WO2005073591A1 - Gripping element wherein a mechanical element is maintained - Google Patents

Abstract

The invention relates to a gripping element wherein a mechanical element is maintained. Said gripping element can be embodied as a rigid gripping element or comprises at least two bearings, preferably a rigid bearing (2) and a moveable bearing (3). The aim of the invention is to compensate in a simple and safe manner alternating loads acting upon the maintained mechanical element. The inventive gripping element is embodied in such a manner that at least one actuator (4), which is suitable for introducing forces and/or torque into the element, is disposed on the gripping element or forms one part of said gripping element.

Description

Clamping in which a mechanical element is held

The invention relates to a clamping in which a mechanical element is held. The clamping can be designed as a fixed clamping or can be formed with at least two bearings, preferably with a fixed and a floating bearing. The use of the solution according to the invention can preferably be used for mechanical elements which are exposed to dynamically changing loads and very preferably occur frequently changing dynamic loads which are not subject to strict rules.

For example, it is often desirable to hold mechanical elements in clamps that are statically determined and for which a calculation can be made with regard to the strengths.

Of course, there are also possibilities to calculate the required strengths in advance when dynamic loads occur and to provide a corresponding proof of strength.

However, many disadvantages cannot be eliminated with conventional solutions, in particular in the case of non-static loads which act on appropriately clamped mechanical elements. As a result of alternating stresses that attack such elements, vibrations can be excited that not only impair the strength of the respective clamping and the elements, but such vibrations can occur in the frequency range of infrasound, the audible and also in the ultrasound range. In particular, the audible sound wave range significantly affects the respective application and there are consequently, often complex measures for a necessary sound insulation to be provided.

This situation is also important, since such sound waves are also converted into structure-borne noise via the fixed clamping and are accordingly also transmitted to other locations.

The problems mentioned do not only occur in the sound wave range, but vibrations on mechanical elements are also excited during their movement by corresponding accelerated movements of the respective elements. This can occur, for example, in the case of corresponding positioning movements of mechanical elements, in which they are moved linearly together with the clamping or are set in rotation until a desired position has been reached and shortly before reaching the respective position, the movement down to a speed of “ 0 "has been slowed down.

As a result of the inertia of mechanical elements, an oscillation then also occurs on the mechanical element, which in many cases has to subside before, for example, an exact measurement can be made

With the help of a probe that functions as a mechanical element or, for example, a lever arm or part of a lever arm that is to be used for manipulating further elements, for example as part of an industrial robot.

It is therefore an object of the invention to propose a possibility with which alternating stresses acting on mechanical elements held in a clamping can be easily and reliably compensated for. According to the invention, this object is achieved with the features of claim 1. Advantageous embodiments and further developments of the invention can be achieved with the features specified in the subordinate claims.

In the solution according to the invention, a mechanical element is held in one clamping and at least one actuator is arranged on the clamping, with which forces and / or moments can be introduced into the element. The at least one actuator can also be a part (e.g. a bearing) of the clamping. The at least one actuator is arranged directly on the clamping. It can be arranged between two bearings or fixed clamps. There is the possibility that it is either arranged between the fixed bearing and the floating bearing or that the respective actuator directly forms a bearing of the clamping, preferably a floating bearing.

Depending on the arrangement and orientation of such actuators, forces and moments counteracting these can be applied in a targeted manner in accordance with the forces acting on the mechanical elements.

It is thus possible to use actuators to preload mechanical elements with specific compressive or tensile forces exerted on them.

For example, forces acting parallel or orthogonally with respect to predetermined axes on the respective mechanical element can be applied.

With such forces or moments acting on the respective mechanical element or a desired deformation of the mechanical element (es) can be achieved.

A variation of the forces or moments introduced can also be achieved by changing the distance of an actuator from the fixed clamping or a bearing of a clamping, which e.g. is possible by moving the actuator.

In addition to the pretensioning forces and / or moments already mentioned, the actuators to be used according to the invention can also be used to react to dynamic forces or moments which act on the respective mechanical element, so that they can be partially or completely compensated for.

This can be achieved, for example, by introducing correspondingly time-shifted or with a suitable phase shift into the mechanical elements in the area of the clamping in the mechanical elements in the area of the clamping, or forces or moments counteracting the forces or moments acting on the mechanical elements from the outside.

Not only the respective amplitudes, but also the frequency and accordingly the wavelength with which dynamic external loads act on the respective mechanical element can be taken into account. So there is at least the possibility of using an actuator to be used according to the invention

Damping, possibly in conjunction with suspension or even to achieve extinction.

In the case of vibrations with an almost constant frequency, which have been initiated by forces or moments exerted on the mechanical elements from outside, These can be at least almost completely compensated for if a corresponding counter-oscillation shifted by IT is introduced into the respective mechanical element by means of at least one actuator, so that there are extinction effects with a corresponding amplitude and energy of the vibrations introduced into the mechanical element by means of the actuators.

With a suitable detection of the vibrations introduced into the mechanical elements from the outside, e.g. A suitable influence on the actuators can also be exerted by means of a suitable sensor system with corresponding electronic control, so that it is also possible to react to frequencies and amplitudes that change over time. ,

An example of this are clamped flat flat elements. Such flat planar elements can be planar or at least partially curved.

The invention can accordingly be used on windows of buildings, as well as on windows of vehicles, in which an influence from the outside due to different wind or wind forces occurs, which leads to vibrations of such flat elements, which then not only additional mechanical stresses on the causes the respective tensions, but also increase the sound level, whereby sound waves are also transmitted through the frame as structure-borne sound.

In the latter case, the different materials can also cause frequency shifts that shift the vibrations into frequency ranges that are unfavorable for the environment. In the case of the windows or panes of vehicles mentioned in particular, the arrangement of the actuators according to the invention is favorable, since they can then be arranged outside the transparent visible surface and lines connected to the respective actuators can also be laid in a concealed arrangement, for example within a frame.

In the case of such plate-shaped elements, such as window panes or panes of vehicles, these are usually held in a radially circumferential clamping. The actuators according to the invention can then be arranged at various points on an outer edge of such a plate-shaped element, that is to say following the fixed clamping or on fixed bearings, and can accordingly introduce their force or moment into such a mechanical element.

In such a case, several actuators can also be individually controlled and activated on a flat element at the different locations, in which case the forces or moments acting on such a flat element from the outside can then be taken into account.

In many cases, however, it can also be advantageous to use different actuators with which, for example, forces or moments with different amplitudes and / or directions of action can be introduced into such a mechanical element.

In addition to such flat elements, rod-shaped elements such as lever arms or parts of lever arms can also be used in conjunction with the one according to the invention

Solution, as clamped mechanical elements be set. These can be, for example, the arms of industrial robots or measuring probes, as was mentioned in the introductory part of the description.

Such lever arms can usually be moved in translation or rotated together with their clamping. In the case of such movements, the alternating accelerations acting on the mechanical elements, which are compensated by means of the actuators, can at least be considerably damped, so that when a speed of “0” is reached, such mechanical elements are either not damped at all or only very strongly via one after a very short period of time.

This can, for example, shorten the time required to carry out a work step or process step.

Actuators to be used according to the invention, in particular if they are arranged between a fixed bearing and a floating bearing of a clamping, can be firmly connected to one another with the respective mechanical element. The connection can be made materially, non-positively and / or positively. Suitable joining methods are, for example, gluing, this being possible over the entire surface of a suitable surface of the respective mechanical element. However, it is also conceivable to include actuators in a correspondingly dimensioned and designed surface contour, alone or in addition to a material connection.

Such a corresponding surface contour can further influence the respective introduction of force or torque into the respective mechanical element be taken, which also applies to the respective axis position and direction.

Piezo elements are particularly preferred for actuators to be used according to the invention, since forces and moments are applied with very small time constants and a very high frequency and these can be controlled electronically favorably, and very high forces and moments can also be achieved.

However, other suitable materials can also be used on actuators, the volume or shape of which can be changed in a targeted manner from the outside.

This applies, for example, to suitable magneto- or electro-strictive ceramics, electro- or magnetorheological liquids, which can be influenced electrically or magnetically in their properties, so that a targeted influencing of forces and moments acting on mechanical elements can be achieved.

In particular for applications in which very short reaction times are not important, shape memory alloys are also suitable materials that can be used as an actuator or for partial elements of actuators. The effect is exploited here that, at a so-called “jump temperature”, the shape changes from one state to a second state when such an actuator is exceeded or undershot, which can also be advantageous for certain applications.

For example, shape memory alloys, referred to as “nitinol”, in which nickel and titanium are the essential alloying elements, are known. This alloy has a crack temperature of approx. 37 ° C, the respective transition temperature of such a shape memory alloy can also be changed within limits by means of the respective alloy composition, so that transition temperatures at approximately 20 ° C or even 25 ° C are also possible.

As already briefly indicated, the invention can be particularly advantageously further developed in that at least one sensor is arranged on the element, the fixed bearing and / or the floating bearing, that is to say as far as possible in the region of the respective clamping. Via such a sensor, paths, forces, pressures, accelerations and / or vibrations that act on the respective mechanical element can be detected and transmitted as measuring signals to an electronic control, for example. Such an electronic control can then control the actuator (s) so that the respective forces and moments to be exerted with the actuators can be influenced in a targeted manner. This applies both to the respective magnitude of the forces or moments per se, but also to their temporal behavior in the case of dynamically changing loads acting on mechanical elements, that is to say, for example, the respective frequency.

In the case of externally moving mechanical elements which are moved or rotated in a translatory manner, a changing acceleration of the respective movement can be detected with the aid of an acceleration sensor. Since the inertia of such mechanical elements is generally known, an actuator can be promptly activated when a detected changing acceleration of the movement, for example a braking process, so that one

Reverberation of the respective mechanical element can not be counteracted only when a target position of a moving mechanical element is reached, but countermeasures can be taken beforehand via activated actuators.

In the case of windscreens of vehicles, however, the driving speed determined in each case can also represent a control variable for activating actuators on such a windshield. The actuators on such windscreens can also be controlled with the assistance of an acceleration sensor, so that changes in the driving speed of the respective vehicles can also be taken into account more quickly.

The invention will be explained in more detail below by way of example.

Show:

FIG. 1 shows in schematic form an example of a clamping with an actuator which is arranged between a fixed bearing and a floating bearing,

Figure 2 shows an example in which an actuator forms a floating bearing for clamping a mechanical element and

FIG. 3 shows a schematic illustration of an example, in which an actuator is in turn arranged between a fixed bearing and a floating bearing of a clamping of a mechanical element. An example of a solution according to the invention is to be illustrated in schematic form with FIG.

In this case, a mechanical element 1, which can be rod-shaped or plate-shaped, for example, is held in place by means of a fixed bearing 2 and a floating bearing 3, which are arranged at a distance from one another.

Between the fixed bearing 2 and the floating bearing 3, an actuator 4 is firmly connected to the mechanical element 1 on one surface, for example by adhesive bonding.

In this example, the actuator 4 is a piezoelectric element which, when the electrical voltage is correspondingly applied, can expand, as indicated by the arrows. The respective linear expansion of the piezoelectric element is proportional to the respective electrical voltage.

Due to the length expansion / changes, specific moments can be introduced into the mechanical element 1, which can lead to a preload of the mechanical element 1 and possibly also to a deformation.

A deformation also causes the distances between the fixed bearing 2 and the floating bearing 3 to change within limits, as a result of which a targeted influence on the forces and moments that can be absorbed by the fixed bearing 2 and floating bearing 3 can be achieved. Such a deformation can influence the transition conditions based on the clamping by changing the curvature / inclination. As indicated by the arrow pointing vertically upwards, forces acting on the mechanical element 1 can be compensated for, or at least counteracted, so that the appropriate activation and activation of the actuator 4 influences the shape, position and vibration of a corresponding mechanical element Element 1 is possible.

The example shown in FIG. 2 is intended to illustrate another alternative.

Here, too, a fixed bearing 2 and a floating bearing 3 form the clamping of a mechanical element 1, the floating bearing 3 simultaneously representing the actuator 4. This can in turn be a piezoelectric element, which changes its length due to the applied electrical voltage and, due to the change in length, a force, as indicated by the double arrow, on the mechanical element 1 parallel to a force which is schematically indicated by the arrow pointing vertically upwards and to the right indicated on a mechanical element 1 external force is exerted.

A change in length of the piezoelectric element, as an actuator 4, leads to a targeted introduction of force onto the mechanical element 1 and consequently the overall force relationships of the mechanical system change. Here, too, the transition conditions (inclination / curvature) can be influenced starting from the clamping to the non-fixed area of the mechanical element 1.

Deformations of the mechanical element 1 can thus be compensated for by forces or moments acting on it from the outside by the coupling of forces in the area of the floating bearing 2 by the actuator 4. Ren or can at least be counteracted, so that a targeted influence on shape, position and vibration can be taken.

The example shown in FIG. 3 again has an actuator 4, which is arranged between the fixed bearing 2 and the floating bearing 3 and acts on the mechanical element 1.

In contrast to the example according to FIG. 1, by changing the length, as indicated by the double arrow on the actuator 4, a corresponding compressive force and possibly also a tensile force acting in the direction of the normal force can be applied, in this area the mechanical element 1 via the Actuator 4 can be counteracted pressure forces opposed, for example, to forces acting in the vertical direction from bottom to top on a mechanical element 1, as indicated with the case arranged on the right.

Of course, in all the examples shown in FIGS. 1 to 3, forces and moments that change over time can also be exerted via the actuators 4, which can take into account corresponding alternating stresses on the mechanical element.

Claims

claims 1. Clamping in which a mechanical element is held, at least one actuator (4) suitable for introducing forces and / or moments into the element (1) is arranged on the clamping or forms part of the clamping. 2. Clamping according to claim 1, characterized in that the clamping is formed from at least two bearings. 3. Clamping according to claim 1 or 2, characterized in that the clamping is formed from a fixed bearing (2) and a floating bearing (3). 4. clamping according to claim 1 or 2, characterized in that the actuator (4) forms a bearing of the clamping. 5. clamping according to claim 3, characterized in that the actuator (4) forms a floating bearing of the clamping. 6. Clamping according to one of the preceding claims, characterized in that the actuator (4) is arranged between the fixed bearing (2) and the floating bearing (3) and engages there on the element (1). 7. Clamping according to one of the preceding claims, characterized in that the clamping is designed as a fixed clamping. 8. clamping according to one of the preceding claims, characterized in that the ele- ment (1) a lever arm, part of a lever arm or is formed as a flat element. 9. Clamping according to one of the preceding claims, characterized in that actuators (4) act on the element (1) with different directions of action. 10. clamping according to one of the preceding claims, characterized in that the distance between the actuator (4) and a fixed clamping or a fixed bearing (2 or 3) is variable. 11. Clamping according to one of the preceding claims, characterized in that the at least one actuator (4) is designed as a piezo element. 12. Clamping according to one of the preceding claims, characterized in that an electrostrictive or magnetostrictive ceramic, an electro- or magnetorheological fluid is present on / at the actuator (s) (4). 13. Clamping according to one of the preceding claims, characterized in that an actuator (4) consists of a shape memory alloy or a partial element is made of a shape memory alloy. 14. Clamping according to one of the preceding claims, characterized in that an actuator (4) between the fixed bearing (2) and the floating bearing (3) is materially, non-positively and / or positively connected to the element (1). 15. Clamping according to one of the preceding claims, characterized in that the element (1) is a planar or at least partially curved disc. 16. Clamping according to one of the preceding claims, characterized in that an actuator (4) is arranged on the outer edge of the element (1) in connection with a fixed bearing (2). 17. Clamping according to one of the preceding claims, characterized in that at least one sensor is arranged on the element (1), the fixed bearing (2) and / or the floating bearing (3). 18. Clamping according to claim 11, characterized in that the sensor is a displacement, force, pressure, acceleration and / or a vibration sensor. 19. Clamping according to one of the preceding claims, characterized in that the at least one actuator (4) and / or sensor are connected to an electronic control.