Bearing with sensor

Abstract: A bearing is mounted within a housing (10) having an acoustic-electric transducer (32) mounted on its outside. A stationary annular outer race (14), has at least one sensor (22), an electric-acoustic transducer (24), and an electronic system (26) interconnecting the sensor and the electric-acoustic transducer. The electric-acoustic transducer is mounted in an opening (36) extending radially through the stationary race, and has an elastic cap (56) pressed into the inside of the housing by a spring.

Description: This invention relates to bearings. More particularly, this invention relates to a bearing mounted within a housing having an acoustic-electric transducer mounted on its outside. The bearing has an electric-acoustic transducer which receives electric signals indicating various parameters within the bearing and converts the electric signals into acoustic signals. These acoustic signals are detected by the acoustic-electric transducer mounted on the outside of the housing. There are numerous bearing applications where the bearing is mounted in a housing that denies access to the bearing by servicing personnel. There are bearing performance characteristics that are best measured from inside the bearing for a number of different reasons. For instance, temperature-measurement devices are more responsive the closer they are to the source of heat generation. Vibration monitors are less affected by noise if they are installed inside the bearing. In using both of these types of sensors, a more reliable measurement is obtained if the sensor is permanently mounted within the bearing eliminating installation differences and misapplication of the sensor. Furthermore, in applications where the bearing is transferred to a number of different locations during its life, the ability to maintain the historical data pertaining to an individual bearing is of great advantage in diagnosing bearing conditions. While better measurements are obtained from within the bearing, the information needs to be made available to the personnel responsible for servicing the bearing for this information to be useful in diagnosing problems occurring in the bearing and surrounding equipment. Therefore, only if a method can be devised to relay this information out of the bearing will a measurement taken inside the bearing be of value. According to the present invention, there is provided a bearing adapted to be mounted within a housing, comprising an annular rotatable race, an annular stationary race having a greater inside diameter than the outside diameter of the annular rotatable race, and a plurality of rollers located in the annular space between said races; characterised by an acoustic-electric transducer mounted on the outside of the housing; at least one electric-acoustic transducer mounted on the annular stationary race, said electric-acoustic transducer having an elastic portion adapted to contact the housing to maximise an acoustic interface between the electric-acoustic transducer and the housing, means for pressing the elastic portion against the housing, and means mounted on the annular stationary race for sensing a parameter within the bearing and feeding electric signals to the electric-acoustic transducer related to the value of the parameter sensed. For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- Figure 1 is a perspective view of a large bearing such as of the type used in steel mills with portions of the housing removed and portions of the inner race of the bearing removed; and Figure 2 is a cross-sectional view of a preferred embodiment of an electric-acoustic transducer. Referring to Figure 1, a housing 10 of the type used for supporting large bearings such as those used in steel mills is shown. A rotatable member 12 is rotatably mounted within the housing 10. As shown in Figure 1, the rotatable member 12 is a rotatable race; however, it is to be understood that under some circumstances and with some bearings, rather than having a rotatable race, a rotatable shaft could extend entirely through the bore in the housing 10 and the shaft serve as a race. A portion of the annular rotatable race 12 is not shown in Figure 1 so that features can be more clearly shown. An annular stationary race 14 is also mounted within the housing 10. The race 14 has a greater inside diameter than the outside diameter of the race 12. A plurality of rollers 16 are located in the annular space between the race 12 and the race 14. The rollers 16 are mounted within the roller pockets of the roller cage 18. The annular ring 20 of the annular case 18 separates the rollers 16 into two axially spaced series of rollers. A sensor 22 is located on the inside surface of the stationary annular race 14. In the drawings, one sensor is shown. However, the actual number of sensors is dependent on how much resolution is wanted and also on the size and length of the bearing and area to be sensed by the sensor. However, of course, at least one sensor must be used. An electric-acoustic transducer 24 is located in the annular stationary race 14. The electric-acoustic transducer 24 is adapted to transmit acoustic signals through the housing 10. The acoustic signals are related to the parameter within the bearing. The electronic system 26 interconnects the sensor 22 and the electric-acoustic transducer 24. In the embodiment shown in Figure 1, a groove 28 extends partially around the inside surface of the stationary annular race 14. However, if desired, the groove may extend around the entire inside surface of the stationery annular race 14 for lower manufacturing costs. That part of the groove which extends from the electronic system 26 to the electric-acoustic transducer 24 is not shown in Figure 1 because it is hidden by the stationary race 14. The sensor 22 is located in the pocket 30 in the inside surface of the stationary annular race 14. Wires extend along the groove 28 from the sensor 22 to the electronic system 26. Wires also extend from the electronic system 26 to the electric-acoustic transducer 24. An acoustic-electric transducer 32 is mounted on the outside surface of the housing 10. In the embodiment shown, the acoustic-electric transducer 32 is in-line with and radially spaced from the electric-acoustic transducer 24. Thus, the acoustic waves from the electric-acoustic transducer 24 are directly fed to the acoustic-electric transducer 32. The acoustic-electric transducer 32 is adapted to receive the acoustic signals transmitted by the electric-acoustic transducer 24 and convert these acoustic signals into electric signals related to the parameter within the bearing. The signals from the acoustic-electric transducer 32 are fed to the electronic system 34 which converts the output from the acoustic-electric transducer 32 into a value that will indicate the parameter within the bearing. The word 'parameter' as used in this description and in the claims is meant to include any value within the bearing which can be sensed electrically and the electric signals converted into corresponding acoustic signals. These values include, but are not limited to, temperatures, vibration and load carried by the bearing. Referring to Figure 2, the stationary race 14 has at least one cylindrical opening 36 extending radially from its inside surface to its outside surface. The electric-acoustic transducer 24 is mounted in the cylindrical opening 36. The electric-acoustic transducer has a cylindrical bushing 38. An annular upwardly facing shoulder 40 is located at the bottom of the bore of the bushing. A sleeve 42 is mounted in the cylindrical bushing 38. The sleeve 42 has an annular downwardly facing shoulder 44 which is spaced above the bushing upwardly facing shoulder 40. This provides an annular recess 46. A wave spring 48 is mounted in the annular recess 46. A cylindrical member 50 which contains a piezoelectric crystal is mounted in the sleeve 42. The member 50 receives the electric signals from the parameter sensing system through wires 54 and converts the electric signals into corresponding acoustic signals. A stem 52 is a potted compound that provides strain relief for the wires 54. The crystals included in the cylindrical member 50 may be any suitable crystal which undergoes mechanical deformation when an electrical field is applied on certain faces of the crystal. Suitable crystals include, but are not limited to, quartz, barium titanate, zirconate titanate and lead. An elastic or elastomeric cap 56 is mounted in the top of the sleeve 42. The sleeve is provided with an annular groove in which the larger diameter portion 58 of the cap 56 is fitted. The top of the cap extends upwardly beyond the top of the sleeve 42 in order to be adapted to contact the inside of the housing 10. The bottom of the cap 56 is in continuous contact with the top of the member 50. Thus the arrangement of the cap 56 and the member 50 is such that the acoustic interface between the member 50 and the inside of the housing 10 is maximised. A snap ring 60 is mounted within an annular groove around the smaller diameter portion 62 of the sleeve 42. This smaller diameter portion extends below the bottom of the bushing 38. The wave spring 48 wraps around the smaller diameter portion 62 of the sleeve 42. The wave spring 48 applies a force against the downwardly facing shoulder 44 of the sleeve 42 to press the elastic cap 56 against the inside surface of the housing 10.

Claims: A bearing mounted within a housing (10), comprising an annular rotatable race, an annular stationary race having a greater inside diameter than the outside diameter of the annular rotatable race, and a plurality of rollers (16) located in the annular space between said races; characterised by an acoustic-electric transducer (32) mounted on the outside of the housing (10); at least one electric-acoustic transducer (24) mounted on the annular stationary race, said electric-acoustic transducer having an elastic portion (56) adapted to contact the housing (10) to maximise an acoustic interface between the electric-acoustic transducer (24) and the housing (10), means (48) for pressing the elastic portion (56) against the housing, and means (22) mounted on the annular stationary race for sensing a parameter within the bearing and feeding electric signals to the electric-acoustic transducer (24) related to the value of the parameter sensed. A bearing according to claim 1, wherein the annular stationary race (14) has an opening (36) extending radially from its inside to its outside surface and the electric-acoustic transducer (24) is mounted in said opening. A bearing according to claim 1, or 2, wherein the means for pressing the elastic portion (56) against the housing is a spring (48). A bearing according to claim 3, wherein the spring is a wave spring (48). A bearing according to any one of the preceding claims, wherein said electric-acoustic transducer (24) has a cylindrical bushing (38) with an annular upwardly facing shoulder (40) and a sleeve (42) is mounted in the cylindrical bushing, said sleeve having an annular downwardly facing shoulder (44) spaced above said upwardly facing shoulder (40) thus providing an annular recess (46) and a cylindrical member (50) containing a piezoelectric crystal mounted in said sleeve, said elastic portion (56) being mounted in the top of said sleeve (42) in contact with said cylindrical member (50). A bearing according to any one of the preceding claims and comprising an electronic system (34) connected to the acoustic-electric transducer (32) for indicating the value of the parameter sensed by said parameter sensing means (22).

Inventors: BRONWER RICHARD W, JURASS MARK I III, LEMOINE RICHARD L, PEARSON JOHN K, BRONWER, RICHARD W., JURASS, MARK I., III, LEMOINE, RICHARD L., PEARSON, JOHN K.
Applicants: TORRINGTON CO, THE TORRINGTON COMPANY
Application year: 1996
Main classification: G01K1
IPC codes: G01K1, B21B38, B21B31, B21B33