Tham khảo tài liệu 'gear geometry and applied theory episode 3 part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Prospects of New Developments 613 where Ehg and Ewg are the center distances between the hob and the worm-gear and between the worm and the worm-gear respectively Ar r ph rpw r ph and rpw are the radii of pitch cylinders of the hob and the worm respectively Ay kw kh kw and kh are the lead angles of the worm and the hob respectively. For instance in the case of an involute worm-gear drive the hob and the worm are two involute helicoids. In the case of K worm-gear drives see Section the hob and the worm are generated by a cone with the same profile angle. Figure shows the output of TCA for a K worm-gear drive wherein the wormgear has been generated by an oversized hob Seol Litvin 1996 . The path of contact is oriented across the worm-gear surface and is located around the center of the wormgear surface Fig. a . The function of transmission errors is of a parabolic type Fig. b . For some cases of misalignment an oversized hob that is too small fails to provide a continuous function of transmission errors. In the opinion of the authors of this book localization of the bearing contact by double crowning of the worm is the approach with much greater potential. 20 Double-Enveloping Worm-Gear Drives INTRODUCTION The invention of the double-enveloping worm-gear drive is a breathtaking story with two dramatic characters Friedrich Wilhelm Lorenz and Samuel I. Cone each acting in distant parts of the world - one in Germany and the other in the United States Litvin 1998 . The double-enveloping worm-gear drive was invented by both Cone and Lorenz independently and we have to credit them both for it Litvin 1998 . The invention of Samuel I. Cone in the United States has been applied by a company that bears the name of the inventor known by the name Cone Drive. The invented gear drive is a significant achievement. The special shape of the worm increases the number of teeth that are simultaneously in mesh and improves the conditions of force .
