NL2003173C2

NL2003173C2 - Ceramic seal assembly.

Info

Publication number: NL2003173C2
Application number: NL2003173A
Authority: NL
Inventors: Gideon Yadin
Original assignee: Geva Sol B V
Priority date: 2009-07-09
Filing date: 2009-07-09
Publication date: 2011-01-11

Description

P29959NLOO/KHO

Title: Ceramic seal assembly

The present invention relates to a sealing assembly.

The sealing assembly may be applied for all kind of devices. The sealing assembly includes a linear movable sliding member within a bearing housing. Examples of devices having such sealing assemblies are valves, pumps, motors, compressors, electro magnetic 5 cylinders etc. The sealing assembly may be applied for all kind of valves, like shut off valves, pneumatic valves, solenoid valves or hydraulic valves, etc.

In particular the sealing assembly is suitable to be used in a contaminating environment or in an environment which requires high hygienic processing requirements. Such an environment is for example a food processing or pharmaceutical environment.

10 Such known sealing assemblies comprise elastomeric, rubber or metal sealing elements to assure that the sealing is sufficient tight. The sealing elements are necessary to separate a working medium from influences out of the direct environment. Especially, in food and pharmaceutical industry, it is important that the working media remains shielded from bacteria and other contaminating materials. However, it has appeared that those sealing 15 elements are susceptible for aggressive media and become easy contaminated. The elastomeric or metal sealing elements often reduce the total lifetime of a valve, cylinder, motor, etc.

It is an object of the present invention to at least partially eliminate the above drawbacks and/or to provide a useable alternative. In particular, it is an object of the 20 invention to provide a sealing assembly which is less susceptible to aggressive media as a working fluid, which provides a proper sealing and which has a relatively long lifetime.

According to the invention, this object is achieved by a sealing assembly as defined in claim 1.

The sealing assembly according to the invention comprises a bearing house and a 25 slide member. The bearing house has a passageway for guiding the slide member. The slide member is linear movable inwards and outwards the passageway over a stroke. The slide member is movable with respect to the bearing house. The slide member partially extends out of the passageway. The passageway of the bearing house comprises an inner sealing surface made of a ceramic material and the slide member comprises an corresponding outer 30 sealing surface out of a ceramic material. Advantageously, it has appeared that due to the ceramic surfaces of the sliding member and the bearing house, the slide member may run smoothly inwards and outwards. The sealing surfaces appear to be good running surfaces.

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Good sealing properties are obtained. No further sealing elements like rubber or elastomeric elements are any longer necessary which may considerably increasing the lifetime of the sealing assembly.

In a preferred embodiment of the sealing assembly according to the invention, a 5 clearance in between the sliding member and the bearing housing is provided which has a radial diameter of at the most 5pm, in particular at most 2pm, but preferably at most 1pm. The small clearance assures that the passageway through the bearing house remain sealed. Advantageously, it has appeared that no scrapers or the like are necessary to prevent working fluid or dirt getting through the passageway.

10 Preferably, the sealing assembly has sealing surfaces made of tungstencarbide.

In an embodiment according to the invention, the sealing assembly comprises a slide member having a plunger and a top seat. The top seat may be connected to the bearing house, wherein the plunger is spring loaded connected to the top seat.

In an embodiment of the sealing assembly according to the invention the bearing 15 house is connected to an actuator for actuating the plunger. The actuator may be an electro magnetic actuator comprising a coil and at least two electric connections to activate a magnetic circuit. The slide member extends into the magnetic circuit.

In an embodiment according to the invention, the sealing assembly comprises a ceramic sealing surface which is provided on a seat which is provided at a distal end of the 20 passageway. The sealing surface of the seat may be combined with the inner and outer cylindrical sealing surfaces in the passageway.

In an embodiment of the sealing assembly according to the invention the seat of the passageway has a chamfered inner edge. An inclined sealing surface may advantageously be less susceptible to damages caused by impacts when the slide member moves inwards. 25 In an embodiment of the sealing assembly according to the invention, the sealing assembly comprises a slide member comprising a seal element having a first counter seat which geometry corresponds to the seat of the passageway, wherein the first counter seat and the seat define a seal.

In an embodiment according to the invention the sealing assembly further comprises 30 a valve housing having a channel, wherein the slide member is moveable to and fro an opening of the channel for respectively closing or opening the channel.

In an embodiment of the sealing assembly according to the invention, the channel of the valve housing has an opening provided with a valve seat out of a ceramic material, wherein the slide member is movable to and fro the valve seat of the channel, wherein the 35 seal element of the slide member comprises a second counter seat which geometry corresponds to the valve seat of the channel.

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Further, the invention relates to an apparatus comprising an array of sealing assemblies as elucidated above, wherein the valve housings together define a manifold for controlling a supply of fluid.

Further, the invention relates to a milking device for milking animals comprising a 5 pulsator for generating a varying pressure difference in a milk conduit. The pulsator comprises a sealing assembly as described above. Advantageously, the pulsator has improved sealing properties, which increases the lifetime of the milking device and reduces costs for maintenance.

In an embodiment according to the invention, the milking device for milking animals 10 further comprises at least one teat cup for connecting the at least one milk conduit to a teat of an animal and a milk reservoir for collecting yielded milk.

Further preferred embodiments are defined in the subclaims.

15 The invention will be explained in more detail with reference to the appended drawings. The drawings show a practical embodiment according to the invention, which may not be interpreted as limiting the scope of the invention. Specific features may also be considered apart from the shown embodiment and may be taken into account in a broader context as a characterizing feature, not only for the shown embodiment but as a common 20 feature for all embodiments falling within the scope of the appended claims, in which:

Fig. 1 shows a schematic cross sectional view of a sealing assembly according to the invention;

Fig. 2 shows a schematic cross sectional view of a sealing assembly according to the 25 invention;

Fig. 3 shows a schematic cross sectional view of a sealing assembly according to the invention;

Fig. 4 shows a schematic cross sectional view of a sealing assembly according to the invention arranged as a valve; 30 Fig. 5a shows a cross sectional view of a sealing assembly applied in a valve according to the invention connected to a manifold;

Fig. 5b shows a side view of the valve out of Fig. 5a;

Fig. 5c shows a front view of the valve out of Fig. 5a;

Fig. 6a and 6b show respectively a side and cross sectional view of a slide member 35 according to the invention;

Fig. 7a and 7b show respectively a side and cross sectional view of a sub assembly of a bearing house and a top seat; -4-

Fig. 8a and 8b show respectively a side and cross sectional view of the top seat out of Fig. 7a and 7b;

Fig. 9a, 9b and 9c show respectively a top, front and cross sectional view of a manifold according to the invention; and 5 Fig. 10 shows a cross sectional view of a sealing assembly having ceramic layers according to the invention.

Fig. 11 shows a cross sectional view of a sealing assembly as a shut off valve.

Fig. 1 shows a schematic cross sectional view of an embodiment of a sealing 10 assembly 1 according to the invention. The sealing assembly comprises a bearing house 7 and a slide member 6. The bearing house 7 has a passageway 72 for guiding the slide member 6. The passageway may have an cylindrical shape. The passageway may be a through hole. The bearing house may be a static disposed component of an apparatus like a valve, compressor, pump, motor etc. The inner dimensions of the passageway correspond 15 at least partially to the outer dimensions of the slide member.

The slide member 6 is shaped as a rod. At least a portion of the slide member has a cylindrical shape. The cylindrical portion extends into the bearing house 7. The slide member extends partially into the passageway of the bearing house 7. The slide member is at least partially linear movable in- and outwards the bearing house. The slide member is 20 movable into the bearing house. The slide member is outwardly movable from a first position to a second position over a stroke. During the movement at least a portion of the slide member may remain outside the passageway. The slide member may be movable over a stroke of at the most 10mm, in particular at most 5mm, more in particular at most 2mm.

During a movement of the slide member into the passageway, a portion of the slide 25 member moves from outside the passageway into the passageway. An inner surface of the passageway and an outer surface of the slide member define a running surface and also a sealing surface. The inner surface of the passageway and the outer surface of the slide member are at least partially made of a ceramic material. Preferably, the sealing surface is at least partially made of a TungstenCarbide TC. The sealing surfaces may e.g. be grinded 30 to obtain a smooth surface finish. In an embodiment the whole bearing house and/or sliding member may be made of a ceramic material, like TungstenCarbide in stead of providing a ceramic layer on a surface of the bearing house or slide member.

A clearance in between the outer surface of the slide member and the inner surface of the passageway exist to allow a sliding movement of the slide member. The clearance at 35 the sealing surface has small dimensions to allow a linear movement and to prevent working media or dirt from outside the bearing house from entering together with the inwards moving slide member into and/or through the passageway of the bearing house. In a particular -5- embodiment the clearance has a radial dimension of at most 5|jm, in particular at most 3 pm,, but preferably at most 1 pm. The sealing surface may have an axial length of at least 1mm, but preferably at least 2mm. Advantageously, in the embodiment according to the invention good sealing and running properties are combined. Due to the small clearance, no 5 scrapers or the like are necessary to prevent dirt from the outside or working media from the inside getting through the passageway.

Fig. 2 shows a schematic cross sectional view of a sealing assembly according to the invention. The sealing assembly has a bearing house and a sliding member 6 as in Fig. 1. However, the bearing house 7 has at a distal end of the passageway a seat which forms 10 together with a counter seat connected to the sliding member a sealing. The seat and the counter seat may be chamfered. The seat 71 has a chamfered inner edge, while the counter seat has a corresponding chamfered outer edge. The seat and the counter seat have corresponding inclined surfaces which may come in contact with each other when the slide member moves inward the passageway of the bearing house. The chamfered edges form a 15 good sealing surface and at the same time reduce the risk of a break as a result of a collision. A sealing surface formed by a small clearance as described above with reference to Fig. 1 may be combined with a sealing surface formed by the seat 71 and the counter seat 71. Herewith, an improved sealing may be obtained. The seat 71 and/or the counter seat 71 may be ring shaped. A ring shaped counter seat 61 may be easily connected to the sliding 20 member by gluing. The ring shaped counter seat may be positioned at a groove of the slide member. The counter seat may be provided at the circumference of the sliding member. Preferably, the seat and the counter seat are made of a tungsten carbide TC ceramic material.

Fig. 3 shows a further schematic cross sectional view of a sealing assembly 25 according to the invention. The sealing assembly comprises a sliding member 6 having a first counter seat 71 and a bearing house 7 having a seat 71 as shown in Fig. 2. The sealing assembly further comprises a valve housing 9. The valve housing 9 has a closable channel 92. The channel may be a through hole. The channel is closable by the sealing element 62. The channel may e.g. be a closable vacuum channel. The sealing element is connected to 30 the sliding member 6. The slide member is movable to and fro a valve seat 91 positioned at an opening of the channel 92.

The sealing element has a first counter seat 611 which cooperates with the seat 71 connected to the bearing house and a second counter seat 612 which cooperates with the valve seat 91. The geometry of the second counter seat 612 corresponds to the valve seat 35 91 of the channel. The second counter seat 612 may engage with the valve seat 91 when the slide member moves outwards from the bearing house. The valve seat 91 may be ring shaped. The valve seat may have a conical shape. The valve seat may have an inner -6- chamfered edge. The second counter seat 612 may have a corresponding outer chamfered edge. Both inclined surfaces define a sealing surface. The sealing surface of the valve seat 91 comprises a ceramic outer surface. Preferably, the sealing surfaces of the sealing assembly are made of TungstenCarbide TC.

5 Fig. 4 shows a schematic cross sectional view of a sealing assembly according to the invention arranged as a valve. The valve has a slide member 6 which extends into a passageway of a bearing house 7. The slide member is movable and sealed with respect to the bearing house as explained with reference to Fig. 1. The slide member and/or the bearing house may be made fully out of a ceramic material, or may have a ceramic 10 respectively outer or inner surface. The valve has further an actuator for actuating the slide member. Due to the improved sealing of the sealing assembly, the actuator may be arranged with conventional means. An aggressive working fluid is effectively sealed from the actuator.

Fig. 5a shows a cross sectional view of a sealing assembly applied in a valve 15 according to the invention. Fig. 5b shows a side view and Fig. 5c a front view of the valve. Fig. 5a is a cross sectional view over the line A-A as shown in Fig. 5c. A plurality of valves are grouped by a manifold. Here the manifold connects four valves together. The valve has a valve housing 9. The valve housing and its channels are disclosed in more detail in Fig. 9. The valve comprises an actuator for moving the slide member to and fro a first and second 20 position. The shown actuator is an electro magnetic actuator. The actuator comprises a magnetic circuit including a coil, at least two electronic connections and a magnetic core.

Due to the improved sealing assembly according to the invention, the actuator may be of a conventional type. The magnetic core is arranged as a slide member 6. The slide member is shown in more detail in Fig. 6. A bearing house 7 is provided which is shown in more detail 25 in Fig. 7 and 8.

A spiral spring is provided to act the slide member 6. The spring is positioned at the proximal end of the slide member 6. The slide member is pressed outwards the bearing housing by the spring.

A seal element 62 is provided at the distal end of the slide member 6. The seal 30 element 62 is made of a ceramic material, in particular a tungstencarbide TC ceramic material. Advantageously, the ceramic seal element provides an improved lifetime of the sealing assembly. Additionally, the ceramic seal provides a hygienic solution which makes the sealing assembly suitable for pharmaceutical and food industry. The seal element 62 may be a sintered component which may be mounted to the distal end of the slide member 35 by e.g. gluing. The shown seal element 62 is ring shaped. The seal element 62 has at both axial ends a sealing surface 611 and 612 which defines a first and second counter seat. The sealing surfaces are inclined with respect to an axial centreline. Both the bearing house as -7- the valve housing are provided with a seat 71,91. As explained with reference to Fig. 3, the first counter seat may contact the seat 71 in a first position and the second counter seat 612 may contact a valve seat 91 in a second position of the slide member. Due to the pressing force of the spring the valve seat 91 is normally closed.

5 Fig. 5b shows a side view of the valve out of Fig. 5a. At a side surface the valve housing has a first outer channel opening 95. A conduit may be mounted to the opening. At

Fig. 5c shows the valve housing 9 as a manifold for grouping several valves. As shown four valves are grouped by the manifold. At the front surface each valve has a second outer channel opening 96. The slide member 6 having the seal element 62 may be 10 activated to open the channel in between the first and second channel opening 95,96.

The valve housing 9 is block shaped. The valve housing Fig. 6a and 6b show respectively a side and cross sectional view of a slide member according to the invention. The slide member has a smooth cylindrical ceramic outer surface. The surface finish has a value of N6. The outer surface of the sliding member may 15 be grinded. The outer surface will be a reference surface to manufacture a corresponding inner surface of a bearing house, as shown in Fig. 7. The drawings indicate maximum tolerances for manufacturing a slide member 6 and a corresponding bearing house 7. At its distal end the slide member has a boss to mount a seal element 62. The slide member is hollow. The slide member, also called a plunger, may have a through hole which may form a 20 second channel which may be opened in connection with the second channel opening 96 when the slide member moves into the second outwards position. The second channel may e.g. be an channel of a pulsator of a milking device. At a proximal end the slide member may have a broadened opening for receiving a spring element, e.g. a spiral spring.

Fig. 7a and 7b show respectively a side and cross sectional view of a sub assembly 25 of a bearing house and a top seat. The bearing house 7 has a cylindrical wall. An inner surface of the cylindrical wall may have a ceramic layer. The top seat 8 has a groove and is connected to the bearing house 7 by a deformed wall portion of the bearing house.

Fig. 8a and 8b show respectively a side and cross sectional view of the top seat out of Fig. 7a and 7b. The top seat has a hollow shaft. The top seat has a threaded portion at a 30 proximal end of the shaft for fixing the top seat as shown in Fig. 5a. The distal end of the top seat may have a stop face to serve as a stopper for a plunger for stopping the plunger in a first inwards position in the passageway of the bearing house.

Fig. 9a, 9b and 9c show respectively a top, front and cross sectional view of a valve housing as a manifold according to the invention. The cross sectional view of Fig. 9c is over 35 a line A-A as shown in Fig. 9b.

Fig. 10 shows in a cross sectional view an embodiment of the sealing assembly according to the invention. The sliding member 6 is provided with a ceramic layer, in -8- particular a tungstencarbide layer, at the outer surface. The passageway of the bearing house 7 is provided with an inner ceramic layer, in particular a tungsten carbide layer. The ceramic outer and inner surfaces serves as a running surface for a linear movement. Additionally, the ceramice outer surface seals the passageway in a bearing house 7. A 5 second sealing is shown comprising the counter seat 612 and the valve seat 91 in the valve housing 9.

Fig. 11 shows a view in cross section of a sealing assembly according to the invention. The assembly is provided with a cylinder. The cylinder may be actuated hydraulic, pneumatic or electro magnetic. The assembly has a sliding member 6 and a bearing housing 10 7 having a passageway for guiding and sealing the sliding member. As explained with Fig. 1, the sliding member is provided at the outer surface with a ceramic outer layer. The bearing house is provided with a ceramic layer at the inner surface of the passageway. Preferably, the ceramic layers are glued to the sliding member and bearing house. Alternatively, the ceramic layers may be welded or screwed to the components.

15 Thus, according to the invention a sealing assembly is provided having at least partially ceramic sealing surfaces resulting in improved sealing properties, a better resistance against aggressive media and an improved performance under hygienic working media.

Claims

A sealing assembly comprising a bearing housing (7) and a sliding body (6), wherein the bearing housing comprises a passage (72) for guiding the sliding body (6), the sliding body being linearly movable in and out of the passage (72) over a stroke with respect to the bearing housing (7), the sliding body (6) extending at least partially outside the passage (72), the passage of the bearing housing (7) having an inner sealing surface made of a ceramic material and wherein the sliding body has a corresponding outer sealing surface of a ceramic material.

A sealing assembly according to claim 1, wherein a space is provided between the sliding body 10 and the bearing housing with a radial diameter of at most 5 µm.

A sealing assembly according to claim 1 or 2, wherein the sealing surfaces are made of tungsten carbide.

4. Sealing assembly according to one of the preceding claims, wherein the sliding body (6) comprises a plunger and wherein the bearing housing (7) is connected to a top seat (8), the plunger being connected to the top seat under spring tension.

A sealing assembly according to claim 4, wherein the bearing housing (7) is connected to an actuator for activating the plunger.

6. Sealing assembly according to any of the preceding claims, wherein a ceramic sealing surface is provided on a seat (71) provided on a distal end of the passage (72).

A sealing assembly according to any one of the preceding claims, wherein the seat (71) of the passage has a beveled inner edge.

8. Sealing assembly according to any of the preceding claims, wherein the sliding body comprises a sealing element (62) with a first counter seat (611), which geometry is similar to the seat (71) of the passage, the first counter seat (611) and the seat (71) define a first seal.

9. Sealing assembly according to any of the preceding claims, wherein the sealing assembly further comprises a valve housing (9) with a channel (92), the sliding body (6) being movable towards and from an opening of the channel for respectively closing or opening of the channel.

A sealing assembly according to any one of the preceding claims, wherein the channel of the valve housing (9) has an opening provided with a valve seat (91) of a ceramic material, the sliding body (6) being movable from and to the valve seat (91) ) of the channel, wherein the sealing element (62) of the sliding body comprises a second counter seat (612), which geometry is similar to the valve seat (91) of the channel. - 10

An apparatus comprising a row of sealing compositions according to claim 9 or 10, wherein the valve housings are grouped together by a manifold for controlling a supply of fluid.

12. Milking device for milking animals, comprising a pulsator for generating a varying pressure difference in a milk line, the pulsator comprising a sealing assembly according to at least one of claims 1-10.

13. Milking device for milking animals according to claim 12, wherein the milking device further comprises at least one teat cup for connecting at least one milk line to a teat of an animal and a milk reservoir for collecting extracted milk.

14. Method for manufacturing a sealing assembly with a sliding body and a bearing housing, the sliding body being linearly movable relative to the bearing housing comprising a step of providing a ceramic layer on two surfaces of the sliding body and the bearing housing arranged opposite each other obtain a seal, wherein there is a space in the assembly of at most 5 µm between the opposite ceramic surfaces.

The method of claim 14, wherein the ceramic layer is a tungsten carbide layer.

16. Method as claimed in claim 14 or 15, wherein the ceramic layer is glued on a surface of a semi-finished product of a part.