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schmidt10613technical articles

When choosing a suitable shaft coupling for the respective drive train, some considerations should be considered. In addition to the identification of the torque to be transmitted and the maximum speed, inter alia, the factors displacement capacity for trouble-free and wear-free working and torsional stiffness play an important role, for example for positioning accuracy. Schmidt coupling offers different product series of torsionally stiff compensating couplings for different applications and requirements.

They offer various application-relevant features and predestine them for a wide variety of applications. For example, encoder applications call for other technical performance data of the clutch as clutches for printing presses. Other criteria must meet couplings, if they have to take over axial control tasks in addition to the torque.

Compensate for high radial displacements without restoring forces

schmidt20613The transmission of the rotational movement and the torque takes place in the Coupling system "Semiflex" by means of two 90 ° offset parallel handlebar pairs. They connect the input and output side with the center disc. When occurring radial displacement, the handlebars move in a group in parallel. Since the coupling members always remain parallel to each other, the clutch system always ensures the same angular velocity of input and output without phase shift and consequently absolute synchronization.

The handlebars are rotatable on the bolts located in the discs, usually via needle bearings. The parallel displacement compensation, which can be up to 6,6 mm, depending on the size of the coupling, is achieved by a pure swiveling movement of the handlebar pairs. This compensation requires only a small length. Due to a defined crowning of the needles of a respective bearing, the functional system compensates for angular errors, which can be up to 1 °, depending on the coupling size.

Basically, the semi-flexes available with an outside diameter range from 50 to 300 mm are designed as steel versions with different positive and non-positive shaft connection forms. They cover a maximum torque range up to 18.800 Nm. Applications include printing, packaging, machine tools, extrusion and conveyor systems. Modified versions such as stainless steel versions are predestined for applications under vacuum conditions, for food processing equipment or for machines in the pharmaceutical industry. For dynamic applications such as automatic assembly machines, which work with high productivity in high cycle rates with exact repeat accuracy, the designer finds the Dynamic range in the spectrum. The couplings of this series are made entirely of aluminum and thus have a low mass moment of inertia. For backlash-free shaft connection even in reversing mode, they have non-positive clamping hubs.

High universal relocations

Many applications call for couplings with a high universal displacement capacity. For example, triggered by deliberate skewing of waves or by process-related adjustment movements in holistic machining operations of materials such as the polishing of surfaces of display and architectural glass or in the production of chassis parts in the automotive sector. For these applications, the Series "Omniflex"Developed.

The torsionally stiff couplings offer a high universal displacement capacity in combination with a compact design. The explanation of this symbiosis lies in the kinematics of the coupling system. The transmission of the rotational movement and the torque takes place in the clutches by means of two 90 ° staggered parallel handlebar pairs. Special spherical plain bearings work in the coupling elements. Here, the choice of the respective bearing pairing in the spherical plain bearings is adjusted to the technical requirements. Depending on requirements, these can be, for example, combinations of steel on steel for robustness and hard cycle operation or steel on PTFE fabric for maintenance-free applications such as in process engineering.

Depending on the size, the couplings offer an angular displacement up to 3 °, a radial displacement of up to 200 mm and an axial compensation of max. 50 mm.
The range of rated torques of the realized and projected Coupling sizes currently range from 150 Nm up to 6400 kNm.
Large gearboxes, press drives, packaging plants, gearbox test stands, process engineering, conveying and coating systems as well as mixing and agitators are potential fields of application.

Plug-in for encoders with electrical insulation function

schmidt30613Other requirements are in the area of ​​sensor technology. Here, a rotary encoder coupling has the task to protect measuring instruments against mechanical overstressing and to ensure the transmission of the rotary motion according to the resolution of the encoder exactly. The "Controlflex"Was designed according to the mechanical and metrological requirements of transducers such as Encoders, encoders and tachogenerators developed. Due to the special design of the functional element, the coupling enables the compensation of radial, axial and angular displacements in a compact design. The angle-synchronous transmission of the rotational movement always remains guaranteed. In addition, the displacement compensation takes place extremely low in restoring force and thus saves storage space.Zudem They offer an electrical insulation function, which is important for a galvanic separation of measurement setups and frequency-controlled drives. Depending on the size of the coupling, the couplings equipped with balanced aluminum clamping hubs are suitable for a speed range up to 25.000 min-1 available.

Axial stiff with fixed bearing function

The previously described coupling systems are characterized by the fact that, in addition to parallel and angular displacements, they additionally provide an axial displacement compensation, for example produced by thermal expansion of shafts.

Another requirement for coupling systems but is then provided when superimposed to be transmitted torques of axial tensile and compressive forces, the clutch must take over a fixed bearing function or even axial strokes are to be accurately transferred. An axial compliance of the compensation element must be excluded accordingly axially stiff "Loewe GK"Combines the kinematic properties of single-shaft joints with those of cross-slide couplings.

In an aluminum inner ring are located at an angle of 90 ° to each other arranged pins. The center part similar to a spider can now pivot on the one hand in the plain bearings. Since, however, it is not fixed in the joint half compared to a universal joint, it can consequently additionally shift by a defined amount in the plastic sliding bushes when the radial offset occurs. This simultaneous pivoting and linear movement in the bearings enables a combined angular and radial displacement compensation.

The "Torque" aluminum clutches offer a rated torque of up to 220 Nm. Areas of application include printed circuit board exposure systems, pick-and-place applications, feeding tasks in machine tools or as compensating couplings in screw jack systems. Couplings of the series "Linear" offer the precise transfer of pure linear control pulses, for example in cylinder applications and valve flap adjustments. The maximum axial load is up to 13.000 N depending on the size of the coupling.

Large, variable radial offset

When it comes to compensating couplings, compensation for misalignments due to production inaccuracies, etc. is often apparent. However, as we have already seen in the displacement values ​​of the Semiflex or Omniflex, this may also be a deliberate functional offset, e.g. As in calender drives and the processing of different material thicknesses and thicknesses. Large and variable in operation radial offsets occur in paper machines, in forming technology, in woodworking and printing machines or in Walzenvorschüben. The Schmidt coupling has been developed for this purpose. The short construction, torsionally rigid power coupling was designed for a large variable radial offset. There are no reaction forces generated. Regardless of the offset, it ensures an always constant angular velocity of the input and output shafts. Depending on the size and series, they offer a maximum permissible radial offset up to 275 mm.

Pictures: possible applications

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