GB2140101A

GB2140101A - Liquid pump seal

Info

Publication number: GB2140101A
Application number: GB08305635A
Authority: GB
Inventors: Alan Gregory Fern
Original assignee: AEROQUIP
Current assignee: AEROQUIP
Priority date: 1983-03-01
Filing date: 1983-03-01
Publication date: 1984-11-21
Also published as: GB2140101B; GB8305635D0

Abstract

A unitised liquid pump seal comprises inner and outer shell members (10 and 14), a sealing element (16) of PTFE secured by a force fit ring to one of the members and having a sealing lip (34) biased into engagement with a sealing surface (20) provided on the other shell member. <IMAGE>

Description

SPECI FICATION Liquid pump seal This invention is concerned with liquid pump seals and is particularly concerned with a water pump seal.

Seals used on the shafts of water pumps in motor vehicles have to face particularly arduous operating conditions in that they must operate over a wide temperature range and deal satsifactorily with large and sudden pressure variations while satisfactorily sealing a fluid that is often severely contaminated by dirt and grit. Conventional designs of such water pump seals are adequate but tend to be complicated and expensive.

It is an object of the present invention to provide a simple and inexpensive liquid pump seal.

The present invention is a liquid pump seal comprising an inner annular shell member, an outer annular shell member, a sealing surface formed on one of said members and a sealing element secured to the other of said members, said sealing element being made of PTFE and having a seal lip biased into en engagement with the sealing surface, said shell members having only limited relative axial movement.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, the twelve figures of which each show a cross section of one half of an embodiment of a water pump seal according to the present invention .

Throughout the description the same reference numerals will be used to describe the same or equivalent parts. Referring now to Fig. 1 a water pump seal according to the present invention comprises an inner shell member 10 which, when in use as shown, seats on and seals against a shaft 12, an outer shell member 14, which in use seats in and seals against a housing, and a sealing element 1 6.

As seen in cross-section the shell member 10 is basically L-shaped with one limb extending axially and the other limb extending radially, the member 10 thus having, facing the member 14, an axial tubular surface 18 and an annular radial surface 20. In this embodiment the radial surface 20 is finished as a sealing surface for the sealing element 16.

The free end 22 of the surface 18 is flared to a diameter greater than the diameter of the adjacent end 30 of the outer shell member 14 thus retaining the two shell members in a unitised construction with only limited relative axial movement.

The outer shell member 14 has a stepped configuration, three radially extending annular portions being interconnected by two axially extending tubular portions. The sealing eie- ment 16 is made of PTFE and is secured between the inner of these tubular portions and a force fitted metal ring 32. In position, as shown, the sealing element is flared from the end at which it is secured to the sealing lip 34 in engagement with the sealing surface 20, the resilience of the element 16 biasing the sealing lip against the surface 20.

In use the inner member 10 rotates with the shaft while the outer member remains fixed in the housing, the stationary sealing element bearing on and sealing against the sealing surface 20. The water is on the right of the seal in Fig. 1 and it can be seen that as the water pressure increases the biasing force on the element 16 is increased and the pressure on the sealing lip 34 is also increased.

The embodiment of Fig. 2 is very similar to that of Fig. 1, the major differences being that the sealing element 16 is shorter, effectively stiffening its spring characteristics, and is secured to the shell element 14 by the folded over end 21 of the element 14. The overall design is axially more compact.

In Fig. 3 the inner shell 10 is shaped at the junction of the surfaces 18 and 20 to make it mechanically stronger. The retaining ring 32 has its free end 38 turned down to restrict the entry of dirt into the area of the sealing lip.

This concept is taken one step further in Fig.

4 where a sealing O-ring 39 is provided between the ring 32 and the inner shell member 10.

The embodiment of Fig. 5 is different in that the sealing element 16 is secured to the inner shell member 10 by a force fitted ring 40, the sealing surface 42 contacted by the sealing lip 34 being a radial surface of the outer shell 14.

Fig. 6 illustrates a seal developed from that off Fig. 1 in that the outer shell element is coated in an elastomer 43.

Fig. 7 is a further modification of Fig. 1 in which the sealing surface 20 is a frustoconical surface rather than an annular radial surface. A leaf or finger spring 44, in Fig. 8, is secured at one end between the sealing element 16 and the outer shell beneath the retaining ring 32 and biases the element in the region of the sealing lip into engagement with the sealing surface.

In Figs. 9 and 10 the seal of Fig. 5 has been modified by making the sealing surface 42 on the outer shell member frusto-conical and, in Fig. 9, the spring 44 has been in clouded.

The embodiment of Fig. 11 is different in that the axial surface 18 of the inner shell element has been formed as the sealing surface and the sealing element 16 is secured to a radially extending part 48 of the outer shell element by a force fitting annular member 50 which is L-shaped in cross section. A gasket 52 is placed between the element 16 and the surface 48 to ensure that no leaks take place between the element 1 6 and the surface 48.

The modification shown in Fig. 1 2 incorporates a second sealing element 56 bearing on the sealing surface 1 8 to protect the element 1 6 against dust and a second washer 58 between the two sealing elements.

It should be noted that for many of the embodiments described the inner or outer shell assemblies are identical or very similar and further useful seals could be formed by picking appropriate combinations of the inner and outer shell members disclosed.

In all embodiments described increasing water pressure (to the right of the seal) causes an increased pressure on the sealing element and greater pressure of the sealing lip on the sealing surface. Moreover all the embodiments are utilised, i.e. after assembly of the two shell assembiies and flaring of the end 22 the complete seal remains as a unit during fitting and use.

The use of PTFE as the material of the sealing element in all embodiments has the advantage of minimising risk of rupture of the element as can happen with the conventional elastomeric materials and while the initial sealing lip load is relatively high it reduces after initial running as a layer of PTFE is deposited on the sealing surface. The PTFE may be pure or filled by any of the many and various fillers available.

While the invention has been primarily described in relation to a water pump seal, the seal of the present invention may also be used to seal against any liquid being pumped at low to medium pressure. Indeed PTFE well known resistance to many chemicals could, in many applications, make the seal of the present invention a particularly attractive choice.

Claims

1. A liquid pump seal comprising an inner annular shell member, an outer annular shell member, a sealing surface formed on one of said members and a sealing element secured to the other of said members, said sealing element being made of PTFE and having a sealing lip biased into engagement with the sealing surface, said shell members having only limited relative axial movement.

2. A seal as claimed in claim 1, in which the sealing element is secured to the other of the said members by means of a force fitting ring.

3. A seal as claimed in claim 1 or claim 2, in which the sealing surface extends radically.

4. A seal as claimed in any preceding claim, in which the sealing surface extends axially.

5. A seal as claimed in any preceding claim, in which a spring biases the sealing element into engagement with the sealing surface.

6. A seal as claimed in any preceding claim, including means to limit the ingress of dirt to the sealing surface.

7. A seal as claimed in claim 6 when dependent on claim 2, in which said means comprises the turned down end of the ring.

8. A seal as claimed in claim 6, in which said means comprises a second sealing element bearing against the sealing surface.

9. A seal as claimed in claim 6 or claim 7, in which said means comprises an O-ring.

10. A seal as claimed in any preceding claim, in which the sealing surface is formed on the inner shell member.

11. A seal as claimed in any of claims 1 to 8, in which the sealing surface is formed on the outer shell member.

1 2. A liquid pump seal substantially as hereinbefore described with reference to, and as shown in, any of the figures of the accompanying drawings.