Device for generating percussive pulses or vibrations for a construction machine

Abstract

The invention relates to a device and a method for generating percussive pulses or vibrations for a construction machine, with a housing, a piston which is reversibly reciprocable in a working space in the housing between a first reversal point and a second reversal point, a pressure fluid supply, through which pressure fluid can in each case be led into and out of the working space in the region of the first reversal point and the second reversal point, wherein the piston can be set into the reversible movement in order to generate the percussive pulses or vibrations, at least one controllable valve, through which the pressure fluid can be led into and/or out of the working space, and a control unit which is connected to the at least one controllable valve, wherein by the control unit the movement of the piston in the working space can be controlled and changed. According to the invention provision is made in that the control unit is designed to move the piston at a frequency that corresponds to a resonance frequency of an overall arrangement comprising the piston and the pressure fluid.

Claims

1. A device for generating percussive pulses or vibrations for a construction machine, with a housing, a vibration generator disposed in a working space in the housing, the vibration generator including a piston configured to reversibly reciprocate in the working space between a first reversal point and a second reversal point, a pressure fluid supply, through which pressure fluid can in each case be led into and out of the working space in the region of the first reversal point and the second reversal point, wherein the piston can be set into the reversible movement in order to generate the percussive pulses or vibrations, at least one controllable valve, through which the pressure fluid can be led into and/or out of the working space, and a control unit which is connected to the at least one controllable valve, wherein by the control unit the movement of the piston in the working space can be controlled and changed, wherein the control unit is designed to move the piston at a frequency that corresponds to a resonance frequency of an overall arrangement comprising the piston and the pressure fluid, the control unit comprises an automatic program for determining the resonance frequency, wherein a frequency band starting from a starting frequency to a target frequency is run through on actuation of the piston and, in doing so, respective response frequencies of the device are detected, wherein a maximum response frequency being detected constitutes the resonance frequency, the response frequencies are detected based on vibrations of the piston, the vibration generator is supported in the housing by a spring which decouples generated percussive pulses or vibrations from the housing, a transducer determines a position of the piston in the working space, and the transducer is movable within the housing.

2. The device according to claim 1, wherein the valve is an electromagnetic valve.

3. The device according to claim 1, wherein the transducer includes a linear sensor.

4. The device according to claim 1, wherein on at least one reversal point a percussion surface is arranged, onto which the piston strikes specifically to generate a percussive pulse.

5. The device according to claim 1, wherein the overall arrangement also comprises the housing.

6. The device according to claim 1, wherein the mass of the piston and/or the housing can be changed by mounting or removing adjustment weights.

7. A construction machine, wherein a device for generating percussive pulses or vibrations according to claim 1 is arranged.

8. A construction machine according to claim 7, wherein the construction machine comprises an earth drilling apparatus.

9. A construction machine according to claim 7, wherein the construction machine comprises a pile driver or a vibrator.

10. A method for generating the percussive pulses or vibrations for the construction machine, with the device according to claim 1, in which the piston is reversibly reciprocated in the working space between the first reversal point and the second reversal point, wherein, for the purpose of generating the percussive pulses or vibrations, the piston is set into the reversible movement by means of the pressure fluid and the pressure fluid is led into and out of the working space in the region of the first reversal point and the second reversal point, wherein the control unit controls the at least one controllable valve, through which the pressure fluid is led into and/or out of the working space, and by the control unit the movement of the piston is controlled, wherein the at least one controllable valve is controlled by the control unit such that the piston is moved at the frequency that corresponds to the resonance frequency of the overall arrangement comprising the piston and the pressure fluid, the resonance frequency determined at the working space.

Description

(1) The invention is described further hereinafter by way of preferred embodiments illustrated schematically in the accompanying drawings, wherein show:

(2) FIG. 1: a schematic cross-sectional view of a device according to the invention;

(3) FIG. 2: a circuit diagram of a device according to the invention; and

(4) FIG. 3: a frequency diagram of a device according to the invention.

(5) FIG. 1 shows the principle depiction of a drill drive that is equipped with a vibration or percussive pulse generator according to the invention. Illustrated here is a housing 1 that comprises all functional components. From this housing projects the drill rod 2 that carries the drill head 3 at its distal end. By means of a hydraulic motor 4 the drill rod 2 is set via a planetary gear 5 into rotational movement about the axis of the drill rod 2. A drilling tool is arranged on the drill head 3. Through rotational movement of the drill head 3 the cutting edge of the drilling tool is able to strip cuttings in the borehole. The thickness of the cuttings depends on the force applied in the axial direction. To generate an alternating axial vibratory force a vibration generator 6 that substantially corresponds to the vibration or percussive pulse generator according to the invention is mounted on the planetary gear 5. The vibration generator 6 is supported in a rubber spring 7 which decouples the generated vibration from the housing. In addition to the oscillation/vibration generator 6 the vibrating and therefore moved masses of the drill drive comprise the drill head 3, the drill rod 2, the planetary gear 5 and the hydraulic motor 4 which are to this end supported in an axial guide 11. Alternatively, the gear 5 can also be operated such that it is decoupled from the vibration cell or vibration generator 6. In this case, the generated vibration can, by way of example, be transmitted via a shaft, which is guided through an output shaft designed as a hollow shaft, directly to the drill rod and thus the drill head. The rotational movement generated by the gear can in this case be transmitted via a toothing or any tooth profile, which decouples the generated axial vibration from the gear, from the hollow shaft into the drill rod and thus to the drill head. Alternatively, it is also possible that the shaft transmits the rotational movement and a hollow shaft the generated vibration.

(6) To generate the vibration in the vibration generator 6 this comprises a vibration cylinder or rather a vibratory piston 8, which is pressurized by a pressure fluid in an alternating manner in pressure chambers located on both sides of the vibratory piston 8. The pressure fluid is provided in a pressure fluid line P and applied in an alternating manner by means of a shuttle valve 9 to the working chambers on both sides of the vibratory piston 8. The shuttle valve can be an electromagnetically operated 2/4 directional control valve for example. However, use can also be made of all other suitable valves, e.g. with rotating valve slides, proportional and/or servo valves. Via the shuttle valve 9 the chamber on the vibratory piston 8 which is non-pressurized in each case is alternatingly connected to a pressureless tank line T. As a result of this alternating pressurization of the vibratory piston 8 this is set into vibration and generates the axial force necessary for the advancement of the drill head 3. The frequency, at which the shuttle valve 9 is actuated by a PLC (=programmable logic controller) is transmitted to the vibratory piston 8 of the vibration generator 6. Via a symbolically indicated measuring transducer 10 the current position of the vibratory piston 8 can be detected and transmitted to the PLC. As variables derived therefrom the actual stroke and the frequency of the vibratory piston 8 can also be determined. Through this measurement value detection the current responses of the overall arrangement, comprising both the oscillating vibratory piston 8 and the pressurizing pressure fluid, can be detected e.g. if the frequency of the shuttle valve 9 is changed. In this way, a control circuit is obtained, through which the vibration generator 6 can be operated dynamically. The detection of the position of the vibratory piston and of the variables derived therefrom, such as piston stroke and frequency, takes place in real time in order to be able to realize a control circuit. The desired reversal points of the vibratory piston 8 can be adapted in almost any chosen way to achieve an improved advancement in the depicted drill drive.

(7) In FIG. 2 a simplified circuit diagram of the hydraulic vibratory drive is illustrated. In this case, too, a piston having the mass m and located in a housing can be set into vibration by applying a working pressure p.sub.max. Shown symbolically here is an electromagnetically controlled directional control valve for alternating pressurization. The pressure fluid supply takes place via a fixed displacement pump with pressure control valve. The parameters of the overall arrangement according to the invention are illustrated schematically here by the mass m and the diameter D of the piston as well as by the length l and the diameter d.sub.N of the supply lines of the pressure fluid.

(8) Finally, in FIG. 3 the frequency response of an overall arrangement on excitation of a vibratory drive according to the invention is shown. The exemplary piston mass of 20 kg with a piston diameter D of 95 mm is excited by a fluid pressure p.sub.max. In this case, the excitation of the vibratory drive was effected in an exemplary manner in a frequency range of 0 to 1000 Hz. Clearly evident is a force maximum deltaF (at the level of approx. 95 kN) at a resonance frequency of approximately 180 Hz which corresponds to a natural frequency of the overall arrangement comprising vibrating piston and pressure fluid. Due to the dynamic and variable alternating pressurization in a control circuit the preferred parameters for the vibration and pulse generator according to the invention can be ascertained in a simple way and these can be adapted promptly in case of changing ancillary conditions. Consequently, the vibration or pulse generator according to the invention enables e.g. an improved penetration into ground of construction machine tools, such as drills, chisels, ripper teeth etc., coupled to the said generator.