US2665555A - Hydraulic mechanism - Google Patents

Description

@uw @N @N www @N @N www @Q1 n @N @N EN IlIv Ww HYDRAULIC MECHANISM Filed July l5, 1949 G. R. C. MARTINSSON Jan. 12, 1954 .M QN mw I Patented Jan. 12, 1954 UNITED STATES PATENT OFFICE HYDRAULIC MECHANISM Gunnar R. C. Martinsson, Chicago, Ill. Application July 15, 1949, Serial No. 104,851

3 Claims.

This invention relates to improvements in hydraulic mechanism and its purpose is to provide an improved system of the type comprising pistons operating in cylinders to which lluid under pressure is admitted in such a manner that the several pistons are caused to move sequentially in timed relation to each other for bringing about the successive operation of various devices to be controlled thereby.

Several forms of hydraulic mechanism for effecting the sequential operation of a plurality of pistons have heretofore 'been devised but none of them has been entirely satisfactory. In some of these prior devices, the successful operation of the pistons by hydraulic pressure requires the use of sequencing valves which are controlled by a trip mechanism or cams and, in some of the systems, check valves have also been required to eifect the proper draining of the cylinders. All of the systems of this form have been objectionable because the use of numerous valves has required a substantial expenditure for piping and connectors, thus increasing the cost of the construction while at the same time requiring an excessive amount of space, frequent replacement and repair, and regular maintenance. An effort has been made to overcome these disadvantages by providing a sequencing hydraulic system in which the admission of fluid to each cylinder is controlled by the opening of a port in response to the movement of the piston in a preceding cylinder of the series. While this form of construction has eliminated the use of sequence valves, check valves are still required and the system has the disadvantage that it is sluggish in operation so that there is a delay between the successive operation of the pistons, besides requiring fluid lines for connecting the cylinders with each other.

The principal object of the present invention is to overcome the above mentioned diiculties by providing a hydraulic system in which the successive operation of a number of pistons in their. cylinders is brought about automaticallyl without the use of sequence valves or check valves. Another object of the invention is to provide a hydraulic system comprising a plurality of pistons and cylinders constructed and arranged to bring about a fast sequential operation of the pistons while at the same time eliminating the use of control valves for the several cylinders. Still another object of the invention is to provide a fixed sequencing hydraulic system which does not require adjustment for maintaining the proper timed relation of the operations of the several pistons. A further object of the invention is to provide a sequencing hydraulic system having a minimum number of iiuid lines and a minimum of valves so that it may be constructed in compact form and employed in places where space is limited. Another object is to provide a sequencing hydraulic system which, because of its fixed timing and use of a minimum of valves, requires very little maintenance as compared with other systems heretofore known. Other objects relate to various features of construction and arrangement which will appear more fully hereinafter.

The nature ofthe invention will be understood from the following specification taken with the accompanying drawing in which one embodiment is illustrated. In the drawing,

Figure l shows a somewhat diagrammatic side elevation of a hydraulic system embodying the features of thepresent invention with the cylinders of the system shown in vertical section;

Fig. 2 shows a horizontal section taken on the line 2 2 of Fig. 1; and

Fig. 3 shows a horizontal section taken on the line 3 3 of Fig. 1.

As illustrated in the drawing, the improved hydraulic system comprises four cylinders Ill, I I, I2 and E3 which have different internal diameters and which have mounted therein the respective pistons I d, I5, I6 and I Iwhich are arranged to reciprocate in response to the fluid pressures set up in-the cylinders. The pistons are of varying diameters in relation to their piston rods la, I5a, ISa and I'Ia so that the ratio of the area of the upper or forward face of each piston to the rarea of its lower or reverse face is different from that of each of the other pistons. This -diiference in the ratio of the surface areas of the opposite faces of the pistons is made use of to bring about their sequential operation in fixed timed relation to each other.

As shown in the drawing, fluid such as oil is drawn from a fluid reservoir 20 by a pump 2l through a pipe 22. The pump discharges oil under pressure through discharge line 23 to which there is connected a pressure relief drum or accumulator 24. This discharge line is connected through an operating valve 25 and a flow control valve 26 with the inlet line 2'I which is connected through the branch inlet pipes Illa, IIa, I2a and I3a to the cylinders I0, II, l2 and I3, respectively. The other ends of the cylinders I0, II, I2 and I3 are connected to a common rreturn line 28 which communicates with the discharge line 23 in advance of the operating-valve 25, The operating.

valve is a three-way valve, having ports 25a, 25h and 25e which may be selectively interconnected through a valve member (not shown) which may be actuated by a handle 25d to cause the hydraulic fluid to be discharged from the discharge line 23 into the inlet line 21 or returned through the return line 29 to the tank 20.

With the foregoing arrangement of apparatus, a constant fluid pressure is applied through the inlet line 23 to the upper faces of the pistons hi, l5, I6 and I1' when thevalve 26 is open and the valve 25 has been adjusted to connect the ports 25a and 25h and thereby permit the flow of oil` through the line 2 to the various branch pipes- Ia, lla, l2a and 43a. The pressure of this oil is thereby applied to the upper or forwardfaces.

of the several pistons. At the Sametime-that, this. constant pressure is applied to the upper faces of the several pistons, a constant uniform pressure is continuously applied to the lower or reverse faces ofv the same pistons through the line 2-8r leading from the discharge line 23 but, after the pressure has been built up and applied, the total effective pressure acting upon the lower or reverse face of eachv piston is less than that acting upon the upper or forward face thereof because the effective area of the lower faceof each piston is reduced` to the extent of the cross-sectional area of its piston rod.

The areas of the upper` faces Ma, a, (6a and Iia of the-pistons are shown in Fig. 2, which illus.- trate p an views of` the upper or forward faces of several pistons, while the edective areas ofthe lower faces Mb, |51), 116D. and 1.119K of thesev pistons are shown in Fig. 31. which show bottom plan views of the lower or reverse faces of the pistons with their respectivepiston,v rods Mc, ic, itc and Ir'ic illustrated in cross section,` Due to the difference in the diameters of the piston rods in relation to the diameters of the pistons to which they are connected, the ratio, of the areasA of the forward and reverse; faces of each piston differs from the ratio of the areas of. these faces f-or each of the other pistons and thisv differential of the surface areas is utilized in bringing about a sequential operationY of, the pistonsI in response to the pressures which are applied to the upper and lower faces thereof.

The speed with which the pressure builds up on thefaces of the pistons is controlled by adjusting theA flow control valve26 and each piston operates through a, forward stroke. whenn the total pressure on the forward side thereoi exceeds the total pressure; acting constantly lon the reverseA face thereof. The piston I4, which has the largestl area, moveslnrst throughs. foi?- ward stroke because the totaljpressureion its forward side Ma, exceeds the total pressure on lits reverse side Mb'beforze a, corresponding condition is reached with respect, to the pressures actingupon the other pistons.V The unbalanced pressure acting on piston I4, thereforecauses this piston to move first and its movement is followed by the successive movements of the other pistons HL, IE4 and Il., in that order. The time interval between the operation of two successive pistons` willi be determined by theA period required' for build-` ing up the pressure on the forward face of the second piston until itbccomes sufficiently unbalanced to cause its movement.l `ln this way,l the four pistons may be caused tooperate successively in a definite timed relation tol each other in rconse eir opposite faces: and withoutthe use` of se quence-valvesor check valves in. connection with to the admission of hydraulicl pressure to.

any of the cylinders. Of course, the same principle may be applied to any number of pistons and cylinders depending upon the number of successive operations which are to be performed by the mechanism.

After all of the pistons have been operated, the operating valve 25 is actuated to break the connection between the ports 25a and 25h and to connect the ports 25h and 25e, thereby causing the fluid pressure acting upon the forward sides of the pistons to be diverted to the return line 2d by which the uid is returned to the fluid reservoir 2G. This causes the pressure on the upper or forward side of each piston to diminish until it is exceeded by the total constantly applied pressure acting upon the opposite faces of these pistons which areY continuously connected to a constant pressure acting through the pipe 28. This changel in the relative pressures acting upon the opposite faces of the pistons will continue until a pressure imbalance again exists with respect to each pistony with. the higher pressures then actingupon the reverse faces of the pistons, so that the pistons return to their initial positionsin the; inverse order of their leaving those positions. Thus, the piston l will return first followed by the successive return movements of the pistons I6, l5 and I4.

It will be apparent that in the system which has been described above, the pressure builds up or falls off simultaneously on ther forward sidesl of all of the pistons so that the pressure per unit of area on the forward sides of the piston is the same for all of the pistons at any instant. This is an. important advantage over other systems where the pressure builds up in` each cylinder individually from a low pressure to a high pres` sure every time that a piston is caused to operate.

The. several piston rods Hic,v 15e, itc and llc may,y of course, be connected to various forms of mechanism to bring. about desired mechanical operations. m timed relation to each other. For example, a sequencing hydraulic mechanism of theV typev herein described may be employed for bringingl about successive operations of different parts of a stapling machiney as set forth in the copendingl application of Chester M. MacChesney, Gunnar. R. C. Martinsson,l and Godfrey Stanius,

I Serial No. 108,674,1led August 5., 1949.

Although` one forml of theA invention has been shown anddescribedby way of illustration, it will be understoodI that it may be constructed. invariousfother embodiments which come withinY the-scope of the appended claims,

I claim:

1. In hydraulicV mechanism, a plurality of pistons and cylinders, each piston having forward and reverse faces of different areas, the ratio of said areas for each` piston being different from said' ratio for each of the other pistons, means` for constantly supplying liquid under auniform pressure to thereverse faces of said pistons, and means for intermittently supplying liquid to the forward faces of said pistons and building up the pressurev thereof to, equal said uniform pressure.

2f. In. hydraulic' mechanism, a plurality of pistons and cylinders, each pistonv having forward and reverse faces of: different areas, the ratic of said areas for each piston being different from said ratio. for each ofl they other pistons, means for constantly supplying liquid under a uniform pressure to the, reverseY faces of said pistons, means for intermittently supplying liquidto thefQlWard faces of said; pistons andbuilding,

said last named means for intermitt ing the pressure in said cylinders adjacent said forward faces.

3. In hydraulicmechanism, a plurality of pistons and cylinders, each piston having for- 6 ing to supply liquid to all of said forward faces simultaneously.

GUNNAR R. C. MARTINSSON.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date Loudon Nov. 30, 1909 Howse July 3, 1923 Chappell et al. May 19, 1925 Ernst Apr. 30, 1935 Niven et al. Apr. 11, 1939 Kline July 6, 1943 Harrington Oct. 5, 1943 Price Oct. 23, 1951

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