Mechanical Power Press Clutch
A mechanical power press clutch is the coupling mechanism that connects the rotating flywheel to the crankshaft, either directly or through a gear train, enabling the press slide to make a stroke when the control is actuated. The clutch type—full-revolution or part-revolution—determines required safeguarding, control reliability, and stopping performance under OSHA, ANSI, CSA, and WorkSafeBC regulations.
On the shop floor, the clutch is central to starting and stopping the press stroke and dictates permissible safeguarding devices. For full-revolution clutches, which cannot stop mid-stroke, fixed or interlocked barrier guards are required; presence-sensing devices are prohibited. Part-revolution clutches allow mid-stroke stopping, enabling use of light curtains, two-hand controls, and gates. Operators must verify stopping time, maintain air valves and friction linings, and ensure brake monitors are functional when hands are in the die area. Control selectors for modes like inch, single stroke, or continuous must be key-controlled and under supervisor oversight to prevent unauthorized changes.
What is the exact difference between a full-revolution and part-revolution clutch in terms of control and safeguarding options?
A full-revolution clutch cannot be disengaged mid-cycle; the crankshaft must complete one full revolution before stopping. Thus, presence-sensing devices cannot be used as primary safeguarding; only fixed or interlocked barrier guards are allowed. A part-revolution clutch can be disengaged at any point, enabling device-based safeguarding like light curtains, two-hand controls, and gates, with brake monitoring required when hands are in the die area.
How do CSA Z142 and WorkSafeBC influence clutch/brake control system design?
WorkSafeBC Part 12 requires compliance with CSA Z142 for point-of-operation safeguarding and control design. CSA Z142 mandates control reliability, redundancy, brake monitoring for part-revolution clutches, and key-controlled selectors for inch/single/continuous modes. In BC, new or modified presses must have dual-channel, monitored safety circuits, and mode selectors must be under supervisor control.
Under OSHA 29 CFR 1910.217, when is a brake monitor mandatory?
A brake monitor is mandatory when: (1) the press has a part-revolution clutch, (2) the operator places hands in the point of operation, and (3) safeguarding uses a two-hand control, presence-sensing device, Type B gate, or movable barrier. The monitor checks stopping time and locks out the clutch if it exceeds safe limits. Full-revolution clutches do not require brake monitors.