E/MJ : engineering and mining journal . cage is suspendedin the usual manner. Afourth long clevis E isattached to the same boltthat holds the clevis 0and hangs down aroundthe yoke of the cage, en-gaging a hook, with aboutan inch free play verti-cally. If the hoistingrope breaks, the cradlehook turns over, puttingthe weight of cage,through the clevis E. en-tirely on the counterbal-ance cable, at the sametime releasing the dogspring and allowing the to grip the guide. II the counterbalance cable breaksJirst, the weight goes on the hoisting cable direct, stillholding the dog spring compressed. If
E/MJ : engineering and mining journal . cage is suspendedin the usual manner. Afourth long clevis E isattached to the same boltthat holds the clevis 0and hangs down aroundthe yoke of the cage, en-gaging a hook, with aboutan inch free play verti-cally. If the hoistingrope breaks, the cradlehook turns over, puttingthe weight of cage,through the clevis E. en-tirely on the counterbal-ance cable, at the sametime releasing the dogspring and allowing the to grip the guide. II the counterbalance cable breaksJirst, the weight goes on the hoisting cable direct, stillholding the dog spring compressed. If the hoisting cablenow breaks from the suddenly added strain, the dogs arefree to work in the usual manner. At the same time thewhole weight of the cage is effective to hold the dogsprings at all times compressed. When the cage is empty, it is nearly in balance and thecradle hook takes an angle of slightly less than 45° fromthe horizontal: when loaded, it assumes the upright posi-tion shown in the drawing. The device has been in oper-. A POSITIVE-ACTING SAFETYDEVICE FOR CAGES ation for some weeks and has been repeatedly tested byputting a trip in the hoisting cable and then suddenlysevering connections. Action has always been quick andpositive, the maximum free drop of the cage before itwas caught and held by the dogs being 2 in. Tests weremade with a loaded car on the cage, probably weighingfrom 2,800 to 3,000 lb. W. By Frank Ayer* Important factors in repairing air drills are speed andeconomy. The average company has too few extra drills,so that speed on the part of the repair man is necessaryto keep the drills underground. If he has extra partson hand, he has only to replace a broken or worn piecewith a good one and the drill can be quickly returned tothe mine. When all the drills have left the shop, he canrepair the disabled parts so that corresponding new partswill be unnecessary for machines that come in later. The following repairs and replacements can be madeto good ad
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Keywords: ., bo, bookcentury1900, bookdecade1910, booksubjectmineralindustries
