Machine tools abstract
It is provided a support and guide device for small machine tools,
in particular for rotating-mass balancing machines, comprising:
a base element (2), at least one moving element (3) in engagement
with the base element (2), support means (4) for the moving element
(3), and drive members (5) controlling shiftings of the moving element
(3), the support means (4) comprising at least one elastically deformable
thin sheet (7) oscillatably supporting the moving element (3), and
the drive members (5) being active on the moving element (3) to
shift the latter against the action of the elastically deformable
thin sheet (7).
Machine tools claims
1. A support and guide device for small machine tools, in particular
for rotating-mass balancing machines, comprising: a base element,
at least one moving element in engagement with said base element,
support means for said moving element, and drive members controlling
shiftings of said moving element, said support means comprising
at least one elastically deformable thin sheet oscillatably supporting
said moving element.
2. A device as claimed in claim 1 wherein said thin sheet is a
metallic thin sheet made of spring steel, which is substantially
flat under rest conditions.
3. A device as claimed in claim 1 wherein said support means comprises
stiffening plates sandwiching first regions of said thin sheet,
and wherein said thin sheet comprises second regions free from said
stiffening plates, the elasticity of said thin plate being substantially
proportional to the width of said second regions.
4. A device as claimed in claim 3 wherein said first regions are
at a substantially central position of said thin sheet and wherein
said second regions are spaced apart from each other.
5. A device as claimed in claim 1 wherein said support means together
with said moving element and base element substantially defines
a four-bar linkage.
6. A device as claimed in claim 1 wherein said support means together
with one said moving element substantially defines a tilting bracket.
7. A device as claimed in claim 1 comprising a first moving element
and a second moving element, said first moving element defining
a four-bar linkage with said base element and the respective support
means, and said second moving element overlying said first moving
element and forming a tilting bracket together with the respective
support means.
8. A device as claimed in claim 2 wherein said at least one moving
element is oscillatably linked through at least one said metallic
thin sheet and through at least one helical spring, said helical
spring being interposed between said moving element and a respective
base element.
9. A device as claimed in claim 1 wherein said drive members are
directly active on said moving element.
10. A device as claimed in claim 1 wherein said drive members
are fitted between one said base element and a respective moving
element.
11. A device as claimed in claim 1 wherein said drive members
comprise a motor and a connecting rod-crank mechanism operated by
said motor, said connecting rod being directly in engagement with
one said moving element.
12. A device as claimed in claim 1 wherein said drive members
comprise a motor and a cam-cam follower assembly operated by said
motor, said cam follower being directly in engagement with said
one moving element.
Machine tools description
FIELD OF THE INVENTION
[0001] The invention relates to a support and guide device for
small machine tools, in particular for rotating-mass balancing machines,
of the type comprising a base element, at least one moving element
in engagement with the base element, support means for the moving
element, and drive members controlling shifting of the moving element.
[0002] 2. Description of the Prior Art
[0003] It is known that all machine tools are provided, in addition
to a work or cutting motion, with an advance or feed motion causing
relative shiftings between the tool and the workpiece.
[0004] These relative shiftings take place following a great variety
of modalities and among other things involve use of different mechanical
members for support and guide. For instance, generally used are
slides that, as known, are supports provided with guides and movable
along predetermined directions.
[0005] Depending on the situations, slides can movably support
the workpiece or the tool and each slide is provided for carrying
out shifting in a given direction. Slides are important and expensive
components in machine tools because accuracy in workings also relies
on stability and movement precision of same and because often very
precise workings are required.
[0006] For instance, in milling machines used as balancing machines
for rotating masses, accuracy in the relative shiftings between
tool and workpiece must be rather high: in the order of one hundredth
of a millimeter.
[0007] Balancing machines intervene in some rotors, such as armatures
of small electric motors used in cars, household electrical appliances,
electrical tooling, to remove small amounts of material at each
balancing plane.
[0008] In order to achieve a final true accuracy of one or two
hundredths of one millimeter in these balancing machines, slides
therein used are relatively complicated and expensive, even if traditional
in themselves.
[0009] Typically, in the concerned slides it is provided that at
least two guides with at least two or four ball runners, one ballscrew
with the related supports and bearings, a servo-motor operating
it and limit sensors, should be mounted on a base. The final cost
of these controlled-motion slides is high and setting of same is
also very demanding and expensive.
[0010] The foregoing is valid in spite of the fact that in this
specific case the requested relative shiftings between the workpiece
to be balanced during working and the milling tool are of minimum
amount.
[0011] In fact, as already pointed out, material removal is very
reduced and the maximum length of a single milling operation to
balance a rotor can be quantified in an amount of about fifteen
millimeters.
[0012] In addition, a maximum milling depth in a balancing machine
is in the order of only three millimeters, although in order to
cover the wide variety of diameters of the different pieces that
may be submitted to working, an overall maximum stroke of about
forty millimeters in the approaching direction between milling tool
and rotor is to be stated.
[0013] In short, the present art teaches how to manufacture support
and guide devices for machine tools having a structure that takes
into account the amount of the shiftings to be made only as a marginal
question and that, if precision shiftings are required, needs complicated
and expensive devices.
[0014] This hinders diffusion of small precision machine tools,
in particular of said balancing machines.
SUMMARY OF THE INVENTION
[0015] Under this situation the technical task of the present invention
is to conceive a support and guide device capable of obviating the
mentioned drawbacks. Within the scope of this technical task it
is an important aim of the invention to conceive a device particularly
adapted for small shiftings in small machine tools and capable of
enabling both high accuracy and minimum costs.
[0016] Another important aim of the invention is to conceive a
device of simple structure, formed of a minimum number of pieces
and of reliable operation.
[0017] The technical task mentioned and the aims specified are
achieved by a support and guide device for small machine tools,
in particular for rotating-mass balancing machines, comprising:
a base element, at least one moving element in engagement with said
base element, support means for said moving element, and drive members
for controlling shifting of same, said support means comprising
at least one elastically deformable thin sheet oscillatably supporting
said moving element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Description of some embodiments of the device of the invention
is now given hereinafter, with reference to the accompanying drawings,
in which:
[0019] FIG. 1 shows the device arranged for shiftings of the horizontal
type;
[0020] FIG. 2 shows the device in FIG. 1 arranged for shiftings
of the vertical type;
[0021] FIG. 3 shows a device consisting of the sum of the structures
shown in the preceding two figures, so as to obtain shiftings both
in the horizontal and in the vertical direction;
[0022] FIG. 4 is a perspective view of a portion in FIG. 1;
[0023] FIGS. 5 and 6 show an elastic thin sheet of the embodiment
in FIG. 1 in a rest position and in an elastically deformed position,
respectively;
[0024] FIG. 7 is a perspective view of a portion in FIG. 2; and
[0025] FIG. 8 shows an elastic thin sheet of the embodiment in
FIG. 2 in a rest position.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] With reference to the drawings, the device of the invention
has been identified by reference numeral 1.
[0027] It generally comprises a base element 2 at least one moving
element 3 in engagement with the base element 2 and shiftable relative
to the latter, and support means 4 for shiftings of the moving element
3.
[0028] Also provided are drive members 5 controlling shiftings
of each moving element 3 relative to the base element 2.
[0029] The base element 2 in the simplest embodiment is the base
of a small machine tool, whereas the moving element 3 is the support
of operating members of the machine tool itself.
[0030] In the preferred instance of small machine tools such as
small milling machines for balancing rotors, elements 2 and 3 are
plate-like bodies of rectangular shapes seen in plan view and of
a bulkiness involving sides of some ten centimeters.
[0031] The moving element 3 at least at a suitably-positioned
work region is in engagement with at least one attachment piece
6 for the tool to be used. For instance, the moving element 3 has
an attachment piece 6 at one end thereof. The attachment piece 6
can be embodied by supports with bearings for a milling spindle.
[0032] The support means 4 of the moving element 3 comprises at
least one elastically deformable thin sheet 7 which engages the
moving element 3 like an oscillatable support wall.
[0033] The thin sheets 7 extend at the ends of elements 2 and 3
to which they are merely screwed up, and have a thickness of about
one or two millimeters, for example.
[0034] Each elastically deformable thin sheet 7 is substantially
flat in a rest condition and is preferably made of high-tensile
steel, or spring steel, in order to ensure the greatest flexibility
and strength.
[0035] The thin sheet sizes are imposed by the overall structure
of the machine tools: for instance, the thin sheets 7 have square
or rectangular shapes and maximum linear sizes in the order of about
ten centimeters.
[0036] Control of elasticity of the thin sheets 7 is obtained,
once thickness has been established, by applying rigid stiffening
plates 9 fastened by bolting and sandwiching the thin sheets 7 on
opposite sides.
[0037] In addition, the stiffening plates 9 preferably engage a
median portion of the thin sheets 7 so as to form flexibility regions
spaced apart from each other. Practically, for each thin sheet 7
two stiffening plates 9 in contact with opposite faces of the thin
sheet 7 are provided so as to sandwich and stiffen a first central
region 7a of each thin sheet.
[0038] The first region 7a has smaller sizes than those of the
thin sheet 7: free regions 7b spaced apart from each other are always
present to ensure the necessary elasticity. Said elasticity is thus
proportionate to the width of the second free regions 7b and can
therefore be adjusted at will by giving appropriate sizes to the
stiffening plates 9. Obviously the stiffening plates 9 can be positioned
on the thin sheets 7 no matter how and even omitted when the device
is formed with thin sheets 7 of very reduced sizes or the elasticity
of which is already adjusted based on the particular needs.
[0039] The device can be made for carrying out shiftings--between
the base element 2 and the moving element 3--parallel or transverse
to each other, or preferably in both directions simultaneously.
[0040] In the first case shown in FIG. 1 the base and moving elements,
2 and 3 define a four-bar linkage together with the support means
4.
[0041] In the second case shown in FIG. 2 the moving element together
with the related support means 4 defines a bracket body provided
with a tilting motion with respect to the base element 2 and having
an attachment piece 6 at its free end. In particular, the technical
solution in FIG. 2 where the stiffening plates 9 only consist of
strips, can be simplified by omitting the stiffening plates 9 and
suitably reducing the available space for the thin sheet 7.
[0042] In the third case, which is the sum of the preceding two
cases and is shown in FIG. 3 two moving elements 3 are mounted
in succession on a single base element 2 i.e. a first moving element
3a forming a four-bar linkage with the underlying base element 2
and a second moving element 3b overlying the first moving element
and the base element 2 so as to form a body in the form of a bracket.
[0043] It is also pointed out that the drive members 5 are preferably
fitted between a moving element 3 and the base element 2 and they
directly act on the moving element 3.
[0044] In other words, the drive members 5 do not act on the support
means 4 but directly on the moving elements 3 so that they operate
with the greatest accuracy without intermediate members.
[0045] In detail, the drive members 5 comprise a motor, preferably
an electric motor, and a connecting rod-crank mechanism or a cam-cam
follower assembly operated by the motor.
[0046] Where a motor operates a connecting rod-crank mechanism,
the connecting rod is in engagement with a moving element 3 and
the crank is supported by a respective base element 2.
[0047] In the preferred case of a motor operating a cam-cam follower
assembly, as shown in the figures, provision is made for a cam 10
which has a rotation axis 10a substantially parallel to the base
element 2 an electric motor 11 adapted to rotate the cam 10 and
coaxial with the rotation axis 10a, and a cam follower 12 engaging
the cam 10 by acting against the action of same.
[0048] The cam follower 12 consists of a roller linked to a moving
element 3 and the cam is linked to the underlying element.
[0049] To enable horizontal shiftings, in FIG. 1 the cam follower
12 is substantially at the same height as the rotation axis 10a
of cam 10 whereas to enable vertical shiftings, in FIG. 2 the
cam follower 12 is above the rotation axis 10a.
[0050] Also provided are helical springs 8 active on each moving
element 3 and the underlying element, so as to keep the cam followers
12 at a position at which they closely counteract the action of
cam 10. In the case shown in FIG. 1 compression springs are present
and in the case shown in FIG. 2 draw-springs are present.
[0051] Since the drive members 5 are also active against the action
of the elastically deformable thin sheets 7 springs 8 can optionally
be omitted. Cam 10 can also be of a type having one degree of freedom
only and therefore directly connected with the cam follower 12
by a shaped groove in which the cam follower runs, for example.
In this way the helical springs 8 are not required. In fact in the
last-mentioned case a complete-constraint system is concerned, with
only one degree of freedom as said, like the already discussed connecting
rod-crank mechanism.
[0052] The electric motor 11 is preferably of the brushless type
and it is provided adapted to angularly position the cam 10 in a
very precise manner.
[0053] Operation of the device is as follows.
[0054] The device is placed at the base of small machine tools
for which relative shiftings of small amount between the workpiece
and the tool are required. As already pointed out, in small balancing
machines operating by material removal, these shiftings are of about
fifteen millimeters in a horizontal direction and forty millimeters
in a vertical direction.
[0055] Shiftings of the moving element or upper plate-like body
3 are obtained by starting the electric motor 11 and therefore starting
the connecting rod-crank mechanism or the cam-cam follower assembly.
[0056] For instance, with a cam-cam follower assembly of the type
shown, cam 10 can impose small shiftings to the cam follower 12
and therefore to the moving element 3 since cam 10 is in engagement
with the base element 2 and the cam follower 12 is directly in engagement
with the moving element 3 in turn supported by one or more thin
sheets 7 in an oscillatable manner.
[0057] The thin sheets 7 perform different functions, i.e. they
act as a support for the moving element 3 as a moving guide for
the same, and as a stabilising elastic member active against the
action of the drive members 5.
[0058] As a support element they must have sufficient dimensions
to place the moving element 3 at correctly raised positions and
as a guide element they must have wide dimensions, so as to enable
the moving element 3 itself to carry out shiftings of sufficient
width.
[0059] In addition, should a four-bar linkage be formed as in FIG.
1 the relatively wide sizes enable the intended longitudinal shiftings
to be achieved without an important lowering in the vertical direction.
[0060] The above can possibly lead to an excessive flexibility
and yielding in the vertical direction, but this drawback is completely
overcome and obviated by arranging sandwiching stiffening plates
9 on the thin sheets 7.
[0061] Said stiffening plates limit the thin sheet yielding in
a simple and efficient manner, even in the presence of important
weights and of thin sheets of very reduced thickness, and in addition
they stiffen the thin sheets themselves to such an extent that,
on deflection, a sufficiently high elastic reaction is obtained.
[0062] The invention achieves important advantages.
[0063] In fact, a device of very simple structure and low cost
has been obtained which enables achievement of small and highly-precise
shiftings.
[0064] Accuracy is in particular connected with the direct control
of the moving elements and the substantial absence of plays.
[0065] The support means 4 and drive members 5 by themselves enable
shiftings having an accuracy in the order of thousandths of a millimeter.
[0066] In addition, the device, due to the presence of the stiffening
plates 9 is very versatile, cheap and of easy setting. in fact,
one and the same elastic thin sheet can take different elasticity
values that can be adjusted with great accuracy, and also thin sheets
of very reduced thickness and wide sizes can be utilized. |