EP3493948B1 - Grinding device and method for operating the grinding device - Google Patents

Description

Technical area

The present invention relates to a device for grinding surfaces of a workpiece, which is preferably formed at least in sections from wood, wooden material, plastic or the like. The present invention also relates to a grinding machine and a method.

State of the art

In the prior art, grinding machines comprise support elements with support element segments, the latter being able to be adjusted individually in order to press a grinding belt against a section of a workpiece to be machined. The deployment movement of the carrier element segments is initiated by a control device to which information relating to the workpiece is fed.

However, if, for example, a workpiece is machined that has height differences over the machining path, the pressure forces on the workpiece vary. This can lead to different grinding results within certain, defined thickness tolerances.

In the document DE 37 16 832 A1 describes a method for operating a belt grinder, the belt grinder with a driven conveyor belt that moves the workpieces to be sanded and with one above the conveyor belt transversely or longitudinally to the Direction of movement of the workpiece is provided endlessly rotating sanding belt.

Presentation of the invention

The aim of the present invention is to provide a device and a method with which a grinding process can be carried out more precisely.

The subject matter of claim 1 provides a device for this. Claim 13 relates to a method for machining a workpiece. Further preferred embodiments are listed in the dependent claims, which can each be combined individually with the independent claims.

The advantages mentioned below can be achieved, inter alia, by the device according to the invention or the method according to the invention. In particular, it is possible to keep the grinding result constant under changing conditions (thickness differences of a workpiece). Furthermore, the forces measured by the sensors can be stored and analyzed later. If the optimal settings for the application of the machine are known, direct feedback with suggestions for improvement can be sent to the operator.

It is also possible to individually determine the optimal settings with regard to the grinding pressure. Together with other collected customer data from the users of the device, it becomes possible for the manufacturer of such a device to better understand the corresponding operating behavior and to improve it further through suggestions or design changes.

If, for example, it is determined that too high a grinding pressure is applied consistently, then individual pressure segments can be readjusted.

The device according to the invention for grinding a workpiece has a carrier element and a plurality of pressure segments which are arranged along the carrier element and which are each designed to press a grinding element, in particular a preferably circumferential grinding belt, against a workpiece. Furthermore, the device comprises at least one sensor which is used to detect a pressure force applied to a workpiece by one of the pressure segments. By recording the pressure force, changing conditions, for example in the case of differences in the thickness of a workpiece, can be recorded and these results can be used to improve the grinding process.

The device further comprises a grinding tongue which extends along the carrier element, the sensor or sensors being / are provided between the grinding tongue and the carrier element. In this way, precise section-by-section detection of the pressure can be guaranteed. Furthermore, the sensors are provided between the grinding tongue and the respective pressure segment. Thus, according to this embodiment, a compact arrangement can be achieved.

The device comprises pressure segments, each of which can be moved electromagnetically. This leads to a quick and accurate control of the corresponding pressure segments.

The device preferably comprises a control device which is set up to compare a pressure force detected by the at least one sensor with a force target value and a type and / or duration of an actuation of the corresponding pressure segment to achieve the force target value to vary. With this device, the grinding result can be kept constant under changing conditions, for example when the thickness of a workpiece is different. For example, magnetic actuators are excited with longer or shorter current pulses in order to vary the corresponding grinding pressure.

The named control device can be the central control device of the device or a decentralized control device arranged in the area or on the carrier element.

In a preferred embodiment of the present invention, a sensor is provided for each pressure segment for detecting a pressure force. This is arranged either continuously on the grinding tongue or in sections for each pressure segment, for example attached to the pressure segments, which ensures efficient and holistic detection of the pressure force.

In one embodiment, it is preferred that a sensor is attached to each of the pressure segments, it being preferred that the sensors are designed in the manner of a film. After a pressure force can be determined on each pressure segment, the pressure segments can be monitored individually and their pressure force applied to the workpiece can be regulated if necessary. The film-like design of the sensors enables an extremely compact design.

According to another embodiment of the device, the sensors or the sensor is attached to the grinding tongue or integrated into the grinding tongue. The grinding tongue is an exchangeable component, so that no complex structural changes are necessary when a sensor is attached in this way.

According to a particular embodiment of the device, the pressure segments each have a, preferably plate-shaped, contact section for bearing against a grinding belt and a, preferably cylindrical, guide section for guiding a movement of the pressure segment, which enables the movement. It is preferred that the preferably film-like sensor is attached to the side of the contact section facing the grinding element, in particular the grinding belt.

The device can also have a light strip, which is in particular an LED strip, which can light up in different colors in sections, and is designed so that the ratio of the force setpoint and the determined pressure force qualitatively via the glow in a specific color of the respective Section. In this way, the user receives visual feedback about this relationship.

The LED bar of the device can also preferably light up in a specific color, which signals that the determined pressure force of the corresponding pressure segment is above the predetermined force target value. The assignment of a certain color to this excessive pressure can thus be communicated to the user so that the user can react to this event.

In this embodiment, the determined pressure forces and the corresponding force target value can optionally be saved additionally. In this way, the stored data can be evaluated at a later point in time.

Furthermore, the determined and stored pressure forces and corresponding force target values can optionally be transmitted to an external server. The data collected in this way can be collected, evaluated and used centrally. For example, data can be sent to an upstream or downstream Machine are transmitted in order to set their characteristic values in coordination with the device according to the invention.

More preferably, the device can be set up to transmit the determined pressure force to the control device by means of wireless data transmission, in particular RFID technology. This reduces the weight of the device. Furthermore, the assembly is simplified.

The invention further relates to a grinding machine with a device according to one of the preceding aspects and a movement device for bringing about a relative movement between a workpiece and the carrier element. More preferably, the movement device can comprise a conveyor belt or one or more conveyor belts. The grinding machine is preferably a wide belt grinding machine or a cross belt grinding machine.

In addition to the device described above, the grinding machine can include a workpiece recognition device with which a workpiece to be machined is recognized. Based on the workpiece recognition, a pressure segment or several pressure segments are actuated in order to carry out a grinding process.

In an alternative embodiment, the carrier element can also be moved, the workpiece being held stationary or likewise moved during the movement of the carrier element.

• Herstellen von einer Relativbewegung zwischen einem Werkstück und einem Trägerelement, wobei entlang des Trägerelements eine Mehrzahl von Drucksegmenten angeordnet ist,
• Bearbeiten des Werkstücks durch ein Schleifelement, insbesondere durch ein Schleifband, wobei zumindest eines der Drucksegmente gegen das Schleifelement gedrückt wird,
• wobei eine von zumindest einem Drucksegment am Werkstück aufgebrachte Druckkraft durch einen Sensor erfasst wird.

The method according to the invention for machining a workpiece, which preferably using a device as described above, comprises:

• Establishing a relative movement between a workpiece and a carrier element, wherein along the Carrier element a plurality of pressure segments is arranged,
• Processing of the workpiece by a grinding element, in particular by a grinding belt, wherein at least one of the pressure segments is pressed against the grinding element,
• wherein a pressure force applied by at least one pressure segment on the workpiece is detected by a sensor.

Furthermore, it is preferred that the detected compressive force is compared with a force target value, and the pressure segment is moved to achieve the force target value. With this method, a grinding result can be kept constant under changing conditions, for example when the thickness of a workpiece is different.

The modifications of the device according to the invention discussed above can also be used in the context of the method.

Brief description of the drawings

Fig. 1

shows a detailed view of an embodiment of the device according to the invention.

Fig. 2a

Figure 3 is a schematic cross-sectional view of the embodiment of the apparatus of the present invention with the pressure segments down.

Figure 2b

Figure 3 is a schematic cross-sectional view of the embodiment of the apparatus of the present invention with the pressure segments raised.

Fig. 3

Figure 13 shows a perspective view of the embodiment of the present invention.

Detailed description of preferred embodiments A preferred embodiment of the present invention is described below with reference to the accompanying figures. Further modifications of certain individual features mentioned in this context can each be individually combined with one another in order to form new embodiments.

Figure 1 shows a detailed view of a device 10 which, in the embodiment explained here, is a sanding unit of a wide belt sanding machine. A perspective view of the wide belt sander, in which several sanding units can be accommodated, is shown in FIG Fig. 3 pictured. It can be seen that the device 10 can also be used in a cross belt grinding machine.

The device 10 comprises a carrier element 11, which extends over an in Figures 1-2 extends machine bed not shown in detail. The carrier element 11 is located within the in Fig. 3 Housing of the wide belt sander shown and extends transversely to the conveying path of a workpiece. In particular, a workpiece 1 can be moved by means of a preferably circulating conveyor belt 22 and thereby guided under the carrier element 11.

A plurality of guides 16a, 16b, 16c are attached to the carrier element 11 and extend in the vertical direction to the machine bed and thus in the direction of the conveyor belt 22. Magnetic actuators are accommodated in the guides 16a, 16b, 16c.

Each of the guides 16a, 16b, 16c is connected to a pressure segment 12a, 12b, 12c, wherein the pressure segments can be moved relative to the guides 16a, 16b, 16c. By moving a pressure segment 12a, 12b, 12c in the direction of an abrasive belt 21, this is pressed in sections against a workpiece 1, as will be explained below.

The pressure segments 12a, 12b, 12c each include a plate-shaped contact section 12a ', 12b', 12c 'to press a sanding belt 21 against a workpiece 1, and a cylindrical guide section 12a ", 12b", 12c "for guiding a movement of the Pressure segment 12a, 12b, 12c within the respective guide 16a, 16b, 16c. When the magnetic actuator accommodated in the respective guide is actuated, the corresponding pressure segment is moved vertically downwards (in the direction of the conveyor belt 22).

To actuate a magnetic actuator, which causes an opening movement of a pressure segment 12a, 12b, 12c, a certain current value is supplied to it. The grinding pressure can be adjusted depending on the type and / or duration of the actuation. The magnetic actuator is with Current impulses stimulated in order to apply a higher or lower pressure force on the workpiece, depending on the type and / or length of the current impulses. In this way the grinding pressure is varied.

In the vertical direction below the plurality of pressure segments 12a, 12b, 12c, a grinding tongue 15 is provided, which extends along the carrier element 11. The grinding tongue 15 is thus provided between the grinding belt 21 (which in the present exemplary embodiment revolves over several rollers) and the pressure segments 12a, 12b, 12c.

The grinding tongue 15 comprises several sections, including a base element 15a and a pad 15b arranged below it. A holder 17, which is fastened to the carrier element 11, is in contact with the base element 15a and thus holds the sanding tongue 15 on the carrier element 11. On the side of the pad 15b facing the back of the sanding belt 21, a sliding layer is provided to protect the sanding belt with as much as possible to slide low friction over the pad 15b.

A sensor 13a, 13b, 13c is inserted between each of the pressure segments 12a, 12b, 12c and the grinding tongue 15 and, according to the present embodiment, is attached to the pressure segments 12a, 12b, 12c. The sensors 13a, 13b, 13c are flat and can thus be advantageously arranged between a respective pressure segment or grinding tongue 15. With the sensors, a force applied by the respective pressure segment on a section of the workpiece 1, and thus the local grinding pressure, can be determined.

The sensors 13a, 13b, 13c are connected to a control device of the device 10 or the wide belt sander. Pressure force setpoints are stored in the control device, with which the pressure segments are each im Application to be pressed against the workpiece 1. The control device is also set up to compare actual compressive force values, which are detected by the sensors of the actuated pressure segments, with a respective desired compressive force value and, based on this comparison, to regulate the compressive force on the workpiece. In this way, deviations in the workpiece thickness can be taken into account and a uniform local grinding pressure can be made possible.

In Figure 3 an embodiment of a wide belt sander with the device 10 according to the invention is shown from the outside. Above an insertion area for placing a workpiece on the conveyor belt 22, a light bar 23, in particular an LED bar, is provided, which extends transversely to the direction of movement of the conveyor belt 22. The light strip 23 is connected to the control device.

The control device can be set up to transmit the determined compressive force in each segment to an external server. This data can be forwarded to an upstream machine for evaluation or information, for example in order to control its processes in this way.

The light strip 23 can shine in different colors in sections, and can thus represent the ratio of the desired force value and the actual force value qualitatively by illuminating in a specific color of the respective section. If, for example, an area of the light strip 23 indicates by means of a red color that grinding is being carried out with too high a pressure, this can be noticed and / or taken into account and / or automatically readjusted by the operating personnel.

Several areas arranged in columns and rows are defined on the LED bar. The rows form, for example. several grinding units lying one behind the other in the machine. In the corresponding fields of the columns, for example, the degree of wear of the units in a specific segment can be displayed to the operator.

A method for processing a workpiece with the wide belt sander comprising the device 10 of the present embodiment is described below.

First, a workpiece 1 is applied or placed on the conveyor belt 22. The revolving conveyor belt 22 moves the workpiece 1 in the direction of the carrier element 11, which comprises the plurality of pressure segments 12a, 12b, 12c. Based on the results of a workpiece recognition device (not shown), which is located in front of the carrier element in the direction of travel of the workpiece and recognizes the presence of a workpiece, certain pressure segments are moved in the direction of the conveyor belt 22 relative to the carrier element 11 in order to move the grinding belt 21 in sections with the workpiece 1 to bring in contact.

In Fig. 2a a cross-sectional view of the embodiment of the device according to the invention with at least some lowered pressure segments is shown, so that the abrasive belt 21 is pressed against the workpiece by the lowered pressure segments.

Such a movement of the pressure segments 12a, 12b, 12c takes place depending on the design of the workpiece 1. If the workpiece 1 is a frame component (such as a window frame), then those pressure segments 12a, 12b, 12c are placed on the longitudinal sides of the workpiece 1 issued, with which the grinding belt 21 is to be brought into contact with the corresponding section of the workpiece 1. In the in Fig. 1 In the situation shown, there are (in this example four) pressure segments in the Edge area in its starting position, while further pressure segments 12a, 12b, 12c are actuated.

The sensors 13a, 13b, 13c provided between the grinding tongue 15 and each pressure segment 12a, 12b, 12c continuously detect forces that are applied to the respective section of the workpiece 1 by the pressure segments 12a, 12b, 12c.

The recorded forces are transmitted to the control device and can be compared with corresponding setpoint values. Based on this comparison, the opening position of the respective printing segment can be readjusted. It is thus possible to compensate for varying workpiece thicknesses that are within the tolerance range of a workpiece recognition device (not shown) and that can arise along the processing path. In other words, a constant grinding pressure can be ensured over the entire workpiece. This grinding pressure can be, for example, a material-specific or application-specific grinding pressure that does not have to be changed after setting.

Claims (13)

1. Device (10) for grinding a workpiece (1) having:

   a carrier element (11),

   a plurality of in particular electromagnetically operable pressure segments (12a, 12b, 12c) which are arranged along the carrier element (11) and which are in each case designed to press a grinding element, in particular a grinding belt (21), against a workpiece (1),

   at least one sensor (13a, 13b, 13c) for registering a compressive force applied to a workpiece by one of the pressure segments,

   wherein the device includes a grinding finger (15) which extends along the carrier element (11), wherein

   the sensor(s) (13a, 13b, 13c) is/are provided between the grinding finger (15) and the respective pressure segment (12a, the 12b, 12c),

   characterised in that

   the pressure segments (12a, 12b, 12c) are in each case electromagnetically moveable by means of a magnetic actuator accommodated in a guide (16a, 16b, 16c) provided on the carrier element (11).
2. Device according to claim 1 which comprises a control unit which is configured to compare a compressive force registered by the at least one sensor (13a, 13b, 13c) with a force setpoint value and to vary a manner and/or duration of an actuation of the corresponding pressure segment (12a, 12b, 12c) in order to achieve the force setpoint value.
3. Device according to claim 1 or 2, wherein a sensor (13a, 13b, 13c) is provided for each pressure segment (12a, 12b, 12c) in order to register a compressive force, or a continuous sensor is provided which has a plurality of sensor sections which are in each case configured to register a compressive force applied to the workpiece by a pressure segment.
4. Device according to one of the preceding claims, wherein a sensor (13a, 13b, 13c) is in each case attached to the pressure segments, wherein it is preferable if the sensors are of foil-type design.
5. Device according to one of the preceding claims, wherein the sensor(s) is/are attached to or integrated in the grinding finger (15), wherein it is preferable if the sensor(s) are of foil-type design.
6. Device according to one of the preceding claims, wherein the pressure segments (12a, 12b, 12c) in each case have a preferably plate-formed contact section (12a', 12b', 12c') for placement against a grinding belt (21) and a preferably cylindrical guide section (12a'', 12b'', 12c'') for guiding a movement of the pressure segment, wherein it is preferable if the preferably foil-type sensor is attached to the side of the contact section facing the grinding element, in particular grinding belt.
7. Device according to one of the preceding claims, further comprising:
   a light strip (23), in particular an LED strip (23), sections of which can light up in different colours, and which is designed to represent the ratio of the force setpoint value to the registered compressive force qualitatively via the lamps in a specific colour of the respective section.
8. Device according to claim 7, wherein the lamps of a section of the LED strip (23) in a particular colour signals that the registered compressive force of the corresponding pressure segment (12a, 12b, 12c) lies above the specified force setpoint value.
9. Device according to one of the preceding claims, wherein the control unit is configured to store the registered compressive force and the corresponding force setpoint value.
10. Device according to one of the preceding claims, wherein the control unit is configured to transmit the registered compressive force to an external server.
11. Device according to one of the preceding claims, wherein the device is configured to transmit the registered compressive force to the control unit by means of wireless data transmission, in particular RFID technology.
12. Grinding machine with a device according to one of the preceding claims and a movement device (22) for bringing about a relative movement between a workpiece (1) and the carrier element (11), wherein it is preferable if the movement device (22) comprises a belt conveyor, or one or more conveyor belts or conveyor rollers.
13. Method for machining a workpiece (1) using a device according to one of the claims 1 to 11 or a grinding machine according to claim 12, comprising:

    creating a relative movement between a workpiece (1) and a carrier element (11), wherein a plurality of pressure segments (12a, 12b, 12c) is arranged along the carrier element (11),

    machining the workpiece (1) by means of a grinding element (21), in particular a grinding belt (21), wherein at least one of the pressure segments (12a, 12b, 12c) presses the grinding element against the workpiece (1) by means of an in particular electromagnetic actuation,

    wherein a compressive force applied to the workpiece (1) by at least one pressure segment is registered by a sensor (13a, 13b, 13c), wherein it is further preferable if the registered compressive force is compared with a force setpoint value and the pressure segment (12a, 12b, 12c) is actuated in order to achieve the force setpoint value, wherein the sensor (13a, 13b, 13c) is provided between a grinding finger (15) extending along the carrier element (11) and the at least one pressure segment (12a, 12b, 12c) and the pressure segments (12a, 12b, 12c) are in each case moved electromagnetically by means of a magnetic actuator accommodated in a guide (16a, 16b, 16c) provided on the carrier element (11).

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