Safety switch with rotatable head

A safety switch including a control head rotatably linked to a casing that encloses an electrical contact assembly. A cylindrical collar of the head, engaged in an opening in the casing, is equipped with an annular groove with which retaining elements cooperate in order to immobilize the head along a predetermined direction. A fixing screw cooperates with re-entrant elements situated on the periphery of the collar in order to lock the head and prevent the head from rotating.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a safety switch of the type that includes a 
casing housing electrical contact devices and a control head fixed to the 
casing, this head being able to take up several positions displaced from 
one another by rotation of for example 90.degree. about an axis oriented 
along a main direction, and including a safety mechanism with a turning 
wheel and a push rod to operate the contact devices and at least one slot 
for an external actuator to pass there through, the actuator being capable 
of operating the safety mechanism. 
2. Discussion of the Background 
Safety switches of this type are known. Their control head generally 
includes a control wheel which is able to be turned about an axis 
perpendicular to the main direction in order to act on the push rod. It is 
useful to be able to choose the position of the control head by rotation 
about the main direction so as to adapt to local mounting conditions for 
the safety switch. 
To this end, it is already known to use safety switches, the control head 
of which, fixed to the casing by screws, can pass from a first position to 
a second position through the following actions: unscrewing the screws so 
as to release the head from its first position, lifting the head in the 
main direction, rotating the head into the second position, then 
tightening up the screws in order to ensure the head is locked in this new 
position. From the point of view of the operator, it would be desirable to 
simplify the method of changing the position of the control head. 
In addition, untimely loosening of the screws fixing the head to the casing 
risks causing a change in the state of the electrical contact devices. In 
effect, since these are being operated by the push rod along the main 
direction, the push rod being part of the head, they risk being no longer 
secured in this direction. It is important therefore to ensure that the 
head is reliably locked along the main direction. 
SUMMARY OF THE INVENTION 
The aim of the invention is to simplify the operation and the means of 
changing the position of the control head by rotation, in a safety switch 
of the type described, as well as to immobilize the head in translation 
with respect to the casing. 
According to the invention, the control head comprises: 
a lower part with a cylindrical collar engaged in an opening in an upper 
wall of the casing, having a central guide passage for the push rod, the 
collar being fitted, on the one hand with an annular groove and on the 
other hand with re-entrant elements distributed at regular intervals on 
its periphery, 
retaining elements engaged perpendicular to the main direction in a side 
opening in the casing and in the annular groove, to prevent translation of 
the head along the main direction, 
a screw for fixing the head in rotation, this screw extending, preferably 
perpendicular to the main direction and co-operating with one or the other 
of the re-entrant elements in order to block rotation of the head. 
The fixing screw may preferably be used to fix a cover to the casing 
closing the compartment where the contact assembly is housed. It may, on 
the other hand, be advantageous to fit the retaining elements onto at 
least one forked shaped component and to provide, between the control head 
and the casing, at least one resilient indexing element movable in the 
main direction in order to facilitate the indexing of the head in its 
chosen position.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The safety switch illustrated in FIG. 1 includes, on the one hand, a casing 
10 in the shape of a parallelepiped, elongated along an axis Z, parallel 
to a main direction Z1 and on the other hand, an approximately cubic 
control head 20, fixed to the casing in such a way that it can take up 
several positions, angularly differentiated by rotation about axis Z. 
The casing 10 has side faces 11a-11d and an upper face 11e adjacent the 
head 20 and a lower face 11f fitted with a feedthrough for the conductors. 
The front side face 11a, has holes 12 for the passage of screws to fix the 
switch to a back support which is not shown and one or two tapped holes 
13, 14 for the passage of screws, respectively 15, 16 for fixing a 
detachable cover 17. A contact assembly C is arranged in a compartment C1 
of the casing capable of being closed by the cover 17. On each of its 
front 11a and rear 11d side faces, the casing includes at least one 
opening, for example a slot 18 for the passage of a pin or a stirrup 19 to 
ensure that the head 20 is locked in translation. The opening may only be 
provided on one side face of the casing. 
The control head 20 houses a safety mechanism 21 that includes at least one 
control wheel 22 rotatably mounted about an axis X perpendicular to Z1, 
and elements, not shown for locking this wheel, and a push rod with an 
axis parallel to Z1, for example coincident with Z, the push rod being 
fixed to the wheel and intended to actuate the mechanical contacts of the 
assembly C. The head 20 has, on one of its side faces 20a, here positioned 
forward, a guide slot 23 for a safety actuator 124 of a particular shape 
that permits, notably during its insertion movement, the locking elements 
to be unlocked before the wheel 22 is turned. The actuator 124 is, for 
example, connected to an enclosure gate for electrical equipment or to a 
machine gate and is displaced approximately along a direction Y 
perpendicular to X and Z. Another slot may be provided for passage of the 
actuator 124 in the upper wall 20e of the head. 
The control head 20 has a lower part 24 with a cylindrical collar 25 and an 
upper part 26. The upper part 26 serves as a support for the safety 
mechanism 21, in particular for the wheels 22, and is covered by a hood 27 
provided with guide slots 23 for the actuator. The hood 27 is fixed to the 
support 26 of the mechanism by means of pins 28 or analogous elements 
accessible outside of the casing. The collar 25 goes into a circular 
opening 11g in the wall 11e of the casing and includes from the top to the 
bottom an annular groove 30 and a group of re-entrant elements, for 
example in the form of four notches 31, distributed on its periphery 
offset at 90.degree. to one another. 
In order to co-operate with the annular groove 30, one or two stirrups 19 
are provided, each going into a slot 18 in a side wall of the casing, in 
such a way that the side branches 19a, 19b of the stirrup go into the 
groove so as to immobilize the head with respect to the casing in the 
direction Z1 and that the core 19c of the stirrup closes up the slot 18 
vis-a-vis the outside. On the other hand, in order to co-operate with each 
notch 31, on the end of the upper screw 15 opposite its head 15a, beyond 
its threaded part 15b, a non-threaded locking finger 15c is provided; the 
finger 15c is intended to go into the notch at the end of the screw travel 
in order to prevent the head from turning about the axis Z. It should be 
noted that the screw 15 passes into an opening 17a in the cover 17 to 
jointly ensure the immobilization in rotation of the control head and the 
fixing of the cover to which the screw 16 also contributes. 
The head 20 has a central passage 40 for the push rod 41 which extends 
along the axis Z and transmits to the contact assembly C, the movement 
communicated by the mechanism 21. It is understood that, in a variant 
where the screw 15 does not participate in the fixing of the cover, it can 
be linked to a wall 11b-11d of the casing other than wall 11a. 
Between the lower face of the lower part 24 of the head and the bottom of 
the casing, a washer 32 is provided that carries four resilient indexing 
elements 33 distributed on its periphery and a central square shaped 
orifice 34; the washer is immobilized in rotation at the bottom of the 
opening 11g by its central orifice engaging with a square boss 11h on the 
bottom. The elements act resiliently in the direction Z1 and can go into 
the open lower end of the notches 31. This allows, on the one hand, 
pre-indexing of the control head 20 in the chosen rotational position, 
while waiting for its immobilization in rotation by the screw 15. On the 
other hand, it facilitates the positioning of the head when one is passing 
from one position to another. 
A version of the safety switch according to the invention with an 
electromagnet is represented in FIG. 4. The head is still engaged in the 
opening 11g in the upper face of the casing, then held in translation by 
the engagement of the stirrup or the two stirrups 19 in the annular groove 
30 and is held in rotation by co-operation of the screw 15 with a notch 
31. 
The device described operates in the following manner. To pass from one 
position of the head to another, the screw 15 is unscrewed in order to 
disengage the finger 15c from the respective notch 31. The head can then 
be turned through the angle desired, equal to 90.degree. or a multiple of 
90.degree., the head collapsing the indexing elements along Z1 until the 
elements 33 go into the notches 31. The head is locked into its new 
position by tightening up the screw 15, the finger of which 15c engages 
with a new notch 31 facing where it was introduced. It may be observed 
that the head 20 changes positions without it having been necessary to 
remove it and by a simple operation of a screw 15, its lower face 20f 
constantly remaining on the upper face 11e of the casing. The head 20 is 
furthermore easily disassembled by operation of the screw 15 and of the 
stirrup or the two stirrups 19.