| 摘要 |
1,185,829. Machinery safety devices; external shoe drum brakes; automatic brakes; controlling clutches. TAYLOR & CHALLEN Ltd. 30 Nov., 1967 [6 Dec., 1966], No. 54504/66. Headings F2E, F2F, F2J and F2L. In a press brake, wherein a crank-shaft 1 drives a tool, and a photo-electric or other sensing device initiates emergency braking of the crank-shaft if an operator's hand is dangerously close to the tool path, the emergency braking force is derived from the rotation of the crank-shaft. External shoes 3, 4 pivoted together at 5 embrace a brake drum 2 on the crank-shaft 1. The shoe 3 has a fixed pivot 23 and the shoe 4 is pivoted to a toggle linkage 7, 8, the lever 8 having a fixed pivot 9 and an extension forming a follower for a cam 14. A positive clutch (13, 17) (Fig. 2, not shown) between the cam 14 and a layshaft 18 geared to the crankshaft is normally held disengaged by a pneumatic cylinder 10 acting via a lever 11. For normal braking a pneumatic cylinder acts on the toggle linkage via a strut 22. In emergency, the sensing device opens a solenoid valve to vent the cylinder 10 to allow a spring (15) to engage the clutch (13, 17) so that the inertia of the crank-shaft rotates the cam and acts via the toggle linkage for powerful brake application. As the lever 11 moves for clutch engagement, it closes a micro-switch 19 to cut off the power supply to an electric motor driving the press. When the brake has worn a predetermined amount, the lever 8 closes a micro-switch 20 on brake application to light a warning lamp to remind the operator to take up the wear by means of a turnbuckle 6. |
