Bearings – Linear bearing – Combined with seal or guard
Reexamination Certificate
2000-03-24
2002-07-02
Footland, Lenard A. (Department: 3682)
Bearings
Linear bearing
Combined with seal or guard
Reexamination Certificate
active
06412981
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention relates to a seal arrangement for a load-carrying bearing which is supported on a guide path provided on a carrying body and which is arranged so as to be movable along the length of the guide path, especially for coordinate measuring devices.
b) Description of the Related Art
Load-carrying bearings which are supported on guide paths that are arranged on carrying bodies and which are movable along these guide paths are used in many areas of technology, e.g., for supporting movable machine tables for machine tools or as supporting bearings for bridges or portals in coordinate measuring devices.
The simplest construction of bearings of the type mentioned above consists in that the bearing in question is only supported so as to be movable on the associated guide path without any special sealing devices being provided in order to prevent penetration by dirt, floating particles, aerosols, moisture, or the like, into the bearing surface. Such arrangements are possible when requirements with respect to the insensitivity of the guide elements to dirt are relatively undemanding or when the device in question operates in a suitable cleanroom.
However, devices of the type mentioned above are increasingly used in manufacturing environments, i.e., the machines are no longer set up in closed, air-conditioned rooms and halls which are protected from access by manufacturing media, but rather in rooms and halls used for manufacturing, so that there is a risk that all of the contaminants and the like which are present in such manufacturing halls will lead to impairment of the guide paths and therefore to impaired quality of the bearing surfaces. This is especially undesirable when the machines in question are high-precision measurement devices in which such influences must be eliminated.
Accordingly, a seal arrangement has already been provided in coordinate measuring devices for sealing bearings of the kind mentioned above. In this seal arrangement, the guide path and the bearing supported on the guide path are covered by a box-shaped cover plate, on whose side opposite to the guide path is formed a central longitudinal slot through which is guided a connection element which connects the bearing with a structure to be supported located outside of the cover plate. Within the space enclosed by the cover plate, near the longitudinal slot, this connection element has a wide guide body which extends on both sides along the lateral edges of the longitudinal slot and which (seen in the longitudinal direction of the longitudinal slot) is penetrated by a through-opening. A cover strip, whose shape is adapted to the through-opening and which extends inside the cover plate along its entire length, runs through this through-opening and serves to cover the longitudinal slot on the inner side of the cover plate. This cover strip, whose width also projects over the sides of the longitudinal slot, is fastened in a suitable manner at both of its ends. Since the cover strip runs through the through-opening of the guide body, the bearing can be moved along the strip with the connection element coupled to it and the structure to be supported which is connected with the latter, so that the longitudinal movement required for the bearing is ensured, but the cover strip still conceals the open longitudinal slot opposite to the inner side of the cover plate at all times in the areas outside of the bearing. Since the cover strip is arranged at a distance from the longitudinal slot of the cover plate because of the overall construction, even though this distance is only slight, a certain sealing can accordingly be provided against penetration of dirt, dust and the like, but the existing gaps are relatively large, so that there is still no guarantee of a particularly good sealing action against contamination of the guide elements or penetration of floating particles.
In another known structural solution, a bellows is connected to each side of the bearing (in its movement direction) and, as seal protection, covers the portion of the guide path on the bearing side that is not covered by the bearing. However, the cost of the encapsulation required for this purpose by means of the bellows over the entire length and width of the guide surface is considerable, and the forces to be applied for the displacement of the bellows are not conducive to the absence of forces which is desired as far as possible in the longitudinal displacement of the utilized bearing.
OBJECT AND SUMMARY OF THE INVENTION
On this basis, the primary object of the invention is to provide an improved seal arrangement which ensures a particularly low susceptibility on the part of the guide elements to soiling and improved protection against the penetration of floating particles, aerosols and moisture while simultaneously providing a good overall static and dynamic characteristic of the moving system.
According to the invention, this object is achieved in a seal arrangement of the type mentioned above in that the bearing is connected with a bearing cover that spans the carrying body at least on one side thereof and that has a side portion which is bent toward its side, each side portion projecting into a labyrinth recess which is arranged on the associated side of the carrying body over the entire length of the guide path to form a labyrinth seal.
The seal arrangement proposed according to the invention results in a remarkably good sealing of the bearing relative to the external surroundings in which a manufacturing atmosphere exists, and even exacting guideline values concerning insensitivity to soiling can easily be met. At the same time, a superior protection is provided against the penetration of floating particles, aerosols and moisture and the overall construction also leads to good static and dynamic overall characteristics of the moving bearing system.
The sealing arrangement according to the invention can also easily be varied with respect to installation position: installation can accordingly be carried out vertically, horizontally or in some other defined position without substantially impairing the sealing action. At the same time, the sealing arrangement according to the invention also allows an economical configuration with a modular construction in the manner of a building block system; such modular components for a building block system are, for example, the bearing cover with its side portions which are bent at both sides and the body forming the labyrinth recess, along with the carrying body with guide path and the bearing itself.
The seal arrangement according to the invention also has a total configuration with easily assembled and service-friendly joints, which is especially advantageous for cleaning within regulation maintenance intervals.
If floating particles and aerosols enter the labyrinth seal from outside the bearing in the sealing arrangement according to the invention, they are slowed down with respect to flow velocity on their way through the labyrinth seal already in the first arm of the labyrinth, so that the heavier particles settle on the bottom of the labyrinth recess during the following labyrinth deflection and when entering the other labyrinth arm running in the opposite direction. This effect is particularly important when the seal arrangement according to the invention is installed in such a way that the labyrinth channels extend substantially vertically, so that the gravitational force within the latter also acts on the entering dirt particles in the same direction. In connection with the 180-degree deflection of the labyrinth channels, the precipitating effect of dirt or residual dirt is very good. The very long and very narrow winding flow channels within the labyrinth seal not only provide for an extremely long flow path, but also for a strong deceleration of the occurring flow velocities, especially with respect to the very narrow channel cross sections in which there are considerable wall friction losses in the case of a gas flowing therein.
A pa
Bernhardt Ralf
Jacobs Klaus
Piwek Volker
Woletz Franz
Carl-Zeiss-Stiftung
Footland Lenard A.
Reed Smith LLP
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