GB2275087A - Spring applied disc brake - Google Patents

Description

2275087 -INDUSTRIAL POWER-FAILURE DISC BRAKE The present invention

concerns, in general terms, industrial power- failure disc brakes, le disc brakes which, being intended for industry, consist for example of emergency brakes on any machines required to control any loads.

These disc brakes include, in overall terms, a disc mounted so as to rotate, two brake shoes each disposed respectively on each side of this disc, application means which permanently urge the brake shoes in the direction of the disc, and freeing means able to act on the brake shoes in order to release the latter.

When in use, these freeing means, duly supplied with power, are normally active, which neutralises the application means, and the brake is therefore normally open, le released.

If, following a fault for example, the power supply to these freeing means is interrupted, the application means, thus duly released at that moment, come into action themselves automatically, which immediately ensures that the brake shoes are applied to the disc, and therefore that the machine or load concerned is braked, if necessary until it comes to a stop.

The object of the present invention is, in general terms, a particularly simple and effective implementation of these application means.

According to the invention there is provided an industrial power-failure disc brake of the type including a disc mounted so as rotate, two brake shoes each disposed respectively on each side of the disc, application means which permanently push the brake shoes in the direction of the disc, and freeing means able to act on the brake shoes in order to release the latter, this disc 2 brake being generally characterised in that, for at least one of the brake shoes, and in practice for each of them, the application means include at least one torsion bar, to which is fixed, with respect to rotation, a lever carrying this brake shoe, and which, at a distance from this lever, is itself fixed, with respect to rotation, to a holding piece.

In practice the torsion bar or bars thus utilised are subjected to torsional prestressing when idle, with the brake being applied, and it is from this torsional prestressing that, when necessary, the application force to which the disc is then subjected and therefore the braking torque thus developed by the latter very simply result.

Because of these torsion bars, the disc brake according to the invention advantageously has only limited dimensions in the proximity of the disc, which can make it easier to install.

In addition, it is in general very simple to produce.

In particular, the number of joints it contains is limited, which facilitates and reduces the maintenance involved.

In practice, these joints are limited to two fixed bearings in which the torsion bars are each mounted respectively so as to pivot in the vicinity of the levers carrying the brake shoes.

Furthermore, the application force due to the torsion bars advantageously develops with great flexibility, and the braking torque resulting therefrom is particularly stable.

Finally, any adjustment of wear intended to take account of the wear on the friction linings carried by the brake shoes can advantageously be avoided if the resulting force, after varying the torsion angle of the torsion bars, is not too great.

3 To achieve this it is in fact sufficient that the initial prestressing of the torsion bars be sufficient for a residual amount of torsional prestressing to remain, at the end of wear on the friction linings, able to allow a variation in the useful torsional moment of about 10% with respect to a duly chosen nominal torsional moment.

The adjustment of the assembly is simplified thereby.

However, if desired, a wear compensating device can nevertheless be used.

Briefly, the disc brake according to the invention is very simple to produce and maintain, and is therefore particularly economical.

The characteristics and advantages of the invention will, moreover, become clear from the following description, given by way of example, with reference to the accompanying diagrammatic drawings in which:

Figure 1 is, with local cutaways, a partial elevation view of the disc brake according to an embodiment of the invention; Figure 2 is a partial view thereof in longitudinal section, along the line II-II in Figure 1; Figure 3 is a partial plan view thereof, along the arrow III in Figure 1; Figure 4 is a partial view thereof in cross section, along the broken line VI-VI in Figure 1, with a local cutaway and a disc removed.

Figure 5 is another partial view thereof in cross section, along the line V-V in Figure 2; 4 Figures 6 and 7 are partial elevational views which, analogous to the view in Figure 1, and with a local cutaway for Figure 7, each concern respectively a variant embodiment; Figure 8 is, with local cutaways, a partial plan view which, analogous to the view in Figure 3, refers to another variant embodiment.

As illustrated in these Figures, and in a manner known per se, the disc brake according to the preferred embodiment of the invention is an industrial power-failure disc brake including, in overall terms, a disc 10 which is mounted so as to rotate about its axis and which annular in shape in the embodiments shown, is only partially visible in the Figures, two brake pads 11 which are each disposed respectively on each side of the disc 10 and which are in practice identical to each other and, in accordance with the arrangements described in greater detail below, on the one hand application means 12 which permanently push the brake shoes 11 in the direction of the disc 10, and on the other hand freeing means 13 which are able to act on the brake shoes 11 in order to release the disc 10.

In a manner also known per se, the brake shoes 11 each include an insert 14, on which the application means 12 act, on the opposite side to the disc 10 and, on the same side as the disc 10, to provide contact with the latter, a friction lining 15, commonly referred to as a brake pad.

The application means 12 include, for at least one of the brake shoes 11 and, in practice, for each of them in the embodiment shown, at least one torsion bar 16 to which is fixed, with respect to rotation, a lever 18 carrying such a brake shoe 11 and which, at a distance from this lever 18, is itself fixed, with respect to rotation, to a holding piece 19.

In the embodiments shown in Figures 1 to 6, only one torsion bar 16 is in practice provided for each brake shoe 11.

There are therefore overall in this case two torsion bars 16 and each of them has substantially the same characteristics.

In the embodiment shown more particularly in Figures 1 to 5, these two torsion bars 16 extend substantially parallel to the radius of the disc 10 corresponding to the median area of the brake shoes 11, and the corresponding levers 18 each extend substantially tangentially to a concentric circumference of the disc 10.

More precisely, in this embodiment, the torsion bars 16 extend parallel to each other in the same direction, and they have in common the holding piece 19.

This holding piece 19 is for example fixed.

It has, for this purpose, in the embodiment shown, a drilled apertures, 20 for any fixing means (not shown) to pass through, suitable for being fixed to any support, also not shown.

As a variant, the holding piece 19 may be in the open.

Whatever the case, it has, parallel to each other, in the embodiment shown, two fluted drilled apertures 22, with which the tLjo torsion bars 16 are each respectively engaged.

The levers 18 are each fixed, with respect to rotation, to the torsion bars 16 at the opposite end of the latter to the holding piece 19.

In the vicinity of these levers 18, the torsion bars 16 are each individually mounted so as to pivot in bearings 23 carried, transversely side by side, in the same plane, by an insert 24 and, designed to be attached to the associated support, for example by means of screws 25, this insert 24 6 itself forms a support for the assembly.

The bearings 23 are therefore fixed bearings.

They serve to guide the torsion bars 16.

In the embodiment shown, the insert 24 has an indentation 26 on the same side as the disc 10 to enable the latter to pass through.

The part 28, at least, of the torsion bars 16 by which the latter are engaged so as to pivot in bearings 23, and which, in the embodiments shown, is formed in practice from a local widening of these torsion bars 16, has of course a circular outline in cross section.

In the embodiments shown, the same applies to the standard part 29 of the torsion bars 16, over their entire length, between the bearings 23 and the holding piece 19.

Let D be the diameter of this standard part 29, and let L1 be the useful length of the torsion bars 16 between the levers 18 and the holding piece 19.

The levers 18 may for example be a push fit in the torsion bars 16, as shown.

They may also be clamped on the latter.

As a variant, they can also form a single piece with these torsion bars 16, like cranks.

In this case the whole is produced, for example, by forging.

Whatever the case, they are each respectively duly fixed, with respect to rotation, to the torsion bars 16 and, parallel to these torsion bars 16 but on the opposite side to the latter, 7 each of them carries, so that it projects, in the embodiments more particularly shown in Figures 1 to 7, a pin 30 on which is likewise fixed with respect to rotation the corresponding brake shoe 11.

In these embodiments, the insert 14 of the brake shoes 11 carries at its rear a cradle 32 by which it is engaged on the corresponding pin 30, and the latter has a flat 33 on which bears a locking pad duly attached to the cradle 32, for example by screws (not shown).

Ribs 35 connect the cradle 32 transversely to the insert 14.

Let L2 be the distance, or lever arm, separating the pins 30 of the levers 18 from the torsion bars 16.

In the embodiments shown, the pins 30 form a single piece with the levers 18.

However, as a variant, they could also be attached to these levers 18, by being duly fixed to the latter with respect to rotation.

In practice, the pins 30 lie in the median area of the levers 18 and the freeing means 13 intervene between these levers 18, at the opposite end of the latter from the torsion bars 16.

In the embodiments shown, these freeing means 13 are hydraulic freeing means.

They include, in one of the levers 18, a chamber 36 forming a cylinder which, being able to be connected to a source of fluid under pressure by means of a joining piece 38 on the same side as its blind end, is sealed by a screwed plug 39 on the same side as its free end and in which is mounted so as to be movable a piston 40 which, by means of a rod 41 passing through the screwed plug 39 so as to form a seal, bears at its 8 free end on the other one of the levers 18, parallel to the axis of the disc 10.

When in use, the freeing means 13 are supplied with power and, being thus active, they hold the brake shoes 11 at a distance from the disc 10.

The brake is then open.

At the same time, the torsion bars 16 are then subject to torsional prestressing, and the corresponding torsional prestressing is substantially the same for each of them.

Consequently, if the freeing means 13 come to be deactivated, the torsion bars 16 elastically cause the brake shoes to be pressed against the disc 10, for the applying and therefore the braking of the latter.

Let F be the force to which each of the brake shoes 11 is then subjected, parallel to the axis of the disc 10, because of the corresponding torsion bar 16, and let Mt be the corresponding torsional moment, for each torsion bar 16. Mt = F.L2 By construction and, more precisely, by an appropriate choice of the diameter D, of the length L1 and of the fatigue factor t of the material forming the torsion bars 16, in practice steel, it is preferably ensured that the initial torsional prestressing of the torsion bars 16 is sufficient, at the end of wear of the friction linings 15 of the brake shoes 11, for there to remain a residual amount of prestressing able to allow a variation in the useful torsional moment of about 10%, for example, with respect to a given nominal torsional moment.

The braking force F then remains within appropriate limits, even at the end of wear of the friction linings 15.

9 For example, for torsion bars 16 made of steel with a diameter D of 33 mm, with a length L1 of 450 mm and with a fatigue factor t equal to 1000 MPa, good results have been obtained with an initial torsional prestressing for these torsion bars 16 corresponding to a prestressing angle of 170 when the brake is open.

Indeed, this prestressing angle can under these conditions vary, for example, between 160 and 300 on braking, depending on the degree of wear on the friction linings 15, which, taking into consideration the other parameters involved, corresponds overall to a variation of 20% for the corresponding braking force F.

Of course, the numerical values given above are given here only by way of an illustrative example, and they must under no circumstances be considered to limit the invention.

In the variant embodiment shown in Figure 6, the torsion bars 16 each respectively extend substantially tangentially to a concentric circumference of the disc 10, and the levers 18 extend substantially parallel to the radius of this disc 10 corresponding to the median area of the brake shoes 11.

In such a case, for each brake shoe 11, the lever 18 is fixed, with respect to rotation, to the torsion bar 16 in the median area of the latter, and there is a fixed holding piece 19 at each end of this torsion bar 16.

In the variant embodiment shown in Figure 7, for at least one of the brake shoes 11, and, in practice, for each of them, there are two torsion bars 161, 1611 in series.

For example, and as shown, the torsion bar 1611 is in the form of a blind sleeve and the torsion bar 161, to which the corresponding lever 18 is fixed, extends axially into this torsion bar 161, being engaged with its end at its opposite end to the lever 18, whilst, at the same time, by its free edge, the torsion bar 1611 is engaged with the holding piece 19.

In the embodiment shown, this holding piece 19 is carried by the insert 24.

It is therefore fixed.

In the variant embodiment shown in Figure 8, a brake shoe 11 is articulated on the corresponding lever 18 by means of a ball joint 30y, instead of the pin 30 as previously, the cradle of the brake shoe 11 being itself replaced by a cup 321.

More precisely, in this variant embodiment, the ball joint 301 is carried at the end of a rod 42 which, perpendicular to the torsion bars 16, is mounted so as to be adjustable in position on the lever 18.

For example, and as-shown, this rod 42 is engaged by screwing in a threaded drilling 43 in the lever 18, and a locking nut 44 is associated with it on the far side of the latter.

Adjustment of the forward movement of the brake shoe 11 can thus be provided if desired, in particular in the case of wear on its friction lining is.

The present invention is not of course limited to the embodiments described and shown, but includes any variant implementation andlor combination of their various elements, in particular as far as the freeing means used are concerned, which, instead of being hydraulic, can just as well be pneumatic, mechanical or electrical freeing means, for example.

In addition, instead of being in a single piece, as more 11 particularly described and shown, the holding piece on which a torsion bar is fixed with respect to rotation may if desired be advantageously in two parts, in particular when it is in common with another torsion bar.

By means of angular adjustment between these two parts it is for example possible to adjust the prestressing of the torsion bar or bars and, in this way, to balance the application forces which they induce.

Furthermore, if desired, a wear compensation device can be used and, for example, a wear compensation device of the same type as the one described in the French patent which, filed on 28 April 1989 under No 89 05708, which was published under No 2646 485.

12

Claims (1)

1. Industrial power-failure disc brake of the type including a disc (10) mounted so as to rotate, two brake shoes (11) each disposed respectively on a side of the disc, application means (12) which permanently urge the brake shoes (11) in the direction of the disc (10), and freeing means (13) able to act on the brake shoes (11) in order to release the latter, characterised in that, for at least one of the brake shoes (11), the application means (12) include at least one torsion bar (16) on which is fixed, with respect to rotation, a lever (18) carrying this brake shoe (11) and which, at a distance from the said lever (18), is itself fixed, with respect to rotation, to a holding piece (19).

2. Disc brake according to Claim 1, characterised in that the torsion bar (16) extends substantially parallel to the radius of the disc (10) corresponding to the median area of the brake shoe (11), and the lever (18) extends substantially tangentially to a concentric circumference of the disc (10).

3. Disc brake according to Claim 2, characterised in that the lever (18) is fixed, with respect to rotation, to the torsion bar (16) at the end of the latter which is opposite the holding piece (19).

4. Disc brake according to either one of Claims 2 or 3, characterised in that, the application means 12 including at least one torsion bar (16) for each of the brake shoes (11), the corresponding torsion bars (16) extend parallel to each other in the same direction, and they have the holding piece (19) in common.

5. Disc brake according to Claim 4, characterised in that the holding piece (19) is fixed.

13 6. Disc brake according to Claim 1, characterised in that the torsion bar (16) extends substantially tangentially to a concentric circumference of the disc (10), and the lever (18) extends substantially parallel to the radius of the disc (10) passing through the median area of the brake shoe (11).

7. Disc brake according to Claim 6, characterised in that the lever (18) is fixed, with respect to rotation, to the torsion bar (16) in the median area of the latter, and there is a holding piece (19) f ixed to each end of the latter.

8. Disc brake according to any one of Claims 1 to 7, characterised in that, in the vicinity of the lever (18), the torsion bar (16) is mounted so as to pivot in a f ixed bearing (23).

9. Disc brake according to any one of Claims 1 to 8, characterised in that, when idle, with the brake being applied the torsion bar (16) is subject to torsional prestressing.

10. Disc brake according to Claim 9, characterised in that the initial torsional prestressing of the torsion bar (16) is sufficient for there to remain, at the end of wear of the friction linings (15) of the brake shoes (11), a residual. amount of prestressing able to permit a variation in the useful torsional moment of about 10% with respect to a given nominal torsion moment.

11. Disc brake according to any one of Claims 1 to 10, characterised in that, for at least one of the brake shoes (16), there are two torsion bars (16', 1611) in series.

12. Disc brake according to any one of Claims 1 to 11, characterised in that the holding piece (19) is in two parts.

13. Disc brake substantially as hereinbefore described with reference to Figures 1 to 5, 6, 7 or 8 of the accompanying drawings.