Product-catalog_2012

Introduction GFC Product Catalog 2012 / 9 the operating efficiency rating ≤ 0.5. This takes effect in worm gearboxes (according to the prevailing surface quality and tooth- bearing size at centre-increase angles ranging from = 2.5° to 4°. Self-locking worm gearboxes are inefficient due to their poor over- all efficiency rating and the correspondingly high loss of output (particularly considering the extensive installation space and long power-on times). In those actuator situations in which the self-lock- ing effect is required, one should always verify whether the instal- lation of a return block or a brake is the more practical solution. A self-locking gearbox cannot replace an actual brake. Self-locking capacity for the GFC worm gearbox, depending on the transmission ratio: >> transmission ratio i = 5 to 25 no self-locking effect >> transmission ratio i = 31.5 to 50 static self-locking effect, possible return under vibration >> transmission ratio i = 63 to 100 static self-locking effect, return only possible with limitations when vibration occurs If self-locking is required, please contact GFC. Start efficiency rating A The start efficiency rating A for a cylindrical worm gearbox is (due to the large tooth-friction coefficient Z for low running speeds) is always less than the efficiency rating at operating output speed under nominal load and continuous operation. For starting a worm gearbox under load (due to the lower start efficiency rating) a greater actuator torque T1A is necessary. T1A is calculated as fol- lows: T1A = in Nm The start efficiency rating is (just as the operating efficiency rat- ing) dependent on the width of the centre-increase angle for the worm shaft. Here, too, the principle applies that a wider centre- increase angle positively influences starting. The start efficiency ratings indicated in the following are guideline values (just as the operating efficiency ratings in the output tables). They apply to the run-in gearbox lubricated with synthetic oil. For a new gearbox, the following start efficiency ratings apply. S 40.1 – S 80.1/SS 50.1 – SS 80.1 i (worm) Factor A 4 ... 14 0.66 14.5 ... 27 0.52 28 ... 54 0.38 62 ... 107 0.28 S 100.1 – S 160.1/SS 100 – SS 250 i (worm) Factor A 4 ... 14 0.68 14.5 ... 27 0.56 28 ... 54 0.4 62 ... 107 0.28 SST 97 – SST 150 i (worm) Factor A 4 ... 11 0.66 13.5 ... 19.5 0.52 ab 27 0.38 Further sizes on request. >> The values indicated in the selection tables (output and torque) apply to warm-running, well-run-in and properly lubricated gear- boxes, with nominal load and tractioning worm shaft – under the following conditions: >> Continuous operation (S1) with consistent loads and 8 hours of daily operation >> Ambient temperature: 20°Celsius >> Lubricant temperature: 100°Celsius >> During the start, the 2-fold actuator torque is transmitted; in the process, five starts per hour are permissible. Operating conditions which deviate from this limit value must be taken into account with certain factors upon selection. The indicated factors are guideline values. A selection of worm gearboxes should preferably be made according to the actuator torque for the working machine. Here, one must differentiate between mechanical and thermal wear: The torque Ta is calculated from the equation Ta = (9550 x Pa )/na Ta = required torque on the working machine (Nm) Pa = required output on the working machine (kW) Guidelines for gearbox selection na = actuator output speed (1/min) of the working machine mat- ches the output, output speed of the gearbox motor Selection according to the mechanical wear Tmech. req. = fB x fH x fS x Ta Tmech. req. = req. mechanical output torque (gearbox) Ta = torque of the working machine (Nm) fB = operation factor (Table 1) fH = factor for start frequency (Table 2) fS = factor for type of lubricant (Table 6) Selection according to the thermal wear Tth.req. = fE x fT x fL x fS x Ta Tth. req. = req. thermal output torque (gearbox) fE = factor for power-on time (Table 3) fT = factor for ambient temperature (Table 4) fL = factor for operation position (Table 5) fS = factor for the type of lubricant (Table 6) >> >> >> T2 i x A