GB2184523A - Vehicle parking brakes - Google Patents

Abstract

An operation mechanism for a parking brake pedal 10 rotatably mounted on a stationary structure 51 in a vehicle compartment is connected to a parking brake (not shown). A cylinder type air damper is interposed between the structure 51 and the pedal 10 to dampen the return of the pedal from its depressed position. The air damper includes a cylinder body 41, a piston 43 axially slidably disposed within the cylinder body to subdivide the interior of the cylinder body into front and rear air chambers R1, R2, a piston rod 42 having one end integral with the piston and extending outwardly from the cylinder body through the rear air chamber in an air-tight manner, a throttle element 46 disposed in the piston for permitting therethrough a flow of air between the air chambers, and an annular member 49 of elastomeric material disposed within the rear air chamber in such a manner as to permit axial movement of the piston rod and to reduce the capacity of the rear air chamber R1 as small as possible when the piston is in its backward stroke end, and is useful to absorb the impact. <IMAGE>

Description

SPECIFICATION Vehicle parking brakes The invention relates to parking brakesforwheeled vehicles, that is to say to an operation mechanism for a parking brake pedal, a lockforthe pedal in its depressed position, and a release mechanism.

Such a conventional operation mechanism has been proposed in Japanese Utility Model Early Publication No. 54-11443, wherein an oil damper is provided for the impact caused by the return movementofthe pedal. Usefora long period oftime leads to oil leakage caused by wear or the fatigue of seal members, and results in oil stains in the vehicle compartment. In manufacture, it is necessary to form a one-way valve or an orifice in the damper piston in a precise menner, and this results in an increase in cost.

According to the present invention there is provided an operation mechanism fora parking brake pedal of a wheeled vehicle comprising a lock for the pedal in a depressed position, a release mechanismforthe lock, and a damperforthe return ofthe pedal from the depressed position,wherein thedamperisintheform ofacylindertypeair damperwhich includes a cylinder body, a piston axially slidably disposed within the cylinder body to subdivide the interior of the cylinder body into front and rearairchambers, a piston rod having one end integral with the piston and extending outwardly from the cylinder body through the rearairchamber in an air-tight manner, a throttle element disposed in the piston for permitting therethrough a flow of air between the air chambers, and an annular member of elastomeric material disposed within the rear air chamber in such a mannerasto permit axial movement ofthe piston rod and to reduce the capacity of the rear air chamber as small as possible when the piston is in its backward stroke end.

Preferably, the annular member is secured in place within the cylinder body in such a manner asto permit axial movementofthe piston rod relative thereto, and an annularcupseal is provided inthe outer periphery ofthe piston to permit the flow of air on depression of the pedal and to blocktheflowofair on return of the pedal. The throttle element may comprise a cup-shaped element formed at its center with an orifice.

The mechanism of the invention involves no oil which might leak and stain, and is comparatively inexpensive to rnanufactureto an appropriate standard. In operation, the annular member causes the capacity of the rear airchamberto rapidly minimize in accordance with approach of the piston to its backward stroke end. This is effective to enhance the dampening function ofthe air damper.

Additionally, the annular member is useful to absorb an impact caused by abutment against the piston in its excessive backward movement.

Drawings Figure lisa side view of an operation mechanism in accordance with the invention; Figure2 is a rearviewofthe mechanism in Figure 1; Figure3 is a longitudinal section of a cylindertype air damper in Figures 1 and 2; Figure4illustrates a modification of an annular member of elastomeric material in Figure3; and Figures 5and 6 illustrate another modification of the annular elastomeric member in Figure 3.

In the Figures 1 and 2, a pedal 10, a locking mechanism 20, a release mechanism 30, and a cylindertypeairdamper40areshown.Thepedal 10 is arranged to operate a parking brake (not shown) of a wheeled vehicle. The pedal 10 has an arm 11 which is formed at its upper end with a sector gear 12 and provided at its lower end with a pedal 13. The foot pedal arm 11 is placed between a stationary base plate 51 secured to a body structure of the vehicle and an attachment plate 52 secured in parallel to the stationary base plate 51. Thus, the foot pedal arm 11 is rotatably mounted on a stepped lateral bolt 14 which is threaded into the attachment plate 52 through the stationary base plate 51 and fastened by a nut.The foot pedal arm 11 has a front end portion operatively connected to the parking brake by means of a parking brake cable 60 and is biased counterclockwise by means of a return spring (not shown) assembled within the parking brake. When the foot pedal 10 is in a released position,thefoot pedal arm 11 is in engagement with a rubber stopper 59 which is fixed to a rear portion of the stationary base plate 51. When the pedal 13 is depressed, the foot pedal arm 11 rotates clockwise aboutthe lateral bolt 14 to operate th e parking brakethroughthe brake cable 60. A normally closed switch 58 is arranged adjacent the rubber stopper 59 and fixed to the stationary base plate 51 to be opened by engagement with the foot pedal arm 11.

The locking mechanism 20 includes a latch member21 which is formed at its one end with a pawl 21 a engageable with the sector gear 12 offoot pedal arm 11. The latch member 21 is placed between the stationary base plate 51 and the attachment plate 52 and rotatably mounted on a lateral support pin 23 fastened to the stationary base plate 51 through an upper portion of attachment plate 52. Atension spring 22 is fixed at its one end to an outer peripheral flange 51a of stationary base plate 51 and connected at its other end to another end of latch member 21 to bias the latch member21 clockwise. When the foot pedal 10 is in the released position, the pawl 21 a of latch member 21 is resiliently engaged with a non-toothed upper end of foot pedal arm 11 under load of the tension spring 22.When the foot pedal 10 is depressed to cause clockwise rotation of the sector gear 12, the pawl 21 a of latch member 21 is brought into engagement with a portion ofthe sector gear 1 to lockthefoot pedal 10 in its depressed position.

The release mechanism 30 is arranged to release the foot pedal 10 from its locked position. The release mechanism 30 includes a release lever 31, a release cable 32, a compression coil spring 33, a release knob 34 and a release stopper 35. The release lever 31 is placed at the outside of attachment plate 52 and rotatably mounted at its upper end on a lateral support pin 36 fastened to the stationary base plate 51 through the attachment plate 52. The release lever 31 has an arm 31 a engageable with the latch member 21. The compression coil spring 33 is anchored at its one end to the attachment plate 52 and engaged at its other end with the lower end of release lever31 to bias the release lever 31 clockwise.The release lever 31 is further connected at its lower end to the release knob 34 by means of the release cable 32, and the release knob 34 is supported in place by means ofthe re[easestopper35which is fixedly mounted on a stationary structure in the vehicle compartment.

When therelease knob 34 is retained by the release stopper 35 in its inoperative position, the arm 31 a of release lever 31 is separated from the latch member 21 under load of the compression coil spring 33.

When the release knob 34 is pulled by the driverto cause counterclockwise rotation ofthe release lever 31 against the compression coil spring 33,the latch member 21 is rotated counterclockwise by engagementwith the arm 31 a of release lever 31 to disengage the pawl 21 a of latch member 21 from the sector gear 12 offoot pedal arm 11.

As shown in Figures 1 and 2, the cylinder type air damper 40 is interposed between the foot pedal arm 11 and a bracket 53 secured to a front end portion of the outer pierpheral flange 51 a of stationary base plate 51.As shown in Figure3,theairdamper40 comprises a cylinder body 41, a piston rod 42 integrally provided with a piston 43, and a closure member 44. The cylinder body 41 has a closed end 41 a pivoted to a lateral stepped bolt 54 fixed to the bracket53 by means of a nut 55 fastened thereto, while the piston rod 42 is provided at its outer end with an end fitting 42a which is pivoted to a lateral stepped bolt 56 secu red to an intermediate portion of foot pedal arm 11 by means of a nut 57 fastened thereto.The piston 43 is axially slidably disposed within the cylinder body 41 through an annularseal cup 45 to subdivide the interior of cylinder body 41 into front and rear air chambers R1 and R2. The piston 43 is formed therein with a passage H for communication between the front and rear air chambers R1 and R2 and furtherformed therein with an end bore in communication with the passage H.A cup-shaped throttle element 46 is formed at its center with an orifice 46a and fixedly coupled within the end bore of piston 43 to permit the flow of air passing therethrough thereby to cause a pneumatic resistance acting on the piston 43.The closure member 44 is disposed within an opening end portion of the cylinder body 41 through an O-ring 47A and fixed in place by means of a pair of axially spaced annular retainers 48A and 48B. The closure member44 is provided at its inner periphery with an O-ring 47B through which the piston rod 42 extends outwardly.

Arranged within the rear air chamber R2 is an annular member 49 of elastomeric material such as syntheticrubberthe hardness ofwhich is determined to resist the pressure exerted in the rear air charnber R2 in backward movement ofthe piston 43 without causing any deformation and to be deformed by abutment against the piston 43. The annular member 49 is secured in place by a press fit with the internal peripheral wall of cylinder body 41 in such a manner as to permit smooth axial movement ofthe piston rod 42 relative thereto. The size of annular member 49 is determined to reduce the capacity of the rear air chamber R2 as smali as possible when the piston 43 is in its backward stroke end. This is effective to enhance the dampening function of the air damper40 as described in detail later.

In depression ofthe foot pedal 10, the parking brake cable 60 is pulled by the foot pedal arm 11 to operate the parking brake, and subsequentlythe locking mechanism 20 acts to lockthe foot pedal 10 in its depressed position. In this instance, the piston rod 42 and piston rod 43 are moved forwards by depression of the foot pedal 10 to compress the air in the front air chamber R1 and to expand the rear air chamber F2. During such forward movementofthe piston rod 42 and piston 43, the throttle element 46 acts to permitthe flow of air passing through the passage H from the front air chamber R1 into the rear air chamber R2, and simultaneously the annular seal cup 45 acts to permit the flow of air passing therethrough from the front air chamber R1 into the rear air chamber R2.Additionally, the pressure in the front air chamber R1 does not increase because of a sufficient capacity ofthe front air chamber R1. Thus, the foot pedal 10 is smoothly depressed without any resistance acting thereon.

When the release knob 34 is pulled by the driverto rotate the release lever 31 counterclockwise against the compression coil spring 33, the latch member 21 is rotated counterclockwise by engagement with the arm 31 a of release lever31 to release lock of the foot pedal 10, and subsequentlythefoot pedal loins returned to the release position under load of the return spring of the parking brake. In this instance, the piston rod 42 and piston 43 are moved backwards underthe load ofthe return spring to compress the air in the rear air chamber R2 and to expand the front air chamber R1.During such backward movement of the piston rod 42 and piston 43, the annular seal cup 45 actsto block the flow of air from the rear air chamber R2 into the front air chamber R1, and the throttle element 46 acts to throttle the flow of air passing therethrough from the rear air chamber R2 into the front air chamber R1 across the passage H.

Additionally, the annular member49 is effective to rapidly minimize the capacity of the rear air chamber R2 in response to approach of the piston 43 to its backward stroke end. Thus, the pneumatic resistance acting on the piston 43 increases up to a maximum value in accordance with approach ofthe piston 43 to its backward stroke end to retard the backward movementoffoot pedal 10 therebyto reduce an impact acting on the rubber stopper 59 caused byabutmentagainstthefoot pedal 10.

In the above embodiment, it is to be noted thatthe cylinder type airdamper40 is adapted as a damper for the foot pedal 1 to avoid problems such as stain of the vehicle compartment caused by oil leakage in use of a conventional cylindertype oil damper. Even if the sealing function of O-rings 47A and 47B is decreased by use for a long period oftime, onlythe dampening function ofthe air dam per will be slightly decreased without causing any other problems. In the air damper 40, the piston 43 is positioned to maximize the capacity of the front air chamber R1 and minimize the capacity of the rear air chamber R2 in its backward stroke end, and the throttle element 46 is disposed within the piston 43 for communication between the air chambers R1 and R2.

Forthis reason, itis notnecessarytoform a conventional orifice in the piston in a precise manner orto provide a conventional one-way valve in the piston. It is, therefore, able to simplify the construction ofthe air damper so asto reduce the manufacturing cost. In addition, the dampening function ofthe air damper40 can be adjusted in a simple manner by replacement ofthethrottle element 46 with another throttle element having a different throttle property.

In the above embodiment, it is also to be noted that in backward movement of the piston 43, the annular member 49 causes the capacity ofthe rear air chamber R2to rapidly minimize in accordance with approach of the piston 43 to its backward stroke end.

This is effective to enhance the dampening function of the air damper 40. Additionally, when the piston 43 is excessively moved backwards due to a strong return force ofthe foot pedal 10 or deformation ofthe rubber stopper 59, the annular member 49 is useful to absorb an impact caused by abutment against the piston 43.

In Figure 4there is illustrated a modification ofthe annular member 49 which is formed to provide an annularspacearoundthepiston rod42whenthe piston 43 is in its backward stroke end. In Figure 5 there is illustrated another modification ofthe annular member 49 which is formed to have a U-shaped cross-section. Figure 6 illustrates a condition where the annular member 49 is radially inwardly deformed by abutment against the piston 43 in its excessive backward movement. In these modifications, the annular member 49 may be secured to the piston 43 for movement therewith.

Aithough in the above embodiment and modifications, the annular seal cup 45 has been adapted to the piston 43, it may be replaced with an O-ring. In such a case, it is desirable that the throttle element46 is modified in consideration with a pneumatic resistance acting on the piston 43 in depression of the foot pedal 10. Furthermore, the frontairchamberR1 in the cylinder body41 may be communicated with the atmospheric airto reduce the resistance acting on the piston 43 in depression of the foot pedal 10. In such a case, it is desirable that an airfilter is provided to prevent entry of dust into the front air chamber R1.

Claims (5)

1. An operation mechanism for a parking brake pedal of a wheeled vehicle comprising a lockforthe pedal in a depressed position, a release mechanism for the lock, and a damperforthe return ofthe pedal from the depressed position, wherein the damper is in theform of a cylindertype air damper including a cylinder body, a piston axially slidably disposed within the cylinder body to subdividethe interior of the cylinder body into front and rear air chambers, a piston rod having one end integral with the piston and extending outwardly from the cylinder body through the rearairchamberinan air-tight manner, a throttle element disposed in the piston for permitting therethrough a flow of air between the air chambers, and an annular member of elastomeric material disposed within the rear air chamber in such a manner as to permit axial movement of the piston rod.

2. A mechanism as claimed in claim 1 in which the annular member is secured in place by a press fit with the internal peripheral wall of the cylinder body in such a manner as to permit axial movement ofthe piston rod.

3. A mechanism as claimed in claim 2 in which the annular member is formed to provide an annular spaced around the piston rod.

4. An operation mechanism for a parking brake pedal substantially as herein described with reference to Figures 1 to 3 of the drawings.

5. An operation mechanism according to claim 4 modified as described with reference to Figures 4 and 5 of the drawings.