GB2068060A

GB2068060A - Sealing devices

Info

Publication number: GB2068060A
Application number: GB8102184A
Authority: GB
Original assignee: Danfoss AS
Current assignee: Danfoss AS
Priority date: 1980-01-25
Filing date: 1981-01-23
Publication date: 1981-08-05
Also published as: FR2474630B1; IT1143294B; FR2474630A1; JPS56109952A; GB2068060B; IT8167073A0; DE3002626C2; JPS6227307B2; CA1156692A; DE3002626A1; DK21481A

Abstract

A sealing device 102 comprises a sealing element 106,108 and a rigid support 104 for the element, the element being in the form of a spring plate having inner and outer peripheral edges, the inner edge defining an aperture in the plate, one peripheral edge portion of the plate being secured as at 110, 112 to the support and the other peripheral edge portion being spaced from the support, wherein the device can be compressed, in use, between two parallel walls 136,138 with the other peripheral edge portion of the plate engaging one of the walls as at 140,142 to effect a seal between the outside and the inside of that edge portion. As shown, the device is used to effect sealing of the actuator in different kinds of slide valve. <IMAGE>

Description

SPECIFICATION Improvements in and relating to sealing devices This invention relates to a sealing device for sealing two chambers of different pressure, wherein a sealing element consisting of a supporting member and a spring connected thereto is inserted under prestress between two parallel walls and is movable relatively to at least one wall having an aperture to be sealed.

In a previously proposed device of this kind, (DE-AS 22 55 278), the plate-like supporting member sealingly abuts the one wall. The spring is bent from sheet metal; its flat central portion is pushed onto pins of the supporting member; four flanged arms lie against the opposite wall under prestress. By reason of the large area of contact, considerable spring forces are required to effect an adequate seal.

In addition, large sealing faces are sensitive to soiling.

The invention is based on the problem of providing a sealing device of the aforementioned kind which is insensitive, can be made cheaply and brings about an adequate seal with comparatively low forces.

According to the invention, this problem is solved in that the spring is a plate spring which is sealingly secured in the region of one of its two peripheries to the supporting member and the portions of which lying against the wall in the region of the other periphery form a closed sealing rim.

Such a sealing device has a comparatively small sealing face which is insensitive to soiling. Low spring forces already suffice to produce comparatively large surface pressures at the sealing rim leading to a correspondingly high sealing effect.

Manufacture is cheap because plate springs are economical. Since the plate spring assumes the function of the pressure spring as well as that of a sealing element, the space required is also small. If the pressure conditions are selected so that the higher pressure can act in the chamber between the plate spring and supporting member, one obtains automatic pressure compensation because the pressure to be sealed supports the force of the plate spring.

In particular, the plate spring may be secured to the supporting member in the region of the hole periphery. The sealing rim is therefore located at the outer periphery of the plate spring and the pressure to be delivered and surrounding the outside ofthe sealing element assists the force of the plate spring.

In a preferred embodiment, a second similar plate spring symmetrical to the first plate spring is provided between the other side of the supporting member and the second wall. In this way one obtains a completely symmetrical sealing element.

This has mechanical advantages because substantially equal frictional forces occur at both sides during the relative motion. Wear is also the same at both sides. If a pressure between the walls is to be sealed from both sides, absolutely the same conditions obtain at both sealing positions. In particular, the supporting member itself is relieved from pressure. The sealing element is also self-centring. In comparison with a construction having a sealingly abutting plate-like supporting member, the planar parallel requirements for the opposed sealing faces are not high.

Advantageously, the sealing rim has a planar face.

This can, for example, be produced by face grinding.

In this way the sealing rim is made flat so that the surface pressure does not attain excessive values.

The supporting member and plate spring can in particular be of steel. This is of interest not only for mechanical reasons. Non-corrosive steel for the sealing element can be employed in many chemical processes. Also, such a seal has a high temperature stability.

In this case it is favourable if the steel of the plate spring is hardened at least at the sealing rim. This extends its life. The safe effect is achieved if the plate spring has a coating of hard material such as titanium carbide at least at the sealing rim.

In other cases, it is also possible to have a plastics supporting member and plate spring. Piastics often has an extraordinarily good sealing effect, even at low pressures. It can often also be selected so as to be stable to the medium to be sealed.

A particularly simple way of sealingly interconnecting the plate spring and supporting member is to spot weld them together. This applies to sealing elements of steel as well as plastics.

In this connection, it is advisable for the supporting member to be provided at one end with a circular edge of a somewhat larger diameter than the hole diameter of the plate spring. The edge gives a defined supporting surface to form a uniform sealed seam during welding.

A plastics sealing element can also be extruded in one piece.

It is a particular advantage that the supporting member can have a central hole. The space beyond the sealing element is sure to be sealed from this central hole because the plate spring is sealingly connected to the supporting member.

Further, the sealing element may be connected to rotate with a rotary shaft passing through the wall aperture. It is therefore not only suitable for relative linear motion such as that occurring with a flat side for a valve but also for rotary motion. The sealing element here assumes the function of the known slide ring seals.

In a preferred embodiment, the supporting member has external teeth cooperating with a further toothed element such as a serrated rotary slide, and the shaft passes through the central hole. The pressure occurring in the region of the tooth elements is reliably sealed at both sides.

Alternatively, the wall apertures are slots in which a shaft connected to the sealing element is displaceable transversely to its length, and the sealing rim diameter of the plate spring is larger than the length of the slots. This will again seal a pressure between the walls at both sides despite the mobility of the sealing element.

The sealing element is particularly suitable for sealing the actuating element of a flat slide from the outside because in this case there is little space available.

The present invention also provides a sealing device comprising a sealing element and a rigid support for the element, the element being in the form of a spring plate having inner and outer peripheral edges, the inner edge defining an aperture in the plate, one peripheral edge portion of the plate being secured to the support and the other peripheral edge portion being spaced from the support, wherein the device can be compressed, in use, between two parallel walls with the other peripheral edge portion of the plate engaging one of the walls to effect a seal between the outside and the inside of that edge portion.

The present invention also provides apparatus including a sealing device according to the invention, the apparatus including two parallel walls between which the device is fitted, the or each sealing element serving to seal an aperture in one, or a respective one of the walls.

Four sealing devices constructed in accordance with the invention and apparatus including those devices will now be described, by way of example, with reference to the accompanying drawing, wherein: Figure 1 is a cross-section through a first sealing device; Figure 2 is a cross section through a part of a first apparatus including the sealing device of Figure 1; Figure 3 is a cross-section through a second sealing device; Figure 4 is a part-section through part of a second apparatus including the sealing device of Figure 3; Figure 5 is a section through a third sealing device; Figure 6 is a part-section through part of a third apparatus including the sealing device of Figure 5; Figure 7 is a cross-section through part of a fourth apparatus including a fifth sealing device; and Figure 8 is a longitudinal section on the line A-A in Figure 7.

Referring to the accompanying drawings and first of all to Figure 1 the sealing device 2 has a plate-like support 4 provided on both sides with an annular plate spring or washer 6 and 8. The support 4 is a circular disc having a circular depression 10 and 12 at each side, the diameter of which is somewhat larger than the diameter of the inner periphery 14 or 16 of the plate springs 6 and 8. At the rim of the depression 10 there is found an annular edge 18 to which the plate spring 6 is tightly and sealingly connected to the support 4 by pressure welding. At the rim of the depression 12 there is formed an annular edge 20 to which the plate spring 8 is tightly and sealingly connected to the support 4 by pressure welding.Both ends are flat ground so that a flat annular face constitutes the sealing rim 22 of the plate spring 6 and a flat annular face constitutes the sealing rim 24 of the plate spring 8.

In Figure 2, the sealing element 2 is inserted as a flat slide in a bore 26 of a valve setting element 28 which is rotatable about an axis in the plane of the drawing. A valve housing 32 is formed by two housing parts 34 and 36 pressed together with an interposed seal. A passage section 38 terminating in a wall 40 is provided in the housing section 34. The housing part 36 contains a passage section 42 terminating in a wall 44. The sealing rims 22 and 24 of the plate springs 6 and 8 lie against these walls 40 and 44 under prestress. In the illustrated position, the passage sections 38 and 42 are separated by two adjacent sealing points. This corresponds to a kind of labrynth seal in which there are two sealing positions 46 and 48 behind each other.If a pressure p1 obtains in the passage section 38 and a lower pressure p2 in the passage section 42, a pressure p3 is set up in the chamber 50 between the two walls 40 and 44, that is roughly halfway between the two pressures p1 and p2. This means that this pressure acts on the back of the plate springs 6 and 8 and thereby assists the spring force. By turning the setting element 28, the passage sections 38 and 42 are interconnected by way of a circumferentially offset bore in the setting element 28.

In Figures 3 and 4, a sealing device 52 consists of a support 54 and the two plate springs 56 and 58.

These are secured to the support plate in a manner similar to that in Figure 1. What is different is that the supporting member has external teeth 60 and a central hole 62 with axial ribs 64 to form a splined connected to a shaft 66.

As shown in Figure 4, the shaft 66 is mounted in two bearing bushes 68 and 70 in two parts 72 and 74 of a housing 76. The ends of the two bearing bushes form walls 78 and 80 against which the sealing rims of plate springs 56 and 58 abut. The teeth 60 cooperate with a further gear 82 which can for example be a rotary flat slide, part of gearing, or the like. The space 84 between the walls 78 and 80 can for example be at a higher pressure p4 sealed from the outside by the two sealing points 86 and 88. It is unnecessary for the shaft 66 to be sealed in the central hole 62.

In both of the aforementioned cases, the sealing rims 22 and 24 may be hardened and coated with titanium carbide to improve wear and sliding properties.

In Figure 5, a sealing device 102 is extruded in one piece from plastics material. A support 104 and two plate springs 106 and 108 are interconnected by internal junctions in the form of annular webs 110 and 112. There is also a central hole 114.

In Figure 6, the sealing element 102 has been connected to a shaft 116 reciprocatabie in the direction of arrow 120 by an actuating element 118.

A housing 122 consists of two parts 124 and 126.

Inserts 128 and 130 each have a vertical slot 132 or 134 in which the shaft 16 is guided vertically. Walls 136 and 138 and the plate springs 106 and 108form two sealing points 140 and 142 which seal from the outside the pressure p5 in the interior 144 between the housing parts 124 and 126. The sealing element 102 is inserted in a bore 146 of a flat slide 148 having several apertures 150 and pressed by a spring 152 against a grid 154 which is held in the housing part 124 and likewise has several apertures 157. By reciprocating the actuating element 118, the flat slide valve is opened or closed, the pressure obtaining in the connecting passages 157 or 158 being sealed from the outside.

In Figures 7 and 8, a fixed grid 162 having apertures 164 is disposed in a housing 160. Aflat slide 166 with apertures 168 is displaceable along it.

The flat slide is subjected to a spring 170 and adjustable by an arm 172 dn an actuating shaft 174.

The actuating shaft 174 has a support 176 at each end of which a respective plate spring 178 and 180 is secured. The sealing rim of the plate spring 178 lies against a wall 182 of a bushing 184 and the sealing rim of plate spring 180 against a wall 186 of a bushing 188. The latter is axially displaceable with the aid of a screwthreaded sleeve 190. This permits the pressure of abutment of the two plate springs 178 and 180 to be set. Here, again, the pressure ps obtaining in the interior 192 of housing 160 is sealed from outside by the sealing effect of the plate spring 180. The plate spring 178 merely serves to position the support member 176 symmetrically. Together with the plate spring 180, it therefore forms a sealing element 194 for sealing off the actuating shaft 174.

The sealing devices described and illustrated above are simple and cheap to make. Each sealing device compensates any irregularities between the two wall faces and is self-adjusting. Adjoining materials can be selected to give a high wear resistance. Also, any materials can be chosen to give a high stability to corrosion even for aggressive media. Since the pressure partly acts on the backs of the plate springs, a higher abutment pressure is also obtained for the seal with increasing pressure in the space between the two walls.

Claims

1. A sealing device comprising a sealing element and a rigid support for the element, the element being in the form of a spring plate having inner and outer peripheral edges, the inner edge defining an aperture in the plate, one peripheral edge portion of the plate being secured to the support and the other peripheral edge portion being spaced from the support, wherein the device can be compressed, in use, between two parallel walls with the other peripheral edge portion of the plate engaging one of the walls to effect a seal between the outside and the inside of that edge portion.

2. A sealing device as claimed in claim 1, in which the inner peripheral edge portion of the plate is secured to the support.

3. A device as claimed in claim 1 or claim 2, in which the said other peripheral edge portion has a planar face.

4. A device as claimed in any one of claims 1 to 3, in which the support and sealing element are made of steel.

5. A device as claimed in claim 4, in which the steel of the plate is hardened at least at its said other peripheral edge portion.

6. A device as claimed in claim 4 or claim 5, in which the plate spring has a coating of relatively hard material at least at its said other peripheral edge portion.

7. A device as claimed in claim 6, in which the material is titanium carbide.

8. A device as claimed in any one of claims 1 to 3, in which the support and the sealing element are made of plastics material.

9. A device as claimed in any one of claims 1 to 8, in which the sealing element is secured to the support by spot welding.

10. A device as claimed in claim 9 when appendant to claim 2, in which the support has an edge portion to which the inner peripheral edge portion of the spring is secured.

11. A device as claimed in any one of claims 1 to 10, in which the sealing element is integrally formed with the support.

12. A device as claimed in claim 11 when appendank to claim 8, in which the device is extruded in one piece.

13. A device as claimed in any one of claims 1 to 12, in which the support has a central hole lying within the inner peripheral edge of the plate spring.

14. A device as claimed in any one of claims 1 to 13, in which the plate spring is annular in form.

15. A device as claimed in any one of claims 1 to 14, in which the device includes another sealing element which is identical to the first mentioned sealing element and is secured to the support in the same way, the two elements being arranged on opposite sides of the support so that when the device is compressed between two parallel walls a peripheral edge portion of the said other sealing element provides a seal in the same way as the first mentioned element.

16. A sealing device for sealing two chambers of different pressure, wherein a sealing element consisting of a supporting member and a spring connected thereto is inserted under prestress between two parallel walls and is movable relatively to at least one wall having an aperture to be sealed, wherein the spring is a plate spring which is sealingly secured in ther region of one of its two peripheries to the supporting member and the portions of which lying against the wall in the region of the other periphery form a closed sealing rim.

17. A sealing device substantially as hereinbefore described with reference to, and as shown in Figure 1 or Figure 3 or Figure 5 or Figures 7 and 8.

18. Apparatus including a device as claimed in any one of claims 1 to 17, the apparatus including two parallel walls between which the device is fitted, the or each sealing element serving to seal an aperture in one, or a respective one of the walls.

19. Apparatus as claimed in claim 18, in which the sealing element is fixed to rotate with a rotary shaft, passing through an aperture in at least one of the walls, that aperture being sealed by the sealing element.

20. Apparatus as claimed in claim 19, wherein the device is as claimed in claim 13, the support has external teeth for cooperating with another toothed element and the shaft passes through the central hole.

21. Apparatus as claimed in claim 18, wherein each wall has an aperture in the form of a slot, the slots being parallel, and a shaft is connected to the sealing element(s) and is displaceable transversely to its length in the slots, at least one of the slots being sealed by the or a respective one of the sealing elements irrespective of the position of the shaft in the slots.

22. Apparatus as claimed in any one of claims 18 to 21, in which the or each sealing element seals an actuating element of a flat slide from the outside.

23. Apparatus including a sealing device as claimed in any one of claims 1 to 17, the apparatus being substantially as hereinbefore described with reference to, and as shown in Figure 2 or Figure 4 or Figures 7 and 8.