Clean room-suitable linear guide

A linear guide including a rail and a carriage joined to an application platform by a plurality of screws, wherein at least one of the plurality of screws is a vacuum screw with an axial channel through which particles can be vacuumed out of an air gap between the rail and the carriage.

Applicants claim, under 35 U.S.C. §§120 and 365, the benefit of priority of the filing date of May 28, 2009 of a Patent Cooperation Treaty patent application, copy attached, Serial Number PCT/EP2009/003813, filed on the aforementioned date, the entire contents of which are incorporated herein by reference, wherein Patent Cooperation Treaty patent application Serial Number PCT/EP2009/003813 was not published under PCT Article 21(2) in English.

Applicants claim, under 35 U.S.C. §119, the benefit of priority of the filing date of Jul. 31, 2008 of a German patent application, copy attached, Serial Number 10 2008 035 949.1, filed on the aforementioned date, the entire contents of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a clean room-suitable linear guide. In operation, such linear guides release as few particles as possible, so that the clean room does not become contaminated.

2. Description of the Related Art

The manufacture of integrated circuits is done today in so-called clean rooms, since the contamination of a wafer, with even the smallest particles, can lead to failure of the circuits to be manufactured. For all the devices and machines used in a clean room, there is accordingly the requirement that as few particles as possible be generated.

Since during the manufacturing process wafers have to be moved, it is not possible to dispense with moving parts. The use of air bearings, which operate in contactless fashion and thus without abrasion, is not always possible for reasons of cost. Thus, guides are also used that are based on conventional bearings, such as ball bearings or slide bearings. Even if such bearings are made from especially low-abrasion materials, the formation of particles cannot be avoided. Apparatuses are therefore known in which particles that occur are vacuumed away by a vacuum device before they can get into the surroundings and contaminate the clean room.

U.S. Pat. No. 4,955,244, for instance, describes a clean room-suitable apparatus with a linear drive resting on a recirculating ball spindle. At the rotor, particles generated in the interior of its housing are vacuumed away through an opening in the housing. For that purpose, a vacuum device is attached to the lubrication nipple of the housing.

SUMMARY AND OBJECTS OF THE INVENTION

It is an object of the present invention to find an embodiment for a linear guide which is as simple as possible, stable, and above all suitable for a clean room, and in which particles created from friction can be vacuumed away.

This object is attained by a linear guide having a rail and a carriage in which the carriage is joined to an application platform by screws. One of the screws is a vacuum screw with an axial channel through which particles can be vacuumed away from an air gap between the rail and the carriage.

Further advantages and details of the present invention will become apparent from the ensuing description of a preferred embodiment in conjunction with the drawings. In the drawings:

DESCRIPTION OF THE PREFERRED EMBODIMENT(S) OF THE INVENTION

FIG. 1shows a linear guide with a rail1, on which a carriage2is supported linearly movably. For special applications, the rail1can also be curved, so that the carriage2can perform rolling, yawing or pitching motions. The carriage2has a covering3on both ends, which closes off a gap, such as the air gap10between the rail1and the carriage2as well as possible, wherein the gap contains air. This makes it more difficult for particles generated by abrasion to escape. An application platform4, hereinafter also simply called a table4, is joined to the carriage2, so that the table4itself is linearly movable. The table4can certainly be held by a plurality of linear guides, or by two or more carriages2that run on a common rail1.

The details of the joining of the table4to the carriage2are shown in the sectional view inFIG. 2.

In section, three bores5penetrating the table4can be seen. Corresponding bores12with a female thread are provided on the carriage2. Via screws6(inFIG. 2, only the middle screw is shown), the table4can be joined to the carriage2.

The middle bore of the three bores12in the carriage2ends in the air gap10between the carriage2and the rail1, preferably, as shown inFIG. 2, centrally of and above the rail1. Since in such linear guides, balls or rollers typically run on both sides of the linear guide, and the rail1, on its upper face opposite the middle bore of the three bores12, itself has openings with screws for securing the rail1to a substrate, this middle bore12above the rail1does not impede the operation of the linear guide.

A vacuum screw6is inserted into each of the middle bores5,12of the table4and carriage2. Such vacuum screws6are typically employed in vacuum technology so that while a screw is being screwed in, an isolated air reservoir that would gradually give off air as the ambient air is pumped out and would thus impair the vacuum will not be created.

In accordance with this present invention, the vacuum screw6is employed in a completely different function. In part, the vacuum screw6contributes to the joining of the table4and the carriage2, even if the conventional screws used in the other bores5,12can exert a markedly higher tightening moment. However, above all, the vacuum screw6makes it possible to vacuum away particles from the air gap10between the rail1and the carriage2. By the term “vacuum away,” one of ordinary skill would understand that the particles would be extracted or removed from the air gap by suction in a manner similar that dirt is removed from a carpet by a vacuum cleaner.

Specifically, vacuum screws have a channel6.1, by way of which the particles can be vacuumed away according to the present invention. For that purpose, the vacuum screw6has an axial bore, extending over the entire length of the vacuum screw6, with a diameter of approximately half of a millimeter. Alternatively, the vacuum screw6can also have a lateral notch, through which air and particles can be vacuumed away.

Above the vacuum screw6, a connection piece7can be seen, which is secured by screws8to the table4. The connection piece7has an opening9for supplying a vacuum. This vacuum supply communicates in the interior of the connection piece with the channel6.1of the vacuum screw6. For that purpose, between the connection piece7and the head6.2of the vacuum screw6, a sealing ring11is inserted, which ensures a tight connection between the connection piece7and the vacuum screw6.

If a vacuum device is now connected to the connection piece7, an air flow and hence an underpressure are generated in the carriage2, which ensure that particles can no longer escape between the covering3of the carriage2and the rail1, since an air flow into the interior of the carriage2is created there. Particles in the interior of the carriage2are furthermore vacuumed away through the channel6.1of the vacuum screw6and through the connection piece7. Accordingly, they cannot accumulate in the interior of the carriage2. The waste air contaminated with the particles can furthermore be filtered without problems and/or can escape to outside the clean room. Thus the surroundings of the linear guide are optimally protected from the particles created by abrasion in the linear guide.

Since a single carriage2can also be secured by two or more vacuum screws6offset in the travel direction, and the table4can be secured on a plurality of carriages, it is advantageous if the carriage4has a vacuum connection from which, via branching vacuum hoses, the suction is distributed among the connection pieces7. This distribution can be disposed in the interior of the table, like the connection pieces7themselves, so that the table4has a plane surface on the side on which it is used.

So-called direct drives, such as linear motors or torque motors, in which a primary part20with coils22is located opposite a secondary part24with a row of magnets26disposed with alternating polarity, are especially well suited as the drive for the carriage2and the table4. Such direct drives have no gear and require no bearings of their own. Thus with direct drives, such components that additionally produce particles can be avoided.

The linear guide, with the vacuuming away of the particles according to the present invention, keeps primary part20and secondary part24movable counter to one another, for instance because the primary part20is joined to the carriage2or the table4, and the secondary part24is joined to the rail1or to the substrate to which the rail1is also secured.