Note: Descriptions are shown in the official language in which they were submitted.
CA 02747448 2011-07-22
GEAR RIM WITH ELASTIC CASSETTES
FIELD OF THE INVENTION
The invention relates to machine building and may be used in large-size
mechanism
drives such as the sweep drives of excavators, gantry cranes, and the rotary
drives
of mills, crushers, rotating furnaces, etc.
BACKGROUND ART
The gear rim of an excavator rotating platform mechanism is known to be
described
in USSR Author's Certificate No. 1164372, with its design including several
interchangeable sections mounted upon the support base to facilitate the
replacement thereof. The top surface of the support base have brackets welded
thereto, the number of the brackets being equal to the number of sections with
each
section being secured to the bracket in two places. The known design provides
for a
segment by segment changeability and allows to replace the whole gear rim or a
defective segment without removing the support base from under the excavator.
At
the same time each section of the known design is a whole non-demountable unit
made of a whole workpiece. The material for such a workpiece is to be chosen
depending on the requirements of teeth strength and hardness. With due regard
for
the fact that alloy steel and complicated shape pattern equipment is used to
manufacture the sections and the sections themselves are disposable spare
parts to
be frequently replaced in the process of operation, the value of the whole
design
grows up significantly, especially on the condition that the section teeth, in
other
words the working part of the gear rim, are most vulnerable to wear and tear.
The problem to be solved by the proposed design is further improvement of the
existing gear rim designs thus allowing to raise efficiency of the materials
used,
reduce the costs incurred in repairs, and meet the requirements to the general
layout
of the design. The technical results that can be achieved when solving this
problem
are a significant increase in the service life, a lower weight, higher quality
of the
finished product, an opportunity to manufacture gear rims with an over 2000 mm
diameter, and elimination of the need to replace large-size parts during
repairs.
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It will be clearly understood that, if a prior art publication is referred to
herein, this
reference does not constitute an admission that the publication forms part of
the
common general knowledge in the art in Australia or in any other country.
Throughout this specification, the term "comprising" and its grammatical
equivalents
shall be taken to have an inclusive meaning unless the context of use
indicates
otherwise.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a gear rim assembly which
may
overcome at least some of the abovementioned disadvantages, or provide a
useful or
commercial choice.
To achieve the above results a gear rim assembly is proposed comprising a
centre,
said centre being either a whole unit or comprising several sectors with their
number
being preferably even in number, each sector being made in the form of a
welded
rolled metal box-like body, and at least two elastic toothed cassettes, each
comprising an elastic rolled or forged metal plate with cut teeth and a
fixture system
upon the centre.
In one aspect, the invention resides broadly in a gear rim assembly consisting
of a
centre which is a whole piece or comprises at least two sectors, each being
made in
the form of a rolled metal welded box-like body with at least two elastic
tooth
cassettes placed thereon, each cassette comprising an elastic plate of sheet
metal
with cut teeth and a fixture system located upon the centre.
Preferably but not necessarily the claimed design may comprise an elastic
cassette
fixture system upon the centre provided the elastic cassettes are tightly
adjacent to
the mating surface; the gear rim may additionally comprise an elastic cassette
positioning system in the form of location pins secured to the centre surface
contacting the cassettes and grooves in the relevant surface on the cassette
plates;
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the thickness of the metal beneath the tooth in the cassette plate may not
exceed 1.5
times the tooth height which makes the cassette elastic enough to assure good
mating with the contact surface.
DESCRIPTION OF THE DRAWINGS
The invention is illustrated with the general view (Fig. 1) and the gear rim
section (Fig.
2).
It will be appreciated that the drawings have been provided for the purposes
of
illustrating preferred embodiments of the present invention and that the
invention
should not be considered to be limited solely to the features as shown in the
drawings.
In general the claimed gear rim consists of centre 1 with several elastic
cassettes 2
mechanically secured to each sector of the gear rim. The centre is the main
power
element of the claimed design and assures the geometrical parameters of the
gear
rim during operation. The sector material is rolled sheet metal with sheets
being
electrically welded into box-like body 3. The advantages of this centre design
are a
lower weight and metal consumption with the operation properties intrinsic of
traditional cast metal gear rims that are much heavier, being retained.
Apertures 4
and 5 are provided in the centre and designed for fixing the gear rim to the
mechanism and for fixing the tooth elastic cassettes to the centre. The latter
consist
of elastic plates 6 with cut straight and slant teeth on the one side and
several
rectangular section grooves on the side opposite to the teeth, with the groove
surfaces mating the location pins on the centre surface. The elastic plates of
the
tooth cassettes are made of rolled or forged alloy steel and have rectangular
sections.
The use of rolled or forged metal allows to reduce the thickness of the metal
layer
beneath the tooth to the value not exceeding 1.5 of the tooth height, thus
contributing
to a significantly lower weight and production costs, at the same time making
the
cassette more elastic to assure its tight contact with the mating surface.
Using
rectangular section workpieces for the manufacture of cassettes allows to
assure the
detection of concealed defects by non-destructive control methods, which is
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impossible when using complicated shape workpieces, thus raising the quality
of the
cassettes per se and of the whole structure.
The gear rim is assembled by initially placing the elastic cassettes at the
relevant
places of installation upon the centre. Nuts 7 of the fixture system placed on
the
threaded parts of the elastic cassette fastening bolts apply the tightening
force to the
cassettes assuring their tight contact with the sector surface. To assure
positioning
and location of the cassettes in relation to each other within the limits of
the tooth
spacing, the gear rim design additionally provides for pins 8 secured to the
centre
surface contacting the cassettes and entering the cassette grooves.
Summing up the above, amongst the advantages arising from the use of rolled
metal
for the components of the claimed structure, a possibility of volume heat
treatment of
the cassette plates should be mentioned to attain the required hardness value.
This
will materially raise the quality of the structure and increase its service
life, at the
same time reducing its weight. Economic advantages of the claimed structure
are
also obvious as the price of the structure is reduced at the expense of a much
lower
weight of the components made of alloy steel as well as the cost of repairs as
it is
cassettes only that will have to be removed and not the whole gear rim
structure
which is much heavier and more expensive than the cassettes.
Those skilled in the art will appreciate that the present invention may be
susceptible
to variations and modifications other than those specifically described. It
will be
understood that the present invention encompasses all such variations and
modifications that fall within its spirit and scope.
