TECHNICAL FIELD

The present invention is directed to a sack truck of special design that can quickly convert into a trolley and back again.

BACKGROUND

A sack truck is a name given to a two wheel hand cart having handles at an upper end, a pair of wheels at a lower end and an L shaped platform on which objects can be placed. The truck is also known as a "hand truck", "dolly" and "two wheel trolley". Figure 1 illustrates a typical sack truck. A disadvantage with this apparatus is that overloading the truck can bring about unsafe usage causing instability, diminished user visibility or loss of load. Thus it is also known to provide a four wheel trolley on which larger loads can be placed. Figure 2 illustrates a typical four wheel platform trolley.

Convertible sack trucks are known which can be converted between the "two wheel" upright truck position and the "four wheel" horizontal trolley position. When converted to the trolley position, part of the sack truck is detached and reconfigured into an upright position and this part can be called a "post member". The present invention is directed to improvements to this type of convertible truck. A disadvantage with existing convertible sack trucks is the rather complicated mechanism present to enable the truck to convert to a trolley and back again. This adds to the maintenance and cost. Another disadvantage is the rather complicated set of steps required to convert the truck. For instance, some devices require parts to be pulled out of the truck and replaced. Other devices have complicated releasable locks that can be difficult to operate and can also cause pinch injuries. Another disadvantage is that many convertible sack trucks retract, or disable, one pair of wheels when the apparatus is converted from the horizontal trolley position to the upright truck position. These wheels are not accessible until the truck is converted back to the trolley position.

Another disadvantage is that when the convertible sack truck is used in its trolley configuration the post member is set upright in a fixed, rigid location. This inflexibility becomes a hindrance to the proper use of necessary safety devices, required on high load bearing vehicles such as these.

There would be an advantage if it were possible to provide a convertible sack truck, which may overcome at least some of the above-mentioned disadvantages or provide a useful or commercial choice.

Any references to methods, apparatus or documents of the prior art are not to be taken as constituting any evidence or admission that they formed, or form part of the common general knowledge.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided sack truck convertible between a truck position and a trolley position and comprising a load bearing back frame having a handle end and a platform end, a platform adjacent the platform end and extending from the frame, an axle adjacent the platform end, a first pair of wheels supported by the axle, at least one wheel adjacent the handle end, and a post member moveable between a folded position where the post member is substantially aligned with the back frame and an erect position where the post member extends from the back frame.

Preferably the at least one wheel adjacent the handle end comprises a second pair of wheels. The sack truck can be manufactured from any suitable material which may include tube steel, aluminum tube, aluminum extrusion, high impact plastics, combinations of materials and the like. Components of the truck can be manufactured using rotation moulding.

The term "truck position" is meant to include the position where the device is in an upright position and contacts the ground using the first pair of wheels. The term "trolley position" is meant to include the position where the device is in a substantially horizontal position and contacts the ground using the first pair of wheels and the at least one wheel adjacent the handle end (typically a second set of wheels). The device has a load bearing back frame. The back frame has a handle end and a platform end. The back frame may comprise one or more elongate members. These members may comprise tubular members. The tubular members may comprise plastic or metal tubular members. The back frame may comprise an outer elongate member and. an inner elongate member. Each member may be substantially U-shaped when viewed in plan. At least one crossbar or transverse member may be provided which can be attached to the outer and/or inner member to provide rigidity.

Alternatively, the back frame may comprise a moulded part which may contain a handle and which may include an elongate opening to accommodate the post member.

A platform will typically be attached to adjacent the platform end. The platform may comprise a plate member which may be substantially rectangular. However, it is envisaged that the platform may comprise other members and may have other shapes and configurations depending inter alia on the objects that are to be placed on or supported by the platform. Typically, the platform comprises a plastic or metal plate which is molded or welded or otherwise fixed to the one or more elongate members.

The platform may be moulded together with the back frame as a single piece an example of which is illustrated in figures 9-15.

An axle is provided to which a first pair of wheels is attached. The axle may comprise a single axle or a number of "stub" axles. Preferably, the axle comprises a single axle which is spaced from the back frame and attached relative to the back frame via one or more spacing members which may comprise brackets.

The spacing members / brackets may be moulded integrally with the back frame as illustrated in figures 9-15.

There may be circumstances where additional wheels may be present. For instance, the sack truck may be provided with stair climbing wheels.

A second pair of wheels may be attached relative to the handle end of the back frame. The second pair of wheels may comprise pivoting or castor wheels. There may be circumstances where additional wheels may be provided. These may be fixed wheels or pivoting wheels. It is also envisaged that under certain circumstances, a single wheel may be provided adjacent the handle end instead of a pair of wheels. It is also envisaged that under certain circumstances that may be provided a closely spaced pair of wheels.

The second pair of wheels is preferably fixed relative to the frame such that the wheels do not retract when the sack truck is converted between the truck position and the trolley position. Thus, the wheels may be attached to one or more stub axles fixed to, or relative to, the frame.

A post member is provided which can pivot between a folded position and an erect position. In the folded position, the post member preferably lies within the plane of the frame and may be substantially aligned with the back frame and preferably does not project to any undesirable extent. In the erect position the post member may be substantially at right angles to the frame. The pivoting post member can be transformed into a rigid brace when the load is secured to the unit by its inbuilt strap.

The post member may comprise a pair of spaced apart elongate members. One end of the elongate members may be fixed to a rotate tube or by some other suitable means and the other end of the elongate members may comprise a continuous curved portion. The post member is preferably able to rotate relative to part of the frame. Suitably, the frame comprises a crossbar adjacent the handle end and the post member is rotatably attached relative to the crossbar. Alternatively, the post member comprises a plastic moulded member.

A rear handle may be provided on the post member. The rear handle may be positioned adjacent the rotatable attachment of the post member to the crossbar.

At least one retaining means may be provided to assist in retaining objects positioned on the sack truck. The retaining means may comprise a strap which may form part of a strap mechanism. The strap mechanism may be attached to or supported by or form part of the post member.

An abutment may be provided on the platform. The abutment may function as an attachment point for the retaining means. Suitably, the abutment may function as an attachment point for the free end of the strap. The abutment may also function to assist in supporting the post member in the folded position. BRIEF DESCRIPTION OF THE DRAWINGS

Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

Figure 1. Illustrates a prior art two wheeled sack truck.

Figure 2. Illustrates a prior art four wheeled trolley.

Figure 3. Illustrates a sack truck according to an embodiment of the invention in the horizontal position.

Figure 4. Illustrates a front view of the sack truck of figure 3 in the upright position.

Figure 5. Illustrates a rear view of the sack truck of figure 4.

Figure 5A Illustrates a catch for retaining a restraining strap in detail.

Figure 6. Illustrates the sack truck converted to the trolley position and with the post member in the upright erected position.

Figure 7. Illustrates use of the restraining strap.

Figure 8. Illustrates a close-up of one of the second pair of wheels.

Figures 9-12. Illustrate various views of a second embodiment of the sack truck in the upright "truck" position.

Figures 13-15. Illustrate various views of the second embodiment in the "trolley" position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring initially to figure 1 there is illustrated a conventional sack truck. The sack truck has a load bearing back frame 40 having a upper handle end 41 and a lower platform end 42. A platform 43 is molded or welded to and extends at right angles from back frame 40. An axle 44 is positioned behind back frame 40 and is attached to the back frame by brackets. A pair of wheels 45 is attached to axle 44. This arrangement is entirely known. Referring now to figure 2, there is illustrated a known trolley which comprises a lower platform 46, two pairs of spaced apart ground wheels 47, and a handle (which can be called a post member 48) which is typically attached relative to platform 46 and which can move between a folded position and a fixed upright erect position.

Referring now to figures 3-8 there is illustrated a preferred embodiment of the convertible sack truck according to the present invention. The sack truck 10 comprises a load bearing back frame 1 t which has an upper handle end 13 and a lower platform end 14. A platform 12 is attached to the lower end of frame 11 and extends generally at right angles therefrom. An axle 15 (best illustrated in figure 5) extends behind frame 11 and is attached thereto via connecting brackets. A first pair of wheels 16 is attached to the ends of axle 15. A post member 18 (best illustrated in figure 6 and figure 7) is attached relative to frame 11 and is moveable between a folded position (best illustrated in figure 3) where the post member 18 aligned with back frame 11, and an erect position (best illustrated in figure 6 and figure 7) with the post member substantially at right angles relative to frame 11. A second pair of wheels 17 is attached to frame 11 and slightly inward from handle end 13.

Referring now in greater detail to the sack truck, back frame 11 comprises an outer generally U-shaped elongate member 20, and an inner generally U- shaped elongate member 21 (see particularly figure 6). The platform 12 comprises a rectangular plastic or metal plate which is molded or welded to the lower end of the outer member 20 and the inner member 21.

A spacing bracket 22 (see figure 5) is molded or welded to the rear of each lower end of outer elongate member 20, and axle 15 is molded or welded to each bracket 22. The first pair of wheels 16 is mounted for rotation about each end of axle 15. Slightly below the handle end 13 of back frame 11 is provided a cross bar 23 (see particularly figure 3). Cross bar 23 is molded or welded to outer elongate member 20 and to inner the elongate member 21 , to provide a solid rigid framework.

The second pair of wheels 17 comprises lockable pivoting wheels (castor wheels) which are pivotly mounted to short stub axles 24 (see figure 8). These wheels remain fixed in position and do not fold or pivot away when the sack truck is converted to the trolley configuration or vice versa.

Post member 18 comprises an elongate U-shaped member which can hinge between the folded position illustrated in figure 3 and the erect position illustrated in figure 6 and figure 7. The lower end of post member 18 is pivotly mounted about cross bar 23. Lower end 26 comprises a hollow tubular member 26 having a diameter which is slightly larger than the outer diameter of crossbar 23 such that member 26 can slide over and about cross bar 23. Member 26 is prevented from movement along cross bar 23 by being trapped between portions 27 and 28 of inner member 21. Upper end of post member 18 comprises a curved portion 29. Strengthening struts 13 are provided along post member 18. A small curved rear handle 31 is provided and is molded or welded to member 26.

The rear edge of platform 12 is provided with a small abutment 32 which assists in supporting post member 18 when in the folded position.

The sack truck 10 can be used as a two wheeled sack truck when in the upright position illustrated in figure 4 and figure 5. A benefit of the present invention is that the sack truck 10 can also be lowered to the horizontal position (see figure 3) to provide a strong platform and enabling all four wheels to be used. In this position, the post member 18 is still in the folded position. The sack truck can be quickl converted to a trolley position by simply lifting post member 18 from the horizontal position (see figure 3) to the erect substantially vertical position as illustrated in figure 6 and figure 7. No complicated mechanism is required and there are no releasable locks and the like that need to be manipulated. As well, there is no need to remove and reinsert parts of the sack truck to convert the truck into the four-wheel trolley configuration. If desired, the struts 30 can be provided with friction end caps or something similar to enable the post member to be held in the folded position by a friction fit.

A retractable ratchet strap mechanism 33 is provided which is attached to a central fixed location on post member 18. The strap mechanism comprises a pull-out strap of set length 34 which can be extended and retracted relative to a reel. The end of strap 34 can be provided with a connection (for instance a D ring) which can be attached to a fixed location on platform 12 this being partially illustrated in figure 7 and shown in close up in figure 5A.

Referring to figures 9-15, there is illustrated a second embodiment of the invention. This embodiment differs primarily from the first embodiment in being manufactured from moulded plastic. The truck has a back platform 50 in the form of a moulded plastic piece containing an elongate central opening 51 to accommodate the post member 52. Platform 50 has an upper moulded handle 53 and a lower integrally formed platform 54. The rear of platform 50 has strengthening ribs 55 which are more pronounced at the lower end and provide a bracket area to support axle 56 which support wheels 57. Upper wheels 58 are provided which are of the pivoting kind.

Referring to figures 13-15, post member 52 is formed of moulded plastic and is hinged 58 at the upper end of platform 50. Post member 52 can pivot between the upright position (figure 13) and the horizontal position (figure 15), and any intermediate position (figure 14). The Post member 52 includes formations 59, visible in Figures 13 to 15, for a securement strap or other type of fastening/securement device. Post member 52 has an upper handle 60 moulded into the post member.

The sack truck can convert between the "two wheel" truck configuration and the "four wheel" trolley configuration is a simple one step operation. When the post member is pulled up, . the frame and the four wheels provide a good strong stable platform. Post member is rested against the load and the securing strap is then pulled out and over the top of the load and attached to location in base plate 12. Slack is retracted from the strap as the ratchet secures the load firmly to the frame. It will be Observed that the securing strap is conveniently placed and simple and effective to use. The truck does not require complicated mechanisms to convert between the configurations, and is not overly heavy due to additional complicated parts. In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features.

The term "comprises" and its variations, such as "comprising" and "comprised of is used throughout in an inclusive sense and not to the exclusion of any additional features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art.

Throughout the- specification and claims (if present), unless the context requires otherwise, the term "substantially" or "about" will be understood to not be limited to the value for the range qualified by the terms.

Any embodiment of the invention is meant to be illustrative- only and is not meant to be limiting to the invention. Therefore, it should be appreciated that various other changes and modifications can be made to any embodiment described without departing from the spirit and scope of the invention.