US2595128A - Rock drill - Google Patents

Description

2 SHEETS-SHEET l ROCK DRILL J. c. CURTIS ETAL $26 3 66 m W665 In 7 7 /4 6 6/ My ma 4 w 4 April 29, 1952 Filed May 4, 1946 P 1952 J. c. CURTIS ETAL 2,595,128

ROCK DRILL Filed Maly 4, 1946 2 sr-mzws-smzw 2 pm 50 86 74 i6 1 hil 6 Jaim 6. 6212 223. (92mg? Q fiaz'iz'n.

Patented Apr. 29, 1952 N. H., assi'gnors to Joy Manufacturing Company, a corporation of Pennsylvania Application May 4, 1946, Serial No. 667,384

12 Claims. 1

This invention relates to rock drills and more particularly, but not exclusively, to improvements in the fluid distributing means and drill steel rotation means of a pressure fluid actuated hammer rock drill.

An object of the present invention is to provide an improved pressure fluid actuated rock drill. Another object is to provide an improved drill steel rotation means for a hammer rock drill.

2 I Fig. 10 is a perspective view of the fluid distributing valve.

Still another object is to provide an improved provide an improved inlet and exhaust passage 2 arrangement for a hammer rock drill. Still another object is to provide an improved hammer rock drill of the type known as a plug drill and embodying automatic rotation mechanism for the drill steel. A further object is to provide an improved rock drill having a novel arrangement and combination of parts. These and other objects and advantages of the invention will,however, hereinafter more fully appear in the course of the following description and as more particularly pointed out in the appended claims.

In the accompanying drawings there is shown for purposes of illustration one form which the invention may assume in practice.

In these drawings:

1 is side elevational view of the improved rock drill.

Fig. 2 is a central longitudinal vertical sectional view taken through the improved rock drill on line 2-2 of Fig. 1.

Fig. 3 is a detail horizontal sectional view taken on line 3-3 of Fig. 2.

Fig. 4 is a central longitudinal vertical seetional view taken substantially on line 4-4 of 2-, showing the moving motor parts in a dif ferent position.

Fig. 5 is a cross-sectional view taken substantially on line 5-5 of Fig. 4.

i Fig. 6 is a cross-sectional view taken substan tially on line 5-6 of Fig. l.

Fi'g. 7 is a cross-sectional View taken substantially on line l-'! of Fig. 4.

Fig. 8 is a front faee view of the valve bo'i'r. Fig. 9 1s a rear face view of the valve box cover.

In this illustrative construction, the improved rock drill,. generally designated I, is of the type known as a hand-held plug drill for drilling plug and feather holes. It will be evident, however. that the various features of the invention may be incorporated in rock drills of other types.

The improved r'cck drill comprises a motor cylinder 2 having a bore 3 containing a reciprocable hammer piston 4. The hammer piston has a rear piston head 5 and a reduced forward 'cylindric extension or striking bar 6 slidingly guided in a reduced front bore 1 in the integral front head or front cylinder portion '8 of the motor cylinder. The forward end of the piston striking bar is formed with an axial bore 9 in which is pressed or otherwise secured a cylindrical striking block or plug 10 of relatively hard metal, and this strik- 0 ing block is adapted. to strike against the shank H of a conventional plug drill steel 12. The piston is formed with an enlarged axial chamber 13 opening through the rear side of the piston head, and this chamber is connected by a reduced 0 axial bore M to the rear end of the bore 9. When the drill is dismantled, a suitable instrument, such as a rod 'or bar, may be inserted through the chamber 13 into thebore I4 into engagement With the Striking block I!) so that the latter may 0 be driven out of the bore 9 for replacement nurposes.

Improved rotation means for the drill steel, operated by the hammer piston, is provided, comprising a rotatable rifle bar l5 having spiral grooves slidingly interlocked with the spiral lugs of a rifle nut l6 secured within the rear end of the piston chamber 13 as by threading at ll. Formed in a rear head [8 of the motor cylinder is an eccentric bore l9 (see Fig. 5) having mounted therein for free rotation an annular'reaction member in the form of a sleevelike annulus 2c having a smooth internal peripheral surface 2!. Also arranged in the bore l9 within the annulus 29 is a cylindrical member 22 formed integral with the rifle bar [5. The cylindrical member 22 has a reduced circular bearing portion 23 j'ournaled in an axial bore 24 in the rear cylinder head I8;. Arranged in the space 25 between the eccentrically disposed inner and outer cylindrical surfaces of the members 29 and 22 is a gripping element in the form of a gripping roller 25 of cylindrical form, having midway between its ends an annular circumferential groove 21. Also arranged in the space 25 is a stationary pin 28 and acting on this pin and engaged in the rollergroove 21 is a loop-bent spring 29 for constantly urging the roller toward frictional gripping engagement with the inner and outer cylindrical surfaces of the members 20 and 22. When the cylindrical member 22 is rotated in a counterclockwise direction, as viewed in Fig. 5, the roller 26 wedges between the inner and outer surfaces of the members 29 and 22 to lock these members together and to expand or spring slightly the sleeve 20 into tight frictional engagement with the walls of the bore 19 of the rear cylinder head, thereby to hold the rifle bar I against rotation. When the cylindrical member 22 is rotated in a clockwise direction, as viewed in Fig. 5, the roller 26 moves against the pressure of the spring 21 out of gripping engagement with the inner and outer surfaces of the members 29 and 22, thereby to permit the rifle bar l5 to rotate. The sleevelike member 29 against which the roller reacts may freely rotate in the bore l9 relative to the rear cylinder head when the gripping roller is released so that the gripping roller may engage the inner cylindrical surface thereof at different points to reduce concentrated wear. It will thus be seen that when the hammer piston moves rearwardly in the cylinder bore, the gripping roller holds the rifle bar against rotation so that the spiral lugs on the rifle nut 16 engaging the spiral groove of the rifle bar I5 cause the hammer piston to rotate. When the hammer piston moves forwardly in the cylinder bore to effect its working stroke, the gripping roller automatically releases to permit free rotation of the bar so that the piston moves forwardly without rotation to strike on unimpeded blow on the drill steel shank. For transmitting the rotary motion of the drill steel, there are provided straight longitudinally extending grooves or splineways 3! on the piston striking bar 5, and these grooves have sliding interlocking engagement with straight lugs or splines 32 formed integral with a rotatable chuck sleeve 33, the latter being rotatably mounted in a bore 34 in a front chuck housing 35. Pressed or otherwise fixed in a bore 35 in the rotatable chuck sleeve 33 is a chuck bushing 31 having an axial bore 31' for receiving the round shank I I of the drill steel. The bushing 3'! has spaced projections 38, 38 at its forward side having inner plane surfaces 39 engaging parallel opposed sides of the square body of the drill steel l2 (Fig. 7). It is accordingly evident that as the hammer piston reciprocates to actuate percussively the drill steel, the latter is concurrently intermittently rotated. The interior of the chuck sleeve in advance of the piston striking bar is vented through the clearance space in the chuck bushing bore around the round shank of the drill steel, in an obvious manner.

Now referring to the improved fluid distributing means for the drill motor, it will be noted that arranged in an enlarged bore 49 in axial alignment with the cylinder bore and formed in the rear head block M is a valve box cover 42. Also arranged in the bore 40 and abutting the rear face of the cover 42 is a valve box 43. A dowel pin 44 fixed in aligned holes in the cylinder and the rear cylinder head engages registering grooves in the rear head block 4| and the valve box parts 42, 43 to hold the parts against relative rotation and in alignment. The pin 28 is fixed in the parts l8 and 42. The-valve box cover 42 has a forwardly projecting cylindrical portion 45 received in a bore 46 in the cylindrical member 22, and this cylindrical portion provides an additicnal bearing support for the rifle bar. Formed chamber 41. bore substantially midway between the ends of in the valve box 43 is a valve chamber 41 in which a reciprocatory fluid distributing valve 43 of the circular plate or disk type is arranged and the valve box parts have annular seating surfaces 49 and 50 at the bottom and top of the valve chamber against which the opposite plane surfaces of the valve are adapted to engage. There is a restricted clearance space between the outer periphery of the valve and the walls of the valve chamber to permit metered flow of pressure fluid past the valve. The front valve box cover 42 has an axial passage 5| extending through the cylindrical bearing portion 45 and communicating with the forward side of the bore 46, and the bearing portion 23 of the rifle bar has passages 52 for connecting the bore 45 with the rearward ends of certain of the spiral grooves of the rifle bar and through these grooves with the rear end of the cylinder bore. The rifle bar has an axial passage 53 for connecting the forward side of the bore 46 with the chamber l3 within the hammer piston. The valve box 43 has an axial passage 54 connecting the valve chamber 41 with a recess 55 in the rear face of the valve box 43, and this recess is closed at its upper side by the rear wall 55 of the bore 49 in the rear head block 4!. The recess 55 is connected by ports 51 with passages 58 and 59 in the valve box cover 42 and the rear cylinder head I8, and the passages 59 communicate with longitudinal passages 69 in the walls of the motor cylinder 2, these latter passages communicating through ports 6| with the forward end of the cylinder bore. Pressure fluid may be supplied to the valve chamber from a fluid supply pipe 63 threadedly secured to a plug 94 in turn threaded at 65 in a combined inlet and exhaust block 56. The block 63 has a curved inner surface 61 which fits the outer cylindrical surface of the motor cylinder, and the block is permanently secured to the side of the cylinder as by welding. The plug 64 acts on a rubber gasket 68 to hold the latter in tight sealing engagement with the curved outer surface of the cylinder. The plug 64 has a passage 69 which connects the supply pipe 63 with a passage 16 through the gasket, the latter communicating with a passagell in the adjacent cylinder wall. The passage TI is connected by a passage 12 in the cylinder and passages 13 and 14 in the rear cylinder head 18 and the valve box cover 42, the passage 14 communicating with a recess 15 in the rear face of the valve box cover. The recess communicates with an annular chamber 1% surrounding the front valve seat 49. A circular recess If! in the front face of the valve box 43 communicates with the recess 75 so that adequate flow of pressure fluid to the chamber E6 is assured. Thus pressure fluid may flow from the supply pipe through passages 39, 10, ll, l2, l3 and I4, recesses 15, TI and annular chamber 15 and through the restricted annular space about the outer periphery of the valve to the valve Formed in the walls of the cylinder the cylinder are exhaust grooves I9 communicating with a chamber with which exhaust ports 81 in turn communicate. Threadedly secured at 82 to the center exhaust port is a hose 33 for conducting cleansing fluid to the drill hole to blow away the cuttings in the manner well known to those skilled in the art.

The drill parts above described are held together by a U-bolt 85 which is seated at its rear portion in a transverse groove 96 on the rear headblock 4i andhas its leg portions 81, 81 extending longitudinally in parallelism along the sides of the motor cylinder and passing through openings 88 in the lateral lugs of a front collar 89,. The chuck housing 35 has an enlarged rearward bore 90 which receives the integral front head 8 of the motor cylinder and the chuck housing is formed with a rearward annular flange 9! which is held by the collar 89 tightly against the front end of the motor cylinder. Threaded on the forward ends of the legs of the U-bolt are -tightening nuts 92, 92. Thus when the U- bolt is tightened by the nuts 92, the chuck housing is firmly secured to the front end of the motor cylinder and the rear cylinder head 1-8, the valve box parts and the rear head block are firmly .secured to the rear end of the motor cyl-" inder.

In this illustrative construction, formed integral with the rear head block 4|, is a handle 93 having a grasping portion 9d, and the operator may grasp the grasping portion of the handle to manipulate the drill during the drilling operation. Formed in the grasping portion of this handle is a lubricant reservoir 95 provided with a suitable filler plug 96, and this reservoir is connected by a' restricted passage 91 in the handle with a passage 98 in the valve box 43, and a restricted shallow groove 99 connects the passage 98 with the annular chamber 75. During operation of the rock drill, pressure fluid may flow from the annular chamber 76 through the restricted groove 99 and passages 98 and 91 to the lubricant reservoir 95 wherein the pressure fluid may act on the surface of the lubricant. During operation of the drilling motor, fluctuations in pressure occur in the chamber 16 so that lubricant may intermittently flow from the lubricant reservoir to the valve chamber -to lu-' bricate the motor parts.

The general mode of operation of the improved rock drill is as follows: Pressure fluid may be supplied to the supply pipe 53 under the control of any conventional throttle valve and pressure fluid may flow through the passages 69, It, ll, l2, l3 and i4 and the recesses 15 and i! to the annular chamber 76, and thence through the restricted metering space about the valve to the opposite ends of the valve chamber ll. When the fluid distributing valve 38 is in its forward position against the front seat 49, as shown in Fig. 2, pressure fluid may flow from the valve chamber 47 transversely past the rear valve seat 59 at the rear side of the valve and through the axial passage 54 to the recess 55, and thence through passages 57, 58, 59 and 5B and ports .6! to the front end of the cylinder bore at the forward side of the piston head. The pressure fluid acting on the front pressure area on the piston head moves the piston rearwardly to effect its return stroke. As the piston moves rearwardly, the leading edge of the piston head first overruns the exhaust grooves 19, and as the piston continues to move rearwardly, the pressure trapped in the rear end of the cylinder bore is compressed by the piston. When the following edge of the piston head overruns the exhaust grooves '79, the front end of the cylinder bore is connected to exhaust, thereby causing the pressure in the passages 60, 59, 58 and 5? and in the recess 55 and axial passage 54 substantially to drop, and the compressed fluid in the rear end of the cyl nder bore acts through the axial passage 5! on the lower face of the valve 98 to throw the valve quickly rearwardly against the opposing reduced pressure from the position shown in Fig. .2 to the position :shownin Fig. 4. When the valve is .in the position shown in 'Fig. 4, against the .rear valve seat 50, pressure fluid may flow from the valve chamber transversely past the forward face .of the valve and through axial passage BI and passages 52 in the rifle bar to the rear end of the cylinder bore. Concurrently, pressure fluid flows through the axial passage 53 in the rifle bar to the piston chamber [3. The pressure fluid acting on the effective rear pressure area of the motor piston moves the piston forwardly to eifect .its working stroke, 1. e., to deliver an impact blow on the shank of the drill steel. During forward piston movement, the leading edge of the piston head first overruns the exhaust grooves 19 so that the fluid trapped in the front end of the cylinder bore is compressed by the piston. As the piston moves forwardly, the following edge of the piston head overruns the exhaust grooves'lil, connecting the rear end-of the cylinder bore to exhaust; and as .a result, the pressure in the valve chamber at the forward side of the valve is substantially reduced. As the piston continues to move forwardly, the fluid compressed by the piston in the front end of the cylinder bore builds up in the passages 60.. 59, 58 and 51 and in the recess 55 and axial passage 54, thereby quickly throwing the valve forwardly against the opposing reduced pressure from its position shown in Fig. 4 to its original position shown in Fig. 2. As the opposing pressures acting on the valve are substantially balanced before the piston overruns the exhaust port, a very slight degree of compression in the cylinder ends will throw the valve. The operations above described are rapidly successively repeated during normal operation of the motor.

During forward piston movement, the ratchet roller 2! automatically releases, permitting the rifle bar 15 to rotate so that the motor piston moves forwardly without rotation to deliver an unimpeded blow on the shank of the drill steel. When the motor piston moves rearwardly, the ratchet roller 21 automatically grips the surfaces of the members 29 and 22 to hold the rifle bar against rotation so that as the piston moves rearward-1y, it is rotated by the spiral grooves of the rifle :bar. Rotation of the piston is transmitted through the straight grooves 3! on the piston striking bar and the straight lugs 32 to the chuck sleeve. .33 and through the chuck bushing 31 to the .drill steel. The projections 33 on the rotatable chuck bushing 31 engage the opposed flat sides of the square body of the drill steel to rotate the latter with the chuck bushing. During operation of the motor, lubricant is automatically supplied from the lubricant reservoir to the pressure chamber [6 and thence through the ports and passages to the moving parts of the motor.

As a result of this invention an improved plug drill is provided having automatic means for rotating the drill steel. It will further be evident that by the provision of the improved fluid distribution means and the associated steel rotation means, an improved rock drill is provided which is not only relatively simple and rugged, but which is also more eflicient in operation. The novel arrangement of the motor and chuck parts together with the improved U-bolt structure for holding the parts together, results in greater ease of assembly and dismantling of the drill, and simplicity in construction. These and other modes of use and advantages of the invention will be clearly apparent to those skilled in the art.

While there is in this application specifically described one form which the invention may assume in practice, it will be understood that this form of the same is shown for purposes of illustration and that the invention may be modified and embodied in various other forms without departing from its spirit or the scope of the appended claims.

What we claim as new and desire to secure by Letters Patent is:

1. In a rock drill, the combination comprising a motor cylinder having a bore, a hammer piston reciprocable in said cylinder bore and adapted a to actuate percussively a drill steel, fluid distribution means for the cylinder for effecting flow of motive fluid with respect to said bore to effect reciprocation of said piston, and means operated by said piston for intermittently rotating the drill steel and including a rotatable rifle bar having spiral grooves in sliding interlocking connection with said piston and an intermittent gripping device for controlling rifle bar rotation,

said fluid distribution means including fluid conducting passages in said rotatable rifle bar and communicating with said cylinder bore.

2. In a rock drill, the combination comprising a motor cylinder having a bore, a hammer piston reciprocable in said cylinder bore and adapted to actuate percussively a drill steel, fluid distribution means for the cylinder for efiecting flow of motive fluid with respect to said bore to effect reciprocation of said piston, and means operated by said piston for intermittently rotating the drill steel and including a rifle bar having spiral grooves in sliding interlocking connection with said piston and an intermittent gripping device for controlling rifle bar rotation, said piston having an axial chamber closed at one end for receiving said rifle bar, said fluid distribution means including fluid conducting passages in said rotatable rifle bar and communieating with said cylinder bore, and also including an axial passage in said rifle bar for conducting pressure fluid to said piston chamber.

3, In a rock drill, the combination comprising a motor cylinder, a piston reciprocable in said cylinder and adapted to actuate percussively a drill steel, fluid distribution means for supplying motive fluid to said cylinder to efiect reciprocation of said piston and including a valve box aligned with said cylinder and having a valve chamber, and drill steel rotation mechanism operated by said piston and including an intermittent gripping device located forwardly of said valve box and including a rotatable rifle bar having a sliding interlocking connection with said piston, said valve box having a forward o lindrical portion on which the rearward portion of said rifle bar is rotatably journaled.

l. In a rock drill, the combination comprising a motor cylinder having a bore, a piston reciprocable in said cylinder bore and adapted to actuate percussively a drill steel, fluid distribution means for supplying motive fluid to said cylinder bore to efiect reciprocation of said piston and including a valve box aligned with said cylinder and having a valve chamber, and drill steel rotation mechanism operated by said piston and including a rotatable rifle bar having a sliding interlocking connection with said piston, said valve box having a forward cylindrical portion on which said rifle bar is journaled, and said fluid distribution means including fluid conducting passages in said cylindrical portion and in said rifle bar and communicating with said cylinder bore.

5. In a rock drill, the combination comprising a motor cylinder having a rear head, said head having an axial bore and an enlarged chamber rearwardly of said bore, a valve box having a valve chamber and said valve box arranged in alignment with said cylinder rearwardly of said head, said valve box having a cylindrical projection extending forwardly into said head chamber, and drill steel rotation mechanism including an intermittent gripping device having a rotatable member, said rotation mechanism also including a rotatable rifle bar projecting through said head bore and having a portion journaled therein, said rifle bar having sliding interlocking connection with said piston, said rotatable member secured to and rotatable with said rifle bar and arranged in said head chamber and journaled for rotation on said valve box projection.

6. In a rock drill, the combination comprising a motor cylinder having a rear head, said head having an axial bore and an enlarged chamber rearwardly of said bore, a valve box having a valve chamber and said valve box arranged in alignment with said cylinder rearwardly of said head, said valve box having a cylindrical projection extending forwardly into said head chamber, drill steel rotation mechanism including an intermittent gripping device having a rotatable member, said. rotation mechanism also including a rotatable rifle bar projecting through said head bore and having a portion journaled therein, said rifle bar having sliding interlocking connection with said piston, said rotatable member secured to and rotatable with said rifle bar and arranged in said head chamber and journaled on said valve box projection, and means for supplying pressure fluid from said valve chamber to said motor cylinder including communicating fluid conducting passages in said cylindrical projection and in said rifle bar, and said passage in said rifle bar communicating with said cylinder.

'7. In a rock drill, the combination comprising a motor cylinder having a bore, a piston reciprocabl in said cylinder bore and adapted to actuate percussively a drill steel, fluid distribution means for effecting supply of pressure fluid to said cylinder bore to efiect reciprocation of said piston, and drill steel rotation means including a grooved bar having sliding interlocking relation with said piston and an associated intermittent gripping device, said fluid distribution means including a fluid conducting passage in said grooved bar and communicating with said cylinder bore.

8. In a rock drill, the combination comprising a motor cylinder having a bore, a hammer piston reciprocable in said cylinder bore and adapted to actuate percussively a drill steel, a rear head for said cylinder bore having a rear chamber and a forward axial bore, a valve box arranged rearwardly of said head and closing the rear side of said head-chamber, said valve box having a valve chamber containing a fluid distributing valve for controlling flow of pressure fluid to the opposite ends of said cylinder bore, and drill steel rotation mechanism operated by said piston including an intermittent grip mechanism distinct from said distributing valve and arranged in said head-chamber and a rifle bar having its rotation controlled by said grip mechanism and extending forwardly through said headbore into sliding interlocking relation with said piston.

9. In a rock drill, the combination comprising a motor cylinder having a bore, a hammer piston reciprocable in said cylinder and adapted to actuate percussively a drill steel, a rear head for said cylinder bore having a rear chamber and a forward axial bore, a valve box arranged rearwardly of said head and closing the rear side of said head-chamber, said valve box having a valve chamber containing a fluid distributing valve for controlling flow of pressure fluid to the opposite ends of said cylinder bore, and drill steel rotation mechanism operated by said piston including an intermittent grip mechanism arranged in said head chamber and a rifle bar having its rotation controlled by said grip mechanism and extending forwardly through said headbore into sliding interlocking relation with said piston, and fluid conducting passages controlled by said valve including passages extending from said valve chamber forwardly through said valve box, and through the intermittent grip mechanism, rear head and rifle bar to the rear end of the cylinder bore.

10. In a rock drill, the combination comprising a motor cylinder having a bore, a hammer piston reciprocable in said cylinder bore and adapted to actuate percussively a drill steel, fluid distribution means for said cylinder for effecting the flow of motive fluid with respect to said cylinder bore to effect reciprocation of said piston, means operated by said piston for intermittently rotating the drill steel and including a rifle bar having spiral grooves in sliding interlocking connection with said piston and an intermittent gripping device for controlling rifle bar rotation, said fluid distribution means including a fluid conducting passage extending axially through said rifle bar and also including fluid conducting passages in said rifle bar exteriorly of said axial passage and communicating with the rear end of said cylinder bore at points rearwardly of the front end of said rifle bar.

11. In a rock drill, the combination comprising a motor cylinder having a hollow rear head, a hammer piston reciprocable in said cylinder and adapted to actuate percussively a drill steel, fluid distribution means for said motor cylinder for effecting fluid supply thereto to effect reciprocation of said piston and including a valve box aligned with said cylinder and having a valve chamber, a fluid distributing valve arranged in said valve chamber, said valve box in-- cluding cooperating front and rear plates, said front plate having a forward cylindrical projection extending into said rear head, and a drill steel rotation mechanism operated by said piston and including an intermittent gripping device arranged within said rear cylinder head in advance of said front plate and having an intermittently rotatable element thereof journaled for Cal rotation on said forward projection and a rifle bar secured to said element and having sliding interlocking connection with said piston.

12. In a rock drill, the combination comprising a motor cylinder having a hollow rear head, a hammer piston reciprocable in said cylinder and adapted to actuate percussively a drill steel, fluid distribution means for said motor cylinder for effecting fluid supply thereto to effect reciprocation of said piston and including a valve box aligned with said cylinder and having a valve chamber, a fluid distributing valve arranged in said valve chamber, said valve box including cooperating front and rear plates, said front plate having a forward cylindrical projection extending into said rear head, and a drill steel rotation mechanism operated by said piston and including an intermittent gripping device arranged within said rear cylinder head in advance of said front plate and having an element thereof journaled on said forward projection and a rifle bar secured to said element and having sliding interlocking connection with said piston, said fluid distribution means including a fluid conducting passage extending through said forward projection and a cooperating passage in said element of said intermittent gripping device, said latter passage having communication with said cylinder.

JOHN C. CURTIS. ELMER G. GAR'IIN.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name Date 872,417 Hellman et al. Dec. 3, 1907 927 940 Brothers July 13, 1909 976,981 Brothers Nov. 29, 1910 1,687,687 Penberthy Oct. 16, 1928 1,700,419 Penberthy Jan. 29, 1929 1,871,429 Smith, Sr. Aug. 9,1932 1,884,652 Gartin Oct. 25, 1932 1,982,701 Smith, Jr. Dec. 4, 1934 2,019,163 Slater Oct. 29, 1935 2,061,903 Huffman Nov. 24, 1936 2,078,924 Clerk May 4, 1937 2,081,918 Gartin June 1, 1937 2,169,637- Gartin Aug. 15, 1939 2,201,485 Forss May 21, 1940 2,210,020 Anderson Aug. 6, 1940 2,258,951 Curtis Oct.- 1'4, 1941 2,333,405 Appton Nov. 2, 1943 2,336,953 Osgood Dec. 14, 1943 2,349,971 Lear May 30, 1944 2,488,270 Curtis et a1 Nov. 15, 1949 FOREIGN PATENTS Number Country Date 1,274 Great Britain Jan. 26, 1915

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