US1713784A - Pneumatic tool - Google Patents

Description

May 21, 1929. F. M. SLATER PNEUMATIC TOOL Filed Sept. 50, 1927 w T QQVN R m m N B v g HNa KHQ N% 2 R. aw f/z? A w Patented May 21, 1929.

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T Iilt'GEESDLL- RAND COM-- CORPOEATIOJ OF NEW" JERSEY.

PNEUMATEC TOOL.

Application filed September This invention relates to pneumatic tools, but more particularly to pneumatic tools of the hammer type in which the drill steel or its equivalent extends into the front end of the cylinder and in its operative position, limits the forward travel of the hammer piston.

One object of the invention is to prevent the hammer piston from striking against the forward extremity of the cylinder whenever the working implement is permitted to with draw from its normal operative position due to the relaxation of the manual pressure necessary for maintaining the said working implement within the range of the blows of the hammer piston.

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

In the drawings illustrating a practical application of the invention,

Figure 1 is a longitudinal vertical section of a pneumatic tool constructed in accord-' ance with the practice of the invention, and

Figure 2 is a view similar to Figure 1 showing the working. implement withdrawn from its normal operative position thusenabling the hammer piston to advance be yond its forward limiting position and cover the front inlet port to the cylinder.

Referring more particularly to the drawings, A designates a cylinder of a pneumatic tool having free exhaust ports B which are controlled by a piston C reciprocable in a piston chamber A of the cylinder A. In the front end of the cylinder A is a bore 1) in which is disposed a bushing, E. A working implement F, such as a coal pick or drill steel, is guided by the bushing E and has a shank G which normally extends into the front endiof the piston chamber a substantial distance to receive the blows of the hammer piston O.

The means which serves to limit the distance which the shank G may extend into the piston chamber A consists of a collar H on the working implement F, preferably of slightly larger diameter than the bushing); E, to enable said collar H to abut against the front end of the cylinder A.

The collar H further acts as a means for preventing complete ejection of the working implement F from the cylinder A. To this end said collar H may contact with an end wall J of a cap K threaded on the front end of the cylinder A, said cap having a bore 30, 1927. Serial No. 223,0d6.

L in its front end to enable the working implement ll to extend slidably therethrough.

The distribution of pressure fluid to the ends of the piston chamber may be effected by any suitable and well. known means. The means shown in the drawings for this purpose comprise a valve mechanism consisting of a plate type oscillatory valve 0 pivoted on a pin P seated in a valve seat Q on the rearward end of the cylinder A. y The valve seat Q; is held in operative position by a back head R having a hood S threaded on the rearward end of the cylinder 21. A valve chamber T in the back head it and in which the val\ c Q is disposed in constant communication with a suitable source of pressure fluid supply (not shown) through a passage U opening at its inner cud into an annular chamber'V above the valve 0.

Leading: from one side of the valve 01121131 her '1 to the front endof the piston chamber is an inlet passage iV, the inlet port X of which is preferably spaced a substantial distance from the front end of the piston chamher A. The admission of pressure fluid to the rearward end ofthe cylinder A is effected through an inlet passage Y in the valve seat Q. v r

In order to prevent the formation of high compression in the front end of the piston chamber A, said piston chamber is provided with a compression relief passage Z which opens into the piston chamber at a suitable point between the exhaust port B and the front end of the piston chamber and leads directly to the atmosphere.

In accordance with the present invention, the piston C is provided with an annular groove .6 so located on the piston C that when said piston occupies a position in the extreme front-end of the piston chamber A, said groove Z) will lie in advance of the inlet port X. The piston, however, may only assume this-position. when the working implement F is permitted to withdraw from the range of the blows of the-hammer piston, since during normal drilling, the shank of the working inmleinent F will extend into the piston chamber a distance suiiicient to prevent complete covering of the inlet port X by the piston C.

The function of the annular groove Z) is to interceptany pressure fluid which would otherwise leak along the piston into the front end of tlie piston chamber when the in the piston chamber. The groove 0 is of such length that when the piston G occupies the extreme forward position, the rearward end of the groove 0 will be uncovered by the corresponding end of the piston over which the pressure fluid may pass into the piston chamber rearwardly of the pistonC and escape through the compression relief passage and the exhaust ports B As will be observed the annular groove 0 and the longitudinal groove 0 are solocated andof such proportions that it will be impossible for live pressure fluid to escape from'the inlet port X through these channels to the atmosphere, since, while the annular groove Z) is in registry with the inlet port X, the rearward end of the longitudinal groove 0 will still be covered by the rearward end of the piston C on both the forward and rearward strokes of the piston.

The front end of the pistonrC carries a reduced projection d which strikes against the shank G of the working implement F and is preferably of slightly smaller diameter than a bore 6 in the bushing E. In this way therewill be sufficient clearance between the projection d and the bore 6 to permit the exhaust of compression from the front end of the piston chamber A to the atmosphere through passages 7 in the bushing E and the front end of the cylinder A. During the normal operation of the device, the working implement F will of course project into the piston chamber A to the full extent permitted by the collar H and,

- aspreviously explained, the working implement will prevent the piston C from overrunning the inlet port X. If, however, the operator carelessly relaxes the manual pressure necessary for holding the working implement properly to the work, the piston C will be forced to the extreme forward end of thepiston chamber A. In such case the inlet'port X will be covered by the piston and the'admission of pressure fluid to the front end of the piston chamber will be prevented.

During the time that the'piston'G occupics the extreme forward position'referred to, pressure fluid will of course leak past the piston in opposite directions, that flowing rearwardly along the piston. will escape to the atmosphere through the exhaust ports B. The-pressure fluid leaking in a forwardly direction will be intercepted by the annular groove 6 in the piston and conveyed thereby to the longitudinal groovec, The pressure fluid thence passes through the groove 0 into the piston chamber rearwardly of the piston and to the atmosphere through the exhaust ports B.

Whenever the workin im )lement F is permitted to withdraw from its normal operative position in the cylinder, the movement of the piston will be quickly arrested and the piston will remain stationary until it is again moved rearwardly by the working implementto uncover the inlet port X.

I claim: 7

1. A pneumatic tool. comprising a cylinder having a piston chamber and inlet and exhaust ports, a work implementextending normally a substantial distance into the piston chamber, a hammer piston reciprocable in the piston chamber having a groove for intercepting pressure fluid 'leaking past the piston toward the front endof thecylinder whenever the piston passes beyond its normal limiting position, and a groove in the piston chamber for conveying such pressure fluid past the end of the'piston from whence it may pass through the exhaust port to the atmosphere. 7

' 2. A pneumatictool comprising a cylinder having a piston chamber and-inlet and'exhaust ports, a hammer piston reciprocable in the piston chamber, a working implement normally extending into the piston chamber sufiicient distance to prevent'the piston from over-running the inlet port, an annular groove in the piston for intercepting pressure fluid leaking along the piston toward the front end of the cylinder whenever the working implement is withdrawn from its normal operative position, thuspermitting the piston to overrun the inlet port, and a groove in the piston chamber registering with the annular groove for conveying the intercepted pressure fluid past the rearward end of the piston from whence it may es cape through the exhaust port to the atmosphere. U

In testimony whereof I have'signed this specification.

FRED S ATER

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