Dynamic Seal

Abstract

A dynamic seal having a contact surface providing poly(norbornene) or a derivative thereof.

Claims

1. A dynamic seal having a contact surface comprising: poly(norbornene) or a derivative thereof.

2. The dynamic seal of claim 1, wherein the poly(norbornene) is provided in the form of a particulate.

3. The dynamic seal of claim 2, wherein a majority of the particles making up the particulate have a longest dimension of from 1 to 500 microns.

4. The dynamic seal of claim 2, wherein the particulate is fixed to the contact surface using an adhesive.

5. The dynamic seal of claim 4, wherein the adhesive comprises a cyanoacrylate adhesive and/or a water-based poly(urethane) adhesive.

6. The dynamic seal of claim 1, wherein the dynamic seal comprises an elastomer.

7. The dynamic seal of claim 6, wherein the elastomer is a fluoroelastomer.

8. A machine arrangement comprising: a dynamic seal having a contact surface providing poly(norbornene) or a derivative thereof.

9. A rolling element bearing comprising: an inner ring; an outer ring; a plurality of rolling elements disposed between an outer surface of the inner ring and an inner surface of the outer ring; and a dynamic seal having a contact surface providing poly(norbornene) or a derivative thereof, wherein the contact surface of the dynamic seal is arranged to be in sliding contact with the inner ring and/or outer ring.

10. The bearing of claim 9, wherein the contact surface of the dynamic seal is loaded with lubricant oil to lubricate the relative motion of the dynamic seal with either the inner ring or the outer ring.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0048] The present invention will now be described further, by way of example, with reference to the following non-limiting drawings in which:

[0049] FIG. 1 shows a cross-sectional view of part of a seal according to the invention.

[0050] FIG. 2 shows a cross-sectional view of part of a rolling element bearing according to the present invention.

[0051] FIG. 3 shows a cross-sectional view of part of a bearing seal according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0052] The invention will now be described with reference to the Figures and the following non-limiting Examples.

[0053] FIG. 1 shows an example of a shaft seal 11 comprising a metal casing 15 to which an elastomeric sealing lip 20 has been bonded. The sealing lip 20 is formed of an elastomer. The seal is mounted in an annular gap between the bore of a bearing housing 30 and a shaft 35, whereby the sealing lip 20 has a contact surface 25 which bears against a counterface on the shaft 35. To ensure that the lip remains in contact with the shaft, the lip is preloaded with a garter spring 40. The contact surface 25 is provided with poly(norbornene) (not shown).

[0054] Referring to FIGS. 2 and 3, an embodiment of a rolling element bearing 1 in accordance with the present invention is shown comprising an inner ring 2, an outer ring 3 and a plurality of rolling elements 4 (in this case a ball, only one rolling element shown) disposed between an outer surface 5 of the inner ring 2 and an inner surface 6 of the outer ring 3. The rolling elements 4 are preferably contained in a ball cage 7.

[0055] The rolling element bearing 1 has bearing seals 8 positioned either side of the rolling elements 4 in the axial direction. The bearing seals extend from the outer ring to the inner ring. A contact surface at the radially innermost edge of each bearing seal 8 is provided with a poly(norbornene) layer 9 in sliding contact with an outer surface 5 of the inner ring 2.

[0056] FIG. 3 shows a close-up of the contact surface of the bearing seal 8 of the rolling element bearing 1 shown in FIG. 2. As shown in FIG. 3, poly(norbornene) layer 9 (shown as a layer or coating, but as noted above will preferably be in the form of a particulate, e.g. a powder) is bonded to bearing seal 8 by an adhesive layer 10.

[0057] Prior to use, the bearing may be loaded with lubricating oil (not shown). In use, due to its oleophilic nature, poly(norbornene) layer 9 forms a gel-like material with the lubricating oil. This serves to maintain a layer of lubricating oil between the bearing seal 8 and the outer surface 5 of the inner ring 2, thereby reducing friction between the bearing seal 8 and the outer surface 5 of the inner ring 2.

[0058] While the bearing 1 shown in FIG. 2 is asymmetric (for reasons of ease of assembly), this is not essential, and the invention may be applied to other types of bearing 1, including symmetric and/or split types.

EXAMPLE 1

[0059] A poly(norbornene)-based powder, NORSOREX® APX (Astrotech Advanced Elastomerproducts GmbH), in dry form, was filtered to a particle size of <125 μm using a sieve to produce a fine, off-white powder. The surface of an FKM elastomer test ring of diameter ˜5 cm and 2 mm surface contact width was coated in a suitable water-based poly(urethane) dispersion coating to produce a wet coating of ˜0.5 mm thickness on the surface of the elastomer test ring. The coated ring was then contacted gently onto a layer of the filtered poly(norbornene)-based powder that had been spread evenly across a flat container so that powder was allowed to adhere to the surface; this was repeated several times to try and obtain full powder coverage of the test ring surface with loose powder removed by gentle tapping. After this the adhesive was allowed to dry and cure by leaving the sample at ambient temperature for one week.

[0060] The particulate coated surface of the test ring was then placed in a shallow bath of clean semi-synthetic engine oil (5W-30) for 30 minutes to allow saturation of the oil absorbing polymer with the oil. After this the excess oil was wiped away and any residual oil left on the surface was removed by contacting the coated surface on a surfactant free tissue several times until oil residue could not be seen on the tissue paper.

[0061] The dynamic friction of the test ring was then tested in a tribometer (CETR UMT-3) at 25° C. and 0.2 MPa contact pressure for a series of increasing rotational speeds at 10 rpm, 20 rpm, 50 rpm, 100 rpm, 200 rpm, 500 rpm, 1000 rpm and 2000 rpm for 30 seconds each. This sequence was then run in reverse order to 20 rpm under the same conditions. Prior to testing for different speeds the sample was run in for several minutes at ambient and 0.2 MPa at 100 rpm. Testing of the sample was repeated with data measured between a duration of 10-30 s of each test speed. An average of the coefficient of dynamic friction (dynamic COF) together with the range between the highest and lowest values was recorded. The results are set out in Table 1 below.

TABLE-US-00001 TABLE 1 Example 1 - Oil saturated oleophilic polymer coating (contact pressure = 0.2 MPa). Dynamic COF Average Range rpm (ascending) 10 0.17 0.14-0.20 20 0.16 0.14-0.19 50 0.17 0.16-0.19 100 0.18 0.16-0.20 200 0.20 0.18-0.23 500 0.24 0.21-0.27 1000 0.28 0.25-0.30 2000 0.29 0.26-0.32 rpm (descending) 1000 0.28 0.26-0.31 500 0.29 0.24-0.34 200 0.22 0.20-0.25 100 0.20 0.17-0.23 50 0.19 0.16-0.21 20 0.18 0.15-0.21

COMPARATIVE EXAMPLE 1

[0062] An FKM reference sample of identical dimensions without a coating was tested and under the same conditions using only lubrication with a premium, mineral oil based grease at 0.2 MPa and 0.5 MPa contact pressures. The results are set out in Tables 2 and 3 below.

TABLE-US-00002 TABLE 2 Comparative Example 1 - FKM elastomer with premium, mineral oil based grease (contact pressure = 0.2 MPa). Dynamic COF Average Range rpm (ascending) 10 0.34 0.31-0.36 20 0.37 0.34-0.42 50 0.35 0.34-0.36 100 0.47 0.42-0.49 200 0.63 0.51-0.70 500 0.73 0.64-0.82 1000 0.61 0.60-0.63 2000 0.47 0.43-0.51 rpm (descending) 1000 0.54 0.52-0.55 500 0.72 0.70-0.74 200 0.50 0.48-0.52 100 0.38 0.36-0.39 50 0.31 0.30-0.31 20 0.30 0.28-0.31

TABLE-US-00003 TABLE 3 Comparative Example 1 - FKM elastomer with a premium, mineral oil based grease (contact pressure = 0.5 MPa). Dynamic COF Average Range rpm (ascending) 10 0.27 0.24-0.3  20 0.26 0.24-0.27 50 0.27 0.25-0.29 100 0.29 0.28-0.32 200 0.33 0.34-0.36 500 0.34 0.34-0.36 1000 0.35 0.34-0.35 2000 0.30 0.29-0.31 rpm (descending) 1000 0.29 0.28-0.29 500 0.28 0.27-0.28 200 0.26 0.24-0.27 100 0.25 0.24-0.26 50 0.25 0.24-0.26 20 0.23 0.23-0.24

[0063] It can be seen that the dynamic coefficient of friction of Comparative Example 1 is higher than that of Example 1 over a range of speeds and pressures

EXAMPLE 2

[0064] An oil absorbing coating on an FKM test ring was made using identical materials and conditions to those used for Example 1. A fully synthetic, 5W-30 grade oil was instead used to lubricate the polymer coating for 30 minutes to allow saturation of the oil absorbing polymer with the oil. After this the excess oil was wiped away and any excess left on the surface was removed by contacting the coated surface on a surfactant free tissue several times until oil residue could not be seen on the tissue paper. The dynamic friction of the test ring was then tested using the same protocol as for Example 1. The results are shown in Table 4 below.

TABLE-US-00004 TABLE 4 Example 2 - Oil saturated oleophilic polymer coating (contact pressure = 0.2 MPa). Dynamic COF Average Range rpm (ascending) 10 0.16 0.15-0.17 20 0.16 0.15-0.16 50 0.16 0.15-0.16 100 0.17 0.16-0.17 200 0.18 0.17-0.19 500 0.22 0.20-0.24 1000 0.25 0.21-0.27 2000 0.29 0.24-0.33 rpm (descending) 1000 0.33 0.30-0.40 500 0.31 0.31-0.32 200 0.24 0.24-0.26 100 0.19 0.19-0.20 50 0.16 0.16-0.17 20 0.16 0.16-0.17

COMPARATIVE EXAMPLE 2

[0065] An FKM reference sample of identical dimensions to Example 2 but without a coating was tested and under the same conditions using only lubrication with a synthetic 5W-30 engine oil (the same lubrication as Example 2) at 0.2 MPa and 0.5 MPa contact pressures. The results are set out in Tables 5 and 6 below.

TABLE-US-00005 TABLE 5 Comparative Example 2 - FKM elastomer with fully synthetic 5W-30 engine oil (contact pressure = 0.5 MPa). Dynamic COF Average Range rpm (ascending) 10 0.42 0.39-0.46 20 0.38 0.37-0.39 50 0.34 0.33-0.35 100 0.32 0.32-0.33 200 0.33 0.32-0.34 500 0.35 0.34-0.36 1000 0.35 0.34-0.36 2000 0.32 0.31-0.33 rpm (descending) 1000 0.32 0.31-0.32 500 0.32 0.31-0.32 200 0.32 0.31-0.32 100 0.33 0.32-0.33 50 0.35 0.34-0.35 20 0.37 0.36-0.37

TABLE-US-00006 TABLE 6 Comparative Example 2 - FKM elastomer with fully synthetic 5W-30 engine oil (contact pressure = 0.2 MPa). Dynamic COF Average Range rpm (ascending) 10 0.55 0.50-0.60 20 0.50 0.49-0.51 50 0.46 0.44-0.47 100 0.45 0.44-0.46 200 0.47 0.46-0.47 500 0.52 0.51-0.52 1000 0.53 0.52-0.54 2000 0.47 0.46-0.48 rpm (descending) 1000 0.48 0.48-0.49 500 0.46 0.46-0.47 200 0.45 0.44-0.46 100 0.45 0.44-0.46 50 0.47 0.45-0.48 20 0.52 0.51-0.52

[0066] It can be seen that the dynamic coefficient of friction of Comparative Example 2 is higher than that of Example 2 over a range of speeds and pressures.

[0067] The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art, and remain within the scope of the appended claims and their equivalents.