[ Principle ] Worm gear is one of interlocking gear consisting of a worm shaft and worm wheel. Shape of worm is screw looking and it will match as a pair of gearing with worm wheel that have the same shape of tooth cut by formed tool . Function of gearing is comparable with screw and nut. Principle of worm gear is the same as those principle of nut and screw. Also, as the design point of view, it has a similar relation with super gear and rack at the center of plan level of worm wheel.
[ Construction ] Construction of speed reducer is simple. As per fig. 1, integral worm shaft and worm wheel with output shaft are assembled in the housing at right angle arrangement supported by bearings.
[ Action ] In case of single thread worm, rotate one tooth of wheel by truning one velovution of worm shaft.In case of double thread, rotate two tooth.
[ Features ]
High reduction ratio : Produce 1/60 ratio with single reduction and 1/120 ratio as special application.
Right angle shaft : Because of the nature of right angle construction,user can obtain the direction of power in right angle arrangement.
Arbitrariness of rotation direction : According to the direction of worm screw which is clockwise or anticlockwise (usually, clockwise), the rotation direction of worm wheel is changable.
Wide selection of shaft arrangement : Because of the interlocking nature, there is wide selection of shaft arrangement. Example, output shaft at right, left, double extended inputs and double extended output shafts etc.14 arrangements as shown in fig 2. Further more, there is more than 40 arrangements theoretically if combined the mounting position together.
Low noise, low vibration : Since contact point of worm shaft and worm wheel is line contact, noise and vibration is much lower than these rolloing contact.Therefore, it is suitable for medical appratus,elevator and escalator applications.
Self-Locking features : A worm gear is self-locking or non-reversible when the gear can't drive the worm. This feature called "self-locking". Using the advantage of this characteristic, it is suitable to use for driving the winch and cam as they can get auxiliary mechanical and electrical brake.
Point of selection
[Selection] Follow the procedure shown in makers catalog for proper selection. When select the unit, be sure to consider the load factor, overhung load and specially thermal rating.
[Cautions before full operation] Before operation, conduct the running in trial operation for about 8 hours with each 1/4, 1/2 and 3/4 rating so that the gear surfaces may be smoothly meshed each other and to have full performance.
[Maintenaance and inspection] After finished of trial operation (about 50 hours), drain old oil and replace with new oil. After that, follow makers instruction and refill every one year.
Application and example
Worm gear reducers are widely accepted by general industrial machinery, such as conveyor, winch, machine tool, amusement equipment, stage equipment, parking, automated assembly machine, food process, medical instrument and crane etc.For typical example, application for vertical carrousel which is required quite operation and accuracy with self-locking and double extended (for emergency drive in case power failure).