CA1059044A - Automatic slack adjusters for vehicle brake linkages - Google Patents
Automatic slack adjusters for vehicle brake linkagesInfo
- Publication number
- CA1059044A CA1059044A CA282,502A CA282502A CA1059044A CA 1059044 A CA1059044 A CA 1059044A CA 282502 A CA282502 A CA 282502A CA 1059044 A CA1059044 A CA 1059044A
- Authority
- CA
- Canada
- Prior art keywords
- clutch
- worm
- pawl
- lever
- clutch means
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D65/00—Parts or details
- F16D65/38—Slack adjusters
- F16D65/40—Slack adjusters mechanical
- F16D65/52—Slack adjusters mechanical self-acting in one direction for adjusting excessive play
- F16D65/60—Slack adjusters mechanical self-acting in one direction for adjusting excessive play for angular adjustment of two concentric parts of the brake control systems
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Braking Arrangements (AREA)
Abstract
ABSTRACT
An automatic slack adjuster for a vehicle brake linkage comprising a housing constituting a lever in the linkage, and the lever is angularly movable about the axis of a shaft to impart to the shaft a brake-applying rotary movement which it transmits to it through a meshing worm and worm wheel assembly. Automatic worm driving means are incorporated for rotating the worm for adjustment of slack in the linkage in response to relative movement between the lever and a relatively stationary part, and the worm driving means incorporates a connec-tion having a degree of lost-motion equivalent to a desired braking clearance, and a spring-loaded two-part clutch disposed between the worm and a slidable pawl connected to the stationary part.
An automatic slack adjuster for a vehicle brake linkage comprising a housing constituting a lever in the linkage, and the lever is angularly movable about the axis of a shaft to impart to the shaft a brake-applying rotary movement which it transmits to it through a meshing worm and worm wheel assembly. Automatic worm driving means are incorporated for rotating the worm for adjustment of slack in the linkage in response to relative movement between the lever and a relatively stationary part, and the worm driving means incorporates a connec-tion having a degree of lost-motion equivalent to a desired braking clearance, and a spring-loaded two-part clutch disposed between the worm and a slidable pawl connected to the stationary part.
Description
~0S9044 This invention relates to an automatic slack adjuster for a vehicle brake linkage, the adjuster being of the kind comprising a housing which constitutes a lever in the linkage and is mounted for rocking movement about the axis of a shaft which is adapted to be partially rotated about an axis for applying or releasing a brake, and force is adapted to be transmitted between the housing and the shaft by means of a worm mounted in the housing and meshing with a worm wheel mounted on and secured against rotation relative to the shaft, the arrangement being such that adjustment of slack in the linkage is effected by rotation of the worm to alter the angular position of the worm wheel with respect to the housing, automatic worm driving means being incorporated for rotating the worm for adjustment of the slack in the linkage in response to relative . movement between the lever and a relatively stationary part.
In some known automatic slack adjusters of the kind set forth the worm drive means includes a one-way clutch and the worm is displaced axially against an energy-storing return spring to disengage the clutch when relative movement between the lever and the stationary part has exceeded a predetermined value and, on release of the brake, the clutch is re-engaged by the release of energy in the spring which is operative to rotate the worm.as the worm is returned axially to its initial po si tlon .
According to the present invention there is provided an automatic slack adjuster for a vehicle brake applying linkage of the type comprising a shaft mounted for rotation about its longitudinal axis for applying or releasing the brake, and a housing which constitutes a lever in the linkage and is mounted for rocking movement about the axis of the shaft and with respect to a relatively stationary part, wherein the adjuster comprises a worm wheel mounted on and secured against rotation relative ywl/~JI~ - 2 - ~
to the shaft, a worm mounted in the housin~ and meshing with the worm wheel to transmit angular movement of the lever to the shaft, and automatic worm driving means for rotating the worm with respect to the housing to compensate for slack in the linkage.in response to relative movement between the lever and the relatively stationary part, the automatic worm driving means incorporating a connection having a degree of lost-motion .equivalent to a desired braking clearance, the connection including a clutch comprising first clutch means coupled to the worm, second clutch means, and resilient means for urglng the second clutch means normally into driving engagement with the first clutch means, and a linearly slidable pawl acting between the second clutch means and the stationary part to effect rotation of the second clutch means whenever relative movement between the lever and the stationary part has exceeded a value equivalent to the degree of lost-motion.
~otation of the second clutch means is transmitted ~: through the first clutch means to cause corresponding rotation of the worm and the worm wheel until the frictional force of.an engagement between the braking surfaces exceeds the force of engagement between the clutch means whereafter the clutch slips to prevent further rotation of the worm with respect to the housing.
Rotation of the worm to compensate for wear of the braking surfaces occurs during brake applying movements, while the braking clearance is being taken up. Thus,such adjustment is independent of thermal or other deflections which may occur in any part of the brake or brake applying mechanism incorporating the slack adjuster.
The connection having lost-motion may be located between the pawl and the second clutch means so ~hat rotation of the second clutch means occurs only upon direct engagement l ywl/Jc~ ~ ~ 3 -of the pawl with the second clutch means, and a one-way drive is disposed between the first clutch means and a spindle with which the worm is fast, a return spring provided for urging the pawl into an inoperative position deflecting to store energy therein as the pawl is moved linearly on each angular movement of the lever, release of the stored energy in a brake application after the lost-motion has been taken up and which is operative to return the pawl to the inoperative position also being operative to effect rotation of both clutch means with respect to the spindle and through the one-way drive, thereby re-establishing the desired degree of lost-motion.
The second clutch means may be provided wi~h at least one tooth which is received in a notch in the pawl and the notch is of greater length than the circumferential length . of the tooth to define the lost-motion.
ywl~" - 3a -i" , lOS9044 The clutch may be of the cone type comprising single first and second interengaging clutch members.
Preferably, however, the clutch comprises a clutch of the multi-plate type with the first clutch means comprising a plurality of primary clutch plates interposed alternatively between a plurality of secondary clutch plates which define the second clutch means, each secondary clutch plate being provided with a tooth and all the teeth being received in the notch in the pawl.
This has the advantage of providing a clutch capable of transmitting a relatively high torque of which the efficiency is less likely to be reduced due to wear of the lining of the clutch plates than is a clutch of the cone type where the clutch means each comprises a single member.
Conveniently a sleeve surrounds and is coupled to a spindle fast with the worm and the clutch plates surround a portion of the sleeve which is of reduced diameter, being clamped into engagement and against a step at the change in diameter by the resilient means which act between the plates and an abutment at the outer end of the spindle remote from the worm, the primary clutch plates are keyed to the sleeve and the secondary clutch plates are freely rotatable in and located by a bore in the housing and by the pawl.
Incorporating the clutch in the sleeve provides a self-contained assembly which can simply be withdrawn for replacement and/or maintenance without affecting the spindle.
Conveniently the pawl is positively urged linearly by means of an engagement with an adjusting shaft which is eccentrically mounted with respect to the axis of rotation of the lever and is angularly movable through an arc of a circle centred on the stationary part with respect to which the lever lS angularly movable.
The adjusting shaft itself rotates within the lever in response to movement of the lever and an arm of the adjusting shaft which locates in a stationary bracket.
.4.
-` ~059044 Two embodiments of our invention are illustrated inthe accompanying drawings in which:-Figure 1 is a side elevation of anautomatic slack ad~uster for a vehicle brake linkage with a side coverplate xemoved;
Figure 2 is a section on the line 2-2 of Figure l;
Fi~ure _ is a section on the line 3-3 of Figure l;
Figure 4 is a section on the line 4-4 of Figure l;
Figure 5 is a section on the line 5-5 of Figure l;
Figure 6 is a section on the line 6-6 of Figure l;
Figure 7 is a modified spring loading for the clutch;
Figure 8 is a side elevation of an automatic slack adjuster for a vehicle brake linkage with a side cover plate removed and including a section substantially on the line 8-8 of Figure 9;
Figure 9 i5 a section on the line 9-9 of Figure 8;
Figure 10 is a section on the line 10-10 of Figure 8;
Figure 11 is a view of one end of the adjuster;and .5.
lOS9044 Figure 12 is a side elevation of the opposite end of the adjuster.
The automatic slack adjuster illustrated in Figures 1 to 7 of the accompanying drawings comprises a housing 1 constituted by a lever of a brake linkage which is adapted to be mounted for rocking movement with respect to the axis of a splined brake-applying shaft (not shown) and which has a free upper end for connection to a brake actuatox through any one of three spaced eyes. The lever 1 acts on the shaft through a worm wheel 2 which is splined at 3 to the shaft and which is journalled for rotation in the housing 1 between spaced end closure plates 4 and 5 clamped against opposite sides of the housing.
The shat is conveniently provided with at least one cam expander for applying friction members, for example shoes, to a rotatable braking member, for example a drum.
A worm 6 engaging with the worm wheel 2 is fast with a spindle 7 which is journalled for rotation in a hore 8 in the housing 1. The bore 8 is tangential to the axis of the brake-applying shaft and is enlarged at an intermediate point in its length to define spaced walls 9 and 10 between which opposite ends of the worm 6 are located in close pro~imity therewith.
One end of the bore 8 is counterbored at 12 into which an end portion 14 of the spindle 7 projects. The free end of that end portion 14 which projects from a closure cap 15 for the counterbore is of square or other non-circular outline to receive a key by means of which the spindle and worm can be rotated.
The housing incorporates automatic worm driving means 16 to rotate the worm 6 and the worm wheel 2 in order to compensate for wear of the linings of the friction members and thereby maintain a predetermined desired braking clearance between the friction members and the braking member. As illustrated the worm driving means comprises an adjuster shaft 17 journalled in the 1~)59044 housing 1 or rotation in a bore 18 parallel to the axis of the worm wheel 2 but spaced radially therefrom in a direction away from the spindle 7. The adjuster shaft 17 is coupled to a member or bracket 19 which is stationary relative to the axis of the brake applying shaft by means of diametrical pin 20 and the pin 20 has an end portion 21 cranked to lie parallel to the axis of the spindle 7 and received in a notch in the bracket 19. As the lever 1 is moved angularly about the axis of the brake-applying shaft, the adjuster shaft 17 also rotates as it is moved with the lever 1. The adjuster shaft 17 is connected to the spindle 7 through a pawl 23 and a clutch assembly 24 located in the counterbore 12 and in a second counterbore 25 at that end of the housing 1.
The pawl 23 comprises a parallel sided elongate strip 26 which is guided for movement in a straight line between the sides of a parallel sided slot 27 which is tangential to the brake-applying shaft and normal to the spindle 7. The pawl 23 is cut back along one edge to define an abutment for one end of a compression return spring 28 which urges the pawl at all times into engagement with a cam formation 29 on the adjuster shaft 17.
The clutch assembly 24 is of the multi-plate type comprising alternately arranged inner and outer relatively rot-àtableprimary and secondary clutch plates 30 and 31 which surr-ound areduced diameter portion 32 of a sleeve 33, in turn surrounding the spindle 14. The sleeve 33 is coupled to the spindle 14 through a one-way drive 34 and the plates 30 and 31 are clamped together and against a shoulder 35 at a step in the change in diameter by means of a compression spring 36. The spring 36 abuts against an abutment washer 37 of U shaped outline of which the limbs are received in diametrically opposed slots 38 in the sleeve 14.
The inner primary plates 30 are keyed to the sleeve 33, and the outer secondary plates 31 are freely rotatable within, and located by, the second counterbore 39 of which the outer end is lOS9044 closed by the closure cap 15, Each outer plate 31 is provided with a pair of angularly spaced axial slots 40 and 41 between which a tooth 42 is defined, and all the teeth 42 are received in a notch 43 at the inner end of the pawl 26. In a normal inoperative pos-ition the teeth 42 are in engagement with a face 44 at the outer end of the notch 43 and the teeth 42 are spaced from a face 45 at the inner end of the notch 43 by a distance corresponding to a predetermined clearance between the friction members and the braking member.
The clutch assembly 24 serves two purposes. The first is to protect the one-way drive 34 by limiting the torque that the drive is required to transmit. This limiting torque is determined by the force exerted by the spring 36. The second purpose is to stop adjustment taking place after-the braking clearances have been taken up. The torque that can be transmitted by the clutch assembly 24 is limited as described above, hence the one-way drive 34 can only rotate the spindle 7 against a limiting reaction torque. Beyond such torque the clutch assembly will slip, with the outer plates 31 rotating relative to inner plates 30 which remain rotationally stationary Lelative to the housing 1. The aforementioned limited reaction torque is derived from the reaction torque in the brake applying shaft and the worm wheel 2 and through the engagement forces between the worm wheel 2 and the worm 6.
In operation, angular movement of the housing 1 in a clockwise brake-applying direction with reference to Figure 1, rotates the brake-applying shaft through the worm 6 and the worm wheel 2, characteristically a one-way drive, until the braking clearances have been taken up. During this movement the adjuster shaft 17 is also rotated to cause the pawl 26 to slide linearly in the slot 27 against the force in the spring 28 with the face 44 moving away from the teeth 42 and the face 45 moving towards them to reduce the lost-motion clearance therebetween.
Normally the face 45 will not contact the teeth 42 unless ad~ustment is required to compensate for wear of the frictio~ members.
105~044 When the angular movement of the lever 1 is trans~
mitted through the worm 6 and worm-wheel 2 to the brake applying shaft to apply the brake and further rotate the adjuster shaft 17, the face 45 of the pawl 23 rotates the outer clutch plates 31 through the teeth 42. Once the aforementioned braking clearances have been taken up the engagement forces between the worm 6 and the worm wheel 2 are of such a magnitude that the aforementioned limiting clutch torque is insufficient to rotate the worm 6. The clutch assembly 24 then slips as described above and no adjustment takes place.
When wear of the friction members has occurred, during the initial angular movement to take up the ~raking clearances once the lost-motion has been taken up, the outer clutch plates 31 are rotated by the pawl 26 and the inner clutch plates 30 rotate with them due to the engagement of adjacent faces of the plates. The inner clutch plates 30 rotate the spindle 7 and hence the worm 6 through the one-way drive 34. The worm rotates the worm wheel 2 relative to the housing 1 and adjustment is achieved. When all the braking clearances have been taken up the clutch assembly 24 slips as described above without impeding movement of the pawl 23 or the adjuster shaft 17.
When the brake is released the stored energy in the spring 28 maintains the pawl 26 in engagement with the adjuster shaft 17 so that the outer clutch plates 31 are returned to their initial positions by the face 44 engag-ing with the tooth 42, Due to the provision of the one-way drive 34 the inner clutch plates 30 also rotate with the outer clutch plates 31, but with respect to the spindle 7.
Annular sealing rings 46 are located between the cover plates 4 and 5 and the wo~m wheel 2, an gaskets 47 are located between the housing 1 and the plates 4 and 5.
Thus the unit is sealed completely against the ingress of dirt and other foreign matter.
.9.
lOS9044 In the modi~lcation of Figure 7 the compression spring 36 is replaced by a series of Belleville or like spring washers 48.
In the automatic slack adjuster illustrated in Figures 8 to 12, the clutch assembly 24 is of the cone type compris-ing inner and outer rotatable clutch members 50 and 51 of which the inner member 50 is rotatable in a friction ring 52 in the ~unterbore 12 and is coupled to the sprindle 7 through the one-way drive 34. The friction ring 52 serves to prevent inadvertant rotation of the clutch assembly. The inner member 50 is of cup-shaped outline and is also rotatably mounted on a reduced diameter portion 52 at that end of the spindle 7. The member 50 has an inclined external clutch face 55 which is urged by means of a spring washer 56 into engagement with a complementary internal clutch face 57 on the outer clutch member 51 which, in turn, is rotatable in the counterbore 25. The outer clutch member 51 is provided in its outer end with a pair of angularly spaced axial slots 58 and 59 between which is defined a tooth 60, and the tooth 60 is received in the notch 43 at the inner end of the pawl 26.
The clutch assembly operates in the same manner as the clutch assembly of the preceding embodiment with the tooth 60 functioning in the same way as the teeth 42.
The closure cap 15 is omitted and the counterbore 25 is closed by a removable resilient sealing disc 61.
The opposite end of the spindle 7 projects into a counterbore 62 at that end of the bore and is provided with an end portion 63 of square or other non-circular outline to receive a key by means of which the spindle 7 and the worm 6 can be rotated, after removal of a closure cap 64 normal]y closing the counterbore 62.
The construction and operation of the adjuster of Figures 8 to 12 is otherwise the same as that of Figures 1 to 7 and corresponding reference numerals have been applied to corresponding parts.
.10.
In some known automatic slack adjusters of the kind set forth the worm drive means includes a one-way clutch and the worm is displaced axially against an energy-storing return spring to disengage the clutch when relative movement between the lever and the stationary part has exceeded a predetermined value and, on release of the brake, the clutch is re-engaged by the release of energy in the spring which is operative to rotate the worm.as the worm is returned axially to its initial po si tlon .
According to the present invention there is provided an automatic slack adjuster for a vehicle brake applying linkage of the type comprising a shaft mounted for rotation about its longitudinal axis for applying or releasing the brake, and a housing which constitutes a lever in the linkage and is mounted for rocking movement about the axis of the shaft and with respect to a relatively stationary part, wherein the adjuster comprises a worm wheel mounted on and secured against rotation relative ywl/~JI~ - 2 - ~
to the shaft, a worm mounted in the housin~ and meshing with the worm wheel to transmit angular movement of the lever to the shaft, and automatic worm driving means for rotating the worm with respect to the housing to compensate for slack in the linkage.in response to relative movement between the lever and the relatively stationary part, the automatic worm driving means incorporating a connection having a degree of lost-motion .equivalent to a desired braking clearance, the connection including a clutch comprising first clutch means coupled to the worm, second clutch means, and resilient means for urglng the second clutch means normally into driving engagement with the first clutch means, and a linearly slidable pawl acting between the second clutch means and the stationary part to effect rotation of the second clutch means whenever relative movement between the lever and the stationary part has exceeded a value equivalent to the degree of lost-motion.
~otation of the second clutch means is transmitted ~: through the first clutch means to cause corresponding rotation of the worm and the worm wheel until the frictional force of.an engagement between the braking surfaces exceeds the force of engagement between the clutch means whereafter the clutch slips to prevent further rotation of the worm with respect to the housing.
Rotation of the worm to compensate for wear of the braking surfaces occurs during brake applying movements, while the braking clearance is being taken up. Thus,such adjustment is independent of thermal or other deflections which may occur in any part of the brake or brake applying mechanism incorporating the slack adjuster.
The connection having lost-motion may be located between the pawl and the second clutch means so ~hat rotation of the second clutch means occurs only upon direct engagement l ywl/Jc~ ~ ~ 3 -of the pawl with the second clutch means, and a one-way drive is disposed between the first clutch means and a spindle with which the worm is fast, a return spring provided for urging the pawl into an inoperative position deflecting to store energy therein as the pawl is moved linearly on each angular movement of the lever, release of the stored energy in a brake application after the lost-motion has been taken up and which is operative to return the pawl to the inoperative position also being operative to effect rotation of both clutch means with respect to the spindle and through the one-way drive, thereby re-establishing the desired degree of lost-motion.
The second clutch means may be provided wi~h at least one tooth which is received in a notch in the pawl and the notch is of greater length than the circumferential length . of the tooth to define the lost-motion.
ywl~" - 3a -i" , lOS9044 The clutch may be of the cone type comprising single first and second interengaging clutch members.
Preferably, however, the clutch comprises a clutch of the multi-plate type with the first clutch means comprising a plurality of primary clutch plates interposed alternatively between a plurality of secondary clutch plates which define the second clutch means, each secondary clutch plate being provided with a tooth and all the teeth being received in the notch in the pawl.
This has the advantage of providing a clutch capable of transmitting a relatively high torque of which the efficiency is less likely to be reduced due to wear of the lining of the clutch plates than is a clutch of the cone type where the clutch means each comprises a single member.
Conveniently a sleeve surrounds and is coupled to a spindle fast with the worm and the clutch plates surround a portion of the sleeve which is of reduced diameter, being clamped into engagement and against a step at the change in diameter by the resilient means which act between the plates and an abutment at the outer end of the spindle remote from the worm, the primary clutch plates are keyed to the sleeve and the secondary clutch plates are freely rotatable in and located by a bore in the housing and by the pawl.
Incorporating the clutch in the sleeve provides a self-contained assembly which can simply be withdrawn for replacement and/or maintenance without affecting the spindle.
Conveniently the pawl is positively urged linearly by means of an engagement with an adjusting shaft which is eccentrically mounted with respect to the axis of rotation of the lever and is angularly movable through an arc of a circle centred on the stationary part with respect to which the lever lS angularly movable.
The adjusting shaft itself rotates within the lever in response to movement of the lever and an arm of the adjusting shaft which locates in a stationary bracket.
.4.
-` ~059044 Two embodiments of our invention are illustrated inthe accompanying drawings in which:-Figure 1 is a side elevation of anautomatic slack ad~uster for a vehicle brake linkage with a side coverplate xemoved;
Figure 2 is a section on the line 2-2 of Figure l;
Fi~ure _ is a section on the line 3-3 of Figure l;
Figure 4 is a section on the line 4-4 of Figure l;
Figure 5 is a section on the line 5-5 of Figure l;
Figure 6 is a section on the line 6-6 of Figure l;
Figure 7 is a modified spring loading for the clutch;
Figure 8 is a side elevation of an automatic slack adjuster for a vehicle brake linkage with a side cover plate removed and including a section substantially on the line 8-8 of Figure 9;
Figure 9 i5 a section on the line 9-9 of Figure 8;
Figure 10 is a section on the line 10-10 of Figure 8;
Figure 11 is a view of one end of the adjuster;and .5.
lOS9044 Figure 12 is a side elevation of the opposite end of the adjuster.
The automatic slack adjuster illustrated in Figures 1 to 7 of the accompanying drawings comprises a housing 1 constituted by a lever of a brake linkage which is adapted to be mounted for rocking movement with respect to the axis of a splined brake-applying shaft (not shown) and which has a free upper end for connection to a brake actuatox through any one of three spaced eyes. The lever 1 acts on the shaft through a worm wheel 2 which is splined at 3 to the shaft and which is journalled for rotation in the housing 1 between spaced end closure plates 4 and 5 clamped against opposite sides of the housing.
The shat is conveniently provided with at least one cam expander for applying friction members, for example shoes, to a rotatable braking member, for example a drum.
A worm 6 engaging with the worm wheel 2 is fast with a spindle 7 which is journalled for rotation in a hore 8 in the housing 1. The bore 8 is tangential to the axis of the brake-applying shaft and is enlarged at an intermediate point in its length to define spaced walls 9 and 10 between which opposite ends of the worm 6 are located in close pro~imity therewith.
One end of the bore 8 is counterbored at 12 into which an end portion 14 of the spindle 7 projects. The free end of that end portion 14 which projects from a closure cap 15 for the counterbore is of square or other non-circular outline to receive a key by means of which the spindle and worm can be rotated.
The housing incorporates automatic worm driving means 16 to rotate the worm 6 and the worm wheel 2 in order to compensate for wear of the linings of the friction members and thereby maintain a predetermined desired braking clearance between the friction members and the braking member. As illustrated the worm driving means comprises an adjuster shaft 17 journalled in the 1~)59044 housing 1 or rotation in a bore 18 parallel to the axis of the worm wheel 2 but spaced radially therefrom in a direction away from the spindle 7. The adjuster shaft 17 is coupled to a member or bracket 19 which is stationary relative to the axis of the brake applying shaft by means of diametrical pin 20 and the pin 20 has an end portion 21 cranked to lie parallel to the axis of the spindle 7 and received in a notch in the bracket 19. As the lever 1 is moved angularly about the axis of the brake-applying shaft, the adjuster shaft 17 also rotates as it is moved with the lever 1. The adjuster shaft 17 is connected to the spindle 7 through a pawl 23 and a clutch assembly 24 located in the counterbore 12 and in a second counterbore 25 at that end of the housing 1.
The pawl 23 comprises a parallel sided elongate strip 26 which is guided for movement in a straight line between the sides of a parallel sided slot 27 which is tangential to the brake-applying shaft and normal to the spindle 7. The pawl 23 is cut back along one edge to define an abutment for one end of a compression return spring 28 which urges the pawl at all times into engagement with a cam formation 29 on the adjuster shaft 17.
The clutch assembly 24 is of the multi-plate type comprising alternately arranged inner and outer relatively rot-àtableprimary and secondary clutch plates 30 and 31 which surr-ound areduced diameter portion 32 of a sleeve 33, in turn surrounding the spindle 14. The sleeve 33 is coupled to the spindle 14 through a one-way drive 34 and the plates 30 and 31 are clamped together and against a shoulder 35 at a step in the change in diameter by means of a compression spring 36. The spring 36 abuts against an abutment washer 37 of U shaped outline of which the limbs are received in diametrically opposed slots 38 in the sleeve 14.
The inner primary plates 30 are keyed to the sleeve 33, and the outer secondary plates 31 are freely rotatable within, and located by, the second counterbore 39 of which the outer end is lOS9044 closed by the closure cap 15, Each outer plate 31 is provided with a pair of angularly spaced axial slots 40 and 41 between which a tooth 42 is defined, and all the teeth 42 are received in a notch 43 at the inner end of the pawl 26. In a normal inoperative pos-ition the teeth 42 are in engagement with a face 44 at the outer end of the notch 43 and the teeth 42 are spaced from a face 45 at the inner end of the notch 43 by a distance corresponding to a predetermined clearance between the friction members and the braking member.
The clutch assembly 24 serves two purposes. The first is to protect the one-way drive 34 by limiting the torque that the drive is required to transmit. This limiting torque is determined by the force exerted by the spring 36. The second purpose is to stop adjustment taking place after-the braking clearances have been taken up. The torque that can be transmitted by the clutch assembly 24 is limited as described above, hence the one-way drive 34 can only rotate the spindle 7 against a limiting reaction torque. Beyond such torque the clutch assembly will slip, with the outer plates 31 rotating relative to inner plates 30 which remain rotationally stationary Lelative to the housing 1. The aforementioned limited reaction torque is derived from the reaction torque in the brake applying shaft and the worm wheel 2 and through the engagement forces between the worm wheel 2 and the worm 6.
In operation, angular movement of the housing 1 in a clockwise brake-applying direction with reference to Figure 1, rotates the brake-applying shaft through the worm 6 and the worm wheel 2, characteristically a one-way drive, until the braking clearances have been taken up. During this movement the adjuster shaft 17 is also rotated to cause the pawl 26 to slide linearly in the slot 27 against the force in the spring 28 with the face 44 moving away from the teeth 42 and the face 45 moving towards them to reduce the lost-motion clearance therebetween.
Normally the face 45 will not contact the teeth 42 unless ad~ustment is required to compensate for wear of the frictio~ members.
105~044 When the angular movement of the lever 1 is trans~
mitted through the worm 6 and worm-wheel 2 to the brake applying shaft to apply the brake and further rotate the adjuster shaft 17, the face 45 of the pawl 23 rotates the outer clutch plates 31 through the teeth 42. Once the aforementioned braking clearances have been taken up the engagement forces between the worm 6 and the worm wheel 2 are of such a magnitude that the aforementioned limiting clutch torque is insufficient to rotate the worm 6. The clutch assembly 24 then slips as described above and no adjustment takes place.
When wear of the friction members has occurred, during the initial angular movement to take up the ~raking clearances once the lost-motion has been taken up, the outer clutch plates 31 are rotated by the pawl 26 and the inner clutch plates 30 rotate with them due to the engagement of adjacent faces of the plates. The inner clutch plates 30 rotate the spindle 7 and hence the worm 6 through the one-way drive 34. The worm rotates the worm wheel 2 relative to the housing 1 and adjustment is achieved. When all the braking clearances have been taken up the clutch assembly 24 slips as described above without impeding movement of the pawl 23 or the adjuster shaft 17.
When the brake is released the stored energy in the spring 28 maintains the pawl 26 in engagement with the adjuster shaft 17 so that the outer clutch plates 31 are returned to their initial positions by the face 44 engag-ing with the tooth 42, Due to the provision of the one-way drive 34 the inner clutch plates 30 also rotate with the outer clutch plates 31, but with respect to the spindle 7.
Annular sealing rings 46 are located between the cover plates 4 and 5 and the wo~m wheel 2, an gaskets 47 are located between the housing 1 and the plates 4 and 5.
Thus the unit is sealed completely against the ingress of dirt and other foreign matter.
.9.
lOS9044 In the modi~lcation of Figure 7 the compression spring 36 is replaced by a series of Belleville or like spring washers 48.
In the automatic slack adjuster illustrated in Figures 8 to 12, the clutch assembly 24 is of the cone type compris-ing inner and outer rotatable clutch members 50 and 51 of which the inner member 50 is rotatable in a friction ring 52 in the ~unterbore 12 and is coupled to the sprindle 7 through the one-way drive 34. The friction ring 52 serves to prevent inadvertant rotation of the clutch assembly. The inner member 50 is of cup-shaped outline and is also rotatably mounted on a reduced diameter portion 52 at that end of the spindle 7. The member 50 has an inclined external clutch face 55 which is urged by means of a spring washer 56 into engagement with a complementary internal clutch face 57 on the outer clutch member 51 which, in turn, is rotatable in the counterbore 25. The outer clutch member 51 is provided in its outer end with a pair of angularly spaced axial slots 58 and 59 between which is defined a tooth 60, and the tooth 60 is received in the notch 43 at the inner end of the pawl 26.
The clutch assembly operates in the same manner as the clutch assembly of the preceding embodiment with the tooth 60 functioning in the same way as the teeth 42.
The closure cap 15 is omitted and the counterbore 25 is closed by a removable resilient sealing disc 61.
The opposite end of the spindle 7 projects into a counterbore 62 at that end of the bore and is provided with an end portion 63 of square or other non-circular outline to receive a key by means of which the spindle 7 and the worm 6 can be rotated, after removal of a closure cap 64 normal]y closing the counterbore 62.
The construction and operation of the adjuster of Figures 8 to 12 is otherwise the same as that of Figures 1 to 7 and corresponding reference numerals have been applied to corresponding parts.
.10.
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An automatic slack adjuster for a vehicle brake applying linkage of the type comprising a shaft mounted for rotation about its longitudinal axis for applying or releasing the brake, and a housing which constitutes a lever in the linkage and is mounted for rocking movement about said axis of said shaft and with respect to a relatively stationary part, wherein said adjuster comprises a worm wheel mounted on and secured against rotation relative to said shaft, a worm mounted in said housing and meshing with said worm wheel to transmit angular movement of said lever to said shaft, and automatic worm driving means for rotating said worm with respect to said housing to compensate fox slack in said linkage in response to relative movement between said lever and said relatively stationary part, said automatic worm driving means incorporating a connection having a degree of lost-motion equivalent to a desired braking clearance, said connection including a clutch comprising first clutch means coupled to said worm, second clutch means,and resil-ient means for urging said second clutch means normally into driving engagement with said first clutch means, and a linearly slidable pawl acting between said second clutch means and said stationary part to effect rotation of said second clutch means whenever relative movement between said lever and said stationary part has exceeded a value equivalent to said degree of lost-motion.
2. An automatic slack adjuster as claimed in Claim 1, wherein a spindle is provided with which said worm is fast, said connection having said degree of lost-motion is located between said pawl and said second clutch means so that rotation of said second clutch means occurs only upon direct engagement of said pawl with said second clutch means, and a one-way drive is disposed between said first clutch means and said spindle, a return spring provided for urging said pawl into an inoperative position deflecting to store energy therein as said pawl is moved linearly on each angular movement of said lever, release of said stored energy in a brake application after said lost-motion has been taken up and which is operative to return .11.
said pawl to said inoperative position also being operative to effect rotation of both clutch means with respect to said spindle and through said one-way drive to re-establish a desired degree of lost-motion.
said pawl to said inoperative position also being operative to effect rotation of both clutch means with respect to said spindle and through said one-way drive to re-establish a desired degree of lost-motion.
3. An automatic slack adjuster as claimed in claim 2, wherein said first clutch means is provided with at least one tooth and said pawl is provided with a notch in which said tooth is received, said notch being of greater length than the circumferential length of said tooth to define said lost-motion.
4. An automatic slack adjuster claimed in any of claims 1 to 3, wherein said clutch is of the cone type comprising a single first and a second interengaging clutch members.
5. An automatic slack adjuster as claimed in claim 1 wherein said clutch comprises a clutch of the multi-plate type with said first clutch means comprising a plurality of primary clutch plates interposed alternately between a plurality of secondary clutch plates which define said second clutch means, each secondary clutch plate being provided with a tooth, and all said teeth being received in said notch in said pawl.
6. An automatic slack adjuster as claimed in claim 2 wherein said clutch comprises a clutch of the multi-plate type with said first clutch means comprising a plurality of primary clutch plates interposed alternately between a plurality of secondary clutch plates which define said second clutch means, each secondary clutch plate being provided with a tooth, and all said teeth being received in said notch in said pawl.
7. An automatic slack adjuster as claimed in claim 5 or claim 6 wherein a sleeve surrounds and is fast with a spindle keyed to said worm, said housing has a bore, said sleeve has a portion of reduced diameter, a shoulder is defined at a step at the change in diameter, and an abutment is located at the outer end of said spindle remote from said worm said clutch plates surrounding said portion of said sleeve which is of reduced diameter and being clamped into engagement against said shoulder by said resilient means which act between said plates and said abutment, said primary clutch plates being keyed to said sleeve, and said secondary clutch plates being freely rotatable in, and located by, said bore in said housing and by said pawl.
8. An automatic slack adjuster as claimed in claim 1 or claim 3, wherein an adjusting shaft is eccentrically mounted with respect to said axis of rotation of said lever and is angularly movable through an arc of a circle centred on said stationary part with respect to which said lever is angularly movable, said pawl being positively urged linearly by means of an engagement with said adjusting shaft.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB29040/76A GB1540237A (en) | 1976-07-13 | 1976-07-13 | Automatic slack adjusters for vehicle brake linkages |
| GB1993277 | 1977-05-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1059044A true CA1059044A (en) | 1979-07-24 |
Family
ID=26254326
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA282,502A Expired CA1059044A (en) | 1976-07-13 | 1977-07-11 | Automatic slack adjusters for vehicle brake linkages |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS5314267A (en) |
| BR (1) | BR7704569A (en) |
| CA (1) | CA1059044A (en) |
| DE (1) | DE2731725A1 (en) |
| FR (1) | FR2358589A1 (en) |
| HU (1) | HU174742B (en) |
| IT (1) | IT1076100B (en) |
| NL (1) | NL7707664A (en) |
| SE (1) | SE414331B (en) |
| SU (1) | SU837315A3 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5669149A (en) * | 1979-11-09 | 1981-06-10 | Daiken Trade & Ind Co Ltd | Manufacturing method of molding material by microwaves irradiation |
| SE420014B (en) * | 1979-12-13 | 1981-09-07 | Sab Automotive Ab | BRAKE HEAT FOR A TRUMBROMS |
| EP0090827A4 (en) * | 1981-10-13 | 1984-11-09 | Cockajemmy Pty Ltd | Apparatus and method for magnetic separation. |
| US4452343A (en) * | 1981-11-24 | 1984-06-05 | Westinghouse Brake And Signal Company Ltd. | Road brake slack adjuster |
| FR2548310B1 (en) * | 1983-06-30 | 1985-12-13 | Valeo | COUPLING APPARATUS SUCH AS A BRAKE OR THE LIKE WITH A WEAR CATCHER |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1532857A (en) * | 1966-08-03 | 1968-07-12 | Westinghouse Bremsen Apparate | Device for automatic readjustment of the camshaft lever of a brake |
| GB1189319A (en) * | 1967-10-31 | 1970-04-22 | Westinghouse Brake & Signal | Automatic Slack Adjusters |
| HU163657B (en) * | 1970-12-28 | 1973-10-27 | ||
| DE2210658A1 (en) * | 1971-03-08 | 1972-09-21 | ||
| DE2346418A1 (en) * | 1973-09-14 | 1975-03-27 | Maschf Augsburg Nuernberg Ag | Automatic drum expansion brake adjuster - has nut and screw adjuster to prevent lock-up after successive heavy braking |
-
1977
- 1977-07-08 NL NL7707664A patent/NL7707664A/en not_active Application Discontinuation
- 1977-07-11 CA CA282,502A patent/CA1059044A/en not_active Expired
- 1977-07-12 HU HU77GI257A patent/HU174742B/en unknown
- 1977-07-12 SE SE7708108A patent/SE414331B/en unknown
- 1977-07-12 FR FR7721468A patent/FR2358589A1/en active Granted
- 1977-07-12 BR BR7704569A patent/BR7704569A/en unknown
- 1977-07-12 SU SU772502197A patent/SU837315A3/en active
- 1977-07-12 JP JP8337677A patent/JPS5314267A/en active Pending
- 1977-07-13 IT IT25665/77A patent/IT1076100B/en active
- 1977-07-13 DE DE19772731725 patent/DE2731725A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| FR2358589B1 (en) | 1983-02-18 |
| DE2731725A1 (en) | 1978-01-19 |
| HU174742B (en) | 1980-03-28 |
| IT1076100B (en) | 1985-04-22 |
| SU837315A3 (en) | 1981-06-07 |
| NL7707664A (en) | 1978-01-17 |
| SE7708108L (en) | 1978-01-14 |
| SE414331B (en) | 1980-07-21 |
| JPS5314267A (en) | 1978-02-08 |
| FR2358589A1 (en) | 1978-02-10 |
| BR7704569A (en) | 1978-05-02 |
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