US1999834A - Multiple hydraulic motor operation - Google Patents

Description

H, ERNST 1,999,834

MULTIPLE HYDRAULIC MOTOR OPERATION Aprl 30, 1935.

Filed June 2, 1932 I Patented Apr. 30, 1935 UNITED STATES PATENT OFFICE Hans Ernst, Cincinnati, Ohio,

assigner to The Cincinnati Milling Machine Company, Cincinnati, Ohio, a corporation of Ohio Application June 2, 1932, Serial No. 614,980

15 Claims.

'I'his invention relates to hydraulic circuits and more particularly to means for connecting a plurality of hydraulic motors to a common pressure source for parallel operation at positively main- 5 tained equal or proportionate rates. y

It is well known that a plurality of hydraulic motors connected in parallel directly to a common source of pressure cannot-be operated at equal rates because the respective work resistances ordinarily do not remain the same. What happens is that the motor having the lower work resistance does not present enough resistance\to build the pressure up to the point where it will overcome the work resistance of the other parallel motor.

The result is that one motor decelerates and the other accelerates thus disturbing the relative rates of operation of the motors.

It is therefore one of the principal objects of this invention to provide mechanism for con 20 necting a plurality of motors in parallel to a common pressure source in such a manner that each may be operated at the same rate or at proportionately diierent rates without reverse retarding eiects of one upon the other.

25 A further object of this invention is to'provide in combination with a mechanism for subdividing a main ow to a plurality of motors, automatic compensating means functionally sensitive to iiow variation in the respective branch 30 lines for maintaining the subdivisions constant irrespective of variation in work resistances.

Anv additional object of this invention is to provide an hydraulic circuit for the\parallel operation of a plurality of hydraulic motors containing adiustable means whereby the relative rates o1 movement of the motors may be varied with respect to each other.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification considered in conjunction with the accompanying drawing illustrative of one embodiment thereof, but it will be understood that any modications may be made in the specific structural details thereof within the scope of the appended claims without departing from or exceeding the spirit of the invention.

Referring to the drawing in which lilre reference characters indicate like or similar parts:

Figure 1 is a semi-diagrammatical view showing parallel to a common pressure source for simultaneous operation.

the coupling of reciprocable motors to a common pressure source for simultaneous operation.

Figure 3 is a modied form of the reversing valve means shown in Figure 2.

Figure 4 is a View showing the method of 5 coupling more than two motors to a common pressure line for simultaneous operation.

Figure 5 is a modified form of circuit-for preventing overrun of the motors.

Figure 6 is a detailed view showing the rela- 10 tionship of the tapered portions of the automatically adjustable resistance compensating valve with respect to themotor delivery ports therein. J

It is a well-known hydraulic principle that the pressure of a fluid in a closed vessel is'equal in all directions. If two hydraulic motors, such as I0 equal, because the channels by motors are connected to the pump may be considered as a single closed vessel in which the pressure must and will be equal in all directions.

Since unequal pressure therefore cannot exist for any appreciable time in the same volume of fluid, it is apparent that if the rotational resistance of motor I0 rises above that of motor Il, the former will slow down, while the speed of the latter. will be increased. This is due to the fact that the pressure in the supply line to motor HV did not rise in proportion to the load and thereby maintain the same rate of uid consumption. Furthermore, it could not rise suiciently Afor this purpose when the existing pressure was suiicient to force the excess fluid not utilized by motor I0 through the motor II causing the same to speed up. In other words if the proportionate rates were maintained,

which the two It thus .folthe two moconnecting a plurality of motors to a common pressure source whereby each will operate at the same rate or at proportionately different rates irof the work resistvelocity. It is therefore apparent that actual movement is determined by volumetric fluid conl,motor I I.

ieinssumint pressure on the -Pressure 0f each motor. I! equal volumetric sc'an be supplied to each motor having similar rates of displacement itis apparent that they will both operate at the same velocity. But work resistances vary, and therefore the respective quantities supplied to the motors will normally vary. As previously explained, the work resistance diilerential in an open system aiiects the quantity supplied and therefore causes a variationinggte It thus beeemesaamarpti-that if v 7m .La -i i-wia. .a constant irrespective of variat1on in the work pressures that each motor will move at the saine velocity.

Since the pressure ineacli oftli'ebrnliilines I3 and I4 leading to therespective:-nrnotorslde-v pends upon the respectivenfavori;'.Qresistances;L.itfA` will be seen that a rise ir'th'ework resistance ofi the moto I0 would cause acorresponding press sure rise in the supply lirie `I3 ifltliere--was`no` other avenue of escape for the iluid in .the system. The same thing would be true with respect to the vlmotxvji andtheichannel-JIhbutdifftheptwo imotors" aredirectlyiconnected,toacommonfsupply; a rise sin the-z, 'work resistanceaof motor `:I l v"causes .f `more fluid to escapethroughathe lower resist ance-:represented by the motor II insteadof effectixig a proportionate risein ftheLpressure' kline I3.,f f

It-should therefore-,beiapparentthat itvarr'esistr ance was insertedinzthe line *Ila equal in effect to vthe-riseinigwork resistance of vthe motor I ...over the workresistance `rofi-themotor` II, that thetotal resistance offline I4 and motor I Izwould then be equal in reect tothe `work resistance `^of the motor I0, andthus the pressure required by the .two lines would then be equal''and the motors :would operate at thesame velocity. lThis resistg ance must haveth'e fpropervalue to maintain, at

the ,-inlet side thereof; ay pressure corresponding vrto' the pressure in channelY I3,'an`d at the outlet Aside thereof,a pressurecorrespndingfto that re- .v quiredl to overcomelthe f work Tresistance Aof 'the VInnan open circuit sucha resistance would eiect this result, becausefany' resistance inserted in `a :.ilow channel causes a drop-of pressure' across the Iresistance inqrelation `toi the @quantity ilowing .through it; and thus thepressureat the inletside will be higherthangthe pressure attheoutlet.- It

i-yis L only-necessary to r adjust the resistance to lobpressure .diierentialso that -the inlet side -`willequalfthe increased d the other `branch'.:-'line`; *andatthe butletyside a pressure corresponding= to'fthatrequiredto overcome the resistance of -ltherespective Vmotor actuated-thereby; v

Furthermore, lfrom a practical standpoint-this :inserted resistance must be automatic 'in opera- ,tionso that the slightest variation in1the`f`r`esista ceci onemotormill be compensated by a correspending increase 1in .the resistance? of `rthe other branch line insorderto maintain equaloperartion n f; the parte.` f In;the '-.presentt instance this resistance is in theliormeoi a .valve which may be` termeda lresistancecompensating valve comprising.- a casing I 5. r .innwhich` is' recipro'c'ably Lmountedfa plunger.r IS. plunger, as shown the drawing, may be f provided' `withvtapered lends I 'I and I 1 vThe -intersectionot .the cylindrica .par-tion, vo fthe valvewitmthe tapered;- portion .i5 Ill'ntedlespeotlyely by. lines lil and'lfi' Spacdports-I 9 andcl:` arezfformedlin? the' valve towhichf-aareaconnected respectively the I leadingrtozfmotorsfIlandfII.

'of port I9;

l'causes y 4across "this port, the pressure 'on the supplyvside thereof `'rising still higher Vabove the pressurey at eration of the valve such as would occur were the yalve ilat at the ends and shortened to provide iullopernngptthe port. Pressure is supplied tooppsiteend'softle valve casing through ports 2|1and322.*.towhichqthe branch lines 23 and 24 are frespectivelyconnected. These branch lines have-.arranged ltherein resistances 30 and 29 respectively and arefconnected to the common pressure channel 25'supp1ied by pump I2 which may `be a constant ora variable displacement type and which may draw iluid from a reservoir 26 through the'inlet=` line 212.5115 'so 'desired' a'n emergency rei lief valve y-28firiaybie inserted the lineZS to protectfthe part-s against v4excessive high pressure.,

case where an equalsupplytoftwo motors is desired, andif thework resistances of the motors are equal, andif theyalve plunger I6 is in a central position, it is obvious that th'ere will ybeian If the resistances"29 aid'30 are equal, as inthe equaldro'p inpressur'e in each" linev "23 ^and 24 y thereby equalizing theflow or volume between the.V

lines,V and lalso equalizing the pressures in 'chambers'SI and 32.' A rise in work resistance in motor I0 will momentarily retard the input ilow'thereto causing apiling up` of iluid in chamber 3I 'and a. momentaryrise in the pressure; existing "therein,`

Sincefthis pressure will be higher than the preslsure in the opposite chamber 32, it willbe yseen that the valve plunger I6 willymove slightly downward as viewed inv Figure 1'. The eifectotthis downward movement is to further close the port 20 and simultaneously add tothe opening of port I9."V As previously explainedv this increases the resistance of port: 20van`d decreases the resistance V'The increase in resistance at port 20 n V increase in the pressuredi'erential the motor side o1 port 20. ".l'ljiis pressure rise V"which will occur invchamber 32 .will continue until iti` equals the pressure chamber 3l which resuusfin re-estabusmng an equal. pressure drop acrossrefsistances 29 and 30 in channels and 23 thereby *maintaining the equal division of `quantity between these channels."4

` The plunger I6 may therefore be consideredas having a valve portion on one end 'and apiston portion at the other end for effecting insertion of the resistance in the'lin'e I4; similarly; if'the vresistancefotmotorv II shouldrise above the work resistance-of motor III the'pressure in Ichamber -32 `will'increaseoverthe pressureof chamber `3l `causing.movement ofthepluger I6 upward and the insertion :ofVl resistance in -the` line I 3.- The plungerxthereforer acts'automatic'ally to raise the resistance ofthe particular motor channel having vthe lower resista nce,thereby .preventingl the cross eect of one motor on the other, that is of constituting' a k lt iw-v resistance; preventing', al sufiicient rise in. pressureof ,thefother to meetfarise in work resistance.`l v` It `,willitlnis I-,be.seen that when the 'Y0 ,ristm 0f ,themamotorsareequaI and l'til'iatthelalflg'leeihe alveul will be in acentral Lposition while a `in work resistance of either will eilect a corresponding shifting of the valve to increase the resistance in the opposing line and thereby make possible the sustaining of a higher pressure.

If it is desired to operate the motors at relatively different speeds such as the operation of the motor at twice the velocity of the motor I0,

the resistances such as 29 and 30 must be inversely proportional to the speeds desired. If the resistance 29 is greater than the resistance 30 as shown in Figure 1 while the pressure drop across themi is equal, it will be seen that more iluid will flow through the resistance 30, and since quantity determines speed, the motor will travel faster than the motor l0. These resistances may be in the form of small tubing provided with couplings at opposite ends for selective coupling in either line and may be of various lengths for providing a selection of relative speeds. Since the valve I6 will shift back and forth until the pressures in chambers 3| and 32 are equal, it will be seen that the pressures at ports 2| and 22 will finally equalize and therefore the drop in pressure across the resistance 29 will be equal to the drop in pressure across the resistance 30. The quantity, however, passing through each resistance will vary in inverse proportion to the value of the resistance itself, and this is true because the pressure in each branch line, that is, at the inlet port of the resistances, is equal. Since, for a limited range the pressure may be considered to be equal to the product of the quantity and the resistance, if the resistances vary, the quantities must vary inversely in order that their product will be the same. Since the valve I6 will operate in the same manner as before, it will be seen that the resistances 29 and 30 divide the flow into proportionate parts and that the valve I6 maintains these proportions irrespective of variations in Work resistances.

Attention is invited to the fact that these proand temperature of the working uid. It is recognized that the value of a resistance will vary as the viscosity which, for a given iluid is an inverse` function of the temperature. 'I'hus the higher the temperature of the oil, the greater will be the ow for a given pressure drop. 'I'hus it will be seen that in thepresent construction the resistances being equal or in denite proportions, that the same proportional eifect will be produced on each branch line by changes in temperature and viscosity and therefore will not have any unbalancing effect.

A more adjustable form of flow dividing device is illustrated in Figure 2 and comprises a casing 33 in which is reciprocably mounted a Valve plunger member 34 which is operatively connected to an adjusting screw 35 threaded in the end of the casing. This plunger has a reduced intermediate portion 36 which is tapered at the ends 3l and 38 to form a throttle for the outlet ports 39 and 40p Pressure is supplied from the pump l2 through the port 42 and in accordance with the longitudinal position of the plunger, the flow will be proportionately divided between the ports 40 and 39. As shown in this figure, the motors may constitute the piston and cylinder type such as Ill' and in which case the usual procedure would be to provide reversing valves 43 and 44 whereby the operated parts may be given a reciprocating motion. The reversing valve plungers 43' and 44' may be joined into a single plunger 45' as shown in Figure 3 for effecting simultaneous reversal of motor movement.

The flow in either branch line may be further subdivided as shown in Figure 4 to effect operation of more than two motors. Only one subdivision is shown but it will be apparent that the subdivision may be carried out with one line or with both lines to effect simultaneous operation of as many motors as desired. If three motors I, 55, and 6 are to be operated at the same rate, the resistance be given the value of twice the resistance 46 whereby one-third oi' the flow will pass through port 41 of valve 48 and two-thirds of the flow pass through port 49. This latter quantity can be divided equally between the ports 50 and 5| of the valve 52 or proportionate resistances such as 53 and 54 may be utilized to eil'ect a rate difierential between the last two motors. The operation-Will be substantially the same, compenstation for differences in the work resistance of motors 55 and 56 being automatically provided by the plunger l while the desired relationship between the flow through outlet port 49 and outlet port 4`| will be maintained by the plunger 58 in valve casing 48. Separate reversing valves similar to those illustrated in Figure 2 may be inserted at 59 in the circuit illustrated in Figure 4 to eil'ect reciprocation of the motors.

In the arrangements so far described it will be apparent that if ow was eut oil.r from either motor, that there is nothing to prevent the motor and actuated parts from overrunning due to their momentum, and therefore in such cases Where it is desired to prevent overrun, an arrangement such as shown in Figure 5 may be utilized. -In this case the resistance compensating valve is inserted in the exhaust or return lines rather than in the forward pressure line. For instance, branch lines 62 and 63 connected respectively with lines 23 and 24 serve to conduct the pressures thereof to opposite chambers 32' and 3| of the valve for action on opposite ends of the plunger |6'. This plunger has annular grooves 64 and 65 having beveled sides 66 and 61 which act to partially close the ports 20 and I9' to which are connected the return channels 60 and 6| respectively of motors I and I0. Ports 2|' and 22' of the valve are connected to a common return line 68 which may in some cases .be connected to the pump intake line 2]. The operation of the valve is the same as just described to maintain proportionate division of flow to the motors with the additional eiect that any or 20 will have a retard-ing eilect to' prevent overrunning of the motor momentum it may have.

It will thus be seen that mechanism has been provided for connecting two or more hydraulically actuated motors in parallel with a common source of pressure for uniform operation thereby, at the same velocity or at respectively diil'erent velocities. It will be noted that the division of flow is effected in such a manner that the divisions are uneil'ected by changes in viscosity or temperature of the iluid or by variations in the work resistances of the respective motors.

That which is claimed is:

l. An hydraulic power system combining a volumetrically constant pressure supply, a'plurality of motors, branch channels connecting the motors in parallel to the pressure supply, and means operable by resistance pressures in the 45 would probably further restriction of port |9' and parts due to any q' i A 1999,834 riesame a ioeze iitw 'remise I i *"1 e Y. f avisar exit input side of the motors to maintain constantI and g y y the quantities delivered by the branch channels hydrlgmgggggi 25 to the respective motors independent of relative andrgrsisrtag ai: s

variations in the work resistances of the respecgg. IiiL r nth dige w A 5 tive motors. 2. An hydraulic system for operating a pluthe'gfioygwdiyi'syiplcch nt wblre' th c no metrically constant source of pressure, parallel p 'etem branch lines connecting the source of pressure to ti *y the respective motors, means to divide all the flow res from said source proportionately between the branch lines in accordance with the relative rates 1W desired in said motors, and means operable by pressure variation in the motor input line due l to variable motor resistance to maintain the 331... volumetric ilow divisions andv thereby the relaff tive rates of said motors constant. .r o 3. In an hydraulic system the combination 01.i volumetrically constant source of pressure, a pliirality oi motors each adapted to overcome v ;aifil-` @113C 11d able work resistances, branch lines connecting' respective motors in parallel to said sourde" pressure, and means to maintain a predeter relation between the velocities of the respl motors comprising a rst resistance mea each branch to determine the normal tional distribution of flow between the bI nc fs of the respective motors; additional vari le` e'- 4sistance means and means coupling said'ya f resistance means for reactance by the input sures of the motors of the respective br' whereby said second variable resistan are automatically actuable to compnshat variation in the work resistance of one tive to the other whereby the notai resist fluid flow in each branch will be gina constant and equal thereby maint velocity ratio of the motors constant 4. An hydraulic system combining 40 rically constant source. of pressure, airlso'iV 0 motors to be actuated thereby, parallelfbranch di lines connecting the pressure towthelminutside of the motors, a variable resistanceiril iebranch line connected to cause a pressure'dropflietwen said source and said input side o 'f v`the mo'torlf and .means responsive to pressure variatfons iii he other line caused by increase inthe wor re fstance thereof to increase ther nv i one branch line to maintain t e, said motors constant. 1

5. An hydraulic system combining vo cally constant source of pressue .4 ai

rality of motors in parallel comprising a volusupplie tmg L .hamm L L a e onstaat 45 quantities esde'te other to increase correspon in the opposite line to mainte. the motor velocities consta 6. In an hydraulic circuit-a stant source of pressur` lur li motors, individual cha speotive motors in parall sure, and valve means," sive to relative variati'o in the respective lines on the motors to maintair 1 f,h-` ntiK 0 the ilow to each c" insure a constant t? were @e me joint- 1gr o iera inligg. .maui(v ding agcomex, a plurality of bra oh lines, a ow div ding valve mon volumetriclly constant source of pressure, for coupling the source of pressure to said lines parallel branch .lines 'extending from the source of pressure to the individual motors, means to divide the flow between the channels, a variable resistance in each channel between the ilow dividing means and the respective motors, and hydraulically actuated means for varying the resistance in one line in accordance with the increase in work resistance in the other line.

13. An hydraulic system for effecting parallel operation of a plurality of hydraulic motors including a common source of pressure, parallel branch lines extending to the individual motors, means to divide the main flow into two divisions, means to connect one division to one of said parallel lines, means to subdivide the other division between the remaining parallel lines, and valve means responsive to pressure changes in said lines to maintain all of said divisions constant irrespective of work resistance variation of the repective motors.

14. An hydraulic system for maintaining predetermined proportionate rates of operation of a. pair of hydraulic motors each of said motors having an inlet port and an exhaust port, comprising a pump, channel means extending from the pump to said motor inlet ports whereby all the output of said pump will be delivered to said motors, said channels including a main conduit for receiving the full output of said pump, branch conduits extending from the main conduit to the respective` motors, means in each branch conduit for determining the volumetric proportion of the main ow to pass therethrough and thereby the rate of operation of the respective motors, valve means in each branch conduit between the ow determining means and the motor for maintaining an equal pressure drop in the branch conduits, each of said valve means being responsive to a rise in pressure in the other branch to effect a rise in pressure in its own branch and means to connect the exhaust ports of said motors to reservoir whereby the back pressure on each motor will be the same.

15. An hydraulic power system combining a volumetrically constant pressure supply, a plurality of motors, branch channels connecting the motors in parallel to the pressure supply, a first resistance means in each channel complementally variable to determine volumetrically the proportions of the main ow passing through each branch and thereby the ratio of the rate of operation of said motors, additional serially arranged resistance means in each channel for maintaining the volumetric ratio of the ows including uid operable means for complementally changing the values of the last named resistances inversely in accordance with changes in working pressures developed by said motors in their respective supply lines.

HANS ERNST.

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