US1678734A - Fluid-operated tool - Google Patents

Description

July 31, 1928. 1,678,734

w. KUHN FLUID OPERATED TOOL Filed March 16, 1927 "wt/y TOR Ln-mm mi/m ATTORNEY Patented July 31, 1928. 1

UNITED STATES WILHELM KI THN, F FRANKFORT-dN-THE-MAIN, GERMANY.

FLUID-OPERATED TOOL.

Application filed March 10, 1927, Serial No.

The invention relates to an improved method of and means for operating the distributing valves of pressure fluid, more particularly pressure air operated tools having a reciprocating piston or striking member.

In tools of this kind one of the principal aims is to'make the distributing member,

usually a sliding sleeve valve, as simple of construction and as light as possible. Heavy 19 slide valves must have large operative surfaces for the pressure air serving toactuate them, and are very liable to wear and tear in consequence of the heavy impacts which arise, which liability is accentuated by the usually complicated forms of the valves.

The construction of the distributing valve may be considerably simplified if the pressure required for reversing the valve is obtained by intermittently stopping a flow of pressure air passing in contact with the distributing valve. This method has, however. so far not been extensively used owing to the fact that it involved a very high additional consumption of pressure air which outweighed the advantages obtained.

One object of the present invention is to minimize to a very large extent the loss of pressure air incidental to this method of operating the distributing valve, so as to avoid the main drawback of this method, whilst retaining all the advantages which may be attained in other directions by the use of said method. ,To this end and according to the invention, the reversal of the distributing valve at the end of the working stroke of the tool, is initiated or started by stopping the outflow of pressure air from a conduit associated with the valve surface to be acted upon, such stopping being effected by the striking member or reciprocating piston of the tool at the required time. The reverse movement of the distributing valve is then completed by an additional and 'direct admission to the same surface of the distributing valve of pressure air passing to the other side of the piston.

Another feature of the invention is the provision of a separate balancing conduit or passage which connects the casing of the distributing valve with the main cylinder of 174,346, and in Germany February 25, 1925.

the tool in. such a manner that one port of the balancing conduit or passage is covered and uncovered by the distributing slide valve, Whilst the other port of the said conduit or passage is adapted to be uncovered by the piston or striking'member of the tool on its return stroke earlier than the port of the previously referred to conduit associated with the distributing slide valve.

A further improvement according to the invention consists in constructing the distributing slide valve as a sleeve valve in such a manner that the valve controls a conduit leading to the front space of the cylinder,

which conduit serves both as a pressure air admission and exhaust conduit, by means of a single annular flange, and thatpressure air passes to the cylinder on. one side of said an nular flange during the return stroke of the piston, whilst exhaust air passes from the cylinder into the atmosphere on the other side of the said annular flange during the working stroke of the piston, so that the slide valve is held securely in both end positions by the pressure of the pressure air or the exhaust air respectively.

The accompanying drawings show by way of example a preferred construction embodying the features of the invention.

Fig. 1 shows a pneumatic hammer with the distributing valve in the position occupied during the working stroke.

Fig. 2 shows the said hammer with the distributing valve in the position occupied during the reverse stroke. 85

Referring to the drawings, A designates the cylinder of the pneumatic tool and B is the piston which is adapted to move to and fro in the cylinder. The piston B is adapted to strike against a tool D, such as a snap set, chipper, slotting tool or the like. 0 designates a cylinder cover screwed upon or otherwise connected to the cylinder A, said cover being providedwith an admission conduit 10 for the pressure air. 11 designates an annular space which communicates with the admission conduit 10 and also communicates through radial passages l and through the distributing sleeve valve S with the space above or behind the piston 13'. The

distributing sleeve valve S is adapted to slide up and down in the cylinder A, and is formed with an annular portion of an internal diameter corresponding to the external diameter of the piston B, an upper annular portion of larger diameter, and an annular flungehaving an upper end surface 12, a lower end surface 13 and a peripheral surface 19 which is the QperativevalVesur the flange 15, to a port 1 l opening into the cylinder. 6 is a passage leading from the annular space 11 to the lowest point of the annular space7. Sis a passage arranged above the passage 6 also leading from the annular space 11 to the annular space 7. 16 is a balancing passage or conduit having aport 17 opening into the cylinder, such port being arranged below the port 14, and a port 18 opening into the annular space? As ma Y be seen fromFi 1 the assa e. 6 communicates with the passage 5 in the lower position of the distributing valve S, only through a very narrow annular space lying below the surface 13 of the flange 15 so that pressure air passing from the passage 6 into the passage 5, is throttled.

During the workingstroke, see Fig. 1, pressure air passes from the conduit 10, through the annular space 11, passages 1 and the sleeve valve S, into the space behind the piston B and drives the piston in the direction of the arrow towards the tool D. At the same time pressure air passes from the annular-space 11, through the small passage 6 and the narrow annular passage under the surface 13 of the valve S to the passage 5, and through the latter passage into the space in front of the piston B by the lateral port 14. The flow of the air into the passage 5, 14 is throttled to a very considerable extent owing to the small area of the aassageti' and the annular space under the slide valve, and consequently only a small amount of pressure :air passesthrough the-conduit 5, 1 1 into the cylinder. This air, together with the era haust air which is being driven out bysthe piston 13 'duringthe working stroke, is dis charged through passage 2, the annular space 3, past the end surface 12 of the slide valve into the exhaust passage iand thence into the atmosphere. The end surface 13 .of the slide valve is therefore during the working stroke of the tool not subjected to. the high pressure of the pressure air, as said piston. 7 charged into t-lieopen through the passages pressure air is throttled whilstflowing past the surface 13 into the conduit 5.

As soon as the piston B covers the port 14: of the passage 5 during the working stroke, the outflow of the pressure air from the passage5 into the cylinder ceases and consequently the pressure in the passage 5 and in the annular space below the surface 13 increases. By this increase-ofthe pressure, the

reverse movement of the slide valve is initiated or started. After a short movement of the slide valve from the position shown in Fig. 1 towards the position shown in 2, the passage 8 is uncovered by the annular .flange 15, and at the same time or very shortly afterwards the conduit 2 is also placed into communication with the annular space,7, see Fig. 2, so that a full flow of pressure air will take place past the surface 13. of the distributing valve and into the conduit. 2, and thence into the space in front of the piston B, whereby the'piston B is returned.

It will thus be seen that the reverse movcment of the slide valve w hich has been initiated by pressure air admitted through the passage 6 as soon as the port 14: was closed by the piston B,-is completed by pressure air admitted through passage 8 which pressure air also serves for returning the piston 13. The surface 13 of the distributing 'valve remains during the whole return movement of the pistonB loaded by the pressure air, and consequently the slide valve is held safely in'it-s upper position of Fig. 2. In the upper position ofthe slide valve S, the air supply passages 1 serving for the working stroke, are closed, whilst the passage Qlead inginto: the exhaustp assage 4 is open.

As soon as the piston B during its return strokeuncovers the port 1d of passage 5, the passage 5 perfo-rmsthe same function as the passage 2, that-is, it admits pressure air in front of the piston B serving to return the The-air behind the piston isdis- 1 and 9. r V p At the end of the return stroke the piston enters the slide valve Sand at the same. time closes the exhaust passage 9. The airwhich remainsbehind the piston, is thus enclosed between the piston and the cover C inknown -mannerand is compressed. This compressed .air cushion exerts pressure on the annular surface. a-? of theslide valve and forces the slide valveback into the position shown in Fig. .1. During this movement of the valve, the passage 8 is closed by the flange 15 so that during the following working stroke only a small quantityof pressure air flows through the narrow passage 6 past the surface 13 into the passage 5. It may be pointed out that during the: working stroke, ex.-

haust air passes past the surface- 12 of the slide valve into the passage4, the slide valve being firmly held in the lower position shown in Fig. 1 by the pressure of the live air acting on the surface a-c, as also by the pressure of the exhaust air from the front of the cylinder.

In order to reduce as far as possible the amount of pressure air passing during the working stroke through the passages 6, 5, 14 into the space in front of the piston B and yet effect the reversal of the slide valve at the correct time, the pressure air admitted through the passage 6 must be strongly throttled and the port 14; of the conduit 5 must be covered by the piston B at the earliest possible moment. In consequence of this, in the case of short stroke pneumatic hammers, the port 14 has to be arranged so high up that it is nolonger uncovered by the front end of the piston B during the return stroke, before the piston has effected the necessary compression, so that the surface 13 of the slide valve is not relieved from pressure at the right time, that is, before the reversal from the position shown in Fig. 2 into that shown in Fig. 1 takes place.

In order to meet this difliculty a balancing conduit 16 may be provided in the case of short stroke tools, which conduit terminates at one end in a port 17 opening into the front cylinder space and at the other end in a port 18 opening into the annular space 7, the arrangement being such that the port 18 remains covered during the working stroke of the valve, but is uncovered during the return stroke of the piston before the compression above the piston commences. The conduit 16 therefore relieves the pressure upon the surface 13 against the pressure existent in the front of the cylinder in time, that is, before the slide valve is moved down.

During the working stroke the piston then first closes the port 14: of the conduit 5 so that pressure air is prevented from flowing out of the conduitfi and by the increase of its pressure is enabled to start the upward reversal of the slide valve. Before the reversal of the valve-commences, the port 17 is also covered by the piston B so that the conduit 16 is inoperative during said reversal at the end of the Working stroke. Before the piston 13 on its return stroke (see Fig. 2) passes the port 9, the port 17 of the balancing conduit 16 is uncovered by the piston so that on the reverse movement of the valve caused by the compression between the piston B and the cover O, pressure air flowing behind the surface 13 can freely pass into the front cylinder space by way of the conduit 16, so that the balancing of the pressure on the surface 13 takes place. In the end position of the slide valve shown in Fig. 1, the flange 15 shuts off the port 18 of the release conduit 16 so that when the pressure in the passage 5 commences to increase, the pressure on the surface 13 will not be prematurely released before the closing ofthe port 17, I

I claim: r

1. In a pressure-air operated tool the combination of: a cylinder, a piston working in said cylinder, means for supplying pressure air to said cylinder, means for discharging air from said cylinder, a distributing valve in said cylinder having both of its ends stepped and being adapted at the upper end to control the supply of air from said pressure air supplying means to the upper end of the cylinder for the working stroke and at the lower end to control the discharge of air through said discharging means from the upper end of the cylinder, a conduit associated with the valve which is open to the pressure air supply and to the cylinder during a part of the working stroke of the piston and is adapted to be closed by the piston before the end of the working stroke for the purpose of increasing the pressure in said conduit and thereby starting the reverse movement of the valve, a second conduit adapted to be rendered operative by the valve shortly after the reverse movement of the valve has started,'for completing the reverse movement of the valve, said second conduit communicating at one end with the pressure air supply and at the other end with the front end of the cylinder, and a third conduit likewise adapted to be rendered operative by the valve shortly after the reverse movement of the valve has started, for the purpose of allowing of the passage of additional pressure air past the lower end of the valve into the cylinder, said third conduit communicating at one end with the lower end of the valve and at the other end with the front end of the cylinder, substantially as described.

2. A fluid operated tool having a casing, a piston adapted to reciprocate in said cas ing, means for admitting pressure fluid to said casing, means for discharging pressure fluid from said casing, a slide valve controlling the admission and discharge of the pressure fluid, and pressure fluid operated means for operating said slide valve, said means comprising a conduit associated with the slide valve which is open to the pressureair supply and to the cylinder during a part of the working stroke of the piston and is adapted'to be closed by the piston before the end of the working stroke for the purpose of increasing the pressure in said conduit and thereby starting the reverse movement of the valve, and a second conduit adapted to bcome operative shortly after the reverse movement of the valve has started, for completing the reverse movement of the valve, said second conduit communicating at one end with the pressure air supplyand at the other end with the front end of the cylinder, substantially as described.

3. A fluid operated tool comprising, a cylinder, a piston adapted to reciprocate in said cylinder, means for admitting pressure air to and discharging exhaust air from the said cylinder, a slide valve controlling the distribution of the pressure air and the exhaust,

pressure air operated means for operating the reverse movement of the valve at the end of the working stroke, and means for passing an additional flow of-pressure air past the same surface of the valve into the front end of the cylinder, said latter means being controlled by the slide valve and becoming operative immediately after the reverse movement has commenced, and means for admitting pressure air to the front end of the cylinder controlled by said slide valve, said means becoming operative just before the completion of the said reverse movement of the valve, substantially as described.

4:. A pressure-air operated tool, comprising in combination a cylinder, a. piston adapted to reciprocate in said cylinder, means for supplying pressure air to said cylinder, meansfor discharging air from said cylinder, a slide valve for controlling the supply and discharge of the air, means for operating said slide valve, said means comprising an annular flange on said slide valve having a peripheral operative surface and an annular operative flat surface, means for supplying a throttled pressure air flow to said annular surface when the slide valve is in the position corresponding to the working stroke of the piston, a conduit leading in said position of said valve from said annular surface to a point in the front part of the cylinder, means on said piston for covering the end of said conduit leading into the cylinder for the purpose of increasing the pressure upon the annular surface, when starting the reverse movement of the valve,

and a balancing conduit leading from the peripheral surface of said flange to a point between the frontend of the cylinder and the end of the first mentioned conduit, said balancing conduit serving to balance the pressure upon the saidannular surface at the end of the return stroke of the piston against the pressure existent in the front of the cylinder, substantially as described.

5. In a pressure-air operated tool the combination of: a cylinder, a piston working in said cylinder, a distributing sleeve valve in said cylinder having a single annular flange, a peripheral valve surface on said annular flange, a first annular end surface on said annular flange, a second annular end surface on said annular flange, means for maintaining a throttled pressure air flow past the said first annular end surface and into the front part of the cylinder, means on the piston for intermittently closing said air flow and increasing the pressure of said air upon said first annular end surface to start the reverse movement of the valve at the end of the working'stroke of the piston, means for passing a further flow of pressure air past the said first annular end surface of the said annular valve flangeand into the front end of the cylinder, said means being controlled by said peripheral valve surface of the said annular flange, and means for passing exhaust air from the front end of the cylinder past the second annular end face of said annular flange, whereby the said valve is held securely in both end positions, namely by the air pressure of the live air flowing into the front of the cylinder acting on the first annular end surface of the flangein the upper position corresponding to the return stroke of the piston and by the pressureof the live air acting on the upper surface of the valve,

as also by the pressure of the exhaust air from the front of the cylinder acting on the second annularend surface in the lower position corresponding to the working stroke of the piston.

' 6. In a pressure-air operated tool the combination of: a cylinder, a piston working in said cylinder, a distributing sleeve valve in said cylinder having a single annular flange, a peripheral valve surface on said annular flange, a first annular end surface on said annular flange, a second annular end surface on said annular flange, means for maintaining a throttled 'pressure air flow past the said first annular end surfaceand into the front part-of the cylinder, means on the piston for intermittently closing said air flow and increasing the pressure of said air upon said first annular end surface to start the reverse movement of the valve at the end of the Working stroke of :the piston,

means for passing a further .flow of presface of said annular flange, whereby the said valve is held securely in both'endpositions, namely by the air pressure of the live air flowing into the front of the cylinder acting on the first annular end surface of the flange inthe upper position corresponding to the return stroke of the piston and said peripheral flange surface for relieving by the pressure of the live air acting on the the pressure on the first annular end surface 1 upper surface of the valve, as also by the before the reversal of the valve into the pressure of the exhaust air from the front position corresponding to the Working 5 of the cylinder acting on the second annustroke of the piston.

lar end surface in the lower position corre- In testimony whereof I have signed my spending to the Working stroke of the pisname to this specification. ton, and a balancing passage controlled by WILHELM KUHN.

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