GB2280272A

GB2280272A - Stretch comparator for elastic trim.

Info

Publication number: GB2280272A
Application number: GB9314970A
Authority: GB
Inventors: Terrence Moran
Original assignee: ELASTIC TRIMS
Current assignee: ELASTIC TRIMS
Priority date: 1993-07-20
Filing date: 1993-07-20
Publication date: 1995-01-25
Anticipated expiration: 2013-07-20
Also published as: GB2280272B; GB9314970D0

Abstract

A stretch comparator (1) comes the disadvantages associated with manually stretch testing of elastic trim by providing a repeatable mode of testing. In the comparator (1) a flat bed has a generally horizontal upper surface (2) with a clamping block (3) mounted at one end, a platen (6) slideable therealong and means for clamping a five inch sample (13) of elastic trim therebetween. A weight (9) is applied to the platen (6) by being suspended from the free end of a toothed belt (7) attached at its other end thereto. To avoid shock loading of the platen (6) the belt (7) passes around and engages a toothed wheel (4) of a frictional damper (5) attached at the other end of the surface (2). The stretch of the sample (13) is measured by means of a cursor (11) and rule (10) once the sample has been fully stretched by the weight (9). <IMAGE>

Description

"Stretch Cowparator" This invention relates to stretch comparators generally and more particularly but not exclusively to a stretch comparator for quality control testing of elastic trim.

Elastic trim used ordinarily in the manufacture of underwear and lingerie is fabricated in long lengths by either knitting or crocheting elongate elastic fibres together with generally inextensible cotton or synthetic fibres to provide an elasticated wab. Typically, elastic trim of a given length when relaxed is required to stretch to a limit of about 150% that length. Such trim is then suitable to be made up for example into the waist band of undergarments.

It will be appreciated that for any given clothing product run the elastic trim used should be of uniform stretch. The actual stretch is not in itself critical as machinery can be set up appropriately at different times to deal with individual batches of elastic trim. However, to set up machinery correctly it is necessary that the stretch of any given batch of trim is accurately ascertained.

Traditionally, the stretch of a batch of elastic trim has been determined during manufacture thereof. Such shapfloor measurement has been carried out by hand. The technique usually employed has been to mark a 5 inch length of the material which is then stretched by hand to its maximum extent and the resultant length (L) measured. The stretch of the sample is then represented in percentage terms using the formula L/5*100%.

The advantage of the aforementioned technique is that it is inexpensive and requires only a simple rule. The disadvantage is that the method is inaccurate and that the results vary according to the load applied by any given operative. Disputes often occur with customers who on testing elastic trim delivered to them arrive at a different stretch from that marked on its packaging.

It is an object of the invention to provide a repeatably accurate mode of stretch testing of elastic trim to ensure efficient quality control of the product which can be relied on by manufacturer and custater alike.

According to the invention a stretch comparator for quality control testing of a length of elastic webbing comprises a bed having a generally horizontal upper surface between opposite ends of the bed, first clasping means mounted on the bed in the region of one said end thereof and adapted to engage said length of elastic at a position spaced fran said one end thereof and slideable along said bed upper surface between said ends of the bed, wheel means mounted to rotate about a horizontal axis adjacent the ather end of the bed by bearing means which incorporates a rokationAl.damper and a flexible but substankially inextensible elongate load bearing rnrber connected at one end to the second clanping means and passing over and engaging said wheel means to suspend a load at its opposite end clear of the bed, with the arrangement prodding that rlnnanent of a suspended load falling under its awn weight is retarded by action of the rotational damper so as to prevent shock loading of the second clamping means.

Preferably, the rotational dapper is in the form of a self-actuating fluid brake adapted to provide a retarding force generally proportional to the angular velocity of its actuating spindle. Additionally, the bed may incorporate stop means against which the second clasping means can abut to provide a predetermined minimum distance between the jaws of the two clanping means. Suitably, the said minimum distance is 5 inches.

The said load may be provided by a weight hanger attached to the free end of said elongate member on which known weights are loaded and the bed may further comprise a graduated scale against which the relative position of the jaws of the clamping members can be measured. Typically, 1500 grammes is loaded on said weight hanger.

Conveniently, a latch mechanism may be attached to the bed and adapted to engage a corresponding keeper formation on the second clasping means so as to retain the second clamping means at a starting position with the jaws of the clanping means being spaced apart by said predetermined distance.

According to further aspect of the invention a method of quality control testing a length of a sample of elastic webbing utilising a stretch cpnparator in accordance with the first aspect of the invention includes the steps of:- first latching the second clamping means in said starting position; securing said length in a taut but unstretched condition between the jaws of the clasping means; applying the suspended load to the clamped elastic by releasing the latch mechanism; permitting the applied load by the action of the rotational damper to extend the length of elastic to the limit of its stretch; measuring the final length of the elastic; and expressing the stretch of the elastic in percentage terns as the product final/initial length.

An embodiment of the invention will now be described by way of example only and with reference to the accompanying Drawing in which Figure 1 illustrates a prototype stretch comparator.

In Figure 1, the stretch comparator 1 comprises a bed having a horizontally disposed and generally flat upper surface 2 at one end of which is fixed a mounting block 3 on which a first spring-loaded clamp (not shown) can be fitted. Adjacent the other end of the surface 2 a toothed wheel 4 of a frictional damper or fluid brake 5 is rotationally mounted. Intermediate the block 3 and wheel 4 a platen 6 is slideably mounted on the surface 2. A second spring-loaded clamp (not shown) is mounted at the end of the platen 6 remote fran the mounting block 3.

A generally inextensible toothed belt 7 attached at one end to the platen 6 passes around and engages the toothed wheel 4 and suspends fran its free end a weight hanger 8 on which weights 9 are loaded. In addition, a graduated rule 10 is attached parallel to one longitudinal edge of the surface 2 and a cursor 11 on the platen 6 indicates the position relative to the surface of the second clamp.

With the platen 6 abutting the mounting block 3 the distance between the two clasps (not shown) is conveniently five inches. A latch, clip or detent means 12 is provided to hold the platen 6 in this position with the cursor 11 reading five inches on the rule 10.

A sarrple of elastic trim 13 is held taut but unstretched parallel to the surface 2 as shown in the drawing and clamped been the two clanps.

The hanger 8 is pre-loaded with about 1500 grammes which is sufficient to stretch the five inch clamped sample of trim to its full extent.

On releasing the latch 12 the weight hanger 8 is allowed to fall under the influence of gravity but retarded by the action of the rotational damper 5. This results in the slow stretching of the sample 13 to its full extent which can then be measured by reading the final position (L) of the cursor 11. The stretch of the elastic trim can then be represented as a percentage using the aforedescribed formula.

If the damper 5 were not present then the resultant shock loading on the sample 13 would lead to excessive stretch and probably damage to the elastic fibres therein. It will be appreciated that the invention is not limited to the specific embodiment described herein but that it may also encanpass other means of ensuring that shock loading of a sample of elastic trim is avoided.

Claims

CLAIMS:

1. A stretch canparator for quality control testing of a length of elastic webbing comprising a bed having a generally horizontal upper surface between opposite ends of the bed, first clamping means mounted on the bed in the region of one said end thereof and adapted to engage said length of elastic at a position spaced from said one end thereof and slideable along said bed upper surface between said ends of the bed, wheel means mounted to rotate about a horizontal axis adjacent the other end of the bed by bearing means which incorporates a rotational damper and a flexible but substantially inextensible elongate load bearing member connected at one end to the second clamping means and passing over and engaging said wheel means to suspend a load at its apposite end clear of the bed, with the arrangement providing that ncvEment of a suspended load falling under its own weight is retarded by action of the rotational damper so as to prevent shock loading of the second clamping means.

2. A stretch comparator in accordance with claim 1, in which the rotational damper is in the form of a self-actuating fluid brake adapted to provide a retarding force generally proportional to the angular velocity of its actuating spindle.

3. A stretch comparator in accordance with claim 1 or claim 2, in which the bed incorporates stop means against which the second clamping means can abut to provide a predetermined minimum distance between the jaws of the two clasping means.

4. A stretch comparator in accordance with claim 3, in which said minimum distance is 5 inches.

5. A stretch canparator in accordance with claim 3 or claim 4, in which said load is provided by a weight hanger attached to the free end of said elongate member on which known weights are loaded and the bed further comprises a graduated scale against which the relative position of the jaws of the clamping members can be measured.

6. A stretch comparator in accordance with claim 5, in which 1500 grammes is loaded on said weight hanger.

7. A stretch comparator in accordance with any one of claims 3 to 6, in which a latch mechanism attached to the bed is adapted to engage a corresponding keeper formation on the second clamping means so as to retain the second clasping means at a starting position with the jaws of the clasping means being spaced apart by said predetermined distance.

8. A method of quality control testing a length of a sample of elastic webbing utilising a stretch comparator in accordance with claim 7 includes the steps of: first latching the second clasping means in said starting position; securing said length in a taut but unstretched condition between the jaws of the clasping means; applying the suspended load to the clamped elastic by releasing the latch mechanism; permitting the applied load by the action of the rotational damper to extend the length of elastic to the limit of its stretch; measuring the final length of the elastic; and expressing the stretch of the elastic in percentage terms as the product final/initial length.

9. A stretch comparator substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

10. A method of quality control testing a length of a sample of elastic webbing substantially as hereinbefore described.