Linear Units - Thomson - #10

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10 www.danahermotion.com Technical Introduction Single Carriage Single carriage units have one carriage. Some linear unit models also have the option of long or short single carriage. The long carriage handle higher loads but will have a longer overall length for a given stroke. Cover Band Cover bands are used on some units to protect then from the ingress of foreign objects through the opening in the profile where the carriage runs. They are made of plastic (A) or stainless steel (B). In the case of plastic the cover band seals the profile by snapping into small grooves running along the carriage opening. In the case of stainless steel the cover band seal the profile magnetically using magnet strips mounted on each side of the carriage opening. Some units equipped with cover bands also have a self-adjusting cover band tensioning mechanism. This eleminates any slack in the cover band that can occur from temperaure changes, thus improving the sealing degree and the expected life of the cover band. Double Carriages Double carriage units have two carriages which gives them higher load capabilites than single carriage units. When ordering a double carriage unit the distance between the two carriages needs to be defined. This distance is called LA or Lc depending on the model. Theoretical Stroke and Practical Stroke The theoretical maximum stroke (S max) is the length that the carriage can travel from one end of the unit to the other. However, using the maximum stroke means that the carriage will collide with the ends of the profile. The practical stroke is therefore shorter. We recommend that you specify a unit that have at least 100 mm longer stroke than the maximum stroke you need so that the unit can stop before colliding with the ends and also allow for some adjustment of the unit postition at the mounting. Units with Left/right Moving Carriages Units with left/right moving carriages have two carriages moving in opposite directions when the drive shaft is rotated. This type of unit has a ball screw where half of the screw has a left hand thread and the other half a right hand thread. A B