MX2008006968A - Collet controlled slack adjuster - Google Patents

Abstract

A slack adjuster for a fluid-actuated brake comprises a slack adjuster collet (24) having a tubular skirt and an enlarged ring section. The enlarged ring section has opposed axial stop faces notched therein that define a conical lift surface facing the tube axis. A forward stop face has a conical or beveled surface arranged to engage the conical or beveled surface on one stop face of the collet when the collet carried by the actuator rod reaches the forward stop face and a retraction stop face has a conical or beveled surface arranged to engage the conical or beveled surface on the other stop face of the collet when the collet carried by the actuator rod reaches retraction stop face. The conical or beveled surfaces are configured so that when they engage, the force of the collet on the push rod is reduced.

Description

VOLTAGE CONTROLLED VOLTAGE ADJUSTER BACKGROUND OF THE INVENTION Field of the invention The present invention relates to tension adjusters which are devices used with brakes operated under fluid pressure to withstand the wear of brake shoes and the like in such a way that the length of the brake actuation stroke remains the same as the wear occurs. .

DESCRIPTION OF THE RELATED TECHNIQUE Fluid-actuated brakes with tension adjusters are well known in the art as seen, for example, in the following: U.S. Patents. Nos. 4,676,346; 4,895,228; 5, 423, 401; 5,848, 550; 5,937,974 and 6,397,986. The fluid-actuated brakes typically have a housing that encloses a piston and cylinder. The piston drives a connecting link that is generally tubular. Inside the tubular link is placed a push rod that can slide inside the tubular link. A certain type of clutch apparatus is placed between the tubular link and the push rod to drive the rod in a brake actuation direction but allowing the rod to retract into the tubular rod. Also associated with the rod is a tension adjuster comprising a movable detent normally engaged in relation to the push rod to restrict the retraction of the push rod by engaging a detent surface on the tubular link or housing. The retainer must be able to disengage and move along the push rod in the opposite direction to the brake actuation direction if the rod moves beyond its normal travel due to brake wear. At that time, the retainer is moved by engaging a detent surface associated with the housing. It should also be possible to manually force the push rod to retract it into the tubular link at the time of replacement of the ballasts. This requires the disengagement of the retainer.

The seals are generally of two types. In one type, the push rod has external threads and the retainer comprises a nut that rotates on the threads of the push rod. The clutch action is caused by restricting the rotation of the nut in relation to the rod as shown, for example, in the US patents. Nos. 4,676,346 and 4,895,228.

In the other type, the push rod has threads or teeth and the retainer comprises a clamp that surrounds the rod and frictionally holds the teeth. The clamp is a tube that has an internal diameter that splices and tightens the teeth of the push rod. Axial grooves in the wall of the tube allow a slight radial expansion of the tube allowing it to be mounted on the teeth of the push rod. At one end of the clamp tube, a ring of elongated diameter is located. Axial surfaces on the ring serve as retainer surfaces for coupling retainers associated with the housing or tubular link. If sufficient axial force is applied, the clamp will disengage and move axially along the push rod. Clamp-type detents in tension adjusters are described, for example, in the U.S. Patents. Nos. 5,423, 401 and 5,937,974. The tension adjuster clips described in these patents have tension adjuster pliers with an enlarged annular end positioned axially away from the brake. The clamping force of the clamp on the teeth of the push rod is the same notwithstanding the axial position of the clamp in relation to the push rod.

BRIEF DESCRIPTION OF THE INVENTION Briefly, in accordance with the present invention, a tension adjuster for a fluid-operated brake comprises a housing that encloses a piston cylinder, a piston and a tubular link extending from the piston to drive a brake, a push rod that extends inside the tubular link and a device to engage the link tubular and push rod when driven in a brake actuation direction. The tension adjuster comprises a clamp that applies a tightening force on the push rod. A retraction stop surface and forward detent surface are fixed relative to the housing. The clip has a tubular skirt section having an example of a tube and an enlarged fixed annular section at one end of the tubular skirt section. The annular section has opposing axial detent surfaces which are generally perpendicular to the ex ee of the tube. These opposing surfaces each have a notch therein which defines a conical or bevelled surface facing the axis of the tube. The forward detent surface has a conical or beveled surface arranged to engage the conical or bevelled surface on a detent surface of the gripper when the gripper carried by the actuator rod reaches the detent surface forward. The retracting retainer surface has a conical or beveled surface arranged to engage the conical or beveled surface onto the other retainer surface of the clamp when the clamp carried by the actuator rod reaches the retraction detent surface. The conical or beveled surfaces are configured in such a way that when they are coupled, the clamp expands and the force of the clamp on the push rod is reduced. More preferably, the tubular skirt section of the clamp extends axially towards the piston.

Preferably, the tubular skirt section of the tension adjuster and the enlarged annular section of the gripper have connected axial grooves or grooves extending along and through the tubular wall or near the end of the tubular skirt section.

Preferably, the conical or beveled surfaces associated with all retainer surfaces form substantially the same angle when the tube axis and the conical or bevelled surfaces on the clamp are separated closer to the axis of the tube than the conical or bevelled surfaces in the clamps. retraction and forward seals.

Most preferably, the fixed annular section of the tension adjuster clamp has an internal diameter slightly smaller than the tubular skirt section forcing part of the skirt wall to be bent elastically and thus to put a clamping force on it. the push rod.

BRIEF DESCRIPTION OF THE DRAWINGS Additional features and other objects and advantages will become clear to those skilled in the art from the following detailed description made with reference to the drawings in which: Fig. 1 is a sectional assembly drawing illustrating a spring-applied parking brake and service brake having a clamp-style tension adjuster according to the present invention.

Figure 2 is an end view of a forward sleeve portion of the tension adjuster shown in Figure 1.

Figure 3 is a sectional view taken along lines 111-111 of Figure 2.

Figure 4 is a part drawing showing the end plate in extreme view for the tension adjuster shown in Figure 1.

Figure 5 is a sectional view taken along lines V-V of Figure 4.

Figure 6 is a side view of a clamp for the tension adjuster shown in Figure 1.

Figure 7 is a right side view of the clamp.

Figure 8 is a left side view of the clip.

Figure 9 is a sectional view taken along line IX-IX of Figure 7 and Fig. 10 is a detailed section of the clip showing grooves with conical lifting surfaces essential for the practice of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring to Figure 1, there is shown a spring applied parking brake and service brake having a clamp-type tension adjuster according to the present invention. The general operation of the brake is of antecedent importance for the present invention. Except for the improvement in the tension adjuster, the operation of the parking brake is exactly as described in the U.S. patent. No. 5, 937,974, which is incorporated herein by reference. In the following description, the balata end of the parking brake is referred to as the forward end and the piston end as the rear end. The brake comprises a housing 12 enclosing a piston cylinder 1 8 and a service brake piston 14. The service brake piston 14 is fluid driven to apply the brakes and is retracted by a coil spring 50. The housing 12 also encloses a second piston cylinder 1 9 and retractor piston 1 7 to retract the parking brake activated by a large spring 28. The service brake piston 14 drives a tubular link 20. A threaded or serrated push rod 26 is it slides inside the tubular link 20 and is engaged by the drive clip 36 which has a beveled or conical surface for splicing a complementary conical surface onto the tubular link. Thus, in the application stroke of the service brake, the drive clamp 36 is urged to engage the push rod 26 in such a way that both the tubular link and the push rod move together. After retraction, the tubular link is disengaged from the push rod.

Extending from the parking brake retraction piston is a tubular link 20 that captures a two-part intermediate sleeve comprising the rear sleeve 42 and front sleeve 22. The release of the fluid pressure in the second piston cylinder 1 9 allows that the large spring 28 transfers force to the balata attached to the end of the push rod 26 to effect a parking brake force on the balata.

Up to this point, what has been described is the same as that shown in the US patent. No. 5,937,974 using identical numbers for corresponding elements. Hereinafter, the description is of the improvements according to the present invention.

Referring to Figures 2 and 3, the forward sleeve 22 has a unique configuration. The forward sleeve has an enlarged internal cylindrical wall 52 which is larger than the diameter of the push rod 26, defining a space for receiving a tension adjuster clamp 24 (to be described). At the rear end of the space, there is a radial end wall or rear detent surface 54 with a projecting ring 55 defined by a tapered rear lifting surface 56 extending from an inner cylindrical surface 58. The inner cylindrical surface 58 is larger that the cylindrical skirt of the tension adjuster clamp 24, which is, in turn, slightly larger than the push rod. The conical rear lifting surface 56 increases in diameter by moving backwards.

The forward end of the forward sleeve 22 has a radial end surface 60 with threaded holes for receiving fasteners to hold the end plate 62.

Referring now to Figures 4 and 5, the end plate 62 is shown which can be secured to the radial end surface 60 of the forward sleeve 22. The end plate 62 serves as a forward detent surface to limit travel. forward of the tension adjuster clamp 24 and push rod 26. The endplate has a ring 64 projecting from the surface of the endplate. The ring 64 has a cylindrical surface 66 which has a diameter larger than the diameter of the push rod 26. In other words, the cylindrical surface 66 is larger than the cylindrical diameter opposite the opening bevel in the adjuster clamp tension for the exit stroke which is, in turn, larger than the push rod. The ring 64 has a conical rising surface 68 that extends between the cylindrical surface of the ring and the back surface of the end plate 62. The conical surface has a larger and larger diameter that moves forward to the end plate 62.

Referring to Figures 6, 7, 8, 9 and 10, the tension adjuster clamp 24 is a tubular structure having an internal cylindrical surface that engages the threads or teeth of the push rod 26 and can be repositioned. axially on the push rod during tension adjustment. The tension adjuster clamp has a cylindrical skirt 78 and an enlarged fixed ring 72 at one end. The fixed ring 72 has two radial end surfaces defining the detent surface 74 and retainer surface 76. These detent surfaces cooperate with the end plate 62 or detent surface 54 in the forward sleeve 22. The detent surfaces forward and rear 74, 76 each have slots 71, 73 with conical lifting surfaces 75, 77 that face radially inwardly. The lifting surfaces 75, 77 have diameters that increase by moving inward from their respective detent surfaces. The skirt of the tension adjuster clamp has axial grooves or grooves 79 extending through the cylindrical wall 78 and the fixed ring 72 (see Figure 9). The end 80 of the skirt 78 opposite the fixed ring 72 has no grooves or grooves. The slots 79 allow a slight expansion of the grooved sections of the ring and skirt. The cylindrical wall portions between the grooves serve as leaf springs when they are bent radially outwardly by putting their outer surface in compression and their inner surface tensioned. According to a preferred aspect of the present invention, the internal diameter of the fixed ring 72 is slightly smaller than the internal diameter of the skirt 78 and slightly smaller than the external diameter of the push rod 26. Thus, when the clamp of the adjuster is put on the push rod, the slotted portion The skirt and the annular section are bent elastically away from the rod so that the fixed ring puts a clutch force on the push rod.

The operation of the tension adjuster is as follows. When due to wear of the brake shoe the push rod 26 moves beyond its normal forward position, the forward detent surface 74 of the clamp 24 butts the end plate 62 and the clamp is forced rearwardly to along the push rod 26. When the forward detent surface 74 on the tension adjuster clamp reaches the end plate 62, the ring 64 projecting from the end wall enters the slot 71 in the detent surface 74, the conical surfaces 68 and 75 are spliced, and the fixed ring 72 is expanded away from the push rod in this manner by disengaging the tension adjuster clamp from the push rod. The ring 64 and the groove 71 are configured in such a way that after the conical surfaces 68 and 75 the ring can continue to move in the groove. This continuous movement expands the fixed ring 72 away from the push rod 26. This makes it possible for the clamp to be moved back along the adjusting rod by significantly reducing the force of the push rod transferred to the balatas. This relocation of the adjuster clamp then restricts the removal of the push rod during release of the brake when the other detent surface 76 on the fixed ring connects the retainer surface 54 on the forward sleeve 22. The force of the spring of retraction that j the push rod back is not enough to force the projecting ring 55 into the groove 73. Accordingly, the clamp adjuster does not become disengaged.

During the maintenance of the brake, for example, replacement of the brake shoes, it is necessary to force the push rod backwards. With manual force on the push rod, the projecting ring 55 on the detent surface 54 in the forward sleeve 22 enters the groove 73 in the rearward detent surface 76 of the ring and the lifting surfaces 56 and 77 are splice by expanding the tension adjuster clamp, thus disengaging the clamp from the push rod.

The operation of the tension adjuster clamp is similar to that which has been used in other clamp actuator designs since it engages and disengages the actuator rod and moves axially along the push rod under certain conditions. However, the tension adjuster clamp according to the present invention has additional advantages.

The clamp has a conical or bevelled surface that aids in the opening of the clamp during the actuator's output stroke. The conical or bevelled surface in conjunction with placing the skirt of the clamp in the forward direction increases the efficiency of the exit stroke by reducing the drag of the clamp on the push rod.

As described herein, a number of the parts have circular cylindrical internal or external surfaces, for example, the tension adjuster clamp, the forward sleeve 22, etc. It is within the contemplation of the present invention that these surfaces could be cylindrical surfaces in the sense of being surfaces traced by a straight line parallel to an axis and intersecting a fixed curve. The fixed curve can, for example, be an octagon. In such a case, the conical surfaces described above could be replaced by bevelled flat surfaces.

The improved tension adjuster clamp described herein allows the designer to more easily control the amount of force required for retraction of the push rod. Since the portion of the clamp that engages the push rod is lifted away from the push rod, the friction between the clamp and the teeth of the push rod is reduced. The force required to move the clamp along the push rod during maintenance can be better controlled by the design of the conical or beveled interacting surfaces than simply based on friction. The angle of the interacting surfaces will control the axial force required to disengage the tension adjuster clamp.

By causing the skirt of the clamp to extend in the backward direction, the moment arm in which the lifting surfaces act to carry out the disengagement during maintenance is shorter than the moment arm in which the surfaces act of lifting during braking. The difference in the length of the moment arm is the width of the ring on the clamp. This means that a larger axial force will be required for disengagement during maintenance. This is desirable to prevent the push rod from slipping during air release after a service brake stroke. If the slippage takes place, the tension adjuster can not absorb the tension resulting in poor brake performance.

Having thus described the invention in detail and particularity required by the patent laws, what is desired to be protected by a patent is shown in the following claims.

Claims (7)

1 . In a tension adjuster for a fluid-operated brake comprising a housing enclosing a piston cylinder, a piston and a tubular link extending from the piston to drive a brake, a push rod extending into the tubular link , and means for engaging the tubular link and push rod when driven in a brake actuation direction, the tension adjuster comprises a clamp which applies a clamping force on the actuator rod, a retraction stop surface and a the forward retaining surface, the fixed retaining surfaces in relation to the housing, the improvement characterized in that it comprises: The clamp has a tubular skirt section having a tube axis and an elongated annular section at one end of the tubular skirt section, the enlarged annular section having opposite axial retainer surfaces which are generally perpendicular to the tube ex. opposing axial detent surfaces each have a notch therein that defines a conical or bevelled surface facing the pipe example; the forward detent surface has a conical or beveled surface arranged to engage the conical or bevelled surface on a detent surface of the clamp when the clamp carried by the actuator rod reaches the detent surface forwardly; the retraction detent surface has a conical or beveled surface arranged to engage the conical or beveled surface on the other retainer surface of the clamp when the clamp carried by the actuator rod reaches the retraction detent surface and the conical or beveled surfaces are configured in such a way that when they are engaged, the force of the clamp on the push rod is reduced.

2. The tension adjuster according to claim 1, characterized in that the tubular skirt section of the clamp extends axially towards the piston.

3. The tension adjuster in accordance with the claim 1, characterized in that the tubular skirt section and the expanded annular section of the clamp have connected axial grooves extending along and through the tubular wall to almost the end of the tubular skirt section.

4. The tension adjuster according to claim 1, characterized in that the conical or beveled surfaces associated with all the retainer surfaces form substantially the same angle with the tube example.

5. The tension adjuster according to claim 4, characterized in that the conical or bevelled surfaces of the clamp are separated closer to the tube ex ect than the conical or beveled surfaces in the retraction and forward seals.

6. The tension adjuster in accordance with the claim 1, characterized in that the annular section of the tension adjuster clamp has an internal diameter slightly smaller than the tubular skirt section forcing part of the wall of the skirt to be bent elastically to thereby put a tightening force in the pushrod.

7. The tension adjuster according to claim 1, characterized in that the push rod is threaded or serrated.