Method of moulding plastics articles and articles produced thereby

Abstract: A method of injection moulding an undercut formation (26) on a circular body (20) wherein said formation is moulded in a series of arcuate sections (28) alternating with spaces (29), and wherein the moulding core (24) which produces the formation is extracted by firstly relatively rotating said body (20) and said core (24) so that the body is expanded radially and then ejecting the body off the core. The method is applicable to the manufacture of novel closure members and coupling elements.

Description: Technical Field This invention relates to a plastics coupling element comprising an undercut formation. Disclosure of Invention EP0641277 provides a method of injection moulding a formation on a circular body, wherein the moulding core which produces the formation comprises an inner core member and an outer core member, characterised in that the formation is an undercut formation moulded in a series of arcuate sections alternating with spaces, and the core is extracted by firstly relatively rotating said body and said outer core member so that the body is expanded radially by a camming action between the core and the arcuate sections and then ejecting the body off the core. EP0641277 also provides a coupling element for use in an ostomy, incontinence, or wound care device, the element comprising an annular body having a circumferentially continuous wall provided with an undercut formation, wherein said formation comprises a series of arcuate sections alternating with spaces, characterised in that a plurality of the undercut arcuate sections each has a radially extending surface which subtends an angle to the axis of the body sufficient to give a required degree of security to the coupling element in respect of its attachment to a counterpart press fit coupling element. In a first aspect, the present invention provides a coupling element (110) for use in an ostomy, incontinence, or wound care device, the element comprising an annular body having a circumferentially continuous wall with an undercut formation, wherein said formation comprises a series of undercut arcuate sections (130) alternating with spaces, characterised in that a tab (110C) is provided to afford a grasping point whereby the wearer may separate the coupling element and a counterpart press fit coupling element (160) by peeling them apart, the positioning, number and arrangement of the arcuate sections being such that ease of separation of the two coupling elements by peeling is readily achieved. Further embodiments are defined in the dependent claims. Preferably the coupling element and coupling of the invention are manufactured using the injection moulding method of EP0641277. The arcuate sections of the undercut formation can be of equal or unequal length, depending upon the application. Usually they will be of equal length. Preferably the arcuate sections occupy as much of the periphery as possible, although for practical reasons, and in order to facilitate removal of the body from the core, preferably the ratio of the circumferential length of the spaces to the circumferential length of the arcuate sections is at least 1:3. The spaces themselves can be of equal or unequal length, depending upon the application. The radial extent of the undercut formation will depend on the application, and to an extent on the wall thickness of the body and the type of plastics material employed. However a radial extent of greater than 0.005 inch (0.0125 cm), and up to 0.020 inch (0.051 cm) or even more, can be achieved using the method of EP0641277 in appropriate circumstances. The respective arcuate sections and the intervening spaces are preferably joined by end surfaces of the arcuate sections which are not radially directed, but which are located at an acute angle to a tangent to the circular body. Preferably the angle is less than 60°, most preferably less than 45°. In the coupling element of the invention preferably each of the arcuate sections has an undercut radially extending surface which subtends an angle to the axis of the body sufficient to give the required degree of security thereto. This angle will usually be at least 70°, preferably 80°, and most preferably 90°. In some circumstances the angle may even exceed 90°, and extend to 95° or more, giving a slope opposite to that necessary using conventional moulding techniques. By the use of a steep angle of slope it is found that, in many applications, when the coupling element is applied over a cooperating lip on a mating coupling element, an audible click can be heard, which provides the user with reassurance that the closure member or coupling element is secure. It is also found that the greater the angle of slope the greater the security of mating on a mating coupling element, particularly when that lip or flange has a radially extending surface which also subtends a steep angle to the axis of the body. This invention is embodied in a coupling element of an ostomy coupling. Such couplings are used to attach a bag for receiving discharged material to a medical grade adhesive pad which is attached to the wearer's peristomal skin surface. Efforts have been made over the years to design an ostomy coupling which remains securely attached when coupled but which can be separated without causing pain to the peristomal region which is of course very tender in the days and weeks immediately following the surgical intervention procedure. A successful design of ostomy coupling is described and claimed in British Patent No. 1571657. This includes a channel-section coupling element which co-operates with a second coupling element carrying a rib of closed-loop form which is designed to inter-engage with the channel of the first coupling element, so that a snap-fit is achieved between the two coupling elements. The channel section element is preferably attached to the bag but may be attached instead to the medical grade adhesive pad. The second element is preferably attached to the pad but may be attached to the bag. It has been found that better results are obtained, in terms of security of attachment of the two coupling elements, if certain ostensibly minor but in fact important new features are included in the coupling device described above. Such features include the provision of an undercut formation comprising a series of arcuate sections alternating with spaces , as previously described. The invention may be applied to a wide range of plastics materials, including for example, olefin polymers and co-polymers such as polyethylene, polypropylene, and ethylene co-polymers such as ethylene-vinyl acetate co-polymers. Brief Description of Drawings In order that the invention may be clearly understood, exemplary embodiments thereof will now be described with reference to the accompanying Drawings, in which: Figure 1 is a plan view of one example of ostomy coupling element according to the invention; Figure 2 is a cross-section in a radial plane on the line II-II in Figure 1; Figure 3 is a plan view, on an enlarged scale compared to Figure 1, of part of the element shown in Figure 1; Figure 4 is a cross-section similar to Figure 2, but taken on the line III-III of Figure 1; Figure 5 is a cross-sectional view, the section being on a radial plane containing the longitudinal central axis of the coupling, and showing an ostomy coupling element which is a counterpart to the element shown in Figure 1; and Figure 6 is a detail view of part of the element shown in Figure 1, illustrating an alternative shape for the undercut portion. Detailed Description of Drawings Referring now to Figures 1-6, these disclose the application of the invention to an ostomy coupling. It will normally be the case that the coupling element shown in Figure 1 will be the bag-side element and that shown in Figure 5 will be the body side element, but these elements may be reversed, that is, the Figure 1 element may be the body side and the Figure 5 element the bag-side, without departing from the invention. Mutually inter-engagable coupling elements designed according to the principles illustrated in Figure 1-6 may also be used as coupling elements in incontinence devices and in wound care appliances. As will be well understood by those skilled in the ostomy art, a relatively thin pad of medical grade adhesive material is normally attached at one of its surfaces to the skin of the wearer and at the other of its surfaces to the surface 163 shown in figure 5. Such a pad may have a stomal orifice therein or may have provision whereby its central portion can be pushed out or detached, so that waste material being discharged from the body of the wearer can pass into an ostomy bag or an incontinence device which is connected by the bag side coupling element 110 to the body side coupling element 160. Suitable materials for such an adhesive pad include, for example, those described by Chen in US Patent 3,339,546; by Chen et al in US Patent No. 4,192,785; by Pawelchak et al in US Patent No. 4,393080; and by Doyle et al in US Patent No. 4,551,490. A particularly suitable material is that sold under the Registered Trade Mark STOMAHESIVE by Bristol-Myers Squibb of Ickenham, Middlesex, England. Referring firstly to Figures 1-4, one example of a bag side coupling element according to the invention is illustrated. It comprises a channel section element 110 of circular form seen in Figure 1. The female ostomy coupling element may be normally made of a synthetic plastics material such as EVA. EVA Grade UL 00209 is one material, available from Esso, which is suitable. The male element may be made of low density polyethylene. The element 110 as seen in Figure 1 has tabs 110A, 110B and 110C. The tabs 110A and 110B are provided to facilitate attachment of a belt, and the tab 110C is provided to afford a grasping point whereby the wearer may separate the two coupling elements by "peeling" them apart. The coupling element 110 has a radially outer wall 112 and a radially inner wall 114. The wall 114 surrounds a stomal orifice 118 at the centre of the coupling. The generally ring-like or annular element 110 has a floor 116 which joins the radially inner and outer walls 112, 114, this floor having a surface 116A to which may be attached, e.g. by adhesive, heat welding, RF plastics welding, or other suitable method, an ostomy bag provided with a suitable hole in one of its walls to serve as an entry for discharges from the wearer. This entry hole is aligned with the stomal orifice 118 as is conventional in ostomy bags. The floor 116 has a surface 116B at the base of the channel, and, into this floor, there are provided a plurality of recesses 120. These recesses 120 in their presently preferred form are relatively shallow, flat bottomed, and are equally spaced peripherally around the coupling element. As seen best in Figure 3, the recesses 120 have a shape which is approximately rectangular. The recesses, however, could be differently shaped according to the design of the moulding equipment, if desired. In a preferred embodiment of the invention, there are 24 such recesses, spaced around the ring at 15° centres. The depth of each such recess is approximately 0.01 inch, i.e. approximately 0.254 millimetres. The remainder of the surface 116B at the base of the channel is substantially flat. The recesses serve to receive one or more mould core members, and serve, in extraction of the annular body from the mould, to prevent rotation of said body relative to the said mould core member. The radially outer wall 112 is provided with a plurality of radially inwardly projecting roof-like portions 130 (also referred to herein as arcuate sections) whose undersides 132 (i.e. top surfaces as seen in Fig. 2, which are undersides of the portions 130 when the female coupling element is laid flat on a horizontal surface) are substantially flat and extend substantially in a plane parallel to the planes of the respective surfaces 116A and 116B. The portion 130 extends inwardly a distance such that it covers from about 10 to about 20%, and preferably about 15%, of the width of the channel as will be discussed later. In moulding terms, the portions 130 define undercut formations. The roof-like portions 130 may have radially inner surfaces defined by respective continuous curves 134 that extend from the end 112B of the wall 112 in a smooth curve to merge with the surface 132. In a peripheral sense, as seen in Figures 1 and 3 the walls 134 curve smoothly to merge with the radially inner surface 112A of the wall 112. This structure is provided so that the portions 130 are forced outwardly by rotation of the core, as described above, so permitting the coupling element to be readily removed from the mould. The radially inner wall 114 is, as seen in Figure 2, of greater height than the wall 112, and has its radially outer corner radiused as seen at 136. In combination, the surfaces 134 and 136 contribute to the ease with which a counterpart coupling element such as is seen in Figure 10 can be pushed into an inter-engaged condition, relative to the coupling element 110. The respective roof portions 130 are equally spaced around the inner periphery of the wall 112, and are preferably located at 45° centres. Other spacings, however, may be used. The extent in a peripheral sense of each roof portion 130 is such that it subtends at the axis of revolution of the coupling element, i.e. at the centre in the case of a geometrically circular ostomy coupling element, an angle of between 15 and 25°, preferably between about 18 and 22°. The number, positioning, and angular extent of the roof portions 130 may be varied. Preferably there are 6, 8, 10 or 12 of the roof portions, and the roof portions are preferably equally angularly spaced in a peripheral sense around the coupling element. The roof portions 130 may extend inwardly of the wall 112 by an amount of up to half the width of the channel, although preferably they extend by an amount equal to about one tenth to one fifth, more preferably one seventh to one fifth, and, most preferably one sixth, of the width of the channel measured in a radial direction. It has been found that this preferred amount of inward extent, taken together with the positioning, number and arrangement of the roof portions, gives an ostomy coupling having a sufficient overlap of the cooperating coupling elements that the security of attachment of the two coupling elements against a direct pull is enhanced, but the ease of separation of the two coupling elements by the "peeling method" referred to above is such that the separation can be readily achieved by most ostomy coupling wearers, except possibly those who are very old and infirm. Figure 5 illustrates, in partial cross-section, an ostomy coupling element 160, which is also of ring-like or annular form and intended to interfit with the element 110. In the preferred embodiment of the present invention, the element 160 would be the body side coupling element. It comprises a radially extending substantially flat flange 162 and a peripherally extending rib member 165 formed for mutual inter-engagement with coupling element 110. The flange 162 has a surface 163 to which is secured, in any suitable manner, a pad (not shown) of medical grade adhesive material. As is conventional in ostomy couplings, provision may be made on the free surface of the medical grade adhesive pad for markings directed to assisting the user to cut out a central portion of the pad, in registry with the stomal orifice 164. The rib member 165 has a radially outer rim 167 and a radially inner flexible deflectable seal strip 168. The purpose of the strip 168 is to assure good sealing between the two coupling elements when they are inter-engaged. The rim 167 has a shaped surface 166, located at substantially 45° to the plane of the flange 162. Of course other angular values may be employed but about 45° is preferred. When the two coupling parts are connected together, the edges of the roof portions 130 engage the surface 166 at peripherally spaced locations. The seal strip 168 is deflected slightly radially outwardly and bears resiliently against the surface 114A of the wall 114, so providing a good seal and taking up any minor tolerance variations which may have arisen in manufacture. In the above description, reference has been made to the surface 132 of the roof portion 130 being located in a plane substantially parallel to the planes of the surfaces 116A and 116B. It is not essential to the present invention that the surface 132 should be planar nor that it should be precisely parallel to the planar surfaces 116A and 116B. A configuration as shown in Figure 6 may alternatively be employed, with good results. Those skilled in the art of design of ostomy couplings will realise that certain changes and modifications may be made, without departing from the scope of the claims. For example, the undercut formation could be positioned so as to extend radially outwardly rather than inwardly and the cooperating element would then have a radially inwardly directed rib member co-operable therewith.

Claims: A coupling element (110) for use in an ostomy, incontinence, or wound care device, the element comprising an annular body having a circumferentially continuous wall with an undercut formation, wherein said formation comprises a series of undercut arcuate sections (130) alternating with spaces, characterised in that a tab (110C) is provided to afford a grasping point whereby the wearer may separate the coupling element and a counterpart press fit coupling element (160) by peeling them apart, the positioning, number and arrangement of the arcuate sections being such that ease of separation of the two coupling elements by peeling is readily achieved. A coupling element according to claim 1, characterised in that the tab (110C) is adjacent or proximate to a space between two arcuate sections. A coupling element according to claim 1, characterised in that the tab (110C) is circumferentially aligned with a space between two arcuate sections. A coupling element according to claim 1, characterised in that a snap-fit is achieved with the counterpart press fit coupling element (160). A coupling element according to claim 1, characterised in that when the coupling element (110) is attached to its counterpart press fit coupling element (160) an audible click is heard. A coupling element according to claim 1, characterised in that said undercut formation is positioned so as to extend radially outwardly and to co-operate with a radially inwardly directed rib member on a co-operating coupling element. A coupling including a coupling element of claim 1 (110) and a counterpart coupling element (160) characterised in that the annular body of the coupling element (110) is channel-shaped, and the counterpart coupling element comprises a flexible, resilient and deflectable seal strip (168) arranged to co-operate with a wall (114A) of the channel-shaped annular body to prevent leakage of bodily discharges. A coupling according to claim 7, characterised in that the coupling element (110) comprising the channel-shaped annular body is the bag-side element and that the counterpart coupling element (160) comprising the seal strip is the body-side element.

Inventors: KILGOUR RICHARD DEREK, KILGOUR, RICHARD DEREK
Applicants: SQUIBB & SONS INC, E.R. SQUIBB & SONS, INC.
Application year: 1993
Main classification: B29C45
IPC codes: B65D43, B29C45