Hydraulic pressing tool and method for controlling a hydraulic pressing tool

Abstract

A hydraulic pressing tool which is particularly suitable for pressing pipe fittings, and which has a hydraulic pump connected to an electric motor is provided. With the aid of the hydraulic pump, hydraulic fluid is pumped from a tank into a piston chamber to operate the hydraulic piston. The pressure prevailing in the piston chamber is determined by a pressure sensor. When a pressure limit is reached, a solenoid valve is opened by the control device such that the hydraulic fluid flows back out of the piston chamber, through the channels, and into a reservoir.

Claims

1. A hydraulic pressing tool for compressing pipe fittings, comprising an electric motor, a hydraulic pump driven by the electric motor, a control device connected to the electric motor, a hydraulic piston that actuates the pressing tool by supplying hydraulic fluid from a reservoir into a piston chamber by means of the hydraulic pump, a valve comprised of a pressure sensor and a solenoid valve having a spring element and a valve plate, wherein the solenoid valve is disposed in a return path between the piston chamber and the reservoir, wherein the solenoid valve opens the return path in accordance with a pressure signal transmitted from the pressure sensor to the control device when a limit pressure detected by the pressure sensor is reached, wherein the spring element maintains the solenoid valve in a closed position, and wherein the spring element is configured to function as a mechanical overload safety device by opening the solenoid valve when a maximum pressure is exceeded, and an emergency opening device comprised of an actuation element having an actuation rod connected with the valve plate for the mechanical opening of the solenoid valve.

2. The hydraulic pressing tool of claim 1, wherein the solenoid valve further comprises a magnetic coil, wherein the solenoid valve opens when the magnetic coil is energized.

3. The hydraulic pressing tool of claim 2, wherein the solenoid valve acts on the valve plate.

4. A method for controlling a hydraulic pressing tool comprised of an electric motor, a hydraulic pump driven by the electric motor, a control device connected to the electric motor, a hydraulic piston that actuates the pressing tool by supplying hydraulic fluid from a reservoir into a piston chamber by means of the hydraulic pump, a valve comprised of a pressure sensor and a solenoid valve having a valve plate and a spring element, wherein the solenoid valve is disposed in a return path between the piston chamber and the reservoir, and an emergency opening device comprised of an actuation element having an actuation rod connected with the valve plate for the mechanical opening of the solenoid valve, the method comprising: detecting, by the pressure sensor, the pressure in the piston chamber, transmitting the pressure to the control device, and opening the solenoid valve when a limit pressure or a maximum pressure is reached.

5. The method of claim 4, wherein the control device deactivates the electric motor when the limit pressure is reached, the maximum pressure is reached, or when the emergency opening device is actuated.

6. The method of claim 4, wherein the limit pressure and/or the maximum pressure are adjustable so that different pressing forces can be applied by the pressing tool.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The FIGURE illustrates, in partial section, a schematic diagram of the portion of a hydraulic pressing tool relevant to the disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(2) The hydraulic pressing tool of the present disclosure comprises an electric motor 10 connected with a control device 12 for its control. The electric motor 10 is used to drive a hydraulic pump 14. Further, the hydraulic pressing tool comprises a hydraulic piston 16 adapted to be displaced within a piston chamber 20 formed by a cylinder 18. A pressing tool or a tool fitting for the pressing tool is connected with the left end of the hydraulic piston 18 that is not illustrated in the FIGURE. By displacing the hydraulic piston 16 in the direction of an arrow 22, the pressing tool is actuated and thereby a press fitting is compressed, for example.

(3) The hydraulic pump 14 is connected with the piston chamber 20 via an infeed 24 and with a reservoir 28 via a line 26. For a displacement of the hydraulic piston 16 in the direction of the arrow 22, the hydraulic pump 14 pumps hydraulic fluid from the reservoir 28 through the lines 24, 26 into the piston chamber 20.

(4) The piston chamber 20 is connected with a pressure chamber 32 via a duct piece 30 such that the same pressure prevails in the pressure chamber 32 as in the piston chamber 20. A pressure sensor 34 is arranged in the pressure chamber 32. The pressure sensor 34 measures, in particular continuously, the pressure prevailing in the pressure chamber 32, and thus the pressure prevailing in the piston chamber 20, and transmits a corresponding signal to the control device 12.

(5) In the embodiment illustrated, a solenoid valve 36 is arranged opposite the pressure sensor 34. A valve plate 38 of the solenoid valve 36 closes an opening of a fluid duct 40 that is also connected with the piston chamber 20. Further, the solenoid valve 36 comprises a magnetic coil 42 connected with the control device 12 via a line 44. Furthermore, the solenoid valve 36 comprises a helical spring 46 which urges the valve plate 38 into the closed position. In the embodiment illustrated, it is possible to open the magnetic valve 36 by energizing the magnetic coil 42. By energizing the magnetic coil 42, the valve plate 38 is moved towards the magnetic coil 42, i.e. downward in the FIGURE.

(6) Moreover, the valve plate 38 is connected with an actuation rod 48. The actuation rod 48 may be actuated via a lever element 50. By pressing on a releasing element 52 of the lever 50, the lever 50 is pivoted about a fulcrum 54 provided at the housing of the pressing tool. Thereby, the actuator rod 48 is pulled outward, or downward in the FIGURE. By moving the valve plate 38 in the direction of the magnetic coil 42, or downward in the FIGURE, the solenoid valve is caused to open against the force of the spring element 46.

(7) Thus, in order to perform a pressing operation, the electric motor 10 is started first and hydraulic fluid is pumped by the hydraulic pump 26 into the piston chamber 20 via the infeed. When a limit pressure detected by the pressure sensor 34 is reached, the control device 12 generates a signal by which the magnetic coil 42 is energized. Simultaneously, the electric motor 10 can be deactivated. Due to the energizing of the magnetic coil 42, the valve plate 38 is attracted and the solenoid valve 36 is opened thereby. Thus, the hydraulic fluid can flow from the piston chamber 20 into a reservoir 28 through the duct 40 as well as through a return path 56. The hydraulic piston 16 is pushed back into its initial position by a spring, not illustrated herein, whereby the hydraulic oil is supplied into the reservoir 28.

(8) In an emergency situation, e.g. when a finger of an operator of the pressing tool gets caught therein, it is possible to press on the releasing element 52 in the direction of an arrow 58 so that the actuator rod 48 is opened downward in the FIGURE and also the valve 36 is opened by moving the valve plate 38. At the same time, the electric motor 10 can be deactivated as a result of the opening of the solenoid valve 36. By opening the solenoid valve 36 using the actuator rod, the hydraulic fluid is pushed back into the reservoir 28 again.

(9) Preferably, the spring element 46 is designed such that upon reaching or exceeding a maximum pressure in the piston chamber 20, which is above the normal limit pressure, the solenoid valve 36 is also opened. The opening is effected mechanically, independent of the energizing of the magnetic coil 42, by pushing the valve plate 38 back against the spring force exerted by the spring element 46. Thereby, a mechanical overload safety device is realized that still prevents overload even in the event of a failure of the pressure sensor 34.