Quick release tube coupling
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to quick release tube couplings of the kind (referred to hereinafter as the &#34;kind described&#34;) having a collet with resilient arms arranged to co-operate with a cam surface on a member surrounding the collet, this cam surface being constituted by an internal surface tapering to a smaller diameter in one axial direction and engaging the arms so that the arms are forced radially inwardly by axial movement in this direction which is the direction to withdraw the tube from the coupling and wherein the collet has its arms spaced apart in the circumferential direction such that, in the absence of any tube within the collet, the arms can move radially inwardly to permit the collet to withdraw from said member by axial movement in said one direction. 
     2. Description of the Prior Art 
     One such coupling of this kind is described and claimed in British Patent Specification No. 1520742. This arrangement in which the collet, in the absence of the tube, can be withdrawn from the coupling enables the body member to be a unitary structure yet permits of the collet being removed and hence enables an O-ring or like sealing member inside the coupling to be replaced. 
     The usual practice has been to make the body members of such couplings of metal. It is an object of the present invention to provide a form of construction which enables the body member to be made out of a plastics material. The collet itself can be made out of plastics material, possibly with a stainless steel insert, as is described for example in British Patent Specification No. 1573757. A coupling formed of plastics material is particularly desirable for use for example in the handling of foodstuffs and beverages. 
     Heretofore it has not been possible to mould a body member for such a coupling out of plastics material with the required degree of accuracy necessary for making an effective coupling. The reason for this is that the body member essentially has a through-bore which is necessarily narrower at its two ends than is the centre part. Between the centre part of the body member and one end of the bore there must be at least one shoulder to provide a support for a resilient seal member, e.g., an O-ring, into which the tube extends when put into the body member from the other end. The tube itself normally abuts against this shoulder or against another abutment. From the shoulder towards said other end, there is the cam surface which has to taper to a narrower diameter in the direction towards said other end. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a method of making a body member for a coupling of the kind described comprises forming first and second portions of the body member of plastics material, one male and the other female, each having a bore therethrough with the bore in the male portion having at least a portion increasing in diameter towards the end of the male portion which enters the female portion and wherein the co-operating male and female surfaces are shaped to provide, on insertion of the male in the female, initial contact in a first annular region between one surface and an annular edge or projection on the other surface, and wherein by ultrasonic relative vibration of the two portions in the direction of the axis of the bore, said annular edge or projection is softened and the male and female portions make contact in a second annular region spaced from the first annular region thereby enabling ultrasonic welding to be effected in two spaced annular regions. 
     Using this method a coupling member can be formed with a bore which tapers from an internal larger diameter down to a smaller diameter at or near the exit using simple moulding techniques without employing any complex core structure by forming the body member in two parts and welding them together; the above technique enables the welding to be effected in two spaced annular regions so ensuring a fluid-tight joint between the two portions of the body member. The technique moreover ensures welding of the nose end of the male to the inside surface of the female member around the bore, which is particularly important in couplings for carrying beverages in ensuring that there are no cracks or crevices which may cause hygiene risks. 
     Preferably the male portion has a conical surface adapted for entering within a conical internal surface of the female portion. The taper angle of the male conical surface is preferably less than the taper angle of the female internal conical surface. 
     For relatively small members, the male member may have a straight taper of smaller taper angle than the female surface and be dimensional so that the nose of the male member, around its periphery, makes contact with the female conical surface a short distance from the inner end, whereby on relative vibration of the two members, the periphery of the nose of the male member softens, allowing the male member to enter fully into the female member. 
     Particularly for larger members, an annular projection may be provided on the male conical surface in a position axially spaced from the nose end of the male portion. This annular projection forms said first annular region when welding takes place. The second annular region may be constituted by at least part of the nose end of the male portion. The male and female portions may have co-operating surfaces adapted to abut and to form a stop limiting further penetration of the male into the female when the material of one or both portions is softened in both said spaced annular regions. These co-operating surfaces may comprise shoulders on the two portions extending radially outwardly to external peripheral surfaces of the two members. It has been found that, using this technique, the two portions of the body can be secured together in intimate contact with negligible or no gap between them around their external surface. 
     According to another aspect of the present invention, a body member for a coupling of the kind described comprises first and second portions, each of plastics material with one male and the other female, each with a bore therethrough and with the bore in the male portion having at least a part increasing in diameter towards that end of the male portion which enters the female portion, the two portions being welded one to the other in two annular regions spaced axially along the length of the male portion lying within the female portion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal section through part of a body member for a coupling formed in two parts with the two parts shown spaced apart before assembly; and 
     FIG. 2 is a longitudinal section of the assembled coupling including a collet. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1 there is shown a first portion 10, referred to as a cap, and part of a second portion 11, referred to as the body portion, which two portions are to be joined together to form a body member for a coupling of the kind described. The two portions 10, 11 constitute the body member of quick release tube coupling of the kind described in the aforementioned United Kingdom Patent Specification No. 1520742. The collet 20 (FIG. 2) may be formed of plastics material, possibly with a stainless steel insert, as described in the specification of United Kingdom Patent Specification No. 1573757. This collet is inserted into the coupling from the left-hand end of the cap member 10 of FIG. 1, the collet arms 21 being movable radially inwardly sufficiently far to permit insertion through the relatively narrow diameter portion 12 of the cap member. These collet arms have bearing portions 22 which engage the tapered surface 13 of the cap member so that, after insertion, outward pull on the collet causes the collet arms to be forced radially inwardly to grip a tube passing through the collet. The tube, shown in chain lines 23 in FIG. 2, is inserted into the coupling through the left-hand end of the member 10 of FIG. 1 and abuts against a shoulder 14 in the body portion 11. A resilient O-ring 24 is provided in this body portion, the tube when inserted passing through the O-ring which is thus supported also by a shoulder 15. 
     The present invention is concerned more particularly with the construction of the body assembly 10, 11 of the coupling. It will be seen that the two parts 10, 11 are each of generally annular form with an internal bore. The part 10 is a male member having an external conical surface 16 which is shaped to mate with a corresponding internal conical surface 17 in the female part 11. The male member surface 16 tapers towards the axis of the bore at a slightly smaller angle than the angle at which the surface 17 in the female tapers with respect to the axis. At its tapered end, the male member terminates in an end nose 16a. 
     Around the surface 16 on the male portion 10 is a peripheral projection or rib 18 which is shaped and dimensioned so that it forms the first contact with the female surface 17 on insertion of the male into the female. On the female member, at the inner end of surface 17 is a shoulder 19 with an axially extending groove 29 at the radially outermost edge of the shoulder. The groove 29 constitutes a flash well into which surplus material from the mating surfaces can flow. Alternatively, an annular groove or recess may be provided around the end of the nose 16a of the male member to receive any such surplus material. 
     Each of the male and female parts 10, 11 is moulded of plastics material, conveniently nylon or an acetyl copolymer, such as that sold under the trade name Kemetal, using conventional moulding techniques with an internal member in the mould dimensioned exactly to define the required shaping and dimensions of the internal bore. In each portion, the internal member of the mould can be withdrawn from one end of the mould after the plastics material has been shaped between internal and external mould members. With this technique, each of these two parts can thus be moulded accurately out of plastics material. 
     On the male member at the larger diameter end of the external conical surface 16, there is an outwardly directed shoulder 30. Similarly, on the female member at the radially outermost end of the conical surface 17, there is an axially facing shoulder 31 which faces the shoulder 30 on the male. 
     The two parts 10, 11 of the coupling body are put together so that the rib 18 on the male comes into contact with the conical surface 17 on the female and then ultrasonic vibrations are applied to cause relative motion of these two parts in the axial direction. This causes rubbing of the rib 18 on the conical surface 17 with softening of the rib and the contacting surface region. The male can then enter further into the female until the nose end 16a of the male contacts the shoulder 19 so causing softening of the material in this region with surplus material forced into the groove 29. Abutment of the shoulders 30, 31 prevents further penetration. The male and female portions are thus welded together in two spaced annular regions, one arising from the rib 18 rubbing on surface 17 and the other where the nose of the male member abuts shoulder 19. This welding gives a fluid-tight seal between the portions 10, 11 with welding occurring at the innermost end of the male, thereby avoiding any undesirable cracks or crevices which are undesirable particularly if the coupling is to be used for beverages or the like. 
     Externally, the shoulders 30, 31 are brought into abutment and, with the above-described technique, they can readily be made accurately and will fit very closely so avoiding any external cracks or crevices in the finished assembly. 
     The ultrasonic welding of the two parts 10, 11 thus joins these parts to form a unitary body structure which has internal dimensions, in particular of the tapered portion 13 which are accurately determined during the moulding operations of the separate parts 10, 11. The close fit and welding together of the two parts 10, 11 prevents any possibility of seepage of a fluid from the coupling after the two parts have been joined. After the two parts have been joined, the O-ring 24 is inserted and then the collet 20, as seen in FIG. 2, to form the complete coupling. 
     It will be noted that the rib 18, provided in the male conical surface ensures that there is a complete annular region of softened plastics material to form a weld between the male and female conical surfaces. This annular region is located a short distance away from the inner end of the female conical surface. Particularly for small members, it may be sufficient, instead of providing a rib 18, to rely on the contact, with the female surface, of the edge formed between the nose and surface of the male member and the conical surface of that member. Provided the nose of the male member is of larger diameter than the inner end of the female conical surface, the male member will make initial contact with the female conical surface a short distance from the inner end of the female conical surface, this edge on the male member acts in the same way as the rib 18 to form an annular region of softened plastics material which permits further inward movement of the male member and which constitutes an annular weld. The further inward movement is limited by abutment of the male nose on a shoulder in the female member or abutment of a shoulder on the male against an outer end or shoulder on the female; in either case the abutment will give, due to the ultrasonic vibrations, a second annular weld region.