Patent ID: 12196189

Elements of identical design or function are provided with the same reference signs across all figures.

Reference is made firstly toFIG.1, which shows a schematic view of an embodiment of a linear drive10according to the invention. The linear drive10can be used for positioning tasks, for valves, for adjusting optical systems or in other applications.

The linear drive10comprises a lever element12which has a through bore14, a first portion16spaced from the through bore14and a second portion18spaced from the first portion16and the through bore14. The second portion18is arranged between the through bore14and the first portion16.

The linear drive10furthermore comprises a rod element20which extends along a rod axis22and through the through bore14.

The linear drive10furthermore comprises a bearing element24. The bearing element24supports the rod element20in such a way that a movement of the rod element20is possible only along the rod axis22and a movement perpendicular to the rod axis22is blocked. In the specific case ofFIG.1, the bearing element24has a first bearing24A and a second bearing24B. The first bearing24A is also located on a first side of the lever member12and the second bearing24B is located on a second side of the lever element12opposite the first side. In other words, the two bearings24A and24B are located on opposite sides with respect to the lever member12.

The linear drive10furthermore comprises a shape memory alloy element28extending along a first axis26. In the specific example ofFIG.1, the shape memory alloy element28is designed as a shape memory alloy wire. By applying electrical power to the shape memory alloy element28, the length thereof can be adjusted. The application of electrical power to the shape memory alloy element28causes the shape memory alloy element28to heat up and, as a result, shortening of the shape memory alloy element28takes place, as is known to the person skilled in the art for such elements. In this case, an increasing shortening of the shape memory alloy element28can take place when electrical power with an increasing electrical power value is applied. However, an increasing shortening of the shape memory alloy element28can also take place when electrical power with a constant electrical power value is applied, because over a longer period of time the energy input into the shape memory alloy element28increases even in the event of a constant power value, as a result of which said shape memory alloy element is increasingly shortened further.

A first end30of the shape memory alloy element28is connected to the first portion16of the lever element12. A second end32of the shape memory alloy element28opposite the first end30is stationarily connected to a fixed bearing34.

The shape memory alloy element28is designed in such a way that, when electrical power is applied to it, it exerts a tensile force acting along the first axis26on the lever element12. The tensile force occurs by shortening of the length of the shape memory alloy element28when electrical power is applied.

The linear drive10furthermore comprises a restoring element38extending along a second axis36. In the specific example ofFIG.1, the restoring element38is designed as a spring element. A first end40of the restoring element38is connected to the second portion18of the lever element12and a second end42of the restoring element38opposite the first end40is stationarily connected to a second fixed bearing44.

The restoring element38is configured in such a way that it exerts a restoring force acting on the lever element12along the second axis36and counter to the tensile force exerted by the shape memory alloy element28.

In the specific example ofFIG.1, when electrical power is applied to the shape memory alloy element28, the tensile force would act downward and the restoring force of the restoring element38would act upward in the opposite direction.

As is furthermore shown inFIG.1, in the specific example ofFIG.1the rod axis22, the first axis26and the second axis36are all arranged parallel to one another. In other embodiments which are not shown, this need not be the case.

By appropriately activating the shape memory alloy element28, it is now possible to move the rod element20along the rod axis22, as is described in more detail in conjunction withFIGS.2to5. The movement of the rod element20along the rod axis22can then be used for the applications described at the beginning, such as, for example, for positioning tasks or the like. For this purpose, the linear drive10has four prominent states, which will now be explained below in conjunction withFIGS.2to5.

Reference will be made firstly toFIG.2, which shows the linear drive10in a first state.

In the first state, electrical power with a first power value is applied to the shape memory alloy element28. The application of a first power value to the shape memory alloy element28results in the shape memory alloy element28being shortened such that the lever element12tilts because of the tensile force exerted by the shape memory alloy element28. In the specific example ofFIG.2, the tensile force acts downward such that the lever element12tilts clockwise. The tilting of the lever element12takes place about an axis of rotation which is arranged substantially perpendicularly to the second axis36and intersects the latter.

Tilting the lever element12in a clockwise direction creates a non-positive connection between the lever element12and the rod element20. The first power value for electrically applying to the shape memory alloy element28is adapted to a diameter of the rod element12and to a diameter of the through bore14in such a way that, because of the shortening of the shape memory alloy element28, tilting of the lever element12by a predetermined angle leads to a non-positive connection between the lever element12and the rod element20. The non-positive connection is distinguished in that forces can be transmitted between the lever element12and the rod element20without the lever element12being able to move in the direction of the rod axis22relative to the rod element20.

The non-positive connection will be explained in more detail in conjunction withFIG.6.

As is also shown inFIG.2, the linear drive10furthermore has two position contacts. A first position contact is an initial position contact46. A second position contact is an end position contact48. The position contacts46,48are used to signal the respective states of the linear drive10, as will be explained later in more detail.

Reference will now be made toFIG.3, which shows the linear drive10in a second state following the first state (FIG.2).

In the second state, electrical power with a second power value, which is greater than or equal to the first power value, is applied to the shape memory alloy element28. By application of the second power value to the shape memory alloy element28, the shape memory alloy element28is shortened further. The further shortening occurs, for example, when the second power value is equal to the first power value, but because of a longer period of time for which electrical power is applied to the shape memory alloy element28, the amount of energy introduced into the shape memory alloy element28overall is increased and, as a result, further conversion processes take place in the shape memory alloy element28. Alternatively or additionally, the shape memory alloy element28can also be further shortened by the second power value being greater than the first power value. However, this is not absolutely necessary.

As can be seen by comparingFIG.3withFIG.2, in the second state the already tilted lever element12is displaced parallel along the first axis26in the direction of the tensile force exerted by the shape memory alloy element28. Since the tilting of lever element12results in a non-positive connection between the rod element20and the lever element12, a parallel displacement of the tilted lever element12leads to an associated movement of the rod element20along the rod axis22and in the direction of the tensile force exerted on the lever element12by the shape memory alloy element28.

As can furthermore be seen inFIG.3, the end position contact48contacts the tilted lever element12, which is displaced parallel in the direction of the tensile force, and thereby signals that the second state has been reached. The end position contact48indicates the earliest possible point in time from which it is possible to change from the second power value to a third power value, explained in conjunction withFIG.4, for applying electrical power to the shape memory alloy element28.

The end position contact48contacts the lever element12at an end position contact portion50, which is arranged such that the first portion16, to which the shape memory alloy element28is fastened, and the second portion18, to which the restoring element38is fastened, are arranged between the through bore14and the end position contact portion50. The advantage of this arrangement is that now, owing to the contact of the lever element12with the end position contact48, an at least partial tilting back of the lever element12, in the present case directed counterclockwise, is initiated, specifically about an axis of rotation which is arranged in the region of the end position contact portion50or in the region of the end position contact48.

As can also be seen inFIG.3, the lever element12has no contact with the initial position contact46in the second state.

Reference will now be made toFIG.4, which shows the linear drive10in a third state following the second state (FIG.3).

In the third state, electrical power with a third power value, which is smaller than the first power value, is applied to the shape memory alloy element28. The third power value can be, for example, a power value of zero, which means that electrical power is no longer applied to the shape memory alloy element28. Of course, however, a third power value that is lower than the first power value can also be selected, wherein, in such a case, electrical power would continue to be applied to the shape memory alloy element28, but with a third power value that is lower than the first power value.

In the third state, the shape memory alloy element28is at least partially lengthened again. In the present case, the lever element12is thus at least partially tilted back counterclockwise. This at least partial tilting back of the lever element12can be initiated by the already mentioned contact between the lever element12and the end position contact48. The result is that, because of the at least partial tilting back of the lever element12, the non-positive connection between the lever element12and the rod element20is released. This enables a relative movement of the lever element12relative to the rod element20along the rod axis22.

Reference will now be made toFIG.5, which shows the linear drive10in a fourth state following the third state (FIG.4).

In the fourth state, electrical power with a fourth power value, which is smaller than or equal to the third power value, is applied to the shape memory alloy element28. For example, the fourth power value can again be a power value of zero, which means that electrical power is still not applied to the shape memory alloy element28.

In the fourth state, the at least partially tilted back lever element12is displaced parallel along the second axis36in the direction of the restoring force exerted by the restoring element38on the lever element12. Since there is no non-positive connection between the lever element12and the rod element20, there is no movement (back) of the rod element20in the direction of the restoring force exerted by the restoring element38. In an example which is not illustrated, the bearing element24or the two bearings24A and24B can be designed in such a way that a movement of the rod element20in the direction of the restoring force acting on the lever element12is blocked.

As is also shown inFIG.5, in the fourth state there is no contact between the lever element12and the end position contact48. However, the at least partially tilted-back lever element12makes contact with the initial position contact46. The initial position contact46signals the fourth state and indicates the earliest possible point in time from which it is possible to change from the fourth power value to the first power value and thereby start a new cycle.

As shown inFIG.5, the initial position contact46contacts the lever element12at an initial position contact portion52of the lever element12, which is arranged in such a way that the initial position contact portion52is arranged between the through bore14and the second portion18of the lever element12. This arrangement has the advantage that, when the lever element12comes into contact with the initial position contact46, the lever element12is tilted back into a predetermined initial position, specifically about an axis of rotation which is arranged in the region of the initial position contact portion52or in the region of the initial position contact46. The initial position produced using the initial position contact46can be, for example, a horizontal position of the lever element12, as shown inFIG.1, and contributes to the “adjustment” of the lever element12for the new, subsequent cycle.

Reference will now be made toFIG.6, which shows a detailed view to clarify the non-positive connection between the lever element12and the rod element20mentioned in conjunction withFIGS.2to5.

The left-hand image inFIG.6shows the non-positive connection between the lever element12and the rod element20. In the right-hand image ofFIG.6, on the other hand, the non-positive connection between the lever element12and the rod element20is released. In the right-hand image ofFIG.6, a movement of the lever element12relative to the rod element20along the rod axis22is therefore possible. However, precisely this relative movement of the lever element12along the rod axis22is prevented in the non-positive connection between the lever element12and the rod element20(left-hand image ofFIG.6).

Reference will now be made toFIG.7, which shows another embodiment of a linear drive10according to the invention.

The linear drive10has in turn the shape memory alloy element28, the lever element12, the rod element20and the bearing element24or the two bearings24A and24B. In the specific example ofFIG.7, however, the restoring element38is designed as an additional shape memory alloy element54, which exerts an additional tensile force on the lever element12when electrical power is applied. For this purpose, a first end56of the additional shape memory alloy element54is fastened to the second portion18and a second end58of the additional shape memory alloy element54opposite the first end56is connected to the second fixed bearing44, which now, owing to the additional tensile force exerted by the additional shape memory element54, is arranged on the opposite side compared toFIGS.1to5.

Reference will now be made toFIG.8, which shows a further embodiment of the linear drive10. With the embodiment of the linear drive10shown inFIG.8, it is possible to move the rod element20in two directions.

For this purpose, the lever element12of the linear drive10comprises, in addition to the first portion16and the second portion18, a third portion60and a fourth portion62. The first portion16and the second portion18are in this case arranged on a first side64of the rod element20. The third portion60and the fourth portion62are arranged on a second side66of the rod element20opposite the first side64. In addition, the fourth portion62is arranged between the third portion60and the through bore14.

In the embodiment ofFIG.8, the linear drive10in turn has the shape memory alloy element28, which extends along the first axis26, and also the restoring element38, which extends along the second axis36.

The linear drive10according to the embodiment ofFIG.8also has a second shape memory alloy element70which extends along a third axis68and the length of which is adjustable by applying electrical power. A first end72of the second shape memory alloy element70is connected to the third portion60. A second end74of the second shape memory alloy element70opposite the first end72is stationarily connected to a third fixed bearing76. The second shape memory alloy element70serves to exert a second tensile force acting along the third axis68on the lever element12when electrical power is applied. The second tensile force acts in the opposite direction to the tensile force exerted by the shape memory alloy element28connected to the first portion16. The shape memory alloy element28connected to the first portion16may thus also be referred to as a “first” shape memory alloy element28, since the shape memory alloy element70is the “second” shape memory alloy element of the linear drive10.

In addition to the additional second shape memory alloy element70, the linear drive10according to the embodiment ofFIG.8also has a second restoring element80extending along a fourth axis78. A first end82of the second restoring element80is connected to the fourth portion62and a second end84of the second restoring element80opposite the first end82is stationarily connected to a fourth fixed bearing86. The second restoring element80exerts a second restoring force acting along the fourth axis78on the lever element12, the second restoring force acting counter to the second tensile force exerted by the second shape memory alloy element70. The linear drive10according to the embodiment ofFIG.8thus has two pairs, each with a shape memory alloy element and a restoring element, which are arranged on opposite sides with respect to the rod element20. Thus, a first pair consisting of the shape memory alloy element28and the restoring element38is arranged on the first side64and a second pair consisting of the second shape memory alloy element70and the second restoring element80is arranged on the second side66.

If electrical power corresponding to the four power values already discussed in conjunction withFIGS.1to5is then applied to the first shape memory alloy element28, and if at the same time electrical power is not applied to the second shape memory alloy element70, then the rod element moves along the rod axis22in a first direction88. If, on the other hand, electrical power is not applied to the first shape memory alloy element28, but electrical power corresponding to the four power values discussed in conjunction withFIGS.1to5is applied to the second shape memory alloy element70, the rod element20moves along the rod axis22in a second direction90opposite to the first direction88. The rod element20can thus be moved either in the first direction88or in the second direction90by appropriately applying electrical power to the first or second shape memory alloy element28,70. Thus, a reversal of the movement of the rod element20can be realized by means of the linear drive10according to the embodiment ofFIG.8.

Reference will now made toFIG.9, which shows a schematic view of another embodiment of the linear drive10. The embodiment according toFIG.9is an alternative embodiment to the embodiment ofFIG.8. It is also possible with the embodiment of the linear drive10shown inFIG.9to move the rod element20both in one direction and in the other direction.

The linear drive10according to the embodiment ofFIG.9in turn comprises the lever element12, the shape memory alloy element28extending along the first axis26with the first fixed bearing36, the restoring element38extending along the second axis36with the second fixed bearing44and the rod element20supported by means of the bearing element24or by means of the bearings24A and24B.

The linear drive10according to the embodiment ofFIG.9furthermore comprises a second shape memory alloy element92which extends along the first axis26and the length of which is adjustable by applying electrical power. A first end94of the second shape memory alloy element92is connected here to the first portion16of the lever element12. A second end96of the second shape memory alloy element92opposite the first end94is stationarily connected to a third fixed bearing98. The second shape memory alloy element92exerts a second tensile force acting along the first axis26on the lever element12when electrical power is applied, the second tensile force acting in the opposite direction to the tensile force exerted by the shape memory alloy element28connected to the first portion16. In other words, the second shape memory alloy element92exerts a tensile force which acts counter to the tensile force exerted by the shape memory alloy element28. However, both shape memory alloy elements28,92are arranged on the first portion16of the lever element12, but on opposite sides with respect to the lever element12.

The linear drive10according to the embodiment ofFIG.9furthermore comprises a second restoring element100extending along the second axis36. A first end102of the second restoring element100is connected to the second portion18of the lever element12. A second end104of the second restoring element100opposite the first end102is stationarily connected to a fourth fixed bearing106. The second restoring element100exerts a second restoring force acting along the second axis36, the second restoring force acting counter to the second tensile force exerted by the second shape memory alloy element92. The second restoring element100accordingly exerts a restoring force which acts counter to the restoring force exerted by the restoring element38. Both restoring elements38,100are arranged on the second portion16of the lever element12, but on opposite sides with respect to the lever element12.

The linear drive10according to the embodiment ofFIG.9thus in turn has two pairs of in each case one shape memory alloy element and one restoring element. However, the two pairs are located on the same side with respect to the rod element20, but on opposite sides with respect to the lever element12. Thus, a first pair consisting of the shape memory alloy member28and the restoring element38is arranged on a first side108of the lever element12and a second pair consisting of the second shape memory alloy element92and the second restoring element100is arranged on a second side110of the lever element12opposite the first side108.

If electrical power corresponding to the four power values already discussed in conjunction withFIGS.1to5is then applied to the first shape memory alloy element28, and if at the same time electrical power is not applied to the second shape memory alloy element92, then the rod element moves along the rod axis22in the first direction88. If, on the other hand, electrical power is not applied to the first shape memory alloy element28, but electrical power corresponding to the four power values discussed in conjunction withFIGS.1to5is applied to the second shape memory alloy element92, the rod element20moves along the rod axis22in the second direction90. The rod element20can thus be moved either in the first direction88or in the second direction90by appropriately applying electrical power to the first or second shape memory alloy element28,92. Thus, the linear drive10according to the embodiment ofFIG.9can also enable the movement of the rod element20to be reversed.

Reference will now be made toFIG.10, which shows a further embodiment of the linear drive10. The embodiment ofFIG.10is based on the linear drive10according to the embodiment ofFIG.9.

The linear drive10according to the embodiment ofFIG.10has the shape memory alloy element28with the first fixed bearing34and the second shape memory alloy element92arranged opposite the latter with the third fixed bearing98, and also the lever element12and the rod element20supported by means of the bearing element24or by means of the bearings24A and24B.

In contrast to the linear drive10according to the embodiment ofFIG.9, the first restoring element38and the second restoring element100are not designed in the form of springs in the linear drive10according to the embodiment ofFIG.10. Instead, the first restoring element38is designed as a first additional shape memory alloy element112, which exerts a first additional tensile force on the lever element12when electrical power is applied. This first additional tensile force acts counter to the first tensile force exerted by the shape memory alloy element28connected to the first portion16. Furthermore, the second restoring element100is designed as a second additional shape memory alloy element114, which exerts a second additional tensile force on the lever element12when electrical power is applied. This second additional tensile force acts counter to the second tensile force exerted by the second shape memory alloy element92connected to the first portion16. A respective first end of the first and second additional shape memory alloy element112,114is connected to the second portion18of the lever element12and a respective opposite second end of the first and second shape memory alloy member112,114is stationarily connected to a fixed bearing. The first fixed bearing34and the fourth fixed bearing106can be combined here to form a common fixed bearing, as indicated inFIG.10. Analogously, the third fixed bearing98and the second fixed bearing44can be combined to form a common fixed bearing, as also indicated inFIG.10.

Reference will now made toFIGS.11to14, which show a linear drive arrangement1000which is produced by combining a plurality of linear drives. In the specific example ofFIGS.11to14, the linear drive arrangement1000has a first linear drive10and a further, second linear drive10, which are arranged adjacent to one another. The rod elements of the respective linear drives are designed here as a common rod element1002. The parallel arrangement of two linear drives10increases the tensile force exerted on the common rod element1002.

The linear drive arrangement1000furthermore comprises an activation unit1004, which is connected to the respective shape memory alloy element of the respective linear drive10and can apply electrical power to said element corresponding to the four power values described in conjunction withFIGS.1to5. The activation unit1004acts on the respective shape memory alloy element of the respective linear drive10in such a way that only in each case one of the two linear drives10changes from the first state toward the second state. This creates a smoother and more continuous movement of the common rod element1002. Of course, in other embodiments that are not shown, the linear drive arrangement1000can have more than the two linear drives10shown.

To clarify the activation of the linear drives10in the linear drive arrangement1000, the respective states of the respective linear drives10are illustrated inFIGS.11to14. InFIG.11, one of the two linear drives10, specifically the upper of the two linear drives10, is in the first state and the other of the two linear drives10, specifically the lower of the two linear drives10, is in the third state. InFIG.12the upper of the two linear drives is in the second state and the lower of the two linear drives is in the fourth state. InFIG.13, the upper of the two linear drives10is in the third state and the lower of the two linear drives10is in the first state. Finally, inFIG.14, the upper of the two linear drives10is in the fourth state and the lower of the two linear drives10is in the second state. The activation unit1004ensures that in each case only one of the two linear drives10changes from the first state in the direction of the second state. If there are more than the two linear drives10shown, the activation unit1004controls the respective states of the respective linear drives10accordingly such that, in turn, only one of the plurality of linear drives10in each case changes from the first state in the direction of the second state.

With the embodiments of the linear drive10described in conjunction withFIGS.1to10and with the linear drive arrangement1000described in conjunction withFIGS.11to14, a translatory movement of the rod element20along the rod axis22can be realized by means of shape memory alloy elements.