Parallel Leaf Springs Research Articles

Wear Tests and Pull-Off Force Measurements of Single Asperities by Using Parallel Leaf Springs Installed on an Atomic Force Microscope

At the micro-scale level, the adhesion force dominates the friction force when the normal load approaches zero. For determining the effects of micro wear on the adhesion (pull-off) force, the wear-induced changes in surface topography of asperities and the pull-off force between the asperities and leaf springs were determined. First, single asperities were formed on a single-crystal gold plate and the asperities were rubbed with a silicon leaf spring attached to an AFM (atomic force microscope). A focused ion beam (FIB) system was used to form gold pyramid-shaped asperities on the surface of a single crystal gold plate. The FIB was also used to create the two types of single crystal silicon leaf springs tested here; single and parallel. The single leaf spring was created by flattening the probe-head of a commercially available AFM cantilever for AC mode. The parallel leaf spring was created by removing the central portion of a single-crystal silicon beam (25 μm×50 μm×300 μm). For the single leaf spring, the pull-off force no longer increased when the sliding distance exceeded 5 mm at a load of more than 200 nN. On the other hand, for the parallel leaf spring, the pull-off force increased monotonically with sliding distance, showing a more rapid increase at the higher normal load. The worn area of the asperity peak (measured by using an ordinary AFM probe) was proportional to the pull-off force. The wear volume per unit distance (i.e., wear rate) was estimated from the change in pull-off force, and was found to increase monotonically with the external load. There was no effect of adhesion force on the wear volume. [S0742-4787(00)01102-4]

A Parallel Leaf Spring Structure Driven by Piezoelectric Bimorph Actuators

A parallel leaf spring structure driven by a piezoelectric bimorph actuator is mod elled using a Rayleigh-Ritz formulation; model truncation is performed for feedback controller design. Using a strain gauge sensor, a precise positioning of the end point mass is realized. The posi tion of the strain gauge sensor is found to be an important factor in achieving a stable response with an estimator based feedback control system. Excitation of higher structural modes, which becomes an obstacle to a wide servo bandwidth actuator, is discussed. Using multi electrodes arranged on the bimorph actuator, and appropriately tuning the voltage ratio applied to them, pole-zero cancellation of the higher modes is experimentally demonstrated.

板ばねを利用した直動および回転機構

The use of leaf springs has found wide application in measuring and scientific instruments. The advantages of the leaf spring mechanisms are as follow: (1) Provide movement without friction or backlash so that high accuracy and good repeatability can be obtained. (2) Simple and low costs, and no lubrication is required. This paper deals with new mechanisms using leaf springs. The parallel movement devices are consisted of a pair of parallel leaf springs having identical length, width and thickness. In these movement devices, the displacement in perpen-dicular direction is increased when the upper member was moved lateral with respect to the bottom member, or increased resistance to any vertical loads, which may be imposed on the mechanism. It was achieved by using original compound leaf spring movement mechanism. In the mechanism, the displacement in perpendicular direction was 0.8μm while the track was 10mm long. A new rotary mechanism was also considered. In the mechanism, the disadvantageous displacement was within 2μm and movement of the axis of rotation was within 5μm where the radius was 92.5 R while the rotation was 6.2 degree.

Flatness control lapping/polishing machine

A lapping/polishing machine has been newly designed and constructed to produce precise flat surfaces efficiently. The machine can control the shape of a base plate to within a few microns by varying pressure distribution and rotating speed. Stable floating and vibration suppression to less than 1 μm for the base plate are attained by using hydrodynamic bearings. Accurate and large loading are also attained by using parallel leaf springs. The base plate surface is lapped within a few microns by controlling the pressure distribution. In silicon wafer polishing, work plates are deformed due to polishing heat. Therefore, two-layer discs with a larger coefficient of thermal expansion in the upper layer were used. As a result, it has been proved that highly accurate polishing may be attained efficiently by using the machine

平面修正制御形ラップ・ポリシ機の試作

A lapping/polishing machine has been newly designed and constructed to produce precise flat surfaces efficiently. The machine can control the shape of a base plate by varying the pressure distribution on the work plates and the conditioning rings. It is also possible to control the shape of the base plate by changing the rotating speeds of the base plate and the work plates. Stable floating characteristics and vibration suppression to less than 1 μm are attained by using hydrodynamic bearings for the base plate bearings. Accurate and large loading are also attained by using parallel leaf springs. The base plate and work plate surfaces are lapped within a few microns by controlling the pressure distribution. The base plate always attains an isothermal state during silicon wafer polishing, because the upper and lower surface temperatures of the base plate rise simultaneously due to polishing and motor power heat. On the other hand, the work plates are deformed thermally. Therefore, two-layer discs with a larger coefficient of thermal expansion in the upper layer were used to reduce thermal deformation. As a result, it has been proved that highly accurate polishing may be attained efficiently by using the machine.

Vibration testing system for gear sets

A pair of gears, which form a gear set, are tested by mounting the gears on parallel axis spindles which are located at a fixed center distance. One of the parallel axis spindles is contained in a spindle housing that is rigidly mounted to a massive base. The other gear of the set is contained in a spindle housing which is supported on top of a pair of parallel leaf springs that are connected to the base. The spindle in the spindle housing that is rigidly mounted on the base carries a pulley at its end that is remote from the gear set which is coupled through a drive belt and a second pulley to a drive motor. The spindle in the resiliently mounted spindle housing on the leaf springs is coupled to an eddy current brake at its end which is remote from the gear set. An accelerometer, which is coupled to a conventional electronic output indicator, is mounted on the resiliently mounted spindle to provide indications of the vibrations caused by the gear sets. The gears of the gear set are driven by the drive motor so that their tooth-to-tooth frequency is approximately the same as the resonant frequency of the resiliently mounted spindle housing. The construction of the testing system in the described manner substantially improves the signal-to-noise ratio of the output signal that is obtained from the accelerometer.

Parallel and rectilinear spring movements

This paper discusses the design of instrument movements in which the moving member is held by two equal and parallel leaf springs; the member can be moved parallel to itself by pushing it normally to the springs. In a constructed specimen the parallelism was maintained to within ± 3.5 sec of arc over 6 mm of travel by a simple method of balancing the springs. Arrangements are described for combining two or more spring systems to develop a rectilinear movement. Performances are quoted for three constructions, the best of which held a straight line within about ± 0.25 μ over 5 mm of travel, and ± 1 μ over 10 mm. In some applications spring movements are superior to kinematic slides.