US2919680A

US2919680A - Piston-slide control valve for hydraulic presses

Info

Publication number: US2919680A
Authority: US
Inventors: Hans Scharringhausen
Original assignee: Scharringhausen Maschb Ges M B
Current assignee: Scharringhausen Maschb Ges M B; Scharringhausen Maschinenbau GmbH
Priority date: 1953-11-30
Filing date: 1954-11-30
Publication date: 1960-01-05
Anticipated expiration: 1977-01-05
Also published as: NL88915C; DE1007627B

Description

Jan. 5, 1960 H. SCHARRINGHAUSEN 2,919,630

PISTON-SLIDE CONTROL VALVE FOR HYDRAULIC PRESSES Filed Nov. 50, 1954 2 Sheets-Sheet 1 Ila INVENTOR HANS SOHARRINGHAUSEN 6" BY .Jm {I g ATTORNEYS Jan. 5, 1960 H. SCHARRINGHAUSEN Filed NOV. 30, 1954 2 Sheets-Sheet 2 Fig. 2.

.55 am 450x 54 Mb 131 I44 54 m 23 I4 g 55 m 55 2| 55 1421 52 454 II: 21s 3 21d- 52/ 2/0 [Z 141 a, 5) 2 1b 5| 121 am 4;

INVENTOR.

HANS SCHARR/NGHAUSEN BY Wm -Wnin ATTORNEYS United States PISTON-SLIDE CONTROL VALVE FOR HYDRAULIC PRESSES Hans Scharringhausen, Merlrlingen (Weser), Germany,

assignor to Scharringhausen Maschiuenbau Gesellschaft m. b. H., Rheinsheim, Germany Application November 30, 1954, Serial No. 472,031

Claims priority, application Germany November 30, 1953 8 Claims. (Cl. 121-465) velocity shall approach the theoretical value.

It is a further object of this invention to provide an improved type of control valve in machines of the aforesaid type, wherein the regulating velocity is increased during the working stroke.

It is another object of the invention to provide for a control valve of the piston-slide valve type which allows for an increased quantity of working fluid to pass there through in the time unit without decreasing the sensitiveness of control of the machine with which it is applied, on the one hand, and without increasing the working stroke velocity and the diameter of the control piston on the other hand.

It is already known to use control valves of the piston slide type with hydraulic presses such as plate working machines having several pressing cylinders. These control valves are usually arranged between the supply source for the pressure medium, such as, for instance, a

high pressure oil pump having a pressure oil tank connected thereto, and the pressure cylinders carrying out the working operation. Control valves of this kind may control the flow of the pressure medium to and from either one single or several working cylinders, depending on the manner of their being arranged in the flow system. In the first case one single piston edge, or both piston edges, i.e., the upper and the lower edge, and in the second case, usually both piston edges, are utilized as steering edges in the valve cylinder. The control pistons are moved by any kind of steering mechanism suitable for this purpose and free or close the passage for influx or outflow of the pressure medium to a greater or smaller degree, thereby controlling the movement of the pistons in the working cylinders.

The working pistons may either be single acting, in which case the return movement of the pressure tools is effected by strong springs, or by special so-called return pistons, or they may be double acting and may effect the return movement themselves.

My invention is based on observations made with double acting working pistons. The upper piston face of such double acting pistons comprising the surface F upon which the pressure medium is acting during the working stroke is known to be substantially larger than the bottom face of the piston having the area F which is acted upon during the back stroke, because the face surface of the latter is diminished by the cross section of the piston rod connected with the piston. On the basis of well known hydraulic laws, the piston velocity during the back stroke, V must be greater than the piston velocity during the working stroke, V according to the atent ice reciprocal ratio of the piston surfaces, if the same pressure of, for instance, atmospheres excess pressure, or more, is acting upon the piston during both movements. Thus, if for instance In a hydraulic press brake or folding press having this ratio of piston surfaces, the practical values found were V =1.9 and V,-=2.1

meters per minute instead of the theoretical values of V =2 and V,=4

- I have further made the unexpected observation that it is also too low during the working stroke. I have discovered in principle a hitherto unknown disadvantage which is common to all piston slide control valves in which the control edges of the piston open annular channels of only very small cross section in the cylinder walls of the valves in order to achieve the highest possible sensitive ness of regulation, which piston edges often open gaps of only a small fraction of a millimeter where extreme sensitiveness of control is required. The hydraulic resistance offered by these narrow annular channels and grooves is, however, so great that it causes a strong braking effect on the flow velocity of the pressure meter. Furthermore, the special kind of pumps which are particularly suitable for use with hydraulically driven plate .working machines have unfavorable characteristics insoso that the working piston velocity and together therewith the working velocity of the entire machine remains smaller than is warranted by the construction of the machine.

It must furthermore be avoided to increase either the diameter, or for instance the back stroke velocity for which the control valve pistons have been laid out, although these would be two ways of increasing the flow cross section'for some or all Working strokes. An increase of the cross section is undesirable since experience has shown that this deteriorates the guidance of the control piston in the valve and makes manufacture of the valve as a whole considerably more expensive. It is, on the other hand, undesirable to increase the back stroke velocity since the control valve pistons 'are usually guided depending upon the position of the tool so that no differences between the movements and/or velocities of the control valve piston during the working stroke and the back stroke are possible.

Finally, it is necessary to maintain a great sensitiveness of regulation so that it is not possible to cut off the flow of pressure medium completely at certain positions by, for instance, a short travel of the control piston. It is rather to insure such sensitiveness of regulation that grooves and channels of a very small diameter are used in the walls of the control cylinders. For the same reason an increase in the diameter of these grooves and channels Patented Jan. 5, 1960 i in the direction of the piston movement is not feasible as a means of overcoming the observed disadvantages.

My invention solves this problem by providing the piston slide of the control valves in the aforesaid and similar cases, with a plurality of control edges and with a corresponding plurality of channels and grooves for the influx and outflow of the pres e medium, which channels and grooves are connected with each other by means of annular feeding and outflow channels, thus replacing the hitherto used single influx and outflow channels for the passage of the pressure means, and the single control edge opening or closing them. Thereby 1 maintainvunchanged on the one hand the high sensitiveness oflregulation, and on the other hand the velocity as Well as the diameter of the control piston, while I nevertheless achieve a considerably reater cross section for the passage ot" the pressure medium. My invention thus achieves an increased regulating velocity at the working stroke as well as the theoretical value of piston velocity at the back stroke.

This invention will be more clearly understood upon reference to the following specification taken in conjunction with the accompanying drawings which explain my invention by way of example in the case of a piston slide control valve which is, for instance, destined for use with a hydraulic folding press.

In the drawings:

Figure 1 represents a schematic view of the arrangement of a piston slide valve control according to my invention, in partial section; and

Figure 2 shows the left hand control piston valve of Figure l in enlarged scale.

Referring to the drawings in detail, the control means comprises as main element (which is usually employed in pairs) two working or pressing cylinders .a and 115, each having a double acting working piston 2a and 21) respectively, and piston rods and 3b, as well as two control cylinders 4a and 25, each having a

control piston

5a and 5b, together with control piston rods 6a and 622 respectively. The piston rods 3:: and 3b engage the pressing or pressure platen of the folding press which is not shown. The control rods 6a and 6b possess at their lower or outer ends racks 7a and 7b respectively which engage control pinions 9a and 9b which are in turn mounted on a common control shaft Th control shaft 8 is preferably mounted on the dis laceable press platen, for instance by means of bearings indicated at Mia and 18b.

The pressure medium, for it stance a pressure oil of 100 atmospheres excess pressure, is supplied from a pressure medium source (not shown) by way of a shiftable main valve 11 and through the conduit 32 to both control cylinders 4a and db, and is returned from the cylinders through the return conduit if). The main valve ll is also represented by way of example as a piston valve. Supplying of the pressure medium, for instance from a pressure tank, takes place way of the check valve 11a provided inthe conduit 12. When the piston 22 of valve 1 moves upwardly the supply of pressure medium is throttled. If the piston 22 moves downwardly, the conduit of the valve is equally interrupted. in its intermediate position, however, the pressure medium supplied from the tank is returned through the valve and in this position of the main valve 11 the working

pistons

2a and 2b remain stationary in their momentary position.

Conduit 12 ends in their

branch conduits

121, 122 and 123 for each control cylinder, and conduit 13 ends in three

branch conduits

131, 132 and 133 for each control cylinder.

As will be seen in detail in Figure 2, the central bore 20 of each control cylinder (4a or 41)) is provided with a number of annular recesses 2la2lp which are distributed at determined distances over the length of bore 2%.

Each. of the aforesaid branch conduits 121, 122 and 123., as well as

branch conduits

131 and 132 end in one of these annular recesses, namely conduit 121 in 2111, 122 in Zia, 123 in 21h, 3131 in 21!, and 132 in 210. Furthermore, two conduits 14a and 14b are provided leading to the top surfaces of the working cylinders, and two conduits 315a 15b lead to the bottom surfaces of the working cylinders in the customary manner. A double check valve or 16b respectively is arranged in each of the conduits 15a and 15b.

Referring againt to Figure 2, the aforesaid conduit 14a is connected to a channel Mil in the control valve cylinder do from which branch channels Mil, 142, 143, 144 and 145 establish communication with annular recesses 21c, 21 211', 21k, and 2111 respectively. On the other hand, conduit 3a is connected to a channel in cylin-- der which communicates by way of branch channels i, 152., 153', and 155 with annular recesses 21a, 21d, Zlm and 21p respectively.

Each long control piston, e.g. piston 5a in Figure 2, comprises a number of lands Sll, 52, 53, 54-, 55 and 5-6 and is provided with

grooves

31, 32, 33, 34 and 35 be-- tween each pair of adiacent lands, thus defining a. plural ity of control edges where each land and groove meet,. which control edges cooperate with corresponding recesses 21a 21p.

Thus the upper control edge 41 formed by land 51 and. groove 31 cooperates with recess 21a; the lower control edge 420 between grove 3i and land 52 cooperates with recess lie, the upper control edge 42b of land 52 cooperates with recess 21d, and so forth.

Branch conduit 133 of return conduit 13 is connected to the top of cylinder bore 28.

The lowermost land 51 in cooperation with the wall portion of bore Zll which it contacts, serves to diminish the pressure on the packing 23 about the control rod 6a, and on the guide bush 17a for the latter.

The great length and the multiple subdivision of the control piston (53:: or 5b) also otters the added advantage-- over a conventional increase in diameter of the piston, that it results in a greatly improved guidance of the pistons in the long cylinder bore 20.

in the embodiment of the control valve according to the invention shown in the drawings, each control piston. is thus provided with five lands and intermediate annular grooves, and consequently possesses ten control edges 41, 42a, -Zb, 43a, 43b, 44a, 44b, 45a, 45b, and 46; and the cylinder wall of each control valve is provided, again by way of a preferred example only, with fifteen annular grooves and corresponding channels in the cylinder block. Five control on the control pistons namely 42a, 43a, l la, 44b and 45b are provided for cooperation with the top surface of the working piston 2a (or 2b) through. opening and closing recesses 141 to M5 respectively; and five control edges, namely ll, 42b, 43b, 45a and 46 cooperate with the bottom surface of the working piston in (or 2b) by opening or closing recesses 151 to 155' respectively. Of these five control edges for each end surface of the working pistons three are for instance, used for controlling the influx of the pressure medium. to, and two for controlling the outflow of the pressure medium from the working pistons. Thereby the hydraulic cross sectional resistance to the pressure medium flow through each control valve is reduced to one-third for the influx and to one-half tor the outflow of the pressure. medium.

In order to remove the pressure medium which has been urged upwardly in the cylinder heads along the. cylinder walls, the cylinder heads are connected by the aforesaid conduits 133 with the return conduit 13. The.

three

lower branch channels

141, 142 and 143 ofchannel 140 leading to the conduit 14a (and in a similar manner. to conduit 14b) serve for feeding the pressure medium.

to the working cylinders la (and 11)) respectively during;

branch channels

151, 152 and 153 which lead to the two conduits 15a and 15b serve for feeding the pressure medium to working cylinder 1a (and 1b) during the back stroke and the two

upper branch channels

154 and 155 serve for withdrawing the pressure medium during the working stroke.

During the first step of operation the cooperating

branch channels

141, 142 and 143 are thus connected in parallel due to a short upward movement of piston 5a, whereby

control edges

42a, 43a and 44a open coordinated annular recesses 21c, 21 and 2li with which they cooperate, and establish simultaneously communication between

conduits

121, 122, 123 and channels 14-1, 142, 143, so as to feed hydraulic medium through conduit 14a to the top surface of working piston 2a.

During this working stroke the piston 2a (or 2b) is thus moved downwardly, pressure medium from below the working piston escaping by way of check valve 16a and conduit 15a and from there through channel 150, control edges 45a and 46 having opened communication from

branch channels

154 and 155 through

recesses

21m and 21p to recesses 21! and 210 and return

conduit branches

131 and 132.

The control edges and annular grooves are so coordinated with each other that (in the case of the embodiment as shown in the drawings) the three parallel feeding recesses 21c, 21] and 211' connected to conduits 14a and 14b) are opened during the working stroke, i.e., when the

pistons

2a and 2b move downwardly, while the two parallel outflow recesses 21k and Ziln connected to conduits 14a (and 1412), as well as the three

parallel feeding recesses

21a, 21d and 21g connected to conduits 15a (and 15b) are closed, while simultaneously the two parallel outflow recesses 21m and 21p connected to the conduits 15a (and 15b) are open. During the back stroke, when the pistons 20 and 25) move upwardly, the opening and closing of the annular grooves takes place in inverted order.

It is a further feature of my invention that all parallel connections, i.e., the connecting channels of the annular grooves are located in the cylinder body of the control valves. This requires the casting of a body having the corresponding number of channels, but it has the advantage of great safety against pressure and permits an easy mounting of the control valves in the machine. The internal channels in the control valves are preferably arranged in different planes. In the drawings the channels are all shown as being arranged in the plane of the drawings for drawing purposes only. However, the interruption of the channels leading from the

conduits

12 and 13 to the annular grooves is intended to show that the channels are to be arranged in different planes. The last-named channels should be arranged, for instance, in a plane perpendicular to the plane of the drawings. It is also indicated in the drawings that the channels through which the pressure medium passes in the same direction, i.e., on the one side the channel connected to

conduits

12 and 13, should in practice be at a level providing the necessary sealing effects of the lands of the pistons above the level of the channels connecting the

conduits

14a, 14b, 15a and 15b respectively. Thus in an arrangement of this kind the shortest possible length of the passages through the valves, and correspondingly the lowest possible flow resistances are obtained.

The method of a diflerentiated feeding of the pressure medium to two or more working cylinders of hydraulic presses and similar machines, which can be carried out with the aid of control valves according to my invention in a particularly advantageous manner, is known as such and need not be described in greater detail. It allows to feed the pressure medium to each Working cylinder under such pressure and in such quantity that the resulting factor of pressures exercised by the hydraulic cylinders coincides with the resulting factor of the counterforce exercised by the pressed working piece. This 6 allows in particular to achieve a parallel and straight guidance of the press platen or other similar tools of hydraulic machines free of binding. The control arrangement according to the embodiment as shown in the drawings provides for the following operation: the piston rods 6a and 6b, and together therewith the

control pistons

5a and 5b are at first adjusted according to the desired control operation. The pinions a and 9b connected with the control shaft 8 are idle at this stage. However, as soon as the pressed platen, which is assumed to be connected to the control shaft 8 adopts an oblique position, one of the pinions will adopt a twisting angle against the other and will adjust its corresponding rack 7a or 7b and together therewith the piston rod 6a or 6b and the control piston 5a or Sb in such a manner that the excessive advance of the

corresponding working piston

2a or 2b is stopped by a corresponding regulation of the influx of pressure medium, until the pressed platen has been readjusted to a straight position. During this adjustment the annular feeding grooves in the one control valve are opened more, while they are partially or completely closed in the other valve. The operation of the entire control arrangement takes place without any complicated insertion of levers, rod mechanisms, or other organs, thus being automatic and at the same time particularly sensitive. The means indicated at 18a and 18b serve for the longitudinal adjustment of the control piston rods 6a and 6b in order to achieve an exact ad justment of the central or starting position of the

control pistons

5a and 5b relative to each other and to their driving means.

Each control piston of the main valve 11 thus reciprocates between two extreme positions. In each of the latter positions, one annular recess is closed entirely by a piston land. In the lowermost position of the piston the upper annular recess (21p) is closed, and in the uppermost piston position the lowest annular recess (21a) is closed.

In both extreme positions the pressure medium rises past the ball in the check valve 1111 into the conduit 12 and therethrough to the control valves; if, however, the control valve pistons are in central position, the pressure medium can be returned directly to the oil tank (not shown). The check valve 11a thus serves to withdraw the pressure medium from the control valves when the control pistons are in central position, and to feed pressure medium to the control valves when the control pistons are in an end position either during upward or downward movement of the working pistons.

A special advantage of my invention resides in the fact that through providing a plurality of control edges on the control valve pistons, heating of the pressure medium is avoided. Such heating occurs frequently through friction of the pressure oil, if only one control edge is available, as is the case in the hitherto known valves. Heat of the pressure oil above F. may cause the oil to be decomposed or saponified and thus to become unsuitable for further use. This will not occur in control valves according to my invention.

The control valves according to my invention may be constructed in a variety of manners and may also be arranged differently from the embodiment shown in the drawings, which has been used as an explanatory example only. In a simplified form, a control valve according to my invention may also be used for controlling machines having only single acting working pistons.

I claim:

I. A piston-slide control valve for use with hydraulic presses and the like, having several pressing cylinders with double-acting working pistons, said valve comprising a cylinder body having a bore therein, a plurality of annular recesses in said bore, a control piston reciprocatingly mounted inside said bore and comprising a plurality of alternate lands and annular grooves forming a first number of control edges on said control piston for opening simultaneously during a given movement of said control piston certain of said recesses and a second number of control edges for closing the remaining recesses and invertedly closing the former and opening the latter recesses during a movement of the control piston in opposite direction, and a number of channels corresponding to the number of said recesses and connecting the latter with conduits for feeding and withdrawing the pressure medium for said pressing cylinders; each of said opening control edges being disposed with regard to the next adjacent one at a distance equal to the distance between those annular recesses cooperating with said opening control edges, thereby causing all of said opening control edges to cooperate simultaneously with said annular grooves so as to open parallel paths therethrough, and all of said closing control edges cooperating with said annular recesses to close such paths simultaneously.

2. A control valve according to claim 1, wherein several of said annular recesses inside said cylinder bore are connected in parallel at a determined distance from one another for feeding the pressure medium, and that separately therefrom the remaining annular recesses are connected in parallel and at said determined distance from one another for withdrawing the pressure medium.

3. A control valve according to claim 1, wherein all of said annular recesses and channels conducting the flow of pressure medium to and from the head surface of said double-acting working cylinders are separate from all of said annular recesses and channels serving the tail end of said double-acting Working pistons.

4. A control valve according to claim 1, wherein said annular recesses and channels are divided into a first and a second group, a first joint conduit being provided for connecting said first group of annular recesses and channels with the head surface of said double-acting working pistons, and a second joint conduit being provided for connecting said second group of annular recesses and channels with the tail surface of said working pistons.

5. A control valve according to claim 4-, wherein all said channels are arranged inside said cylinder body of said valve, said channels being provided in different planes through the axis of said cylinder, each pair of a feeding and a corresponding withdrawing channel being arranged on opposite sides of said bore with regard to one another, in planes spaced only by the distance required for sealing by said control piston lands.

6. A control valve according to claim 4, wherein the total number of said control edges is ten and wherein five of said control edges are provided by certain lands on said control piston for controlling the flow of pressure medium to and from the head surfaces of said working pistons, and five other control edges are provided by certain lands on said control piston for controlling the flow of pressure medium to and from the tail surfaces of said working pistons, three of the former and three of the latter control edges controlling the flow of pressure medium to said working pistons, and two of the former as well as two of the latter control edges controlling the flow of pressure medium from the same.

7. A piston slide control valve for use with a hydraulic press having at least one pressing cylinder with a doubleacting piston therein, a source of hydraulic pressure fluid, and connecting lines from said control valve to said pressing cylinder and from said valve to said source of hydraulic pressure fluid for the passage of said fluid therethrough, in either direction, said valve comprising a casing having a central bore being closed at both ends, and a plurality of annular recesses in the wall of said bore, a control piston disposed for reciprocating movement in said bore, said piston comprising several lands and annular grooves therebetween, each land and adjacent groove forming a circumferential control edge of said piston, and a plurality of channels in said casing connecting said connecting lines with said annular recesses so as to establish communication with determined groups of the latter for the flow of pressure fluid in parallel through the same in a given direction of flow, said annular recesses in the wall of said bore, and said annular grooves of said piston being so distributed over the length of the bore and piston respectively, that by the movement of said piston in a given direction, several of said control edges always open simultaneously communication between certain of said annular recesses and certain of said annular grooves so as to allow the flow of pressure fluid through several parallel paths between said valve and said pressing cylinder, and that by the movement of the piston in the opposite direction, the same control edges always interrupt simultaneously the aforesaid communication.

8. A piston slide control valve for use with hydraulic presses and the like which presses have several pressing cylinders with double-acting working pistons and a source of hydraulic fluid therefor, said control valve comprising a cylinder body having a bore therein, a control piston reciprocatingly mounted inside said bore, a

plurality of first, second and third annular recesses inthe wall of said bore, first conduit means for feeding hydraulic fluid from said fluid source to said valve and comprising a first number of parallel channels opening each into one of said first annular recesses, second conduit means for withdrawing hydraulic fluid from said valve and comprising a second number of parallel channels each opening into one of said second annular recesses, third conduit means for the flow of fluid alternatingly in different direction between said control valve and one of said pressing cylinders, and comprising a plurality of channels each connected to one of said third annular recesses, said control piston comprising a plurality of lands bearing two groups of control edges, one of which groups opens communication between certain of said third annular recesses simultaneously with all of said first and second annular recesses so as to cause fluid flow between said valve and said pressing cylinder in one direction during a given direction of movement of said piston in said valve bore, and the other group opens communication between the other recesses of said third annular recesses simultaneously with all of said first and second annular recesses so as to cause fluid flow between said valve and said pressing cylinder in opposite direction during opposite movement of said piston in said-bore.

References Cited in the file of this patent UNlTED STATES PATENTS