Patent Application
20160286955
1. Field of the Invention
In general, the present invention relates to portable serving carts and tray tables that are foldable using scissor support legs. More particularly, the present invention relates to collapsible serving carts and tray tables that support two parallel tray platforms at different heights.
2. Prior Art Description
Serving carts are typically wheeled carts that are used to support and transport food or other items. Typically, a serving cart will have two parallel support platforms. An upper platform is supported at the top of the serving cart. The upper platform is readily accessible by a person standing next to the serving cart. A lower platform is positioned between one and two feet below the upper platform. The lower platform is typically used to hold supplies or materials that are less in demand than those held on the upper platform.
Many versions of the service cart exist. However, the present invention is primarily directed toward service trays that are lightweight, portable and collapsible. In the prior art, service carts with these features are commonly made with X-shaped side frames, often called scissor frames. These scissor frames enable the upper support surface and the lower support surface to fold flush against each other. Examples of such prior art designs include U.S. Pat. No. 3,215,096 to Holtz, entitled Collapsible Serving Cart. This patent shows a serving cart with two support surfaces and a scissor frame support. Both the upper platform and the lower platform are permanently attached to only two of the four legs. The other legs are only engaged by the platforms when the service cart is fully opened. Even at such times, the platforms merely engage the non-attached legs with insubstantial snap connections or similar mechanical engagements.
U.S. Pat. No. 3,602,160 to Heal, entitled Folding Trolleys and the Like, also shows a serving cart with two support platforms and an X-shaped framework. Both the upper support surface and the lower support surface are permanently attached to only two of the four legs. The support platforms snap connect to the secondary legs only when the serving cart is fully unfolded. This same configuration is also shown in U.S. Pat. No. 2,544,220 to Concklin; U.S. Pat. No. 2,196,914 to Goldman; and U.S. Pat. No. 3,099,356 to Burnett.
The common prior art design of permanently attaching the supported platform to only two of the four legs is used to allow the service trays to collapse. However, this configuration does have certain inherent disadvantages. Permanently attaching the platforms to only two of the four legs, tends to make the service cart wobbly. Since the attachment with the second leg is typically a snap connection, there is little rigidity between the second leg, the fourth leg, and the platforms. Forces are, therefore, not effectively exchanged between the legs and the service cart tends to be weaker than would be expected from its component parts.
A second disadvantage of the traditional service cart design is that a user must bend down and attach the lower service tray to the second leg once the service cart is fully unfolded. This action is difficult in confined areas where a service cart is often used. Furthermore, such actions are difficult for the elderly and frail who may want to use a service cart to help transport food or other materials from one point to another.
A need therefore exists for an improved collapsible service tray design where the lower platform is permanently affixed to all four support legs, yet the service cart is lightweight, portable and collapsible. A need also exists for a lightweight collapsible service cart that has improved strength and can hold more weight with more stability than prior art carts of the same size. These needs are met by the present invention as described and claimed below.
The present invention is a collapsible service cart, cart. The service cart can be configured in an open operational configuration for use, or a collapsed configuration for storage. The collapsible service cart has four legs, which include a first leg, a second leg, a third leg and a fourth leg. The first leg and the third leg are joined at a first pivot connection in a first scissor arrangement. Likewise, the second leg and the fourth leg are joined together at a second pivot connection in a second scissor arrangement.
The first and second scissor arrangement are joined together by a handle, a cross bar and two axles. The cross bar extends from the first leg to the second leg. The first axle extends through both the first leg and the second leg. The second axle extends through both the third leg and the fourth leg. A first set of wheels is coupled to the first axle. A second set of wheels is coupled to the second axle. Both sets of wheels support the collapsible cart assembly.
A first platform is provided that is pivotably connected to both the third leg and the fourth leg. The first platform has a catch that can selectively receive and engage the cross bar.
A second platform is provided that is pivotably connected to the first axle. Slides are attached to the second platform with pivot joints. The slides run along the first leg and the second leg as the service cart is changed between its open configuration and collapsed configuration. However, the slides remain attached to the first and second legs in both configurations.
For a better understanding of the present invention, reference is made to the following description of an exemplary embodiment thereof, considered in conjunction with the accompanying drawings, in which:
Although the present invention collapsible service cart can be configured into many different styles, only one exemplary embodiment is being illustrated. The embodiment illustrated shows a simple version of the collapsible service cart that is useful for description and discussion. The embodiment is selected only for the purposes of explanation, and should not be considered a limitation when interpreting the scope of the claims when filed.
Referring to
A cross bar 32 extends between the first leg 21 and the second leg 22 a short distance before the handle 30. The cross bar 32 is used to support the upper platform 14 when the service cart 10 is open. Furthermore, the cross bar 32 provides rigidity to the service cart 10 and works in unison with the handle 30 to maintain the first leg 21 and the second leg 22 in parallel orientations.
The second leg set 20 includes the third leg 23 and the fourth leg 24. The third leg 23 and the fourth leg 24 are separate elements. The third leg 23 has a first end 34 and an opposite second end 36. Likewise, the fourth leg 24 has a first end 38 and an opposite second end 39. The third leg 23 is connected to the first leg 21 at a first pivot joint 40. The first pivot joint 40 is located at or near the center of the third leg 23 between its first end 34 and second end 36. This creates a first scissor arrangement 25. Likewise, the fourth leg 24 is connected to the second leg 22 at a second pivot joint 42. The second pivot joint 42 is located at or near the center of the fourth leg 24 between its first end 38 and second end 39. This creates a second scissor arrangement 27.
The upper platform 14 has a flat section 44 and a tray section 46 that are unistructurally molded together. The flat section 44 has a flat top surface 48. The tray section 46 defines a tray 47 with an open top. The tray 47 has a significant depth, which makes the tray section 46 thicker than the remaining flat section 44. The flat section 44 has a bottom surface 49. A catch groove 50 is formed in the bottom surface 49.
A pivot rod 52 is provided. The pivot rod 52 extends from the first end 34 of the third leg 23 to the first end 38 of the fourth leg 38. The pivot rod 52 is rigid. As such, it provides rigidity to the second leg set 20 and helps maintain the parallel configuration between the third leg 23 and the fourth leg 24. The pivot rod 52 extends through the upper platform 14 at a point just before where the flat section 44 transitions into the tray section 46. The upper platform 14 is free to pivot about the pivot rod 52. However, the upper platform 14 cannot detach from the pivot rod 52.
The lower platform 16 is planar in shape. The lower platform 16 has a rear edge 54 that extends in the direction of the handle 30, and a forward edge 56 that extends in the opposite direction. Two slides 60, 62 are connected to the lower platform 16 near its rear edge 54. The slides 60, 62 are attached to the lower platform 16 with pivot joints 63. However, the slides 60, 62 cannot detach from the lower platform 16. The slides 60, 62 engage the second leg set 20, wherein the slides 60, 62 are free to move up and down the lengths of the third leg 23 and fourth leg 24.
A front axle rod 64 is provided. The front axle rod 64 extends between the free ends 26, 28 of the first leg 21 and the second leg 22. The front axle rod 64 extends through the lower platform 16 near the forward edge 56 of the lower platform 16. The lower platform 16 is free to rotate about the front axle rod 64 while remaining attached to the front axle rod 64. The front axle rod 64 is overlong and extends beyond the free ends 26, 28 of the first leg set 18. Large diameter wheels 66 are attached to the front axle rod 64.
A rear axle rod 68 extends between the second end 36 of the third leg 23 and the second end 39 of the fourth leg 24 in the second leg set 20. The rear axle rod 68 is rigid and reinforces the position and orientation of both the third leg 23 and the fourth leg 24. The rear axle rod 68 is overlong and extends beyond the second ends 36, 39 of the second leg set 20. Small diameter wheels 70 are attached to the rear axle rod 68.
Referring to
In the open configuration 100, the service cart 10 is both strong and stable. The service cart 10 can be lifted, pushed and/or pulled by the handle 30 without compromising the interconnection between the upper platform 14 and the cross bar 32. In this manner, the service cart 10 can be manipulated without concerns of accidentally collapsing the service cart 10.
In
Referring to
In the collapsed configuration, large diameter wheels 66 are the forward most element of the service cart 10. In this manner, the service cart 10 can be lifted by the handle 30 while in the collapsed configuration 110 and can still roll on the large diameter wheels 66. When the service cart 10 is laid flat in its collapsed configuration, it still is supported by both the large diameter wheels 66 and the small diameter wheels 70. The service cart 10 can therefore be rolled under a couch, bed or other confined space for storage.
It will be understood that the embodiment of the present invention that is illustrated and described is merely exemplary and that a person skilled in the art can make many variations to that embodiment. All such embodiments are intended to be included within the scope of the present invention as defined by the claims.
