Brake actuator having collet style slack adjuster

A brake actuator includes a tubular housing member, connected at a first end to a cylindrical housing with a member for admitting fluid, a piston with a sealing member mounted for reciprocal movement within such cylindrical housing, a tubular stem connected at one end to such piston, the tubular stem having a first conical surface at its other end, a piston return disposed intermediate such first piston and the tubular housing, a flange connected at one end to another end of the tubular housing, a pair of abutment surfaces carried by such flange and an externally threaded rod having a first portion extending inside the tubular housing and such tubular stem and a second portion extending outwardly from such tubular housing and through the flange, the improvement of a collet style slack adjuster to adjust for wear of braking elements. Such collet style slack adjuster including a power collet threadedly engaging such threaded rod and a first plurality of flexible fingers connected to such power collet and positioned around such threaded rod. A second conical surface carried by such power collet matingly engages the first tubular stem conical surface for providing a clutch surface. A slack adjuster collet threadedly engages such threaded rod intermediate the power collet and the second end of such threaded rod. A portion of the slack adjuster collet is disposed between the flange abutment surfaces and a second plurality of flexible fingers are connected to the slack adjuster collet and positioned around such threaded rod.

FIELD OF THE INVENTION 
The present invention relates, in general, to fluid pressure responsive 
type brake actuators for use on railway or other similar type vehicles 
and, more particularly, this invention relates to such a fluid pressure 
responsive type brake actuator having an improved collet style slack 
adjusting arrangement incorporated therein which enables substantially 
fewer operating components to be used in such brake actuator. 
BACKGROUND OF THE INVENTION 
Prior to the present invention, it is generally recognized in the art that 
fluid pressure responsive railway car brake actuators have been used on 
passenger transit type vehicles. 
These brake actuators generally consist of a tubular housing member which 
is equipped with a cylinder portion adjacent one end thereof. A piston 
member is slidably disposed within such cylinder portion of the brake 
actuator. Such piston member is positioned to slide under the action of a 
predetermined fluid being communicated to the cylinder portion under 
pressure and against the action of at least one elastic type spring 
retraction means. Such piston member includes a generally hollow shaft 
member connected thereto, which normally does not rotate in relation to 
the tubular housing and in which is axially connected a threaded rod 
member to operate the braking means disposed on the vehicle. 
In this particular prior art type brake actuator, the threaded rod member 
is likewise a nonrotating member with respect to such tubular housing 
member. During the braking action of the threaded rod member, a 
clutch-type, self-adjusting mechanism is provided which will cause the 
relative axial positions between the threaded rod member and the hollow 
shaft member to be changed as necessary when such above-mentioned vehicle 
braking means begins to exhibit excessive brake shoe wear. Such 
self-adjusting mechanism generally consists of an internally threaded 
stopping ring member which is threadedly engaged with a threaded rod 
member and includes a front coupling portion which matingly engages with a 
corresponding front coupling portion of the hollow shaft member to block 
the rotation of the stopping ring member, in relation to the generally 
hollow shaft member, and elastic spring retraction means are provided to 
restore the engagement of these front coupling portions, by the screwing 
of the retaining element in relation to the threaded rod member, after an 
axial separation between these front coupling elements has been achieved. 
In addition, there is a friction ring member disposed between the tubular 
housing member and the threaded rod member. Such friction ring member acts 
on the threaded rod member and slides together with such threaded rod 
member in relation to the tubular housing member, during the normal 
braking operation of such fluid pressure responsive brake actuator, for a 
predetermined brake stroke length. 
There are limit stop means positioned on the tubular housing member in 
order to limit the longitudinal movement of such friction ring member at 
the completion of such predetermined stroke length and to additionally 
allow for an axial sliding movement of the threaded rod member in 
relationship to the hollow shaft member, in order to automatically adjust 
the stroke length of the brake actuator for any excess wear exhibited by 
the vehicle braking means. 
As is evident, therefore, in this known prior art type fluid pressure 
responsive brake actuator the threaded rod member will slide out of the 
hollow shaft member every time the advancement of such hollow shaft member 
is greater than the predetermined normal brake stroke length as defined by 
the above-mentioned limit stop means. 
This brake stroke overtravel length may be due, in most cases, to the 
normal wearing of the brake shoes disposed on the vehicle, the braking 
actuator itself and, also, it can be at least partially due to the normal 
elastic give of the brake force transmission elements, which connect the 
brake actuator to the vehicle brake unit. 
These brake force transmission elements generally consist of two caliper 
arm members. One of such caliper arm members being connected, in a known 
manner, to the brake actuator housing member and the other one of such 
caliper arm members being connected to the free end of such threaded rod 
member. These caliper arm members include a pair of friction brake pads 
which are adapted to engage a disc of the railway car or similar passenger 
transit type vehicle. 
The required action to adjust for the above-mentioned play and/or elastic 
give of the brake actuator has generally been found to be negligible in 
nature. In other words, such play and elastic give encountered is normally 
not of sufficient magnitude to have any adverse effect on the correct 
operation of the fluid pressure responsive brake actuator. However, in 
some particular known applications, the adjustment action required to be 
taken by such self-adjusting mechanism to take up the play encountered due 
to such elastic give of the brake actuator is undesirable and must, 
therefore, be eliminated. 
For a more complete understanding of known prior art type fluid pressure 
responsive brake actuators reference can be made to U.S. Pat. Nos. 
4,676,346 and 4,895,228, the disclosures of which are incorporated herein 
by reference thereto. 
SUMMARY OF THE INVENTION 
In a first aspect, the present invention provides in a brake actuator, for 
use on passenger transit railway and/or similar type vehicles, having a 
tubular housing member, a cylindrical housing member which is closed at a 
first end thereof and is connected at a radially opposed second end 
thereof to a first end of such tubular housing member in a substantially 
fluid tight manner, a fluid communication means is connected to such 
cylindrical housing member for communicating a predetermined fluid, such 
as compressed air, under a predetermined pressure to an interior portion 
of such cylindrical housing member during a brake application on such 
vehicle, a piston member is mounted for reciprocal movement within such 
cylindrical housing member, a sealing means is connected to such piston 
member for sealing the piston member in a fluid tight manner against an 
inner surface of such cylindrical housing member, a hollow tubular portion 
is connected at a first end thereof to and extending outwardly from a 
first surface of such piston member, a first conical surface is disposed 
on an axially opposed second end of such hollow tubular portion, a piston 
member return means is disposed intermediate a first seat carried by the 
first surface of the piston member and a second seat carried by such 
tubular housing member, a flange member is connected at a first end 
thereof to a second end of such tubular housing member, there is a pair of 
abutment surfaces carried by the flange member and an externally threaded 
rod member having a first predetermined portion disposed adjacent a first 
end thereof extending coaxially inside such tubular housing member and 
such tubular housing portion. A second predetermined portion of such 
threaded rod member extends outwardly from the tubular housing member and 
through the flange member adjacent a second end thereof, the improvement 
therewith of a collet style slack adjusting mechanism which adjusts for 
wear of the braking elements disposed on such vehicle. Such collet style 
slack adjusting mechanism includes a power collet member threadedly 
engaged with such threaded rod member. Such collet style slack adjusting 
mechanism further includes a first predetermined plurality of elongated 
and generally flexible finger members connected to the power collet member 
which are positioned around a periphery of the threaded rod member. A 
second conical surface is carried by the power collet member. Such second 
conical surface is matingly engageable with the first conical surface 
carried by the tubular housing portion for providing a clutch surface. 
There is a slack adjuster collet member threadedly engaged with such 
threaded rod member which is disposed intermediate the power collet member 
and the second end of such threaded rod member. At least a portion of such 
slack adjuster collet member is disposed between such pair of abutment 
surfaces carried by the flange member. Additionally, there is a second 
predetermined plurality of elongated and generally flexible finger members 
connected to such slack adjuster collet member which are also positioned 
around the periphery of such threaded rod member. 
In a second aspect, the present invention provides a fluid pressure 
responsive brake actuator having an improved collet style slack adjusting 
mechanism incorporated therein, for use on passenger transit railway and 
other similar type vehicles, to adjust for any excess wear exhibited by 
the braking elements disposed on such vehicles. The brake actuator, 
according to the present invention, includes an elongated generally hollow 
tubular housing member. A cylindrical housing member, closed at a first 
end thereof, is connected at a radially opposed second end thereof to a 
first end of such tubular housing member in a substantially fluid tight 
manner. There is a fluid communication means connected to such cylindrical 
housing member for communicating a predetermined fluid under a 
predetermined pressure to an interior portion of the cylindrical housing 
member during a brake application on such vehicle. A piston member is 
mounted for reciprocal longitudinal movement within such cylindrical 
housing member. There is a sealing means connected to the piston member 
for sealing such piston member in a fluid tight manner against an inner 
surface of the cylindrical housing member. An elongated and generally 
hollow tubular housing portion is connected at a first end thereof to and 
extends outwardly from a first surface of such piston member. A first 
conical surface is disposed at an axially opposed second end of the hollow 
tubular housing portion. The brake actuator further includes a piston 
member return means which is disposed between a first seat carried by the 
first surface of such piston member and a second seat carried by such 
tubular housing member for returning the piston member to a non brake 
applying position upon evacuation of such predetermined fluid pressure 
from the interior portion of such cylindrical housing member. A flange 
member is connected at a first end thereof to a second end of such tubular 
housing member. Such flange member carries a pair of abutment surfaces. 
There is an externally threaded rod member which has a first predetermined 
portion disposed adjacent a first end thereof extending coaxially inside 
such tubular housing member and the tubular housing portion and a second 
predetermined portion which extends outwardly from such tubular housing 
member and through the flange member adjacent a second end thereof. A 
power collet member is threadedly engaged with such threaded rod member. 
Such power collet member has a first predetermined plurality of elongated 
and generally flexible finger members connected thereto which are 
positioned around a periphery of such threaded rod member. A second 
conical surface is carried by the power collet member which is matingly 
engageable with such first conical surface carried by the tubular housing 
portion for providing a clutch surface. There is a slack adjuster collet 
member threadedly engaged with the threaded rod member intermediate such 
power collet member and the second end of such threaded rod member. At 
least a portion of the slack adjuster collet member is disposed between 
such pair of abutment surfaces carried by such flange member. There is a 
second predetermined plurality of elongated and generally flexible finger 
members connected to such slack adjuster collet member. Such second 
plurality of finger members are also positioned around the periphery of 
such threaded rod member. 
OBJECTS OF THE INVENTION 
It is, therefore, one of the primary objects of the present invention to 
provide a railway and/or other similar type vehicle fluid pressure 
operated brake actuator having an improved collet style slack adjusting 
mechanism which requires significantly fewer operating components. 
Another object of the present invention is to provide a railway and/or 
other similar type vehicle fluid pressure operated brake actuator having 
an improved collet style slack adjusting mechanism which is significantly 
more maintenance free than previously used fluid pressure responsive brake 
actuators. 
Still another object of the present invention is to provide a railway 
and/or other similar type vehicle fluid pressure operated brake actuator 
having an improved collet style slack adjusting mechanism which is 
generally less expensive to manufacture, due to significantly reduced 
assembly time required when compared to the assembly time which was 
required for previously used fluid pressure responsive brake actuators. 
Yet still another object of the present invention is to provide a railway 
and/or other similar type vehicle fluid pressure operated brake actuator 
having an improved collet style slack adjusting mechanism which can be 
easily retrofitted to existing railway and/or other similar type passenger 
transit vehicles. 
An additional object of the present invention is to provide a railway 
and/or other similar type vehicle fluid pressure operated brake actuator 
having an improved collet style slack adjusting mechanism which does not 
require any special equipment to install on a railway and/or other similar 
type passenger transit vehicle. 
A further object of the present invention is to provide a railway and/or 
other similar type vehicle fluid pressure operated brake actuator having 
an improved collet style slack adjusting mechanism which is considerably 
lighter in weight than previously used fluid pressure responsive brake 
actuators. 
Still yet another object of the present invention is to provide a railway 
and/or other similar type vehicle fluid pressure operated brake actuator 
having an improved collet style slack adjusting mechanism which will 
exhibit a relatively long operating life. 
In addition to the numerous objects and advantages of the present invention 
which have been described in some detail above, various other objects and 
advantages of the instant invention will become more readily apparent to 
those persons who are skilled in the railway and/or other similar type 
vehicle braking art from the following more detailed description of the 
invention, particularly, when such description is taken in conjunction 
with the attached drawing Figures and with the appended claims.

BRIEF DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS OF THE INVENTION 
Prior to proceeding to the more detailed description of the present 
invention, it should be pointed out that, for the sake of clarity, 
identical components, having identical functions, have been identified 
with identical reference numerals throughout the several views illustrated 
in the drawings. 
Now reference is made more particularly to FIGS. 1 through 4 of the 
drawings. Illustrated therein is a presently preferred embodiment of a 
fluid pressure operated brake actuator, generally designated, 10 for use 
on railway and/or similar type vehicles for controlling a braking caliper 
(not shown) which, in turn, is connected to a pair of friction brake pads 
(not shown). Such brake actuator 10 has incorporated therein an improved 
collet style slack adjusting mechanism, generally designated, 20 which is 
constructed according to the present invention. 
The fluid pressure operated brake actuator 10, also, includes a generally 
hollow tubular housing member 12 which is equipped at one end thereof with 
a cylindrical housing member 14 which, preferably, is generally 
cup-shaped. Such cylindrical housing member 14 is equipped with a fluid 
connection fitting (not shown) on a predetermined portion of an end wall 
thereof to enable communication of a predetermined fluid, under a 
predetermined pressure, to a predetermined portion of the interior portion 
of such cylindrical housing member 14 during a brake application stroke 
being called for on the vehicle's brake system. Although the instant 
invention is not intended to be limited thereto, the presently preferred 
fluid to be used in the brake actuator 10 will normally be compressed air. 
Mounted for reciprocal longitudinal movement within the cylindrical housing 
member 14 is a piston member 16. There is a sealing means, generally 
designated, 30 provided for sealing such piston member 16, in a 
substantially fluid tight manner, against the inner surface of the 
cylindrical housing member 14. According to the presently preferred 
embodiment of the instant invention, such sealing means 30 will generally 
be in the form of a packing cup 18 engaged with a first surface 21 of such 
piston member 16. As is clearly shown in the drawing Figures, this first 
surface of such piston member 16 faces the end wall of the cylindrical 
housing member 14. 
It should be noted here that other forms of sealing means 30, such as, by 
way of example only, an o-ring type seal (not shown) can be disposed 
around the outer periphery of such piston member 16 may be used just as 
effectively. Accordingly, it is to be understood that such other forms of 
sealing means 30 are considered to be within the scope of the present 
invention. 
Secured at a first end thereof to an axially opposed second surface 38 of 
such piston member 16 is a stem-like member comprised of an elongated and 
generally hollow tubular portion 40. Such hollow tubular portion 40 
carries a first conical surface 42 at an axially opposed second end 
thereof. The functional operation of such conical surface 42 will become 
more clear to those skilled in the art as the detailed description of the 
presently preferred embodiment of the invention proceeds. 
When a braking application is being called for on the vehicle and fluid 
pressure is being communicated to the brake actuator 10, thereby causing 
the piston member 16 to move to the right as seen in the drawing Figures, 
such piston member 16 is operating against the action of a coil spring 
member 22 disposed between an axially opposed second surface 24 of such 
piston member 16 and a surface 27 located on the tubular housing member 
12. 
Secured to the outer portion of the tubular housing member 12, adjacent the 
cylindrical housing member 14, is a brake actuator 10 mounting flange 26 
used for attaching such brake actuator 10 to the vehicle (not shown). 
At least a predetermined portion of an externally threaded rod member 28 is 
positioned in a manner such that it extends coaxially inside such tubular 
housing member 12. The threaded rod member 28 has an external end thereof 
which projects outwardly from such tubular housing member 12 and through a 
flange member 32. 
Such flange member 32 is connected, in any convenient manner, to the outer 
end of such tubular housing member 12 which is disposed radially opposite 
the cylindrical housing member 14. This flange member 32 carries a pair of 
abutment shoulder portions 34 and 36 which serve as axially opposed limit 
stop means. The functional operation of such pair of abutment shoulder 
portions 34 and 36 disposed on such flange member 32 will become more 
clear as the detailed description of the invention proceeds. 
The improved collet style slack adjusting mechanism 20, manufactured 
according to the presently preferred embodiment of the invention, includes 
a power collet member 44. Such power collet member 44 is threadedly 
engaged with the threaded rod member 28. The power collet member 44 
includes a predetermined plurality of elongated and generally flexible 
finger members 46 which are disposed around a portion of the periphery of 
the threaded rod member 28. 
Another essential element of the improved collet style slack adjusting 
mechanism is a slack adjuster collet member 48 which, also, includes a 
second predetermined plurality of elongated and generally flexible finger 
members 50 which are disposed around another portion of the threaded rod 
member 28. 
During a normal operation of the brake actuator 10, i.e., with a correct 
friction brake shoe clearance on the vehicle, a predetermined fluid under 
a predetermined pressure is directly communicated to the interior portion 
52 of the cylindrical housing member 14 behind the packing cup 18. This 
predetermined fluid pressure will be at least sufficient to force the 
piston member 16 to advance in a forward direction. As the piston member 
16 continues to move in such forward direction, the conical surface 42, 
carried by the tubular housing portion 40, starts to engage a mating 
conical surface 43 disposed on the power collet member 44. With continued 
movement of the conical surface 42 over the conical surface 43 on the 
power collet member 44 such conical surface 42 forces the first plurality 
of flexible finger members 46 of the power collet member 44 to close onto 
the threaded rod member 28. This action causes extension of the threaded 
rod member 28 forward and applies a braking force to the disc brake 
caliper assembly (not shown). 
At the time such fluid pressure is released from such interior portion 52 
of the cylindrical housing member 14, the coil spring member 22 will force 
the piston member 16 and the packing cup 18 secured thereto to return to 
it's original non brake application position. It should be noted that on 
the return stroke of the piston member 16, the abutment shoulder portion 
54 disposed on the power collet member 44 and the abutment shoulder 
portion 56 disposed on the tubular housing portion 40 of piston member 16 
will engage and thereby pull the threaded rod member 28 back. 
When, on the other hand, there is exhibited an excessive brake shoe 
clearance on the brake system disposed on the vehicle, the slack adjuster 
collet member 48 will bottom on the abutment shoulder portion 34 disposed 
on flange member 32. Once the slack adjuster collet member 48 bottoms out 
on the abutment shoulder portion 34 the threaded rod member 28 will be 
pushed through the slack adjuster collet member 48 and the plurality of 
flexible finger members 50 will flex outwardly, thereby enabling the 
threads on the slack adjuster collet member 48 and the threaded rod member 
28 to become disengaged. In the meantime, the threads disposed on the 
power collet member 44 will not be disengaged from the threads on the 
threaded rod member 28 because they are still wedged down tightly by the 
conical surface 42 carried by the tubular housing portion 40 of the piston 
member 16. 
On the return stroke of the brake actuator 10, the slack adjuster collet 
member 48 and the threaded rod member 28 will generally travel back until 
the slack adjuster collet member 48 bottoms out on the axially opposed 
abutment shoulder portion 36 disposed on the flange member 32. At this 
point, the slack adjuster collet member 48 will hold the threaded rod 
member 28 in place. At the same time, however, The plurality of flexible 
finger members 46 attached to the power collet member 44, being unwedged 
from the conical surface 42 and pulled by the surface 56 contacting 
surface 54, will flex outwardly thereby allowing the power collet member 
to slip over the threaded rod member 28. It should be noted that the 
plurality of flexible finger members 50 which are attached to the slack 
adjuster collet member 48 are shorter than the plurality of flexible 
finger members 46 attached to the power collet member 44. For this reason, 
such plurality of flexible finger members 46 are generally more flexible 
and, consequently, hold less force. The positive clearance depends on the 
clearance provided between the pair of abutment shoulder portions 34 and 
36 disposed on the flange member 32 as well as the length of the end of 
the slack adjuster collet member 48. 
While a number of presently preferred embodiments of the brake actuator 
collet style slack adjuster have been described in detail above with 
particular reference to the drawing Figures, it should be understood that 
various other modifications and adaptations of the present invention may 
be made by those persons who are skilled in the passenger transit vehicle 
braking art without departing from the spirit and scope of the appended 
claims.