MANUAL AND AUTOMATIC GOVERNOR FOR A HYDROSTATIC TRANSMISSION

Abstract: The proposed governor consists of a single-acting cylinder (11), the piston (61) of which, subjected to an elastic thrust, comprises internally a slider (62) with free abutting end, which is connected to the pump servocontrol. A preferred embodiment provides for the elastic thrust to be produced by a set of springs (4) arranged in a pack, which are calibrated so as to adapt to the pressure curve arriving at the cylinder (11) when actuated. Provision is also made for the cylinder (11) to be actuated by using the pressure produced by an auxiliary pump (1E) which, for example, is fitted directly on the prime mover.

Description: tomatic governor for a hydrostatic The subject of this present invention is a governor which acts on the servocontrol of. a variable-delivery pump, the latter being suitable for a closed circuit and such as to drive the motor at constant revs, whatever the number of revs of the prime mover driving the pump. Said servocontrol normally consists of a distributor which continues to oscillate in its equilibrium position, determined by a manual control lever connected to the distributor by means of gears. These also comprise an elastic means which can istantaneously free said manual control lever from said servocontrol. The proposed governor may be used for any kind of automatic control of the variable-delivery pump, without excluding the possibility of also controlling said pump manually. For example, using the 5. proposed device, the r.p.m. of the drum in truck mixers or other mixing equipment, agitators or the like can be maintained constant, the movement of vehicles in general can be controlled and also the actuating of auxiliary movement in road finishing machines, steamrollers, etc. 10. Until now a variable-delivery pump has been controlled only by using very complicated devices, which frequently break down. *» In particular patent US-A-3,212,263 illustrates a known type of variable-delivery hydraulic pump. French patent application 2,264,991 describes a device 15. suitable for limiting the pressure in an open hydraulic circui . German patent application 1,943,601 only describes the power control, not the governing of the motor speed. Lastly, German patent application 2,252,557 describes an 20. autαnatic device suitable for allowing variation in the number of revs of a pump. There is no mention at all of being able to obtain a constant number of revs in a motor. The problem of transmitting motion from a variable-delivery pump to a hydraulic motor has never been completely sa¬ tisfactorily solved, especially where the variable-delivery pump is a second use of a variable-revs prime mover. Usually 5. the latter also drives -a first use; for example, in truck mixers it provides for vehicle movement. When this first use requires the number of revs of the prime mover to be increased - for example, need to accelerate the engine because the vehicle is driving up a slope or overtaking - the hydraulic 10. pump sends a greater quantity of oil to the hydraulic motor. Consequently this motor runs faster, absorbing a greater amount of power. This is an utmost undesired effect, either because the second use must noπnally be driven at a predetermined speed independent frαn that of the prime mover, 1 . or because this second use wastefully absorbs a greater share of power, required instead by the first use, which has caused the number of revs of the prime mover to vary for this precise reason. Therefore, the object of this invention is to carry out an 20. automatic control of the variable-delivery pump, while allowing also a manual control of the pump at the same time. In particular, in a transmission unit comprising at least two uses driven by a single prime mover, the proposed governor allows hydraulic driving of the second use at constant speed, 25. even when the number of revs of the prime mover varies. The aforesaid object has been carried out by providing for the variable-delivery pump servocontrol to be actuated automatic¬ ally by means of a single-acting cylinder, the piston of which, subjected to the action of a spring, comprises 5. internally a slider .with free abutting end, which is connected to the servocontrol. A preferred embodiment provides for the piston to be subjected to the action of a set of springs arranged in a pack, which have been calibrated differently one from the other so as to 10. adapt to the pressure curve imparted to the cylinder when being actuated. A specific embodiment provides for the cylinder to be actuated by using the pressure produced by an auxiliary pump which, for example, is fitted directly on the prime mover. 15. This invention will now be illustrated more clearly on the basis of two non-binding exemplary embodiments shown in the accompanying drawings, in which: Fig. 1 shows the hydraulic diagram of the proposed governor and, purely as an indication, its main mechanical 20. parts; Fig. 2 shows a longitudinal section of the governor; Fig. 3 shows a section similar to Fig. 2, but forming part of a second embodiment; and Fig. 4 is a cross section 4-4 of Fig. 2. The proposed governor has been used in the examples which will be described as a governor for a variable-delivery pump 1 , connected to an motor M which must run at constant speed. This should however in no way be considered as binding. 5 Referring to Figs. 1 and 4, it will be seen that the varia¬ ble-delivery pump 1 is driven by a prime mover MP, which impresses motion to the shaft 1A whereto is also splined the gear pump 1E. The variable-delivery pump, now being described, has an oscillating plate 1B pivoted at a fixed central point 10. 1C. Furthermore, two ends of the oscillating plate 1B are connected to servocylinders indicated by 1D. After the oscillating plate 1B has been positioned, the pump delivery is directly proportional to the speed of rotation of the prime mover MP; this speed is indicated schematically by arrow E. If 15. the number of revs E of the prime mover MP varies it is evident that, no governor being present, the speed of rotation of the hydraulic motor M will also vary. As is known, variable-delivery pumps are fitted with a system for controlling the oscillating plate 1B driven by cylinders 20. 1D. By inclining the external manual control 12, consisting of a lever with fulcrum 2A (Figs. 1 and 4), pin 6B integral with said manual control 12 is displaced. Because of the resistance applied by the servocylinders 1D, connected to the oscillating plate 1B, displacement of pin 6B 25. simply causes the opening of spring 2B, made up of a fork pivoted at fulcrum 2A and having two arms wherein pins 6B and 7B are contained. The elastic action of the spring 2B on pin 7B is transmitted by the connecting rod 23, pivoted on the latter, to the lever 5. 21 which in this case will move as if its fulcrum were at end 4B due to the aforesaid resistance from the servo-cylinders 1D. The inclination given to the external manual control 12 is thus transmitted by the described gears to rod 2C of the 10. servocontrol 17. When rod 2C inside casing 17A is displaced from its neutral position, it sends oil to one of the servocylinders 1D, which inclines the oscillating plate 1B to the angle set .using the manual control lever 12. By means of the connecting rod 20 pivoted on an extension of 15. the oscillating plate 1B, lever 21 is displaced. Said lever 21 connected to the connecting rod 23 thus moves pin 7B into a position such as to close the forked spring 2B. At the same time lever 21 moves rod 2C into the neutral position thereby stopping the flow of oil to the servocylinder 1D. As a result 20. of oil oozing into the cylinder 1D, which is being actuated, and also due to the counteraction of the spring of the other cylinder 1D, opposed to the pressurized one being actuated, a displacement of the linkages is obtained equal to that given using the manual control 12, thus moving rod 2C of servo- 25. control 17 from its neutral position. Through this play of balance between opening and closing of rod 2C of servocontrol 17 the displacement determined by the manual control 12 or the proposed governor is maintained constant. 5. In order to achieve the latter a cylinder 11 has been provided, which is typically fitted so as to be integral with the servocontrol 17, as can be seen in Figs. 2 and 3. The cylinder 11 is actuated by a lever 2, integral with pin 7B, and having its fulcrum at 2A. In this arrangement, when 10. inserted, cylinder 11 overides manual control 12 because it acts directly on pin 7B and through the latter on connecting rod 23, and thereby on lever 21 and rod 2C. Lever 2 is linked to connecting rod 24 and the latter to the slider 62, said lever not being however integral with the piston 61 in order 15. to also permit movement in the linkages of the complex system of the servocontrol 17, which maintains constant the fixed displacement of the pump 1. With the governor disconnected the lever 12 is free for manual control of displacement, since said lever 12 is not connected 20. directly to piston 61 by connecting rod 24 but to the slider 62, which moves freely in the governor cylinder until it strikes against the piston 61. In order to have the hydraulic motor M run at constant revs with the prime mover at varying revs, it is necessary to have 2 . available the variable pump 1 , the servocontrol 17 and a pump 1E directly connected to the prime mover MP. Pump 1E, indicated in Fig. 1, is fitted with a maximum pressure valve 3E. In order to prevent intervention by said valve at a setting 5- fixed below the required signal, the throttling 2E has been applied, which diverts the oil flow to the selector 9 for connecting or disconnecting the governing body 11. The signal obtained before the throttling 2E is directly proportional to the revs of the prime mover MP. 1°* Inside the cylinder chamber 11B of the governor 11 said signal actuates the piston 61 and then the slider 62, if the latter's free abutting end 62A is touching the piston head 61A; subsequently the servocontrol 17 of the variable-delivery pump is actuated by connecting rod 24, lever 2, connecting rods 23 1 5. and 20 and lever 21. The spings 4, arranged in a pack and suitably calibrated, oppose the force exerted by the piston 61 due to the variable pressure signal, allowing said piston 61 to be displaced in proportion to the said pressure. 20. Fig. 2 shows the constructional anbodiment of the proposed governing body 11. As stated above, it is constructed in such a way as to be integral with the servocontrol 17; in particular, it is placed above the latter and connected thereto by lever 2. This governing body may be used for a given direction of rotation of the hydraulic motor M; if the hydraulic motor rotates in the opposite direction, the 5. proposed governor is constructed as can be seen in Fig. 3. However, it is possible to provide a governor which governs for both directions of rotation of the hydraulic motor M. The proposed governor works as follows- After having set lever 12 so as to supply the required amount 10. of oil, thereby determining the desired speed of the hydraulic motor M, selector 9 is positioned as shown in Fig.- 1. As a result the pressure produced by the fixed delivery pump 1E - this pressure is a function of the speed of the shaft 1A in the prime mover means - displaces the piston 61 as a function 15. of the oil pressure inside the body 11B of cylinder 11 , said piston being opposed by the different force of the springs 4 arranged in a pack. When the slider 62 is free to run again, the piston 61 actuates lever 2 by means of connecting rod 24. As it is integral with pin 7B, said lever moves the linkages 20. for controlling displacement, causing it to decrease and ii ntaining constant the number of revs of the hydraulic motor M, independently of the torque absorbed by said hydraulic motor. It will be seen in particular that, according to Fig. 2, the springs are compressed when the lever 2 is displaced 25. from right to left, whereas according to Fig. 3 the springs are cαπpressed when the lever 2 is displaced in the opposite direction.

Claims: C L A I M S 1. A manual and automatic governor for a hydraulic motor which is actuated by a variable delivery pump (1 ) in a closed circuit, said pump being driven by a prime mover Injrning at a variable number of revs, said governor comprising - * * • a servo-control (17) consisting of a distributor positioned by a manual control lever (12) connected to said distributor by gears, which also include an elastic means (2A) for instantan¬ eously freeing said manual control lever (12) from said servocontrol (17); characterized in that provision is made to 10. automatically actuate the variable delivery pump (1 ) servo¬ control (17) by means of a single-acting cylinder (11), the piston (61 ) of which, subjected to the action of the spring (4), comprises internally a slider (62) with free abutting end (62A) which is connected to the servocontrol (17). 15. 2. A governor according to claim 1, characterized in that the piston (61 ) is subjected to the action of a set of springs (4), arranged in a pack, which are calibrated differently from one another so as to adapt to the pressure curve arriving at the cylinder (11 ) when actuated. 3. A governor according to claim 1 , characterized in 5. that the cylinder (11 ) is driven using the pressure produced by an auxiliary pump (1E) which, for example, is fitted directly on the prime mover (MP), which also drives the variable delivery pump (1 ).

Inventors: VIELMI ELIO, VIELMI, ELIO
Applicants: SAUER SPA, SAUER ITALIANA S.P.A.
Application year: 1985
Main classification: F04B49
IPC codes: F04B49, F16H61