Escapement for timepiece
An escapement for a timepiece includes an escape wheel that rotates about a shaft center and a pallet that oscillates. The escape wheel includes fifteen teeth. The pallet includes an entry pallet jewel and an exit pallet jewel that switch the rotation and stop of the escape wheel and receive torque from the escape wheel by contacting the teeth. The escape wheel and a balance (an impulse pin) apply and receive torque only via the pallet. The pallet includes a third pallet jewel (a torque applying and receiving member) that receives torque from a convex portion of the escape wheel in addition to the entry pallet jewel and the exit pallet jewel.
1. An escapement for a timepiece comprising:
an escape wheel that is configured to rotate about a shaft center and comprises a plurality of teeth and a torque applying member that applies torque; and
a pallet that oscillates, and comprises an entry pallet jewel and an exit pallet jewel,
wherein the entry pallet jewel switches a rotation of the escape wheel and a stop of the escape wheel and receives torque from the escape wheel by contacting a tooth of the teeth, and the exit pallet jewel at least switches the rotation of the escape wheel and the stop of the escape wheel,
wherein the escape wheel and a balance apply and receive torque only via the pallet,
wherein in addition to the entry pallet jewel and the exit pallet jewel, the pallet comprises a torque receiving member that receives torque from the torque applying member by contacting the torque applying member, and
wherein a thickness of the torque receiving member in a direction parallel to an axis of rotation of the pallet is less than a thickness of the entry pallet jewel and a thickness of the exit pallet jewel.
2. The escapement according to claim 1 , wherein the entry pallet jewel receives torque from the escape wheel by contacting the tooth.
3. The escapement according to claim 1 ,
wherein the exit pallet jewel comprises
an impact surface that is inclined to face an outside of the pallet,
a stop surface that stops the escape wheel, and
a locking corner that connects the impact surface and the stop surface,
wherein torque is applied from an other tooth of the teeth of the escape wheel to the exit pallet jewel by a surface of the other tooth contacting the locking corner.
4. The escapement according to claim 1 , wherein the torque applying member is formed on a portion that has a shorter radius from the shaft center than a surface of the tooth that applies torque to the exit pallet jewel.
5. The escapement according claim 1 , wherein the torque applying member and the torque receiving member are arranged to contact each other before a contact of a surface of the tooth and the exit pallet jewel is terminated.
6. The escapement according to claim 1 , wherein the torque receiving member is at a portion of the pallet having a distance from a center of the oscillation of the pallet that is longer than a distance from the center of the oscillation of the pallet to the entry pallet jewel, and
wherein the torque receiving member receives torque by contacting the torque applying member during a period from when the entry pallet jewel disengages from the tooth until the exit pallet jewel contacts the tooth.
7. The escapement according to claim 6 , wherein the torque receiving member is an arm portion, and the arm portion is formed on an outside of the entry pallet jewel when viewed from a shaft center of a pallet pivot.
8. The escapement according to claim 1 , wherein the torque receiving member is disposed at a position that receives torque for rotating the pallet in a same direction as a rotation direction of the pallet when the entry pallet jewel disengages from the tooth of the escape wheel.
9. The escapement according to claim 1 , wherein the torque applying member and the torque receiving member contact at a position where an angle at which a rotation direction of the escape wheel intersects an oscillating direction of the pallet at a portion where the torque applying member and the torque receiving member contact each other becomes smaller than an angle at which a rotation direction of the escape wheel intersects an oscillating direction of the pallet at a portion where the tooth and the entry pallet jewel contact each other.
10. The escapement according to claim 1 , wherein the entry pallet jewel contacts the escape wheel only at a surface that stops the escape wheel.
11. The escapement according to claim 1 , wherein the torque applying member is a convex portion formed to protrude from an end surface of the escape wheel that is perpendicular to the shaft center.
12. The escapement according to claim 1 , wherein a width dimension of the torque receiving member in a direction perpendicular to the axis of rotation of the pallet is smaller than a width dimension of the entry pallet jewel and a width dimension of the exit pallet jewel.