Abstract:
A power-assist hand truck for assisting in the movement of objects. The powered hand truck includes two electric disc gearmotors, an overrunning clutch hub for each driven wheel, an e-stop switch, a speed control, a power source, a motor controller, and other necessary electronics, which can be integrated into an existing hand truck or platform cart or compose a new handtruck or platform cart. Power is provided by replaceable/rechargeable batteries. The batteries can be charged from a stationary power source or by a mobile power source such as that of a vehicle battery. In forward motion the speed control and motor controller provide variable power-assist levels, however, the overrunning clutch hubs allow the user to walk as quickly as desired. The e-stop switch engages and disengages the gearmotors from the power supply, thereby allowing the user to selectively switch between regenerative braking and low rolling resistance operation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of PPA Application Ser. No. 61/364,810, filed Jul. 16, 2010 by the present inventors, which is incorporated by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
       [0003]    Not Applicable 
       BACKGROUND—PRIOR ART 
       [0004]    The common 2-wheel manual hand truck as shown in  FIG. 1A  and  FIG. 1B  has been used for decades to assist in the movement of heavy and bulky objects. Some hand trucks, referred to as convertible and as shown in  FIG. 2A ,  FIG. 2B , and  FIG. 3 , were developed to be converted into a 4-wheel platform mode. In platform mode the hand truck functions as a platform cart. 
         [0005]    Convertible hand trucks are commonly used by delivery drivers to allow them to transport heavier and bulkier items than they could with a 2-wheel hand truck, while still having the option to transport small loads on 2-wheels and to be stored in the smaller 2-wheel profile. In some cases these delivery drivers repetitively push and pull loads in excess of 600 lbs over long distances. Driver fatigue decreases efficiency and increases the possibility of injury. 
         [0006]    According to the 2009 Liberty Mutual Workplace Safety Index (WSI), overexertion was the number one cause of workplace disabling injuries in 2007. Injuries from overexertion encompassing excessive lifting, pushing, pulling, holding, carrying, and throwing cost U.S. companies over $12.7 Billion in 2007. 
         [0007]    In order to address this problem several powered convertible hand trucks have been developed and marketed specifically to the delivery industry. Examples include the “Powered Gemini” by Magliner Inc., the CobraPro by Wesco Industrial Product Inc., and the “Powered Hand Truck” shown in U.S. Pat. No. 7,163,212 invented by Steven J. Chambers and sold by Industry Assist Inc. The Gemini and Wesco hand trucks are sold fully assembled, whereas the Industry Assist unit can be purchased as a retrofit kit for an existing hand truck or as a complete hand truck. 
         [0008]    Although these powered hand trucks would logically seem to be useful in reducing operator fatigue none of them has been widely adopted by the industry. We were able to identify and understand the needs of the delivery drivers, which is key to understanding the disadvantages of the prior art powered hand trucks. The most important aspects of any powered hand truck to the delivery drivers are that it help move a heavy load, that it be lightweight, and that it allow them to work at their traditional work pace. All three of the aforementioned prior art powered hand trucks share the same fundamental disadvantages to the delivery drivers as outlined below. 
         [0009]    Manual hand trucks weigh around 45 lbs and delivery drivers normally lift them into and out of their trucks by hand. For safety, most delivery drivers working for companies such as FedEx and UPS are limited to lifting around 70 lbs. The weight of the prior art powered convertible hand trucks exceeds 110 lbs. The excessive weight of the hand trucks requires a truck lift or ramp to load and unload them, both of which slow the operators down as compared to their traditional work pace. 
         [0010]    Maximum operating speed is another disadvantage of all prior art powered hand trucks. The maximum operating speed of the prior art powered hand trucks is around 4 mph. However, many delivery drivers often exceed 5 mph with their traditional manual hand trucks. Over long distances this speed restriction slows the operator down. 
         [0011]    The prior art powered hand trucks also present several disadvantages to delivery drivers in cases of failure during a delivery. First, the excessive weight of these powered hand trucks makes them more difficult to push, pull and maneuver than a manual hand truck would be. Second, the replacement of the exposed axle on a manual hand truck with a bulky transaxle reduces the operators&#39; ability to brace the hand truck with his foot during initial load balancing in 2-wheel mode. 
       BRIEF SUMMARY OF THE INVENTION 
       [0012]    In accordance with one embodiment a power-assist hand truck comprises a convertible hand truck frame, right and left wheels each driven by a disc style gearmotor, an overrunning clutch for each driven wheel, a motor controller, a variable speed throttle, and a plurality of batteries. 
       ADVANTAGES 
       [0013]    Accordingly, several advantages of one or more aspects are to provide a power-assist hand truck or platform cart that is lighter weight, has a faster maximum speed, and allows the operator to work at his or her traditional work pace. These and other advantages of one or more aspects will become apparent from a consideration of the ensuring description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0014]    Corresponding reference characters indicate corresponding components throughout the several views of the drawings. 
           [0015]      FIG. 1A  is a side view of a prior art hand truck. 
           [0016]      FIG. 1B  is a front view of the prior art hand truck. 
           [0017]      FIG. 2A  is a side view of a prior art convertible hand truck. 
           [0018]      FIG. 2B  is a front view of the prior art convertible hand truck. 
           [0019]      FIG. 3  is a side view of the prior art convertible hand truck in a platform (i.e. four-wheel) mode. 
           [0020]      FIG. 4A  is a side view of a power-assist hand truck according to the present invention. 
           [0021]      FIG. 4B  is a front view of the power-assist hand truck according to the present invention. 
           [0022]      FIG. 5  is a side view of the power-assist hand truck or platform cart according to the present invention in a platform mode. 
           [0023]      FIG. 6A  is a side view of the control handle attached to the convertible frame including handgrips and a grip mountable speed control according to the present invention. 
           [0024]      FIG. 6B  is a front view of the control handle attached to the convertible frame including handgrips and a grip mountable speed control according to the present invention. 
           [0025]      FIG. 7A  is a top view of the grip mountable speed control according to the present invention. 
           [0026]      FIG. 7B  is a side view of the grip mountable speed control according to the present invention. 
           [0027]      FIG. 7C  is an end view of the grip mountable speed control according to the present invention. 
           [0028]      FIG. 8A  is a side view of the lower third of the convertible hand truck according to the present invention, which includes the gearmotors, batteries, controller, side plates, and right skid rail. Both wheels, the left side grease cover used to cover the hub gear and mating gear, and the left skid rail are not shown. 
           [0029]      FIG. 8B  is a front view of the lower third of the convertible hand truck according to the present invention, which includes the gearmotors, batteries, controller, side plates, and right skid rail. Both wheels, the left side grease cover used to cover the hub gear and mating gear, and the left skid rails are not shown. 
           [0030]      FIG. 9A  is a side view with respect to the power-assist hand truck of an overrunning clutch hub used to engage and disengage the wheel from the drivetrain according to the present invention. 
           [0031]      FIG. 9B  is a front view with respect to the power-assist hand truck of an overrunning clutch hub used to engage and disengage the wheel from the drivetrain according to the present invention. 
           [0032]      FIG. 10A  is a wheel (outside) side view of a side plate and gearmotor according to the present invention. 
           [0033]      FIG. 10B  is a bottom view of a side plate and gearmotor according to the present invention. 
           [0034]      FIG. 10C  is an axle (inside) side view of a side plate and gearmotor according to the present invention. 
           [0035]      FIG. 11A  is a front view of the controller and batteries according to the present invention. 
           [0036]      FIG. 11B  is a side view of the controller and batteries according to the present invention. 
           [0037]      FIG. 11C  is a back view of the controller and batteries according to the present invention. 
           [0038]      FIG. 12A  is a front view with respect to the power-assist hand truck of a grease cover used to cover the hub gear and mating gear. 
           [0039]      FIG. 12B  is a side view with respect to the power-assist hand truck of a grease cover used to cover the hub gear and mating gear. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0040]    The following description is of the best mode presently contemplated for carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. 
         [0041]    An example of prior art hand truck hand truck  10  is shown in side view in  FIG. 1A , and in front view in  FIG. 1B . Such hand truck comprises a first frame  12   a , hand truck wheels  14 , and a nose  16 . Such hand truck  10  is useful for moving objects, which may be balanced on the nose  16 . An example of a prior art convertible hand truck  20  is shown in side view in  FIG. 2A , and in front view in  FIG. 2B , and is further shown in  FIG. 3  converted from a hand truck to a platform. The convertible hand truck  20  comprises a second frame  12   b , the hand truck wheels  14 , the nose  16 , and additionally, caster wheels  22  supported by a convertible frame  24 , second frame handle  26  mounted on second frame  12   b , convertible frame handle  34  mounted on second frame  12   b , a latching member  28  attached to the convertible frame  24  proximal to the caster wheels  22 , pivot/slide member  30  slideably cooperating with convertible frame  24 , and a latch receiving member  32  attached to the second frame  12   b  and adapted to cooperate with the latching member  28 . 
         [0042]    The convertible hand truck  20  may be configured as a standard hand truck as seen in  FIGS. 2A and 2B  by substantially aligning the convertible frame  24  with the second frame  12   b  and latching the latching member  28  with the latching receiving member  32 . The convertible hand truck  20  may be converted to a four-wheel hand truck (or platform mode) by unlatching the latching member  28  from the latch receiving member  32 , rotating the convertible frame  24  at the pivot/slide member  30  to be substantially perpendicular to the second frame  12   b , and sliding the convertible in the pivot/slide member  30 , as seen in  FIG. 3 . 
         [0043]    Prior art convertible hand truck  20  as shown in  FIGS. 2A ,  2 B, and  3  is sold by several companies and commonly used, especially in the truck delivery industry. These convertible hand trucks  20  are typically specified as being able to carry over 1,000 lbs in platform mode as seen in  FIG. 3  and are typically around twenty-one inches in overall width and have frame widths of around twelve inches. 
         [0044]    The present invention consists of a power-assist hand truck  18  shown in side view in  FIG. 4A , in front view in  FIG. 4B , and in platform mode in  FIG. 5 .  FIG. 5  also represents a platform cart. 
         [0045]    The power-assist hand truck consists of a convertible hand truck  20  frame, gearmotors  40 , controller  48 , and cooperating components. The different and additional components that comprise the power-assist hand truck  18  when compared to the prior art hand trucks  10  and  20  could be used to convert a used prior art hand truck, a new prior art hand truck, or incorporated in the initial manufacturing of a hand truck. 
         [0046]    The gearmotors  40  are preferably positioned immediately above and in proximity to the second frame  12   b  as shown in  FIG. 4B  thereby leaving the axle  61  mostly exposed in similarity to prior art hand truck  10  and prior art convertible hand truck  20 . 
         [0047]    The speed control components can be seen specifically in side view  FIG. 6A  and in front view  FIG. 6B  as attached to convertible frame  24  and as seen with second frame  12   b  when the power-assist hand truck  18  is in two-wheel mode, and additionally as part of the power-assist hand truck  18  in  FIGS. 4A ,  4 B, and  5 . The speed control assembly consists of the speed control handle  44  attached to the convertible frame  24  by two speed control handle brackets  52 , a grip mountable speed control  36  attached to speed control handle  44  and set in horizontal and rotational place by means of a mechanical setscrew engaged on the speed control handle  44 , two identical speed control handle grips  54 , and a speed control cable  38 . 
         [0048]    Speed control handle  44  is an aluminum tube preferably one-half inch to one and one-half inches in diameter and more preferably seven-eighths inch in diameter extending approximately sixteen and one-half inches in length. The diameter, material, curvature, design, and length of speed control handle  44  can be varied. Additionally, the speed control handle  44  may be omitted entirely if the speed control  36  is directly or indirectly mounted to an alternate handle or frame. The speed control handle  44 , speed control brackets  52 , speed control cable  38 , and speed control handle grips  54  may be omitted entirely if the speed control  36  is made to be wireless. 
         [0049]    Speed control handle brackets  52  whereby said brackets have a left and right hand version are formed specifically to attach to and be mechanically supported by the contour of convertible frame  24  and additionally preferably by bolts utilizing existing mounting holes in convertible frame  24 . The speed control handle brackets  52  are attached to the speed control handle  44  by means of a machine screw placed through a hole in the bracket and secured into a threaded insert attached internally in each end of the speed control handle  44  tube. The speed control handle brackets  52  are made of formed aluminum sheet metal but could also be made of various materials including but not limited to plastic, steel, aluminum alloys, or a combination thereof. Speed control handle brackets  52  could be mounted in locations other than shown, could consist of a singular unit rather then two units, could be symmetrically designed to avoid the need for right and left hand versions, and could be designed for and mechanically secured by methods including friction, riveting, and bolting. The speed control handle grips  54  are preferably one to two inches in diameter and more preferably one and one-eighth inches in diameter and five to eight inches in length. The speed control handle grips  54  are preferably made of durable rubber, vinyl, or foam rubber tubing. The internal diameter of the speed control handle grips  54  is preferably such that friction between the internal surface and the outer diameter of the speed control handle  44  hold the grips in place. The speed control handle grips  54  could be made of various materials and could be secured using other methods including setscrews or they may be omitted entirely if desired. 
         [0050]    The speed control cable  38  is connected to the bottom of speed control  36  routed under the speed control handle grip  54  inside speed control handle  44  exiting orthogonally at its end, coiling, running against and parallel to second frame  12   b  in the direction of the controller  48 , and finally exiting the second frame  12   b  perpendicularly and entering into the controller  48 . In  FIGS. 4A and 4B  the speed control cable  38  can be seen with excess cable coiled to the side of and immediately below the speed control handle  44 . When converted to platform mode as in  FIG. 5  the speed control cable  38  stretches and extends parallel to convertible frame  24 . The routing of speed control cable  38  may vary, the speed control cable  38  may or may not include coils, may be divided into multiple cables, and may include electrical contactors along its path. 
         [0051]    The speed control  36  is shown in top view in  FIG. 7A , in side view in  FIG. 7B , and in end view in  FIG. 7C . Battery indicator lights are located on the top of the speed control  36 , which includes a full battery light  56   a , a partial battery indicator  56   b , and a low/dead battery indicator light  56   c . Alternatively, the battery level indicator may take many forms including that of a digital readout. A push-button e-stop switch  58  is located on the end of the speed control  36  and is positioned as to be easily accessible to the operators thumb, but may also be located elsewhere on the power-assist hand truck  18 . Engaging the e-stop switch  36  severs electrical power to the gearmotors  40 , whereas disengaging the e-stop switch  36  re-connects electrical power to the gearmotors  40 . As such, the speed control  36  thumb throttle  60  has no effect when the e-stop switch  36  is engaged. The e-stop switch  58  may work in various ways in order to have the primary effect as to stop the operation of the power-assist hand truck  18  and to additionally effect the un-powered resistance of the power-assist hand truck  18  to rolling either forward or reverse (toward the operator). In the present invention embodiment the gearmotors  40  provide very little rolling resistance to reverse motion of the power-assist hand truck  18  when the e-stop switch  58  is engaged. Alternatively, when the e-stop switch  58  is disengaged the regenerative braking of the gearmotors greatly increases the reverse rolling resistance and thereby reduces and limits the power-assist hand truck  18  reverse speed. The thumb throttle  60  is mounted to the end of the speed control  36  in such position as to be easily accessible by either the operators left or right hand thumb. The speed control  36  is infinitely variable by depressing the thumb lever  60  and through the controller  48  controls the output torque and thereby the speed of the power-assist hand truck  18  preferably between the speeds of 0 mph and 8 mph, more preferably between 0 mph and 6 mph, and most preferably between 0 mph and 4 mph. Additionally, the controller  48  may be programmed to maintain a given speed, control acceleration, control deceleration, and/or provide independent speed ranges for the 2-wheel mode and the platform mode. The variable thumb throttle  60  may also be replaced by an automatic throttle control utilizing sensory technologies including, but not limited to the ability to sense speed and directional intent of the operator and automatic adjustments in speed and direction to aid in balancing of the load. 
         [0052]    The lower third of the power-assist hand truck  18  as seen in side view  FIG. 8A  and front view  FIG. 8B  wherein the wheels  14 , left skid rail  46 , and left grease cover  66  are not shown in order to provide an unobstructed view of the overrunning clutch hub  62 , secondary gear  64 , secondary input gear  74 , and right grease cover  66 . 
         [0053]    The skid rails  46  are preferably constructed of steel tubing and bolted to the side plates  42  on the lower end and bolted to the second frame  12   b  on the upper end. Skid rails  46  may be constructed of aluminum, steel, plastic, or a combination of various materials. The skid rails  46  may vary in design and mounting preferably while acting as barriers to damage of the power-assist components and additionally as aids to movement over obstacles. Preferably the side plates  42  may be so designed to act as skid rails  46  in addition to their other functions. 
         [0054]    The overrunning clutch hub  62  can be seen in side view with respect to the power-assist hand truck  18  in  FIG. 9A  and front view with respect to the power-assist hand truck  18  in  FIG. 9B . The overrunning clutch hub  62  consists of four wheel mounting studs  68  which protrude through and bolt to the wheels  14 , a secondary gear  64  which is mated to and powered by the secondary input gear  74 , bearings  63  which are mounted to the axle  61 , and an overrunning clutch  72  which allows for free rotation of the wheels  14  in forward motion during all modes of power-assist hand truck  18  operation. Thus, an operator may move the power-assist hand truck  18  faster than the motor-assist can independently move the load without encountering resistance due to the motors and transmission. 
         [0055]    Side plate  42  can be seen from wheel side (outside) view in  FIG. 10A , end view in  FIG. 10B , and axle side (inside) view in  FIG. 10C . The side plate  42  design consists of a thru-hole where secondary input gear  74  protrudes through the plate, mounting holes and a second frame mounting rail  76  which respectively mount and align the side plate  42  to the second frame  12   b , and an axle pin rotary lock  78  which encapsulates a spring pin located through axle  61  and prevents axle  61  from rotating during operation. 
         [0056]    The controller  48  and batteries  50  can be seen in the front view of  FIG. 11A , side view of  FIG. 11B , and back view of  FIG. 11C . The batteries  50  are preferably twelve volt, twenty four volt, or thirty six volt and preferably replaceable and/or rechargeable batteries, and more preferably two twelve volt batteries in series providing a total of twenty four volts and 10 amp-hrs, and most preferably are approximately two and one-half inches wide by three and one-half inches tall by six inches long. The batteries  50  may be lead acid, lithium, nickel metal hydride, nickel cadmium, or lithium iron phosphate, most preferably lithium iron phosphate batteries. The controller  48  can switch connection of the batteries  50  from twenty-four volt series used to power the gearmotors  40  to twelve volt parallel allowing direct charging from 12V sources such as automotive electrical systems. Battery connectors are preferably quickly connected and disconnected using spring connectors or quick disconnect plugs. Charging contacts  84  can be seen in  FIG. 11B  and  FIG. 11C . The contacts are connected to controller  48 . To re-charge the batteries  50  the charging contacts  84  should be connected to an external power source. 
         [0057]    The speed control cable plug  80  and gearmotor cable plugs  82  as seen in  FIGS. 11A ,  11 B, and  11 C are preferably weather resistant and more preferably weatherproof. The plugs may be located nearer the gearmotors  40  and speed control  36  or may be located nearer the control circuitry inside the controller  48 . 
         [0058]    The power-assist hand truck  18  power switch  86  can be seen in  FIG. 11B . The power switch  86  connects and disconnects the controller  48  from the batteries  50 , thus turning the power-assist hand truck  18  on and off. The power switch  86  is preferably located in a visible and easily accessible area. The status indicator light  88  can be seen in  FIG. 11B . The status indicator light  88  is governed by the controller  48  and displays diagnostic information and current mode of operation information by turning on, off, or blinking at given intervals. Preferably the status indicator light  88  is placed in a highly visible location with respect to the operator and provides confirmation of charging mode, on, off, and system faults. 
         [0059]    The grease cover  66  can be seen in front view in  FIG. 12A  and in side view in  FIG. 12B . The grease cover preferably encapsulates the second gear  64  and second input gear  74  thereby protecting the gear set from the environment and containing the grease. The grease cover hub thru-hole  67  preferably provides a close fit around the overrunning clutch hub  62 . The grease cover  66  is made preferably from sheet metal and more preferably from molded plastic. 
       ADVANTAGES 
       [0060]    From the description above, a number of advantages of some embodiments of our Power-assist Hand Truck or Platform Cart become evident. 
         [0061]    The fully assembled power-assist hand truck weighs less than 70 lbs, almost one-third to one-half the weight of the prior art powered hand trucks, thus providing several advantages. Delivery drivers can safely lift the power-assist hand truck onto and off of their delivery trucks without the use of time consuming lifts or ramps. Additionally, this makes it easier for any operator to maneuver the power-assist hand truck, including during power-assist failure. 
         [0062]    The maximum speed of the power-assist hand truck is not limited by the drive components. The overrunning clutches allow the operator to walk as quickly as they desire without resistance from the drive components. 
         [0063]    A convenient pushbutton on the speed control handle allows the operator to engage and disengage the resistance of the drive components very quickly. 
         [0064]    An exposed axle is available so the operator can use the power-assist hand truck in similar fashion to a common manual hand truck. They can rest their foot against the axle to initiate balancing the load in two-wheel mode. 
       CONCLUSIONS, RAMIFICATIONS, AND SCOPE 
       [0065]    Thus the reader will see that at least one embodiment of the Power-Assist Hand Truck or Platform Cart provides a lightweight and user-friendly device that will help an operator reduce exertion on their body while maintaining a productive work pace. 
         [0066]    While the above description contains many specificities, these should not be construed as limitations on the scope of any embodiment, but as exemplifications of various embodiments thereof. Many variations and ramifications are possible within the teachings of the various embodiments. For example, the convertible hand truck embodiment may take the form of a platform cart, which is not convertible, but permanently confined to a platform state and may be substantially larger than a hand truck. 
         [0067]    Thus the scope should be determined by the appended claims and their legal equivalents, and not by the examples given.