STAIR CLIMBING HAND TRUCK

FIELD OF THE INVENTION The present invention relates to a hand truck useful for carrying heavy loads such as pieces of furniture, household appliances and the like, up and down a staircase. The hand truck of the present invention is also useful for transporting heavy merchandises around a warehouse or the like.

More particularly, the invention relates to a hand truck that is provided with a wheel assembly which allows it to be readily moved while loaded, more particularly up and down a stair.

BACKGROUND OF THE INVENTION

Hand trucks are commonly used for carrying loads, especially heavy loads. Conventional hand trucks usually comprise an elongated frame having a forwardly protruding platform at the bottom, a pair of opposite wheels beneath the platform and one or more handles at the top. Such devices are efficient but are not necessarily convenient, especially for moving heavy loads and articles up stairways. For example, a lot of effort on the part of the operator is required to adjust the inclination of the hand truck in order to provide for a stable transportation of the loads. The use of a conventional hand truck in the stairs may also present a danger if the operator gets out of control and the load roll back. Another problem is that these conventional hand trucks have a pair of ground engaging wheels which wear quickly because of the heavy load bearing downwardly directly on the wheels.

Other types of hand trucks have thus been developed. Examples of such hand trucks are disclosed, by way of non restrictive examples, in US patent No. 3,450,219, US patent No. 3,515,401 and US patent No. 4,264,082. Such hand trucks possess a pair of wheel assemblies on each side of the frame rotating freely about a transversal main axle. Each assembly comprises three wheels mounted on a star-shaped plate, each wheel being mounted on stub

axles on the legs of the star-shaped plate. Such a triangular configuration of the wheels aims at providing easier moving up stairs and a braking action when moving down stairs.

Similarly, US patent No. 4,312,417 discloses a hand truck having also a pair of star-shaped wheel assemblies. However, in this patent, each star-shaped assembly comprises four wheels instead of three, thereby forming a square configuration. Moreover, the hand truck also comprises a motor for simultaneously rotating the wheel assemblies.

The "multiple" wheel assemblies described above are efficient. However, they involve costly complicated mechanical structure which is susceptible to breakage, jamming and other mechanical problems. Also, the hand trucks provided with these wheel assemblies are heavy due to their structure that requires numerous pieces. Moreover, they may be used only for small stairs because of the size of their wheels which is limited to a maximum diameter due to the star-shape plate. Finally, these hand trucks have automatically four wheels in contact with the ground (two on each side), and are thus less easy to handle when moving loads on flat grounds, for example in a warehouse, or with no-load, and they need more space to be put away when not used. Thus, there is still a need for an improved, low cost hand truck for safely carrying loads up and down staircases, which will be able to overcome the above mentioned existing problems.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved hand truck for moving loads upstairs and downstairs while ensuring a controllable transportation of the load along the staircase.

More specifically, the invention is directed to a hand truck for carrying loads and making carriage easier up and down a staircase, which comprises: a) an elongated body structure having an upper part, a lower part and

two sides, the upper part being provided with at least one handle; b) a load support projecting from the lower part of the body structure; c) a pair of brackets projecting from a lower end of each side of the body structure; and d) a wheel assembly including:

- a pair of rotary arms having a first end and a second end, the first end of each of the rotary arms being rotatably connected to one of the brackets;

- a pair of rotary shafts having two tips, each shaft being pivotally and rotatably attached to the second end of one of the rotary arms. Each tip of the rotary shafts has a wheel rotatably connected thereto by suitable attachment means; and

- at least one fastening means for detachably fastening the rotary arms to the brackets in a given position.

Other features and advantages of the present invention will be better understood upon reading the following non restrictive description made with reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of a hand truck according to a preferred embodiment of the invention, having its wheel assembly in a vertical position.

FIG. 2 is a side elevational view of the hand truck shown in Fig. 1.

FIG. 3 is a back perspective view of the wheel assembly of the hand truck shown in Fig. 1.

FIG. 4 is back perspective view of the wheel assembly of the hand truck shown in Fig. 1 when the wheel assembly is in a horizontal position.

FIG. 5 is a cross-sectional top plan view of the wheel assembly of the hand truck shown in Fig. 1 when the wheel assembly is in a horizontal position.

FIG. 6 is a side elevational view of a hand truck according to another preferred embodiment of the invention having its wheel assembly in a horizontal position.

FIGS. 7a to 7f are side elevational views of the hand truck shown in Fig. 1 in use in a staircase.

DETAILED DESCRIPTION OF THE INVENTION

As aforesaid, the object of the present invention is to provide a hand truck useful for carrying loads up and down a staircase and/or for transporting heavy merchandise around a warehouse or the like.

By load and merchandise there is meant any object having an appropriate size for being transported using the hand truck of the invention. Such objects may be, for example, furniture, household appliances, boxes, luggage and the like. Figs. 1 and 2 illustrate a hand truck 10 according to a preferred embodiment of the invention. This hand truck 10 comprises an elongated body structure 20, a load support 30 and a wheel assembly 50. In Figs. 1 and 2, the wheel assembly 50 is represented in a vertical position. In this position, the hand truck may be used for carrying loads as any conventional hand truck. The elongated body structure 20 of the hand truck 10 comprises an upper part 22, a lower part 24 and two sides 26. Any conventional body structure known in the art for such a type of trolley may be used according to the present invention. At least one handle 28 is provided at the upper part 22 of the body structure 20. As illustrated, the handle 28 preferably consists of a loop handle projecting from the upper part 22. However, the hand truck 10 could include two separate handle members projecting from each side 26 at the upper part 22 of the body structure 20.

The load support 30 projects from the lower part 24 of the body structure 20. This load support may consist of a platform or of a pallet fork. The hand truck 10 also comprises a pair of brackets 40 to which the

assembly wheel 50 is connected. Each bracket 40 projects from a lower end of each side 26 of the body structure 20. In the preferred embodiment illustrated in Figs 1 and 2 of the drawings, the load support 30 and the pair of brackets 40 project in a same direction from the body structure 20, the load support 30 being positioned above the pair of brackets 40. It is worth mentioning however that the hand truck 10 could have the load support 30 and the pair of brackets 40 projecting in opposite directions from the body structure 20, as illustrated in Fig. 6.

Figs. 3 to 5 show in greater details the wheel assembly 50 of the hand truck 10. Fig. 3 shows the wheel assembly in a vertical position along the body structure 20, while Fig. 4 and 5 represent the wheel assembly in a horizontal position. As illustrated, the wheel assembly 50 comprises a pair of rotary arms 52 having a first end and a second end. The first end of each rotary arm

52 is rotatably connected to one adjacent bracket 40. The rotary arms 52 and the brackets 40 are preferably connected with bolts and nuts.

A pair of rotary shafts 54 having each two tips 58 are pivotally attached to a common axle 56 extending transversally from the second end of each rotary arm 52 is also provided. It is worth noting that the rotary shafts could also simply be pivotally attached to the second end of the adjacent rotary arms, independently one from another, for example by means of short axles, both axles extended of course along a same axis. A wheel 60 is rotatably connected at each tip 58 of the rotary shafts 54 using an appropriate attachment means.

The wheel assembly 50 also comprises at least one fastening means 62 for detachably fastening the rotary arms 52 to the brackets 40 in a given position. As is shown in Fig. 4, the fastening means 62 may be devised so as to hold the rotary arm 52 in a horizontal position in a same line as the bracket.

Advantageously, the wheel assembly 50 may also comprise a cross bar 64 having two ends, extending transversally from the two rotary arms 52 at about an equal distance from the first and the second end of each rotary arm

52. The addition of such a cross bar 64 has the advantage of strengthening the whole wheel assembly structure.

The fastening means 62 used for fastening the rotary arm 52 to the brackets 40 is preferably placed between one of the ends of the cross bar 64 and an end of an adjacent bracket 40. As illustrated in Fig. 3 and 4, the fastening means 62 even more preferably consists of a first element 66 extending perpendicularly from the end of the cross bar 64 and a second element 68 extending perpendicularly from the end of the adjacent bracket 40. The first element 66 and the second element 68 each includes a hole in which a fastener can be inserted for fixing these two elements together. The fastener is preferably a locking pin. Preferably, the wheel assembly 50 comprises two fastening means 62.

As more particularly illustrated in Fig. 3, the hand truck 10 may also include at least one other fastening means 70 for fixing the wheel assembly 50 in a vertical position along the body structure 20, thereby leaving only two wheels 60 in contact with the ground. Preferably, the hand truck 10 comprises two such fastening means 70, each one consisting of a two teeth fork projecting from each side 26 of the structure body 20 in a same direction than and above the bracket 40. The fork is advantageously shaped to receive the rotary shaft 54 when the wheel assembly 50 is in vertical position. Moreover, each tooth of the fork is provided with a hole in which another fastener can be inserted for locking the rotary shaft 54 when the wheel assembly 50 is in vertical position. The fastener is preferably a locking pin. Other type of fastening means for holding the wheel assembly in the vertical position could however be considered. The fastening means 70 could for example be positioned directly between the brackets and the rotary shafts. Various fastening means could also be advantageously combined.

Advantageously, each wheel 60 of the hand truck 10 is detachably connected to the tip 58 of the rotary shaft 54 and replaceable with another wheel having a diameter adapted to the height of the stairs of the staircase. Advantageously also, the wheels are provided with tires, so as to allow an easier handling of the hand truck, especially for carrying heavy loads. The

use of such tires also allows a more stable transportation, more particularly in the stairs. Moreover, the tire wheels do not damage the stairs as other wheels may.

In Figs. 7a to 7f, the hand truck 10 according to the present invention is represented with a load placed on the support load, in use in a staircase. More particularly, and by way of example only, the hand truck 10 is represented as climbing stairs. Of course, the same hand truck could be used for going down the staircase, in a reverse manner as compared to what will be explained hereinafter.

In Fig. 7a, the hand truck 10 is represented with the wheel assembly locked in a vertical position. The operator may then drive the hand truck up to the bottom of the staircase in a conventional manner. Then, the operator may unlock the fastening means 70 holding the wheel assembly in the vertical position. When the four wheels of the hand truck have reached the ground, the operator will fasten each rotary arm 52 to the adjacent bracket by engaging a fastener into the hole of the fastening means 62. In Fig. 7b, the hand truck is represented with its back wheels positioned at the bottom of the first stair of the staircase. The next step involves the operator who is standing upper in the staircase, to pull the hand truck up. Such involves the rotary shafts 54 rotating in a clockwise manner around the axle 56, thus lifting the front wheels and thus the body structure 20 of the hand truck up (Fig. 7c) until the front wheels reach the top of the first stair (Fig. 7d). At this point, the front wheels become the back wheels. The operator can further pull the hand truck so that the back wheels get into position at the bottom of the second stair (Fig. 7e). In the same way as previously described, the operator may then pull again the hand truck towards him involving the rotary shafts rotating around the central axle and lifting the body structure (Fig. 7f) until the front wheels reach the top of the second stair. This operation is then repeated until the hand truck reaches the top of the stair case. Once at the top of the stair case, the operator can choose to keep the four wheels on the ground to move the hand truck, or he can choose to move the hand truck up to the

delivery place by using it in a conventional manner having the wheel assembly in the vertical position, by locking the fastening means 70 around the rotary shafts.

Of course, numerous modifications could be made to the above-described embodiment without departing from the scope of the invention, as apparent to a person skilled in the art. While specific embodiments of the present invention have been described and illustrated, it will be apparent to those skilled in the art that numerous modifications could be made without departing from the scope of the scope of the appended claims.