Gear drive

A self-aligning gear train of enhanced load transmitting capacity comprises a pair of cylindrical gear wheels having intermeshing teeth with concavo-convex side surfaces. The opposed, peripheral surfaces of the intermeshing cylindrical gear wheels are square providing increased surface contact between meshing gear teeth from the base to the edges of the teeth with the convex tooth surface of one gear engaging a concave tooth surface of the other gear to provide self alignment of one cylindrical wheel with the other.

This invention relates to gear drives and, more particularly, relates to a 
gear train having cylindrical gear wheels with intermeshing gear teeth 
having concavo-convex surfaces. 
Conventional cylindrical gear wheels have planar teeth adapted to intermesh 
for transmission of torque by linear contact between the teeth as the 
gears rotate. This type of gearing is not self-aligning and is prone to 
wear. 
The use of herringbone gears increases the contact surfaces between 
intermeshing gears and assists self alignment of the gears. However, the 
teeth surfaces have complex shapes and are not only difficult but also 
costly to manufacture. 
U.S. Pat. No. 4,047,449 discloses a complex and costly gear train having a 
worm wheel with a transversely concave periphery and convex teeth to 
increase linear contact with the side surfaces of the intermeshing globoid 
worm thread. 
I have found that an effective, self-aligning gear train of enhanced load 
transmitting capacity can be provided by the use of a gear assembly 
comprising a pair of cylindrical gear wheels having intermeshing teeth 
with concavo-convex side surfaces. The opposed, peripheral surfaces of the 
inter-meshing cylindrical gear wheels are square providing increased 
surface contact between meshing gear teeth from the base to the edges of 
the teeth with the convex tooth surface of one gear engaging a concave 
tooth surface of the other gear to provide self alignment of one 
cylindrical wheel with the other while further increasing surfacing 
contact. 
The cylindrical gear wheels can be easily manufactured by means of a rotary 
cutting tool to obtain the desired convex and concave arcuate teeth 
surfaces. 
In its broad aspect, the gear train of my invention comprises a first 
cylindrical gear wheel having a plurality of teeth formed equispaced 
therearound, each tooth having a transversely concavo-convex shape with a 
convex side surface and an opposite concave side surface, and a second 
cylindrical gear wheel having a plurality of teeth equispaced thereabout 
with the same circumferential spacing as the spacing of the teeth formed 
on the first cylindrical gear wheel, the teeth of said second gear wheel 
having a concavo-convex shape with a convex side surface and an opposite 
concave side surface, and means for rotatably mounting said cylindrical 
gear wheels for meshing of the gear teeth with each other. 
More particularly, the teeth of the gear drive cylindrical wheels have 
opposite convex and concave side surfaces with the same radius of 
curvature, the ends of the teeth being square in transverse cross-section.

The gear train of my invention illustrated in FIG. 1 normally comprises a 
small diameter cylindrical gear wheel 10, i.e. a pinion gear, mounted on a 
shaft or axle 11 for rotation. Gear 10 has a plurality of teeth 12 formed 
equispaced about the periphery thereof, teeth 12 gradually diminishing in 
thickness, as shown in FIGS. 2 and 3, from base 14 to free end 16 in a 
conventional manner. With reference to FIG. 4, each of teeth 12 has a 
transversely concavo-convex shape with a convex surface 18 on one side and 
a corresponding concave surface 20 on the other side, each of surfaces 18, 
20 having a radius r. The chord 22 passing through each tooth is 
perpendicular to a longitudinal plane 24 passing through the gear. 
Large gear wheel 26, normally a driven gear wheel, mounted for rotation on 
a shaft or axle 27, has mating teeth 30 which correspond in shape and size 
both radially and transversely with the teeth 12 of cylindrical gear wheel 
10, said teeth having an equal radius for the convex and concave surfaces. 
The teeth of gear wheel 26 having transversely convex and concave surfaces 
32, 34 respectively engage with and disengage with the mating teeth of 
cylindrical gear wheel 10 as they enter at the gear train 36 and leave at 
38. I have found, for example, that the combination of a pinion gear 10 
having a diameter of 15 inches with a normally driven gear 26 having a 
diameter of 60 inches, each gear having concavo-convex teeth with a 
transverse radius r of 16 inches, provides effective transmission of 
torque with excellent self alignment of the gear wheels. The extended 
transverse length and the radial length of the concavo-convex intermeshing 
teeth terminating in a square transverse periphery or end surface 40 
having a uniform width across the length thereof increase the 
load-carrying capacity of the gear train while maintaining the gear wheels 
in alignment. 
The gears can be of different size, as illustrated, or of substantially 
equal diameter. 
The present invention provides a number of important advantages. The gear 
wheels comprising the gear train can be easily manufactured at low cost. 
The gear wheels are self-aligning at assembly, provide enhanced load 
transmission with reduced wear due to the increased surface contact 
between meshing teeth, and are quiet in operation. 
It will be understood, of course, that modifications can be made in the 
embodiment of the invention described and illustrated herein without 
departing from the scope and purview of the invention as defined in the 
appended claims.