Land vehicles – Wheeled – Tiltable vehicles – stabilized by attendant or article
Reexamination Certificate
1999-06-15
2001-05-29
Johnson, Brian L. (Department: 3618)
Land vehicles
Wheeled
Tiltable vehicles, stabilized by attendant or article
C280S047280
Reexamination Certificate
active
06237925
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to hand trucks, and more particularly to single axle hand trucks having load shifting apparatus. The load shifting apparatus is employed to assist in inclining the hand truck from a vertical stance in preparation for wheeling the hand truck and its load to a new location.
2. Description of the Prior Art
In operation, hand trucks are usually loaded with bulky and heavy objects when the load bearing frame of the hand truck is substantially vertical. The load is placed on a supporting plate, or load plate. To roll the loaded hand truck to a new location, the hand truck is tilted from its initial vertical stance and drawn by hand. When the hand truck arrives at its destination, where it is unloaded, it is again placed in the vertical stance. It is very difficult for a single person to tilt and upright the hand truck if the load is heavy or particularly bulky. The same holds true when the hand truck is being uprighted after arriving at it destination.
Modifications to hand trucks for shifting loads and the center of gravity have been proposed in the prior art. U.S. Pat. No. 3,746,360, issued to Burdette B. Crawford on Jul. 17, 1973, sets forth an arrangement enabling a load bearing frame of a hand truck to be tilted and supported on a member engaging the ground. However, in the hand truck of Crawford, the main load bearing wheels are mounted on side frames which are vertically slidably connected to the load bearing frame and load plate. By contrast, both the wheels and ground engaging members are rotatably fixed to the load bearing frame in the present invention. The load bearing frame is monolithic in that there are no relatively moving parts corresponding to the side frames of Crawford. The device of Crawford includes a hand operated linkage absent in the present invention. The present invention utilizes a foot operated lever pivotally fixed to the load bearing frame to accomplish load shifting, whereas the device of Crawford causes the main wheels to be retracted relative to the load bearing frame and load plate.
A hand truck seen in U.S. Pat. No. 2,607,606, issued to Stanley S. Millen on Aug. 19, 1952 has an auxiliary axle disposed below the principal axle and located near the load plate, in the manner of the present invention. However, the auxiliary axle supports rollers which supplement the principal wheels. Unlike the device of Millen, the present invention has solid members which selectively engage the ground to prop the novel hand truck relative to the ground when shifting the load as the hand truck is inclined from the vertical stance.
U.S. Pat. No. 2,653,033, issued to Joseph C. Chinette et al. On Sep. 22, 1953, describes a hand truck which is adjustable to vary position of the load plate relative to the principal wheels. However, there is no fixed member which selectively engages the ground when shifting the load as the hand truck is inclined from the vertical, as seen in the present invention.
A hand truck seen in U.S. Pat. No. 2,710,106, issued to Alfred H. Hanson on Jun. 7, 1955, includes spurs fixed solidly to the frame which engage the ground when a load is being shifted. However, these spurs are fixed in their positions, and do not project only when moved by a lever, as occurs in the present invention.
In U.S. Pat. No. 4,762,333, issued to Carl N. Mortenson on Aug. 9, 1988, the wheels are movable relative to the load bearing frame, whereas the wheels are rotatably mounted in fixed location on the load bearing frame in the present invention. Load shifting is accomplished by Mortenson with the weight of the load and hand truck imposed on the wheels. In the present invention, a ground engaging member pivotally mounted to the load bearing frame projects downwardly to engage the ground responsive to operation of a foot lever, so that the load is partially braced against the ground.
U.S. Pat. No. 5,118,124, issued to Craig F. Storay et al. On Jun. 2, 1992, illustrates another hand truck wherein the main wheels are adjustably positioned relative to the load bearing frame. In the device of Storay et al., rockers come to contact the ground and temporarily support the load bearing frame. However, the rockers and wheels are not rotatably or pivotally secured to the load bearing frame in a fixed location, as occurs in the present invention.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.
SUMMARY OF THE INVENTION
The present invention sets forth improvements to hand trucks which enable a single person to tilt the hand truck when the hand truck is loaded. Briefly stated, the hand truck is tilted under conditions of relatively great leverage by a retractable tilting or load shifting mechanism. Final tilting is accomplished after retracting the tilting mechanism by grasping the load bearing frame in conventional manner, which affords reduced leverage compared to that available from the tilting mechanism.
The load bearing frame comprises a single, rigid assembly devoid of longitudinally movable parts. A novel tilting or load shifting mechanism is fixed to the load bearing frame, and is constrained only to pivot or rotate about its axis of pivot. Thus overall construction of the novel hand truck is uncomplicated compared to the many prior art devices which achieve similar results. Moreover, the present invention may be practiced by modifying a conventional hand truck to include the novel tilting or load shifting mechanism.
In some embodiments, the tilting mechanism is foot operated, thereby freeing the hands to grasp the load bearing frame. A foot pedal moves a ground engaging member in a manner shifting the load and the center of gravity. The ground engaging member is arranged to provide a more advantageous lever ratio than is available by grasping the load bearing frame near the top of the upright hand truck. Also, the fulcrum of the leverage arrangement provided by the ground engaging member is more advantageously located relative to the load. Whereas the carriage wheels of the hand truck are usually located well behind the load bearing frame, the fulcrum of the novel leverage arrangement is both closer to the load and lower to the ground than is the axle of the carriage wheels.
Foot operation of the novel leverage arrangement enables a user to control the hand truck by grasping the upper end of the load bearing frame while simultaneously shifting the load with one foot. The hand truck gently tilts towards the user, which position is readily controlled by hand. It is then an easy matter to wheel the hand truck to a new location. The foot controls can then be employed to assist in slowly and carefully elevating the loaded hand truck into an erect position, as well as tilting it from the erect position.
The leverage arrangement may be hand operated. While the principles are similar, the hand arrangement avoids interference of foot pedals with environmental elements in some situations. In the hand operated embodiment, an elongate lever corresponding to the foot pedal projects upwardly, generally parallel to the back of the hand truck, to a location where it is conveniently grasped by hand.
The load shifting mechanism operates in one of either of two ways. In one embodiment, ground engaging members lift the wheels of the hand truck off the ground. In this embodiment, the ground engaging members also serve as a fulcrum. In another embodiment, ground engaging members elevate the front of the hand truck, with the wheels remaining in contact with the ground and serving as a fulcrum. In both embodiments, the ground engaging members selectively project downwardly to engage the ground and to assume at least part of the burden of weight of the loaded hand truck. Each ground engagement style is usable with both hand and foot operators.
Accordingly, it is one object of the invention to enable a single person to maneuver and wheel a loaded hand truck.
It is another object of the invention to free the hands to grasp the load
Johnson Brian L.
Siemens Patent Services LC
Sliteris Joselynn Y.
LandOfFree
Hand truck having ground engaging lever for tilting does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hand truck having ground engaging lever for tilting, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hand truck having ground engaging lever for tilting will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2568339