CA1155368A - Single lever operating device for an earth moving machine or the like - Google Patents
Single lever operating device for an earth moving machine or the likeInfo
- Publication number
- CA1155368A CA1155368A CA000368669A CA368669A CA1155368A CA 1155368 A CA1155368 A CA 1155368A CA 000368669 A CA000368669 A CA 000368669A CA 368669 A CA368669 A CA 368669A CA 1155368 A CA1155368 A CA 1155368A
- Authority
- CA
- Canada
- Prior art keywords
- valves
- pressure
- valve
- shuttle
- pilot pressure
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D11/00—Steering non-deflectable wheels; Steering endless tracks or the like
- B62D11/02—Steering non-deflectable wheels; Steering endless tracks or the like by differentially driving ground-engaging elements on opposite vehicle sides
- B62D11/06—Steering non-deflectable wheels; Steering endless tracks or the like by differentially driving ground-engaging elements on opposite vehicle sides by means of a single main power source
- B62D11/10—Steering non-deflectable wheels; Steering endless tracks or the like by differentially driving ground-engaging elements on opposite vehicle sides by means of a single main power source using gearings with differential power outputs on opposite sides, e.g. twin-differential or epicyclic gears
- B62D11/14—Steering non-deflectable wheels; Steering endless tracks or the like by differentially driving ground-engaging elements on opposite vehicle sides by means of a single main power source using gearings with differential power outputs on opposite sides, e.g. twin-differential or epicyclic gears differential power outputs being effected by additional power supply to one side, e.g. power originating from secondary power source
- B62D11/18—Steering non-deflectable wheels; Steering endless tracks or the like by differentially driving ground-engaging elements on opposite vehicle sides by means of a single main power source using gearings with differential power outputs on opposite sides, e.g. twin-differential or epicyclic gears differential power outputs being effected by additional power supply to one side, e.g. power originating from secondary power source the additional power supply being supplied hydraulically
- B62D11/183—Control systems therefor
Landscapes
- Engineering & Computer Science (AREA)
- Automation & Control Theory (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Non-Deflectable Wheels, Steering Of Trailers, Or Other Steering (AREA)
- Operation Control Of Excavators (AREA)
- Control Of Fluid Gearings (AREA)
Abstract
.age 17 SINGLE-LEVER OPERATING DEVICE FOR AN EARTH
MOVING MACHINE OR THE LIKE
ABSTRACT OF THE DISCLOSURE
A steering system for a steer-by-drive vehicle having a control lever operatively connected to a multi-position controller having four valves which control operation of a pair of distributor valves, after one or more of the four valves has been pre-selectively coupled in fluid communication in a hydraulic circuit to operate a plurality of shuttle-valves.
MOVING MACHINE OR THE LIKE
ABSTRACT OF THE DISCLOSURE
A steering system for a steer-by-drive vehicle having a control lever operatively connected to a multi-position controller having four valves which control operation of a pair of distributor valves, after one or more of the four valves has been pre-selectively coupled in fluid communication in a hydraulic circuit to operate a plurality of shuttle-valves.
Description
1 ~5536~
BACKGROUND OF THE INVENTION
This invention relates in general to steering control systems for vehicles and, in particular, to a single lever system for controlling the operation of a vehicle drive mechanism that is located on each side of the vehicle. More specifically, but without restriction to the particular use which is shown and described, this invention relates to a single-lever control system especially suitable for controlling the speed and directional movement of a vehicle having two drive or propulsion units which are mutually exclusively connected to one fo two vehicle drive systems on opposLte sides of the vehLcle.
In the operation of certain types of earthmoving equipment and construction machinery such as crawler vehicles, the vehicle steering is effected by movement of the vehicle. By varying the rotational speed of the crawler drive systems, located on opposite sides of the vehicle, the directional movement of the crawler can be changed. Such steering systems, referred to as steering by driving, have customarily been effected through the operation of two separate control levers which, respectively, controlled the speed and rotational direction of the two drive units.
Such earthmoving machines may have two separate hydrostatic transmissions, each of which controls the operation of one of the drive sprockets which rotate an endless track on each side of the vehicle to support and propel the vehicle over the ground. However, multiple control lever systems require the highest degree of skill from the machine operator, and a long q~
period of experience is necessary in order to control machine operation. The relative position of one lever with respect to the other, as well as the absolute position of each lever, will effect vehicle operation.
5 The proper operation of such machines requires constant attention and a degree of skill acquired through extensive experience.
Therefore, to eliminate some of the problems associated with such two-lever control systems, it is 10 desirable to control the operation of a vehicle by a single control lever which can control both the speed and the rotational direction of the drive units for each side of the vehicle. Such single lever control systems are disclosed in United States Patent Nos.
4,085,812 and RE 27,488. While the systems disclosed in these patents utilize a single control lever to control both the rotational speed and direction of a pair of hydrostatic transmission units, the systems dLsclosed herein require complicated hydraulic circuits. Other examples are United States Patent No.
4,076,090 and German Auslegeschrift 21 33 956 which disclose a hydraulic circuit and single control lever which utilizes a single control lever having a pressure ring which actuates a plunger or a valve to selectively direct pressurized fluid to the hydrostatic transmission. Such complex hydraulic circuitry is both costly and in view of its complexity, susceptible to malfunctions and a higher degree of unreliability.
To overcome such difficulties and to eliminate the necessity of complicated structural linkage systems such as disclosed in United States Patent No. 4,023,636, the present invention was developed.
SUMMARY OF THE INVENTION
It is, therefore, an object of this invention to improve the control of vehicles which utilize two ~ ~5a~S8 separate power drives to effect vehicle movement.
Another object of this invention :is to control the operation of independent power drives to a vehicle through a single control lever.
A further object of this invention is to control the speed and directional movement of an earthmoving vehicle which utilizes separate hydrostatic transmiss:ion drives, by the operation of a single control lever which is effective to control both the vehicle speed and direction of movement in an efficient and reliable manner.
These and other objects are attained in accordance with the present invention wherein there is provided a control lever operatively connected to a 1; multi-position controller having four valves which control operation of a pair of distributor valves, after one or more of the four valves has been pre-selectively coupled :in fluid communication in a hydraulic circuit to operate a plurality of shuttle-valves DESCRIPTION OF THE DRAWINGS
Further objects of this invention together with additional features contributing thereto and the advantages accruing therefrom will be apparent from the following description of a preferred embodiment of the invention which is shown in the accompanying drawings with like reference numerals indicating corresponding parts throughout, wherein:
; Figure 1 is a schematic diagram of a hydraulic circuit incorporating the present invention;
Figure 2 is a perspective view of a single control lever for selectively coupling certain elements of the hydraulic control system into fluid communication;
Figure 3 is a diagrammatic plan v:iew of the positions for the single control lever to effect 1 1~536~
movement of the vehicle;
Figures 4 through 7 are hydraulic schematic views of the fluid flow paths of the operating fluid for the hydraulic circuit of Figure l under various operating conditions; and Figure 8 is a circular diagram of the speed pattern of the two hydrostatic transmissions to better illustrate the resultant output from the hydrostatic transmissions for corresponding positions of the single control lever.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to Figure l, there is illustrated a pair of hydrostatic transmissions 1 and 2 of a type known to those skilled in the art. As is known, the transmissions l and 2 are capable of effecting clockwise and counter-clockwise movement to the tracks of a crawler vehicle for controlling the forward and backward motion of the vehicle and its steering.
Pressurized hydraulic fluid is coupled to each of the hydrostatic transmissions l and 2 through an inlet conduit 3 and is discharged therefrom through an outlet conduit 4 under the control of a slide valve 5 or 6, respectively. Each of the slide valves 5 and 6 is of a pilot fluid operated type wherein a movable valve spool is used to provide a metered flow of hydraulic fluid to the hydrostatic transmissions l and
BACKGROUND OF THE INVENTION
This invention relates in general to steering control systems for vehicles and, in particular, to a single lever system for controlling the operation of a vehicle drive mechanism that is located on each side of the vehicle. More specifically, but without restriction to the particular use which is shown and described, this invention relates to a single-lever control system especially suitable for controlling the speed and directional movement of a vehicle having two drive or propulsion units which are mutually exclusively connected to one fo two vehicle drive systems on opposLte sides of the vehLcle.
In the operation of certain types of earthmoving equipment and construction machinery such as crawler vehicles, the vehicle steering is effected by movement of the vehicle. By varying the rotational speed of the crawler drive systems, located on opposite sides of the vehicle, the directional movement of the crawler can be changed. Such steering systems, referred to as steering by driving, have customarily been effected through the operation of two separate control levers which, respectively, controlled the speed and rotational direction of the two drive units.
Such earthmoving machines may have two separate hydrostatic transmissions, each of which controls the operation of one of the drive sprockets which rotate an endless track on each side of the vehicle to support and propel the vehicle over the ground. However, multiple control lever systems require the highest degree of skill from the machine operator, and a long q~
period of experience is necessary in order to control machine operation. The relative position of one lever with respect to the other, as well as the absolute position of each lever, will effect vehicle operation.
5 The proper operation of such machines requires constant attention and a degree of skill acquired through extensive experience.
Therefore, to eliminate some of the problems associated with such two-lever control systems, it is 10 desirable to control the operation of a vehicle by a single control lever which can control both the speed and the rotational direction of the drive units for each side of the vehicle. Such single lever control systems are disclosed in United States Patent Nos.
4,085,812 and RE 27,488. While the systems disclosed in these patents utilize a single control lever to control both the rotational speed and direction of a pair of hydrostatic transmission units, the systems dLsclosed herein require complicated hydraulic circuits. Other examples are United States Patent No.
4,076,090 and German Auslegeschrift 21 33 956 which disclose a hydraulic circuit and single control lever which utilizes a single control lever having a pressure ring which actuates a plunger or a valve to selectively direct pressurized fluid to the hydrostatic transmission. Such complex hydraulic circuitry is both costly and in view of its complexity, susceptible to malfunctions and a higher degree of unreliability.
To overcome such difficulties and to eliminate the necessity of complicated structural linkage systems such as disclosed in United States Patent No. 4,023,636, the present invention was developed.
SUMMARY OF THE INVENTION
It is, therefore, an object of this invention to improve the control of vehicles which utilize two ~ ~5a~S8 separate power drives to effect vehicle movement.
Another object of this invention :is to control the operation of independent power drives to a vehicle through a single control lever.
A further object of this invention is to control the speed and directional movement of an earthmoving vehicle which utilizes separate hydrostatic transmiss:ion drives, by the operation of a single control lever which is effective to control both the vehicle speed and direction of movement in an efficient and reliable manner.
These and other objects are attained in accordance with the present invention wherein there is provided a control lever operatively connected to a 1; multi-position controller having four valves which control operation of a pair of distributor valves, after one or more of the four valves has been pre-selectively coupled :in fluid communication in a hydraulic circuit to operate a plurality of shuttle-valves DESCRIPTION OF THE DRAWINGS
Further objects of this invention together with additional features contributing thereto and the advantages accruing therefrom will be apparent from the following description of a preferred embodiment of the invention which is shown in the accompanying drawings with like reference numerals indicating corresponding parts throughout, wherein:
; Figure 1 is a schematic diagram of a hydraulic circuit incorporating the present invention;
Figure 2 is a perspective view of a single control lever for selectively coupling certain elements of the hydraulic control system into fluid communication;
Figure 3 is a diagrammatic plan v:iew of the positions for the single control lever to effect 1 1~536~
movement of the vehicle;
Figures 4 through 7 are hydraulic schematic views of the fluid flow paths of the operating fluid for the hydraulic circuit of Figure l under various operating conditions; and Figure 8 is a circular diagram of the speed pattern of the two hydrostatic transmissions to better illustrate the resultant output from the hydrostatic transmissions for corresponding positions of the single control lever.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to Figure l, there is illustrated a pair of hydrostatic transmissions 1 and 2 of a type known to those skilled in the art. As is known, the transmissions l and 2 are capable of effecting clockwise and counter-clockwise movement to the tracks of a crawler vehicle for controlling the forward and backward motion of the vehicle and its steering.
Pressurized hydraulic fluid is coupled to each of the hydrostatic transmissions l and 2 through an inlet conduit 3 and is discharged therefrom through an outlet conduit 4 under the control of a slide valve 5 or 6, respectively. Each of the slide valves 5 and 6 is of a pilot fluid operated type wherein a movable valve spool is used to provide a metered flow of hydraulic fluid to the hydrostatic transmissions l and
2, respectively, in response to the position of the inlet and discharge ports of the slide valve. Movement of the spool or the metering element of the slide valves S and 6 is effected by coupling pressurized hydraulic fluid through a pilot control line to each side of the slide valve.
As best shown in Figure l, conduits 7 and 8 control the movement of the spool or metering element of slide valve 5, and conduits 9 and 10 control the movement of the corresponding element of slide valve 6.
In operation, when the hydraulic fluid creates a pressure through conduit 7, the metering element of slide valve 5 is positioned to cause the hydrostatic s transmission 1 to rotate in a first direction which propels the drive unit associated therewith in a direction to move the vehicle forward. Coupling of hydraulic pressure through conduit 8, will move the metering element of the slide valve 5 in an opposite direction to cause the hydrostatic transmission l to rotate in an opposite direction, thereby causing the drive unit to move in a reverse direction. Similarly, by coupling pressure through the conduits 9 and lO, coupled in fluid communication to the slide valve 6, the movable element thereof will be positioned to effect the coupling of hydraulic fluid to the hydrostatic transmission 2 in the same manner previously described, and as illustrated in the hydraulic schematic.
Two pairs of selector valves, a first pair indicated by reference numerals 15 and 16, and a second pair identified by reference numerals 17 and 18 are coupled into the hydraulic control circuit to control the passage of hydraulic fluid through the pilot pressure lines 7, 8, 9 and lO. Each of the selector valves 15, 16, 17 and 18 include a valve body having two inlets and an outlet. The valve body is formed with a cavity in which a shut-off member, normally in ; the form of a ball 19, may be moved between one of two valve inlet seats for closing one of the inlets in the valve cavity in order to control the direction of flow of the hydraulic fluid, or the ball l9 may be held by the fluid pressure in a position between the two valve inlets.
The shut-off member or ball 19 will be moved within the valve cavity to close one of the two inlets when the pressure of the hydraulic fluid entering from ~553~
one of the inlets exceeds that of the fluid entering from the other inlet. When the pressure of the fluid entering from both inlets is the same, both Lnlets will remain open and the shut-off member 19 held in equilibrium under the action of the pressure exerted by the hydraulic fluid passing into the valve body from both of the inlets. The selector valves 15 and 16 of the first pair have inlets 20 and 21, respectively, coupled together by a common conduit portion 22. The selector valves 17 and 18 of the second pair have inlets 23 and 24, respectively, coupled together by a common conduit portion 25. Each of the selector valves 15, 16, 17 and 18 has a discharge outlet from the internal cavity. Selector valve 15 has a discharge outlet 26 and selector valve 16 has a discharge outlet 27 which are connected, respectively, to the conduits 9 and 8 coupled in fluid communication with the slLde valves 6 and 5, respectively. Selector valve 17 has a discharge outlet 28 and selector valve 18 has a discharge outlet 29 which are coupled in fluid communication to the conduits 7 and 10 of the selector valves 5 and 6, respectively. IJ1 this manner the pilot pressure fluid can be coupled to the selector valves 15, 16, 17 and 18 through four branches of a hydraulic circuit with each branch of the hydraulic circuit having pressure control valve associated therewith.
A first branch of the hydraulic circuit, indicated by reference numeral 35a, couples fluid to an inlet port 35 of the selector valve 15 and an inlet port 36 of the selector valve 17 under the control of a pressure control valve indicated by reference numeral A. A second branch of the hydraulic circuit, indicated by reference numeral 36a, communicates hydraulic fluid to an inlet port 37 of the selector valve 16 and an inlet port 38 of the selector valve 18, under the control of a pressure control valve indicated by I. A
third and fourth branch of the hydraulic circuit, 1:l553~
indicated respectively by reference numerals 39 and 40, coupled hydraulic fluid respectively to the conduit portion 22 and the conduit portion 25. These third and fourth branches are controlled, respectively, by a 5 pressure control valve indicated by reference numerals D and S.
Each of the pressure control valves A, I, D
and S, is of a type comprising a movable member, the position of which determines the pressure of the fluid in circuit branches 35a, 36a, 39 and 40, respectively.
Fluid pressure to these pressure control valves is coupled by means of an inlet conduit 41, and the fluid discharged from the pressure control valves is conveyed through a discharge conduit 42. Displacement of the relative mobile member associated with each one of the pressure control valves, A, I, D and S is effected by an axially mobile pin which is biased in a return direction by means of a return spring as best shown in Figure 1.
The four axially mobile pins of the pressure control valves A, I, D and S are supported by a box 44 best shown in Figure 2, and are operated by means of a disc 45 rigidly connected with a single control lever 46 hinged to the support box 44 by means of a ball joint 47. The position of the pins relative to the control lever 46 is best shown with reference to Figures 2 and 3, with each of the axes of movement of the pins being circumferentially off-set relative to one another about the center of the box 44, which coincides with the center of a ball joint 47, by gO
degrees. The dimensions of the actuator disc 45 and the position of the metering pins, which control the fluid flow through the pressure control valves A, I, D
and S, are chosen such that when the axis of the control lever 46 is moved substantially over a conical surface having its vertex at the center of the ball joint 47, the control disc 45 is able to operate one or ~ ~5~36~
two of the control pins.
Referring now to Figure 3, as shown therein, the control pins are disposed about the box 44 such that those pins which are movable to control the flow of fluid through pressure control valves A and I are movable in a plane through an X-X axis which is parallel to a plane normal to the vehicle and extending through the vehicle's longitudinal axis (i.e., its normal running plane). The pin associated with pressure control valve A is disposed in a position corresponding to the front of the vehicle or the X-X
axis throuqh the ball joint 47, which corresponds to actuation of the vehicle in a forward direction. The pin associated with pressure control valve I is disposed in an opposed position on the X-X axis corresponding to actuation of the vehicle in a reverse direction. The metering pins associated with each of the pressure control valves D and S are positioned for movement in a plane through a Y-Y axis, which is normal to the preceeding X-X axis. In this manner, operation of the single control lever to the right or left, as shown with respect to Figure 3, will cause the vehicle to turn in either of these directions in the shortest possible turning radius in order to effect the maximum turn.
For a better understanding of the invention, ~ the operation of the hydraulic circuit will be ; described. If the machine operator wishes to move the vehicle in a forward direction, the control lever 46 is moved forward so that the actuator disc 45 will actuate the pin of pressure control valve A. Therefore, the pressure control valve A will be opened to an extend depending upon the amount the pin is depressed, which corresponds to the angle through which the lever 46 is moved. Depression of the control pin of pressure control valve A will meter hydraulic fluid from conduit 41 through the branch 35a of the control circuit to 1 1~536~
cause the fluid to enter the inlets 35 and 36 of the selector valves 15 and 17, respectively. Fluid entering into these valves will cause each shut-off member, ball 19, associated therewith to close the respective inlets 20 and 23. Fluid is thereby directed from outlets 26 and 28 through conduits 9 and 7, respectively, to the inlet ports 11 and 14 of the slide valves 6 and 5, respectively. Pressurization of the slide valves 5 and 6 in this manner will cause the metering element thereof to shift, thereby enabling the hydrostatic transmissions 1 and 2, respectively, to rotate at the same speed and in the same direction to propel the vehicle in a forward direction.
If the control lever 46 is moved in an opposite direction to contact the metering pin of pressure control valve I, the hydraulic fluid will be fed through pressure control valve I and the branch 36a of the hydraulic circuit, to the inlet ports 37 and 38 of selector valves 16 and 18, respectively. The shut-off members 19 of these valves will be moved to close the inlets 21 and 24, respectively, enabling the hydraulic fluid to pass through the outlet ports 27 and 29, respectively, through respective conduits 8 and 10 to the inlet ports 13 and 12 of slide valves 5 and 6.
The coupling of the slide valves 5 and 6 in fluid communication with the hydraulic pressure in this manner, will be effective to move the metering elements associated therewith to cause flow of hydraulic fluid to the hydrostratic transmissions 1 and 2. Each of the transmissions 1 and 2 will be caused to rotate at the same speed, but in an opposite direction to that effected by actuation of pressure control valve A, resulting in movement of the vehicle in a reverse direction.
When the machine operator desires to steer the vehicle in a maximum right or left turn, this is accomplished by rotating the vehicle tracks -in opposite 11553B~
direction. To effect such movement, the machine operator moves the control lever 46 into a posit;on to actuate the metering pin assoc-iated with pressure control valve D or S, depending upon whether a right or S left turn, respectively, is desired. If a right turn is desired, movement of the lever 46 to operate pressure control valve D opens that valve the amount determined by axial movement of the actuator pin associated therewith. Therefore, hydraulic fluid will be metered through the branch 39 of the hydraulic circuit, to the conduit portion 22 for passage to the inlet ports 20 and 21 of the selector valves 15 and 16, respectively. Such fluid passage will be effective to close the respective inlets 35 and 37 associated with these valves. Fluid communication will thereby be effected through the valves 15 and 16, and discharge from the outlet ports 26 and 27 into pilot pressure lines 9 and 8 which are in fluid communication with inlet ports 11 and 13 of the slide valves 6 and 5, respectively~ Pressurizat-ion of these inlet ports will cause the metering elements associated with each of the slide valves 6 and 5 to shift, causing the hydrostatic transmission 2 to rotate in a direction to cause the vehicle to move forward while hydrostatic transmission 1 will rotate in a direction to effect a reverse movement of the vehicle.
When it is desired to make a maximum left turn, the control lever 46 is moved into contact with the metering pin of pressure control valve S. Fluid flow is thereby established from the pressure control valve S through the branch 40 of the hydraulic circuit and into the conduit portion 25. By this action, the inlet ports 36 and 38 of selector valves 17 and 18 are closed, and the fluid is passed through conduits 7 and 10 toward the respective inlet ports 14 and 12 of the slide valves 5 and 6, respectively. Such pressurization of the slide valves 5 and 6 is effective to cause the hydrostatic transmission 1 to rotate in a direction for forward movement of the vehicle, and the hydrostatic transmission 2 is operated to effect a reverse direction to the machine, thereby turning the vehicle in a left turn in its shortest turning radius.
To effect more gradual turns of the vehicle, the control lever 46 can be moved into a position which is best described with reference to Figure 3. In this drawing examplary intermediate positions between two of the main positions already discussed (indicated by DA, DI, SI, SA) are shown. The control disc 45 is moved to simultaneously actuate two of the metering pins associated with two of the four pressure control valves A, I, D, or S. The degree of actuation of the metering pins will determine the corresponding degree of turning of the vehicle by metering the flow through these pressure control valves.
For example, when the lever 46 is moved into an intermediate position between positions A and D
Lllustrated as DA Ln Figure 3, both of the pressure control valves A and D will be simultaneously operated.
Hydraulic fluid flow will be set up in the hydraulic control circuit as indicated by the heavier lines and arrowheads shown in Figure 4. Operation of pressure control valve A couples hydraulic fluid to selector valves 17 and 15. The hydraulic fluid entering selector valve 17 closes the inlet port 23 so that fluid will only flow through the outlet port 28, to pilot pressure line 7 to the inlet port 14 of the slide valve 5. Fluid entering the selector valve 15 is effective to close the inlet 20 of this valve and thus the fluid must flow solely from the outlet port 26, through conduit 9 through the inlet port 11 of selector valve 6. Simultaneously, actuation of pressure control valve D will communicate fluid through the branch 39 of the hydraulic circuit to the conduit 22 to be passed through inlet 20 of selector valve 15, and the inlet 1 ~5~3~8 port 21 of selector valve 16.
Pressure control valves A, I, D, and S are all metering valves, and for a small opening of pressure control valve D, as the pressure of hydraulic fluid entering inlet port 35 of selector valve 15 exceeds the pressure of the hydraulic fluid entering inlet port 20 of this same valve, inlet valve 20 will be closed by movement of the valve shut-off member 19.
Fluid entering selector valve 16 is effective to close the inlet port 37 resulting in the fluid flow passing through outlet port 27, through conduit 8, and into fluid communication with the inlet port 13 of slide valve 5. Consequently, for intermediate positions of the lever 46 between positions shown as A and DA, the hydraulic fluid will be coupled to slide valve 5 for effecting the fluid communication of the hydraulic pressure to hydrostatic transmission 1 at both inlet ports 13 and 14, but at different pressures. Since the pressure at the inlet port 14 is greater than the pressure at the inlet port 13, the metering element of slide valve 5 is moved to cause the hydrostatic transmission 1 to rotate in a forward direction, but at a speed less than the maximum. This will be further reduced if the control lever is moved more towards position DA, which would correspond to a change in the axial displacement of the metering pins of the pressure control valves A and D. Pressurized fluid communication with the slide valve 6, associated with hydrostatic transmission 2, is coupled only to the inlet port 11. Thus, the hydrostatic transmission 2 is caused to be coupled to the hydraulic pressure lines 3 and 4 such that it is rotated in a forward direction at the maximum speed. Under these circumstances, both of the track units will be moved in a forward direction, but the track unit on the left hand side moves at a speed greater than the speed of the track unit on the right hand side of the vehicle, and thus the machine ~ 1S536~
will turn towards the right.
If the lever control 46 is further moved towards the position DA, the valve D will be opened to an increasing extent until the maximum port area is exposed, equivalent to that of pressure control valve A. The fluid pressure at the inlet ports 35 and 20 of slide valve 15 thereby become equal and the shut-off member l9 will be moved to an intermediate position bet~een these two inlets. The hydraulic fluid reaching inlet 13 of slide valve 5 will also have the same pressure as that reaching the inlet 14. Slide valve 5 will therefore be moved to the neutral center position terminating the flow of hydraulic fluid to hydrostatic transmission l which thereby stops. The right hand track will thereby be held at rest, and steering towards the right will be effected by movement of the left hand track through operation of hydrostatic transmission 2.
When the control lever 46 is moved to other intermediate positions between the main positions A, I, D, S, or into intermediate positions such as DA, DI, SA, SI, or into positions between the main positions and the intermediate positions, various possible movements of the machine are determined in accordance with that previously disclosed. For example, Figures 5, 6, and 7, which are analogous to Figure 4, illustrate diagrammatically the flow of hydraulic fluid shown by the heavier arrowhead lines which occurs in such intermediate positions corresponding to the positioning of the control lever 46 at positions DI, SI
and SA. The speed and direction of rotation of the two hydrostatic transmissions 1 and 2 are illustrated in Figure 8 by a circular diagram which illustrates these possibilities in accordance with the setting of the control lever 46. In this diagrammatic illustration, for each angular position of the control lever 46, the speed of each drive unit 1 and 2 is represented by the . .
~ 15~36~
radial segment lying between the two circular-like figures associated with motor units 1 and 2. This diagram is d.irectionally oriented to correspond with the drive positions shown in Figure 3 as to forward, reverse, left and right. This figure, when associated with the diagram of Figures ~ through 7, illustrates the operation of the device under all operating conditions by showing the d:irectional movement and relative speed of the drive units 1 and 2 relative to each other.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition any modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the :invention not be l.imited to the part:icular embodiment disclosed as the best mode contemplated for carrying out this invention but that the invention will include all embodiments falling within the scope of the appended claims.
As best shown in Figure l, conduits 7 and 8 control the movement of the spool or metering element of slide valve 5, and conduits 9 and 10 control the movement of the corresponding element of slide valve 6.
In operation, when the hydraulic fluid creates a pressure through conduit 7, the metering element of slide valve 5 is positioned to cause the hydrostatic s transmission 1 to rotate in a first direction which propels the drive unit associated therewith in a direction to move the vehicle forward. Coupling of hydraulic pressure through conduit 8, will move the metering element of the slide valve 5 in an opposite direction to cause the hydrostatic transmission l to rotate in an opposite direction, thereby causing the drive unit to move in a reverse direction. Similarly, by coupling pressure through the conduits 9 and lO, coupled in fluid communication to the slide valve 6, the movable element thereof will be positioned to effect the coupling of hydraulic fluid to the hydrostatic transmission 2 in the same manner previously described, and as illustrated in the hydraulic schematic.
Two pairs of selector valves, a first pair indicated by reference numerals 15 and 16, and a second pair identified by reference numerals 17 and 18 are coupled into the hydraulic control circuit to control the passage of hydraulic fluid through the pilot pressure lines 7, 8, 9 and lO. Each of the selector valves 15, 16, 17 and 18 include a valve body having two inlets and an outlet. The valve body is formed with a cavity in which a shut-off member, normally in ; the form of a ball 19, may be moved between one of two valve inlet seats for closing one of the inlets in the valve cavity in order to control the direction of flow of the hydraulic fluid, or the ball l9 may be held by the fluid pressure in a position between the two valve inlets.
The shut-off member or ball 19 will be moved within the valve cavity to close one of the two inlets when the pressure of the hydraulic fluid entering from ~553~
one of the inlets exceeds that of the fluid entering from the other inlet. When the pressure of the fluid entering from both inlets is the same, both Lnlets will remain open and the shut-off member 19 held in equilibrium under the action of the pressure exerted by the hydraulic fluid passing into the valve body from both of the inlets. The selector valves 15 and 16 of the first pair have inlets 20 and 21, respectively, coupled together by a common conduit portion 22. The selector valves 17 and 18 of the second pair have inlets 23 and 24, respectively, coupled together by a common conduit portion 25. Each of the selector valves 15, 16, 17 and 18 has a discharge outlet from the internal cavity. Selector valve 15 has a discharge outlet 26 and selector valve 16 has a discharge outlet 27 which are connected, respectively, to the conduits 9 and 8 coupled in fluid communication with the slLde valves 6 and 5, respectively. Selector valve 17 has a discharge outlet 28 and selector valve 18 has a discharge outlet 29 which are coupled in fluid communication to the conduits 7 and 10 of the selector valves 5 and 6, respectively. IJ1 this manner the pilot pressure fluid can be coupled to the selector valves 15, 16, 17 and 18 through four branches of a hydraulic circuit with each branch of the hydraulic circuit having pressure control valve associated therewith.
A first branch of the hydraulic circuit, indicated by reference numeral 35a, couples fluid to an inlet port 35 of the selector valve 15 and an inlet port 36 of the selector valve 17 under the control of a pressure control valve indicated by reference numeral A. A second branch of the hydraulic circuit, indicated by reference numeral 36a, communicates hydraulic fluid to an inlet port 37 of the selector valve 16 and an inlet port 38 of the selector valve 18, under the control of a pressure control valve indicated by I. A
third and fourth branch of the hydraulic circuit, 1:l553~
indicated respectively by reference numerals 39 and 40, coupled hydraulic fluid respectively to the conduit portion 22 and the conduit portion 25. These third and fourth branches are controlled, respectively, by a 5 pressure control valve indicated by reference numerals D and S.
Each of the pressure control valves A, I, D
and S, is of a type comprising a movable member, the position of which determines the pressure of the fluid in circuit branches 35a, 36a, 39 and 40, respectively.
Fluid pressure to these pressure control valves is coupled by means of an inlet conduit 41, and the fluid discharged from the pressure control valves is conveyed through a discharge conduit 42. Displacement of the relative mobile member associated with each one of the pressure control valves, A, I, D and S is effected by an axially mobile pin which is biased in a return direction by means of a return spring as best shown in Figure 1.
The four axially mobile pins of the pressure control valves A, I, D and S are supported by a box 44 best shown in Figure 2, and are operated by means of a disc 45 rigidly connected with a single control lever 46 hinged to the support box 44 by means of a ball joint 47. The position of the pins relative to the control lever 46 is best shown with reference to Figures 2 and 3, with each of the axes of movement of the pins being circumferentially off-set relative to one another about the center of the box 44, which coincides with the center of a ball joint 47, by gO
degrees. The dimensions of the actuator disc 45 and the position of the metering pins, which control the fluid flow through the pressure control valves A, I, D
and S, are chosen such that when the axis of the control lever 46 is moved substantially over a conical surface having its vertex at the center of the ball joint 47, the control disc 45 is able to operate one or ~ ~5~36~
two of the control pins.
Referring now to Figure 3, as shown therein, the control pins are disposed about the box 44 such that those pins which are movable to control the flow of fluid through pressure control valves A and I are movable in a plane through an X-X axis which is parallel to a plane normal to the vehicle and extending through the vehicle's longitudinal axis (i.e., its normal running plane). The pin associated with pressure control valve A is disposed in a position corresponding to the front of the vehicle or the X-X
axis throuqh the ball joint 47, which corresponds to actuation of the vehicle in a forward direction. The pin associated with pressure control valve I is disposed in an opposed position on the X-X axis corresponding to actuation of the vehicle in a reverse direction. The metering pins associated with each of the pressure control valves D and S are positioned for movement in a plane through a Y-Y axis, which is normal to the preceeding X-X axis. In this manner, operation of the single control lever to the right or left, as shown with respect to Figure 3, will cause the vehicle to turn in either of these directions in the shortest possible turning radius in order to effect the maximum turn.
For a better understanding of the invention, ~ the operation of the hydraulic circuit will be ; described. If the machine operator wishes to move the vehicle in a forward direction, the control lever 46 is moved forward so that the actuator disc 45 will actuate the pin of pressure control valve A. Therefore, the pressure control valve A will be opened to an extend depending upon the amount the pin is depressed, which corresponds to the angle through which the lever 46 is moved. Depression of the control pin of pressure control valve A will meter hydraulic fluid from conduit 41 through the branch 35a of the control circuit to 1 1~536~
cause the fluid to enter the inlets 35 and 36 of the selector valves 15 and 17, respectively. Fluid entering into these valves will cause each shut-off member, ball 19, associated therewith to close the respective inlets 20 and 23. Fluid is thereby directed from outlets 26 and 28 through conduits 9 and 7, respectively, to the inlet ports 11 and 14 of the slide valves 6 and 5, respectively. Pressurization of the slide valves 5 and 6 in this manner will cause the metering element thereof to shift, thereby enabling the hydrostatic transmissions 1 and 2, respectively, to rotate at the same speed and in the same direction to propel the vehicle in a forward direction.
If the control lever 46 is moved in an opposite direction to contact the metering pin of pressure control valve I, the hydraulic fluid will be fed through pressure control valve I and the branch 36a of the hydraulic circuit, to the inlet ports 37 and 38 of selector valves 16 and 18, respectively. The shut-off members 19 of these valves will be moved to close the inlets 21 and 24, respectively, enabling the hydraulic fluid to pass through the outlet ports 27 and 29, respectively, through respective conduits 8 and 10 to the inlet ports 13 and 12 of slide valves 5 and 6.
The coupling of the slide valves 5 and 6 in fluid communication with the hydraulic pressure in this manner, will be effective to move the metering elements associated therewith to cause flow of hydraulic fluid to the hydrostratic transmissions 1 and 2. Each of the transmissions 1 and 2 will be caused to rotate at the same speed, but in an opposite direction to that effected by actuation of pressure control valve A, resulting in movement of the vehicle in a reverse direction.
When the machine operator desires to steer the vehicle in a maximum right or left turn, this is accomplished by rotating the vehicle tracks -in opposite 11553B~
direction. To effect such movement, the machine operator moves the control lever 46 into a posit;on to actuate the metering pin assoc-iated with pressure control valve D or S, depending upon whether a right or S left turn, respectively, is desired. If a right turn is desired, movement of the lever 46 to operate pressure control valve D opens that valve the amount determined by axial movement of the actuator pin associated therewith. Therefore, hydraulic fluid will be metered through the branch 39 of the hydraulic circuit, to the conduit portion 22 for passage to the inlet ports 20 and 21 of the selector valves 15 and 16, respectively. Such fluid passage will be effective to close the respective inlets 35 and 37 associated with these valves. Fluid communication will thereby be effected through the valves 15 and 16, and discharge from the outlet ports 26 and 27 into pilot pressure lines 9 and 8 which are in fluid communication with inlet ports 11 and 13 of the slide valves 6 and 5, respectively~ Pressurizat-ion of these inlet ports will cause the metering elements associated with each of the slide valves 6 and 5 to shift, causing the hydrostatic transmission 2 to rotate in a direction to cause the vehicle to move forward while hydrostatic transmission 1 will rotate in a direction to effect a reverse movement of the vehicle.
When it is desired to make a maximum left turn, the control lever 46 is moved into contact with the metering pin of pressure control valve S. Fluid flow is thereby established from the pressure control valve S through the branch 40 of the hydraulic circuit and into the conduit portion 25. By this action, the inlet ports 36 and 38 of selector valves 17 and 18 are closed, and the fluid is passed through conduits 7 and 10 toward the respective inlet ports 14 and 12 of the slide valves 5 and 6, respectively. Such pressurization of the slide valves 5 and 6 is effective to cause the hydrostatic transmission 1 to rotate in a direction for forward movement of the vehicle, and the hydrostatic transmission 2 is operated to effect a reverse direction to the machine, thereby turning the vehicle in a left turn in its shortest turning radius.
To effect more gradual turns of the vehicle, the control lever 46 can be moved into a position which is best described with reference to Figure 3. In this drawing examplary intermediate positions between two of the main positions already discussed (indicated by DA, DI, SI, SA) are shown. The control disc 45 is moved to simultaneously actuate two of the metering pins associated with two of the four pressure control valves A, I, D, or S. The degree of actuation of the metering pins will determine the corresponding degree of turning of the vehicle by metering the flow through these pressure control valves.
For example, when the lever 46 is moved into an intermediate position between positions A and D
Lllustrated as DA Ln Figure 3, both of the pressure control valves A and D will be simultaneously operated.
Hydraulic fluid flow will be set up in the hydraulic control circuit as indicated by the heavier lines and arrowheads shown in Figure 4. Operation of pressure control valve A couples hydraulic fluid to selector valves 17 and 15. The hydraulic fluid entering selector valve 17 closes the inlet port 23 so that fluid will only flow through the outlet port 28, to pilot pressure line 7 to the inlet port 14 of the slide valve 5. Fluid entering the selector valve 15 is effective to close the inlet 20 of this valve and thus the fluid must flow solely from the outlet port 26, through conduit 9 through the inlet port 11 of selector valve 6. Simultaneously, actuation of pressure control valve D will communicate fluid through the branch 39 of the hydraulic circuit to the conduit 22 to be passed through inlet 20 of selector valve 15, and the inlet 1 ~5~3~8 port 21 of selector valve 16.
Pressure control valves A, I, D, and S are all metering valves, and for a small opening of pressure control valve D, as the pressure of hydraulic fluid entering inlet port 35 of selector valve 15 exceeds the pressure of the hydraulic fluid entering inlet port 20 of this same valve, inlet valve 20 will be closed by movement of the valve shut-off member 19.
Fluid entering selector valve 16 is effective to close the inlet port 37 resulting in the fluid flow passing through outlet port 27, through conduit 8, and into fluid communication with the inlet port 13 of slide valve 5. Consequently, for intermediate positions of the lever 46 between positions shown as A and DA, the hydraulic fluid will be coupled to slide valve 5 for effecting the fluid communication of the hydraulic pressure to hydrostatic transmission 1 at both inlet ports 13 and 14, but at different pressures. Since the pressure at the inlet port 14 is greater than the pressure at the inlet port 13, the metering element of slide valve 5 is moved to cause the hydrostatic transmission 1 to rotate in a forward direction, but at a speed less than the maximum. This will be further reduced if the control lever is moved more towards position DA, which would correspond to a change in the axial displacement of the metering pins of the pressure control valves A and D. Pressurized fluid communication with the slide valve 6, associated with hydrostatic transmission 2, is coupled only to the inlet port 11. Thus, the hydrostatic transmission 2 is caused to be coupled to the hydraulic pressure lines 3 and 4 such that it is rotated in a forward direction at the maximum speed. Under these circumstances, both of the track units will be moved in a forward direction, but the track unit on the left hand side moves at a speed greater than the speed of the track unit on the right hand side of the vehicle, and thus the machine ~ 1S536~
will turn towards the right.
If the lever control 46 is further moved towards the position DA, the valve D will be opened to an increasing extent until the maximum port area is exposed, equivalent to that of pressure control valve A. The fluid pressure at the inlet ports 35 and 20 of slide valve 15 thereby become equal and the shut-off member l9 will be moved to an intermediate position bet~een these two inlets. The hydraulic fluid reaching inlet 13 of slide valve 5 will also have the same pressure as that reaching the inlet 14. Slide valve 5 will therefore be moved to the neutral center position terminating the flow of hydraulic fluid to hydrostatic transmission l which thereby stops. The right hand track will thereby be held at rest, and steering towards the right will be effected by movement of the left hand track through operation of hydrostatic transmission 2.
When the control lever 46 is moved to other intermediate positions between the main positions A, I, D, S, or into intermediate positions such as DA, DI, SA, SI, or into positions between the main positions and the intermediate positions, various possible movements of the machine are determined in accordance with that previously disclosed. For example, Figures 5, 6, and 7, which are analogous to Figure 4, illustrate diagrammatically the flow of hydraulic fluid shown by the heavier arrowhead lines which occurs in such intermediate positions corresponding to the positioning of the control lever 46 at positions DI, SI
and SA. The speed and direction of rotation of the two hydrostatic transmissions 1 and 2 are illustrated in Figure 8 by a circular diagram which illustrates these possibilities in accordance with the setting of the control lever 46. In this diagrammatic illustration, for each angular position of the control lever 46, the speed of each drive unit 1 and 2 is represented by the . .
~ 15~36~
radial segment lying between the two circular-like figures associated with motor units 1 and 2. This diagram is d.irectionally oriented to correspond with the drive positions shown in Figure 3 as to forward, reverse, left and right. This figure, when associated with the diagram of Figures ~ through 7, illustrates the operation of the device under all operating conditions by showing the d:irectional movement and relative speed of the drive units 1 and 2 relative to each other.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition any modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the :invention not be l.imited to the part:icular embodiment disclosed as the best mode contemplated for carrying out this invention but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a steering system for a vehicle having at least two separate hydraulically actuated drive systems for propelling and steering the vehicle in response to the flow of hydraulic fluid to the drive system, a pilot pressure operated metering valve, first conduit means for establishing fluid communication between said metering valve and said drive system and having pilot pressure ports effective to control the metering of hydraulic fluid to the drive systems in response to the pilot pressure applied thereto, a plurality of pressure valves each having an actuator operable to meter the application of pilot pressure to said pilot pressure operated metering valves in response to the movement of the actuator, a control lever movable to actuate one or more of said pressure valves by displacement of the actuator thereof, the improvement comprising a plurality of shuttle valves, second conduit means for establishing fluid communication between said shuttle valves, said pressure valves and the pilot pressure inlet ports of said pilot pressure operated metering valves for con-trolling the application of pilot pressure thereto to effect the flow of hydraulic fluid to the hydraulically actuated drive systems, said control lever being selectively movable to constantly adjust the flow of hydraulic fluid to the drive system so that the vehicle may be moved in any preselected combination of rectilinear and curvilinear direction.
2. The apparatus of Claim 1, wherein said plurality of shuttle valves comprise at least two pairs of shuttle valves one of said pairs being connected to said pilot pressure ports of one of said pilot pressure operated metering valves for effecting the flow of hydraulic fluid to the hydraulically actuated drive system.
3. The apparatus of Claim 1, wherein each of said plurality of pressure valves is connected to two of said plurality of shuttle valves for controlling flow of pilot pressure therethrough.
4. The apparatus of Claim 3, wherein said plurality of shuttle valves comprises four shuttle valves, each said shuttle valve having a discharge outlet connected to one of the pilot pressure ports of said pilot pressure operated metering valves.
5. The apparatus of claim 3, wherein said plurality of shuttle valves comprises four shuttle valves, each said shuttle valve having two inlets with each of said inlet being mutually exclusively connected to one of said plurality of pressure valves.
6. The apparatus of claim 1, wherein said plurality of pressure valves comprises four pressure valves each having a dis-charge outlet, said plurality of shuttle valves comprises four shuttle valves, each said shuttle valve having two inlets connected to one of said pressure valve discharge outlet, and each of said pressure valve discharge outlets being coupled to one of the inlets of two of said shuttle valves.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT67115/80A IT1127989B (en) | 1980-01-29 | 1980-01-29 | SINGLE LEVER OPERATING DEVICE FOR A GROUND MOVING MACHINE OR SIMILAR |
| IT67,115-A/80 | 1980-01-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1155368A true CA1155368A (en) | 1983-10-18 |
Family
ID=11299694
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000368669A Expired CA1155368A (en) | 1980-01-29 | 1981-01-16 | Single lever operating device for an earth moving machine or the like |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS56124564A (en) |
| CA (1) | CA1155368A (en) |
| DE (1) | DE3102953A1 (en) |
| FR (1) | FR2474428B1 (en) |
| IT (1) | IT1127989B (en) |
| PL (1) | PL229448A1 (en) |
| SE (1) | SE8100352L (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4457387A (en) * | 1980-05-19 | 1984-07-03 | Vickers, Incorporated | Hydraulic steering system for full-track vehicles |
| IT1150232B (en) * | 1981-03-12 | 1986-12-10 | Linde Ag | COMMAND DEVICE FOR A STEERED VEHICLE WITH DIFFERENTIAL SPEED |
| EP0183684A1 (en) * | 1983-09-27 | 1986-06-11 | EDGERTON, Edgar Robert Charles | Skid steer loaders |
| JPS60160274U (en) * | 1984-04-03 | 1985-10-24 | 油谷重工株式会社 | Traveling device for crawler construction machinery |
| JP2527629B2 (en) * | 1989-12-01 | 1996-08-28 | 油谷重工株式会社 | Travel control device |
| JPH07112827B2 (en) * | 1990-03-30 | 1995-12-06 | 株式会社小松製作所 | Closed circuit hydraulic transmission hydraulic circuit |
| FR2747432B1 (en) * | 1996-04-16 | 1998-06-26 | Rexroth Sigma | SINGLE LEVER DIRECTIONAL CONTROL HYDRAULIC DEVICE FOR VEHICLE |
| FR2747636B1 (en) * | 1996-04-18 | 1998-07-03 | Rexroth Sigma | SINGLE LEVER DIRECTIONAL CONTROL HYDRAULIC DEVICE FOR VEHICLE |
| KR20110055998A (en) * | 2009-11-20 | 2011-05-26 | 볼보 컨스트럭션 이큅먼트 에이비 | Straight and turning drive device of construction machine with generation function |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2511176C2 (en) * | 1975-03-14 | 1984-08-30 | Linde Ag, 6200 Wiesbaden | Steering control device for a vehicle with differential speed steering |
| US4085812A (en) * | 1976-11-24 | 1978-04-25 | Sundstrand Corporation | Actuator system for dual path transmission |
-
1980
- 1980-01-29 IT IT67115/80A patent/IT1127989B/en active
-
1981
- 1981-01-16 CA CA000368669A patent/CA1155368A/en not_active Expired
- 1981-01-22 SE SE8100352A patent/SE8100352L/en not_active Application Discontinuation
- 1981-01-29 DE DE19813102953 patent/DE3102953A1/en not_active Withdrawn
- 1981-01-29 JP JP1091581A patent/JPS56124564A/en active Pending
- 1981-01-29 PL PL22944881A patent/PL229448A1/xx unknown
- 1981-01-29 FR FR8101721A patent/FR2474428B1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE3102953A1 (en) | 1981-12-24 |
| FR2474428B1 (en) | 1985-10-25 |
| JPS56124564A (en) | 1981-09-30 |
| IT8067115A0 (en) | 1980-01-29 |
| IT1127989B (en) | 1986-05-28 |
| FR2474428A1 (en) | 1981-07-31 |
| SE8100352L (en) | 1981-07-30 |
| PL229448A1 (en) | 1981-10-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |