake switch 101 from being activated. As a result, the pallet truck 20 is allowed to coast to a stop after the traction motor 110 is de-actuated.
Activation of the pick button 108 will cause the pallet truck 20 to move in the forward direction, towards the forks 10, up to the maximum allowable travel speed in the low speed travel mode, and will also override the return spring 31. The pallet truck 20 will continue being accelerated in the forward direction so long as the pick button 108 is being depressed. When the operator releases the pick button 108, the pallet truck 20 coasts to a stop regardless of whether or not the operator maintains physical contact with the pallet truck 20 or control arm 2, thereby allowing the operator to walk alongside, or ahead of the pallet truck 20 to pick the next load. While the pallet truck 20 is in the pick state, the operator is able to repeatedly accelerate the pallet truck 20 within the low speed travel range by either reactivating the pick button 108, or by holding open the throttle 107. The pallet truck 20 will remain in the pick state until the vehicle brake switch 101 is activated, the high speed travel button 4 is activated, the battery 111 is disconnected, or the key switch 100 is turned off. The battery 111 may become disconnected from the electrical circuit by physical removal of connecting wiring or if the operator presses an emergency off button (not shown), and in either case the pallet truck 20 will no longer be operating in the pick state. If the operator manually forces the control arm 2 into either a vertical or horizontal position, the vehicle brake switch 101 will be activated, the traction motor 108 will be de-actuated as the low and high speed travel circuits are open, and the pallet truck 20 will no longer be operating in the pick state.
Activation of the throttle 107, pick button 108, and the high speed button 4 is only possible with the control arm 2 in the non-braking position. The braking positions of the control arm 2 is specified by an approximate vertical position V and approximate horizontal position H as shown in
With the control arm 2 located in a non-braking position, the operator can activate the pick state by pressing the pick button 108. Pressing the pick button 108 will close the pick switch 103, thereby activating the coast control system 109, and will also close the traction switch 104 and actuate the traction motor 110 in the low speed travel mode as limited to a predetermined rate of travel for the pallet truck 10 according to the current restriction provided by the pick state resistor 106. Pick state resistor 106 provides for the same current restriction as discussed for the low speed travel mode resistor 105. Pick switch 103 will remain closed even after the pick button 108 is released, and will remain closed in the pick state until one of the following conditions occurs: the vehicle brake switch 101 is activated, the high speed switch 102 is activated, the battery 111 is disconnected, or the key switch 100 is turned off. Traction switch 104 will remain closed only so long as the pick button 108 is pressed. Therefore, the traction motor 110 will be de-actuated when the pick button 108 is released.
With the pick switch 103 closed, and the coast control system 109 activated, the control arm 2 is held in a fixed position between vertical and horizontal by the coast control system 109 which thereby overrides the return spring 31. The coast control system 109 is further described in
The operator may activate the high speed travel mode by simultaneously or sequentially engaging the throttle 107 and pressing the high speed button 4, which closes the high speed switch 102. After the throttle 107 is engaged, the high speed switch 102, will remain closed until the throttle 107 is placed in neutral, the battery 111 is disconnected, or the key switch 100 is turned off. When the high speed switch 102 is closed, the pick button 108 is disabled, and both the pick switch 103 and the traction switch 104 become open. This results in the de-activation of the coast control system 109 if the pallet truck 20 was in the pick state prior to activation of the high speed travel mode.
Disconnecting the battery 111, opening the key switch 100, or opening the brake switch 101, will cause all other switches in the circuit to become open, preventing engagement of the traction motor 110 in any of the travel modes or operating states discussed.
An alternative embodiment of this invention provides for a coast control enable button 25 (
Other components, methods, and systems of the pallet truck 20 that are not described in this patent are understood to operate in a similar manner to other conventional pallet trucks known in the existing art. The system and apparatus described above can use dedicated processor systems, micro controllers, programmable logic devices, or microprocessors that perform some or all of the operations. Some of the operations described above may be implemented in software and other operations may be implemented in hardware.
For the sake of convenience, the operations are described as various interconnected functional blocks or diagrams. This is not necessary, however, and there may be cases where these functional blocks or diagrams are equivalently aggregated into a single logic device, program or operation with unclear boundaries.
Having described and illustrated the principles of the invention in a preferred embodiment thereof, it should be apparent that the invention may be modified in arrangement and detail without departing from such principles. I claim all modifications and variation coming within the spirit and scope of the following claims.
