Abstract:
A portable backrest for a picnic bench or bleacher. The backrest includes a back-engaging member having a substantially U-shaped frame; support posts for supporting the back-engaging member in any of a plurality of upright positions; and a clamping mechanism for urging the two prongs of the U-shaped frame against the bench or bleacher for securement thereto.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates to a collapsible backrest device, and particularly to a portable, collapsible backrest for use with a picnic table or other bench. 
     2. Description of the Relevant Art 
     There are known backrests. For example, Vieira U.S. Pat. No. 1,363,697 discloses a folding backrest for use in sitting on lawns, beaches, etc. The Vieira reference, however, fails to disclose a portable backrest which secures to a picnic table bench for use therewith. 
     Flanders U.S. Pat. No. 2,108,531 discloses a portable seat which is adapted for use with benches or bleachers, but provides limited space due to diagonal support bars 12 disposed on either side of the person seated in the seat, provides no adjustable backrest support when associated with a bench, and provides no resistance to forward movement of the seat. 
     Schafer U.S. Pat. No. 1,447,486 discloses a beach chair but fails to disclose a portable seat which attaches to a picnic table or bench plank. 
     Burgess U.S. Pat. No. 1,209,808 discloses a beach chair, but fails to disclose an adjustable backrest which securely attaches to a picnic table, bench, or bleacher. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the above-discussed limitations and shortcomings of known portable backrests and satisfies a significant need for a portable, collapsible backrest which securely engages with a picnic table bench or other bench so as to provide support for a person seated thereon. 
     According to the present invention, there is provided a portable backrest comprising a back-engaging panel formed by a substantially U-shaped frame and material connected between the two prongs thereof; a support structure for adjustably supporting the panel member in one of a plurality of angular positions relative to the bench; a clamping device for securely attaching the backrest to the bench; and wherein the back-engaging panel member, the support structure and the clamping device are connected to each other in such a manner that the backrest is substantially collapsible for convenient transport or storage. 
     In use, the backrest is slid over the bench. Next, the back-engaging panel is adjusted to the desired angular position relative to the bench. Thereafter, the clamping device is activated so as to secure the backrest to the bench. The secured backrest is positioned laterally across the bench so that a user thereof may be comfortably seated and rest her legs and feet on the bench. 
     When not in use, these steps are repeated in reverse order so as to disconnect and collapse the backrest for storage or transport. 
     It is an object of the invention to provide a portable backrest which securely engages with a picnic table bench or similar article so as to substantially restrict any movement relative thereto. 
     It is another object of the invention to provide such a backrest having means for adjusting the backrest in a plurality of positions. 
     A further object of the present invention is to provide a portable backrest which attaches to a picnic table bench or similar article in such a manner so as to allow support for the user&#39;s feet and legs by the bench. 
     Another object of the present invention is to provide a backrest which substantially collapses for convenient storage or transport. 
     Still another object of the present invention is to provide a backrest which is simple in design and inexpensive to manufacture. 
     Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a preferred embodiment of the present invention in its operable position. 
     FIG. 2 is a perspective view of a preferred embodiment of the present invention in its collapsed, inoperable position for storage. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 and 2, there is shown a portable backrest 1 comprising back-engaging panel 2, 3; diagonal support posts 4; clamp crank 7; adjustment tabs 11; biasing spring 10; and plank extension members 8. 
     The frame members of the portable backrest 1, most notably members 2 and 4-9 are preferably but not necessarily made from a lightweight, rigid, inexpensive and substantially weather resistant composition, such as steel, heavy aluminum, fiberglass, or extruded plastic. Alternatively, such frame members are constructed from other materials. 
     The portable backrest according to the preferred embodiments of the present invention includes a panel for comfortably engaging and supporting the user&#39;s back and neck region, comprising frame member 2 and lateral supports 3. Frame member 2 is preferably but not necessarily shaped as a substantially inverted &#34;U&#34;, having two substantially parallel prongs 2a. Frame member 2 is preferably sized and constructed so that prongs 2a are slightly resiliently movable at their free ends. 
     Lateral supports 3 are preferably connected between prongs 2a of frame member 2 and substantially equally spaced therealong. Lateral supports 3 are preferably but not necessarily tightly connected between prongs 2a so as to provide comfortable support to the user&#39;s back. The number of lateral supports 3 depends in part upon the width of each lateral support 3 and the length of prongs 2a. Lateral supports 3 are preferably but not necessarily constructed from a resilient, weather resistant material such as canvas or thinly cut plastic. 
     The preferred embodiment of the present invention includes a means for supporting the back-engaging panel in an upright position. As shown in FIG. 1, the supporting means preferably but not necessarily comprises diagonal panel support posts 4, longitudinal posts 5, and lateral post 6. Each longitudinal post 5 has a first end which is connected to a prong 2a near the free end thereof, and a second end which is pivotally connected to one end of a diagonal support post 4 (FIG. 1). The second end of each diagonal support post 4 preferably but not necessarily engages with a prong 2a proximal to the top portion of frame 2, so that the back-engaging panel is supported in an upright position and is substantially resistant to backward movement due to pressure exerted thereon while in use. Lateral post 6 is connected between longitudinal posts 5 at the rearward end thereof, so that post 6 rests on top of the bench plank in order to support the backrest thereover. 
     According to the present invention, the backrest preferably but not necessarily includes a means for adjusting the angular position of the back-engaging panel member relative to the bench to which the backrest is connected. The adjusting means preferably but not necessarily includes a plurality of tab members 11, each of which extends outwardly from U-shaped frame 2 in a backwardly direction and is aligned with a corresponding tab member 11 disposed along the opposite prong 2a, as shown in FIG. 1; and an aperture defined through the end portions of each diagonal support post 4 and sized so as to slidably engage with tab members 11. In this way, the user can selectively engage diagonal support posts 4 with a desired pair of tab members 11 so that the back-engaging panel member is positioned at the desired angle for supporting the user. 
     The preferred embodiment of the present invention further includes means for selectively securing the backrest to a plank, such as a picnic table bench or a bleacher, in a substantially fixed position. As shown in FIG. 1, the securing means preferably but not necessarily comprises a clamping device which urges prongs 2a of frame member 2 substantially inwardly against the substantially vertical sides of the bench plank. The clamping device preferably includes elongated crank 7 having one end which is threaded and a second end which is formed as a handle. Crank 7 is slidably inserted through a first prong 2a and threadingly engages with the second prong 2a, so that by manually rotating handle 7a, the second prong 2a moves inwardly towards the first prong 2a along crank 7. When the bench plank is positioned between prongs 2a (FIG. 1), the inward movement of one prong 2a towards the other prong 2a acts to substantially clamp frame 2 to the bench plank. 
     The backrest device according to the present invention preferably but not necessarily includes extension members 8, which extend inwardly from each free end of prongs 2a, so that the bench plank fits between prongs 2a, the central portion of crank 7, and extension members 8 (FIG. 1). 
     The backrest preferably but not necessarily includes means for substantially maintaining engagement between the back-engaging panel and diagonal support posts 4. As shown in FIG. 1, the engagement maintaining means comprises second lateral post 9, which is connected between diagonal support posts 4 at a substantially central portion therealong; and spring member 10, which is connected between second lateral post 9 and substantially U-shaped frame 2. Spring member 10 urges frame member 2 towards diagonal support posts 4 so that the engagement between tab members 11 and posts 4 is maintained. The tension of spring member 10 is preferably but not necessarily set so that such engagement is maintained while allowing frame member 2 to easily disengage from diagonal supports 4 by manual effort in order to adjust the operable position of the panel member or collapse the backrest for storage and/or transport. 
     The pivotal connections A between diagonal supports 4 and longitudinal supports 5, and the pivotal connections B between frame member 2 and longitudinal supports 5 provide collapsibility to the backrest. When collapsed, frame 2 and diagonal posts 4 are each substantially collapsed along longitudinal posts 5, as shown in FIG. 2. 
     In use, the backrest is first slid into position along the bench or bleacher so that the bench is located between extension members 8, the central portion of crank 7, and prongs 2a (FIG. 1). Next, the back-engaging panel is adjusted to the desired angle by engaging the apertures of diagonal posts 4 with the appropriate pair of tab members 11. Then spring member 10 is connected between second lateral post 9 and frame 2. The clamping device is then activated so as to firmly secure the backrest to the bench by manually rotating crank 7 so that the free ends of prongs 2a are brought towards each other and sufficiently squeeze the longitudinal edges of the bench, until the backrest is substantially locked into position. Thereafter, the backrest is positioned relative to the bench so that a person may sit on the bench, lean against the backrest and rest her feet on the bench. 
     The backrest is easily readjusted to another inclined position relative to the bench by manually lifting frame 2 away from diagonal posts 4 until tab members 11 are disengaged therefrom, and then engaging posts 4 with the appropriate tab members 11. 
     The backrest is collapsed for storage or transport by first releasing the engagement between the backrest and the bench through rotation of crank 7 until the end portions of prongs 2a are sufficiently separated so that the backrest can be easily slid out from the bench. Next, spring member 10 is disconnected from second lateral support 9. Then the engagement between frame member 2 and diagonal posts 4 is released. Thereafter, frame member 2 and diagonal posts 4 are pivoted about connections B and A, respectively, until they are substantially collapsed against longitudinal posts 5. 
     Although there has been described what is at present considered to be the preferred embodiments of the present invention, it will be understood that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. 
     The described embodiments are, therefore, to be considered in all aspects as illustrative, and not restrictive. The scope of the invention is indicated by the appended claims rather than the foregoing description.