Safety switch

A safety switch, operable by a removable coded actuator, is designed for mounting on a support surface in four different orientations. The switch has a substantially square cross-section and grooves or holes for receiving mounting fasteners extend across each side of the switch housing, the grooves being located in a common plane intermediate the ends of the housing.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to access control and, particularly, to the 
prevention of the unauthorized operation of machinery. More specifically, 
this invention is directed to improvements in safety switches and, 
especially, to code "key" operated safety switches which may be easily 
mounted in a plurality of different orientations. Accordingly, the general 
objects of the present invention are to provide novel and improved methods 
and apparatus of such character. 
2. Description of the Prior Art 
Electrical safety switches having a reciprocally mounted contact carrier to 
which movement is imparted by means of an encoded actuating roller are 
known in the art. In such known switches, rotational movement is imparted 
to the roller by means of a properly coded mechanical actuator, i.e. a 
"key", which is inserted into the switch housing via an opening. 
Rotational motion of the actuating roller, produced by linear directed 
force transmitted via the mechanical actuator, is translated into 
reciprocal motion of the contact carrier with a resultant change in the 
state of the switch contacts. 
U.S. Pat. No. 4,558,102 discloses an exemplary prior art safety switch of 
the type briefly described above. The switch of U.S. Pat. No. 4,658,102 
has a cuboid housing of rectangular cross-section. An actuating roller 
assembly is mounted within this housing and is coupled to a reciprocal 
plunger "tappet" which forms part of the carrier for the movable contacts 
of the switch. When the actuating roller is "unlocked" by the insertion of 
a properly coded actuator, the actuating roller may be rotated about its 
axis and this rotational motion is translated into linear motion of the 
tappet and thus motion of the movable switch contacts. The configuration 
of the actuating roller and the location of the orifices through which the 
mechanical actuator may be introduced into the housing, so as to be 
operatively coupled to the roller, are such that the switch may be 
operated from either of two opposite sides or an end face of the housing, 
the actuator introduction orifices typically being in the form of slots. 
The actuator introduction orifices are provided in a cap which is 
removably attached to the main housing of the switch, the orientation of 
the cap being determined by the requisite or desired installation position 
of the switch. The installation position is determined by mounting holes 
which extend from a front side of the main housing to the rear side 
thereof. While a safety switch of the type disclosed in U.S. Pat. No. 
4,658,102 presents several installation alternatives, manipulation of the 
cap is generally required if the mounting orientation is to be changed. 
Further, and most importantly, a mounting alternative wherein the housing 
is rotated through an angle of 90.degree. about its longitudinal axis is 
not possible without the use of an additional housing carrier which must 
be installed on the support surface to which the switch is to be fastened. 
Published German Patent Application 3,330,109 discloses another safety 
switch of the type generally discussed above. The safety switch of this 
published application is provided with a cap having four slot-like 
actuator introduction orifices. In this case, manipulation of the cap to 
reconfigure the safety switch to each desired mounting orientation is not 
required. However, the elimination of the need to reconfigure has been 
accomplished at the expense of the added complexity of an actuating roller 
which is rotatable in two directions. Further, the installation 
alternative of rotation of the switch housing through an angle of 
90.degree. about its longitudinal axis is still not possible without the 
use of the above-discussed additional housing carrier. As a further 
"deficiency", in some operating environments it has been found necessary 
to provide a dust guard or other closure for the actuator introduction 
orifices which are not to be used, i.e., the addition of two "key" 
introduction slots significantly increases the possibility of 
contamination with concomitant switch failure. 
SUMMARY OF THE INVENTION 
The present invention overcomes the above-briefly discussed and other 
deficiencies and disadvantages of the prior art by providing a novel and 
improved safety switch having the maximum number of installation 
alternatives without imposing the requirement of mechanical modification 
or conversion of the switch. 
A safety switch in accordance with the present invention is characterized 
by a square-section when viewed in a direction transverse to its 
longitudinal axis. The switch housing is provided, approximately midpoint 
along its length and in a plane transverse to the longitudinal axis, with 
a fastener receiving recess or through-hole on each side. These fastener 
receiving recesses extend the length of their respective sides and are 
open at their opposite ends.

DESCRIPTION OF THE DISCLOSED EMBODIMENT 
With reference initially to FIGS. 1-4, a safety switch in accordance with 
the invention comprises a housing, indicated generally at 1, which defines 
a longitudinal axis A--A. The housing 1 includes a central or main portion 
2, a lower end cap or cover 4 and an upper end cap 5. The lower cover 4 is 
affixed to the main housing portion 2 by means of screws 3 while the upper 
end cap 5 engages main portion 2 by means of cooperating ribs and grooves, 
i.e., end cap 5 is snap-fit onto main housing portion 2 as best seen from 
FIG. 2. Housing 1 has a generally square cross-section when viewed in a 
direction transverse to longitudinal axis A--A. 
In accordance with the present invention, the main portion 2 of housing 1 
is provided, on each of its four lateral sides, with a mounting fastener 
receiver in the form of a cut-out or recess as indicated at 6 in FIG. 1. 
The 6 fastener receivers are sized and shaped to accept mounting screws, 
not shown, and are located with their axes in a common plane which is 
desirably located approximately mid-way between the opposite ends of 
switch housing 1, the common plane being transverse to axis A--A. The 
fastener receivers 6 extend completely across the respective sides of 
housing portion 2 and are open at both ends. A safety switch in accordance 
with the present invention is capable of being mounted on a support 
surface, i.e., a wall or the like, by means of a pair of screws which are 
received in an oppositely disposed pair of the receivers 6. The receivers 
6 are expediently provided, at each end thereof, with a counter-sink 7 for 
receiving the head of a mounting screw. 
As depicted in FIG. 1, the mounting screw receiving recesses 6 can be in 
the form of peripheral, outwardly open grooves. Alternatively, as depicted 
in FIG. 2, the fastener receiving recesses may be provided with outer 
covers, i.e., may be in the form of bores or through-holes 6a. The covers, 
if employed, may be integral with the upper end cap 5. 
The upper end cap 5 is provided, in both a end and the side thereof, with a 
slot-like actuator introduction orifice having parallelly aligned lateral 
edges. The orifice 8 in the end wall of end cap 5 will be adjacent to the 
side wall of cap 5 which is disposed oppositely with respect to the side 
wall having the other, i.e., the lateral, actuator introduction orifice 
8'. Orifice 8 also, as clearly shown in FIG. 2, defines a plane oriented 
generally parallel with respect to this oppositely disposed side wall. In 
the embodiment being described, at least the end cap side wall which has 
the actuator introduction orifice 8' and the oppositely disposed side wall 
will be interlocked with the main portion 2 of housing 1 by means of 
cooperating projections on housing portion 2 and openings in end cap 5 as 
may be seen from FIG. 2. 
The main portion 2 of housing 1 receives and supports an axle 9. Axle 9 is 
held in position, as shown FIGS. 1 and 4c, by means of transversely 
oriented pins 10 which are press fit into receiving apertures in lateral 
recesses 11 of housing portion 2. The pins 10 preferably also extend 
through and engage a pair of opposite sidewalls of the upper end cap 5 and 
thus assist in preventing unauthorized removal of cap 5. 
An actuating roller 12, i.e., an assembly or device which translates the 
insertion motion of an actuator "key" to motion of a switch contact, is 
rotatably mounted on axle 9. Roller 12 is comprised of a plurality of 
individually rotatable discs 23 which cooperate to define, on the outer 
circumference of roller 12, at least a pair of radially inwardly extending 
recesses 13. With roller 12 oriented as shown in FIG. 2, the recesses 13 
are located in registration with respective of the actuator introduction 
orifices 8 and 8'. Accordingly, when a coded actuator 14, see FIG. 4a, is 
introduced into one of the introduction orifices, the roller 12 will be 
caused to rotate in the direction of arrow 15 (FIG. 2). 
A contact carrier is associated with, and caused to move linearly in 
response to rotation of, the roller 12. This contact carrier includes a 
reciprocally movable "tappet" 16. Tappet 16 is guided, i.e., its motion is 
constrained to be linear, in housing 1 generally along the longitudinal 
axis A--A. Tappet 16 carries a pair of movable electrical contacts 17 
which, in the disclosed embodiment, are short-circuited. Each of the 
movable contacts 17 cooperates with a stationary electrical contact 20 
provided at the upper end of an electrically conductive connector 18 which 
is affixed to the housing. 
The lower cover 4 defines a nipple 19 which is sized and shaped for the 
moisture proof introduction of a multi-conductor electrical cable, one of 
the conductors of such cable being indicated at 32 in FIG. 2. As best seen 
from FIG. 3, the connectors 18 are expediently designed to present 
knife-edge type contacts 18' at the end thereof disposed oppositely with 
respect to the integral contacts 20. Accordingly, when an insulated 
conductor 32 is introduced into the slot 18" between the contact blades 
18', the connector will cut through the insulation and establish 
electrical contact with the underlying conductor. The connectors 18 will 
be formed from sheet-metal by stamping and bending. 
The cooperating pairs of electrical contacts 17 and 20 are located in a 
portion of housing 1 which is sealed, to the extent possible, from the 
ambient atmosphere. This sealing is accomplished, in part, by means of a 
peripheral sealing ring 21 interposed between main housing portion 2 and 
lower cover 4. Additional hermetic isolation is provided by means of an 
accordion-like gasket 22 which is sealed, about the periphery of a central 
aperture therein, to tappet 16 and is sealed, at its outer periphery, to 
housing portion 2. 
In the embodiment of FIGS. 1-4, as may best be seen from FIGS. 4b and 4c, 
the actuating roller 12 consists of a plurality of individual disks 23 
mounted on axle 9 so as to be rotatable independently of one another. The 
disks 23 are provided with cut-outs of different shape for engagement with 
actuating portions 14' of the actuator 14, these cut-outs defining the 
radial recesses 13 in the roller 12. The irregular shape of the radial 
recesses 13, as established by the different disks 23, defines the access 
"code" for operating the safety switch which must be present on the 
actuator 14. 
Referring to FIG. 2, aligned and identically shaped non-linear cam slots 24 
extend through all of the disks 23. A pin 25, which is oriented with its 
axis parallel to axle 9, extends through the aligned slots 24. Pin 25 is 
received in a yoke-like extension 26 of tappet 16. 
Movement of extension 26, and thus of tappet 16, is guided by main portion 
2 of housing 1. The tappet and its yoke extension are shown at the limit 
of motion in the downward direction in FIGS. 1 and 2. 
A further yoke member 27 is fixedly mounted on axle 9. Yoke 27 is provided 
with elongated guide holes 28 in which the opposite ends of pin 25 are 
received. A compression spring 29 extends between a stop on yoke 27 and 
the bottom of a spring-receiving recess in the upper end of tappet 16. 
Spring 29, accordingly, biases tappet 16 in the direction of the lower 
cover 4 and thus, in the disclosed embodiment, biases the switch contacts 
17, 20 to a normally closed state. 
Through the cam-like cooperation between the walls of the aligned slots 24 
in discs 23 and pin 25, actuator induced rotation of roller 12 will result 
in pin 25 being pulled in the direction of the upper cap 5. Accordingly, 
in response to insertion of a properly coded actuator 14 into either of 
slots 8 or 8', tappet 16 will pull contacts 17 away from contacts 20, 
against the bias of spring 29, to thereby change the state of the switch. 
Referring to FIGS. 2 and 4b, the assumption of a neutral or initial 
position of disks 23 is accomplished through the action of a comb-like 
leaf spring 30 mounted on yoke 27. The active portions of the spring 
elements of spring 30 engage circumferential recesses 31 in the disks 23 
upon withdrawal of the actuator 14 from an introduction orifice 8 or 8'. 
The interposition of the compression spring 29 between the tappet 16 and a 
stop fixed to the housing, i.e., a reaction surface located on yoke 27 
adjacent to roller 12, leads to a reduction in the length of housing 1 in 
its longitudinal direction. 
It should be noted that, in an alternative construction, the cam drive, 
i.e., coupling, pin 25 can be connected to tappet 16 via connecting rods. 
However, this alternative construction will result in a lengthening of the 
housing 1. 
The cover 4 is provided, on its inner surface, with two pair of spaced webs 
33. The webs 33 receive the insulated conductors 32 of the electrical 
cable inserted in nipple 19. Each pair of webs defines a recess 34 in 
which an insulated conductor 32 will be captured upon insertion. The 
pushing of the cover 4 onto the main portion 2 of the housing, and the 
subsequent fastening of the cover 4 to housing portion 2 by means of the 
screws 32, will result in the knife edge contacts 18' penetrating between 
two adjacent pairs of webs 33 in a direction transversely to the conductor 
32, so as to slice through the insulation of or captured conductor 32 and 
establish the desired electrical contact. In the disclosed embodiment, the 
double pairs of webs 33 are arranged in opposite corners of the cover 4 so 
that the conductors 32 will be directed in diagonal directions. 
Referring to FIG. 5, in accordance with an alternative construction, the 
actuating roller 12 may in the form of a single rotatable member 23' 
rather than a plurality of individually rotatable disks. In the FIG. 5 
embodiment, a pair of "bolts" 35 are arranged on opposite sides of roller 
23' and offset from the axle about which the disk rotates. The roller is 
provided with recesses having shapes which are complementary to the 
configuration of the ends of "bolts" 35. The "bolts" 35 are spring biased 
in the direction of actuating roller 23' by means of springs 36. When the 
shaped ends of the "bolts" 35 engage the complementary shaped recesses in 
actuating roller 23', the actuating roller is locked against rotation. An 
unlocking disk 35' is fixed to each "bolt" 35 and these unlocking disks 
are provided with camming surfaces, facing an actuator introduction 
orifice, which at least in part define the "code" of the switch. As a 
result of the introduction of the appropriate actuator 14", the actuator 
engaging the cam surfaces on the unlocking disks, the "bolts" 35 are 
forced axially outwardly as shown in FIG. 5 and the actuating roller 23' 
is unlocked and subsequently rotated by continued insertion of the 
actuator. In an alternative construction, the bolts 35 may be radially 
oriented with respect to the actuating roller. 
FIG. 6 depicts a third embodiment of the invention wherein, rather than 
employing the lateral "bolts" 35 of the FIG. 5 embodiment, a stationary 
bolt 36 is utilized. In the FIG. 6 embodiment, each disk 23 of the 
actuating roller may be pressed axially outwardly into an actuating 
position in opposition to force provided by a spring 37. A safety switch 
of the same general construction is shown in above referenced U.S. No. Pat 
4,658,102. 
While preferred embodiments have been shown and described, various 
modifications and substitutions may be made thereto without departing from 
the spirit and scope of the invention. Accordingly, it is to be understood 
that the present invention has been described by way of illustration and 
not limitation.