CROSS-REFERENCE TO RELATED APPLICATION

This application is a U.S. 371 national stage application of International Application No. PCT/EP2018/086461, filed 21 Dec. 2018, which claims priority to Austrian Patent Application No. A51082/2017, filed 22 Dec. 2017, both of which are herein incorporated by reference in their entireties.

The invention relates to a hydraulic rotary drive with a first rotary drive element, at least two annular pistons connected to the first rotary drive element in a rotationally fixed manner and axially movable on the first rotary drive element between in each case two end positions along a sliding path by being acted upon by a hydraulic fluid, each annular piston having two annular spur serrations directed away from one another, a second rotary drive element with ring type serrations complementary to the spur serrations of the annular pistons, whereby the spur serrations of the annular pistons are engageable and disengageable with the associated annular ring type serrations of the second rotary drive element by moving the annular pistons on the first rotary drive element, thereby causing a rotary movement of said second rotary drive element relative to said first rotary drive element, and a control unit which controls the supply of hydraulic fluid to the annular pistons, wherein the control unit is arranged to cause a reciprocating movement of the annular pistons on the shaft in accordance with an operating signal. Further the invention relates to a large manipulator with such a rotary drive and a truck mounted concrete pump with such a large manipulator.

A corresponding rotary drive is known from EP 2 776 360 B1. To control the drive described here, a mechanical control by means of a control disc is proposed, which controls the switching pulses for the hydraulic valves for the supply of the hydraulic fluid to the two annular pistons. Such a mechanical control is disadvantageous, because it cannot control the change-over phase so precisely that the engagement position of the interacting spur serrations can be set reliably. On the one hand, this can lead to an early engagement of the teeth and thus to a transmission of force at the tooth tips, although the tooth tips are not suitable to transmit correspondingly high acting forces. On the other hand, the moment of load transfer between the annular pistons is not clearly defined, making it difficult to achieve uniformity of rotation, especially under load.

Against this background, the task of the invention is to provide an improved rotary drive which offers improved control of the reciprocating motion of the annular pistons by supplying the annular pistons with the hydraulic fluid. In particular, the uniformity of the rotary motion shall be improved and damage to the tooth tips of the spur serrations of the annular pistons and the complementary ring type serrations shall be avoided.

The invention solves this problem starting from a hydraulic rotary drive of the type mentioned above by providing a sensor arrangement connected to the control unit is for detecting the positions of the annular pistons along the respective sliding path. With the exact detection of the position of the annular pistons along the respective sliding path, the control unit can control the supply of hydraulic fluid to the annular pistons, and thus also their speed, in a more targeted manner in order to generate a controlled reciprocating movement of the annular pistons on the shaft, thereby improving the uniformity of the rotary movement of the rotary drive and also preventing damage to the tooth tips of the spur serrations, to the annular pistons and to the complementary annular serrations.

Advantageous embodiments and further developments of the invention result from the dependent claims. It should be pointed out that the features individually listed in the claims can also be combined with each other in any technologically meaningful way and thus show further embodiments of the invention.

According to an advantageous embodiment of the invention, it is provided that the sensor arrangement is designed to detect the positions of the annular pistons when the respective end position is reached. With the detection of the annular piston position when the respective end position is reached, a simple possibility is given with the sensor arrangement to detect the position of the annular pistons along the sliding path at least in the end position, whereby the control unit can be enabled to control the switch-over phase for a back and forth movement of the annular pistons.

An advantageous embodiment is that the sensor arrangement includes at least one switch that switches when the respective annular piston reaches a predetermined position. With a simple switch, the reaching of the piston at a predetermined position can be reliably detected, so that the control device can initiate the changeover phase in a targeted manner by supplying the annular piston with the hydraulic fluid.

A preferred embodiment is that the switch is designed as an inductive limit position switch. With an inductive limit position switch, a reliable and low-wear option is available for detecting the position of the annular pistons along the sliding path when a predetermined position is reached.

In a further preferred embodiment it is provided that the sensor arrangement comprises at least one displacement sensor which detects the instantaneous position of at least one annular piston along the sliding path. With the detection of the instantaneous position of at least one annular piston via a displacement sensor, the speed of the reciprocating movement of the annular pistons at the first rotary drive element in particular can be set particularly accurately by the control unit, since the hydraulic fluid can be applied to the annular pistons depending on the instantaneous position of the annular piston along the sliding path. This allows the speed of the piston movement to be controlled over the entire position of each annular piston, so that in particular the load transfer from one annular piston to the other can be defined by different piston speeds, which considerably improves the uniformity of the rotary movement.

It is particularly advantageous that the displacement sensor is designed for inductive detection. An inductive displacement sensor provides a particularly low-wear option for detecting the current position of the annular piston along the sliding path.

Further advantageous is the design of the displacement sensor with capacitive detection. A capacitive displacement sensor provides a particularly low-wear and insensitive means of detecting the current position of the annular piston along the sliding path.

Further advantageous is the embodiment that the displacement sensor has an annular electrode insulated from a rotary drive element, preferably the second rotary drive element, into which at least a section of the annular piston detected by the displacement sensor is immersed to different depths during displacement along the sliding path. With such a ring electrode insulated with respect to a rotary drive element, preferably the second rotary drive element, it is very easy to ensure capacitive detection of the instantaneous position of the annular piston. This is done by immersing at least a section of the annular piston to different depths in the insulated annular electrode when it is moved along the sliding path. Depending on the immersion depth of the section in the area of the ring electrode, a changed capacitance can be measured at the ring electrode. The ring electrode is insulated against a rotary drive element, preferably the second rotary drive element, preferably by a plastic ring. In addition, an air gap may be formed between the immersing portion of the annular piston and the annular electrode to provide insulation of the annular electrode from the immersing portion.

In a further preferred embodiment, it is intended that the displacement sensor includes a strain gauge which provides a signal dependent on the instantaneous position of at least one annular piston along the sliding path. The instantaneous position of at least one annular piston along the sliding path can be detected particularly easily with a strain gauge. Preferably, the strain gauge is mounted on a preloaded bending spring which engages the at least one annular piston to detect its instantaneous position. Due to the preload of the bending spring, it can remain in engagement with the annular piston. The resistance of the strain gauge changes when the bending of the bending spring changes, so that the momentary position of the annular piston can be detected along the sliding path. The pretensioned bending spring can either act with one end on the piston shoulder of the annular piston or be guided in a groove on the piston.

An advantageous embodiment of the invention provides that the displacement sensor is arranged outside an external rotary drive element, preferably outside the second rotary drive element. With the arrangement of the displacement sensor outside the outer rotary drive element, an easily accessible displacement sensor can be specified for the sensor arrangement. In addition, the outer rotary drive element can be made smaller by arranging the displacement sensor outside, so that more installation space is available for the annular pistons.

A preferred embodiment provides that the displacement sensor of the sensor assembly is located in an additional housing, which is arranged on the outside of the outer rotary drive element, preferably outside the second rotary drive element. With an additional housing outside the outer rotary drive element, the displacement sensor can be arranged in a protected and yet easily accessible position. This facilitates maintenance work and further reduces errors caused by external influences such as moisture and dirt.

Further advantageous is an embodiment where the displacement sensor uses a sensing rod to detect the instantaneous position of the at least one annular piston along the sliding path in the outer rotary drive element, preferably in the second rotary drive element, the sensing rod being guided through a feedthrough into the outer rotary drive element, preferably into the second rotary drive element. With the proposed sensing rod, which is guided through the passage into the outer rotary drive element, preferably into the second rotary drive element, the instantaneous position of the annular piston along the sliding path can be sensed in a simple manner and detected by sensors outside the outer rotary drive element, preferably outside the second rotary drive element.

It is particularly advantageous that the sensing rod is in engagement with at least one annular piston. In order to be able to reliably detect the current position of the annular piston via a displacement sensor arranged outside, the outer rotary drive element, preferably outside the second rotary drive element, the sensing rod is in engagement with the annular piston. For this purpose, the sensing rod can either engage with one end on the piston shoulder of the annular piston or be guided in a groove on the piston.

An advantageous embodiment is that the control unit regulates the speed of the annular pistons depending on the signals of the sensor arrangement. With a control unit designed in this way, in particular the switching phase of the reciprocating movement of the annular pistons can be precisely controlled so that, when the load is transferred, the load on the tooth tips of the ring type serrations and the spur type serrations is reduced and the speed of the two annular pistons relative to each other can be adjusted so that a defined load transfer takes place, which ensures the uniformity of the rotary movement of the drive. With the invention's control of the speed of the annular pistons, defined positions of the annular pistons can also be adjusted at the right time in order to further improve the load transfer behavior between the serrations.

A preferred embodiment of the invention provides that the first rotary drive element is designed as a shaft and the second rotary drive element is designed as a cylinder housing, the annular pistons being axially movable on the shaft between the respective two end positions along the sliding path by being acted upon by the hydraulic fluid. A further preferred embodiment of the invention provides that the cylinder housing forms the outer rotary drive element.

Furthermore, the object of the invention is a large manipulator, wherein the large manipulator described before and in more detail below has an articulated boom comprising two or more boom sections, wherein the boom sections are connected to the respective adjacent boom section in a pivotally movable manner via articulated joints by means of one drive each, wherein at least one of the drives is designed as a rotary drive according to the invention. A large manipulator designed in this way can be swivelled particularly flexibly by means of an articulated boom with such a rotary drive, so that the articulated boom can be brought into very special unfolding forms. This makes its use flexible. The specially designed rotary drive also offers a long service life and low wear.

Furthermore, the object of the invention is a truck-mounted concrete pump, whereby the truck-mounted concrete pump already described above and in more detail below has a large manipulator carrying a concrete conveying line, as already described above and in more detail below. With such a large manipulator on a truck-mounted concrete pump, the concrete can be distributed on the construction site particularly easily and flexibly.

