Abstract: A chuck mechanism is described, which is easy to handle with a chuck clamping handle of increased diameter and is capable of achieving smooth movement of its reciprocally movable portion of reduced weight and assures safe operation with the least exposure of outwardly moving portion. Rotating a knurled portion of a body case rotates an intermediate transmission member which in turn rotates a slide shaft stopping member to tighten or loosen its engagement with a slide shaft, causing clamping or releasing of a collet chuck. The slide shaft, slide shaft locking member, chuck and a saw can reciprocally move as a single unit.

Abstract: A power transmission device for connecting a rotation shaft with a mechanism for converting rotational movement into reciprocal movement. The rotation shaft is concentrically accommodated in a rotation shaft sleeve having an outer wall with a circumferential groove. A connecting sleeve, with a plurality of circumferentially arranged through-holes with a ball mounted in each through-hole, slidably receives the rotation shaft sleeve. A sliding sleeve having a circularly formed internal recess is mounted over the connecting sleeve and is slidable to position the balls in the through-holes such as to either connect or disconnect the connecting sleeve from the rotation shaft sleeve.

Abstract: A power transmission device for converting rotational movement of a rotation shaft into reciprocal movement in an axial direction of the rotation shaft. This device comprises a bevel gear for converting rotation of the rotation shaft into rotational movement of a-second rotation shaft, a-first eccentric shaft turnable with an eccentricity to the second rotation shaft, a-second eccentric shaft turnable with an eccentricity of 180.degree. apart from the first eccentric shaft, a-first reciprocating member reciprocally movable in the axial direction only of the rotation shaft in response to the rotational movement of the second eccentric shaft, and a-second reciprocating member reciprocally movable in the axial direction only of the rotation shaft in response to the rotational movement of the first eccentric shaft. The second reciprocating member exerts a damping effect on the first reciprocating member.

Abstract: A power transmission device for converting rotational movement of a rotation shaft having a rotation shaft axis and a top end, into oscillatory movement having a primary component of movement in a direction perpendicular to the rotation shaft axis in a plane parallel to or containing the rotation shaft axis, includes a recessed portion formed in the top end of the rotation shaft, a bearing with an outer race rockably mounted in the recessed portion, an inner race positioned within the outer race, and balls positioned between the outer race and the inner race for permitting relative rotation between the outer race and the inner race, an extending link having a first end fit in the inner race such that rotation of the rotating shaft causes rotation of the outer race therewith about the inner race, the link also having a second, opposite end, a rotary plate, a pin for connecting the rotary plate to the second end of the extending link, the pin having a central axis, and a supporting mechanism for providing that

Abstract: There is disclosed a device for detecting the position of an apical foramen of a tooth's root by measuring a change in the impedance between a measuring needle inserted into a tooth's root canal and an electrode abutting on oral mucosa. This device includes a circuit for generating two kinds of different frequency signals, detection circuits for detecting a change in the impedance in response to the respective frequencies and a "difference" detection circuit for successively comparing outputs of the detection circuits and for producing a "difference" signal, and a feed back circuit for feeding an output of the "difference" detection circuit to one of the input terminals of the "difference" detection circuit so as to equalize its two inputs by addition or by subtraction and thereby to make its output equal to zero.

Abstract: A spinal needle for performing medical treatment is inserted into the vertebral pulp, a laser probe is inserted into the spinal needle, and then laser rays are radiated onto the vertebral pulp. An air-escape tube is unitarily provided parallel to the spinal needle or a flow-passage connected with the interior of the spinal needle is provided in the vicinity of the handle portion of the spinal needle.