US1717818A - Pneumatic tool - Google Patents

Description

F. H. THOMAS PNEUMATIC TOOL June i8, 1929.

Filed oct. 5. 1927 'INI/ENTOR.

Patented June 1.8, 1929.

UNTED STATES PATENT OFFECE.

FLOYD H. THOMAS, OF MILAN, PENNSYLVANIA, ASSIGNOR TO INGERSOLL-RAND OOM- PANY, 0F JERSEY CITY, NEW JERSEY, A CORPORATION OF NEIN JERSEY.

PNEUMATIC TOOL.

,Application filed October 5, 1927. Serial'No. 224,145`

rllhis invention relates to pneumatic tools, but more particularly to an exhaust valve for pneumatic tools of the hammer type.

The objects of the invention are to relieve the compression from the ends of the cylinder, to effect such relief from one end of the cylinder in synclironism with the admission of pressure fluid to the opposite end of the cylinder, and to control the flow of exhaust fluid from the ends of the cylinder.

Other objects will appear hereinafter, and to all of these ends the invention consists of the combination ofelements and arrangement of parts having the general modeof operation D substantially as hereinafter described and claimed and illustrated in the ing drawings, in which Figure l is an elevation in section of a pneumatic tool constructed in accordance with the practice of the invention and showing the distributing and relief valves in the respective position which they will assume during the admission of pressure Huid to the rearward end of the cylinder, and

Figure 2 is a view similar to Figure 1 showing the valves in their other extreme positions.

Referring more particularly to the draw ings, A designates a cylinder of a pneumatic tool and B a piston reciprocable in the cylinder for delivering' blows of impact on a working implement, only the shank C of which is shown projecting into the front end 'of the cylinder A.

On the back end of the cylinder A is a valve block D which forms a closure for the rearward end of the cylinder and has a valve chamber E in the form of a cylindrical bore opening from the rearward end of the valve block D in this instance supports a plate F having a reari 1ard surface Gr` which serves as a seat for an oscillatory plate type distributing valve H and also forms a closure for the rearward end of the valve chamber E.

The distributing valve H may be of a well known type adapted to control inlet passages J and K leading to the rearward and front ends of the cylinder respectively. The valve H is preferably pivoted on a pin L suitably anchored in a back head O to project into an aperture P in the valve H for holding said valve against lateral movement with respect to a valve chamber Q. wherein said valve is disposed. The valve chamber Q in this instance is formed within the back head O provided with a passage S through which pressure fluid from a suitable source of supply may pass to the valve chamber Q for distribution by the valve H.

Disposed within the valve chamber E is a relief valve T of the spool type having a rearward head U and a forward head V connected to the rearward head by a stem lV.

The valve T in this instance is adapted to be,

actuated by pressure fluid under full line pressure, and to this end a kicker passage X formed in the plate F affords communication between the inlet passage K and the upper end of the valve chamber E for admitting pressure fluid against the head U to vactuate the valve T forwardly.

In order to actuate the valve T in a rearwardly direction simultaneously with the admission of pressure'fluid into the rearward end of the cylinder A, a similar kicker pas sage Y is formed in the front end of the valve block D to establish communication between the rearward end of the cylinder and the front end of the valve chamber E.

Leading from the front end of the cylinder A to a point near the rearward end of the valve chest E is an exhaust passage Z for conveying exhaust fluid from the-front end of the cylinder. The rearward end of the exhaust passage Z is in this instance controlled by the head U of the valve 'I' which thus also controls communication between the exhaust passage Z and an exhaust port b in the valve block D, preferably located about midway between the ends of the valve chamber E.

The exhaust passage Z in this instance has a forward port c and a port d located rearwardly of the port c to establish communication between said exhaust passage Z and the forward portion of the cylinder.

The port d is so located that it may be overrun by the piston B on its forward stroke and this port thus serves as an exhaust port for the pressure fluid utilized for actuating the piston B in a forwardly direction. The port c being located near the front end of the cylinder serves exclusively as a compression relief port, such compression being exhausted through the exhaust passage Z and through the exhaust port b as will be more fully described hereinafter.

In order to convey the exhaust fluid from the front end of the cylinder and the com pression from the rearward end of the cylinder, an exhaust passage e leads from a point rearwardly of the transverse median line of the cylinder to a point in the valve chamber E intermediate the free exhaust port Z) and the front end of said valve chamber. The passage e communicates at its front end with the cylinder through a port f, and a port g suitably located near the rearward end of the cylinder affords communication at this point between the cylinder and the passage e.

Communication between the passage e and the valve chamber E is in this instance controlled by the head V of the valve T which overruns the passage e at this point to establish communication between said passage e and the exhaust port b.

In the operation of the device, with the left hand end of the valve H raised as illustrated in Figure l, pressure fluid will flow through `the inlet passage J into the rearward end of the cylinder to actuate the piston B in a forwardly direction against the working implement C. Upon the admission of pressure fluid into the rearward end of the cylinder a portion thereof will pass through the kicker passage Y against the head V of the valve T and move said valve T rearwardly against the plate F to open communication between the exhaust passage Z and the exhaust port In this way is established a direct path for the escape of compression of that portion of the cylinder forwardly of the piston B. Throughout the greater portion of the forward stroke of the piston B compression may flow from the cylinder through both ports CZ and c. However, after the piston B covers the exhaust port cl, the port 0 alone will serve as an escape for the compression from the front end ofthe cylinder.

Immediately prior to the delivery of the blow of the piston B against the working implement C and port CZ will be uncovered by the piston and the pressure fluid utilized for actuating the piston B forwardly will then be exhausted through the port CZ, the exhaust passage Z into the valve chamber E between the heads U and V of the valve and thence through the exhaust port Z) to the atmosphere.

Upon the exhaust of fluid from the rearward end of the cylinder' in the manner described, the pressure beneath the left hand end of the valve H will drop to such a value that the pressure fluid passing over said end will create a suction of suliicient force there-` on to tip the valve H to a position wherein the inlet passage eI will be closed and the front inlet passage K will be uncovered. lith the valve in this position pressure fluid will flow into the inlet passage K into the front end of the cylinder A for reversing the travel of the piston B.

At the instant of admission of pressure fluid to the front end of the cylinder, a portion of the pressure fluid flowing into the inlet passage K will pass through the kicker passage X against the rearward head U of the valve 'I" and actuate said valve to its extreme forwardmost position wherein the head U of the valve T will cover the outlet opening of the exhaust passage Z and communication will be established between the exhaust passage c and the exhaust port As the piston B proceeds in a rearwardly direction, the air in the rearward end of the cylinder A will be expelled through the ports f and g into the exhaust passage e, thence through the valve chamber E and through the exhaust port Z) to the atmosphere. The compression will be thus expelled through the ports f and g until the port f is cov` ered by the piston B, thereafter the port g only will function for this purpose. At about the time the piston B overruns the port f the port g will be covered by the piston B. The pressure fluid utilized for actuating the piston B rearwardly will then be exhausted through the exhaust passage e and associated passages leading to the atmosphere and the compression trapped in the rearward end of the cylinder A will serve to 'cushion the piston B to prevent impact against the valve block D.

I claim:

In a pneumatic tool, the combination of a cylinder and a piston, a back head having a distributing valve chamber, a distributing valve in the distributing valve chamber, a valve block forming a closure for the cylinder and having a relief valve chamber, an exhaustl port in the valve block affording communication between the relief valve chamber and the atmosphere, a plate interposed between the back head and the valve block to form a closure for the relief valve chamber and to act as a seat for the distributing valve, inlet passages leading` from the distributing valve chamber to the cylinder and controlled by the distributing valve, kicker passages in the valve block and the plate for conveying pressure fluid into the ends of the relief valve chamber to actuate the relief valve simulta neously with the admission of pressure fluid to the ends of the cylinder, and exhaust passages leading from the ends of the cylinder to the relief valve chamber for conveying exhaust fluid and compression from the cylinder to the relief valve chamber, said exhaust passages being controlled by the relief' valve. y

In testimony whereof I have signed this specification.

FLOYD I-I. THOMAS.

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