GB2078321A - Brake shoe construction for haulages, hoists, winches and the like - Google Patents

Abstract

A brake shoe 10 or 11 comprises a pair of plates 20, 21 connected together in parallel formation, a series of plane surfaces 25 machined on the inner surfaces of the plates tangentially to a drum 6 and spaced apart on different brake drum radii, mounting blocks 24 located respectively on said surfaces 25, and brake lining blocks 23 fixed on said mounting blocks. Each mounting block may have a spigot 50 located between the plates, said spigot having a bolt therein in alignment with holes 31-34 in the plates 20, 21, said plates and spigots being fixed together by bolts in said holes. Details are given of drilling the holes 31-34 and holes 30, 35 on an arc 29, which holes are used as datum for obtaining the correct angle for machining surfaces 25, utilising pegs in the holes and a straight edge. Figures 7, 8 illustrate modifications with respectively three and eight blocks 24, and whereof projections (F, F1) are provided between mounting blocks 24 and lining blocks 23 to contain the tangential effort of braking. <IMAGE>

Description

SPECIFICATION Brake shoe construction for haulages, hoists, win ches and the like This invention relates to brake shoes suitable for example for haulages, hoists and winches.

The object of the invention is to simplify the construction and cheapen the manufacture of brake shoes.

A typical form of known brake consists of two curved shoes located on opposite sides of a brake drum and fitted with brake lining blocks, the shoes being pivotally mounted at one pair of adjacent ends on fixed pivots and connected together at the other ends by a tie rod means and urged towards each other to engage the drum by spring means. Such shoes have heretofore included a curved plate to carry brake lining blocks, this plate being machined to a cylindrical form and welded to brake shoe plates so that the resultant fit between the brake block linings and the outside diameter of the brake drum are correct. This is a difficult and costly manufacturing process.

The specification of Patent No. 1473342 describes the use of rectangular brake lining blocks set into the aforesaid curved plate whereby rectangular blocks can be adapted to a cylindrical brake path. The rolling and machining of the plate is still required for this construction.

We have now developed a form of brake shoe whereby rectangular brake lining blocks can be used without requiring the production of a rolled and machined curved plate.

According to the invention we provide a brake shoe consisting of a pair of plates connected together in parallel formation, a series of plane surfaces machined on the inner surfaces of the plates tangentially to the drum and spaced apart on different brake drum radii, mounting blocks located on said surfaces, and brake lining blocks fixed on said mounting blocks. Each mounting block may have a spigot located between the plates, said spigot having a bolt therein in alignment with holes in the plates, said plates and spigots being fixed together by bolts in said holes.

By means of this construction the bolt holes can serve to provide accurate datum positions for measurement of the positions of the plane surfaces to be machined by a conventional machine tool e.g. a milling machine or shaping machine.

The holes are preferably located at equiangular distances apart.

A mounting block can conveniently carry two rectangular brake lining blocks spaced apart on either side of the radius of the associated holes, the plane surface being at right angles to the radius of the holes.

The sets of holes may be arranged on a common circular arc and additional holes may be provided one each side of the bolts to serve for establishing datum planes.

In order to arrive at this construction it has been necessary to conceive of a novel method of making it.

Also therefore according to this invention, a brake shoe comprises fixing two shoe plates together parallel to each other, making a series of holes through said plates equidistantly spaced on an arc on an extended radius of the brake drum, providing locating means in said holes, locating datum planes across each pair of holes on opposite sides of the radius of each hole other than the end holes, machining flat surfaces on the inner side of the plates each with a centre line on such radius and measured parallel to said datum planes, seating the mounting blocks against said flat surfaces, and fixing the plates together.

The invention will be further described by way of example with reference to the accompanying diagrammatic drawings wherein Figure 7 is an axial view of a brake made in accordance with the invention; Figure 2 is a side view thereof omitting the brake drum; Figure 3 is an enlarged view of part of Figure 1; Figure 4 is a view of a pair of brake lining blocks and mounting blocktherefor; Figure 5 is a side view of the parts shown in Figure 3; Figure 6 is a plan view of said parts; and Figures 7 and 8show modified forms of brake shoe.

In Figure 1 a brake drum 6 has brake shoes 10, 11 on opposite sides thereof. The shoes are mounted at their lower ends on fixed pivots 13, 14 and their upper ends are connected together by a tie rod device 16 and bell crank lever 17. The lever 17 is acted on by a spring nest located on a centre line 18.

Each shoe consists of four flat steel shoe plates 20, 21 disposed parallel to each other. These are bored through at 14 and 22 (and 13 and 16A) and are secured together temporarily by pins and set down on a flat surface for marking out using a portable drill with a drill jig mounted on a trammel to provide a true radius R2 and by angular measurement or by linear co-ordinates set out the angles Al, A2, A3, A4, A5, A6 and corresponding radii which will be the centre lines for brake lining mounting blocks 24 each of which carries two brake lining blocks 23. The raduis of the brake drum is shown at R1. The blocks 23 are located at equal and opposite angles to the centre line of the spigot.

Each shoe is to be machined with flat surfaces 25 on which the mounting blocks 24 are respectively seated. Each surface 25 is to be a tangent to a point 26 (Figure 3) on the appropriate radius.

The dimension B from the drum perimeter to the surface 25 must be accurately determined by angles A7 and dimensions P and G (Figures 3 and 5).

A dimension C is controlled by the selected thickness of the brake lining blocks so that radius R2 can be established accurately by adding together R1, B and C to produce an arc 29.

Holes 30,31,32,33,34,35 are now drilled on the arc 29 spaced apart equiangularly. The holes can now be used as datum for obtaining the correct angle for machining the required flat surfaces 25.

Pegs are placed in the holes and a straight edge placed against the pegs in holes 31 and 33 provides a true parallel for the flat surface 42 and correct distance C. Similarly with the other flat surfaces.

Each of the mounting blocks 24 has a rectangular spigot 50 with a width E (Figure 6). These spigots are placed between the shoe plates 10, 11 and serve as spacers, the mounting blocks seating on the flat surfaces. Holes are bored in the spigots matching the holes 31-34. Holes 30 and 35 are spare holes used only for the pegs to provide parallel datum planes as above described. Bolts are inserted in the holes 31-34 to bolt the shoe plates together thereby avoiding welding.

The brake lining blocks may be attached to the mounting blocks 24 by rivetting bonding or bolting.

The brake lining blocks initially have plane brake surfaces which rapidly wear to the curvature of the drum.

Figure 7 shows a form of brake shoe provided with only three blocks 24, and Figure 8 shows a form of brake shoe having eight blocks 24.

Figures 7 and 8 show also a modification comprising small projections marked 'F' which project from the inner edges of the plates 21,22 between each adjacent pair of the blocks 24. Similar projections F1 are provided on the blocks 24 between the lining blocks 23. The tangential effort of braking is contained on abutment faces 'F' and F1.

In Figure 7 only three lining mounting plates are used. In this case it is impossible without extending the length of the shoe to provide two further holes beyond the three required for the shoe itself.

Consequently in this construction a further hole S is drilled at a radius exeeding R2 by a suitable increment so that the centre line between the extra hole and the outer holes are parallel to the faces upon which the lining mounting blocks are to be secured.

Claims (12)

1. A brake shoe comprising a pair of plates connected together in parallel formation, a series of plane surfaces machined on the inner surfaces of the plates tangentially to the drum and spaced apart on different brake drum radii, mounting blocks located on said surfaces, and brake lining blocks fixed on said mounting blocks.

2. A brake shoe as claimed in claim 1 wherein each mounting block has a spigot located between the plates, said spigot having a bolt therein in alignment with holes in the plates, said plates and spigots being fixed together by bolts in said holes.

3. A brake shoe as claimed in claim 2 wherein said holes are spaced equiangularly.

4. A brake shoe as claimed in claim 1 wherein each mounting block carries two lining blocks mounted tangentially to the drum.

5. A brake shoe as claimed in any of the preceding claims wherein the plates are provided with inwardly extending projections providing abutment faces engaged by the ends of the mounting blocks.

6. A brake shoe as claimed in any of the preceding claims wherein the mounting blocks have projec tionsforming abutmentfaces engaging the ends of the lining blocks.

7. A brake shoe as claimed in claim 2 with or without any of the other preceding claims having additional holes (30,35) of the same radius equiangularly spaced from the other holes for use in machining the tangential surfaces.

8. A brake shoe as claimed in claim 2 with or without any of claims 1 to 6 having an additional hole (S) of greater radius than the other holes.

9. A brake mounting block formed with a spigot having opposed flat faces suitable for spacing two brake plates apart, and provided with two brake blocks suitable for being disposed tangentially to a brake drum and located at equal and opposite angles to the centre line of the spigot, and projections on the mounting blocks engaging.

10. A method of making a brake shoe as claimed in claim 2 wherein pegs are placed in said holes, locating datum planes across the pegs, and machining said surfaces measured parallel to said surfaces.

11. A brake shoe substantially as described with reference to Figures 1 to 6, or 7 or 8.

12. A brake mounting block as claimed in claim 9 substantially as described and substantially as illustrated in Figures 1 to 6 or 7 or 8.

New claims or amendments to claims filed on 28th September 1981.

Claims 9 and 12 deleted.

Original claims 10 and 11 renumbered as 9 and 10 respectively.