US3443586A

US3443586A - Four-way change-over device for hydraulic installations

Info

Publication number: US3443586A
Authority: US
Inventors: Helge K Christensen
Original assignee: Danfoss AS
Current assignee: Danfoss AS
Priority date: 1966-06-07
Filing date: 1967-06-07
Publication date: 1969-05-13
Anticipated expiration: 1986-05-13
Also published as: DK134918B; DE1550187B1; DK134918C; GB1154689A

Description

y 1969 I H. K. CHRISTENSEN 3,443,586

FOUR- WAY CHANGE-OVER DEVICE FOR HYDRAULIC INSTALLATIONS Filed June 7, 1967 Sheet of s ,jjigil INVENTOR. //L 6 h. ("Aw/J TEA/SEN May 13, 1969 FOUR-WAY CHANGE-OVER DEVICE FOR HYDRAULIC INSTALLATIONS .Filed June 7, 1967 H. K. CHRISTENSEN Sheet 7 42 W I II I j v A //Z% %/ALW C) O O O O 3 7 I L! 3 I INVENTOR. f aez fffs e/snm/aa/v H. K. CHRISTENSEN 3,443,586

' FOUR-WAY CHANGE-0VER DEVICE FOR HYDRAULIC INSTALLATIONS Filed June 7, 1967 Sheet i of 3 INVENTOR. H5465 hf (H/W: TEA/JEN United States Patent 50,258 Int. Cl. F16]: 11/02; F010. 21/14 US. Cl. 137-59612 14 Claims ABSTRACT OF THE DISCLOSURE The invention is a control for a hydraulically operated motor which in general facilitates changing the direction of operation of the motor and provides a neutral position. In addition, the control has a manual and an automatic throttling function for controlling the speed of the motor and for controlling the volume and pressure of the pressurized fluid delivered to the motor.

More specifically the invention relates to a four-way change-over device, for hydraulic installations comprising a delivery pipe, a return pipe and two working ducts which lead to the hydraulic machine via change-over orifices.

Such change-over devices are necessary, in order to achieve dynamic reversal for a hydraulic machine, for example a motor. To achieve this purpose, in a first working position the delivery pipe is connected to one of the working ducts, and the return pipe to the other working duct, where-as in a second working position these connections are reversed. Frequently the change-over devices can be switched to neutral in which position the delivery pipe and the return pipe are connected to one another through a bypass duct.

Conventional change-over devices merely perform a change-over function. If, in addition to this, the volume of flow which passes through the hydraulic machine is to be varied, for example in order to control the speed of the motor, a throttle valve is used which is inserted in the delivery pipe. However this throttle varies the pressure characteristics in such a way that linear control is not possible. Besides, several manipulations are necessary to operate the hydraulic machine. If the change-over device is operated while the motor runs, the latter, or parts connected thereto, may suffer damage due to the forces of inertia. Moreover, the number of connecting pipes and of connections rises with the number of devices used, so that the lay-out of the hydraulic installation becomes more complicated. This is an important consideration in view of the fact that, in addition to the above-mentioned switching and control devices, usually also safety devices are provided, for example an overpressure valve inserted between delivery pipe and return pipe, and a non-return valve shunting the change-over device.

The present invention has for its object, to obviate the above-mentioned disadvantages entirely or partly.

The invention is based on a four-way change-over device of the type referred to and is characterized by a bypass duct effective in the working position of the de vice, a throttle device being incorporated in the said bypass duct which can be varied in dependence on the change-over displacement in such a way that the throttle resistance increases as the clearance of the change-over orifices is enlarged. Preferably the bypass duct is of a type such as used in known change-over devices, where it is operative in the neutral position.

In this way a device is obtained which not only performs a change-over operation but also enables the volume of flow to be controlled. The further the change-over ice device is displaced from neutral, the more effectively will the bypass duct be throttled, Le. a larger volume of working fluid is directed towards the machine. Actuation of the device is by a single manipulation such that when this manipulation is effected by way of a continuous displacement, the volume of working fluid fed to the machine varies continuously from a positive maximum to a negative maximum. The direction of flow is reversed when the volume of flow is near zero, so that the moments of inertia during reversal are low. Furthermore, control via the bypass duct makes it possible to achieve a substantially linear volume variation for the working fluid during the adjustment. Finally, the device of the invention oper-ates with only four connections. No pipes are needed between the change-over device and a separate flow control device.

In a preferred embodiment of the invention the throttle resistance, or at least part of this resistance in the bypass duct is variable also in dependence on the pressure drop of the working fluid in the bypass duct. This has the effect of improving the linearity of the flow volume characteristic. In particular, the throttle device in the bypass duct may be provided with a pressure-dependent throttle point in series with a shift-dependent throttle point. In that case the two throttle functions are clearly separated and can each be easily calculated, designed and adjusted apart from one another.

In this context it may be advisable to let the pressuredependent throttle consist of two control orifices in front of and behind a control pressure chamber both of which orifices close as the pressure drop increases, and to control this throttle point in dependence on the pressure drop at the control orifice behind this chamber and at the series-connected, shift-dependent throttle.

The design is simplified if the change-over device is a rotary slide in the case of which not only the orifices required for the change-over function, but also the orifices for the shift-dependent throttle of the bypass duct are provided on the control surface, for example on the circumference. As -a result of the displacement from neutral the cross-sectional area of the change-over orifices is increased, whereas the cross-sectional area of the throttle orifices provided on the same control surface is reduced.

In further development of the invention the rotary slide may be a cylindrical hollow element in the cavity of which the pressure-dependent throttle is arranged. This embodiment offers the further possibility of accommodating in the cavity also an overpressure valve and/or a non-return valve. This possibility exists not only because the cavity offers sutficient space for this purpose, but also because all ducts required for the connection of these valves converge in the device. If this concept is carried to its extreme, a single device between pump and machine which caters for all switching, control and safety arrangements will be sufficient, and this constitutes a considerable simplification in the lay-out and assembly of the hydraulic installation.

In a preferred embodiment the change-over device is designed in such a way that, in known manner, the control surface of one part of the rotary slide is provided with first and second orifices, for example longitudinal grooves, which, in circumferential direction are alternately connected with the delivery pipe and the return pipe, while the control surface of the other part of the rotary slide is provided with first and second orifices on lines axially displaced relative to one another of which the orifices on one line communicate with one of the working ducts and the orifices on the other line with the other working duct but which are displaced relative to one another by the circumferential division of the orifices of the other part (change-over orifices), and that in the control surface of one part of the rotary slide there are provided third orifices communicating with the delivery pipe which cooperate with third orifices on the control surface of the other part of the rotary slide and are connected to the return pipe, their largest cross-sectional area becoming available in the neutral position (shift-dependent throttle).

For the actual construction of the pressure-dependent throttle we recommend a spring-loaded, hollow plunger provided in the cavity of the inner component of the rotary slide, which is axially displaceable and envelops the control pressure chamber and is influenced by the discharge pressure as well as by the higher pressure in the control chamber and which is provided in its wall with first control orifices cooperating with ducts in the inner rotary slide component so as to constitute the pressuredependent throttle, the said ducts communicating with the shift-dependent throttle and the return pipe. The wall of the plunger may be provided with second control orifices cooperating with ducts in the inner rotary slide component so as to provide a further pressure-dependent throttle, the said ducts communicating with the delivery pipe.

In an embodiment giving a very short axal length provides for the third orifices of one of the rotary slide components to be arranged axially in line with the first orifices and on the same circumferential line as the ends of the second orifices.

In further development of the invention the case of the rotary slide may be a cylindrical insert situated in a fixed case, the latter case being provided with the connections. Such an insert can be much more easily machined than the case itself. Besides, also a rotary-slide casing which is already available for other purposes may be used in which case adaptation of the fixed rotary-slide compo nent is achieved by the design of the cylindrical insert.

Advantageously, a peg passes through radial apertures in the case, in the cylindrical rotary-slide insert and in the interior rotary-slide component, the apertures in the inner rotary-slide component being of a size permitting of a limited angular displacement of the latter component relative to the cylindrical rotary-slide insert or the case. In such an arrangement the peg serves not only as a fixing means, but also limits the angular displacement between the two rotary-slide components, i.e. it determines the range of displacement.

One embodiment of the invention is characterized by an open sector in the inner as well as the outer rotary-slide component, both sectors having substantially the same angle, and by a volute spring with two bent ends which engage the open sectors and, in the relaxed condition, enclose a slightly larger angle, one of the ends being led through the spring coil into the plane of the other. Such a spring is of short axial length and holds the two rotaryslide components in their neutral position with a slight bias. The rotary slide can be turned against the force of the spring in one or the other direction, the loading of the spring being the same in each direction.

The invention will now be described in further detail with reference to an embodiment thereof given by way of example and illustrated in the drawings. There are shown 1n:

FIG. 1 a fiow diagram of a hydraulic installation comprising the device of the invention;

FIG. 2 the device of the invention in plan view, without end plate and bolts;

FIG. 3 the device of the invention in longitudinal section, mainly along the vertical centre line and, only in the upper part at the level of line A-A, through the connections for the delivery and return pipes;

FIG. 4 a cylindrical rotary-slide insert in plan view;

FIG. 5 the inner rotary-slide component in elevation;

FIG. 6 the inner rotary-slide component in vertical section;

FIG. 7 a development of the control surface of the inner rotary-slide component (outer circumference);

FIG. 8 a development of the control surface of the rotary-slide insert (inner circumference);

FIG. 9 a part-sectional view along the line BB of FIGURE 3, and

FIG. 10 a side view of a return spring.

The flow diagram of FIGURE 1 shows a pump 1 which is driven at constant speed by a motor 2 and conveys working fluid to the device of the invention 4 via a delivery pipe 3. From this device a return pipe 5 is taken to the reservoir 7 via a filter 6. A hydraulic machine 8, for example a motor, is connected to the device 4 through two working ducts 9, 10. The device 4 is therefore provided with a connection 11 for the delivery pipe 3, a connection 12 for the return pipe 5, and two

connections

13, 14 for the working ducts 9, 10. From the device 4 projects a rotatable shaft 15 by means of which the working fluid passing through the motor can be controlled as regards its volume of flow and also its direction.

The device of the invention comprises a case 16, shown in FIGURE 2 in plan view, which is provided with the delivery pipe connection 11, the return pipe connection 12, and the two working

duct connections

13 and 14. The casing comprises an axially symmetrical cavity 17, indicated by broken lines, of which only section 18 and section 19, the latter with a somewhat enlarged diameter, are relevant to the invention. From the four connection points 11-14, four ducts 20-23 lead to the cavity 17 in such a way that duct 21 terminates in section 19, whereas duct 20 terminates at the opposite end of section 18, and the

ducts

22, 23 terminate at dilferent points of a central region.

In the

cavity sections

18, 19 is inserted a rotary-slide insert 24. At its outer circumference it is provided with four circumferential grooves 25-28 at an axial distance from one another such that the circumferential groove 25 communicates with the duct 20, the circumferential groove 26 with the duct 22, the circumferential groove 27 with the duct 23 and the circumferential groove 28 with the duct 21. Consequently, the circumferential groove 25 communicates with the delivery pipe, the circumferential groove 26 with one of the working ducts, the circumferential groove 27 with the other working duct and the circumferential groove 28 with the return pipe. The change-over functions are performed by the first orifices 29 in the circumferential groove 26 and the second orifices 30 in the circumferential groove 27. Throttling within the bypass duct is effected by the third orifices 31 in the circumferential groove 28. The orifices 32 in the circumferential groove 28 and the orifices 33 in the circumferential groove 25 merely pass liquid and have no proper control function of their own.

The inner rotary-slide component 34 (FIGS. 5 and 6) consists of a cylindrical hollow body whose cavity comprises essentially a large-diameter section 35 and a smalldiameter section 36. To the holder 37 may be attached a handle 15 for rotation. The outer diameter of the rotaryslide component 34 which, together with the inner circumference of the insert 24 constitutes the actual control surface, is provided with first orifices in the shape of longitudinal grooves 38 and, displaced relatively thereto in circumferential direction, second orifices in the shape of longitudinal grooves 39 all of which function in the change-over operation. Furthermore, third orifices 40 are provided as terminations of the ducts 41 which participate in the throttling function. The orifices 40 are arranged in line with the longitudinal grooves 38 and on the same circumferential line as the ends of the longitudinal grooves 39. A circumferential groove 42 enables distribution of the pressure fluid in the longitudinal grooves 38. Bores 43 lead from the circumferential groove to the extreme front section of the cavity of the rotary-slide component 34. From the longitudinal grooves 38, bores 44 lead to the section 35 and bores 45 to the section 36. From the longitudinal grooves 39, bores 46 lead to the section 35. The inner terminations 47 of the duct 41, and 48 of the duct 45, are identified here, because they participate in the pressure-dependent throttling operation. Finally, a bore 49 connects the left end of the cavity 36 with return pressure in the section 19 of the casing.

Inserted in the cavity section 36 is a hollow plunger 50, loaded at one end by a spring 51 and the return pressure prevailing in the chamber 52 and, at the other end, by the pressure prevailing in the control pressure chamber 53. In the wall of the plunger 50 is provided a first control orifice in the shape of a circumferential groove 54 and a second control orifice in the shape of a circumferential groove 55. Both these circumferential grooves communicate with the control pressure chamber 53 via bores 56, 57. The first control orifice 54 cooperates with the orifices 47 of the ducts 41, being the first pressure-dependent throttling point, whereas the second control orifice 55 cooperates with the orifices 48 of the ducts 45, being the second pressure-dependent throttling point.

Inserted in the cavity section 35 is an overpressure valve 58 which may be of any desired type and which opens when the pressure between delivery pipe and return pipe exceeds a predetermined value. In the present case a cartridge is used which causes any overpressure which may exist in the chamber 80 to displace a first valve element 59 against the force of a spring. The pressure which then builds up underneath the actual valve element 60 lifts the latter from its seat 61. The whole assembly is held in the rotary slide 34 by means of a retainer 62.

As becomes apparent from FIG. 9, the right-hand end face of the case 16 is provided with a recess 63 at each one of opposite points in which a peg 64 is placed during assembly. This peg is fixed by the end plate 65 of the housing when the latter is secured by means of screws 66. The peg passes through two recesses 67 provided on the end faces of the insert 24, and through two open recesses 68 on the end face of the inner rotary-slide component 34, the said recesses being of enlarged, sector-shaped crosssection. The angular displaceability of the rotary-slide section 34 is thus limited relative to the insert 24. Furthermore, the two rotary-

slide components

24, 34 are provided with sector-shaped recesses, 69, 70 at their end faces which enclose an angle of substantially the same value. The two ends 71, 72 of a volute spring 73 apply themselves to the walls of these recesses, forcing the rotaryslide component 34 into its neutral position, while allowing it to be turned against the force of the spring. When the spring 73 is relaxed, the two ends 71, 72 enclose a slightly larger angle than that determined by the sector shaped recesses 69, 70. The spring end 72 is taken into the plane of the other end 71 through the spring coil itself. The spring 73 is likewise prevented from dropping out by the peg 64.

To explain the operation of the device, I refer to FIGURES 7 and 8 which show developments of the outer circumference of the inner rotary-slide component 34 and of the inner circumference of the insert 24. For the purpose of the embodiment illustrated here it should be assumed that the several control orifices are distributed three times over the circumference, i.e. that they are spaced apart from one another by an angular distance of 120. The component 34 is rotatable relative to the component 24 in the directions indicated by the double-arrow P.

Through the orifices 33, fluid is fed at pump pressure to the circumferential groove 42 and the longitudinal grooves 38. With the device in the neutral position, the

orifices

31 and 40 of the throttle assembly coincide, whereas the

longitudinal grooves

38 and 39 are situated every time between the

orifices

29 and 30. Therefore the entire volume of fluid delivered by the pump passes via the longitudinal grooves 38, the bores 45, the pressure-dependent throttle 48, 55, the control pressure chamber 53, the pressure-dependent throttle 54, 47, the duct 40 and the completely open, shift-

dependent throttle

40, 31 towards the return connection. When the slide component 34 is rotated a little, the longitudinal groove 38 begins to communicate with one of the

orifices

29, 30, while the longitudinal groove 39 begins to communicate with the other orifice. Therefore an amount of pumped fluid which depends on the size of the change-over

clearances

38, 29 and 39, 30 is now enabled to pass to the motor. At the same time, the clear cross-section of the shift-

dependent throttle

31, 40 has become reduced, so that in the bypass duct an increased throttle resistance becomes operative. Consequently, the pressure drop across the bypass duct remains substantially constant, notwithstanding the reduced volume of working fluid passing through it, while the working pressure remains substantially constant. This mode of operation does not depend on whether the slide component 34 is rotated clockwise or anticlockwise. The longitudinal grooves 39 communicate in each case with the return side through the orifices 32.

Apart from the shift-

dependent throttle

31, 40, I have still to consider the pressure-

dependent throttle

48, 55 and 47, 54 in the bypass duct. As the pressure drop across the two

throttles

47, 54 and 48, 55 increases, the plunger 50 is displaced towards the left. In this way, the throttle resistance of the pressure-dependent throttle 48, 55 grows, so that the pressure drop across the pressure-dependent throttle 47, 54 and across the shift-

dependent throttle

31, 40 remains substantially constant. However, as the pressure rises, also the throttle resistance at the throttle 47, 54 is increased. This is to compensate for the fact that, with increasing pressure, the leakages of the hydraulic devices increase, so that, if the desired output is to be maintained by the device, it becomes necessary to pass a somewhat increased amount of working fluid through the machine than would correspond to a linear rise.

When overpressure occurs between the delivery pipe and the return pipe, the overpressure valve, 58 opens. The principle of the invention can of course also be applied to a rotary slide in which the end faces are used as control surfaces. It would also be possible to employ a flat slide, or to couple the displacement of the changeover valve with an adjustment of the throttle resistance in a bypass duct in some other way.

I claim:

1. A four way change-over fluid pressure control device of the type having inlet and outlet ports and two control ports which are alternately connectable to opposite ports of a hydraulic load device such as a motor, comprising rotary valve control means having passages for selectively and alternately connecting said control ports to said inlet and outlet ports in a graduated rnanner from fully closed to fully opened positions, bypass means between said inlet and outlet ports, and throttle means in with said bypass means operable in response to said control to gradually increase the resistance of said bypass means as said control ports are opened by said control means.

2. A fluid pressure control device according to claim 1 wherein said control means has a neutral P sition and said bypass means connects said inlet and outlet ports to provide fluid flow therebetween when said control means is in a neutral position.

3. A fluid pressure control device according to claim 1 having second throttle means in with said bypass means for providing additional fluid flow resistance in response to an increase in the pressure drop of the fluid flowing in said bypass means.

4. A fluid pressure control device according to claim 3 wherein said first and second throttle means are arranged in series and said second throttle means is shiftable relative to said control means.

5. A fluid pressure control device according to claim 4 wherein said second throttle means is on the upstream side from said first throttle means and has a chamber with inlet and outlet control orifices communicating with said inlet port when said control means is in a neutral position and said orifices are gradually closed as said second throttle means is shifted relative to said control means.

6. A fluid pressure control device according to claim 1 wherein said control means includes a rotary slide valve having on the circumference thereof passages for selectively supplying and exhausting fluid to and from said control ports and having upstream and downstream axially spaced sets of orifices forming a part of said first and second throttle means.

7. A fluid pressure control device according to claim 6 in which said rotary slide valve has a cylindrically shaped bore portion in which said second throttle means is slidably disposed.

8. A fluid pressure control device according to claim 7 wherein said rotary slide valve has a second cylindrically shaped bore portion, and a pressure relief valve disposed in said second bore portion which is operative when the pressure difference of the fluid in said inlet and outlet ports exceeds a predetermined value.

9. A fluid pressure control device according to claim 6, said fluid pressure control device comprising a casing defining a cylindrically shaped cavity, an annularly shaped valve member fixedly disposed in said cavity and having a bore in which said rotary slide valve is slidably disposed, said passages of said rotary slide valve comprising two sets of alternately and circumferentially arranged axially extending grooves with said sets being in respective fluid communication with said inlet and outlet ports, said annularly shaped valve member having two sets of orifices which are axially and circumferentially spaced from each other and which have respective fluid communication with said control ports, said annularly shaped valve member having a third set of orifices communicating with said outlet port and said downstream set of throttle orifices of said rotary slide valve, said third set of orifices being fully aligned with said downstream set of throttle orifices when said rotary slide valve is in its neutral position.

10. A fluid pressure control device according to claim 7 in which said second throttle means has the form of a hollow plunger closed at one end thereof, spring means in said cylindrically shaped bore portion of said rotary slide valve for biasing said plunger in an axial direction against the fluid pressure differential existing between the fluid flowing from said inlet port to said outlet port, said plunger having a first set of orifices in the wall thereof which cooperate with said upstream set of orifices of said rotary slide valve and said inlet port to effect increased and decreased throttling of the inlet fluid in response to axial movement of said plunger.

11. A fluid pressure control device according to claim 10, where said plunger has a second set of orifices in the wall thereof having communication with said downstream set of orifices of said rotary slide valve and said outlet port to effect increased and decreased throttling of the inlet fluid in response to axial movement of said plunger.

12. A fluid pressure control device according to claim 9 in which said downstream set of orifices of said rotary slide valve are arranged axially in line with said set of grooves which are in fluid communication with said inlet port.

13. A fluid pressure control device according to claim 1 wherein said control means comprises a rotary slide valve having a neutral position, means for limiting the angular displacement of said valve in opposite directions from said neutral position to effect the selective and alternate supplying and exhausting of fluid to and from said control ports.

14. A fluid pressure control device according to claim 13 in which spring means are provided to maintain said rotary slide valve in its neutral position.

References Cited UNITED STATES PATENTS 1,947,973 2/1934 Davis l3'7625.24 2,239,139 4/1941 Allin 137--596.l2 XR 2,499,425 3/1950 Stephens 137596.l2 2,607,558 8/1952 Wright l37596.12 XR 2,893,357 7/1959 Clarke 137596.l2

HENRY T. KLINKSIEK, Primary Examiner.

US. Cl. X.R. l37--625.24