Power-assisted pallet truck

• US 6,260,646 B1
• Filed: 04/29/1999
• Issued: 07/17/2001
• Est. Priority Date: 04/29/1999
• Status: Expired due to Fees

• Current Assignee: Daniel C. Mullock, Raul U. Fernandez
• Original Assignee: Daniel C. Mullock, Raul U. Fernandez
• Inventors: Fernandez, Raul U., Mullock, Daniel C.
• Primary Examiner(s): Mai, Lanna
• Assistant Examiner(s): TO, TOAN C
• Application Number:
  US09/302,131
• Time in Patent Office: 810 Days
• Field of Search: 180/65.6, 180/65, 280/43.12, 280/43.23, 280/109
• US Class Current: 180/65.6
• CPC Class Codes: B62B 3/0612 power operated
• CPC Class Codes: H01H 2009/068 with switches mounted on a handlebar, e.g. for motorcycles, fork lift trucks, etc.

Abstract

A pallet truck for manually transporting loaded pallets is provided with a momentary locomotion means that assists an operator in starting a load moving from a state of rest. The locomotion subsystem is of suitable weight and size to allow the power-assisted pallet truck to be manually operated, and to allow for use of the pallet truck in similar space constraints as manual pallet trucks. In an enhanced embodiment, a governor switch is provided which disables the power-assistance after the load has been accelerated to walking speed in order to protect the motor from use as a full-time locomotion means.

Claims

1. A power-assisted pallet truck for transporting loaded pallets over flat surfaces under the primary power of a single operator, said pallet truck comprising:

one or more load bed forks for lifting and carrying a loaded pallet;

a steering yoke pivotally mounted to said load bed forks, said steering yoke providing mechanical support to one or more steering wheels which contact the surface;

a tow bar attached to said steering yoke, said tow bar being equipped with an operator handle, and said tow bar being mechanically attached to said steering yoke such that an operator can pull and steer the pallet truck using the operator handle;

an energy storage means having an energy output connector, said energy storage means being mounted to said pallet truck such that it travels with the pallet truck;

a motor means for imparting rotational energy to said steering wheels when engaged, said motor means having motor input connector and a mechanical rotational energy output;

a motor control means adapted to selectively and momentarily engage said motor means by conduction of energy from said energy storage means to said motor means responsive to operator-induced acceleration of the pallet truck, further adapted to automatically disengage said motor means responsive to relatively steady velocity of the pallet truck by interruption of energy from said energy storage means to said motor means, said motor control means having a control input connector and a control output connector;

a first energy conduit for communicating energy from said energy storage means output connector to said motor control input connector;

a second energy conduit for communicating energy from said motor control output connector to said motor input connector; and

a transmission means suitably disposed between said motor means mechanical rotational energy output and said steering wheels such that when the operator momentarily applies force to said operator handle sufficient to accelerate the pallet truck, energy is conducted from the energy storage means to the motor means such that the motor means momentarily drives the steering wheels to assist the operator during acceleration of the loaded pallet, and such that the motor means is disengaged automatically by said motor control means when the pallet truck attains a stable velocity.

2. The power-assisted pallet truck of claim 1 wherein said energy storage means comprises an electric battery, said first and second energy conduits comprise electrical conductors, said motor control means comprises an acceleration-activated momentary electric switch, and said motor means comprises an electric motor.

3. The power-assisted pallet truck of claim 1 wherein said energy storage means is a compressed gas tank, said first and second energy conduits are compressed gas hoses, and said operator control means is a momentary gas valve.

4. The power-assisted pallet truck of claim 3 wherein said motor means is an air motor.

5. The power-assisted pallet truck of claim 3 wherein said motor means is a telescoping strut.

6. The power-assisted pallet truck of claim 3 wherein said motor means is a rack-and-pinion actuator.

7. The power-assisted pallet truck of claim 1 wherein said transmission means further comprises

an output gear mounted on said motor means rotational energy output;

a steering wheel gear mounted on said steering wheels; and

a chain drive means for communicating rotational force from said output gear to said steering wheel gear.

8. The power-assisted pallet truck of claim 7 wherein said output gear further comprises a ratcheting means for allowing coasting of said output gear with respect to said motor means rotational energy output in one direction of rotation.

9. The power-assisted pallet truck of claim 1 wherein said transmission means further comprises

an output pulley mounted on said motor means rotational energy output;

a steering wheel pulley mounted on said steering wheels; and

a belt drive means for communicating rotational force from said output pulley to said steering wheel pulley.

10. The power-assisted pallet truck of claim 9 wherein said output pulley further comprises a ratcheting means for allowing coasting of said output pulley with respect to said motor means rotational energy output in one direction of rotation.

11. The power-assisted pallet truck of claim 1 wherein:

said tow bar further comprises an upper and a lower section, said upper section being attached to said operator handle, said lower section being attached to said steering yoke, with a spring-loaded limited-range slidable mechanical interconnect between said upper section and said lower section; and

said motor control means further comprises a governor momentary switch which is operated momentarily during the compression of the slidable interconnect of the tow bar such that during a transition from rest to stable velocity of the loaded pallet, force applied to the operator handle by the operator to accelerate the load compresses the slidable interconnect and allows the motor means to be engaged, and such that as the loaded pallet reaches a stable speed, the spring-loaded slidable interconnect returns to its normal position and the governor switch disengages the motor means.

12. The power-assisted pallet truck of claim 11 wherein said governor switch comprises a momentary electrical switch.

13. The power-assisted pallet truck of claim 12 wherein said governor switch comprises a momentary gas valve assembly.