METHOD FOR MANUFACTURING A SEALING BODY, PARTICULARLY FOR A PIPE JOINT, AND A SEALING BODY PRODUCED BY THIS METHOD

Abstract: In the manufacture of a sealing body for a pipe joint comprising a retaining ring (2) of thermoplastic material, which is to be fastened on the end portion of a pipe part, and a sealing ring of thermoplastic material, preferably thermo­ plastic rubber, the mould cavity (11) for the sealing ring which is partly bounded by a portion (12) of the wall of the retaining ring (2), is sealed, at the transitions (18, 19) from said wall portion (12) to adjoining wall portions (15, 16 respectively) bounding the mould cavity (11) during injection moulding of the sealing ring. The mould cavity (11) is sealed, at the first transition (18), by an annular lip (6) on the retaining ring (2) which lies against the wall portion (15) and, at the second transition (19), by an annular ridge (10) on the retaining ring (2) which cooperates clampingly with the outer periphery (20) of a mould part (21).

Description: Method for manufacturing a sealing body, particularly for a pipe joint, and a sealing body produced by this method sne invention relates to a method for manufacturing a sealing body, particularly for a pipe joint, comprising a retaining ring of thermoplastic material, which is to be fastened to an end portion of a pipe part, and a sealing ring disposed coaxially to said retaining ring and bonded thereto, the retaining ring being previously moulded and tne sealing ring being moulded in a mould cavity which is partly bounded by a portion of the wall of the retaining ring. A method of this kind is known. In this known method a retaining ring of thermoplastic material, having a substantially J-shaped cross-section, is previously moulded and is placed between a number of cooperating parts of a mould. Together with that part of the retaining ring which projects substantially inwards, these mould parts form a mould cavity for the sealing ring which is moulded by casting or injection moulding in this mould cavity, whereby a connection is made between the sealing ring and the retaining ring. problems occur with this method, particularly in the case of the injection moulding of the sealing ring. During the injection moulding the relatively soft material of the retaining ring is pressed away, at the transition from the retaining ring wall bounding the mould cavity to tre mould part walls bonding the mould cavity, by the hignly fluid material of the sealing ring whicn is injected under very high pressure into the mould cavity. The material of te sealing ring thus passes to places where it is not #esire# and an end product of poor quality, which in many eases in unusdble, is obtained. t is the object of the invention to provide a solution to ;nose problems. This object is attained by a method of the abovementioned kind, which is characterized in that during the injection moulding of the sealing ring the mould cavity for the sealing ring is sealed, at at least one transition from tne wall portion, bounding the mould cavity, of the retaining ring to an adjoining wall portion bounding the mould cavity. In this way a sealing body of very good quality is obtained, without so-called "butterflies". The retaining ring is preferably provided with sealing means which during the injection moulding of the sealing ring form a seal with the adjoining wall portion at at least one transition from the wall portion, bounding the mould cavity, of the retaining ring to an adjoining wall portion bounding the mould cavity. The sealing means preferably comprise at least an annular lip which is disposed at a first transition on the retaining ring and extends in the direction of the sealing ring to be moulded, and which during the moulding of the sealing ring lies against a first adjoining wall portion. The thickness of the lip expediently decreases in the direction of the free end. Through the action of the sealing ring material flowing at high speed into the mould cavity, the lip is thus pressed against the wall of the mould cavity during the injection, so that a very good sealing action is obtained. Tne sealing means preferably also comprise an annular ridge provides on the retaining ring at a second transition and co#per=ting clampingly during the moulding of the sealing ring with an oppositely situated portion of a second adjoining wall portion. The invention likewise relates to a scaling body for a pipe joint, comprising a retaining ring of thermoplastic material, which is to be fastened on the end portion of a pipe part, and a sealing ring disposed coaxially to said retaining ring and bonded thereto, which sealing body is characterized in that the retaining ring is provided, at a first transition from the wall of the retaining ring to the wall of thesealing ring, with an annular lip which, viewed in a cross-section of the sealing body, extends on the outer periphery of the said cross-section of the sealing body in the direction of the sealing ring. In a preferred embodiment the retaining ring is provided with an annular ridge at a second transition from the wall of the retaining ring to the wall of the sealing ring, which transition, viewed in a cross-section of the sealing body, is situated on the inner periphery of said cross-section of the sealing body. The invention will now be explained through the description of an example of embodiment and with reference to the drawing, wherein: Figure 1 shows a sealing body according to the invention, partly in cross-section and partly in elevation, and Figure 2 is a cross-section on a larger scale of the mould cavity for the sealing ring of the sealing body shown in Figure 1. Figure 3 shows a part of the walls bounding the mould cavity for the sealing ring on a larger scale, with the mould cavity not yet completely closed. In figure 1 is shown a sealing body 1 for a pipe joint, comprising a retaining ring 2 of thermoplastic material, which is to be fastened to an end portion (not shown) of a pipe part, and a sealing ring 3 disposed coaxially to said retaining ring and bonded thereto. The sealing ring 3 preferably consists of a thermoplastic rubber. The retaining ring 2 is provided on its inner side with annular ridges 4 adapted to cooperate with complementarily shaped annular depressions on an end portion of a pipe part, for the purpose of fastening a sealing body 1 to the pipe part. At a first transition 5 from the wall of the retaining ring 2 to the wall of the sealing ring 3 the retaining ring 2 is provided with an annular lip 6 extending in the direction of the sealing ring 3. The wall 7 of the lip 6, situated on the outer periphery of the cross-section of the sealing body 1, lies substantially in the same plane as the adjoining part 8 of the wall of the retaining ring 2. The thickness of the lip 6 decreases in the direction of its free end. At a second transition 9 from the wall of the retaining ring 2 to the wall of the sealing ring 3 the retaining ring 2 is provided with an annular ridge 10. Figure 2 is a cross-section of the mould cavity 11 for the sealing ring 3 of the sealing body 1. The mould cavity 11 is bounded by a portion 12 of the wall of the previously moulded retaining ring 2, which is placed in a recess in a part 13 of a mould 14, and is further bounded by a portion 15 of the wall of a mould part 13 and a portion 16 of the wall of a mould part 17 which is situated partly inside the retaining ring 2. The retaining ring 2 is provided with sealing means 6, 10 in the form of an annular lip 6 and an annular ridge 10, which during the injection moulding of the sealing ring ; cooperate to form a seal with the respective adjoining wall portions 15 and 16 of the mould cavity 11 at the transitions 1S, 19 from the wall portion 12, bounding the mould cavity 11, of the retaining ring 2 to an adjoining wall portion 15 and 16 respectively of a wall bounding the mould cavity. At the transition 18 from the wall portion 12 of the retaining ring 2 to the wall portion 15 of the mould part 13, the outer wall 7 of the lip 6 lies against the wall 15 of the mould part 13. At the transition 19 from the wall portion of the retaining ring 2 to the wall portion 16 of the die part 17, the annular ridge 10 lies clampingly against the oppositely situated outer periphery 20 of that part 21 of the mould part 17 which lies inside the retaining ring (see also Figure 3). Because of the abovementioned sealing means 6, 10 good sealing is effected at the transitions 18, 19 during the injection under high pressure of the highly liquid material of the sealing ring into the mould cavity 11. Particularly when the gate is situated at the end 22 of the mould cavity 11, the lip 6 is pressed against the wall 15 through the action of the material flowing in at high speed, so that very good sealing is achieved at the transition 18. Through the application of the steps described above a sealing body is obtained which is of very good quality and at the transitions 6, 9 is free from so-called "butterflies" of sealing ring material. Tne invention is not restricted to the embodiment of the sealing body described in the example, but also extends to other embodiments of a composite sealing body in the production of which the sealing problems previously referred to occur.

Claims: CLAIMS: 1. Method for manufacturing a sealing body (1), particu larly for a pipe joint, comprising a retaining ring (2) of thermoplastic material, which is to be fastened to an end portion of a pipe part, and a sealing ring (3) disposed coaxially to said retaining ring and bonded thereto, the retaining ring (2) being previously moulded and the sealing ring (3) being moulded in a mould cavity (11) which is partly bounded by a portion (12) of the wall of the retaining ring (2), characteri zed in that during the injection moulding of the sealing ring (3) the mould cavity (11) for the sealing ring (3) is sealed, at at least one transition (18 and 19 respectively) from the wall portion (12), bounding the mould cavity (11), of the retaining ring (2) to an adjoining wall portion (15 and 16 respectively) boun ding the mould cavity (11). 2. Method according to Claim 1, characterized in that the retaining ring (2) is provided with sealing means which during the injection moulding of the sealing ring (3) form a seal with the adjoining wall portion (15 and 16 respectively) at at least one transition (18 and 19 respectively) from the wall portion (12), bounding the mould cavity (11), of the retaining ring (2) to an adjoining wall portion (15 and 16 respectively) boun ding the mould cavity (11). 3. Method according to Claim 2, characterized in that the sealing means comprise at least an annular lip (G) which is disposed at a first transition (18) on the retaining ring (2) and extends in the direction of the sealing ring (3) to be moulded, and which during the moulding of the sealing ring (3) lies against a first adjoining wall portion (15), and the thickness of which expediently decreases in the direction of its free end. 4. Method according to one of Claims 1 to 3, characterized in that the sealing means also comprise an annular ridge (10) provided on the retaining ring (2) at a second transition (19) and cooperating clampingly during the moulding of the sealing ring (3) with an oppositely situated portion (20) of a second adjoining wall portion (16). 5. Method according to one of Claim 4, characterized in that the annular ridge (10) is clamped on the outer periphery (20) of a part (21) of a mould, which part is situated inside the retaining ring (2) and bounds the moulding cavity (11). 6. Sealing body for a pipe joint, comprising a retaining ring of thermoplastic material, which is to be fastened on the end portion of a pipe part, and a sealing ring disposed coaxially to said retaining ring and bonded thereto, characterized in that the retaining ring (2) is provided, at a first transition (5) from the wall of the retaining ring (2) to the wall of the sealing ring (3), with an annular lip (6) which, viewed in a cross section of the sealing body (1), extends on the outer periphery of said cross-section of the sealing body in the direction of the sealing ring (3). 7. Sealing body according to Claim 6, characterized in that that wall of the lip (6) which is situated on the outer periphery lies substantially in the same plane as the adjoining part ( a ) of the wall of the retaining ring (2). 8. sealing body according to Claim 6 or 7, characterized in that the thickness of the lip (6) decreases in the direction of its free end. 9. . Sealing body according to one of the Claims 6 to 8, characterized in that the retaining ring (2) is provi ded with an annular ridge (10) at a second transition (9) from the wall of the retaining ring (2) to the wall of the sealing ring (3), which transition (9), viewed in a cross-section of the sealing body (1) is situated on the inner periphery of said cross-3tction of the sealing body. 14 J. Sealing body according to one or more Df Claims 6 to 9, characterized in that the sealing rir (3) consists of a thermoplastic material, particularSj a thermoplastic rubber.

Inventors: BEUNE, JOHANNES HENDRIKUS, LAARHOVEN, JOHANNES JOSEPHUS
Applicants: WAVIN B.V.
Application year: 1986
Main classification: B29C45
IPC codes: F16L21, B29L31, F16L47, F16L11, B29C45