Device for fastening a C-shaped mounting rail to a wall provided with screw holes

The invention relates to a device for fastening the end of a C-shaped mounting rail to a wall with holes of a control cabinet or of a frame piece of a control cabinet frame, having a fastening block which can be inserted into the end of the rail and which is adapted to the inside cross section of the mounting rail and fastened to the wall by means of a fastening screw. Fastening of the mounting rail only from the fastening side of the wall is achieved by the wall having a row of rectangular or square cutouts and, placed between them and offset by one-half spacing, a row of screw holes. The fastening block is closed off with a fastening plate on the side facing the wall. The fastening plate has an L-shaped hanger on the side facing the wall, which is adapted to the cutouts and the thickness of the wall and can be hung in a cutout. The fastening plate has a screw hole outside of the fastening block for receiving of a fastening tap screw, which can be screwed into a screw hole in the wall when the fastening plate has been hung.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a device for fastening the end of a C-shaped 
mounting rail to a wall with holes of a control cabinet or to a wall with 
holes of a frame piece of a control cabinet frame. The device has a 
fastening block which can be inserted into the end of the rail, which is 
adapted to the inside cross section of the mounting rail and which can be 
fastened to the wall by means of a fastening screw. 
2. Description of the Prior Art 
A similar device is known from German Utility Model DE-GM 88 05 118. In 
this known device the fastening block is provided with a stop plate 
limiting the insertion movement of the fastening block in the inner 
receptacle of the mounting rail. The side of the stop plate facing the 
wall includes the fastening screw hole for the fastening screw, which is 
inserted into the screw hole in the wall from the backside of the wall and 
screwed into the fastening screw hole of the fastening block. This 
requires that the wall with the screw holes must be accessible from the 
back. But this is not always the case. An example would be the fastening 
of a mounting rail to a frame of a control cabinet, where the screw holes 
are provided in a wall of the frame which essentially is composed of 
rectangular profile sections which are not accessible from the interior of 
the rectangular profile sections. 
SUMMARY OF THE INVENTION 
The object of the invention is to provide a device of the type mentioned 
above, where the fastening of the end of a mounting rail to a wall with 
screw holes is easily done when this wall is only accessible from the 
fastening side. 
This object is attained in accordance with the invention where the wall has 
a row of rectangular or square cutouts and, placed between them and offset 
by one-half spacing, a row of screw holes. The fastening block is closed 
off with a fastening plate on the side facing the wall. The fastening 
plate has an L-shaped hanger on the side facing the wall, which is adapted 
to the cutouts and the thickness of the wall and can be hung in a cutout. 
The fastening plate has a screw hole for receiving a fastening tap screw 
outside of the fastening block, which can be screwed into a screw hole in 
the wall when the fastening plate has been hung. 
Because the wall is provided with rows of interspersed cutouts and screw 
holes, the fastening block can first be hung from the fastening side in a 
cutout of the wall by means of the hanger of the fastening plate. Then the 
fastening plate is screwed with the fastening screw into the appropriately 
offset screw hole of the wall. In this case the fastening screw must be 
self-tapping in order to be sufficiently well seated in the screw hole. 
In accordance with one embodiment of this invention, where the fastening 
block has a U-shaped recess which defines a square nut with a threaded 
bore on three sides, and where the threaded bore is directed crosswise to 
the longitudinal axis of the mounting rail and vertically to the base leg 
of the same and receives a tensioning screw for the axial seating of the 
fastening block in the mounting rail, it is possible to fasten the 
mounting rail without axial play between two walls. This has the 
additional advantage that the mounting rail, which is cut into sections, 
does not need to be exactly adapted to the distance between the two walls. 
To prevent lateral play of the mounting rail, it is provided in accordance 
with a further embodiment that the legs of the L-shaped fastener have a 
width adapted to the associated size of the cutouts. Hanging, together 
with screw fastening, results in fixing the mounting rail so it cannot 
twist. The device can be designed and made in a simple way in that the 
fastening plate with the hanger is made of one piece with the fastening 
block. In this connection it has been preferably provided that the 
fastening block with the square nut and the fastening plate be formed as a 
metal-cast component, in particular an injection die-cast metal component. 
Handling of the device is made easier by rounding of the corners of the 
fastening plate. 
In another embodiment of the invention, the weight of the fastening block 
can be reduced to a minimum by using a U-shaped cutout leaving the 
fastening block open, so that only two pieces of its frame remain, 
supporting the square nut. 
Variations in the dimensions of the interior cross section of the mounting 
rail can be compensated for the most part by providing the outsides of the 
fastening block frame pieces with crosswise directed grooves, fins, or the 
like. 
The invention will be described in detail by means of an exemplary 
embodiment shown in the drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Only a section of the C-shaped mounting rail 10 is shown in FIG. 1, the 
left end of which is intended to be fastened to the piece of a frame of a 
control cabinet. The right end of the mounting rail 10 may be fastened in 
the same way to another piece of the same frame disposed at a distance. 
The device has a cuboid fastening block 20 adapted to the interior cross 
section of the mounting rail 10, which can be inserted into the interior 
of the mounting rail 10 until the fastening plate 24 abuts the end of the 
rail. The U-shaped recess 21 defines the square nut 22, into which the 
threaded bore 23 has been cut, in the fastening block 20. This threaded 
bore 23 extends crosswise to the longitudinal axis of the mounting rail 10 
and vertically to the base leg of the mounting rail. Thus the square nut 
22, the two frame pieces, and the fastening plate 24 form one piece. The 
fastening plate 24 extends on at least one short side beyond the mounting 
rail 10 and has in this area the screw hole 26 for the fastening screw 27. 
The long sides of the fastening plate 24 can end flush with the facing 
exteriors of the mounting rail 10. The L-shaped hanger 25 is formed out of 
the fastening plate 24 on its side facing the wall 14 of the frame piece 
11. A row of square cutouts 12, arranged with regular spacing, has been 
cut in each of the walls 14 and 15 of the frame piece 11. A row of 
threaded holes 13 has been cut in each one of these rows of cutouts 12, 
which are each offset by one-half space in respect to the cutouts 12. If 
the hangers 25 have a width which corresponds to the length of the sides 
of the cutouts 12, the fastening block 20 can be hung in a cutout 12. 
The L-shaped hanger 25 is disposed on the fastening plate 24 with its end 
leg protruding at a distance which corresponds to the thickness of the 
wall 14. The screw hole 26 in the fastening plate 24 is matched with the 
hanger 25 in such a way that, in the hung position, the screw hole 26 of 
the fastening plate 24 is aligned with the screw hole 13 in the wall 14, 
which has been offset by 1/2 spacings in respect to the cutout 12 in which 
the hanger 25 is hung. In this way the fastening block 20 and with it the 
mounting rail 10 supported by the fastening block 20 is supported in the 
frame piece 11 in a way that it cannot be twisted, in spite of only a 
single screw connection. The threaded bore 23 in the square nut 22 is 
accessible through the slit in the mounting rail 10 and it is therefore 
possible for the tensioning screw 28, formed as a headless screw with a 
hexagon socket, to fix the mounting rail 10 axially non-movable on the 
fastening block 20, so that the mounting rail 10 can have substantial 
axial play on the fastening block 20 before the tensioning screw 28 is 
tightened. When the mounting rail 10 is fastened at both ends, this play 
permits both hangers 25 to be hung in the associated frame pieces. Axial 
fixing by means of the tension screws can take place after fastening of 
the fastening plates. 
In place of the frame pieces 11 any other wall of the control cabinet may 
be used for fastening of mounting rails, as long as it has rows of cutouts 
12 and screw holes 13.