Cooling Arrangement For Cooling Weld Caps Having A Check Device And Method Of Monitoring

Abstract

A cooling arrangement for cooling weld caps of a welding device includes a local cooling pipe having a feed portion through which coolant can flow to the weld caps, and a return portion through which coolant can flow away from the weld caps. The cooling arrangement has at least one sensor and at least one actuator arranged at the cooling pipe. A check device is connected to the sensor and the actuator. The check device is arranged in an immediate vicinity of the sensor and/or the actuator and/or the local cooling pipe, and is adapted to receive measured values of the sensor and to check, based on pre-established criteria, whether the measured values are within a predefined desired range. In response to a negative check result, the check device can drive the actuator in a predetermined manner such that the cooling arrangement is placed in a safe condition.

Description

RELATED APPLICATION

This application claims priority to German Application No. 10 2013 101 104.7, filed 5 Feb. 2013.

TECHNICAL FIELD

The present invention relates to a cooling arrangement for cooling weld caps of a welding device. The invention further relates to a method of monitoring such a cooling arrangement.

BACKGROUND

In robot welding technology, welding tongs with exchangeable weld caps are made use of, the wear of which can be significantly delayed by good cooling. To this end, provision is made for cooling systems having cooling pipes in which water is used as a coolant, to which glycol and further additives have been added, for example. When the weld caps are replaced, the cooling pipe is automatically sealed in the region of the weld caps, more precisely at the coolant supply and return lines thereof, to prevent an escape of the pressurized coolant. Since the cooling pipe cannot be sealed instantly in spite of the employment of quick-closing valves, an undesirable splashing of coolant will occur due to the pressure that continues to prevail in the sealed portion of the cooling pipe.

EP 1 688 205 A1 discloses a device for cooling weld caps of a welding device, which includes a cooling pipe in which a coolant is kept pressurized when the weld caps are removed. When the weld caps are exchanged, an expansion device that is connected to the cooling pipe, and has an expansion chamber, provides the possibility of an instant pressure reduction within the cooling pipe, so that no coolant under high pressure can escape.

It is the object of the invention to improve the monitoring of a cooling arrangement, in particular with respect to an error analysis.

SUMMARY

A cooling arrangement for cooling weld caps of a welding device includes a local cooling pipe having a feed portion through which coolant can flow to the weld caps, and a return portion through which coolant can flow away from the weld caps. The cooling arrangement further includes at least one sensor arranged at the cooling pipe and at least one actuator arranged at the cooling pipe. Furthermore, the cooling arrangement includes a check device which is connected to the at least one sensor and the at least one actuator. The check device means is arranged in an immediate vicinity of the at least one sensor and/or the at least one actuator and/or the local cooling pipe, and is adapted to receive measured values of the at least one sensor and to check, based on pre-established criteria, whether the measured values are within a predefined desired range. In response to a negative check result, the check device can drive the at least one actuator in a predetermined manner such that the cooling arrangement is placed in a safe condition.

The cooling arrangement is intended for an application in automated welding devices (welding robots). The objects to be cooled are weld caps which, in operation, assume very high temperatures.

The at least one sensor of the cooling arrangement measures a quantity related to the coolant or to some other component that is critical to the cooling arrangement, such as the flow rate, temperature, or pressure of the coolant. The at least one actuator of the cooling arrangement, which is driven directly by the check device when necessary, makes sure that an immediate reaction is caused in case of a problem, so that no excessive damage occurs.

The invention is based on the finding that monitoring a cooling arrangement can be carried out considerably more easily and effectively if a separate check device for the cooling arrangement is available directly on-site. In this way, staff is readily enabled to detect an error immediately on the associated cooling arrangement, without an intervention in a superordinate system control being necessary for this. The same applies to the automatic response of the check device, i.e. driving the at least one actuator need not be embedded in the superordinate system control which would be complicated. These aspects are of particular importance in the case of welding robots, which have a complex system control that is not readily comprehensible to everyone. In addition, the system control and the local cooling arrangements of the welding robots may be part of an overall system control or of a larger cooling system, something which would even aggravate the above-mentioned problems.

The at least one actuator may comprise a closing valve for shutting off the cooling pipe and/or a device for pressure reduction in the cooling pipe. Actuation of the shut-off valve allows the coolant flow to be interrupted quickly, which is important especially in the event of a leak of the cooling pipe, to prevent any larger amounts of coolant from escaping in an uncontrolled manner. With the aid of the pressure reduction device, the pressure in the cooling pipe can be reduced after the cooling pipe is shut off, so that during repair or maintenance works in which an outlet opening for the coolant is necessarily provided, the amount of splashing coolant is kept as low as possible.

According to a special embodiment of the device for pressure reduction, for an accelerated pressure compensation, it includes an expansion cylinder with a built-in compensating spring and/or a pilot valve. The coolant flows into the expansion cylinder which provides a volume for receiving coolant, the volume expanding under the pressure of the coolant. The compensating spring and/or the pilot valve allow(s) to adjust a backpressure, which can be made use of for damping the expansion movement or preloading it against the spring.

For a useful monitoring of the cooling arrangement, the at least one sensor should comprise a flow meter and/or a temperature sensor and a pressure sensor. The flow rate, temperature, and pressure parameters are of utmost importance to a proper operation of the cooling arrangement.

In a particularly compact embodiment of the invention, the check device is placed on the flow meter or the pressure sensor. A separate holder and an external connecting line to the respective sensor are therefore dispensed with.

The check device is preferably adapted such that threshold values can be stored and compared with measured values of the at least one sensor. This means that the check device is independent of a superordinate system control to the greatest possible extent. With a view to a simple and uncomplicated handling, the threshold values can be entered directly on the check device by keys or the like, preferably interactively in a dialog with instructions on a display of the check device.

For a more differentiated error assessment, an evaluation unit of the check device is advantageous which takes into account whether measured values of the at least one sensor are outside of the desired range temporarily or permanently. This allows any temporarily occurring errors to be filtered out, such as pressure peaks which by themselves do not yet require any safety measures to be taken. Also helpful are a more extensive evaluation and display of the point of time of the error and, when there is a plurality of sensors, for which parameters and in which order errors have occurred.

Additionally, provision may be made in the cooling arrangement that the check device is adapted to be connected to a superordinate system control, and such that results of the check of whether the measured values of the at least one sensor are within the predefined desired range can be transmitted to the superordinate system control. Depending on the mode of operation, the error information may be only logged by the superordinate system control, or else the system control—instead of the check device—then arranges for appropriate safety measures to be carried out.

According to an extension of the cooling arrangement, at least two flow meters are connected to the check device so that the flow rate can be monitored at at least two different points. One of the flow meters may be provided inside or outside of the local cooling arrangement, for example at a coolant supply line or a coolant discharge line. An incorporation of such an external flow meter provides the possibility of monitoring the pressure differential. The external flow meter may also be arranged at a local cooling pipe of a different local cooling arrangement, e.g. a different cooling arrangement of the same cooling system or a cooling arrangement for a motor. This allows a more differentiated error assessment and provides an evaluation assistance.

For a comfortable monitoring of the cooling arrangement by on-site staff, the check device should include a display for a continuous display of measured values of the at least one sensor and/or for a display of errors.

According to an especially advantageous embodiment, the cooling arrangement is a prefabricated assembly and includes at least one fastener for mounting the cooling arrangement to a wall or a board. This allows the cooling arrangement to be mounted in a simple and space-saving manner. In addition, transportation and storage are simplified.

A method of monitoring a cooling arrangement according to the invention, comprises the steps of:

• • receiving measured values of the at least one sensor by the check device;
  • checking, based on pre-established criteria, whether the measured values are within a predefined desired range; and
  • in response to a negative check result, driving the at least one actuator such that the cooling arrangement is placed in a safe condition.

With respect to the advantages of the method, reference is made to the corresponding annotations on the cooling arrangement.

In order to take account of varying circumstances or to allow a flexible use of the cooling arrangement in different applications, it is of advantage that one or more threshold values defining the desired range can be manually stored in the check device.

For the filtering of any temporarily occurring errors as already previously mentioned, in its evaluation of the measured values of the sensor(s) the check device should take into account whether the measured values are only temporarily or actually permanently outside of the desired range.

To be able to identify the cause of a problem of the cooling arrangement as clearly and quickly as possible in a serious situation, in one example embodiment of the method provision is made that in a case in which a plurality of errors occur in the form of measured values of various sensors being outside of their desired ranges, the check device at first displays that error which occurred first.

According to a further development of the method, based on a plurality of threshold values the check device distinguishes between whether a minor or a major deviation from the desired range has occurred. In this further development, it is only in the event of a major deviation that the at least one actuator is driven such that the cooling arrangement is placed in a safe condition. In case of a minor error it is then possible to remove the error manually during normal operation of the cooling arrangement, without the cooling arrangement being transferred to a safe condition right away.

These and other features may be best understood from the following drawings and specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the structure of a cooling arrangement with a check device according to the invention in a top view; and

FIG. 2 shows the structure from FIG. 1 in a side view.

DETAILED DESCRIPTION

FIGS. 1 and 2 show a local cooling arrangement by way of example, which is suitable in particular for cooling weld caps of a welding device. The cooling arrangement comprises a cooling pipe 10 through which a coolant flows and which can be divided into a feed portion 14 leading from a coolant inlet 12 to the weld caps (not illustrated) to be cooled and a return portion 18 leading from the weld caps to be cooled to a coolant outlet 16. The cooling pipe 10 should be understood as a local pipe which is only intended for the weld caps to be cooled. The cooling arrangement itself may be part of a larger cooling system including a plurality of local cooling arrangements, for example for a multitude of individual welding robots.

The components of the cooling arrangement that are to be emphasized are: a flow meter 20; a temperature sensor 21 (integrated in the housing of the flow meter 20 here); a closing valve 22 for completely shutting off the coolant flow; a pressure sensor 24; a device 26 for reducing the pressure in the cooling pipe 10 (pressure reduction device); a valve 28 for section regulation (section regulating valve), preferably with a hand wheel 30 for manual adjustment of the valve 28; a nonreturn valve 32; and a special check device 34. The cited components may, together with the coolant inlet 12, a connection 36 to a supply line to the weld caps, a connection 38 to a return line from the weld caps, and the coolant outlet 16, be fitted to a wall or a board as a prefabricated assembly. For this purpose, fasteners are provided, for example in the form of clamps 40 and, where required, a fastening board 42, which may be arranged in particular in the vicinity of the coolant inlet 12 and the coolant outlet 16 or the connections 36, 38.

In the exemplary embodiment illustrated, as viewed in the flow direction, first the flow meter 20 with the temperature sensor 21 and, behind them, the closing valve 22 are arranged in the feed portion 14. Arranged one behind the other in the return portion 18 are the pressure sensor 24, the pressure reduction device 26 at a branch-off of the cooling pipe 10, the section regulating valve 28, and the nonreturn valve 32. The check device 34 is placed on the pressure sensor 24 as a unit, but could just as well be placed on the flow meter 20 or be formed as an independent unit. At any rate, the check device 34 is connected to the sensors of the cooling arrangement, i.e. in this case to the flow meter 20, the temperature sensor 21 and the pressure sensor 24, as well as to the closing valve 22 serving as an actuator. The connecting lines are not illustrated in the Figures. For the error analysis to be described further below, it is advantageous that the check device 34 is placed in the immediate vicinity of the other components of the local cooling arrangement.

Other arrangements of the components within the cooling arrangement are also conceivable, and it is also possible to provide fewer, or still additional sensors, or also actuators connected to the check device 34 (in addition to the closing valve 22, the pressure reduction device 26, the section regulating valve 28 and the nonreturn valve 32).

When the cooling pipe 10 is shut off by the closing valve 22 for a replacement of weld caps, the pressure reduction device 26 allows an immediate pressure reduction to be obtained in the cooling pipe 10, so that a splashing of the pressurized coolant is avoided to the greatest possible extent. The pressure reduction device 26 may be an expansion cylinder 44 having a pilot valve 46 and a restrictor 48, as disclosed in EP 1 688 205 A1. In addition to, or in place of, the pilot valve and the restrictor, provision may also be made for a compensating spring which preloads the piston in the expansion cylinder. But instead of the expansion cylinder, a pump or an active cylinder, or some other type of suction device may also be used.

The mode of operation of the cooling arrangement and, more particularly, of the check device 34 thereof will now be described below. Cold coolant flows through the coolant inlet 12 into the cooling pipe 10 and reaches the weld caps via the feed portion 14, the weld caps giving off heat to the coolant. The heated coolant flows out of the cooling pipe 10 via the return portion 18.

During normal operation of the cooling arrangement, the flow meter 20, the temperature sensor 21 and the pressure sensor 24 transmit their measured values to the check device 34. Stored in the check device 34 are application-specific threshold values which can be adjusted individually and which each define a desired range. The measured values are shown on a display of the check device 34 and updated at specific time intervals.

In case a measured value is outside its desired range, a respective alert is output on the display of the check device 34, i.e. it is indicated which parameter (flow rate, temperature, pressure, etc.) has fallen below a lower threshold value or has exceeded an upper threshold value. Such falling below, or exceedance of, a threshold value constitutes an error and, possibly after a check of further pre-established criteria, is rated as a negative check result. In case this applies to a plurality of parameters, the parameter that left the desired range first is displayed first. In this way, it is usually possible to immediately identify the cause of error on the spot, e.g.: was the temperature too high, the pressure too low, or did a cooling pipe burst? In addition to the visual display of the error, an acoustic alert may also further be output.

In a first operating mode—to be referred to as “autarkic” here—of the check device 34, in the event of an error the check device 34 will initiate measures on its own to ensure the safety of the cooling arrangement. More precisely, one or more of the actuators connected to the check device 34, i.e. here the closing valve 22 and the pressure reduction device 26, are driven such that the cooling arrangement is placed in a safe condition.

To this end, provision is made in particular that in case of an abrupt drop in flow or pressure, the check device 34 causes the closing valve 22 to shut off the cooling pipe 10 in the feed portion 12 to prevent any larger amounts of coolant from escaping in the event of a leakage. After actuation of the closing valve 22, the pressure reduction device 26 is activated with an adjustable time delay, so that coolant enclosed under pressure is removed from the cooling pipe 10 and pressure is thereby reduced. In the case of an expansion cylinder 44, activation means that the coolant can flow into a dynamic expansion chamber of the expansion cylinder 44 and displace a piston mounted therein, accompanied by an expansion of the expansion chamber. The movement of the piston is damped to a suitable extent by a backpressure on the other side of the piston, the backpressure being adjusted by the pilot valve 46 and the restrictor 48 or the compensating spring.

After removal of the error or errors and acknowledgement of the error message(s) to the check device 34, the check device 34 then first causes the closing valve 22 to be opened and, after an adjustable time delay, the pressure reduction device 26 to be deactivated. In the case of the expansion cylinder 44, deactivation means that the piston is displaced towards the cooling pipe 10 again by a backpressure that is suitably adjusted by means of the pilot valve 46 and the restrictor 48 or the compensating spring, so that the expansion volume is available again in case it is needed again.

In an extended embodiment of the check device 34, a plurality of threshold values (steps) for each parameter may be stored, so as to allow a distinction between a minor and a major deviation from the respective desired range. In addition, a special evaluation of the measured values may be provided for, which takes into account whether a falling below or exceeding of a threshold value is only temporary or permanent (filter function). Taking one or more of these measures allows to distinguish between slight and serious errors.

In the event of a slight error which is not yet rated as a negative check result, the cooling arrangement is not switched off immediately, but (for the time being) only an alert is output. This provides the possibility of manually removing the error during normal operation of the cooling arrangement. For example, when the pressure is slightly too low, the pressure can be slightly increased by adjusting the section regulating valve 28 or, when the temperature of the coolant is slightly too high, the flow rate can be increased to lower the temperature in this way.

In a second operating mode—to be referred to as “monitor” here—of the check device 34, an error that has been detected is also indicated as an alert output on the display of the check device 34. However, the check device 34 will not initiate any measures itself, but will pass the error information in the form of characteristic signals on to a superordinate system control, in particular to the robot control when a welding robot is involved. In this case, the system control then takes appropriate measures to ensure the safety of the cooling arrangement or of the entire system.

In the previously described operating mode called “autarkic”, error information can also be transmitted to the superordinate system control. In this operating mode, however, the system control will not arrange for any specific measures which directly concern the cooling arrangement.

Finally, a third operating mode is available for the check device 34, which is to be referred to as “cap replacement” here. When this mode is selected, the check device 34 will cause the closing valve 22 to shut off the cooling pipe 10 in the feed portion. Subsequently, the pressure reduction device 26 activated after an adjustable time delay makes sure, with the assistance of the compensating spring, if required, that excess coolant is removed from the cooling pipe, so that the pressure therein is reduced. The weld caps can then be replaced, without a splashing of pressurized coolant occurring. In this operating mode, the error monitoring of the check device 34 is inactive, which is signaled to the operating staff by the current operating mode being indicated on the display. After completion of the weld cap replacement, first the closing valve 22 is opened again before the pressure reduction device 26 is then deactivated again after an adjustable time delay.

In an extended embodiment of the local cooling arrangement, at least two flow meters are provided, which are both connected to the check device 34. The values from both flow meters can then be displayed by the check device 34 with an appropriate reference to the respective flow meter and can be monitored for errors. It is basically also possible to provide two or more flow meters one of which is arranged on the local cooling pipe 10 as described above and the other is arranged externally on a coolant supply line or a coolant discharge line, i.e. beyond the coolant inlet 12 or the coolant outlet 16. Such a structure allows a display and monitoring of the pressure differential, which apart from that is carried out as described above.

The check device 34 is connected to the actuators and to the superordinate system control by suitable multipolar plug connectors or other suitable interfaces. The electrical connections between the components involved may run directly or indirectly (for example as part of a bus system). Wireless connections (radio) are also feasible.

In addition to the display for displaying the measured values, the operating mode, etc., the check device 34 further includes keys for configuration, in particular for a direct input of threshold values, for an acknowledgement of error messages, etc..

Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the true scope and content of this disclosure.

Claims

1. A cooling arrangement for cooling weld caps of a welding device, the cooling arrangement comprising:

a local cooling pipe having a feed portion through which coolant can flow to the weld caps, and a return portion through which coolant can flow away from the weld caps;

at least one sensor arranged at the local cooling pipe;

at least one actuator arranged at the local cooling pipe; and

a check device which is connected to the at least one sensor and the at least one actuator, wherein the check device is arranged in an immediate vicinity of the at least one sensor and/or the at least one actuator and/or the local cooling pipe and is adapted to receive measured values of the at least one sensor and to check, based on pre-established criteria, whether the measured values are within a predefined desired range and, in response to a negative check result, to drive the at least one actuator in a predetermined manner such that the cooling arrangement is placed in a safe condition.

2. The cooling arrangement according to claim 1, wherein the at least one actuator comprises at least one of a closing valve for shutting off the local cooling pipe and a device for pressure reduction in the local cooling pipe.

3. The cooling arrangement according to claim 2, wherein the device for pressure reduction in the local cooling pipe includes an expansion cylinder with at least one of a built-in compensating spring and a pilot valve.

4. The cooling arrangement according to claim 1, wherein the at least one sensor comprises at least one of a flow meter, a temperature sensor, and a pressure sensor.

5. The cooling arrangement according to claim 4, wherein the check device is placed on one of the flow meter and the pressure sensor.

6. The cooling arrangement according to claim 1, wherein the check device is adapted such that threshold values can be stored and compared with measured values of the at least one sensor.

7. The cooling arrangement according to claim 1, wherein the check device includes an evaluation unit which takes into account whether measured values of the at least one sensor are outside of predefined the desired range temporarily or permanently.

8. The cooling arrangement according to claim 1, wherein the check device is adapted to be connected to a superordinate system control and to transmit results as to whether the measured values of the at least one sensor are within the predefined desired range to the superordinate system control.

9. The cooling arrangement according to claim 1, wherein the check device is connected to a first flow meter arranged at the local cooling pipe and to a second flow meter that is internal or external of the cooling arrangement.

10. The cooling arrangement according to claim 1, wherein the check device includes a display for at least one of a continuous display of measured values of the at least one sensor and for a display of errors.

11. The cooling arrangement according to claim 1, wherein the cooling arrangement is a prefabricated assembly and includes at least one fastener to mount the cooling arrangement to one of a wall and a board.

12. A method of monitoring a cooling arrangement comprising the steps of:

providing a local cooling pipe having a feed portion through which coolant can flow to the weld caps, and a return portion through which coolant can flow away from the weld caps, at least one sensor arranged at the local cooling pipe, at least one actuator arranged at the local cooling pipe, and a check device which is connected to the at least one sensor and the at least one actuator

receiving measured values of the at least one sensor by the check device;

checking, based on pre-established criteria, whether the measured values are within a predefined desired range; and

in response to a negative check result, driving the at least one actuator such that the cooling arrangement is placed in a safe condition.

13. The method according to claim 12, wherein one or more threshold values defining the predefined desired range are manually stored in the check device.

14. The method according to claim 12, wherein the check device evaluates the measured values of the at least one sensor, taking into account whether the measured values are outside of the predefined desired range temporarily or permanently.

15. The method according to claim 12, wherein in a case in which a plurality of errors occur in the form of measured values of various sensors being outside of their predefined desired ranges, the check device at first displays that error which occurred first.

16. The method according to claim 12, wherein based on a plurality of threshold values, the check device distinguishes between whether a minor or a major deviation from the predefined desired range has occurred, and only in the event of a major deviation is the at least one actuator driven such that the cooling arrangement is placed in a safe condition.