Reversible radial vane air motor

The invention relates to a reversible radial vane air motor with manual speed control that is capable of attaining excellent forward horsepower. The invention includes a bypass air passage and an exhaust deflector that routes pressurized air through the backside of the motor when the motor is operated in reverse. A reverse control lever controls the flow of air through the bypass passage and opens a reverse exhaust passage. The motor may also be equipped with a centrifugal governor for controlling the flow of air in the forward operation with the governor being bypassed in reverse operation.

TECHNICAL FIELD 
This invention relates to a reversible air motor to be used in portable 
pneumatic tools such as a pneumatic drill or nutrunner. The motor is 
capable of achieving nearly the full horsepower of a "forward only" motor 
in a forward rotation. Pressurized air is routed through a bypass passage 
into the back of the motor through the forward exhaust. The motor provides 
fingertip control of the motor speed in a reverse mode. 
BACKGROUND 
Radial vane air motors, or pneumatic motors, are widely used in industry 
particularly in portable tools. The design of such motors has evolved over 
the years to an optimum geometry for both "forward only" and "reversible" 
types. The design of the reversible motors, however, provides limited 
horsepower in forward operation as compared with a "forward only" motor. 
For example, one type of reversible motor is a mirror image type that is 
capable of producing in a forward rotation only seventy to eighty-five 
percent as much horsepower as a "forward only" type motor with the same 
displacement. 
Conventional reversible radial vane air motors have ports and passages that 
conduct all or a part of the exhaust air through a reversing valve located 
on the end plate of the motor or in a backhead adjacent to the motor. 
Incorporating a governor into reversible motors makes these passages more 
complex, and the forward horsepower is reduced even further by 
backpressure through the reversing valve and the ports and passages. 
Horsepower in the forward direction of a reversible motor is often enhanced 
by non-symmetric placement of ports. This results in a reduction of 
horsepower in the reverse direction. Another means for increasing 
horsepower in the forward direction is to include complex and elaborate 
slides and valves, but these complex motors have proven impractical in 
portable air tools. Thus, a need existed for a reversible radial vane 
governed air motor that can be easily incorporated into a portable 
pneumatic tool and achieve near full horsepower in the forward direction. 
SUMMARY OF THE INVENTION 
The present invention provides a reversible radial vane air motor with 
manual speed control that is capable of nearly attaining the full forward 
horsepower of a "forward only" radial vane motor and providing greater 
horsepower in a forward operation than conventional reversible motors. The 
invention also provides means for utilizing a centrifugal speed governor 
in a forward rotation while bypassing it in a reverse rotation. 
Conventional types of reversing valves are not used, but rather, the 
invention provides a direct and unencumbered air conducting system for 
both forward and reverse operation of the motor. 
The invention provides a reversible radial vane air motor that includes 
forward inlets and exhaust means, a reverse conducting means, a reverse 
exhaust means, and a reverse control means. In one embodiment of the 
invention, the reverse conducting means includes a bypass passage for 
conducting pressurized air from an external source to a rotor cavity of 
the motor such that the rotor is turned in reverse. An exhaust deflector 
acts to close the forward exhaust means and route the incoming air from 
the bypass passage into the rotor cavity. The reverse exhaust means 
includes a passage and an atmospheric exhaust valve. The reverse control 
means controls the flow of air in the bypass passage by variably opening a 
control valve. The reverse control means also variably controls the 
exhaust valve. During forward operation of the motor, both the reverse 
conducting means and the reverse exhaust means are closed to the flow of 
air. 
In another embodiment of the invention, the motor is operated in reverse by 
first closing the air inlet means for forward operation. After the air 
supply to the motor is shut off, a reverse control lever is shifted from 
its forward position to a variable reverse position. This action actuates 
the reverse control means and opens the bypass air passage to the flow of 
air. The bypass passage allows the air to bypass air controls means for 10 
forward operation of the motor. In one embodiment, these forward controls 
may include a throttle valve and a centrifugal governor. The exhaust 
deflector closes the forward exhaust means and routes the pressurized air 
in the bypass passage into the rotor cavity. The air flows in the opposite 
direction of the forward rotation thereby turning the rotor in reverse. 
The reverse air bypasses the forward air control means and exits the motor 
through a reverse air exhaust that is also opened by the shifting of the 
reverse control lever. When the reverse lever is returned to the forward 
position, the bypass passage is closed to the flow of air, the exhaust 
deflector is returned to its forward position, and the reverse exhaust is 
closed as the motor is returned to the forward operation mode.

DETAILED DESCRIPTION 
The present invention relates to a reversible air motor that has radial 
vanes. The invention provides manual means to reverse the motor and a 
unique means of routing the pressurized air through the motor in a reverse 
direction. The motor is so designed as to achieve nearly full horsepower 
in a forward rotation as a "forward only" motor and to provide manual 
speed control in a reverse rotation. The motor may include a centrifugal 
governor that governs the flow of air to the motor in a forward rotation 
but is bypassed in reverse operation. The invention may be used in almost 
any pneumatic tool and is particularly adapted for use in portable 
pneumatic tools. 
Referring to the drawing, FIG. 1 shows a partial cutaway and 
cross-sectional view of one embodiment of the invention. A reversible 
motor 10 is included within a housing 12. For forward operation, 
pressurized air enters an inlet bushing 14 from an external source and 
flows through a tiltable throttle valve 16 (shown closed in FIG. 1). 
Tiltable throttle valve 16 is operated by a throttle lever 15 which acts 
on push rod 21 which is engaged with lever arm 17 to tilt open throttle 
valve 16 against a compression throttle spring 19. As throttle valve 16 is 
opened, pressurized air flows through inlet passage 18, past a centrifugal 
governor 20 (shown open) and into cavity 22. The pressurized air then 
flows into a slot in rear end plate 24, enters a rotor cavity 25 (shown in 
FIG. 2) and turns rotor 26 in a forward direction. The spent air is then 
exhausted through slots 28 in motor cylinder 30 into annular cavity 32. 
The air is then routed through radial holes 34 into muffler cavity 36, 
through muffler element 38 and vented to the atmosphere through 
atmospheric exhaust slots 40. 
FIG. 2 illustrates the inner workings of motor 10 and the relation of the 
inlet and exhaust air slots. For forward operation of the motor, 
pressurized air enters through inlet port 42 into rotor cavity 25. The air 
pushes on radial vanes 46 such that the rotor 26 turns in a clockwise 
rotation as viewed in FIG. 2, and the air exhausts through slots 28, 
cavity 32, radial holes 34, muffler cavity 36 and out atmospheric exhaust 
slots 40 (not shown in the cross-sectional view of FIG. 2). This 
configuration provides a reversible radial vane motor with good horsepower 
and air efficiency in the forward direction. 
To operate the motor in reverse, the tiltable throttle valve 16 must be 
closed. This may be accomplished as shown in FIG. 1 by releasing throttle 
lever 15 and allowing throttle spring 19 to close throttle valve 16. This 
shuts off the flow of air through inlet passage 18 to the motor, thereby 
stopping the forward rotation of the rotor 26. 
In one embodiment of the invention, the motor is operated in the reverse 
mode by shifting lever 48, shown in phantom lines in FIG. 1 and shown in 
an exploded view in FIG. 4, to the reverse position. This results in 
several things happening. First, it opens the bypass air passage 50 to the 
flow of pressurized air. Passage 50 receives the incoming pressurized air 
through an opening 55 from cavity 56 which is located on the feed side of 
throttle valve 16. Opening 55 is always open to receive incoming air, but 
in the forward operation of the motor, passage 50 is closed by a ball 
valve 62 which is held against seat 64 by a compression spring 66. The 
ball valve 62 also controls the flow of air through passage 50 in reverse 
operation of the motor. When the lever 48 is shifted to the reverse 
position, lift pin 68, which is attached to lever 48, forces ball 62 
against spring 66 and opens passage 50. Incoming pressurized air flows 
from inlet cavity 56 through passage 50, past ball 62 and into passage 70. 
The air in passage 70 then flows through annular passage 72 and into 
deflector cavity 74. In a preferred embodiment of the invention, 
pressurized air in cavity 74 imposes a force against a pressure-actuated 
exhaust deflector 76 which is slidably mounted on motor housing 12. The 
exhaust deflector 76 is forced by the pressurized air in cavity 74 against 
a compression spring 78, until the deflector stops against a 
circumferential ridge 80 on the motor housing 12. The exhaust deflector 
may be actuated by means other than the air pressure in cavity 74, such as 
by a valve or switch. 
As the exhaust deflector 76 slides up against the ridge 80, it closes off 
the atmospheric exhaust route used for forward rotation. A portion of 
deflector 76 is positioned to block the flow of air from radial holes 34 
to muffler cavity 36. The incoming pressurized air in deflector cavity 74 
is routed by deflector 76 from cavity 74 through the radial holes 34 to 
annular cavity 32. The pressurized air enters the rotor cavity 25 through 
slots 28 and drives the rotor 26 in a reverse direction (counterclockwise 
as shown in FIG. 2), causing the motor to run in reverse. A suitable 
method must be used to "kick-out" the rotor vanes 46, such as spring-means 
47. The expended air is then exhausted from rotor cavity 25 through port 
42, the rear end plate 24 and into cavity 22. 
Shifting lever 48 to the reverse position also opens a reverse exhaust 
port, thereby allowing air to flow from cavity 22 through passage 82 and 
out of the motor housing 12. In a preferred embodiment, as lever 48 is 
shifted to the reverse position, a rotary valve 84 rotates inside bushing 
86 to match up the openings 88 and 90 in the valve 84 and the bushing 86 
respectively. These are illustrated in an exploded fashion in FIG. 4. FIG. 
3 shows a cross-sectional view along line 3--3 of the reverse air exhaust 
system showing the rotary valve 84 inside bushing 86. In reverse mode, the 
air in cavity 22 is exhausted through passage 82, through openings 88 and 
90 into the interior of valve 84. The air is then vented through an 
exhaust hole 92 in valve 84 into muffler cavity 94 and out slots 96 to the 
atmosphere. In forward operation of the motor, this reverse exhaust is 
shut off by the positioning of control lever 48 in the forward position 
which does not create any opening through valve 84 since the openings 88 
and 90 are not matched up. 
The speed of the motor in reverse can be controlled with lever 48. As lever 
48 is shifted to reverse mode, lift pin 68 forces ball 62 against spring 
66, thereby opening the passage 50 to the flow of incoming pressurized 
air. The range of movement on lever 48 is variable and controls the flow 
of air through passage 50 and the motor speed in reverse by variably 
forcing ball 62 against spring 66 through lift pin 68 to allow air to flow 
through passage 50 in the reverse operation of the motor. 
When lever 48 is released from a reverse mode position, spring 66 forces 
ball 62 back against seat 64 thereby closing the reverse air passage 50 
and shutting off the flow of reverse air to the motor 10. Spring 66 also 
forces lift pin 68 down on lever 48 thereby returning lever 48 to its 
forward mode position. This also causes valve 84 to rotate within bushing 
86 to a closed position thereby closing the reverse exhaust through 
passage 82. As the reverse air flow through passage 50 into cavity 74 is 
cut off, spring 78 forces exhaust deflector 76 back to its forward mode 
position, thereby opening the forward exhaust through holes 34, cavity 36 
and slots 40. Thus, with the return of lever 48 to the forward mode 
position, all other components are returned to readiness for forward 
operation of the motor. 
The embodiment of the present invention shown in FIG. 1 includes a 
turnbuckle collar 97 that contains deflector cavity 74. The collar 97 has 
an internal right-hand thread and an internal left-hand thread allowing 
the motor backhead to be oriented in any rotational position while 
orienting the motor into the motor housing 12. 
The reversible motor of the present invention can be used in almost any 
pneumatic tool. It is particularly adapted for use in a portable pneumatic 
tool such as a drill or nutrunner. FIG. 5 shows the motor 100 of the 
present invention incorporated within an automatic positive feed drill 
102, although it would be capable of use in any type of drill. The drill 
102 includes a drill head 104, a spindle 106, a gear section 108 and an 
air inlet 110. Similarly, FIG. 6 shows the motor of the present invention 
incorporated into a nutrunner 114. The nutrunner 114 includes air inlet 
116, motor 118, transmission section 122 and tool attachment 124. 
From the foregoing Detailed Description, it is apparent that the invention 
describes a reversible air motor with radial vanes that is designed to 
achieve nearly the same horsepower in a forward rotation as a 
"forward-only" type of air motor. The invention also provides for manual 
control of the motor speed in a reverse rotation. Having described but one 
embodiment of the invention, it will be apparent to those skilled in the 
art that there may be many changes and modifications to the invention 
without departing from the spirit and scope of the invention. In 
particular, automatic controls may replace the manually operated lever to 
control the operation of the motor in reverse mode.