U.S. patent application number 11/695380 was filed with the patent office on 2008-05-08 for device for linearly moving a useful mass.
This patent application is currently assigned to Siemens Aktiengesellschaft. Invention is credited to JENS HAMANN, Elmar Schafers, Bernd Wedel.
Application Number | 20080105071 11/695380 |
Document ID | / |
Family ID | 32841751 |
Filed Date | 2008-05-08 |
United States Patent
Application |
20080105071 |
Kind Code |
A1 |
HAMANN; JENS ; et
al. |
May 8, 2008 |
DEVICE FOR LINEARLY MOVING A USEFUL MASS
Abstract
A device for linearly moving a useful mass is described.
Typically, when a large useful mass is moved, relatively large
forces are transferred by a spindle or a toothed rack to the
corresponding machine or machine frame. These forces can be
compensated by moving a compensating mass in the opposite direction
of the useful mass.
Inventors: |
HAMANN; JENS; (Furth,
DE) ; Schafers; Elmar; (Nurnberg, DE) ; Wedel;
Bernd; (Nurnberg, DE) |
Correspondence
Address: |
Henry M. Feiereisen;Henry M. Feiereisen, LLC
Suite 4714, 350 Fifth Avenue
New York
NY
10118
US
|
Assignee: |
Siemens Aktiengesellschaft
Munchen
DE
|
Family ID: |
32841751 |
Appl. No.: |
11/695380 |
Filed: |
April 2, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10783965 |
Feb 20, 2004 |
|
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11695380 |
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Current U.S.
Class: |
74/422 |
Current CPC
Class: |
F16H 25/20 20130101;
Y10T 74/19837 20150115; B23Q 5/40 20130101; Y10T 74/18576 20150115;
Y10T 74/19702 20150115; Y10T 74/1967 20150115; Y10T 74/19726
20150115; Y10T 74/19698 20150115; H02K 7/06 20130101; F16F 2232/04
20130101; F16F 7/10 20130101; Y10T 74/19828 20150115; F16F 15/28
20130101 |
Class at
Publication: |
74/422 |
International
Class: |
F16H 1/04 20060101
F16H001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 2003 |
DE |
103 07 308.6 |
Claims
1. A device for linearly moving a useful mass, comprising: at least
one first toothed rack; at least one first pinion engaging with the
toothed rack and coupled to the useful mass; at least one first
drive rotatably driving the at least one pinion for moving the
useful mass along the toothed rack; and a compensating mass movable
synchronously with the useful mass in a second direction opposite
to the first direction, so that a momentum of the useful mass is
compensated by a momentum of the compensating mass.
2. The device of claim 1, further comprising a second pinion in
engagement with the toothed rack for support of the compensating
mass, and a second drive rotatably driving the second pinion,
wherein the first and second pinions are constructed to have
different diameters, or different tooth spacing, or both.
3. The device of claim 1, further comprising a second toothed rack
and a second pinion mounted on the second toothed rack and operated
by the first drive, said compensating mass being coupled to the
second toothed rack, said first and second pinions having different
diameters, or different tooth spacing, or both so as to move the
first and second toothed racks linearly in opposite directions.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a divisional of prior filed copending
U.S. application Ser. No. 10/783,965, filed Feb. 20, 2004, the
priority of which is hereby claimed under 35 U.S.C. .sctn.120, and
which claims the priority of German Patent Application, Serial No.
103 07 308.6, filed Feb. 20, 2003, pursuant to 35 U.S.C.
119(a)-(d), the contents of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a device for linearly
moving a useful mass and by decoupling the momentum generated
during the movement of the useful mass from the machine or machine
foundation.
[0003] Devices of this type have been used since many years with
machine tools. It is also known that dynamic processes used to
accelerate useful masses along linear axes produce significant
forces that have to be transferred to or absorbed by the machine
bed or machine foundation. Dynamic movements along one axis can
accidentally be transferred through the machine bed to another
axis, which can result in processing inaccuracies, in particular
workpieces that have low-quality surfaces. In addition, when a
rotary motion is transformed into a translational motion--either by
a transformation through a ball roller spindle or alternatively a
rack/pinion assembly--the forces generated by the linear element
can result in a loss in stiffness of the entire system. The
transformation from a rotary motion into a translational motion is
in general also associated with a significant loss in stiffness,
which can be aggravated by the elasticity of the machine bed and/or
the support of the drive train. This limits the dynamic
characteristic of the machine, unless substantial changes are made
in the machine design.
[0004] It would be desirable and advantageous to provide devices of
this type so as to reduce and/or compensate disturbances caused by
the motion transformation.
[0005] It would also be desirable and advantageous to provide an
improved device for moving useful masses, which obviates prior art
shortcomings and is able to specifically reduce the momentum
transferred to the machine or machine foundation and compensate for
disturbances caused by the transformation from rotary to
translational motion.
SUMMARY OF THE INVENTION
[0006] According to one aspect of the invention, a device for
linearly moving a useful mass includes at least one spindle, at
least one drive rotating the at least one spindle, a first spindle
nut coupled with the useful mass and moving the useful mass in a
first direction, and a second spindle nut coupled with a
compensating mass and moving the compensating mass synchronously
with the useful mass in a second direction opposite to the first
direction, so that a momentum of the useful mass is compensated by
a momentum of the compensating mass.
[0007] According to another advantageous aspect of the invention, a
device for linearly moving a useful mass includes at least one
toothed rack, at least one pinion engaging with the toothed rack,
and at least one drive rotatably driving the pinion. A pinion is
coupled with the useful mass, and a pinion is coupled with a
compensating mass and moves the compensating mass synchronously
with the useful mass in a second direction opposite to the first
direction, so that a momentum of the useful mass is compensated by
a momentum of the compensating mass.
[0008] According to an advantageous feature of the invention, the
useful mass and the compensating mass can be moved in cooperation
with a spindle that has two threads with an opposite lead, whereby
the thread pitch for driving the compensating mass is smaller than
the thread pitch for driving the useful mass. The travel of the
compensating mass is thus kept small and the compensating mass can
move at a relatively low speed, which advantageously reduces the
power requirement.
[0009] According to an advantageous feature of the invention, the
useful mass and the compensating mass can also be moved by using
corresponding spindle/spindle-nut assemblies associated with
drives. Mechanical coupling elements can be employed to maintain a
linear alignment between the assemblies and absorb the forces
generated in the two spindles. The mechanical coupling element can
be implemented either by providing a rotatable connection between
the spindles or by connecting both spindles with each other through
a base frame, or both.
[0010] According to an advantageous feature of the invention, in
the device employing a rack/pinion assembly, one pinion can have
more closely spaced teeth while the other pinion has more widely
spaced teeth. Alternatively or in combination, one pinion can have
a smaller diameter while the other pinion can have a larger
diameter. The pinions can move on two racks that face each other in
opposite directions. The racks with the more widely spaced teeth
and/or the larger diameter is connected with the useful mass, while
the other pinion with the more closely spaced teeth and/or the
smaller diameter drives the compensating mass.
BRIEF DESCRIPTION OF THE DRAWING
[0011] Other features and advantages of the present invention will
be more readily apparent upon reading the following description of
currently preferred exemplified embodiments of the invention with
reference to the accompanying drawing, in which:
[0012] FIG. 1 is a schematic illustration of a first embodiment of
a spindle assembly according to the present invention, including a
single drive and a ball roller spindle with opposite lead;
[0013] FIG. 2 is a schematic illustration of a second embodiment of
a spindle assembly according to the present invention, including
two driven ball roller spindles connected by a mechanical
coupling;
[0014] FIG. 3 is a schematic illustration of a first embodiment of
a rack/pinion assembly with separate drives for the useful mass and
the compensating mass; and
[0015] FIG. 4 is a schematic illustration of a second embodiment of
a rack/pinion assembly with a single drive and pinions having
different diameters/tooth spacings.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0016] Throughout all the Figures, same or corresponding elements
are generally indicated by same reference numerals. These depicted
embodiments are to be understood as illustrative of the invention
and not as limiting in any way. It should also be understood that
the drawings are not necessarily to scale and that the embodiments
are sometimes illustrated by graphic symbols, phantom lines,
diagrammatic representations and fragmentary views. In certain
instances, details which are not necessary for an understanding of
the present invention or which render other details difficult to
perceive may have been omitted.
[0017] Turning now to the drawing, and in particular to FIG. 1,
there is shown a first embodiment of the invention with a single
solid spindle SP1 coupled to a drive A1, in the present example a
direct drive. The spindle SP1 can rotate, for example, with a speed
w in the rotation direction indicated by a curved arrow. The
exemplary spindle SP1 has a left-handed threaded section 12 with a
relatively high pitch h.sub.N and a right -handed threaded section
14 with a pitch hi that is comparatively smaller than the pitch
h.sub.N. The threaded section 12 engages with a spindle nut SM1
that is connected with a useful mass NM1, as indicated by a heavy
line. The useful mass NM1 has an exemplary physical mass m. In the
right -handed threaded 14 of the spindle SP1 engages with a spindle
nut SM2 that is mechanically connected with a compensating mass GM1
having an exemplary physical mass M. When the spindle SP1 rotates
with the rotation speed .omega., then the opposing lead of the
spindle thread causes the spindle nuts SM1 and SM2 to move in
opposite directions, as indicated in FIG. 1, with corresponding
speeds v.sub.N and v.sub.I. It follows:
v N = .omega. h N 2 .pi. ##EQU00001##
and since the compensating mass moves in the opposite direction
v I = - .omega. h I 2 .pi. ##EQU00002##
[0018] The force F.sub.N required to accelerate the useful mass NM1
with the physical mass m is:
F N = m h N 2 .pi. .omega. . ##EQU00003##
whereas the force F.sub.I required to accelerate the compensating
mass GM1 with the physical mass M is:
F I = m h I 2 .pi. .omega. . ##EQU00004##
[0019] The forces F.sub.N and F.sub.I are fully compensated if
|F.sub.N|=|F.sub.I|, i.e. both forces have the same magnitude. This
is the case when the product of mass and spindle pitch are
equal:
Mh.sub.I=mh.sub.N
[0020] Advantageously, the compensating mass GM1 and the physical
mass M associated therewith should be made as large as possible and
the corresponding pitch h.sub.I as small as possible for the
following two reasons:
[0021] On one hand, a small travel path for moving this additional
element advantageously also reduces the size of the required
installation space. On the other hand, it is known from mechanical
principles that the work to be performed by the system increases
linearly with the mass and as the square of the speed. Conversely,
the transferred momentum increases linearly with both the mass and
the speed. In other words, for the same transferred momentum, the
required work doubles when the mass is doubled and the speed
remains the same, whereas four times the work is required when the
speed doubles and the mass remains the same. Making the
compensating mass as large as possible is therefore advantageous to
decrease the energy consumption.
[0022] FIG. 2 illustrates another embodiment using two spindles SP2
and SP3 having the same pitch. However, this embodiment requires
two drives A2 and A3, with the drive A2 driving the spindle SP2 and
the drive A3 driving the spindle SP3. As in the first embodiment
depicted in FIG. 1, the spindle SP2 engages with a spindle nut SM3
that is connected with a useful mass NM2, as indicated by a heavy
line. Likewise, the spindle SP3 engages with a spindle nut SM4 that
is connected with a compensating mass GM2. The curved arrows
indicate the rotation speeds .omega..sub.2 and .omega..sub.3 which
are preferably different from each other for the reasons listed
above. The straight arrows indicate the corresponding speeds
v.sub.N and v.sub.I of the masses NM2 and NM3. Corresponding
physical masses (not indicated in FIG. 2) are associated with the
masses NM2 and NM3, with the compensating mass GM2 preferably being
significantly greater than the useful mass NM2, as before. The
spindle SP2 is connected via a coupling K, for example an
articulated joint, with the spindle SP3 in such a way that the
spindle SP2 is collinear with the spindle SP3. The axial forces of
the two spindles SP2 and SP3 are then compensated over a short
travel path.
[0023] As described above, the spindle SP3 has an identical pitch
and also the same thread direction (or lead) as the spindle SP2.
The desired linear speed v.sub.I of the compensating mass GM2 which
is preferably smaller than the speed v.sub.N of the useful mass NM2
and in the opposite direction can be easily obtained by rotating
the drive A3 that is connected with a spindle SP3 in the opposite
direction to drive A2. The rotation speeds .omega..sub.2 and
.omega..sub.3 can be adjusted according to the desired
compensation.
[0024] When the useful mass is changed, the force in such system
can be readily compensated by varying the rotation speed
.omega..sub.3 of the drive A3, without requiring a change in the
compensating mass GM3.
[0025] Alternatively, instead of connecting the two spindles SP2
and SP3 with a coupling, frames or other components disposed
between the two drive systems can also be employed to absorb the
forces. The spindle/spindle-nut system can also include ball roller
spindles.
[0026] FIG. 3 shows a third embodiment of the invention which
employs a rack and pinion system instead of a spindle/spindle-nut
system. This embodiment employs a stationary toothed rack ZS1 which
engages with pinions R1 and R2. The exemplary useful mass NM3 is
moved in a linear direction parallel to the rack ZS1 by a rotary
drive A4 coupled to pinion R1 at a speed v.sub.N. The rotary drive
A4 rotates with an angular rotation speed .omega..sub.4 as
indicated by a curved arrow. A compensating mass GM3 is moved on
the rack ZS1 in the opposite direction of the useful mass NM3 by a
rotary drive A5 coupled to pinion R2 at a speed v.sub.I. The rotary
drive A5 rotates with an angular rotation speed .omega..sub.5 in
the opposite sense as the rotary drive A4. This arrangement
eliminates or at least reduces undesired forces from being
introduced by the toothed rack ZS into the machine. The equations
for the physical motion listed above can be similarly applied to
the rack/pinion configuration.
[0027] It will be understood that at least two racks can be used
instead of the single rack depicted in FIG. 3.
[0028] FIG. 4 depicts yet another embodiment using two toothed
racks ZS2 and ZS3 and two pinions R3 and R4 commonly driven by a
drive A6. Pinion R3 engages with rack ZS2, whereas pinion R4
engages with rack ZS3. The racks ZS2 and ZS3 can be aligned
parallel with each other, with the toothed section either facing
each other or facing in the same direction. Other arrangements are
also feasible, such as racks that are not parallel to each other
and/or employ gears between pinions R3 and R4. Since it is
desirable, as discussed above, to move the useful mass NM4 and the
compensating mass GM4 at different linear speeds v.sub.N and
v.sub.I, respectively, the rack/pinion combinations ZS2/R3 and
ZS3/R4 can either have different tooth spacings (pitch) or the
pinions R3 and R4 can have different diameters, or both.
Preferably, the teeth of the pinion R3 and the rack ZS2 have a
wider spacing than the teeth of the pinion R4 and the rack ZS3.
Likewise, pinion R3 has preferably a greater diameter than pinion
R4. Accordingly, a compensating mass GM4 connected with the rack
ZS3 is moved at a speed v.sub.I that is smaller than and in the
opposite direction to the speed v.sub.N of the useful mass NM4
connected to rack ZS2.
[0029] While the invention has been illustrated and described in
connection with currently preferred embodiments shown and described
in detail, it is not intended to be limited to the details shown
since various modifications and structural changes may be made
without departing in any way from the spirit of the present
invention. The embodiments were chosen and described in order to
best explain the principles of the invention and practical
application to thereby enable a person skilled in the art to best
utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated.
[0030] What is claimed as new and desired to be protected by
Letters Patent is set forth in the appended claims and includes
equivalents of the elements recited therein:
* * * * *