AU715647B2 - Strain relief device for hoses - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION

APPLICANT:

ADDRESS:

Moss Products Pty Ltd 711 Clayton Rd, Clayton South, Vic.

ACTUAL INVENTOR: ADDRESS FOR SERVICE: Paul A Grant and Associates PO Box Fisher, ACT 2611 INVENTION TITLE: STRAIN-RELIEF DEVICE FOR HOSES ASSOCIATED PROVISIONAL: P01168 Filed 22 July 1996 9 9 The invention is a full description of the invention including the best method of performing it known to us: TECHNICAL FIELD This invention relates to strain-relief devices and fittings suitable for use with flexible hoses, including soft flexible hoses such as garden hoses.

BACKGROUND TO THE INVENTION A variety of strain-relief fittings for hoses are known. In general, such fittings comprise a hose coupling, connector or terminating device to which is attached a loose-fitting, short, flexible reinforcing tube which fits over the end of the hose and supports it against kinking in the vicinity of the coupling or terminal. It is common, for example, with many air and hydraulic pressure hoses to use a metal ferrule to not only clamp the hose to the connector but also anchor the end of a short wire coil that acts as the strain relief. Such fittings have a number of disadvantages from the standpoint of the present invention: they are expensive, usually factory-fitted and unsuited for fitting by householders.

Strain relief fittings for electrical chords are also well known. These are typically short reinforcing tubes made of soft rubber-like materials, the tubes being externally necked at one end to form a short head that is held within the body of an electrical appliance. Here there is usually no need to hermetically seal the exterior of the chord to the appliance, so this type of strain-relief is not suited to hoses because a separate fitting is then needed to effect the necessary hermetic sealing.

Furthermore, the soft material makes the neck of the strain-relief tube vulnerable to eT tearing in use.

OBJECTIVES OF THE INVENTION It is therefore an object of the present invention to provide a strain-relief fitting for hoses, including garden hoses, where hermetic sealing, durability and low-cost ";."considerations are important.

OUTLINE OF INVENTION From one aspect, the present invention involves the use of a support-tube moulded from plastics material which has a collet formed on one end thereof, the end having the collet being called the 'head' and the opposite end being called the lail' of the support tube. The tube may be formed so that its flexibility increases from head to the tail; for example, by tapering the wall thickness, by forming radial slots in its wall, and/or by forming a widening helical slot therein. In use, the collet of the supporttube may be tightened onto the external end of the hose by the use of a collet nut which is threaded onto a tubular body that has a short hollow spigot over which the hose-end is fitted and against which it is clamped by the collet under pressure from the nut.

From another aspect, the invention comprises a strain-relief fitting suitable for use with hoses, including: an externally-threaded body, a short hollow spigot formed on one end of the body, a conical face formed around said spigot on said one end of the body so as to slope inwards, an open-ended support-tube having head end and a tail end and being moulded from plastics material, S a tubular collet head integrally moulded on the head end of the supporttube, the tubular collet head having an internal diameter approximating the external diameter of the hose to be supported, and a collet nut internally threaded for engagement with the body and adapted to fit over, capture and retain the collet head so that said head can be forced into engagement with said conical face to thereby close the collet upon a hose-end fitted over said spigot.

25 The collet head is preferably slotted axially so that it can close on the hose when the nut is tighten. The slots may extend radially through the wall-thickness of the head, or they may be angled to the radial. Thus, the collet head is formed from a series of fingers which extend from the end of the support tube. The internal faces of these fingers may be toothed or serrated so that they tend to bight into the wall of the hose. The collet head may be separated from the support tube by a neck portion, so that the back of the collet nut can be forced over the head and onto the neck so as to capture the support-tube while being free to turn thereon. The collet head may be circumferentially tapered at its outer extremity to conform to the conical face on the body, and it may also be tapered oppositely to engage an opposing conical annular surface on the inside of the back of the collet nut.

It will be appreciated that the body of such a fitting can take many different forms.

It may be part of a 'click-on' coupling, part of a nozzle or spray-gun, part of a hose repair (joining) fitting, or part of a some hydraulic or pneumatic appliance. Many other fittings are also envisaged.

DESCRIPTION OF EXAMPLES Having broadly portrayed the nature of the present invention, one particular example will now be described by way of illustration only. In the following description, reference will be made to the accompanying drawings in which: Figure 1 is an exploded perspective of a repair coupling for a domestic waterhose formed in accordance with the principles of the invention outlined above.

Figures 2A and 2B are respectively enlarged perspective and sectional views o.

of the body of the fitting of Figure 1.

20 Figures 3A is an enlarged perspective view of the collet nut of the fitting of Figure 1, while Figure 3B is a sectional elevation of the nut taken on section plane B-B of Figure 3A.

Figures 4A is a longitudinal section of the collet tube of the fitting of Figure 1, while Figure 4B is an enlarged sectional detail (indicated at B in Figure 4A) of the collet-fingers of the collet tube.

*.The hose repair or connector 10 of the chosen example is made up of four injectionmoulded plastics components, one tubular body 12, a pair of identical collet-nuts 14 and a pair of collet members 16 which also serve as strain-relief tubes. Body 12 and nuts 14 are moulded from rigid polypropylene or ABS, while collet-tubes 16 are formed from a softer grade of polypropylene with a Shore hardness of 80-100, this being at least double that of normal garden hose.

To function as a connector, body 12 is double ended, having short smooth-surfaced spigots 18 projecting from each end with an external diameter approximating the internal diameter of the hose to be joined (not shown). Spigots 18 are let into body 12 so that recesses 20 are formed within the body concentric with the spigots, the radial dimension of each recess being slightly greater than the external diameter of the hose to be joined. The annulus 22 that forms the outer radial border of each recess 20 terminates in a conical annulus 24 which serves to guide a hose end into the recess and (ii) to close the fingers of collet tube 16. A screw thread 26 (not depicted) is formed on the external cylindrical periphery of each end of the body 12, the centre of the body having three knurl-finished rings 28 which for finger-grips to enhance the hand-grip of the coupling.

Each nut 14 is internally threaded (diagrammatically indicated at 30) at one end to engage the externally-threaded portion 26 of body 12, while the internal diameter of the other end is substantially reduced to form a short bore 32 adapted to fit loosely about the neck of the collet tube 16. Bore 32 opens out to the substantially larger diameter of threads 30 via a taper or conical annulus 34 which serves to close the fingers of the collet tube 16.

20 The moulded collet tube 16 comprises a bulbous head 36 divided axially into between six and ten fingers 38, each of which is moulded integrally with the large end of a tapered tubular body portion 40 that has a bore 41 which is an easy fit over *l the external diameter of the hose to be joined. To provide the desired degree of S•flexibility, body portion 40 is divided into a series of rings 42 of decreasing radial thickness and which are joined axially by thin flexible elements 44 that are arranged in a staggered fashion in the axial direction.

The collet head 36 is bulbous, being joined to the largest diameter ring 42a of body portion 40 by a neck 46 of smaller diameter. A series of teeth 48 are formed on the inner face of each finger 38 for gripping the external surface of a hose (when the collet head is tightened). The outer portion of the collet head 36 is formed with an external conical annulus 50 that is of substantially the same diameter and taper as that of the tapered annulus 24 of body 12, while the inner portion of head 36 which meets neck 46 is formed with an opposing tapered annulus 54 which matches annulus 34 of nut 14. The largest diameter of collet head 36 is chosen so that the head can be forced into bore 32 of a nut 14 (from the small-diameter end of the nut) so that, once inserted, fingers 38 are free to spring open again, thus retaining each collet tube 16 on its respective nut 14.

Preferably, as shown best in Figure 4B, the diameter of the bore of collet head 26 (as formed by teeth 48) is somewhat smaller than the diameter of bore 41 of the body portion 40 of the collet tube. Indeed, while bore 41 is best made to be an easy fit on the hose, it is desirable that the hose is a firm fit in the fingers 38 before the fitting is assembled.

In use, the end of a hose to be joined is pushed through an assembled collet tube 16 and nut 14 from the small diameter end of the collet tube to protrude from the large diameter of the nut by, say, 100 mm. This protruding end of the hose is then grasped in one hand and forced over a spigot 18 of the coupling body 12 until it has been pushed firmly home into recess 20 of body 12. The nut and collet tube are S"then slipped as a unit along the hose and threads 30 of nut 14 are engaged with threads 26 of body 12 and the nut it tightened on the body. As the nut is screwed onto the body the collet head 36 is jammed between tapered annulus 34 of the nut and tapered annulus 24 of the body, forcing the toothed ends fingers 38 into the softer material of the hose wall. This serves to form a hermetic seal between spigot 18 and the hose, (ii) prevent the hose from being pulled from the fitting and (iii) firmly anchor the strain-support (formed by collet tube 16) to the rigid body 12 of fitting If the tapers of the conical annuli 50 and 52 of the collet head 36 are suitably designed (together with their coacting annuli 24 and 34), tightening of the nut on the S- body of the fitting will serve to push the bulbous portion of each finger 38 inwards in a substantially radial manner. This ensures that all the teeth of each finger bight into the hose wall in a substantially equal manner. It has been found less desirable to form face 54 as a radial shoulder, for example, as this tends to put undue stress on the outermost tooth of each finger, thereby increasing the danger of stripping the 7 outer sheath from the hose when it is under tension. However, radial or near radial faces 45 and 34 are not excluded from the scope of this invention. Another way in which the danger of hose-stripping is mitigated is by the use of recess 20 to accommodate a portion of the hose which extends beyond the collet fingers when the fitting is assembled.

It will be appreciated that the collet tube or strain-support disclosed in the example, and the combination of the collet nut and tube, as well as the fitting as a whole meet all the objectives of the invention as set out above. However, as also indicated above, many variants are possible without departing from the invention as outlined.

Many other types of hose fitting are possible using the same type of integrated strain -relief tube and collet grip; and, many other types of fluid-carrying hoses other than garden hoses may be supported in this way.

S.*

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