WO2012037579A2

WO2012037579A2 - Rotary air motor housing assembly

Info

Publication number: WO2012037579A2
Application number: PCT/US2011/060325
Authority: WO
Inventors: Corey Dean Johnson; Jonathan R. Mcmichael; Steven R. Sinders
Original assignee: Graco Minnesota Inc.
Priority date: 2010-09-13
Filing date: 2011-11-11
Publication date: 2012-03-22
Also published as: WO2012037579A3; WO2012037579A9

Abstract

A rotary vane air motor housing assembly comprises a U-shaped stator housing and an end cap. The U-shaped stator housing extends from a first axial end to a second axial end. The U-shaped stator housing comprises an annular portion and an end wall portion. The annular portion comprises a cylindrical outer surface having a first center axis, and a cylindrical inner surface having a second center axis offset from the first center axis. The cylindrical inner surface defines a rotor pocket for receiving a rotor vane assembly. The end wall portion integrally joins the cylindrical outer surface to the cylindrical inner surface at the first axial end to close off a first end of the rotor pocket. The end cap is mechanically fastened to the second axial end of the U-shaped stator housing to close off a second end of the rotor pocket.

Description

ROTARY AIR MOTOR HOUSING ASSEMBLY

BACKGROUND

The present invention is generally directed to rotary vane air motors and more particularly to stator housings for receiving a rotor vane assembly.

Off-the-shelf rotary vane air motors are typically used to drive power tools, such as fiber roving chopper devices. These air motors are designed as general purpose motors and therefore include generic features that must be accommodated when the motor is applied to a specific purpose, such as a hand-held power tool. For example, stator housings for off-the-shelf air motors are typically fabricated from a cylindrical body, the ends of which are closed off by end plates mechanically fastened to the cylindrical body. Such an air motor is disclosed in U.S. Pat. No. 6,881,044 to Thomas, Jr. et al. The end plates must be sealed to the cylindrical body to prevent leakage of pressurized air. In order to do so, the plates and body must be carefully machined such that mating surfaces flushly engage, which increases manufacturing cost and time. Additionally, the end plates typically include National Pipe Thread (NPT) ports that must be plumbed to a pressurized air source and to an exhaust muffler. This plumbing requires hoses and fittings that increase the cost and size of the power tool. There is, therefore, a need for improved housing assemblies for rotary vane air motors.

SUMMARY

The present invention is directed to a rotary vane air motor housing assembly such that can be used in a hand-help power tool. The housing assembly comprises a U-shaped stator housing and an end cap. The U-shaped stator housing extends from a first axial end to a second axial end. The U-shaped stator housing comprises an annular portion and an end wall portion. The annular portion comprises a cylindrical outer surface having a first center axis, and a cylindrical inner surface having a second center axis offset from the first center axis. The cylindrical inner surface defines a rotor pocket for receiving a rotor vane assembly. The end wall portion integrally joins the cylindrical outer surface to the cylindrical inner surface at the first axial end to close off a first end of the rotor pocket. The end cap is mechanically fastened to the second axial end of the U-shaped stator housing to close off a second end of the rotor pocket.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded view of a hand-held power tool comprising 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 rotary speed control housing surrounding a two-piece 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 two-piece stator housing to show a rotor vane assembly.

FIG. 4 is a side cross sectional view of the air motor of FIG. 2 showing the rotary speed control housing and the two-piece stator housing surrounding the rotor vane assembly.

FIG. 5 is an end cross sectional view of the air motor taken at section 5-5 of FIG. 4 to show an eccentric position of the rotor vane assembly within a rotor pocket of the stator housing.

DETAILED DESCRIPTION FIG. 1 is an exploded view of a hand-held power tool assembly of liquid spray gun 10 and fiber roving chopper 12 in which air motor 14 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 16, valve body 18, nozzle 20 and trigger 22. Fiber roving chopper 12 includes air motor 14, housing 24 and cover 26. Valve body 18 of spray gun 10 includes valve assembly 28, air inlets 30A and 30B, material inlet 32, catalyst inlet 34 and air outlet 36. Housing 24 of fiber roving chopper 12 includes fiber inlet 38, including openings 40, tensioning device 42, hard stop 44, fasteners 46 A and 46B and knob 48. Cover 26 includes dispenser chute 50.

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 18 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 18 at catalyst inlet 34. Material inlet 32 and catalyst inlet 34 feed materials, respectively, into valves seated within valve body 18 and connected to valve assembly 28. Other inlets are provided to gun 10 for other fluids such as a solvent. Actuation of trigger 22 simultaneously causes valves of valve assembly 28 to open and causes pressurized components to flow into nozzle 20. As shown, spray gun 10 comprises an internal mixer where the two components are pressurized at inlets 32 and 34 by an external source (such as a pressurized fluid tank not shown) and mixed within tube 52 before entering nozzle 20. Pressurized air may also be provided to nozzle 20 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 18 (such as by an external pump (not shown) powered with air form inlets 30 A and 30B) and atomized by a mixing nozzle.

Fiber roving chopper 12 is face-mounted to air motor 14. Pressurized air from air inlets 30A is fed through valve body 18 to outlet 36, which connects to inlet ports (FIG. 3) on air motor 14 of fiber chopper 12. Rovings or strands of a fiber material, such as fiberglass, are fed into cover 26 through openings 40 in fiber inlet 38. Activation of air motor 14 by actuation of trigger 22 causes the rovings to be pulled into a cutter blade head by an anvil head and idler wheel mounted on housing 24 within cover 26, as is discussed in greater detail in PCT application Serial No. PCT/2010/003029, entitled "CUTTER BLADE HEAD 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 50 into the mixed stream of resin and catalyst materials from nozzle 20 such that the hardened material includes fiber reinforcements that increase strength of the final product. Roving chopper 12 can accommodate different sized rovings and can chop the rovings into different sized pieces by adjusting tensioning device 42 and hard stop 44, as is discussed in greater detail in PCT application Serial No. PCT/2011/001572, entitled "ADJUSTABLE TENSIONING DEVICE FOR FIBER ROVING CHOPPER," filed September 13, 2011 by inventors Corey D. Johnson and Jonathan R. McMichael, the contents of which are incorporated by this reference.

Air motor 14 includes a rotary speed control and muffler assembly that adjusts the flow of compressed air through air motor 14 to vary the speed of a rotor vane assembly within air motor 14, as is discussed in greater detail in PCT application Serial No. PCT/2011/001574, entitled "ROTARY AIR MOTOR SPEED CONTROL ASSEMBLY," filed September 13, 2011 by inventor Corey D. Johnson, the contents of which are incorporated by this reference. Air motor 14 of the present invention includes a two-piece stator housing that receives a rotor vane assembly for driving motor 14. Although the present invention is described herein with reference to fiber roving chopper 12, air motor 14 and the two-piece stator housing of the present invention can be used in other applications.

FIG. 2 is a perspective view of air motor 14 of FIG. 1 showing muffler assembly 54 extending from rotary speed control housing 56 surrounding stator housing 58. Rotary speed control housing 56 comprises an annular body having rim 60. Muffler assembly 54 includes housing 62, fasteners 64 and keyway slots 66. Stator housing 58 includes mounting plate 68, bearing pocket 70 and mounting bores 72. Drive shaft 74A of a rotor vane assembly extends from within stator housing 58 through front bearing 76. Housing 62 of muffler assembly 54 is secured to housing 56 at the location of exhaust slots (FIG. 3) extending through housing 56 via a plurality of threaded fasteners 64 or any other suitable means. Air distributed to air motor 14 from outlet 36 (FIG. 1) drives air motor 14 before exiting at keyway slots 66 of muffler assembly 54.

Stator housing 58 comprises an annular body that extends into housing 56. Rotary speed control housing 56 is rotatably adjustable about stator housing 58. As discussed with reference to FIG. 5, housing 56 and housing 58 are eccentric, that is to say they are not concentric. Rim 60 provides structural support to housing 56 and a place to grip housing 56 when rotating about housing 58. Drive shaft 74A extends through mounting plate 68, which is machined integrally from housing 58, to join with housing 24 of roving chopper 12 (FIG. 1). Within housing 58, shaft 74A connects to a rotor vane assembly (FIG. 3), which is supported by front bearing 76 within mounting plate 68 and by a rear bearing assembly supported radially inward of rim 60. Rotary speed control housing 56 adjusts the location of muffler assembly 54 with respect to exit slots (FIG. 3) in stator housing 58 to control the speed at which the rotor vane assembly rotates within housing 58. Muffler assembly 54 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 12. Stator housing 58 of the present invention comprises a two-piece member having a cup-shaped or U- shaped housing for receiving the rotor vane assembly and an end cap that slips onto the housing to receive the rear bearing assembly and a locking mechanism, as shown in FIG. 3.

FIG. 3 is an exploded view of air motor 14 of FIG. 2 in which rotary speed control housing 56 is removed from stator housing 58 to show front bearing 76, end cap 78, rotor vane assembly 80, bearing cap 82, locking mechanism 84 and rear bearing 86. Rotary speed control housing 56 includes rim 60 and exhaust port 88. Stator housing 58 includes mounting plate 68, end cap 78, annular portion 89, exit slots 90A and 90B and end wall portion 91. Rotor vane assembly 80 comprises drive shaft 74A, stub shaft 74B, rotor 92 and vanes 94. Muffler assembly 54 includes housing 62, fasteners 64, slots 66 and muffler baffles 96. Locking mechanism 84 includes seal 97, stop 98, spring 100 and washer 102.

Muffler housing 62 is coupled to rotary speed control housing 56 at exhaust port 88 via threaded fasteners 64. Baffles 96 are positioned within housing 62 between exhaust port 88 and slots 66. Rotary speed control housing 56 is positioned around stator housing 58 so that exhaust port 88 aligns with exit slots 90A and 90B. Front bearing 76 is positioned within bearing pocket 70, and rear bearing 86 is positioned within bearing cap 82. Bearing cap 82 includes bearing pocket 101 (FIG. 4) in which bearing 86 is positioned. In one embodiment of the invention, bearing 76 is press fit into pocket 70 and bearing 86 is press fit into cap 82. Rotor vane assembly 80 is positioned within stator housing 58 such that drive shaft 74A is supported within front bearing 76, stub shaft 74B is supported in rear bearing 86 and rotor 92 is disposed within annular portion 89. End cap 78 couples to annular portion 89 to hold rotor vane assembly 80 and locking mechanism 84 together with air motor 14.

End cap 78 secures locking mechanism 84 between end cap 78 and bearing cap 82. Specifically, washer 102 is positioned against bearing cap 82 and stop 98 includes a flange that abuts an opening in end cap 78. With end cap 78 coupled to annular portion 89, spring 100 pushes stop 98 away from bearing cap 82 and stub shaft 74B. An operator pushes stop 98 to compress spring 100 and push a lug on stop 98 into a mating socket in stub shaft 74B. Operation of locking mechanism 84 is discussed in co-pending application entitled "ROTARY AIR MOTOR LOCKING ASSEMBLY" filed on the same day herewith by inventors Corey D. Johnson, Jonathan R. McMichael and Ronald W. Mangus.

Mounting plate 68 permits housing 58 to be coupled to housing 24 of chopper 12 (FIG. 1). For example, mounting surface 103 is flat for mating flush with housing 24. Compressed air is provided to air motor 14 through inlet ports 104 in end wall 91 of stator housing 58. O-ring seal 106 seals between mounting plate 68 and housing 24, and O-ring seal 97 seals between stop 98 and end cap 78. Inlet ports 104 extend from openings in housing 24 through to the interior of housing 58. The compressed air induces rotation of rotor 92 by asserting pressure against vanes 94. Specifically, rotor 92 is eccentrically positioned within housing 58, as is known in the art, to produce pressure differentials across vanes 94. Vanes 94 slide in and out of slots 105 (FIGS. 3 & 4) within rotor 92 due to the eccentricity of rotor 92 within the bore of annular portion 89. The compressed air exits stator housing 58 at exit slots 90A and 90B. Rotary speed control housing 56 is rotated on stator housing 58 to adjust the position of exhaust port 88 with respect to exit slots 90 A and 90B to control the speed of rotor vane assembly 80, as is discussed in greater detail in the aforementioned PCT application to Johnson. From exhaust port 88, the compressed air travels into muffler housing 62 and passes through baffles 96 and slots 66 to dampen sound produced by expansion of the compressed air. Annular portion 89 extends axially from end wall portion 91 to form U- shaped body 107. Annular portion 89 extends between end wall portion 91 and end cap 78 to form a rotor pocket for receiving rotor vane assembly 80. The rotor pocket is closed off by end cap 78 and end wall portion 91, save for openings to permit access to locking mechanism 84 and drive shaft 74A, respectively. These openings are sealed by seal 106 on mounting plate 68 and seal 97 on stop 98. Stator housing 58 and end cap 78 provide mating surfaces that rotor 92 and vanes 94 engage during operation of air motor 14. Annular portion 89 and end cap 78 are configured to reduce the number of critical dimensions in air motor 14 that must be precisely fabricated to provide efficient operation of rotor vane assembly 80, e.g. to prevent leaking of compressed air. For example, stator housing 58 includes only a single mating interface along which annular portion 89 and end cap 78 engage.

FIG. 4 is a side cross sectional view of air motor 14 taken at section 4-4 of FIG. 5 to show rotary speed control housing 56 and two-piece stator housing 58 surrounding rotor vane assembly 80. FIG. 5 is an end cross sectional view of air motor 14 taken at section 5-5 of FIG. 4 to show the eccentric position of rotor vane assembly 80 within stator housing 58. FIGS. 4 and 5 are discussed concurrently.

With reference to FIG. 4, rotary speed control housing 56 comprises an annular body having outer surface 108 and inner surface 110, into which stator housing 58 is inserted. Annular portion 89 of stator housing 58 has outer surface 112 that fits against inner surface 110, and inner surface 114 that forms rotor pocket 115 into which rotor vane assembly 80 is inserted. Inner surface 110 of housing 56 includes grooves 116A and 116B into which seals 118A and 118B are positioned to seal against housing 58. Seals 118A and 118B comprise O-rings that permit slippage of housing 56 against housing 58 while preventing air leakage between the two bodies. Speed control housing 56 fits firmly around stator housing 58 so that the position of housing 56 will not freely move during operation of air motor 14 without an externally applied force, such as from an operator of air motor 14.

End wall portion 91 comprises a disk that joins inner surface 114 within pocket 115 and that joins outer surface 112 outside of pocket 115 to close off rotor assembly 80 within pocket 115. Mounting plate 68 comprises a rectilinear, axial extension of end wall portion 91, but may have other cross-sectional profiles. Shaft bore 120 extends through end wall portion 91 and mounting plate 68 along rotational axis RA of rotor 92. Bearing pocket 70 comprises a counterbore surrounding shaft bore 120 to receive front bearing 76. Bearing pocket 70 extends through the thickness of mounting plate 68 and into end wall portion 91. Bearing pocket 70 includes groove 122 for receiving seal 106.

End cap 78 comprises end plate 124, annular flange 126 and pocket 128. End plate 124 and annular flange 126 close off rotor assembly 80 within pocket 115 inside annular portion 89. Specifically, annular flange 126 engages annular portion 89 along threaded engagement 130. In one embodiment of the invention, annular portion 89 includes male threads and flange 126 includes female threads. Threaded engagement 130 extends across less than the width of annular flange 126 such that end plate 124 does not contact annular portion 89. The inner diameter surface of annular flange 126 thus contacts outer surface 112 of annular portion 89 along a mating interface. End cap 78 and U- shaped body 107 engage each other along only a single mating interface to minimize tolerance stack-up and the like.

As previously mentioned, locking mechanism 84 is disposed within pocket 128 of end cap 78. Specifically, stop 98 comprises knob 132, flange 134 and lug 136. Knob 132 extends through bore 137 in pocket 128 to provide access to an operator of air motor 14. Flange 134 engages mating flange 138 of pocket 128 within cap 78. Flange 134 includes a channel for receiving O-ring seal 97. Washer 102 is disposed within counterbore 140 in cap 78. Counterbore 140 lies flush with end plate 124 of cap 78 so that washer 102 and end plate 124 both flushly engage bearing cap 82. Spring 100 is disposed around lug 136 and within flange 134 to as to apply spring force between knob 132 and washer 102. Flange 134 prevents stop 98 from being pushed out of bore 137. The inner diameter of washer 140 is larger than lug 136, but smaller than the diameter of spring 100. In the state shown in FIG. 4, lug 136 extends from knob 132 so as to fall short of contacting stub shaft 74B. In the particular embodiment shown, lug 136 penetrates washer 140, but need not extend that far. Stub shaft 74B includes socket 142 into which lug 136 is inserted when an operator pushes knob 132 to overcome the force of spring 100, thus preventing rotation of rotor 92. As explained in greater detail in the aforementioned copending application, compressed air prevents operation of locking mechanism 84 while air motor 14 is operating.

Rotor 92 of rotor vane assembly 80, including shafts 74A and 74B, extends axially from mechanism 84 to the outside of housing 58. Stub shaft 74B is disposed concentrically within rear bearing 86 and bearing cap 82. Drive shaft 74A is disposed concentrically within front bearing 76 and bearing pocket 70. Bearings 76 and 86 comprise any known bearings that are typically used in the art, such as ball bearings. Bearing cap 82 is positioned within shoulder 143 of stator housing 58. Rotor 92 contacts bearing cap 82 and end wall portion 91, and is configured to rotate within pocket 115. Vanes 94 are inserted into slots 105 (FIG. 5) within rotor 92. Compressed air is introduced into inlet ports 104 (FIG. 5) to cause rotor 92 to rotate within inner surface 114 by producing a pressure differential across vanes 94. Springs 144 maintain vanes 94 biased out of slots 105 toward surface 114. Vanes 94 slide in and out of slots 105 as rotor 92 rotates within housing 58.

With reference to FIG. 5, speed control housing 56 comprises an annular cylinder having outer surface 108. Inner surface 110 extends into the cylinder to form a bore for receiving stator housing 58. The center of inner surface 110 is offset from the center of outer surface 108 such that surfaces 108 and 110 are eccentric. As discussed with reference to FIG. 3, a passage extends through housings 56 and 58 to connect the interior of air motor 14 to muffler assembly 54. Stator housing 58 comprises an annular cylinder having outer surface 112. Inner surface 114 extends into the cylinder to form a bore comprising pocket 115 for receiving rotor vane assembly 80. The center of inner surface 114 is offset from the center of outer surface 112 such that surfaces 112 and 114 are eccentric. Such eccentricity is a feature of rotary vane air motors, as is known in the art. The center of rotor 92, about which rotor vane assembly 80 rotates, is concentric with outer surface 112 of housing 58 and inner surface 110 of housing 56 along rotational axis RA.

Compressed air enters housing 58 through inlet ports 104 and pressurizes the area behind vane 94A. The increase in pressure behind vane 94A causes vane 94A and rotor 92 to rotate counter-clockwise with reference to FIG. 5. As vane 94A rotates, it extends further from slot 105A under force of spring 144. At the same time, the space between rotor 92 and inner surface 114 increases, decreasing the pressure in front of vane 94A. As such, rotor 92 is caused to continuously rotate counter-clockwise. Once vane 94A reaches muffler assembly 54, the compressed air escapes air motor 14 at keyway slots 66. O-ring 106 and O-ring 97 seal the air path between inlet ports 104 and exit slots 90A and 90B. For example, compressed air is able to pass through, or blow by, bearings 76 and 86. O-rings 106 and 97 prevent leakage of the air and improve the efficiency of air motor 14.

In the present invention, U-shaped body 107 and end cap 78 form a two- piece housing that forms rotor pocket 115. Body 107 and end cap 78 are typically fabricated from aluminum and aluminum alloys, but can be made from other materials in other embodiments. In one embodiment, stator housing 58 includes a hard, anodized coating for improving resistance to wear. U-shaped body 107 and end cap 78 are machined with several critical dimensions to permit rotor vane assembly 80 to rotate true within pocket 115. The diameter of inner surface 114 comprises a first critical dimension. The amount of offset of inner surface 114 within outer surface 112 is a second critical dimension. The first and second critical dimensions improve the torque applied to rotor vane assembly 80 by the compressed air. These critical dimensions are controlled by machining annular portion 89 and end wall portion 91 from a single block of material. As such, the position of end wall portion 91 with respect to annular portion 89 and pocket 115 is fixed.

The third critical dimension is the depth of pocket 115, which in the present invention is controlled by the interaction of bearing cap 82 with annular portion 89. Bearing cap 82 is positioned within shoulder 143 such that the depth of shoulder 143 correctly positions bearing cap 82 with respect to end wall portion 91. Shoulder 143 is machined into annular portion 89 and is thus fixed with respect to annular portion 89 and pocket 115. Consequently, the distance between shoulder 143 and end wall portion 91 is fixed, fixing the depth of pocket 115. All features needed for critical dimensioning of stator housing 58 are thus located on a single body. For example, interaction of end cap 78 with annular portion 89 is not critical, other than to hold bearing cap 82 in place. Thus, end plate 124 is spaced from annular portion 89 via bearing cap 82 so that end cap 78 and annular portion 89 engage along only a single mating interface at threaded engagement 130.

Such a configuration eliminates variables in machining housing 58, particularly with respect to prior art housings where two end caps are mechanically fastened to an annular body, necessitating critical dimensioning between three movable parts. The joining of end caps to the annular body in conventional configurations requires two end caps to have flat surfaces that must mate flushly with two flat surfaces on the annular body. The configuration of the present invention eliminates stacking of flat surfaces against one another to form pocket 115.

Furthermore, stator housing 58 can be incorporated into a flush-mounted or face-mounted system on a hand-held power tool, such as by mating mounting surface 103 of mounting plate 68 directly to housing 24. Additional external hoses are not needed to couple air motor 14 to the source of pressurized air in the hand-held power tool. For example, air inlet ports 104 of mounting plate 68 can mate directly to outlet ports in housing 24, and muffler assembly 54 mounts directly to speed control housing 56. Thus, air motor 14 of the present invention is more compact, lighter and less expensive. 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.

Claims

CLAIMS:

1. A rotary vane air motor housing assembly comprising:

a U-shaped stator housing extending from a first axial end to a second axial end, the U-shaped stator housing comprising:

an annular portion comprising:

a cylindrical outer surface having a first center axis; and a cylindrical inner surface having a second center axis offset from the first center axis, the cylindrical inner surface defining a rotor pocket for receiving a rotor vane assembly; and

an end wall portion integrally joining the cylindrical outer surface to the cylindrical inner surface at the first axial end to close off a first end of the rotor pocket; and

an end cap mechanically fastened to the second axial end of the U-shaped stator housing to close off a second end of the rotor pocket.

2. The rotary vane air motor housing assembly of claim 1 wherein the end wall further comprises:

a rotor bore for receiving a shaft of the rotor vane assembly.

3. The rotary vane air motor housing assembly of claim 2 wherein the end wall further comprises:

a bearing pocket disposed on an exterior of the end wall to face away from the rotor pocket, wherein the bearing pocket is concentric with the rotor bore.

4. The rotary vane air motor housing assembly of claim 3 wherein the bearing pocket further comprises:

a mounting surface extending perpendicular to the first center axis and the second center axis, the mounting surface including mounting bores for joining the mounting face to a power tool housing; and a channel for receiving a seal surrounding the bearing pocket.

5. The rotary vane air motor housing assembly of claim 1 wherein the end cap is threaded onto the annular portion.

6. The rotary vane air motor housing assembly of claim 1 wherein the end cap further comprises:

an end plate; and an annular flange extending from the end plate to engage the annular portion.

7. The rotary vane air motor housing assembly of claim 6 wherein the annular flange surrounds the cylindrical outer surface at the second axial end of the U-shaped stator housing.

8. The rotary vane air motor housing assembly of claim 6 wherein the end plate is spaced from the second axial end of the U-shaped stator housing.

9. The rotary vane air motor housing assembly of claim 6 wherein the annular portion of the U-shaped stator housing further comprises:

a shoulder disposed at the second axial end of the cylindrical inner surface.

10. The rotary vane air motor housing assembly of claim 9 and further comprising:

a bearing cap seated within the shoulder and against the end plate to space the end plate from the annular portion.

11. The rotary vane air motor housing assembly of claim 10 wherein the bearing cap comprises:

a bearing pocket disposed on an exterior of the bearing cap to face away from the rotor pocket; and

a rotor bore for receiving a shaft of the rotor vane assembly, the rotor bore being concentric with the bearing pocket.

12. The rotary vane air motor housing assembly of claim 6 and further comprising:

a bore extending through the end plate;

an annular pocket surrounding the bore on an exterior of the end cap; and a flange extending from an end of the annular pocket into the annular pocket.

13. The rotary vane air motor housing assembly of claim 1 and further comprising a lock assembly comprising:

a washer disposed within the end cap;

a stop extending between the end cap and the washer; and

a spring extending between the stop and the washer to bias the stop away from the annular portion.

14. The rotary vane air motor housing assembly of claim 1 and further comprising:

a first bearing pocket disposed in the end wall; a first bearing disposed in the first bearing pocket;

a bearing cap positioned between the end cap and the annular portion, the bearing cap comprising a second bearing pocket;

a second bearing disposed in the second bearing pocket; and a rotor vane assembly extending between the first and second bearing pockets, the rotor vane assembly comprising:

a rotor disposed within the rotor pocket;

a plurality of vanes disposed within slots in the rotor;

a drive shaft extending from the rotor into the first bearing; and a stub shaft extending from the rotor into the second bearing.

15. The rotary vane air motor housing assembly of claim 1 wherein the end cap adjoins the annular portion along a single mating interface.

16. A rotary vane air motor comprising:

a rotor vane assembly comprising:

a rotor having an axis of rotation;

a plurality of slots disposed within the rotor;

a plurality of vanes disposed within the plurality of slots;

a drive shaft extending from a front end of the rotor along the axis of rotation; and

a stub shaft extending from a rear end of the rotor along the axis of rotation;

a two-piece stator housing surrounding the rotor vane assembly, the two- piece stator housing comprising:

a cup-shaped portion comprising:

a rotor pocket extending along the axis of rotation; and a first bearing pocket through which the drive shaft extends; and

an end cap portion coupled to the cup-shaped portion; and a bearing cap disposed between the cup-shaped portion and the end cap portion and having a second bearing pocket through which the stub shaft extends.

16. The rotary vane air motor of claim 15 wherein the cup- shaped portion comprises:

a shoulder that receives the bearing cap such that the second bearing pocket and first bearing pocket define a width of the rotor pocket.

17. The rotary vane air motor of claim 15 wherein the end cap portion comprises:

an end plate that abuts the bearing cap; and

an annular flange extending from the end plate to engage the cup- shaped portion.

18. The rotary vane air motor of claim 17 wherein the annular flange engages an exterior of the cup-shaped portion along a threaded engagement, wherein the threaded engagement defines a single mating interface between the cup-shaped portion and the end cap portion.

19. The rotary vane air motor of claim 18 wherein the end cap portion further comprises:

a spring-loaded locking mechanism.

20. The rotary vane air motor of claim 15 wherein the first bearing pocket comprises:

a wall portion extending across the rotor pocket;

a rotor bore extending through the wall portion;

a counterbore extending into an exterior of the wall portion about the rotor bore to face away from the rotor pocket;

a mounting surface surrounding the counterbore; and

mounting bores extending into the mounting surface for joining the mounting face to a power tool housing.