Adapter for coupling two shaft ends in a defined angular orientation

An adapter for the coupling of two shaft ends in a defined angular orientation with respect to the longitudinal shaft axes. The adapter is mounted in a defined angular orientation on a first shaft, and on the side associated with a second shaft it has a receptacle for receiving the second shaft. The second shaft has an end that is partially flattened The receptacle is surrounded by a flange in one partial segment of which is at least one projection having inclined surfaces of such dimensions, that the projection fits interlockingly into the flattened part of the second shaft upon reaching the desired angular orientation of the two shafts. The adapter according to the invention is particularly suited for the connection of the shaft of a drive unit with the shaft of an rotary encoder.

FIELD OF THE INVENTION 
The invention relates to an adapter for coupling two shaft ends in a 
defined angular orientation with respect to the longitudinal axes of the 
shafts. The adapter according to the invention is particularly suited for 
connecting the shafts of a drive unit and a rotary encoder. 
BACKGROUND OF THE INVENTION 
Several possibilities for connecting the shaft of a drive unit with the 
shaft of an rotary encoder are known. For example, the connection can be 
established with the aid of suitable couplings, perhaps such as those 
described on page 41 of "Digital Longitudinal and Angular Metrology" by A. 
Ernst, Verlag Moderne Industrie, publs., 3rd ed., 1989. With extreme 
measuring demands, correspondingly high demands are also made regarding 
the torsional rigidity on such couplings. An alternative for avoiding the 
problems arising in this connection lies in the use of a so-called stator 
coupling where the actual coupling is not disposed on the rotor side but 
rather is disposed between the drive housing and the scanning unit of the 
rotary encoder, i.e. on the stator side. Such a coupling is known, for 
example, from FIG. 24 on page 43 of the above mentioned book. 
In the case of stator coupling of the drive and rotary encoder shafts, the 
driveshaft is rigidly connected with the rotary encoder shaft by the aid 
of a center screw which is arranged coaxially with respect to both shafts. 
However, problems arise under certain conditions with this type of rotary 
encoder mounting. For example, the place where the two shafts meet each 
other may not directly accessible. If at the same time a defined angular 
orientation between the two shafts is demanded, for example, because of 
the defined association of a reference pulse of the rotary encoder to the 
driveshaft, an elaborate adjusting process of the two systems with respect 
to each other is the result. There is furthermore the danger that, 
following the performance of an adjustment of the two shafts with respect 
to each other, the two shafts are again twisted with respect to each other 
in an undesirable way because of the tightening of the central screw. 
SUMMARY OF THE INVENTION 
According to a first aspect of the invention there is provided an adapter 
for coupling a first and a second shaft end in a defined angular 
orientation with respect to the longitudinal axes of the shafts. The 
second shaft end is partially flattened. The adapter includes one end for 
receiving in a defined angular orientation, the first shaft end and a 
receptacle for receiving the second shaft end. A flange surrounds the 
receptacle and has a partial segment which has at least one projection 
having inclined surfaces of such dimensions that the projection 
interlockingly fits into the flattened area of the second shaft end when 
the desired angular orientation has been achieved. 
It is therefore an object of the present invention to create an adapter 
which offers a simple defined angular alignment of two shafts if, for 
example, the shaft ends are not directly accessible. In this case the 
actual coupling function between the two shafts is not provided by the 
adapter; instead, a rigid coupling of the two shafts with each other is 
provided in which the angular orientation, once it has been established, 
is intended to be maintained. 
The adapter according to the invention permits simple mounting of an rotary 
encoder on a drive unit where simultaneously a defined angular orientation 
of the two shafts to each other is assured. If, for example, the 
disposition of a rotary encoder in a cylinder-shaped receptacle of a drive 
unit is provided, the rotary encoder can be inserted into the receptacle 
roughly aligned once the adapter has been mounted on the rotary encoder 
shaft. The adapter according to a preferred embodiment of the invention 
allows the two shafts to align themselves exactly in the desired angular 
orientation with respect to each other without the shaft ends having to be 
visible or accessible. In the course of the subsequent tightening of the 
central screw for the rigid coupling of the two shafts with each other, it 
is furthermore assured that the two aligned shafts can no longer become 
twisted with respect to each other. 
The adapter according to the invention is advantageously embodied as an 
inexpensively manufactured injection-molded part since no special 
mechanical demands are made on the adapter in the actual measuring 
operation. 
Further advantages as well as details of the adapter according to the 
invention ensue from the following description of preferred embodiments 
through the attached drawings.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
FIG. 1 is a cross-sectional view of two shafts 1, 2 to be connected of a 
drive unit 3 and of a rotary encoder 4 respectively through an adapter 6 
according to a preferred embodiment of the present invention. Both the 
drive unit 3 and the rotary encoder 4 are only partially shown. In the 
coupled state the two shaft ends are not directly accessible because of 
the arrangement of the rotary encoder 4 in the cylinder-shaped receptacle 
12, and can therefore not be angularly adjusted. 
A central screw (not shown) is provided coaxially with the two shafts 1, 2, 
and rigidly connects the two shafts 1, 2 with each other. To this end the 
central screw is tightened from the side of the rotary encoder 4. The 
actual coupling between the drive unit 3 and the rotary encoder 4 is also 
not visible in FIG. 1. A so-called stator coupling is provided as the 
coupling which is fastened on the stator side toward the rotary encoder 4, 
i.e. on the rotary encoder, and on the side toward the drive unit 3 on the 
housing of the latter. 
In order to solve the problems referred to above, the adapter 6 according 
to the invention is disposed between the two shafts. In a preferred 
embodiment it is designed as a simple, rotationally symmetrical 
injection-molded element preferably made of fiberglass-reinforced 
polycarbonate, which has respectively one receptacle for the shaft ends of 
the drive and the rotary encoder shafts on two oppositely located sides. 
The connections between the two shaft ends and the adapter 6 can be 
embodied in different ways, for example, as releasable connections in the 
form of plug connections. Besides this, a connection between the adapter 6 
and the rotary encoder shaft can be provided in such a way that the 
adapter 6 is pressed on the rotary encoder shaft 2, for example. 
Furthermore, the connection between the adapter 6 and the rotary encoder 
shaft 2 is embodied in such a way that a clear angular orientation of the 
adapter 6 with respect to the longitudinal axis 5 of this shaft 2 results, 
i.e. that no twisting with respect to it is possible. This can be assured, 
for example, in that the end of the rotary encoder shaft 2 is embodied to 
be flattened and that the receptacle on the side of the adapter 6 has a 
corresponding cross section, so that an interlocking connection results. 
A circumferential flange is provided on the side of the adapter 6 which is 
associated with the driveshaft 1. The flange has, at least in a partial 
segment, a flattened projection oriented in the direction toward the 
driveshaft 1 with conical surfaces oriented toward each other. The 
flattening of the conical surfaces or the dimension of the projection is 
of such a size that for a desired angular orientation of the two shafts 1, 
2 with respect to each other the projection fits interlockingly into a 
corresponding, oppositely located cutout in the driveshaft 1 as seen in 
FIG. 1. For example, in the preferred embodiment as shown in FIG. 1, the 
required cutout in the driveshaft 1 is embodied as a flattening of the 
shaft end into which the projection fits. 
If, accordingly, the two shafts 1, 2 are roughly aligned with respect to 
each other during the mounting of the drive unit 3 and the rotary encoder 
4, and if the projection on the adapter 6 arranged on the rotary encoder 
shaft 2 already partially engages the cutout in the driveshaft 1, the 
desired defined angular orientation of the two shafts 1, 2 results when 
they are pushed together. Because of the design of the projection with the 
two conically oriented surfaces, the shaft which turns easier of the two 
shafts 1, 2 is given a rotating movement until the projection fits 
interlockingly into the oppositely located cutout, i.e., the desired 
angular orientation is assured. The rigid fixation of the two shafts 1, 2 
follows thereafter by tightening the central screw (not shown). Here, too, 
the embodiment of the adapter 6 in accordance with the invention proves to 
be advantageous, since twisting of the two shafts 1, 2 with respect to 
each other cannot occur when the screw is tightened as long as the 
projection has been interlockingly fitted into the cutout of shaft 1. 
FIG. 2 is a cross-sectional view of the adapter shown in FIG. 1. The two 
receptacles 7, 8 of the adapter 6 for the shaft ends to be connected can 
be seen there, as well as the circumferential flange 10 on which the 
projection 9 is disposed in a partial segment. 
FIG. 3 is a cross-sectional view of the adapter shown in FIG. 2 taken in a 
plane perpendicular to the cross-section shown in FIG. 2. The projection 
provided on the adapter 6 and its cooperation with the opposite cutout 13 
in the driveshaft 1 become visible. In the representation of FIG. 3, the 
driveshaft 1 does not yet have the desired angular orientation with 
relation to the adapter 6, and instead was only roughly oriented with 
respect to it. However, the obliquely disposed surfaces 11a, 11b of the 
projection already partially engage the cutout 13 in the form of a 
flattening on the part of the shaft 1. In the course of pushing the shaft 
1 and the adapter 6 or of the rotary encoder connected therewith further 
together, the adapter 6 and the driveshaft 1 turn toward each other 
because of the design of the projection until the projection fits 
interlockingly into the cutout 13 and the desired angular orientation is 
made. The design of the cutout 13 on the side of the shaft 1 in the form 
of a flattening of the shaft end is also clearly visible in this 
representation. 
Alternatives to the described embodiment and to the arrangement of the 
adapter in accordance with the invention are of course also possible. For 
example, in principle the adapter can be connected with the driveshaft and 
the orientation of the two shafts takes place by the projection engaging a 
corresponding cutout in the rotary encoder shaft. In addition alternative 
embodiments regarding the design of the projection are possible, including 
the correspondingly dimensioned cutout on the side of the shaft arranged 
on the opposite side. 
It is to be understood that the forms of the invention as described 
herewith are to be taken as preferred examples and that various changes or 
modifications in the shape, size and arrangement of parts may be resorted 
to without departing from the spirit of the invention or scope of the 
claims.