WELDING CAP COOLING WATER CONTROL SYSTEM

Abstract

A welding cap cooling water control system has a cooling water conduit with a cooling water inflow leading in direction of the welding cap and a cooling water return flow leading away from the welding cap, in which a flow sensor and a control valve are seated. On the side of the inflow or the return flow the cooling water flow is controlled by a flow control valve which also serves for emergency shut-off in the case of pressure loss.

Claims

1. A welding cap cooling water control system, comprising a cooling water conduit which includes a cooling water inflow leading in direction of at least one welding cap and a cooling water return flow leading away from the at least one welding cap, wherein in the cooling water return flow a switchable control valve for closing the cooling water return flow during a cap change and at least one flow sensor are provided, wherein in the cooling water inflow or cooling water return flow an electronically controlled flow control valve is seated.

2. The welding cap cooling water control system according to claim 1, wherein a control unit is provided, which is coupled with the flow sensor, the control valve and the flow control valve and controls the same or picks up data from the same.

3. The welding cap cooling water control system according to claim 2, wherein the control unit includes a PID controller.

4. The welding cap cooling water control system according claim 1, wherein a switchable water receiving device is present, which during a cap change is actuatable electrically and takes up cooling water from a conduit portion between the flow control valve and the control valve.

5. The welding cap cooling water control system according to claim 4, wherein the water receiving device includes an expansion space which has a movable wall.

6. The welding cap cooling water control system according to claim 5, wherein an adjustable counterpressure to the water pressure of the cooling water in the conduit portion can be applied on the movable wall.

7. The welding cap cooling water control system according to claim 4, wherein the water receiving device is provided with a pilot control valve.

8. The welding cap cooling water control system according to claim 2, wherein the control unit is formed and programmed such that on the inflow side only the flow control valve is electrically switched in the case of a cap change and/or a leakage in the cooling water conduit, in order to stop the inflow of cooling water to the at least one welding cap.

9. The welding cap cooling water control system according to claim 1, wherein the cooling water conduit extends along several welding caps one after the other, in order to cool the same.

10. The welding cap cooling water control system according to claim 9, wherein only one flow control valve is present.

11. The welding cap cooling water control system according to claim 10, wherein the flow control valve is arranged in the inflow to the first welding cap.

12. The welding cap cooling water control system according to claim 1, wherein several welding caps are cooled via the cooling water conduit and that in total only one single or several flow sensors are present.

13. The welding cap cooling water control system according to claim 1, wherein an associated flow sensor is provided downstream of at least one welding cap.

14. The welding cap cooling water control system according to claim 2, wherein the control unit is formed such that in the case of a pressure drop below a predetermined pressure, which is detected by the at least one flow sensor, the flow control valve is closed.

15. The welding cap cooling water control system according to claim 1, wherein the flow control valve has a flow cross-section which can be amended stepless.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 shows a circuit diagram of the welding cap cooling water control system according to the invention.

[0021] FIG. 2 shows a sectional view through the flow control valve which is used in the welding cap cooling water control system according to the invention, and

[0022] FIGS. 3 to 5 show successive stages during the movement of the flow control valve according to FIG. 2 from the open into the partly open and finally into the closed position.

DETAILED DESCRIPTION

[0023] FIG. 1 shows a welding cap cooling water control system for one or more welding caps 10 which are seated on a welding robot or on a plurality of welding robots. By way of example, series and parallel arrangements of welding caps are shown. A cooling water conduit is configured as circuit and comprises a cooling water inflow 12 as well as a cooling water return flow 14, which lead to and away from the welding caps 10.

[0024] When several welding caps 10 are present, which are cooled with a welding cap cooling water control system, a series connection of the welding caps 10 in the cooling water conduit preferably is obtained in technical terms.

[0025] In the cooling water inflow 12 an electronically actuatable and controllable flow control valve 16 is seated, namely before the first welding cap 10. Between the first welding cap 10 and the flow control valve 16 a conduit (dead-end conduit) leading to a water receiving device 18 branches off from the cooling water inflow. Optionally, the flow control valve 16 can be seated in the return flow 14, as is symbolized with the arrow shown in broken lines. At the position of the flow control valve 16 in the inflow 12 a shut-off valve is arranged.

[0026] After the last welding cap 10 a flow sensor 20 is arranged in the cooling water return conduit 14, and after the flow sensor an electrically switchable control valve 22, here a 2-2-way valve. This control valve is spring-loaded, namely into a closed position. Of course, an open position also might be provided in the case of a power failure.

[0027] On the control side, a so-called PLC, also referred to as SPS, is coupled with a downstream PID controller. Preferably, the PLC is provided on the system side, i.e. provided by the system operator, whereas the PID is coupled with a control unit 24 of the cooling water control system or forms a part of the same.

[0028] The flow control valve 16, the water receiving device 18, the flow sensor 20 and the control valve 22 are electrically coupled with the control unit 24 and send data or receive control data from the control unit 24. The corresponding conduit routing is shown in FIG. 1.

[0029] The control unit 24 for example controls hydraulic or pneumatic valves 26, which in turn actuate the flow control valve 16.

[0030] In addition, the water receiving device 18 is controlled. In the illustrated exemplary embodiment the water receiving device 18 comprises a cylinder 30 in which a shiftable piston 32 is located as movable wall. The right-hand space separated by the piston 32 in the cylinder 30 is coupled with the cooling water inflow 12, and the opposite space is coupled with a conduit 34 in which a throttle 36 is seated. The conduit 34 leads to a pilot control valve 38 which either opens the conduit 34 to the environment or separates it from the same. The conduit 34 either is pressurized or vented.

[0031] Depending on the data provided by the flow sensor 20, the control unit 24 actuates the flow control valve 16, in order to proportionally open or close the same.

[0032] The flow control valve 16 can be opened and closed steplessly, possibly also be closed completely.

[0033] Depending on the resistance in the cooling water conduit, on the number of welding caps 10 to be cooled and also on the cooling water temperature (in particular in the return conduit), the optimum throughflow of cooling water is set in the flow control valve 16.

[0034] A non-illustrated pump, which however also is actuated via the control unit 24, can additionally be operated steplessly more or less strongly, in order to let cooling water flow through the cooling water conduit.

[0035] Possible temperature sensors are not shown either in this connection, which possibly are arranged in the flow sensor 20 or in its vicinity, so that not only the flow rate, but also the temperature of the cooling water is detected and taken into account in the control unit 24 for setting the flow control valve 16.

[0036] When a leakage is detected due to an abrupt decrease in throughflow, for example in the flow sensor 20, the control unit 24 immediately actuates the flow control valve 16, which is responsible, preferably solely responsible for inhibiting the flow of coolant to the welding caps 10. Correspondingly, the control valve 22 also is switched to CLOSED.

[0037] In the case of a pressure drop, the pilot control valve 38 furthermore is actuated, which couples the space on the left of the piston 32 with the environment, so that the overpressure in the conduit portion between the flow control valve 16 and the control valve 22 leads to the fact that the piston 32 is urged to the left. Pressure peaks thus are reduced immediately.

[0038] The pressure course present in the left space in the cylinder 30 is adjustable, namely via the throttle 36, possibly also via a control valve as pilot control valve 38.

[0039] When more welding caps 10 are connected, it is detected at this point via the flow sensor 20 or via the plurality of sensors that more cooling capacity must be provided, and the control unit 24 correspondingly actuates the control valve 16 and possibly the pump, in order to supply more cooling water.

[0040] FIGS. 2-5 show the flow control valve 16 in various stages of movement.

[0041] The flow control valve 16 is an electronically controlled valve which includes a controllable electric drive 100 which is able to steplessly axially shift a linearly movable spindle 101.

[0042] The spindle 101 moves in a valve housing 102 symbolically represented here as block, which is traversed by flow passages 103, 104. On the spindle 101 a closing element 120 is mounted, which more or less clears or closes a flow connection between the flow passages 103 and 104 transitioning into each other. This is effected without steps, i.e. stepless.

[0043] The valve comprises a so-called control opening 105 in which the closing element 120 can move. On an edge, more exactly on a kind of shoulder of the control opening 105 a valve seat 106 is formed.

[0044] On the closing element 120 a sealing element 122 is mounted, here in the form of an O-ring. Furthermore, a so-called control cone 123 is formed, which conically tapers towards the tip of the closing element 120. The control cone 123 has a special shape which provides a characteristic flow path. The control cone 123 hence is designed and optimized for certain flow characteristics which result from the axial movement of the closing element 120 in the control opening 105.

[0045] In the illustrated exemplary embodiment the so-called control quality is optimized towards small flow rates. In FIG. 4 such small throughflow is possible. This is shown by the fact that the cleared flow cross-section is increased only slowly on opening of the valve. Only when the control cone 123 still dips into the control opening 105 for about 30-50% of its axial length is the free flow cross-section changed distinctly. When the valve is closed, the sealing element 122, as this is shown in FIG. 5, rests against the valve seat 106 and separates the flow passages 103 and 104 in a fluid-tight manner.

[0046] The drive 100 is an electromotive or pneumatic drive. The welding cap cooling water control system is able to continuously compensate the usual fluctuations in the cooling water system, so that there is always obtained an optimum welding result. With the illustrated flow control valve 16 the cooling system can optimally be adjusted continuously in line with the welding parameters (current intensity, sheet thickness, number of sheet layers, material, welding quality, etc.). In addition, by active control of the throughflow a diagnosis of the cooling water system can be carried out. It also is possible to diagnose the wear of the welding caps via the position of the closing element 120 or by the setpoint specification of the flow control valve.