GB2131959A

GB2131959A - Apparatus for providing a hermetic connection to a hollow body

Info

Publication number: GB2131959A
Application number: GB08331276A
Authority: GB
Inventors: Adam Flink
Original assignee: Leybold Heraeus GmbH
Current assignee: Balzers und Leybold Deutschland Holding AG
Priority date: 1982-12-03
Filing date: 1983-11-23
Publication date: 1984-06-27
Also published as: IT1169631B; GB8331276D0; DE3244759A1; IT8323507A0; DE3244759C2; GB2131959B

Abstract

For the purpose of hermetically connecting, to a vacuum pump, a compressor, a gas-source and/or the like, a connecting port (7) provided on; a hollow body (1), that is placed in a test chamber (2) for leak-testing and/or determining its resistance to bursting, the use is proposed of a preferably automatically operating coupling device (4) having a sealing head (16, 71) which is axially displaceable and which, for the purpose of suiting its position to that of connecting ports (7) deviating from their nominal positions, is also mounted to be laterally displaceable and to be swivellable e.g. by ball and socket joints 14, 15. <IMAGE>

Description

SPECIFICATION Apparatus for providing a hermetic connection to a hollow body The invention concerns apparatus, particularly for leak and/or burst testing installations, for providing a hermetic connection between a hollow body equipped with a connecting port, and a gas-source, a compressor, a vacuum pump or the like, comprising a sealing head adapted to establish the connection to the port.

In industrial manufacturing processes, it is often required, for quality-testing and safety reasons to test hollow components for leakage prior to their installation. As a rule, this is carried out by means of an integral leakage test in which the product under examination is put into a test chamber, different pressures are produced inside and outside the product and a test gas, preferably helium, is introduced at the higher pressure side. If the test gas penetrates to the side at the lower pressure, then the hollow body under test must be leaking.

In installations of this kind, the connections between the hollow body and the vacuum pump, the compressor or the source of test gas must be made with particular care, since if the connecting means are not sound, test gas penetrates to the side having the lower pressure, and the hollow body is therefore indicated as being unsound even though this is not the case. Special difficulties arise in the sealing zone when very short cycle times of only a few seconds have to be adhered to.

With cycle times of this kind, it is not possible to attach the hollow bodies by hand to the various units of the leakage-testing installation.

Short cycle times also assume high differences in pressure during the test phase, so that the test gas can pass very rapidly through any leaks present to the side at the lower pressure where it can be detected. Furthermore, high differences in pressure are necessary if the container that is to be tested for leaks is at the same time to be tested for its resistance to bursting. For this purpose it is necessary, for a certain period, to produce in the present product under test, a test pressure which exceeds the normal operating pressure.

However, the greater the differences in pressure, the more essential it is to provide sealing means which operate in a precise manner.

It is known from DE-OS 28 02 645 to connect a hollow body, contained in a test chamber, to the attachment means of a leakage-testing installation. For this purpose, the cover of the test chamber is equipped with a connecting tube which has a socket-like extension which is pushed over a connecting port arranged on a carrier for the hollow body under test. The inner face of this coupling means is provided with two sealing rings so that after the cover has been lowered, a tight connection is established. Equipment of this kind can be used only if the connecting port and the coupling means are exactly positioned relatively to each other after the product under test has been placed in the test chamber.

This is always the case with the equipment in accordance with this prior art, since the connecting port is located on a carefully produced and always exactly positioned carrier for the hollow body to be tested. An exact position of the connecting port is not, however, assured if it should be fitted on the test body itself and if the latter is a mass-produced article having wide dimensional tolerances. This is the case, for example, with enclosure means for cold compressors where the connecting ports, welded and/or brazed to them, have relatively wide tolerances as regards the location of the weld and-to a considerable extent as regards the inclination of the connecting port.

Prior to the leakage test, the connecting port is bent over the correspond to the later assembly position, and relatively wide tolerances are likewise involved in this connection.

Finally, a connecting port may become bent over during transportation so that is deviates from its nominal position. It is not possible to use a coupling means in accordance with DE OS 28 02 645 since it cannot be adapted to suit the connecting ports of various hollow bodies, which ports are inclined to differing extents from their nominal positions.

The object of the present invention is to provide apparatus of the initially stated kind which permits the fluid-tight connection of a hollow body (by the way of the sealing head) to different units, e.g. those of a leakagetesting installation, even when the connecting port occupies different positions on the product under test.

According to the invention, this object is achieved in that the sealing head is so mounted as to be both swivellable and laterally displaceable. Preferably two ball-andsocket joints are used for mounting of the sealing head. As a result of this step, the position of the sealing head can be adjusted to suit differently positioned connecting ports.

Furthermore, the ball-and-socket joints can be of relatively simple form in which they are gas-tight at high pressure differentials (25 bars and more). If the points of rotation of the sealing head are located very close to the port of the test product, relatively large deviations in position and angle can be offset.

Fluid-tight connection of the sealing head to the connecting port is expediently achieved with the aid of a pair of sealing rings with which is associated a clamping device so that at this zone too, high internal pressures can be reliably sealed off against the exterior.

The sealing head and its mounting are preferably displaceable with the aid of a pis ton-and-cylinder arrangement so that automatic operation of the connecting apparatus is possible. Actuation of the clamping device for the pair of sealing rings in the sealing head is preferably also achieved by means of a further piston-and-cylinder arrangement which is actuated after the sealing head has been pushed on to the connecting port. A completely automatic mode of operation is thus possible.

The invention will now be further described with reference to the accompanying drawings, wherein: 'Figure 1 shows, diagrammatically and partly in section, an embodiment of connecting apparatus in accordance with the invention; Figure 2 shows the connecting apparatus of Fig. 1 comprising a swivellable sealing head pushed on to a connecting port; Figure 3 is a section through the front part of the connecting apparatus together with an outer sealing element; and Figure 4 illustrates a sealing head which is of a different shape from that of Fig. 3 and which comprises an inner sealing element.

Referring the drawings, hollow body 1 to be tested and its test chamber 2 are illustrated only partially in Figs. 1 and 2. The front portion of the sealing apparatus projects into the test chamber 2 through an opening 3 in the chamber. A housing 5 on the connecting apparatus 4 is attached to the wall of the test chamber 2 by means of a flange 6.

A hollow body 1 to be tested for fluidtightness has a connecting port 7 which deviates from its nominal position (indicated in broken lines and designated by the numeral 8). However, a helium-tight connection between this connecting port 7 and a leakagetesting installation, not illustrated, is required to be established. Said installation is coupled to the connecting apparatus 4 by a screwthreaded connector 9.

To enable a fluid-tight connection to be made to the port 7, the front portion of the connecting apparatus 4 comprises three tubular members 11, 12 and 1 3 which are interconnected by ball-and-socket joints 14 and 1 5. Thus, a sealing head 16, arranged at the distal end, is pivotable as well as laterally displacable so that it can be readily brought into the position illustrated in Fig. 2. Deviations in position and angle of up to 10 mm and 1 5, respectively and resulting from manufacturing tolerances can thus be catered for.

The interior of the housing 1 can be connected to the leakage-testing installation by way of a central gas duct formed by the tubular members 11, 12, 1 3 (in part) and a tubular member 1 7 which passes centrally through the housing 5 of the connecting apparatus 4. The connector 9 is screwed on to its outer end face.

That end of the tubular member 1 3 that is presented to the housing forms an annular piston 1 8 which is contained in a cylinder 1 9 formed by the tubular member 1 7 and the housing 5. The equipment is operated by supplying a pressurized medium through lines 20 and 21 at each required moment.

A further cylinder 22, formed by the tubular member 1 3 and a reduced part of the tubular member 17, is accommodated within the housing 5 and the tubular member 1 3. Contained in the cylinder 22 is an annular piston 24, displaceable against the pressure of a spring 23, and having a cylindrical extension or piston rod 25 which prolongs it in the direction of the sealing head 1 6 and which is closed off at the end by an endface 26, concave on the outside, and which has lateral openings 27. One end of a pin 28 bears against the concave endface 26, and the other end of the pin acts on a clamping device which is associated with sealing rings 29 and 31 of the sealing head 16 and which will be described in greater detail by reference to Fig. 3.

The connecting apparatus illustrated in Figs.

1 and 2 operates in the following manner.

After the product 1 to be tested has been brought into position in the test chamber 2, the sealing head 1 6 is pushed on to the connecting port 7 by actuating the piston-andcylinder arrangement 18, 1 9 (See Fig. 2). By means of limit switches (not illustrated) associated with the annular piston 18, a signal is sent when the sealing head has reached its position. Thereafter the annular piston 24 is actuated by supplying a pressure medium by way of the connecting port 32 and the bore 33 in the tubular portion 1 7. As will be described in greater detail by reference to Fig.

3, the movement of the annular piston 24 brings about compression of the seals 29 and 31 in the sealing head 16, so that a sealing effect capable of catering for a great pressure differential is set up between the connecting port 7 and the sealing head 1 6. The test chamber 2 is then evacuated and the pressure in the product 1 is increased. As this increase in pressure takes place, test gas is introduced into the interior of the product 1. If the product leaks, test gas forces its way into the test chamber 2 and is recorded by a detector (not illustrated) which is sensitive to the test gas.

With the described construction, gas pressures of 25 bars and more can be used without difficulty. Furthermore, the clamping device for the sealing rings 29 and 31 can be actuated by pressures of this order of magnitude, so that with a fully automatically controlled cycle of movements, very short times can be achieved.

Fig. 3 shows details of the front part of the connecting apparatus 4 that carrier the sealing head 16. The sealing head 16 is so formed that it encloses the connecting port 7. Its end 35 is funnel-shaped. The sealing rings 29 and 31 are arranged in the zone of its inner faces, a support ring 36 being located between them. A displaceable cylinder portion 37 lies against the inner sealing ring 31 and its end 38 presented to the pin 28 is closed except for apertures 39 and is of concave shape. The pin 28 bears against the concave face zone, so that displacement of the cylindrical extension 25 toward the sealing head causes pressure to be applied through the pin 28 to the cylinder portion 37 and hence to the sealing rings 29 and 31.This pressure causes compression of the sealing rings and therefore -when a connecting port is present in the sealing head 1 6-the application thereto of the pressure of the sealing rings 29 and 31.

This clamping pressure is further increased if a high pressure is produced in the container under test and therefore also in the tubular members 11, 1 2 and 1 3. This pressure acts on the outer annular surface of the endface 38 in the direction of the sealing rings 29 and 31.

The sealing head 1 6 is releasably held on the tubular member 11 by means of a bayonet connection 41, 42. The illustrated sealing head 1 6 can thus be replaced in a simple manner when the sealing rings become worn or when the nominal width of the connecting ports changes. At its end in the housing 5, the pin 28 is provided with a transverse pin 43 so that it cannot slide out when the sealing head 16 is being changed.

The tubular members 11, 1 2 and 1 3 are interconnected by ball-and-socket joints designated generally 14 and 15. For this purpose, the tubular portion 1 2 has a smaller diameter than the tubular portions 11 and 1 3. Its ends projects into the tubular portions 11 and 1 3 and are provided with annular domed surfaces 44 and 45 respectively which fit into and are supported by ring systems each consisting of three rings 46 to 48 and 51 to 53 respectively and held together by clamping rings 54 and 55 respectively. Each of the median rings 47 and 52 is flexible, is substantially Ushaped in section and is so arranged that the outer face of one of the limbs of the U bears against a domed face.Each of the outwardly directed cavities 56 and 57 so formed communicates with the main cavity by way of bores, not illustrated, in the outer rings 46 and 53. This arrangement offers the advantage that, when high pressures obtain in the interior of the system, the rings 47 and 52 bear particularly firmly and tightly against the domed faces. The pairs of bearing rings 46, 48; 51, 53 which enclose the rings 47 and 52 respectively preferably consist of self-lubricating materials.

The tubular members 11 and 1 3 are interconnected by means of a resilient sleeve 58 which may be made of rubber or from a helical spring and which, when the sealing head 1 6 is swivelled or linearly displaced, generated return forces. For the purpose of increasing this effect, the tubular portion 1 2 has, roughly halfway along its length, an annular widened portion 59 which bears against the inner face of the sleeve 58.

For the purpose of checking the sealing function of the sealing head 16, the pair of sealing ring 29, 31 is provided with an intermediate exhaust means. The support ring 36 is provided with bores 61, which communicate by way of a duct system with a port 62 on the housing 5. The duct system includes a bore 63 in the sealing head 16, bores 64, 65 and 66 in the tubular member 11, bores 67 in the annular widened portion 59 of the tubular member 12, and bores 68, 69 and 70 in the tubular member 1 3. Not only is the above-mentioned checking of the sealing rings 29 and 30 carried out by way of this duct system, but it is also possible to produce a continual suction effect so that test gas used in a preceding test stage can be removed in a reliable manner and no incorrect signals can be produced.All of the systems which close off the interior of the apparatus 4 from the interior of the test chamber 2 are expediently designed as double seals with intermediate exhaust. This ensures that any test gas, such as helium, passing through one of the two seals by diffusion is drawn off to the maximum extent before it is able to penetrate into the second seal. In the case of the systems for sealing off the ball-and-socket joints 1 4 and 15, intermediate exhaust is achieved in that the rings 48 and 51 have bores, not illustrated individually, which connect the "rear side" (the side remote from the cavities 56 and 57) of the sealing rings 47 and 52 to the duct system 66 and 69.

Fig. 4 illustrates a sealing head 71 which is suitable for introducing into a sealing port 7 and which is likewise held in the front tubular member 11 by means of a bayonet connection 72 which is illustrated only in part. Only the sealing head 71 itself is shown in solid lines. The remaining parts are identical to corresponding parts seen in Fig. 3 and are therefore shown only in broken lines.

The sealing head 71 comprises of two parts which are movable relatively to each other and between which is fitted a return spring 73. One part surrounds the sleeve 74 with its concave closure face 75 which bears against the pin 28 and which is provided with several openings 76 for permitting the passage of gases. Rigidly connected to the sleeve 74 is an end disc 77 which carries a further sleeve 78. The endface of this sleeve 78 bears against the sealing ring 79. The second part of the sealing head 71 encloses a piston 81 which is displaceably arranged within the sleeve 74, said second part also enclosing a tube 83, passing centrally through this piston 81, the disc 77 and seals 79 and 82, as well as the distal tip 84 of the sealing head 71.

Tip 84 is tapered to facilitate introduction into the connecting port 7. The central tube 83 is firmly connected to the tip 84 and the piston 81. Furthermore, the piston 81 is in turn firmly connected to the tubular member 11 by a pin 72, which is also a component of the bayonet connection. For the purpose of accommodating the pin 72 and the spring 73, the sleeve 74 is provided with a slot 85, the opening of which faces forwardly. The return spring 73 is secured to the disc 77 by means of a further pin 86.

Displacement of the pin 28 toward the connecting port 7 causes displacement of the sleeve 74 and therefore of the disc 77 as well as the sleeve 78 toward the sealing rings 79 and 82. Since the piston 81 and therefore the tube 83 as well as the tip 84 are firmly connected to the tubular portion 11, the sealing rings 79 and 82 are compressed and therefore these sealing rings are pressed against the inner wall of the connecting port 7.

Provided between the sealing rings 79 and 82 is a support ring 87 having intermediate exhaust bores 88. To form a duct system for connecting these bores 88 to the connecting port 62 (Fig. 3), a further tube 89 is arranged concentrically within the tube 83 and is held therein by means of thickened wall portions 91 and 92 formed at its ends. Thus an annular duct 83 is formed and communicates, by way of bores 94 in the piston 81, with an annular channel 95 formed in the face of the inner wall of the sleeve 74. The width of the annular channel 95 is so selected that the connection is maintained whatever the position of the piston 81. Connection with the duct system in the other two tubular members is established by way of bores 96 formed in the sleeve 74.

Claims

1. Apparatus for providing a hermetic connection between a connecting port of a hollow body and a gas-source, a compressor, a vacuum pump or the like, comprising sealing head adapted to establish the connection to the port, wherein the sealing head is so mounted as to be both swivellable and laterally displaceable.

2. Apparatus according to Claim 1, including two ball-and-socket joints mounting the sealing head.

3. Apparatus according to Claim- 1 or Claim 2, wherein the sealing head is substantially cylindrical, has a funnel-shaped distal end and is provided with two internal sealing rings.

4. Apparatus according to Claim 1 or Claim 2, wherein the sealing head is substantially cylindrical, has a tapered distal end and is provided with two external rings.

5. Apparatus according to Claim 3 or Claim 4, including a clamping device associated with the sealing rings.

6. Apparatus according to Claim 5, wherein the sealing head includes a displacea- ble cylindrical portion which acts on the seal- ing rings.

7. Apparatus according to any one of the preceding Claims, in which the sealing head displaceably held by means of a piston-andcylinder actuating means.

8. Apparatus according to any one of the preceding Claims, comprising three flexibly interconnected tubular members holding the sealing head.

9. Apparatus according to Claim 8, wherein a forward said tubular member releasably supports the sealing head.

10. Apparatus according to Claim 8 or Claim 9, wherein the two ends of the median said tubular member have domed outer faces with which are associated bearing faces on the two other tubular members.

11. Apparatus according to Claim 10, wherein the bearing faces comprise at least three bearing rings, the median of which rings is made of flexible material.

12. Apparatus according to Claim 11, wherein the median bearing ring is of substantially U-shaped cross-section and is so arranged that the outer face of one limb of the U forms a bearing face, and the space within the U communicates through bores in the adjacent bearing ring with the interior of the tubular members.

1 3. Apparatus according to any one of Claim 8 to 1 2 comprising a resilient sleeve surrounding the median tubular member and interconnecting the front and rear tubular members to produce return forces.

14. Apparatus according to Claim 7 or Claim 7 and any one of Claims 8 to 1 3 wherein the wall of the actuating cylinder is a component of a housing of the apparatus and the rear tubular member is connected to the piston ofthe actuating means.

15. Apparatus according to Claim Sand any one of Claims 8 to 14, comprising means to actuate the clamping device, including a pin passing through the median tubular member and a further piston-and-cylinder arrangement arranged in the rear tubular member for actuating the pin.

1 6. Apparatus according to any one of the preceding Claims, wherein the tubular portions are provided with a central gas duct which extends from the sealing head to a connector arranged on the opposite side of the apparatus.

1 7. Apparatus according to Claims 15 and 1 6, wherein the further piston-and-cylinder arrangement comprises a cylinder and an annular piston surrounding the central gas duct.

1 8. Apparatus according to Claim 3 or 4 and Claim 1 6 or 17, comprising a- duct system connecting the space between the two sealing rings on the sealing head and a port on the housing.

19. Apparatus according to Claims 5, 15 and 17, wherein the clamping means acting on the seals of the sealing head and the piston rod of the actuating means for the pin have concave faces between which the actuating pin is arranged.

20. Apparatus according to any of the the preceding Claims, secured on the wall of a test chamber so that the sealing head projects into the interior of the chamber through an opening in the wall.

21. Apparatus according to Claim 20, wherein all of the systems that seal off its interior from the interior of the test chamber are in the form of double seals with intermediate exhaust.

22. Apparatus including a sealing head, substantially as hereinbefore described with reference to the accompanying drawings.