Safety device on a quill

A safety device on a quill with a sensing head fixably connected thereto interrupts a positioning motion of the quill in case of a collision of the sensing head. For this purpose there is fastened to the quill a mounting plate 6, on which rests a bearing plate on at least three balls 20. The sensing head is fixable to the bearing plate. Several switches and switching cams assigned to them are offset relative to the balls on the bearing plate. In case of a collision of the sensing head, the bearing plate is deflected relative to the mounting plate, thereby causing at least one switch to interrupt the driving motion of the quill.

FIELD AND BACKGROUND OF THE INVENTION 
The invention relates in general to sensing devices and in particular to a 
new and useful safety device on a quill with a sensing head which can be 
attached to it, the safety device interrupting the movement of the quill 
in case of a collision of the sensing head. 
If a quill of a measuring machine with a sensing head is moved towards the 
workpiece to be measured, it is not impossible for the quill to collide 
with an object in its travel. Especially at high travel speeds, e.g. 80 to 
100 mm/s or more, it is important for a safety device to respond with very 
short time delay in case of such a collision in order to avoid a shift of 
or damage to the quill. Such a safety device is described in the older 
patent application No. P 35 26 633.3. 
In the event that the sensing head itself collides in its travel, the 
deflection of its respective sensing finger occurring thereby is utilized 
to stop or reverse the travel motion. At high travel speeds this is hardly 
possible because the possible deflection of the sensing fingers would then 
have to be correspondingly great. Such an amplification of the deflection 
of sensing heads is not achievable off-hand. 
SUMMARY OF THE INVENTION 
The invention provides a safety device which interrupts a quill motion if 
the sensing head hits an object at high travel speed. 
According to the invention, the safety device includes a mounting plate 
which is fastened to the quill. A bearing plate rests on the mounting 
plate over at least three balls distributed over the circumference. The 
sensing head can be fixed to the bearing plae and at least two switches 
are provided on the one plate and switching cams for the switches on the 
other plate. 
If, in its travel, the sensing head hits an object, the bearing plate 
supporting the sensing head will move relative to the mounting plate, in 
which process at least one of the two switches will be actuated 
immediately, switching off continued motion of the quill or reversing its 
motion into the opposite direction. It is also advantageous here that the 
possible deflection of the fingers of the sensing head does not 
structurally have to be enlarged for this purpose. 
What is also achieved by the loose mounting of the bearing plate of the 
mounting plate is that the safety device responds in the same manner to 
collisions in +-x,ty-,-y- direction and in +z- direction. 
Also, the ball mounting makes certain that, after the collision, the 
bearing plate returns naturally, under the weight of the sensing heads, 
into its position aligned with the mounting plate. 
These springs are preferably extension springs active between the bearing 
plate and the mounting plate. 
Provided between the quill and the sensing head is an electrical plug 
connection to connect the sensing head, closing automatically when 
attaching the sensing head to the quill. To avoid that this plug 
connection interferes with the deflection of the sensing head in case of a 
collision, a preferred embodiment of the invention provides that the part 
of the plug connection attached to the quill is fastened to a strip fixed 
to a quill holding means, when the sensing head is not attached to the 
quill, and automatically disengaging from the holding means after plugging 
in the part of the plug connection fastened to the sensing head when 
attaching the sensing head. 
Accordingly it is an object of the invention to provide a safety device on 
a quill which has a sensing head which is flexibly connected to the quill 
in an arrangement where the quill is driven in a positioning motion and in 
which a collision of the sensing head occurs and which includes a mounting 
plate having a bearing plate mounted thereon over at least three widely 
spaced support balls and wherein the sensing head is fixable to the 
bearing plate and which includes several switches and switching cams 
carried by the plate and offset relative to the balls so that when 
collision of the sensing head occurs the bearing plate is deflected 
relative to a mounting plate causing at least one switch to be contacted 
by the cams and interrupt the driving motion of the quill. 
A further object of the invention is to provide a safety support 
construction for a sensing head relative to its quill which is simple in 
design, rugged in construction and economical to manufacture. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its uses, reference 
is made to the accompanying drawings and descriptive matter in which 
preferred embodiments of the invention are illustrated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings in particular the invention embodied therein 
comprises a safety device including actuating cams 28 which are carried on 
the bearing plate so that movement of the bearing plate relative to the 
mounting plate 6 causes actuation of the switches 27 by the cams to stop 
the movement of the quill in a particular drive direction. 
A sensing head 2 with feelers 3 is disposed at the lower end of a quill 1. 
The quill 1 has a supporting tube 4. At its bottom are fastened by means 
of threaded bolts 5 (see FIGS. 3,4) a mounting plate 6, a spacing ring 7 
and a disc 8. The spacing ring 7 forms a free space 9 between the mounting 
plate 6 and the disc 8. A cover 10 is provided on the mounting plate 6. 
In the free space lies a bearing plate 11 formed by partial plates 13 and 
14 screwed together by screws 12. The mounting plate 6, the disc 8, the 
cover 10 and the bearing plate 11 have a central hole 15 to push the 
sensing head 2 through. At the periphery of its central hole 15 the 
bearing plate 11 is designed as bayonet lock 16. To fix the sensing head 2 
to the bearing plate 11 it is pushed through the hole 15 until it strikes 
a tapered surface 17 (see FIG. 2) of the partial plate 14. Then the 
sensing head 2 is turned by about 45.degree. until it hits a stop 18 so 
that rim parts stand on the partial plate 13. Finally the sensing head 2 
is secured by pressure screws 19 (see FIGS. 2 and 5). 
Disposed on the bearing plate 11, especially on its partial plate 13, in 
hemispherical depressions 21, 22 and 23, are three balls 20 distributed 
over the circumference. The balls 20 are staggered by 120.degree. on a 
circle around the center axis M. The balls are offset on the circle 
relative to the X-Y direction. For instance, the hemispherical depression 
21 is offset by about 10.degree. to 20.degree. relative to the Y axis. 
Prism or Vees 24 (see FIG. 4) are provided on the mounting plate 6 for the 
accommodation of the balls 20. 
Between the bearing plate 11 and the mounting plate 6 near the 
hemispherical depressions 21, 22, 23 or the associated Vees or prism 
extension springs 25 are disposed. 
Two guide pins 26 (see FIG. 5 and 7) are provided between the mounting 
plate 6 and the bearing plate 11. They are positioned symmetrical to the Y 
axis and are equidistant from the X axis. 
Fastened to the disc 8, which is fixed to the quill like the mounting plate 
6, are two switches 27. To each switch 27 is assigned a switching cam 28 
(see FIGS. 5 and 6). The actuation points between the switches 27 and the 
switching cams 28 are symmetrical to the Y axis in mirror image and 
equidistant from the X axis, this distance approximating also the distance 
of the guide pins 26 from the X axis. 
The device describes roughly as follows: 
At rest, the bearing plate 11 (FIG. 4) is retained in adjustment on the 
mounting plate 6 by the balls 20 and the Vees prisms 24. The guide pins 26 
prevent the bearing plate 11 from turning relative to the mounting plate 
6, although the tendency to do so exists when attaching or detaching the 
sensing head 2. The balls 20 lie in Vees or prisms 24 under the weight of 
the sensing head 2 and also under the action of the extension spring 25. 
If, in moving the quill 1 in X direction, the sensing head 2 strikes an 
obstruction, the bearing plate 11 experiences a tilt deflection about the 
ball 20 lying in the hemispherical depression 22, the balls 20 in the 
hemispherical depressions 21 and 23 rising slightly out of the associated 
prisms or Vees 24. This causes the switching cam 28 (FIG. 6) located 
between the hemispherical depressions 21 and 23 to switch the switch 27 
assigned to it, the left one in FIG. 5. This, in turn, causes the quill 
drive to be shut off or reversed before the sensing head can be damaged. 
In case of a collision of the sensing head 2 in X direction, the bearing 
plate 11 is tilt-deflected bout the ball lying in the depression 23. Then 
the opposite switch 27, the right one in FIG. 5 is switched. 
In case of a collision of the sensing head 2 in a Y direction, the bearing 
plate 11 tilts about a strip 32 on tongues 33 and 34 of the holding means 
30 (FIG. 8). Fastened to the strip 32 by means of a yoke 35 is a plug 36 
fitting the socket 29. 
When sliding the sensing head 2 through the hole 15 into the quill 1, the 
socket 29 slides over the plug 36. If the sensing head 2 is subsequently 
turned by about 45.degree. for locking (see FIG. 9), the strip 32 is 
detached from the compression spring elements 31 and the tongues 33, 34. 
In other words, it is in a free position and thus cannot interfere with 
tilt deflections occurring in the event of a collision. A cable 37 
connected to the plug 37 does not disturb the tilt deflections. To remove 
the sensing head 2, it is turned in the opposite direction in the bayonet 
lock 16. In so doing, the strip 32 slides at the same time between the 
compression spring elements 31 and the tongues 33 and 34 again so that the 
plug 36, after removal of the sensing head 2, is immediately in the 
position again required for the subsequent attachment of a sensing head. 
While specific embodiments of the invention have been shown and described 
in detail to illustrate the application of the principles of the 
invention, it will be understood that the invention may be embodied 
otherwise without departing from such principles.