GB587235A - Improvements in or relating to collapsible pit-props - Google Patents

Abstract

587,235. Pit - props. APPLEBY -FRODING - HAM STEEL CO., Ltd., and HENDERSON, H. M. April 24, 1945, No. 7924/44. [Class 20 (ii)] A collapsable pit-prop having a head portion 2 connected to a strut portion 1 by side plates 3 which are pivotally mounted at 4, 5, the pivots having sufficient clearance to prevent them taking any load when the prop is in use, and a locking bolt 8, has the complementary surfaces of the bearing pads 6, 7 of arcuate form and set at an angle such that the chord of the arc is at 5‹ to 15‹ to the normal to the centre line of the prop. The prop is thus stable under load, no load being taken by the locking means, but can be easily collapsed on release of the locking means. To release the locking bolt 8, the handle 15, Fig. 2, is timed to cause the nose 13 of a cam 14 to engage a shoulder 12 on the bolt and depress the bolt against the pressure of a loading spring 11. Further movement of the handle 15 causes a second nose 25 on the cam to press against the bearing pad 7, on the head, and initiate movement of the head. A locking pin may be placed through a hole 18 in the strut and a slot 16 in the bolt to prevent accidental release of the prop. The handle 15 is pivotally mounted in plates 23, Fig. 1, which extend above the pads 6 to prevent the head passing beyond its working position, in axial alignment with the strut. The head and strut are made from H girder, the web of which, at the ends of the prop, is cut away and the flanges bent over.