The American watchmaker and jeweler; an encyclopedia for the horologist, jeweler, gold and silversmith .. . amountallowed for locking alters the direction of the planes. When, from setting the hands of a watch back, or from a sudden jerk,there is a tendency for the pallets to unlock, the safety pin butts againstthe edge of the roller. It will be observed that when the ruby pin unlocksthe pallets, the safety pin is allowed to pass the roller by means of thecrescent which is cut out of the roller opposite the ruby pin. The teethof the escape wheel make a considerable angle with a radial line (24
The American watchmaker and jeweler; an encyclopedia for the horologist, jeweler, gold and silversmith .. . amountallowed for locking alters the direction of the planes. When, from setting the hands of a watch back, or from a sudden jerk,there is a tendency for the pallets to unlock, the safety pin butts againstthe edge of the roller. It will be observed that when the ruby pin unlocksthe pallets, the safety pin is allowed to pass the roller by means of thecrescent which is cut out of the roller opposite the ruby pin. The teethof the escape wheel make a considerable angle with a radial line (24°), sathat only their tips touch the locking faces of the pallets. The lockingfaces of the pallets, instead of being curves struck from the center ofmotion of the pallets, as would be otherwise the case, are cut back at anangle so as to interlock with the wheel teeth. The locking face formsan angle of 6° or 8° with a tangent to a circle representing the path ofthe locking corner. This is done so that the safety pin shall not drag on 221 Lever Escapement. ENGLISH LEVER ESCAPEMENT. C o a. u 5 O u* X w. Fig. 199. Lever Escapement. 222 the edge o£ the roller, but be drawn back till the lever touches the bank-ing pin. When the operation of setting the hands back is finished, or theother cause of disturbance removed, the pressure of the wheel tooth onthe locking face of the pallet draws the pallet into the wheel as far asthe banking pin will allow. The amount of this run should not bemore than sufficient to give proper clearance between the safety pin andthe roller, for the more the run, the greater is the resistance to unlock,ing. This rule is sometimes sadlj transgressed, and occasionally thelocking is found to be, from excessive run, almost equal in extent to theimpulse. It will generally be found that in these cases the escapementis so badly proportioned that the extra run has had to be given to securea sound safety action. In common watches the safety action is a fre-quent s
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