Strap fastener

A strap fastener for releasably connecting a strap, cord or belt on a garment article is disclosed, the fastener comprising a base member, a strap retainer member and a slider. The base member has an upper plate and a lower plate defining therebetween a guide channel through which the slider is movable. The slider has a guide rail at such a lower edge of a side flange which lies above the lower surface of the base member. A hook is formed, extending integrally from the lower plate of the base and releasably engageable with the slider through a ridge-and-groove formation alternately provided on the hook and the slider.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a strap fastener for releasably connecting a 
strap, cord or belt on a garment article such as a bag, sack, sports wear 
and the like. 
2. Prior Art 
There are known numerous fastening devices for releasably connecting 
opposite terminal ends of an elongate strap or belt attached to a bag or 
other garment articles. A typical example of one such fastening device 
over and relating to which the present invention contemplates an 
improvement is disclosed in Japanese Patent Publication No. 62-39285 in 
which it was proposed to use a fastening device in the form of a plastic 
snap hook engageable with a ring attached to a handbag, a sack or the 
like. The snap hook is comprised of a base member having at one of its 
ends a folded-back hook portion, at the other end a resilient plate-like 
tongue portion and a slider movable over and along the tongue portion 
between a position in which the hook is open and a position in which the 
hook is closed, the arrangement being that the slider is urged by the 
resilient force of the tongue normally toward the hook to close the latter 
and moved by the wearer's fingers against the tension of the tongue 
retractively away from the hook to open the latter. Since the slider is 
arranged to reciprocate with its lower peripheral wall protruding beyond 
the lower surface of the base member, the portion of the snap hook at 
which the slider is connected to the base member becomes objectionably 
thick and bulky making the whole device look unsightly, a disadvantage 
particularly where the snap hook is used in connection with a ladies' 
shoulder-bag or similar ornamental garment article. Another drawback of 
the prior art device is that since the plate-like tongue yields a 
relatively strong resilient action upon the slider to urge the latter into 
snapping engagement with the hook, so much finger pressure is required to 
retract the slider away from the hook to provide an opening for inserting 
therethrough the connecting ring of the bag. 
SUMMARY OF THE INVENTION 
The present invention seeks to provide a strap fastener which has 
structural features such that will eliminate or alleviate the foregoing 
drawbacks of the prior art and which is relatively simple in construction 
and reliable in operation. 
More specifically, the invention seeks to provide a strap fastener 
comprised of a slider and a hook which requires a relatively small amount 
of force to move the slider away from the hook and which has a relatively 
low structural profile leading to attractive product appearance. 
The invention further seeks to provide a strap fastener comprised of a 
slider and a hook which includes means of holding the slider and the hook 
securely in interengaged relation against torsional stresses. 
The above and other objects and features of the invention will be better 
understood from the following detailed description taken in connection 
with the accompanying drawings which illustrate by way of example a 
preferred embodiment. 
According to the invention, there is provided a strap fastener which 
comprises: a base member having an upper plate and a lower plate spaced 
apart from each other to define therebetween a guide chamber, the upper 
plate having a pair of slits and a pair of cantilevered resilient strips 
elastically deformably supported therein; a strap retainer member 
connected to one end of the base member for receiving and retaining a 
loose end of a strap; a hook connected to the opposite end of the base 
member and extending integrally from the lower plate; and a slider having 
a base plate having side flanges including inwardly directed guide rails 
slidably movable in the guide channel and lying above the lower surface of 
the base member, a ledge extending integrally centrally from the base 
plate between the side flanges and releasably engageable with the hook and 
a pair of spaced engaging ribs diverging toward the ledge and adapted to 
engage the resilient strips.

Like reference numerals refer to like or corresponding parts throughout the 
several views. 
DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings and FIG. 1 in particular, there is shown a 
strap fastener 10 which essentially comprises a support base member 11, a 
strap retainer member 12 connected to one end of the base member 11 and a 
slider member 13 slidably mounted on the base member 11, all these 
component members being formed from a suitable plastic material to enable 
certain of their operative parts to undergo elastic deformation as 
hereinafter described. 
The base member 11 is in the form of a rectangular casing having an upper 
plate 14 and a lower plate 15 spaced apart in parallel to define 
therebetween a guide channel 16 which is subdivided into identical halves 
(FIG. 3) by a partition wall 17 extending centrally longitudinally of the 
base 11 and joining together the upper and lower plates 14, 15. 
A connecting bar 18 is formed, extending integrally transversely of the 
base 11 at one end thereof and provided with a transverse pin 19 
projecting slightly from opposite ends of the bar 18. 
The strap retainer member 12 has a pair of arms 20, 20 interconnected at 
one ends thereof by a transverse cross bar 21 and provided at the opposite 
ends with bores 22, 22 for receiving rotatably therein the pin 19 of the 
connecting bar 18. The cross bar 21 extends in parallel spaced relation to 
and defines with the connecting bar 18 an elongate transverse slot 23 for 
receiving and retaining one loose end of a strap or belt S (FIG. 8). 
At the opposite end of the base 11 remote from the connecting bar 18 is 
formed a resilient tongue 24 which extends integrally from the lower plate 
15 of the base 11 and is folded back to form a hook 25 at a level higher 
than the guide channel 16 (as better shown in FIG. 6) for engagement with 
a mating strap retainer or coupling device 26 (FIG. 8). The hook 25 is 
provided at its distal end with an engaging ridge 25a and a pair of 
engaging grooves 25b, 25b on opposite sides thereof as better shown in 
FIG. 3. 
The upper plate 14 of the base 11 is provided adjacent to an end thereof 
remote from the connecting bar 18 with a pair of spaced parallel elongate 
slits 27, 27 each consisting of a wide portion 27a and a narrow portion 
27b. 
A pair of relatively thin cantilevered resilient strips 28, 28 integral 
with the upper plate 14 of the base 11 extend in parallel relation within 
the wide portions 27a, 27a and terminate short of the narrow portions 27b, 
27b of the respective slits 27, 27. The cantilevered resilient strips 28, 
28 have respective prongs 28', 28' directed inwardly toward each other for 
purposes hereinafter to be described. 
The slider member 13 generally in the form of a rectangular bottomless box 
comprises a base plate 29 and a pair of inwardly arcuately curved side 
flanges 30, 30 integral therewith having respective inwardly directed 
guide rail portions 30a, 30a defining with the lower surface of the plate 
29 respective guide recesses 30b, 30b dimensioned to receive opposite 
longitudinal edges 14' of the upper plate 14. Thus, the slider 13, when 
mounted on the base 11, is slidably movable along the base 11 with its 
flanges 30, 30 held astride the longitudinal edges 14' of the plate 14 and 
with its guide rail portions 30a, 30a received within the guide channel 16 
lying above and not protruding beyond the lower surface of the base 11, 
the arrangement being contributory to reduction in the thickness of the 
strap fastener as a whole, leading to a relatively low profile as better 
shown in FIG. 6. 
At one or front end of the slider 13 is formed a ledge 31 protruding 
centrally from one end of the plate 29 between the two side flanges 30, 30 
and having at its distal end an engaging groove 31a and a pair of engaging 
ridges 31b, 31b on opposite sides thereof, the groove 31a and the engaging 
ridges 31b, 31b being dimensioned to be fittingly interengageable with the 
ridge 25a and the grooves 25b, 25b, respectively, of the hook 25 as shown 
in FIGS. 5, 6 and 7, this ridge and groove formation constituting a means 
according to the invention for holding the slider 13 and the hook 25 
securely in interengaged relation against torsional stresses which would 
otherwise result in separation of the slider 13 from the body of the strap 
fastener 10. 
The slider 13 is further provided in the lower surface of its plate member 
29 with a pair of spaced engaging ribs 32, 32 diverging toward the ledge 
31 and having outer guide surfaces 32', 32' as shown in FIG. 4, the ribs 
32, 32 being adapted to engage receptively in the respective slits 27, 27 
formed in the upper plate 14 of the base 11. 
With this construction, the slider 13 is mounted on the base 11 of the 
strap fastener 10 by bringing the engaging ribs 32, 32 into registry with 
corresponding slits 27, 27 and depressing the slider 13 so that the ribs 
32, 32 engage resiliently with respective resilient strips 28, 28 in the 
slits 27, 27, in which instance the guide rails 30a, 30a is likewise 
resiliently received in and rendered movable along the guide channel 16 of 
the base 11. Consequently, the slider 13 is urged to move forward toward 
the tongue 24 under the influence of biasing action of the resilient 
strips 28, 28 tending to urge the ribs 32, 32 to move all way up till they 
abut against the end walls of the slits 27, 27 in the narrow portions 27b, 
27b thereof, at which time the ledge 31 of the slider 13 is coupled 
together with the hook 25 on the base 11 with ridge 25a and grooves 25b, 
25b interengaged with mating groove 31a and ridges 31b, 31b, respectively, 
as illustrated in FIGS. 5 and 6, thus closing a gap 33 between the ledge 
31 and the hook 25 which would otherwise be open for inserting the 
coupling device 26 (FIG. 8). 
When connecting the mating coupling device 26 to the strap fastener 10 of 
the invention as despicted in FIG. 8, this is done by moving the slider 13 
backward toward the connecting bar 18 of the base 11 with the wearer's 
fingers gripping the side flanges 30, 30 and/or a transverse groove 34 in 
the upper surface of the slider 13. This retractive movement of the slider 
13 causes the ledge 31 to disengage from the hook 25 to reveal the gap 33 
therebetween and simultaneously the resilient strips 28, 28 to elastically 
spread against their tension within the wide portions 27a, 27a of the 
slits 27, 27 as the engaging ribs 32, 32 slide back with their guide 
surfaces 32', 32' held in contact with the prongs 28', 28' of the 
resilient strips 28, 28, as shown in FIG. 7. 
Releasing the finger pressure will allow the resilient strips 28, 28 to 
restore to the original position by their own resiliency whereby the 
engaging ribs 32, 32 are biased to move forward and snap into the narrow 
portions 27b, 27b of the slits 27, 27 until the gap 33 is closed, as shown 
in FIGS. 5 and 6. 
In the above reciprocating movement of the slider 13 relative to the base 
11, it is to a great advantage that a pull force required to retract the 
slider 13 is very small compared to the prior art discussed at the outset 
of this specification and that the provision of alternate ridge and groove 
engagement (25a, 25b, 25b, and 31a, 31b, 31b) of the ledge 31 with the 
hook 25 ensures freedom of deformation of these parts when subjected to 
torsional stresses. 
Reference to FIGS. 9 and 10 shows a modified form of strap fastener 10' 
according to the invention. This modified strap fastener 10' differs from 
the first advanced strap fastener 10 in that the base member 11 is made 
rotatable relative to the retainer member 12 so that the strap S wound on 
the cross bar 21 can be held free from getting twisted when external 
stresses are applied to the fastener 10'. The base member 11 is provided 
at one end thereof with a circular flange 34 for abutting engagement with 
the connecting bar 18 and an engaging pin 35 integral with the flange 34 
and extending axially of the base member 11. As better shown in FIG. 10, 
the pin 35 is subdivided internally by a criss-cross slit 36 into four 
sections 35a-35d which are rendered radially contractible and expansible. 
As viewed in FIGS. 9 and 11, the pin 35 is divided externally into an 
upper larger annular portion 35e and a lower smaller annular portion 35f, 
the upper annular portion 35e having a lower peripheral edge 35g extending 
circumferentially slightly beyond the lower annular portion 35f, and the 
lower annular portion 35f having a circumferentially protruding annular 
rib 35h. 
The connecting bar 18 is provided centrally with a transversely extending 
annular aperture 37 which is divided into an upper larger-diameter portion 
37a and a lower smaller-diameter portion 37b, the upper portion 37a having 
its lower peripheral edge radially inwardly directed as defined by an 
annular projection 38 of the inner wall of the aperture 37. 
The base member 11 is pivotably connected to the retainer member 12 by 
inserting the engaging pin 35 into the aperture 37 until the flange 34 
rests against the connecting bar 18, in which instance the upper annular 
portion 35e of the pin 35 contracts on passage through the lower portion 
37b of the aperture 37 and expands to its original dimension upon entry 
into the upper portion 37a of the aperture 37, when the peripheral edge 
35g of the pin 35 is seated on the annular projection 38 of the aperture 
wall. 
The base member 11 thus connected to the retainer member is allowed to 
rotate through 360.degree., in which instance the annular rib 35h around 
the lower portion 35f of the pin 35 is held in contact with the wall of 
the lower portion 37b of the aperture 37 and serves to prevent the lower 
subdivided section 35c and 35d from collapsing. 
The modified strap fastener 10' further features the provision of toothed 
side flanges 39, 39 in place of the arcuately curved flanges 30, 30 for 
facilitating the manipulation of the slider member 13 as shown in FIG. 9. 
Obviously, various modifications and variations of the present invention 
are possible in the light of the above teaching. It is therefore to be 
understood that within the scope of the appended claims the invention may 
be practiced otherwise than as specifically described.