US2646778A - Fluid operated control system - Google Patents

Description

July 28, 1953 Filed June 23, 1949 C. E. WEBB FLUID OPERATED CONTROL SYSTEM 3 Sheets-Sheet l IN VEN TOR.

BY (1nd, $7,

A TTDRNE'YQ July 28, 1953 c. E. WEBB 2,646,773

FLUID OPERATED CONTROL SYSTEM Filed June 25, 1949 3 Sheet's-Sheet' 2 15.9 M ZVINVENTOR.

ly 8. 95 c. E. WEBB 2,646,778

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INVEN TOR. M 9. w 3' BY I 1% M M Patented July 28, 1953 FLUID OPERATED CONTROL SYSTEM Cecil E. Webb, Norwood, Ohio, assignor to M. S. Bowne, Clearfield, Ky., as trustee Application June 23, 1949, Serial No. 100,943

This invention relates to servo-motor apparatus for controlling steam extrusion presses and other equipment having pressure operated pistons requiring accurate stroke regulation by a hand operated control valve or throttle. As applied to a steam press, the apparatus constitutes a relay or auxiliary power system interposed between the main steam control valve and hand lever or other control device, the control apparatus being arranged to operate the main valve by fluid pressure in response to movements of the hand lever and thus to regulate piston movements accurately but with very little manual effort.

Steam operated presses have been in use for a great many years for extruding plastic clay tubes which are made into tile drainage and sewer pipes. Such presses essentially consist of a steam cylinder having a piston connected to an extruder ram, the movements of the piston being controlled by a reversible steam valve arranged to admit steam into one end of the cylinder to drive the piston forwardly during the extrusion stroke and to admit steam into the opposite end of the cylinder to retract the piston at completion of the stroke. In retracted position, the ram is withdrawn from its chamber to provide an opening for charging plastic clay into the chamber for the next operation.

The general practice has been to operate the main steam valve 'by a hand lever connected di rectly to the steam valve plunger in such a way that by manipulating the handle the piston can be moved in either direction and the valve throttled to control rate of piston movement. These machines are quite massive and the control valve offers considerable resistance to movement because of steam pressure and friction between moving parts. The valve must be operated almost continuously while the machine is in operation to control extrusion speed and to stop the piston as each tube length is extruded. Because of resistance, it is difiicult for the operator to throttle the valve accurately, hence the extrusion process oftentimes is not controlled as precisely as it should be for best results. Since the pressure required to move the lever is in the neighborhood of 60 pounds on large machines, it

will be appreciated that operation of such a press is very fatiguing to the operator.

To prevent the piston from retracting beyond a fixed limit and striking the top cylinder head with possible damage, it has been customary to provide a safety device operable to move the hand lever automatically to valve closing position when the limit of travel is reached. This causes the 5 Claims. (Cl. 121-41) hand lever to be kicked rather violently to neutral or valve closing position and is dangerous to the operator,

The present apparatus was designed primarily to reduce the effort of controlling the steam valve and to protect the operator from injury and for this reason the structure is disclosed in conjunction with a steam extrusion press, although it is contemplated to apply the apparatus to other machinery having pistons or rams powered by fluid pressure other than steam.

The primary objects of. the invention have been to provide a simplified fluid operated control apparatus which may be applied readily to conventional hand controlled presses to render valve operation almost effortless, whereby responsiveness and sensitivity are increased; also to provide an automatic safety arrangement to limit piston movement but at the same time to protect the operator from injury if the piston should overrun its stroke limit.

Essentially, the apparatus constitutes a fluid relay system interposed between the hand lever and main steam control valve, arranged to transmit the movements of the hand lever to the control valve in duplicate and almost instantly, by fluid pressure. In its preferred form, the apparatus is powered by hydraulic pressure for more positive operation, actuating force to move the main steam valve being developed by a hydraulic cylinder having a piston connected to the control rod of the steam valve. A plunger type hydraulic pilot valve is hydraulically connected to the cylinder, the pilot valve being arranged to lock the piston hydraulically in fixed position or to move the piston in either direction depending upon pilot plunger movement. is connected to the pilot valve plunger and the pilot valve casing is connected to and movable with the piston of the hydraulic cylinder.

When the handle is moved in a given direction from neutral, the pilot valve plunger is moved from a neutral position to admit hydraulic pres sure to an end of the cylinder to move the piston and steam valve in a corresponding direction. Since the pilot valve casing moves with the hydraulic piston and steam valve stem, it moves relative to its plunger to reestablish the neutral condition, thus hydraulically locking piston and steam'valve in open position so long as the handle is held in that position. The steam reversing valve normally is maintained in a neutral closed position corresponding to the handle neutral position and when the handle thus is actuated,

the steam valve is Opened to drive the steam- A control handle 3 piston in a corresponding direction. In other words, the hydraulic piston and steam valve follow precisely the movements of the pilot valve plunger in either direction.

There is very little lag between the movements of the hydraulic valve plunger and operation of the hydraulic piston steam valve follows handle movements almost as if the handle were connected directly tothe steam valve stem exceptthat the effort to move the handle is eliminated.

This leads to greater precision in controlling the extrusion operation as well as relieving the oper-- atcr of physical strain.

A safety interlock is interconnected between the steam piston and hydraulic control-apparatusto close the steam control valve before-the-piston contacts the top cylinder head, This device-reverses the pilot valve so as to close the steam valve when the piston actuates the interlock-nearits retracting stroke limit. Since the operator is at this time holding the handle in piston'retracting. position, the safety apparatusjs ;yieldably connected to the handle to absorb the impact; and

the variousother uses to which-the invention may be applied.

In the drawings Figure l is afragmentary side elevation of a steam extrusion press equipped with the, improved hydraulic control apparatus-.

Figure 2 is a view of the structure as projected from Figure 1, further illustratingthe complete structure.

Figure 3 is an enlarged fragmentary view of the hydraulic apparatus and control linkage as viewed in Figure 2, shown separated from the extrusion press;

Figure 4 is a fragmentary view'projected fromii Figure 3, furtherillustrating the control apparatus;

Figure 5 is afragmentary diagrammaticvlew illustrating the operation of the apparatus-with the secondarycontrol rod-at its upper limit of 1 travel.

Figure 6- is a fragmentary view similar to Fl ure 5, illustrating the operation ofthe safety interlock with respect to the pilot valve when the steam piston reaches its upper stroke limit;-

Figure '7 is an enlarged fragmentary view-taken on line 7-7, Figure 4, illustrating the yieldable connecticnbetween-the actuating lever and secondary control rod.

Figure 8 is an enlarged fragmentary -sectional view taken on line 38, Figure 1, illustrating the-v safety interlock connection and spring arrangement at the upper'end or" the steam valve stem.

Figure 9 is a diagrammatic view illustrating, a I reversible pilot valve and hydraulic cylinderv hy draulically and mechanically interconnected .to

provide the hydraulic relay operation.

As disclosed in its preferredembodiment, the control apparatus is applied toia steam-operated clay extrusion machine but it will be evidentthat; it canlbe applied as .well to various-.hydraulic..-oi 1 all; operated machines. The press illustratedis a conventional machine which is in extensive use in the clay pipe industry. The pipe lengths are extruded from clay and while still in plastic condition they are trimmed accurately to length, their ends are shaped according to type and other necessary operations are performed, after which the sections are baked and fired.

As disclosed in Figure 1, the machine rests upon abase or foundation formedjfrom, steel I-pbeams l0'l 9 whiclr maybe located at iloor level. Rising from the foundation is a steam cylinder indicated generally at l l and beneath the foundation thereis securedamextrusion unit generally indicated at I2 through which the plastic clay is vv forced under pressure developed by the steam cylinden Thecylinder assembly H is supported uponvertical studs. or tie bolts i3 rising from the foundation I-beams and secured to the lower cylinderhead I l. The cylinder includes a top cylinder head i5 and a piston it having a piston rod passing through a packing gland ii! for sing a part ofthe lower cylinder-head it. The lower end of thepiston rod'carries an extrusion ram.

it which traverses the extrusion chamberwzc-lte 7 forcethe-plastic clay under v pressure through the extrusionidie 2 i atthe'lower, end of the chamber.

The extruder chamber ischarged with the 1 rain in an elevated position in whichnposi-tion the-- upper end of the extrusion chamber isexposedr- The piston andrammoveme nts are controlled by the steam throttle valveit ehaving-neutrale forward and reverse positionsto control the direc- 1 tion and rate of piston travel-. This valvemay follow any conventional design-andfor thisreason-is not disclosed in detail. It is'to. be-notedthat this valve in the pastvhasbeen actuated manually by .a control lever connected directly to the valve stem 24. The operation'of the valveis regulated by vertical movements of the-stem 24 and the valve is provided with a ,steamsupply pipe ZS aneXhaust pipe 28,- andrespective steam pipes 2? and-28 leading from the-valve to ,the' top-and bottom of the cylinder assembly.

When the. valve stem 24 is in neutral or intermediateaposit-ion, the steam supplypipe 25 is: blocked and piston itisstationary. Whenthe stemjis lowered, steam-is passedfromsupply pipe- 25, through the valve to pipe 21, into-theupper end of thecylinder-to force piston i6 downwardly while steam is exhausted from the lower .end'of the cylinder through pipe 28, through the -valve to exhaustpipe 25: When-the valve stem is raised r above neutralposition, the passageof steam is. reversed to raise the piston. Rateof piston travel is controlled by the degree of sten-i: movement whichprovides a throttling action. Thesteam press .is-provided with other strueturesuitable to guide-and support the extruded :clay tubeoperablemanually bythes-apphcationof very.-

slight force As shown, the-hydraulic apparatus.

in general constitutes a hydraulic cylinder and piston assembly {29 :mounted upon; the baseaiii and 3 having its piston rod connected.;.to -.:the

valve stem 24- by. an intermediate rod-. 3 it; Appli cation of hydraulicpressure:tothe top cr -bottomof.,the cylinder imoves the steamvalve-stem"to actuate the steam piston'in the same direction.

Gperation of the hydrauliccylinder is controlled by a hydraulic pilot valve, the casing 32 of which is mounted upon andmovable with the steam valve rod 3|. The pilot valve includes a valve plunger 33 operatively connected to a secondary manually actuated control rod 34 which is moved vertically by a control lever 35.

As hereinafter disclosed with reference to the hydraulic diagram of Figure 9, the hydraulic pilot valve acts as a reversing valve for which purpose it has a neutral, forward and reverse position, corresponding to the positions of steam valve 22, and is connected by the flexible conduits 36 and 31 to the top and bottom of the hydraulic cylinder. Pressure and exhaust conduits 38 and 39 connect the pilot valve with a hydraulic supply system (not shown) to supply hydraulic pressure to the cylinder 29 under control of the valve. The operation is such that the valve and its cylinder operate as a. servo-motor interconnecting the secondary rod 34 with the steam valve stem 24. In other words, upward movement of the secondary control rod shifts the valve plunger 33 upwardly, whichin turn conditions the valve to apply hydraulic pressure through conduit 31 to the bottom of hydraulic cylinder 29 to cause the valve stem to' move upwardly. Upward movement of 'the valve stem carries with it the casing of the pilot valve until the valve regains is neutral condition at which point movement is halted.

The manual control lever therefore may be swung in either direction and the valve thereupon is in condition to move the valve stem in the'same direction and this follow-up movement will continue so long as the secondary control rod is in motion. The steam valve therefore will be shifted to supply steam to the cylinder in accordance with the direction of movement of the control lever 35 from its neutral position. As previously noted, the hydraulic cylinder assemmy 29 is quickly responsive to pilot valve movements so that a very slight movement of the valve plunger 33 is reproduced almost instantly by the hydraulic piston and steam valve stem 24.

Described in detail, the hydraulic cylinder 29 is mounted upon a pair of channel members 40-40 extending crosswise of the I-beams lBl0 (Figure 3 and 4). A mounting plate M is secured upon the top of the channel irons and anI-bolt 42 is screwthreaded into the mounting plate. The hydraulic cylinder is connected to the I-bolt by means of a pair of spaced lugs 43 embracing the opposite'sidesof the I-bolt and connected to the bolt by a pivot pin 44. l The application of hydraulic pressure to the top or bottom of the cylinder therefore will cause the valve stem to move in the appropriate direction. The pilot valve 32 is fixed upon the intermediate valve stem rod 31 by means of the lugs 45--45, forming a part ofthe valve casing and secured in fixed position upon the stem by means of set screws 46 threaded through the lugs and engaging the stem. The upper end of the rod 3| includes a knuckle joint formed by an I-bolt 41 connected to the valve stem 24 just below the steam valve. Incorporated in the knuckle joint is a drain guard 48 to collect leakage which may pass through the packing gland 50 of the valve. Valve stem 24 extends through the steam valve, passing through a packing gland 5| at the top of the valve. I

The secondary control rod 34 constitutes a lower section 52 and an upper section 53, both of tubular construction and slidably connected together by a stud 54 having its lower end secured rigidly in the lower rod section52 and its upper end slidably disposed within the upper rod section 53 (Figure 3). The secondary rod is connected to the actuating lever 35 by means of a bellcrank lever 55 pivotally connected by a pivot pin 56 secured to the channel 51 which is mounted upon the bottom of the channels 4040.

The bellcrank lever includes a detent sector 58 (Figure 4) having a V-shaped notch 60 in which is cradled a roller 6| mounted upon the swinging end of an arm 62 having its opposite end pivotally mounted in a bearing block 63 mounted upon channel 51. A spring 64 has its upper end hooked upon a pin 65 extending from arm 62 and its lower end anchored upon a bolt 66 mounted in the channel 51. This spring is maintained under tension to urge the roller 6| into engagement with the V-shaped notch 60 to maintain the control lever 35 and its linkage in a neutral position by virtue of the cam action of the roller with respect to the notch. Opera tion of the lever in either direction is resisted by the spring 64.

The secondary rod 34 is connected to the plunger 33 of the pilot valve by a lateral arm 61 secured upon the secondary rod section 52 and having its outer end pivotally connected as at 68 to an adjustable link 10, the upper end of which is pivotally connected as at 1| to the end of the valve plunger 33. It will be observed therefore that when the control lever is swun to the right as viewed in Figure 4, the secondary control rod and valve plunger will be elevated and when the lever is swun to the left the rod and stem will be lowered. When the lever is swung to elevate the valve plunger, the valve will supply hydraulic fluid to the lower end of the hydraulic cylinder 29 causing the piston rod 30 and valve stem 24 to rise, carrying with it the pilot valve casing relative to its plunger until the valve reaches a neutral position. The apparatus will remain in this position until the lever either is returned to neutral or advanced further; in either case the pilot valve casing will follow movements of the pilot plunger. In the position shown in Figure 4, the steam control valve 22 is in neutral position with the steam piston stationary and when the lever 35 is swung in either direction the steam valve will be conditioned to apply steam pressure for operation in the appropriate direction by operation of the hydraulic valve and cylinder.

In order to prevent the steam piston from rising beyond its upper stroke limit, there is provided an automatic linkage system which re-- verses the hydraulic pilot valve to close the steam valve as the piston approaches its upper limit. The linkage structure is best shown in Figures 1 and 8 and the operation is illustrated diagrammatically in Figures 5 and 6. For this purpose, there is provided a plunger 12 (Figure 1) passing through the top cylinder head l5 and slidably sealed with respect to the cylinder head by a packing gland 13. A lever 14, centrally pivoted as at 15, has one end in operating engagement with the plunger 12 and its opposite end pivotally connected as at 15 to a sleeve 11 slidably mounted upon the upper end of the valve stem 24. A spring is mounted under compression between the top of the valve and a collar 82 forming a part of sleeve 11, the spring serving tomaintain the sleeve and its associated linkage in an elevated positionas shown. Fixed to the lower end'of thesleeve is a lateral'arm 83 to relative to the casing; said operating mechanism comprising a longitudinally shiftable control rod mounted in parallelism with the steam valve stem, a member extending laterally from the control rod connected to said movable pilot valve plunger for shifting the same relative to the valve casing directly in unison with the longitudinal movements of the control rod, a hand lever mounted. upon a pivot point adjacent an end of the control rod, said hand lever having a lever extended from the pivot point and connected to the end of the control rod for shifting the control rod and valve plunger upon swinging movement of the hand lever, and yieldable means adapted to maintain the hand lever normally in an intermediate position, the pilot valve constituting a reversing valve having hydraulic pressure supply and exhaust conduits connected to a source of hydraulic pressure and having flexiblevconduits extending from the casing to the opposite ends of the hydraulic relay cylinder arranged to supply hydraulic fluid to the'opposite ends of the cylinder upon longitudinal movement of the pilot valve plunger relative to the valve casing, the valve plunger having an intermediate closed position for blocking the said flexible conduits whereby the hydraulic relay cylinder and steam valve stem are locked hydraulically in fixed position when the control lever is released and swung to said intermediate position by said yieldable means, the hydraulic pilot valve being operable to shift the steam valve stem in alternate directions from the intermediate position in response to swinging movements of the control lever in either direction from said intermediate position.

2. An operating mechanism for shifting the longitudinally movable stem of a reversing steam valve through the medium of a hydraulic servomotor apparatus, the steam valve having an intermediate closed position, the servo-motor apparatus having a hydraulic relay cylinder including a piston connected to the steam valve stem for moving the same in alternate directions from the intermediate position, a hydraulic pilot valve casing mounted on the steam valve stem, and a plunger within the pilot valve casing movable relative to the casing; said operating mechanism comprising a longitudinally shiftable control rod mounted in parallelism with the steam valve stem, a member extending laterally from the control rod connected to said movable pilot valve plunger for shifting the same relative to the valve casing directly in unison with the longitudinal movements of the control rod, a hand lever mounted upon a pivot point adjacent an end of the control rod, said hand lever having a lever extended from the pivot point and connected. to the end of the control rod for shifting the control rod and valve plunger upon swinging movement of the hand lever, and a detent device adapted to maintain the hand lever normally in an intermediate position, the detent device having a sector mounted upon the hand lever for swinging movement in unison therewith, the sector including a detent notch, a yieldable detent member in pressure engagement with said notch adapted to urge the detent sector and hand lever normally to said intermediate position, the pilot valve constituting a reversing valve having hydraulic supply and exhaust conduits connected to a source of hydraulic pressure and having flexible conduits extending from the casing to the opposite ends of the hydraulic relay cylinder arranged to supply hydraulic fluid to the opposite 10 ends of the cylinder upon longitudinal movement of the pilot valve plunger relative to the valve casing, the valve plunger having an intermediate closed position for blocking the said flexible con-- duits whereby the hydraulic relay cylinder and steam valve stem are locked hydraulically in fixed position when the control lever is released and swung to said intermediate position by said detent device, the hydraulic pilot valve being operable to shift the steam valve stem in a1ter-' nate directions from the intermediate position in response to swinging movements of the control lever in either direction from said intermediate position.

3., An operating mechanism for controlling the piston of a steam cylinder through the medium of a hydraulic servo-motor apparatus, the steam,

cylinder being controlled by a reversible steam valve having a longitudinally movable stem, said servo-motor apparatus having a hydraulic relay cylinder including a piston connected to the steam valve stem for moving the stem, a hydraulic pilot valve casing mounted on the steam valve stem, and a pilot valve plunger mounted for relative movement within the casing, said pilot valve casing being hydraulically connected to the relay cylinder and being adapted to shift the relay piston from a neutral position in response to a corresponding'movement of the pilot valve plunger; said operating mechanism comprising a longitudinally movable sectional con-, trol rod, a pivotally mounted hand lever having a lever extension pivotally connected to one section of said control rod for manually shifting the same longitudinally, means connecting the pilot valve plunger to said control rod section for movement of the valve plunger directly in unison with the longitudinal movements of said control rod section, the control rod having a second section including an end telescopically engaged upon the firstsection and adapted to be moved longitudinally relative to the first section, an interlock lever pivotally mounted upon the steam cylinder, means connecting an end of said interlock lever to the second control rod section, a push rod slidably mounted in said steam cylinder and connected to'the opposite end of said interlock lever,:said push rod adapted to be engaged and shifted by the steam piston when the piston reaches a predetermined stroke limit, stop means on the first control rod section engageable by the telescopically engaged end of the second control rod section upon longitudinal movement thereof by said interlocls'lever whereby the second control rod section is operable to move said first control rod section and shift the pilot valve plunger to neutral position.

4. An operating mechanism for controlling the piston of a steam cylinder through the medium of a hydraulic servo-motor apparatus, the steam cylinder being controlled by a reversible steam valve having a longitudinally movable stem, said servomotor apparatus having a hydraulic relay cylinder including a piston connected to the steam valve stem for moving the stem, a hydraulic pilot valve casing mounted on the steam valve stem, and a pilot valve plunger mounted for relative movement within the casing, said pilot valve casing being hydraulically connected to the relay cylinder and being adapted to shift the relay piston from a neutral position in response to a corresponding movement of the pilot valve plunger; said operating mechanism comprising a sectional control rod, a pivotally mounted hand lever having a lever extension pivotally connected to one section of said control rod for manually shifting 1e same longitudinally, means connecting the pilot valve plunger to said control rod section for movement of the valve plunger in unison with the longitudinal movements of said control rod section, a compression spring interposed between the lever extension and said control rod section, said compression spring providing longitudinal movement of the'control rod section and valve plunger relative to the lever extension in a direction to shift the valve plunger to said neutral position, the control rod having a second section includingan end telescopically engaged upon the first section and adapted to be moved longitudinally relative to the first section, an interlock lever pivotally mounted upon the steam cylinder, pivot meansconnecting an end of said interlock lever to the second control rod section, a push rod slidably'mounted in saidsteam cylinder and connected to the opposite end of said interlock lever, said push rod adapted to be engaged and shifted b the steam piston when the piston reaches a predetermined stroke limit, stop means on the first control rod section engageable by the telescopically engaged end of the second control rod section, said stop means being spaced from said engaged end adapting the first rod section to be shifted longitudinally relative to the second rod section in response to hand lever movements, said stop means bein engaged by the second rod section upon shifting of the interlock lever, whereby the second rod section is eiiective to move the first rod section counter to said compression spring and thereby shift the pilot valve plunger to neutral position.

5. An operating mechanism for controlling the piston of a vertical steam cylinder through the medium of a hydraulic servo-motor apparatus, the steam cylinder having a reversible steam valve including a longitudinally movable stem extending verticallytherethrough, said servo-motor apparatus having a relay cylinder including a piston connected to the steam valve .stem for moving the same, a pilot valve'casing mounted on the steam valve stem, and atpilot valve plunger in said casing movable relative to the casing, the valve casing being hydraulically connected to the relay cylinder and adaptedto' shift the .relay piston from a neutral position in response to a corresponding movement of the pilot valve piston; said operating mechanism comprising a longitudinally shiftable control rod mounted vertically in parallelism with the steam valve stem, a lateral member connecting the control rod to the pilot valve plunger for moving the plunger in unison with the control rod, a hand lever pivotally mounted adjacent the lower end of the control rod and connected thereto, the hand lever being adapted to shift the control rod and pilot valve plunger upon movement of the hand lever, a yieldable member interposed between the hand lever and control rod adapted to yield when the control rod is forced downwardly toward the hand lever, a second control rod telescopically en aged upon'the upper end of the first mentioned control rod, a sleeve slidably mounted upon the steam valve stem above the valve, a compression spring interposed between the sleeve and valve adapted to urge the sleeve upwardly, a lateral member connecting the sleeve to the second control rod, an interlock lever pivotally mounted above the steam cylinder having an end connected to the sleeve, means on the opposite end of the interlock lever for shifting the same in response to movement of the steam piston to its stroke limit Whereby the sleeve is shifted downwardly, and stop means on the first mentioned control rod adapted to be engaged by the second control rod section upon downward movement thereof by said interlock lever whereby the interlock lever is effective to shift the control rod and pilot valve plunger to a neutral position independently of the position of the hand lever.

CECIL E. WEBB.

References Cited in the file of this patent UNITED STATES PATENTS Number

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