GB2238134A

GB2238134A - Fabric tester

Info

Publication number: GB2238134A
Application number: GB8925626A
Authority: GB
Inventors: Julian Richard Allan; William James Corbett
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 1989-11-13
Filing date: 1989-11-13
Publication date: 1991-05-22
Anticipated expiration: 2009-11-13
Also published as: GB8925626D0; GB2238134B

Abstract

In apparatus for testing the permeability of fabrics on impact with water, being especially useful for testing ventile materials used in the manufacture of immersion suits, a test piece of fabric 3 is held in a clamping device 1, 4 which is releasably attachable to a pipe 10. Radial grooves 6 in the impact face of clamping ring 4 provide an escape path for air when the fabric impacts water. In use, the pipe is allowed to fall vertically into a water tank, being guided along a track by rollers. Subsequently, the fabric-carrying clamping device 1 can be removed and inspected for the presence of water droplets e.g. by weighing, and the fabric can be visually inspected for damage. <IMAGE>

Description

FABRIC TESTER This invention relates to apparatus for testing the permeability of fabrics and, in particular, for testing their permeability to water on impact.

Ventile fabrics which are used to make immersion suits for aircrew have been found to provide inadequate thermal insulation after impacting with water eg after a parachute jump. Although these fabrics are substantially impermeable when wet (due to a swelling action which closes the weave and prevents water passing through) it has been found that the fabric can be damaged on impact with water, thus allowing liquid to pass through from one side of the fabric to the other.

This invention provides a means for ascertaining whether or not a certain fabric under test becomes permeable on impact with a liquid and to what extent ie it also provides a quantitative measure of permeability.

The present invention therefore consists of apparatus for testing the permeability of a fabric to liquids comprising an annular body and a retaining member between which the fabric under test can be held, and sealing means located between said body and member, the retaining member having a plurality of radial grooves machined into one of its faces.

The sealing means may be an '0' ring which is located in an annular groove which is machined into either the retaining member, or.

preferably, the annular body.

The provision of the radial grooves prevents air from becoming trapped between the fabric and the water surface which it impacts under test conditions by providing an escape path for the air away from the region of the fabric.

The invention also provides means whereby only one side of the test fabric is permitted to come into contact with liquid under test conditions, said means also allowing a predetermined hydrostatic pressure to be applied to the test fabric and being releasably attachable to the hollow body.

An embodiment of the invention will now be described, by way of example only, with reference to the drawings of which: Fig 1 is an underside view of a device in accordance with the invention; Fig 2 is a sectional view along a line II-II in Fig 1 and Fig 3 is a side view of the device of Figs 1 and 2 in use.

A hollow cylindrical body 1, made of aluminium, carries a rubber '0' ring 2 which sits in a groove machined into the body 1. A circular piece of test fabric 3 is placed across one face of the body 1 so that it covers the '0' ring 2. The fabric is held in this position by a clamping ring 4 which is secured to the body 1 by six countersunk screws 5. The '0' ring 2 provides a water-tight seal.

The face of the clamping ring 4 which is remote from the fabric 3 has six shallow grooves 6 machined into it. The grooves provide an air escape path as explained above.

The cylindrical body is a push fit inside a plastics plug 7. The outer wall of the plug 7 is threaded and carries an'or ring seal 8 on a tapered portion of the wall so that it can be firmly located within a plastics housing 9 whose inner wall is also threaded and contoured accordingly. The housing 9 is a push fit around a hollow plastics pipe 10. Watertight seals between the cylindrical body 1 and the plug 7 and between the pipe 10 and the housing 9 are ensured by the application of a suitable sealant (such as one containing iso-cyanates) to the joints and the surrounding areas.

In use, the plastics plug 7 is screwed into the housing 9 and the resulting assembly is hoisted into a position above a water tank 11 (see Fig 3). This is achieved by means of a rope 12 (guided over pulleys 13) and a quick-release fastener 14. The assembly is then released from the fastener 14 and falls into the water tank 11, in this embodiment being guided by two sets of near-frictionless plastics rollers 15a/15b which are free to run along a guide track 16 and which are connected by mountings 17a/17b to the pipe 10.

After impact, the plug 7 is unscrewed from the housing 9 for visual inspection of the fabric 3.

The amount of water which has collected inside the space bounded by the body 1, plug 7 and fabric 3 gives an indication of the permeability of the fabric under test. A quantitative assessment may be made by weighing the appropriate portions of the apparatus before and after immersion.

In order to test for any relationship between fabric permeability and the velocity of impact of the apparatus, the velocity can be varied by adjusting the height from which the apparatus is dropped.

The hydrostatic pressure exerted on the fabric during testing can be varied by controlling the depth of water in the tank 11.

As an alternative to visual inspection, a miniature camera may be installed inside the pipe 10.

In an alternative embodiment, the plug 7 and housing 9 are dispensed with and the cylindrical body 1 and pipe 10 are directly and releasably coupled to one another by means of, for example, a screw thread.

Claims

1. Apparatus for testing the permeability of a fabric to liquids comprising an annular body and a retaining member between which the fabric under test can be held, and sealing means located between said body and member, the retaining member having a plurality of radial grooves machined into one of its faces.

2. Apparatus as claimed in claim 1 in which the sealing means is an '0' ring located in an annular groove which is machined into either the annular body or the retaining member.

3. Apparatus as claimed in either preceding daim further comprising a hollow pipe releasably attachable to the annular body for permitting only one side of the test fabric to come into contact with liquid under test conditions.

4. Apparatus as claimed in claim 3 in which the pipe is fitted with rollers for guiding the vertical motion of the pipe along a guide track.

5. A method for testing the permeability of a fabric to liquids wherein a piece of test fabric is secured within apparatus as daimed in claim 4, the apparatus is dropped from a known height into a known depth of liquid, said apparatus is then raised out of the liquid, the pipe is removed from the annular body and the fabric is inspected for the pressure of water droplets.

6. Apparatus substantially as hereinbefore described with reference to the drawings.