Sealed Incremental Measuring Device Having an Articulated Fastening Means for Mounting the Housing

The invention relates to a measuring installation for length measurements in order to measure or adjust the relative position of two objects, whose measuring graduation and the displaceable sensor housing unit associated with it are embedded in an elongated hollow body which is resistant to bending for screening against environmental influences.

The invention is based on the problem which exists in an encapsulated installation for longitudinal measurements of the above mentioned kind of providing a fastening means between the hollow body which is resistant to bending and one of the objects to be measured which exerts practically no compulsive forces on the hollow body. Moreover, the fastening means for the hollow body should be easy to manufacture and permit a rapid mounting of the hollow body for example at a processing or a measuring machine.

This problem is solved in a longitudinal measuring installation for measuring or adjusting the relative position of two objectives according to the invention in that the hollow body is fastened to one of the aforementioned objects which is being measured via a fastening means having an articulated design which fastening means extends beyond the hollow body so that the hollow body itself is free from direct contact with and is not supported by the object to which it is fastened via the fastening means.

In an advantageous embodiment, a fastening free from compulsive forces between the hollow body and the object (for example a machine bed) is accomplished by the interposition of angle parts having a weak place in the form of a groove in the apex area of the legs.

Additional features and advantages of this invention are described in, and will appear from, the description of the preferred embodiment which follows and from the drawing which represents an embodiment of the invention and to which reference is now made.

FIG. 1 shows a section taken along line 1--1 in FIG. 2 through a longitudinal measuring instrument according to the invention.

FIG. 2 shows a top view of the longitudinal measuring instrument.

FIG. 3 shows a side view of the longitudinal measuring instrument.

FIG. 4 shows a section taken along line 4--4 in FIG. 2 through the photoelectric sensor housing unit of the longitudinal measuring instrument of the invention.

The embodiment illustrated shows a photoelectric incremental longitudinal measuring system for the measuring or adjusting of the relative position of two objects, for example, the bed and the carriage of a processing or measuring machine.

The measuring graduation 1 which is a transmission grid and the sensor plate 2 (FIG. 4) are illuminated by way of a light 3 via a lens 4. The light passing through the grids 1, 2 is projected upon photo elements 5, 6 whose electric output signal is fed via the outlets 7, 8 directly to an electronic up and down count meter of a known type (not shown).

The measuring graduation 1 and the sensor housing unit 9 associated with it are placed for screening against environmental influences in a hollow body 10 resistant to bending which appropriately is made from extruded aluminum. The measuring gradution 1, which is a glass body, is fastened to the metallic hollow body 10, without directly contacting it, with the interposition of a highly elastic layer 11, preferably a silicon rubber adhesive layer. This type of fastening for the measuring graduation 1 offers the advantage that unevennesses in the heat expansion of measuring graduation 1 and the hollow body 10 will practically cause no adulteration of the readings.

The sensor housing unit 9 is guided in the embodiment via sliding shoes 12, 13, preferably made from plastic, directly at the measuring graduation 1 and via ball bearings 14, 15 at the hollow body 10. The guiding of the sensor housing unit 9 at the measuring graduation 1 and at the hollow body 10 makes possible a small compact design assuring a trouble-free scanning and easy manufacturing from a production-engineering point of view. The sensor unit 9 which appropriately is produced as a plastic injection molding part is urged with the aid of a spring wire 16 against the guiding surfaces at the measuring graduation 1 and at the hollow body 10. At the same time, the wire 16, which is resistant to bending in the direction of displacement of the housing unit 9, represents the coupling part between the sensor housing unit 9 and an entrainment means 17.

According to the invention, the hollow body 10 is fastened at one of the objectives, whose relative position is to be measured, via two fastening members 18 provided at its ends and designed in an articulated manner. For the sake of simplicity, the drawing only shows one of the articulated parts 18. An attachment means 19 is fastened to the second object and is connected to the sensor unit 9 by an entrainment means 17. The two fastening members 18 fastened to the frontal side of the hollow body 10 are angled parts in the embodiment having a weak place in the shape of a groove 20. In the embodiment illustrated, the portion of the angled part 18 fastened directly to hollow body 10 extends below the bottom of hollow body 10 (see FIG. 3) so that the hollow body is maintained away from any direct contact with the object to which the other portion of angled part is fastened. By fastening the hollow body 10 via two fastening members 18 having an articulated design, practically no compulsive forces are exerted upon the hollow body 10 during the assembly and the use of the measuring system, which means that the hollow body 10 and the measuring graduation 1 fastened therein will not be deformed.

One side of the hollow body 10 is sealed by flexible sealing lips 21, 22 designed in a roof-like manner, the slender entrainment means 17 of sword-like design extending therethrough. The sealing lips 21, 22 are fastened in slots 23, 24 of the hollow body 10 at sheet metal strips 25, 26. The legs of the U-shaped hollow body 10 extend far enough so that they slightly protrude beyond the roof-shaped sealing lips 21, 22, and offer protection to the sealing lips 21, 22 against meachnical damages.

The light 3 is fastened via a support 27 to the displaceable scanning or sensor unit 9. The electrical conduits 28, 29 (FIG. 2) for the light 3 and the electric conduits 7, 8 of the photo elements 5, 6 extend out of the hollow body 10 through an opening 30 in the entrainment means 17. The photo elements 5, 6 are located in a support 31 fastened to the sensor unit 9. The capacitor 4 and the sensor plate 2 are fastened in a recess 32 in the sensor unit 9. The spring wire 16 representing the coupling and pressing member is fastened to the sensor unit 9 and to an assembly 33 formed on the entrainment means 17.

The embodiment described herein is intended to be exemplary of the types of incremental length measuring instruments and articulated fastening means for fastening one of the objects to be measured to the instrument which fall within the scope of the invention. However, one skilled in the art would certainly be expected to be able to make modifications and variations of this embodiment without departing from the spirit and scope of the invention as defined in the following claims.