GB2065774A

GB2065774A - Pneumomechanical Braking Cylinder

Info

Publication number: GB2065774A
Application number: GB8035494A
Authority: GB
Original assignee: Fabbrica Italiana Magneti Marelli SpA; Magneti Marelli SpA
Current assignee: Industrie Magneti Marelli SRL; Marelli Europe SpA
Priority date: 1979-12-19
Filing date: 1980-11-05
Publication date: 1981-07-01
Also published as: IT1126619B; FR2472994A1; DE3044807A1; IT7928233A0

Abstract

In a pneumomechanical braking cylinder braking is releasable by disconnection of the hollow stem of a mechanical actuator from a related plunger or piston upon manual operation of a control rod. The release mechanism is provided by means of balls (20) housed in radial holes (19) presented by the hollow stem (9) of the mechanical actuator (B) of the cylinder, which balls engage either with a bush or sleeve (21) externally of the stem, integral with the actuator plunger or piston (6), or with an inner bush or sleeve (10) mounted on a control rod (11) operated by the operator. The release of the mechanical braking occurs by a slight rotation of the control rod against the action of a return spring (12). During this operation, said inner bush or sleeve is moved to such an angular position as to accommodate said balls (20), thus allowing the release of the stem from the outer bush or sleeve and hence from the plunger or piston. <IMAGE>

Description

SPECIFICATION Pneumomechanical Braking Cylinder This invention relates to a pneumomechanical braking cylinder for a vehicle provided with manual release mechanism of the mechanical braking, and particularly to a cylinder enabling such a braking to be released by disconnection of the stem of the mechanical actuator from the relative plunger or piston upon operation of a control or drive rod operated by the operator.

As well known, pneumomechanical braking cylinders comprise two coaxial actuators, of which one under pneumatic control for duty braking, and the other under mechanical control for vehicle aid or parking braking.

The pneumatic actuator comprises a membrane plunger or piston directly acting upon the brake operating members, vvhereas the mechanical actuator comprises a plunger or piston, normally subjected at one side to the action of a compressed spring acting through its stem on said members through the membrane of the pneumatic actuator.

For duty braking, air is fed into the supply chamber of the pneumatic actuator, which causes the displacement of the membrane plunger or piston and accordingly the operation of the braking members.

On the other hand, for aid or parking braking, the supply chamber of the mechanical actuator is exhausted or vented so that, by being stretched out the compressed spring transmits the strain through the actuator stem to the membrane and accordingly to the brake operating members.

It clearly appears that, by feeding air back to said supply chamber, the plunger or piston and relative stem are moved back to unbraking position, that is to position of standard running of the vehicle.

When due to accidental causes, said chamber cannot be any further supplied, then said plunger or piston and stem stay at braking position and accordingly the vehicle remains at blocked condition.

When desiring to move the vehicle from the location at which the brake blocking occurred, for example, desiring to bring it to shop for repairs, the release of the mechanical braking has to be effected.

Normally, this operation is carried out by acting on manual release devices, which are operated from outside by the operator through a control rod.

The operation of this rod has as resulting effect the disconnection of the stem from the plunger or piston, so that said stem as urged by the reaction of the brake operating members will return to unoperative position (unbraking position).

According to a known approach, the disconnection between said stem and plunger or piston occurs by axially displacing said control rod. However, this does not assure a full reliability of the release mechanism in normal operation, due to the coincidence of the (axial) displacement direction of the plunger or piston with the (axial) operation direction of the rod to obtain a disconnection of the parts.

Moreover, said control rod is not readily accessible when the vehicle is mechanically braked, and finally the braking cylinder is quite cumbersome in axial direction.

The present invention enables us to provide a pneumomechanical cylinder with manual release device, capable of overcoming the above mentioned disadvaniages and further enabling disconnection by a ready and fast operation.

Broadly stated the invention provides a pneumomechanical braking cylinder for a vehicle provided with a mechanical release mechanism for the mechanical braking, and particularly a braking cylinder for unbraking, by release of the hollow stem of a mechanical actuator from the related plunger or piston on operation of a control or drive rod by the operator, in which the stem axially draws an inner bush or sleeve mounted about the control rod, to which it is relatively restrained, and in which the rod-sleeve assembly may take two angular positions, that is a rest position on return of resilient means, and a working position upon rotation of said control rod against the return action of said resilient means.

Moreover, the stem carries radially displaceable coupling means for: (a) axial blocking of the stem with an outer bush or sleeve integral with the plunger or piston when said means are urged outwardly of the inner bush or sleeve during the return step to rest position of the latter and the outer bush or sleeve is at such an axial position as to partly accommodate said means, or, (b) rotational blocking of the stem with the inner bush or sleeve when said coupling means are inwardly urged by the outer bush or sleeve due to the thrust being transmitted by the braking members to said stem and the inner bush or sleeve is at such an angular position as to partly accommodate said means, said position being provided on rotation of the control rod to working or operating position.

According to a preferred embodiment, the resilient return means comprise a torsional spring, and the coupling means comprise two balls sliding in radial holes of the stem and capable of partial engagement in corresponding seats of said inner bush or sleeve and said outer bush or sleeve.

The further details and features of a pneumomechanical cylinder according to the invention will become more apparent from the following description given with reference to the accompanying drawings, in which: Fig. 1 is an axial sectional view showing a cylinder under unbraking conditions, provided with braking release device in accordance with the invention; Fig. 2 is a partial cross-sectional view of the cylinder shown in Fig. 1, taken along the line 11- ll; Fig. 3 is stiil an axial sectional view of the cylinder shown in Fig. 1 under mechanical braking conditions; Fig. 4 is an axial sectional view of the cylinder shown in Fig. 1 under release condition of the mechanical braking; and Fig. 5 is a partial cross-sectional view of the cylinder shown in Fig. 4, taken along line V-V.

Referring to Fig. 1, reference letter A designates the pneumatic actuator of the braking cylinder and reference letter B designates the coaxial mechanical actuator.

As well known, said actuator A comprises a membrane plunger or piston 1 acting through a cap 2 on a stem 3, the latter transmitting the braking strain or force to the brake operating members (not shown).

This actuator is operated during duty braking which is provided by supplying on operation of the brake pedal air into the supply chamber 4 through connection Al.

Said mechanical actuator B, separated by means of wall 5 from actuator A, comprises a plunger or piston 6 which is normally subjected at one side to pressure air in supply chamber 7, and at the other side to the action of a normally compressed spring 8.

The above mentioned plunger or piston 6 has a hollow stem 9 sealingly sliding within a collar 5a of said wall 5 and terminating by its free end 9a in said chamber 4.

This mechanical actuator B is operated during vehicle aid or parking braking, which braking is provided by venting said chamber 7 through connection B1 upon operation of a manual or hand operated distributor (not shown).

By such a vent, said spring 8 is allowed to stretch out and hence to thrust said plunger or piston 6 which thereby is effective through the end 9a of stem 9 on membrane 1, thus providing the above mentioned aid or parking braking (see Fig. 3). In order to move the piston-stem assembly back to vehicle unbraking position (see Fig. 1), air must be supplied to said chamber 7 through said connection B1, operating said manual distributor.

However, when such a distributor is inefficient, or when the duct or line leading to connection B1 is broken or, more generally, when the system fails, the supply to chamber 7 cannot occur, so that to unbrake the vehicle it is necessary to manually act upon a release device, just allowing to move said plunger or piston 6 back from the mechanical braking position shown in Fig. 3 to the unbraking position shown in Fig. 1.

In order to provide this unbraking, a pneumomechanical cylinder according to the illustrated embodiment of the invention, has a hollow stem 9 axially drawing an inner bush or sleeve 10, which is mounted about a manual control rod 1 to which it is rotarily restrained.

Therefore, said bush or sleeve 10 and rod 11 make up a rotary assembly which may assume two angular positions, that is to say a rest position, as shown in Figs. 1 and 3 and which is provided upon return of a torsional spring 12, and a working or operating position, as shown in Fig.

4 and which is provided upon rotationof rod 11 by an operator against the action of said return spring 12. The operator will control said rod 11 by acting on the head 11 a projecting from the lid or cover 1 3 having the seat of rotation 1 3a for said rod 11.

Said bush or sleeve 10 is accommodated between an inner abutment 14 of said stem 9 and a stop ring 15, the latter being anchored to the end of said stem.

By one end 12a, said torsional spring 12 is anchored to the inner bush or sleeve 10 and by its other end 1 2b to stem 9. The inner bush or sleeve 10 is rotationally restrained to said control rod 11 by means of a ball 16 partly housing within a seat 1 7 formed within said bush or sleeve and partly within an axial groove 18 formed on said rod 11.

The above mentioned hollow stem 9 has radial holes 19 which, in the embodiment shown, are in number of three and arranged at 1200. Each of these holes has a ball 20 housed therein, which ball, depending on its radial position, can block said stem, or with an outer bush or sleeve 21 integral with said plunger or piston 6, or with said inner bush or sleeve 10.

To this end, said outer bush or sleeve 21 and inner bush or sleeve 10 respectively have a circular slot or groove 22 and suitable seats 23 for accommodating said balls 20.

The length of said radial holes 19 is less than the diameter of said balls 20, so that the latter at the two blocking positions are partially housed in said holes 1 9 and slot or groove 22, or in said holes and seats 23.

The blocking of stem 9 with said outer bush or sleeve 21 occurs when said balls 20 are outwardly urged by the inner bush or sleeve as the latter is moving back to rest position on return of said spring 1 2 and the outer bush or sleeve is at such an axial position as to present said slot or groove 22 at said balls 20.

Under these conditions, said stem 9 is restrained to plunger or piston 6, so that these elements will make up a single moving eiement.

The blocking of stem 9 with said inner bush or sleeve 10 occurs when said balls 20 are inwardly urged with respect to said outer bush or sleeve 21 and the inner bush or sleeve is at such an angular position as to present said seats 23 at said balls 20. Such an angular position is provided upon rotation of the control rod 11 by the operator and corresponds to the working or operating position, or to the release condition of said stem 9 from said plunger or piston 6.

The inward displacement of balls 20 is caused by the reaction being exerted by said slot or groove 222 of the outer bush or sleeve 21 on said balls as a result of the thrust being transmitted to the latter by the braking members through said stem 9.

Said outer bush or sleeve 21 has a flange 21 a for attachment to said plunger or piston 6 by means of screws 24 or the like.

Such a bush or sleeve also has a radial pin 25 engaging with an axial groove 26 in said stem 9, so that the latter can be given only axial sliding movements.

Under normal operating conditions of the braking cylinder, as shown in Fig. 1 (unbraking condition) and in Fig 3 (mechanical braking condition), said stem 9 is restrained to said plunger or piston 6 owing to the coupling provided between said stem 9 and outer bush or sleeve 21 by means of said balls 20 (see Fig. 2).

Due to this restraint, said stem and plunger or piston are bodily displaced, while said control rod 11 remains at angular rest position, so that said seats 23 in said inner bush or sleeve 10 are out of phase from the radial holes 19 of the stem (see Fig. 2).

Supposing that air cannot be any longer supplied back to chamber 7 to provide for pneumatic unbraking of the vehicle, then said unbraking for the latter is provided by rotating said control rod 11 through such an angle as to bring said seats 23 of bush or sleeve 10 at said holes 1 9 of stem 9. Following this rotation, against the action of spring 12, the position of elements 10, 20 and 21 is that as shown in Figs.

4 and 5.

Particularly, it will be seen from Fig. 5 that said balls 20 cooperate with said seats 23 of bush or sleeve 10, thus releasing said stem 9 from said bush or sleeve 21 and hence from said plunger or piston 6.

Therefore, said stem can be upward displaced to unbraking position (see Fig. 4) due to the reaction being transmitted thereto by the braking members through the stem 3 of the pneumatic actuator A.

When the system is repaired and accordingly air is supplied to chamber 7, the bush-piston assembly 21, 6, which was at the position shown in Fig. 4, is upward urged, and when said slot or groove 22 of bush or sleeve 21 is in front of the radial holes 19 of stem 9, then said balls 20 are urged or pushed into said slot or groove due to the rotation of the inner bush or sleeve 10, thus providing again the blocking condition between said stem and plunger or piston, as shown in Fig.

1.

Such a blocking is automatically carried out, as due to the rotation of bush or sleeve 10 caused by said spring 12, which was under tension after the rotation of said control rod 11 carried out by the operator.

The insertion of balls 20 in said slot or groove 22 is aided by an inclined surface 23a presented by each of said seats 23 of said bush or sleeve 10.

It would result from the foregoing that the release operation of the mechanical braking should involve a mere rotation of said control rod.

On the other hand, the operation is a very rapid operation, requiring a small angle of rotation.

By the release mechanism described above, the axial overail dimensions are reduced, since the various parts or elements providing it are all within said stem 9.

It is also apparent that the mechanism is highly reliable, since the release operation which is effected through a rotation of rod 11 is different from the direction of displacement for the plunger or piston, which is an axial direction. Therefore, such a release cannot accidentally occur.

In the above description, balls 20 engaging in corresponding seats of the bushes or sleeves have been provided as coupling means for the stem to said bushes or sleeves 10 and 21.

However, it clearly appears that the form of the coupling means could be other than that above provided, as far as said means are capable of being displaced in the radial passages 1 9 of the stem to provide the release or blocking of the latter with said bushes or sleeves at facing position.

Claims

1. A pneumomechanical braking cylinder for a vehicle provided with manual release mechanism for the mechanical braking, and particularly a braking cylinder for unbraking by release of the hollow stem of the mechanical actuator from the relative plunger or piston on operation of a control rod operated by the operator, characterized in that the stem axially draws an inner bush or sleeve (10) mounted about the manual control rod (11), bush or sleeve being rotarily restrained thereto; the rod-bush assembly (11, 10) being capable of taking two angular positions, that is a rest position on return of resilient means, and a working or operative position on rotation of the control rod against the return action of said resilient means; said stem carrying radially displaceable coupling means allowing: (a) the stem blocking with an outer bush or sleeve (21) integral with the plunger or piston, when said means are outwardly urged by the inner bush or sleeve as the latter is moving back to rest position and the outer bush or sleeve is at such an axial position as to partly accomodate said means, so that said stem is restrained to the plunger or piston to make up a single moving element, or:: (b) the rotary blocking of the stem with the inner bush or sleeve (10) when said coupling means are inwardly urged by the outer bush or sleeve as a result of the thrust being transmitted by the braking members to the stem and the inner bush or sleeve is at such an angular position as to partly accomodate said means, said position being provided on rotation of the control rod to working or operative position, so that said stem (9) is released from the plunger or piston.

2. A pneumomechanical braking cylinders in vehicles according to Claim 1, characterized in that said inner bush or sleeve (10) is axially retained to the stem (9) by means of an abutment (14) of the latter and a stop ring (15) anchored thereto.

3. A pneumomechanical braking cylinder in vehicles according to Claims 1 or 2, characterized in that said resilient means for return of the rodinner bush assembly (11, 10) comprise a torsional spring (12) mounted about the control rod and connected by one end (12a! to said inner bush or sleeve (10) and by the other end (1 2b) to said stem (9).

4. A pneumomechanical braking cylinder in vehicles according to any one of Claims 1 to 3, characterized in that said inner bush or sleeve (10) is rotarily restrained to said control rod (11) by means of at least one coupling ball (16) partly accomodated within a corresponding seat (17) formed in said bush or sleeve, and partly within an axial groove (18) formed on said control rod.

5. A pneumomechanical braking cylinder in vehicles according to any one of the preceding claims, characterized in that said radially displaceable coupling maans comprise one or more balls (20), each of which sliding in a radial passage (19) of the stem, the length of which is less than the ball diameter, and intended for partial engagement either with a circular slot or groove (22) presented by the outer bush or sleeve (21), or with a corresponding seat (23) presented by the inner bush or sleeve (10).

6. A pneumomechanical braking cylinder in vehicles according to any one of the preceding claims, characterized in that said outer bush or sleeve (21) has a flange (21 a) preset for attachment to the plunger or piston and a radial pin (25) cooperating with an axial groove (26) of the stem to prevent the latter from rotating.

7. A pneumomechanical braking cylinder for a vehicle substantially as hereinbefore described with reference to the accompanying drawings.