A double-acting type dynamic back spacing removed driving system comprises non-reversible transmission worm gear and worm set including two sets of worms coupling with worm gear. When the system is driven, one prime worm continues applying rotary driving force. Whether or not the worm gear is driven, such force would engage upon the prime worm permanently, and another set of worm gear (or co-axially secured at respective worm gear with same or different pitch), due to application worm applies force to worm gear permanently. The displacement-controlling worm is packed always due to worm set being non-reversibly transmitted so no spacing appears between the worm gear and the worm. At this moment, when the displacement-controlling worm is driven backward against compressed direction, and worm gear set is engaged in chasing displacement to reach packing condition again due to being driven by applied prime worm to form self-adjusting speed difference dynamic back spacing removed driving system according to load back spacing state. This principle can be used to accomplish dynamic back spacing removal when operation speed of displacement-controlling worm is lower than application prime worm.

The present invention relates to a double-acting type dynamic back clearance relief driving system having two sets of worm shafts coupled with a worm gear, one worm shaft set acting as a prime mover worm shaft and the other acting as a displacement control worm shaft. When the system is driving, one of the worm shaft sets is applied with faster rotary driving motion and always applies forces on the worm gear set. Another worm shaft set is a displacement control worm shaft coupled also with the worm gear set, or an individual worm gear set of the same pitch or different pitch to be locked upon the same shaft. The acting force to be applied constantly on the gear by the force applying worm shaft always causes the displacement control worm shaft to stress the worm gear reversely, and since the worm shaft is irreversibly driven, there is no clearance between the worm gear and the two worm shafts.

A vertical blind apparatus having a wand operated control for traversing the slats along a headrail and for rotating the slats. The blind apparatus has an actuator shaft with its axis disposed in a central vertical plane equidistant from the sidewalls of the headrail; slat carriers are mounted on slat carriages for rotation about vertical axes disposed in the central vertical plane and a control shaft for the wand operated control is also mounted for rotation in the central vertical plane. The wand operated vertical blind apparatus can be used in either left or right draw installations and in two-way draw installations.

The present invention relates to a double-acting type dynamic back clearance relief driving system having two sets of worm shafts coupled with a worm gear, one worm shaft set acting as a prime mover worm shaft and the other acting as a displacement control worm shaft. When the system is driving, one of the worm shaft sets is applied with faster rotary driving motion and always applies forces on the worm gear set. Another worm shaft set is a displacement control worm shaft coupled also with the worm gear set, or an individual worm gear set of the same pitch or different pitch to be locked upon the same shaft. The acting force to be applied constantly on the gear by the force applying worm shaft always causes the displacement control worm shaft to stress the worm gear reversely, and since the worm shaft is irreversibly driven, there is no clearance between the worm gear and the two worm shafts.

In a turret indexing device, a coupling containing three gear members is employed in a turret indexing device to cooperate with an indexing disc mounted on an output shaft which is adapted to hold an indexing head. The coupling is operated by a first cam fixedly mounted on an input shaft through a lever mechanism, and the indexing disc is driven by a second cam fixedly mounted on the same input shaft. The three gear members include a first gear member fixedly mounted on a collar slidably mounted on the output shaft, a second gear member which is fixedly mounted on a stationary housing, and third gear member fixedly mounted on a head end of the output shaft. The collar with the first gear member is operated by the lever mechanism to cause the first gear to engage with and disengage from the second gear member and the third gear member while the first cam rotates, in a present timing sequence, and the indexing disc is caused to rotate only when the first gear member is disengaged from the second gear member and the third gear member.