US1586849A - Fluid-pressure-actuated tool - Google Patents

Description

June- -l 1926.

. E. H. SHAFF FLUID PRESSURE ACTUATED TOOL Filed Des. 15, 1920 l o5 wummw ,bu ww 6 i x MM .W w wh.

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Patented .lune 1, 1926.

narran 4rires l 1,586,849 @ffii @Fllltfl ERNEST IjI. SHAPE, F GRAND HAVEN, MICHIGAN, ASSIGNOR TO WLLIAM H. KELLER, NC., 0F GRAND HAVEN, MICHIGAN, A CORPORATION OF MICHIGAN.

FLUID-PRESSUEE-ACTUATED TOOL.

Application filed December 15, 1920.r Serial No. 430,890.

My invention relates to finiti-pressure.- actuated tools and more specifically to an improvement in tools of the general type disclosed and claimed in my copending applications Serial No. 371,445, filed April 5, 1920, and Serial No. 417,320,1iled October 16, 1920.

One object of the invention is to provide means whereby tools of this type may be operated at slower speeds than heretofore.

Another object of the inventionis to provide for a more rapid decrease in the pressure returning` the piston towardthe end of the stroke than has heretofore been obtainable, thereby reducingthe recoil at the end fluid. l

Further objects and advantages of my invention will become apparent as the description proceeds. y

lu the accompanying drawings, Figure 1 is a. longitudinal sectional view of a pneumatic hannner illustratin the application of my invention thereto and Fig. 2 is a similar view on a somewhat enlarged, scale showing the valve in the other position. Fig. 3 is a fragmentary longitudinal sectional view illustrating a detail of construction. The general construction and operation of this type of hammer being disclosed in detail in inycopending application Serial No. 371,445, hereinabove referred to, detailed explanation thereof is deemed unnecessary. The tool comprises, briefly, a body member defining a cylinder in which the piston 12 reciprocates to strike a suitable working tool 14; a valve casing comprising annular members 1G and 18 supporting and guiding the valve Q0, and a head threaded onto the body and locked in assembled position by a locking clip 24. A throttle valve con* trolled by the lever 2G delivers air through passage 223 to an annular chamber 30.

V ith the valve'in the position shown in Fig. 1, live motive fluid enters through radial passages terminating in the annular groove 34 -and forces the piston forward to strike a blow against the tool. The dead air in front of the piston flows from the front end of the tool through one or more passages 3G to the annular groove 38 in the valve casing which, as shown in Fig.` 1, is

in communication,with theeXhaust groove 40 from which exhaust groove, passages 42 opening under the clip 24 allow the fluid to escape into the atmosphere.

In its forward movement the piston uncovers the small port 44 which raises the pressure in the passage 46 considerably before the piston toward the end of its stroke covers the end of passage 48 and uncovers the end of passage 46. When this occurs, live motive fluid flows through passage 46 and enters the large valve chamber 50. The point at which the valve shifts, however, is determined by the position of the forward end of the piston, because until the forward end of the passage 48 is covered by the piston the pressure in the large pressure chamber 50 is vented to the atmosphere through the forward passage 48, the forward piston chamber and the passage 36. rThus if, as is sometimes the case, an extremely short piston is used, so that the forward end of the passage 46 is uncovered `before the forward end of the passage 48 is covered by the piston, the latter passage, acting to vent the large forward pressure area, prevents a premature shiftingoof the valve. Consequently the valve shifts Vonly when the forward end of the piston is the proper distance from the rivet set 14. After the initial rearward movement of the valve has talien place, the extreme forward end thereof becomes posed to the live pressure in the rear piston chamber and this high pressure accelerates the rearward movement of the valve. valve is held in its rear position by motive fluid trapped in the passage 4S by the rear-` ward movement of the valve cutting off the passage 46 from the large valve chamber 50. The air in chamber 50 baclr of the valve `flange may escape through passage l into exhaust passage 42. During` this movement of the valve live motive fluid fills the pasage 48 which, after passage 4G has been eut olf from the large valve chamber. 5l), continues to exert pressure on the valve and hold it in its rearmost position.

The movement of the valve to the position shown in Fig. 2 covers groove 34 and` uncovers the exhaust groove 40 so that live motive fluid is out off from the rear portion of thevcylinder and the latter is placed in direct communication with the atmosphere, thus relieving pressure upon the rea-rend of the valve. The valve in its rearward move- The.

ment also uncovers the forward end of a passage 52 (Fig. 3) putting it into communication with groove 38 and passage 36. Pas sage 52 extends radially outward at 54 to receive live moti-ve iiuid from the annular chamber 30, which fluid is delivered through passage 36 to the front end of the cylinder to return the piston. On account of the rela tively small size of passage 52, the pressure during the return stroke will fall off rather rapidly especially toward the end of the stroke when the piston has attained a fairly high velocity. lVhen the piston on its return stroke uncovers passage 48, the fluid in this passage will fall to the same pressure as that in the front end of the cylinder, which pressure as above noted will decrease considerably during the return stroke.

Farther on in its rearward movement the piston uncovers the forward end of passage 46 and port 44 placing the forward piston chamber in communication with the atmosphere through the passage 4G and the port 62 at the extreme forward `end of the valve chamber. This port in the rearward position of the valve connnunicates with groove 40 connected with the atmosphere by ein haust ports 42. lf the hammer is running at full sp-eed very little pressure fluid will exhaust from the forward piston chamber, but the arrangement permits of 4such exhaust in the event that t-he hammer is ruiming at low speed, so as to prevent a building up of pressure in the forward piston chamber which would iow through passage 48 to the large valve chamber 50 and prevent the valve from shifting forward.

Toward the end of the return stroke the piston covers the end of the passage 5G, the other end of which commu-nicates with Ithe small valve chamber 58. A lsmall port 60 continuously communicates with this passage and with the annular chamber 30. The pressure in the passage 56 cannot rise during the return stroke because the end of the passage is in communication with the rear end of the cylinder until the piston covers it. TWhen this occurs, the pressure in the passage 56 immediately rises and the valve is thrown forward again into the position shown in Fig. l. This takes place against the pressure existing at the instant in the large valve chamber 50 which isl the same as the pressure in the front end of the cylinder by .reason of passage 48 which is continually in communication with the large valve chamber and the front end of the cylinder. As soon yas the valve has shifted, however, the front end of the cylinder is again connected to the exhaust passages through passage 36 so that during the forward stroke the pressure in the large valve chamber will be practically `atmospheric and the valve will be held firmly in the position shown in Fig. l.

During 'the initial portion of the forward movement of the valve member there is no pressure on the forward end thereof, but as soon as the groove 40 is covered the forward end of the valve is subjected to the same pressure as exists in the forward piston chamber through the port 62 and the passage 46, the piston being near the forward end of its travel. This serves to retard the forward movement of the valve and opens the inlet groove 34 gradually so as to pre vent a large amount of motive fluid from suddenly entering the rear piston chamber and striking the rearwardly moving piston. Thus the piston is brought to a stop gradu ally and the vibration or kick-back of the tool greatly lessened.

lt is often desirable for the workman to strike one or two light preliminary blows before delivering full power to the tool, and for this purpose the supply of air to the tool is throttled. When the supply of air is throttled down by the workman, a limit is reached below which the tool will not operate and this limit occurs when with the pis ton in its rearmost position and the valve in the position shown in Fig. 2, the supply pressure in the small valve chamber 58 is not sufficient to shift the valve forward. rl`he point at which this limit is reached ldepends largely on the pressure in the front end of the cylinder, which through passage 48 controls the pressure in the large valve chamber.

According to my invention, I provide a small auxiliary port 62 extending from passage 48 toward the chamber adjacent the exhaust groove 4() so as to be covered by the end of the valve during the forward stroke. lVhen in the forward `travel of the piston the forward end of passage 46 is uncovered by the piston, pressure is admitted by the port G2 to the pressure area formed by the forward end of the valve vto assist in shifting the valve rearwardly. Then the valve shifts rearwardly this port opening directly into the cylinder adjacent the exhaust passages connects the end of passage 46 directly with the atmosphere. lv`l7hen the piston uncovers the end of passage 46 in its rearward travel, therefore, the space in front of the piston is immediately connected with the atmosphere so that the pressure will drop rapidly, the piston travelling the remainder of the rearward stroke with relatively little further increase in speed. It is thus possible by slightly increasing the size of passage 52 to secure the same speed of operation by accelerating the piston faster during the first half of the return stroke. and less Iafter passage 4G is uncovered, getting the piston back to the rear end of the cylinder in the same length of time, but with a materially lower final velocity and with less pressure in front of it at the instant of reversal. The decrease in the pres lim lll)

sure in the front of the piston accomplishes the same decrease in passages 48 and in the large valve chamber 50, which decrease cuts down on the. resistance to forward shifting of the valve, making the forward movement of the same quicker and more uniform and certain. Also the port 62 serves to vent the extreme forward end of the valve during the forward shifting movement thereof, thus preventing a premature building up of pressure at this point, and on the other hand when the groove l0 has been closed in the forward movement of the valve, this port 62 serves to supply air, to retard and cushion the final portion of the movement of the valve.

ll/hile l have illustrated and described in detail the preferred embodiment of my in vention, it should beclearly understood that the disclosure is merely for purposes of illustration and that many modifications and variations will naturally occur to those skilled in the art. I aim in the subjoined claims to cover all such legitimate variations and niodifications,

l claim as my invention:

l. ln a fluid-pressure-actuated tool, having a reciprocating piston, means including a valve for delivering, live motive fluid to recipro fate the piston, and means controlled by said valve so as to be operative during the latter portion lof the return stroke of the piston to cut down the pressure returning the piston, said means being inoperative during the entire forward stroke.

ln a tluid-pressure-actuated tool having a recii'froeating` piston, a valve, means for K cate the piston, passageways connected by movement of the valve to effect the return stroke of the piston, and means rendered operative upon such movement of the valve and by the movement of the piston past a predetermined point in the return stroke for cutting; down the pressure returning the piston.

:3. ln a fluid-pressure-actuated tool having' a reciprocating piston, an automatic valve controlling' the movement of the piston, a valve control passage uncovered by the piston toward the end of the forwa 1d stroke for shifting the valve, means for again shifting the valve toward the end of the rearward stroke, and discharge means associated with the valve control passage and iincovered by the valve in its rearward movement whereby uncovering said passage by the piston on its return stroke will operate `during` the remainder of the stroke to reduce the pressure returning the piston.

l. In a fluid-pressureactuated tool having` a reciprocating piston, a passageway uncovered by theirear end of the piston tcward the end of the forward stroke and by the front end of the piston during,` the reardeiivering live motive fluid to reciproward stroke, a valve, and means including` part of the valve for automatically connecting said passageway to a valve chamber to control the movement of the valve during the forward stroke, and for disconnecting it from said valve chamber and connecting` it to the atmosphere during the stroke.

5. ln a 'luid-preassure-actuated tool having, la reci procating piston and a valve, means for returning the piston in a minimum time with a minimum nal velocity comprising' means for impartin,r a high accelerationto the piston at the beginning,` of the return stroke by delivering motive fluid at high pressure to the front end of the cylinder, and two independent means for din'iinishingv the acceleration duringl the stroke by cutting down the pressure, one means operating by liniitation of the supply of motive fluid to the front end of the cylinder and the other means operating by discharge of motive fluid from the front end of the cylinder, said discharge means being covered by the valve during the forward stroke.

6. ln a fluid pressure actuated tool, the combination of a cylinder' having` a piston chamber, a piston reciprocable in the chamber, valve means for controlling the movements of the piston including a reciprocatory valve member, and means controlled by the movement of the valve member to effect the return of the piston whereby to connect the forward portion of the piston chamber with the atmosphere as the piston approaches the rear end of its travel.

7. ln a fluid pressure actuated tool, the combination of a cylinder having a piston chamber, a piston reeiprocable in the chamber, a reoiprocatoryvalve member, means controlled by the forward movement of the piston to shift the valve member, means for sujiiplying a restricted amount of pressure tluid to the `front end of the piston chamber to return the piston, means independent of the two last mentioned means for holding,l the valve member in its rearmost position, and means controlled by the valve member and operable in the rearward movement of the piston to decrease the returning` speed of the latter and to facilitate the forward movement, of thc valve member.

8. in a liuid pressure actuated tool, the combination of a cylinder providing` a piston chamber, valve means including;- a reciprocatory valve member, means controlled by the n'iovements of the piston for shifting the valve member in opposite directions, and means controlledv by the valve member and operableas the gisten moves toward its initial position to decrease the returning; speed of the piston and to facilitate the shifting of the valve member.

9. A fluid pressure actuated tool having` rearward 'ill liltl a reciprocating piston, a valve controlling the movements of the piston, a valve-control passage uncovered by the piston toward the end of the forward stroke for shifting the vulve, means for again shifting the valve toward the end of the rearward stroke, means for trapping pressure fluid received from the valve control passage during the forward movement of the piston to hold the valve in its rearward position, and discharge means associated with the valve-control passage and uncovered by the valve during its rearward stroke whereby uncovering the valve-control passage by the piston on its return stroke will operate during the remainder of the stroke to reduce the pressure in the forward piston chamber.

lO. A fluid pressure actuated tool having a reciprocatory piston, a passage opening at one end into the piston chamber at its midportion, an exhaust duct, a port communicating with the other end of said passage, and a valve adapted in one position to establish communication between said port and said duct and in another position to close said port and cut olf communication between the passage and said duct.

ll. A pressure fluid actuated tool having a cylinder, a piston reciprocable in the cylinder, a. rcciprocatory valve, inlet and exhaust passages controlled by said valve, the exhaust passage being located near one end of the valve, a valve-control passage opening into the mid-portion of the cylinder .and adapted to be uncovered by the forward end of the piston as it travels rearwardly and a port communicating at all times with said control passage and adapted to communicate under the control of the valve with the exhaust passage.

l2. A pressure fluid actuated tool having a reciprocating piston, a reciprocatory valve, inlet and exhaust passages controlled by opposite ends of said valve, a valve-control passage opening into the mid-portion of tne cylinder and adapted to be uncovered by the forward end of the piston as it travels rearwardly, means controlled by the valve operating when the valve is in its rearmost position. to supply pressure fluid to the forward piston chamber to move thepiston rearwardly, and a. port communicating at all times with said control passage and with said exhaust passage when the valve member is in its rearmost position.

13. A pressure iiuid actuated 'tool having a. reciprocating piston, a control valve having large and small pressure chambers, means for supplying pressure fluid to the small pressure chamber to shift the valve in one direction, and means for shifting the valve in the opposite direction including a valve control passage opening i-nto the mid-portion of the piston chamber and' communicating at its rear `end with the large pressure chamber in the forward position of the valve, and a port for supplying pressure fluid from said control passage to the forward end of the valve whereby to assist in shifting it rearward-ly.

lil. A pressure fluid actuated tool having a reciprocating piston, a control valve having large and small pressure chambers,

means for supplying pressure fluid to the small pressure chamber to shift the valve in one direction, and means for'fshifting the valve in the opposite direction including a valverontrol passage `opening into the midportion of the piston chamber and communi eating at its rear end with the large pressure chamber in the forward position of thevalve, anda port for supplying pressure fluid from said control passage to the forward end of the valve whereby to assist in shifting it rearwardly, said port communicating with the atmosphere in the rearward position of the valve member whereby, when the piston in its rearward travel uncovers the forward end of said control passage the forward piston chamber is also connected with the atmosphere.

l5. A pressure fluid actuated tool having a reciprocating piston, a control valve, means operating during the rearward stroke of the piston to hold the control valve in its rearward position, means operating as the piston approaches the rear :end of its stroke to move the valve to its forward position, passages arranged to be connected in the rearward travel of the piston and operating to hold the valve member rearwardly, and a port connecting one of said passages with the atmosphere in the rearward position of the valve member whereby to reduce the pressure in the forward piston chamber.

lf3. A pressure fluid actuated tool having a reciprocating piston, a `control valve, inlet and exhaust passages controlled by said valve, the exhaust passage being adapted to be closed by the forward end of the valve in the initial portion of its forward movement, a valve-control passage opening into the mid-portion of the cylinder and adapted to be uncovered by the rear end of the piston as it approaches the forward end of its stroke, and a port leading from said valvecontrol passage to the eXtreme forward end of the valve chamber so as to admit pressure .fluid from the control passage to the extreme forward end of the valve after the latter closes said exhaust passage, whereby to retard the final portion of the forward movement of the valve.

In testimony whereof, I have hereunto set 1n hand.

y ERNEST H. SHAFF.

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