US3753469A

US3753469A - Air tool

Info

Publication number: US3753469A
Application number: US00175474A
Authority: US
Inventors: H Tuttle
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-07-15
Filing date: 1971-08-27
Publication date: 1973-08-21
Anticipated expiration: 1990-08-21

Abstract

A portable air tool having a rotary air motor mounted in a tubular valve sleeve or housing so that relative axial movement between the motor exhaust ports and the valve sleeve or housing opens and closes said exhaust ports. A spring biases the air motor or the valve sleeve in one direction to choke the exhaust and to effect rapid deceleration of the rotor shaft when the air supply is cut off, and an air chamber is provided in communication with the air supply and the motor inlet ports to effect movement of the motor or valve sleeve in the opposite direction to open the exhaust ports during operation of the tool.

Description

llnited States Patent [63] Continuation-impart of Ser. No. 841,875, July 15,

1969, Pat. No. 3,602,315.

[52] U.S. Cl. 173/163, 173/1 [51] Int. Cl B231) 45/04 [58] Field of Search 173/1, 12, 163

[56] References Cited UNITED STATES PATENTS 3,602,315 8/1971 Tuttle 173/1 Tuttle Aug. 21, 1973 AIR TOOL Primary Examiner-Emest R. Purser I [76] Inventor: Herman c. Tuttle, 26720 Whiteway Greene Dr., Richmond Heights, Ohio 44143 [22] Filed: Aug. 27, 1971 [57] ABSTRACT A portable air tool having a rotary air motor mounted in a tubular valve sleeve or housing so that relative axial movement between the motor exhaust ports and the valve sleeve or housing opens and closes said exhaust ports. A spring biases the air motor or the valve sleeve in one direction to choke the exhaust and to effect rapid deceleration of the rotor shaft when the air supply is cut off, and an air chamber is provided in communication with the air supply and the motor inlet ports to effect movement of the motor or valve sleeve in the opposite direction to open the exhaust ports during operation of the tool.

5 Claims, 7 Drawing Figures AIR TOOL The present application is a continuation-in-part of my copending application Ser. No. 841,875, filed July 15, 1969, now U.S. Pat. No. 3,602,315.

For many years there has been extensive use of small portable rotary pneumatic tools which rotate at speeds of 10,000 to 20,000 revolutions per minute or higher. These tools have tended to wear out rapidly at such high speeds, especially when used in foundries and other dirty atmospheres, but they have nevertheless been considered superior to other types of portable equipment for the particular purpose. Although wear remained a serious problem, it was not an insuperable one because of the special construction of the air tools to facilitate rebuilding or replacement of the air motors.

in order to be acceptable commercially, rotary air tools must not only have provision for quick and simple replacement of tools and quick replacement of worn motor parts, but must also be small, compact and light in weight so that they can easily be operated by one hand. Added accessories, such as brakes and tool guards, which were not absolutely necessary and which added materially to the size and weight of the tool or made it more difficult to operate, were not considered acceptable and were not used. Thus, conventional air tools were not provided with brakes and continued. to rotate for substantial periods of time after the air supply was shut off due to the inertia of the parts. Such rotation caused the air motors to act as suction pumps and to draw in air laden with dirt or abrasive material, thereby causing rapid wear, especially because of the extremely high rotational speeds (e.g., 10,000 to 20,000 r.p.m. or higher). This problem has existed for more than a decade but no one had a practical solution to the problem.

Brakes to stop rotation of the rotor shaft did not provide a solution to this problem for various reasons. A brake which caused a sudden stop was not acceptable because of shock damage to the tools and the danger of tool fracture at high rotational speeds. Slower stops could avoid such shocks but would not prevent operation of the air motor as a suction pump for brief periods of time and could not prevent dirt from being sucked into the motor. Furthermore it was not known, prior to this invention, how to provide a reliable brake which would be effective and commercially acceptable on a small rotary air tool of the type commonly used.

The present invention involves the discovery of a basically new method for solving the wear problem in rotary air motors and a new portable air tool having essentially all the advantages of the presently used air tools as set forth above, such as small size, quick tool replacement, easy motor replacement, etc., and also having novel means for providing choking and cushioned stopping of the rotor shaft while simultaneously preventing dirty air from being sucked into the motor. The new method of stopping rotation of the rotary air motor not only provides an exceptional solution to the dirt and wear problem but also provides protection for the grinding wheel, deburring tool or other tool being used, and makes it feasible to use rotational speeds which have heretofore been considered excessive or to employ diamond tools, carbide tools and other grinding or cutting tools which are not in use today on portable air tools because of their expense and/or their fragile or brittle nature.

The process of this invention is unusual in that, when the air supply is shut off, the exhaust is choked and the rotor shaft is rapidly decelerated by relative axial movement between the motor exhaust and a tubular valve sleeve or housing surrounding the motor. ln one embodiment of the invention the air motor is moved axially in a tubular housing by a strong spring to effect choking of the exhaust. In this embodiment an air chamber is provided adjacent the air motor and the air therein is rapidly compressed by the axial movement to force air through the motor whereby the rotor quickly decelerates and stops rotating. This is a cushioned stop free of shocks which could damage the equipment or cause tool breakage. Because the air is forced out the motor exhaust during the deceleration, the motor does not suck dirt into the motor and wear of the parts is minimized. The air motor will, therefore, have a long life even when used in a dirty atmosphere.

An air tool constructed according to the present invention can be about the same size as or only slightly larger than a conventional rotary air tool and can readily be supported and operated by one hand. Such a motor can have a closed tubular housing, with a diam eter of 1 inch to 2 inches and a length of 4 to 8 inches, and can have a rotary air motor with a piston-like stator mounted to slide axially in the housing, whereby an expansible air chamber is formed at the rear of the housing.'Tool gripping means, such as a conventional collet, may be mounted on the end of the rotor shaft, and a conventional manual control valve may be provided at the rear of the housing to control the admission of air to said expansible chamber and said motor. Means are provided for automatically causing a cushioned deceleration and stopping of the rotor shaft comprising a powerful spring means at the front of the housing biasing the stator rearwardly. When the control valve is opened to admit air to the rear of the housing, the air in the expansible chamber enters the inlet of the air motor and the air pressure causes the stator to move axially to its advanced operating position while compressing the spring. A strong spring is used to prevent acceleration of the tool in an axial direction at a dangerous rate. The air from said chamber passes from the inlet to the exhaust of the motor to drive the motor at a high speed, such as 10,000 to 20,000 r.p.m. or higher.

When the control valve is shut off, as by releasing the handle, the spring moves the entire air motor rearwardly to compress the air trapped at the rear of the housing and to cause partial blocking of the motor exhaust ports by the tubular housing which acts as a valve sleeve. This causes the air trapped in the housing to move through the air motor to the exhaust and surprisingly effects rapid deceleration and stopping of the rotor shaft rotation. Because of the absence of shock during deceleration, the novel process of this invention is well suited for the air motors of grinders whose grinding wheels are subjected to extremely high centrifugal forces and, therefore, cannot tolerate shocks due to sudden stops.

The embodiment of the invention described above having the air motor mounted for reciprocation is advantageous because it can retract the rotating grinding wheel or tool to a protected position when within the housing. However, such retraction is not so important when using grinding wheels having a substantial diameter. In carrying out the present invention, it is often preferable to mount the rotary air motor so that it cannot reciprocate and to provide an axially aliding pistonvalve, valve sleeve or the like to effect choking of the exhaust ports when the air supply is cut off. Such a valve sleeve is preferably a piston-valve provided with an annular air chamber in communication with the air supply and with the inlet ports of the motor so that the inlet air pressure acting on the valve sleeve opens the exhaust ports and holds them open during the operation of the tool. When the air supply is cut off, a spring or other biasing means immediately retracts the sleeve to close the exhaust ports and rapidly decelerate the rotor shaft. This construction provides a rapid cushioned deceleration and prevents dirt from being sucked into the motor.

Prior to this invention, the use of valves to control or restrict the flow of air exhausting from a high speed rotary air motor was considered unsatisfactory or undesirable because of inefficiency, interference with proper operation of the air motor, and waste of power. For these and other reasons, commercial rotary air tools have controlled the rotary motors by means of control valves in the air supply, rather than in the exhaust, and have kept the exhausts open except where some restriction was considered desirable to minimize noise. At the time of the present invention, those skilled in the art could see no practical advantages in high speed rotary air motors for exhaust valves which could offset their known disadvantages.

The present invention involves the discivery that a grinding wheel of a high speed rotary air tool can be brought to a quick stop without jerking or shock damage to the grinding wheel and without reducing the power or efficiency of the air motor while at the same time preventing entry of dirt into the motor. This involves a giant step forward in the portable grinder art and is also extremely important in the rotary air motor art because is solves the dirt and wear problem which has plagued the industry for decades and does so in a very simple way without sacrifice of motor efficiency and without substantial increase in the cost of manufacture.

The above advantages are obtained in the unique air tool of this invention by providing relative axial movement between the piston-valve-sleeve or tubular motor housing and the motor exhaust ports to effect instantaneous closing of the exhaust ports independently of exhaust pressure when the air supply to the tool is cut off and to effect quick opening of these ports when operation of the motor is resumed so that the exhaust is unobstructed.

An object of the present invention is to provide a small, compact, inexpensive rotary air tool with essentially all of the advantages of commonly used rotary air tools but which has a greater useful life and provides more protection against damage to the tool and injury to the operator.

A further object of the invention is to minimize wear in rotary air tools by preventing operation of the air motor as a suction pump to draw dirt into the motor.

A still further object of the invention is to provide reliable cushioned stopping of a rotary air motor which does not create objectionable shocks or cause dangerous tool fractures.

Another object is to provide a simple rotary air tool that can be assembled and disassembled readily, that permits rapid replacement of tools or grinding wheels, that is of the proper size for operaton by one hand, and

that provides economical, safe, reliable operation with minimum maintenance costs.

A still further object of the invention is to provide a reciprocating exhaust valve sleeve which may readily be adapted for use with standard air motors already in use.

These and other objects, uses and advantages of the invention will become apparent to those skilled in the art from the drawings, description and claims which follow.

In the drawings:

FIG. 1 is a vertical sectional view of one form of air tool constructed according to the present invention, the parts being shown in their positions when the grinding tool is in its advanced operating position;

FIG. 2 is vertical sectional view taken on the line 2-2 of FIG. 1;

FIG. 3 is a vertical sectional view looking at the end of the air motor;

FIG. 4 is a foreshonened fragmentary side elevational view of the air tool when the supply of air is discontinued with the grinding tool held in its advanced position by a special tool to permit placing of a wrench on the collet body;

FIG. 5 is a vertical sectional view of a modified form of air tool constructed according to the present invention, the parts being shown in their positions during rotation of the air motor;

FIG. 6 is a transverse vertical sectional view taken on the line 6-6 of FIG. 5; and

FIG. 7 is a transverse vertical sectional view taken on the line 77 of FIG. 5 and on the same scale.

Referring more particularly to the drawings, which are drawn substantially to scale and in which like parts are identified by the same numerals throughout the several views, FIGS. 1 to 4 show a small hand-supported portable air tool A constructed according to the present invention and having a piston-like air motor B mounted for reciprocation therein between the advanced position indicated in FIG. 1 and a fully retracted position against the rear wall of the tubular housing 1. The housing is preferably a closed cylindrical metal tube having a diameter of 1 inch to 2 inches and a length of 4 to 8 inches and is adapted to be held in the hand of an operator gripping a conventional throttle lever 10. When the lever is depressed against the outer surface of the housing to open the control valve 9, high pressure air is admitted to the expansible chamber 2 at the rear of the housing and forces the air motor B against the helical return spring 3 to compress the spring and advance the cutting or grinding tool 7 to an operating position as shown in FIG. 1.

The spring 3 must be heavy and very strong to function properly and is strong enough to prevent advancing movement of the air motor when the air pressure in chamber 2 is 20 pounds per square inch or below. The spring is constructed so that it can exert a force on the air motor equal to that exerted by air in chamber 2 at a pressure of at least 25 pounds per square inch (preferably at least 30 pounds per square inch).

The portable air tool of this invention is preferably small and of light weight for ease of operation. The tubular barrel or housing 1 is closed at the rear end and has a front portion l2 which is threaded to receive an internally threaded cap 11 having an internal cylindrical surface 37 coaxial with the smooth cylindrical internal surface 35 of the housing.

As herein shown, the front half of the housing is thickened forwardly of the annular shoulder 17 and has an annular groove 14 of uniform width which receives a split metal exhaust deflector 13 having flat end edges 16 spaced apart as shown in FIG. 2. The housing has a series of circumferentially spaced radial exhaust ports 15 midway between the sides of the groove 14 for communication with the annular chamber 59 of the air motor B, and the deflector 13 has an arcuate cross section to provide an annular space 38 around the housing; whereby the exhaust air from the motor flows around the groove 14 and discharges between the deflector edges 16 as indicated by the arrows in FIG. 2. The operator may readily turn the deflector 13 by sliding it in its groove 14 to change the location of the exhaust discharge so that the motor will exhaust in the desired direction (i.e., away from his body). The chamber 59 is optional and may be omitted if the slots 15 are elongated circumferentially like the slots 115 described hereafter.

The housing 1 has a thin cylindrical portion 18 extending from the annular shoulder 17 to the thick rear portion 19, which has a flat face 36 perpendicular to the axis of the housing and parallel to the flat rear piston face 47 of the air motor B for engaging the face 47 when the piston-like motor is retracted by its spring 3. The portion 19 has a vertical cylindrical bore 20 and a counterbore 21 coaxial therewith with a tapered valve seat 28 therebetween. The counterbore is threaded to receive a hollow screw plug 22, which supports a helical valve spring 33.

A cylindrical passage 24 is formed in the portion 19 near the axis of the housing to provide communication between the expansible chamber 2 and the lower portion of the bore 20, and a cylindrical inlet opening 23 is provided in the portion 19 to provide communication between the counterbore 21 and a flexible rubber air supply hose 25, which is connected to an air pump, air tank or other conventional source of high pressure air (not shown). A conventional inlet connection is provided at 26.

The flow of air from the hose 25 to the expansible chamber 2 is normally cut off by a conventional control valve 9, which has an elastic rubber O-ring 29 sealingly engaging the valve seat 28. The valve may be opened by depressing a conventional throttle lever 10 which is pivotally mounted on the housing by a pivot pin 34. The lever engages the rounded upper end portion 32 of the valve stem.

As herein shown, the control valve 9 comprises a cylindrical guide portion 31, which slides in the bore 20, a tapered intermediate portion 27 with the same diameter as the portion 31, a bottom portion 69 with a greater diameter, and a portion 30 between the portions 27 and 31 with a diameter which is reduced to facilitate air flow from the counterbore 21 through the port 24 to the chamber 2. The circular O-ring 29 is supported in the annular groove between the portions 27 and 69 and functions to shut off the air flow when the throttle lever 10 is released so that the spring 33 can move the O-ring against the valve seat 28.

The portable tool described above is unique in that the sliding-vane air motor is mounted for reciprocation, like a piston, and is rapidly decelerated and stopped by the action of the strong return spring 3 when the throttle lever is released. However, the basic elements of the air motor used in the tool are conventional. It will be understood that conventional air motors of various types may be mounted for reciprocation in an air tool constructed according to this invention. Conventional air motors are shown, for example, in the following U.S. Pat. Nos.: 1,940,024; 2,401,957; 2,423,957; 2,507,009; 2,575,524; 2,575,640; 2,830,560; and 2,905,149.

The air motor B may have a conventional rotor and stator. As herein shown, the rotor 5 is mounted on the rotor shaft 6 coaxial therewith for rotation in unison with said shaft and has four sliding vanes 58 which may be urged outwardly against the internal cylindrical surface of the stator by air pressure, springs or other conventional means or by centrifugal force alone. The stator comprises a main cylinder 39 with an external cylindrical surface 40 coaxial with the housing surface 35 and the rotor shaft 6 and an eccentric internal cylindrical surface 41 which engages the vanes 58. The main cylinder has a pair of inlet ports 42 connected by one or more longitudinal passages 43 and has a series of conventional circumferentially elongated exhaust slots or ports 44 which discharge into the annular chamber 59. The opposite ends of thecylinder 39 are closed by internally threaded front and rear end caps 45 and 46 which screw onto the externally threaded end portions of the main cylinder axially outwardly of the ports 44. Conventional flat circular wear plates 48 and 49 are provided at the front and rear of the cylinder 39 and are clamped against the ends of said cylinder by said end caps. The end caps provide supports for conventional front and rear bearings 50 and 51, which support the rotor shaft 6 for rotation about the axis of the housing 1. It is preferable to provide an annular bearing spacer 52 between the wear plate 48 and the shaft 6, but the wear plate 49 may be of a size to fit the shaft 6 if such spacer is omitted.

The end caps 45 and 46 are shaped to fit the wear plates 48 and 49, and the outer races of the bearings 50 and 51 and may be of the same or different shapes. Each has smooth external surface with a diameter substantially equal to the diameter of the housing surface 35 and is adapted to reciprocate like a piston. The cap 46 is externally cylindrical and has a flat end surface 47, whereas the cap 45 is specially shaped to receive the return spring 3 and may be specially shaped to provide axial exhaust passages at 68. It contains no air passages, whereas the cap 46 has a cylindrical air inlet port 57 axially aligned with the air inlet port 56 of the wear plate 49 to admit air to the inlet ports 42 of the air motor. The end cap 45 has a front portion which fits the outer race of bearing 50 and extends axially into the chamber and within the spring 3 and has a rear portion 66 which is internally threaded to fit the threads of the main cylinder 39.

The external shape of the end cap 45 is shown in FIG. 3. The portion 66 of the cap has regularly spaced cylindrical surface portions 67 and regularly spaced flat surface portions 68. The outer surface of the portion 66 is initially formed as a cylinder, like the outer surface of the other end cap 46, and with a diameter substantially equal to that of the internal barrel surface 35. Circumferentially spaced portions of said outer surface are then ground away at 68, leaving the portions 67. As herein shown, each surface 68 is flat and has a uniform width along the length of the portion 66. An optional exhaust air passage is thus formed in the assembled tool A at each surface 68 between the surface 35 and the surface 68 leading from the exhaust chamber 59 to the chamber 70 containing the spring 3. Part of the exhaust air from the motor B may, therefore, pass to the chamber 70 and out of the tool through the annular space between the collet body 53 and the surface 37. This outward exhaust flow helps to keep the dirt out of the chamber 70 during operation of the tool.

The inertia of the grinding or cutting tool 7, the rotor 5, and the collet 8 tends to keep these parts rotating when the control valve 9 is closed, and it would be expected that the air motor would, therefore, tend to act as a suction pump to draw dirty air into the chamber 70 and into the motor. However, in the tool of this invention, this is avoided because of the action of the strong spring 3 in conjunction with the restricted exhaust pas sages leading from the motor.

When the air supply is cut off by releasing the throttle lever 10, the return spring 3 rapidly moves the air motor toward the surface 36 to retract the tool 7. This moves the portion 66 of the end cap 45 past the ports and restricts the exhaust flow so that any air flowing to or from the exhaust chamber 59 of the motor must flow over the axial exhaust passages at 68 or other restricted outlets which limit the air flow and, therefore, yieldably resist the axial acceleration of the motor toward its retracted position. As the air is forced out of the chamber 2 through the motor to the exhaust passages at 68, the rotation of the motor is rapidly decelerated and brought to a halt, usually in a period of less than one second with the air tool illustrated in FIGS. 14. For example, in a typical small diameter air tool constructed according to this invention where its air motor is rotated at a speed of 20,000 to 25,000 revolutions per minute, the contraction of the air chamber 2 during axial retraction of the air motor by its spring 3 may be accompanied by a speed reduction of 10,000 to 20,000 revolutions per minute in a period of one second or less. This is a cushioned deceleration which avoids dangerous shocks and avoids tool breakage. The same is true with the larger air tools of this invention when using grinding wheels having a diameter of 6 inches or more, but these tools rotate at a lower speed, such as 5,000 to 10,000 revolutions per minute, and may require a few seconds to stop rotating because of the high inertia of the grinding wheel.

The spring 3 will hold the air motor in its retracted position against the surface 36 so that the tool 7 is retracted within and protected by the front cap 11. The external diameter of the tool 7 must, therefore, be less than the diameter of the surface 37 of such cap which is usually in the range of 0.5 to 0.1 inch. Where a grinding wheel is used at 7 having a diameter of l to 1.5 inches, the cap 11 may be replaced with one having a surface 37 of greater diameter. I

The collet 8 has an external cylindrical surface with a diameter less than that of the surface 37 and may be of a conventional type. As herein shown, the rotor shaft 6 has a threaded end portion 55, which screws into the internally threaded collet body 53, and said body engages the inner race of the bearing 50. The collet nut 54 is conventional and screws onto the conventional split externally threaded front portion of the collet body.

Although the spring 3 is very strong and may require a force of 40 to 60 pounds or more to effect full compression of the spring, the tool 7 can be held in an advanced position to permit tool replacement. This is done by employing a special tool 60 illustrated in FIG. 4 which has a long thin portion 61 and a small end flange 62 shaped to fit against the collet nut 54. If the surface 37 is not notched to receive the tool 60, the portions 61 and 62 must be small enough to fit between the surface 37 and the outer surface of the collet 8 or the tool 7 so that the tool can be inserted axially into the chamber to a position wherein the flange 62 hooks onto and engages the bottom surface of the collet nut 54. Then the tool 60 is moved axially relative to the tool A to compress the spring 3. Preferably the tool 60 is clamped in a vise and the air tool is pulled away from the vise to expose the collet 8.

When the two straight tool-receiving grooves 63 of the collet body 53 are exposed beyond the end of the cap 11, a conventional crescent wrench w or similar tool can be placed on the grooves 63, and the tool 60 can be removed because the wrench will engage the cap 11 to prevent expansion of the spring 3. The wrench w is thus tightly held by the spring 3 against the cap 11. The nut 54 may then be unscrewed by a suitable wrench, and the shaft 64 of the grinding tool 7 may easily be withdrawn. Thus it is simple to replace a worn or broken tool in a short period of time. As soon as the tool is replaced, the wrench w is removed from the grooves 63 to release the collet body. The spring 3 then returns the air'motor B to its retracted position against the surface 36.

The air tool of this invention is so far superior to the air tools heretofore used that it may be considered a pioneer development. Its ability to stop rotation of the cutting tool in about one second after it is operating at a speed of 10,000 to 20,000 revolutions per minute or greater makes the air tool idea] from the standpoint of cost of operation and also from the standpoint of safety. This is particularly important when the tool is operated in a dirty atmosphere. In such atmosphere, the air tool of this invention minimizes wear and can be operated several times as long without being overhauled.

The quick deceleration and cushioned stopping of the cutting tool not only prevents dirt from being sucked into the air motor but also reduces tool breakage. When a hard brittle cutting tool continues to rotate at 5,000 to 10,000 r.p.m. or higher after the air supply to the motor is cut ofi', a slight impact on the end of the tool is apt to break it and result in a sharp projectile which can cause serious bodily harm to any person in the vicinity. This type of breakage is common when using conventional portable air tools, particularly when using hard brittle cutting'tools of the type commonly used for deburring operations made of expansive tool steel.

The portable air tool described above may be made in different sizes and shapes and may be provided with a generally cylindrical barrel or housing having an internal cylindrical surface 35 with a diameter of 1 inch to 2 inches. The air tool A shown in FIGS. 1 to 4 has a diameter in the neighborhood of 1% inches and an overall length in the neighborhood of 6 inches. The rotor 5 of the air motor B has an axial length greater than the diameter of the internal surface 35 of the housing, and the air motor moves axially in the housing, from its retracted position against the surface 36 to its advanced operating position shown in FIG. 1, an axial distance greater than said diameter and greater than the axial length of said rotor. Such axial distance may be equal to or greater than the axial length of the air motor B and is usually about 1.2 to about two times the diameter of the surface 35 so that a large volume of air is present in the expanded chamber 2. Such axial distance is usually at least one inch and preferably at least 1.5 inches in a portable tool constructed according to this invention. The retraction of the motor by the strong return spring 3 forces this large volume of air through the motor to cause rapid deceleration and stopping of the motor in a short period of time.

Where more poser is required to drive larger tools or to drive gringing wheels of substantial diameter, the diameter of the air tool of this invention may be somewhat greater than 2 inches. However, it is usually preferable to employ motors with a diameter or 3 inches or less. The diameter of the air motor seldom is in excess of 4 inches, even in the larger air tools.

FIGS. 5, 6 and 7 show a modified form of air tool according to the present invention wherein the air motor is held against axial movement relative to the housing and a reciprocating piston valve is provided to open and close the exhaust ports of the motor. Such valve is shown herein as a piston-sleeve which reciprocates parallel to the axis of rotation of the motor, which surrounds the rotor and stator of the motor, and which is moved rapidly to an exhaust closing position when the air supply is shut off.

Referring more particularly to FIGS. 5, 6 and 7, there is shown therein a small hand-supported portable air tool A having a conventional rotary sliding-vane air motor B mounted in a fixed position in an aluminum housing 72.- The housing has front and rear sections 73 and 74 which are rigidly connected together by four longitudinal connecting bolts 75. The front section 73 has an internally cylindrical, externally threaded portion 76 which receives conventional roller or needle bearings 77 located between the annular portion '76 and the front portion 78 of the rotor shaft 106. An internally threaded annular cap 79 screws on the portion 76 and has radial flanges to hold the bearings in position. The shaft portion 78 projects beyond the cap 79 and has a threaded end portion 155 for receiving a collet or the holding portion of a tool. Said threaded portion could, for example, receive the collet 8 of the air tool A previously described. As herein shown, a conventional abrasive grinding tool 107 of generally conical shape is mounted on the threaded portion 155 by means of an internally threaded annular metal hub 100.

The front section 73 of the housing 72 has a hollow cylindrical portion 80 which extends from the front portion 76 to a thickened intermediate portion 81 which extends radially outwardly to a tubular portion 82 which extends axially parallel to the rotor axis and surrounds the air motor B. The portion 82 has an internal cylindrical surface 82 with its longitudinal axis parallel to and spaced from the axis of the rotor shaft 106. The surface 83 is concentric to the main cylinder of the air motor which will be described in more detail hereinafter.

The rear section 74 of the aluminum housing 72 has a cylindrical handle portion 84 with an axis parallel to the axis of rotation and is machined to provide a threaded inlet 85, a curved air inlet passage 86 and a transverse cylindrical bore 87. A counterbore88 is provided at the upper end of the bore 87 and is threaded to receive a hollow hex-head screw plug 122. The inlet passage 86 extends from the inlet 85 to the lower end of the counterbore 88 below the plug 122 as shown in FIG. 5, and the thickened portion 89 of the rear section 74 has a curved air inlet passage 123 extending from the upper end of the bore 87 below the counterbore 88 to the inlet opening 99 of the front section 73 so that air under pressure may be conveyed from the air supply hose 125 to the air motor B when the control valve 109 is opened by depressing the throttle lever l 10 from the normal position shown in broken lines in FIG. 5 to the operating position shown in solid lines in that figure. The thick portion 89 shown herein is provided with a pair of vertical ribs 90 which receive the cylindrical pivot pin 134 of the throttle lever 110. The thick portion 89 also has a circular recess 91 concentric to the rotor shaft 106 which receives the threaded end portion 92 of the shaft and also receives the roller bearing A cylindrical metal valve plug 93 is rigidly mounted in the bore 87 and preferably has a press fit in said bore. The plug has a cylindrical bore 120 and a cylindrical counterbore 94 coaxial therewith. A circular radial port 95 is provided at the front side of the counterbore in alignment with the entrance to the passage 123 to permit flow of air from passage 86 through the counterbore 88 and 94 to the passage 123. An annular tapered valve seat 128 is provided at the top of the counterbore 94 for engagement with the tapered flat annular valve head 96 of the control valve 109. The head 96 is normally biased downwardly by a helical valve spring 133 which fits on the upper part 97 of the valve stem 131 within the cylindrical recess 98 of the screw plug 122. Thus, when the lever is released, the tapered annular surface of the valve head 96 engages the valve seat 128 throughout its circumference to close off communication between the counterbore 88 and the counterbore 94 and cut of? the supply of air to the motor B. The valve stem 131 is cylindrical and slides vertically in the bore to guide the valve 109 between such closed position and the open position shown in FIG. 5, the rounded lower end portion 132 of the stern engaging the upper surface of the lever 110. The control valve 109 and the throttle lever 110 are conventional and may, of course, be replaced by other conventional control valves as disclosed, for example, in US. Pat. No. 1,940,024.

The portions of the air tool A described above are conventional and form no part of the present invention, it being understood that conventional air motors and conventional housings may be employed when carrying out the present invention and that the particular shape of the housing and the air motor may be varied within wide limits. f

The air motor of the present invention is unique in that an axially sliding valve-piston is employed to open and close the exhaust ports of the air motor. In the form of the invention shown in FIGS. 5, 6 and 7, the axial sliding movement which closes the exhaust ports is similar to that provided by the axial movement of the air motor in the embodiment of FIGS. 1 4. In order to emphasize this similarity or equivalency, parts of the air tool A are identified by numerals which are 100 greater than the numerals identifying equivalent or corresponding parts of the air tool A. Thus, the

elements

101, 102, 103, 105, 106, 107, 109, 110, 115, 120, 122, 123, 125, 126, 128, 131, 132, 133, 134, 139, 141, 142, 143, 144, 147, 148, 149, 150, 151, 152, and 158 of the air tool A identify elements which correspond to or are equivalent to elements of the air tool A. There are differences, of course, because of reversals of parts and other changes. Also, there are differences in the shape and size of the housing because the air tool A is designed to handle larger grinding tools than the tool A. It will be apparent that the tool A may be enlarged and that the tool A may be redesigned and made of a smaller size if desired.

The expansible chamber air motor used with the piston-sleeve-valve 101 of this invention may be similar to the motor B of the air tool A or any other conventional rotary air motor as mentioned previously in connection with the air tool A. Details of the air motor B aredescribed in my copending application, Ser. No. 841,875, which is incorporated herein by reference. As herein shown, the motor B' has a conventional cylindrical rotor 105 mounted on the rotor shaft 106 and coaxial therewith and has four conventional sliding vanes 58 which are mounted in radial slots 177 and which are urged outwardly against the internal cylindrical surface 141 of the stator ring 139 by centrifugal force and optionally by air pressure, springs or other conventional means (not shown). An expansible air chamber 200 is formed between each adjacent pair of vanes. The stator of the motor B has a main ring or cylinder 139 with an external cylindrical surface 140 concentric to the internal cylindrical surface 141 and eccentric with respect to the rotor 105. The main cylinder 139 has a pair of conventional circumferentially elongated inlet ports or slots 142, which are placed in communication by one or more longitudinal passages 143 in the housing portion 82, and has at least two and usually a series of conventional narrow circumferentially elongated exhaust ports or slots 144. The inlet and exhaust ports may, for example, be similar to those of US. Pat. No. 1,940,024.

The opposite ends of the cylinder 139 are closed by

circular end plates

148 and 149 having flat wearing faces perpendicular to the axis of rotation for engaging the vanes 158 and/or the flat end faces of the cylinder 139 or the rotor 105. As shown, the end plates have

annular portions

171 and 172 with outer surfaces which fit the

housing portions

89 and 81, and such portions project axially outwardly to receive and support the outer races of the

ball bearings

150 and 151, respectively. The inner races of the bearings are mounted on the long cylindrical portion 173 of the rotor shaft, which is keyed to the rotor by a key 178 and which extends from the threaded end portion 92 to the annular shoulder 174 at the end of the thicker cylindrical shaft portion 175. A nut 176 on portion 92 may be tightened against the bearing 150 to draw the latter against the annular bearing spacer 152, to pull the shoulder 174 against the bearing 151, and to limit or prevent axial movement of the shaft 106. The nut 176 maintains the parts in the position shown in FIG. with the flat

vertical faces

179 and 180 of the

housing portions

89 and 81, respectively, in engagement with the

end plates

148 and 149 while the connecting bolts 75 hold the flat end face of the tubular housing portion 82 against flat face 179. The air motor B may readily be removed for cleaning, repair or replacement by disconnecting the bolts 75, removing the nut 176, and sliding the motor axially off the shaft 106.

The air tool A of this invention is constructed to permit rapid axial sliding of the piston-sleeve-valve 101 relative to the exhaust ports 144 of the air motor B. The desired uniform radial spacing between the external cylindrical surface 140 of the stator and the concentric internal cylindrical surface 83 of the housing 72 is obtained by providing a pair of annular metal spacer rings 181 and 182 of uniform radial thickness which may be held against rotation relative to the housing 72 and relative to the stator by suitable means, such as

keys

183 and 184. These spacer rings have concentric internal and external cylindrical surfaces engaging the concentric

cylindrical surfaces

83 and 140 and have flat end faces engaging the

flat surfaces

179 and 180 of the housing as shown in FIG. 5. They preferably fit tightly in the tubular housing portion 82 so as to be held against axial movement.

In accordance with the present invention, an annular piston-sleeve-valve 101 is slidably mounted between the smooth

concentric surfaces

83 and 140 to reciprocate in an axial direction between the spacer rings or

sleeves

181 and 182 and to open and close the exhaust ports 144 of the air motor. This valve is biased in an axial direction to a normally-closed position against the spacer ring 182 by a series of helical compression springs 103 with a diameter less than the radial thickness of the sleeve 101 which are regularly spaced around the periphery of the sleeve. The opposite ends of each spring 103 fit in axially aligned circular bores in the

sleeves

101 and 181 as shown in FIG. 5. The number of springs used may be two to four or more, but three springs provide excellent results, when spaced 120 apart around the circumference.

The spacer rings 181 and 182 are provided with circumferentially elongated ports or-slots ,185 and 186, respectively, which are aligned with and of the same size as the air inlet ports 142 and which are aligned with similarly shaped discharge openings of the air passage 143 so that there is unobstructed flow of air from the air inlet 123 to the air motor B.

One or more small axial air passages 187 is provided in the spacer ring 182 to provide communication between the inlet port 186 and the expansible air chamher 102, which is formed between the ring 182 and the piston-valve 101, so that the full air inlet pressure is applied to the flat annular front face 147 of the pistonvalve to hole the flat annular rear face 188 of said valve against the corresponding flat front face of the spacer ring 181 as shown in FIG. 5 during operation of the air tool A. In this open position of the valve 101, the narrow circumferentially elongated exhaust ports or slots of the pisotn-valve are in alignment with the exhaust slots 144 so that the exhaust of the motor is not obstructed by the piston-valve.

The slots 115 are preferably of the same size as the slots 144 or somewhat larger so as not to interfere with the exhaust flow. The width of the slots 115 is preferably uniform and the same as that of the slots 144 so that axial closing movement of the piston-valve 101 effects immediate restriction or closing of the exhaust ports 144.

The tubular portion 82 of the motor housing may be open or cut away in the vicinity of the exhaust slots 1 15 but is preferably provided with deflector means or means to direct the exhaust gases out of the housing in the desired direction. This may be considered important, expecially where the exhaust is associated with a muffer or noise reduction means. As herein shown, the housing portion 82 is provided with circumferential slots 192 aligned with the slots 144 and extending the full length of the slots 144 and 115 (eg., to

as shown in FIG. 7. Each slot 192 has shallow

enclosed portions

193 and 194 and a central open portion discharging to atmosphere. As shown in FIG. 7, each pair of slots 144 arranged end-to-end and is separated by a connecting portion 196 of trapezoidal cross section and each pair of slots 115 is similarly arranged and separated by a connecting portion 197 of generally rectangular cross section. Because of the long length of the exhaust ports, the connecting

portions

196 and 197 are preferred to reinforce the

cylinders

101 and 139.

When the throttle lever 110 is released and returned by the spring 133 and the stem 131 to the normal position shown in broken lines in FIG. 5, the control valve 109 closes to cut off the air supply to the motor, the pressure in chamber 102 drops, and the compressed return springs 103 expand to force the face 147 of the piston-valve 101 against the flat annular rear face 189 of the ring 182. The piston-valve 101 is then located in a closed position wherein the ports 144 of the air motor are cut off. In this closed position, the intermediate portion 190 between the axially spaced front and rear slots 115 closes the front ports 144, and the rear portion 191 between the rear slots 115 and the rear face 188 closes the rear ports 144. In order to obtain such closing of the ports, the axial length of the intermediate portion 190 and the rear portion 191 is at least equal to the maximum stroke of the piston-valve 101 or the maximum distance between faces 147 and 189, and such stroke is greater than the width of the exhaust slots 144.

The piston-valve 101 has a sliding fit and is provided with smooth cylindrical inner and

outer surfaces

198 and 199 which slide freely on the smooth

cylindrical surfaces

140 and 83, respectively. These surfaces may be accurately machined to minimize air leakage along the length of the valve sleeve 101 and to provide the sleeve with a uniform thickness approximately equal to the radial distance between the

concentric surfaces

140 and 83.

Although additional sealing may not be needed, sealing means may be provided to prevent leakage of air from the expansible annular chamber 102 formed between the faces 147 and 189. As herein shown, the valve sleeve 101 has an integral axially elongated front portion 201 of narrow uniform rectangular cross section, and the spacer ring 182 is machined to provide an annular recess 202 of the same size and cross section as the portion 201. An elastic rubber O-ring 201 of small diameter fits in a small annular groove in the externally cylindrical rear portion of the ring 182 and sealingly engages the internal cylindrical surface of the portion 201 to prevent leakage from chamber 102. A similar rubber O-ring 204 fits in a small annular groove in the internal cylindrical surface of the valve sleeve 101 and sealingly engages the external surface 140 of the stator ring 139 to prevent leakage between the stator ring and the valve sleeve. If desired, additional seals of a similar type may be employed.

The air tool A can be supported and operated by one hand gripping the handle portion 74 and the lever 110 to hold the valve 109 in the open position of FIG. 5. At the moment the valve 109 is opened to admit air under pressure to the passages 123 and 143, the air pressure in chamber 102 immediately causes the piston-valvesleeve 101 to move axially to the open position against the ring 181 so that the exhaust ports 144 are unobstructed. The air motor B can then operate at maximum efficiency at a normal speed of perhaps 5,000 to 10,000 revolutions per minute (or higher in the case of smaller tools). The motor speed may be controlled and maintained at the proper speed for the specifiee type of grinding wheel by a conventional governor built into the tool for controlling the air supply to the motor. For example, the speed may be set at 6,000 r.p.m. for a 6-inch grinding wheel and only 5,000 r.p.m. for an 8- inch wheel.

While the tool is operating at full speed, the throttle lever may be released at any time to allow immediate closing of the valve 109. This results in a drop in pressure in the inlet passage 143 and in the chamber 102 so that the piston-valve 101 is immediately closed by the springs 103 to cut off the exhaust ports 144. The effect is similar to that obtained in the tool A of FIGS. 1 to 4 in that there is a rapid cushioned deceleration and stopping of rotor shaft rotation without damaging shock. Thus, when operating the tool at a speed of 6,000 revolutions per minute with a grinding wheel having a diameter of 6 inches or so, it is possible to stop rotation of the wheel in a few seconds without jerking and without damage to the wheel in spite of the great inertia of such a wheel. The tool will stop much faster, of course, with grinding wheels or tools of smaller diameter.

The tool of FIGS. 5, 6 and 7 is designed for use with grinding wheels with a substantial diameter, such as 3 to 8 inches, and the main cylinder 139 of the air motor may have an external diameter of 2 to 3 inches. The handle portion 84 usually has a diameter of about 1 inch to about 1% inches so that it can be gripped easily. A vertical handle of the type shown in U.S. Pat. No. 1,940,024 could also be used, if desired.

A piston-valve-sleeve, such as sleeve 101, can also be designed for use with smaller air motors, such as the motor B, having main cylinders with external diameters of l to 2 inches or less. Because the sleeve'valve surrounds the motor like a conventional motor housing, such a sleeve can replace the motor housing of many different types of air tools now in use. It is relatively simple to design a motor housing similar to the housing 72 with a piston-valve-sleeve which can receive an existing air motor which has been in use for several years. The advantages of the present invention can, therefore, be obtained by simple modification of existing tools without making new air motors or radically changing their construction.

In the air tool A of FIGS. 5 to 7, the exhaust ports and 144 are so arranged that the exhaust can be cut off quickly with an axial movement of the valve sleeve 101 which is a small fraction of an inch, such as 0.2 inch or less. Such axial movement is preferably 0.1 inch or greater and sufficient to effect complete closing of the exhaust ports 144. The same is true of an air tool of the type shown in FIGS. 1 to 4 having the air motor mounted to reciprocate in the housing.

The stator 4 of the air motor B moves axially a substantial distance to effect closing of the exhaust ports 15 because of the particular construction shown in the drawings, but such distance may obviaously be reduced to a fraction of an inch when using a valve-sleeve construction similar to that of FIGS. 5 to 7 and omitting the optional auxiliary exhaust passages at 59 and 68.

Examples are given herein which specify the sizes and proportions of certain devices, but it will be apparent that the invention can be applied to air tools of many different sizes and shapes which operate at widely varying speeds.

It will be understood that, in accordance with the provisions of the patent laws, variations and modifications of the specific devices disclosed herein may be made without departing from the spirit of the invention I agree that any patent granted on this application shall expire on Aug. 30, 1988, and shall be enforceable only for and during such period that the ownership of and legal title to said patent shall be the same as that of my US. Pat. No. 3,602,315 and that such agreement runs with any patent granted on the present application and is binding upon the grantee and the successors and assigns of the grantee.

Having described my invention, I claim:

1. A high-speed portable air tool of the character described comprising a housing having a valve sleeve, a one-direction rotary expansible-chamber air motor mounted in said housing and having an internally cylindrical stator, a rotor within said stator and eccentric thereto having a series of radially sliding vanes engaging the internal cylindrical surface of said stator, a rotor shaft having a tool-mounting end portion accessible from the exterior of said housing, said motor having an e inlet means to admit motive fluid under pressure to the expansible chambers formed between the vanes of said motor, control valve means for connecting said air inlet means to a source of air under pressure, exhaust ports in said stator, and exhaust ports in said sleeve for receiving the air exhausted from said stator and for discharging it from the motor during operation thereof, said stator and said sleeve being mounted for relative axial movement from a normal closed retracted position wherein outward flow of the exhaust gases through said sleeve is prevented and an advanced open position wherein the exhaust ports of the sleeve are adjacent the exhaust ports of the stator to facilitate such radial outward flow, pneumatic motor means responsive to air inlet pressure for causing relative axial movement of said sleeve and said stator in one direction to said advanced open position including a closed expansible chamber in communication with said air inlet means, and yieldable means for causing relative axial movement of said sleeve and said stator in the opposite direction to said closed retracted position to effect rapid deceleration and stopping of tool rotation when the supply of air to said expansible chamber is cut off by said valve means.

2. A portable air tool as defined in claim 1 wherein said sleeve is held against axial movement relative to said housing and said stator is mounted to reciprocate axially within said housing a distance sufficient to effect opening and closing of said exhaust ports.

3. A high-speed portable air tool of the character described comprising a housing having a piston-valvesleeve, a one-direction rotary expansible-chamber air motor mounted in siad housing and having a stator within said sleeve, a rotor within said stator having coaxial tool-driving spindle mounted for rotation therewith, said motor having air inlet means to admit motive fluid under pressure to the motor, control valve means for connecting said air inlet means to a source of air under pressure, exhaust ports in said stator, and exhaust ports in said piston-valve-sleeve for receiving the air exhausted from said stator and for discharging it from the motor during operation thereof, said sleeve being mounted to reciprocate axially in said housing from a normal retracted position wherein outward flow of the exhaust gases through said sleeve is prevented and an advanced open position wherein the exhaust ports of the sleeve are aligned with the exhaust ports of the stator, pneumatic motor means responsive to air inlet pressure for moving said sleeve axially in one direction from said retracted to said advanced open position including an expansible chamber in communication with said air inlet means, and yieldable means for causing rapid movement of said sleeve in the opposite direction to said retracted position to effect rapid deceleration and stopping of tool rotation when the supply of motive fluid to said exapansible chamber is cut off by said valve means.

4. A portable air tool as defined in claim 3 wherein the piston-valve-sleeve is independent of the air inlet means.

5. A portable air tool as defined in claim 3 wherein said piston-valve-sleeve has an internal diameter of about 1 to about 3 inches and the distance from said advanced to said retracted position is a small fraction of an inch and greater than the width of said exhaust ports.

Claims

1. A high-speed portable air tool of the character described comprising a housing having a valve sleeve, a one-direction rotary expansible-chamber air motor mounted in said housing and having an internally cylindrical stator, a rotor within said stator and eccentric thereto having a series of radially sliding vanes engaging the internal cylindrical surface of said stator, a rotor shaft having a tool-mounting end portion accessible from the exterior of said housing, said motor having an inlet means to admit motive fluid under pressure to the expansible chambers Formed between the vanes of said motor, control valve means for connecting said air inlet means to a source of air under pressure, exhaust ports in said stator, and exhaust ports in said sleeve for receiving the air exhausted from said stator and for discharging it from the motor during operation thereof, said stator and said sleeve being mounted for relative axial movement from a normal closed retracted position wherein outward flow of the exhaust gases through said sleeve is prevented and an advanced open position wherein the exhaust ports of the sleeve are adjacent the exhaust ports of the stator to facilitate such radial outward flow, pneumatic motor means responsive to air inlet pressure for causing relative axial movement of said sleeve and said stator in one direction to said advanced open position including a closed expansible chamber in communication with said air inlet means, and yieldable means for causing relative axial movement of said sleeve and said stator in the opposite direction to said closed retracted position to effect rapid deceleration and stopping of tool rotation when the supply of air to said expansible chamber is cut off by said valve means.

3. A high-speed portable air tool of the character described comprising a housing having a piston-valve-sleeve, a one-direction rotary expansible-chamber air motor mounted in siad housing and having a stator within said sleeve, a rotor within said stator having coaxial tool-driving spindle mounted for rotation therewith, said motor having air inlet means to admit motive fluid under pressure to the motor, control valve means for connecting said air inlet means to a source of air under pressure, exhaust ports in said stator, and exhaust ports in said piston-valve-sleeve for receiving the air exhausted from said stator and for discharging it from the motor during operation thereof, said sleeve being mounted to reciprocate axially in said housing from a normal retracted position wherein outward flow of the exhaust gases through said sleeve is prevented and an advanced open position wherein the exhaust ports of the sleeve are aligned with the exhaust ports of the stator, pneumatic motor means responsive to air inlet pressure for moving said sleeve axially in one direction from said retracted to said advanced open position including an expansible chamber in communication with said air inlet means, and yieldable means for causing rapid movement of said sleeve in the opposite direction to said retracted position to effect rapid deceleration and stopping of tool rotation when the supply of motive fluid to said exapansible chamber is cut off by said valve means.