Note: Descriptions are shown in the official language in which they were submitted.
CA 02127131 2003-11-14
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Arrangement for the rotary actuation of a machine and plant
part with worm gear
The invention relates to an arrangement for the rotary
actuation of a machine or plant part, for example of a
crane, on a chassis or foundation, using a worm gear, the
housing of which is secured on the chassis or foundation.
On known drives for mobile cranes, the pivoting movements
are brought about, for example, by means of two hydraulic
cylinders, which are formed as gear racks and are disposed
to the left and right of a king trunnion mounting. The
rotatory forces are transmitted onto a largely dimensioned
pinion by means of the gear rack. Through this arrangement
of the hydraulic cylinder drives, the gear used maintains
considerable elongation in order to transmit high tilting
moments.
A gear arrangement is known (DE-OS 34 46 438) wherein the
worm wheel is mounted through only one cross roller bearing.
Through the single-shear bearing arrangement a tilting
moment arises through the drive (worm wheel, worm). This
has an adverse effect, because through this, supporting
capability of the single-shear bearing is lost and such high
external forces cannot be transmitted. Furthermore, a
higher tilting of the worm wheel arises through the single-
shear bearing arrangement, which has a very adverse effect
on the engagement relationships of the worm gearing. The
single-shear bearing connects through a screw connection of
the outer ring with the housing and of the inner ring with
the worm wheel. This is associated with extra expenditure
of production and assembly.
Furthermore, arrangements with worm gears of approximately
the initially named kind are known (US-A-4 616 528,
CA 02127131 2003-11-14
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US-A-3 710 640, EP-A-O 031 873, DE-A-33 21 854), on which
the worm wheel in the gear housing is incorporated twice or
two-shear. Two-shear bearing arrangement means that two
separate bearings for the worm wheel, for example rolling
bearings, are disposed coaxially to one another. In_the
arrangements from the named sources, the worm gears are used
without exception as a gear stage for valve applications,
multiple drives particularly with d.c. motors or spindle
lifting gears and spindle sliding gears. Common to these
embodiments is that no particular arrangements are made
against the influences of extraordinary tilting moments onto
the shaft or axis of the worm wheel. The housings, as far
as can be seen, are without exception one-pieced and on the
basis of their structure, cannot contribute to guaranteeing
or to at all increasing the solidity and stability of the
axis or shaft of the worm wheel, which is used for example
for output.
The object of the invention is to create a worm gear
arrangement for rotary actuation, which on the one hand has
a compact, space saving construction and on the other hand
has the capability to take up and transmit extraordinarily
high external forces (axial and radial forces) and moments,
above all tilting moments.
The gear housing then, is divided into an upper and lower
part, one of the two parts being interspersed by the
connection attachment of the worm wheel to the machine or
plant- part to be rotated. In that the outer rings of the
two rolling bearings are each secured at an upper and lower
part of the housing and the corresponding inner rings are
secured at the worm wheel, and following that, the upper
part and lower part axe tightly screwed together to form the
entire housing, a compact, space saving and solid unit
results, in which the gear and bearing arrangement are
constructionally integrated into one another. In
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particular, the rolling bearings are braced and additionally
stabilized by this. In this way the part to be rotated with
extraordinary weight can be assembled on the worm wheel,
whereby not only high axial and radial forces, but also high
tilting moments can be taken up in an operationally safe
way.
The gear arrangement according to the invention is suitable
above all for directly driving machines and plant parts. It
can replace the known rotatory connections and pinion with
intermediate gearing, with less constructional expenditure
and increased reliability. In that the two-shear bearing
arrangement of the worm wheel cooperates, according to the
invention, with the housing parts which are screwed
together, a worm wheel with simple construction and large
coat saving can be taken up in the gearing housing, which is
also robust relative to tilting moments.
Due to the closed housing, the drive arrangement according
to the invention is largely screened against parasitic
induction from the surroundings, which increases the ease of
maintenance. No such high demands of constructional
exactness need be placed on the connection construction with
the connecting attachment, since the drive arrangement
according to the invention has a high intrinsic rigidity to
start with. Thia results, among other things, from the
measure according to the invention that, on the one hand the
worm wheel and on the other hand the upper and lower part
(base or cover part) of the gear housing are each used as
carrier elements for the hardened raceway shells (inner and
outer rings) of the two-shear bearing arrangement.
Furthermore, the two housing parts are rigidly connected
with one another or fixed to each other. The bearings of
the worm wheel can be four-point bearings (ball), as well as
roller bearings. The bearing forces are transmitted by
means of further securing screws at outer flanges of the
housing or the like, into the surrounding construction. Due
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to the measures according to the invention, the housing and
the worm wheel are in the position to take up the high
external forces stemming from the heavy machine and plant
parts, said high external forces being transmitted by means
of the bearings. The upper part or cover part of the
housing can for example take over the function of taking up
the external tensile forces. Furthermore, the housing can
hold the bearing free of backlash or hold the initial
tension.
According to a particular embodiment, the housing parts lie
together via sealing means in order to be sealed against the
environment.
The basic principle according to the invention of spatially
extending, as it were, the bearings of the highly loaded
worm wheel in the applications contemplated, corresponds to
a further development of the invention according to which
the worm wheel is mounted rotationally by means of two
separate inclined rolling bearings, on which the rolling
elements are each encompassed, by the inlays or by the inner
and outer ring, with a peripheral section between 60° and
120°, preferably approximately 90°. This excludes the way
known per se (see above) of arranging the worm wheel with a
single cross rolling bearing. Radial, axial loads and
tilting moments can be advantageously taken up by means of
the two angular ball bearings.
To achieve a constructively simple coupling of the part to
be rotated to the gear arrangement it is suggested,
according to another further development of the invention,
that at least one end face or other non-geared side wall of
the worm wheel is specifically formed to connect with the
part to be rotated, be it through a ring of bores to be
screwed, or through hook-shaped locking elements for. example
or latching devices. A one-piece connection between worm
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wheel anal the part to be rotated is also conceivable within
the framework of the invention.
The manufacturing costs are lowered when, according to
another further development of the invention, the inlays or
inner and outer ring of the rolling bearings are radially
slotted throughout. The possibility is then created of not
only manufacturing the inlays economically from a single
run, but of also being able to spread the inlays out quickly
during the incorporation or the assembly.
By using rolling bearings, the outer ring is expediently
fixed at the inner wall of the gear housing and the inner
ring at the worm wheel to be rotated. The rolling bearings
are connected by the gear cover to form one unit.
So that as high a torque as possible can be transmitted, two
or more worms according to another development of the
invention are disposed which act upon the (common) worm
wheel.
With extreme loading it can also be expedient within the
framework of the invention to embody rolling bearings with
several rolling ring elements which roll off tracks and
which are angled to each other. Here for example, a rolling
ring element can be provided exclusively for transmitting
radial forces and each further rolling ring element for
transmitting axial forces in both directions of moments.
The first rolling element set would roll off cylindrical
running tracks whereas the two other rolling ring elements
roll off on flat surfaces perpendicular thereto. Such
bearing modules are known per se as double axial radial
bearings.
In known worm drives, particularly when they are not used
purely as transmitting drives but in the sense of the type
according to the invention for directly driving machines and
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plant parts, (DE-OS 34 46 438), the following problem can
easily arise: The rotating worm wheel must sometime be
braked in the shortest possible time. since, as a rule, a
lot of mass moves with the rotating worm wheel in the named
applications, kinetic energy is to be converted to a large
extend. As a result of this, it can happen when braking
quickly, that the worm wheel gearing or the worm thread
engaging it, breaks.
Consequently, the further problem within the framework of
the invention is raised, of intercepting dynamic forces
arising during the running and in particular the braking of
the worm wheels which are coupled with a machine part and to
compensate such that a destruction of the gear engagement
between worm and worm wheel is prevented. To achieve this,
in a worm gear arrangement with the initially named features
according to the invention, it is suggested that the worm is
not only rotationally mounted, but is also mounted
displaceably in its longitudinal direction against spring
force (linear). In other words, one or several spring
elements are disposed within the gear housing such that they
stand in the way of the linear displacement of the worm with
their spring force. This can be expediently achieved in
that the spring element or elements on the one hand are
supported or engaged against the housing wall and on the
other hand at the worm. With this embodiment according to
the invention, mass forces of the rotating parts can be
compensated without the gearing being damaged due to
overloading. A shock-type braking is avoided.
Spring devices are advantageously combined in the set after
one or both ends of the worm thread, for example one or
several screws or adjacent Belleville spring washers, which
each engage between a thread end side and the worm shaft end
while supported against the housing wall.
7
With the spring compliance according to the invention, the
worm is allowed a certain stroke within the housing or
framework by means of which braking forces and deceleration
loading can be balanced out or compensated.
The worm in each case is advantageously mounted on both
sides at its ends with a radial and axial bearing, because
through this the external mass forces or impacts can be
softened and pretensioned Belleville spring washers can be
disposed between the axial bearings and the worm.
With the aim of strengthening the robustness against tilting
moments, an expedient embodiment exists in that the cover
and base part of the housing are placed on top of each other
in the direction of the worm wheel axis or parallel thereto.
The adjacent support surfaces of the two housing parts
increase the solidness and then prevent the tilting together
of said housing parts, a stable support being also
guaranteed for the outer rings of the two-shear worm wheel
bearing arrangement. Advantageously the common support
surfaces of the housing parts are dimensioned such that they
can be interspersed by fixing means, particularly screw
means. The tilting is further reacted,against when the
fixing or screw means extend parallel to the worm wheel
axis, the common support surfaces of the housing parts being
pressed together with maximum force. By this means the
stability of the bearing arrangement is optimized.
Within the framework of the invention the connecting
attachment of the worm wheel intersperses the cover or base
part or one of the two housing parts axially or parallel to
the axis. By this means the connection extension can
particularly easily be used for receiving and for carrying
the machine or plant part to be rotated.
The worm gear actuation drive arrangement according to the
invention can be used particularly in mobile, construction,
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harbour and industrial cranes, excavators, lifting
platforms, deep shovel dredgers, concrete mixers, fork
lifting ancillary equipment, revolving welding tables and
concrete pumps, for forming the necessary rotatory
connection in each case. Further areas of application for
the drive arrangement according to the invention are
swinging devices for grabs, track pinch bars, working load
turning machines, ancillary manipulators, swinging stacker
equipment, car park systems, swinging lifting platforms,
motor vehicle winches and wall winches, body bolsters for
heavy road vehicles, steering drive units for heavy goods
vehicles, machines for packing and filling, labelling,
sorting, mixing and stirring works, thickening plants and
research plants for discharge water and mud treatment,
construction machines, drag bearings, dredger-loaders,
universal dredgers, robots, feeding machines, rotary
indexing tables and reversible clamping devices.
Further details, features and advantages on the basis of the
invention result from the sub claims as well as the
following description of a preferred embodiment of the
invention with reference to the drawings, in which:
Fig: 1 is a perspective illustration of a drive arrangement
with worm gear,
Fig: 2 is a plan view according to the direction II in
Figure 1,
Fig: 3 is a section according to the line III - III in
Figure 2
Fig: 4 is an enlarged illustration of the details IV in
Figure 3 and
Fig: 5 is the ball bearing used in the arrangement
according to Figures 1 - 4 in axial plan view.
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According to Figure 1 the worm gear 1 for the actuation
arrangement used according to the invention, comprises a
gear housing 2, (Fig. 3) with a base part 2a, in which a
worm 3 and a worm wheel 4 are mounted rotationally. The
base part 2a has a support surface 20, interspersed by a row
of inner thread bores 21 axially parallel to the worm wheel
4. At the straight front side of the base part 2a largely
bent in the example, a projecting securing flange 22 is
formed, over the securing holes 23 of which a fixing to a
foundation or chassis (not shown) can be effected. The worm
3 which engages with the gearing 6 of the worm wheel 4 by
means of its screw-shaped thread 5, is provided for coupling
with a torque drive motor (not shown).
The worm wheel 4 has at its end side an axially parallel or
cylindrically projecting connection attachment 7, in the end
wall 8 of which a multitude of securing elements, e.g. screw
bores 9 are formed in rows in the direction of the periphery
or in rings. These are used to secure a machine or plant
part to be rotated (not shown). Lying on the end side of
the worm wheel-gearing 6, is the smaller inner ring 10 of an
angular ball bearing (Figure 4) visible in Figure 1. By
inserting a multitude of balls 11 (Figures 3 and 4) into
this inner ring 10 and setting on of a (larger) outer ring
12, the complete angular ball bearing l0, 11, 12, is formed.
As can be seen from Figure 1 and above all from Figure 2, a
atop shoulder 13 in each case at a distance from the two end
faces of the worm thread 5 is raised and projects in an
annular fashion around the worm shaft. Between each of
these stop shoulders 13 and the worm end sections 14 mounted
rotationally in the wall of the housing 6, one or several
sets 15 of a multitude of individual Belleville spring
washers 16 are disposed particularly such that they clamp.
The Belleville spring washers 16 or the corresponding sets
15 are slipped onto the worm 3 on both sides of the worm
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thread 5 via their inner recesses until they abut the
corresponding stop shoulder 13.
The Belleville spring washers 16 are annular platelets
which, according to the partial cross-section illustration
in Figure 2, increasing from their planes, deviate in their
two dimensional annular areas by an inclined angle. Within
a spring set 15 at least two such Belleville spring washers
16 are laid mirror-imaged to one another such that only
their outer edges, which project the most from the said
annular plane area, make contact. This deviation is
elastically reversibly reduced during axial force, for
example, due to transient deceleration or acceleration of
the worm wheel 4. The possibility of linear stroke
movements 17 for the worm 3 in the gear housing 2 results
from this. By means of these stroke movements 17 of the
worm 3, dynamic forces arising with abrupt acceleration or
deceleration of the worm wheel 2, for example when braking
or running, can be taken up on both sides by the spring sets
15, so that an abrupt braking of load is possible without
destroying the gearing 6 and/or the thread 5.
According to Figure 3 an (upper) cover part 2b is to be set
flatly onto the support surface 20 (Fig. 1) of the lower
base part 2a to form the entire housing 2. Connection
screws 24 which are screwed into the inner thread bores 21
of the base part 2a and engage the cover part 2b by means of
flush through bores, are used to rigidly fix together part
2a and part 2b. The worm wheel 4 is mounted such that it is
rotatable opposite the gear housing 2 through two ball
bearing sets 10, 11, 12, which each lie on one of the two
and sides 6a, 6b of the worm wheel gearing 6. With this,
the smaller inner ring 10 is always fixed at the
corresponding end side 6a or 6b of the worm wheel gearing 6
and the larger outer ring 11 at the inner wall of the
housing 2. Therefore, in that the bearing arrangement of
the worm wheel 4 is spatially extended by the division of
11
the bearing arrangement, each into a separate ball bearing
set Z0, 11, 12 for the end sides 6a, 6b at the worm wheel
gearing, radial loads Frad, axial loads FaX and tilting
moments M~ can be taken up to an extraordinary extent, the
torque Md of the worm wheel 4 required for the part to be
driven, remaining largely unimpaired around its centre axis
18.
This advantageous effect of the two-shear bearing
arrangement is further conveyed by the use of angular ball
bearings according to Figure 4. The inlays or inner and
outer rings 10, 12, each surround the bearing balls 11 with
only a peripheral section of approximately 90°. If these
are disposed flush according to Figure 3, coaxially or
parallel to the axis, to the centre axis 18, a tilting
moment Mk can be taken up with greater operational certainty
by two cooperating bearings 10, 11, 12 at each one end side
6a, 6b of the worm wheel.
In Figure 5 a complete angular ball bearing set 10, 11, 12
is shown in plan view. Here, radial slits 19 can be seen
which intersperse each of the inlays or smaller and larger
rings 10 or 12.
