1. Field of the Invention
The present invention relates to a linear encoder and a linear guide assembly including the linear encoder.
2. Description of the Prior Art
Pre-assembled guide units, which consist of a hardened and ground guide rail and a displaceable thereon, on roller or ball elements, carriage, are used more and more in machine-tools and measuring machines. The guide unit is formed as an independent modular unit, with the guide rail being mountable with its mounting surface on a machine base and with the carriage being mounted on a machine slide.
For measuring the relative position of the carriage relative to the guide rail, international publication WO91/16594 discloses, e.g., gluing a scale directly on a surface of the guide rail. Because during the operation, the carriage is displaced above the scale, in case of damage, it is very difficult to replace the scale.
U.S. Pat. No. 5,687,489 discloses mounting on the guide rail, before the guide assembly is mounted in the machine, of a relatively easily replaceable, linear encoder. The linear encoder consists of a scale and a scanning head arranged in a housing. For mounting the encoder housing on the guide rail, the housing is provided with means that formlockingly engage in a recess provided on the guide rail. For mounting the linear encoder on the guide rail, relatively complicated retaining and receiving elements are provided in the guide rail for which in addition to guide surfaces, a space along the entire length of the guide rail must be available.
Accordingly, an object of the invention is an easily replaceable linear encoder that can be mounted on a guide rail of a guide assembly in a space-saving manner.
Another object of the invention is to provide a linear encoder of the type described above that would permit an easy alignment of the linear encoder scale parallel to and along the guide rail.
These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a linear encoder for use with a linear guide assembly formed as a separate unit and having a guide rail extending in a longitudinal direction having a mounting surface of a machine, with the linear encoder including a scale, a scanning head for scanning the scale, and mounting means for releasably attaching the scale to the guide rail of the guide assembly, with the mounting means being arrangeable outside of the mounting surface of the guide rail and having stop surfaces extending perpendicular to the longitudinal direction of the guide rail for a parallel alignment of the scale along the guide rail, and with the stop surfaces encompassing and engaging reference surfaces of the guide rail.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.