U.S. patent application number 09/785586 was filed with the patent office on 2001-09-13 for drive device.
Invention is credited to Godel, Martin, Hoffmann, Markus.
Application Number | 20010020788 09/785586 |
Document ID | / |
Family ID | 7633034 |
Filed Date | 2001-09-13 |
United States Patent
Application |
20010020788 |
Kind Code |
A1 |
Godel, Martin ; et
al. |
September 13, 2001 |
Drive device
Abstract
A drive device comprising at least one drive unit having two
mutually spaced apart pressing bodies. On the pressing bodies
mutual facing pressing faces are provided diverging in a drive
direction and having between them a stroke unit engaging the
pressing faces of both pressing bodies. Furthermore drive means are
present by means of which a drawing together of the pressing bodies
may be caused and, as a result of this a displacement of the stroke
unit in the drive direction along the pressing faces for the
purpose of producing a drive movement able to be externally
employed.
Inventors: |
Godel, Martin; (Owen/Teck,
DE) ; Hoffmann, Markus; (Wolfschlugen, DE) |
Correspondence
Address: |
Charles R. Hoffmann, Esq.
HOFFMANN & BARON, LLP
6900 Jericho Turnpike
Syosset
NY
11791
US
|
Family ID: |
7633034 |
Appl. No.: |
09/785586 |
Filed: |
February 16, 2001 |
Current U.S.
Class: |
290/1C ;
290/3 |
Current CPC
Class: |
F16H 25/18 20130101;
H02N 2/043 20130101; Y10T 74/18568 20150115 |
Class at
Publication: |
290/1.00C ;
290/3 |
International
Class: |
H02P 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2000 |
DE |
100 09 862.2 |
Claims
1. A drive device comprising at least one drive unit with two
mutually spaced pressing bodies on which facing pressing faces are
provided, which diverge in a drive direction and between which a
stroke unit is located engaging the pressing faces of the two
pressing bodies, and furthermore drive means for causing a mutual
motion together of the pressing bodies and a displacement,
resulting therefrom of the stroke unit in the drive direction along
the pressing faces for the production of a drive movement which can
be utilized externally.
2. The drive device as set forth in claim 1, wherein the pressing
faces of both pressing bodies, as considered in a spaced apart home
position, have an inclined form as related to the drive
direction.
3. The drive device as set forth in claim 1, wherein the pressing
face of at least one pressing body possess a straight or curved
form in the drive direction.
4. The drive device as set forth in claim 1, wherein the pressing
bodies are so designed that during mutual movement of the pressing
faces toward each other, both pressing bodies move.
5. The drive device as set forth in claim 1, wherein the mutual
movement together, able to be caused by the drive means, of the
pressing faces is produced by a forced pivotal motion of at least
one pressing body.
6. The drive device as set forth in claim 6, wherein the two
pressing bodies are coupled together in a pivoting manner in
relation to each other in a bearing zone, extend generally in the
same direction from the bearing zone and delimit a pressing space
which at least partially receives the stroke unit, said space being
preferably open on the outer end opposite to the bearing zone.
7. The drive device as set forth in claim 5, wherein for causing
movement together of the pressing faces using drive means placed
between the pressing bodies pulling and/or thrust forces may be
exerted on the pressing bodies, the application of such pulling
forces being on the face facing the pressing faces and the
application of the thrust forces being on the side facing away from
the pressing faces of the center of pivoting, of the at least one
pressing body.
8. The drive device as set forth in claim 7, wherein the two
pressing bodies are coupled together in a pivoting manner in
relation to each other in a bearing zone, extend generally in the
same direction from the bearing zone and delimit a pressing space
which at least partially receives the stroke unit, said space being
preferably open on the outer end opposite to the bearing zone and
wherein means are provided at the bearing zone.
9. The drive device as set forth in claim 1, wherein at least the
mutual movement together and preferably also the opposite return
movement of the two pressing bodies is produced by electrical drive
means and/or by drive means operated by fluid power.
10. The drive device as set forth in claim 9, comprising
electrically operated drive means in the form of a piezoelectric
transducer means.
11. The drive device as set forth in claim 10, wherein the
piezoelectric transducer means comprises one or more stack
translator units.
12. The drive device as set forth in claim 11, comprising two stack
translator units connected in parallel and able to be operated to
produce preferably both pulling forces and also thrust forces
simultaneously in opposite directions.
13. The drive device as set forth in claim 1, wherein said drive
means comprise at least one spring means for causing the return
movement opposite to the drive movement, of the stroke unit.
14. The drive device as set forth in claim 13, comprising at least
one spring means adapted to act on at least one of said pressing
bodies and/or on the stroke unit.
15. The drive device as set forth in claim 1, wherein said stroke
unit is constituted by a rolling body unit adapted to roll on the
pressing faces of the pressing bodies during the drive
movement.
16. The drive device as set forth in claim 15, wherein the rolling
body unit comprises at least two independently rotating and for
example rolling-like rolling bodies, which respectively engage only
one of the pressing faces of the two pressing bodies.
17. The drive device as set forth in claim 6, having a coaxial
arrangement of the rolling bodies of the rolling body unit and an
accordingly relatively laterally offset arrangement of the pressing
faces.
18. The drive device as set forth in claim 1, comprising two drive
units constituting an assembly, whose pressing bodies are so placed
in pairs to form two flexurally rigid pressing elements that the
pressing faces of the two drive units diverge toward oppositely
facing, opposite sides and the stroke units thereof are so
kinematically coupled for opposite motion that during drive
movement of respectively one stroke unit the respectively other
stroke unit is entrained therewith.
19. The drive device as set forth in claim 18, wherein the two
pressing elements are so movingly mounted relative to each other in
a bearing zone provided in the transition zone between the two
drive units that at least one pressing element may be caused to
perform rocking movements by the drive means, in the case of which
the pressing faces move toward one another and at the same time the
pressing faces of the other drive unit move apart.
20. The drive device as set forth in claim 18, wherein the
connecting yoke is designed in the form of a member for the
transmission of drive movement for external use.
21. The drive device as set forth in claim 18, wherein the
connecting yoke is so resiliently elastic in its stroke direction
that slight relative movements of the stroke units are rendered
possible.
22. The drive device as set forth in claim 1, adapted for use as a
drive for a valve serving for the control of fluid medium.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a drive device or transmission,
which may for example be employed in the pneumatic equipment sector
as a valve drive.
THE PRIOR ART
[0002] In connection with valves serving for the control of fluid
flows in the pneumatic equipment sector so far as a rule valve
drives have been utilized, which are constituted by electromagnets
or piezoelectric transducers. While being suitable for the
transmission of large forces such drives generally only perform a
drive movement with relatively small force strokes. Furthermore,
there are design limitations as regards presetting the force-stroke
characteristic, this restricting the field of application.
SHORT SUMMARY OF THE INVENTION
[0003] One object of the invention is to create a drive device
whose characteristics are able to be varied using comparatively
simple means and which in case of need renders possible performing
drive movements with a large force and simultaneously a large
stroke.
[0004] In order to achieve these and/or other objects appearing
from the present specification, claims and drawings, the present
invention provides at least one drive unit, which comprises two
mutually spaced pressing bodies on which facing pressing faces are
provided, which diverge in a drive direction and between which a
stroke unit is located engaging the pressing faces of the two
pressing bodies, and furthermore drive means for causing a mutual
motion together of the pressing bodies and a displacement,
resulting therefrom of the stroke unit in the drive direction along
the pressing faces for the production of a drive movement which can
be utilized externally.
[0005] The drive device thus comprises at least one drive unit,
which possesses a stroke unit, which is arranged between the
pressing faces, which are moving apart, of two spaced pressing
bodies. By way of drive means cooperating with one or both pressing
bodies it is possible for the pressing bodies to be so moved in
relation to one another that the pressing faces draw closer
together. Owing to their diverging configuration this results in a
displacement of the stroke unit in a direction athwart the
direction of movement together of the pressing faces, the direction
of displacement being termed the drive direction. The stroke unit
is practically displaced out of the way by the pressing faces
acting on it, there being a redirecting of the force in the said
drive direction. The displacement of the stroke unit may then be
utilized externally as a drive movement, which acts directly or
indirectly on a component to be moved, as for example on the valve
member to be actuated of a control valve.
[0006] Because the configuration of the pressing faces can be
preset in a predetermined manner by the manufacturer, drive devices
with a customized adaptation of the force-stroke characteristic may
be produced in a relatively simple fashion. Inherently means may be
employed as a drive which produces only a small stroke but a high
actuating force, the design of the pressing faces being able to be
configured to yield a transmission ratio, which converts a
relatively small stroke of the drive means into a sufficiently
large stroke of the drive movement able to be employed as an
output. It is for this reason that the drive device is particularly
suitable for the production of small and miniature designs, a
piezoelectric transducer device means being for example employed as
a drive means. As an alternative it would be possible as well to
use drive means operated by fluid power as are supplied by the
assignee under the trade name of "Fluidic Muscles".
[0007] The drive device offers the further advantage that it may in
case of need be so designed and operated that it provides for a
constant drive characteristic and different stroke positions of the
stroke unit may be set in a stepless manner.
[0008] Further advantageous developments of the invention are
defined in the claims.
[0009] The two pressing bodies are preferably moved toward each
other by activation of the drive means starting from a home
position, the pressing face of at least one, and preferably both of
the pressing bodies being so shaped that as considered in the home
position, there is an inclination of the faces in relation to the
drive direction produced.
[0010] In the simplest case the pressing faces present are in the
form of oblique faces with a linear form. By presetting the angle
of inclination in relation to the drive direction it is possible
for the transmission ratio or, respectively, the force-stroke
characteristic to be predetermined. In order to produce customized
drive movements, the pressing faces may be also provided with a
curved shape in order to produce a non-linear motion
characteristic.
[0011] The drive device may in principle be so designed that the
relative movement of the two pressing bodies is produced by the
movement of only one pressing body, the other pressing body
remaining stationary and for instance being fixedly attached to an
associated housing part. However it is preferred to have a design
which ensures simultaneous motion of the two pressing bodies during
movement together.
[0012] The mutual movement together of the pressing faces is
preferably produced by a pivoting movement of one or both pressing
bodies. For this purpose the pressing bodies may be coupled
together in a pivoting manner in relation to one another in a
bearing zone and extend approximately in the same direction away
from the bearing zone, and furthermore delimit a pressing space
wherein the moving stroke unit is located. The drive means are in
this case preferably placed at the bearing zone, a pull and/or
thrust action being provided in a manner dependent on the side of
the application of the drive forces in order to cause a pivoting
action of at least one pressing body.
[0013] It is particularly advantageous for a piezoelectric
transducer means to be installed, which possesses at least two
stack translators connected in parallel and rendering possible a
simultaneous opposite operation so that on the one side of the
pivot zone a pulling force is produced and on the other side at the
same time a thrust force may be exerted on the pressing bodies. It
would for instance be possible to utilize a piezoelectric
transducer means as sold by the company "marco Systemanalyse und
Entwicklung GmbH", of 85221 Dachau, Germany under the name of
"Torque-Blocks".
[0014] In order to produce the return motion, opposite to the drive
movement, of the stroke unit it is possible to use a passive spring
means instead of an active actuating means. This spring means could
act between the pressing bodies and/or engage the stroke unit.
[0015] Principally it would be feasible as well to design the
stroke unit like a slide so that it could be displaced on the
pressing faces as part of a sliding movement. In order to ensure a
reliable manner of operation with minimum friction it is however
preferred to utilize a stroke unit in the form of a rolling body
unit, which during its drive movement rolls on the pressing faces
of the pressing bodies. In order to prevent jamming in this
connection the rolling body unit comprises more particularly at
least two independently rotatable rolling bodies, which
respectively engage only one of the pressing faces on the two
pressing bodies so that the one rolling body may roll on the
pressing face of the one pressing body and the other rolling body
may roll on the pressing face of the other pressing body.
[0016] In the case of a further and more particularly advantageous
embodiment of the invention the drive device is provided with two
drive units, which are fitted together as an assembly, the pressing
bodies of the two drive units being so fitted together in pairs as
two flexurally rigid pressing elements that the pressing faces of
the two drive units run apart from opposite sides which face away
from the one another. Using a connecting yoke it is possible then
for the two stroke units present to be so kinematically coupled
that during a drive movement of the respectively one stroke unit
the respectively other stroke unit is entrained and practically
performs the return movement.
[0017] The two pressing elements are mounted in a bearing zone
preferably in a relatively pivoting manner so that a rocking or
see-saw movement of one or both pressing elements may be caused,
always resulting in a movement together of the pressing faces and
simultaneously a movement apart of the pressing faces of the other
drive unit. In the case of a particularly economic design the drive
units are arranged with bilateral symmetry with respect to the
bearing zone.
[0018] The drive movement produced can be transmitted to other
means from any point of the movement unit constituted by the stroke
unit and the connecting yoke. It is more especially convenient
however for such output drive movement to be taken from the
connecting yoke and preferably in the area at the mid point the
between the two stroke units.
[0019] In order to prevent jamming on shifting the movement unit it
has turned out to be expedient to make the connecting yoke so
resiliently elastic in its stroke direction that small relative
movements of the two stroke units are possible in the direction of
the motion produced. This means that inaccuracies in manufacture
are compensated for.
[0020] Further advantageous developments and convenient forms of
the invention will be understood from the following detailed
descriptive disclosure of one embodiment thereof with possible
modifications in conjunction with the accompanying drawings.
LIST OF THE SEVERAL VIEWS OF THE FIGURES
[0021] FIG. 1 shows a preferred embodiment of the drive device of
the invention in a perspective elevation.
[0022] FIG. 2 shows device of FIG. 1 in an inverted position, the
part of the connecting yoke present to the fore and parts of the
stroke units being omitted in order to render the drawing more
straightforward.
[0023] FIG. 3 is a cross section taken through the drive device on
the section line III-III of FIG. 2.
[0024] FIG. 4 is a plan view of the resiliently elastic component
of the connecting yoke looking in the direction of the arrow IV of
FIG. 3.
[0025] FIGS. 5 and 6 show in a diagrammatic elevation various
operational phases of the drive, some possible modifications being
indicated in chained lines as might be adopted in alternative
designs of the invention.
DETAILED ACCOUNT OF WORKING EMBODIMENT OF THE INVENTION
[0026] The drive device 1 illustrated in the drawings comprises two
drive units 2a and 2b integrated as a single assembly, which
possesses bilateral symmetry with respect to a plane containing a
center axis 3.
[0027] Each drive unit 2a and 2b comprises an elongated flexurally
stiff and preferably beam-like first pressing body 4a and 4b
opposite which at a distance there is a second respective pressing
body 5a and 5b. The first pressing bodies 4a and 4b are components
of a rigid elongated first pressing element 6, and the second
pressing bodies 5a and 5b are joined together as a similar second
pressing element 7.
[0028] The two pressing elements 6 and 7 are pivotally mounted in a
bearing zone 8 (for pivoting motion in relation to one another) in
a plane containing the respective pressing elements 6 and 7. The
possible pivotal movements are indicated by double arrows 14. The
bearing zone is located adjacent to the center axis 3.
[0029] The two pressing elements 6 and 7 are clamped together using
attachment elements 13 with a spacer member 12 in between. In the
case of the attachment elements 13 it may, as illustrated, be a
question of attachment screws, which extend through the pressing
element 6, run past on either side of the spacer member 12 and are
screwed into the second pressing element 7.
[0030] In the case of the member 12 it is a question here of
electrically operated drive means 15, which are able to drive the
two pressing elements 5 to perform the pivoting movement 14. They
are biased by the pressing elements 6 and 7 and the attachment
elements 13 acting on same. As related to the bearing zone 8 a
respective rocking or see-saw movement of the pressing elements 6
and 7 is possible so that the elements 6 and 7 can be termed
rocking elements. The angle of pivot is extremely small and may
more particularly be permitted by the elasticity of the pressing
elements 6 and 7 and/or of the attachment elements 13.
[0031] On the mutually facing sides of each first 4a and 4b and
second 5a and 5b pressing body respectively facing first pressing
faces 16a and 16b and second pressing faces 17a and 17b are
provided. They are so designed that within a respective drive unit
2a and 2b a diverging configuration of the mutually opposite first
and second pressing faces 16a, 17a; 16b and 17b results in a drive
direction 18a and 18b extending away from the bearing zone 8. The
respective pressing faces hence extend toward the free end of the
respective pressing element 6 and 7 in a diverging manner, as is
indicated clearly in FIG. 5, where the divergence is
exaggerated.
[0032] The pressing bodies 4a, 5a; 4b and 5b, extending away from
the bearing zone 8 in generally the same direction, of a respective
drive unit 2a and 2b define between them a pressing space 22a and
22b, open toward on the outer side opposite to the bearing zone 8,
in which space a respective stroke unit 23a and 23b is arranged.
Each stroke unit 23a and 23b simultaneously abuts the first and the
second pressing faces of the associated drive unit 2a and 2b. The
contact does however render possible a relative movement of each
stroke unit 23a and 23b while still maintaining contact, along the
respectively associated pressing faces 16, 17a; 17a and 17b, the
direction 24 of movement, in the following termed the "stroke
direction" and indicated by a double arrow, extending in
parallelism to the respective drive direction 18a and 18b.
[0033] Using an essentially rigid connecting yoke 25 the two stroke
units 23a and 23b are coupled together in the stroke direction 24.
The above mentioned components constitute a movement unit 26, which
at all times is only able to be shifted together in a ganged manner
in the stroke direction 24.
[0034] When the drive means 15 is not actuated the pressing bodies
4a, 4b: 5a and 5b assume a home position, which may be identical to
the position indicated in FIG. 5. If the drive means 15 are
actuated, they will in the case of one of the drive units cause a
mutual movement together of the respective pressing bodies and thus
of the pressing faces as well, as is indicated in FIG. 6. Here a
condition is illustrated in the case of which the first and the
second pressing faces 16a and 17a of the first drive unit 2a have
moved together each other, something which owing to the above
mentioned pivoting caused by the rocking movement results in the
first and the second pressing faces 16b and 17b of the second drive
unit 2b moving farther apart.
[0035] The drive means 15 may be so actuated that as regards the
increase and the reduction of the mutually opposite pressing faces
of the two drive units 2a and 2b a state is reached which is just
the reverse of the that of FIG. 6.
[0036] Owing to the drawing together of the pressing faces there
will be, because of the diverging configuration of the faces in the
home position, a displacement of the associated stroke unit 23a and
23b in the respective drive direction 18a and 18b, the stroke unit
running on the associated pressing faces. Dependent on the
direction of pivoting of the pressing elements 6 and 7 therefore
the one or other stroke unit 23a and 23b is forced outward. The
corresponding movement of the stroke unit, in the case of which it
is preferably a question of a strictly linear movement, can be
transmitted to drive any desired external means or, respectively,
any component for power output.
[0037] Since the stroke units 23a and 23b are joined together by
way of the connecting yoke 25 as a moving unit 26, on forcing one
respective stroke unit out of the way the other stroke unit will be
simultaneously entrained and shifted into the interior of the
associated pressing space 22 toward the bearing zone 8. Since the
pressing faces of the two drive units 2a and 2b are identical in
design, it is possible to ensure reliable operation without trouble
conditions.
[0038] The drive movement produced may be transmitted from any
suitable point on the movement unit 26. However, transmission from
the connecting yoke 25 is recommended, which for this purpose may
have a suitable force coupling means 27 (f. i. an attachment means)
rendering possible the attachment of a component to be moved.
[0039] It is particularly preferred to transmit force from the
median region of the connecting yoke 25 between the two spaced
stroke units 23a and 23b.
[0040] By suitable selection of the configuration of the pressing
faces 16 and 17--when reference is made to identical components of
the two drive units 2a and 2b, this will be with the omission of
the index letter "a" and "b"--the operating characteristics of the
drive device 1 may be customized for the user. There is more
particularly the possibility of an optimum adaptation of the
force-stroke characteristic of the drive movement which is
transmitted, to suit each individual case in the best possible
way.
[0041] It would for example be possible--considering the home
position in accordance with FIG. 5--provide respectively only one
pressing face on a respective drive unit 2a and 2b with an inclined
configuration in relation to the resulting drive direction 18a and
18b. It has turned out however that an improved movement
characteristic results when both pressing faces 16a, 17a; 16b and
17b of a respective drive unit 2a and 2b have an oblique
configuration, it being preferred for there to be identical angles
of inclination in relation to the desired stroke direction 24.
[0042] There is furthermore the possibility of so designing that
the face configuration of the pressing faces in the respectively
associated drive direction 18a and 18b, that is to say toward the
free end of a respective pressing element 6 and 7, is not linear as
in the drawings, but curved with an arcuate or curved shape, as is
indicated in FIG. 5 at 28 in chained lines.
[0043] Dependent on how the drive device 1 is held during use--it
is preferred for it to be accommodate in a housing not illustrated
in detail--it is possible on actuation of the drive means 15 for
either both pressing elements 6 and 7 to be actuated simultaneously
or only of them to perform a movement.
[0044] The drive device 1 of the embodiment of the invention is
characterized by the possibility of being produced with a
particularly small size. This is associated with the fact that as a
drive means 15 a piezoelectric transducer means is employed, which
may be optimally adapted to the intermediate space between the two
pressing elements 6 and 7.
[0045] The piezoelectric transducer means preferably has a stack
translator design, there being in the working example two
adjacently placed stack translator units 28a and 28b, which however
may be integrated with each other as a single assembly. The two
stack translator units 28a and 28b are so arranged that they engage
the pressing elements on either side of the center 32 of pivot of a
respective pressing element 6 and 7. As related to the region of
the center 32 of pivoting the one stack translator unit 28a is on
the side facing the one stroke unit 28a and the other stack
translator unit 28b is on the side facing the other stroke unit
23b.
[0046] By means of the attachment elements 13 the pressing elements
6 and 7 are thrust with a certain biasing effect from opposite
sides against the two stack translator units 28a and 28b. During
operation the two stack translator units 28a and 28b are connected
in parallel and they are operated in the opposite direction
simultaneously so that one stack translator unit is shortened and
the other one is extended in length. The stack translator unit
which is extended in length thrusts against the associated pressing
bodies so that same are spread apart and acting as a two-armed
(second class) lever cause a pivoting movement 14 accompanied by a
mutual movement together of the pressing bodies of the other drive
unit. Since the other stack translator unit is shortened at the
same time, it does not hinder the movement together of the
associated pressing bodies. It is even possible to provide a
connection able to resist pulling forces, between the stack
translator units and the pressing bodies, which will ensure that
the pressing bodies are additionally actively drawn together by the
shortening of the stack translator unit.
[0047] As a piezoelectric transducer means it would for instance be
possible to utilize a piezoelectric transducer means as sold by the
company "marco Systemanalyse und Entwicklung GmbH", of 85221
Dachau, Germany under the name of "Torque-Blocks". It is a question
here practically of an active rotary joint with the faces center as
an axis of rotation. The angles of rocking and the rigidity are
selected more particularly by varying the length, thickness the
width of the block as may be desired.
[0048] It is more particularly in the case of designs with a large
overall volume that instead of electrical drive means the use of
fluid driven drive means could come into question, as for instance
linear motors or traction elements designed like hoses or flexible
tubes which shorten when pressurized. Such drives are sold by the
assignee under the trade name of "Fluidic Muscles" and are for
instance described in the European patent publication 0 161 750 B1
so that a more detailed description is not necessary at this
point.
[0049] In FIG. 6 arrows 33a and 33b again indicate the pulling or
traction and thrust direction of the drive means, when the movement
unit 26 is to be shifted in the first drive direction 18a.
[0050] The drive device 1 of the embodiment of the invention offers
the advantage that drive movements may be produced in two opposite
drive directions 18a and 18b may be produced by active drive means
15 in connection with the application of external energy and force
may be supplied by the device. However it would also be feasible to
provide the return movement opposite to a drive movement by passive
drive means, a spring means being more particularly considered as
is indicate FIG. 5 in chained lines at 34. It is able to return the
movement unit 26 after deactivation of the drive means 15 from the
displaced position into the starting position, the contact with the
associated pressing faces ensuring simultaneous return of the
pressing elements 6 and 7 into the home position.
[0051] As an alternative or in addition to a spring means, which
operates between the movement unit 26 and at least one pressing
body, it would also be possible to employ a further spring means
35, which is again indicated in FIG. 5 in chained lines, such means
being effective between the two spaced pressing bodies of the one
of the drive units.
[0052] It would in principle be possible to design the stroke units
23a and 23b as sliding units, which during the drive movement slide
on the associated pressing faces 16 and 17. Preferably however a
design in the form of rolling body units 36a and 36b is employed,
which is substantially better as regards frictional resistance,
such design being used in the embodiment of the invention. The
rolling body units 36a and 36b roll along the associated pressing
faces in the course of the drive movement.
[0053] In order to prevent jamming or locking the rolling body
units 36 possess two coaxially aligned rolling bodies 37 and 38
which are able to be rotated independently and which engage only
one of the pressing faces 16 and 17 of the two associated pressing
bodies 4 and 5. Thus while one rolling body cooperates exclusively
with the one pressing face 16, the other rolling body 38 cooperates
exclusively with the other pressing face 17 so that during the
drive movement there will be an opposite rotary movement of the two
rolling bodies 37 and 38 of a respective rolling body unit 36.
[0054] A preferred design is more particularly clearly depicted in
the sectional view of FIG. 3. Here there is a rolling-like or
wheel-like inner rolling body 37, which is flanked axially on
either side by two parts 42 of an external rolling body 38.
Ignoring the division of the outer rolling body 38, same will be
seen to have a H-like cross section, the inner rolling body 37
being seated coaxially on the connecting rib or web of the letter
H. Owing to the division the fitting of the inner rolling body 37
is rendered possible, the two parts 42 preferably being identical
in form.
[0055] Between the two rolling bodies 37 and 38 there is a
coaxially placed bearing means 43, preferably constituted by a
rolling element or anti-friction bearing means, f. i. in the form
of a bearing sleeve, radially holding the two rolling bodies 37 and
38 in relation to one another and which simultaneously ensures free
relative rotation of the two rolling bodies 37 and 38. The axis of
rotation 44 coincides with the longitudinal axis of the rolling
bodies 37 and 38.
[0056] An outwardly facing first running face 45 of the inner
rolling body 37 is in constant rolling engagement with the first
pressing face 16 of the first pressing body 4. The second running
face 46, cooperating with the second pressing body 5, of the outer
rolling body 38 is divided up into face sections at the two rolling
body parts 42, such face sections accordingly cooperating with a
second pressing face 17, such second face being laterally offset in
relation to the first pressing face 16 in the direction of the axis
44 of rotation, the face 17, which in this case engage the arms 47
(which are parallel to each other) of the second pressing body 5.
These arms are laterally spaced apart so that a collision with the
inner intermediately placed rolling body 37 is avoided. The second
pressing face is accordingly also divided up into spaced apart face
sections.
[0057] Connecting means 48, f. i. connecting screws, hold each
respective rolling body unit 36 together and preferably serve at
the same time to fix the connecting yoke 25. In the working
embodiment illustrated this yoke comprises two mutually parallel
strut-, rail- or rod-like connecting elements 49, which extend from
the two axial outer sides and are mounted on the respective stroke
unit 23 and extend between the two stroke units. They extend
externally past the drive means 15 and attachment elements 13
arranged adjacent to the bearing zone 8.
[0058] Investigations have shown that even in an ideal case and
with an identical design of the pressing faces 16 and 17 the
strokes of the stroke units 23 differ. In order to compensate for
this the connecting yoke is preferably made so resiliently elastic
in its stroke direction that small relative movements of the two
stroke units 23 are possible in the stroke direction 24. In the
working embodiment illustrated this is made possible because of a
slightly curved form of the connecting elements 49 consisting of
resiliently elastic material, such curved form coinciding with the
stroke direction 45, one of such connecting elements being depicted
in FIG. 4. It will be clear that the deformation region 52, which
renders possible a certain elastic deformation, could be produced
by other configurations of the connecting yoke 25. In any case the
elastic design of the connecting yoke 25 does offer the advantage
of allowing for inaccuracies in manufacture and thus countering any
accidental jamming of the moving components.
[0059] In order to ensure that the stroke units 23 exactly follow
the associated pressing faces 16 and 17 during their displacement
additional guide means 53 may be provided in case of need. Such
means preferably act between a respective stroke unit 23 and at
least one associated pressing body 4 and 5. In the working
embodiment illustrated the guide means 53 take effect between the
inner rolling body 37 and the associated first pressing body 4
because at least one annular groove is formed in the first running
face 45, into which groove a longitudinal projection provided on
the first pressing face 16 fits. This arrangement may also be
reversed with the groove and the projection in and on the
respectively other parts.
[0060] While the drive device 1 of the working example possesses
two drive units 2a and 2b, it would naturally be possible as well
to design the device 1 with only one drive unit. As related to the
diagrammatic view of FIG. 5 then for example the second drive unit
2b would be left out and the first drive unit 2a would terminate at
the chained line 54 adjacent to bearing zone 8. The two pressing
bodies 4a and 4b could here, together with the bearing zone 8, form
a generally U-like configuration, the single stroke unit 23a being
returned, after causing the drive movement, by a spring means 34
into the starting position. In other respects the explanations so
far on the drive device 1 would apply as regards the drive device
provided with only one drive unit.
[0061] By way of conclusion there will now follow a general
explanation of the preferred design and manner of operation of the
drive device. As we have seen the drive means 15 may be constituted
by a piezoelectric flexural actuator, which on operation undergoes
deflection through an angle of bend. The torque produced by this
actuator is transmitted to the flexurally rigid, beam-like pressing
elements 6 and 7, whose inner faces open or diverge obliquely
outwardly so that a sort of scissors is formed. If the flexural
actuator is now deflected in one direction, on the one side there
will be an increase of the angles defined by the inner faces and,
respectively, the pressing faces 16 and 17 and on the other side a
decrease. A rolling system 36 employed here, which is connected by
the connecting yoke 25, consequently performs a linear movement at
a right angle to the longitudinal extent of the drive means 15 and,
respectively, to the middle axis 3. Then the rolling body unit of
the closing scissors will be actively driven. Owing to the design
of the rolling body unit with an inner wheel and a two-part outer
wheel, which are connected together by way of a bearing means 43,
jamming of the system is prevented.
[0062] In the case of depicted "double scissors drive" the
connecting yoke 25 should be made elastic in the case of a
straight, oblique arrangement of the pressing faces 16 and 17,
since the two rolling body units 36 moved in relation to one
another on alternate opening of the drive units, something which,
if there is no possibility of compensation, might result in jamming
of the drive. An elastic connecting yoke 25 is furthermore also
advantageous in order to ensure play-free engagement of the rolling
bodies 37 and 38 with the pressing faces 16 and 17. In order to
prevent relative motion of the second rolling body units 36, it
would however be possible to provide specially designed pressing
faces 16 and 17, which would not be straight but curved.
[0063] The drive device may be designed as a "double scissors
drive" with two drive units or also as a "single scissors drive"
functioning with a single spring and having only one drive
unit.
[0064] The drive device may be manufactured to be compact and
simple. Furthermore, the force-stroke ratio may be selected freely
selected in limits and essentially depends of the angle of
inclination of the pressing faces 16 and 17. In the case of use of
a piezoelectric transducer as a drive means it is accordingly
possible to produce a drive system having a lower power requirement
and capable of continuously operating, which for instance may be
utilized for the drive of valves.
* * * * *