Method of and Arrangement for Controlling the Speed of the Movements of Hydraulic Booms

This invention relates to a method of and an arrangement for controlling the speed of the movements of hydraulic booms and of members attached thereto, wherein the movements are preformed by hydraulic motors.

Manually actuated directional control valves of the mobile type are usually used for controlling the movements of booms. Such valves, however, have in most cases unsatisfactory inching capabilities and require great operating forces.

It is an object of the present invention to provide an improved control of the movements of booms in these respects. Another object of the invention is to attain a good inching with an exceedingly small contribution from auxiliary equipment.

According to one aspect of the present invention there is provided a method of controlling the speed of the movements of a hydraulic boom which is pivotally arranged with respect to a support, carries a working implement, and is of the type wherein the movements of the boom are performed by at least one hydraulic motor, and the return flow from said cylinder is conducted to low pressure, the method comprising selectively ramifying the return flow into one of at least two branches, and providing flow restriction in at least one of said branches, for adjusting the speed in steps of predetermined sizes.

According to another aspect of the invention there is provided an improved hydraulic boom arrangement comprising a boom which is pivotally arranged with respect to a support, the boom carrying a working implement, at least one hydraulic motor connected to said boom for swinging the boom, a pressure fluid source, means for supplying pressure fluid to said motors, and means for conducting the return flow from said at least one motor to a tank via a conduit, the improvement comprising a valve connected in said conduit the conduit having, at least two branches between said valve and said tank, fluid restriction means connected in at least one of said at least two branches, and means adapted to set said valve for selectively conducting said return flow through either one of said at least two branches.

The above and other purposes of the invention will become apparent from the following description and from the accompanying drawings in which one embodiment of the invention is illustrated by way of example. It should be understood that this embodiment is only illustrative of the invention and that various modifications thereof may be made within the scope of the claims following hereinafter.

FIG. 1 shows a side view of a drill boom and a feed bar of a rock drilling machine, where the speed of the pistons in the shown cylinders is regulated according to the invention;

FIG. 2 is a top view of the drill boom of FIG. 1;

FIG. 3 diagrammatically shows the hydraulic circuitry of the cylinders in FIGS. 1 and 2;

FIG. 4 shows in a longitudinal section a conventional hydraulic lock for a cylinder included in the hydraulic circuitry of FIG. 3; and

FIGS. 5, 6 and 7 respectively show the moving pattern of the operating means placed on an operator's panel, which operating means are intended for controlling respectively the elevating and swinging of the drill boom, the tilting and swinging of the feed bar and the displacement of the feed bar.

In FIGS. 1 and 2, the drill boom 10 is elevated and lowered by means of hydraulic cylinders 12, 13 and is swung laterally by means of a hydraulic cylinder 14. A rock drilling apparatus mounted on the outer end of the boom 10 is tilted by means of a hydraulic cylinder 16 and is swung by means of a hydraulic cylinder 15. A hydraulic cylinder 17 is provided for the displacement of the rock drilling apparatus. The rock drilling apparatus comprises a feed bar 11 and a rock drilling machine mechanically fed therealong.

As may be seen in the hydraulic coupling circuitry shown in FIG. 3 a remote controlled, directional control valve 22 is connected between a pump 21 and the cylinder 12. Valves 23, 24, 25 and 26 respectively of the same sort are connected between the pump 21 and the respective cylinders 14, 17, 15 and l6. In conventional manner, respective hydraulic locks 34-38 are connected to each of the cylinders to lock the pistons when the valves are unactuated. A valve 27 is connected in the conduits of the return flow from the cylinders 12, 14, 15 and 16. Two restrictions 28, 29 are connected in separate conduits between the outlet of said valve 27 and the tank 30, the one restriction 28 having a smaller area and the other 29 having a larger area. The valves 22-27 are shown mounted in a block 2.

As may be seen in the circuitry in FIG. 3, each of the hydraulic cylinders 12, 14, 15, 16 and 17 respectively is provided with a conventional hydraulic lock respectively 34, 35, 36, 37 and 38. As shown in FIG. 4, the hydraulic locks are provided with a reversing piston 39 which cooperates with a pair of check valves 40, 41.

In FIGS. 5, 6 and 7, the moving pattern of the operating means 31, 32 and 33 mounted on the operator's panel is shown diagrammatically. The operating means 31, which is a control lever of the combination type, is intended to control the movements of the boom 10. In the shown embodiment, the operating means 31 is movable in two steps in each of the four indicated directions. In the positions I and II the boom is lowered, in the positions III and IV it is elevated, in the positions V and VI it is swung leftwards and in the positions VII and VIII it is swung rightwards. With the control means in the positions I, III, V or VII the boom moves at a lower speed in the respective directions than with the operating means in the positions II, IV, VI or VIII.

In the hydraulic coupling circuitry shown in FIG. 3 the valves 22-27 are controlled by electromagnets. With the operating means 31-33 in any of the positions I-VIII contacts are closed, whereby the magnets of the valves are actuated in the way shown diagrammatically in FIGS. 5, 6 and 7. In a preferred embodiment of the invention, with the operating means 31 in position I, the valves 22 and 27 are adjusted via the coils of the magnets a and j in such a way that pressure fluid is supplied to the upper chamber of the cylinder 12 and the return flow from the lower chamber is caused to pass through the restriction 28. If the operating means 31 is moved to position II the adjustment of the valve 22 is maintained by the coil of the magnet a but the valve 27 is adjusted via the coil of the magnet i in such a way that the return flow is caused to pass through the restriction 29 provided with the larger area. The speed by which the boom 10 is moved is thereby increased stepwise. With the operating means 31 in the positions V, VI and VII, VIII respectively the swinging speed of the boom is altered in the same way stepwise by adjustment of the valves 23 and 27 via respectively the coils c, d and i, j. In the preferred embodiment, the step between the different speeds upwards of the boom has been made greater by the fact that the operating means 31 in position III adjusts the valve 27 via the coil j for conducting the return flow through the restriction 28 provided with the smaller area while the operating means 31 in position IV leaves the valve 27 unactuated for conducting the return flow directly to the tank 30.

The tilting and swinging speed of the feed bar 11 can in the same way be adjusted stepwise by means of the operating means 32. In a preferred embodiment, however, the greatest swinging speed of the feed bar has been increased by leaving the valve 27 unactuated when the operating means 32 are in the positions VI and VIII. With the valve 27 unactuated, the return flow from the cylinder 15 is conducted via a by-pass line directly to the tank 30, as may be seen in FIG. 3. The displacement of the feed bar 11, for which there is no need of adjusting the speed, is controlled by the operating means 33 which adjusts the valve 24 via the coils k, l. The return flow from the cylinder 14 is conducted directly to the tank 30.

With the speed control of a piston carried out according to the invention there is attained improved inching characteristics, small operating forces, no main valves placed in direct connection to the operator's panel, the possibility of controlling the piston from several places and a feeling of a continuous speed control by the stepwise movement of the operating means.

The embodiment shown by way of example is only illustrative of the invention and various modifications thereof may be made. For example, the number of steps for the speed of the pistons as well as the size of the steps can be varied in a suitable manner according to circumstances. The type of valve and operating means can be chosen arbitrarily. The valves can, besides electrically, also be controlled pneumatically or hydraulically. The invention may of course be used for controlling the movements of any hydraulic motor, such as rotary motors.