US2141727A - Valve for pneumatic tools - Google Patents

Description

Dec.. 27, .1938. F. M, sLATER 2,141,727

'VALVE Foa PNEUMATIC TooLs FiledJuly 13, 195e il f o@ 5? 447 48 mi Even? Mlaez.

H15 ATTORNEY,

Patented Dec. 27, 1938 UNETED STATES VALVE Foa PNEUMA'rIc TooLs Y Freu M. slater, Philupsburg, N. J., assignm to Ingersoll-Rand Company, Jersey City, N. J., a corporation of New `Iersey Application July 13, 1936, sei-iai No. 90,355

2 Claims. (ol.- 121-19) rThis invention relates to pneumatic tools,l and more particularly to a distributing valve for pneumatic tools of the hammer type.

One object of the invention is to obtain a quick 5 and positive action of the valve and, therefore, a rapid reciprocatory movement of the percussive element of the tool.

Other objects will be in part obvious and in part pointed out hereinafter.

In the drawing illustrating the invention and in which similar reference numerals refer to similar parts, Y

Figure 1 is an elevation, in section, of a pneu- Y matic tool equipped with a valve constructed in accordance with the practice of the invention and showing the valve in position to supply pressure duid behind th-e piston for driving it on its working stroke,

Figure 2 is a View similar to Figure 1 showing "the valve in the other limiting position, and

Figure 3 is a transverse View taken through Figure l on the line 3 3.

Referring-more particularly to the drawing, the invention is shown embodied in a pneumatic 25. tool 2d comprising a cylinder 2l having a piston chamber 22 to accommodate a reciprocatory hammer piston 23 which controls an exhaust port I9 and actuates .a working implement 24.

The piston 23 is of the differential type having 3@ a head 25 and a stem 25, the latter extending slidably through a front cylinder washer 2l serv- 'ing as a closure for that end of the piston chambei"v 22.

The Working implement 2li extends into a front A head 23 forming the front casing part of the pneumatic tool. The front head serves as a housing for a chuck 29 which guides the working implement 2d and wherewith the Working implement is slidably interlocked. Within the chuck 0 29 are ribs 33 extending into grooves 3l in the stern 2G of the piston to slidably interlock the piston to the chuck.

Seated on the rear end of the cylinder 2| is a cylinder extension 32 which in turn serves as a seat for a back head 33 forming the rearmost casing part of the tool 253. The back head 33 may, as is customary, serve as a housing for the head (not shown) of a rifle bar 35 which extends into the piston chamber 22 and is interlocked with the piston 23 in a well known manner to cause rotary movement of the piston during one of its strokes.

In accordance with the practice of the invention, the back head 33 is provided with a boss 35 that extends into a bore 36 in the cylinder extension 32. The boss is recessed in its free end to form a valve chamber 31 comprising, in the present instance, a front enlarged portion 38 and a rear reducedY portion 39.

Intermediate the ends of the reduced portion 5 ber is eifected through a passage 43 in a wall d4 155 which is an integral portion of the cylinder extension 32 and serves as a closure for the rear end of the piston chamber.

Inthe rearward surface of the wall M is an annular groove 55 which lies outside of the plane 20'r of the valve chamber to serve as a supply reservoir for pressure fluid. Pressure fluid is admitted into the groove i5 through a passage or passages G5' in thev extension 35 leading from an annular supply chamber 41 in the periphery of the boss 25 35, and the admission of pressure fluid into the tool 2e from a suitable source of supply (not shown) is controlled by a throttle valve 48 housed, in the present instance, in the cylinder extension 32. 30

Arranged within the valve chamber 3l is a valve [i9 of the reciprocatory type for distributing the pressure' fluid tothe end of the piston chamber. The valve comprises a flange 5l] which lies within the' enlarged portion' of the valve chamber 35 and an integral hollow stem 5I which lies Within the reduced portion 39. The periphery of the stem 5i seats slidably upon the wall of the reduced portion 39 and the bore 52 in the valve is suiiiciently larger than the rifle bar, which the 40 extension 5l encircles, to at all times assure free communication between the rear ends of the enlarged portion 38 and the piston chamber.

Likewise, the periphery of the ange 5B seats slidably on the wall of the enlarged portion 38 45 to assist in guiding the valve. In the periphery of the flange 55 are a series of notches 53 through which pressure uid flows from the groove 45 into and through the rear end of the enlarged portion 33 thence through the channels connecting said 50 enlarged portion with the front end of the piston chamber.

On'the opposed surfaces of the boss 35 and the wall d5 are raised seating surfaces 54 and 55, respectively, for the adjacent surfaces of the 55 Vinside of the seating surface 55 constitutes an actuating surface 58 which is in constant cornmunication with the rear end of the piston chamber through the passage 43 and is, therefore, intermittently subjected to the compression in the rear end of the Ypiston chamber to assist in throwing the valve rearwardly,V The valve'is,

moreover, provided withan opposed actuating surface 59 on the rear end of the flange 59' and lying between the seating surface 56 and the extension 5l.

The operation of the device is asrfollows: With the valve i9 and the piston 23 in the positions illustrated in Figure 1 pressure fluid ows from `the groove 5 through the space between the Vliange 59 and the seating surface 55, thence through the passage 43 into the rear Yend of theV piston chamber 22 to actuate the piston 23 forwardly against the working implement. During the forward movementof the piston, and

after the piston has closed the exhaust port i9, the air in the front end of the piston chamber is compressed and expelled through the passage '32 into the annular groove 40 and the passage ll and acts upon the actuating surface 59. When the rear end o f the piston uncovers the exhaust port li? pressure fluid used for actuating thepiston exhausts tothe atmosphere, and the compression actingY against the surface 59, togetherV with the pressure iluid acting against the pressure surface'56 will then immediately throw the valve forwardly against the. seatingsurface 55.

In the new position of the valve pressure iiuid flows from the groove 45'throu'gh the notches 53 and the rear end of the enlarged portion 38 of the valve chamber, Ythence through the passage 4I, the groove 45 and the inletpassage 42 into the front end of the piston chamber to return the piston to its initial position. During its rearward or rising movement the piston again covers Y the exhaust port I9. rlrhe air in the rear end of the piston chamber 22 is then compressed and will act against the actuating surface 58.

As the piston nears its rearward stroke it un-V Y covers the exhaust port I9 and the pressure fluid used for driving the piston rearwardly will escape to the atmosphere. In consequence, there will be an abrupt drop in the pressure value of the fluid acting against the rear surface of the flange 5D. The compression acting against the surface 58 will then act to throw the Yvalve rearwardly to its initial position. Such compression is assisted, however, by the force of suction of the pressure fluid flowing through the notches 53 and exerting a drag on the valve and also by the pressure iiuid acting against the pressure surface 51.

I claim:

I. In a pneumatic tool, the combination of a cylinder and a piston therein, a valve chest having a valve chamber and front and rear inlet passages for supplying pressure fluid to the cylinder, a valve in the valve chamber, a flange on the valve slidably engaging the chest controlling the flow of pressure fluid to the inlet passages, said flange having channels Vin its periphery through which pressure uid flows .to one inlet passage, said channels having their Vsurfaces subjected to the suction of the pressure fluidrfor throwing the valve in one direction, opposed actuating surfaces on the valve, one of said'actuating surfaces being intermittently subjected to compression from the cylinder to assist the force of suction in throwing the valve and another actuating surface being intermittently subjected to compression Vfrom the cylinder to throw the Valve'in an opposite direction, and opposed differential pressure surfaces on the valve constantly exposed to Ypressure fluid to assist in throwing the valve.

Ysingle flange on the valve slidably engagingY the Val've'chest and cooperating with the seating surfaces to control the flow of pressure iiuid to the inlet passages, opposed actuating surfaces on the flange intermittently subjected to compression from the cylinder `for throwing the valve, and channels in the periphery of the flange through which pressure fluid flows to only the front inlet `passage and being subjected to the suctionrof the pressure fluid to assist in throwing Vthe valve'for cutting off the ow of pressure Vfluid to the front inlet passage.Y

Y Y I Y FRED M. sLATER-

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