METHOD AND CUTTING MACHINE WITH SAFETY-MONITORED REVERSING OF THE DANGEROUS CUTTING BLADE MOVEMENT IN THE EVENT OF DANGER

Abstract

A method for the cutting of material is to be cut by means of a cutting machine which includes a horizontal cutting support for material to be cut, a horizontal cutting blade displaceable in height above the cutting support for cutting the material to be cut supported on the cutting support, a drive motor for the height displacement of the cutting blade, a manual control for the drive motor, and a protection device safeguarding the working region of the cutting machine. The method has the steps of: lowering the cutting blade, when the protection device is not interrupted, by actuating the manual control; and stopping the cutting blade which is being lowered when the protection device is interrupted. Immediately after stopping the cutting blade which is being lowered, the drive motor is operated to reverse the cutting blade under safety monitoring into a nondangerous upper safety location.

Claims

1. A method for the cutting of a material to be cut by a cutting machine comprising a horizontal cutting support for the material to be cut, a horizontal cutting blade displaceable in height above the cutting support for cutting the material to be cut supported on the cutting support, a drive motor for the height displacement of the cutting blade, a manual control, for the drive motor, and a protection device safeguarding the working region of the cutting machine, the method comprising the following steps of: lowering the cutting blade, when the protection device is not interrupted, by actuating the manual control; and stopping the cutting blade which is being lowered when the protection device is interrupted; wherein immediately after stopping the cutting blade which is being lowered, operating the drive motor to reverse the cutting blade under position or motion monitoring into a nondangerous upper safety location; wherein the safety monitoring comprises the determination of the actual displacement direction of the cutting blade and, if a downward movement of the cutting blade is established, the secure stopping of the drive motor and wherein the actual displacement direction of the cutting blade is monitored only after a reversing time, required for the direction reverse of the motor driving, following the stopping of the cutting blade which is being lowered.

2. The method according to claim 1, wherein the actual displacement direction of the cutting blade is determined with the aid of a rotary field of the phase currents applied to the drive motor and, if a downward movement of the cutting blade is established with the aid of the rotary field, the rotary field generating the torque-forming currents is turned off and the drive motor is thereby stopped.

3. The method according to claim 1, wherein the rotary field of the phase currents applied to the drive motor is generated by at least a first of at least two mutually monitoring processors by means of control signals, wherein the phase currents actually applied to the drive motor are registered by the two processors, and wherein in order to stop the drive motor at least one or both processors interrupt at least some of the control signals or no longer vary them as a function of time.

4. The method according to claim 1, wherein simultaneously with the stopping of the cutting blade which is being lowered, a brake is operated to brake the drive motor to a rest and block it, unless this operation is negated within the activation time of the brake by establishing that the actual displacement direction of the cutting blade is directed upwards.

5. The cutting machine comprising the horizontal cutting support for the material to be cut, the horizontal cutting blade displaceable in height above the cutting support for cutting the material to be cut supported on the cutting support, the drive motor for the height displacement of the cutting blade, the manual control, for the drive motor, the protection device safeguarding the working region of the cutting machine, and the machine drive controller which controls the cutting process and is programmed to operate the drive motor according to the method according to claim 1.

6. The cutting machine according to claim 5, wherein the drive motor is a polyphase motor and the machine drive controller comprises at least one processor which outputs the control signals, required for generating the phase currents of a rotary field for the drive motor and registers the phase currents actually applied to the drive motor and, in order to stop the drive motor, interrupts at least some of the control signals or no longer varies them as a function of time.

7. The cutting machine according to claim 5, wherein the machine drive controller comprises two mutually monitoring processors, at least one of the two processors generating the control signals, both processors registering the phase currents actually applied to the drive motor and at least one of the two processors or both processors, in order to stop the drive motor, interrupting at least some of the control signals or no longer varying them as a function of time.

8. The cutting machine according to claim 6, wherein the at least one processor comprises a monitoring unit which determines the actual displacement direction of the cutting blade with the aid of the registered phase currents of the drive motor and stops the drive motor if a downward movement of the cutting blade is established.

9. The cutting machine according to claim 6, wherein a power driver, which generates the phase currents for the drive motor with the aid of the control signals, of the processor, is arranged downstream of the at least one of the two processors.

10. The cutting machine according to claim 6, wherein the signal lines of the control signals respectively comprise a switch, operated by the at least one processor for connecting through or interrupting the signal line.

11. The cutting machine according to claim 6, wherein all signal-relevant inputs and outputs of the at least one processor are respectively safeguarded by means of DC isolation.

12. The cutting machine according to claim 5, wherein the machine drive controller is formed by a frequency converter with functional as well as safety-oriented control.

13. The cutting machine according to claim 5, including a brake, operated by the machine drive controller, for braking and blocking the drive motor.

14. The cutting machine according to claim 6, wherein the machine drive controller comprises two mutually monitoring processors, at least one of the two processors generating the control signals, both processors registering the phase currents actually applied to the drive motor and at least one of the two processors or both processors, in order to stop the drive motor, interrupting at least some of the control signals or no longer varying them as a function of time.

15. The cutting machine according to claim 6, wherein the at least one of the two processors comprises a monitoring unit which determines the actual displacement direction of the cutting blade with the aid of the registered phase currents of the drive motor and stops the drive motor if a downward movement of the cutting blade is established.

16. The cutting machine according to claim 8, wherein a power driver, which generates the phase currents for the drive motor with the aid of the control signals, of the processor, is arranged downstream of the at least one processor.

17. The cutting machine according to claim 8, wherein a power driver, which generates the phase currents for the drive motor with the aid of the control signals, of the processor, is arranged downstream of the at least one processor.

18. The cutting machine according to claim 7, wherein the signal lines of the control signals respectively comprise a switch, operated by the at least one of the two processors for connecting through or interrupting the signal line.

19. The cutting machine according to claim 8, wherein the signal lines of the control signals respectively comprise a switch, operated by the at least one processor for connecting through or interrupting the signal line.

20. The cutting machine according to claim 9, wherein the signal lines of the control signals respectively comprise a switch, operated by the at least one processor for connecting through or interrupting the signal line.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The invention is represented in the drawings and will be explained in more detail with the aid of an exemplary embodiment, in which:

[0039] FIG. 1 shows a cutting machine according to the invention having a machine drive controller for the safety-monitored displacement of a height-displaceable cutting blade; and

[0040] FIG. 2 shows a block diagram of a machine drive controller according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] The cutting machine 1 shown in FIG. 1 comprises a horizontal cutting support 2 for material to be cut, a cutting blade 3 displaceable in height above the cutting support 2 for cutting the supported material to be cut, a drive motor 4 for the height displacement of the cutting blade 3, a manual control (for example a two-hand control) 5 for the drive motor 4, a protection device (configured here for example as a photoelectric barrier) 6 safeguarding the working region of the cutting machine 1, and a machine drive controller 7 controlling the cutting process. A height-displaceable clamping bar 8 for pressing down the material to be cut is also arranged behind the cutting blade 3, a pressing drive (not shown here) being manually actuated or electrically driven for the height displacement of the clamping bar 8. Preferably, the machine drive controller 7 is formed by a frequency converter with functional as well as safety-oriented control.

[0042] The operator places the material to be cut on the cutting support 2 and positions it under the cutting blade 3, which is located above the material to be cut in a safe upper starting position in which the blade edge is generally covered by the clamping bar 8. By actuation of the manual control 5 when the protection device 6 is not interrupted, the cutting blade 3 is lowered as far as the cutting support 2. If the protection device 6 is interrupted, the downward movement of the cutting blade 3 is stopped and immediately after this the cutting blade 3 is reversed under safety monitoring into the nondangerous upper starting position. The safety monitoring comprises the determination of the actual displacement direction of the cutting blade 3 and, if a downward movement of the cutting blade 3 is established, the stopping of the drive motor 4.

[0043] FIG. 2 schematically shows a block diagram of the machine drive controller 7 for a drive motor 4 configured as a three-phase motor. The machine drive controller 7 comprises two processors (CPUs) 9a, 9b which monitor one another at the input and output signal level, as indicated by the dashed double arrow. The two processors 9a, 9b are both respectively connected to the hand control 5 and to the protection device 6.

[0044] The one, first processor 9a has the main task of regulating the drive motor 4 close to the tilting moment; the other, second processor 9b is a dedicated safety CPU with a monitoring function. All the safety functions are evaluated and monitored by the two processors 9a, 9b. Both processors 9a, 9b can initiate safety-relevant processes independently of one another.

[0045] The first processor 9a generates PWM control signals on six signal lines 101 to 106, which are connected to a power driver (output stage) 13 by means of three PWM-Hi optocouplers 11 and three PWM-Lo optocouplers 12. The PWM-Hi optocouplers 11 are driven by the first processor 9a and the PWM-Lo optocouplers 12 are driven by the second processor 9b, respectively via lines 14, in order either to connect through or interrupt the signal lines 101 to 106. The power driver 13 is connected to the drive motor 4 by means of three output lines 15 and generates three phase currents, which generate a rotary field for the drive motor 4, according to the PWM control signals. The phase currents actually applied to the drive motor 4 are at 16 tapped from two of the three output lines 15 and sent via lines 17 to the two processors 9a, 9b. Via lines 18, the two processors 9a, 9b together—by means of an AND gate 19—respectively operate a brake 20 in order to mechanically brake and block the drive motor 4.

[0046] All safety-relevant inputs and outputs of the two processors 9a, 9b are DC-isolated by means of optocouplers (not shown).

[0047] If an intervention is carried out in the protection device 6, the first processor 9a ends the downward movement of the cutting blade. So that the blade edge does not remain open and secondary injuries to the operator are therefore avoided, the machine drive controller 7 reverses so that the drive motor 4 returns the cutting blade 3 into the upper starting position.

[0048] As soon as the protection device 6 is interrupted, the rotary field is respectively monitored in a monitoring unit 21a, 21b of the two processors 9a, 9b (after the timer for the reversing has run down, 180 ms), by determining the actual displacement direction of the cutting blade 3 with the aid of the registered phase currents. If one of the two monitoring units 21a, 21b still establishes a downward movement of the cutting blade 3, or of the rotary field, with the aid of the registered phase currents after the reversing time has elapsed, the complex PWM pattern which is required for generating the rotary field is interrupted by at least one of the two processors 9a, 9b so that the drive motor 4 no longer sustains a torque and the blade drive is in a safe resting state. In order to interrupt the PWM pattern, the voltage of the three PWM-Hi optocouplers 11 is turned off by the first processor 9a or the voltage of the three PWM-Lo optocouplers 12 is turned off by the second processor 9b, which corresponds to the secure STO (Safe Torque Off) for the drive motor 4.

[0049] If the protection device 6 is interrupted, simultaneously with the stopping of the cutting blade 3 being lowered, the brake 20 is operated in order to brake the drive motor 4 to a rest and block it, unless this operation is negated within the activation time of the brake 20 by establishing that the actual displacement direction of the cutting blade 3 is directed upwards.

[0050] In comparison with usual controllers on the market, much more sophisticated safety functions are thus possible, such as the rotation direction reversal with rotation direction monitoring (reversing the pressing/blade displacement direction in the event of intervention by the operator in the safety region) instead of just an emergency stop or turning off the torque (STO). Latencies due to signal propagation times and longer reaction and slowing times resulting therefrom are minimized, whereby required safety margins from the danger location are reduced.

[0051] The cutting machine 1 according to the invention fulfils the following central requirement aspects: [0052] performance level e (PLe)—construction/functionality; [0053] maximum machine power even on differently fused single-phase household installations; [0054] intelligent, variable control of the cutting speed; [0055] operator assistance for safe blade replacement; [0056] regulation of the machine function as a function of the temperature of particular machine components; [0057] output of machine parameters and other information such as maintenance recommendations to the operator.