CA2126613A1

CA2126613A1 - Cassette seal

Info

Publication number: CA2126613A1
Application number: CA002126613A
Authority: CA
Inventors: Gerhard Kilthau; Hermann Metzner; Hermann Rapp; Hans-Gerd Eckel; Ulrich Dahlhaus; Rolf Vogt; Hanno Wentzler; Fernando Guthardt
Original assignee: Individual
Current assignee: Carl Freudenberg KG
Priority date: 1993-06-24
Filing date: 1994-06-23
Publication date: 1994-12-25
Also published as: DE4320940A1; BR9402133A; MX9405116A; EP0631139A1

Abstract

ABSTRACT

A cassette seal includes two rings of opposite, angular profile which mutually overlap and together define an inner cavity, whereby one ring includes at least one sealing lip which relatively rotatably engages the other ring. One ring is provided with a sensor and the other ring with an impulse generator for the detection of relative rotation between the rings. The sensor and the impulse generator are at least partly positioned in the cavity.
The cassette seal requires less installation space, and all functional components thereof are well protected from environmental influences.

Description

2.~2~613 CASSETTE SEAL : :
.
The invention relates to cassette seals which include a pair of relatively rotatable :: .
rings of opposite, angular profile that together deflne an inner cavity and respectively : . :
include a sensor and an impulse generator. More particularly, the invention relates to a cassette seal wherein the angled rings overlap each other to define the inner cavity and one 5 of the rings includes at least one sealing lip which sealingly rotatably engages the other rlng.
Such a cassette seal is known from European Patent EP-PS438624. It is used for :
detection of the speed of rotation of a pair of relatively rotatable parts of a bearing supporting a vehicle wheel. In particular, the relative rotation between a pair of seal rings is detected. This is accomplished with an impulse generator and sensor combination which ~ ~ ~
is positioned on the outside of the cassette seal. This requires additional installation space ~ :
for the seal, which is not satisfactory. It is furthermore difficult to establish and maintain ..
the correct mutual orientation of the sensor in relation to the impulse generator.
Furthermore, both the sensor and the impulse generator are subject to contamination by 15 dirt and dust from the surrounding area which can lead to measurement errors.It is now an object of the invention to further develop a cassette seal of the above .:
described type which overcomes the disadvantages of the prior art seal. ~:
This object is achieved in accordance with the invention with a cassette seal of the .:
general type disclosed above, wherein the sensor and the impulse generator are at least 20 partly positioned in the inner cavity defined by the rings and the sealing lip. The result is a seal which requires less space for installation and wherein the important functional components are well protected from environmental influences. The sensor and the impulse generator can also be positioned completely within the cavity defined between the rings and the sealing lip. Optimal protection from secondary environmental influences is .
25 thereby achieved, which is especially advantageous.
Accordingly, the invention provides a cassette seal including a pair of seal rings of opposite, ~mg~ular profile which overlap each other and together define an inner cavity in . .
the seal, a sealing lip mounted to one of the seal rings and relatively rotatably engaging ~.-the other seal ring, an impulse generator provided on one of the seal rings and a sensor 30 mounted to the other of the seal rings, whereby the sensor and the impulse generator are at least partly positioned within the inner cavity.

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2 2~ 2~5~3 The impulse generator can be a separate part mounted directly to one of the sealrings or to the sealing lip or may be an integral part of one of the seal rings. In the latter case, the impulse is preferably provided by circumferentially spaced cut-outs in one of the seal rings which cut-outs are separated by radial webs each capable of generating an S impulse. The movement of each web of the impulse generator past the sensor during the relative rotation of the rings generates a signal in the sensor which can be transferred to analyzing equipment. The webs may be magnetized.
A subsequent installation of the impulse generator/sensor combination onto the seal is obviated by integration thereof into the inner cavity of the seal. l~urthermore, a precise 10 mutual positioning of the sensor and the impulse generator at a selected distance and orientation is guaranteed and secondaty marginal conditions, for example, the precision of a vehicle wheel bearing in which the seal is used, no longer have a major influence on the operation of the sensor/impulse generator combination.
In a cassette seal in accordance with the invention, the impulse generator and the 15 sensor are protected from environmental influences such as dust, mud, water and corrosion. This results in a reduced number of impulse detection errors thereby inhibiting distortion of the measurements obtained.
The sensor and the impulse generator are spaced apart with an intermediate gap therebet~,veen. The interrnediate gap is preferably separa$ed from arnbient air by an 20 adjacent annular gap, which can have different shapes. In a preferred embodiment, the annular gap has an L-shaped cross-section in axial direction with a bend at least at one location between the inner cavity and the ambient air. The intrusion of humidity and dirt -:
from arnbient into the area of the intermediate gap is thereby further obstructed and, consequently, signal cletection is optimized. The annular gap can also have a labyrinth-25 shaped cross-section. Good sealing characteristics can be achieved thereby.
In embodiments, where the annular gap has an L-shaped cross-section7 the distance .
of the bend in the annular gap from ambient air is at least five times the distance between the sensor ~md the impulse generator. The intrusion of dirt into the intermediate gap is ~ ~.
thereby retarded and reduced. In order to achieve an even better protection from :
30 environmental influences, the intermediate gap in a pteferred embodiment is delimited at least on one side by a current free buffer space. Improved conditions for the impulse detection are thereby achieved for a long period, since dirt which enters the area of the : .: . " ,, ~ .

3 2~266~3 intermediate gap no longer settles directly in the gap but in the current reduced ..
neighbouring areas. This does not result in additional installation costs. Variations of this ~ :
embodiment and the one described in the following can be easily achieved withoutdeparting from the invention.
In a further preferred embodiment, the positioning of the two detection elements, namely the impulse generator and the sensor, can be such that the intermediate gap is defined on both sides by a current free buffer space. The ratio of the total buffer space volume to the volume of the intermediate gap between the sensor and the impulse generator is thereby preferably at least 1 to 50.
The cassette seal in accordance with the invention provides an arrangement which :~
incorporates a seal, a sensor and an impulse generator in an enclosed, robust unit. The use of the impulse generator and the sensor within the cassette seal provides for a simple construction and an exact and reliable detection of the signals. The manufactuIe of cassette seal systems in accordance with the invention does not require any expensive installation steps and thereby lowers the associated costs for signal detection and processing.
The invention will now be further described by way of example only and with reference to the following drawings, wherein . . .
FIGURES I and la illustrate the integration of the impulse generator and the sensor within a cassette seal and the detailed construction of the impulse generator,. -~ .
respectively;
~IG~lRE 2 shows a second preferred embodiment with a different arrangement of the impulse generator and the sensor;
FIGURES 3a and b are an illustration of a third preferred embodiment with another arrangement of the impwlse generator and the sensor and a detailed construction of the:.
associated impulse generator, respectively;
FIGURES 4 and 5 show preferred embodiments wherein the impulse generator is a circular element;
FIGURES 6 and 7 illustrate preferred embodiments wherein the impulse generator is affixed to the sealing lip; and 4 2 ~ 2 ~
FIGU~ES 8 to 10 are cross sections through cassette seals in accordance with theinvention for use with rotatable shafts.
FIGURES I to 7 relate to embodiments wherein an outer ring 1 of the seal rotatesand an inner ring 4 is stationary.
S FIGllRES 8 to 10 illustrate cassette seals for rotatable shafts wherein the outer ring is stationary and the inner ring rotates.
Figure la shows a cassette seal including outer and inner seal rings 1 and 4 of opposite angular profile which are rotatable in relation to each other. The rings mutually ::
overlap and together define an inner cavity 10. The outer ring I bears a sealing lip 3 which relatively movably rests against the inner ring 4. A sensor 6 is mounted to the : -inner ring 4 for detection of the relative rotation of the rings. The sensor 6 is af~lxed to the ring by way of a sensor mount 5 which also electrically connects the sensor 6 with a controller (not shown). An impulse generator 7 is mounted to the outer ring 1. The position of the sensor 6 and the impulse generator 7 within the seal is selected so that they :
are least partly positioned in the cavity 10 defined by the inner and outer rings 1, 4 and the sealing lip 3. The sensor 6 and the impulse generator 7 are thereby integrated into the cassette seal without the requirement for additional installation space for the seal.
Purthermore, a possible distortion by environmental influences of the measurements . .. ~.
obtained can be avoided. The impulse generator 7 and the sensor 6 can also be completely ~ :~
integrated into the cavity 10. -The impulse generator 7 partially shown in Figure lb is an integral part of the outer ring and has circumferentially evenly spaced cut-outs 7.1 which are respectively separated by a web 7.2. The webs 7.2 function as impulse generators and can be rnagnetized, whereby adjacent webs always have opposite poles as shown in Figure lb. In that case, the sensor is preferably a Hall-effect sensor. The sensor detects the impulses and transmits a corresponding signal to a control element. Axial tolerances and ;:
displacements of the sensor relative to the impulse generator caused, for example7 by heat ;
expansion, installation and/or during the intended use are automatically compensated with such a construction.
In Figure 2, the impulse generator 7 is a separate metal ring or a magnetizable plastic ring mounted to the outer ring 1. It is also possible to use an impulse generator 7 in the form of a spring element. The impulse generator Gan be adhered to the sealing lip 3 2~2~3 during vulcanization of that lip onto the inner ring 4. The sensor 6 and the impulse ~ ;
generator 7 are protected in all embodiments from all environmental influences such as dust, mud, and water and, consequently, from corrosion. As in the above described embodirnent, the irnpulse generator 7 and the sensor 6 are separated by an intermediate S gap 8 which provides for an optimal detection of the impulses and is separated -from ambient air by an annular gap 11. The size of the intermediate gap 8 is variable.
The cassette seal shown in Figure 3a is similar in construction to the one of Figure 2. The separate impulse generator 7 in the form of a metal ring illustrated in Figure 3b, : .
has circumferentially distributed radial grooves 7.3, 7.4, which are easily achievable with a ~ .
punching tool. The sensor 6 and the impulse generator 7 are preferably positioned at an angle of 45 to the axis of rotation of the outer ring 1. This provides the advantage that the size of the intermediate gap varies less upon axial displacement of the sensor 6 and the impulse generator 7 and the impulse detection remains optimal. :
A further preferred embodiment is shown in Figures 4 and 5. The sensor 6 is integrated into the inner ring 4 and radially detects the impulses. In this embodiment, the impulse generator 7 is a closed, circular element which is magneti~able and is connected to the outer ring 1. .
In the embodiments of Figures 6 and 7, the sensor 6 is integrated into the inner :: ~
ring 4 and the impulse generator 7 is connected to the sealing lip 3. This connection is .
achieved by vulcanizing the impulse generator directly onto the elastomeric sealing lip 3.
This is advantageous since the size of the intermediate gap 8 between the impulse generator 7 and the sensor 6 can then be exactly controlled. The impulse generator 7 can ~ :
be a spring element. The impulse generator 7 can also be shaped to conform to the shape of the sealing lip 3. : `
Figures 8 to 10 illustrate preferred embodiments of the cassette seal of the ~.
invention for use with rotating shafts. ~n those embodiments, the outer ring 1 is StationMy, whereas the inner ring 4 rotates with the shaft during the intended use. The sensor 6 is integrated into the inner ring 4, while the impulse generator 7 is provided on the outer ring 1. The impulse generator 7 can be achieved with cut-outs in the outer ring 1 or with a separate metal ring of a construction as shown in Figures 1 to 7. The annular gap 11 shown in Figure 8 which is located between the intermediate gap 8 and theambient air changes direction at least at one location giving it an L-shape~ cross-section.

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2~2~6~
This has the advantage that contaminated ambient air cannot unimpedely enter into the cavity lO and negatively affect the impulse detection. The distance between the bend of the annular gap 11 and the ambient air is at least five times the distance between the sensor 6 and the impulse generator 7. The annular gap 11 can have other shapes. For 5 example, the annular gap can be a labyrinth-type gap. The intermediate gap 8 is preferably delimited at least on one side, but most preferably on both sides, by a current free buffer space 9 (see Figure 2). This provides for an optimal impulse detection free of :-:
environmental iniluences, which results in a reduced number of measurement errors. The ratio of the volume of the total available buffer space 9 to the volume of the intermediate 10 gap 8 is preferably I to 50. This means that the positioning of the impulse detection elements 6 and 7 integrated into the cassette seal can be varied and that these elements can : ~
simultaneously be of different types without impeding the seal's function, namely the ` ~.
detection of impulses for subsequent analysis and processing. Furthermore, the detect;on can be carried out with less errors.
The cassette seal consisting of a seal, a sensor and an impulse generator can, depending on the respective embodiment, also be used for the detection and transmission of signals other than the speed of rotation, such as temperature, humidity or the pressure in the space to be sealed. The simple impulse generation and the reduced size achieved by - .
housing the elements 6 and 7 within the cassette seal make the seal an economical, robust . `
20 and easily manufactured article.

Claims

1. A cassette seal comprising a pair of seal rings of opposite, angular profile which seal rings overlap each other and together define an inner cavity in the seal, at least one sealing lip mounted to one of the seal rings which sealing lip relatively rotatably engages the other seal ring a sensor mounted to one of the seal rings and an impulse generator mounted to the other seal ring, the sensor and the impulse generator being at least partly positioned in the cavity.

2. A cassette seal as defined in claim 1, wherein the sensor and the impulse generator are completely positioned within the cavity.

3. A cassette seal as defined in claim 1, wherein the sensor and the impulse generator are spaced apart with an intermediate gap therebetween which intermediate gap is separated from ambient air by an adjacent annular gap located between opposing portions of the seal.

4. A cassette seal as defined in claim 3, wherein the annular gap between the intermediate gap and the ambient air is bent at an angle.

5. A cassette seal as defined in claim 4, wherein the distance of the bend in the annular gap from the ambient air is at least five times as large as the distance between the sensor and the impulse generator.

6. A cassette seal as defined in claim 3, 4 or 5, wherein the intermediate gap is at least on one side delimited by a current free buffer space.

7. A cassette seal as defined in claim 3, 4 or 5, wherein the intermediate gap is on both sides delimited by a current free buffer space.

8. A cassette seal as defined in claim 6, wherein the ratio of the volume of thetotal available buffer space to the volume of the intermediate gap is at least 1 to 50.

9. A cassette seal as defined in claim 7, wherein the ratio of the volume of thetotal available buffer space to the volume of the intermediate gap is at least 1 to 50.