CMDCompact Multiple DiscFriction Torque Limiters

The CMD Advantage...

Mid-Spindle Mounting

CMD’s that are mounted within the spindles are long and slender. They are staggered in order to maximize the radial envelop. See sketch.

High Torque Radially Limited Applications Custom DesignPT Tech’s Compact Multiple Disc Friction

PT Tech’s CMD Series are friction-type compact multiple disc torque limiters for levelers and flatteners on steel processing lines and other high torque, limited radial space applications. They perform best on the slow speed side of a gearbox. The torque setting is set at the factory and does not require adjusting throughout its wear life. Wear life indicators are available on most designs.

CMD units protect drive components from damaging torque overloads. Also, when a significant tension differential exists between the early and exit rolls, the CMD’s will slip just enough to evenly distribute the load. Typically, CMD units are custom designed. There are two different design configurations, output shaft mounted and mid-spindle mounted. Examples of each configuration are shown. Maximum torque is affected by the available shaft engagement length (Dimension E), distance between the centerlines of the output shafts, and the strength of the available springs.

Shaft MountedThis design mounts on all of the distribution gearbox’s output shafts. The endplate can be machined to accept an industrial universal joint or gear coupling spindles. In some cases, the in-ner hub is removed to accomodate a large shaft diameter and high torque setting. In this design, the friction plates are in direct contact with the shaft’s key.

How CMD WorksA complement of springs (#1) exert a force on the disc pack. The disc pack includes friction plates (#2) and separa-tors (#3).

When the drive system torque exceeds the setting, the friction plates will slip relateive to the separators, while con-tinuing to transmit torque equal to the setting. The separator plates are splined to the housing (#4). Frictionplates are laster-cut to accept the shaft-key (#5).

A leveler’s distribution gearbox has one input shaft and up to 19 output shafts The output shafts are geared together to distribute the motor’s horsepower. In a leveler, the strip is worked back and forth as it passes over the rolls. The rolls are configured to work the strip more on the entry side than the exit side. This puts an uneven torque demand on the gearbox output shafts and creates atension differential is too uneven, several problems can arise.

First:

The uneven loading on the rolls can result in one or more rolls slipping on the strip. This leaves a blemished surface that affects the quality of the finished product.

Second:

CMD series torque limiters slip just enough to absorb damaging torque loads. Typically, the slip speed or difference between the input and output speeds of the CMD is quite small. Also, the CMD will slip instead of the rolls slipping on the strip.

The torque demand can exceed component design limits. This contributes to premature failure of gearboxes and spindles. In some cases when a spindle fails, its whipping motion will break other spindles will break other spindles before the leveler can be brought to a stop.

Typically, the yoke shaft is square (Dimension D) and slides into the torque limiter. It is secured to the torque limiter with a keeperplate. The stub adapter bolts onto the other end of the torque limiter. The stub slides within the slip yoke allowing for axial length compensation during roll positioning.

Torque Limiter Slip Yoke

Yoke Shaft Stub Adapter

Mid-Spindle Mounted: Output Shaft Mounted:

PT Tech, Inc. 1441 Wolf Creek Trail, PO Box 305 Sharon Center, OH 44274Phone: (330) 239-4933Website: www.pttech.com Powering Innovation

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57 83 105 121 140 165 180 210_____________________________________________________________________________________________________

A1 inches 2.25 3.25 4.13 4.75 5.50 6.50 7.12 8.25mm 57.2 82.6 104.9 120.7 139.7 165.1 180.8 209.6_____________________________________________________________________________________________________

B inches 5.63 8.06 7.56 6.77 10.56 9.50 6.25 12.44mm 143.0 204.7 192.0 172.0 268.2 241.3 158.8 316.0_____________________________________________________________________________________________________

C inches 1.0 1.1 1.8 2.0 2.3 4.0 3.0 4.3mm 25 28 46 51 58 102 76 109_____________________________________________________________________________________________________

D inches 1.500 1.710 3.000 2.500 3.500 4.000 3.000 4.500mm 38.10 43.43 76.20 63.50 88.90 102.00 76.00 114.30_____________________________________________________________________________________________________

E inches 4.75 5.88 6.61 5.50 8.38 8.50 5.30 11.46mm 120.7 149.4 167.9 139.7 212.9 215.9 134.6 291.1_____________________________________________________________________________________________________

Max T. lb-ft 183 495 1667 1492 4583 8000 2667 12833Nm 248 671 2259 2022 6210 10840 3614 17389_____________________________________________________________________________________________________

ImperialOutput Shaft MountedMid-Spindle Mounted