US2505392A - Transmitter unit for hydraulic telemotor systems - Google Patents

Description

April 25, 1950 P. E. FORSYTHE 2,505,392

TRANSMITTER UNIT FOR HYDRAULIC TELEMOTOR SYSTEMS Filed Dec 2a, 1944 4 Sheeis-Sheet 1 IN V EN TOR.

I I i Pau/ E. Way/he A 7"7'ORNE X April 1950 P; E. FORSYTHE 2,

TRANSMITTER UNIT FOR HYDRAULIC TELEMOTOR SYSTEMS Filed Dec. 26. 1944 '4 Sheets-Sheet 2 NVENTO. 4 au/ orgy/2e I! 4 I o #2,. x. b.. o e 1 r H v Y O 2 l 0 fll e l W x a AT 7'0/PNE Y.

April 25, 1950 FORSYTHE 2,505,392

TRANSMITTER UNIT FOR HYDRAULIC TELEMOTOR SYSTEMS.-

Filed Dec. 26, 1944 4 Sheets-Sheet 5 IN VEN TOR.

Pau/ foray/he Patented Apr. 25, 1950 UNITED srArEs Paul E. Eorsythe, Seattle, W sh assi pqr t9 Webster-Brinkley-0o., Sea tt r i 9i washings? Ap a o ec m er 2 S r l 6%? wt area 9 C aims- This invention relates to thetransmitterunit tioularity, is essentially characterized in that the,

same operates automatically through activation of the transmitters hand-wheel to constantly hold the oil bodies related to the two rams in a state of equalization and thereby maintain functional exacti-tude as betweenthe associated transmitter and motor units ofthesystem. to enlarge somewhat upon the abovefthe present invention, as with most hydraulic'transmitter units as now customarilyeng'ineered, utilizes a'replenishing tank from which hydraulic fluid" is periodically supplied to the cylinders of the rams or, as may be necessary in the event of a temperature rise, into which oil may be bled from the cylinders, the purpose being to hold the oil bodies under a pressure this work with the hand-.wheel placed in an amidships position. It was tobe expected that an effort would be made .to. obviate. this need for manual attention, and various automatic arrangements have accordingly been engineered. These automatic arrangements can be said to be of two. 7 types, one said type resorting to the use of wall ports which connect with the replenishing tank and which are cleared by the rams .as thelatter. traverse their neutral positions, and the. other said'type employing mechanically operated closure valves actuated through various. mechanical means responding directly or indirectly to. the movements of the hand wheel and similarly correlated to therams such as to give access across the ram-cylinders and with the replenishing tank as the rams traverse neutral. The objection to the first-mentioned type lies in a, tendency, for.

ieakas o. the por s mus beext cmelyna r o in o er thatthe oi bodie ay e r p d motor-operating impulses transmitted there:

y theramsa e cau ed to move outOf neutral positions, the resulting constriction precluding a ready flow of replenishing oil. The other of the two types, and in which class the present invention falls, has been consequently. favored by vessel operators, but the valve systems heretofore. provided have not been completely satisfactory in that thesame have a more, or less common fault of failing to open thereplenishing .lines to fully 11 Wv capacity at precisely the, moment, and only at the moment, that the rams. pass neutral. Otherwise stated, the open period has run somewhat beyond true neutral into the initial stage of a rams working travel with the self-evident resuit that the steering wheel of the vessel, or which is to say the hand;yvheel of the transmitter unit, fails to transmit operating impulses to the motor unit of the system until the wheel has moved through several degrees of travel.

The present invention aims to devise improved valve-opening mechanism producing an excepe tionally fast action attaining a full opening and a following complete closing of the valves during a momentary interval in the travel of the rams to and beyond neutral which can be said to very nearly coincide with the exact neutral positioning of. the rams."

The invention has the further and important.

object of providing a system including two independent sources of oil supply and, as an adjunct to automatically acting valves functionally associated with one said source, providing a separate and hand-operated valve associated with the other said source' anden'abling the transmitter unit to be kept 'in an operatingcondition in the event that it becomes necessary to repair or replace the automatically actingvalves.

As a further object still, the invention aims to structurally improve the transmitter unit through incorporation of advanced reduction gearing planetary 'in nature-between the hand-wheel and the rams toward minimizing the energy necessaril'y exerted in. giving motor-operating movements to. the latter.

A still further object of the invention is to provide a transmitter unit of the described character so engineered asto adapt this reduction drive to the movements of either of two selectively employed wheels, one a primary wheel carried di-.

rectly by andmade a part of the transmitter unit proper and the other a secondary and remote wheel, for example the wheel found upon the,

3 understood in the course of the following description and claims, the invention consists in the novel construction and in the adaptation and combination of parts hereinafter described and claimed.

In the accompanying drawings Figure 1 is a vertical sectional view taken on the substantial longitudinal median line of a transmitter unit having its parts constructed and arranged according to the now preferred embodiment of the invention, the view being fragmentary in part to the extent, principally, that only the tail end of the remote-control connection leading, say, from a flying bridge is'shown in the view, parts of the oil-conducting pipes are deleted, and a partitioning wall which lies between two compartments-the hereinbefore mentioned separate sources of oil supply-of the replenishing tank is broken away to give a clear portrayal of the particular chamberfrom which the several I illustrated oil-supply pipes draw their replenishing fluid.

Fig. 2 is a transverse vertical section on line 22 of'Fig. 1.

Fig. 3'i's a fragmentary transverse vertical sec- ;ion taken to an enlarged scale on line 3-3 of Fig. 4 is a fragmentary transverse vertical section on line 4- 3 of Fig. 1.

Fig. '5 is a horizontal section taken to an enlarged scale on line 55 of Fig. 1; and

- Fig. 6 is a fragmentary transverse vertical section taken to an enlarged scale on line 6-6 of Fig. 5.

Referring to said drawings, the numeral i denotes a wheel-stand arranged and adapted to be fixedly secured upon the bridge-deck of a marine vessel and formed to provide, at its lower end, companion parallel cylinders 8 and 9 of a diameter somewhat greater than that of the pis- A tons or rams i0 and II which work therein. The usual stuffing-box assemblies are applied to the upper open ends of the cylinders.

Occupying perpendicular positions, said rams extend bytheir upper ends into a gear chamber produced in the head part of the stand, and are coupled to spaced-apart racks l2 and I3 aligned therewith and which are guidably supported for reciprocatory vertical movement. A driving pinion M for the racks, and which is disposed to mesh'the latter from a position therebetween, is madeintegral with a hub element extended as an axial prolongation from a planet spider l5, and this spider, with its'complement in a second and axially aligned planet spider !6, produces a cage by which to revolubly support a severalty of planet gears l1. l8 designates the journal pins for these gears.

The said spiders, and which extend through and receive 'a rotary mounting in opposite end walls of the wheel-stand, are each center-bored, and there is received through these registering center-bores a main shaft 22 with suitable bushings being provided to admit of. free relative rotation as between the planetary cage and the shaft. The shaft extends by each of its two ends outwardly beyond the end limits of the cage; or which is to say beyond the spider hubs, and there is formed upon the shaft to occupy a position between the spiders a sun gear 23 in mesh with the teeth of the planet gears. Completing the planetary gearing is an internal gear 24 held stationary by the wheel-stand.

The hand-wheel for the transmitter unit is indicated 'by 25, and is fitted with a bushing 26 which finds a rotary journal upon the exposed front end of the main shaft, and for purposes of releasably coupling the wheel to the shaft there is splined upon the shaft a jaw-clutch 2? manually shiftable in an axial direction and by such shifting bringing the clutching teeth into couple with mating teeth produced upon the frontal face of the wheel.

Denoted by 28, there is fixedly applied to the exposed rear end of the main shaft a miter gear arranged and adapted to mesh a second miter gear 29, and powering this latter gear is a normally inactive stub shaft 3!] carried for rotary movement about a perpendicular axis. The first-named miter gear, and for a purpose which will hereinafter appear, is formed with a somewhat extended hub and introduced between this hub and the projecting end of the hub prolongation of spider i5 is a suitable thrust bearing. The said stub shaft has a jaw-clutch element 3i fixedly applied to its upper end, and as a complement thereto there is provided a second jawclutch element 32 splined to and axially shiftable upon a driving shaft 33 which is powered, through a universal connection, from an auxiliary steering wheel (not shown). The stub shaft and its complementing drive shaft are given a coaxial mounting in a bracket 34 boltably attached to the back wall of the wheel-stand, and suspended from this bracket to guard the otherwise exposed miter gears is a plate 35. Detailed in respect of the last-described jaw-clutch assembly, and represented by dotted lines in respect of the first-described jawclutch assembly, is a bullet catch comprised of the customary springpressed ball 38 arranged to find engagement in either of two axially-spaced surface recesses.

It will be apparent from the foregoing that the main shaft may derive its power from the hand movements given to either of two selectively employed steering wheels. As the main shaft turns in concert with this selected wheel, the planet gears walk about the internal gear 24 and give to the cage a reduced-speed rotary travel in the same direction as the shaft, transmitting through pinion M to the twin racks the oppositely directedrectilineal travel which will cause one ram to express oil from its cylinder through a related oil pipe 3'! while the other ram draws oil'into its cylinder through pipe 38, these two pipes making connection by their other ends with the motor end of the telemotor system. The Wheel-stand isprovided with the usual indicator dial, and to operate the pointer therefor, indicated at 39, employs bevel gears 46 driven from a rock-shaft 4| to which is pinned a gear segment 4! in mesh with the pinion M.

-Now describing the means by which equalization is automatically obtained as between the oil bodies in the two 'motor-control lines as the rams traverse neutral in response to hand movements given to the wheel, the supply tank which is parent to these two lines is denoted by :12 and occupies a position to the rear of the stand proper subjacent to the exposed tail ends of said main shaft and the spider l5 and such as will place the level of the liquid therein above the upper limit of the ram cylinders. This tank is divided by a partitioning wall 43 into two ostensibly isolated compartmentsa main compartment 3 4 and a reserve compartment 45-and is filled through a top opening normally closed by a vented filling plug 4%. Drain plugs (not shown) are provided for said compartments, and there is also-provided a liquid-level gauge, as. Al Access 2 {moi-3921.

lie-th ein ee niuartmerit ro ine h eush the ;l2 .QY ,SiQ -Q 1a ihansirhele -.n ma v s a tra e e 1 --aid :rnain compartment, its bottom wall, prese ts w t r ugh-o nin w c are 80 located a t occupy posit ons spaced eq san v at epp s te s d s. t sv e y s e d f-a perpendicolandropped; from the axialline of t ermainehe t 2-2,- Rele ed t em Closing es hole are ubula ne k elemen s extending pwardly intoithe liquid contents-ofthe tankand giving access to the tank; from valve chambers pljmiided in valve bodies, as 49 and at, these valve cha bers ein p e d cula ly ned withthe neck ducts andhaviilgza; diameter somewhat en-. larged from the latter to produce seats for ball at thepoint of juncture between said oh rnbers and the, ducts. Springs 52 act upon the ball checks to: urge the latter into seated positions. 0ilside-farm branches with the respective valve chambers and make connection by their opposite ends one with the coilvcylinder 8 and the other with the oil cylinder ii, the latter connection beingdesirably made to o-nebranch of a respective ii-fitting 55. There is provided for each of said oil pipes a normally open shut-off cock (not shown), and a desirable arrangement is one in which this cock iscarried'by and becomes a part of; the branch arm' of the T-fitting to which the pipe v is attached,

Reverting .to the ball-checks, the same are caused ,to be unseated against the resistance. ofiered' by the springs through the action of valve rods 56-5! which work freely through the neck ducts and are adjustably carried as perpendicular dependencies of a yoking cross-arm 5-8, and flX- edly carrying this yoke isa push-rod 6i! guided by and extending for vertical sliding movement through the head wall of the tank. Functional upon the push-rod to urge the latter upwardly is a spring 59. This push-rod has a rocker-arm MLcarried upon its exposed head extremity, and belowsaid arm presents a chordal slot 6|, and associated with this slot is a stationary stop bar fiiilwhich serves the two-fold end of resisting rotation of thepush-rod and of limiting the springurged upward travel of thelatter.

The rocker-arm is of a bowed form presenting upwardlyturnedfurcate extremities, and within its length there is provided an offset which serves toplaceone of these forked ends in a transverse vertical plane common to the exposed rear extremity of the. spider l5 and the other forked end in a transverse vertical plane common to the aforementioned hub of the miter gear 28. Rollers, as 66 and G5, are carried by these forked ends. for rotary movement about axes paralleling that ofthe main; shaft, and functional upon such rollers are respective cams 66 and 61 one of which is fixedly sleeved upon the tail end of the spider and the otherupon the said hub of the miter gear. such cams perforce turn at difierent speeds and, to reflect the reduction ratio-approximately l -to- '7 A -which obtains between the spider and the main shaft, and hence between therespective camsfi' and 21, these two cams will be herein-. aftertermed the-slow and the fast cam, respectively. As will be apparent from an inspection of Figfi, the development of the roller-activating eccentricfaces of these cams isdiflerent, the rise Qf 'll hfi SlQW' cam being comparatively minor and progressing to-an arched media-n crest while the fastcamdevelops; quite rapidly to a sharp median crest. Thestwfl learnsareienahle .todepress the.

conducting pipes, as 53 and-5 3, connect by r several turns to'the steering wheel without, in

so-doing, effecting the-,push-rod as the fast cam passes center, and'which=is to say that thetwocams will; occupy -the positions necessary to actin occupying thefiposition in which it isillustratedin Fig. '3. The weighting may be readily accomplished by boring the fastcam end of the rocker-- arm andfillingwith molten lead.

In addition to the above-described means by which movements of thehand-wheelof thetransmitter unit are-madecoperative, automatically, ;to periodically; equalize the two hydraulic transmit ter lines, it becomes desirable tointroducemeans by which the equalization can be accomplished; through-a hand controlan'd which; under certain circumstances, can beset todevelop and maintain a condition which will give constant connection-across the two ram-cylinders. The purpose as respects saidmanually-controlled equalizing is to enable the main compartment of'thereplenishe ingctank to'be completely isolated for draining and, when so drained, permitting the ball checksv or any part-of the mechanism-related thereto to be replaced or repaired should the need therefor arise without, duringsuch period, cutting out the; transmitterunlt. Themaintain-ing of a constant; connection across the two 'ra'mcylinders becomes desirable under circumstances where recourse, for steering, is had to :a vessels stern helm and, to enable-the motor end of the telemotor system to operate freely without the resistant load of the: rams and associated partsof the transmitter unit, it becomes'necessa-ryto isolate the working parts of the transmitterunit and give free passage to the 'oil f romone toanother of the two oil columns.

Inpermittingeitherof-said ends tobe attained, I-by-pass the-mai-ncompartment-of the replenishi-ng tankbyproviding a connection as 18, leading fromthereserve compartment 65 to a valve body H, and connecting this valve body-by branch lines; 'l 2 --?;3 to the tworam-cylinders, the said lines 12 and T3 making connection with the cylinders, by means ofthe otherbranches of the referred-to is formed with coeaxially disposed valve chamhers i i; and Iii-separatedby-a connecting passage 16, and has respective ports-as 11, 1'8 and 19-for each said chamber and for the passage connecting, as respects the valve-chambers, with theoil pipes wand 13 and, as respects the passage,

with the oil pipe '10. Ball valves Bl] and 8! received inthe valvechambers and-madesubject to the forceof spring 82 normally isolate the center nessae i mx hei hamhe sgand .iune ionai upon The valve body here referred to these valves for unseating the same are push-rods 83 and 84. The push-rods abut the camming end of a spindle 85, and fixed to the exposed'head of this spindle is an operating handle 86 which is given a limited range of movement through employment of a pin 81 tracking in a slot 88. A bullet catch is provided to releasably hold the handle in operative or inoperative positions, selectively. In using the by-pass'line it will be understood that the cocks for the two oil-conducting pipes 53 and 54 are closed, and the helmsman, upon placing the hand-wheel in a neutral position, opens and again closes the two ball valves 83 and 8| by activation of the'handle 86. If the transmitter unit is to be made inactive, the handle is turned to its valve-opening position and left in such position.

It is believed unnecessary to here trace the operation of the system other than, perhaps, to expressly consider the working of the fluid-equalizing valves 5! and the operating instrumentality therefor. The parts, as they are illustrated in Fig. 3, lie in the positions which they occupy when the steering wheel and the responding rams Ili are in neutral. Both rollers 64 and 65 are depressed, each in consequence of its related cam having been brought into a position whereat its highest point is in contact with the roller, and this simultaneous depression forces the rocker-arm 62 bodily downwardly with a resulting depression of the push-rod 60. The push-rod acts through the crossarm 58 to depress the two valve rods 58 and 51 which, in turn, open the two valves 55, and such opening of the valves produces a communication from one to the other valve chamber of the two valve bodies 49 and 50 as connection is had from each said valve chamber with the reservoir. Assume, now, that the he'lmsman in the performance of his steering office swings the steering wheel out of neutral, the sharp crest of the fast cam B'l-tied directly to the wheel by means of the shaft 22--instantly falls away from the roller, and the latter, by force of the spring 59, rises about the center of the as-yet depressed roller 64 as an axis and the fulcrum of the rocker-arm 62 perforce rises with the rise of the said roller 65. Such elevation of the fulcrum-point of the rocker-arm lifts the push-rod, the cross-arm, and the valve rods, a1- lowing the valves 5! to close by force of the springs 52, and this valve-closing action is completed by practically negligible movement of the steering wheel out of neutral. Roller 64 will, of course. continue to maintain contact with the slow cam 56, although perforce progressively falling away from the high point. Asthe same has been illustrated, the slow cam has a total span of approximately 60, and by this token the roller 64 will be free of the cam when the slow cam has been turned a total of 30 from the neutralposition shown in Fig. 3. Considering that the'ratic between'the fast and the slow cam is approximately 7 /2 to 1, it follows that the slow cam will move approximately 48 as the fast cam moves 360", and hence the slow cam will have left the roller B l and moved through an additional arc of 18 before the fast cam has completed one revolution of turn from neutral. Due to the weighting of the fast-cam end of the rocker-arm, this end will drop as the other end is permitted torise in consequence of the cam 66 being withdrawn from roller Ed, and what might otherwise be an objectionable slapping of the roller 65 as the fast cam 61 completes the first and success'ive following revolutions bfanumber of wheel turns is precluded. Seven and one-half turns of the steering wheel would perforce be necessary to give 360 of travel to the slow cam, or which is to say again bring the peak of the slow cam against the roller 64, and, at this particular point in the travel of the slow cam, the fast cam 61 will occupy a position diametrically opposite the position of Fig. 3 and hence be inactive to the roller 65. When turned the additional half-turn which would be necessary to contact the roller 65, the slow cam will have travelled an added 24 and the contact between cam 66 and roller 64 will be on the low point of the cam 66 to elevates-aid roller 64 and responsively lower the roller 65 in a degree sufiicient to clear the fast:

From the cam as the'latter passes thereover. foregoing, it will be readily apparent that, using the stated 7% to 1 ratio, a total of fifteen complete turns of the steering wheel would be re quired in order that the two cams simultaneously arrive at points coinciding with the positions which they occupy when the wheel is at neutral. This number of turns is well above any hard over usage of the wheel, and which is to say that a steering wheel is never turned to this extent. Numerous departures from the illustrated and-described embodiment will suggest themselves having knowledge of my teachings, and

it is seif-evident that recourse may be freely had thereto without sacrifice of, the inventive concept. It is my intention that all forms of construction and variation in detail coming within the scope of the hereto annexed claims are to be considered as comprehended by the invention.

What I claim, is:

l. A hydraulic control apparatus comprising, in combination with a control wheel swingable in opposite directions from a neutral position, and with a hydraulic impulse-transmitting system providing a pair of operating cylinders and rams for said cylinders, the rams being operatively interconnected with the wheel to cause the.

rams to move oppositely from neutral positions by movements of the wheel from neutral: an oilreplenishing tank having separate and parallel delivery ducts extending through the bottom wall thereof and making connection one with one and the other with the other of the two ram-cylinders; spring-urged valves for said ducts closing against the weight of the oil within the tank;

a push-rod extending into the oil within the tank and fitted upon its lower end with thrust stems registering with said delivery ducts and functional by depression of the rod to engage and unseat the valves; a rocker arm supported upon eccentricit-ies so placed and developed as to de-" press the push-rod by concerted action of the twocams only as the control wheel occupies its neutral position.

2. In a hydraulic control apparatus having a control wheel swingable in opposite directions from a neutral position, and providing a hydraulic impulse-transmitting system employing a pair of operating cylinders and rams for said cylinders,

'16 the rams being operatively interconnected with the wheel tocause the rams to move oppositely from neutral positions by movements of the'wheel from neutral, automatic means for equalizing the oil within the said impulse-transmitting system and comprising: an oil-replenishing tank having connection by separate fluid-flow lines withthe two--ram-cylinders; spring-urged valves for said fluid-flow lines closing against the'weight of the oil within the tank; a push-rod functional tosaid valves and acting to open the same by movement in onedirectionofits endwise travel; a Spring opposing said valve-opening movement of the push-rod; a rocker arm carried by the push-rod for rocker movements about anaxis transverse to; the latters, slide axis;- a pair of rotary cams; means connecting the control wheel with'one of the cams and imparting rotary motionth'ereto; and means also connecting the, control'wheel with the other'cam' to likewise impart rotary motion to the" -mentioned camw but characterized in't'hat the rotation transmitted is of a different speedthanthe rotation transmitted to the first-mentioned cam; said'cams acting one to engage one end and the other to engage the other end of the rocker arm, and having their eccentricities so placed and developed as to impart valve-opening movement to the push-rod, by action of the two cams working in concert, only as the control wheel occupies its said neutral position.

3. In a hydraulic control apparatus having a control wheel swingable in opposite directions from a neutral position, and providing a hydraulic impulse-transmitting system employing a pair of operating cylinders and rams for said cylinders, the rams being operatively interconnected with the wheel to cause the rams to move oppositely from neutral position by movements of the wheel from neutral, automatic means for equalizing the oil within the said impulse-transmitting system and comprising: an oil-replenishing tank having gravity-flow connection by separate fluid-flow lines with the two ram-cylinders; valves for said fluid-flow lines closing against the weight of the oil within the tank; springs influencing said valves into closed positions; a rocker arm supported for rocker movements about a transverse median axis and also admitting to bodily reciprocal movement in a median path at right angles to said rocker axis; operative interconnection from the rocker arm to the valves causing the latter to open against the resistance of the springs by bodily movement of said rocker arm in one direction of its said reciprocal travel; a pair of rotary cams; means connecting the control wheel with one of the cams and imparting rotary motion thereto; and means also connecting the control wheel with the other cam to likewise impart rotary motion to the last-mentioned cam but characterized in that the rotation transmitted is of a different speed than the rotation to the first-mentioned cam, said cams being uperatively interconnected with the control wheel such that the cams are driven by the latter at different rotary speeds, one cam in relation to the other cam, said cams being functionally associated one with one and the other with the other end of the rocker arm, and having their eccentricities so placed and developed as to impart valve-opening bodily movement to the rocker arm, by action of the two cams working in concert, only as the control wheel occupies its said neutral position.

4. Structure according to claim 3 in which the two cams are co-axially mounted.

iii

5; Structure according to claim Ii inpwhlch the two cams are mounted for:rotation'about a comamon axis coinciding with that" of the. control wheel, one-of said cams-being direct-driven from the wheel to turn with thelatter at the same speed and in' the same rotary direction, and. wherein the-powering connection from the wheel to theother said-"cam comprises planetary reduc-'- tion gearing.

6. Theistructure of, claim 3 in which the eccentricity of the 'slower moving of the two' cams is such as gives a gradual development, and in which that of the other and faster-moving cam is quite abrupt.

7. A hydraulic control apparatus comprising, in combination with a controlwheel swingable: in oppositerotary directions to and from a neutral position, and with a hydraulic impulse-transmitting system employing a pair of'operating cyl inders and oppositely acting rams for saidcylinders: a main shaft rotatively responding to. swinging movements. of; the wheeljandlhaving a sun gear anda cam element carriedin axially spaced relation thereon; a stationary gear wheel placed proximate to the sun gear and concentrio with the shaft; a hollow shaft received over main shaft for relative rotation about a coinciding axis, and occupying a position between the sun gear and the cam to extend by its ends into proximity of the latter, said hollow shaft being for-med intermediate its length with external pinion teeth, having a spider element upon the end thereof which lies proximate to the sun gear, and carrying a cam element upon the other end; planet gears carried. by said spider and functionally associated with the sun gear and the stationary gear wheel to cause the hollow shaft, by rotation given to the main shaft, to turn in concert with the main shaft but at a reduced rotary speed; racks engaging said pinion teeth and connected to and operating the rams such as will cause the rams to work in opposition, functionally considered, and directively toward and from neutral positions coincident with swing movements of the control wheel into and from neutral; an oil-replenishing tank having gravityflow connection by separate fiuid-fiow lines with the two ram-cylinders; closure valves for the fluid-flow lines; springs functional upon the valves to influence the latter into their closed positions; a walking beam supported to lie transverse to the axis of said shafts subjacent to the cams and, in addition to its permitted rocker movement, admitting to bodily movement along a slide axis radial to said axis of the shafts; rollers functionally associated one with one and the other with the other of the two cams and rotatively journaled in the free ends of the walking beam to occupy positions restricted to the rotary path of travel of a respective said cam; and operative interconnection from said walking beam to the two valves causing the valves to open against the resistance of the springs by bodily depressing the walking beam, said cams having their eccentricities so placed and developed as to impart said valve-opening bodily movement to the walking beam, by action of the two cams working in concert, only as the control Wheel occupies its said neutral position.

8. Hydraulic control apparatus according to claim 7 characterized in that the end of the walk ing beam related to the faster-moving of the two cams is weighted in respect of the beams other end.

9. In a hydraulic control apparatus having a control wheel swingable in opposite directions from a neutral position, and providing a hydraulic impulse-transmitting system employing a pair of operating cylinders and rams for said cylinders, the rams being operatively interconnected with the wheel to cause the rams to move oppositely from neutral positions by movements of the wheel from neutral, automatic means for equalizing the oil within the said impulse-transmitting'system and comprising, in combination: an oil-replenishing tank having connection by separate fluid-flow lines with the two ram-cylinders; spring-closing valves for the respective lines; means for opening said valves against the pressure of the springs; a pair of rotary cams; means connecting the control wheel with one of the cams for imparting rotary motion thereto; means also connecting the control wheel with the'other cam to likewise impart rotary motion to the last-mentioned cam but characterized in that the rotation transmitted is of a different speed than the rotation transmitted to the cam 12 mentioned in the first instance, and means arranged to be activated by the cams and in turn activating the valve-opening means in the latters valve-opening action, the arrangement between the cams and the means last recited being such as to require, for the opening of the valves, a positioning of both cams at points within their respective circles of rotation reflecting a neutral positioning of the control wheel.

PAUL E. FORSYTHE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 622,600 Brown Apr. 4, 1899 1,213,721 Williamson Jan. 23, 1917 1,446,261 McLeod Feb. 20, 1923 1,633,463 Sperry June 21, 1927 2,194,816 Vestraut Mar. 26, 1940 2,348,323 Binder May 9, 1944

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