Abstract:
A leveling shoe with a base plate ( 1 ) that has a base surface ( 2 ) and with a support plate ( 4 ) for an object that can be adjusted by means of an adjusting wedge device ( 3 ) in rectangular height direction relative to the base surface ( 2 ). The leveling shoe has an improved stability and is yet simple and inexpensive in its production. The adjusting wedge device ( 3 ) includes two wedges ( 7,10 ) that can be moved towards or away from each other by actuating a screw spindle ( 6 ). The wedges are provided with support surfaces ( 11,12 ) for the support of the plate ( 4 ). The support surfaces ( 11,12 ), in every position of the wedges ( 7,10 ), are disposed symmetrically with respect to a first plane (E 1 ) that is perpendicular to the base surface. The screw spindle axis ( 6 ) is provided with two screw parts ( 6   a,    6   b ) that have identical thread pitches but opposite thread directions.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention concerns a levelling shoe. 
   2. Description of Related Art 
   A levelling shoe of this type is prior art from, for example, CH-PS 652 186. This levelling shoe also displays a base plate and a supporting plate for an object, for example a machine or a device. The supporting plate can be displaced in a perpendicular direction relative to a base surface of the base plate by means of an adjusting wedge device. The adjusting wedge device comprises an adjusting wedge which in top view is essentially U-shaped, displaying a middle section and two wings which can be displaced by means of a screw spindle transversely to the vertical direction and is at the same time guided with a pair of lower supporting surfaces inclined towards each other on corresponding surfaces of the base plate. The direction of displacement of the adjusting wedge is inclined with respect to the base surface. Both the middle section and the wings are provided with upper supporting surfaces for the supporting plate, while these in turn form a pair of surfaces that are inclined towards each other. When the adjusting wedge is moved in one direction the supporting plate is raised, being impeded by a lateral stop element permanently connected to the base plate from moving transversely and is moved only in a perpendicular direction. When this occurs, especially when raising large loads, enormous lateral forces are exerted on the stop element, which can even cause breakage of the latter. The screw spindle and/or a bearing in which the screw spindle rests are also exposed to a powerful axial stress. 
   The U-shape of the adjusting wedge is necessary so that there is space on one side for the screw spindle and on the other for a connecting bolt arranged at a right angle to the base surface connecting the object with the base plate. Both the screw spindle and the connecting bolt, however, are located at a distance from a central plane perpendicular to the base surface (i.e. a gravitational plane), which results in an uneven load distribution on the adjusting wedge and an additional moment loading and stress on the screw spindle and/or the bearing, and additionally affects the stability of the levelling shoe. 
   A further disadvantage lies in the fact that the adjusting wedge displays a relatively complicated form (U-shape, precise seat surfaces and guidance surfaces, etc.). Especially when the levelling shoe is used for large heavy loads, for example, machine tools, which are also exposed to powerful changing loads, so that it is vital for the adjusting wedge to be extremely rigid, and the adjusting wedge must be manufactured precisely from steel, and thus the levelling shoe is expensive to produce. 
   SUMMARY OF THE INVENTION 
   This invention is based on the problem of creating a levelling shoe which is simple and cheap to manufacture and displays improved stability. 
   This problem is solved by a levelling shoe constructed in accordance with the present invention. 
   Because the adjusting wedge device, in addition to the adjusting wedge, displays a further counterwedge, where both wedges can be moved reciprocally towards or away from each other such that due to the fact that in every position their supporting surfaces for the supporting plate are arranged symmetrically to a plane perpendicular to the base surface, in which plane the axis of the connecting bolt also runs, the enormous, unilaterally-acting forces, as occur in the case of the levelling shoe according to CH-PS 652 186, are eliminated and the load is evenly distributed over both wedges. The screw spindle provided with two threaded parts displaying the same thread pitch, but opposing direction of pitch, arranged perpendicular to the plane of symmetry of the wedges and parallel to the base surface no longer requires an expensive axial bearing, as was previously necessary, since the axial forces transferred onto the two thread parts counteract each other and thus cancel each other out. Although, in place of one adjusting wedge, two wedges are used, the levelling shoe is simpler and cheaper to manufacture than ordinary levelling shoes. 
   In an especially advantageous fashion, the screw spindle engages with one threaded part in the adjusting wedge and with the other threaded part in a plate arranged on the other side of the adjusting wedge from the counterwedge. The plate is permanently attached to the counterwedge. This attachment is made advantageously via two connecting bolts projecting through the adjusting wedge each surrounded by a spacer sleeve guided so as to slide into the adjusting wedge, which connecting bolts are arranged parallel to the base surface and also serve as guide elements for the wedge. Advantageously the two connecting screws are arranged on both sides and at the same distance from a plane perpendicular to the base surface in which the screw spindle axis runs. As the result of this, a centering sleeve screwed with the base plate can be placed centrally between the two connecting bolts, on which the supporting plate is vertically guided, and which is provided to accept the connecting bolt connecting the object with the base plate. The central arrangement of both the centering sleeve and also the screw spindle considerably increases the stability of the levelling shoe, especially where heavy loads or changing loads are involved. Advantageously both wedges, in the position corresponding to the maximum height adjustment of the supporting plate, come to rest on reciprocal stop faces, so that this end position is clearly defined. 
   One example of execution of the levelling shoe according to invention is illustrated in the drawing figures and will be described in more detail below. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a levelling shoe in longitudinal section; and 
       FIG. 2  shows the levelling shoe according to  FIG. 1  in top view and partly in sectional view. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   According to  FIG. 1 , a levelling shoe displays a base plate  1  with a base surface  2  resting on the floor and also a supporting plate  4  for an object, not shown, for example a machine or a device. The supporting plate  4  is adjustable in height perpendicular to the base surface  2  by means of an adjusting wedge device  3 . The adjusting wedge device  3  comprises a screw spindle  6 , the axis (a) of which is arranged parallel to the base surface  2  and which displays a first threaded part  6   a  which engages in a thread bore hole  7   a  of an adjusting wedge  7  arranged moveably on an upper surface  8  of the base plate  1 . The screw spindle  6  is further provided with a second threaded part  6   b,  which displays the same thread pitch, but an opposing direction of the threads with respect to the first threaded part (left/right thread). The second threaded part  6   b  engages in a thread bore hole  9   a  of a plate  9 , which—as described below in more detail—is also permanently attached to a counterwedge  10  which is arranged moveably on the upper surface  8  of the base plate  1 . Both wedges  7 ,  10  are provided with a supporting surface  11 ,  12  at an angle relative to the base surface  2  for the supporting plate  4 , which in turn is fitted with corresponding supporting surfaces  14 ,  15 . The supporting surfaces  11 ,  12  of both wedges  7 ,  10  which can move by means of the screw spindle reciprocally towards or away from each other are, in every position of the wedge  7 ,  10 , arranged symmetrically with a plane E 1  which is perpendicular to the screw axis (a) and to the base surface  2 . 
   The connection of the plate  9  with the counterwedge  10 , which is arranged—(as seen in the longitudinal axis of the screw spindle) on the opposite side of the adjusting wedge  7  from the plate  9 , is performed by means of the example illustrated in  FIG. 2  by means of two connecting bolts  18  projecting through the adjusting wedge  7 . The bolts  18  can optionally have their screw head  18   a  sunk into the plate  9  and screwed into the counterwedge  10 . The connecting bolts are positioned parallel and at the same distance from a plane E 2  perpendicular to the base surface  2  and to the symmetrical plane E 1 , in which the spindle axis (a) also lies (only one of the two connecting bolts  18  is visible from the drawing). 
   One spacer sleeve  20  is assigned to each connecting bolt  18 , through which spacer sleeve  20  the connecting bolt projects, and which is guided so as to slide through a bore hole in the adjusting wedge  7 . In the axial direction each spacer sleeve  20  is supported on one side on a stop area  22  of the plate  9  and a stop area  23  of the counterwedge  10  on the other side, where both stop areas  22 ,  23  are placed perpendicular to the base surface  2 . In the drawing the position of the two wedges  7 ,  10  is illustrated in which the stop area  22  of the plate  9  rests on a stop area  24  of the adjusting wedge  7  facing away from the counterwedge  10 . In this position the two wedges  7 ,  10  are at a maximum distance from each other which is defined by the spacer sleeve  20 . The adjusting wedge  7  is provided on the side facing the counterwedge  10  with a stop area  25 , which corresponds to the stop area  23  of the counterwedge  10 . Furthermore each of the two wedges  7 ,  10  also displays a semi-cylindrical recess  27 ,  28  facing towards each other. 
   A centering sleeve  30 , positioned perpendicular to the base surface  2 , is screwed into a thread bore hole  31  ( FIG. 1 ) of the base plate  1 . The supporting plate  4  is provided with a central bore hole  29  which moveably receives the centering sleeve. The centering sleeve  30  determines the arrangement of the supporting plate  4  resting on the wedges  7 ,  10 , and thus too the arrangement of the entire adjusting wedge device  3  on the upper surface  8  of the base plate  1 . The axis (b) of the thread bore hole  31  aligned perpendicular to the base surface  2 , the centering sleeve  30  and the supporting plate  4  thereby coincides with the intersection lines of both previously described planes E 1  and E 2 . The centering sleeve  30  runs centrally between the two spacer sleeves  20 ; the position of the adjusting wedge device  3  with respect to the centering sleeve  30  and the supporting plate  4  guided vertically on the centering sleeve  30  in a transverse direction parallel to the base surface  2  and perpendicular to the spindle axis (a) is, for example, defined by side areas  36  of the supporting plate  4  co-operating with the side areas  34 ,  35  of both wedges  7 ,  10  (see for example FIG.  2 ). Both spacer sleeves  20  can, however, also touch the centering sleeve  30  tangentially and thereby define the position of the adjusting wedge device  3  with respect to the centering sleeve  30  transverse to the direction of displacement of the wedges  7 ,  10 . 
   The supporting plate  4  is provided with an upper, slightly concave, recess  39  on which a disc  40 , which is dome-shaped on its under side, rests. The disc  40  displays a bore hole  41  which surrounds the centering sleeve  30  with play and an upper area  42 . The area  42  is provided with two indentations  43  positioned symmetrically with respect to the axis of the disc, one of which can be seen from FIG.  2 . Both indentations  43  are provided for the insertion of a spacer sleeve (not shown) or a number of spacer sleeves/discs laid one on top of another and protect the latter from lateral slippage. 
   To screw in the centering sleeve  30  in the bore hole  31  of the base plate  1  the centering sleeve  30  is provided with a fitting hole  44 . The sleeve  30  is axially secured by an O-ring  46  which rests in a ring groove  45  of the centering sleeve  30  in the area of the disc bore hole  41 . The centering sleeve  30  also displays an inner thread bore hole  47 , into which a connecting bolt connecting the object with the base plate  1  (not shown in the illustration) can be screwed. 
   The levelling shoe is equipped with a covering cap  50  encompassing the supporting plate  4  on its circumference and protecting the adjusting wedge device  3 , said cap bestowing an aesthetic external appearance on the levelling shoe. The screw spindle  6  is guided through the covering cap  50  with its guiding collar  6   d  and projects with its head  6   c  (which can if appropriate be designed as a hexagonal nut) out of the covering cap  50 . 
   In an initial position, both wedges  7 ,  10  of the adjusting wedge device  3  are in the position shown in the drawing, which corresponds to the lowest position of the supporting plate  4  resting on the wedges  7 , 10  due to dead weight. Depending on whether the maximum possible lift of the supporting plate  4  determined by the shape and the means of displacement of the wedges  7 ,  10  is sufficient, the object to be aligned vertically, for example a machine foot, is placed directly on the area  42  of the disc  40  or one or more spacer discs are laid between this area  42  and the object (slip prevention guaranteed by indentations  43  and corresponding projections of the spacer discs). Then a bore hole provided in the object, e.g. in the machine foot, for the connecting bolt is placed in a position coaxial to the disc bore hole  41  and the connecting bolt is screwed into the centering sleeve  30 . The dome-shaped disc  40  resting on the supporting plate  4  serves at this point to compensate for any angular differences between the machine foot and the base surface  2 . By rotating the screw spindle  6  the two wedges  7 , 10  are then moved towards each other and the supporting plate  4  is thereby raised—guided vertically on the centering sleeve  30 —together with the load into the desired position. In a position corresponding to the maximum lift of the supporting plate  4 , the stop areas  25 ,  23  come to rest on the wedges  7 ,  10 , where both of the semi-cylindrical recesses  27 ,  28  together form an opening encompassing the centering sleeve  30 . The load is distributed evenly on both wedges  7 ,  10  and transferred via the latter to the base plate  1 . The axial forces transferred to both threaded parts  6   a,    6   b  of the screw spindle  6  via the wedges  7 ,  10  counteract each other and thus cancel each other out. The result of this is to dispense with the expensive axial bearing for the screw spindle, which is essential in ordinary levelling shoes. 
   Due to the fact that the spindle axis (a) is positioned in the central plane E 2  (i.e. a gravitational plane), in which the axis of the connecting bolt also runs, the screw spindle  6  is not loaded with any additional moments, which would have to be picked up by a bearing. The counterwedge  10  connected to the plate  9  cuts out the precise guidance and/or supporting of the screw spindle necessary with ordinary levelling shoes. 
   Both wedges  7 , 10  are guided in their direction of displacement by means of the connecting bolts  18  sheathed by spacer sleeves  20 , so that an arrangement of for example precise supporting areas or guidance areas on the wedges inclined in pairs towards each other on the one hand and on the supporting plate on the other hand, such as those on the levelling shoe according to CH-PS 652 186, is not necessary. Wedges  7 , 10  display a simple external form and can be produced economically. This is important especially when the levelling shoe is used for heavy loads or changing loads, where the wedges  7 ,  10 , must display sufficient rigidity, and which therefore cannot, for example, be produced using the cheap aluminium die-cast process, but have to be made from steel. 
   The supporting plate  4  resting on the wedges  7 , 10  due to dead weight is advantageously also secured against improper removal, e.g. on the occasion of transport or assembly, in a way which is not described in more detail (for example by screw bolts connecting the transport plate  4  with the base plate  1 , allowing the transport plate  4  to be raised vertically or by a corresponding design of the centering sleeve screwed into the base plate  1 ). 
   The design example shown is a levelling shoe which can be screwed up or down with the object and together with the latter forms a free-standing unit with respect to the fundament. The levelling shoe according to invention can, however, also be used for machines which require anchoring to the fundament. In this case the thread bore hole  41  in the centering sleeve is omitted, and an anchor bolt guided through the centering sleeve is anchored in the fundament. 
   It would also theoretically be possible to have the screw spindle engage directly in the counterwedge with one of the two thread parts displaying the opposite direction of pitch and to screw the object up or down with two connecting bolts placed in plane E 1  on both sides of the screw spindle arranged symmetrically to plane E 2  with the base plate ( 1 ) of with the fundament. The solution according to invention with a centrally-positioned connecting bolt does, however, allow simpler positioning of the object with respect to the base plate ( 1 ) and a simple compensation of angular differences between the object and the base surface  2 .