Patent ID: 12191749

DETAILED DESCRIPTION OF THE EMBODIMENTS

First Embodiment

FIG.2shows a galvanometer drive according to a first embodiment of the invention. The galvanometer drive shown inFIG.2is very similar to that ofFIG.1. The same elements are therefore generally provided with the same reference signs. According to the first embodiment, in order to limit the radial movement of the floating bearing with respect to the stator unit130, which can lead to undesired radial movements of the rotor110, a rolling guide170is arranged between the floating bearing (reference sign155inFIG.2) and the housing130to effect a limitation of the radial movement. Specifically, the rolling guide170is inserted between a guide shaft160and the stator unit130. The guide shaft160is a hollow cylindrical element that is rigidly connected to the outer ring155aof the floating bearing155. Furthermore, the guide shaft160is rigidly connected to the rolling guide170. InFIG.2, in this regard, the guide shaft160acts as the “inner ring” of the rolling guide170. The outer ring of the rolling guide170(the guide sleeve) is rigidly connected to the stator unit130, withFIG.2showing the example in which the outer ring is integrally formed with the stator unit130.

In the arrangement described, the outer ring155aof the floating bearing155can move against the spring force of the wave spring200. Due to the rigid connection of the floating bearing155to the guide shaft160and the presence of the rolling guide170, movement of the floating bearing155in the axial direction causes the guide shaft160and the floating bearing155to be able to move in the axial direction relative to the stator unit130. On the one hand, movement of the floating bearing in the radial direction is prevented by the rigid connections between the floating bearing155and the guide shaft160, on the one hand, and between the guide shaft160and the stator unit130, on the other hand. On the other hand, radial mobility within the rolling guide can be prevented by a preload, for example by the rolling elements (balls) having an oversize with respect to the distance between the guide shaft and guide sleeve.

A rigid connection of the floating bearing155to the guide shaft160or of the guide sleeve to the stator unit cannot be achieved only by a one-piece or integrally formed design of floating bearing outer ring155aand guide shaft160or guide sleeve and stator unit. Other possibilities for a zero-backlash connection would be an interference fit, gluing or other types of connection that eliminate mobility in the axial and radial directions.

Second Embodiment

FIG.3shows a second embodiment of the galvanometer drive according to the invention. Again, identical or analogous elements to those inFIG.1are generally provided with the same reference signs. In particular, the floating bearing150with its outer ring150acan be designed in the same way as the floating bearing155, except for the rigid or integral connection of the outer ring155ato the guide shaft160. In contrast to the embodiment ofFIG.1, in the second embodiment inFIG.3there is no wave spring200on the front side of the floating bearing150. Instead, the stator unit is provided on the front side with a recess135for receiving a spring element280. The spring element280surrounds the floating bearing150in the radial direction and engages radially on the outer ring150aof the floating bearing150. The spring element in this case extends substantially in a radial direction, i.e. perpendicular to the axis of rotation R. With the outer side (in radial direction), the spring element280engages the stator unit130. For clamping the spring element280, both the outer ring150aof the floating bearing150and the stator unit130can be provided with a groove into which the spring element280is inserted. The spring element280is characterized by the fact that, in the mounted state, its dimension in the radial direction is preferably at least eight times greater than its dimension in the axial direction. Here, the dimension in the radial direction refers to the extension between the floating bearing150and the stator unit130, i.e. a radius (if the spring element280is circular) rather than a diameter. It should be noted that the spring element does not necessarily have to be mounted in a recess135of the stator unit130, but optionally the recess can also be omitted, provided that sufficient space is available to attach the spring element externally on the outer ring of the floating bearing.

Due to the special shape and dimensions of the spring element280, it is able to exhibit significantly greater stiffness in the radial direction than in the axial direction. Thus, instead of the wave spring, it can restrict the mobility of the floating bearing in the axial direction, but not completely prevent it, so that, for example, thermal expansion of the rotor can take place. In contrast, movement in the radial direction is suppressed as a result of the greater stiffness in the radial direction. The ratio of the spring constants or spring stiffnesses in the radial direction and axial direction to one another can be adjusted by the shape of the spring element and, above all, via its outer diameter. The larger the outer diameter, the larger the ratio of the spring constants or spring stiffnesses in the radial and axial directions to each other for a given inner diameter. A value to be set for the spring stiffness or spring constant in the radial direction also depends on the dimension of the spring element in the radial direction and also on the masses to be moved. It has been shown that for the usual areas of application of the galvanometer drive, a value above 4 kN/mm is sufficient for the spring stiffness or spring constant in the radial direction; preferably, a value above 20 kN/mm is selected. Of course, in reality there will also be an upper limit for the possible spring constant or spring stiffness in the radial direction, but this should probably only be reached at about 1000 kN/mm.

The spring element can, for example, be formed from a steel sheet with a sheet thickness of, for example, 0.5 mm. In particular, it can be a disc spring. Among other things, the latter can be designed in such a way that, if radial symmetry is present in the mounted state, the axial position of an annular region of the disc spring changes periodically (e.g. sinusoidally) with the position of the region in the radial direction.

Larger ratios between radial spring constant and axial spring constant can be achieved if a kind of spring star is used instead of a full-surface disc spring, as shown inFIG.4. A spring element280can be seen inFIG.4, which is formed by an inner ring281abutting the floating bearing150and an outer ring282abutting the stator unit130. The inner ring281and the outer ring282are connected to each other via a rotationally symmetrical, star-shaped arrangement of three leaf spring elements283. The leaf spring elements283have an elongate shape similar to the spokes of a steering wheel. Preferably, a ratio of the dimension in radial direction to the dimension in tangential direction is at least 3:1, particularly preferably at least 10:1. The exact shape of the leaf spring elements also depends on the number of leaf spring elements provided. Thus, there need not necessarily be three leaf spring elements, this is only the minimum number. In principle, any other number n of leaf spring elements is possible (e.g. n=4, 5, 6, 7, 8, 9, 10, 11, 12, etc.). Of course, at some point it becomes uneconomical to further increase the number of leaf spring elements, resulting in an upper limit for the number of leaf spring elements. The spring element shown inFIG.4can, for example, be formed from steel sheet with a sheet thickness of 0.5 mm.

FIG.5shows a mounting situation for the spring element280using the example of the spring star shown inFIG.4. A spring force in the axial direction is generated by mounting the spring element280with preload. Accordingly,FIG.5shows a curvature of the leaf spring elements283, whileFIG.4shows straight leaf spring elements283, corresponding to the relaxed state of the spring element280inFIG.4. To bring about the preload, for example, the outer ring282can be mounted in such a way that in the relaxed state of the spring element the outer ring is displaced in the axial direction relative to the inner ring and in this state the spring element is fixed to the stator unit130and to the floating bearing150. For example, the axial displacement of the outer ring282relative to the inner ring281can be adjusted by inserting distance elements of different thickness (depending on which preload is to be set) between the stator unit and the outer ring282(in the axial direction).

To prevent undesirable radial play between the floating bearing and the spring element280or between the spring element280and the stator unit130, the spring element should be fixedly connected to the stator unit130or the floating bearing150(e.g. by welding, gluing, screwing, pressing, etc.). It should also be noted that the described mounting with preload of the spring element280is implemented in the same way for other shapes of the spring element than those shown inFIGS.4and5, e.g. if the spring element280is a disc spring.

Third Embodiment

FIGS.6to8show variants of a third embodiment of the invention in which, with the exception of the particular features described in each case, the same configuration as inFIG.1is present. The basic idea of the third embodiment is to severely restrict radial movement of the floating bearing relative to the stator unit (i.e. the bearing seat) by exerting a radial force on the floating bearing.

In the first variant of the third embodiment shown inFIG.6, the same or analogous elements to those ofFIG.1are generally designated with the same reference signs. In contrast toFIG.1,FIG.6also shows a rotating mirror1000attached to the rotor110, which can deflect a laser beam in a laser processing device, for example. However, this rotating mirror1000is not a necessary component of the third embodiment.

One can see inFIG.6a radial spring600designed as a helical spring, which is in contact with both the stator unit130and the outer ring150aof the floating bearing150and can thus exert a force in the radial direction on the outer ring150aof the floating bearing150from the outside. In this case, the inner ring150bof the floating bearing150is rigidly connected to the rotor110as in the embodiment ofFIG.1, while the outer ring150ahas axial mobility relative to the stator unit130. As a result of the spring force acting in the radial direction, the radial mobility of the outer ring150arelative to the stator unit is restricted. The extent to which axial play is also restricted depends on the spring force. The radial spring600generally does not make a significant contribution to the axial stiffness of the arrangement (this is done by the wave spring), but the low radial mobility is ensured with high radial stiffness. In this regard, an adjustment screw610can be used to adjust the extension of the radial spring600in the radial direction, thereby adjusting a desired radial stiffness. In particular, the radial spring does not necessarily have to press the floating bearing150inward in the radial direction. Rather, it is also possible for the helical spring to be mounted in a condition in which it has an increased length compared to the relaxed (forceless) condition. In the latter case, a force acts on the floating bearing outwardly in a radial direction. In particular, it is possible to mount the spring in the relaxed state and to adjust it to the desired length by means of the adjusting screw610.

FIG.7shows a second variant of the third embodiment, in which a force is exerted in the radial direction not by means of a radial spring, but by means of a magnet. In the example ofFIG.7, a magnet700is attached to the deflection mirror1000. Only by way of example, an attachment to the rear side of the deflection mirror is shown. The magnet700can, of course, also be attached at other locations of a part rigidly connected to the rotor. By means of a bracket750, a force is exerted across a gap710on the deflection mirror1000and thus also on the rotor110, which is fixedly connected to the deflection mirror, whereby a radial movement is significantly made more difficult. For this purpose, the bracket comprises a magnet or magnetic material at the gap710at least at the end opposite the magnet700. In particular, the entire bracket750can also consist of a magnet or of a material that has been magnetized.

In the example shown inFIG.7, the bracket750is fixedly (rigidly) connected to the stator unit130. In this example, the angular movement of the rotor110(and of the deflection mirror1000) is limited to a range of ±20°, which is acceptable in many applications. Preferably, the angular movement of the rotor110(and of the deflection mirror1000) is restricted to a range of ±10°. The force in the radial direction should be as high as possible while still not overly restricting axial mobility as well as rotational movement. The inventors assume that for usual vibrations with accelerations in the range of 5 to 50 g (g: gravitational acceleration), the radial force should be greater than five to 50 times the weight force of the system consisting of rotor and mirror.

Of course, instead of the magnet700, the rear side of the deflection mirror1000can be covered with a magnetic layer. Furthermore, the bracket750can be brought into a magnetized state at least partially, preferably as a whole, by means of an electromagnet.

FIG.8shows a third variant of the third embodiment, in particular a section in the radial direction through the rotor110and the stator unit130with the coil125.

In the variant of the third embodiment shown inFIG.8, a radially asymmetric magnetic flux is provided, which results in a radial magnetic force on the rotor, which greatly limits its radial mobility relative to the stator unit. One can see inFIG.8a magnetic rotor110(for example, a permanent magnet), the coil125, and a stator unit130that is asymmetrically formed insofar that a cavity filled with air is formed on one side. As can be seen inFIG.8, the cavity800deflects the magnetic field lines such that a radial asymmetry of magnetic flux is created. Again, the radially exerted force should not exceed approximately five to 50 times the weight force of the system of rotor110and rotating mirror1000.

It is immediately apparent that, in the third variant of the third embodiment, the rotor can alternatively or additionally have an asymmetrical shape to thereby cause or enhance asymmetry of the magnetic flux.

Furthermore, it can be seen that combinations of the different embodiments are also possible. Merely by way of example, a combination of the first and second embodiments, the first and third embodiments, or specifically a combination of the first embodiment with the third variant of the third embodiment may be mentioned here.

Finally, it should be emphasized that the present invention in all its embodiments and variants is not limited to the described axial preloading of the floating bearing by means of a spring. It is also conceivable that axial preloading of the floating bearing is provided by means of a suitable adhesive. This is done, for example, by preloading the floating bearing in the axial direction by means of a spring during assembly and introducing the adhesive into an existing gap between the floating bearing outer ring and the stator unit in the preloaded state. After the adhesive has cured, the spring used for axial preloading is then removed so that the adhesive now applies the preloading force. The adhesive can be any material that still has sufficient elasticity in the cured state to absorb the axial movement of the outer ring. In particular, the adhesive should show no or only very low plastic deformation under the influence of the preloading force in the cured state.