Patent Application
20130153194
The invention relates to the technical field of thermal conductivity in a vacuum and in particular to a heat-conducting element according to claim 1 as well as an assembly of said type of heat-conducting element according to claim 7.
The utilization of fluid streams such as air or water for cooling components or entire assemblies has already been disclosed in the prior art. Similarly, Peltier elements are used for cooling electrical circuits, although their efficiency is limited. Consequently, these technologies for removing large quantities of heat from a vacuum are either not feasible or their realization is associated with major expenditures or maintenance.
The object of the present invention is to overcome the disadvantages of the prior art and to provide a heat-conducting element for removing large quantities of heat from a vacuum, which features a simple design, is reliable and efficient as well as scalable and can hence be used flexibly and operated virtually maintenance-free and therefore cost-effectively.
Said object is solved with a heat-conducting element according to claim 1.
One key aspect of the heat-conducting element according to the invention is the fact that it is indeed designed like a linear bearing, without having to transfer (almost) any loads thanks to its elasticity. Its elastic pre-load is utilized exclusively to establish a solid thermal contact between the movable components. In the process, the heat flux predominantly passes over the supporting element, the running surfaces and the rolling elements retained between them. The connection between the supporting element and the running surface facing said supporting element is of particular significance, because they are both mounted such that they spring back elastically against each other. They establish contact in such a way that a thermal bridge exists between said supporting element and the running surface. In this respect, a particularly wide area of contact is created across the heat-conducting element, said area of contact itself removing large quantities of heat, such as it is released e.g. from electric servomotors. Furthermore, the simple design of the heat-conducting element facilitates an extremely reliable operation which requires hardly any maintenance. At the same time, the element is scalable to almost any size, i.e. adjustable to a large variety of applications by adjusting its dimensions and in particular by selecting the number, type and size of its rolling elements. By providing the rolling elements at a distance from each other that is less than half of their respective diameter, their area of contact on the side of the running surface and hence the cross-section of each individual heat-conducting element increases, via which the heat flux can be removed.
Preferred embodiments of the heat-conducting element according to the invention are described in the sub-claims 2 to 6.
The rolling elements can essentially have any suitable shape that enables a two-way movement of the running faces relative to each other. A common spherical shape can obviously be selected for this purpose. However, a particularly wide two-sided area of contact between the rolling elements and the running surfaces is created if the rolling elements have an elongated cylindrical shape. Because the area of contact is increased, the thermal conductivity of the element according to the invention improves analogously.
The thermal conductivity between the supporting element and the running surface facing said supporting element is in particular also improved if the supporting element comprises at least one projecting part and one of the running surfaces comprises at least one opening allocated to said projecting part and/or vice versa, and the respective projecting part engages in or penetrates said opening. This helps considerably enlarge the thermal bridge between the two parts mounted elastically springing back against each other, which in turn increases the thermal conductivity between the two.
Alternatively or in addition, it can also be preferred if the supporting element at least partly encompasses the running surface and/or the running surface at least partly encompasses the supporting element. This again enlarges the area of contact between the running surface on the side of the supporting element and the supporting element itself and improves the thermal conductivity of the thermal bridge between the two parts.
The individual parts of the heat-conducting element can basically consist of a material whose thermal conductivity meets the specific requirements of the intended area of application. However, in order to achieve a particularly favorable heat conductivity, the supporting element preferably consists of a metallic material.
At least one spring element is preferably provided between the supporting element and the running surface. Depending on the requirement, it is also possible to provide a plurality of them such that an elastic restoring force of the heat-conducting element is flexibly adjustable. The contact between the rolling elements and the running surfaces can in particular be improved with an especially high restoring force. At the same time, the spring elements also form a thermal bridge between the running surface and the supporting element mounted elastically springing back against said running surface. Likewise, if the spring elements are made e.g. of an especially conductive material, the thermal bridge between these two parts is enhanced as the number of spring elements increases.
The object of the present invention mentioned above is solved with an assembly according to claim 7.
One key aspect of the assembly according to the invention consists in the fact that the heat-conducting element described above is indeed used between two movable components similar to a linear bearing although it is (almost) not carrying any load here. In fact, it is restricted to mere pre-load. Consequently, it simply acts as a thermal bridge, without countering the movement of the components with the frictional resistance commonly generated by a linear bearing under load. Consequently, the design of the heat-conducting element is intent on thermal optimization, while load-related disadvantages have deliberately been excluded. All in all, this achieves an optimal heat removal between components in a vacuum.
Preferred embodiments of the assembly according to the invention are described in the sub-claims 8 and 9.
Accordingly, it is advantageous if a drive is arranged between the components for moving them relative to each other. The heat of the drive, e.g. an electric motor, normally accumulates between the components and heats in particular the top one when viewed in a vertical direction. As a consequence, thermal stress is generated between the two components, which can lead to an unacceptably high expansion of materials resulting in processing inaccuracies especially in ultra-precise production facilities. While the drive predominantly releases heat to the component at the top, the pre-loaded heat-conducting element arranged between the components counters this phenomenon by ensuring an effective heat removal from the component at the top to the one at the bottom. If the latter is e.g. installed permanently, the heat can finally be removed into the surroundings through its base. Thus, a heat flux is created that originates from the drive and passes the component at the top, the heat-conducting element according to the invention, the component at the bottom before it is released into the surroundings. If a plurality of heat-conducting elements is provided, said heat flux can be multiplied analogously. So far, said type of heat removal in a vacuum cannot yet be produced with common technologies, neither at this scale nor in such a simple and reliable manner. It helps minimize the temperature difference between the two components, thus preventing further thermal stress.
In so doing, it is preferred if the drive is arranged closer with respect to space to the at least one heat-conducting element than to the at least one linear bearing. This way, the linear bearing is not directly exposed to heat which might impact its efficiency, in particular increase its frictional losses. On the contrary, the heat is conducted away from said bearing and can be removed into the surroundings.
The assembly described above should preferably be used in a manufacturing device for wafers, because especially their ultra-precise orientation to the laser beam should not be subject to any fluctuations.
The present invention is explained in detail below, based on an exemplary embodiment with reference to the enclosed figures. Identical components or components with identical functions are labeled with the same reference numbers. In the figures:
The thermal bridge between the supporting element 14 and the associated running surface 12 can alternatively or additionally be created or upgraded with projecting parts or openings (not illustrated) arranged opposite of each other in said parts 14 and 12, in which the projecting parts are engaged with the respective openings, in particular irrespective of the respective position of the spring element 15. This creates or further enlarges an area via which heat can be transferred from one part to the other part, thus considerably improving the thermal conductivity of the heat-conducting element.
At the same time, the supporting element 14 including spring 15 and running surface 12 can be moved linearly relative to the running surface 13, albeit without picking up and transferring any loads. Potential heat stress and the associated possible expansion of materials of the individual parts are compensated by the spring element 15 such that—unlike with a load-bearing linear bearing—no increased frictional losses develop in connection with this movement. Moreover, a high directional stability is achieved because the rolling elements 11 . . . 11″″′ are encompassed and guided by the running surface 13 at the bottom in a similar fashion as the running surface 12 at the top is encompassed and guided by the supporting element 14. Furthermore, the simple design facilitates an (almost) maintenance-free operation of the heat-conducting element 10.
The heat-conducting element itself consists of three already known parts 11 . . . 15 and is ideally arranged near a drive such that the heat of the drive is conducted past component B1 at the top and the heat-conducting element 10 to component B2. In the present example, a drive could be arranged e.g. between the linear bearing 20 and the heat-conducting element 10. Its supporting element 14 can be permanently connected with component B1 at the top and its lower running surface 13 can be permanently connected with component B2, e.g. by means of a screwed connection. If component B2 is arranged permanently and component B1 is mounted linearly movable, the heat can be removed into the surroundings e.g. through a suitable base of component B2. This helps minimize a temperature difference between the components B1 and B2 such that the development of heat stress between them is prevented. Therefore, the assembly 10 is especially suitable for storing wafers which are transported on component B1 and processed under vacuum. A corresponding processing table can be movable e.g. in two spatial axes, wherein said axes are designed in the form of assemblies 30 according to the invention. In the process, the heat to be removed can also be guided across multi-stage series-connected heat-conducting elements 10, including multiple times parallel to each other. The basic design of the assembly 30 according to the invention remains unaffected thereof.
Structural adaptations of the exemplary embodiment above can also comprise a spring mounted support of both running surfaces 12 and 13, wherever this is needed because of the specific requirements of the area of application, without impairing the heat-removing effect of the heat-conducting element according to the invention.
In any case, a simple and effective, at the same time low-maintenance and flexibly adjustable heat removal is provided which has never been disclosed in the past.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202010007905.5 | Jun 2010 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CH2011/000138 | 6/9/2011 | WO | 00 | 2/28/2013 |
