Planetary gear transmission systems or components – Planetary gearing or element – Planet pinion is worm gear
Patent
1991-05-20
1992-12-15
Wright, Dirk
Planetary gear transmission systems or components
Planetary gearing or element
Planet pinion is worm gear
F16H 130
Patent
active
051711931
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a mechanical reduction gear.
Mechanisms are known which, when inserted between a driving shaft and a driven shaft, reduce the speed of the second with respect to that of the first at a fixed ratio (reduction ratio).
Reduction gears already known generally consist of gears wheels with different diameters. In reduction gears, usually the high speed elements, that is the first drive elements are subjected to low stress, while the low-speed elements, that is the last drive elements, are subjected to high stress. In known reduction gears, in order to avoid the said high stress being borne by one gear only, the number of gears is increased, with a consequent increase in the dimension of the reduction gear. All the return forces are released on the first transmission element only, for example a worm screw.
U.S. Pat. No. 4,697,476 discloses a reduction worm gear comprising an input worm shaft meshing with two diametrically opposite planetary worm gears which have a central gear meshing with the input worm and two lateral globoid worms engaging with a split ring, internal, double enveloping gear.
A reduction gear as described could not be assembled in practice and does not allow therefore a useful teaching in the field.
The aim of the invention is to produce a reduction gear, with a sturdy structure which will allow high reduction ratios.
The above aim has been achieved by providing a reduction gear as claimed in claim 1. The reduction gear comprises a driving means, preferably a worm screw driving shaft engaging with at least a first portion, shaped so as to provide a gear wheel mating to the driving means, at least one worm screw shaped second portion, connected to said at least first portion, engaging with a rack integral with a gear wheel, which acts as a power take-off.
The first portion and the second portion can be connected by means of a clutch plate.
Preferably the gear wheel shaped first portion mating with the driving means, suitable for engaging with the driving means, and the worm screw shaped second portion, suitable for engaging with the rack, are provided on the body of a spool or pinion. A spool may also be provided with a gear wheel shaped central portion and two worm screw shaped side portions.
The worm screw shaped side portions of the spool are tapered at the ends, having a spindle-shaped form, whose larger base is adiacent to the central portion.
Preferably the rack is provided on the inner surface of an element, which surrounds the unit consisting of the driving means and at least one spool.
The element which surrounds the unit consisting of the driving means and at least one spool can be a cup-shaped element, with a rack-shaped cylindrical inner surface, while its closed base supports a small gear wheel acting as a power take-off.
In a different embodiment, the element surrounding the unit consisting of the driving means and said at least one spool is a ring, having an inner rack and an external gear wheel shape which acts as a peripheral power take-off.
A preferred embodiment of the reduction gear according to the invention foresees two spools, diametrically opposed with respect to the worm screw driving means, whose central portions engage with the driving means, while the two side portions of each spool engage with the rack.
In the embodiment with two spools, the reduction gear according to the invention allows high reduction ratios without excessive loading of the mechanical drive parts. The problem of extension of action and reaction forces from fast motion to slow motion is, in fact, solved by increasing the mechanical parts in the passage from fast to slow motion, without any considerable increase in the dimension of the structure. The passage is from a driving means, for example a worm screw shaft, to two joined toothed portions, and the transmission to the rack finally takes place through four worm screw shaped portions.
The particular structure of the reduction gear according to the invention has the additional advantage of not allowing inversed str
REFERENCES:
patent: Re17704 (1930-06-01), Sifton
patent: 1594987 (1926-08-01), Adams
patent: 2208614 (1940-07-01), Watson
patent: 2505434 (1950-04-01), Schmidt
patent: 3552225 (1971-01-01), Van Voorhis
patent: 4697476 (1987-10-01), Maxwell
A.T. Avanzata Tecnologia S.r.l.
Wright Dirk
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