Abstract:
A mounting device for mounting a length measuring system extending in a measurement direction, the mounting device including a basic body, a steadying device attached to the basic body and a retainer attached to the basic body. A length measuring system that extends in a measurement direction is fixable on the basic body by clamping between the steadying device and the retainer, wherein the basic body and the retainer are embodied for guiding the retainer on the basic body longitudinally in a manner fixed against relative rotation in a direction of the steadying device by an adjusting element.

Description:
RELATED APPLICATIONS 
       [0001]    Applicants claim, under 35 U.S.C. §119, the benefit of priority of the filing date of Sep. 15, 2011 of a German patent application, copy attached, Serial Number 10 2011 082 755.2, filed on the aforementioned date, the entire contents of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a mounting device for mounting a length measuring system on a machine part, in particular on a machine tool. 
         [0004]    2. Background Information 
         [0005]    One such mounting device, in the form of a mounting rail, is described in European patent disclosure EP 0 185 072 B1. The mounting rail includes a wall, a lower protrusion, and an upper protrusion, wherein the space between the two protrusions serves to receive a scale housing. The lower protrusion acts as a steadying device on which the scale housing is braced. A plurality of screws in the form of pressure screws are screwed into the upper protrusion. The screws press on a chamfered face of the scale housing and, thus, force the scale housing against the wall of the mounting rail, on the one hand, and against the lower protrusion of the mounting rail, on the other hand. 
       OBJECTS AND SUMMARY OF THE INVENTION 
       [0006]    It is an object of the present invention to provide a mounting device of minimal structural size with which a length measuring system can be retained as stably as possible. 
         [0007]    This object is attained by a mounting device for mounting a length measuring system extending in a measurement direction, wherein the length measuring system is fixable on a basic body by clamping between a steadying device and a retainer. The basic body and the retainer are embodied for guiding the retainer on the basic body longitudinally in a manner fixed against relative rotation in the direction of the steadying device by an adjusting element. 
         [0008]    For longitudinal guidance, at least one guide face is embodied on the basic body for guiding the retainer thereon in a manner fixed against relative rotation in the direction of the steadying device. 
         [0009]    Advantageously, the retainer has a first portion that is capable of being brought into engagement with both the length measuring system and a second portion of the retainer. The second portion of the retainer is embodied for guiding the retainer on the at least one guide face of the basic body in a manner fixed against relative rotation in the direction of the steadying device. The first portion of the retainer can have at least one lug-like protrusion, which is embodied for effecting a compression of material upon the engagement with the length measuring system. 
         [0010]    For especially stable longitudinal guidance of the retainer on the basic body, the basic body has a recess in which the retainer is guided in a manner fixed against relative rotation. 
         [0011]    Advantageously, the recess has two guide faces extending parallel to one another and which constrain the retainer in the measurement direction. 
         [0012]    For the sake of saving space, the basic body has a wall with an inner attachment face on which, with the length measuring system received on it, a face of the length measuring system rests. The recess is made in the above mentioned wall of the basic body so that the retainer is guided in a manner fixed against relative rotation at a back side of the length measuring system on the basic body. 
         [0013]    Preferably, the steadying device is a protrusion integrally formed on the basic body. 
         [0014]    The adjusting element for shifting the position of the retainer on the basic body is preferably a screw that engages a female thread of the retainer. 
         [0015]    The screw can be embodied to be drivable on both ends, wherein on both ends of the screw is a profile for a screwdriver. 
         [0016]    The retainer preferably has a hook with which the retainer forms a positive locking with the basic body. 
         [0017]    In a preferred embodiment, the basic body is a mounting rail extending in the measurement direction. The mounting rail includes a plurality of recesses, each of which is for the guidance in a manner fixed against relative rotation of a respective retainer and spaced apart from one another in the measurement direction. 
         [0018]    For retaining the scale housing, a single retainer on the basic body may suffice. For longer scale housings, a plurality of retainers can be provided that are spaced apart longitudinally from one another on the basic body embodied as a mounting rail. In the alternative, a plurality of basic bodies, each with at least one retainer, are disposed in succession in the longitudinal direction. 
         [0019]    In particular, the mounting device has as its basic body a mounting rail, which, on the one hand, is embodied for fastening a scale housing onto itself and, on the other hand, for mounting the scale housing on a machine part. To that end, the mounting rail has a retention mechanism. 
         [0020]    An object of the present invention is furthermore to provide a structural unit having a mounting device and a mounted length measuring system. 
         [0021]    The structural unit includes the mounting device for attaching the length measuring system extending in a measurement direction. The length measuring system is fixed on a basic body between a steadying device and a retainer by clamping, and the basic body and the retainer are embodied for longitudinally guiding the retainer on the basic body in a manner fixed against relative rotation in the direction of the steadying device by an adjusting element. 
         [0022]    The structural unit is preferably designed such that the basic body has at least one recess in which the retainer is guided in a manner fixed against relative rotation, and the at least one recess is provided at the back side of the length measuring system. 
         [0023]    The present invention will now be described in further detail in terms of an exemplary embodiment. 
         [0024]    In the drawings: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a perspective, exploded view of an embodiment of a mounting rail and a scale housing prior to being attached to one another in accordance with the present invention; 
           [0026]      FIG. 2  shows a cross-section of the mounting rail of  FIG. 1 ; 
           [0027]      FIG. 3  shows a cross-section of the mounting rail with the scale housing of  FIG. 1  attached to one another; 
           [0028]      FIG. 4  shows the cross-section of the mounting rail of  FIG. 3  in the state in which it is attached to a machine part in accordance with the present invention; 
           [0029]      FIG. 5  shows a perspective view of an embodiment of a retainer of the mounting rail of  FIG. 1 ; and 
           [0030]      FIG. 6  is a section through the retainer of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]      FIG. 1  shows a perspective exploded view of a mounting rail  1  and a scale housing  2  on being assembled. The mounting rail  1  serves to mount the scale housing  2  on a machine part  3 . To that end, the mounting rail  1  has a structure for screwing the mounting rail onto an attachment face  31  of the machine part  3 . The structure includes bores  11 ,  111  formed in the mounting rail  1  and fastening screws  12  for screwing into the machine part  3 . The bore  111  is designed to create a fixed point, also called a reference point, of the mounting rail  1  and the machine part  3 . The remaining bores  11  are designed for attaching the mounting rail  1  movably to the machine part  3  at these fastening points in the measurement direction X. To that end, the regions of the fastening bores  11  are connected to the rest of the mounting rail  1  via compensation elements, embodied here in the form of solid-state joints  19  that are deflectable in the measurement direction X by bending. The provision of compensation elements ensures that different thermal expansions of the mounting rail  1  compared to the machine part  3  are compensated for and do not cause any warping of the mounting rail  1 . 
         [0032]    The mounting rail  1  also has a retention mechanism for retaining the scale housing  2  on the mounting rail  1 . This retention mechanism is designed for suspending the scale housing  2  from the mounting rail  1  in the manner shown in  FIG. 3 . The retention mechanism of the mounting rail  1  includes at least one retainer  4 . In an exemplary embodiment, there are two identical retainers  4  spaced apart from one another in the measurement direction X. The retainers  4  can each be shifted in the direction of a steadying device  13  of the mounting rail  1  as shown in  FIGS. 2-3  by an adjusting element  5 . This shifting takes place in a direction Z that is perpendicular to the measurement direction X. By this displacement of the retainers  4 , the scale housing  2  is fastened by clamping between the steadying device  13  and the retainers  4  to the mounting rail  1 . 
         [0033]    A retainer  4  is shown enlarged in  FIGS. 5 and 6 . Each of the retainers  4  has a first portion  41  and a second portion  42 . The first portion  41  is designed for engagement with the scale housing  2  and is embodied as a protrusion projecting from the wall  16  of the mounting rail  1 , in particular as a hook-like protrusion with a slot-like receptacle  411 . The slot-like receptacle  411  is engaged in positive locking fashion by a protrusion  23  of the scale housing  2  as shown in  FIGS. 3-4 . The first portion  41  of the retainer  4  forms a kind of hook catch for the scale housing  2 , into which the scale housing  2  can be hooked in positive locking fashion and which braces the scale housing  2  from below (in the Z direction). 
         [0034]    On the first portion  41  of the retainer  4 , at least one lug-like protrusion  412  is provided, which is embodied for forcing itself into the material of the scale housing  2 . In other words, the protrusion  412  is used for attaining a material compression. If the scale housing  2  is made of aluminum, then the outer surface is anodized and is electrically insulating. The lug-like protrusion  412  pierces the anodized layer of an outer surface of the scale housing  2  and establishes an electrically conductive connection between the scale housing  2  and the retainer  4 . Moreover, the protrusion  412  penetrating the scale housing  2  forms a positive locking, operative in the measurement direction X, between the scale housing  2  and the retainer  4 . 
         [0035]    The second portion  42  of the retainer  4  is guided in the Z direction in a recess  14  in the mounting rail  1 , and the recess  14  and the second portion  42  of the retainer  4  are embodied such that the retainer  4  is displaceable, in a manner fixed against relative rotation, in the mounting rail  1  in the direction of the steadying device  13 . Advantageously, the retainer  4  has a rectangular outer contour and the second portion  42  includes two side faces extending parallel to one another. In addition, the recess  14  has side faces extending parallel to one another, which form guide faces and a positive locking, operative in the measurement direction X, for both side faces of the retainer  4 . This positive locking has a structure for preventing relative rotation and constrains the retainer  4  in the measurement direction X. The retainer  4  with the two portions  41  and  42  is in one piece and, in particular, is embodied as a one-piece milled part and accordingly can be manufactured inexpensively and is especially stable. 
         [0036]      FIG. 2  shows a cross-section of the mounting rail  1  in the vicinity of one of the retainers  4  without the scale housing  2 .  FIG. 3  shows the same cross-section with the scale housing  2  fastened to the mounting rail  1 , and  FIG. 4  shows the same cross-section through the mounting rail  1  in a state in which the mounting rail  1 , with the scale housing  2  fastened to it, is attached to a machine part  3 . In these cross-sectional views, it can be seen that the recess  14  forming the guide for the retainer  4  is disposed in a wall  16  of the mounting rail  1 . Specifically, the recess  14  is formed in a region of the mounting rail  1  between the back side  22  of the scale housing  2  and the attachment face  17  on the back side of the mounting rail  1 . If the mounting rail  1  is attached to the machine part  3 , this back side of the mounting rail  1  is brought into contact with the machine part  3 . The second portion  42  of the retainer  4  is, thus, accommodated in an especially space-saving way and is guided stably on the mounting rail  1 . 
         [0037]    The steadying device  13  is a protrusion formed integrally and in one piece with the wall  16  of the mounting rail  1 . The steadying device  13  includes a contact-pressure face that corresponds to a face of the scale housing  2 , in such a way that a contact-pressure force F (see  FIG. 3 ) with one component in the direction of the inner attachment face  15  of the mounting rail  1  and one component in the direction of the scale housing  2  results. 
         [0038]    Once the scale housing  2  has been mounted on the mounting rail  1  as shown in  FIG. 3 , the scale housing  2  rests with its back side  22  on the mounting rail, and the recess  14 , with the second portion  42  of the retainer  4  guided in it, extends in the wall  16  of the mounting rail  1  between the attachment face  31  and the scale housing  2 . The adjusting element  5  and the guided section portion  42  of the retainer  4  are accommodated in a space-saving way in the wall  16  of the mounting rail  1  behind the reception chamber that forms the mounting rail  1  for the scale housing  2 . The reception chamber is the space between the steadying device  13  and the first portion  41  of the retainer  4 . 
         [0039]    The retainer  4  can be shifted in the direction of the steadying device  13  by the adjusting element  5 . The adjusting element is a screw  5 , which is introduced into a bore  18  in the mounting rail  1  and is braced on the mounting rail  1  by a screw head  51 . As shown in  FIGS. 2 and 6 , the retainer  4  has a female thread  43  into which the screw  5  can be screwed. 
         [0040]    The retainer  4  has a through bore  45 . The screw  5  is advantageously embodied such that it is rotatable on both ends by an actuating tool. To that end, each end of the screw has a profile against which a screwdriver can be placed and into which torque can be introduced. The profiles are inside profiles, such as a hexagon socket for a hex screwdriver and/or a hexagon ball socket for a torque screwdriver. In the example shown, the head  51  of the screw  5  has a hexagon socket  52 . The other end of the screw  5  has a rounded hexagon socket  53  that extends into the through bore  45  and is, thus, accessible and actuatable from outside with a torque screwdriver. 
         [0041]    As shown in  FIG. 2 , the center axis A 1  of the female thread  43  of the retainer  4  is offset from the center axis A 2  of the bore  18  in the mounting rail  1  in the Y direction toward the attachment face  15  when the scale housing  2  has been suspended from the mounting rail  1 , but the screw  5  has not yet been inserted into the bore  18 . When the screw  5  is screwed into the female thread  43 , an initial stress on the retainer  4  in the Y direction is initiated, which as the screw  5  is screwed in forces the screw in the direction of the inner attachment face of the mounting rail  1 . The offset of the two center axes A 1 , A 2  is in a range from 0.4 to 1.0 mm. 
         [0042]    On its back, the retainer  4  has a hook  44  that engages behind the wall  16  of the mounting rail  1  and is braced on the wall  16  such that shifting of the retainer  4  in the Y direction (to the right in terms of  FIGS. 2-4 ) is prevented. In other words, shifting of the scale housing  2  away from the attachment face  15  is prevented. The hook  44  and the wall  16  of the mounting rail  1 , thus, form a wraparound grip and hence a positive locking that prevents a tilting motion in the Y direction, and accordingly brings about a positive locking in a direction that is perpendicular to the measurement direction X and also perpendicular to the Z direction. 
         [0043]    The hook  44  engaging the wall  16  from behind also functions to prevent the retainer from being lost in a state in which the screw  5  has not been screwed into the female thread  43 , or, in other words, in the position shown in  FIG. 2 . The force of gravity of the retainer  4 , acting downward in the Z direction, secures the position of the retainer  4  on the mounting rail  1 . As can be seen in  FIG. 4 , the hook  44  in the attached state is positioned between the attachment face  31  and a region of the wall  16  of the mounting rail  1  and, thus, forms a sort of wraparound grip. 
         [0044]    As shown in  FIG. 3 , the scale housing  2  has a scale  21  in its interior, which in a known manner is scanned in the position measurement by a scanner unit (not shown) that is movable in the measurement direction X relative to the scale  21 . 
         [0045]    If high-precision position measurement is desired, a measurement graduation of the scale  21  is designed so that it can be scanned photoelectrically. Alternatively, the measurement graduation can be designed to be scanned magnetically, capacitively, or inductively. 
         [0046]    Besides the exemplary embodiments described, it is understood that still other modifications are possible within the scope of the present invention.