GB2139713A

GB2139713A - Seals

Info

Publication number: GB2139713A
Application number: GB08310703A
Authority: GB
Inventors: Lionel Vivian Frank Russell
Original assignee: VINTEN Ltd; W Vinten Ltd
Current assignee: VINTEN Ltd; W Vinten Ltd
Priority date: 1983-04-20
Filing date: 1983-04-20
Publication date: 1984-11-14
Also published as: GB8310703D0; FR2544831A1; DE3414620A1

Abstract

A seal 4 of resilient, pressurisable, thin walled continuous tube for location between two contrarotatable juxtaposed surfaces 5, 6 of a container 1 and closure means 3 to prevent ingress of foreign matter or egress of such as lubricants so that actual seal breakaway - the point of surface sliding - occurs away from the point of first movement thereby allowing small angles of rotation (from B to b) to be achieved within the resilience of the seal. <IMAGE>

Description

SPECIFICATION Improvements in or relating to Seals This invention relates to seals in rotating machinery and more particularly, though not exclusively, to weather and environmental rotational sealing.

Such seals as '0' rings, gaskets, spring loaded knife-edgeseals and felt seals are well known in the engineering field but with all these previously known seals, when compressed to form the seal cause a breakaway stiction in rotating machinery. Though in many cases this stiction or resistance to initial motion is slight, in certain applications, such as servo driven systems involving large diameter bearings such as slewing rings, etc., or pan and tilt heads ortracking mounts, the factthat maximum seal stiction occurs at the point of precise alignment is a disadvantagewhich has to be overcome to provide a smooth, non resistive, breakaway action.

The seal design philosophy described herein, seeks to achieve rotational resilience at this high accuracy alignment point and to move the point of actual stiction breakaway, to a point rotationallyfurther away, when the servo or manual drive will be well underway.

It is therefore an object of this invention to provide a sealing meanswhereinthese disadvantages are considerably reduced, if not eliminated.

According to the invention we provide a seal formed from a thin walled pressurised continuous tube of resilient material for insertion between two contrar otatablejuxtaposed surfaces to form a sealing means fora containerofwhich said contrarotatablejuxta- posed surfacesform the closure means.

The invention will now be described, by way of example only, in conjunction with the accompanying diagrams in which: Figure 1 shows an example ofthe seal in situ between two surfaces Figure 2 shows a cross section XX of figure 1 and, Figure3 showsthetheory of operation ofthe seal to reduce stiction.

Referring to figures 1 and 2 wherein the seal is used in a typical situation a container (1) has a circular hole formed therein. The container may be fixed or rotatable about the centre line CL point (2), and may contain machinery where the ingress of foreign matter would be detrimental or may contain equipment in a lubricant where the egress of the lubricant and/or ingress offoreign matter would be detrimental. A closure member (3), which mayalso be fixed or rotatable about point (2) so that the closure member may rotate within the container, orthe container rotate about the closure member, or both rotate, eithertogetheror in contrarotation, about point (2).A seal (4) formed from a thin walled pressurised continuous tube of resilient material, which in general terms could be likened to a cycle inner-tube, is located between the two juxtaposed surfaces (5) and (6) of the container opening and the closure member respectively and is in contact with both surfaces. The surface area of contact of the seal withthetwo juxtaposed surfaces would vary considerably dependent on application, e.g. very delicate machinery where critical movement and/or adjustment between the two juxtaposed surfaces is required surface area contact would be maintained at a minimum to obtain a seal, but with heavy machinery where fine adjustment is not critical a larger surface area of contact may prove desirable.The surface area of contact is easily adjustable by one or any of the following criteria, pressurisation, cross section of endless tube, or proximity of juxtaposed surfaces (5) and (6). Press urisation of the endless tube may be pneumatic or fluid and may be adjustable for example by using a self sealing material for the tube and pressurising with such as a pump or hypodermic syringe.

Referring nowto figure 2 wherein the same numerals are used to represent the same parts an imaginery lineAB along part of a radius is drawn between the two radial points of contactA and B of the seal. As the closure member (2) rotates clockwise the line AB tends to re-align to a position ab. For small angles of rotation the seal behaves as a resilient structure due to the filling and thin wall.

In operation, under static conditions sealing is maintained bythe internal pressure and under small movement conditions, such as servo alignments, limited rotational freedom is achieved within the thin wall stretch and pneumatic resilience of the seal.

Hence there will be no breakaway stiction to be overcome at the first point of movement.

Actual seal breakaway-the point ofsurface sliding - occurs away from the point offirst movement, allowing small angles of rotation to be achieved within the resilience of the seal only. Once the static friction is broken away the amount of seal stretch, up to this point, will tend to resurrect due to the lesser frictional drag amount, after movement has started.

Though the seal is described in relation to two flat surfaces, one rotatable within the other, it will be obvious to one skilled in the artthatotherconfigurations of juxtaposed surfaces will equally well accept a seal in accordance with the invention, for example, the surface (5) may be the top of a container wall and the surface (6) may be part of a closure member which fits overor on the top of the containerwall.

1. A seal formed from a thin walled pressurised continuous tube of resilient material for insertion between two contrarotatable juxtaposed surfaces to form a sealing means for a container of which said contrarotatable juxtaposed surfaces form the closure means.

2. Aseal as claimed in Claim 1 wherein said resilient material is rubber based.

3. A seal as claimed in Claim 1 wherein said resilient material is synthetic rubber.

4. A seal as claimed in Claim 1 wherein said resilient material is a polymer.

5. Aseal as claimed in Claim 1 wherein the pressure within said continuoustube is variable.

6. Aseal as claimed in Claim 1 substantially as herein described in conjunction with the accompanying diagrams.

Superseded claims.

1. A seal formed from a fhin walled pressurised

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in or relating to Seals This invention relates to seals in rotating machinery and more particularly, though not exclusively, to weather and environmental rotational sealing. Such seals as '0' rings, gaskets, spring loaded knife-edgeseals and felt seals are well known in the engineering field but with all these previously known seals, when compressed to form the seal cause a breakaway stiction in rotating machinery. Though in many cases this stiction or resistance to initial motion is slight, in certain applications, such as servo driven systems involving large diameter bearings such as slewing rings, etc., or pan and tilt heads ortracking mounts, the factthat maximum seal stiction occurs at the point of precise alignment is a disadvantagewhich has to be overcome to provide a smooth, non resistive, breakaway action. The seal design philosophy described herein, seeks to achieve rotational resilience at this high accuracy alignment point and to move the point of actual stiction breakaway, to a point rotationallyfurther away, when the servo or manual drive will be well underway. It is therefore an object of this invention to provide a sealing meanswhereinthese disadvantages are considerably reduced, if not eliminated. According to the invention we provide a seal formed from a thin walled pressurised continuous tube of resilient material for insertion between two contrar otatablejuxtaposed surfaces to form a sealing means fora containerofwhich said contrarotatablejuxta- posed surfacesform the closure means. The invention will now be described, by way of example only, in conjunction with the accompanying diagrams in which: Figure 1 shows an example ofthe seal in situ between two surfaces Figure 2 shows a cross section XX of figure 1 and, Figure3 showsthetheory of operation ofthe seal to reduce stiction. Referring to figures 1 and 2 wherein the seal is used in a typical situation a container (1) has a circular hole formed therein. The container may be fixed or rotatable about the centre line CL point (2), and may contain machinery where the ingress of foreign matter would be detrimental or may contain equipment in a lubricant where the egress of the lubricant and/or ingress offoreign matter would be detrimental. A closure member (3), which mayalso be fixed or rotatable about point (2) so that the closure member may rotate within the container, orthe container rotate about the closure member, or both rotate, eithertogetheror in contrarotation, about point (2).A seal (4) formed from a thin walled pressurised continuous tube of resilient material, which in general terms could be likened to a cycle inner-tube, is located between the two juxtaposed surfaces (5) and (6) of the container opening and the closure member respectively and is in contact with both surfaces. The surface area of contact of the seal withthetwo juxtaposed surfaces would vary considerably dependent on application, e.g. very delicate machinery where critical movement and/or adjustment between the two juxtaposed surfaces is required surface area contact would be maintained at a minimum to obtain a seal, but with heavy machinery where fine adjustment is not critical a larger surface area of contact may prove desirable.The surface area of contact is easily adjustable by one or any of the following criteria, pressurisation, cross section of endless tube, or proximity of juxtaposed surfaces (5) and (6). Press urisation of the endless tube may be pneumatic or fluid and may be adjustable for example by using a self sealing material for the tube and pressurising with such as a pump or hypodermic syringe. Referring nowto figure 2 wherein the same numerals are used to represent the same parts an imaginery lineAB along part of a radius is drawn between the two radial points of contactA and B of the seal. As the closure member (2) rotates clockwise the line AB tends to re-align to a position ab. For small angles of rotation the seal behaves as a resilient structure due to the filling and thin wall. In operation, under static conditions sealing is maintained bythe internal pressure and under small movement conditions, such as servo alignments, limited rotational freedom is achieved within the thin wall stretch and pneumatic resilience of the seal. Hence there will be no breakaway stiction to be overcome at the first point of movement. Actual seal breakaway-the point ofsurface sliding - occurs away from the point offirst movement, allowing small angles of rotation to be achieved within the resilience of the seal only. Once the static friction is broken away the amount of seal stretch, up to this point, will tend to resurrect due to the lesser frictional drag amount, after movement has started. Though the seal is described in relation to two flat surfaces, one rotatable within the other, it will be obvious to one skilled in the artthatotherconfigurations of juxtaposed surfaces will equally well accept a seal in accordance with the invention, for example, the surface (5) may be the top of a container wall and the surface (6) may be part of a closure member which fits overor on the top of the containerwall. CLAIMS

2. Aseal as claimed in Claim 1 whereintheseal stretch at actual seal breakaway tends to resurrect due to the lesserfrictional drag after movement has started.

2. Aseal as claimed in Claim 1 wherein said resilient material is rubber based.

4. A seal as claimed in Claim 1 wherein said resilient material is a polymer.

Superseded claims.

1. A seal formed from a fhin walled pressurised continuous tube of resilient material for insertion between two contra rotatable juxtaposed surfaces to form a sealing meansfora containerofwhich said contrarotatablejuxtaposed surfaces form a closure means and wherein, in use, small angles of rotation may be achieved within the thin wall stretch and pneumatic resilience ofthetube priorto actual seal breakaway.