Grinding machine

A grinding machine comprises a grinding spindle which can be displaced in a horizontal plane relative to a workpiece. The grinding spindle drives a grinding wheel, which is mounted for rotary movement about a horizontal axis, and is arranged on a swivel carriage arranged for rotary movement about a vertical axis relative to a base plate. A measuring device is provided for detecting the rotary position of the swivel carriage relative to the base plate comprise a first sensor element which is rigidly connected to the base plate and a second sensor element that can be rotated together with the swivel carriage. In order to simplify the measuring device and to make it easily accessible the sensor elements are arranged outside the said swivel carriage and the second sensor element is connected to the swivel carriage via a power transmission.

The present invention relates to a grinding machine comprising a grinding 
spindle which can be displaced in a horizontal plane relative to a 
workpiece, the grinding spindle driving a grinding wheel, which is mounted 
for rotary movement about a horizontal axis, and being arranged on a 
swivel carriage arranged for rotary movement about a vertical axis 
relative to a base plate, and comprising further measuring means for 
detecting the rotary position of the swivel carriage relative to the base 
plate, which measuring means comprises a first sensor element which is 
rigidly connected to the base plate and a second sensor element that can 
be rotated together with the swivel carriage. 
BACKGROUND OF THE INVENTION 
A grinding machine of the type described above has been known in the art. 
The known grinding machine serves for cylindrical surface grinding of 
rotational-symmetrical workpieces. When in the case of such workpieces an 
outer contour is to be ground which comprises, for example, a first 
cylindrical portion and a second cylindrical portion of different diameter 
with a conical transition zone arranged therebetween, all the three 
surface areas can be ground with the aid of the known grinding machine in 
a single operation, by changing the angular position of the grinding 
spindle, without the need to perform any resetting or resharpening 
operations first. 
However, the known grinding machine is of rather complex design, as regards 
its swivelling mechanism, the control unit required for actuating the 
latter and as regards the measuring device enabling the position of the 
swivel carriage relative to the mounting plate to be measured. In the case 
of the known machine, for example, the measuring device is arranged 
directly in the area of the swivel carriage and, accordingly, not readily 
accessible with the result that on the one hand a complex structure is 
obtained and, on the other hand, time-consuming work is required for 
servicing or, if necessary, exchanging the swivel mechanism and the 
measuring device of the known grinding machine. 
It has been found, therefore, that the measuring device of the known 
grinding machine does not in all cases meet today's demands regarding the 
required measuring precision for the rotary position of the grinding 
spindle. 
SUMMARY OF THE INVENTION 
Now, it is the object of the present invention to improve a grinding 
machine of the type described above in such a manner that a simple and 
sturdy structure of the measuring device is obtained and that the 
measuring device enables the rotary position of the grinding spindle to be 
measured with the degree of precision achievable today with the aid of 
rotary-angle sensors. 
This object is achieved according to the invention by the fact that the 
sensor elements are arranged outside the swivel carriage and that the 
second sensor element is connected to the swivel carriage via a power 
transmission. 
This solves the object underlying the present invention completely and 
perfectly as the measuring device, which is now arranged a long way 
outside the swivel carriage, together with the two sensor elements, are 
now freely accessible almost at desire, which facilitates on the one hand 
the electrical wiring operations and makes the unit on the other hand 
easily accessible for servicing and repair work if this should become 
necessary. The power transmission between the swivel carriage and the 
second sensor element may be designed with extreme mechanical precision to 
ensure that the second sensor element follows the rotary movement of the 
swivel carriage without any notable measuring error, either by synchronous 
angular movement or with a transmission ratio. 
According to a particularly preferred variant, the power transmission 
causes the swivel carriage and the second sensor element to perform 
synchronous rotary movements. 
This feature provides the advantage that any conversion operations or any 
linearization of non-linear characteristics is avoided and the output 
signal of the measuring device provides a direct measure for the angular 
position of the grinding spindle. 
According to a further preferred embodiment of the invention, the power 
transmission is designed as a parallelogram linkage. 
This feature provides the substantial advantage that the power transmission 
consists exclusively of elements capable of rotating relative to each 
other, with the resulting advantage that the extremely high precision of 
today's pivot bearings can be utilized without the need to allow, for 
example, for hysteresis errors of the type encountered when rotary 
movements have to be translated into linear movements via toothed 
mechanisms or the like. In addition, the parallelogram linkage offers the 
advantage that when the parallelogram is rotated about a given angle, the 
pivot bearings arranged at the corner points of the parallelogram will 
turn about the same angle so that in this case synchronous rotation of the 
second sensor elements can be achieved exclusively by making use of rotary 
movements. 
According to a particularly preferred improvement of this variant, a first 
corner point of the parallelogram linkage is located on the vertical axis, 
while a second point adjacent the said first corner point is located at 
the geometrical position of the second sensor element. 
This feature provides the advantage that the geometrical position of the 
vertical axis, i.e. the center of rotation of the grinding spindle is 
"reflected" upon the geometrical position of the second sensor element so 
that the second sensor element follows the rotary movement of the grinding 
spindle directly and synchronously by a corresponding rotary movement 
about the vertical axis. 
One practical embodiment of this variant distinguishes itself by the fact 
that a first pivot point for a first link rod is arranged at a point of 
the swivel carriage spaced from the vertical axis, the free end of the 
said link rod being pivotally connected, at a pivot point, with a second 
link rod the other end of which carries the second sensor element at a 
second pivot point, that the length of the first link rod is equal to the 
length of the connection line between the second pivot point and the 
vertical axis, and that the length of the second link rod is equal to the 
length of the connection line between the first pivot point and the 
vertical axis. 
This feature provides the advantage that the desired parallelogram linkage, 
with reflection of the rotary movement of the grinding spindle upon a 
point outside of the swivel carriage, can be implemented by the use of 
only two link rods with three pivot points. One obtains in this manner a 
particularly compact, sturdy arrangement which is suitable for use also 
under the rough operating conditions of machine tools and which enables 
the measuring device to be arranged in an easily accessible manner outside 
the area of movement of the swivel carriage. 
Finally, another variant of this embodiment is preferred where a pivot 
bearing acting at the first pivot point is braced in the axial direction 
while a pivot bearing acting at the hinge point is movable in the axial 
direction. 
This feature provides the advantage that the swivel carriage can be raised 
and lowered in the direction of the vertical axis without this movement 
interfering with the function of the measuring device. The raising and 
lowering movement of the swivel carriage may advantageously serve for 
lifting the swivel carriage off the base plate, on an air cushion, during 
its pivotal movement so that low torques will be required only for turning 
the swivel carriage with the units mounted thereon. 
Other advantages of the present invention will become apparent from the 
following description and the attached drawing. 
It is understood that the features that have been described above and which 
will be explained further below may be used not only in the described 
combinations, but also in other combinations or individually without 
leaving the scope and intent of the present invention.

Referring now to FIGS. 1 and 2, reference numeral 10 indicates generally a 
cylindrical surface grinding machine. A rotational-symmetrical workpiece 
13 mounted between a work spindle 11 and a tailstock 12 extends along a 
first axis 14, usually described as z axis. In the case of 
non-rotational-symmetrical workpieces, the workpiece is rotated about the 
z axis by defined angular steps; one speaks in this case of the so-called 
c axis. 
It is understood that the grinding machine 10 has been illustrated in the 
drawing, and will be explained hereafter, in the form of a cylindrical 
surface grinder only for the sake of clarity, but that the invention is by 
no means limited to this particular application because the explanations 
given hereafter may also be related to an internal grinding machine or to 
grinding machines for non-rotational-symmetrical workpieces. 
A base plate 19 of the grinding machine 10 carries a grinding carriage 20 
which is mounted thereon for being displaced along a second axis 21, which 
is usually described as x axis. The second axis 21 extends to the first 
axis 14 at an angle .alpha..sub.1, for example an angle of 55.degree.. 
The grinding carriage 20 carries a grinding spindle 22 driving a grinding 
wheel 23, the latter being mounted to rotate about a grinding-wheel axis 
24 which usually extends at a right angle relative to the second axis 21. 
The grinding spindle 22, together with the grinding carriage 20, are 
adapted to rotate about a third axis 25 constituting the vertical axis and 
extending perpendicularly to the drawing plane of FIG. 1. 
This rotation of the grinding wheel 23 about the vertical axis 25 may be 
used, for example, for cylindrical surface grinding of the workpiece which 
is shown in FIG. 1a in enlarged scale and whose outer contour comprises a 
first thicker cylindrical portion 26, followed by a conical portion 27 
and, finally, a second cylindrical portion 28 of smaller diameter. 
For cylindrical surface grinding of such a workpiece, the grinding wheel 23 
is initially pivoted into a position in which its forward grinding face 
extends parallel to the outer surface of the cylindrical portion 26. Upon 
completion of the grinding operation on the first cylindrical portion 26, 
the grinding spindle 22 is pivoted about the vertical axis 25 until the 
forward grinding face of the grinding wheel 23 extends parallel to the 
conical outer surface of the conical portion 27. It is not necessary for 
this purpose to re-mount the workpiece or to re-sharpen the grinding wheel 
23. Finally, the second cylindrical portion 28 can also be ground, after 
re-setting of the angular position of the grinding wheel 23. 
A linear drive 30 serves for pivoting the grinding carriage 20, which is 
mounted on a swivel carriage, together with the grinding spindle 22. The 
housing of the linear drive 30 is seated on the hose plate 19, by means of 
a first pivot mount 31, for pivotal movement about a vertical axis 
extending in parallel to the vertical axis 25. An operating rod 34, which 
can be displaced linearly in the housing of the linear drive 30, is 
pivoted on the swivel carriage 50, by means of a second pivot mount 32 
exhibiting likewise a vertical pivot axis. One obtains in this manner a 
crank drive effecting the pivotal movement of the grinding carriage 20 
about the vertical axis 25. 
In order to determine exactly the rotary position of the grinding carriage 
20 during the pivotal movement, by means of the linear drive 30, a linkage 
triangle 40 is provided comprising a first link 41 having its one end 
pivoted on the swivel carriage 50, at a first pivot point 42, while a 
second link 43 of the linkage triangle 40 is pivoted on the base plate 19 
at a second pivot point 44. The free ends of the links 41, 43 are 
connected at a pivot point 45. The linkage triangle 40, defined by the 
corner points 42, 44 and 45, changes its configuration when the linear 
drive 30 is operated for pivoting the grinding carriage 20. 
FIG. 1 shows a first extreme rotary position of the grinding carriage 20, 
where the latter has been pivoted relative to the z axis 14 by an angle 
.alpha..sub.1 in the range of 55.degree.. The operating rod 34 of the 
linear drive is fully retracted in this position, and the linkage triangle 
40 occupies the first extreme position illustrated in FIG. 1. 
Now, when the linear drive 30 is moved to the other extreme position, by 
extending the operating rod 34, the grinding carriage 20 is pivoted into 
the second extreme position illustrated in FIG. 2, in which the x axis 21 
and the z axis 14 include between them an angle .alpha..sub.2 of approx. 
100.degree.. 
As will be seen when comparing FIGS. 1 and 2 the second pivot point 44 has 
been displaced during this pivotal movement, due to the corresponding 
displacement of the second link 43, by a defined angular amount equalling 
exactly the angular amount by which the grinding carriage 20 has been 
pivoted about the vertical axis 25, the points 25, 42, 44 and 45 
coinciding with the corner points of the parallelogram. Accordingly, a 
rotary angle sensor is provided at the geometrical position of the pivot 
point 44, which rotary-angle sensor is actuated by the second link 43 
relative to the base plate 19 so as to reflect in synchronism the rotary 
position of the grinding spindle 22. 
FIG. 3 shows the power transmission once more in the two positions 
illustrated in FIGS. 1 and 2, with the positions occupied by the 
individual elements in the condition of FIG. 2 marked by an apostrophy. 
It appears from this illustration that the grinding spindle 22, together 
with the swivel carriage 50, travel between the two illustrated end 
positions through an angle .alpha., and that the x axis travels from 21 to 
21'. 
If the connection line from the third vertical axis 25 to the first pivot 
point 42 is designated by reference numeral 60, and that to the second 
pivot point 44 is designated by 61, then it will be readily seen that a 
parallelogram linkage is obtained where the length of the first link 41 is 
equal to the length of the connection line 61 and the length of the second 
link 41 is equal to the length of the connection line 60. 
Now, when the swivelling carriage 50 is displaced by operation of the 
linear drive 30, the first pivot point 42 will be displaced in the 
direction indicated by arrow 62 into a position 42' and the pivot point 45 
will be displaced in the direction indicated by arrow 63 into a position 
45', while the points on the third vertical axis 25 and on the pivot point 
44 are stationary and will not change at all. 
As a result of this pivotal movement of the parallelogram linkage the 
second link 43 is pivoted about the same angle .alpha. by which the 
imaginary ccnnection line 60 is pivoted to 60', and this pivot angle 
.alpha. corresponds exactly to the angle .alpha. by which the x axis will 
be pivoted from 21 to 21'. 
This means that the rotary movement of the point on the third vertical axis 
25 is reflected by the rotary movement of the second pivot point 44 
because the rotary movement of the latter follows synchronously the rotary 
movement about the third vertical axis 25. 
It is therefore possible to arrange measuring means for measuring the 
rotary movement of the grinding spindle 22 at the second pivot point 44, 
in which case one sensor element of the measuring means can be rigidly 
connected with the base plate 19, while a second sensor element is rotated 
by the second link 43 in synchronism with the rotation of the grinding 
spindle 22. 
One practical embodiment of the linakge triangle 40 is represented in FIG. 
4. 
At the first pivot point 42 a pin 70 is screwed to the swivel carriage 50 
in fixed relationship. The pin 70 engages a pivot bearing 72 which is 
braced in the axial direction relative to the sleeve 73. Accordingly, the 
link 41 fixed to the sleeve 73 is permitted to rotate in the pivot bearing 
72 about an axis 74, but is fixed in the axial direction. 
The first link 41 is fixed, at the pivot point 45, to a sleeve 80 which, 
being seated in a pivot bearing 81 not braced in the axial direction is 
permitted to rotate about an axis 84, relative to a pin 82, and can also 
move along the same axis 84. The pin 82 is fixed against rotation to 
another sleeve 83 which in turn is connected rigidly to the second link 
43. 
Due to the arrangement described before, the swivel carriage 50 is capable 
of performing a lifting and lowering movement in the direction of arrow 85 
although the second link 83 cannot be displaced vertically. The swivel 
carriage 50 travels in this case together with the entire pivot point 82 
and the first link 41, as well as the sleeve 80, the latter travelling 
axially on the pin 82 which is not braced in the axial direction by the 
pivot bearing 81. This arrangement, therefore, provides the possibility to 
balance out the lifting and lowering movement of the swivel carriage 50 
which is necessary for rotating the swivel carriage 50 between two angular 
positions .alpha.. 
The second link 43 is connected rigidly to the sleeve 90 in which a pin 91 
is seated, fixed against rotation. The pin 91 is retained against axial 
movment in a lower pivot bearing 92, but permitted to rotate about an axis 
100. A holding part 93, which is rigidly connected with the base plate 19, 
accommodates the lower pivot bearing 92 and an upper pivot bearing 94 
which is engaged by the upper end of the pin 91. An end 95 of the pin 91 
projecting beyond the upper pivot bearing 94 is provided with markings 96. 
A sensor element 97 arranged near the end 95 coacts with the markings 96. 
A connection 98 enables measuring signals to be received from the sensor 
element 97. The arrangement of the sensor element 97 and of the end 95 
with the markings 96 is fully enclosed by the housing 99. 
It is understood that the sensor element 97 and the markings 96 have been 
described here only as one example of many different sensor techniques 
that are used in the art for rotary-angle detection, such as optical, 
magnetic or resistive techniques which are generally known in the field of 
rotary-angle technology so that they need not be described here in detail. 
FIG. 4 shows very clearly that any pivotal movement of the first pivot 
point 42 on the swivel carriage 50 causes directly the pin 91 to perform a 
corresponding rotary movement at the second pivot point 44 and, thus, the 
markings 96 to move past the sensor element 97. Given the fact that, for 
the reasons outlined above in connection with FIG. 3, the pin 91 moves in 
synchronism with the grinding spindle 22 about the parallel axes 100 and 
25, respectively, the output signal of the sensor element 97 can be taken 
as a direct measure of the rotary movement of the grinding spindle 22. 
It is understood that numerous modifications of the above embodiments are 
available to the man skilled in the art without leaving the scope and 
intent of the present invention. 
For example, instead of using a parallelogram linkage, one may also employ 
other polygonal linkages, crank drives or the like for translating the 
rotary movement of the grinding spindle into a rotary movement of a 
sensor. Numerous variants are possible also as regards the design and 
operation of the pivot bearings, and also as regards the use of specific 
types of sensors, as has been mentioned before. Finally, the invention may 
be used for all types of grinding machines, but also for any other machine 
tools using swivelling spindles.