US3399494A

US3399494A - Air operated sanding machine

Info

Publication number: US3399494A
Application number: US463511A
Authority: US
Inventors: Hendrickson Otto
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-06-14
Filing date: 1965-06-14
Publication date: 1968-09-03
Anticipated expiration: 1985-09-03

Description

Sept. 3, 1968 O. HENDRICKSON 3,399,494

AIR OPERATED SANDING MACHINE Filed June 14, 1965 4 ShGGtS -ShQGT. 1

1 Of/o Hendr/t/rson 1N VENTOR.

P 3, 1968 o. HENDRICKSON 3,399,494

AIR OPERATED SANDING MACHINE Filed June 14, 1965 4 Sheets-Sheet 2 Fig.5

224' 225 Q 603432 0Q I70 2 v m 1 g 6 23 e I 6 22a 4 fit lm I I II lao

m I Otto Hendr/fckson 2/2 L 208 INVENTOR.

P 1968 o. HENDRICKSON 3,399,494

AIR OPERATED SANDING MACHINE Filed June 14, 1965 4 Sheets-Sheet 5 V 1 I Offo Henar/c/rson INVENTOR.

Sept. 3, 1968 o. HENDRICKSON 3,399,494

AIR OPERATED SANDING MACHINE Filed June 14, 1965 4 Sheets-Sheet 4 Otto Hendr/ckson 1N V15 N TO K United States Patent 3,399,494 AIR OPERATED SANDING MACHINE Otto Hendrickson, Riverside, Calif., assignor 0f one-third to Al Lohbeck, Arcadia, Calif. Filed June 14, 1965, Ser. No. 463,511 9 Claims. (Cl. 51-62) ABSTRACT OF THE DISCLOSURE A pneumatically driven rubbing machine including a piston reciprocated by means of an alternately directed flow of compressed air which is eifectuated by inserting a flow directing valve in series with an air intake. Expansion of air against one end of the piston causes a stroke in one direction. The valve is coupled to the piston so that motion of the piston causes rotation of the valve which in turn re-directs the air intake to the opposite end of the piston resulting in an oppositely directed stroke. The piston is gear-linked to a reciprocating rubbing member which operates upon a work surface.

The present invention generally relates to an air operated sanding machine and more particularly to such a machine having certain novel structural features therein which enable a more effective operation of a sanding or operating element driven by a pneumatic motor.

One object of the present invention is to provide an air operated sander including an air motor having a reciprocating piston therein in which the piston rings on the piston are expanded by air pressure so that the air pressure when driving the piston will at the same time expand the rings against the cylinder wall so that the piston rings will be sealingly retained against the cylinder wall carrying both the power stroke and exhaust stroke of the piston.

Another object of the present invention is to provide an air operated sanding machine having an air motor for driving an abrading element incorporating a novel valve assembly therein, which employs ports orientated directly across from one another so that at the same instant air begins to enter one cylinder, it is exhausted from the other cylinder. Incorporated into the assembly is a slightly slack or lag at the actuator and valve joint thus permitting the valve to stay open for a period of time when the piston is moving on the power stroke before beginning to close the inlet port thus keeping the exhaust open on the other side of the piston and in the other cylinder for better venting of the other cylinder.

Yet another object of the present invetion is to provide an air operated sanding machine having a motor of the reciprocating piston type connected with a sanding shoe or the like in which the piston travels in the opposite direction to the sanding shoe with there being equal force exerted against the cylinder head connected to the machine body and the piston which forces the machine body toward the direction the sanding shoe is moving. Thus, the harder one presses on the machine, the more the air driving the machine will help to balance the machine.

A further important feature of the present invention is to provide an air motor for driving a sanding machine including a reciprocating piston and oscillating valve assembly orientated with the piston close to the center of the machine body thereby substantially eliminating side wiggle of the machine thus reducing fatigue incident to operation of the machine. Further, the structure of the interconnection between the piston and the sanding shoe permits the piston to be placed very close to the bottom of the machine thus overcoming up and down motion of the machine body.

A still further significant feature of the invention is to provide a machine body with a cylinder extending therethrough with each end of the cylinder forming a working cylinder and each end of the cylinder being closed by a cap at the end thereof to prevent air blow-by due to the cylinder being close to the bottom of the machine body.

Another feature of the present invention resides in its relative simplicity of construction, compactness, dependability, ease of assembly and repair and relatively inexpensive manufacturing cost.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIGURE 1 is a top plan view of the air operated sanding machine of the present invention;

FIGURE 2 is a side elevational view of the air operated sanding machine of this invention;

FIGURE 3 is a transverse, sectional view taken substantially upon a plane passing along section line 3-3 of FIGURE 2 illustrating the orientation of the valve and the operating handle therefor;

FIGURE 4 is an end view of the present invention as viewed from the right hand end of FIGURE 2;

FIGURE 5 is a longitudinal, plan sectional view taken substantially upon a plane passing along section line 5-5 of FIGURE 2 with certain areas of the structure being broken away;

FIGURE 6 is a longitudinal sectional view taken substantially along section line 6-6 of FIGURE 5 illustrating further structural details of the invention illustrating in particular the construction of the oscillating valve;

FIGURE 7 is a transverse, sectional view taken substantially upon a plan passing along section line 7-7 of FIGURE 5 illustrating further structural details of the machine body and oscillating valve;

FIGURE 8 is a perspective view of the reciprocating piston employed in the air motor;

FIGURE 9 is a longitudinal sectional view taken substantially upon a plane passing along section line 9-9 of FIGURE 6 illustrating the mechanism for reciprocating the sanding shoe;

FIGURE 10 is a perspective view of the valve body and the oscillating valve member;

FIGURE 11 is an exploded perspective view of the valve body and valve member illustrated in FIGURE 10 with the bearings omitted;

FIGURE 12 is a detail sectional view taken substantially along a plane passing along section line 12-12 of FIGURE 6 illustrating the structure of the valve member and its association with the valve body;

FIGURE 13 is an end view of the right hand end of the machine with the end plate exploded therefrom;

'FIGURE 14 is an end view similar to FIGURE 13 but illustrating the left end View of the machine;

FIGURE 15 is a detailed sectional view taken substantially upon a plane passing along section line 15-15 of FIGURE 6 illustrating the air flow passage and pressure seal arrangement for the cylinder and the expansion passage for the piston rings; and

FIGURE 16 is a detailed sectional view taken substantially upon a plane passing along section line 16-16 of FIGURE 15 illustrating further structural details of the cylinder seal and piston rings and the air passageways.

Referring now specifically to the drawings, the air operated sanding machine of the present invention is generally designated by the numeral 10 and includes an air motor 12 and a sanding pad 14 which is driven in a reciprocating manner by the air motor 12. The air motor 12 includes a one-piece block or body 16 of generally rectangular configuration but having longitudinally extending concave areas 18 in the side walls thereof to provide rounded and outwardly flared upper corners 20 to provide means for effectively gripping the machine with the thumb orientated in one concave area and the ends of the fingers orientated in the other. All of the fingers could be provided in one concave area or the forefinger could be orientated along the top surface of a downwardly curved forward end 22 of the body 16. The size, shape and dimensions of the body as just defined enables a person to conveniently support and move the sanding machine by grasping the body 16 in the manner described.

The body 16 has a longitudinal passageway extending therethrough in the form of a bore 22 which is of constant diameter with the end portions thereof defining

cylinders

24 and 26. The bore 22 receives a reciprocating piston generally designated by numeral 28 which includes oppositely disposed

piston heads

30 and 32 interconnected by a narrow central portion 34 that is partially cylindrical and the

piston heads

30 and 32 are cylindrical in configuration and each

piston head

30 and 32 includes a peripheral groove 36 disposed adjacent the respective piston head such as the head 32 illustrated in FIGURE 16. A pair of split piston rings 38 are disposed in each groove 36 with the slit in the rings being inclined as at 40. The piston rings 38 are constructed of a plastic-type material which has considerable wear resistance and is relatively easy to lubricate or provided with impregnated lubrication. Communicated with the groove 36 is a pair of

diametrical passageways

42 and 44 with the passageway 42 communicating with the portion of the grooves 36 underlying one of the rings 38 and the passageway 44 communicating with the groove 36 underlying the other of the rings 38. The

passageways

42 and 44 are communicated with each other by a longitudinal passageway 46 which intersects both the

passageways

42 and 44 and extends to the surface of the piston head such as the piston head 30 illustrated in FIGURE 16. Thus, the air exerting pressure on the piston head 30 will also pass inwardly through the passageway 46 and then radially outwardly through the

passageways

42 and 44 for urging the sealing rings 38 outwardly in relation to the groove 36 into sealing contact with the wall of the cylinder 26 for sealing the piston 28 in relation thereto during reciprocation thereof.

The ends of the

piston heads

30 and 32 have a chamfered peripheral edge 48 to facilitate their reciprocation and the narrow central portion 34 of the piston 28 is provided with end shoulders 50. Disposed between the shoulders 50 adjacent the lower end edge thereof is a mounting plate or gear plate 52 having a plurality of gear teeth 54 extending from one surface thereof thus forming a rack gear rigid with the piston 28. The rack gear is generally designated by numeral 56 and the plate 52 thereof is secured to the central portion 34 of the piston 28 by rivet type fasteners 58 which have the heads thereof received in recesses 60 formed in the opposite wall of the central portion 34. Also received in each recess 60 is a wick 62 in the form of a cylindrical absorbent pad which are in the form of oil wicks and which will conform to the internal surface of the bore 22 for facilitating lubrication of the wall of the bore 22 during reciprocation of the piston 28.

Disposed vertically in the body 16 is a bore 64 receiving a generally cylindrical valve body 66 that is secured in the bore 64 by a press fit or in a removable manner if desired. Disposed in said valve body 66 is an oscillating valve member generally designated by numeral 68 and a valve actuator generally designated by the numeral 70 which includes a tubular member 72 having a spur gear 74 on the lower end thereof with the spur gear 74 and tubular shaft 72 being of one-piece construction. The spur gear 74 has peripherally spaced gear teeth 76 thereon which are in meshing engagement with the gear teeth 54 on the rack gear 56. Thus, when the rack gear 56 is reciprocated due to reciprocation of the piston 28, the valve actuator 70 will also be oscillated about the longitudinal axis of the tubular shaft 72. The upper end of the tubular shaft 72 is provided with a semicylindrical recess 78 which extends diametrically of the tubular shaft and thus defines a pair of longitudinally extending shoulders or lobes 80 which are disposed at diametrically opposed points on the tubular shaft 72. A cylindrical insert 82 is press fitted into the valve body or sleeve 66 and includes a central bore 84 which receives the upper end portion of the tubular shaft 72 with the bottom of the recess 78 generally aligned with the bottom of the insert 84. The insert 84 is provided with a pair of diametrically disposed

arcuate slots

86 and 88 therein for a purpose described hereinafter.

The valve member 68 is in the form of a cylindrical rod-like body 90 having an upper axial extension 92 of slightly less diameter with the juncture between the cylindrical body 90 and the projection 92 being formed by a peripheral shoulder 94 which supportingly engages the upper end of the insert 82 with the cylindrical body 90 being rotatably disposed in the bore 80 and the projection 92 being disposed above the insert 82 as illustrated in FIGURE 6.

The lower end of the valve member 68 is provided with a recess 96 which defines a pair of axial shoulders or lobes 98 engageable with the shoulders or lobes on the tubular shaft 70 whereby the actuator 70 will be drivingly joined or connected with the valve member 68 for oscillation thereof in response to oscillation of the tubular shaft 72. While the shoulders or lobes 80 are disposed diametrically across the tubular shaft 72, the shoulders or lobes 98 are angularly disposed with the extent of the cylindrical portion between the lobes 98 being less than one-half a circle thus providing a space or slack 100 between one of the lobes 98 and one of the lobes 80 when the valve actuator and valve are assembled.

The two lobes 98 on the cylindrical body 90 are formed by a longitudinal groove or slot 102 communicating with the bottom edge of the valve member at a point between the shoulders 98 and extending upwardly and diametrically of the cylindrical body 90 to a point generally midway the distance between the shoulder 94 and the recess 96 as illustrated in FIGURES 6 and 11. The groove or slot 102 has a smoothly arcuating bottom for guiding air therethrough in a manner described hereinafter.

The upper end of the valve member 68 is also provided with a slot or groove 104 which has an arcuate bottom surface which terminates in spaced relation to the bottom end of the cylindrical body 90 and generally slightly above the horizontal plane of the recess 96. The upper end of the slot or groove 104 extends to the top surface of the projection 92 as illustrated in FIGURES 6 and 11 for inlet of air in a manner described hereinafter. A screw-threaded cap 106 is threaded into the internally threaded upper end portion 108 of the valve body or sleeve 66 with a suitable O-ring or other seal 110 being provided for the cap 106 and with the cap 106 including a polygonal socket 112 for receiving a suitable wrench. By removing the cap 106. the valve member 68 may be removed by turning the machine upside down so that the valve member will drop out thus enabling another valve member to be inserted with the valve members having different slack or lag characteristics for determining the length of stroke of the sanding shoe 14. If a longer stroke is desired more clearance between the

lobes

80 and 98 should be provided.

For rotatably supporting the tubular shaft 72, there is provided a pair of

ball bearing assemblies

114 and 116 which are press fitted onto the exterior surface of the tubular shaft 72 and into the interior surface of the sleeve or body 66. Inner and

outer spaces

118 and 120 are provided with the spacer 118 spacing the inner races of the

ball bearing assemblies

116 and 114 and the outer spacer 120 spacing the outer races of the

ball bearing assemblies

114 and 116.

Also, the sleeve or body 66 is provided with a pair of diametrically opposed

circumferential slots

122 and 124 therein which are aligned with the

slots

86 and 88 respectively. Disposed above the slot 122 is an arcuate slot 126 which is an inlet slot. The slot 126 is a high pressure inlet slot and is slightly offset in relation to the rear port 122. As illustrated, the upper end of the insert 82 is aligned with the lower edge of the port 126 and the shoulder 94 and groove 104 is communicated with the chamber defined by the interior of the valve sleeve or body 66, the closure cap 106 and the reduced projection 92 so that high pressure air enters the inlet port 126 and is at all times communicated with the slot or groove 104.

For supplying high pressure air to the high pressure inlet port 126, the body 16 is provided with an inlet passageway 128 that extends rearwardly from the port 126 to a rear head 130 which includes a passageway 132 communicating with the passageway 128 and which is retained in place by suitable fastening screws 134 or the like. The passageway 132 is of angular orientation and extends into a valve body 136 that is integral with the head 130. The valve body includes an inlet passageway 136 having a suitable fitting 138 attached thereto by which a high pressure air inlet hose 140 is connected to the passageway 136. The passageway 136 is connected to the passageway 132 through a valve seat 142 that is engaged by a ball valve member 144 having a stem 146 extending upwardly therefrom through a suitable guide 148. A spring 150 retains the ball valve 144 against the seat 142 and the spring 150 is retained in place by a retaining plug 152. The upper end of the valve stem 146 is rounded and engages the surface of an elongated operating handle 154 that has depending lugs or ears 156 pivotally attached to the valve body 134 by pivot bolt or pins 158. The operating end 160 of the handle extends longitudinally of the top surface of the body 16 in an upwardly inclined manner and generally underlies the palm of a hand grasping the sanding machine so that by exerting downward pressure thereon, the ball valve 144 may be depressed thus admitting high pressure air into the passageway 132 and subsequently through the passageway 128, port 126 and down through the slot 104 in the valve member 68.

Extending rearwardly from the port 122 is a passageway 162 and extending forwardly from the port 124 is a passageway 164. The outer end of the passageway 162 extends downwardly as at 166 and the outer end of the passageway 164 extends downwardly as at 168 and in each instance, the downwardly extending

passageways

166 and 168 terminate above the top edge of the longitudinal bore 22 or above the

cylinders

22 and 24. The outer limit of the passageway 166 is defined by the rear head 130 while the outer limit of the passageway 168 is defined by a removable front head 170 secured in place by fastener bolts 172 or the like.

Formed in the head 170 is a groove 174 which communicates with the passageway 168 and also communicates with an opening 176 in a closure plug or seal 178 in the end of the cylinder 24. The head 130 is provided with a similar passageway 180 which communicates with a similar aperture 182 in an end closure plug or seal 184 in the cylinder 26. The caps or plugs 170 and 184 have their apertures adjacent the upper end thereof which prevents air blow-by due to the cylinder being close to the bottom of the machine. The plug 184 is retained in place by being press fit therein or retained in place by the end head.

The

passageways

162 and 164 are combination exhaust and inlet ports and in one position of the valve member 68 such as is illustrated in FIGURES 5 and 6, high pressure air comes in through the passageway 128, down through the slot or groove 104, through the port 86, through the port 122 subsequently throughthe passage 122, passage 166, passage 180 and aperture 182 into the cylinder 26 for forcing the piston to the right as illustrated in FIGURE 6. The passageway 164 is then acting as an exhaust with the exhaust products passing through the aperture 176, passageway -174, passageway 168, passageway 164, port 124, port 88, through the slot or groove 102 and down through the tubular shaft 72 for discharge from the bottom of the gear 74. As the piston'is forced to the right, the valve actuator 70 and the valve member 68 will be rotated a partial revolution until such time as the groove 104 communicates with the passageway 164 and the groove 102 communicates with the passageway 162 which then will supply air through the passageway 164 to the cylinder 24 and exhaust products from the cylinder 26 through the passageway 162.

The bottom of the body 16 has a recess 186 which communicates with the bore 22 in the center thereof and this bore receives the gear 74 which is in meshing engagement with the rack gear 56. Communicating with the recess 186 is an elongated recess or groove 188 which has an oillite strip bearing 190 secured to the outer surface thereof for hearing engagement with a reciprocating rack gear 192 which has teeth 194 thereon in meshing engagement with the teeth 76 on the gear 74. Thus, as the rack gear 56 is moved in one direction, the gear 74 is rotated thus moving the rack gear 192 in the opposite direction. The rack gear 192 is secured to the sanding pad by the use of rivets or other suitable fasteners 196 which extend through the supporting plate for the rack gear 192 as designated by numeral 198, spacer plates 200, a connecting plate 202 and a bottom plate 204 having a sandpaper panel 206 or the like secured thereto. A suitable cushioning pad may be provided behind the sandpaper anel as deemed appropriate. For guiding reciprocation of the sandpaper pad, there is provided a pair of elongated L-shaped guide members 208 that are received in recesses 210 in the body 16 and secured in place by screwthreaded fasteners 212 or the like. The lower edge of the guide member 208 are inturned and are received under the plates 200 for sliding reciprocation in relation thereto and the plates are retained in place by their connection with the body 16. Thus, as the sandpaper pad is reciprocated, the movement thereof will be guided by the L-shaped guide members 208 sandwiched between

plates

200 and 204 thus retaining the structures in assembled and aligned relationship.

A spring clamp structure 214 is provided for retaining the sandpaper panel 206 in place with the sandpaper panel having the ends thereof wrapped around the bottom plate 204 with the spring clamps 214 releasable retaining the sandpaper panel 206 associated with the plate 204 for abrading a surface when engaged therewith.

A hearing plate 216 underlies the gear 74 in spaced relation thereto and enables discharge of air therefrom and this plate is connected to the reciprocating sandpaper pad for reciprocation therewith and this serves to clean the working components of the sanding machine and also cleans the work. To further seal the structure, dust seals 218 are provided along the bottom edges of the

heads

130 and 170.

The valve body 134 also is connected with a water tube or hose 220 connected to a fitting 222 that is communicated with a longitudinal passageway 224 extending into a vertical passageway 226 which in turn is communicated with an inclined passageway 228 extending horizontally and communicating with a vertical passageway 230 which communicates with a transverse passageway 232 having a pair of nozzles 234 connected to the outer ends thereof for discharging water or other solution downwardly onto the surface being sanded. In some instances, the water supply may be provided or eliminated as deemed necessary. A similar valve structure to that employed in connection with the air is employed including a valve stem 236 which is engaged by the undersurface of the operating handle for the valve thus spraying water from the nozzle 234 when the operating handle for the valve is depressed.

During the working strokes of the piston, the air which causes movement of the piston will also expand the piston rings by entering the

passageways

46, 42 and 44 and discharging behind the rings which will expand the rings and also serve to retain the rings in a clean condition. The rings are retained in expanded position in both the exhaust and power stroke. The valve assembly is quite efiicient with the ports in the valve member being directly across from one another so that at the same instant that air begins to enter one cylinder, it is let out of the other cylinder. The slight slack or lag at the point of connection between the actuator 70 and the valve member 68 permits the valve member to stay in open position for a period of time when the piston is moving on the power stroke before beginning to close the inlet port and in this manner, the valve assembly keeps the exhaust open on the other side for better venting of the other cylinder.

The construction of the valve assembly including the actuator and the piston is such that the piston is close to the center of the machine body thus eliminating side wiggle of the machine and provides fatigueless operation. The manner of attaching the rack gear to the piston and the construction of the rack gear itself permits the piston to be placed very close to the bottom of the machine thus overcoming the up and down motion of the machine body.

It is pointed out that the piston travels in the opposite direction of the sanding shoe and by so doing, when air is driving the piston, there is equal force of air against the cylinder head which is fastened to the machine body thus forcing the whole machine toward the direction the sanding shoe is moving. By this method, the harder you press on the machine, the more the air driving the machine will help balance the machine. In this invention, full travel on the sanding shoe is provided since it will travel the same length as the piston does however the machine body stands still without any lost motion.

The relationship of the lobes 80 to the lobes 98 is significant inasmuch as the clearance between the lobes will determine the length of stroke of the piston and, of course, the sanding shoe. If a longer stroke is desired, more clearance should be provided between the actuator lobes 80 and the valve lobes 98 thus letting the piston travel a longer stroke before the valve returns for the exhaust position. If the actuator and valve lobes Were tight, the stroke would be short but much faster. The advantage of this type of valve is that the operator can have various stroke lengths out of the same machine by changing the valves. This can be done very easily by removing the valve cover cap 106, turning the machine upside down so that the valve will drop out and placing another valve 68 with desired lobe clearance in place. The valve 68 will fit in only one place thus eliminating any necessity of timing.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

What is claimed as new is as follows:

1. An air operated sanding machine comprising a body having a longitudinal bore therein, a piston reciprocally mounted in said bore, means forming a closure for each end of the bore thus combining with each end of the piston to form two working chambers, a sanding pad underlying the body, means reciprocally guiding the sanding pad in relation to said body, means interconnecting the sanding pad and the piston for reciprocating the sanding pad in opposite relation to the piston, rotatable valve means on said body operatively connected to said piston for selectively admitting and exhausting air from the working chambers along smooth curved surfaces through said valve means, said piston including at least one seal ring on each end thereof, and passage means in 8 each end portion of said piston to communicate the adjacent working chamber with the inner surface of the seal ring for expanding the seal ring into contacting relation with the bore thus maintaining a seal therebetween during reciprocation of the piston.

2. The structure as defined in claim 1 wherein said sanding pad includes a rack gear projecting upwardly therefrom, said piston including a rack gear attached longitudinally in the central portion thereof, said means interconnecting the piston and sanding pad including a rotatable gear meshing with each of said rack gears with the rack gears being disposed on the opposite sides thereof.

3. The structure as defined in claim 2 wherein said valve means includes an actuator connected to the rotary gear, a valve member joined with the valve actuator, interfitting joints between the valve actuator and valve member with a variable lag space therebetween to enable variation in the characteristics of the stroke of the piston.

4. An air operated sanding machine comprising a body having a longitudinal bore therein, a piston reciprocally mounted in said bore, means forming a closure for each end of the bore thus combining with each end of the piston to form two working chambers, a sanding pad underlying the body, means reciprocally guiding the sanding paid in relation to said body, means interconnecting the sanding pad and the piston for reciprocating the sanding paid in opposite relation to the piston, valve means on said body operatively connected to said piston for selectively admitting and exhausting air from the working chambers, said piston including at least one seal ring on each end thereof, and passage means in each end portion of said piston to communicate the adjacent working chamber with the inner surface of the seal ring for expanding the seal ring into contacting relation with the bore thus maintaining a seal therebetween during reiprocating of the piston, said sanding pad including a rack gear projecting upwardly therefrom, said piston including a rack gear attached longitudinally in the central portion thereof, said means interconnecting the piston and sanding pad including a rotatable gear meshing with each of said rack gears with the rack gears being disposed on the opposite sides thereof, said valve means including an actuator connected to the rotary gear, a valve member joined with the valve actuator, interfitting joints between the valve actuator and valve member with a variable lag space therebetween to enable variation in the characteristics of the stroke of the piston, said valve member including a generally cylindrical body having an arcuate slot communicating with the bottom thereof and one side wall, a second arcuate slot communicating with the top and the side wall thereof opposite to the bottom slot, air inlet means communicated continuously with the top slot, and oppositely disposed passageways in said body communicating with the working chambers and selectively communicated with the top slot and the lower slot for admitting and exhausting air from the working chambers.

5. The structure as defined in claim 4 wherein each end of the bore is provided with a closure cap, said cap including an air inlet opening at the upper end thereof communicated with the respective air passageway to prevent blow-by of the air at the bottom of the bore.

6. The structure as defined in claim 5 wherein said valve member is connected with the actuator by generally semicircular axial extension on the end of the valve member and the end of the actuator with the projections being in overlapping engagement thus defining engaging lobes, said body including a retaining plug for retaining the valve member in place thus enabling valve members having different lobe characteristics to be inserted for varying the lag between the actuator and the valve member for enabling inlet of air in working chamber before the exhaust in the other chamber is actuated to enable more effective venting of the other working chamber.

7. The structure as defined in claim 6 together with a manually operated valve in the inlet passageway, said valve including a stern projecting above the body, and operating handle having one end connected to the body and the other end extending in overlying spaced relation to the central portion of the body for engagment by the hand of a person gripping the body to enable operation of the air valve.

8. The structure as defined in claim 7 wherein said body includes a pair of water discharge nozzle means at opposite sides thereof, a water supply passage in said body and communicated with a supply line for water, and a manually operated valve for said water supply with the manually operated valve including a stem engaged by the operating handle for the air thereby enabling simultaneous operation of the sanding machine and discharge of water from said nozzle means.

9. In a pneumatic motor of the type having a reciprocating piston, a valve assembly including an actuator operatively connected to the reciprocating piston for oscil lation in response to reciprocation of the piston, a valve member connected with the actuator, said actuator and valve member having overlapping and engaging axial extensions of generally semi-circular configuration and including confronting lobes, at least one of said lobes being spaced from an adjacent lobe a distance to provide a leg between the valve member and valve actuator, said valve actuator being hollow and said valve member including passageways defining an exhaust passage communicating with the hollow actuator for exhaust of air therethrough before cleaning portions of a tool driven by the motor.

References Cited UNITED STATES PATENTS 987,940 3/1911 Anderson 51170 1,590,353 6/1926 Ekstrom 51179 X 2,194,102 3/1940 Taylor 92182 2,635,396 4/1953 Johnson 51-170 2,914,368 11/ 1959 Farmer 92184 JAMES L. JONES, 1a., Primary Examiner.