US3083730A

US3083730A - Fluid pressure operated apparatus

Info

Publication number: US3083730A
Application number: US82600A
Authority: US
Inventors: Hay Claude Henry
Original assignee: Baldwin Instrument Co Ltd
Current assignee: Baldwin Instrument Co Ltd
Priority date: 1961-01-13
Filing date: 1961-01-13
Publication date: 1963-04-02
Anticipated expiration: 1980-04-02

Description

April 2, 1963 C. H. HAY 3,083,730

FLUID PRESSURE OPERATED APPARATUS Filed Jan. l5, 1961 4 Sheets-Sheet 1 l my, 7, l 1 l l CLHUDE HEN Ky HHY pril 2, 1963 c. H. HAY

FLUID PRESSURE OPERATED APPARATUS 4 Sheets-Sheei'l 2 Filed Jan. 15, 1961 CLm/DE HEL/Ry HHY uw MMM/Ma #TTM/H5 pril 2, 1963 C. H. HAY

FLUID PRESSURE OPERATED APPARATUS 4 Sheets-Sheet 3 Filed Jan. 15, 1961 IENVENTOKv CLAUDE Hr-wiy Hff/ 6%, 06AM/ M/ #WMA/Ew April 2, 1963 c. H. HAY 3,083,730

' FLUID PRESSURE OPERATED APPARATUS Filed Jan. 15, 1961 4 Sheets-Sheet 4 1 l 1f f/ @a jajjgg 2117 0% 15)@ 951325550 VTM/wf f 3,03,73 FLUlD PRESSURE @PERATED MARA'EUS Claude Henry Hay, Dartford, Kent, England, assigner to Baldwin Instrument Company Limited, Dartiord, England, a British company Filed lan. 13, lll, Ser. No. 82,6%@ il@ Claims. Cl. IE7-62%) This invention relates to iiuid pressure operated apparatus in which a main control valve is operated by a pilot piston and cylinder. The invention is applicable both to pneumatically and hydraulically controlled apparatus.

In many types of uid pressure operated apparatus, a luid pressure signal for initiating operation of the main control valve is available. In some machines, for example, a signal pressure is oi for part of a complete cycle of operation and on for the remainder of the cycle and the onset of the signal pressure is used to initiate an operation of the main control valve. It is often necessary, therefore, to ensure that the main control valve can be reversed irrespective of whether the original signal pressure is still on or not. Heretotore this has generally necessitated the provision of complex arrangements in which the movement of part of the apparatus operates some clearing valve to remove the signal nid pressure from the pilot piston. For example, in an automatic drilling machine, the signal pressure system is commonly arranged so that the signal pressure is on for the whole cycle of operation except whilst the feed system for feed ing the drill is operating, during which period the signal pipe controlling the feed or" the drill unit may be open to exhaust. As soon as the feed slide clears the drilling zone, a signal pressure is provided which is applied to the drill unit valve to operate the drill and this signal pressure will stay on until the next cycle. This means that the drill valve has to reverse with the pressure still on the pilot piston. It is an object of the present invention to provide an improved arrangement enabling the main control valve to be operated by a signal pressure and returned subsequently irrespective of whether the signal pressure is still applied or not.

According to this invention there is provided duid pressure operated apparatus in which a feed movement is initiated or effected by the application of a iluid pressure signal to a pilot piston, which fluid pressure operated apparatus comprises in combination a main control valve which is operated by the pilot piston, pressure equalising means operative to equalise the pressure on the two sides of the pilot piston after the latter is moved, under the action of the fluid pressure signal, a predetermined distance such as to eiect operation of the main control valve, and means eective to restore the pressure equalising means to their inoperative condition. With this arrangement, when the signal uid pressure is applied, the pilot piston operates the main control valve, but when the pressures on the two sides of the pilot piston are equalised, the pilot piston no longer exerts any force on the main control valve. Thus the main control valve can be reversed although the signal pressure is still on. Moreover, if the pilot piston is not rigidly connected to the main control valve, the pilot piston can be moved to a certain extent without effecting the main control valve, even though the signal pressure is still applied. As soon as the signal pressure has been shut ofi, however, the pressure equalising means are returned to their inoperative condition so that subsequent application of signal pressure will eiiect movement of the pilot piston again. It will thus be seen that the signal pressure has to be shut off and restored in order to start a further cycle of operation.

rates atet To equalise the pressures on the two sides of the pilot piston, both sides of the latter may be opened to atrnosphere, or the signal pressure may be applied to both of said sides. The restoration of the measure equalising means to their inoperative condition takes place when the signal pressure is shut oft", and preferably these pressure equalising or neutralising means include a diilerential piston. This diierential piston may be spring-urged in the direction to seal a passage between the two sides of the pilot piston and means may be provided effective to move the dilerential piston to open said passage when the pilot piston has moved a predetermined distance.

In one arrangement, the aforesaid dierential piston is movably mounted within the pilot piston and stop means are provided which are elective after a predetermined distance of movement ot' the dierential piston with the pilot piston to move the diierential piston relatively to the pilot piston to open said passage. Thus when the signal pressure is applied, the pilot piston is operated but, after a predetermined movement, the stop means operate the dilerential piston to equalise the pressures on the two sides of the pilot piston. As soon as the signal pressure is cut oi, the differential piston under the aforesaid spring-urge will seal the passage through the pilot piston and the system will be ready for the next cycle of operation.

Most conveniently, the differential piston is spring-urged in the direction of movement of the pilot piston to operate the main control valve, and the stop means are arranged to stop the diterential pistou and allow continued movement of the pilot piston.

Preferably means are provided for applying the signal pressure to the dilerential piston to hold that piston in the position in which said passage is open; thus the diterential piston is re-set when the signal pressure is shut od. This may be achieved by arranging that the movement of the differential piston relatively to the pilot pistou uncovers a port to admit the signal pressure to one side of the differential piston to move it in opposition to the said spring-urge.

For a more complete understanding of the invention, there will now be described, by way of example only, and with reference to the accompanying drawings, certain constructional forms of iluid pressure operated apparatus according to the invention. It is to be understood, however, that the invention is not restricted to the precise constructional details set forth.

In these drawings:

FlGURES l-5 are sectional views showing one coustruction according to the invention in different settings of the parts.

FIGURES 6-S are similar views of a modied construction,

FIGURE 9 is a detail part-sectional View on an enlarged scale, of certain of the parts shown in FGURES 1 5, the sectional plane of FIGURE 9 being at right angles to the sectional plane of FIGURES 15, and

FIGURE 1G illustrates a modification of the arrangement shown in FIGURES 1 to 5 and 9.

Like reference numerals indicate like parts throughout the drawings.

Referring firstly to FIGURE-S l-5 and 9, a valve block l@ is formed with a bore to receive a main control valve 1l in annular packing members 12, `and is also formed with a larger -bore to receive a pilot piston 13, the head of which carries another annular packing member 14. rIlse block lil has a passage 1S leading to the cylinder of the fluid pressure operated apparatus (not shown in the drawings), which is to be controlled and `also has two

other passages

16 and 17 which can be separately connected to the passage 15 by the valve l1 as described below. The passage 16 leads from the main pressure supply and the passage 17 leads to exhaust. There is also an axial passage 18 the function of which is to supply pressure to reset the valve 11. A further passage 19 admits the signal pressure to the pilot piston 13, land :a vent passage 20 leads from one end of the bore in which the pilot piston 13 is received. v

The main control valve 11 is formed with a waist 21 past which the passage 15 can be interconnected with either the passage 16 or Ithe passage 17 according to the position of the valve 1-1, and the annular packing members 12 arecarried by stationary ported sleeves 22 which permit the said interconnection through appropriate ports and a clearance between the inner surface of the sleeves and the outside of the

valve

1,1.

`One end portion of the valvell is bored to receive a spigot 23 on Va head 24 which slides in a bore in the block 1 0 and carries its own ,annular packing member. The head 24 is arranged to bear against the end of the valve 11. The other end portion of the valve 11 is formed with a somewhat similar bore which receives a tubular Yprojection 25 reaching axially from the pilot piston 13, and also receives -a control spring 26 which bears at one end Y against the end -face of the bore and'at their other end againstthe end of the projection 25. The tubular pro- Vjection 25 has opposed' apertures 27 in it through which reaches, with freedom for lost motion, a cross pin 28 carried byl the valve 11 (see particularly FIGURE 9).

The bore in the block 10 which receives the pilot piston 13 has an internal annular shoulder 29 spaced sufliciently from one end of the said bore to accommodate, and determine the limit of, the travel of the piston head, the inner diameter of the shoulder 29 is such as to leave a clear-ance between it and the outer surface of the shank 30 of the piston. Two other annular. packing members 31, spaced apart by a stationary ported sleeve 32, are held between the shoulder v29 and the other vend of the bore in the block 10, `and closely engage the outer surface of the piston shank 30.

The piston shank 30 is tubular 'and has a port 33 which in all positions of the piston 13 is in communication with the passage 19 Vfwhich admits the signal pressure. The piston shank 30 also has another port 34 which is close to lthe piston head. yThe function of the port 34 is described below. The end of the piston shank A3ft carries a tubular extension 35, and received in the interior of 'the

parts

30 and 35 is adifferential piston comprising a body 36 and a head 37, The bore of the piston shank 30 carries three annular packing vmembers m1-separated by ported sleeves 4'5 which lare allocated to the

ports

33 and 34. The packing members 44 are alwaysrin engagement *with* the bore of the piston shank and at times certain of them are in engagement with the external surface ot' Ythe differential piston body 36 to make a seal therewith. g This piston body 36 has a waist 38 and its end remote from the Yhead 37 yis extended in the form of a pin 39 Iwhich reaches into lthe interior of the projection 25 from the vpilot piston. The head `37 'of the diierential piston 36 is grooved at 40 to receive an annular packing member 41 to seal against the interior of the extension 35 incertain relative positions of the pilot piston and the diierential piston. The end ofthe tubular extension 35 is closed by a plate 42 between which and the head 37 of the diierential piston a spring 43 is situated. The pilot piston 13 is formed with Ya passage 46 which extends from the end face of the pilot piston to the bore in the latter.

The operation of the construction according to the invention shown in FIGURES land 9 may beV described as follows. In FIGURE l, the main control valve 11 and the pilot piston 13 are located at the right hand limit of their travel ,and the differential piston 36 is 1ocated at the left hand limit of its travel. The passage 15, leading to the cylinder in the fluid pressure apparatus being controlled, is connected tothe exhaust passage 17.

4 Signal pressure in the passage 419 will pass through the port 33 to the interior of the pilot piston shank 30, thence to the port 34 and out -to the left of the shoulder 29 to move the pilot piston 13 to the position shown in FIGURE 2. During this movement the projection 25 on the pilot piston, bearing against the spring 26, will correspondingly move the main control valve 11 to the position shown in FIGURE 2, in which the passage 1:5 is cut ott from both of the

passages

16 and 17. =In FIGURE 3, the main control valve 11 has lreached the left hand limit of its travel, but the pilot piston 13 has not yet done this and is being urged to the left by the signal pressure. The passage 15 is still cut o from `the passage 17 but is open to the supply passage 16. In FIGURE 4, the pilot piston 13 has taken up the lost motion, between it andthe main control valve 11, permitted by the apertures Y2,7 tou-the cross pin 28, and has compressed the spring 26. The passage 15 is still open to the passage 16 and closed to the Vpassage 17. The pin 39 extending from the dilerd ential piston 36 has encountered the cross pin -28 thus causing the dilerent-ial piston 36 to be moved to the right with respect to the pilot piston 13. As the result of this, the signal pressure from passage 19 is now shut 0E from the head of the pilot piston but is permitted Yto reach the left hand face of the head 37 Vof the diie'rentia'l piston. Signal pressure uid remains trapped in the space between the shoulder 29 and the opposed end of the pilot piston head. In FIGURE 5, -the signal pressure on the head of the diierential piston has moved the latter further to the right, compressing the spring 43. As Vthe result of this movement, which may be quite sudden, the signal pressure lluid trapped in the space between the shoulder 29 and the opposed end of the pilot piston head is able to pass throughV the port 34 to the passage 46 and thus to the vent 20. The spring 26 has in consequence been able to restore vthe relative positions of the main control valve and the pilot piston'to that lshown in A.FIG- URE 3. The pressure on both sides ofthe Apilot piston having been equalised, viz., opened to atmosphere, reversing pressuregapplied through the passage 18 will reset the main control valve and the pilot piston. soon as the signal pressure in the passage y19 is 'shut Voft, Vthe spring 43 will return the differential piston to the position shown in FIGURE l. Until this has occurred the cycle of operation cannot recommence. y

The construction shown in FIGURES 6-8, is in some respects similar to the construction shown in FIG- URES 1-5 and 9. However, a `different form of main control valve 47 is shown, and the bore inthe pilot piston 13 only has two annular packing members '44. The body of the differential piston 36 does not have any waistv but it has an internal conduit 48 which opens at one end into the interior of the extension 35 of the .pilot piston shank, and at the other end to the surface of a portion 49 of the diierential piston -36 larger than the aforesaid pin 39. There is no vent passage corresponding With the passages 20 in'FIGURES l-5.

The construction shown in FIGURES '6-8, operates, in some respects, in exactly the same way as the 'construction shown in FIGURES 1-5 and 9. The setting Vshown in FIGURE 6 corresponds withthat shown in FIGURE l, the setting shown in FIGURE 7 corresponds with that shown in FIGURE 4, and the setting Yshtiwr'i in FIGURE 8 corresponds with that shownrin FIGURE 5. The equalisation of the pressure on the two sides o'f'tlie pilot piston 13 is elected, as shown in FIGURES 7 and 8, by applying the signal pressure to both of said sides, through the port 34 and the passage 46 respectively. The Vpassage 48 enables the signal pressure to complete the movement of the differential piston 36 to the right after that movement has been initiated by the lost motion connection between the pilot piston 13 and the main control valve 47.

A modified form of fluid pressure operatedapparatus is shown in FIGURE 10 which corresponds to VFIG- URE 1. The apparatus is the same as that shown in FIGURES 1 to 5 except that the reversing piston 24 is returned to the left-hand end of its travel by a spring 124 after cut-od of the reversing pressure from passage 18, that the travel of the main valve 11 to the left is limited by a xed shoulder 125a on a liner retaining ring 125, that the lost lmotion means 26, 27, 2S between the main valve 11 and the pilot piston 13 are eliminated, the valve 11 abutting the pilot piston 13 in all positions thereof, and in that the differential piston 36 is displaced to the right with respect to the pilot piston 13 by a pin 139, which extends from the piston 36 through the main valve 11, coming into contact with the spigot 23 on the reversing piston 24 towards the left-hand end of the travel of the main valve 11 and pilot piston 13.

The operation is the same as in FIGURES 1 to 5, except that in this construction the movement of the diterential piston 36 to the right relative to Ithe pilot piston 13 to connect the space between shoulder 29 and the head of the pilot piston to vent so equalising the pressures on each side of the head of the pilot piston 13, is eiected first by engagement of the pin 139 with spigot 23 and then by pressure acting on head 37 of the diierential piston 36, and that on application of reversing pressure through passage 1S to the reversing piston 24, the spigot 23 enters a recess in the main valve 11 and abuts a shoulder 11a to return the main valve 11 and pilot piston 13 to the positions shown in FIGURE 10. On release of reversing pressure, spring 124 returns the reversing piston 24 to the position shown.

It is to be understood that the invention is not restricted to the precise constructional details set forth.

yl. Fluid pressure operated apparatus comprising 1n combination (a) valve means comprising a :Erst valve member movable between first and second positions,

(b) a pilot piston and a rst cylinder, the pilot piston being reciprocable in the first cylinder between rst and second positions,

(c) means operative on movement of the pilot piston from its said rst position to its said second position to move the irst valve member from its said rst position to its said second position,

(d) a pressure fluid inlet to the irst cylinder on one side of the pilot piston, through which inlet pressure tluid may be admitted to move the pilot piston from its said first position to its said second position, and

(e) pressure equalizing means operative to equalize the pressure in the first cylinder on both sides of the pilot piston, when the pilot piston is in its said second position,

(f) the said pressure equalizing means being biased against operation and being operated by fluid pressure admitted through said pressure uid inlet.

2. Fluid pressure operated apparatus according to claim l, said pressure equalizing means comprising (a) a second piston and a second cylinder, the second piston being reciprocable in the second cylinder between rst and second positions,

(b) biasing means urging the second piston towards its first position,

(c) lirst ducting interconnecting the part of the rst cylinder on the side of the pilot piston opposite said one side and the second cylinder whereby -uid pressure from that part of the first cylinder is admitted to the second cylinder to urge the second piston against the biasing means towards its second position,

(d) second ducting interconnecting the parts of the rst cylinder on each side of the pilot piston, and

(e) a second valve member carried by said second Ipiston, and closing said second ducting when the second piston is in its said rst position, and opening said ducting when the second piston is in its second position.

3. Fluid pressure operated apparatus according to claim 2, the said pilot piston bounding a bore forming the said second cylinder, and the said ducting comprising porting interconnecting the parts of the said iirst cylinder and the said bore.

4. Fluid pressure operated apparatus according to claim 2, the said biasing means comprising a spring.

5. Fluid premure operated apparatus according to claim 2, comprising abutment means cooperating with the said second piston to limit movement of Ilthe said second piston during movement of the pilot piston from its said rst to its said second position.

6. Fluid pressure operated apparatus according to claim 2, the said ducting terminating at one end in porting opening into the said second cylinder, and the said second piston being operative to close said porting when in its first position, and to open said porting when in a position other than its lirst position.

7. Fluid pressure operated apparatus according to claim l, the said pressure equalizing means comprising (a) ducting interconnecting the parts of Ithe first cylinder on each side of the pilot piston, and

(b) valving operative to open and close said ducting.

8. Fluid pressure operated apparatus according to claim 1, the said pressure equalizing means comprising (a) ducting connecting the parts of the rst cylinder on each side of the pilot piston to atmosphere, and

(b) valving operative to open and close said ducting.

9. Fluid pressure operated apparatus comprising in combination,

(a) valve means comprising a rst valve member movable between first and second positions,

(b) a pilot piston and a first cylinder, the pilot piston being reciprocable in the rst cylinder between first .and second positions,

(c) means operative on movement of the pilot piston from its said rst position to its said second position to move the valve member from its said iirst position to its said second position,

(d) a pressure uid inlet to the rst cylinder on one 'side of the pilot piston, through which inlet pressure uid may be admitted to move the pilot piston from its said first position to its said second position,

(e) the said pilot piston bounding a bore constituting a second cylinder,

(f) said pilot piston embodying porting interconnecting the parts of the rst cylinder on each side of the pilot piston and the said bore,

(g) the said bore having a part of enlarged diameter,

(h) a second piston reciprocable in the said bore,

lbetween tirst and second positions,

(i) the second piston having a part of enlarged diameter Working in the part of enlarged diameter,

(j) the second piston carrying a second valve member cooperating with the porting embodied in the said pilot piston, in its rst position -to prevent com munication via the said bore between the parts of the rst cylinder on opposite sides of the pilot piston, and in -its second position to permit such communication,

(k) biasing means urging the said second piston towards its irst position,

(l) abutment means limiting movement of the second piston during movement of the pilot piston between its iirst and second positions, whereby the second piston is caused to move relatively to the pilot piston during such movement of the pilot piston,

(m) ducting interconnecting the part of the first cylinder on the side of the pilot piston opposite said one side and the enlarged part of the second cylinder,

(n) said ducting terminating in porting in the second cylinder, and the second piston being operative to close said porting when in its first position, and to open said porting when in a position other than its rstpositiom; whereby when pressure uid is in the said opposite part of the first cylinder and the' second piston, is in a position other than its rst position, the second piston' is subjected tov pressure against the action of the biasing means.

110. Fluid` pressure operated apparatus according. to

claim 9, comprising Y (a) athird piston, and atfhirdvcylinder, the thrdpiston Ibeing reciprocable in thev third cylinder,4 between a iirst positionvand alsec'on'd position,

(5;) a pressure iuidv inlet tothe third cylinder, whereby pressure fluid may be admitted to the third cylinder 8:l to move the third piston'frorn` its. iirstV position toitssecond position,

(1c). means operativeY onA movement' ofY theA third pistonV from its second position. to its first position when.

the supply of pressure uid'to the third cylinder is cut oi.

References CitedY in the tile of this patent UNITED STATES PATENTS Leonard etV a1; Mar. 1, 1960'.

Claims

1. FLUID PRESSURE OPERATED APPARATUS COMPRISING IN COMBINATION (A) VALVE MEANS COMPRISING A FIRST VALVE MEMBER MOVABLE BETWEEN FIRST AND SECOND POSITIONS, (B) A PILOT PISTON AND A FIRST CYLINDER, THE PILOT PISTON BEING RECIPROCABLE IN THE FIRST CYLINDER BETWEEN FIRST AND SECOND POSITIONS, (C) MEANS OPERATIVE ON MOVEMENT OF THE PILOT PISTON FROM ITS SAID FIRST POSITION TO ITS SAID SECOND POSITION TO MOVE THE FIRST VALVE MEMBER FROM ITS SAID FIRST POSITION TO ITS SAID SECOND POSITION, (D) A PRESSURE FLUID INLET TO THE FIRST CYLINDER ON ONE SIDE OF THE PILOT PISTON, THROUGH WHICH INLET PRESSURE FLUID MAY BE ADMITTED TO MOVE THE PILOT PISTON FROM ITS SAID FIRST POSITION TO ITS SAID SECOND POSITION, AND (E) PRESSURE EQUALIZING MEANS OPERATIVE TO EQUALIZE THE PRESSURE IN THE FIRST CYLINDER ON BOTH SIDES OF THE PILOT PISTON, WHEN THE PILOT PISTON IS IN ITS SAID SECOND POSITION, (F) THE SAID PRESSURE EQUALIZING MEANS BEING BIASED AGAINST OPERATION AND BEING OPERATED BY FLUID PRESSURE ADMITTED THROUGH SAID PRESSURE FLUID INLET.