ABRASIVE FINISHING TOOL HAVING A ROTARY PNEUMATIC MOTOR
A pneumatic abrading or polishing tool is provided that includes a motor having a rotor, a motor housing, a carrier part having a shaft and a key extending from the shaft, and an abrading or polishing head attached to the carrier part. The motor housing contains a progressive exhaust passage including a preliminary portion that relieves at least some of the air pressure inside the motor before the exhaust passage fully opens.
This patent application claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 60/882,907, filed on Dec. 30, 2006 and entitled “IMPROVED ROTOR AND ROTOR HOUSING FOR A PNEUMATIC ABRADING OR POLISHING TOOL,” the entire content of which is hereby expressly incorporated by reference.
FIELD OF THE INVENTIONThis invention relates generally to an improved motor housing for an abrading or polishing tool, such as an orbital abrading or polishing tool, and more particularly to such a motor housing having a progressive exhaust.
BACKGROUNDA known orbital abrading or polishing tool includes a motor having a rotor which rotates inside a motor housing. The rotor transmits a rotational force to a carrier part having an abrading or polishing head attached thereto. In this tool, a key extends from the carrier part and engages a keyway in the rotor, such that rotation of the rotor causes a corresponding rotation of the carrier part and the abrading or polishing head. The rotation of the rotor is caused by the introduction of compressed air through an inlet in the motor housing to one or more chambers formed between vanes in the rotor body. The compressed air flows through the inlet and contacts the rotor, causing it to rotate. As the rotor spins, the chambers progressively increase in size, permitting the compressed air to expand. The expanded air is then exhausted through one or more exhaust passages in the motor housing.
The exhaust passages of such tools are typically formed as abrupt openings in the motor housing. When the rotor spins to a position in which a particular one of the chambers overlaps the exhaust passages, the compressed air that was introduced into that chamber to rotate the rotor exhausts abruptly through these passages. This sudden release of air from the spinning motor can be very loud and distracting. Accordingly, a need exists for an improved motor housing for a rotary abrasive tool.
SUMMARY OF THE INVENTIONIn accordance with the present invention, an abrasive finishing tool having a rotary pneumatic motor is provided. The motor includes a rotor that rotates inside a motor housing. Compressed air enters the motor housing through an inlet and causes the rotor to rotate. The motor housing contains a progressive exhaust passage including a preliminary portion that relieves at least some of the air pressure inside the motor before the exhaust passage fully opens. This progressive design can reduce the sudden noise caused by an abrupt exhaust opening.
In one embodiment of the present invention, an abrasive finishing tool having a rotary pneumatic motor is provided. The tool includes an abrading or polishing surface; a carrier part connected to the abrading surface; a stator having an inner surface defining a motor cavity; and a rotor contained within the motor cavity and engaging the carrier part in a driving relationship; the stator has an inlet opening for introducing an expandable fluid into the motor cavity, and further has a progressive exhaust channel having a preliminary portion that relieves at least some of the air pressure inside the motor cavity before the progressive exhaust channel fully opens.
In another embodiment of the present invention, an abrasive finishing tool having a rotary pneumatic motor includes a motor having a rotor and a housing containing the rotor; a carrier part engaging the rotor; and an abrading head attached to the carrier part; the housing comprising an inlet passage configured to introduce air into the motor and a progressive exhaust passage having a preliminary portion configured to release air from the motor prior to the release of air through a secondary portion greater in cross section than the preliminary portion. The preliminary portion of the progressive exhaust passage may comprise a preliminary slot, and the secondary portion of the progressive exhaust passage may comprise a secondary slot offset from the preliminary slot.
Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the features of the present invention.
The detailed description set forth below in connection with the drawings is intended as a description of the presently preferred embodiments of an abrasive finishing tool having a rotary pneumatic motor provided in accordance with the present invention and is not intended to represent the only forms in which the present invention may be constructed or utilized. It is to be understood that the same or equivalent functions and structures may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention. For example, whereas the pneumatic tools of the invention are described herein as using compressed air, in fact any suitable other compressed gas or expandable fluid can be used. As denoted elsewhere herein, like element numbers indicate like elements or features.
As shown in
As shown in
As shown in
When compressed air enters the motor cavity 43, it causes the rotor 42 of the motor 13 to rotate. The air driven motor 13 drives a carrier part 14 rotatively about a primary vertical axis 15. An orbitally driven part 16 is connected to the carrier part 14 for free rotation about a secondary vertical axis 17 displaced horizontally from the primary vertical axis 15. The part 16 carries an abrading or polishing head or shoe 18 and an abrasive or polishing sheet 19 as the part 16 moves orbitally about the axis 15 to sand or polish the surface 12. Thus, when the user grasps the tool 10 and presses down on the lever 107, the compressed air enters the motor cavity 43 and causes the rotor 42 to rotate, causing orbital motion of the abrading head 18.
The rotor 42 spins inside a stator or housing 35 of the motor 13. The housing 35 has a vertical inside wall 47 which may be cylindrical but eccentric with respect to the primary axis 15. Externally, the rotor 42 has a vertical cylindrical surface 66 centered about the axis 15 and therefore eccentric with respect to the inside wall 47 of the motor housing 35 as seen in
Compressed air enters an individual chamber 69 through the inlet passage 70 and begins to expand inside that individual chamber 69. This expanding air causes the rotor 42 to rotate against the inside wall 47 of the housing 35. As the rotor rotates, the individual chamber 69 increases in size. The air expands and the rotor rotates until the chamber 69 overlaps the exhaust passages 302 and 304. The expanded air is then free to exit through these exhaust passages 302 and 304 and flow through outlet passages 86 in the body 22 and block 84. The outlet passages 86 lead to a vertical tube 87 in the block 84, and this tube 87 delivers the exhaust downwardly into an exhaust tube 88 leading to a discharge hose 89.
In the embodiment shown in
When the compressed air enters an individual chamber 69 inside the motor cavity 43, it begins to expand and causes the rotor 42 to rotate in a clockwise direction. The rotor spins until the chamber 69 is aligned with the exhaust passages. The preliminary portion P is the first portion of the exhaust passage that the chamber reaches. The preliminary portion P of the primary exhaust passage 302 allows some of this air to escape and thus provides initial relief to the air pressure inside the cavity 43. The rotor continues to rotate, bringing the chamber 69 into open alignment with the secondary portion S, where both exhaust passages are open. This secondary portion S has a larger cross sectional area than the preliminary portion P and provides the greatest area for exhausting the air from the chamber 69. As the rotor continues to rotate along the inside wall 47 of the housing 35, the chamber 69 moves past the secondary portion S. The rotor then begins another rotation cycle around the motor cavity 43.
Because the two passages 302 and 304 are offset, the preliminary portion P provides preliminary pressure relief without abruptly opening both exhaust passages to their full volume. In the embodiment, shown, the preliminary portion P has a smaller cross-sectional area than that of the secondary portion S. This progressive design provides a more gradual opening of the exhaust passage. Because the air inside the chamber 69 begins to leak out through the preliminary portion P before fully exhausting through both passages 302 and 304 in the secondary portion S, the exhaust process is more gradual than an abrupt opening of both passages at the same point. This progressive opening can help to reduce the loud noise caused by an abrupt exhaust.
In the embodiment shown in
As shown in
Even within the preliminary portion P, the exhaust passage may have a progressive design where the air first flows down the primary passage 302 toward the recess 306, as shown in
This progressive exhaust is further shown in
As shown in
As shown in
The bottom wall 39 of the motor housing or stator is similar to the top wall portion 37, but inverted with respect to the top wall. More particularly, the bottom wall 39 has an upper planar horizontal surface 56, a cylindrical outer edge surface 57 which fits fairly closely within the cylindrical surface 23 of the body part 22, and a horizontal annular undersurface 58 which is engaged annularly by the shoulder surface 31 of the retainer 29 to clamp the bottom wall 39 upwardly against the side wall 36 of the motor housing 35. Radially inwardly of the surface 58, the bottom wall 39 has a downwardly projecting annular portion 60 defining an essentially cylindrical recess 61 within which the bottom ball bearing assembly 40 is received and located. The inner race of the bearing 40 is a close fit about the externally cylindrical shaft portion 44 of the carrier 14, to contact with the upper bearing 38 in the mounting part 14 for its desired rotation about the axis 15. The top wall portion 37, bottom wall 39, and motor housing 35 form the motor cavity 43 within which the rotor 42 spins. As shown in
As shown in
As shown in
In one embodiment, as shown in
In one embodiment, as shown in
In one embodiment, the outside diameter (OD) of the rotor 42 is approximately 1.35 inches, the depth (D) of each radial slot 68 is approximately 0.415 inches, and the width (W) of each radial slot 68 is approximately 0.070 inches. As such, each radial slot 68 is formed to a depth that is approximately 30% of the outer diameter (OD) of the rotor 42.
As is also shown in
As described above, a key 64 extends from the carrier part 14 and engages the keyway 124 in the rotor such that rotation of the rotor causes a corresponding rotation of the carrier part 14 and the abrading or polishing head 18. Beneath the level of the lower bearing 40, the carrier part 14 has an enlarged portion 89′ which is typically externally cylindrical about the axis 15. The enlarged portion 89′ then contains a recess 90 centered about the second axis 17 which is parallel to but offset laterally from the axis 15. The orbitally driven part 16 has an upper reduced diameter portion 91 projecting upwardly into the recess 90 and is centered about the axis 17 and journaled by two bearings 92 and 93 for rotation about the axis 17 relative to the carrier 14, so that as the carrier turns the part 16 is given an orbital motion. The rotation of the lower enlarged portion 89′ of carrier 14 causes orbital movement of the head 18 and its carried sandpaper sheet 19, to abrade the work surface 12.
A lower enlarged diameter flange portion 94 of the part 16 has an annular horizontal undersurface 95 disposed transversely of the axis 17. A threaded bore 96 extends upwardly into the part 16 and is centered about the vertical axis 17, for engagement with an externally threaded screw 97 which detachably secures the head 18 to the rest of the device. A counterweight plate 98 may be located vertically between the carrier 14 and the flange 94 of the part 16, and be secured rigidly to the part 14 by appropriate fasteners. It may be externally non-circular about the axis 15 to counterbalance the eccentrically mounted part 16, the head 18, and any other connected elements.
The carrier part 14 carries the part 16 and the abrading head 18. The head 18 may be rectangular in horizontal section, including an upper horizontally rectangular rigid flat metal backing plate 99 having a rectangular resiliently deformable cushion 100 at its underside, typically formed of foam rubber or the like. The sheet of sandpaper 19 extends along the undersurface of the cushion 100, and then extends upwardly at opposite ends of the head for retention of its ends by two clips 101. The screw 97 extends upwardly through an opening in the plate 99 to secure the head 19 to the orbitally moving part 16. In other embodiments, the head 18 and sandpaper 19 may have other cross-sections, such as a circular cross-section.
As shown in
The lower end 102 of the flexible tubular boot 33 carries and is permanently attached to a plate 103 preferably formed of sheet metal which is essentially rigid. Plate 103 has a horizontal circular portion 104 extending parallel to the upper surface of plate 99, and at its periphery has an upwardly turned cylindrical side wall portion 105 fitting closely about and bonded annularly to the lower externally cylindrical portion 102 of rubber boot 33. The plate 103 has a central opening 106 through which the screw 96 extends upwardly, so that upon tightening of the screw the plate 103 is rigidly clamped between the plate 99 and the element 16, with the boot 33 then functioning to retain the head 18 against rotation relative to the upper portion of the tool.
The head 18 rotates against the work surface 12 to polish or sand the surface. In operation, the user presses down on the lever 107 to open the valve 83 and introduce compressed air into the individual chambers 69 inside the motor cavity 43. The air expands and causes the rotor 42 and chambers 69 to rotate, bringing them into alignment with the exhaust passages 302 and 304. The progressive design of the exhaust gradually relieves the air pressure and helps to reduce the loud noise associated with a sudden and abrupt exhaust of air.
Although the drawings illustrate the invention as applied to a pneumatic orbital sander, it will be apparent that the novel aspects of the air motor arrangement of the invention may also be utilized in other types of portable pneumatic abrading or polishing tools. The preceding description has been presented with reference to various embodiments of the invention. Persons skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structures and methods of operation can be practiced without meaningfully departing from the principles, spirit and scope of this invention.
Claims
1. An abrasive finishing tool having a rotary pneumatic motor comprising:
- a motor having a rotor and a housing containing the rotor;
- a carrier part engaging the rotor; and
- an abrading head attached to the carrier part,
- wherein the housing comprises an inlet passage configured to introduce air into the motor and a progressive exhaust passage having a preliminary portion configured to release air from the motor prior to the release of air through a secondary portion greater in cross section than the preliminary portion.
2. The abrasive finishing tool of claim 1, wherein the preliminary portion of the progressive exhaust passage comprises a preliminary slot and the secondary portion of the progressive exhaust passage comprises a secondary slot offset from the preliminary slot.
3. The abrasive finishing tool of claim 2 wherein the preliminary slot overlaps the secondary slot.
4. The abrasive finishing tool of claim 2 wherein the preliminary slot opens before the secondary slot opens and closes after the secondary slot opens.
5. The abrasive finishing tool of claim 1, wherein the housing further comprises a recess formed in an outer surface of the housing and encompassing at least a portion of the progressive exhaust passage.
6. The abrasive finishing tool of claim 1, wherein the rotor comprises a keyway that mates with a key on the carrier part to engage the rotor with the carrier part.
7. The abrasive finishing tool of claim 1, wherein the housing is made of steel.
8. The abrasive finishing tool of claim 1, wherein the tool is a pneumatic orbital abrading or polishing tool.
9. The abrasive finishing tool of claim 1, wherein the rotor comprises an outer body and a central core.
10. The abrasive finishing tool of claim 9, wherein the outer body and central core comprise mating protrusions that lock the outer body to the central core to prevent relative rotation therebetween.
11. The abrasive finishing tool of claim 9, wherein the central core comprises steel.
12. The abrasive finishing tool of claim 1, wherein the preliminary portion comprises a first portion of a first slot and the secondary portion comprises a second slot and a second portion of the first slot, such that the preliminary portion has a cross-sectional area that is less than the cross-sectional area of the secondary portion.
13. An abrasive finishing tool having a rotary pneumatic motor comprising:
- an abrading or polishing surface;
- a carrier part connected to the abrading or polishing surface;
- a stator having an inner surface defining a motor cavity; and
- a rotor contained within the motor cavity and engaging the carrier part in a driving relationship,
- the stator comprising an inlet opening for introducing an expandable fluid into the motor cavity, and further comprising a progressive exhaust channel having a preliminary portion that releases at least some of the fluid inside the motor cavity before the progressive exhaust channel fully opens.
14. The abrasive finishing tool of claim 13, wherein the progressive exhaust channel has a secondary portion configured to fully open the progressive exhaust channel, and wherein the preliminary portion has a cross-sectional area that is less than a cross-sectional area of the secondary portion.
15. The abrasive finishing tool of claim 13, wherein the progressive exhaust channel comprises a plurality of offset slots.
16. The abrasive finishing tool of claim 13, wherein the stator further comprises a recess formed in an outer surface of the stator and overlapping with at least a portion of the progressive exhaust channel.
17. The abrasive finishing tool of claim 13, wherein the preliminary portion comprises a preliminary slot and the progressive exhaust channel comprises a secondary slot offset from the preliminary slot.
18. The abrasive finishing tool of claim 13, wherein the rotor comprises an outer body surrounding a central core having a keyway that engages a key on the carrier part.
19. An abrasive finishing tool having a rotary pneumatic motor comprising:
- a motor comprising a rotor configured to rotate inside a motor housing;
- a carrier part engaged with the rotor;
- an abrasive surface attached to the carrier part;
- the motor housing comprising an inlet and a progressive exhaust, and the progressive exhaust comprising a preliminary portion and a secondary portion, the preliminary portion being configured to release air from the motor before the secondary portion opens.
20. The abrasive finishing tool of claim 19 wherein the preliminary portion is smaller in cross section than the secondary portion.
Type: Application
Filed: Dec 20, 2007
Publication Date: Jul 3, 2008
Inventor: Donald H. Hutchins (Sierra Madre, CA)
Application Number: 11/961,986
International Classification: B24B 23/03 (20060101);