Dynamic Seal

Abstract

A dynamic seal having a contact surface including a fabric is provided. A fatty acid ester is incorporated into the fabric.

Claims

1. A dynamic seal having a contact surface comprising: a fabric, wherein a fatty acid ester is incorporated into the fabric.

2. The dynamic seal of claim 1, wherein the fabric comprises a woven fabric.

3. The dynamic seal of claim 1, wherein the fatty acid ester comprises cellulose fatty acid ester.

4. The dynamic seal of claim 3, wherein the cellulose fatty acid ester comprises cellulose palmitoylate and/or cellulose decyl ester.

5. The dynamic seal of claim 3, wherein the cellulose comprises beta-cellulose.

6. The dynamic seal of claim 1, wherein the fatty acid ester comprises a carbon chain having at least 13 carbon atoms.

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

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

9. A machine arrangement comprising: a fabric, wherein a fatty acid ester is incorporated into the fabric.

10. 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 including a fabric, wherein a fatty acid ester is incorporated into the fabric, wherein the contact surface of the dynamic seal is arranged to be in sliding contact with the inner ring or the outer ring.

11. The bearing of claim 10, wherein the fabric 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

[0049] The present invention will now be described further, by way of example, with reference to the following non-limiting drawings in which:

[0050] FIG. 1 shows a cross-section of part of a seal according to the invention.

[0051] FIG. 2 shows a cross-sectional view of part of a first embodiment of a rolling element bearing according to the present invention.

[0052] FIG. 3 shows a cross-sectional view of part of a bearing seal according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0053] The invention will now be described with reference to the Figures and the following non-limiting Examples.

[0054] 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 provides a fabric (not shown) having a fatty acid ester (not shown) incorporated therein.

[0055] 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.

[0056] 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 counter surface at the radially innermost edge of each bearing seal 8 is provided with a fabric 9, which is in sliding contact with the outer surface 5 of the inner ring 2 during bearing operation. The fabric 9 provides a fatty acid ester.

[0057] 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, fabric 9 is bonded to bearing seal 8 by an adhesive layer 10.

[0058] Prior to use, the bearing may be loaded with lubricating oil (not shown). In use, due to its oleophilic nature, fabric 9 becomes impregnated with lubricating oil. This serves to maintain a layer of lubricating oil between bearing seal 8 and the outer surface 5 of the inner ring 6, thereby reducing friction between the bearing seal 8 and the outer surface 5 of the inner ring 6.

[0059] 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

[0060] An oleophilic treatment on a dry, finely woven Ventile® cotton textile was performed by placing a small piece of the textile (˜10 cm×10 cm) into a dilute solution of palmitoyl chloride in toluene (70 ml, 2.8% w/v). Swirling of the textile in solution textile was maintained for 2 minutes to help enable full saturation of the textile, followed by heating of the solution to 50° C. and maintaining that temperature for 30 minutes. The sample was then removed from the solution and excess solution forced out of the textile, followed by washing the treated textile in a solution of triethylamine in 2-propanol (100 ml, 10% v/v). Repeat rinsing in 2-propanol then water was then performed to remove side products and other impurities. The textile was then dried under gentle heating until all solvent was removed.

[0061] A single circular ring was cut from the treated textile and bonded onto the surface of an FKM test ring of diameter ˜5 cm and 2 mm surface contact using a thin layer of cyanoacrylate adhesive. The sample was then immersed in a semi-synthetic 5W-30 engine oil for 30 minutes until full saturation into the textile was achieved, after which the excess oil was removed by wiping and then contacting the surface of the textile with a surfactant-free tissue until no oil residue was left on the tissue.

[0062] 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 0.16  0.16-0.17 20 0.17 0.165-0.17 50 0.18  0.17-0.18 100 0.19 0.185-0.19 200 0.21  0.20-0.21 500 0.23 0.23 1000 0.25  0.24-0.25 2000 0.26  0.25-0.26 rpm (descending) 1000 0.24 0.235-0.24 500 0.22 0.22 200 0.20 0.20 100 0.19 0.185-0.19 50 0.18 0.175-0.18 20 0.17 0.165-0.17

Comparative Example 1

[0063] 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 pressure. 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 0.32-0.36 500 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

[0064] 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

[0065] A sample of finely woven cotton material bonded to an FKM elastomer test ring was made in an identical way to that Example 1. The textile layer was then instead saturated with a fully synthetic 5W-30 engine oil for 30 minutes until full saturation into the textile was achieved, after which the excess oil was removed by wiping and then contacting the surface of the textile with a surfactant-free tissue until no oil residue was left on the tissue. 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 0.18 0.17-0.18 20 0.17 0.17-0.18 50 0.17 0.16-0.17 100 0.17 0.16-0.17 200 0.19 0.17-0.19 500 0.22 0.20-0.22 1000 0.24 0.21-0.28 2000 0.25 0.24-0.30 rpm (descending) 1000 0.23 0.22-0.23 500 0.20 0.20-0.21 200 0.19 0.18-0.19 100 0.18 0.18-0.19 50 0.17 0.16-0.17 20 0.17 0.16-0.17

Comparative Example 2

[0066] 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 premium, mineral oil based grease at 0.2 MPa and 0.5 MPa contact pressure. The results are set out in Tables 5 and 6 below.

TABLE-US-00005 TABLE 5 Comparative Example 2 - FKM elastomer with a 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-00006 TABLE 6 Comparative Example 2 - 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 0.32-0.36 500 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

[0067] 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.

Comparative Example 3

[0068] 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 7 and 8 below.

[0069] FKM elastomer with fully synthetic 5W-30 engine oil (Contact pressure=0.5 MPa)

TABLE-US-00007 TABLE 7 Comparative Example 3 - 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-00008 TABLE 8 Comparative Example 3 - 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

[0070] It can be seen that the dynamic coefficient of friction of Comparative Example 3 is higher than that of Example 2 over a range of speeds and pressures.

[0071] 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.