GB2216971A

GB2216971A - Hose end fitting

Info

Publication number: GB2216971A
Application number: GB8905437A
Authority: GB
Inventors: Frederick Russell Duffield
Original assignee: Frederick Duffield Pty Ltd
Current assignee: Frederick Duffield Pty Ltd
Priority date: 1988-03-15
Filing date: 1989-03-09
Publication date: 1989-10-18
Anticipated expiration: 2009-03-09
Also published as: AU3109289A; GB2216971B; NZ228278A; ZA891899B; GB8905437D0

Abstract

A stem for a hose end fitting, the stem being arranged to locate within the interior of a hose, having a bore for conveying fluid which passes through the hose and having a series of spaced apart circumferential barbs 17 formed along at least a portion of its length. Each barb 17 has a land 18 which is inclined at angle theta to the axis of the bore of the end fitting and the stem is characterised in that the angle theta increases for barbs 17 which are located progressively further from the tail end 16 of the stem. <IMAGE>

Description

HOSE END FITTING This invention relates to hose end fittings and, in particular, to fittings of the type that have a stem which is inserted into the bore of a hose and held captive in the bore by barbs or the like.

The stem portions of hose fittings are usually formed with a series of spaced apart circumferential ridges, projections or barbs (referred to herein simply as "barbs") which serve to distort the shape of a hose bore when the hose is clamped onto the stem by a surrounding ferrule member. By forcing the material of the hose to flow around the barbs under compression from the ferrule member, a greater degree of tensile loading must be exerted to break the joint between the hose and the stem than would otherwise be required.

Various manufacturers employ different types of barbs, in the sense that various barbs have different shapes in profile, but one feature which is common to all known fittings is that the barbs in any given fitting have substantially constant size and shape.

However, it has for some time been recognised by the present applicant that hoses which fail at the stem under the influence of impulse or other loading, usually fail in the region of contact between the interior of the hose and the barb which is nearest to the tail of the stem, the tail being the end of the stem farthest from the end of the hose into which the stem is inserted. Having come to understand this problem, it is thought that the incidence of failure may be reduced if anchoring could be effected in a graduated manner, such that some of the load is shifted from the tail end barb to other barbs of the stem.

Recognising that the existing arrangements, which use constant profile barbs, do not function adequately to spread the load over a number of the barbs, it is proposed in accordance with the present invention that the shape of the barbs be varied so as to achieve the desired result.

Thus, the present invention provides a stem for a hose end fitting, the stem being arranged to locate within the interior of a hose, having a bore for conveying fluid which passes through the hose and having a series of spaced apart circumferential barbs formed along at least a portion of its length. Each barb has a land which is inclined at an angle o to the axis of the bore of the end fitting and the stem is characterised in that the angle o increases for barbs which are located progressively further from the tail end of the stem.

Each barb has a step which is inclined at an angle ss to a line that lies normal to the axis of the bore of the end fitting, and the angle ss is preferably varied by reducing the angle for barbs which are located progressively further from the tail end of the stem.

The diameter of the stem for all barbs along the stem may be either constant, or varied such that the diameter increases for barbs which are located progressively further from the tail end of the stem.

That is to say, that the average diameter of the stem may remain constant along its length or alternatively the stem may taper with the average diameter increasing away from the tail end.

The invention will be more fully understood from the following description of the stem member (having a constant average diameter) shown in figures 1 and 2, which is intended to be used as part of a complete hose end fitting for a wire reinforced synthetic rubber hose.

As illustrated in figure 1, the stem member comprises a metal body having a forward male fitting component 10 which is separated from a nut-shaped shoulder 11 by a groove 12. To the right of the shoulder 11 is further groove 13 which is intended to receive a forward projection of a ferrule (not shown) which in use would normally be clamped onto the stem fitting. A further shoulder 14 functions to prevent the ferrule from being withdrawn from the stem member under the influence of a tensile load.

The remaining portion 15 of the stem member is intended to locate within the bore of a hose and it extends from the shoulder 14 through to the tail end 16 of the fitting. The portion 15 is formed with a plurality of circumferentially extending spaced apart barbs 17.

Figure 2 is a more detailed view of the portion 15 in which each of the barbs 17 is formed with a land 18 and a step 19, the land 18 being inclined at an angle o to the horizontal or, in other words, to the axis of the bore of the end fitting. The step 19 is inclined at an angle ss to the vertical. The angle o increases as the barbs are located further to the left of the tail 16 of the stem member, whereas the angle ss decreases as the barbs are located further to the left of the tail 16 of the stem member.

As indicated in figure 2 by way of example only, the tail end of the end fitting has a land which is inclined at an angle e of 10 to the horizontal and the subsequent lands are inclined at angles of 50 0 70 and 10 to the horizontal. The angle ss of the step between successive barbs is 70, 30 and 10, the angles being with respect to the vertical and being shown in an exaggerated manner in the drawing.

Alternative embodiments of the present invention are illustrated in the longitudinal part cross-sectional views of figures 3, 4 and 5, wherein the reference numerals are as used in figures 1 and 2. The particular barb configuration and degree of taper of any particular stem is dependent upon the characteristics of the hose with which the stem is to be utilized.

Figure 3 illustrates an embodiment that may be used with a loosely woven hose wherein the stem portion 15 increases in diameter from the tail end 16 to the shoulder 14 of the fitting. The taper is represented by dashed lines 20 and 21 which converge toward the right of the drawing. This is to be contrasted with the embodiment illustrated in figure 2 wherein average diameter remains constant along the length of the stem.

Claims

CLAIMS:

1. A stem for a hose end fitting, the stem being arranged to locate within the interior of a hose, having a bore for conveying fluid which passes through the hose, having a series of spaced apart circumferential barbs formed along at least a portion of its length, with each barb having a land which is inclined at an angle o to the axis of the bore of the end fitting; the stem being characterised in that the angle o increases for barbs which are located progressively further from the tail end of the stem.

2. The stem as claimed in claim 1 wherein each barb has a step which is inclined at an angle ss to a line that lies normal to the axis of the bore of the end fitting, characterised in that the angle ss decreases for barbs which are located progressively further from the tail end of the stem.

3. The stem as claimed in either claim 1 or claim 2 wherein the distance as measured from the axis of the bore of the end fitting to the apex of a barb along a line normal to the axis of the bore is constant for all barbs located along the stem.

4. The stem as claimed in either claim 1 or claim 2 wherein the distance as measured from the axis of the bore of the end fitting to the apex of a barb along a line normal to the axis of the bore increases for barbs which are located progressively further from the tail end of the stem.

5. A stem for a hose end fitting substantially as hereinbefore described with reference to the accompanying drawings.