Adjustable strap fastener

A molded strap fastener of a generally rectangular shape includes a first cross bar for retaining therearound a looped end portion of a strap, a retainer portion disposed laterally adjacent to the cross bar and frictionally engageable with the strap end portion, and a second cross bar fixedly connected to the other strap end. The first cross bar includes a pair of diametrically opposite sharp corners and the retainer portion has a sharp corner, these sharp corners serving as stops to retain the strap in position against accidental displacement even under heavy tensioning forces. To provide a greater resistance to strap loosening, the first and second cross bars lie in different levels so that a rotational force is created upon the fastener when the latter is in actual use, said force growing greater the larger the tension and thus urging the retainer portion to firmly grip the strap end at its sharp corner. This gripping is further enhanced by the retainer portion which projects beyond the bottom surface of the fastener.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a strap fastener for adjustably connecting a 
strap, belt or band to a variety of articles. 
2. Prior Art 
Various adjustable strap fasteners or buckles have been proposed which may 
be manipulated to adjust the effective length of a strap attached to for 
example a bag or a safety seat belt. 
Advanced such fasteners are made of a plastic material formed into an 
integrally molded structure which generally comprises a pair of opposing 
side flanges, a grip end portion at one end of the side flanges, an anchor 
end portion at the opposite ends of the side flanges and a plurality of 
parallel cross bars disposed in between the grip and anchor end portions 
and extending transversely across and between the side flanges. In use, 
one end portion of a strap or the like is looped about one of the cross 
bars, passed under the anchor end of the fastener and secured in place as 
by riveting. The other end portion of the strap which is adapted for 
length adjustment is looped about another cross bar, passed under the grip 
end of the fastener and gripped therebetween against displacement. For 
ease of insertion of the strap between the cross bar and the grip end 
portion, the gap therebetween is desirably the larger the better. 
Conversely, however, the larger the gap, the tendency will be greater for 
the strap to get loose under tension. Vice versa, this tendency is less 
the smaller the gap, but the insertion of the strap becomes more 
difficult. 
A proposition has been made whereby the gap defining surfaces are inclined 
progressively toward the reverse side of the fastener, instead of 
enlarging the insertion gap, as disclosed in Japanese Patent Laid-open 
(Kokai) Publication No. 54-144244. Such an attempt is however still not 
satisfactory in that the strap is more difficult to insert or otherwise 
manipulate. 
SUMMARY OF THE INVENTION 
The present invention seeks to provide an adjustable strap fastener which 
enables easy insertion of a strap or the like and is highly resistant to 
stresses tending to loosen the strap. 
More specifically, the present invention seeks to provide an adjustable 
strap fastener which has multi-point stops to retain the strap in position 
against accidental movement even under heavy tensioning forces. 
The present invention further seeks to provide an adjustable strap fastener 
which has a relatively wide opening or gap to permit insertion or 
adjustment of the strap with utmost ease. 
A molded strap fastener of a generally rectangular shape includes a first 
cross bar for retaining therearound a looped end portion of a strap, a 
retainer portion disposed laterally adjacent to the cross bar and 
frictionally engageable with the strap end portion, and a second cross bar 
fixedly connected to the other strap end. The first cross bar includes a 
pair of diametrically opposite sharp corners and the retainer portion has 
a sharp corner, these sharp corners serving as stops to retain the strap 
in position against accidental displacement even under heavy tensioning 
forces. To provide a greater resistance to strap loosening, the first and 
second cross bars lie in different levels so that a rotational force is 
created upon the fastener when the latter is in actual use, said force 
growing greater the larger the tension and thus urging the retainer 
portion to firmly grip the strap end at its sharp corner. This gripping is 
further enhanced by the retainer portion which projects beyond the bottom 
surface of the fastener. 
Many other advantages and features of the present invention will become 
manifest to those versed in the art upon making reference to the detailed 
description and the accompanying sheets of drawings in which a preferred 
structural embodiment incorporating the principles of the present 
invention is shown by way of illustrative example.

DETAILED DESCRIPTION 
FIGS. 1 through 7 show an adjustable strap fastener generally designated 10 
according to the present invention. 
The strap fastener 10 is made of a plastic material formed into an integral 
molded construction generally rectangular in shape as shown in FIGS. 1 and 
2. The strap fastener 10 comprises a grip head portion 11 at one of its 
end, a connecting portion 12 at the other ends, a pair of opposed side 
flange portions 13, 14 extending longitudinally between opposite ends of 
the head portion 11 and the connecting portion 12, a first or strap 
turn-over cross bar 15 adjacent to the head portion 11 and a second or 
strap anchoring cross bar 16 adjacent to the connecting portion 12, the 
cross bars 15 and 16 extending in spaced parallel relation to each other 
between and connected to the opposed side flanges 13 and 14. 
The head portion 11, as better shown in FIG. 4, includes an apertured 
flared projecting tab 11a, and a strap retainer portion 11b extending 
therefrom downwardly substantially at a right angle to the plane of the 
fastener 10 adjacent to the first cross bar 15, the retainer portion 11b 
terminating with a flat bottom end surface 11c projecting a small distance 
D.sub.1 beyond the bottom surfaces of the opposed side flanges 13, 14 for 
reasons hereafter to be described. The retainer portion 11b has a sharp 
corner 11d defined by the flat bottom surface 11c and a flat side surface 
11e which extends perpendicularly to the general plane of the fastener 10. 
The sharp corner 11d serves as a first strap stop as later described. The 
connecting portion 12 has a lowermost surface lying flush with the flat 
bottom surfaces 13a, 14a of the flange portions 13, 14. 
The strap anchoring bar 16 is positioned slightly above the connecting 
portion 12 as viewed from the side elevation or as shown in FIG. 4. The 
strap turn-over bar 15 is positioned slightly above the anchoring bar 16 
and closer to the upper surface of the flanges 13, 14 so as to make the 
strap S between the turn-over bar 15 and the bottom surface 11c run 
substantially parallel with the retainer portion 11b or at a right angle 
to the general plane of the fastener 10. 
The turn-over bar 15, as better shown in FIG. 4, includes a pair of 
integral top and bottom portions 15a, 15b displaced from one another in a 
direction parallel to the side flange portions 13 so as to provide a pair 
of first and second projections 15a', 15b'. The first projection 15a' 
extends toward the grip head portion 11 and terminates in a second sharp 
corner edge 15e which is defined jointly by a flat bottom surface 15c and 
an arcuate top surface 15c', while the second projection 15b' extends 
toward the connecting portion 12 and terminates in a third sharp corner 
edge 15f which is defined jointly by a flat top surface 15d and an arcuate 
bottom surface 15d'. The flat bottom surface 15c of the first projection 
15a' and the flat top surface 15d of the second projection 15b' extend in 
opposite directions from substantially the midpoint of the thickness of 
the bar 15 and in a plane substantially parallel to the general plane of 
the fastener 10. The second sharp corner edge 15e is spaced from the 
vertical plane of first sharp corner edge 11d by a distance D.sub.2 larger 
than the thickness of the strap S to facilitate insertion of the latter. 
The second and third sharp corner edges 15e, 15f serve respectively as 
second and third stops to retain the strap S thereof against unintentional 
movement. The turn-over bar 15 includes a plurality of elongated recesses 
15g extending along the bottom portion 15b at longitudinal intervals for 
saving the amount of plastic material used. 
FIGS. 5-7 show the behavior of the strap or belt S with respect to the 
fastener 10, in which the strap S is inserted into the strap fastener 10, 
first with one of its ends S.sub.1 looped about the anchoring bar 16 and 
passed underneath the connecting portion 12, the extension of the strap S 
at this end being secured in place as by riveting or stitching. The other 
end of the strap S.sub.2 is looped about the turn-over bar 15 and passed 
underneath the retainer portion 11b of the head 11, in which instance the 
leading end portion of the strap S.sub.2 is brought into contact with the 
flat bottom surface 11c of the grip head portion 11. 
While the strap end S.sub.1 is held stationary, the strap end S.sub.2 is 
adjustable in length to suit the particular application. This adjustment 
may be made by pulling out the leading strap end S.sub.2 to thereby 
shorten the effective length of the strap S, or by rotating the fastener 
10 counter-clockwise about the connecting portion 12 as shown in FIG. 7 to 
release the strap end S.sub.2 and pulling the strap S out to thereby 
shorten or shoving the strap in to thereby lengthen the effective length 
of the strap S as desired. This rotation can be done most conveniently by 
handling the flared tab 11a of the grip head 11. 
The strap fastener 10 thus constructed is, as shown in FIGS. 5 and 6, 
provided with multi-point stops, namely, at corners 11d, 15e and 15f along 
the path of the strap S.sub.2 ', so that the strap S is firmly held in 
place against shifting which would otherwise occur under the influence of 
heavy stresses applied in use. 
The relative positions, in which the turn-over bar 15 lies at a level above 
the anchoring bar 16 and the anchoring bar 16 lies above the connecting 
portion 12 in a cascade fashion, create a clockwise rotational force upon 
the strap fastener 10 when in actual use as shown in FIG. 6, such force 
growing greater the larger the tension and thus urging the retainer 
portion 11b to firmly grip the strap S.sub.2 at the first stop 11d. 
At the same, this gripping is further enhanced by the fact that a run of 
the strap S between the projecting surface 11c of the head 11 and the 
turn-over bar 15 is substantially parallel with the vertical retainer 
portion 11b, that is, substantially perpendicular to the general plane of 
the strap fastener 10, so that the strap S.sub.2 is also caught and 
gripped by the second stop 15e. To further ensure firm retention of the 
strap S, the bottom end surface 11c of the retainer portion 11b is 
corrugated to have a plurality of grooves 11f extending parallel to the 
flanges 13, 14, thereby imparting frictional grip upon the strap S. 
The multi-point stop arrangement (11d, 15e and 15f) together with the 
presence of added length D.sub.1 of the retainer portion 11b will permit 
an increase in the space D.sub.2 for passage of the strap S whereby it is 
rendered extremely easy to thread the strap S through the fastener 10. 
Although various minor modifications may be suggested by those versed in 
the art, it should be understood that I wish to embody within the scope of 
the patent warranted hereon, all such embodiments as reasonably and 
properly come within the scope of my contribution to the art.