Bevel Gears3 ME350 .Hypoid and Spiroid >These are bevel gears that have the shafts offset,not intersecting. >Hypoids have a relatively small shaft offset. >For larger offsets,the pinion begins to resemble a tapered worm >Set is then called spiroid gearing. 21
ME 350 21 Bevel Gears3 •Hypoid and Spiroid ¾These are bevel gears that have the shafts offset, not intersecting. ¾Hypoids have a relatively small shaft offset. ¾For larger offsets, the pinion begins to resemble a tapered worm ¾Set is then called spiroid gearing
Bevel Gears3 ME350- (d)Hypoid gears (a)Straight bevel gears Outside cone Back cone Front cone Genera:o (b)Spiral bevel gears Pitch cones 22
ME 350 22 Bevel Gears 3
Bevel Gears3 ME350- GLE5-4 Companson ol ntersectng-and oftset-shatt bevel-type goenngs. (By permession.from Gear rand- book.McGraw-H，Ne York. 1962.÷224.」 Hypod gears Flgre 14.1.3 Five vaneties of beve-type gears.Note the change n tooth curvature of the typord 3
ME 350 23 Bevel Gears 3
Worms and Worm Gears3 ME350 .Worm and worm gears connect nonparallel,non- intersecting a axes. .Worm is similar to a screw thread,having one or a few teeth .Helix angle is very large. .Worm mates with a special gear called a worm gear or worm wheel Analogous to a nut being advanced by the thread of the worm. .Their axes are typically at 90 degrees to one another. 24
ME 350 24 Worms and Worm Gears 3 •Worm and worm gears connect nonparallel, nonintersecting axes. •Worm is similar to a screw thread, having one or a few teeth •Helix angle is very large. •Worm mates with a special gear called a worm gear or worm wheel ¾Analogous to a nut being advanced by the thread of the worm. •Their axes are typically at 90 degrees to one another
Worms and Worm Gears3 ME350 .The worm set can give very large gear ratios (up to about 360:1)in a compact package Because of the small number of teeth on the worm. .If the lead angle of the worm is small enough ( about 6 degree)the worm set can be self-locking In other words,it cannot be back-driven from the worm gear,i.e.it will hold a load. 25
ME 350 25 Worms and Worm Gears 3 •The worm set can give very large gear ratios (up to about 360:1) in a compact package ¾Because of the small number of teeth on the worm. •If the lead angle of the worm is small enough (< about 6 degree) the worm set can be self-locking ¾In other words, it cannot be back-driven from the worm gear, i.e. it will hold a load