GB469992A - Improvements in bevel gear wheels and the process of manufacturing the same - Google Patents

Abstract

469,992. Toothed gearing. KLINGELNBERG, G. A., KLINGELNBERG, W. H., and KLINGELNBERG, H. W., (trading as KLINGELNBERG SOHNE, W. F.). Dec. 31, 1935, No. 36088. Convention date, Jan. 12. [Class 80 (i)] [Also in Group XXII] A pair of bevel gears have oblique teeth cut so that when in mesh neither of the apices O<1>, O<11> of the pitch cones of the gears coincide with the point O of intersection of the gear axes. Gears cut in this way have a decreased area over which there is thrust slip between intermeshing tooth surfaces and vibration between the gears is reduced. In the usual spiral or oblique toothed bevel gear the spiral angle Qi varies from the small end to the larger end. Assuming a uniform peripheral force Pu over the length of a tooth, the normal force Pn in the case of a spiral gear increases from the small to the large end as shown in Fig. 1. In the dedendum portion of a driving tooth the sliding velocity is in the nature of a thrust between the engaging tooth surfaces while in the addendum portion the sliding produces a drag between the tooth surfaces, the change from thrust to drag occurring at points on the pitch cone. The thrusting action produces vibration between the engaging gears and according to the invention a higher sliding velocity at a part of the gear where the normal force Pn is least allowed for the addendum D of Fig. 5, the driving tooth and a lower for the dedendum portion E thereby reducing the thrusting action. In the case of bevel gears it is shown that the slip increases with decrease of spiral angle. Thus in Fig 1 there is less sliding between the tooth, profiles at the large end and the vibration effects are therefore low. Hence the profile is not modified at the point of largest spiral angle. In making gears according to the invention, the pinion 1 and gear 2 have pitch cone angles alpha- and #-respectively while the rolling cones from which the generating motions are derived have angles alpha# and ## with a common centre 9, a trace of the rolling plane being shown at A Ca. The tools are moved in an imaginary crown gear plane B Ca having a point Ca common with the rolling plane and located near the large end of a gear of the form shown in Fig. 1. The centre O<11> of the basic crown gear lies on the axis of the driven gear 2. By setting a generator of the surface cone of the work at an angle to the crown gear plane, the profile of the teeth may be modified in the manner shown in Fig. 8. Where the concave face of the gear is the driving face the surface generator is set, Fig. 6, so that it contacts the theoretical gear plane at the large end but is spaced therefrom at the small end.