Comparison between oms Intermediate Gear and Chain Drive for Public Transport Escalator Applications

Transcription

1 Comparison between oms Intermediate Gear and Chain Drive for Public Transport Escalator Applications The current standard escalator traction drive for public transport uses a chain to connect the output from the machine to the escalators main shaft. Depending on the particular design of the escalator and the requirements of transmitted torque, chains with a pitch of 1¼ to 2 in ¼ increments and with widths from Duplex to Quadruplex are usually being used. Chain Drive Over decades the quality of the traction chains have been improved in terms of longevity and low maintenance requirements. Nonetheless, a lengthening of the chain due to the chain pulling forces is inevitable. This first of all requires maintenance to re-tension the chain periodically. And when the lengthening of the chain has increased to > 1%, it will need to be replaced. When continuing to run the escalator with a chain which has lengthened by more than 1%, the pitch of the chain will not match the pitch of neither the chain wheel on the traction machine nor the drive wheel on the escalator main shaft. The result will be that the bolts of the chain will carve themselves into the material of the chain wheel. Subsequently then not only the chain will need to be replaced, but also the damaged chain wheel. Even worse, the constantly hammering of the bolts onto the chain wheel may have adverse effects on the traction machine, affecting bearings or even the toothing of the machine. When this is being unnoticed for a prolonged duration, it may even affect the safety of the machine and thus the operation of the escalator. The function of the chain drive, together with the chain wheel on the traction machines output shaft and the wheel on the escalator main shaft, is to bridge the distance between the two shafts and to further reduce the turning speed of the traction machine to adjust the speed of the escalator to the desired value. Common values for the speed of escalators for public transport range from v = 0,50 ms -1, v = 0,65 ms -1 to v = 0,75 ms -1. Intermediate Gear In place of the chain for transmitting the torque to the escalator main shaft, an Intermediate Gear ( IG ) may be used. Like the chain drive, it bridges the distance between the traction machines output shaft and the escalator main shaft. Also, it provides the required speed reduction by its internal spur gear stages. However, unlike the chain drive, no readjustment of the IG is necessary due to geometric changes, and thus no replacement is necessary either. The lifetime of the IG is t = h at an equivalent load of pequiv = 0,63, which is governed by the bearing lifetime. The gear toothing itself has indefinite lifetime, so when replacing the bearings the IG is up for another lifetime of again t = h in the field ( which is 20h/day, 365 days, 20 years ). TN 20 E - Page 1 of 5 - Rev:

2 Picture 1: Schindler Escalator: traction machine and escalator main shaft 1. Rear fastening 2. Duplex chain 3. Chain tensioning mechanism On the next page in picture 2 an omshypodrive high power EC 2-25 escalator traction machine for public transport, coupled to an IG via a high torque elastic coupling is shown. The connection to the escalator main shaft is accomplished with a space saving involute spline coupling. In contrast to the Chain Drive, the IG is environmental friendly, since no greasing, and thus possible oil leakage from the chain, is being required. In addition, in the completely sealed housing of the IG, the fully synthetic premium quality gear oil has an oil shelf lifetime of more than toil = h. This is due to the high efficiency of the IG of more than 97%, resulting in a very low operating temperature of the IG. Apart from the very low maintenance requirements of the IG and its environmental friendliness, the IG has a very high safety factor which is not changing due to fatigue as is the chain, which is requiring a very high initial safety to warrant acceptable safety over its useful lifetime. The safety against breakage, warranted by design of the IG, is not altered during operation. TN 20 E - Page 2 of 5 - Rev:

3 Picture 2: EC 2-25 with elastic high torque coupling between omshypodrive escalator traction machine and OMS Intermediate Gear Depending on the escalator speed, the OMS Intermediate Gear has an applicable power range of up to PMAX = 24 kw at v = 0,5 ms -1, and up to PMAX = 33 kw at an escalator speed of v = 0,75ms -1. The riding comfort of an escalator using an OMS Intermediate Gear is perfectly smooth, since the polygon effect* introduced when using a chain drive is completely absent. This way no speed modulation of the escalators movement is overlaid on the linear movement of the escalator or travellator, resulting in a perfect riding comfort, satisfying the highest standards. Big Metros all over the world are relying on OMS superior technology in both omshypodrive escalator traction machines and OMS Intermedeate Gears due to its high safety, reliability, availability, low maintenance requirements and high riding comfort. The vast range of reduction ratios and options available with the OMS escalator traction machines and the Intermediate Gears allow for the installation into the majority of the escalator and travellator designs from all the leading manufacturers today. * for a discussion of the Polygon Effect in Chain Drives see OMS Technical Note TN17 TN 20 E - Page 3 of 5 - Rev:

4 OMS Technical Note TN20 Picture 3: OMS DUPLEX arrangement of EC 2-25 with elastic high torque couplings and IGs Special version EC 2-25 for London Underground ( and TfL: Transport for London ) At v = 0,75ms-1 power is up to P = 2x 30kW for high rise escalators Conclusion The OMS escalator traction machine EC 2-25 and OMS Intermediate Gears are the perfect combination for an unsurpassed technical and economical drive solution for public escalators and moving walkways of very high quality and application flexibility. Today these solutions are found in a variety of escalator products from the top world class suppliers in the most modern metros worldwide. If the standard products from OMS will not fit into the escalator manufacturers particular truss design, OMS can and has designed and is producing both the Traction Machines and Intermediate Gears to the technical requirements of its customers as an OEM product. OMS is observing a rising demand for this superior escalator drive technology, with a rising demand in international markets, reaching out more and more to China as well. TN 20 E - Page 4 of 5 - Rev:

5 OMS Technical Note TN20 Picture 4: DUPLEX application of omshypodrive OEM machine and IG in a high rise escalator, OPTION: Weather Proof, turned brake arrangement TN 20 E - Page 5 of 5 - Rev: