US1867317A - Rock-drill and like tool - Google Patents

Description

Patented July 12, 1932 "nine 0 STATES PATENT o F-FfiCE JOHN LEONARD I-IOLMAN AND ARTHUR TREVE HOLMAN, 0F CAMBORN E, CORNWALL, ENGLAND, ASSIGNORS TO HOLMAN BROTHERS LIMITED, OF CAMBORNE, CORNWALL,

' ENGLAND, A BRITISH COMPANY ROCK-DRILL AND LIKE TOOL Application filed January 19, 1929, Serial No. 333,635, and in Great Britain August" 11, 1928.

This invention consists in improvements in or relating to rock-drills and like tools such as pneumatic hammers, riveters, caulkers, picks and such like and where the term rockdrill appears hereafter it is to be understood as including all tools by compressed fluid, such as compressed air, to which the improvements, to be described below, are applicable. In tools of the above type, the'compressed driving fluid, is distributed to the working cylinder by means of a distributing valve whereby the driving fluid is admitted alternately to opposite ends of the main cylinder. The primary object of the present invention is to improve such distributing valves. 7

According to the present invention the means which controls the admission of driving'fiuid to one or to each end of the cylinder, comprises in combination a floating plate valve, a seating on one or each sideof the valve extending completely around the latter at or near its outer margin, and a fluid inlet passage for delivering fluid to the outer margin of the valve (for example, aninlet passage completely surrounding the valve margin).

In a modification of the invention thefdistributing valve is of annular form and is situated at the rear end of the cylinder surrounding amember (for example a twist bar) constituting part of the tool. It is free to move bodily between valve seats that are spaced apart on opposite sides of it, and so constitutes a floating valve, as distinct from the known type of hinged valve employed; heretofore which is constrained to swing about afixed axis. 1

Preferably where the valve is of annular form its inner periphery, is made to constitute abearing surface by which the valve is guided in engagement with an inner member constituting a part, of the tool. This member may be a sleeve'surrounding the twist barabove-mentioned. r

In one example of the invention, the valve has an axial extension of annular form affording by its inner periphery an additional bearing surface extending on one or both sides of'thevalve. The total length manner to be described hereinafter.

The rock-drill comprises a main hammer of the bearing. surface is thus increased beyond'that which wouldbe afiorded-by the thickness of v the valve-plate alone. This axial extension may also help'to balance the pressures on the two side-s of the valve in a In order that the invention may be more readily understood one preferred example of rock-drill and a modification thereof embodying the features of the invention, will now 7 65 be described with reference to the-accompanying drawing, in which :n

Figure 1 illustrates diagrammatically in section those parts of a rock-drill necessary to theunderstanding of the 'invention; and

Figure 2 shows a modified form of a portion of the apparatus shown in Figure 1.

Like reference numerals indicatelike parts in the drawing. I

7 7 cyllnder 10 having a hammer piston 11 recip: rocating therein. A twist-bar or rifle-bar' l2 ext-ends coaxially into the cylinder from its rear end and engages a correspondingly fluted aperture formed coaxially inthepiston. The twist-bar is associated with the usual or any preferred form of mechanism, such, for example, "as ratchet mechanism, designated as a whole by the numeral 18, whereby apartial' rotation'is imparted to the 80 piston as it moves in one direc'tion,-but when it moves in the reverse direction no such partial rotation is effected.

All these parts are of well-known construd tion'and arrangement.

Surrounding the twist-bar or its? equivalent is an annular valve-casing 14: within which is situated an annular plate valve 15. At the rear endof the drill there is-a main inlet passage 16 for driving fluid-and in the passage there is a main control'cocktherefor (not illustrated). The passage 16 communicates with the interior of the'valve-chamber 17 which contains the valve 15 andthe'zouter diameter of which is greater than the outer 9a diameter of the jvalve 15 so that therefisa clearance between the outer WfiglltQf the 01mm; berand the outer margin of thevalve. posed valve- seats 18, 19 are provided in the valmahamber, i n the Valve-seats there i are provided annular ports 20, 21 communieating respectively with passages 22, 23 opening into opposite ends of the cylinder.

In recesses situated behind the valvechamber are accommodated two pressure-re-.

lease- valves 32 and 33. From near one end of the cylinder a passage 30 communicates with a port 34 that 'iscontrolled by one face of the valve32; and an exhaust port 36 is controlled simultaneously by the same face thereof. The other valve 33 controls in a similar. manner by its one face an exhaust port 37 and a port 35 which communicates with a passage 31 opening into the cylinder near its opposite end. Ports 38 and 39 which are controlled by opposite faces of the valve 15 lead to the other facesof the valves.32 V

and 33 respectively. When either of the ports 38 or 39 is uncovered driving fluid-forces the corresponding release-valve firmly on to its seating, thus closing the connection between its release-passage (30 or 31) and exhaust.

Inorder'. partly to balance the pressures on the two sides of thevalve 15 an, annular cavity 40 is provided connected with the valve chamber 17 by a passage 41. The pressure exertedby the drivingfiuid in this cavity a rearward direction tends to balancethe pressure of the driving fluidacting in a forward direction on the other face of the valve.

The valve 15 is provided with a cylindrical extension which is'accommodated in a recess 47 shaped to receive it as a sliding fit.

This cylindrical extension servestwopunposes. Firstly, it guides the valve and prevents it from tilting, and secondly it helps furtherv toeffect the balanceof the valve. The rear endofthe recess-47 opens through a passage 49' to exhaust. The guiding of the valve 15 is effected by the external surface of the extension45 and also by its internal surface and that of, the valve-plate itself. The

' internal surfaces of the valve-plateand ex tension form an extended bearing surface which engages with the-outside surfaceofi a sleeve 50 surrounding-therifle-bar 12.

It is convenient in this construction to provide. the usual water-tube 5 1.

The operation of the drill is as follows It is assumed that, at the commencement of; the cycle of operations, the distributing valve 15, is at the front end of its stroke and the ports 20 are opened by the distributing valve whichwill also. open the port 39 admitting driving fluid to; the pressure-releasevalve 33. The.release-valve- 33 is thereby held-onitsseating so as toclose'communication between its 'presshrerelease-passage 31 and exhaust vport 37 j The other pressurerelease-valve 32 will, however, have opened itsappropriate release passage30 to exhaust and the-piston '11 willcommence to move rearwardlyin the cylinder. Asit does so air is mainl' I fie of the piston th'roughan open ex expelled during the first portion of the stro contemplated modification.

i,sc7,317

haust port 48, situated approximately midway in the cylinder wall. Further passage 7 sure will accumulate behind the piston and in front of the-main valve. Almost immediately after the closing of the passage 30, the trailing edge of the piston uncoversthe open exhaust port 48 causing a sudden drop in pressure in the front end of the cylinder, in the passage 22 and on the rear face of the valve. This sudden drop of pressure combined with the accumulation of pressure in the rear end of the cylinder and the ports 21 causes the valve to flyover on to its other seat. f

r This movement of the valve 15 will close the port 39 leading to. pressure-release-valve 33. and open the port 38 leading to pressurerelease-valve 32. This will close the valve 32 on to its seating and'permit the valve 33 to open immediately pressure is exerted upon it (through the release-passage 31') as the piston commences to move towards the front end and after the main exhaust port 48 has again been closed. It will be appreciated that when the valve '15 is in theposition shown, the whole of the area of one face of it which lies outside the boundary of the axial extension 45 is subjectedto'the full fluid-pressure. If the extension 45Were omitted, as it may be in a modified form-of the invention, the whole area of one face of the valve would be subjected to this pressure. o v The provision of the cavity 40 enables air pressure to action the opposite face of the valve and so partially balancethe pressures on. the two faces. Thus, at the end 'of the rearward stroke of'the piston it is only necessary fora comparatively small pressure'to be accumulated by the last portion of the piston travel and/or asmall dissipation ofv the pressure through the passage 22. to throw the valve 15 very rapidly on to its other seat. By the provisionof'the extension 45 the area of the rear face subjected to the. full fluid-pressure is reduced, and a better balance'of' the pressures on the two valve'face's is thus obtainable than would be possible were the extension 45 not present as in the above 7 v The provision of'the passage 49 allows the extension 45 freedom of movement in the recess 47.

In the modification illustrated in Figure 2, the rear'end of the'recess 47, instead of opening to exhaust, is connected by a passage 55 to a port'56 in the seating'of the release valve 32 containingtheports34and 36..

Apassageffi is provided in the side of the recess. 4'? connecting it to the'passage that terminates in theport 38. Thus, driving fluid all) is admitted from the port 38 to the end-face, of the axial extension 45 of the valve when the latter is in the rearward position, i. e. at the end of its stroke opposite to that shown in Figure 2. Thus, with the valve in its forward position, as illustrated, the end-face of the extension 45 is connected through the passage 55, port 56 and port 86, to exhaust, thus favouring a rapid rearward movement of the valve as before. When, however, the valve 15 moves rearwardly to admit air for the for ward stroke of the piston 11 the port 38 is opened, the valve 32 is forced on to its seating and the full driving fluid-pressure is admitted to the end of the extension 45 through the passage 57 thus favouring a rapid forward movement of the valve 15. This overcomes any tendency which the valve 15 might otherwise have to stick as, for example, when boring a tight hole which results in considerable reduction in the speed of the piston 11.

WVe claim z- 1. For a rock-drill or like tool, means which, for controlling the admission of driving-fluid to opposite ends of the cylinder, comprises, in combination, an annular valvechamber that is coaxial with the cylinder, an internal guide-member, an annular distributing valve which surrounds and engages said internal guide-member, valve-seats spaced apart on opposite sides of the valve wherein'the valve is free to move bodily between said valve seats and lies in a plane transverse to the cylinder axis, a fluid inlet passage for delivering driving-fluid to the outer margin of the valve from which it can pass to either side of the valve, and an axial extension on the valve, which extension affords an additional bearing surface, and whereby the areas of the twoopposite valve faces are unequal.

2. For a rock-drill or like tool, means which, for controlling admission of drivingfluid to opposite ends of the cylinder, comprises, in combination, an annular valvechamber that is co-axial with the cylinder, a recess in said valve-chamber from which driving-fluid is excluded, a floating platevalve therein that is bodily movable in the direction of the cylinder axis, and lies in a plane transverse to the cylinder axis, a seating on each side of the valve approximately at its outer margin, and a fluid inlet passage for delivering driving-fluid to the outer margin of the valve from which it can pass to either side of the valve, and an axial extension on the valve which extension is a sliding fit in said recess from which driving-fluid is excluded, and whereby the effective area of one face of the valve as compared with that of the other face is reduced.

3. For a rock-drill or like tool, means for controlling admission ofdriving fluid to opposite ends of the cylinder comprising the combination of parts according to claim 2,

and, in the valve chamber, an internal guidememberwhich is co-axial with the cylinder and'on which the valve is a sliding fit; where- 4. For a rock-drill or like tool, means for controlling admission of driving fluid to'opposite ends of the cylinder, comprising the combination of parts according to claim 2, with-'an'internal guide member in the valve chamber on whichguide memberthe valve is a sliding fit, wherein the recess in which the said axial extension is a sliding fit is alternatelyput into communication with the full driving-fluid pressure and the exhaust.

5. For a rock-drill or like tool, means for controlling admission of driving fiuid'to opposite ends of the cylinder, comprisingthe combination of parts accordingto claim 1, with a recess in the body of the valve chainber in which the axial extension is a sliding fit, and from which driving-fiuidis excluded.

6. For a rock-drill or like tool, means for controlling admission'of driving fluid to'opposite ends of the cylinder, comprising the combination of parts according to claim 1, and in the body of the valve casing, a cylindrical recess in which the said axial 'exten sion is a sliding fit. I

7.- For a rock-drill or like to0l,--means for controlling admission of driving fluid to opposite ends of the cylinder, comprising the combination of parts according to claim 1, in i the body of the valve casing, a cylindrical recess in which the said axial extension is a posite ends of the cylinder, comprising the.

combination of parts according to claim 1, and, in the body of the valve casing, a cylindrical recess in which the said axial extension is a sliding fit and which is alternately put into communication with the full driving fluid pressure and the exhaust.

9. A valve assembly comprising in combination an annular valve-chamber that is co axial with the cylinder, an internal guide member in said chamber, an annular distributing valve having a hollow cylindrical axial extension which valve surrounds and engages said internal guide-member, annular valve-seats spaced apart on opposite sides of the valve at or near its outer margin wherein the valve is free to move bodily between said. valve seats and lies in a plane transverse-to the cylinder axis, a fluid inlet-passage for delivering driving-fluid to the outer margin of the valve and completely surrounding that margin from which it can pass to either side of the valve, and a recess in the body of the valve-casing, in which recess the axial extension on thealve is aslidi'ng .fit, and-from which driving-fluid is excluded and which is closed except for a passage connecting the interior of the recess with exhaust, whereby the efiective area of one face of the valve as compared with that of the other face is reduced. 1

10. A valveassembly comprising in combination an annular valve-chamber that is coaxial with the cylinder, an internal guide member in said chamber, an annuar distributing valve having a hollow cylindrical axial extension, which valve surrounds and engages said internal guide-member, annular valve-seats spaced apart on opposite sides of the valve at or near its outer margin wherein the valve is free to move bodily between said valveseats and lies in a plane transverse to the cylinder axis, a fluid inlet-passage for delivering driving-fluid to the outer margin of the valve and completely surroundingthat margin from which it can pass to either side of the valve, and a recess in the body of the V valve-casing, in vwhich recess the axial extension is a sliding fit, and which is alternately V 7 put into coinrnunicatiton with the full driving-fluid pressure and exhaust.

In testimony whereof we have signed our names to this specification.

' JOHN LEONARDHOLMAN. ARTHUR TREVE HOLMAN.

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