PROTECTIVE CIRCUIT ARRANGEMENT FOR BAND CUTTER MACHINES

• US 3,858,095 A
• Filed: 08/28/1973
• Issued: 12/31/1974
• Est. Priority Date: 08/28/1973
• Status: Expired due to Term

• Current Assignee: Josef Proschka, Wolfgang Friemann
• Original Assignee: Josef Proschka, Wolfgang Friemann
• Inventors: Friemann, Wolfgang, Proschka, Josef
• Primary Examiner(s): Trammell, James D.
• Application Number:
  US05/392,276
• Time in Patent Office: 490 Days
• Field of Search: 317/DIG.2,146 340/38L
• US Class Current: 192/129.00A
• CPC Class Codes: F16P 3/12 with means, e.g. feelers, which in case of the presence of a body part of a person in or near the danger zone influence the control or operation of the machine F16P3/08 takes precedence
• CPC Class Codes: G01V 3/088 operating with electric fields G01V3/082 takes precedence

Abstract

A protective circuit arrangement for a motor driven band cutter machine, wherein the band cutter is electrically insulated from the rest of the machine and is connected as capacitance in a bridge circuit which is balanced during normal operation and which when unbalanced provides an output signal by which full braking of the band cutter is triggered.

Claims

1. A protective device for use in cutting machines having a moving cutting member comprising:

safety circuit means, responsive to touching of the cutting member by an operator, for generating an Output signal; and

braking means electrically connected to said safety circuit means for substantially instantaneously stopping the cutting member in response to said generated output signal of said safety circuit means.

2. The protective device of claim 1 wherein said cutting member comprises a band cutter having a drive motor;

and said safety circuit means comprises a bridge circuit balanced during normal operation and when unbalanced by the operator touching the band cutter provides an output signal by which full braking of said band cutter is triggered, wherein said band cutter is electrically insulated from the rest of the cutting machine and is connected as capacitance in said bridge circuit.

3. A protective device according to claim 2 wherein said bridge circuit is energized by an oscillator voltage.

4. A protective device according to claim 2 comprising an amplifier circuit and a circuit element connected to said output from said bridge circuit by way of said amplifier circuit.

5. A protective device according to claim 2 comprising a D.C. supply connected to the drive motor for the rapid braking of said drive motor when said drive motor is switched off, wherein said drive motor is a three-phase electric motor.

6. A protective circuit arrangement according to claim 2 wherein the band cutter has an electromechanical brake which is operated when the drive motor is switched off.

7. A protective device according to claim 4, wherein the balancing of said bridge circuit and the design of said circuit element and of said amplifier circuit is such that when said band cutter is touched by objects which are normally to be cut said circuit element is not operated.

8. A protective device according to claim 2 comprising an amplifier, and a reversing switch connected to said output from said bridge circuit by way of said amplifier, said reversing switch reversing the direction of said drive motor upon operation of said reversing switch.

9. A protective device according to claim 3 comprising an amplifier, and a reversing switch connected to said output from said bridge circuit by way of said amplifier, said reversing switch reversing the direction of said drive motor upon operation of said reversing switch.

10. A protective device according to claim 7 comprising an amplifier, and a reversing switch connected to said output from said bridge circuit by way of said amplifier, said reversing switch reversing the direction of said drive motor upon operation of said reversingg switch.

11. A protective device according to claim 3 comprising an amplifier circuit, and a circuit element connected to said output from said bridge circuit by way of said amplifier circuit.