Press control system

• US 4,206,666 A
• Filed: 11/16/1978
• Issued: 06/10/1980
• Est. Priority Date: 11/16/1978
• Status: Expired due to Term

• Current Assignee: James Joseph Morrison Management Limited
• Original Assignee: James Joseph Morrison Management Limited
• Inventors: Ashton, Bruce F.
• Primary Examiner(s): Schran, Donald R.
• Application Number:
  US05/961,301
• Time in Patent Office: 572 Days
• Field of Search: 83/63, 83/58, 83/66, 83/362, 83/361, 83/360, 192/125 A, 192/127, 192/129 A
• US Class Current: 83/63
• CPC Class Codes: B21D 43/025 Fault detection, e.g. misfeed detection
• CPC Class Codes: B21D 55/00 Safety devices protecting the machine or the operator, specially adapted for apparatus or machines dealt with in this subclass for presses in general B30B; safety devices in general F16P
• CPC Class Codes: B23Q 11/00 Accessories fitted to machine tools for keeping tools or parts of the machine in good working condition or for cooling work accessories specially designed for sawing machines or sawing devices B23D59/00; Safety devices specially combined with or arranged in, or specially adapted for use in connection with, machine tools in respect of boring or drilling machines B23B47/32 takes precedence; safety devices in general F16P
• CPC Class Codes: B26D 7/24 arranged to disable the operating means for the cutting member
• CPC Class Codes: Y10T 83/091 Responsive to work sensing means
• CPC Class Codes: Y10T 83/096 Detector supported on or urged against work
• CPC Class Codes: Y10T 83/528 To delay response to work-senser

Abstract

A continuous feed stamping machine, press or the like, has a control system for automatically stopping the machine in the absence of material to be stamped. The control system includes a normally closed limit switch which is held open by the presence of material to be stamped. After each stamping operation, as the stamped product is released from the die area, the limit switch returns to its normally closed position. If the limit switch is not opened by the feed of more material, within a predetermined time interval, the machine is stopped. The time interval is related to the operating frequency of the machine such that in the absence of material the machine will be stopped before the machine is damaged. The control system, which may operate in either the astable (oscillating) or monostable (one-shot) mode, effects the charging of a capacitor when the limit switch closes, and the capacitor discharges when the limit switch opens. If the limit switch is not opened by the feed of new material, within the preselected time interval, the charging of the capacitor above a threshold voltage causes the machine to be stopped.

Claims

1. In a continuous machine press system having a motor driven press with a reciprocal ram wherein material to be stamped or punched is fed into the die area beneath the ram, the improvement of a control circuit comprising:

first switch means to detect the presence and absence of said material in the die area;

timing means responsive to said first switch means to provide a signal when material is absent from said die area for a predetermined time interval less than the time for the ram to travel from an extreme position to the die area; and

second switch means actuated by said timing means to stop said ram in response to said signal from said timing means.

2. The invention of claim 1 wherein said timing means operates in the astable mode for constantly recycling even if said timing means actuates said second switch means.

3. The invention of claim 1 wherein said timing means operates in the monostable mode for automatically recycling only if said timing means does not actuate said second switch means.

4. The invention of claim 1 wherein said first switch means comprises a normally closed limit switch which is opened by the presence of material in the die area.

5. The invention of claim 1 wherein said control circuit further includes a test switch for testing the operation of said timing means while said normally closed limit switch is open.

6. The invention as defined in claim 1 wherein said timing means includes a capacitor which is charged when no material is in the die area.

7. The invention as defined in claim 6 wherein the capacitor is discharged externally of the timer if the presence of material in the die area is detected before the capacitor charges to a predetermined value.

8. Circuitry for detecting and signaling the absence of material from the die area of a motor driven press having a reciprocating ram comprising:

a limit switch which detects the presence of material by opening a first set of contacts and closing a second set of contacts in response to said material;

timing means including a capacitor and capacitor charging means for detecting the amount of time said first set of contacts are closed, said timing means providing a signal to stop said press motor when said charge on said capacitor exceeds a threshold value;

capacitor discharge means comprising a resistor coupling said capacitor to said second set of contacts wherein the closing of said second set of contacts activates said discharge means to ground said capacitor before said capacitor charges to said threshold value; and

second switch means responsive to said timing means signal to stop said reciprocating ram.

9. The invention of claim 8 wherein said threshold value charge on said capacitor is adjustable.

10. The invention of claim 8 and further comprising a test switch to test the operation of said timing means while said first set of contacts are open.