US2038272A - Servomotor control - Google Patents

Description

April 21, 1936 w. ERNST 2,038,272

SERVOMOTOR CONTROL Filed Oct. 21, 1952 '2 SheQts-Shet 1 Fig.1

INVENTOR. v

2 WALTER Enusr 5 ATTORNEY.

April 21, 1936." w. ERNST SERVOMOTOR CONTROL 2 Sheets-Sheet 2 Filed 001;. 21, 1932 m m m N W H Nm 1f v M Th U eh A m r\ W A? rk mV 9% 35. 1| N9 Q 9? .v9 9%. N\\ :2 I 3 m g 1 am) 7 w 0Q r 1 09 Q i m N: m hm AFN N 5 h wk m 3 0* %.w m Q h ATTORNEY.

. shifter ring la and Patented A r. 21, i936 UNITED. STATES PATENT pm:

Walter Ernst, Mount-Gilead, mesne assignments, to The Corporation, Inc., Wilmington,

ration of Delaware Application October 21, 1932, Se n No. 638,905

. 2 Claims.

This invention relates to control mechanism for regulating the flow of variable discharge and other hydraulic machines having movable flow-controlling elements. v

One object of this invention is to provide a simple, efficient and highly responsive flow-control mechanism for a variable discharge in which the flow will be automatically controlled to meet the exact operating requirements.

. A further object is to provide a simple and emcient means for limiting the maximum discharge pressure of the pump. v

A further object is to provide means for adjusting the regulating or control means, so

may be made to operate at any desired predetermined pressure.

In the drawings:

that it Figurel is'a diagrammatic view of the circuits, showing a pump with the control and actuating valves in longitudinal cross section.

Figure 2 is a similar view showing a pump with adjustable means for limiting its maximum discharge pressure, the control unit being shown in elevation, and the press and compensating valve and its connections being omitted.

In order to illustrate more clearly the con struction, the drawings show the control and actuating units as disproportionately large relative to the size of the pump.

Referring to the drawings in any suitable of pump with detail, I in a movable member of any desired dicates reversible variable-discharge type a discharge control element or connected, through suitable havin kind, for moving that member in any operation in which such movement may be a factor. As a iamiliar example of such a machine, an ordinary hydraulic press is illustrated, comprising a press cylinder 2, and a piston 3 reciprocable therein. Piston 3 is provided with a piston rod 4, which carriesa manner with the ram 5 cooperating in the usual stationary press member or anvil 6. The cylinder 2 and anvil 6 may, as usual, he carried by the press frame 1. other types of reciprocableor parts may be substituted without departing from the scope tion. a v

of the Throughout the application, unless the context otherwise, the term fluid is to clearly indicates part 01' or suitably A wide range of otherwise movable tor the press here shown invenbe construed broadly as including all fluids applicable to the field of use. Wherever a definite fluid is named, such as oil, unless the context under.-

clearly mdicates otherwise, it is to be Ohio, assignor, by Hydraulic Press 1301., a corpostood as including all other fluids; as above. stated. Theflow oithepump l maybechangedin direction by moving the shifter ring or discha-IK control element In in one direction or the other 5 from its neutral position in which the pump runs idle or without delivery. The degree or rate of flow in either direction will be in proportion to the movement of the shifter ring la. The means for accomplishing this shifting is. well known to 10 those skilled in the art and, therefore, requires no detailed description in the present application. 1 shows the shifter ring oi. the pump in its neutral position, the pump running idle without discharge in either direction. t

Connected in any suitable manner to the shifter ring or the pump, and extending toward the leitin' Figure 1, is a piston or valve member 8 provided with two longitudinally spaced heads 9 and Hi. The piston rod 8 is also provided with a longitudinal bore H running irom'its free end lengthwise toward its connected end and terminating in a port l2 beyond the innermost head 10. Surrounding the valve member 8 is a'reciprocable sleeve I3 provided with a perforated ear ll by which it may be connected to a suitable link IS. The opposite end of the link I5 is connected to a hand lever l6 suitably mounted in thebracket 18. The hand lever I6 is provided with the usual spring-actuated pawl engaging the cooperating ratchet plate H to lock the lever in various adjusted positions. In order to adjust the movement or the sleeve, a turnbuckle or other similar connection may be used between the lever and the sleeve end. The form shown 5 comprises two clevi'ses l9, each being threaded onto the end of the line l5 and connected to the lever and sleeve respectively. Stop nuts are also turned on the link l5 to engage the clevises l9 and prevent them from traveling beyond their 40 set positions. The sleeve I3 is reclprocable in the control valve casing 20, which has a central bore 2| to slidably receive the sleeve, and three longitudinallyspaced annular chambers 22, 23 and 24. Sleeve I3 is provided with ports 25, 26, and 21 through its side walls and adapted to register with the annular chambers 22, 23, and 24. The ports 25, 28 and 21 are so spaced that 25 and 21 may be registered with and-closed by the heads 9 and I0, respec- 5o The bore II in valve member 3 is of such length that its outlet port l2 will at all times communicate with chamber 29. Since the bore H extends from port l2 completely through the valve member 8, it establishes communication between the chambers 28 and 29. The control valve casing 20 is provided with lateral bores or passages 33, 3|, 32 and 33 communicating with chambers 22, 23, 24, and 23, respectively.

The movement of the sleeve l3 relative to the valve member 8 or vice versa, controls the passage of fluid through the control valve and thence through the lines 53 .and 59 leading to the actuating unit of the servomotor. Communicating with chamber 23 is the pressure line 34 through which servomotor fluid is supplied under low pressure by a suitable gear pump 35 or other suitable supply medium. Pump 35 draws its fluid through the suction line 36 from the tank 31 orother reservoir. To avoid possible strain or overload in line 34 or pump 35, a branch 33 is provided establishing communication between pressure line 34 and the tank 31 through a relief valve 39 to permit excess fluid to return to tank 31. An exhaust line 43 leads from the bore 33 at the end of chamber 29 to the tank 31. Thus with the parts in the neutral position of Figure l, the low pressure servomotor fluid from the pump 35 will circulate from the tank through the pump and back to the tank by the branch line 33 and 'relief valve 39.

The actuating unit of the servomotor is mounted on the opposite side of the pump from the control valve. It comprises a piston rod 4| reciprocably mounted in the actuating piston casing, and connected in any suitable manner to the shifter ring of the pump at a point opposite the connectibn between the valve member 3 and the same ring. The piston rod 4| is provided with an enlarged cylindrical portion which provides an annular shoulder 43. This annular shoulder 43 is reciprocably mounted in the chamber 44 provided witha lateral communicating bore or passage 45, for a purpose to be later disclosed. To the opposite or'outer end of the piston rod 4| is secured a piston 46 reciprocable in the cylinder 41 of the casing 42. The cylinder 41 is provided with lateral ports 43 and 49 near its opposite ends for delivery of pressure fluid to or from the opposite sides of the piston 43. The cylinder head 53 of cylinder 41 is provided with a bore or chamber 5| in which is reciprocably mounted a pilot piston 52 of sufficient length to remain in contact with piston 43 in all of its positions within its cylinder 41 and yet remain partly within and guided by the chamber 5|. A port 53 in the outer end of chamber 5| serves for admission and exhaust of fluid toactuate thepilot piston 52.

From the pump I, the two power lines 54 and 55 lead to the pressing and pullback sides, respectively, of the press piston 3 to move the ram downward during its pressing operation or to return it upward during the pullback operation. From the line 54 a branch 51 leads to the bore 45 of chamber 44. From the line 55 a branch 53 leads through port 53 into the chamber 5| of the pilot piston. servomotor-pressure line 53 establishes communication between bores or passages 32 and 43. Servomotor line 59 establishes communicatio'n between bores or passages 30 and 49.

To compensate for the differences in area between the upper and lower faces of piston 3, a two-way compensating valve 39 connects the an obvious manner.

2,038,272 said sleeve is in its innermost operative position.

power lines and is provided with a branch 3| leading back to the tank 31, as is disclosed in my United States Patents 1,653,350 and 1,861,116, to both of which reference is hereby made.

To perform a pressing stroke with the parts in thepositions of Figure 1, the lever i 6 is swung to move the sleeve l3 toward the left. This will uncover the opening 21 which is in communication with chamber 24. Servomotor pressure fluid will then pass through the sleeve l3 and chamber 24 and into the servomotor line 58, entering the cylinder 41 to the right of the piston 46 and moving it to the left. As it moves to the left, fluidon the opposite side of. piston 43 will exhaust through port 49 into servomotor line 59, thence by way of bore 30, chamber 22, and chamber 28, bore H, port l2, chamber 29 and exhaust line 40, back to the tank 31. This movement of piston 46 carries the pump shifter ring from its neutral position of Figure 1 into a discharge position where the pump will force power fluid through the line 54 to the upper side of the piston 3, starting the pressing stroke of the hydraulic press.

As the piston rod 4| travels toward the left under the influence of the servomotor fluid and carries the shifter ring with it, the valve member 3 at the opposite side of the ring will be correspondingly moved toward the left. The piston heads 9 and Ill will thus again shut off the respective ports or openings through the sleeve i3 into the servomotor lines 58 and 59, but flow of power fluid through the power lines 54 and 55 will continue, as established by the movement of the shifting ring la. Thus the movement of the valve sleeve l3 establishes the rate or magnitude of the flow in the power lines 54 and 55. The pump may be run in the opposite direction simply by shifting sleeve |3 so that the flow through the servomotor lines 53 and 59 will be reversed, as will be readily understood. To do this, the pump is brought back through its neutral position in Should there be an overload in the pull-back or return line 55 and the pressure built up beyond a-predetermined point, this excess pressure will be transmitted through the branch line 55 tcr'the end of pilot piston 52, forcing it inward and moving piston 45 toward the left. This, of course, will carry the shifter ring of the pump to the left toward its neutral position thereby reducing the discharge of the pump and lowering the pressure in the return line 55. The excess discharge of the servomotor pump 35 at such time returns to the tank 31 through its relief valve 33.

Should there be an overload in the pressing or working line 54, the excess pressure will be transmitted through branch line 51 into the chamber 44 where'it will act on the annular shoulder 43 moving piston rod 4| to the right. This, in turn moves the shifter ring la to the right toward its neutral position, thereby reducing the discharge of the pump and lowering the pressure in the pressing line 54. The excess discharge of the servomotor pump 35 at this time returns as before to the tank 31 through its relief valve 33.

It will be seen that there is thorough and adeare the same as in Figure v Figure 2' illustrates stop I05.

pressure is reached in the respective main power lines 54 and I and their corresponding branches 51 and 56, respectively.- The overload actuated elements in .both instances return the pump to its neutral position.

v I an arrangement in which the actuating unit of the servomotor embodies means for selectively and adjustably setting the mechanism to operate automatically at any one of a wide range of diiierent pressures, as may be desired-under various circumstances and conditions. In this arrangement, unit and its circuits (to the left of the pump) 1 and operate in the same way. The piston rod 4| is also connected to the pump shifter ring la in the same way and for the same purpose as in'Figure 1. However, instead of carrying a single piston, the machine of Figure 2 carries a casing I00 having two cylindrical chambe'rs I0| in which are reciprocably mounted pistons I02 provided with piston rods I03. The piston rods I03 are secured to a yoke I04 slidably mounted on piston rod 4| and adapted to seat against a shoulder or The yoke I04 is held yieldingly in engagement with the stop I05 by a coil spring I 06 or other suitable variable pressure means. Casing I00 is suitably anchored on the bed of the pump or other'suitable foundation. .A cup I01 is slidably mounted on the piston rod 4| and encloses the spring I06. In order to vary the compression of spring I06, a hand wheel I08 or other meansis adjustably mounted, as by screw threading, upon the outer end-of the piston rod 4|. Suitable anti-friction bearings are interposed between the hand wheel I08 and the adjacent end of the spring cup I01. A 'nut or other stop element may be provided on the extreme end of The piston rod 4| is enlarged to provide a piston shoulder I I0 within the pressure chamber III of the casing I09. Two other pressure chambers H2 in the casing I09 are adaptedto reciprocably receive pilot pistons I I3, each of which is adapted to engage the end of the corresponding piston rod I03. The movement of the pistons I02 toward the left is resisted by fluid pressure in the chambers I I2 acting on pistons 3 also by fluid pressure in the left ends of the cylinders II. The action of the spring I06 and of pressure fluid within the chamber II I will oppose this tendency. As described above, this opposing force may be varied and regulated by turning the hand wheel To move the piston rod 4| toward the right, as

in Figure 1, the sleeve I3 is also moved toward the right, allowing fluid pressure to pass through the servomotor line 59 into the two cylinders IOI- through the-ports pipe connecting them.

In case of an overload'or' excess pressure in the pull-back line 55, relief is provided, as in Figure l, by causing this pressure to pass through branch 56 into chamber III acting on the pilot piston shoulder I I0 to return the pump shift ring Ia toward its neutral position. Similar relief in the pressing line 54 is provided through branch 51, communicating with both chambers III the entire. control other suitable piston rod 4|, to retain the hand wheel thereon.

' discharge control 49', by way of the branch through ports 45; the excess pressure acts upon pilot pistons 3 to force'the pump shift ring toward its neutral position. The substantially the same as previously descrlbed'in connection with Figure l and therefore will not be repeated in detail.

Thus it will be seen servomotor for hydraulic machinery which is very compact and of few parts. The servomotor mechanism is arranged in substantially a straight diametrically through the pump shifter ring, and auxiliary pistons and floating levers or fulcrums are thereby eliminated. The servomotor valve rod and the piston rod on the opposite side from the valve rod are integrally attached to the shifter ring and move with it as line passing a unit, avoiding the wear and lost motion oc-' operations arethat i have provided a casioned by the use of levers or gears. The over- I load mechanism of my servomotoris likewise of more simple and more rugged construction than has heretofore been used, replacing auxiliary pistons by a simple enlargement of the main piston 'rod. Accordingly, my servomotor. construction represents an increase in efliciency, economy of construction and long life as compared with other previous constructions.

It will be understood that many changesmay be made in the construction, arrangement and disposition of the various parts of the invention, within the field of the appended claims,,withcut departing from the scope of the invention. It is meant to include all such modifications within this application. A single application of the idea has been shown merely as an example, and with no thought or intention of limiting the invention thereby.

Having thus described my invention, what I claim and wish to protect by Letters Patent is:-- l. A control mechanism for a variable discharge pump of the type including a movable pump discharge control element, said mechanism comprising in combination with said control ele-.

ment; a cylinder, a piston therein, a piston rod rigidly connecting said discharge control element and said piston, overload responsive means associated with said piston rod and responsive to the pump discharge to shift said piston rod and said element to the no-discharge position thereof, a valve assembly comprising a valve housing and a pair of cooperating valve elements in said valve housing, one of said valve elements being rigidly connected to said discharge control element, the second valve element being adiustably mounted relatively thereto, means for shifting said second valve element, and conduits interconnecting the valve assembly and the cylinder, whereby actuation of said second valve element will admit fluid to said cylinder to cause said piston to actuate said discharge control element to vary the pump discharge and to actuate the first valve element in follow-up relationship to said second valve element without lost motion between said elements.

- 2. A control mechanism for a variable discharge pump of the type including a movable pump discharge control element, said mechanism comprising in combination with said control ele-' ment; a cylinder, a piston therein, a piston rod rigidly connecting said discharge control element and said piston, overload responsive means asprising a valve housing and a pair oi cooperating valve elements in said valve housing, one of said valve elements being rigidly connected to said discharge control element on the side opposite said piston, the second valve element being adjustably mounted relatively thereto, means for shifting said second valve element, and conduits interconnecting the valve assembly and the cyl-

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