Abstract: The invention relates to a piezoelectric adjusting element, in particular a piezoelectric motor in the form of a monolithic plate-shaped or cylindrical piezoelectric oscillator comprised of a first and of a second kind of main surfaces and of groups of electrodes that are allocated to them, comprised of a housing, a driven element, at least one friction layer arranged on the housing or on the driven element, a driving element that is connected to an electric excitation source and that is in friction contact with the friction layer, and the piezoelectric oscillator is excited by way of the groups of electrodes standing longitudinal acoustic waves in the direction of an oscillator resonant length and in the direction of an oscillator resonant height of this piezoelectric oscillator, and the oscillator resonant length is equal to an integral multiple of the wave length of the standing longitudinal wave that vibrates in its direction, and the oscillator resonant height is equal to one half of the wave length of t

Abstract: A linear motion mechanism comprises a supersonic motor having a rotor which is rotationally driven by vibration of a vibrating body having a piezoelectric element. A transmission mechanism is disposed on the rotor for rotation therewith. A moving body undergoes linear movement in a direction crosswise to a longitudinal axis of a rotational shaft of the rotor in accordance with rotation of the transmission mechanism. A pressurizing mechanism presses the moving body into pressure contact with the transmission mechanism.

Abstract: The present invention provides a method and system for stabilizing a rotor about its geometric center in a magnetic bearing system at a constant rotor speed. In the method, the controller for controlling the magnetic bearing uses an adaptive control algorithm which simultaneously identifies and compensates for synchronous sensor runout and rotor mass unbalance while determining a control action that drives the rotor rotating at a constant speed to its geometric center. The identification of sensor runout and mass unbalance is by varying the magnetic stiffness which is achieved by perturbation of the bias currents in opposing electromagnet coils in a manner that does not alter the equilibrium of the rotor while it is rotating at a constant speed.

Abstract: The present invention is to provide a stacked type electro-mechanical energy conversion element comprising a stack of superimposed layers with an electro-mechanical energy conversion function having an electrode film formed on a superimposed surface so as to improve the driving efficiency thereof. A part of the electrode film is connected to an electrode film formed on an edge portion of a layer, and on a side face of the stacked electro-mechanical energy conversion element, there are provided a connection terminal connectable to an external power supply, and a wiring portion connecting the connection terminal to the electrode film formed on the edge portion of the layer.

Abstract: An electromechanical motor according to the present invention has a stator with a drive element consisting of two serially connected bending sections and a central drive pad, for actuating on a body to be moved. The drive element extends parallel to the body. The drive pad and/or the body is elastic. Preferably, the drive pad has a lower stiffness than the body. The elasticity of the drive pad allows an assimilation of a part of the travelling wave energy applied to the drive element. The backbone of the stator is arranged to restrict the drive element from being removed from the body, but at the same time allow the drive element to be translated towards the body and even leave the mechanical contact with the backbone for shorter periods of time. Support means are preferably designed with convex surfaces in order to allow self-centering of the different parts of the motor.

Abstract: The present invention concerns a piezoelectric motor of the type including: a stator (2); a rotor (20) capable of moving in rotation in a plane (Pdm) called the mean movement plane perpendicular to a geometrical rotational axis (X1) on which the rotor (20) is centred; coupling means (8) for driving the rotor (20) arranged between the stator (2) and said rotor (20); piezoelectric means (12) capable of being electrically excited to impart a vibratory movement onto the coupling means (8); transmission means (40) able to transmit the vibratory movement from the coupling means (8) to the rotor (20) in order to drive said rotor (20) in rotation about its axis (X1), and holding means (44) for applying the rotor (20) onto the coupling means (8), characterised in that the coupling means (8) are arranged freely about the geometrical rotational axis (X1) on which they are centred, and in that the coupling means (8) rest on the stator (2) via support means (10) shaped to convert the vibratory movement of the point

Abstract: The invention relates to an electromechanical drive element which comprises a rotor that is received in a bearing and at least one piezoelectric element that is impinged upon with an electric voltage. Said bearing is provided with a rotor seat that is mounted on a bearing block and that can be rotated to a limited extent. Said rotor seat is rotated by the extension and/or contraction of the at least one piezoelectric element that is evoked by the electric voltage.

Abstract: A smooth impact drive mechanism utilizing an electromechanical conversion element, in which a preheating voltage to preheat the electromechanical conversion element is impressed thereto before the impression of a drive voltage to the electromechanical conversion element, in order to realize stable drive characteristics by reducing fluctuation in the speed of the moving unit. In addition, drive parameters are changed in accordance with the temperature of the electromechanical conversion element. Furthermore, drive parameters are changed in accordance with the moving speed of the moving unit.

Abstract: An ultrastiff precision sonic bearing assembly and method thereof for controlling an effective coefficient of friction between two elements in slidable contact configured along an interface under a force sufficient to maintain contact and having static friction therebetween, by inducing a repetitive motion in one of the elements parallel to the interface thereby altering the effective coefficient of friction therebetween. The bearing assembly also provides for additional and independent electronic control over the average thickness thereof and senses the force thereon to allow the bearing assembly stiffness to be altered.

Abstract: A vibration type actuator has an elastic member in which a shaft center portion is formed in hollow shape along an axial direction and in which driving vibration is generated in a driving portion, a fastening member which fastens the elastic member to an electro-mechanical energy conversion element, an output shaft which penetrates the shaft center portion of the elastic member, a moving member which is kept in press contact with the driving portion of the elastic member and which rotates together with the output shaft, and a bearing member which is located between an inner periphery portion of the elastic member and a distal end portion of the fastening member and which journals the output shaft.

Abstract: An actuator using vibration caused by a piezoelectric element. The actuator includes: an driving rod bonded to one of the piezoelectric element; a engaging member for engaging frictionally with the driving rod; and a control circuit for applying the piezoelectric element with a driving voltage. The control circuit is provided with a drive circuit which generates a first set of the driving voltage for driving the engaging member, and with a friction reducing circuit which generates a second set of the driving voltage for reducing a frictional force exerting between the driving rod and the engaging member.

Abstract: This specification discloses a piezoelectric ultrasonic motor with multi-layer thin disks. A buzzer disk made of a piezoelectric material is supplied with an alternate voltage to produce alternately expanding and shrinking deformation. An elastic vibration disk in connection with the buzzer disk produces standing waves to transport kinetic energy to the exterior. A driving module symmetric in the vertical or horizontal direction is also formed. This does not only reduce the abrasion among the components, but also provide homogeneous forward and reverse driving forces.

Abstract: By obtaining a support structure capable of performing a stable support by means of a simple constitution and without suppressing vibration of a vibrating body, there are aimed at improvements in positioning precision and positioning controllability and a positioning stability, thereby providing a piezoelectric motor whose dispersion of performance is made small. In a piezoelectric motor operating, by vibration of a vibrating body having a piezoelectric element, a contact member contacting with the vibrating body or a friction member provided in the vibrating member or the vibrating body itself, there are possessed plural concave portions provided in the vibrating body, and a support member having plural convex portions engaging with the concave portions.

Abstract: The present invention aims at providing a moving member for a surface acoustic wave actuator which undergoes little change of phase under the action of a pressing force and which can improve the drive efficiency of the surface acoustic wave actuator, as well as a surface acoustic wave actuator using the moving member. For achieving this object, projection-arranged portions and gap portions are formed in parallel with a surface acoustic wave propagating direction on a contact surface of the moving member for contact with a stationary member in such a manner that the ratio of the width of each of the projection-arranged portions to that of each of the gap portions is in the range of between 1:4 and 1:10. With this configuration, it is possible to suppress the influence of a phase change of a surface acoustic wave having passed the projection-arranged portions.

Abstract: An ultrasonic motor has a vibrating body and a piezoelectric element disposed on the vibrating body for generating a vibration wave to vibrate the vibrating body. The vibration wave has a vibration node disposed on a diagonal line of the vibrating body. At least one protrusion is connected to the vibrating body for vibration therewith. The protrusion is disposed on the vibrating body at a position which does not correspond to the position of the vibration node. A moving body is disposed in contact with and driven by the protrusion during vibration thereof.

Abstract: A rotary drive device is configured to be reduced in size while still delivering a prescribed torque. The rotary drive device has a base part with a vibrating body and a rotating body attached to the base part. The vibrating body has at least one piezoelectric element that vibrates an abutting part, which rotates the rotating body. Specifically, the rotating body has a contact part that is positioned at a prescribed distance from the rotational center and that is abutted against by the abutting part. When voltage is applied to the piezoelectric element, the vibrating body vibrates to repetitively press the abutting part against the contact part to rotate the rotating body. The vibrating body is positioned in a plane that intersects the rotational axis of the rotating body, and is disposed at least as close to the rotational axis of the rotating body as that of the contact part.

Abstract: A harmonic motor includes a first annular member, a second member, and device for flexing the first annular member. The first annular member has a longitudinal axis and is flexible. The second member is substantially coaxially aligned with the first annular member. One of the first annular and second members is rotatable about the longitudinal axis, and the other of the first annular and second members is nonrotatable about the longitudinal axis. The flexing device flexes the first annular member into at least two spaced-apart points of contact with the second member and sequentially flexes the first annular member to rotate the at least two points of contact about the longitudinal axis which rotates the rotatable one of the first annular and second members about the longitudinal axis. The flexing device is nonrotatable about the longitudinal axis.

Abstract: An electromechanical motor and method for operating same result in a motor low-wear, quiet, slip-free and simple structure, wherein the drive shaft is driven free of bending moments, can be arrested in quiescent position and can be operated at low speed. A drive ring is disposed for line contact with the shaft and moved by a combination of linear displacements of respective electromechanical drive elements to execute a circulatory motion.

Abstract: An ultrasonic motor is described which uses radial vibrations of an electro-active material disc (7) amplified by one or more flextensional diaphragms (6) to drive a rotor (4) pressed in frictional contact with the diaphragm (6) by a force imposed by a spring (3) or magentic attraction. The vibrations are converted by elastic fins (5) into rotary motion of the rotor (4). The motor can be operated in any resonant mode that generates vibration at the surface perpendicular to the contact area. Versions of the motor with one or two rotors are disclosed with the two rotor version being used to produce an output in the same direction or opposite directions.

Abstract: In a truss-type driving apparatus, the amplitude of each displacement member and the phase difference therebetween are detected, and by adjusting the amplitudes or the phases of the impressed voltages to drive the displacement members based on the results of such detection, the elliptical locus drawn by the synthesizing member of the truss-type driving apparatus during driving is adjusted such that the desired driving characteristics are obtained.

Abstract: The invention relates to a piezoelectric drive device with a bimodal piezoelectric resonator, with at least a first control electrode for triggering the resonator in a first drive direction, with at least a second control electrode for triggering the resonator in a second drive direction, and with a trigger circuit for supplying control signals to the first and the second control electrode. The invention is characterized in that a regulating circuit is provided for regulating the control signals, the second control electrode is designed for supplying a feedback signal to the regulating circuit when the resonator is being triggered in the first drive direction by means of the first control electrode, and the first control electrode is designed for supplying a feedback signal to the regulating circuit when the resonator is being triggered in the second drive direction by means of the second control electrode.

Abstract: A driving apparatus that improves the precision of driving control for a driven member by reliably ensuring the desired motion of the tip member. Regulating members, which hold a piezoelectric actuator at positions opposite a rotor R, are located at positions separated from the piezoelectric actuator by a distance L that equals or exceeds the amplitude of the oscillation generated in the piezoelectric actuator.

Abstract: A vibration motor comprising at least one stationary part and one part driven to move relative to the fixed part, together with excitation that is suitable for exerting forces that tend to move rigid contact sectors presented by the fixed part and/or the moving part and to cause the rigid sectors to vibrate in vibration modes that combine tangential vibration and normal vibration, thereby driving the movement of the moving part, the motor presenting for the tangential vibration or the normal vibration a main resonant mode and at least one secondary resonant mode, wherein the secondary resonant mode is at a frequency that is substantially equal to a harmonic frequency of the main resonant mode.

Abstract: The present invention relates to a ring-type piezoelectric ultrasonic motor that is different from the electro-magnetically driven conventional motors and that has applications in robots and automation equipments. More specifically, the present invention relates to a ring-type piezoelectric ultrasonic motor that is driven by a frictional force between rotor and stator, and stator is produced a mechanical displacement by a piezoelectric ceramics applying an alternate electric field with an ultrasonic frequency (above 16 kHz).

Abstract: The present invention relates to a piezo-electric drive consisting of a stator (2) and a rotor (4).

Abstract: In frequency-admittance characteristics of a stator, the frequency with a resonance point at which the admittance value is minimum and that with a resonance point adjacent thereto are set to be apart from each other and thereby an ultrasonic motor having less variations and high output power is provided. In addition, an ultrasonic motor is provided in which support and pressing structures and a conduction structure are improved for the purpose of achieving a size reduction. Two elastic bodies are disposed in upper and lower positions and have grooves at their respective surfaces. These grooves are provided at regions corresponding to nodes of standing waves that are stress concentration zones so as to cause large torsional displacement. The grooves are provided in places other than the upper and lower surfaces of the elastic members. In addition, these grooves have a smaller angle than 90 degrees.

Abstract: A linear piezoelectric motor which includes a piezoelectric actuator; an actuator container which contains the piezoelectric actuator; an actuator slope which is supported by and slidably connected to an actuator slope support, the actuator slope is able to correspond with a surface portion of the actuator container; an output bar which shares a common axis with the actuator and the actuator container and comes in contact with at least one of the actuator and the actuator container on one end of the output bar and an axial load is applied on an opposite end of the output bar; and at least one output slope which is slidably connected to at least one output support.

Abstract: In a self-excited oscillator circuit, a buffer is connected to an electrode or electrodes, and a buffer and an inverter are connected to an electrode or electrodes. Each of the inverters and and the buffer has a tri-state configuration and is capable of setting an output terminal in a high-impedance state, i.e., turning off an output signal, according to a signal input to a control terminal. Therefore, it is possible to turn off a drive circuit and the ultrasonic motor by setting the inverter in the high-impedance state. It is also possible to change the direction of movement of the moving member by setting one of the buffer and the inverter in the high-impedance state.

Abstract: An ultrasonic motor has a stator and a rotor which is press fit to the stator and rotates in accordance with the vibration of the stator. The stator includes a pair of metal blocks, a piezoelectric element located between the metal blocks, a tightening member and a positioning member. The tightening member is inserted through the metal blocks and the piezoelectric element to tighten the metal blocks and the piezoelectric element in the axial direction. The positioning member determines the radial position of the metal blocks. This reduces misalignment of metal blocks and the tightening member, and the stator for the ultrasonic motor.

Abstract: A drive mechanism has an ultrasonic motor having a rotor which is rotationally driven by vibration of a vibrating member having a piezoelectric element. The rotor has a projecting portion for rotation therewith. A driven member is connected to the rotor for undergoing movement along a surface extending in a radial direction of the rotor. A guide member restricts movement of the driven member and guides movement of the receiving member in a given direction. A receiving member contacts the projecting portion of the rotor to limit a range of rotation of the rotor and limit a range of movement of the driven member.

Abstract: The invention relates to a piezoelectric actuator (1) for driving a movable part (2), for example a rotor, having an elongate piezoelectric resonator (3), which serves to perform longitudinal vibrations and which is acted upon by elastic means (10), for example a spring (10). The elastic means (10) acts upon the piezoelectric resonator (3) mainly in the longitudinal direction (11) and serves to exert a force on the resonator (3) in a direction towards the movable part (2), the resonant frequency of the elastic means (10) being substantially smaller than the resonant frequency of the piezoelectric resonator (3), and the piezoelectric resonator (3) is guided by at least one guide element (4, 5) in a direction perpendicular to its longitudinal direction (11). This enables the resonator (3) to vibrate as freely as possible, which leads to a higher efficiency.

Abstract: A stacked electro-mechanical energy conversion element includes a plurality of layers made of a material having an electro-mechanical energy conversion function on which a plurality of electrode areas are formed, a first layer having an electro-conductive portion formed from the electrode area to a side face which is a non-stacked surface area, a second layer having a through-hole formed therein by an electro-conductive member, a third layer having an electro-conductive film which communicates the electro-conductive portion of the first layer and the through-hole of the second layer, and an external electro-conductive film formed on the side surface of the first layer so as to communicate with the electro-conductive portion.

Abstract: The invention relates to a piezoelectric motor having a rotor and supply means (S0, S1) for supplying an electrical control voltage to at least one piezoelectric element (9) of the stator. According to the invention, the supply means (S0, S1) are arranged to supply an electrical control voltage having a DC component (V0) for shifting towards the expansion state of the piezoelectric elements (9).

Abstract: An ultrasonic motor comprises a stator, a rotor and a fixing portion. The stator has a first block, a second block and a piezoelectric element, which is held between the first and second blocks. The piezoelectric element vibrates when receiving a drive voltage having a predetermined frequency, and the stator produces resonance vibration in accordance with vibration of the piezoelectric element. The rotor is pressed on the stator in a slidable manner and rotates due to the vibration of the stator. The fixing portion is provided on the stator to fix the stator to a predetermined support portion. The fixing portion is formed in such a way that a natural frequency of the fixing portion comes off a frequency range of the drive voltage where the rotor is rotatable. This structure provides an ultrasonic motor which is quiet and has high energy conversion efficiency.

Abstract: A driving apparatus enjoying improved performance through the prevention of fluctuations in the driving characteristic, wherein a driven member, which is frictionally engaged with a driving member fixed to an electromechanical conversion element, is driven based on driving that is not symmetrical as to the timing of extension and contraction of the electromechanical conversion element, and wherein the electromechanical conversion element is elastically held by the housing.

Abstract: A piezoelectric motor having a stator in which piezoelectric elements are contained in slots formed in the stator transverse to the desired wave motion. When an electric field is imposed on the elements, deformation of the elements imposes a force perpendicular to the sides of the slot, deforming the stator. Appropriate frequency and phase-shifting of the electric field will produce a wave in the stator and motion in a rotor. In a preferred aspect, the piezoelectric elements are configured so that deformation of the elements in the direction of an imposed electric field, generally referred to as the d33 direction, is utilized to produce wave motion in the stator. In a further aspect, the elements are compressed into the slots so as to minimize tensile stresses on the elements in use.

Abstract: A driving apparatus includes an electromechanical conversion element that expands and contracts through the application of a drive voltage, the electromechanical conversion element includes a first end and a second end. The apparatus further includes a support member that is fixed to the first end of the electromechanical conversion element in a direction of expansion or contraction of the electromechanical conversion element; a drive member that is fixed to the second end of the electromechanical conversion element in the direction of expansion or contraction; an engaging member that engages with the drive member with a friction force; and a drive circuit that drives the electromechanical conversion element.

Abstract: An ultrasonic motor includes a stator and a rotor. A plurality of slits are arranged at substantially equal angular intervals along an outer peripheral surface of the rotor. A photosensor is supported inside of an upper housing of the motor. The photosensor is arranged to oppose each one of the slits in a radial direction of the rotor when the slit comes in front of the photosensor during rotation of the rotor. Based on a signal outputted from the photosensor, a control device applies a high frequency alternating voltage between first and second electrode plates of the stator.

Abstract: A micro-mechanical actuator is disclosed for actuating an object in a micro-electro-mechanical system. One end of the object is flexibly connected a substrate, and another end is flexibly connected to an auxiliary lever which is further connected to an actuating force generator. The auxiliary lever receives an actuating force generated from the actuating force generator to perform a levering operation about a fulcrum. The position of the fulcrum allows an portion of the auxiliary lever connected to the object has a shift larger than a shift of another portion of the auxiliary lever connected to the actuating force generator in response to the actuating force.

Abstract: A truss type actuator including two piezoelectric devices drives a chip member provided at a crossing point of the piezoelectric devices for moving along an elliptic or a circular trail. Only one piezoelectric device is driven for transmitting vibrations thereof to the other non-driven piezoelectric device. By selecting a frequency of driving signals, both of the piezoelectric devices are resonantly vibrated with a phase difference of 90 degrees.

Abstract: A thin-disc piezoelectric actuating ultrasonic motor includes a stator made up of a commercially available piezoelectric element that includes a piezoelectric ceramic membrane bonded on a metal plate to form a concentric disk. An ultrasonic motor driving mechanism induces mechanical vibration in the piezoelectric element by extension and shrinkage of the metal back plate, upon application of single phase AC power. There are two propagating directions in the induced mechanical vibrating wave. One is a radial component, and the other is a transverse component. The outer edge of the piezoelectric element thus forms traveling waves in different directions. These traveling waves may be used to provide a torque so as to drive the rotor to rotate.

Abstract: The present invention provides a truss actuator offering reduced noise, vibration and wear, which is capable of speed control of the driven member and can control the output to the driven member at a constant level regardless of fluctuations in the load on the actuator or in the environment in which the actuator is used. In the truss actuator, one displacement unit 2 or 3 is driven and this oscillation is transmitted to the other displacement unit 3 or 2, and the truss actuator includes two displacement sensors 11 and 12 that respectively detect the displacement of the displacement units, a phase difference detecting unit 13 that detects via the displacement sensors the phase difference between the detected displacement values, a target phase difference setting unit (a CPU 20, etc.

Abstract: A piezoelectric motor having a stator and a rotor. The stator and the rotor are in mechanical contact with one another along at least one cylindrical friction surface by means of curved, elastic and longitudinally elongated pusher plates, the pusher plates being held against the friction surface at a first end of the pusher plates, and arranged at an angle to the friction surface. A piezoelectric element is connected to either the rotor or the stator. The piezoelectric element has electrodes placed on opposing surfaces of the piezoelectric element, and is connectable to an alternating current source via the electrodes for providing longitudinal oscillations in the piezoelectric element. A first ring plate and a second ring plate are arranged on opposite sides of the piezoelectric element, so that at least a portion of surfaces of the piezoelectric element are pressed against surfaces of the first ring plate and the second ring plate, respectively, by a clamping device.

Abstract: A stator includes a longitudinal-vibration sensing electrode. The stator also includes a torsional-vibration sensing piezoelectric element and a torsional-vibration sensing electrode plate for sensing torsional vibrations. A voltage signal from the torsional-vibration sensing electrode plate or a voltage signal from the longitudinal-vibration sensing electrode is sensed. Then, a drive voltage signal for driving the stator is generated in a self-excited oscillation drive circuit in such a manner that an actual vibrational frequency of the stator substantially coincides with a resonance frequency. Thereafter, the generated drive voltage signal is applied between a drive electrode and each one of first and second electrode plates.

Abstract: The invention described herein is a novel power circuit capable of electrically driving devices whose mechanical action is accomplished by induced strain transducers. The power circuit neither recycles nor dissipates the energy returned from the near lossless transducer, instead redirects power either to another transducer of the same type or to the transducer itself. The invention is based on a balanced capacitive loading method wherein the load itself acts as the energy storage element in the energy balance system. In the preferred mode, the circuit directs power to a symmetric couple where both loads in the couple consist of one or more transductive elements. The invention eliminates the need for a large power-supply bypass capacitor in driving reactive loads thereby reducing the peak power handled by the d.c. power section.

Abstract: The invention relates to a piezoelectric motor having a rotor and supply means (S0, S1) for supplying an electrical control voltage to at least one piezoelectric element (9) of the stator. According to the invention, the supply means (S0, S1) are arranged to supply an electrical control voltage having a DC component (V0) for shifting towards the expansion state of the piezoelectric elements (9).

Abstract: The present invention is actuator having a shaft delivering mechanical power to a load, a first active element adapted to be driven by an oscillating signal, and at least one mechanical diode operatively connected to the shaft in the act of development. A plurality of mechanical diodes may also be used. Mechanical diodes can be either rotary mechanical diodes or linear mechanical diodes. The mechanical diodes can also be bi-directional.

Abstract: A vibration type actuator comprises a vibration member for generating vibration displacements in at least three different directions and a contact member in contact with the vibration member. In the actuator the vibration displacements in at least three different directions are excited in the vibration member to generate synthetic vibrations that cause relative movement between the vibration member and contact member in a desired direction.

Abstract: An ultrasonic motor with increased output power per unit volume is provided by simultaneously driving all of a plurality of polarized segments of a piezoelectric element having a circular disk shape and divided into a multiple of four polarized segments in a circumferential direction. Projections are provided at upper faces of the polarized segments of the piezoelectric element and spaced apart by an odd number of polarized segments. Polarities of adjacent polarized segments are the same and polarities of adjacent pairs are reverse to each other. A first polarized segment group comprises every other polarized segment and a second polarized segment group comprises the remaining polarized segments. By selecting whether phases of alternating voltages supplied to the first and second polarized segment groups are the same or are 180 degrees out of phase, the direction of the motor is determined.

Abstract: Embodiments of the present invention are directed to rotational actuators or rotators that rotate an object in a worm-like manner. One rotator includes piezoelectric members that are controlled to expand and contract in a predetermined sequence to rotate a ring. The rotator includes first and second coupling members which are adjustable in length to move between a coupled position being coupled with the ring and a decoupled position being decoupled from the ring. A top advancing member is connected between the top coupling end of the first coupling member and the top coupling end of the second coupling member. A bottom advancing member is connected between the bottom coupling end of the first coupling member and the bottom coupling end of the second coupling member. The top and bottom advancing members are adjustable in length to produce relative movements between the top coupling ends and between the bottom coupling ends, respectively.