US2372945A - Distributing valve for pneumatic tools - Google Patents

Description

F. P. FORSS DISTRIBUTING VALVE FOR PNEUMATIC TooLs vFiled July 12, 1945 l April 3, 1945.

INVENToR. /WH/af H Fons Patented Apr. 3, 1945 DISTRIBUTING VALVE FOR PNEUMATIC rJIOOL Frithiof P. Forss, Aurora, Ill., assignor to Independent Pneumatic Tool Company, Chicago, Ill., a corporation of Delaware Application July 12, 1943, Serial No. 494,300

1 Claim. (Cl. 121-19) This invention relates to improvements in cylindric distributing valves of the character disclosed in my co-pending application Serial No. 372.227, led December 30, 1940, now Patent No. 2,334,403, granted November 16, 1943, for portable pneumatic tools such as chipping hammers, riveting hammers, clay diggers or clay spades and the like.

The object and purpose of my present invention is to provide the valve member of a construction which will absorb the shock of the repeated impacts of the valve member against the valve block in the rapid lateral shifting of the valve member in effecting reciprocation of the hammering piston and from the severe Vibrations set up from the :power blows of the piston on the chisel or other work element inserted into and supported by the tool barrel to prevent cracking of the valve member.

In carrying out the object of my invention, I comprise the Valve member of an outer cylindric shell of a heat treated alloy steel or other hard metal to take a high grinding finish and to resist the wear on the valve member in its operation Within the valve block and an inner portion or liner of aluminum or other soft material havin-g intimate contact or a pressed fit within the outer shell to absorb the shocks to which the valve member is subjected in the operation of the tool as above mentioned.

In the accompanying drawing:

Fig. 1 is a longitudinal sectional view with parts in elevation of a portable pneumatic chipping hammer equipped with a cylindrical distributing valve member constructed in accordance with my invention, the Valve member. being shown in its shifted position for supplying air pressure to the rear end of the tool cylinder;

Fig. 2 is a Vertical sectional View taken on line 2-,2 of Fig. 1;

Fig. 3 is a horizontal sectional View taken on line 3-3 of Fig. 1;

Fig. 4 is an enlarged View of the assembled Valve member and valve block removed `from the tool and in section on line 4-4 of Fig. 3; and

Fig. 5 is a perspective view of the improved cylindric valve member.

In the accompanying drawing, I have shown the valve member of my invention embodied in a portable pneumatic chipping hammer wherein I is the tool barrel and 2 is the cylinder which the barrel provides for the reciprocable hammering piston 3. A chisel 4 extends into the cylinder 2 at the front end of the barrel through a supporting bushing 5 to receive the power blows of the piston in the operation of the tool.

A handle member 6 is secured to the rear end of the barrel through a tubular extension 'I on the handle member fitting over and having a screw threaded connection with the barrel as shown herein. The handle member 6 closes the rear end of the barrel and clamps a valve block 8 therein. A pressure iiuid, such as compressed air, is supplied to the barrel through a main supply passage 9 contained Within the handle member and opening into the barrel over the valve block asshown. The handle member 6 carries a fitting IIJ at the outer'end of the passage 9 for connection with an air supply hose (not shown). A manually operable throttle valve, also not shown, is mounted Within the handle member for controlling the flow of live air to the tool cylinder 2. Said throttle Valve has an actuating lever iI accessible at the handle as in these pneumatic tools.

The valve block `8 is located at the rear endA of the barrel I within a recess I2 therein and is clamped by the handle member `Ii when screwed onto the barrel against a seat I3 which the barrel provides at the base of said recess. The block 8 is provided with a bore I4 extending diametrically therethrough to mount a hollow cylindric distributing Valve member I5 constructed in accordance with my present invention.

The valve block 8 has a snug iit within the recess I2, the contacting surfaces of the parts having a ground iit to avoid air leakage. v

The block 8 closes the rear end of the cylinder 2 and the bore I4 is closed at its opposite ends by plugs I6, Il which engage' the surrounding wall of the recess I2 to hold the valve member i5 in place within the bore I4. The valve member I5 extends axially ofthe bore I4 between the plugs and has sliding contact at its ends with the plugs. One of the plugs engages a key-way in the recess I2 to hold the block from turning for the purpose disclosed in my said co-pending application.

The block 8 has ports I8, I9 at the opposite sides of the valve member I5 and these ports respectively connect the bore I4 to the opposite ends of the cylinder 2. The bore I4 at the ports I8, I9 is laterally Wider than the diameter of the valve member I5 whereby the air pressure supplied to the tool will .automatically shift the valve member laterally to alternately open and close said ports. The bore I4 at these ports is provided with arcuate valve seats 20, 2| on the same radius as the valve member to close the ports when the valve member contacts these seats. Between-the seats', the bore I4 has valve supports 22, 23 in the form of substantially straight surfaces tangential to the valve member to support the same for lateral and revoluble shifting. The valve seats and the valve supports have a ground nish similar to that of the valve member, the block bein-g made of a heat treated alloy steel.

'The distance the valve member travels in lateral shifting is only a small fraction of the radius of the valve member I5. This is due to the fact that the bore between the valve seats 20, 2I isv only slightly wider than the diameter of the valve member. Hence, the valve member I is required to make only an extremely small lateral stroke to open and close the ports I8, I9 resulting in a quick acting tool.

'Ihe valve member I5 is hollow as before stated and in accordance with my invention is comprised of an outer cylindric shell portion 24 and an inner cylindric liner portion 25. The outer shell portion is made of a heat treated alloy steel or other hard metal to take a high finish by grinding and to resist wear on the valve member in its lateral and revoluble shifting within the bore. The inner liner portion 25 is made of aluminum or other soft material and has a lpressed t within the outer shell 24 to absorb the shocks to which the valve member is subjected in the operation of the tool. These shocks result from the impacts of the valve member with the valve seats 2B, 2I in the lateral shifting of the valve member in response to the air pressure thereon and jars of the valve member between the valve supports 22, 23 and against the end plugs I6, I'I from the more or less severe vibrations set up from the power blows of the piston 3 on the chisel 4. 4While the distance between the valve supports conforms substantially to the diameter of the valve member and the length of the valve member accords with the spacing between the plugs, yet in practice there must be sufficient clearances provided between the partsfor a quick and rapid valve action which results in the valve member being subject to these tool vibrations. With the soft inner portion 25 of the valve member absorbing these shocks l the outer shell 24 of the valve member is prevented from being cracked and the life of the valve member is materially prolonged.

As in my co-pending application and as shown herein, the valve block 8 has inlet ports 2E, 21 leading from the upper surface of the block to the upper part of the bore I4. The inlet ports convey air pressure from the handle member 5 to the bore, the latter having a pair of upper channels 28, 29 to which the inlet ports are respectively connected. The block 8 has a pair of lower channels 30, 3I which supply live air to the underside of the valve member. The channels 20 to 3| are located on opposite sides of the valve axis and are disposed between the valve seats and the valve supports, respectively, to supply air pressure to the bore in any shifted position of the valve member.

The channels 23 to 3| extend longitudinally of the bore I4 for the greater portion of the length of the valve member I5 and occupy the greater portion of the circumference of the bore between the valve seats and the valve supports to provide relatively large channels for a large flow of air pressure to the cylinder at the instant of shifting of the valve member to open a port. This results in instantaneous starting of the tool when held in any position. The ports I8, I9 are elongated longitudinally of the bore I4 to convey the large air ow to the cylinder as shown in Fie'. 3.

To reciprocate the piston 3 within the cylinder 2, the barrel I is provided with longitudinally extending passages 32, 33, the former connecting the block port I8 and opening into the front end of the cylinder 2 through a port 34. 'I'he passages 33 are closed at their inner ends by the valve block 8 and open into the cylinder 2 at two points in its length through ports 35, 36.

In operation, when the parts are in the positions shown in Figs. 1 and 4, the valve member I5 closes the port I8 and opens the port I9. Live air now enters the rear end of the cylinder 2 and the piston 3 is driven forward on its power stroke. The front end of the cylinder is at this time connected by the port 35 to the exhaust port 3'I in the barrel I. As soon as the piston uncovers the upper or rear port 36 the rear end of the cylinder 2 is opened to the exhaust. By this time the forward end of the piston 3 has closed the port 35 and the air entrapped between the piston and the front end of the cylinder is compressed by the -pistcn and forced into the passages 32 to unseat the valve member I5 and shift it towards the valve seat 2|. This shifting movement is aided by the live air pressure on the valve member and the latter closes the port I9. This opens the port I8 and live air is admitted to the front end of the cylinder to force the piston 3 on its return stroke. As soon as the piston uncovers the port 35 the front end of the cylinder is connected to the exhaust whereupon the piston closes the port 38 and the air entrapped between the rearwardly moving piston and the rear end of the cylinder is compressed and the valve member is shifted into closing relation with the port I8 to repeat the reciprocation of the piston.

The details of construction and arrangement of parts shown and described may be variously changed and modified without departing from the spirit and scope of my invention, except as pointed out inthe annexed claim.

I claim as my invention:

In a portable pneumatic hammer, a barrel providing a cylinder and adapted to support a chisel or like tool at the forward end of the barrel, a piston reciprocable within the cylinder for de liverlng hammer blows on the chisel, a valve block clamped to the barrel at the rear end of the cylinder and having a bore, said block having inlet ports for supplying pressure fluid to the bore and service ports for connecting the bore to the opposite ends of the cylinder, and a hollow cylindrical distributing valve member located within the bore and shiftable laterally thereof by the pressure uid supplied to the cylinder through the bore, said valve member in shifting having contact with the block at the service ports for alternately opening and closing the same to reciprocate the piston within the cylinder, said valve member being comprised of a relatively thin outer cylindrical shell of hard metal and an inner cylindrical liner of a softer, bulkier, lighter, deadening material, said liner being substantially equal in length to the outer shell and having a tight nt within and supported by the shell to absorb the impacts of the shell with the block in the shifting of the valve member and from the jars of the valve member against the block from the vibrations set up in the barrel from the hammer blows of the piston on the chisel to prevent cracking of the shell and to reduce the thickness of the same to lighten the valve member for a rapid lateral shifting movement.

FRI'I'HIOF P. FORSS.

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