Locking system

Abstract: A locking system is described for detachably securing two workpieces together (e.g., two housing sections). Elongated arms (12, 14) are carried by one workpiece (40) and a corresponding opening(s) is present in the other workpiece (50). The outer end of each elongated arm is resiliently deflectable so that it is deflected when being inserted into the opening in the one workpiece; then the arm springs back. A locking arm on the second workpiece is then able to move behind the end of the elongated arm to restrict deflection of the arm, thus prevent­ ing any unintentional unlocking of the two workpieces.

Description: Field of the Invention The invention relates to a locking system for detachably securing first and second workpieces together according to the precharacterising part of claim 1. Such a locking system is known from AU-B-497 454. There are many situations where it is necessary or desirable to detachably secure two items or workpieces together. For example, housing sections used to enclose or contain a product must be fastened in some manner so as to be secure when the product is used, but preferably the housing sections are detachable so that they can be removed to allow access to the product (e.g., for repair purposes). Various types of products require the type of enclosure or containment described. Such products include, for example, gears, electronics, linkages, tubing or wiring which must be clamped or secured in place, and other various mechanisms. The workpieces may be housings for electrical components, mounting or clamping devices, or locating components of a mechanical gear train or linkage. Various types of fastening devices can be used to detachably secure items such as housing sections to each other or to a product to be enclosed. For example, various types of threaded fasteners or other mechanical fasteners have been used for this purpose. However, this requires that additional components be used, thereby increasing the cost of the enclosure. The use of a conventional cantilever beam with a hook on its outer end is also known as a means for securing two workpieces together. In such case, the outer end of the cantilever beam is inserted into an opening in the second workpiece. However, when a tensile load is exerted on the arm it can pull free of the second workpiece relatively easily. This is because the force exerted on the hook portion of a cantilever beam is not centrally applied to the beam. As a result, when a tensile load is exerted on the arm a moment is created which forces the beam to deflect. As the beam deflects, the angle of the hook portion changes such that a component of the force pushes the end of the beam back even further. Eventually the hook portion slips free and the workpieces become detached. Other conventional types of fastening systems include hook and loop fasteners (such as Velcro brand fasteners), over-center latches, and press fit fasteners (e.g., where a post is pushed into an opening with great force to frictionally engage the walls of the opening). Each of these systems has limitations, however. Hook and loop fasteners have structural limitations. Latches can be complex and also costly. Press fit fasteners may lose their effectiveness after being detached one or more times. The elongated arms according to AU-B-497 454 include ramp- and hook portions which, when the workpiece carrying the elongated arms is inserted into a mating opening in a second workpiece engage respective ramp- and hook portions provided at flanges of said opening in said second workpiece so that said elongated arms are detachably engaging said second workpiece and the two workpieces are detachably secured together. In order to withstand a tensile load e.g. on the workpiece carrying the elongated arms, the thickness of the latter and the sizes hook and ramp portions on the elongated arms and the second workpiece must have a considerable amount and the length of the elongated arms should be restricted in accordance with the demand of a strong resilient force exerted by the elongated arms. It is the object of the invention to provide a locking system by which a first and second workpiece can be detachably secured together in which the safety against undesireable detachment is improved and structural limitations are minimized. The above object is solved by the features of claim 1. According to the invention, the locking system is characterised in that a locking arm which is carried by said second workpiece is movable between an open position and a closed position, wherein said locking arm is movable to said open position when said second end of said elongated arm is passed through said opening and said locking arm is movable to said closed position to restrict deflection of said second end of said elongated arm when said hook portion of said elongated arm has engaged said second workpiece. The depending claims 2 to 15 characterise advantageous developments thereof. The second end of the elongated arm can be deflected by the lead in ramp means when the first workpiece is urged toward the second workpiece. This enables the second end of the elongated arm to pass through the opening. The locking arm is movable to its closed position behind the second end of the elongated arm to restrict movement of the second end. The hook portion or engagement means on the end of the elongated arm engages the second workpiece. The locking arm prevents the hook portion of the elongated arm from backing out of the opening in the second workpiece when the elongated arm is loaded in tension, thereby preventing the previously-described failure. Unlocking requires that the locking arm be moved from its closed to its open position. Then the second end of the elongated arm can be deflected so that the hook portion or engagement means is released from the second workpiece, allowing the elongated arm to be moved out of the opening in the second workpiece. Preferably there are a plurality of such elongated arms carried by the first workpiece and a corresponding plurality of openings in the second workpieces. If desired, there may also be one or more of such elongated arms on the second workpiece, and one or more corresponding openings in the first workpiece. In another embodiment there are a plurality of pairs of elongated arms carried by the first workpiece. After the free ends of the arms are passed through an opening in the second workpiece, the locking arm moves to its closed position between the parallel arms to restrict movement of the arms towards each other. Other advantages of the locking systems of this invention will be apparent from the following detailed description and the accompanying drawings. Brief Description of the Drawings The invention is described in more detail hereinafter with reference to the accompanying drawings, wherein like reference characters refer to the same parts throughout the several views and in which: FIGURE 1 is a perspective view of two housing sections which are adapted to be detachably secured together using the locking system of the invention; FIGURES 2, 3 and 4 are top views (partially cut-away) of the locking system illustrating the manner in which the elongated arms are guided into an opening in the second workpiece and locked in position; FIGURE 5 is a side elevational view showing the arms secured to the second workpiece; FIGURE 6 is a perspective view of another embodiment of locking system of this invention; and FIGURE 7 is a perspective view illustrating another embodiment of locking system of this invention Detailed Description of the Invention In Figures 1-5 there is illustrated one embodiment of locking system of the invention. As illustrated in the drawings, the two workpieces may be housing sections which are used to enclose a product (e.g., a gear train, electronics system, etc.) The locking system illustrated includes pairs of elongated, parallel arms 12 and 14. At one end the parallel arms are secured to one of the workpieces 40. Preferably, the arms are integrally molded as a part of the workpiece 40. Alternatively, the arms could be attached to the workpiece with adhesive or other fasteners. The second workpiece 50 includes a plurality of openings 18 corresponding to the number of pairs of parallel arms carried by the first workpiece 40. On the interior surface of the second workpiece there are shown lead in ramp members 20 and 21 adjacent opposite side edges of each opening 18. Extending into the opening 18 is a locking arm 22 which is movable between an open position and a closed position. Preferably the locking arm is integral with the work piece at one end in a manner such that the opposite end of the locking arm is deflectable out of the opening but will return to its normal position within the opening. The outer ends of the elongated arms 12 and 14 include hook portions 13 and 15, respectively. The outer ends of the arms are resiliently deflectable so that they may be urged towards each other to fit within the corresponding opening in the second workpiece Then the arms spring away from each other again in a manner such that the hook portions 13 and 15 engage the second workpiece. The locking arm can then deflect back to its closed position where it is situated between the ends of the elongated arms to restrict movement of the ends towards each other. These features are illustrated in Figures 2-5. In Figure 2 the outer ends of the elongated arms 12 and 14 are shown contacting the lead in ramp members 20 and 21, respectively, which are located adjacent opposite side edges of opening 18. The lead in ramp members serve as guide members to urge the outer ends of the elongated arms towards each other when the first workpiece 40 is moved toward the second workpiece 50. In Figure 3 the outer ends of the arms 12 and 14 have been urged towards each other so that they can be passed into opening 18 in the second workpiece. At the same time the outer ends urge or deflect the free end of locking arm 22 outwardly away from the opening. In Figure 4 the outer ends of arms 12 and 14 have passed completely through the opening 18 and have sprung outwardly so that the hook portions have engaged the second workpiece. The free end of the locking arm has deflected back to its normal closed position within opening 18. In this position the locking arm is positioned between the outer ends of the elongated arms to prevent them from moving towards each other. Thus, the locking arm prevents the elongated arms from coming loose from the second workpiece when tension is applied to the elongated arms. Yet the two workpieces can be easily separated from each other when desired by first moving each locking arm 22 away from the ends of the arms 12 and 14 to allow them to be moved towards each other. In this manner the hook portions are disengaged from the second workpiece. As shown in Figure 1, side walls 23 and 24 of workpiece 40 serve to establish the desired minimum spacing between the two workpieces. Thus, when the sidewalls contact the other workpiece the desired spacing is maintained. Another manner of establishing the desired spacing between the two workpieces is illustrated in Figure 7. In this figure there is shown the free end of an elongated arm 60 which is supported by one workpiece (not shown). The other workpiece 70 includes an opening 71 in which a locking arm 72 is disposed. Ramp member 74 is carried by workpiece 70 adjacent one edge of opening 71. When elongated arm 60 is moved towards workpiece 70, ramp member 74 guides the end of arm 60 into opening 71 where it deflects the upper end of locking arm 72 out of opening 71. Then when the end of arm 60 is through opening 71, locking arm 72 springs back behind arm 60 so that hook member 62 remains in engagement with workpiece 70. Ledge or stop member 64 on arm 60 serves to limit the extent to which arm 60 may pass through opening 71. In this manner the minimum spacing between the two workpieces is maintained. Positional alignment between the two workpieces may be provided by referencing pins 25 on one workpiece and alignment apertures 26 on the other workpiece, as illustrated in Figure 1. Such alignment is not required in all cases but it may be helpful in situations where a high degree of positional accuracy is required. Figure 6 illustrates another embodiment of the locking system of this invention. One workpiece 30 includes opening 31. Locking arm 33 is disposed in opening 31, as illustrated. Ramp member 32 is carried by workpiece 30 adjacent the top edge of opening 31. An elongated arm 42 carried by another workpiece (not shown) is adapted to pass through opening 31 in workpiece 30. The outer or free end of arm 42 includes an upstanding wall or hook member 43 which is adapted to engage the outer surface of workpiece 30 after it has been passed through opening 31. The leading end of arm 42 includes a ramp member 44 to assist in guiding this end of arm 42 into opening 31 when the two workpieces are brought together. Locking arm 33 is deflected out of opening 31 by the end of arm 42. Then arm 33 springs back into its original position where it holds arm 42 against the upper edge of opening 31. This assures that hook portion 43 is maintained in engagement with workpiece 30. In order to detach one workpiece from the other, the locking arm 33 is deflected out of the way. Then the arm 42 can be deflected downwardly so that the hook member 43 is disengaged from workpiece 30. At that point the arm 42 may be moved out of opening 31.

Claims: A locking system, comprising: a first workpiece (40); a second workpiece (50); at least one elongated arm (12, 14; 42; 60) having first and second ends, wherein said first end is secured to said first workpiece (40), wherein said elongated arm (12, 14; 42; 60) projects outwardly from said first workpiece (40) and wherein said second end is resiliently deflectable and includes a hook portion (13, 15; 43; 62); an opening (18; 31; 71) in said second workpiece (50); a lead-in ramp means (20, 21; 32; 74) adapted to guide said second end of said elongated arm (12, 14; 42; 60) into said opening (18; 31; 71), wherein said second end of said elongated arm (12, 14; 42; 60) is adapted to be deflected by said lead-in ramp means (20, 21; 32; 74) when said first workpiece (40) is moved toward said second workpiece (50) so as to enable said second end of said elongated arm (12, 14; 42; 60) to pass through said opening (18; 31; 71); and wherein said hook portion (13, 15; 43; 62) of said elongated arm (12, 14; 42; 60) engages said second workpiece (50); characterized in that a locking arm (22; 33; 72) which is carried by said second workpiece (50) is movable between an open position and a closed position, wherein said locking arm (22; 33; 72) is movable to said open position when said second end of said elongated arm (12, 14; 42; 60) is passed through said opening (18; 31; 71) and said locking arm (22; 33; 72) is movable to said closed position to restrict deflection of said second end of said elongated arm (12, 14; 42; 60) when said hook portion (13, 15; 43; 62) of said elongated arm (12, 14; 42; 60) has engaged said second workpiece (50). A locking system in accordance with claim 1, wherein said first workpiece includes a plurality of pairs of said elongated arms (12,14), and wherein said second workpiece includes a corresponding plurality of said openings (18) and said locking arms (22). A locking system in accordance with claim 1, wherein said locking arm (22) includes first and second ends, wherein said first end is secured to said second workpiece, and wherein said second end is adapted to be deflected away from said opening when said second end of said elongated arm (12,14) is inserted into said opening (18). A locking system in accordance with claim 3, wherein said locking arm (22) and said second workpiece comprise plastic, and wherein said locking arm (22) is integral with said second workpiece (50). A locking system in accordance with claim 1, wherein said lead in ramp means (20,21;32;74) are carried by said second workpiece (50;30;70) and are disposed adjacent an edge of said opening (18;31;71). A locking system in accordance with claim 5, wherein said lead in ramp means (20,21;32;74) are integral with said second workpiece (50;30;70). A locking system in accordance with one of claim 2 to 6, wherein each of said pairs of elongated arms (12,14) projects outwardly from said first workpiece (40) such that said arms (12,14) of each of that pairs are generally parallel. A locking system in accordance with claim 7, wherein said lead in ramp means (20,21) are disposed adjacent opposite side edges of said opening (18). A locking system in accordance with claim 8, wherein said locking arm (22) is movable to said closed position between said second ends of said elongated arms (12,14) to restrict movement of said ends towards each other. A locking system in accordance with claim 1, wherein said second of each of said elongated arms (42) includes a said lead in ramp means (44) (Fig. 6). A locking system in accordance with claim 1, wherein said second end (60) further includes a stop member (64) which is adapted to rest against said second workpiece (70) to restrict additional movement of said workpieces towards each other after said second end of each of that elongated arms is passed through a said opening (71) (Fig. 7). A locking system in accordance with claim 1, wherein each of that elongated arms (12,14;42;60) projects outwardly from said first workpiece (40) at a right angle. A locking system in accordance with claim 10, wherein said second workpiece includes a second lead in means (32;74) adjacent an edge of said opening (31;71) (Figs. 6,7). A locking system in accordance with claim 1, wherein said elongated arm (12,14;42;60) is perpendicular to said first workpiece (40). A locking system in accordance with one of the preceding claims, wherein said first and second workpieces (40,50;30;70) comprise mating sections of a housing.

Inventors: RASMUSSEN STEVE O, RASMUSSEN, STEVE O.
Applicants: HEWLETT PACKARD CO, HEWLETT-PACKARD COMPANY
Application year: 1988
Main classification: F16B5
IPC codes: F16B21, F16B17, H05K5