Note: Descriptions are shown in the official language in which they were submitted.
- 1328986
~ethod for the Production of a Hardened Guide Sha~t
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for a Linear Guide
The invention relates to a method for the production
of a hardened guide shaft for a linear guide, in par-
ticular for a linear guide with a guide carriage pro-
vided with spherical bushes, and a guide shaft manu-
factured according to this.
Linear guides are used for the performance of linear
movements in a multiplicity of fields, as, for example
in mechanical engineering, in handling systems, in the
construction of jigs and fixtures and in precision
engineering. Linear guides can, for examole, be used
as modules for grabs, robots, sliding tables, supports,
measuring instruments, etc. The heart of the linear
guide is one or two guide shafts on which is arranged
a guide carriage which is slidable along the shaft or
shafts.
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In reversal, however, the guide carriage can also re-
main stationary and the shaft or the two shafts are
shifted. For low-friction displacement and a high
load-carrying capacity so-called spherical bushes or
linear ball bearings with several ball revolutions (races)
are generally arranged in the guide carriage.
The relative movement between the guide shaft and the
guide carriage arranged thereon can be accomplished
in different ways. Known for this are ball roll spindles,
with a spindle running parallel to the guide shaft and
a spindle nut being arranged in the guide carriage. If
the spindle is driven, the guide carriage moves accord-
ingly.
A disadvantage with this, however, is that besides an
additionally necessary constructional area for the
spindle, this cannot be mounted with a support, so that
its overall length is limited.
Well known are also drive systems with toothed belts or
the like, however, this likewise means an increased ex-
penditure on additional components and on constructional
space. Furthermore, in this case in part the guide shaft
cannot be supported, which thus likewise has a disadvan-
tageous effect on the overall length.
What is likewise already well known is to arrange a toothed
rod (rack) parallel to the guide shaft, which works to-
gether with a counter-element, in general a pinion, for
shifting the guide carriage. For this, however, addition-
al components and a higher expenditure are also necessary.
Furthermore, such a linear guide is likewise subject to
limitations in respect of its applicability.
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1328986
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~3 The task of the present invention is therefore to
~ create a linear guide or a guide shaft for a linear
`~ guide which can be used very universally and by means
r which a linear guide with a short overall length
and a high load-carrying capacity can be obtained.
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According to the invention, this problem is solved in
that a toothing is introduced into a shaft over a
~ partial circumferential area, after which the shaft
¦ with the teeth is heat-treated (hardened) and sub-
i~, sequently - as is actuallv well known - trued and
ground.
s According to the invention a necessary part 'or the
;~ shifting between a guide shaft and a guide carriage
is now integrated into the guide shaft itself, namely
a toothing. In this way it is solely necessary to
arrange the counter-element, which will in general be
a pinion, in the guide carriage. Further components -
besides the usual drive equipment, such as, for example,
a drive motor - are no longer necessary. The guide
~ shaft thus assumes a dual function, through which
`;~ additional components can be omitted and at the same
i time thus a size reduction is also achieved. The tooth
system may be either straight or helical toothing.
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A very significant further advantage of the invention
consists in that in this way the drive base or guide
shaft can at the same time also be mounted and fastened
with support, e.g. bolted. In this way a geometrically
defined and vibration-free guideway is created, which
can withstand very high loads. Furthermore, any desired
number of guide shafts can be arranged one after the
other, the only thing having to be ensured being a
trouble-free transition of the toothed section.
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1328986
In this way linear guides of any desired length can
virtually be arranged in a row. In an embodiment of
a linear guide with only one guide shaft, in this
case too a lock against rotation, such as, for exam~le,
by means of grooves, bars or flattening of the guide
shaft, can be obtained in a sim~le and well-known way.
A sufficient hardness of the shaft, which is necessary
in particular for guide carriages with spherical bushes,
can be achieved in several ways.
It is of advantage if the shaft is hardened inductively
with a circular inductor, with the magnetic flux being
controlled in such a wav that the magnetic flux is lower
in the area of the toothing than in the remaining area.
Until now it has been considered impossible to provide
a guide shaft which because of the occurring loads has
to be surface-hardened, in an economical way with a tooth
system.
A subsequent grinding-in of a tooth system into the
hardened guide shaft would have been an unjustifiably
high expenditure. Furthermore, with increasing tooth
size the unhardened portion in the central and lower
area of the teeth in the tooth roll-off region would
increase, since the hardened surface layer would be
partly penetrated during grinding-in. An introduction
of the-toothing before a hardening operation has also
been regarded as infeasible. With inductive hardening
using a circular inductor, which should also aim at
a sufficient hardening of the non-toothed part of the
shaft, distinct overheating in the tooth area was to
be expected, which would have led to the breaking-out
of teeth during a subsequent quenching.
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_ 5 _ 1328986
Although basically case-hardening of a guide shaft
would also come into consideration, in addition to
other disadvantages the depth of hardness thereby
obtained would not be sufficient especially for large
carrying loads and with the use of spherical bushes.
Furthermore, in the case of non-rusting materials such
a hardened guide shaft would lose, at least extensively,
its freedom from corrosion due to recarburization.
Through the control of the magnetic flux according to
the invention during inductive hardening, however, the
problems to be expected are, in a surprising way, avoided.
By means of appropriate reduction Oc the magnetic Clux
in the area of the toothing and thus a reduction of the
vortex flows, heat is supplied to a small extent in this
area, but this is sufficient to bring the toothed area
of the guide shaCt up to the desired hardness without
disadvantageous overheating occurring. The toothing can,
in the process, also become tougher in an advantageous
way and thus better withstand jerky loads.
The major feature in the inductive hardening according
to the invention is thus that a situation is created
through which the toothed area does not receive such a
high temperature as the remaining area of the guide shaft.
In a further embodiment according to the invention it
is planned that the guide shaft to be hardened is pushed
through the circular inductor at least approximately
unturned, and that the circular inductor is provided in
the non-toothed area of the guide shaft with the magnetic
flux increasing parts or changes.
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By means of a suitable arrangements of parts which change
the magnetic flux, such as sheet-metal packages, through
their appropriate arrangement the magnetic flux can be
controlled in the desired manner and thus the hardness
of the teeth selectively influenced.
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A prerequisite for this is that, deviating from customary
inductive hardening, the guide shaft to be hardened is
now pushed through the inductor without any rotation, as
otherwise the magnetic flux could no longer be readily
controlled or take effect in the desired manner.
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If necessary, control of the hardening of the teeth
could be achieved by specially controlled coolin~ mea-
sures after the inductive hardening operation, too.
As basic material for the production of the guide shaft
according to the invention various materials are possible.
For example, inductively hardenable carbon steels of the
5, following composition can be used:
Carbon: 0.5 - 0.6%
Silicon: 0.15 - 0.35%
Manganese: 0.4 - 0.7%
Phosphorus: max. 0.025%
Sulphur: max. 0.035%
5uch steels are listed in DIN 1712.
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Likewise rustfree and acid-resistant, hardenable marten-
sitic steels can be used for thiS. A possible material
composition for this is exhibited by the following alloy
$~ components:
Carbon: 0.85 . 0.95%
~ Silicon: max. 1%
'! Manganese: max. 1~
Chromium: 17 - 19%
Molybdenum: 0.9 - 1.3%
~ Vanadium: 0.07 - 0.12
;~ Phosphorus: max. 0.045%
~ Sulphur: max. 0.030%
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~ 7 ~ ~328986
Also possible for this purpose are anti-friction bearing
steels, possibly also rustfree.
A further advantage compared to the well-known hardening
method consists in that with the inductive hardening ac-
cording to the invention the guide shaft can be subjected
to heat treatment before inductive hardening.
In this way the core and transition area of the guide shaft
can be heat treated in order to increase the core strength,
by means of which a very high strength load of the shaft
becomed possible. In this case the teeth of the toothin~
can be made before or even after the heat treatment opera-
tion, after which the inductive hardening operation is then
carried out. Due to the previous heat treatment, the core
cross-section is significantly increased in its yield point
and strength.
The arrangement of the toothed area of the guide shaft on
installation in a linear guide can be as desired, which
represents a further advantage of the invention. In par-
ticular, in this way the drive unit can always be optimally
adapted to the current conditions. For example, the tooth-
; ing can be arranged on the upper side, on the underside
and also, in case of need, laterally. In particular an ar-
rangement of the toothing on the upper side or laterally
~I has the advantage that in this way the guide shaft can be
supported on the underside for high loads.
Described in principle in the following is an embodiment
of the invention with reference to the drawing.
Shown are:
Fig. 1: a linear guide with a guide shaft, partially in
cross-section
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Fig. 2: a linear guide with a guide shaft
in a different embodiment
Fig. 3: a further variant of a linear guide with
a guide shaft
Fig. 4: two interconnected linear guides, each with
two guide shafts for a two-axis shifting.
In a simple embodiment the linear guide exhibits a guide
shaft 1, which is surrounded by a suide carriage 2. Dis-
posed in the interior of the guide carriage 2 is a spher-
ical bush 3 with a total of four ball races 4 arransed
distributed over the circumference. Instead of a spherical
bush a sliding guide or a plain bearing can of course
also be provided for this. As guide shafts, solid or of
course also hollow shafts can be used, since the nature
and embodiment of the guide shaft is rundamentally as
desired for the invention.
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In the lower area the guide shaft 1 is provided on aoprox.
one fifth of its circumferential area with a transverse
toothing 5. The width and the height of the teeth in this
case each depend on the application. The size of the
circumferential area in which the toothing is introduced
into the guide shaft 1 is thus of course also dependent
on the spacing of the ball races 4, since the toothing
can extend only in the intermediate space.
In the guide carriage 2 is furthermore fastened a pinion 6
on a drive shaft 7. The drive shaft 7 is mounted in ball
bearings 8 and 9. On one side a drive motor 10 (see Fig. 4)
is connected to the guide shaft 7 and at the same time
flange-mounted on this side to the guide carriage 2.
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1328986
The drive shaft 7 can of course also terminate in the
guide carriage 2. If, however, as in the shown embodi-
ment of Fig. 1, it is led out on the opposite side, in
this way a drive connection to a second guide shaft can
be achieved, with which a linear guide with two guide
shafts 1 arranged at a distance from each other is ob-
tained.
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Fig. 2 shows diagrammatically a similar linear guide
to that in Fig. 1. The only difference consists solely
in that in this embodiment the toothing 5 lies on the
upper side of the guide shaft 1, or the guide shaft 1
is so installed that the toothing lies on the upper
side. The drive connection can in this case be made in
the same way as shown in Fig. 1, with in this case
solely the ends of the drive shaft 7 projecting out of
j the guide carriage 2 are shown. As can be seen, the
i advantage of this embodiment is that the guide shaft 1
mounts on the underside on a bearing pedestal or a
bearing rail 11 and can thus be supported. It is there-
by solely necessary to provide a spherical bush 3 in
the customary way, which is provided on the underside
with a slot 12.
- Shown in Fig. 3 is a third embodiment where, in this case,
the guide shaft 1 is so installed that the toothing 5
is arranged laterally and works together with a drive
shaft 7, on which the pinion 6 is arranged, this shaft
possessing a vertical longitudinal axis. As can be seen,
in this way the guide shaft can likewise be supported on
a bearing rail 11 .
The drive motor 10 for the drive is in this case flange-
mounted on the upper side of the guide carriage 2.
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With the guide shaft 1 provided with the toothing 5 as
core, linear guides can be arranged in any desired way
and in particular also put together in the form of mod-
ules. Such an embodiment is shown as an example in Fig. 4.
As can be seen, two guide shafts 1A and lB and 21A and
21 B each work together with guide carriages 2A and 2B
and 22A and 22B, respectively. As can be seen, in each
case guide shaft 1A or 21A is provided with a toothing 5,
with in each case a drive motor 10 ensuring drive. The
two guide shafts lB and 21B do not possess any separate
drive and thus also no toothing 5. It goes without say-
ing, however, that in case of need these two guide
shafts can also each be driven by the same drive motor.
The shown combined linear guide, which makes possible
movements in two axial directions, is mounted in bear-
ing 13. As further evident, the guide carraiges 2A, 2B
and 22A and 22B are identical in design and also possess
connecting parts at the same points (not shown). In
this way the guide carriages can be connected to each
other in any desired way, resulting in a virtually free~
possibility of combination. For example, in this case
it is also possible to provide one or two guide carriages
in addition to the two guide rails 22A and 22B at the top
fastened to the bottom guide carriages 2A and 2B and in
this way to make possible a movement into the third axial
direction.
The guide shaft l can be manufactured in the following way:
.
The transverse toothing 5 is, for example, ground into
a still soft guide shaft. Of course it can, if required,
be milled, slotted, rolled or made in any desired way.
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If required, a heat treatment of the shaft can be con-
- ducted in the customary way beforehand, for which pur-
pose it is heated up, subsequently quenched and finally
again reheated until the desired heat treatment is reached.
This method is the general state of the art, which is
i why it will not be explained in further detail at this
point.
The inductive heating operation takes place in a circular
j inductor through which the guide shaft to be hardened is
~ pushed without rotation. Used for control of the ~agnetic
r" flux are sheet-metal packages arranged around the circum-
- ference of the circular inductor, which are appropriately
so shifted or so disposed that a higher magnetic flux and
thus a higher temperature arises in areas without toothing.
The inductive heating operation itself is likewise commonly
known, which is why it will not be explained in further
detail here.
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1 Inductive surface hardening is a process in which a very
`''! high temperature is generated in a surface zone of the
- workpiece limited according to depth and through quenching
~ of the heated areas a local hardening of them is achieved.
I Depending on the frequency, case-hardening depths of sev-
eral millimetres can be produced. An induction system con-
sists essentially of a frequency generator and a working
device. In the frequency generator the frequency of the mains
supply system is converted into a single-phase alternating
current of higher frequency. The working device itself is
.j the inductor proper, which has to accommodate the work-
piece to be heated and perform all necessary movements.
In the case of lengthy workpieces, as in the present case
with the guide shafts, either the guide shaft is pushed
through the inductor or the inductor is guided along the
`1 guide shaft. By means of a uniform movement of the inductor
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to the stationary workpiec_ or also vice versa, it is
possible to progressively generate an annealing zone
on the guide shaft. The water jet of a quenching spray
running along with it then continuously executes the
hardening operation.
The case-hardening depths are adapted to the respective
diameter range and take into account, among other things,
also the surfaces pressures to be taken up, which are
transmitted to or exerted on the linear guide shaft by,
for example, linear longitudinal ball bearings at dif-
ferent loAds.
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