GB2410774A

GB2410774A - A rotary shaft seal including a seal element with energising means

Info

Publication number: GB2410774A
Application number: GB0402349A
Authority: GB
Inventors: Andrew Hugh Longdon; Clive J Stanley; Mike G Gleed
Original assignee: Trelleborg Sealing Solutions US Inc
Current assignee: Trelleborg Sealing Solutions US Inc
Priority date: 2004-02-04
Filing date: 2004-02-04
Publication date: 2005-08-10
Anticipated expiration: 2024-02-04
Also published as: GB0402349D0; GB2410774B

Abstract

A rotary shaft seal comprising a sealing element, the sealing element comprising an annular body 12 which secures the seal element in place about a rotatable shaft 1, and a flexible sealing lip 5 formed integrally with the body 12 and extending therefrom to sealingly engage with the rotary shaft 1. The body 12 includes an energised annular element 4, 14 adapted to be received between two components 7, 10 of the seal assembly so as to form a seal between these components 7,10 when they are secured together.

Description

. 1 ' 2410774 "Rotary Shaft Seal" This invention relates to a rotary

shaft seal and an assembly incorporating the same.

According to the invention a rotary shaft seal comprises an annular body by which the seal is secured in place in a seal assembly about a rotatable shaft, and a flexible sealing ring formed integrally with the body and extending from it to engage with and forms a seal around the periphery of the shaft passing through the ring, characterized in that the body comprises an energised sealing element adapted to be received between two components of the seal assembly so as to form a seal between these components when they are secured together.

The shaft seal therefore incorporates two seals within one integral sealing component, one seal being that of the flexible sealing ring with the shaft, and the other being the static seal between the energised sealing element and the two components of the seal assembly. This onepiece design simplifies manufacture and installation, and thereby reduces costs.

An annular spring such as a coil spring is preferably provided to energise the sealing element so as to ensure a good static seal and to prevent rotation of the seal between the components. The energising element also compensates for any creep in the material from which the seal is composed, and allows relatively wide tolerances to be accommodated within the seal assembly.

Preferably, the energised sealing element is shaped to sit in a recess formed in one of the two components so that it is contained within the recess and resists extrusion.

The invention will now be described by way of example with reference to the accompanying drawings in which; Figure 1 is a cross-section through part of a shaft seal according to a first embodiment of the invention shown fitted over a shaft; Figure 2 is a cross-section of the first embodiment as fitted in a shaft seal assembly; : c: C 8 C 1 Figure 3 is a view similar to figure 1 of a shaft seal according to a second embodiment of the invention; Figure 4 is a view similar to figure 2 of the second embodiment of the invention; Figure 5 is a view similar to figure 1 of a third embodiment of the invention; Figure 6 is a view similar to figure 2 of the third embodiment of the invention Figure 7 is a view similar to figure 1 of a fourth embodiment of the invention; and Figure 8 is a view similar to figure 2 of a fourth embodiment of the invention.

Figure 1 discloses a shaft seal according to a first embodiment of the invention, fitted around a central shaft 1. The shaft seal comprises an annular body 2 composed of a polymer sealing material such as PTFE having a channel 3 formed around it's outer periphery to receive an energising device in the form of a coil spring 4 or O-ring or other energising device. A flexible sealing ring 5 extends radially inwards from the annular body 2 to engage the shaft 1 passing through the central aperture 6 of the angular body. Before the seal is engaged around the shaft, the sealing ring 5 extends radially inwards in a single plane. This ring is deflected and expanded by insertion of the shaft 1 and creates a face-to-face contact seal between the inner surface of the ring and the periphery of the shaft. The ring 5 is offset towards one side of the annular body 2 and its outer face is coplanar with the adjacent side face of the annular body.

Figure 2 shows the shaft seal fitted in a seal assembly comprising a housing component 7 having a collar 8 which surrounds the shaft. The aperture 6 in the annular body fits over the collar 8 until the end of the collar abuts the inner side face of the flexible ring 5. A second component 10 is then fastened to the first component 7 so as to secure the annular body 2 therebetween. The two components 7, 10 abut at their outer edge 11 and overlap radially at their inner edge 12 so as to support the inner end of the sealing ring 5 therebetween. The coil spring 4 and the side walls 14 of the annular body are compressed between the two components 7, 10 and ensure a good seal between these interfaces.

As shown in Figures 1 and 2, the sealing face of the sealing ring which engages the shaft is formed with a groove or grooves 13 which improve the sealing action between these two surfaces. For example, the groove or grooves may have a hydrodynamic sealing action as the shaft rotates relative to the seal assembly. c a.e

8 C The embodiment of the invention illustrated in Figures 3 and 4 is similar to that of Figures 1 and 2 except that a second sealing ring 15 is formed on the inner edge of the annular body 2 to extend radially inwardly and engage the shaft 1. As shown in Figures 2 and 3, the second sealing ring 15 is centrally located where it is secured to the annular body 2 and is deflected in the opposite direction compared with the first sealing ring 5. The collar 9 is shortened to accommodate the second sealing ring as shown in Figure 4. The inner face of the second sealing ring 15 engages the periphery of the shaft 1 in face-to-face sealing contact like the f ret sealing ring 5.

In a third embodiment of the invention illustrated in Figures 5 and 6, the second sealing ring 15 is deflected less than that in the embodiment of Figures 3 and 4, and the free end of the second sealing ring contacts the periphery of the shaft I to form a seal.

In a fourth embodiment of the invention as illustrated in Figures 7 and 8, the sealing body 2 is formed with the annular channel 3 in it's inner edge to receive the coil spring 4. The outer end of the body 2 is then formed with an axial annular projection 17 to engage in an annular recess in the component 7 so as to locate the seal more positively. Also, the sealing ring 5, instead of being deflected out of the central aperture of the seal, is deflected into this aperture so as to produce an axially more compact design.

It will be appreciated that in other embodiments of the invention, three or more sealing rings may be formed on the annular body 2.

In other embodiments of the invention, the annular body 2 may be formed with a radially extending passage 16 connecting the outer channel 3 to the interior aperture 6, such as shown in dotted lining in Figures 3 and 4, so as to provided a drainage channel or flush channel for fluid being sealed.

In yet other embodiments of the invention, instead of forming the channel 3 in the outer edge of the annular body 2, it is formed in the inner edge of the annular body so as to be pressurised by fluid being sealed.

e . Annular shaft seals according to the invention are particularly suitable for forming seals around shafts of larger diameter, for example, shafts of paper and steel rolling mills where oil or grease on one side is sealed from dust and water splashes on the other side.

It will be appreciated that the characteristics and performance of the static seal formed by the annular body 2 and energising spring 4 can be optimised for the application, and that the integral sealing ring or rings can be optimised for the sealing function with the shaftl. .

Claims

Claims 1. A rotary shaft seal comprising an annular body by which the seal

is secured in place in a seal assembly about a rotatable shaft, and a flexible sealing ring formed integrally with the body and extending from it to engage with and form a seal around the periphery of the shaft passing through the ring, characterised in that the body comprises an energised sealing element adapted to be received between two components of the seal assembly so as to form a seal between these components when they are secured together.
2. A rotary shaft seal as claimed in claim 1, in which an annular spring is provided to energise the sealing element.
3. A rotary shaft seal as claimed in claim 2, in which the annular body includes a channel for receiving the annular spring therein.
4. A rotary shaft seal as claimed in any preceding claim, in which the energised sealing element is compressed when received between the two components.
5. A rotary shaft seal as claimed in any preceding claim, in which the energised sealing element is shaped to sit in a recess formed in one of the two components.
6. A rotary shaft seal as claimed in claim 5, in which the annular body includes an axial annular projection for engaging with an annular recess in the one of the two components.
7. A rotary shaft seal as claimed in any preceding claim, in which the flexible sealing ring is adapted to be deflected by the shaft to form a face-to-face contact seal therebetween.
8. A rotary shaft seal as claimed in claim 7, in which the flexible sealing ring is deflected into an aperture in the annular body through which the shaft passes.
9. A rotary shaft seal as claimed in any preceding claim, in which the annular body includes a second sealing ring for engaging with and forming a seal around the periphery of the shaft.
l O. A rotary shaft seal as claimed in claim 9, in which the second sealing ring is adapted to be deflected by the shaft to form a face-toface contact seal therebetween.
11. A rotary shaft seal as claimed in claim 9, in which a free end of the second sealing ring engages the periphery of the shaft to form the seal.
12. A rotary shaft seal as claimed in any preceding claim, in which the annular body is composed of a polymer sealing material such as PTFE.
13. A rotary shaft seal as claimed in any preceding claim, in which the annular body includes a radially extending passage connecting an aperture through which the shaft passes to an outer channel in the annular body.
14. A rotary shaft seal substantially as herein described with reference to, and as illustrated in the accompanying drawings.