GB1585789A - Disc assemblies for vehicle disc brakes - Google Patents

Description

(54) IMPROVEMENTS IN DISC ASSEMBLIES FOR VEHICLE DISC BRAKES (71) We, GIRLING LIMITED, a British Company of Kings Road, Tyseley, Birmingham, 11, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to disc assemblies for vehicle disc brakes of the kind in which a respective brake ring is secured to both of a pair of opposite faces of a rotor, such as a supporting wheel of a rail vehicle, by bolts or other fasteners which are passed through clearance openings in the rotor and are stressed substantially only in tension, thermal expansion being accommodated by movement of the ring or rings and the bolts or other fasteners relative to the rotor.

In disc assemblies of the kind set forth the rings, whether continuous or comprising two or more segments, must also be keyed locally to the rotor to maintain the disc assembly in balance. Hitherto this has been achieved by dowel bolts of which the shanks are close fits in openings both in the rings and the rotor, or by sleeves which are close fits in the openings, and which comprise clearance bores through which the bolts extend. In both cases the heads of the bolts and the nuts are received in counterbores in the outer faces of the rings, in abutment with the steps in diameter. When thermal expansion and the centrifugal forces are considerable, for example when heated to the considerable temperatures experienced at the high rotational speeds of wheels of high speed trains, the rings expand by amounts sufficient to cause the portions of the dowel bolts or the sleeves which are received in the rings to be subjected to shear forces sufficient to cause the dowel bolts or the sleeves to adopt a permanent stepped configuration known as "crank shafting".

This hinders ring replacement due to difficulty in removing deformed bolts or sleeves and misshaped openings have to be rereamed with larger diameter bolts or sleeves having to be fitted. In addition, when sleeves are fitted and the length of a sleeve is less than the length of the shank of a bolt between the head and a nut, movement of the sleeve on the shank from a central position will reduce the bearing area for one of the rings to a value which may be unacceptable. Also the diameter to which the openings can be increased by re-reaming is limited by the size to which counterbores at the outer ends of the rings can also be increased, whilst maintaining a desired pad to disc engagement in which no distortion of the pads on brake application occur.

According to our invention in a disc assembly of the kind set forth the rings are keyed locally to the rotor by a coupling assembly comprising a pair of spaced bushes which have enlarged heads at their outer ends, at least one of the bushes being a close fit in the opening in at least one of the rings and in an opening in the rotor, the heads being received in counterbores in the outer ends of the openings in the rings, and a bolt projecting through one of the bushes is screwed into the other bush to clamp the heads into engagement with shoulders at the steps in diameter between the openings in the rings and the counterbores.

By providing separate bushes, the diameter of the openings and the external diameter of the bushes can be increased as necessary provided the shoulders are maintained, and there is no necessity to increase the size of the bolt, which otherwise would mean a corresponding increase in the diameter of the bolt and the size of its head. This results in extremely low bearing stress, even with adverse tolerance conditions.

Both bushes may be close fits in the openings in the rings and in the opening in the rotor into opposite ends of which the inner ends of the bushes project in an axially spaced relationship.

By providing separate bushes which are clamped against the shoulders the bearing areas between the rotor and the rings can be arranged to be equal and can be maintained at these values simply by providing bushes of equal lengths and counterbores of equal depths, in rings of equal thickness.

It is preferred however that one of the bushes should be a close fit in the opening in both rings and in the opening in the rotor, and that a substantial clearance should be provided between the other bush and the opening in the ring in which it is located.

Conveniently the shank of the bolt projects through the longer bush and is screwed into the shorter bush.

The head of the bolt may be received within a recess in one of the bushes of which the recess is of countersunk or counterbored outline. This enables the head to be accommodated within a minimum axial depth thus making available for a bearing area, a correspondingly greater bush length.

In each construction a clearance may be provided between the shank of the bolt and the bush or bushes to facilitate bolt removal and to prevent the bolt from being subjected to transverse stresses due to "crank shafting" which otherwise might cause it to fail.

This has the advantage that bush withdrawal in opposite directions is facilitated, even though "crank shafting" has taken place.

Two embodiments of our invention are illustrated in the accompanying drawings in which: Figure I is a longitudinal section through a disc assembly showing our coupling assembly; and Figure 2 is a similar section through another disc assembly.

The disc assembly illustrated in Figure 1 of the drawings comprises a rotor 1 in the form of a supporting wheel for a rail vehicle, and a pair of brake rings 2, 3 which are sec ured to opposite sides of a central web 4 of the wheel.

Each ring 2, 3 may be continuous or it may be discontinuous and comprise two or more segments of which the ends of adjacent segments are spaced from each other.

When segments are provided, the segments on opposite sides of the rotor are superimposed upon each other.

Bolts (not shown) or other fasteners stressed substantially only in tension pass through superimposed openings in the web 4 with substantial clearances. The bolts pass through complementary openings in one of the rings being screwed into a tapped opening in the other ring, and the head of the bolt and the locking nut into which the bolt is screwed are received in counterbores at the outer ends of the openings.

At each of a number of convenient positions, for example three angularly spaced positions when the rings are continuous, the rings are keyed locally to the rotor by the coupling assembly illustrated in the drawing.

As illustrated the coupling assembly comprises a pair of spaced bushes 5 and 6 each having an enlarged head 7 respectively 8.

The bush 5 projects through an opening 9 in the ring 2 and into one end of a superimposed opening 10 in the web 4, and the head 7 is located in a counterbore 11 at the outer end of the opening 9 with the head located below the outer surface of the ring 2. Similarly the bush 6 projects through an opening 12 in the ring 3 and into the opposite end of the opening 10 in the web 4 with the head received in a counterbore 13 at the outer end of the opening 12. The three openings 9, 10 and 12 are all equal in diameter and the bushes 6 and 7 are close fits in their respective openings and openings portions.

The coupling assembly is completed by a bolt 14 which projects through the bush 6 and is screwed into a threaded bore 15 in the bush 5 to clamp inclined shoulders 16 between the bushes 5 and 6 and the heads 7 and 8 into engagement with complementary shoulders 17 between the openings 9 and 12 and the respective counterbores 11 and 13.

In this position the bushes 5 and 6 are spaced from each other at their inner ends by a relatively small distance, thereby providing a substantial bearing area between the bushes and the rings 2 and 3 and the web 4.

The bushes 2 and 3 are substantially of equal length to provide two substantially equal bearing areas, and the head 18 of the bolt 14 is of conical outline and is received in a countersunk recess 19 in the bush 6 to conserve space. is provided A clearance between the shank of the bolt 14 and the bushes 5 and 6 so that substantially no lateral forces due to movement of the rings 2 and 3 are applied to the bolt through the bushes 5 and 6.

The threaded end of the bush 5 may have a diametrical slot 20 by means of which the bush 5 can be rotated whilst the bolt 14 is held against rotation. Also that end of the bush 5 may be peened over or otherwise deformed to prevent the bolt 14 from unscrewing accidently.

The external diameter of the bushes 5 and 6, to suit re-reaming of the openings 9, 10 and 12, can be increased without increasing the size of the bolt and, in consequence, the size of the counterbore 13.

In the disc assembly illustrated in Figure 2 of the drawings the bush 6 is increased in length to project through the openings 12 and 10 in the ring 3 and in the web 4, respectively, and into the opening 9 in the ring 2. The bush 5 is reduced in length and projects into a clearance counterbore 21 in the adjacent end of the bush 6 with respect to the bore of which it is spaced. A substantial clearance is provided between the bush 5 and the opening 9. The shoulders 16 and 17 are all normal to the respective openings, and the head 18 is of conventional configuration with the recess 19 in which it is received being countersunk to conserve space in an axial direction.

The construction of the disc assembly illustrated in Figure 2 is otherwise the same as that of Figure 1, and corresponding reference numerals have been applied to corresponding parts.

WHAT WE CLAIM IS:- 1. A disc assembly of the kind set forth in which the rings are keyed locally to the rotor by a coupling assembly comprising a pair of spaced bushes which have enlarged heads at their outer ends, at least one of the bushes being a close fit in an opening in at least one of the rings and in an opening in the rotor, and the heads being received in counterbores in the outer ends of the openings in the rings, and a bolt projecting through one of the bushes is screwed into the other bush to clamp the heads into engagement with shoulders at the steps in diameter between the openings in the rings and the counterbores.

2. A disc assembly as claimed in Claim 1, in which both bushes are close fits in the openings in the rings and in the opening in the rotor into opposite ends of which the inner ends of the bushes project in an axially spaced relationship.

3. A disc assembly as claimed in Claim 1, in which one of the bushes is a close fit in the openings in both rings and in the opening in the rotor, and a substantial clearance is provided between the other bush and the opening in the ring in which it is located.

4. disc assembly as claimed in Claim 3, in which the shank of the bolt projects through the longer bush and is screwed into the shorter bush.

5. A disc assembly as claimed in any preceding claim in which the head of the bolt is received in a recess in one of the bushes, and the recess is of countersunk or counterbored outline.

6. A disc assembly as claimed in any preceding claim in which a clearance is provided between the shank of the bolt and the bush, or each bush, through which it extends.

7. A disc assembly substantially as described herein with reference to and as illustrated in Figure 1 of the accompanying drawings.

8. A disc assembly substantially as described herein with reference to and as illustrated in Figure 2 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. illustrated in Figure 2 is otherwise the same as that of Figure 1, and corresponding reference numerals have been applied to corresponding parts. WHAT WE CLAIM IS:-

1. A disc assembly of the kind set forth in which the rings are keyed locally to the rotor by a coupling assembly comprising a pair of spaced bushes which have enlarged heads at their outer ends, at least one of the bushes being a close fit in an opening in at least one of the rings and in an opening in the rotor, and the heads being received in counterbores in the outer ends of the openings in the rings, and a bolt projecting through one of the bushes is screwed into the other bush to clamp the heads into engagement with shoulders at the steps in diameter between the openings in the rings and the counterbores.

2. A disc assembly as claimed in Claim 1, in which both bushes are close fits in the openings in the rings and in the opening in the rotor into opposite ends of which the inner ends of the bushes project in an axially spaced relationship.

3. A disc assembly as claimed in Claim 1, in which one of the bushes is a close fit in the openings in both rings and in the opening in the rotor, and a substantial clearance is provided between the other bush and the opening in the ring in which it is located.

4. disc assembly as claimed in Claim 3, in which the shank of the bolt projects through the longer bush and is screwed into the shorter bush.

5. A disc assembly as claimed in any preceding claim in which the head of the bolt is received in a recess in one of the bushes, and the recess is of countersunk or counterbored outline.

6. A disc assembly as claimed in any preceding claim in which a clearance is provided between the shank of the bolt and the bush, or each bush, through which it extends.

7. A disc assembly substantially as described herein with reference to and as illustrated in Figure 1 of the accompanying drawings.

8. A disc assembly substantially as described herein with reference to and as illustrated in Figure 2 of the accompanying drawings.