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Patent Abstract
A hand truck having load shifting member which tilts the hand truck
under conditions of greater leverage than that available by grasping
the frame of the hand truck is disclosed. The load shifting member
comprises a spring retracting lever rotatably attached to an axle
journaled from the frame of the hand truck such that when in a retracted
position, the lever is substantially parallel to the frame. Pulling
on the upper end of the lever rotates the lever such that the lower
end of the lever engages the lower portion of the hand truck frame,
shifting the center of gravity of the loaded hand truck such that
it may be more easily tilted to a position for moving the hand truck.
A spring returns the lever to a retracted position when not in use.
Patent Claims
I claim:
1. A hand truck comprising: an upright load bearing frame of fixed
geometry having a front side, a load plate rigidly fixed to said
load bearing frame at said front side, a rear side, and two carriage
wheels rotatably mounted to said load bearing frame at said rear
side at a fixed point on said load bearing frame, said carriage
wheels having an axis of rotation about an axle therebetween, a
load shifting assembly, said load shifting assembly disposed to
move the center of gravity of said load bearing frame, said load
shifting assembly comprising a retracting lever member rotatably
mounted to said axle at a fixed point spaced apart from said carriage
wheels, and a load shifting assembly stop assembly, said stop assembly
adapted to limit the degree of rotation of said load shifting assembly
about said axle; a lower end of said load shifting assembly adapted
to engage a lower portion of said load bearing frame at said stop
assembly when an upper end of said load shifting assembly is pulled
from a retracted position by a user.
2. The hand truck according to claim 1, wherein said axle is disposed
in journaled supported relation to said load bearing frame.
3. The hand truck according to claim 2, wherein said load shifting
assembly comprises a retracting lever member substantially parallel
said load bearing frame in a first, retracted position and substantially
oblique said load bearing frame when in a second, actuated position.
4. The hand truck according to claim 3, further comprising a return
spring having a proximal end anchored at said load bearing frame
and a distal end anchored at said retracting lever member, wherein
said return spring is disposed to urge said retracting lever member
into said first, retracted position.
5. The hand truck according to claim 1, wherein said lever stop
assembly comprises a threaded rod, said threaded rod engaging a
threaded aperture at a lower end of said load bearing frame at a
first end and having a lever engaging head at a second end, said
stop disposed to limit movement of said retracting lever member
to prevent excessive inclination of said frame of said hand truck.
6. The hand truck, according to claim 5, further comprising a load
plate extension, said load plate extension hingedly attached at
a juncture between said load bearing frame and said load plate such
that an increased load bearing surface is formed.
7. A hand truck comprising: an upright load bearing frame of fixed
geometry having a front side; a load plate rigidly fixed to said
load bearing frame at a lower extreme of said front side; a load
plate extension hingedly attached at a juncture of said load plate
and said load bearing frame such that an increased load bearing
surface is formed; a rear side; and two carriage wheels rotatably
mounted to said load bearing frame at said rear side at a fixed
point on said load bearing frame, said carriage wheels having an
axis of rotation about an axle therebetween, said axle being disposed
in journaled supported relationship to said load bearing frame;
a load shifting assembly, said load shifting assembly disposed to
move the center of gravity of said load bearing frame, said load
shifting assembly comprising a retracting lever member rotatably
mounted to said axle at a fixed point spaced apar from said carriage
wheels, said retracting lever member being substantially parallel
said load bearing frame in a first, retracted posiiton and substantially
oblique said load bearing fram when in a second, actuated, position;
and a return spring having a proximal end anchored at said load
bearing frame and a distal end anchored at said retracting lever
member, wherein said return spring is disposed to urge said retracting
lever member into said first, retracted position; a load shifting
assembly stop assembly, said lever stop assembly comprising a threaded
rod, said threaded rod engaging a threaded aperture at a lower end
of said load bearing fram at a first end and having a lever engaging
head at a second end, said stop assembly adapted to limit the degree
of rotation of said load shifting assembly about said axle to prevent
excessive inclination of said frame of said hand truck.
Patent Description
RELATED APPLICATION
[0001] This application is related to U.S. Patent patent application
Ser. No. 09/332,859, filed on Jun. 15, 1999, subsequently issued
as U.S. Pat. No. 6,237,925 B1, on May 29, 2001.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] 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
[0004] 2. Description of the Prior Art
[0005] 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
or pushed by hand. When the hand truck arrives at its destination,
where it is unloaded, it is again placed in the vertical stance.
It is often very difficult for a single person to tilt and upright
the hand truck if the load is heavy or particularly bulky.
[0006] 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, the load
bearing frame of the present invention 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 hand operated lever pivotally fixed to the axle 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.
[0007] 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. The auxiliary axle supports rollers
which supplement the principal wheels. Unlike the device of Millen,
the present invention has only a single axle and a lever which selectively
engages the frame of the novel hand truck, thereby shifting the
load of the hand truck from the vertical to a tilted position.
[0008] 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 lever which selectively engages the frame when
shifting the load as the hand truck is inclined from the vertical,
as seen in the present invention.
[0009] 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, the hand truck of Hanson does not utilize a lever to shift
the load from the vertical stance to a tilted position, as in the
present invention.
[0010] 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 frame engaging
lever pivotally mounted to the axle assists in shifting the load
from the vertical stance to a tilted position.
[0011] 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. By contrast, the
present invention utilizes only a single axle and pair of wheels,
and an axle mounted lever for assisting in shifting the load from
the vertical stance to a tilted position.
[0012] 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
[0013] The present invention sets forth improvements to hand trucks
which enable a single person to tilt the hand truck more easily
when the hand truck is loaded. Briefly stated, the hand truck is
tilted under conditions of relatively great leverage by a retracting
lever or load shifting mechanism. Final tilting is accomplished
after retracting the lever mechanism by grasping the load bearing
frame in conventional manner, which affords reduced leverage compared
to that available from the tilting mechanism.
[0014] The load bearing frame comprises a single, rigid assembly
devoid of longitudinally movable parts. A novel tilting or load
shifting lever is fixed to the axle, and is constrained only to
pivot or rotate about its axis of pivot and engage the lower portion
of the load bearing frame. 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.
[0015] The leverage arrangement is hand operated. An elongate lever
projects upwardly, generally parallel to the back of the hand truck,
to a location where it is conveniently grasped by hand. Pulling
the upper end of the lever toward the user tilts the load bearing
frame from the vertical stance to a tilted position without the
need for excessive exertion by the user.
[0016] Accordingly, it is one object of the invention to enable
a single person to maneuver and wheel a loaded hand truck.
[0017] It is another object of the invention to keep the users
hands in a position to easily grasp the load bearing frame after
tilting the hand truck from the erect position.
[0018] It is a further object of the invention to assist a person
in tilting and uprighting a loaded hand truck.
[0019] Another object of the invention is to easily return an inclined
hand truck to the upright position while maintaining balance and
control by the user.
[0020] A further object of the invention is to eliminate back strain
and other injuries to users of hand trucks.
[0021] Still another object of the invention is to provide a tilting
mechanism offering a relatively great level of leverage compared
to that available by manually grasping and maneuvering the load
bearing frame.
[0022] An additional object of the invention is to form the load
bearing frame as a single, rigid assembly devoid of longitudinally
movable parts.
[0023] Still another object of the invention is to employ a conventional
hand truck in practicing the invention, the improvement being achieved
by securing the novel load shifting mechanism to the conventional
hand truck.
[0024] It is an object of the invention to provide improved elements
and arrangements thereof in an apparatus for the purposes described
which is inexpensive, dependable and fully effective in accomplishing
its intended purposes.
[0025] These and other objects of the present invention will become
readily apparent upon further review of the following specification
and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Various other objects, features, and attendant advantages
of the present invention will become more fully appreciated as the
same becomes better understood when considered in conjunction with
the accompanying drawings, in which like reference characters designate
the same or similar parts throughout the several views, and wherein:
[0027] FIG. 1 is a front perspective view of the invention.
[0028] FIG. 2 is a partial, rear perspective view of the invention
showing detail of the tilting mechanism in the retracted position.
[0029] FIG. 3 is a partial, rear perspective view of the invention
showing detail of the tilting mechanism in the actuated position.
[0030] FIG. 4 is a side view of the invention with the hand truck
shown, loaded, in an upright position.
[0031] FIG. 5 is a side view of the invention with a user shown
operating the retracting lever to tilt the hand truck
[0032] FIG. 6 is a side view of the invention, in a tilted position,
with the retracting lever in its retracted position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] A preferred embodiment of the invention is shown in FIGS.
1 thru 3. Hand truck 10 comprises an upright load bearing frame
12 of fixed geometry. As employed herein, "fixed geometry"
signifies that the frame is formed as a single part, generally monolithic
in construction, with no components which move relative to others.
Frame 12 is a box style frame, having right and left vertical channels
14, 16 joined by upper and lower cross bars 18, 20. Horizontal braces
22 span vertical channels 14, 16. Frame 12 is typically formed from
steel tubing and is typically assembled by welding. Designation
of frame 12 as upright signifies that in normal usage, the longitudinal
dimension of frame 12 is vertical, or slightly inclined from the
vertical.
[0034] A toe or load plate 24 is welded or otherwise firmly fixed
to frame 12 at the bottom and on the front side of frame 12. Load
plate 24 is generally planar. Articles being transported by hand
truck 10 are loaded onto load plate 24 and may be propped against
frame 12, if desired.
[0035] Two carriage wheels 26 are rotatably mounted to frame 12.
Frame 12, load plate 24, and wheels 26 are generally conventional,
and need not be more explicitly described herein, other than to
note that axle 28 and journaled support of the wheels 26, indicated
at 30, are located on the rear side of frame 12. Axle 28 establishes
an axis of rotation of the wheels 26. It is further noted that attachment
and support of the wheels 26 is fixed in location to frame 12. By
contrast, some prior art hand trucks (not shown) have axle mountings
which are adjustably positioned on their respective frames.
[0036] Hand truck 10 is characterized by a novel load shifting
arrangement which when operated moves the center of gravity of hand
truck 10. The load shifting arrangement includes a retracting lever
32, having an upper end and a lower end, substantially parallel
to frame 12 in the retracted position, which is rotatably mounted
to axle 30 at a fixed point by a sleeve 34. Retracting lever 32
has an "S" curve proximate axle 30, whereby the upper
portion of retracting lever 32, while substantially parallel the
lower portion of retracting lever 32, it is offset such that is
proximate frame 12. Retracting lever 32 is spaced apart on axle
28 from the location of the carriage wheels 26 by a restraining
bar 36. It would be evident to one of ordinary skill in the art
that sleeve 34 could extend the length of axle 27 between journaled
supports 30 in lieu of a shorter sleeve 34 restrained by a restraining
bar 36.
[0037] Retracting lever 32 is normally retained in the retracted,
substantially vertical, position by a spring 38, spring 38 being
attached at retracting lever member 32 and a lower portion of frame
12 at apertures 40.
[0038] A lever stop 50 controls the degree of rotation of retracting
lever member 32 around axle 28, and thus the degree of rotation
of the upper end of retracting lever member 32. Lever stop 50 consists
of a flange 52, having a threaded aperture 54 therethru, a threaded
rod 56 and a stop head 58. The threading of threaded rod 56 thru
threaded aperture 54 adjusts the position of stop head 58 relative
to the lower end of retracting lever 32, thereby adjusting the degree
of rotation of retracting lever 32 about axle 28. The adjustability
of the degree of rotation of retracting lever 32 facilitates use
of the load shifting element of hand truck 10 for users of varying
height.
[0039] By grasping the upper end of retracting lever 32 and pulling
toward the user, retracting lever 32 is levered between axle 28
and lever stop 50. Downward pressure exerted on the upper end of
retracting lever 32 by the user is transferred to lever stop 50,
thereby shifting the center of gravity of the loaded hand truck
10 to assist in tilting the loaded hand truck 10 to a position for
movement of hand truck 10. It is an easy matter to tilt hand truck
10 by grasping the upper portion of frame 12 by hand after the weight
of hand truck 10 is shifted utilizing retracting lever 32. Conversely,
pulling retracting lever 32 to engage lever stop 50 allows hand
truck 10 to be returned to the vertical position with less effort
on the part of the user.
[0040] One of the significant advantages of the present invention
is that the hands are left free to control and maneuver hand truck
10 without the user being obliged to attempt to place his or her
feet as far away from hand truck 10 as possible in order to develop
sufficient mechanical advantage over the weight of hand truck 10,
particularly when hand truck 10 is laden.
[0041] FIGS. 4 thru 6 illustrate operation of hand truck 10. Hand
truck 10 is shown in FIG. 4 to be laden with bags 2, standing in
the upright position on the ground. When a user pulls retracting
lever 32 to a point at which it engages lever stop 50, he may more
easily tilt hand truck 10 than is possible by using only upper cross
bar 18. The user then controls and maneuvers hand truck 10 by grasping
the upper portion of load bearing frame 12 with one or both hands
6.
[0042] Optionally, in addition to load plate 24, load plate extension
25 is hingedly attached at the juncture of frame 12 and load plate
24, such that load plate extension 25 may be folded up against frame
12, fitting between vertical channels 14 and 16. In the down position,
load plate extension 25 rests on the upper surface of load plate
24, extending beyond the forward edge of load plate 24, extending
the load bearing surface of the load plate, thereby accommodating
larger items. Load plate extension 25 is generally conventional,
and need not be more explicitly described herein.
[0043] It is to be understood that the present invention is not
limited to the embodiments described above, but encompasses any
and all embodiments within the scope of the following claims. |