Air brake slack adjustment and measurement tools

Air brake adjustment and measurement tools where the adjustment tool includes a long handle portion having a gripper assembly attached to one end and a socket wrench drive attached to the other end. The gripper assembly has a pair of facing jaw members adapted to engage opposing edges of a vehicle's air brake slack adjustment. The measuring tool includes a scale, and a permanent magnet attached to one end of the scale. In use, the measuring tool is placed next to the clevis rod of the vehicle's air brake assembly, and the adjustment tool is used to move the air brake slack adjustment between a braking and a non-braking position. The stroke of the clevis rod is measured by the measuring tool, and is adjusted by a socket wrench attached to a socket drive of the adjustment tool.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to hand tools, and more particularly to 
hand tools used to adjust the brake mechanism of a motor vehicle. 
2. Description of the Prior Art 
Large motorized vehicles such as multiple-wheeled trucks often use air 
brakes on their rear wheels. A typical air brake assembly includes a 
mounting bracket, an air brake chamber attached to the bracket, a clevis 
rod extending from the air brake chamber, and an air brake slack 
adjustment having one end pivotably supported by the bracket and having 
its other end pivotably attached to end of the clevis rod. The air brake 
chamber includes a diaphragm which is exposed to atmospheric pressure on 
one side and which is coupled to a pressurized air source on its other 
side. When air pressure is applied to the air brake chamber, the diaphragm 
causes the clevis rod to extend outwardly from the air brake chamber to 
pivot the air brake slack adjustment from a non-braking position to a 
braking position. The distance that the clevis rod moves between the 
non-braking and braking position is known as the clevis rod stroke. 
As the brake linings wear, the air brake slack adjustment must be adjusted 
to maintain the clevis rod stroke within specified limits. Thus, it is 
necessary for a large vehicle operator to periodically check and readjust 
the air brake slack adjustments of the vehicle to maintain the clevis rod 
stroke within a specified range. 
A problem is encountered during the aforementioned procedure in that it is 
difficult to manually move the air brake slack adjustment between its 
non-braking and its braking position. Located within the air brake chamber 
is a strong compression spring which biases the clevis rod towards the air 
brake chamber and thus its non-braking position. It is very difficult to 
manually overcome this biasing force and to simultaneously measure the 
stroke of the clevis rod. 
Some maintenance manuals recommend that the mechanic performing the 
adjustment procedure disconnect the pressure hose from the air brake 
chamber and connect the air brake chamber to an 80 PSI air pressure source 
to cause the clevis rod to move to its braking position. This method for 
moving the clevis rod from its non-braking to its braking position is, 
however, inconvenient and requires compressors or other special equipment. 
Most commonly, a mechanic will attempt to move the air brake slack 
adjustment with one hand, and measure the length of the clevis rod stroke 
with a ruler held in his other hand. This tiresome two-handed operation is 
made even more difficult by the cramped quarters around the air brake 
mechanism in which the mechanic must work. 
What the prior art fails to disclose is a simple, manually operated tool 
for pivoting the air brake slack adjustment between its braking and 
non-braking position and for measuring the clevis rod stroke. Furthermore, 
the prior art does not disclose a pair of tools which allow the clevis rod 
stroke to be measured and adjusted with one hand. 
SUMMARY OF THE INVENTION 
A major object of this invention is to provide a pair of simple, manual 
tools for measuring and adjusting the air brake slack adjustment of a 
vehicle's air brake assembly. 
A further object of this invention is to provide a multi-purpose adjustment 
tool which can both aid in the measurement of the clevis rod stroke and 
which can further be used to adjust the adjustment screw on the air brake 
slack adjustment. 
Yet another object of this invention is to provide air brake measurement 
and adjustment tools that only require one hand to operate. 
Briefly, the invention comprises an adjustment tool and a measuring tool. 
The adjustment tool includes an elongated handle portion, a gripper 
assembly attached to one end of the handle portion, and a drive member 
attached to the other end of the handle portion. The gripper assembly 
includes an inner jaw member attached to the handle, an outer jaw member 
spaced from the inner jaw member, and a connector member coupling the 
outer jaw member to the inner jaw member. Preferably the connector member 
is substantially trapezoidal in shape and the two jaw members are attached 
to opposing non-parallel edges of the connector member such that they are 
angled towards each other. The socket wrench drive is adapted to hold a 
standard socket wrench which engages the adjustment screw of the air brake 
slack adjustment. 
The measuring tool includes an elongated scale and a permanent magnet 
attached to one end of the scale to hold the scale substantially parallel 
to the air brake assembly's clevis rod. The scale is used to measure the 
length of the stroke of the clevis rod as it moves from a non-braking to a 
braking position. 
In use, the magnet of the measuring tool is placed against a portion of the 
air brake assembly such that the scale portion is substantially parallel 
to the clevis rod. The gripper assembly of the adjustment tool is engaged 
with opposing edges of the vehicle's air brake slack adjustment, such that 
torque applied to the handle will move the air brake slack adjustment and 
the clevis rod between their braking and non-braking positions. The stroke 
of the clevis rod is read directly from the scale. If the stroke is too 
long or too short, a socket wrench is engaged with the socket wrench drive 
of the adjustment tool and the adjustment screw of the air slack 
adjustment is rotated until the clevis rod stroke is within its proscribed 
limits. 
An advantage of this invention is that a pair of simple, manual tools can 
be used to properly adjust the clevis rod stroke of a vehicle's air brake 
assembly. 
Another advantage of this invention is that a mechanic can measure and 
adjust the clevis rod stroke while using only one hand. 
These and other objects and advantages of the present invention will no 
doubt become apparent upon a reading of the following descriptions and a 
study of the several figures of the drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
Referring to FIGS. 1-4 and 6, an air brake adjustment tool in accordance 
with the present invention includes an elongated handle 1 provided with a 
gripper portion at one end and a socket wrench drive at the other end. The 
gripper portion includes an outer jaw member 2, an inner jaw member 3, and 
a connector member 4. Inner jaw member 3 is attached to the tapered end of 
handle 6, preferably by welding. 
As best seen in FIG. 3, connector member 4 is substantially trapezoidal in 
shape having two non-parallel edges of substantially equal length and two 
parallel edges of different lengths. The shorter of the two parallel edges 
of connector member 4 is provided with an arc shaped relief 5 for a 
purpose to be discussed subsequently. 
As seen in the figures, jaw members 2 and 3 are attached to the opposing, 
non-parallel edges of connector member 4. Thus, the two jaw members are 
angled towards each other in the direction of the handle 1. As best seen 
in FIGS. 1 and 6, connector member 4 is attached to mid-length portions of 
jaw members 2 and 3, preferably by weldments or the like. 
Referring once again to FIGS. 1 and 6, the attachment of the connector 
member 4 to the jaw members 2 and 3 divides the jaw members into left side 
portions and right side portions. More specifically, portion 2L of jaw 
member 2 and portion 3L of jaw member 3 are the left side portion of the 
gripper member, and portion 2R of jaw member 2 and portion 3R of jaw 
member 3 are the right hand portion of the gripper member. The 
significance of the left side portion and the right side portion of the 
gripper member will be discussed subsequently with reference to the 
operation of this device. 
Handle portion 1 is preferably provided with a grip area 6 which, in the 
illustrated embodiment, is created by knurling a portion of handle 1 that 
is distal from the gripper member. Of course, other grips could be 
provided, such as a rubber or plastic sleeve around all or a portion of 
handle 1. 
Referring now more specifically to FIGS. 1, 2, and 4, a socket wrench 
square drive 7 is attached to an opposing end of handle 1, preferably by a 
weldment 9. The square drive 7 is preferably beveled on the top, as shown 
in FIG. 2, and is provided with a detent mechanism 8. Square drive 7 is 
preferably a standard 3/8" drive, and is attached at substantially right 
angles to the length of handle 1. As seen in FIG. 2, a standard socket 
wrench 10 can engage square drive 7 for purposes to be discussed 
subsequently. 
In FIG. 5, an air brake assembly's air brake slack adjustment 11 is shown 
to be pivotably supported by a slack adjustment pin 12. Attached to the 
side of slack adjustment 11 is a locking sleeve 13 and an adjustment screw 
14. The locking sleeve 13 is coaxially disposed around adjustment screw 14 
and is axially movable between a locking position and a non-locking 
position. When socket wrench 10 is engaged with square drive 7 of the 
present invention, adjustment screw 14 can engage the inner faces of 
socket wrench 10 while the outer rim of the socket wrench pushes sleeve 13 
axially towards air brake slack adjustment 11 to its unlocked position. 
Then, by applying torque to handle 1, the air brake slack adjustment may 
be adjusted. 
Referring now to FIG. 7, a vehicle's air brake assembly further includes a 
mounting bracket 15, a clevis pin 17 attaching a clevis 18 to air brake 
slack adjustment 11, a clevis rod 19, a connector 20 attaching an end of 
clevis rod 19 to clevis 18, a mounting bracket flange 21, and an air brake 
chamber 22 attached to mounting bracket flange 21. 
Disposed within air brake chamber 22 is a diaphragm (not shown) which 
causes clevis rod 19 to move between its braking and its non-braking 
position. A strong compression spring (also not shown) within the air 
brake chamber 22 biases the clevis rod 19 towards its static or 
non-braking position. The stroke of clevis rod 19 is indicated by the 
distance between lines 11A and 11B. At 11A, clevis rod 19, clevis 18, and 
air brake slack adjustment 11 are at their static or non-braking position. 
At position 11B, clevis rod 19, clevis 18, and air brake slack adjustment 
11 are in their braking position. 
Also shown in FIG. 7 is the measuring tool of the present invention. The 
tool includes a scale portion 23 provided with a number of gradations, and 
a permanent magnet 24 attached to one end of scale 23. The exposed face of 
magnet 24 is preferably at substantially right angles to the length of 
scale 23. In use, magnet 24 attaches either to mounting bracket 15 or 
bracket 21 such that scale 23 is substantially parallel to clevis rod 19. 
It should be noted that the stroke of clevis rod 19 is not quite parallel 
to scale 23, but the amount of deviation is not substantial enough to make 
a difference to the measurement. 
In FIG. 8, an air brake adjustment tool of the present invention is shown 
to be engaged with the air brake slack adjustment 11 of a slightly 
different air brake assembly. In this assembly type, clevis 18 is eyebolt 
shaped, as shown, and a hole 16 is provided at a lower extremity of air 
brake slack adjustment 11 to provide additional travel adjustment of the 
clevis rod. Arc shaped relief 5 is provided in connector member 4 to allow 
the gripper assembly of the tool to be placed as far down as possible on 
air brake slack adjustment 11 to provide the greatest mechanical 
advantage. As can be seen in the figure, jaw member 2 and jaw member 3 
engage opposing edges of air brake slack adjustment 11 such that torque 
exerted on handle 1 will easily pull clevis rod 19 to its extended or 
non-braking position against the biasing force of the spring within air 
brake chamber 22. 
In operation, and with special reference to FIGS. 7 and 8, the measuring 
device 23/24 is first placed in position next to clevis rod 19, and jaws 2 
and 3 of the gripper portion of the adjustment tool are engaged with 
opposing edges of air brake slack adjustment 11. Torque is then applied to 
handle 1 at grip 6 to move the air brake slack adjustment against the 
biasing force of the spring within air brake member 22 from the 
non-braking position shown in FIG. 7 at 11/18 to a non-braking position 
shown at 11'/18'. The stroke of clevis rod 19 is determined by subtracting 
the measurements taken at 11A and 11B along scale 23. If the travel or 
stroke of clevis rod 19 is out of the recommended range, air brake slack 
adjustment 11 can be adjusted by adjustment screw 14, as was previously 
described with reference to FIG. 5. The measurement procedure is then 
repeated to ensure that the newly adjusted clevis rod stroke is within the 
prescribed range. 
The air brake adjustment tool of FIG. 8 is engaged with the air brake slack 
adjustment of a right-side air brake assembly. Thus, portions 2R and 3R of 
jaw members 2 and 3, respectively, are engaged with the edges of the air 
brake slack adjustment 11. On the other side of the truck, the situation 
would be reversed with portions 2L and 3L of jaws 2 and 3, respectively, 
engaging the opposing edges of air brake slack adjustment 11 of a 
left-side air brake assembly. 
While this invention has been described in terms of a few preferred 
embodiments, it is contemplated that persons reading the preceding 
descriptions and studying the drawing will realize various alterations, 
permutations and modifications thereof. It is therefore intended that the 
following appended claims be interpreted as including all such 
alterations, permutations and modifications as fall within the true spirit 
and scope of the present invention.