Hydraulic system

Abstract: The invention relates to a device, which comprises: at least two separately functioning motors for hydraulic driving; at least one source of medium under pressure; lines for guiding the medium under pressure from the source to each of the motors; and operating means for selectively feeding hydraulic fluid to at least one of the motors. The device is characterized by controllability of the source, detecting means for detecting actuation of the operating means and control means for controlling the source in order to provide medium under pressure specifically required by a motor for setting into operation when actuation of the operating means is detected. The invention further relates to a truck, such as a refuse collection truck, which comprises a frame and a drive with a propulsion engine. The truck is provided with a device as claimed in any of the foregoing claims, wherein the source of medium under pressure is coupled mechanically to the propulsion engine.

Description: The present invention relates to a device, which comprises: at least two separately functioning motors for hydraulic driving; at least one controllable source of medium under pressure; lines for guiding the medium under pressure from the source to each of the motors; operating means for selectively feeding hydraulic fluid to at least one of the motors; detecting means for detecting actuation of the operating means; and control means for controlling the source in order to provide medium under pressure specifically required by the motor for setting into operation when actuation of the operating means is detected. Such a device is in general known from the prior art discussion in European patent application 0,504,415, where the control means form a load sensing control for the medium source. It is an object of the present invention to provide an improved hydraulic device which is distinguished in that the source is arranged to generate a minimum pressure in an unloaded state, where said minimum pressure is discharged via a discharge line connected to the control means, where the control means comprise a hydraulic feedback line for pressure dependent control of the source, where the discharge line comprises valve means, which are closeable in reaction to actuation of one of the motors, and where the control means are arranged for increasing in reaction to actuation of at least one of the motors pressure in the feedback line in reaction to load of the motor concerned. By this configuration of new features where the source is controllable dependent upon the ambient pressure in the feedback line, a robust and relatively cheap system is provided. Moreover, the minimum pressure is in its entirity fed through the feedback line to the source, when the closable valve means have been closed after actuation of one of the motors as a result of generating the minimum pressure by the source and providing the discharge line with the valve means therein. Because the source is then controlled with the minimum pressure, which is higher than the pressure provided to the source, when the valve means in the discharge line are not closed, the source is charged to generate a higher pressure. At this point one or more than one of the motors is actuated, i.e. the feed line thereto has been opened, whereby also as a result of load of the motor pressure in the feedback line is increased corresponding to this load, when the output of the source is increased. In this way gradual increase of the power provided by the source is achieved, which is nevertheless sufficiently quick to be able to actuate the motors without any detrimental delays. Once the motor has been actuated, i.e. when the source has generated sufficient pressure in the line connected to the motor, the source is not charged any further, as the ambient pressure in the feed back line does not increase any further. The invention is further elucidated with reference to the figure description following hereinafter of embodiments of the invention. In the drawing: fig. 1 shows a partly cut away perspective view of a truck with a device according to the present invention; fig. 2 is a schematic view of a first embodiment of a device according to the present invention; and fig. 3 is a schematic view of a second embodiment of a device according to the present invention. Shown in fig. 1 is a refuse collection truck 1 which is equipped with a device according to the present invention. The device forms a hydraulic system which comprises: a pulling arm cylinder 2 as motor for a pulling arm 9 with which a container 7 can be placed onto and removed from the supporting surface of a truck 10; a slide cylinder 3 as motor for a slide 8 placed hingedly in container 7 in order to displace in forward direction refuse tipped into the container 7; a valve cylinder 4 as motor for a flap 11 arranged hingedly on container 7 in order to close and open the container; and a first loading cylinder 5 and a second loading cylinder 6 as motors for a lifting and tipping device 12 with which refuse bins 13 can be discharged into container 7. For optimum use of the space available in container 7 only the hydraulic cylinders 2, 3, 4, 5 and 6 as motors, lines for guiding medium under pressure and a number of control buttons are arranged in and on container 7. Together with control valves (not shown) the control buttons form operating means, wherein the control valves, a source of medium under pressure, control means and detecting means are arranged on truck 10. The mutual relation and operation of the components of the device according to the present invention will be further described hereinbelow. The lines run from the cylinders 2-6 to the control means on the truck 10 and connections (not shown) run from the control buttons to the control means via quick-detachable couplings (not shown) in order to enable simple placing and removal of container 10 on and off the chassis of truck 10. Optimum use is hereby further made of the space available in container 7 and only components of the device according to the present invention are arranged in and on container 7 which are relatively inexpensive and not susceptible to malfunction in relation to for instance a source of medium under pressure. In addition, a fully laden container 7 can be removed simply and a new empty container placed so that operations are interrupted for only a minimized time period once a container has been fully loaded. Shown schematically in fig. 2 is an embodiment of a device in the application according to the present invention shown in fig. 1. The device substantially comprises: pumps 15 as sources of medium under pressure, feed lines 16, control blocks 18 as control means, through-feed lines 19, drain lines 20 and an oil tank 21. The pumps 15 are embodied in the embodiment shown here as discharge pumps for pumping through an adjustable quantity of oil per unit of time. Pumps 15 draw off oil from oil tank 21 to send a minimum flow, which amounts for instance to 6 litres per minute, to the control blocks 18 via feed lines 16. In the embodiment shown here filters 17 are arranged in feed lines 16. The pumps 15 supply the minimum flow when none of the cylinders 2-6 is operating. In this case this minimum flow is returned to oil tank 21 via drain lines 20. Since the operation of the device according to the present invention shown here is the same for each of the cylinders 2-6, this operation will only be described here for the case where the pulling arm cylinder 2 is set into operation. To this end the control button 23 is energized, whereby in the control block 18 the through-feed line 19 is placed into connection with the feed line 16, for instance via a system of servo-valves. This can be effected for instance by means of a simple valve. A control pressure for supplying to a closing valve 22 over a closing line 24 is herein drawn off in order to close the drain line 20 by means of the closing valve 22. A controlling pressure for supplying to the pump 15 over a feedback line 25 is also drawn off in control block 18 in order to control pump 15. The detecting means are therefore formed by the taps in control block 18. In response to this controlling pressure over feedback line 25 the pump 15 produces a higher output. The pressure in through-feed line 19 will then increase rapidly as will the output related thereto which is produced by the source 15, here in the form of volume/unit of time, for instance 60 litres/min., until the pressure in through-feed line 19 is sufficient to cause the pulling arm cylinder 2 with the load acting thereon to function. The control pressure in feedback line 25 does not increase further herein, so that the pump 15 produces a constant output. In order to prevent damage to the device pressure limiting means are preferably arranged in control blocks 18. After reaching the extreme position of pulling arm cylinder 2 and optionally after a delay, the pump 15 is controlled by the control block via the feedback line 25 to cause the pressure to decrease. The excess oil is herein returned to oil tank 21 via control block 18 and a second drain line 27 in which an oil cooler 26 is accommodated. With a device according to the present invention as described above a power is therefore supplied to pulling arm cylinder 2 which is dependent on the load on pulling arm cylinder 2, since pump 15 is controlled over feedback line 25 by the control pressure so as to provide a higher output in the case of a greater load on pulling arm cylinder 2. The same applies to the other cylinders 3-6, wherein in the device according to the present invention shown here schematically the power required thereby can be supplied simultaneously or successively to one or more than one of the cylinders 2-6 associated with one of the control blocks 18. The only limitation is that the power required by the motors to be set into combined operation may not exceed the maximum output of the pump. A different pressure with an associated flow rate can herein be provided with the pumps 15 to each of the motors which are to be set into operation separately but simultaneously, provided the total required flow rate for one of the control blocks 18 does not exceed the output of the associated pump 15. Control blocks 18 are provided with pressure limiting valves (not shown) in order to ensure that the pressure in through-feed line 19 does not rise so quickly to a high value such that the piston will move in the cylinder in juddering manner or too rapidly. The first loading cylinder 5 and the second loading cylinder 6 of the loading device 12 are suitable to each separately discharge a refuse bin 13 as shown in fig. 1 or to jointly discharge a larger refuse bin (not shown). It is desirable herein that a large refuse bin be discharged more slowly and gradually than a smaller refuse bin 13. The control blocks 18 for the first loading cylinder 5 and the second loading cylinder 6 of the lifting and tipping device 12 are accordingly provided with pressure limiting means, wherein the operation thereof depends on the operational situation of lifting and tipping device 12, wherein a single large refuse bin is being discharged using both loading cylinders 5, 6 or smaller refuse bins 13 are being discharged using one of the loading cylinders 5, 6. The embodiment shown in fig. 3 of a device according to the present invention corresponds closely with that shown in fig. 2. In the embodiment shown here, however, the device comprises only one pump 15 and one control block 18. Such a device can be applied particularly advantageously when the cylinders 2-6 for driving require a comparatively low power which is smaller than the output of the pump or when a pump with a relatively high output is available. For the operation of the device further reference is made to the description of fig. 2. Although devices according to the present invention are described above wherein such devices are arranged on a truck, it is equally possible within the scope of the present invention to place these in a fixed arrangement. In addition, hydraulic feedback lines 25 are used to control the pumps 15 wherein it must be noted that within the scope of the present invention use can also be made of connections carrying electric signals. The control block herein contains detecting means and control means for generating such an electric control signal for the pumps 15. It is otherwise noted here that the motors for driving are not limited to cylinders but comprise all motors for hydraulic driving. Other embodiments are also possible within the scope of the present invention.

Claims: Device, which comprises: at least two separately functioning motors (2-6) for hydraulic driving; at least one controllable source (15) of medium under pressure; lines (16-19) for guiding the medium under pressure from the source (15) to each of the motors (2-6); operating means (23) for selectively feeding hydraulic fluid to at least one of the motors; detecting means for detecting actuation of the operating means (23); and control means (18) for controlling the source (15) in order to provide medium under pressure specifically required by the motor (2-6) for setting into operation when actuation of the operating means is detected, characterized in that the source (15) is arranged to generate a minimum pressure in an unloaded state, where said minimum pressure is discharged via a discharge line (20) connected to the control means, where the control means comprise a hydraulic feedback line (25) for pressure dependent control of the source, where the discharge line comprises valve means (22), which are closeable in reaction to actuation of one of the motors (2-6), and where the control means (18) are arranged for increasing pressure in the feedback line in reaction to actuation of at least one of the motors (2-6) and load of the motor concerned. Device as claimed in claim 1, characterized in that the detecting means and the control means (18) form a unit with the operating means (23) for each of the motors (2-6). Device as claimed in claim 2, characterized in that at least two units are jointly connected to the source (15) by means of one line (16) and one feedback line (25). Device as claimed in any of the foregoing claims, characterized in that the control means (18) comprise pressure limiting means dependent on the desired operational state of the motors (2-6) for driving. Truck (1), such as a refuse collection truck, which comprises a frame (10) and a drive with a propulsion engine, characterized in that the truck is provided with a device as claimed in any of the foregoing claims, wherein the source (15) of medium under pressure is coupled mechanically to the propulsion engine. Truck as claimed in claim 5, wherein a separate container (7) can be placed on a truck chassis, characterized in that on the container are arranged at least lines, motors, control buttons as part of the operating means (23) and quick-detachable couplings, wherein the lines and control buttons (23) can be placed into connection via the quick-detachable couplings with the control means (18) and the detecting means during placing of the container on the truck chassis.

Inventors: VERSTEEG JAN HENDRIK, VERSTEEG, JAN HENDRIK
Applicants: TERBERG MACHINES, TERBERG MACHINES B.V.
Application year: 1996
Main classification: B65F3
IPC codes: B65F3, F15B11