Latch assembly for covered containers

[0002] This application is a continuation-in-part of Ser. No. 09/997,789, filed Nov. 30, 2001, now U.S. Pat. No. 6,508,495.

[0003] This invention relates to covered containers. It relates more particularly to a latch assembly for releasably retaining a cover to a container. The latch assembly is especially advantageous for use on surgical instrument sterilization trays.

[0004] A sterilization tray usually comprises a base container with an open top for holding surgical instruments or other articles. The open top of the base container may be closed by a cover which engages over the top of the container. Preferably, the cover and/or the base container are perforated so that steam can circulate through the closed container. To prevent the cover from becoming disengaged from the base container during handling, means are usually provided for releasably securing the cover to that container.

[0005] Conventionally, the securing means often consist of at least one latch which is usually mounted to one of the base container and cover and which is movable between a locked position wherein the latch engages over the other of the base container and cover, and an unlocked position wherein the latch is released from the other of the base container and cover. One such prior latch in widespread use consists of a rolled metal bracket hinged to the edge of the cover and a rolled metal hook pivotally connected to the bracket at a location thereon spaced from the bracket hinge. To lock the cover, the hook is swung down so that the hook engages a hole or projection in the base container and then the bracket is swung down to a stable over center position against the cover so that tension is applied to the hook whereupon the hook remains tightly engaged to the base container.

[0006] While that prior cover securement operates satisfactorily in many respects, it is disadvantaged in that if the closed container should be dropped onto a hard surface, the bracket may move away from it's over-center position due to inertia. Resultantly, the hook member may become disengaged from the base container thereby allowing the cover to separate from the base container so that the contents of the container can spill onto the floor.

[0007] As an improvement to that over center-type latch arrangement, we developed a safety clasp assembly disclosed in U.S. Pat. No. 5,706,968. It comprises a rocker, an axle pivotally connecting the rocker to the container cover and a slider positioned between the axle and the cover. The slider is slidable along the cover in a direction perpendicular to the axle between a locked position wherein the slider interfits with the base container and an unlocked position wherein the slider is disengaged from that container. When the slider is in its locked position, portions of the rocker and slider interfit preventing movement of the latter. In order to move the slider to its unlocked position, the rocker has to be rocked about its axle against a spring bias to disengage the rocker from the slider allowing the latter to move to be moved to its unlocked position.

[0008] While that safety clasp assembly has definite advantages over the then prior art, it also has a few drawbacks. More particularly, the container cover has to be modified to form eyes in the container cover to anchor the axle ends of each clasp assembly. Also, some people find it difficult to move simultaneously both the rocker and the slider as necessary to release the clasp using only one hand. Resultantly, some people have been reluctant to use sterilization trays incorporating such clasp assemblies.

[0009] Accordingly, it would be desirable to be able to provide securing means for reliably releasably securing a cover to a sterilization tray or other base container, which is easy to operate using only one hand, yet does not require modification of the cover or container.

[0010] Accordingly, it is an object of the present invention to provide an improved latch assembly for releasably securing a cover to a sterilization tray or other such base container.

[0011] Another object of the invention is to provide a latch assembly of this type which can be moved between its latched and unlatched positions quite easily only using one hand.

[0012] Another object of the invention is to provide such a latch assembly which is relatively easy and inexpensive to make and to assemble.

[0013] A further object of the invention is to provide a latch assembly of this general type which can be installed on a conventional cover without requiring any appreciable modification of the cover or container.

[0014] A further object of the invention is to provide a latch assembly which signals when it is in its latched and unlatched conditions.

[0015] Other objects will, in part, be obvious and will, in part, appear hereinafter.

[0016] The invention accordingly comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the following detailed description, and the scope of the invention will be indicated in the claims.

[0017] Briefly, the present latch assembly for securing a cover to a container comprises a base for mounting to the container cover adjacent to an edge thereof, a cover member secured to the base and a slider slidable along a passage between the base and cover member between a latched position wherein a portion of the slider interfits with the container and an unlatched position wherein the slider portion is disengaged from the container. A headed spring member interposed between the slider and the base resiliently interfits with holes in the slider to signal when the slider has reached its latched and unlatched positions and to releasably retain the slider at those positions.

[0018] For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in connection with the accompanying drawing, in which:

[0019] FIG. 1 is a perspective view with parts broken away of an instrument sterilization tray having latch assemblies incorporating the invention;

[0020] FIG. 2 is an exploded perspective view on a larger scale showing in greater detail the components of each latch assembly in the FIG. 1 tray;

[0021] FIGS. 3A and 3B are sectional views on a larger scale taken along line 3A—3A of FIG. 1, showing the latch assembly in its latched and unlatched conditions, respectively;

[0022] FIG. 4 is a view similar to FIG. 2 of the components of a second latch embodiment, and

[0023] FIG. 5 is a sectional view showing the components of the FIG. 4 latch embodiment in their assembled condition.

[0024] Refer now to FIG. 1 of the drawings which shows a generally rectangular surgical instrument sterilization tray 10. Tray 10 is composed of a relatively deep base container 12 having a pair of opposite sidewalls 12a,12aand a pair of opposite endwalls 12b,12b.The top of the base container 12 is normally open but may be closed by a cover 14 having a pair of opposite sidewalls 14a,14a,and a pair of opposite endwalls 14b,14b.When cover 14 is seated on container 12, the cover walls 14a,14b,overlap or interfit with the corresponding container walls 12a,12b.Preferably, container 12 and cover 14 are made of a strong impact-resistant plastic material able to withstand sterilization temperatures. Preferably also, the cover and/or the base container is formed with a multiplicity of holes 16 through which steam may circulate when instruments in tray 10 are being sterilized.

[0025] In order to releasably lock cover 14 to container 12, the tray 10 is provided with a pair of mirror-image latch assemblies shown generally at 20 situated at opposite ends of the tray. Latch assemblies 20 lock cover 14 to base container 12 during the sterilization process and during handling. However, the assemblies 20 can be released easily by operating room personnel, using only one hand, when it is necessary to remove cover 14 in order to use the sterilized instruments in container 12.

[0026] Each latch assembly 20 is secured by fasteners 22 to cover 14 near an endwall 14bthereof and is adapted to releasably interfit with the underlying endwall 12bof base container 12 when the assembly is in its locked position shown in FIGS. 1 and 3A and to be spaced and disengaged from that container endwall when the assembly is in its unlocked position shown in FIG. 3B.

[0027] As best seen in FIG. 2, each assembly 20 comprises four main parts which are stacked one on top of the other. More particularly, the assembly includes a base shown generally at 28 which may be an essentially flat, generally rectangular, metal plate formed with a relatively long center segment 28awhich may be raised relative to a pair of opposite end segments 28b.Fastener holes 32 are present at the four comers of base 28 in segments 28band a relatively large, generally rectangular window or hole 34 is present in the raised segment 28afor reasons that will become apparent.

[0028] The second component of assembly 20 is a spring member shown generally at 36. Member 36 is essentially a thin flat plate preferably of a metal such as spring steel. The spring member 36 has more or less the same dimensions as the raised segment 28aof base 28. Member 36 is also notched to form a pair of generally rectangular, full-width end sections 36a,36a,which bracket a narrower laterally extending section or tab 36b.When spring member 36 is centered on the raised segment 28aof base 28, tab 36bis cantilevered out over the window or hole 34 in raised segment 28a.As shown in FIG. 2, for reasons that will become apparent, a raised head or protuberance 38 is formed adjacent to the free edge of tab 36b.That head may be a blind fastener inserted through tab 36bor the head may be created by deforming tab 36bto form a mesa or rib or by adhering, welding or brazing the head to the tab. In any event, head or protuberance 38 should be on the side of the spring member 36 facing away from base 28.

[0029] Still referring to FIG. 2, the third element of latch assembly 20 is a slider shown generally at 42. The illustrated slider is a stamped metal part having a generally rectangular top wall 42awhose length is comparable to that of the base segment 28aand whose width is appreciably greater than that segment. The slider also includes an integral hook 42bwhich extends down from a long edge of top wall 42a.The hook has one or more legs 42cextending back parallel to top wall 42afrom a location spaced appreciably below that wall. Also, slider 42 is formed with a lip 42dat the opposite long edge of top wall 42a.The lip may extend up as shown in solid lines in the drawings or down as shown in phantom in FIG. 3A. As we shall see, lip 42dprovides a finger grip for operating the latch assembly.

[0030] Positioned more or less midway along the length of top wall 42aof slider 42 is a is pair of holes or dimples 44aand 44bopening to the underside of the slider. These holes or dimples are spaced apart laterally on wall 42aso that when the slider 42 is centered on the spring member 36, the imaginary line extending between holes or dimples 44aand 44bis aligned with the head 38 on spring member 36.

[0031] The final component of latch assembly 20 is a cover member shown generally at 46 in FIG. 2. Cover member 46 is a stamped metal part having a raised central segment 46abracketed by two end segments 46b.The width of raised segment 46ais comparable to that of the raised segment 28aof base 28. However, its length is slightly greater than that of base segment 28a.As with base 28, fastener holes 48 are provided at the four corners of cover member 46 in the end segments 46bthereof.

[0032] When the latch assembly parts shown in FIG. 2 are properly assembled as seen in FIGS. 3A and 3B, they are stacked one above the other such that the holes 48 in the cover member 46 line up with the corresponding holes 32 in the base 28 and such that the spring member tab 36boverlies the window 34 in the base member. During such assembly, the spring member 36 is preferably spot-welded or otherwise secured to base segment 28aby spot welds 58 (FIG. 4) to fix the relative positions of those parts. Likewise, after cover member 46 is properly aligned with base 28, those two members may be permanently secured together by spot-welds 49 (FIG. 1) at end segments 46band 28b.In that completed assembly, the holes 48 in the cover member 46 and the holes 32 in the base 28 are in alignment to receive the fasteners 22 that secure the latch assembly to cover 14 as shown in FIG. 1.

[0033] Also when the parts are assembled, the spring tab 36bis deflected downward by the engagement of the head 38 against the underside of the slider so that the head is biased upward. The window or hole 34 in base 28 provides clearance for the deflected tab 36b;see FIG. 5.

[0034] When the latch assembly 20 is in its latched condition shown in FIGS. 1 and 3A, slider 42 is positioned inwardly on the tray cover 14 so that the slider hook 42bis close enough to the corresponding endwall 12bof container 12 that the hook leg(s) 42cproject through slot(s) 50 formed in that wall. This interfitting engagement of the slider with the container endwall prevents cover 14 from becoming separated from container 12.

[0035] As noted previously, the head 38 on the spring tab 36bis biased upwardly against the underside of slider 42. Therefore, when the slider reaches its latched position shown in FIG. 3A, the head 38 snaps into the hole or dimple 44ain the underside of the slider top wall 42athereby providing an audible and tactile signal that the slider is in its latched position. Also, the resilient engagement of the head 38 in hole or dimple 44areleasably retains the slider in its latched position. Overtravel of the slider in the latching directing is prevented by the engagement of slider hook 42bagainst the adjacent side edge of the base which edge thus functions as a stop.

[0036] To unlock latch assembly 20 in order to remove cover 14 from base container 12, the operator, using a thumb or finger, exerts an outward force on slider lip 42dthat is sufficiently strong to overcome the bias of spring tab 36band dislodge head 38 from hole or dimple 44a.The outward motion of the slider retracts the hook leg(s) 42cfrom slot(s) 50 in the base endwall 12bas shown in FIG. 3B. When the slider reaches its unlatched position, the head 38 on spring member 36 will snap into the other hole or dimple 44bin the underside of the slider top wall 42athereby providing an unlatch signal and releasably retaining the slider in its unlatched position. Overtravel of the slider beyond that position is prevented by the engagement of lip 42dagainst the adjacent side edge of cover member 46 (or base 28) which edge thus functions as a stop.

[0037] When all of the components of latch 10 are made of metal as described above, there may be a tendency for the head 38 to wear a track in the underside of slider portion 42abetween holes or depressions 44aand 44bafter prolonged use of the latch. FIGS. 4 and 5 depicted a latch assembly 51 which avoids that potential problem.

[0038] Latch assembly 51 comprises a flat metal base 52 formed with a central window or depression 54 and corner fastening means 56 which in this case are fastener holes 56aat the forward comers of the base and hooks 56bat the rear corner thereof which help to secure the latch assembly to the associated tray cover as will be described later.

[0039] Centered on base 52 and secured thereto by spot welds 58 is a flat spring member 62 having a cantilevered tab 62aoverlying the window or depression 54 in the base 52. Tab 62ais deformed to form a raised rib 64 adjacent to the free end of the tab.

[0040] Latch assembly 51 also includes a slider 72 which is similar to slider 42 except that it has a large rectangular opening 74 in its top wall 72ain lieu of holes or depressions 44a,44b.Seated in opening 74 is an insert 76 which is shaped like a capitol letter I in that it is formed with a pair of aligned notches 78aand 78bbetween its ends leaving a narrow strip portion 78cbetween the notches, all of which define with the edge of the slider opening 54 a pair of holes or recesses in the underside of the slider as a whole. Preferably insert 78 is of a relatively rigid plastic material having a low coefficient of friction, such as ultra high molecular weight polyethylene or polytetrafluorethylene.

[0041] The final component of latch assembly 51 is a cover member 82 which is similar to cover member 46 shown in FIG. 2 except that it has corner fastening means 84 in the form of holes 84aat its front comers and hooks 84bat its rear comers. As with assembly 10, when cover member 82 is superimposed on, and secured by spot-welds 49 (FIG. 1) to, the base 52 with slider 72 in between, the fastening means 84 are in register with the similar means 56 on base 52. The latch assembly 51 is secured to the top of tray cover 14 by engaging hooks 56b,84bin slots present in a raised rib R extending around the top of cover 14 as shown in phantom in FIG. 1.

[0042] Latch assembly 51 operates in the same way as assembly 10. That is, when the slider is in its locked position, the rib 64 on spring tab 62aengages in the insert notch 78aand when the slider is in its unlocked position, the rib 64 seats in notch 78b.When the slider is moving between those two positions as shown in FIG. 5, the rib 64 makes line contact with, and slides along the underside of, the strip portion 78cbetween notches 78aand 78b,of the plastic insert 78, the base window 54 providing clearance for the deflected spring member tab 62aas shown in that figure. Due to the relatively large area line contact of rib 64 with the low friction insert 78, there is minimal wear of the insert due to the repetitive sliding motion of the slider 72.

[0043] Of course it is also possible to make slider 72 in its entirety (as well as, perhaps, the other latch components) of a strong low friction plastic material such as polyphenyl sulphone, in which case the insert 78 would be integrated right into the slider; i.e., the notches 78a,78bwould be formed as holes or depressions in the plastic slider 72.

[0044] The latch assemblies described herein are composed of a minimum number of parts which are easy and inexpensive to make in quantity. Therefore, the assembly should not appreciably increase the overall cost of the sterilization tray on which it is installed. Furthermore, such installation does not require any alteration in the basic design of the tray to accommodate the assembly.

[0045] It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained. Also, certain changes may be made in the above construction without departing from the scope of the invention. For example, the holes 34, 44aand 44bcould be depressions instead of through holes and still fulfill their stated purposes. Also, the hook 42bof each assembly could just as well engage under a projection or ledge on the corresponding container endwall 12b.Therefore, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

[0046] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention described herein.