Device for fixing, clamping, lifting and / or moving objects by suction using negative pressure with provided protective functions

Abstract

Device (2) for fixing, clamping, lifting and / or moving objects (10) by suction using negative pressure, in particular for fixing and clamping workpieces for workpiece machining or negative pressure handling device (4) for suction, lifting and / or moving objects (10), with an electrically driven negative pressure generating device (16) with a variable-speed electric motor (18) and with an electronic control unit (20) for speed control of the electric motor (18) and with a negative pressure limiting device (24), wherein the negative pressure limiting device (24) is designed such that it not only opens when a predetermined or predeterminable negative pressure is undershot, allowing air to flow from the outside into the interior of the device, but that it can be actuated in an opening and closing direction by a control device (26) depending on at least one further parameter,and wherein the control unit (20) for the electric motor (18) is designed to increase the speed of the electric motor (18) as a result of or during actuation of the vacuum limiting device (24) in the opening direction.

Description

[0001] The invention relates to a device for fixing, clamping, lifting and / or moving objects by suction using negative pressure, in particular for fixing and clamping workpieces for workpiece processing or a negative pressure handling device for suction, lifting and / or moving objects, with an electrically driven negative pressure generating device with a variable speed electric motor and with an electronic control unit for speed control of the electric motor and with a negative pressure limiting device.

[0002] For the vacuum supply of the aforementioned equipment, electrically driven blowers have been used in the known manner, typically consisting of a fixed-speed three-phase asynchronous motor. However, for reasons of energy efficiency and optimal process adaptation, it is also desirable to use variable-speed electric motors with an electronic control unit. This allows for reliable vacuum control with good energy efficiency. In both cases, the vacuum limiting device serves to reliably prevent the vacuum within the vacuum-carrying components of the equipment from exceeding a predetermined or predeterminable value, i.e., from falling below a certain threshold, thus preventing the risk of implosion, particularly when using lifting hoses or other thin-walled components.In previously known devices, the vacuum limiting device is typically formed by a vacuum limiting valve, which opens when a predetermined vacuum level is exceeded, allowing outside air to enter the vacuum-carrying components of the device and reach the vacuum-generating device, where it subsequently also provides cooling for the electric motor. In operation, these vacuum limiting valves are usually set to a constant value to achieve the most optimal operation possible with regard to a defined operating point of the electric motor, which works reasonably well when using three-phase asynchronous motors with a fixed speed.However, when variable-speed electric motors are used, this previously known vacuum limitation can only fulfill its primary purpose, namely to prevent exceeding a predetermined vacuum, since with variable-speed electric motors the optimal operating range and, in particular, a maximum permissible vacuum to reliably avoid overheating is dependent on the speed.

[0003] Vacuum handling devices with electrically driven vacuum-generating devices are known from DE 295 16 052 U1 and DE 10 2011 006 825 A1. A vacuum cleaner with an electric motor is known from DE 101 29 596 A1.

[0004] The present invention is based on the objective of enabling a reliable and trouble-free operation of devices for fixing, clamping, lifting and / or moving objects by suction using negative pressure, in which at the same time a high degree of protection of the negative pressure generating device against damage, in particular due to overheating and / or due to operation of the electric motor far from the optimal operating point, is realized.

[0005] This problem is solved in a device of the aforementioned type according to the invention by the fact that the vacuum limiting device is designed in such a way that it not only opens when a predetermined or predeterminable vacuum is undershot, so that air flows from the outside into the interior of the device, but that it can be actuated in an opening and closing direction by a control device depending on at least one further parameter, and that the control unit for the electric motor is designed to increase the speed of the electric motor as a result of or when the vacuum limiting device is actuated in the opening direction.

[0006] Because the vacuum relief device, in particular a vacuum relief valve, is no longer rigidly set to a vacuum value at which external air is admitted into the system, but can be actuated in an opening and closing direction depending on at least one other parameter, additional overheating protection for all system components can be implemented, in principle at any speed at which the variable-speed electric motor is driven. When the vacuum relief device is actuated in the opening direction, air flows from outside into the interior of the device and directly cools all components. Furthermore, this initially reduces the power consumption of the electric motor and thus also the associated power loss and heat generation due to the initially decreasing vacuum.As soon as the other recorded and monitored parameter signals that the device is operating near the optimal operating point of the electric motor, the vacuum limiting device can be actuated again in the closing direction. Thus, according to the invention, a kind of self-regulating system is realized, which facilitates operation of the device near the optimal operating point, especially when variable-speed electric motors are used, which, unlike a three-phase asynchronous motor, do not have a single characteristic curve but rather many characteristic curves depending on the frequency control.

[0007] When the vacuum relief device opens, leakage air naturally enters. However, by increasing the speed of the electric motor, the vacuum required for the application can still be achieved or maintained at a constant level.

[0008] Leakage, that is, the ingress of outside air due to an opening of the vacuum relief valve, can then be compensated for by an increase in rotational speed initiated by the control unit, so that the vacuum available in the system is maintained or quickly restored for the tasks at hand. Furthermore, the use of variable-speed electric motors and thus variable characteristic curves opens up new application possibilities for the energy-efficient operation of the system in question.

[0009] It is preferred that at least one additional parameter is a temperature, in particular an exhaust air temperature from the vacuum-generating device and / or a temperature of a motor bearing of the electric motor. The exhaust air temperature of the vacuum-generating device responds quickly as a control variable with regard to overheating of the electric motor. In contrast, the temperature of a motor bearing, especially the A-bearing, is slower to respond. However, it is also possible and advantageous to measure and evaluate several temperatures in order to safeguard against various temperature-critical situations during the operation of the device and its electric motor. In such cases, several temperature sensors interacting with the control device are provided.

[0010] Furthermore, it can be advantageous if at least one parameter is a temperature and / or a frequency specified by the control unit and / or a current draw of the electric motor and / or a volumetric flow rate (flow) through the vacuum-generating device and / or a vacuum on an intake side of the vacuum-generating device. One or more of these process parameters can also provide information about potential damage to components of the device, particularly the risk of overheating, which can then be addressed by actuating the vacuum limiting device in the opening direction. Suitable sensors are provided for the detection of this or these additional parameters.- In particular, by taking into account the frequency specified by the control unit, it is possible to adapt the vacuum limiting device to virtually any characteristic curve of the variable-speed electric motor, whereas prior art only considered a fixed threshold value. This allows for the implementation of diverse protective functions for the device and its electric motor in a variety of ways.

[0011] It is further advantageous if the control device for actuating the vacuum limiting device is integrated into the control unit for the electric motor, and / or is designed as a control device dependent on the control unit in a master / slave configuration. The control unit itself preferably includes a frequency converter.

[0012] As already indicated, the invention opens up new application possibilities for energy-efficient vacuum handling and for more versatile operation of the device. In one embodiment, for example, it is conceivable and advantageous that, for suctioning an object, the control unit is designed to first increase the speed of the electric motor, in particular by 5-15% of the initial speed, in order to quickly suction an object, and then to actuate the vacuum limiting device in the opening direction to provide cooling for the electric motor and to reduce the instantaneous power consumption and thus the power loss and heat generation of the electric motor. Afterwards, the speed could, if necessary, be reduced again, according to the vacuum level to be achieved that is deemed sufficient after suctioning an object to be clamped or lifted.

[0013] The vacuum limiting device can comprise a motorized actuator, particularly a linear motor or servo motor, or an electromagnetic actuator. Furthermore, the vacuum limiting device can include a proportional valve upon which the actuator acts. Such a proportional valve can, for example, be designed as a poppet valve or a spool valve.

[0014] In order to be able to use the device even in dirty environments, it proves advantageous if the vacuum limiting device has an intake filter.

[0015] To reduce noise, it proves advantageous if the vacuum limiting device has an intake silencer.

[0016] One embodiment of the device according to the invention is characterized by a clamping device, in particular a clamping table, clamping plate, or suction cup, with a suction side and a vacuum guide opening into the suction side for suction and thus fixing and clamping a workpiece for workpiece machining.

[0017] Another embodiment of the device according to the invention is characterized by a hand-held or robot-assisted handling device, or one formed by a robot, with a vacuum-actuated end effector for grasping an object to be handled by suction. The vacuum-actuated end effector is, in particular, a so-called suction gripper or an array-like arrangement of suction grippers.

[0018] The invention also relates to a method for operating a device of the type mentioned at the outset with the features of claims 11 to 13.

[0019] Further features, details, and advantages of the invention will become apparent from the attached claims and from the drawing and subsequent description of a preferred embodiment of the invention. The drawing shows: The figure is a schematic view of a device according to the invention for fixing, clamping, lifting and / or moving objects by suction using negative pressure.

[0020] The figure schematically illustrates a device, designated by reference numeral 2, for fixing, clamping, lifting, and / or moving objects by suction using a vacuum. In the exemplary case shown, this device 2 is a vacuum handling device 4 for suctioning, lifting, and / or moving objects. It comprises a so-called vacuum-operated suction gripper device 6 with valve components (not shown) and a suction gripper element 8, which is also only schematically indicated, and to which an object 10 to be handled can be suctioned so that it can be lifted from a base 12 and typically moved by means of the vacuum handling device 4. Instead of the indicated suction gripper device 6, however, a clamping table with suction openings for fixing workpieces could also be provided and be part of the device according to the invention.

[0021] The device 2 further comprises a vacuum-operated line 14, which connects the suction gripper device 6 or a workpiece suction interface of any type to an electrically driven vacuum-generating device 16. The vacuum-generating device 16, often also referred to as a vacuum generator, can be a blower device with a fan or compressor wheel. It includes, in any case, an electric motor 18, which is a variable-speed electric motor 18 with a control unit 20 for the motor and the motor speed, preferably operating with frequency converter technology.

[0022] To protect the device 2, and in particular the vacuum-carrying components of the device 2, against implosion, a vacuum limiting device 24 is also provided. Unlike previous devices, this device does not merely comprise a vacuum limiting valve that opens only when a predetermined vacuum is exceeded. Instead, the vacuum limiting device 24 is designed such that it can be actuated by a control device 26 in an opening direction and subsequently in a closing direction, depending on at least one further parameter. The control device 26 can include a motorized or electromagnetic actuator that acts on a valve 30, preferably a proportional valve 30, in either the opening or closing direction. The control device 26 is operatively connected to this vacuum limiting device 24 via a control line 32.The control device 26 for the vacuum limiting device 24 is preferably integrated into the electronic control unit 20 for the electric motor 18 or interacts with it in a master-slave configuration. In the exemplary case shown, at least one parameter for controlling the vacuum limiting device 24 is a temperature, for which a temperature sensor 34 is provided. This sensor detects the temperature of the exhaust air from the vacuum-generating device 16 and transmits it to the control device 26. By way of example, a further temperature sensor 35 is provided for detecting a temperature in the area of ​​a shaft bearing of the electric motor 18. Finally, by way of example, a vacuum sensor 36 is arranged on an intake side of the vacuum-generating device 16 in the vacuum-operated line 14.The aforementioned sensors 34, 35, 36 are connected to the control device 26 via respective signal lines 38, 39, 40. A speed sensor or a sensor for detecting the instantaneous current consumption of the electric motor 18 could also be provided, with such information preferably being made available by the control unit 20 for the electric motor 18 for the purpose of controlling the vacuum limiting device 24 or already being taken into account when generating control signals.

[0023] The advantage of such a device 2 is that safe operation and protection of the device can be ensured not only for a single motor speed, as is the case when using a three-phase asynchronous motor, but the vacuum limiting device 24 can be dynamically controlled and operated depending on the frequency selected by the control unit 20 for the electric motor 18 and the resulting vacuum. This results in, for example, the following application situations: When vacuuming dense and lightweight workpieces, for example, a speed setting of 50 Hz and a vacuum safety device at 200 mbar are provided. The vacuum limiting device 24, or rather its valve 30, opens as soon as a vacuum of 200 mbar is exceeded, i.e., the absolute pressure drops below approximately 0.8 bar. Typically, when vacuuming a dense workpiece, little or, in extreme cases, no leakage air enters the system. This will lead to an increase in the power consumption of the electric motor 18 and, consequently, its power loss, as well as a rise in temperature, especially since, with a relatively low speed setting of 50 Hz, the motor speed is rather low for effective motor cooling.Such a temperature increase can now be detected in the device 2 designed according to the invention via temperature sensors 34, 35 and / or other characteristic values ​​and parameters, and the control unit 20 of the electric motor 18 or the control device 26 can then open the vacuum limiting device 24 or its valve 30, so that cool outside air can enter and lead to immediate cooling of the electric motor 18. As a result of the initially decreasing vacuum due to the entering outside air, the instantaneous power consumption of the electric motor is also reduced, which leads to less power loss and heat generation.

[0024] If, on the other hand, a porous and light workpiece is sucked in, the safety mechanism is again set at 200 mbar negative pressure, and the negative pressure limiting device 24 or its valve 30 typically do not need to be opened because the air drawn in through the sucked-in product and the associated higher motor speed sufficiently cools the negative pressure generating device 16 including the electric motor 18.

[0025] Another application could involve the suction of dense and heavy workpieces, which might involve a speed setting for the electric motor 18 of, for example, 80 Hz and a safety device at 400 mbar vacuum. Here, too, the vacuum limiting device 24 or its valve 30 can be activated in the opening direction as soon as the temperature rises above a predetermined or predeterminable value and the motor speed alone is insufficient to adequately cool the system.

[0026] In another application involving the suction of porous and heavy workpieces, a safety mechanism could be implemented at, for example, a vacuum of 400 mbar. In such a case, a rotational speed above 90 Hz, for example 95 Hz, may be necessary to ensure sufficient vacuum in the system. Here, too, temperature protection can be achieved by opening the vacuum limiting device 24 and its valve 30 when a predetermined or predeterminable temperature is reached.

[0027] It is further proposed that the control unit 20 be designed in such a way that the ingress of extraneous air, namely by opening the vacuum limiting device 24 and its valve 30, always leads to at least a temporary, possibly also permanent, increase in speed when controlling the electric motor 18, so that the vacuum for a pending handling task is maintained or at least reached again as soon as possible.

[0028] The present invention thus opens up new application possibilities for energy-efficient vacuum handling technology, in which a vacuum limiting device is no longer purely passively designed and operated, but is actively controlled by the control device 26 depending on the operating parameters of the system. This ensures variable adaptation to the respective process parameters and reliable overheating protection, while maintaining optimal operation of the device close to the respective frequency-dependent operating point of the electric motor.

[0029] The following operational situations are also conceivable: At the start of the vacuum handling operation, the vacuum limiting device 24, or its valve 30, is completely closed. At temperatures below 80°C, particularly storage or exhaust air temperatures at the vacuum-generating device 16, it remains closed at all frequencies controlling the electric motor 18. At higher temperatures, particularly storage or exhaust air temperatures between 80 and 100°C, the speed of the electric motor 18 is increased by the control unit 20, for example, by 5 Hz. Simultaneously, the vacuum limiting device 24, or its valve 30, is opened sufficiently to maintain the vacuum during the process, and the additional air admitted through the valve 30 serves to cool the vacuum-generating device 16.

[0030] Should the temperatures rise above 100°C, in particular to temperatures between 100°C and 120°C, the vacuum limiting device 24 or its valve 30 can be opened further, in particular in linear relation to the increase in temperature, in order to provide further cooling capacity and a reduction in the power consumption of the electric motor 18, if necessary temporarily accepting a drop in vacuum.

[0031] The vacuum limiting device 24 is, for example, designed with a combined intake filter 42 and intake silencer 44. At least one silencer 46 is provided at the exhaust outlet.

Claims

[1] Device (2) for fixing, clamping, lifting and / or moving objects (10) by suction using negative pressure, in particular for fixing and clamping workpieces for workpiece machining or negative pressure handling device (4) for suction, lifting and / or moving objects (10), with an electrically driven negative pressure generating device (16) with a variable speed electric motor (18) and with an electronic control unit (20) for speed control of the electric motor (18) and with a negative pressure limiting device (24), wherein the negative pressure limiting device (24) is designed such that it not only opens when a predetermined or predeterminable negative pressure is undershot, allowing air to flow from the outside into the interior of the device, but that it can be actuated in an opening and closing direction by a control device (26) depending on at least one further parameter,and wherein the control unit (20) for the electric motor (18) is designed to increase the speed of the electric motor (18) as a result of or during actuation of the vacuum limiting device (24) in the opening direction. [2] Device (2) according to claim 1, characterized by that at least one further parameter is a temperature, in particular an exhaust air temperature of the negative pressure generating device (16) and / or a temperature of a motor bearing of the electric motor (18). [3] Device according to claim 1 or 2, characterized by, that at least one further parameter is a temperature and / or a frequency specified by the control unit (20) and / or a current consumption of the electric motor (18) and / or a volume flow (flow rate) through the vacuum-generating device (16) and / or a vacuum on an intake side of the vacuum-generating device (16), and that sensors (34, 35, 36) for detecting this parameter are provided. [4] Device (2) according to claim 1, 2 or 3, characterized by , that the control device (26) for actuating the vacuum limiting device (24) is integrated into the control unit (20) for the electric motor (18), and / or is designed as a control device (26) dependent on the control unit (20) (master / slave). [5] Device (2) according to one or more of the preceding claims, characterized by, that to draw in an object (10) the control unit (20) is designed to first increase the speed of the electric motor (18), in particular by 5-15% of an output speed, in order to draw in an object (10) quickly, and then to actuate the vacuum limiting device (24) in an opening direction in order to provide cooling for the electric motor (18) and to reduce the instantaneous power consumption and thus the power loss and heat generation of the electric motor (18). [6] Device (2) according to one or more of the preceding claims, characterized by , that the vacuum limiting device (24) comprises a motorized, in particular linear motorized, in particular servo motorized actuator (28) or an electromagnetic actuator (28). [7] Device (2) according to one or more of the preceding claims, characterized bythat the vacuum limiting device (24) has a valve (30), in particular a proportional valve. [8] Device (2) according to one or more of the preceding claims, characterized by that the vacuum limiting device (24) has an intake filter (42) and / or an intake silencer (44). [9] Device (2) according to one or more of the preceding claims, characterized by A clamping device, in particular a clamping table, clamping plate, block vacuum, with a suction side and with a vacuum guide opening into the suction side for suction and thus fixing and clamping a workpiece for workpiece machining. [10] Device (2) according to one or more of the preceding claims, characterized bya hand-operated or robot-assisted or robot-formed handling device (4) with a vacuum-operated end effector, in particular a suction gripper element (8) for grasping an object to be handled (10) by suctioning the object. [11] Method for operating a device with the features of claim 1, wherein the vacuum limiting device (24) is not only opened when a predetermined or predeterminable vacuum is undershot, but wherein at least one further parameter is detected and monitored and, depending on the detection and monitoring of this parameter, the vacuum limiting device (24) is actuated in an opening and closing direction, and wherein the speed of the electric motor (18) is increased as a result of or during actuation of the vacuum limiting device (24) in the opening direction. [12] Method according to claim 11, characterized by, that at least one further parameter is a temperature and / or a frequency specified by the control unit (20) and / or a current consumption of the electric motor and / or a volume flow (flow rate) through the vacuum-generating device (16) and / or a vacuum on an intake side of the vacuum-generating device (16) is detected and monitored. [13] Method according to claim 11 or 12, characterized by , that to draw in an object (10) the speed of the electric motor (18) is first increased, in particular by 5-15% of an initial speed, in order to draw in an object (10) quickly, and that afterwards the vacuum limiting device (24) is actuated in an opening direction to provide cooling for the electric motor (18) and to reduce the instantaneous power consumption and thus the power loss and heat generation of the electric motor (18).

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