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Title:
ROTARY AIR MOTOR SPEED CONTROL ASSEMBLY
Document Type and Number:
WIPO Patent Application WO/2012/036729
Kind Code:
A2
Abstract:
An air motor speed control comprises an annular speed control housing and an annular stator housing. The speed control housing comprises a cylindrical outer first surface having a first center axis, a cylindrical inner second surface having a second center axis, and a first exhaust slot connecting the first surface to the second surface. The stator housing comprises a cylindrical outer third surface having a third center axis aligned with the second center axis, a cylindrical inner fourth surface having a fourth center axis offset from the third center axis, and a first exit slot connecting the third surface to the fourth surface to overlap the first exhaust slot. The speed control housing is rotatable about the cylindrical outer third surface to adjust overlap between the first exhaust slot and first exit slot.

Inventors:
JOHNSON COREY D (US)
Application Number:
US2011/001574
Publication Date:
March 22, 2012
Filing Date:
September 13, 2011
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
GRACO MINNESOTA INC (US)
JOHNSON COREY D (US)
International Classes:
B26D5/00; B02C13/00; B02C18/16; B26D1/36; B26D5/26; D01G1/00
Foreign References:
US5064120A1991-11-12
US5319888A1994-06-14
JPS5720503A1982-02-03
Attorney, Agent or Firm:
KOMAREC, Stephen, M. et al. (P.A.312 South Third Stree, Minneapolis Minnesota, US)
Download PDF:
Claims:
CLAIMS:

1 . An air motor speed control comprising:

an annular speed control housing comprising:

a cylindrical outer first surface having a first center axis;

a cylindrical inner second surface having a second center axis offset from the first center; and

a first exhaust slot connecting the first surface to the second surface; and

an annular stator housing comprising:

a cylindrical outer third surface having a third center axis aligned with the second center;

a cylindrical inner fourth surface having a fourth center axis offset from the third center; and

a first exit slot connecting the third surface to the fourth surface to overlap the first exhaust slot;

wherein the annular speed control housing is configured to rotate about the cylindrical outer third surface to adjust overlap between the first exhaust slot and the first exit slot.

2. The air motor speed control of claim 1 wherein the annular stator housing further comprises:

first and second ends of the first exit slot; and

a passageway extending along the fourth surface and connecting the first end of the first exit slot to the second end of the first exit slot.

3. The air motor speed control of claim 2 and further comprising:

a pair of first exhaust slots;

a pair of first exhit slots; and

a pair of passageways.

4. The air motor speed control of claim 2 wherein the annular stator housing further comprises:

an inlet port connecting an exterior of the annular stator housing to the

passageway.

5. The air motor speed control of claim 4 and further comprising a plate positioned in the inlet port, the plate comprising a plurality of openings.

6. The air motor speed control of claim 4 wherein the second cer offset from the first center axis to define a thickened portion of the annular speed control housing and a thinned portion of the annular speed control housing.

7. The air motor speed control of claim 6 wherein the annular speed control housing further comprises:

an outlet connecting the first exhaust slot to an exterior of the annular speed control housing.

8. The air motor speed control of claim 7 wherein the outlet port extends through the thickened portion.

9. The air motor speed control of claim 7 and further comprising:

a muffler housing coupled to the outlet, the muffler housing comprising: an external surface;

an internal passage axially aligned with the outlet; and

a plurality of keyway slots extending from the internal passage to the external surface.

10. The air motor speed control of claim 9 wherein the plurality of keyway slots extend from the internal passage at right angles.

1 1 . The air motor speed control of claim 9 wherein the plurality of keyway slots through less than fifty percent of the external surface so as to be direct noise in less than a one-hundred-eighty degree range.

12. The air motor speed control of claim 9 and further comprising:

an annular baffle disposed within the internal passage to obstruct flow from the internal passage to the plurality of keyway slots.

13. The air motor speed control of claim 1 2 wherein the annular baffle comprises a felt material.

14. The air motor speed control of claim 1 and further comprising:

a rotor assembly configured to rotate about the third center within the

cylindrical inner fourth surface.

1 5. A rotary vane air motor comprising:

a rotor vane assembly;

a stator comprising a first annular body having an eccentric bore for

receiving the rotor vane assembly;

a first slot extending through the first annular body to intersect the eccentric bore; a speed control comprising a second annular body having a sta

receiving the first annular body; and

a second slot extending through the second annular body to intersect the stator bore;

wherein the second annular body rotates about the first annular body to

control airflow from the first slot to the second slot.

The rotary vane air motor of claim 1 5 wherein:

the stator bore is eccentrically disposed within the second annular body to define a thickened portion of the second annular body and a thinned portion of the second annular body; and

the second annular body further comprises an outlet connecting the second slot to an exterior of the second annular body.

The rotary vane air motor of claim 16 and further comprising:

a muffler housing coupled to the outlet, the muffler housing comprising: an external surface;

an internal passage axially aligned with the outlet; and

a plurality of keyway slots extending from the internal passage to the external surface.

The rotary vane air motor of claim 16 and further comprising:

first and second ends of the first slot; and

a passageway extending along the eccentric bore and connecting the first end of the first slot to the second end of the first slot.

A method for controlling speed of a rotary air motor, the method comprising: directing compressed air into an annular stator vane housing to produce

pressure differentials across vanes of a rotor vane assembly;

rotating the rotor vane assembly with the compressed air;

passing the compressed air through an exit slot in the annular stator vane housing;

passing the compressed air through an exhaust slot in an annular speed

control housing circumscribing the annular stator vane housing; and rotating the annular speed control housing to vary the position of the exhaust slot adjacent the exit slot to control the pressure differential across the vanes and change a speed of the rotor vane assembly. The method of claim 19 and further comprising:

passing the compressed air through a muffler assembly mounted to the annular speed control housing at an exhaust port.

Description:
ROTARY AIR MOTOR SPEED CONTROL ASSEMBLY

BACKGROUND

The present invention relates generally to a chopper device that distributes fiber material into a stream of resin material dispensed from a spray gun. In particular, the present invention relates to a speed control assembly for regulating speed of an air motor that drives a cutter blade head or an anvil head within the chopper device.

Chopper guns are frequently used in the composite material industry to form large, shaped products, such as in the marine and watercraft industries and pool and spa industries. Chopper guns comprise assemblies of a fiber chopper and a liquid spray gun. Compressed air is typically supplied to the chopper gun to power a pumping mechanism in the spray gun and an air motor in the fiber chopper. The spray gun typically receives a liquid resin material and a liquid catalyst material. Actuation of a trigger on the gun dispenses the materials into a mix chamber before being sprayed out of a nozzle of the gun. Mixing of the catalyst with the resin begins a solidification process, which eventually leads to a hard, rigid material being formed upon complete curing of the materials. The fiber chopper is typically mounted on top of the spray gun. The fiber chopper receives rovings of a fiber material, such as fiberglass, which passes between an idler wheel, an anvil head and a cutter blade head. The fiber rovings are cut into small segments between the anvil head and cutter blade head while being propelled out of the chopper by rotation of the anvil head and the cutter blade head by the air motor. The segments of fiber are mixed into the sprayed mixture of resin and catalyst such that the final cured product is fiber reinforced.

An air motor is used to drive either the cutter blade head or the anvil head in typical fiber chopper designs. Conventionally, the speed of the driven fiber chopper head is controlled by varying the volume of compressed air delivered to the chopper gun. However, adjusting the compressed air volume to control the fiber chopper reduces starting torque and air motor performance. Any compressed air delivered to the air motor is ultimately discharged through a muffler to reduce noise generated by expansion of the compressed air. Mufflers typically operate by passing compressed air through porous material before discharging the air from the device, which can affect power and speed generated by the air motor. Thus, flow of compressed air through the chopper gun needs to be controlled for two competing performance reasons. One approach is to provide a separate speed control and muffler, as shown in U.S. Pat. No. 4,001 ,935 to Krohn et al. Another approach involves integrating an adjustable muffler into the air motor housing, as shown in U.S. Pat. No. 4, 1 35,602 to Clark. Such an approach, however, resi muffling when the muffler is positioned away from the air motor exit, or a lack of power when the muffler is positioned to obstruct the air motor exit. There is, therefore, a need for an adjustable speed control that provides adequate muffling for all speeds of the air motor.

SUMMARY

The present invention is directed to a speed control for an air motor. The speed control comprises an annular speed control housing and an annular stator housing. The speed control housing comprises a cylindrical outer first surface having a first center axis, a cylindrical inner second surface having a second center axis, and a first exhaust slot connecting the first surface to the second surface. The stator housing comprises a cylindrical outer third surface having a third center axis aligned with the second center, a cylindrical inner fourth surface having a fourth center axis offset from the third center, and a first exit slot connecting the third surface to the fourth surface to overlap the first exhaust slot. The speed control housing is rotatable about the cylindrical outer third surface to adjust overlap between the first exhaust slot and the first exit slot.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded view of a liquid spray gun and a fiber roving chopper assembly in which an air motor of the present invention is used.

FIG. 2 is a perspective view of the air motor of FIG. 1 showing a muffler extending from a rotary speed control housing surrounding a stator housing.

FIG. 3 is an exploded view of the air motor of FIG. 2 in which the rotary speed control housing is removed from the stator housing to show a pair of exit slots.

FIG. 4 is a side cross sectional view of the air motor showing the rotary speed control housing and a rotor vane assembly disposed within the stator housing.

FIG. 5 is an end cross sectional view of the air motor taken at section 5-5 of FIG. 4 to show the position of inlet ports in the stator housing with respect to the rotor vane assembly.

FIG. 6 is a side cross sectional view of the air motor taken at section 6-6 of FIG. 5 to show distribution passageways of the stator housing intersecting an exhaust port of the rotary speed control housing.

FIG. 7 is an end cross sectional view of the air motor taken at section 7-7 of FIG. 6 to show a distribution passageway intersecting an exit slot and aligning with an exhaust slot in the rotary speed control housing. DETAILED DESCRIPTION

FIG. 1 is an exploded view of an assembly of liquid spray gun 10 and fiber roving chopper 12 in which air motor 22 of the present invention may be used. In FIG. 1 , fiber roving chopper 12 is shown slightly enlarged with respect to liquid spray gun 10. Liquid spray gun 10 comprises a two component internal mixing gun having handle 14, valve body 16, nozzle 18 and trigger 20. Fiber roving chopper 12 includes air motor 22, housing 24 and cover 26. Valve body 16 of spray gun 10 includes valve assembly 28, air inlet 30, material inlet 32, catalyst inlet 34 and air outlet 36. Housing 24 of fiber roving chopper 1 2 includes fiber inlet 38, openings 39, locking device 40, adjustable hard stop 41 , fasteners 43 A and 43B, knob 45, and cover 26 includes dispenser chute 42.

In the embodiment shown, spray gun 10 comprises a two component mixing gun that receives two liquid components that mix when dispensed to produce a mixture that cures into a hardened material. A first component comprises a resin material, such as a polyester resin or a vinyl ester, and is fed into valve body 16 at material inlet 32. A second component comprises a catalyst material that causes the resin material to harden, such as Methyl Ethyl Ketone Peroxide (MEKP), and is fed into valve body 16 at catalyst inlet 34. Material inlet 32 and catalyst inlet 34 feed materials, respectively, into valves seated within valve body 16 and connected to valve assembly 28. Other inlets are provided to gun 10 for other fluids such as a solvent. Actuation of trigger 20 simultaneously causes valves of valve assembly 28 to open and causes pressurized components to flow into nozzle 1 8. As shown, spray gun 10 comprises an internal mixer where the two components are pressurized at inlets 32 and 34 by an external source (not shown) and mixed within tube 44 before entering nozzle 1 8. Pressurized air may also be provided to nozzle 1 8 to shape or direct the mixed flow stream. In other embodiments, the materials are mixed outside of gun 10 after being pressurized within valve body 1 6 from an external source (such as a pump) with air from inlet 3 1 and atomized by a mixing nozzle.

Pressurized air from air inlet 30 is fed through valve body 1 6 to outlet 36, which connects to an inlet (not shown) on air motor 22 of fiber chopper 1 2. Rovings or strands of a fiber material, such as fiberglass, are fed into cover 26 through openings 39 in fiber inlet 38. Activation of air motor 22 by actuation of trigger 20 causes the rovings to be pulled into a cutter blade head by an anvil head and idler wheel mounted on housing 24, as is discussed in greater detail in PCT application Serial No. PCT/2010/003029, entitled "CUTTER BLADE H EAD FOR FIBER ROVING CHOPPER," filed November 23, 2010 by inventors James H. Rohrer and Jonathan R. McMichael, the contents of which are incorporated by this reference. The chopped roving pieces are expelled from dispenser chute 42 stream of resin and catalyst materials from nozzle 1 8 such that the hardened material includes fiber reinforcements that increase strength of the final product. Air motor 22 of the present invention includes a rotary speed control that adjusts the flow of compressed air through air motor 22 to vary the speed of a rotor vane assembly within air motor 22. Additionally, the rotary speed control incorporates a muffler for controlling discharge of the compressed air from air motor 22. Although the present invention is described herein with reference to fiber roving chopper 12, air motor 22 and the rotary speed control of the present invention can be used in other applications.

FIG. 2 is a perspective view of air motor 22 of FIG. 1 showing muffler assembly

102 extending from rotary speed control housing 104 surrounding stator housing 106. Rotary speed control housing 104 comprises an annular body having rim 105, which provides structural support to housing 104. Muffler assembly 102 is secured to housing 104 at the location of exhaust slots (not shown) extending through housing 104 via a plurality of threaded fasteners or any other suitable means. Air distributed to air motor 22 from outlet 36 (FIG. 1 ) drives air motor 22 before exiting at keyway slots 103 of muffler assembly 1 02. Stator housing 106 comprises an annular body that extends into housing 104. Rotary speed control housing 1 04 is rotatably adjustable about stator housing 106. As discussed with reference to FIG. 5, housing 1 04 and housing 106 are eccentric, that is to say they are not concentric. Rim 105 provides a place to grip housing 104 when rotating about housing 106. Drive shaft 1 09 extends through mounting pad 1 08, which is machined integrally from housing 106, to join with housing 24 of roving chopper 1 2 (FIG. 1 ). Within housing 106, shaft 109 connects to a rotor vane assembly (not shown) which is supported within rim 1 05. Rotary speed control housing 104 adjusts the location of muffler assembly 1 02 with respect to the exit slots in stator housing 106 to control the speed at which the rotor vane assembly rotates within housing 106. Muffler assembly 1 02 is configured to dampen the exhausted air as it expands and is situated so as to direct the air away from an operator of chopper 1 2.

FIG. 3 is an exploded view of air motor 22 of FIG. 2 in which rotary speed control housing 1 04 is removed from stator housing 106 to show a pair of exit slots 1 1 2A and 1 1 2B. Rotary speed control housing 104 includes rim 105 and exhaust port 1 07. Stator housing 1 06 includes mounting pad 108, end cap 1 10, first exit slot 1 1 2A and second exit slot 1 1 2B. First exit slot 1 1 2A comprises sidewall 1 14A, first end 1 16A and second end 1 1 8A. Second exit slot 1 1 2B comprises sidewall 1 14B, first end 1 16B and second end 1 1 8B. Exhaust port 1 07 includes first window 1 19A and second window 1 1 9B. A rotor vane assembly disposed within housing 106 comprises rotor 122 and vanes vane assembly is eccentrically positioned within housing 106, as is known in the art, to produce pressure differentials across vanes 126. End plate 1 1 0 retains the rotor vane assembly within rim 105 of housing 106, while mounting pad 108 permits housing 106 to be coupled to housing 24 of chopper 12 (FIG. 1 ).

Compressed air is directed into motor 22 through inlet ports (not shown) disposed in housing 104 adjacent mounting pad 108. The inlet ports extend from openings in housing 24 through to the interior of housing 1 06. Within housing 106 the compressed air drives the rotor vane assembly and exits housing 106 at exit slots 1 12A and 1 12B before passing through windows 1 19A and 1 1 9B and into muffler assembly 1 02. Rotary speed control housing 104 is rotated on stator housing 106 to adjust the position of exhaust port 1 07 with respect to exit slots 1 1 2A and 1 12B. Specifically, the positions of windows 1 19A and 1 1 9B of plate 120 are adjusted above slots 1 12A and 1 12B, respectively. When windows 1 1 9A and 1 19B of exhaust port 107 are centered on slots 1 12A and 1 12B, the rotational speed of shaft 109 of motor 22 is fastest because the pressure differential across vanes 126 is smallest. Windows 1 19A and 1 19B are slid away from exit slots 1 12A and 1 12B to increase the pressure differential across vanes 126, thereby decreasing the speed of shaft 109. As shown in FIG. 3, sidewalls 1 14A and 1 14B of slots 1 12A and 1 12B have varying heights due to the eccentric position of rotor 122 within housing 106.

FIG. 4 is a side cross sectional view of air motor 22 showing rotary speed control housing 104 and rotor vane assembly 1 2 1 disposed within stator housing 106. FIG. 5 is an end cross sectional view of air motor 22 taken at section 5-5 of FIG. 4 to show the position of inlet ports 128 in stator housing 106 with respect to rotor vane assembly 12 1 . FIGS. 4 and 5 are discussed concurrently.

With reference to FIG. 4, rotary speed control housing 1 04 comprises an annular body having outer surface 1 30 and inner surface 1 32, into which stator housing 1 06 is inserted. Stator housing comprises an annular body having outer surface 1 34 that fits against inner surface 132, and inner surface 1 36, into which rotor vane assembly 1 2 1 is inserted. Inner surface 1 32 of housing 1 04 includes grooves 106A and 1 06B into which seals 1 38A and 1 38B are positioned to seal against housing 1 06. The seals comprise O- rings that permit slippage of housing 104 against housing 1 06 while preventing air leakage between the two. Speed control housing 104 fits firmly around stator housing 1 06 so that the position of housing 1 04 will not freely move during operation of air motor 22 without an externally applied force, such as from an operator of air motor 22. End cap 1 1 0 coupled with housing 106 and is positioned within rim 105 of housing 104. End cz mechanism 140 for locking rotation of rotor vane assembly 121 .

Rotor 122 of rotor vane assembly 121 extends axially from mechanism 140 into housing 106 such that shaft 109 extends through mounting pad 108. Vanes 126 are inserted into slots 142 (FIG. 5) within rotor 122. Compressed air is introduced into inlet ports 128 (FIG. 5) to cause rotor 122 to rotate within inner surface 1 36 by producing a pressure differential across vanes 126. Springs 144 maintain vanes 1 26 biased out of slots 142 toward surface 136. Vanes 126 slide in and out of slots 142 as rotor 122 rotates within housing 106.

With reference to FIG. 5, speed control housing 104 comprises an annular cylinder having outer surface 1 30. Inner surface 132 extends into the cylinder to form a bore for receiving stator housing 106. The center of inner surface 1 32 is offset from the center of outer surface 130 such that surfaces 1 30 and 132 are eccentric. As such, housing 1 04 comprises thickened portion 146 and thinned portion 148. Portions 146 and 148 are thickened and thinned, respectively, with respect to the thickness of housing 106 that would result if inner surface 1 32 were centered within, or concentric, with outer surface 130. Thickened portion 146 provides a space on housing 104 of suitable strength for mounting muffler assembly 102. As discussed with reference to FIGS. 6 and 7, a passage extends through housing 104 to connect the interior of air motor 22 to muffler assembly 102.

Stator housing 1 06 comprises an annular cylinder having outer surface 1 34. Inner surface 136 extends into the cylinder to form a bore for receiving rotor vane assembly 1 2 1 . The center of inner surface 136 is offset from the center of outer surface 1 34 such that surfaces 134 and 136 are eccentric. Such eccentricity is a feature of rotary vane air motors, as is known in the art. The center of rotor 1 22, about which rotor vane assembly 1 21 rotates, is concentric with outer surface 1 34 of housing 1 06 and inner surface 1 32 of housing 104.

Compressed air enters housing 1 06 through inlet ports 1 28 and pressurizes the area behind vane 126A. The increase in pressure behind vane 1 26A causes vane 1 26A and rotor 1 22 to rotate counter-clockwise with reference to FIG. 5. As vane 1 26A rotates, it extends further from slot 142A under force of spings 1 44. At the same time, the space between rotor 122 and inner surface 1 36 increases, decreasing the pressure in front of vane 1 26A. As such, rotor 122 is caused to continuously rotate counter-clockwise. Once vane 126A reaches muffler assembly 1 02, the compressed air escapes air motor 22 at keyway slots 1 03. Operation of air motor 22 is facilitated by distribution passages entrenched in inner surface 136, which form a complete path between inlet ports 128 and an exhaust p assembly 102 in housing 104, as shown in FIG. 6.

FIG. 6 is a side cross sectional view of air motor 22 of taken at section 6-6 of FIG. 5 to show distribution passageways 150A and 150B of stator housing 106 intersecting exhaust port 107 of housing 104. Rotor vane assembly 121 operates as shown and explained with reference to FIGS. 4 and 5. Operation of rotor vane assembly 121 is actuated by the introduction of compressed air into distribution passageways 1 50A and 1 50B from inlet ports 128 (FIG. 5). Inlet ports 128 extend from axial end surface 1 52 of housing 106 adjacent mounting pad 1 08. Inlet ports 128 extend to intersect passageways 1 50A and 150B. From within distribution passageways 1 50A and 1 50B, compressed air is able to enter space between adjacent vanes 126 and cause rotation of rotor 122. Compressed air between vanes 126 exits stator housing 1 06 at exit slots 1 1 2 A and 1 12B and passes into speed control housing 1 04 at exhaust slots 1 54A and 1 54B adjacent plate 120 of exhaust port 107.

From exhaust port 107 in housing 104, the compressed air travels into muffler assembly 102. Muffler assembly 102 comprises housing 1 56, into which keyway slots 103 are formed. Housing 1 56 includes internal passage 1 58, into which baffles 160A-160C are inserted. Internal passage 1 58 extends straight out of air motor 22. In other words, internal passage 1 58 extends radially from the axis about which rotor 122 rotates. Such a configuration provides an unobstructed path for high revolution per minute (rpm) noise from air motor 22 to travel into and dissipate. Keyway slots 1 03 intersect internal passage 1 58 at right angles. Configured as such, keyway slots 1 03 provide a path for low rpm noise to escape from air motor 22. Keyway slots 1 03 extend around only a portion of the perimeter of housing 1 56 to directionally orient the compressed air, and the noise related to expansion of the compressed air, away from an operator of fiber chopper 1 2 (FIG. 1 ). For example, in the embodiment disclosed, keyway slots 1 03 extend through only about fifty percent of housing 1 56 and are located on the same half of housing 1 56 so as to direct noise in a one-hundred-eighty degree range. Internal passage 1 58 is lined with baffles 1 60A- 160C to dampen the noise generated by the expansion of the compressed air. In one embodiment, baffles 160A- 1 60C comprise hollow felt pads stacked within housing 1 56.

FIG. 7 is an end cross sectional view of air motor 22 of FIG. 6 taken at section 7-7 showing distribution passageway 1 50B intersecting exit slot 1 14B and aligning with exhaust slot 1 54B in rotary speed control housing 1 04. As shown, stator housing 1 06 rotates within inner surface 1 32 of speed control housing 104. Rotor 1 22 rotates within housing 104 such that vanes 126 contact inner surface 1 36. Distribution pas extends across surface 1 36 to provide a path for air to travel within housing 106. As shown in FIG. 6, passageway 1 50B is much narrower than the width of housing 106 so that compressed air is able to rotate rotor 122. Passageway 150B permits the compressed air to enter the spaces between vanes 126. Passageway 150B also connects to exit slot 1 14B to permit compressed air to leave housing 106. As depicted, exit slot 1 14B aligns radially with exhaust slot 154B in housing 104. Exhaust slot 154B connects to exhaust port 107, which leads into internal passage 1 58 within muffler assembly 1 02.

The position of exhaust slot 1 54B can be adjusted by rotating speed control housing 1 04. As shown, exhaust slot 154B is aligned with exit slot 1 14B so that exhaust slot 1 54B is completely within exit slot 1 1 I B. In such a position, compressed air is most easily able to escape air motor 22. Thus, the pressure differential produced across vanes 126 is the most, resulting in the rotational speed of rotor 122 being at a maximum for the given supply of compressed air. Speed control housing 1 14 can be rotated so that less of exhaust slot 154B is radially outward of exit slot 1 14B. In that situation, compressed air is more restricted in escaping air motor 22 than the configuration depicted. Thus, the back pressure behind vanes 126 increases, reducing the pressure differential across vanes 126 and decreasing the speed of rotor 1 22. The position of exhaust slot 1 54B can be varied over a range of positions to change the speed of rotor 122 over a range of speeds.

The speed control mechanism of the present invention allows operators of an air motor to vary the speed of a rotor assembly to vary output of the motor. Speed of the air motor is controlled with a manual, one-handed operation that can be done from the exterior of the air motor without any disassembly. Speed adjustments can be made while the air motor is operating so that the speed can be varied until the desired output is achieved. The speed control mechanism remains in place until actuated or changed by an operator, avoiding the need for an additional lockdown mechanism to keep the adjustment in place. The speed control mechanism includes an integrated muffler that permits a high flow of compressed air to avoid interfering with power and torque generated by the air motor, while still providing a substantial reduction in noise. Thus, the rotary speed control mechanism with an integrated muffler system provides operators with ability to control speed output of the air motor, without interfering with torque production.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.