Apparatus for gapping a stringer chain

An apparatus for gapping a stringer chain at predetermined intervals is disclosed, which comprises an anvil and a cutter cooperating therwith in cutting a length of coupling elements on a pair of support tapes. The cutter includes a vertically movable punch which is provided with a plurality of positioning prongs adapted to engage in between adjacent elements and hold the stringer chain firmly in place during gapping thereof.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an apparatus for gapping an elongate stringer 
chain at predetermined intervals to be assembled with various slide 
fastener component parts. 
2. Prior Art 
Generally, a substantially endless elongated stringer chain comprising a 
pair of support tapes and rows of coupling elements secured to the 
respective tapes is cut successively to predetermined lengths to provide 
individual slide fasteners. Prior to cutting, it has been a common 
practice to gap the stringer chain to form element-free portions or gaps 
at predetermined intervals along the inner longitudinal edges of the 
stringer chain, the gaps being utilized for mounting various slide 
fastener component parts such as sliders, bottom end stops and top end 
stops. The element-free portions or gaps of the stringer chain are formed 
by removing a predetermined number of coupling elements by means of a 
cutting tool having an operative edge length corresponding to a 
pre-calculated gap length. For one reason or another, the cutter would 
leave some of the endmost coupling elements half or partly cut away at 
either or both of the leading and trailing ends of the gaps, with 
resultant uncut debris interfering with a subsequent parts applying 
operation. To eliminate this problem, it has been proposed, as disclosed 
for example in Japanese Laid-Open Utility Model Publications 53-16713 and 
63-31611, to provide a positioning pawl or pin adjacent to each of the 
leading and trailing ends of a cutter for engaging the coupling elements 
and thus setting the stringer chain up in position for gapping by the 
cutter. Since such positioning pawls or pins are spaced apart from each 
other by a distance greater than the operative length of the cutter, it 
would often occur that the number of coupling elements actually existing 
between the respective positioning pawls or pins differs from a 
predetermined number of coupling elements to be removed to provide gaps of 
a predetermined length. This discrepancy is believed attributable to 
changes in the tension exerted longitudinally of the stringer chain during 
feeding thereof, or dimensional errors of the coupling elements. The 
resultant gaps therefore would often carry irregularly severed endmost 
coupling elements differing in shape between those in one row and those in 
the other row on the respective support tapes, rendering it difficult to 
fit properly in place such component parts as top and bottom end stops 
particularly separable end stops. 
SUMMARY OF THE INVENTION 
With the foregoing difficulties of the prior art in view, the present 
invention seeks to provide an apparatus for gapping a stringer chain for 
slide fastener having a pair of opposed support tapes and respective rows 
of coupling elements secured thereon, which apparatus incorporates 
operating structural features designed to gap the stringer chain at 
predetermined intervals along its length to provide element-free portions 
or gaps having such endmost or terminal coupling elements at their 
opposite ends which are cut neatly, substantially symmetrically and at the 
same position throughout a series of gaps. 
The above and other features and advantages of the invention will appear 
clear from the following detailed description taken with reference to the 
accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings and FIG. 1 in particular, there is shown a 
gapping apparatus 10 provided in accordance with the invention, which 
apparatus generally comprises a machine frame 11 having on its top surface 
a working table 12 centrally defining a horizontal path of travel 13 for a 
slide fastener stringer chain C to follow. The term stringer chain C is 
used to designate a pair of oppositely disposed support tapes T, T each 
carrying along their respective inner longitudinal edges a row of 
continuous coupling elements E of a helical coil structure which is 
secured in place typically by sewing threads S passing through cords R 
that extend longitudinally through the coil structure as shown in FIG. 8, 
or which may be alternatively woven from a filamentary material into the 
respective tapes simultaneously as the latter are woven as is well known 
in the art. Each of the individual coupling element E consists of a 
coupling head Ea, an upper leg Eb, a lower leg Ec and a heel Ed 
interconnecting between neighboring coupling elements. 
The apparatus 10 includes a pair of clamping jaws 14, 14 secured on the 
table 12 and having inner edges 15 confronting across a gap slightly 
larger in width than the two opposed rows of coupling elements E that are 
coupled together. The clamping jaws 14, 14 each have a plurality of 
grooves 16 engageable with corresponding ridges 17 formed on a pair of 
pressure pads 18, 18 which are vertically movable toward and away from the 
path 13 of the stringer chain C. When brought to a stop at a predetermined 
position on the table 12, the stringer chain C is clamped in place between 
the jaws 14 and the pressure pads 18 so that the chain C is prepared for a 
gapping operation later described. The pressure pads 18, 18 are connected 
by a first spring 19 to a holder 20 vertically movably supported in the 
frame 11. The holder 20 is driven by a pneumatic cylinder or the like not 
shown to move upwardly, compressing the spring 19 with which to move the 
pressure pads 18 up into engagement with the clamping jaws 14. 
A second spring 21 is interposed between the frame 11 and the holder 20 for 
biasing the holder 20 downwardly as it descends. 
An anvil 22 consists of a pair of die blocks 23, 24 having a knock-out 
plate 25 movably supported therebetween. The anvil 22 is accommodated in 
the pressure pads 18 and secured to the frame 11. 
As shown in FIGS. 2 and 7, each of the die blocks 23, 24 has formed on its 
top surface a plurality of transverse guide grooves 26 each dimentioned to 
fittingly receive the lower leg Ec of the coupling element E on the 
support tape T. The guide grooves 26 in one die block 23 are shifted a 
half pitch apart from those in the other die block 24. 
A cutter 27 is vertically movable by a suitable drive not shown toward and 
away from the anvil 22, and has a pair of blades 28, 29 whose cutting 
edges 30, 31 are spaced apart by a distance such that they overlie the 
upper legs Eb of the respective elements E adjacent to the respective 
heels Ed. The blades 28, 29 each have a length corresponding to a gap G to 
be formed at predetermined intervals in the stringer chain C and have 
their respective terminal ends 28a, 29a displaced relative to each other 
by one upper leg Eb or a half pitch of the element E as indicated by solid 
lines 32, 33 in FIG. 8 such that the terminal or endmost coupling elements 
Ex on the respective tapes T, T can be cut across their legs Eb merging 
with the heels Ed. 
A punch 34 is supported centrally in the body of the cutter 27 and 
vertically movable relative thereto by means not shown toward and away 
from the anvil 22, more specifically in vertical alignment with the 
knock-out plate 25. The punch 34 is provided on its lower or operative end 
surface 35 with two rows of saw-tooth like positioning prongs 36 displaced 
relative to each other by a half pitch of the upper legs Eb of the 
elements E and distributed in spaced relation to span over a few 
(presently illustrated to be every three) upper legs Eb of the coupling 
elements and engage between adjacent upper legs Eb as better shown in FIG. 
7. The operative length of the punch 34 is substantially equal to or 
slightly greater than the cutter blades 28, 29 depending upon the mode of 
gapping operation. 
With this construction, the gapping apparatus 10 operates as follows. The 
stringer chain C, while being advanced intermittently, is stopped at a 
predetermined position on the path of travel 13, when the holder 20, 
pressure pads 18, anvil 22 and knock-out plate 25 are all retracted 
downwardly in their respective non-operative positions, with the cutter 27 
and punch 34 likewise held in raised non-operative position. In this 
instance, the stringer chain C is still held free from being clamped or 
gripped between the clamping jaws 14, 14 and the pressure pads 18, 18 so 
as to permit the stringer chain C to flexibly move longitudinally a small 
distance required for the positioning prongs 36 to adjustably fit in 
between adjacent upper legs Eb of the coupling elements E. Otherwise, the 
positioning prongs 36 would often ride over and get stuck directly on the 
upper legs Eb of the elements E in the event that the stringer chain C is 
shifted out of the proper operative position on the working table 12, or 
the coupling elements E are mounted with irregular pitch on the respective 
tapes T, T. Such errors may be detected by a sensor such as a microswitch 
not shown provided at the drive for the punch 34 so that the punch 34 may 
be repeatedly moved up and down until the positioning prongs 36 find their 
way into the spaces between adjacent upper legs Eb of the elements as 
depicted in FIG. 7. This is followed by ascending movement of the pressure 
pads 18, 18 to clamp the stringer chain C in place on table 12 in 
cooperation with the clamping jaws 14, 14. During descending movement of 
the punch 34, the cutter 27 may be arranged to stay in retracted position 
or may also move downwardly to a position closely above the rows of 
coupling elements E. Simultaneously with pressure engagement of the punch 
34 with the stringer chain C, the die blocks 23, 24 ascend until the guide 
grooves 26 therein receive and support the lower legs Ec of the elements 
from the lower surface of each of the tapes T, T, thus firmly holding the 
stringer chain C in proper position ready for gapping as shown in FIG. 7. 
The cutter 27 is now actuated to come down into engagement with and cut 
the upper legs Eb over a predetermined length of the stringer chain C as 
shown in FIG. 5, in which instance the blades 28, 29 are disposed with 
their respective terminal ends 28a, 29a substantially registering with the 
upper legs Eb adjacent to the heel portions Ed of the endmost elements Ex 
on the respective tapes T, T as shown in FIG. 8. This ensures freedom of 
those neighbouring coupling elements Ey immediately adjoining the endmost 
elements Ex from being inadvertently cut or impaired by the cutter 27. The 
length of the coupling elements E which has been cut is removed from the 
stringer chain C by the knock-out plate 25 as the latter makes a further 
upward movement clear across the level of the horizontal path of travel 13 
as shown in FIG. 6, thereby providing an element-free portion or gap G at 
predetermined intervals longitudinally along the stringer chain C for 
subsequent mounting of the slide fastener component parts in a manner well 
known in the art. 
FIG. 9 shows a modification in which the die block 23 (24) has a flat top 
surface 37 devoid of guide grooves 26. 
FIG. 10 shows another modification in which the punch 34 has as many 
positioning prongs 36 as to engage between each adjacent upper leg Eb of 
the coupling elements E. 
Many other modifications and changes may be made in the apparatus 10 herein 
advanced, without departing from the scope of the appended claims.