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Drive control with overload protection for a drill device

  • US 4,885,511 A
  • Filed: 08/26/1988
  • Issued: 12/05/1989
  • Est. Priority Date: 04/11/1986
  • Status: Expired due to Fees
First Claim
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1. A drive control for a drilling device with a series wound universal motor, comprising means for effecting current limitation to said motor when a load limit moment (M limit) is reached, wherein the improvement comprises:

  • a circuit containing said motor (1), said circuit is connected to a supply voltage;

    an rpm regulator (4) located in the circuit for comparing an actual rpm value (N act) of said motor with a constant reference rpm value (N ref), said regulator (4) having an output voltage;

    means in said circuit and responsive to said regulator output voltage for maintaining the actual rpm value corresponding to the constant reference rpm value;

    said means for maintaining comprises a first decoupler diode (5) and a second decoupler diode (10), said first and second decoupler diodes (5,

         10) having a junction point, wherein said rpm regulator (4) reaches maximum output voltage at a fraction point (Mn) of the load limit moment (M limit), and wherein the voltage at the junction point of said decoupler diodes remains constant during an increase in torque from the fraction point (Mn) to the load limit moment (M limit); and

    a current regulator (9) in said circuit for reducing the voltage at said junction point only when the load limit moment (M limit) is reached.

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