1. Field of the Invention
The present invention relates to an expandable gate. More specifically, it relates to an expandable gate which utilizes spring members to hold adjacent vertical bar members in a compact collapsed position.
2. Description of the Prior Art
A variety of expandable gate structures have been proposed over the years. Examples of some of such prior art structures include the following. Snead, U.S. Pat. No. 67,143 discloses a very early version of a collapsible gate the type which is now known as a “lazy tongs” door or gate. Snead also teaches the use of an intermediate washer C to prevent the rubbing of the bars and slots D to allow for the extension and limit of the same. This patent teaches that the general field of collapsible gates was known at least as early as 1867.
Shonnard, U.S. Pat. No. 1,790,027 discloses a safety device for elevator doors which essentially provides guards or curtains 14. This patent was selected because it also shows in FIG. 1 a well known form of “lazy tongs” gates 9 which are composed of vertical bars 10 united by slidable crossed bars 11.
Catalano et al., U.S. Pat. No. 2,990,880 discloses a gate which includes as its main parts a mesh 12 and rails 14. The mesh 12 includes four sets of strips or links as compared with two sets in folding gates as theretofore known. Catalano teaches that as far back as anyone in the folding gate industry can remember, folding gates have been made with only two sets of strips, and it has been the universal belief until the Catalano invention that a smaller mesh could not be produced on the basic or standard construction of strips. Basic or standard construction includes two sets of strips such as shown in FIG. 1 as 24 and 26. All the strips 24 are parallel and lie in a common plane and similarly all of the strips 26 are parallel and lie in a common plane.
Mutch, U.S. Pat. No. 2,348,561 discloses yet another “lazy tongs” form of collapsible gate but which includes springs 41 and 42 in sleeves 38 and 39 which house telescopic rods 37 and 38. The springs have a normal tendency to slide the rods outwardly leaving the gate in an open position as shown in FIGS. 1 and 3. The gate is collapsed by lifting operating member 34 upwardly as shown in FIG. 2. Upon a downward push or force on the operating member 34 when in the position shown in FIG. 2 the rods 37 and 38 are forced inwardly in sleeves 39 and 40 against the normal outward thrust of the springs 41 and 42 at the same time said sleeves moving downwardly and opening the gate during this downward thrust.
Horn, U.S. Pat. No. 3,213,555 discloses a self-opening gate which may use a single folding or collapsible gate but preferably embodies two companion gates 14 and 15. Each gate is foldable or collapsible and comprises an upper normally horizontal rail 16 and a similar horizontal lower rail 17 and vertical pickets 18, these vertical pickets having upper ends crossing and pivotally connected at 19 to the upper rail 16. When a person walks from left to right along a boardwalk and toward the gates the depressible end portion of the boardwalk gradually swings or pivots down and tensions the springs 74. This causes the gate to move to the phantom open position shown in FIG. 3.
Kiesling, U.S. Pat. No. 2,433,763 discloses a vertically operating collapsible gate 31 which includes frame parts 15 and 16 which constitute channel members. This device discloses yet another “lazy tongs” arrangement. Kiesling employs a strong spring 25 which controls certain leftwardly and rightwardly loose play in the gate.
Newton, U.S. Pat. No. 3,722,140 discloses a vertical gate which includes a shaft 10 which carries three pulleys 12, 14 and 16 which are secured to the shaft for rotation. Barrier members 32 are secured to cables 24 and 26. In operation, the gate normally assumes the position shown in FIGS. 1 and 2 with cables 24 and 26 maintaining the barrier members in a raised or closed position to prevent livestock or the like from passing through the gate with the cables 40 and 42 supporting the free ends of the treadle means 34 and 36 in a raised position. To open the gate, the operator of a vehicle merely drives the vehicle onto the treadle means 34, as shown in FIG. 3. The weight of the vehicle depresses the inner end of the treadle means 34 and acts through cables 40 and pulleys 12 to rotate the shaft 10 and the pulleys 14 and 16. Rotation of the pulley 16 acts to raise the counter-weights 28 and 30 to increase their potential energy, allowing the barrier means 32 to fall under the force of gravity to a collapsed position.
There remains a need for an expandable gate which easily opens to an expanded open position and easily and automatically closes to a compact closed position. There further remains a need for an expandable gate which eliminates the need to utilize the “lazy tongs” type of design which is often prone to causing pinching injuries by the scissor action of the gate bar members.
USPTO Backgrounds
USPTO Backgrounds