Small motors offer extra torque

A simple, compact, low cost electric motor with enough torque to overcome jams

Problem: There are many applications that require a simple, compact, low cost electric motor with has enough torque to overcome jams. Such problems occur, for example, when the mechanism perforating an ingredients sachet in a hot drinks dispensing machine fails to complete its cycle. This is normally due to a slightly out of tolerance moulding at the sachet neck causing a jam in the piercing mechanism. Solution: Crailcrest has launched a range of robust, low cost, high-torque gearmotors which fit into particularly short spaces thanks to a clever gearbox arrangement. The CR04 gearmotors are permanent magnet DC motors running on 6, 12 or 18V. Unlike gearmotors with in-line epicyclic gearheads, the motors have a series of spur gears mounted on two parallel shafts which, in turn, are parallel to the motor axis. The gears are plastic or sintered metal or a combination of plastic and metal for the final reduction stages where torque is highest. Final output speeds range from 15 to 155rpm and torques from 4.5 to 20Ncm. Size, in all cases, is 40.5mm long, 23.3mm wide and 38.5mm high and weight is 100g with plastic gears or 150g with metal. Prices range from £5 for 10,000 off although they can be also supplied in single quantities. Applications: As well as vending machines, the motors may be found in inkjet printers, greenhouse plant feeders and sanitising systems in public toilets. Quiet, plastic geared versions are finding favour with makers of hotel minibars which lock when guests are not in rooms, to prevent thefts and, in some US states, to lock up out of licensing hours. Crailcrest’s sales manager, Fred Woolven, sees considerable future markets in home automation “for the disabled or those who are just lazy”. This can include door and curtain openers and toilet operating systems. £5 each is still too much for the car industry, but Crailcrest is developing a range of motors for automotive customers too, for applications such as powering servo systems when required, as opposed to powering them at all times from the engine. TS