Latch with spring

[0002] The present invention relates to fasteners for removably securing together two panels or other objects. More particularly, the present invention relates to a quarter-turn panel fastener having a spring.

[0003] Many types of fasteners are used to removably attach one panel to another. Often, sheet metal screws or machine screws, with or without nuts, are used for these tasks. Although these screw type fasteners will securely fasten one panel to another and are readily unfastened, they are inadequate for many applications. For instance, screw type fasteners take too long to assemble and disassemble, require relatively precise tolerances in panel fit, and are subject to cross-threading, stripping, and under- or over-tightening. There is a need for fasteners that are quick and easy to use, and that positively engage. This is particularly true in light industrial applications such as the computer industry, where it is desired to attach various loose-fitting components and covers in a positive secure fashion that allows such covers and components to be easily installed and removed.

[0004] Quarter-turn latches are used for latching a variety of cabinets, doors and other enclosures. It has been suggested to construct a quarter-turn fastener as shown in FIG. 1. A bolt 1 has a disk-shaped head 2 and a cylindrical shank 3. Two projecting keys 4, 5 project radially outward from the shank 3 opposite one another. A keyhole 6, shown in FIG. 2, is made in each panel 10, 11 to be adjoined. The keyhole 6 consists of a circular hole 7 with two radially extending rectangular slots 8, 9 opposite one another. In operation, the top panel 10 is placed over the bottom panel 11 with the keyhole in each panel aligned. The bolt 1 is guided through the panels 10, 11 and the keys 4, 5 simultaneously pass through the slots 8, 9.

[0005] The bolt is twisted 90°, placing the keys 4, 5 in the positions 12, 13 shown by dotted lines in FIG. 2, effectively locking the panels 10, 11 together. A coil spring 14 coaxially surrounds the shank 3 and is compressed between the bolt head 2 and the top panel 10. The compressed spring 14 pulls the keys 4, 5 against the underside of the bottom panel 11, holding the bolt 1 in position by friction. Thus, the spring 14 provides a compressive biasing force that pulls the panels 10, 11 together for positive engagement and to avoid rattles.

[0006] Drawbacks exist with many quarter-turn latches. For instance, they can be susceptible to operator error. Without positive engagement, the operator can turn the bolt too far, or not far enough. The bolt can rotate to the unlocked position due to vibration. In addition, the coil spring adds purchase and assembly costs, and can be lost. Consequently, there is a need for a quarter-turn fastener which is simple, inexpensive, requires a minimum number of parts, and provides positive engagement.

[0007] The present invention relates to a fastener system for fastening a first panel in which is formed a first keyhole to a second panel in which is formed a second keyhole. According to one aspect of the invention, the fastener system includes a bolt with a head, a spring member integrally formed with the head, a shank, and a first key attached to the shank opposite the head. The bolt passes through the first keyhole and the second keyhole, when the first key is aligned with a first slot in the first keyhole and a second slot in the second keyhole. The bolt is rotatable from an open position where the first key is aligned with the first slot and the second slot, to a closed position where the first key bears against a back surface of the second panel. The spring cooperates with the first key to bias the first panel to the second panel.

[0008] In a preferred embodiment of the invention, an annular track is located on the back surface of the second panel and slopes to a crest and recedes to a landing area. The first key is retained in the landing area by the biasing force of the spring member. An open bump stop is located on the back surface of the second panel adjacent the first slot portion and is engageable with the first key when the bolt is in the open position. A closed bump stop is located on the back surface of the second panel adjacent the landing area and is engageable with the first key when the bolt is in the closed position.

[0009] The bolt may have a second key located on its shank between the head and the first key. In a preferred embodiment of the present invention, the second key fits through the first slot in the first panel and engages a back surface of the first panel when the bolt is rotated away from the entry position of the second key in the first slot. The second panel may be recessed away from the first panel to provide room for the second key.

[0010] The present invention should not be limited to the preferred embodiments shown and described in detail herein. The above and other advantages and features of the invention will be more readily understood from the following detailed description and the accompanying drawings.

[0011] FIG. 1 is sectional side view of a quarter-turn latch system.

[0012] FIG. 2 is a plan view of a portion of a panel illustrating the keyhole of the quarter-turn latch system of FIG. 1.

[0013] FlG. 3 is sectional side view of a quarter-turn latch system constructed in accordance with the present invention.

[0014] FIG. 4 is a front view of the bolt of the quarter-turn latch system of FIG. 3.

[0015] FIG. 5 is an axial sectional view of the underside of the head of the bolt of FIG. 4.

[0016] FIG. 6 is a plan view of the keyhole in the top panel of the system of FIG. 3.

[0017] FIG. 7 is a bottom view of the bottom panel of the quarter-turn latch system of FIG. 3.

[0018] FIG. 8 is a profile projection view of the track and bump stops of FIG. 7.

[0019] FIG. 9 is a sectional side view of another quarter-turn latch system constructed in accordance with the present invention.

[0020] FIG. 3 shows a quarter-turn latch system 100 that has a rotatable bolt 102 for locking a top panel 104 to a bottom panel 106. The panels 104, 106 are referred to as top and bottom for ease in exposition. It should be understood, however, that the invention can be employed in many different orientations. The bolt 102 is preferably integrally formed in one piece. In a preferred embodiment of the invention, the bolt 102 is integrally molded from plastic resin. The bolt 102 consists of a cylindrical shank 108 with a disk-shaped head 110. The head 110 is coaxially located at one end of the shank 108.

[0021] The head 110 consists of a hexagon-shaped portion 112 and a circular shoulder 114. The hexagon-shaped portion 112 may be engaged by a wrench (not shown). The shoulder 114 is located between the hexagon-shaped portion 112 and the shank 108. The shoulder 114 may be used to promote positive wrench engagement and to prevent the wrench from marring the top panel 104. Alternatively, other types of heads may be used, including those incorporating screwdriver slots, thumb screws and other suitable torque transmitting means.

[0022] The end 103 of the shank 108 opposite the head 110 has a chamfered shoulder 109. Near the end 103 of the shank 108 is a rectilinear bayonet key 116, extending radially away from the shank 108. The key 116 has rounded surfaces 118, 119 facing towards and away from the head 110. A capture key 125 also extends radially from the shank 108 between the head 110 and the bayonet key 116. The capture key 125 is out of phase with the bayonet key by 90°. Two integral, resilient, flexible, curved spring members 120, 122 emanate from the head 110 of the bolt 102 facing the top panel 104. As shown in FIG. 4, each spring member 120, 122 defines a gentle, S-shaped curve, with one end of the “S” being integrally attached in one piece to the head 110. Viewed in the axial direction of the bolt 102, as shown in FIG. 5, each spring member 120, 122 defines a curved arc (a portion of a circle). Alternatively, each spring member could define a straight section when viewed in the axial direction. When compressed between the head 110 and the top panel 104, the spring members 120, 122 store elastic energy.

[0023] Referring now to FIG. 6, the top panel 104 has a keyhole 124. The keyhole 124 extends through the top panel 104. The keyhole 124 consists of a circular hole 126 with a rectangular slot 128. The slot 128 projects radially away from the center of the hole 126. Referring back to FIG. 3, the bottom panel 106 has a recessed portion 130 dimpled away from the top panel 104. As shown in FIG. 7, the recessed portion 130 has a keyhole 132 through it, of identical shape to the keyhole 124 of the top panel 104. The bottom panel keyhole 132 consists of a circular hole 134 with a rectangular slot 136 projecting radially from the center of the hole 134. As noted above, the present invention should not be limited to the specific structures and instrumentalities described herein.

[0024] The underside 138 of the bottom panel 106 (the side 138 facing away from the top panel 104) has a rectilinear open bump stop 140. The open bump stop 140 projects downwardly from the bottom panel 106 (away from the top panel 104). In the illustrated embodiment, the open bump stop 140 is located immediately and rotationally adjacent to the rectangular slot 136 of the keyhole 132. A rectilinear closed bump stop 142 also projects from the underside 138 of the bottom panel 106. The closed bump stop 142 is located in a position that would be immediately and rotationally adjacent to the rectangular slot 136 opposite the open bump stop 140, if the keyhole 132 were rotated 90° counterclockwise (as viewed in FIG. 7). As discussed in more detail below, the open bump stop 140 and the closed bump stop 142 prevent rotation of the bolt 102 past its fully open or fully closed positions.

[0025] Located between the rectangular slot 136 and the closed bump stop 142 on the underside 138 of the bottom panel 106 is a raised, annular (curved) track 144. The track 144 is straightened out in the projection of FIG. 8 to illustrate its profile. Starting at the rectangular slot 136, the track 144 gently projects away from the underside 138 of the bottom panel 106 forming a first sloped portion 146. The sloped portion 146 may form an angle of about 35° with respect to the underside 138 of the panel 106. The track 144 then gently curves back towards the underside 138, forming a crest 148 and then a second sloped portion 150 returns to the underside 138 of the bottom panel 106.

[0026] The second sloped portion 150 may form, for example, an angle of approximately 60° with respect to the panel underside 138. The track 144 ends prior to reaching the closed bump stop 142, such that a landing area 152 is defined adjacent to the closed bump stop 142. In a preferred embodiment of the invention, the depth of the crest 148 above the underside 138 is approximately equal to the thickness of the key 116. The length of the landing area 152, measured from the closed bump stop 142 to the transition from the slope 150 to the crest 148, may be about one and one-half the thickness of the key 116.

[0027] In operation, the bolt 102 is axially guided through the keyhole 124 so that the bayonet key 116 passes through the rectangular slot 128. The bolt 102 is then twisted 90° so that the capture key 125 also passes through the rectangular slot 128. The chamfered shoulder 109 of the bolt 102 and the rounded surface 119 of the key 116 promote entry of the bolt 102 through the keyhole 124. The bolt 102 is then twisted further, loosely locking it into engagement with the top panel 104. The capture key 125 is axially located along the bolt shank 108 so that the spring members 120, 122 are either lightly compressed or uncompressed. In this manner, the bolt 102 can be easily engaged or disengaged with the top panel 104, but is unlikely to accidentally disengage. Accidental disengagement would require the bolt 102 to randomly move until both the capture key 125 and the bayonet key 116 are sequentially aligned with and pass through the rectangular slot 128.

[0028] To fasten the top panel 104 to the bottom panel 106, the top panel 104 is brought into engagement with the bottom panel 106. The chamfered point 109 of the bolt 102 engages with the keyhole 134. The operator (not shown) then simultaneously pushes the bolt 102 against the resisting force of the spring members 120, 122, and twists the bolt 102 until the key 116 engages with the rectangular slot 136. At this point, the key 116 will pass through the keyhole 134 and the quarter-turn latch will be ready for engagement.

[0029] The operator then twists the bolt 102 clockwise 90°. During this twisting movement, mild resistance will be felt by the operator as the key 116 travels over the sloped portion 146 and the crest 148. The key 116 then settles into the landing area 152 and is stopped by the closed bump stop 142. The rounded surface 118 promotes a smooth cam operation between the key 116 and the track 144. The arrest of angular motion effected by the closed bump stop 142 is a positive indicator to the operator that the quarter-turn latch system 100 is in the closed position.

[0030] In the closed position, the force provided by the compressed spring members 120, 122 keeps the key 116 in the landing area 152 by resisting movement of the key 116 over the sloped portion 150. The spring force also prevents rattles and other movements by drawing the top panel tightly against the bottom panel 106. The spring members 120, 122 also compensate for any minor misalignment of the latch system 100.

[0031] To unfasten the top panel 104 from the bottom panel 106, the operator twists the bolt 102 counterclockwise, overcoming the resistance required to pass the key 116 over the sloped portion 150 and the crest 148 of the track 144. The bolt 102 is twisted until the key 116 is stopped by the open bump stop 140. The arrest of angular motion effected by the open bump stop 140 is a positive indication that the bolt 102 is in the open position. When the operator releases the bolt 102 in the open position, the bolt 102 pops up through the keyhole 134 as the integral springs 120, 122 decompress. Thus, release of the bolt 102 in the open position causes the key 116 to move into the space between the two panels 104, 106.

[0032] In an alternative embodiment of the invention shown in FIG. 9, the capture key 125 is omitted and the bottom panel 106 is not dimpled. The embodiment of FIG. 9 is otherwise essentially the same as the embodiment shown in FIGS. 3-8.

[0033] The present invention provides an economical quarter-turn latch system that easily and positively fastens panels together and that features one or more integral springs. Variations of the disclosed embodiments will be apparent to those skilled in the art. For instance, the invention could be practiced with different shaped springs, different numbers of springs, or with two bayonet keys. Accordingly, it is to be understood that although the present invention has been described with reference to exemplary embodiments, various modifications may be made without departing from the spirit or scope of the invention which is defined by the claims appended hereto.