Antifriction bearing with pulse ring for measurement of speed rotation

An antifriction bearing with an outer ring, inner ring, a row of balls between the rings and an open radial space between the rings. A sealing disc at one axial side of the rings seals the open space between the outer and inner rings. The sealing disc also serves as a pulse ring. It comprises a metal part having a plurality of openings of preferably rectangular cross-section through it. The metal part is at least partially surrounded by a covering nonmetallic layer of plastic or rubber which also fills the openings. The sealing disc is attached to one of the rings, and preferably to the outer ring to rotate with the outer ring with respect to the other, inner ring and the sealing disc is sealed to the inner ring.

BACKGROUND OF THE INVENTION 
The present invention relates to an antifriction bearing and particularly 
to a pulse ring for measuring the speed of bearing rotation. 
Antifriction bearings of this type are known from Federal Republic of 
Germany Published Application Nos. OS 2,218,047 and OS 2,831,637. In both 
cases, a pulse ring having teeth on it is arranged between the races of an 
antifriction bearing. The inhomogeneities produced by the teeth permit 
measurement of the rotation speed by a sensor while the pulse ring moves 
past the sensor. These embodiments, however, have a substantial drawback. 
They require an additional part in the form of a pulse ring, which must 
also be mounted The additional part also increases the weight of the 
bearing. 
SUMMARY OF THE INVENTION 
The object of the present invention is to improve an antifriction bearing 
which measures rotation speed and which is simple, light, dependably 
operable and precise embodiment of a pulse ring. 
An antifriction bearing according to the invention includes the outer ring, 
the inner ring radially inward of the outer ring and the row of bearing 
rolling elements, particularly balls, disposed between the rings, which 
roll over the raceways of the rings. At at least one axial end of the 
rings, the radial space between the rings is sealed by an annular shape 
sealing disc. The sealing disc is held to and moves with one of the rings, 
preferably the outer ring, and sealingly but slidingly engages the other 
ring, preferably the inner ring. 
The sealing disc according to the invention serves as a pulse ring. It is 
comprised of an annular shape metal strip or ring. The metal pulse ring 
rotates with the one bearing ring, particularly the outer ring. A 
plurality of openings, having a preferably rectangular cross-section, are 
defined in the metal ring at spaced intervals around the ring. A sensor 
senses the passage of the rectangular openings past the sensor. With 
stored information as to the number, width and spacing of the openings and 
as to the size of the bearing, the sensor can measure the speed of 
rotation of the ring on which the sealing disc is supported with respect 
to the sensor. The sensor may be supported stationary and/or may be 
supported on the other ring past which the sealing disc slides. In the 
latter case, the other ring may be stationary. Alternatively the sensor 
may also be supported to the other ring to rotate with the other ring and 
thereby to provide an accurate measurement of the speed of rotation of the 
one ring to which the sensor is not supported. 
Any known appropriate sensor might be used, an electrical sensor, a sensor 
that determines the presence of metal by measuring a change in an electric 
and/or a magnetic field as the metal moves past, or even an optical sensor 
if the openings are exposed. 
The openings in the metal ring are preferably of rectangular cross-section 
so that the sensor will achieve an accurate reading that is not dependent 
upon the precise radial position over the sealing disc at which the 
reading is made. For example, readings made at circular openings require 
precise radial positioning of the readings so that the readings are not 
affected by the change in cross-section of circular openings over their 
radial height. 
In a preferred embodiment, the metallic part of the sealing disc is 
surrounded, either in whole or in part, by plastic or rubber or other 
resilient material covering. The plastic or rubber covering defines a lip 
which is held in a receptacle in the one bearing ring to which the sealing 
disc is secured and also defines a sealing lip or lips at the other 
bearing ring over which the covering slides. The resilience of that 
covering material helps assure the seal. Although the plastic or rubber 
covering material may fill the openings in the metal part, nonetheless a 
sensor dependent upon the presence or absence of metal will not have its 
sensing function adversely affected. 
Because the metal part of a sealing disc is also developed as a pulse ring, 
no additional parts are required on the bearing to achieve the additional 
rotation speed count. It is merely necessary to provide openings on the 
metal part of the sealing disc, and such a sealing disc is normally 
required anyway. These openings can be produced in a simple manner by 
being stamped simultaneously during the production of the metal part. No 
increase in the weight of the bearing results. In fact, the sealing disc 
even is lighter, since portions of its metal are removed by the stamping. 
So that a precise speed measurement can be carried out, the metal part has 
a plurality of preferably rectangular openings This assures that even at 
low speeds of rotation of the antifriction bearing, precise measurement of 
the speed of rotation is possible. The rectangular openings permit precise 
determination of the number and spacing of pulses and thus permit exact 
determination of the speed of rotation. In contrast to the requirement for 
sensing round openings, exact positioning of the sensor is unnecessary and 
changes in position between the pulse ring and the sensor caused by 
operation do not impair the precision of the measurement. The particular 
advantage therefore resides in the fact that the pulse ring and sealing 
disc are integrated with each other and perform both functions without 
problems 
Despite the presence of the openings, in order that an optimally 
functioning sealing disc be obtained, the metal part may be surrounded in 
whole or in part by plastic or rubber covering material. The openings are 
also thereby filled up. This does not have a negative effect on the 
rotation measurement since the sensor is acted on only by the 
inhomogeneities in the metal part. But the surrounding plastic or rubber 
material does increase the sealing effect. 
Sealing discs provided with holes in their metal part are already known, as 
in British Patent No. 862,171. However, those holes serve the entirely 
different purpose of insertion openings for relubricating devices. 
Furthermore, the holes are round and are only few in number, which would 
make exact measurement of the speed of rotation impossible. 
Other objects and features of the present invention will become apparent 
from the following description of the preferred embodiments of the 
invention considered in conjunction with the accompanying drawings.

DESCRIPTION OF A PREFERRED EMBODIMENT 
The ball bearing of FIG. 1 comprises the outer ring 1, the row of bearing 
balls 2, the inner ring 3 and the sealing disc 4 sealing the axial end of 
the opening between the rings. 
The sealing disc 4 comprises an annular metal part 5 in the form of an 
annular strip or ring, which is practically completely surrounded by a 
nonmetallic plastic material or a rubber material covering layer and part 
6. The metal part is of a shorter radial height than the space between the 
rings and does not engage the rings. The part 6 extends radially above and 
below the metal part and also forms the attachment flange 7 for attaching 
the sealing disc to the outer ring 1 for their rotation together and forms 
the sealing lips 8 which are resiliently biased to rest against and slide 
over the outer surface of the inner ring. 
As can be noted particularly from FIG. 2, a plurality of identically sized 
and shaped rectangular openings 9 are provided in the metal part 5. The 
openings are all oriented so that, measured around the sealing disc, each 
rectangular opening has a center line along a radius of the bearing. The 
sealing disc 4 can be used as a pulse ring for measuring the speed of 
rotation of the outer ring if the openings 9 are arranged opposite a 
sensor 10, and the outer ring 1 rotates together with the sealing disc 4. 
This method of measurement is not disturbed even if the openings 9 are 
filled with plastic, which occurs as the metal part is surrounded by the 
covering layer. A large enough number of rectangular openings 9 in the 
part 5 permits an exact measurement of the speed of rotation even at low 
speeds of rotation of the ball bearing. 
Although the present invention has been described in connection with a 
preferred embodiment thereof, many other variations and modifications will 
now become apparent to those skilled in the art. It is preferred, 
therefore, that the present invention be limited not by the specific 
disclosure herein, but only by the appended claims.