US2232514A - Hydraulic cylinder and control means therefor - Google Patents

Description

Feb. 18, 1941. O .DAY 7 2,232,514

HYDRAULIC CYLINDER AND CONTROL MEANS THEREFOR Filed April 13, 1938 2 Sheets-Sheet 1 O "a INVENTOR. #574 51??? 0. Q4)

A TTORNEY.

Feb. 18, 1941. H. 0. DAY. 2,232,514

HYDRAULIC CYLINDER AND common MEANS THEREFOR Filed April 13, 1938 2 Sheets-Sheet 2 IN VENTOR.

ATTORNEY.

Patented Feb. 18, 1941 HYDRAULIC CYLINDER AND CONTROL S THEREFOR Herbert 0. Day, St. Paul, Minn. Application April 13, 1938, Serial No. 201,733

2 Claims.

This invention relates to hydraulic power cylinders or jacks and to, systems for the operation and-control thereof.

More particularly it comprises an improved hydraulically operated apparatus which is particularly useful in the raising and lowering of truck dump bodies and is efiective in raising such bodies into a high dumping position in avery simple and efi'ective manner.

.One of the objects of the invention is to provide an hydraulically operated power cylinder of rugged construction and which is simple and highly eflicient in operation.

Another object is to provide a system of control for hydraulic power cylinders which is simply and effectively operable to supply fluid under pressure to either end of the cylinderor to maintain the same in inoperative position.

A further object is to provide means effective for cushioning the travel of the piston as it ap proaches its outer limit.

Another object is to provide for automatically relieving pressure within the cylinder when the same becomes higher than desired.

A stillfurther object is to provide a fluid circulating system for hydraulic cylinders arranged in a manner so that air will not be bled into the circulatory system.

With these and other objects in view, the

invention consists in the construction and novel combination and .arrangement of parts hereindetails of construction, within the scope of the claims, may be resorted towithout departing from. the spirit of the invention or sacrificing any of the advantages thereof.

In the drawings-- 7 "Fig. 1 is an end elevation of a device embodying features of the present invention and showing the pressure fluid reservoir, pump, piping" system and control valve, looking from the rear end, the cylinder itself not being shown; Fig. 2 is a; top plan viewof. a complete device embodying the features or .the invention with certain parts broken away to show the control meansmore'clearly;

Fig. 3 is a detail plan view, partly in section,

of the forward or outer 'end' of the cylinder showing the piston in one operating position;

F g. 4 is a horizontal section at the rear end of the cylinder showing the control valve in one operating position; and

Fig. 5 is a view similar to Fig. 4 and showing the control valve in another operating position.

Briefly speaking, the device of the present invention comprises a cylinder-having a piston therein with a piston rod projecting through'the outer end of the cylinder. A fluid reservoir is provided for containing oil or other suitable fluid with a pump for supplying'fluid from the reservoir to the cylinder at one side or the other of the piston, and a control valve'for directing the fluid to either side of the piston or for bypassing the pumped fluid back to the reservoir and thus maintaining the piston in inoperative mounted on or attached to the cross-beam I of Extending 2 a motor truck or other vehicle. downwardly from. the reservoir is a casing ll which encloses a pump generally indicated at 9 which may be conveniently operated from the engine that supplies the motive power for the truck. A pipe Ill connects the pump with the 3 lower part of the reservoir i whereby fluid may be drawn from the reservoir by operation of the pump. At the discharge side of the pump 9 a pipeline ll carries the pumped liquid up to the manifold II where the liquid under pressure 35 may be directed as desired by means of the three-way valve l3. Extending downwardly into the reservoir 6 from the manifold l2 at its opposite end,"is a tube I4 constituting a return pipe for conducting the circulating liquid back 40 into the reservoir. This pipe ll terminates near the bottom of the reservoirso that it always extends downwardly a substantial distance below the minimum liquid level, indicated by the broken line M, for a purpose to be hereinafter described. 45

The liquid supply pipe II, at its point of communication with the manifold I2, is normally closed by ball check valve l5*which wilr open under pressure allowing liquid to flow into the passageway l6 and, with the valve in the posi- 50 tion shown in Fig. 2, pass through the central opening I! of the valve and thence into the passageway It with which the tube ll communicates but which is normally closed by ball check valve 19. With the valve in the position shown I of the cylinder may be avoided.

in Fig. 2' and the pump in operation, it will be obvious that liquid will be forced past the check valve i5 and through the valve opening I! and passageway l8, the check valve is opening under the pressure. to allow the liquid to drain back into the reservoir through return pipe it. Thus in this manner, even with the pump 9 in operation, thefluid under pressurejmay be conducted by the valve ll directly back into the reservoir so that the application of pressure to either end Extending forwardly from the manifold l2 and in communication with the -valve I3 is a tubular member'or port 2| which, at its other end communicates with the interior of the cylinder 2| whichiis a'ttachedto the reservoir tor firmly secured in-place in other suitable manher. Arranged for reciprocation within the (2371- inder, but in close fitting relationship with the interior walls thereof, is a piston 22 carrying the piston rod 23 which projects through a,

gland 24 in the free end of the cylinder in con ventional manner. It will be understood that the outer 'or free end of the piston 23 is adapted to be connected with the dumping body of a truck, or with any other object to be actuated. whereby reciprocation of the piston in one direction or the other will cause the dumping body to be raised, in order to discharge its contents, or lowered into normal horizontal position. In

' order tothol'ollghly drain the dumping body it -ordertoadvance the pistonandthusraisethe dump body,the, valve I3 is caused to assume the position shown in Fig. 4. with the motor 0 in operation, oil is drawn from the reservoir and forced under premi e through the pipe ll, check valve II and my I from which the valve willdirect it through the port and into the cylinder in back of the piston, thus forcing the piston outward in the direction of the arrows in Fig. 4. Oil in the cylinder on the oppomte side a of the piston betweenthe same and the free end 26 of the cylinder will unseat the check valves 21 and 28 in the forward valve manifold 2! and -will flow through the pipe Ill back into the passageway II of the manifold l2 and thence through the valve l2 into the passage II, as indicated by the arrows, unseating check valve II and returning to the reservoir through the pipe l4. In normal operation the oil is forced to follow this path because'check valve I2 is, of course, positively seated by the pressure and check valve SI is arranged to unseat only in the event of the development of abnormally high pressure in the returning oil.

In lowering the dump body by the application of pressure the valve 13 is-caused to assume the position shown in Fig. 5. With the pump in operation oil will then be pumped past the check valve I! through the passage I6 and directed by the check valve 33 will come into operation only under abnormal pressures so that the oil is forcedfrom the passage 3| through the pipe 30 into the manifold 29, where the pressure, will maintain the check valves 21 and 28 closed and will unseat check valve 34 whereby the oil will be forced into the cylinder in front of the piston 22 between it and the front end 28 of the cylinder, thus causing the piston and piston rod 23 to move back toward the rear end of the cylinder, thereby lowering'the dump body. The oil in back of the piston at the same time is forccdout of the cylinder through'the port 20 and is directed by the I valve 13 into the passageway l8 and through the check valve 19 back into the reservoir.

When it is desired to halt the travel of the piston 22 at any particular point, the valve l3 may be causedto assume the position shown in Fig. 2 where, without stopping the operation of the pump, the oil may flow directly through the center of the control valve and back into the reservoir through the passage l8 and check valve I9. The liquid at either side of the piston 22 thus being completely sealed from the pressuresupply or relief means, the piston will be maintained in stationary relationship.

Of prime importance in the arrangement of the present invention is the manner in which the various check valves are set, or rather their varying degrees of pressure responsiveness. In convenient practice the ball I! maybe set so that it will be unseated by pressure of, say 10 lbs., the ball 32 at 5 lbs., the ball I} at 200 lbs., and the ball 34 at 2 lbs. With the control valve It in the locked position as in Fig. 2, oi is taken from 35 the reservoir by the pump and orced through ball check I! through the center .of the control valve and throughball- I! set at 10 lbs., back through tube M to the body of the reservoir. Ball.2 2, set at 5 lbs., cannot operate, due to pressure of the oil filling the passage 3] and, since ball Ills set at 200 lbs., the oil will follow the path of least resistance which is through the check valve I9. I

In'advancing thepiston with the control valve inthepositionshown inF ig. 4, oil willbetaken from the reservoir by the pump, forced through ball check I! through valve l3 and port 20 into the cylinder to.force the piston outwardly. Oil ahead of the-piston is forced through ball checks 5o 21 and 28, since hall 3 tends to remain closed, through pipe 30 into the passageway I i and thence through the control valve and the ball i9, set at 10 lbs. and back to the reservoir. Ball 32, of course, is maintained closed, due to the pressure built up by the returning oil, and ball 33 zvbisll not open unless the pressure rises above 200 In retracting the piston the control valve I3 is set in the position of Fig. 5 whereupon, with the m pump in operation, oil is forced through ball check l5, through the control valve and into passageway 3| where the pressure causes ball 22 to remain seated. From the passageway 3| the pressure forces the oil through the pipe 20 and into the manifold 29 where the pressure seats balls 21 and 28 and'opens ball 34, thus allowing the oil to enter the forward part of the cylinder and force the piston 22 backward. Oil behind the piston 22- is forced by the same out of the cylinder through the port 20, through the control valve and passageway l8, unseating ball I! and returning into the reservoir, the high pressure in the passageway SI, of course, maintaining the ball 62 iirmlyseated.

In allowing the .dumping body to return .to

- its lowered" position by gravity, that is with the pump 3 not in operation, the pressure responsiveness diflerential of the ball checks I3, 32 and 33 automatically functions in allowing the operation to occur in a smooth manner and without undue strain upon the system. with the control valve in the position of Fig. 5, the pump not in operation, and the dump body back of the center of gravity, the weight of the body will cause it to return to its lowered position, thus retracting the piston 22 and forcing oil out of the cylinder through the port 23 where it is directed by the control valve into the passageway l3. However, since there is now no pressure in the passageway 3| behind the ball 32, this bah set at 5 lbs. will now be raised in preference to ball l3 set at 10 lbs. so that the oil may circulate through a bypass passageway l3 past the ball 32 and through the pipe 33 and ball 33, set at 2 lbs., and back into the cylinder on the opposite side of the piston. The by-pass passageway i3 connects the exhaust passageway l3 at a point between the control valve l1 and the exhaust check valve I3 5 with the passage 3| and pipe 33 respectively. Since all of the oil forced out of the cylinder from behind the piston cannot be accommodated in the cylinder at the other side of the piston, due to displacement of the piston rod 23,

the pressure of the oil in'the passageway l3 soon will be raised beyond 10 lbs., whereupon ball I! will open and allow the surplus oil to return through the tube l4 into the reservoir. Due to the setting of the ball l3 at 10 lbs. and the ball 32 at 5 lbs., the head end of the cylinder is filled before any oil drains into the reservoir, thus confining the pressureto the manifold l2 and pipe 33. If ball 32 were not set to respond to less I pressure than ball l3, or if ball l3. were omitted. the fluid expelled from the cylinder would naturally pass into the reservoir and pressure would be exerted over the. entire area of the reservoir before ball 32 would be raised to allow the oil to pass around to the fore side of the piston and any shortage of oil in the tank would result in the fore part of the cylinder being only partially filled. In lowering the dump body by power, with the control valve set as in Fig. 5, oil is taken from the reservoir by the pump, through ball l3, control valve l3, e 3|, pipe 33 and ball 33 into- .the fore part of the eylinderand forces the-piston backward. Oil at the-rear side. of the piston .is forced thro h Por 33. valve i3, passageway 13 and ball I. through tube and into the reservoir. when the piston "has reached the rear limit of its traveLfor instance, whenit, isilush against therear wall 23' of the cylinder, with the dump body in its lowered position on the frame, with pump s .stillin operation. and-with valve i3 set in theslow'erlng position as in Fig. 5, pressurewouldbe-developed in the. piston rod side of the cylinder, pipe 33 and way 3| in the manifold 12, and continued operation of the pump would build upga tremendous pressure which, if unrelieved, would cause considerable strain if not actual breakage. In the specific illustration given it has'been stated that the ball 7o 33 is responsive when pressure reaches 200 lbs.

Therefore, after pressure reaches 200 lbs., or whateverisflthe'fsetting of ball 33, which is calculatedfto be sufllcient: at all times to lower the'body, the'ballfl3 will be unseated and oil can then by-pass'through this ball and through described manner, to check or cushion the travel the tube l3 into the reservoir, thus relieving the pressure and preventing any damage.

' The function of the tube H, which extends well below the minimum liquid level in the reservoir, is of considerable advantage and impor- 5 tance. When the piston 22 is forced as far out as the balls 21 and 23', the oil level in the reservoir, due to the piston rod displacement, will drop in proportion to the displacement. Thereafter, when forcing the piston backward. in the 10 cylinder by using the pump with the control valve in the lowering position of Fig. 5, oil is taken from the tank and forced into the fore part of the cylinder as previously described. If tube It were eliminated, the air in the upper por- 15 tion of the reservoir would be taken in through balls 32 and I3 with'the oil as it is pumped through ball is, valve l3, passageway 3|, pipe 33 and ball 33 to force the piston backward. This wouldcause the oil to become aerated and thus 20 to increase in volume. When the piston reaches the base of the cylinder, the increased volume of the oil which has been forced back into the reservoir, creates excessive pressure in the tank which must be relieved by a suitable relief valve, 25 which generally causes a loss of oil. Through the use of the tube [3, extending always below the oil level in the reservoir, all air is trapped in the upper portion of the reservoir and, regardless of the direction of the flow of oil 30 through the control valve 13, no aeration can take place to cause foam and loss of oil.

A further item of prime importance is the function of ball check valves 21, 23 and 33. These valves become efiective, in the following of piston 22 as it nears the forward end 23 of the cylinder and as the dump body approaches and passes a dead center position. Manifestly, in actuating the dump body past dead center, a 40 tremendous strain would ordinarily be imposed upon the actuating device and upon other parts of the truck if the dump body were allowed to move past dead center freely with pressure behind the piston and with nothing to retard its 45 advance, and the piston would bring up against the forward end of the cylinderwlth a tremendous impact andconsequent strain.

In the present arrangement as the piston isforced out, with the control valve as in Fig. 4,..50 oil is returned through both balls 21 and 23 to pipe 30 and through the control valve back into the reservoir. As the piston covers ball 21, as indicated in dotted lines in Fig. 2, oil will still pass through ball 23 and returnto the reservoir, and as pressure is still maintained in the section of the cylinder behind the piston, thus eliminating any dead point in the-piston travel such as would-be the case if only one of thevalves 21 or 23 were provided.v As the piston starts to closeyalve-33 so it.le aves. the valve 23 fre'e'to open, as a: conse-. quence of the oil pressure in the section of the cylinder behind thepiston, and allow the oil to circulate back to the tank, thus relieving the pressure inback of the piston. This is the ape5 proximate point at which dead'center is passed by the dump body and there is new little or no pressure behind the piston to force it forward.

, time allowing it to advance slowly so that the dump body can move a short distance beyond Is dead center or beyond the vertical. As will be i seen in Figs. z-and 3, the ball 34 does not seat around its entire circumference. It is not responsive to pressure from within the cylinder since such pressure will normally tend to seat the ball against the longitudinal ribs 85 and 3G in the manifold 29. However, the fact that the ball 34 does not seat in the valve opening around its entire circumference will allow oil to flow past it through the valve opening in a restricted manner and to then flow around the ball and, by virtue of the ribs 35 and 36, pass on into the manitold 29 and thence through the circulatory system back into the reservoir. ,In'this manner, an hydraulic check or cushion is provided by the ball valve 34 by its restriction of the flow of liquid from the fore part of the cylinder, while at the same time allowing the dump body totravel slowly' and without Jerkiness past the vertical.

Another important feature to be noted is that, with the control valve manifold l2 arranged with thecheck valves as shown, all balls, with the exceptlon of ball Ii, which is purely a check valve to prevent the dump body from dropping in case of drive line failure, operate on the so-called low pressure side of the control valve 13. Thus, this arrangement permits full capacity of the pump to operate against the piston to force it'out and raise the load.

'lhe device of the present invention has been described in a particular environment, namely, that of the application to a dumping truck for the purpose of raising and lowering the dump body of the same. It will be manifest,;however, that the application and use of the invention are not at all restricted to this environment and that a power cylinders embodying features of the-ino for the moving or actuation of any object.

, What is claimed is:

1. In means for controlling-the application of fluid under pressure to hydraulic power cylinders the combination including a manifold, a control I valve therein, conduit means for conducting fluid from said valve to one end or the other of a a double acting motor cylinder, an exhaust passageway leading from the control valve; an exhaust check valve normally closing the exhaust passageway, a by-pass passageway connecting said exhaust passageway at a point between the control valve and the'exhaust check valve with one of the passageways for directing fluid to the cylinder, and a check valve normally closing said by-pass passageway, said by-pass check valve being responsive to relatively low pressure developed in the exhaust and by-pass passageways and said,

" exhaust check valve being responsive only to higher pressures.

2. A device of the character described comp ing a cylinder a piston in said cylinder, 3, con.

' trol valve, a ptiinp for supplying fluid under pressagewa a by-pass passageway connecting said exhaust passageway at a point between the control valve and the exhaust check valve with one of the passageways directing fluid to the cylinder, and a check valve normally closing said bypass passageway. said by-pass check valve being responsive to relatively low pressure developed in the exhaust and by-pass passageways and said exhaust check valve beingresponsive only to a higher pressure. v

1 HERBERT 0. DAY.

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