Coupling Resists Leakage In Solar Panel Capacitor

Huco Dynatork has supplied its Multi-Beam coupler for use in a solar panel high-voltage capacitor manufactured by a Japanese consumer electronics company.

The flexible misalignment coupling is used to connect the drive from the gearbox to a lead screw and had to be able to resist any current leakage.

Servo Couplings Use Dampening Attributes For Vibrations

Specialist mechanical components supplier, Ondrives Ltd of Chesterfield, England have recently introduced a high quality range of servo-insert couplings into their extensive coupling range via their biggest ever catalogue, now that they have merged with sister company, Rino Industries Ltd.

Typically, they are used in applications where vibrations and crushes may appear. The dampening attributes of those couplings are caused by the spider element which is positioned between the two hubs. This spider element is available in different shore hardnesses. Depending on the requirements it is recommended customers use a spider element with low dampening properties for applications with low vibrations and crushes (higher torsional stiffness of the coupling) and to use a spider element with high dampening properties for application of high grades of vibrations or crushes (lower torsional stiffness of the coupling).

A further positive property of the servo insert couplings is that they are pluggable, so they can be assembled quickly and easily even under difficult assembly conditions. The many different varieties of the hub style include shaft fixing with set screws, with clamp hubs and with outer conical hubs. Customers will find that the most popular type, as always, is with the clamping hubs as they ensure the fastest assembly/disassembly without leaving marks on the shafts. Torque range varies from as low as 1.2Nm up to 940Nm on the largest sizes. Other advantages include an extremely compact design and minimum mass and inertia as standard. They offer high resistance against environmental influences and temperatures as well as being non-wearing and therefore maintenance free.

A misalignment of the shafts in axial, lateral and angular directions can be compensated by a servo insert coupling as well but it should only be a minimum of misalignment because relatively high reset forces are caused by the coupling which do negatively influence the lifetime of components such as bearings in this environment, the company states.

Typical applications include -

Stepping motors, servo drives, machine tools, CNC machines, wood working and packaging machines, factory automation machinery, printing machines, sheet metal forming machines, industrial robots, textile machines and control and feedback control systems.

www.ondrives.com

Zero Backlash Coupling Ideal for Belt Driven Linear Actuators

Due to greater demands in modern machine design and construction, R+W has developed its EK7 series of SERVOMAX Zero Backlash Elastomer Couplings.

This coupling was specifically designed to mount to hollow bores with an expanding tapered clamping element, making it ideal for belt driven linear actuators. The EK7 provides design engineers with a number of advantages, including:

· Most belt driven linear actuators require a shaft adapter in order to couple the pulley to a motor or gear head. The EK7 eliminates the need for this additional hardware.

· In designs where motor shafts are typically mounted directly into the pulley, customer specified products often provide shafting that is too large. The EK7 can couple to the large shaft with a smaller expanding element to link the two together.

· Assemblies involving a motor, gear head and coupling used to drive the actuator can become quite large and cumbersome. The EK7 plays a small part in reducing that system size by reducing the coupling adapter flange by the length of one hub.

In addition to providing these and other novel mechanical linkage solutions, the EK7 also offers the benefits of all SERVOMAX couplings, particularly in its zero backlash torque transmission. The moment of inertia is also very low due to its low mass and low weight; ideal for high-speed servo applications where rapid acceleration/deceleration cycles exist.

The couplings are manufactured with precision machined jaws and an elastomer insert press fit between them for vibration damping and zero backlash transmission of torque. The coupling hub is custom bored and can accommodate shaft diameters from 4 to 60 mm (3/16 to 2.25 in.) and the expanding hub can accommodate bores from 12 to 70 mm (1/2 to 2.75 in.). Sizes are available for torque capacities up to 450 Nm (4,000 in. lbs.).

Shoulder Couplings Ideal For Abrasive Surfaces

Victaulic now offers a new line of products for joining standard shouldered steel pipe. The product line features the Style SC77, a flexible coupling featuring Victaulic patented installation-ready technology, and a variety of prefabricated shouldered fittings designed to make pipe joining even more efficient. The product line is ideal for abrasive services, particularly in the mining industry, where maintaining full pipe-wall thickness is important.

www.victaulic.com

High Torque Motor Turns At Speeds Up To 3,500 RPM

Today’s turning centers can be economical without sacrificing power or precision. Demonstrating this is the Lynx 300, a new turning center from Doosan that’s just now entering the United States.

The Lynx’s 20 Hp, high torque motor provides the power for heavy cuts and the speed to produce near-mirror finishes. Its 10″ diameter 3-jaw power chuck turns 3″ bar stock at speeds up to 3,500 rpm, and its recommended price is well below others that do less and cost more.

The Lynx’s bed is a one-piece Meehanite casting to absorb vibration and help dissipate heat, while its heavy ribbing resists twisting and distortion. A 30° slant bed maintains a minimal and constant distance between tool tip and guideway. This maximizes rigidity while eliminating distortion under heavy loads. The headstock is mounted on the same plane as the tailstock to assure perfect alignment and center height regardless of the bed temperature. Widely-spaced linear motion guideways allow high-speed rapid traverses – 945 IPM on the X-axis, and 1,181 on the Z.

Each axis is driven by a large diameter, high precision ball screw that is selected for its outstanding combination of accuracy, rapid traverse speeds, and high feed thrust. The ball screws are mounted directly to the A.C. servo motors. This design minimizes backlash for superior machining accuracy. Ball screws on each axis are protected in case of a crash by an electric torque limiter. Upon impact, the torque limiter senses the load and immediately reverses the servo motor and stops the axis movement.

Lynx’s 12-station turret features an 8.26″ diam. curvic coupling and 11,465 lbs of hydraulic clamp force. This configuration provides high rigidity for superior accuracy and surface finish, long boring bar overhang ratios, and extended tool life. Indexing repeatability is +/-0.0005°. Turret indexing is non-stop and bi-directional, with 0.15 sec. next-station index time. A rotary encoder determines the turret position, and a proximity switch confirms the clamp.

Additional standard features of importance include a waylube separation system, a tool setter that eliminates skim cuts and manually entering tool offsets, automatic forced lubrication, coolant system with a 42 gal. coolant tank, and a part catcher. The controller is a Fanuc 0iTD.

www.doosaninfracore.co.kr

Torque Limiters that Keep Overload in Check for Heavy Equipment

A different approach is needed when designing mechanical torque limiters for high horsepower drives.

The basic principles of mechanical torque limiter design are similar to those that have been known since some of the first machines were built, yet it remains a dynamic field. Function, space restrictions, safety considerations and continuously changing machinery design drive the need for these components to evolve.

Typically, safety element torque limiters are supplied as a pre-set and self-contained package for integration into timing sprockets, sheaves and cardan shafts, like the one shown here.

In particular, high horsepower drives often call for mechanical design to be approached from different perspectives. As motors, gearboxes, and machines increase in size, power density can become disproportionate from one driveline component to the next, emphasizing the need for more rugged, robust and compact equipment. Precision mechanical components used in the packaging and light manufacturing automation industries, for example, may not be adequately scalable, and so be outsized quickly as drive requirements reach into the thousands of horsepower.

This disparity is seen in the design of modern torque overload release devices, the majority of which have torque release values inappropriately low for use on heavy equipment requiring operation and disconnect at torque levels beyond 10 KNm, such as large recycling equipment, gas turbines, windmill test stands, and industrial crushers. While market demand may be greater for smaller torque limiters, the availability of heavy-duty devices is critical as mass, inertia and destructive forces increase in high-powered machinery.

One exception to the rule of disproportionate size increase is perhaps the oldest and most rudimentary form of torque overload release device; the shear pin coupling. In this case, one or more pins link two rotating bodies with known yield strength located at a pre-defined radius from the center of the rotational axis. At some torque level near the calculated maximum, the pin(s) will break for a complete separation of the driving and driven shafts and fail to transmit the excessive torque.

Shear pins have protected rotating equipment for centuries, but they lack accuracy and can require much time to repair after overload. To maximize plant uptime and improve the accuracy of release torque, vendors have developed a variety of torque overload release devices with integral bearings and simple mechanical reset features. A limited number of these torque overload release devices have been reconfigured for high horsepower.

Spring tensioned torque limiters
The first widely used modern overload release devices came about in the 1930s for use in the steel industry where downtime can be expensive, and replacement of shear pins time consuming and dangerous. These parameters led to the development of the spring-tensioned form-fit torque limiter, which uses the same fundamental principle of a set release force located at a specific center distance.

In spring tensioned torque limiters, ball or roller bearings are precisely loaded into detents machined into an output flange that will break away quickly and accurately at a predefined torque level. This type of torque limiter will either ratchet or free wheel during and after overload, depending on size considerations and the rotational speed of the axis.

A slightly more sophisticated form of torque limiter is the ball-detent design. After overload release it reengages quickly.

The shear pin coupling is a rudimentary form of torque overload release device. It links two rotating bodies with known yield strength located at a pre-defined radius from the center of the rotational axis. It will break at a specific torque level and separate the driving and driven shafts so as not to transmit excessive torque. The problem with shear pins is that they lack accuracy and take time to repair.

In general, you can adjust the torque of these overload release devices by turning a single screw or spanner nut. Their ratcheting features represent a very fast and convenient means of recovery from overload, since all they require is either low speed operation or manual back driving of the axis after the blockage has been cleared. Since their initial development, hundreds of designs of “ball-detent” and “pawl-detent” mechanical torque limiters have been introduced, with a variety of adaptations made for high speed, high accuracy, light weight, and backlash free operation.

Higher horsepower needs
But, however convenient, these torque limiter designs tend to fall off at torque levels any greater than a few thousand Neutonmeters. The basic problem is that overload breakaway devices rely almost exclusively on torque as a measurable component of power.

Practical implementation of high horsepower drive systems normally involves a slow steady increase in the rotational speed of an axis, where the torque required for instantaneous acceleration would be overwhelming. Drive shafts and gearboxes, therefore, are not typically required to handle the severe peak torques associated with rapid acceleration and deceleration of the load inertia, as might be found in lighter manufacturing systems. As a result they tend not to be as large as a proportionate size increase might require in terms of pure torque capacity. This situation poses a torque density problem for mechanical overload devices.

Beyond 10 KNm common overload release designs become impractically large in outside diameter; the primary limiting factor being the spring set used to load the components together. Since industrial gearboxes, motors, and pumps tend to grow in diameter at a much slower rate than these types of torque limiters, as power increases there comes a certain point at which a traditional single spring form fit torque limiter makes no sense at all, and would tower over the equipment it was designed to protect. Clearly the lever arm component of the torque limiter design must be addressed. The simple answer is to substantially increase the force by which the individual transmission elements are loaded into the output.

There are two widely accepted approaches to overload release devices for torque in excess of 10 KNm, both of which seek to increase force over a reduced lever arm distance. One is a compact, simple design involving hydraulic pressure applied between the two otherwise free spinning surfaces. The other is based on a modified spring tensioned device similar to those previously addressed. Each has their advantages depending on the desired result.

Hydraulic versions
Hydraulic torque limiters basically apply hydraulic pressure between the two otherwise freely spinning surfaces. One or more chambers are inflated by hand to the desired pressure level, calculated as a function of release torque and based on charts provided in the manufacturer documentation. Special fluids guarantee a constant coefficient of friction throughout various operating conditions. These chambers let you apply a high level of force over a very small surface area. When the desired release torque is reached, the output will begin to slip against the input, causing the hydraulic valves to shear off, purging the fluid and fully releasing the input and output components of the torque limiter. Through an integral bearing, the load inertia coasts to a stop without further damage to the machine components or the torque limiter itself. Reconnection involves replacing the valves, refilling the chambers, and resetting the pressure.

Compared with shear pins, hydraulic torque limiters let you maintain strict control over the disengagement torque setting, which can be unpredictable with shear pins. They otherwise represent a compact choice for accurate torque overload release at tremendously high torque values, handling as much as 10,000 KNm. What they do not offer is a major reduction in the time required to recover from an overload event.

Modified spring tensioned device
For maximum plant uptime, a slightly more sophisticated form of the ball-detent design still offers the fastest means of re-engagement after overload release. Several decades ago, torque limiter manufacturers developed self-contained tangential force modules based on a plunger design. The torque density problems associated with traditional ball-detent torque limiters are then addressed through the use of one or more of these individually spring tensioned elements, which can tolerate very large tangential forces.

Spring tensioned torque limiters contain ball or roller bearings that are precisely loaded into detents machined into an output flange that will break away quickly and accurately at a predefined torque level. This type of torque limiter will either ratchet or free wheel during and after overload.

Since the individual torque transmission elements provide their own back stop for the spring tension, an array of small blocks are used, which are forced outward to clear the way for the plunger core to retract into the housing after sufficient tangential force actuates the system. The result is a “snap action,” which causes the plunger to quickly retract into the housing within a few milliseconds of overload. Once again, an integral bearing enables the load inertia to coast to a stop without further damage to the machine components or the torque limiter itself.

The key advantage to this design is the quick reloading of the individual elements into the output flange with either a gentle blow from a mallet or light pressure from a pry bar. Once the driving and driven components of the torque limiter are rotated back into the necessary orientation, re-engagement takes place quickly and easily. Depending on practical considerations, you can use pneumatic actuation systems to automate re-engagement, though future designs are likely to incorporate a more widely applicable, self contained and fully mechanical reset function.

As with traditional ball-detent torque limiters, spring tension is adjusted through the rotation of a nut, only in this case the elements are individually adjusted to the desired tangential force value, and a torque calculation is made based on the number of elements and their distance from the center of the rotational axis. While the earlier designs of safety element torque limiters involved special datasheets used in conjunction with measurements taken from the spring height, increasingly manufacturers indicate the correct nut location with a marked scale. You can make a coarse adjustment by adding or removing safety elements, which is made more plausible by torque limiter designs with the maximum number of receptacles pre-machined into the base element and with simple covers installed to guard them from contamination. The ability to make such adjustments means you do not need to ship the torque limiter back to the manufacturer for rebuilding in the case of gross miscalculation of the torque requirement.

Because of the modular design, safety element type torque limiters can be used for almost any torque release value, depending on the size and number of elements used, and limited by the maximum diameter allowed by adjacent equipment. For this reason, individual safety elements are normally made available for use into existing machinery designs or for custom coupling systems, including some used for linear force limitation.
For the most part, safety element torque limiters are supplied as a pre-set and self-contained package for integration into timing sprockets, sheaves and cardan shafts. Some manufacturers provide them as fully integrated flexible safety couplings, such as jaw, gear, and disc pack types to name a few. Custom options often include special materials, integral brake discs, high temperature felt seals, and added bearing support. As is the case in any field of design, manufacturers are driven to improve reliability and ease of use, while simultaneously reducing weight and space requirements for installation.

A Novel Way To Use Jaw Couplings In Extreme Temperatures

The German couplings specialist, KTR, has come up with a novel way to use jaw couplings in temperatures too high for the elastomer materials conventionally used for coupling spiders. It has developed a spider made from “knitted” steel wire, similar to the steel wool used to clean pots and pans.

Standard spiders are made from thermoplastic polyurethane materials that can be used in temperatures from –30° to +90°C. The materials are produced in various hardness ratings, depending on the damping capacity and the torsional stiffness required. Both of these parameters are linked closely to the operating temperature.

KTR’s knitted-wire spider (above) allows vibration-damping couplings to operate in temperatures from –40°C to +180°C without affecting their torque capacities, torsional stiffness or damping. For an ambient temperature of 30°C, the characteristic curves of the knitted-wire spider are similar to those of standard elastomer spiders.

KTR expects the benefits of the knitted spiders to be most significant for applications with operating temperatures above 120°C. The stainless-steel spiders are also suitable for use in corrosive environments.

The knitted-wire spiders can be used with steel, cast-iron or hard-coated aluminium hubs. Initially, KTR is producing the spiders for its Rotex couplings. Damping figures are the same as for elastomer versions, while torque capacities and torsional stiffness are said to remain almost constant, even under permanent loads. The steel spiders are available in sizes from 14 to 90, corresponding to rated torques from 12.5–3,600kN (with peak torque ratings twice as high).

www.KTR.com

Breakaway Connectors Allow A Quick Disconnect

ITT Interconnect Solutions offers a line of breakaway connectors. The Nemesis Series and MKJ Series breakaway connectors incorporate a simple push/pull mating mechanism to engage and disengage the connector systems. The coupling mechanism utilizes a canted spring design, which allows for a quick disconnect and ratings of more than 5000 cycles.

The breakaway connectors also feature ITT’s spring probe pin/pad contact system. The contact design utilizes an internal clip mechanism that stays in constant contact with the contact itself, helping to reduce electrical contact resistance. Additionally, the spring probe contact system accommodates misalignment issues, making the contact system much more forgiving.

The spring probe system allows the connector receptacle to house individual touch pad contact areas, providing a highly effective electrical engagement point of contact. Further, the spring probe contact system and touch pads allow for ease of cleanability in the field, where dirt, moisture, mud, sand, and other contaminants may be present. The individual touch pad contacts contain no crevices for contaminants to accumulate.

The Nemesis Series sealed, lightweight, miniature connectors are resistant to salt spray for more than 500 hours, measure less than 15mm in diameter, and have an anti-reflecting coat. Maximum current rating for the Nemesis WT connectors is 3A and voltage rating is 200VAC RMS at sea level. Minimum insulation resistance is 5000MΩ, and maximum contact resistance is 8mΩ. Operating temperature ranges from -40°C to +100°C.  Life span is to 2500 cycles.

The MKJ Series miniature, circular connectors are available with a variety of mounting options for both crimp and PC board contacts, including in-line, jam nut, front mount, square flange mount and flange mount. The connectors are up to 71% lighter and 52% smaller than comparable devices, and feature size 23 pin-and-socket contacts that have the equivalent electrical performance of size 22 contacts. Dielectric withstanding voltage at sea level is 500VAC RMS, 60Hz. Operating temperature ranges from -55°C to +150°C.

Typical pricing for the Nemesis breakaway connectors is approximately $90.00 per mated pair for 1,000 sets. The breakaway connectors will be available in Q2 2010.

www.ittcannon.com

LEM Engineers Invent Unique Magnetic Coupling Technology

LEM has introduced the first of its AC current sensor families based on Perfect Loop Technology. After calibration, the new RT series achieves absolute accuracy of better than 0,65% – including position error – making them the first split-core Rogowski coils to be suitable for use in Class 1 power devices.

An imperfect coil structure induces an unbalanced geometry and increases sensitivity to the position of the measured conductor within the sensor, or to the proximity of external electric cables. The RT series of sensors overcomes the problem of asymmetry resulting from the discontinuity at the sensor opening, which is inherent in conventional split-core Rogowski coils. LEM engineers have invented a unique magnetic coupling technology that allows a perfect extension of the magnetic flux at the loop opening, which compensates for coil asymmetry.

The thin, light and flexible format of the RT sensors allows them to fit into applications in which traditional current transformers are typically too heavy and bulky, especially when measuring high currents. Their split-core construction allows them to be easily wrapped around the conductor without dismantling cables or shutting down operation. The benchmark accuracy of RT series sensors provides enhanced performance in current and power monitors as well as energy meters.

www.instrumentation.co.za

Corrosion-Resistant Couplings Suitable For Multiple Applications

A full line of shaft collars and couplings for pump drive and structural systems in water treatment, pollution control, and similar facilities is available from Stafford Manufacturing Corp. of Wilmington, Massachusetts.

Stafford Corrosion-Resistant Collars and Couplings are offered in 303 and 316 stainless steel, brass, bronze, and other materials for various power transmission and structural system requirements. Featuring a wide range of sizes and styles, they are suitable for use in pump drive systems, mixing equipment, flow control instruments, and other applications exposed to water, harsh chemicals, solvents, and detergents.

Developed for water treatment, pollution control, pulp and paper, chemical plants and related facilities, Stafford Corrosion-Resistant Collars come in 1-pc, 2-pc and set-screw styles in sizes up to 16″ I.D. and the couplings in 1-pc, 2-pc, and 3-pc styles up to 6″ I.D. All can be modified with special bores, keyways, mounting holes, flats, hinges, threads, and more.

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