Incremental length measuring system.

(42) Date of commencement of the patent: 15. 9.1991 (45) Date of issue: 25. 3.1992 (73) Patentee:

RSF ELECTRONICS SOCIETY MBH

A-5121 TARSDORF, UPPER AUSTRIA (AT).

(72) Inventor:

SCHWAIGER MAX

OSTERMIETHING, UPPER AUSTRIA (AT).

RIEDER HEINZ

OBERNDORF, SALZBURG (AT).

(54) INCREMENTAL LENGTH MEASUREMENT SYSTEM (57) An incremental length measuring system has a measuring scale (3) having scale (2), a scanning unit (5) with scanning elements for generating measuring signals during the scanning of the measuring graduation (3) and an evaluation unit for these measuring signals, a reference track parallel to the measuring graduation (3) having a plurality of reference marks (4) each corresponding to a reference point, associated scanning elements in the scanning unit (5) and one of an assignable to a reference mark in a protective housing (1) for the scale (2) and the scanning unit (5) attachable permanent magnet (13), with the scanning unit adjustable selector switch (14) are provided, the one generation or Provision of a reference pulse only at least one on the permanent magnet selected reference mark (4a) permits. To facilitate the selection of each selectable reference mark (4) in SchutzgeCD housing (1) permanently assigned a permanent magnet (13) and over

Actuators from one with respect to the selector switch (14) inactive in an active position adjustable.

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AT 394 446

ΠΒ 0078018

AT 394 446 Β

The invention relates to an incremental length measuring system, with a scale having a graduation, a scanning unit with scanning elements for generating measuring signals during the scanning of the measuring graduation and an evaluation unit for these measuring signals, a reference track parallel to the measuring graduation having a plurality of reference marks corresponding to each reference point, associated scanning elements in the scanning unit and one of an assignable in association with a reference mark in a protective housing for the scale and the scanning unit attachable permanent magnet, provided with the scanning unit adjustable selector switch, the one generation or Delivery of a reference pulse only on at least one selected over the permanent magnet Referenzmaike allows.

In such length measuring a selection of reference marks is provided to facilitate the production of the measuring systems and possible without external intervention in the encapsulation of the measuring system, the selection of a particular, z. B. allow the machine zero point of a machine tool corresponding reference point and thus relate the measurements to the machine zero point. A selection of reference marks is also useful in other cases when measurements related to them are to be made. From DE-OS 18 14 785 mechanical on-off switch are known, which are actuated during the adjustment of the scanning unit via stops and activate the evaluation circuit only to preselected reference marks. Length measuring systems of the type mentioned, in which attachable to selectable scale locations permanent magnets for the operation of integrated as in the scanning unit reed relay use are known from DE-AS 25 40 412. The attachment of such permanent magnets on the scale requires encapsulated length measuring an undesirable interference with the interior of the protective housing. Furthermore, there is the danger that this permanent magnet slips or falls off during prolonged operation in the most usual clamping of the permanent magnet on the scale body. It has therefore already been proposed to provide in the protective housing one of the scale and scanning unit receiving interior separate longitudinal bore into which the permanent magnet is inserted from the housing end, said permanent magnet is secured by the bore to both ends filling spacers in position. This results in a complex assembly and the scale housing must be at the ends for threading or Pulling out the permanent magnet and because spacers be accessible.

For more accurate measurements, it is desirable that at different thermal expansions of the scale body, the protective housing and the object on which the length measuring is mounted, usually takes the bed of a machine tool, no noticeable adjustment of the selected reference mark relative to the machine zero point. It has been tried, set the scale only in the region of its longitudinal center using an adhesive of low elasticity in the protective housing, but by permissive attachment of the remaining scale parts to allow a longitudinal adjustment of these parts relative to the protective housing and also to set the protective housing by means of a central attachment to the object, although so far for the ends of the protective housing rigid attachment points on the object, but between these mounting blocks and the end of the protective housing linearly adjustable elements, z. b. specially shaped Fedem, joints with intersecting joint axes u. like. be provided. This type of assembly is expensive and only actually fulfills the task, if the rigid attachment of the scale housing or the determination of the scale body against the protective housing actually happens at random at the machine zero point

The main object of the invention is to provide a length measuring system of the type mentioned, in which a selection of any reference marks with simple means and without interference with the interior of the protective housing is made possible and the choice made can be changed if necessary. A subtask of the invention is the provision of a length measuring system in which longitudinal displacements of the scale body in the region of the selected reference mark are prevented even if the selected reference mark is not located exactly in the center of scale

The asked main task is solved in that each selectable reference mark in the protective housing permanently assigned a permanent magnet and is adjustable via actuators from a respect to the selection switch inactive in an active position.

For the adjustment of the permanent magnets from the active to the inactive position and vice versa simple facilities can be used. Since each of the selectable Referenzmaike a permanent magnet is assigned anyway, no modifications or prolonged assembly work on the length measuring system are required.

According to a preferred embodiment, each permanent magnet is adjustably mounted with a rotatable in the housing or carrier from a repellent from the path of movement of the selector switch position in a switch in its passing movement activating position

According to a development of the selector switch in an outer driver for the scanning unit and the permanent magnets are mounted with their carriers in a next to this driver in the protective housing provided in the longitudinal direction Aufiiahmebohrung or groove and adjustable from the outside of the housing. This embodiment has the advantage that the scanning unit and scale for length measuring without reference point selection can be made the same, wherein when the protective housing corresponding receiving devices for the permanent magnets and the driver receptacles for the switch also contains a subsequent equipment of the measuring system with selectors is possible.

According to another embodiment possibility are at at the scanning unit within the tube opening of the

Protective housing mounted selector switch the permanent magnets on outer actuators adjustable supports

-2AT394446B housed in the protective housing. In this case, these permanent magnets can sit on with foot parts in longitudinal grooves of the housing usually formed of a Aluminiumstrangpreßprofil pivotally mounted, pivotable through lockable housing openings and lockable in the Schwenkendstellungen flaps.

A variant embodiment, which allows a simple construction and easy mounting of the permanent magnets, is characterized that as a carrier for the permanent magnets at least over the length of the attachment region of the selectable reference marks on the scale but preferably over the entire Maßstablänge continuous profile strip made of elastic, is provided in particular elastically deformable material, which engages with a foot part on an edge in the press fit in a retaining groove in the interior of the tubular protective housing and carries the individual reference marks associated permanent magnets at a distance from the foot part outside the activation range for the switch, wherein in the region of each reference mark a closable housing opening is provided, over which the band is deflectable by inserted screws or press-fit in this area around the foot part, so that the associated permanent magnet is moved into the activation range for the switch. It is also possible to use an elastically deformable band held in grooves of the protective housing at both edges. which is concavely curved with respect to the housing interior in the inactive position and in the region of an activated magnet by pushing in by means of the screw or of the press-fit body assumes a concave curvature. By means of such an attached band, the housing against the housing openings for the screws or Compression body additionally sealed

To solve the mentioned subtask, it is provided that the adjusting drives and / or support for the permanent magnets in their holding the permanent magnet in the activation position at the same time in the housing in a groove to compensate for different thermal expansion of the housing, scale or set the object equipped with the length measuring system in the required extent by means of flexible holders longitudinally adjustable held scale body in the region of the selected reference mark, in particular clamp. In this case, preferably, the protective housing forming a carrier in the region of the selected Referenzmaike with one or more holding elements in the longitudinal direction immovably fixed to the object, so that the selected reference mark coincides with the fixed point of the protective housing and thus in the normal case also with the machine zero point. Here, given a simple overall structure of the housing and the mounting elements, different thermal expansions can not have a disturbing effect, is planned that in addition to the immovable holder in the region of the selected reference mark in the longitudinal direction yielding holders for the protective housing are provided in the form of spaced from the longitudinal ends of this protective housing holding elements, engage longitudinally displaceable with foot parts through housing slots in the serving in the central region of the housing for holding the magnetic carrier Gehäuselängsnuten or bores. The described overall construction can also be used according to a variant if no permanent magnets are used to select a reference mark. Here, these permanent magnets are replaced by the same adjusting body, with the help of the scale can be clamped. Normally, no selectable reference marks are present in the end region of the scale body, so that here space remains free for the attachment of the foot parts of the holding elements.

Further details and advantages of the subject invention is taken from the following description of the drawing.

In the drawing, the subject invention is illustrated, for example. Show it

1 in a highly schematized representation scale, protective housing, scanning unit and driver of a length measuring system in the case shown in section,

2 and 3 simplified cross-sectional views of FIG. 1 in the region of a permanent magnet in an active or inactive position,

4 and 5 show two cross-sectional views through a somewhat äbwandeltes measuring system with mounted inside the housing permanent magnet in the active or inactive position,

6 shows a further cross-sectional view through a newly modified measuring system in the region of an inactive permanent magnet,

Fig. 7 shows a cross section through the measuring system according to Fig. 6 in the region of a distance from the longitudinal end attached holding element and

Fig. 8 shows the measuring system according to FIGS. 6 and 7 schematized in view

After the Fig. 1 to 3 is in a carrier-forming, Tubular protective housing (1) a scale (2) with a measuring graduation (3) and distance-mounted reference marks (4) housed along the scale (2) is a scanning unit (5) adjustable, which has been illustrated only in its outlines and has known lighting and receiving devices for optoelectronic scanning of the measuring scale (3) and the reference marks (4), with the aid of which by scanning the measuring graduation (3) in counting signals to convertible measuring signals and by scanning the reference marks (4) reference pulses can be generated. The scanning unit (5) is seated on a sword-like support (6) and is guided with this between sealing lips (7) through a slot-shaped housing opening (8) to the outside, where it is coupled to a driver (9), of which a in FIG , 8th apparent cable (10) to an evaluation or Display unit for displaying the measurement result leads. As far as described so far, the length measuring system is known in principle

In a downwardly open an undercut circular cross-section having groove in a housing leg (11) adjacent to the slot (8) with their ends abutting carrier (12) housed by means of

-3AT394446B unillustrated tools, e.g. B. with the help of needle-like tools insertable in radial bores from the in FIG. 2 and in FIG. 1 left and right of the scanning unit shown in the position shown in FIG. 1 in the region of the scanning unit (5) and in FIG. 3 shown activation position can be adjusted. Each carrier (12) or (12a) is equipped with a permanent magnet (13), which is only in its activation position able to activate a in the driver (9) mounted relay or other switch (14). Each carrier (12) is associated with a reference mark (4), so that in the measuring system only when the switch (14) is activated, a reference pulse generated at the associated reference mike (4a) during scanning is utilized.

In the Figs. 4 and 5 were equivalent parts with the same reference numerals as in Figs. 1 to 3 designates. In contrast to the Fig. 1 to 3, the activation switch (14) is formed as part of the scanning unit (5). Each reference mark on the scale body (2) is associated with a foot part (15) held in a molded housing groove (16) flap-like support (17) carrying a permanent magnet (18). In the housing each selectable reference mark and thus each flap (17) is associated with a closable by a plug (19) opening. After removal of the plug (19), the flap (17) with the aid of a suitable tool from the position shown in FIG. 5 in the position of FIG. 4 adjusted, whereby also by permanent deformation of the edge (20) of said opening a position securing the flap (17) in the in Fig. 4 shown position can be made. Furthermore, the flap is secured by a larger plug (21). A in the position of FIG. 4 located permanent magnet (18) activated during the passage of the scanning unit (5) the switch (14) in the sense of an evaluation of the reference pulse generated at the associated Referenzmaike.

In a modification of the construction according to FIGS. 4 and 5, it is also possible, instead of individual, flap-like supports (17), to provide a band running over the region of the selectable reference marks and having the same profile shape, to which the permanent magnets (18) are assigned to the reference marks. are attached. In this embodiment, a selected permanent magnet is moved inward bending the tape by means of the plug (21).

In the embodiment of FIGS. 6 to 8, the scale body (2) with its longitudinal edge in a groove (22) of the protective housing (1) limited longitudinally mounted, for what purpose an elastically yielding the groove (22) around the edge of the scale body (2) filling holder (23) is provided. This bracket may be made of an elastomer, for. B. silicone rubber, exist. But it is also possible to use transversely to the longitudinal direction or obliquely thereto corrugated spring body.

The scanning unit (5) is again provided with a selection switch (24). Each selectable reference mark is associated in a cross-sectionally circular cross-section having, to the groove (22) open towards the groove (25) a cylindrical in its basic form, one side abgegefaster carrier body (26) with a permanent magnet (27), in Fig. 6 is illustrated in its inactive position. In the ceiling of the housing are provided by plug (28) closable openings through which the body (26) as the body (12) of FIG. 2 and 3 can be rotated so that the permanent magnet (27) enters an activation range for the switch (24). During rotation, the originally aligned with its chamfer with the groove wall body (26) adjusted from the side into the groove (22) and thereby clamps because of the narrowing of the groove (22) while compressing the element (23) the scale body ( 2) fixed to the housing (1) in the region of the selected reference mark The openings which can be closed by the plugs (28) can be formed as threaded openings, so that in the region of the selected reference mark a retaining element (29) for the scale housing (1) by means of its foot part (30) passing through and engaging in the by the plug (28) released openings engaging screws (31) can be attached. Through slots (32) of the element (29) fixing screws for fixing the measuring system can be attached to a machine.

Outside the attachment region of the selectable reference marks, the openings forming the openings in the middle area are connected by a longitudinal slot (33) against the scale ends. Provided here holding elements (34) for the housing (1) carry at its lower flange (35) foot parts (36) which are adapted in shape to the contiguous cross section of slot (33) and groove (25) so that they are guided longitudinally displaceable be and allow the required extent, a longitudinal adjustment of the housing relative to the attachment points of these fasteners (34) on the object. The ends of the housing (1) can be closed by covers (37).