Molded plastic snap-on latch for plastic receptacle

A molded plastic latch structure for molded two-part receptacles comprising a base and a cover forming a closure for various types of articles, wherein the latch structure includes opposed mounting lug and latching post members adjacent the confronting edges of the receptacle base and cover, and a latching buckle adapted to be secured to the lug member against accidental detachment from the base or cover, wherein the buckle incorporates a flexible bail for releasable engagement with the post member in the closed condition of the receptacle to maintain it in such condition.

BACKGROUND OF THE INVENTION 
This invention is directed generally to latch constructions for securing 
separable base and cover members of a receptacle or container in closed 
condition, and is more particularly directed to molded plastic latch 
constructions for molded plastic receptacles. The invention constitutes an 
improvement over the latch construction shown in my prior U.S. Pat. No. 
3,730,576. 
As discussed in the foregoing patent, blow molding of separate receptacle 
base and cover members provides an effective and economical way of 
fabricating a separable closure for a variety of articles. Particularly 
where the molded members are of the conventional double-wall construction, 
the blow molding technique provides an excellent way of matching the 
configuration of the receptacle base and cover to the particular shape of 
the article or articles to be contained. The double-wall construction 
facilitates receptacle design of suitably smooth or regular exterior 
surface, yet may be configured internally to produce retaining wells or 
abutments to accommodate the contour of the article contained, so as to 
securely restrain it against movement within the receptacle when closed. 
This is of great advantage for packaging tools, test instruments, 
electronic equipment and the like which are subject to damage during 
storage and transport. Double-wall constructions also provide a shock 
resistant cushion against damage to contained articles if the receptacle 
is dropped or is exposed to sudden contact with surrounding objects. The 
trade is familiar with these and other advantages of double-walled blow 
molded receptacles, but experience has indicated the desirability of 
further improvement in the latch constructions which have previously been 
used to maintain the cover and base members in closed condition. A need 
for improved latch constructions is indicated in not only maintaining the 
economical compatibility of the previous constructions with blow molded 
containers, but in giving greater assurance against accidental detachment 
or failure under load. In the latch construction disclosed in my aforesaid 
patent, the means for securing the latching buckle to the receptacle 
employs a latch anchor bar on the container and a continuous slot in the 
buckle, with interference nibs along opposite sides of the slot which snap 
over the head of the anchor bar. Resilient compressibility of the plastic 
material of the head of the anchor bar and nibs of the buckle is relied 
upon to permit the attachment to be made. But this inherent resiliency of 
the plastic also allows for detachment to occur, so a compromise must be 
made in determining the degree of interference to permit attachment yet 
resist detachment. 
It is accordingly an object of this invention to provide an improved latch 
construction of the type and for the purpose above indicated, it being 
particularly desired to provide a latch which is more secure against 
accidental detachment, particularly under stress, than has been available 
heretofore but which is nevertheless simple and economical to make, and is 
also easily assembled to the container or receptacle which it serves to 
keep in closed condition. These and other objects will become apparent 
from the following description of a preferred latch construction 
incorporating the characterizing features of this invention, as embodied 
in a double wall, blow molded receptacle shown in the accompanying 
drawings.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
The improved latch structure of the invention is illustrated in FIGS. 1 and 
2 where it is shown as incorporated in a blow molded double-wall carrying 
case 10 adapted for enclosing a chain saw, for example. Case 10 is 
partible along a medial plane, being composed of a base member 12 with a 
cover member 14 which are complementary and whose confronting edges 
coincide in the medial plane. Base 12 and cover 14 are hinged along a rear 
edge, visible in FIG. 2, to permit the case to be swung open so that the 
members are disposed in side-by-side relation to give full access to the 
interior of the case for removal and replacement of the chain saw. Case 10 
when closed is maintained in such position by a pair of the latch 
structures indicated generally at 16 which bridge across the unhinged 
edges at spaced points on the front side of the case. In closed and 
latched condition, case 10 can be picked up by means of a handle 18 
secured in the upper face of cover 14 to facilitate carrying. 
FIG. 3 illustrates one of latch structures 16 in greater detail. As there 
seen, latch structure 16 bridges across the confronting edges 20, 22 of 
base and cover members 12 and 14, respectively. Latch structure 16 is 
comprised of a buckle 24 which is mounted in this case on a boss or 
mounting lug 26 molded integrally adjacent the confronting edge 22 of 
cover 14. Buckle 24 also makes detachable engagement with a latching post 
28 which in this case is molded integrally adjacent confronting edge 20 of 
base 12. 
Further details of the mounting lug and latching post are illustrated in 
FIG. 4 which is similar to that of FIG. 3 but from which the latching 
buckle has been omitted. Lug 26 protrudes outwardly of the face of cover 
14, as best seen in FIGS. 9 and 10, and is provided with cooperating 
recesses 30, 32 on the upper and lower surfaces of lug 26, extending 
parallel to confronting edge 22. Lug 26 is formed to provide a cam surface 
32, again as best seen in FIGS. 9 and 10, sloping away from confronting 
edge 22. Recesses 30 and 32 are adapted to receive and retain cooperating 
members of buckle 24, more fully described hereinafter, when the buckle is 
assembled to cover 14, and cam surface 32 facilitates such assembly of the 
buckle to the cover, as will also be further described hereinafter. 
Latching post 28 which complements mounting lug 26 of latch construction 
16, also projects forwardly from the corresponding confronting edge 20 of 
base 12, terminating flush with the forward projection of lug 26. See FIG. 
9. Latching post 28 is formed on its under surface (i.e., the surface 
remote from confronting edge 20) with a double step recess 34 providing a 
latching detent which is engageable by a bail portion of buckle 24, as 
more fully described presently, when the buckle is pressed toward the 
receptacle. 
Latching buckle 24 is illustrated more fully in FIGS. 5 through 8. Buckle 
24 is of generally flat, rectangular form having a mounting lug receiving 
aperture 36 and a latch post receiving aperture 38, each defined by a pair 
of spaced parallel side rails 40, by parallel bridging bars 42 or 44 at 
opposite ends of rails 40, and by an intermediate bar 46. 
Mounting lug receiving aperture 36 is of relatively narrow, generally 
rectangular form whose longer sides are formed by intermediate bar 46 and 
end bar 42. In width, aperture 36 is substantially less than the height or 
thickness of outer camming face of lug 26, but is substantially equal to 
the thickness of the lug between recesses 30 and 32. Bar 42 is provided 
with an arcuate tab 48 which extends into aperture 36 in the plane thereof 
such that the gap in aperture 36 at the peak of tab 48 is slightly less 
than the thickness of lug 26 between recesses 30 and 32. Each of bars 42, 
46 is here shown as being recessed or slotted on its undersurface (see 
FIG. 6) to provide lengthwise slots 50, 52, respectively, to impart 
resilience to these members transversely of their length in the plane of 
the buckle. Depending on dimensional design considerations in the several 
parts of the buckle, the recessing of the undersurface at these points and 
particularly at the intermediate bar 46 is optional. The recessing serves 
primarily to facilitate assembly of the buckle to mounting lug 26, as is 
illustrated more particularly in FIG. 10. In other words, the normal 
distance between them (i.e. the width of aperture 36) can be made 
substantially less than the outer face dimension of lug 26 and even 
slightly less than the distance between recesses 30 and 32 as mentioned 
above, so that buckle 24 is securely retained on lug 26 after it has been 
snapped into position on it. The arrangement for effecting such assembly 
of the buckle to lug 26 is illustrated more specifically in FIG. 10, which 
shows how the buckle is initially manipulated to position intermediate bar 
46 under the lower face of lug 26 with bar 46 seated in recess 30; after 
which the upper end of buckle 24 is then pressed inwardly toward the cover 
member, causing tab 48 on bar 42 to be cammed over the sloping cam surface 
32 of lug 26 until tab 48 can drop into upper recess 30 behind lug 26, 
thereby securely locking buckle 24 onto lug 26. The arcuate formation of 
tab 48 permits some rocking of the buckle during assembly, further 
facilitating assembly, yet tab 48 then increases resistance to detachment 
of the mounted buckle. 
As seen more particularly in FIGS. 5 and 10, the latch post receiving 
aperture 38 of buckle 24 is defined at its upper end by bridging bar 46 
and at its lower end by bar 44, while the portions of side rails 40 
defining the lateral sides of the buckle are of reduced thickness, 
constituting flexible straps acting with bar 44 to form a bail. End bar 44 
is provided on its undersurface with a pawl 54 adapted to make a resilient 
interference engagement with the double step recess 34 on the undersurface 
of latching post 28 when the buckle is in latched position on the 
container. See particularly FIG. 9. The double step of recess 34 provides 
extra latching security. A finger tab 56 at the underface of bar 44 gives 
an access grip for unlatching the bail of buckle 24 from latching post 28 
when the receptacle is to be opened.