Proximity switch operable without physical contact

A proximity switch, operable without physical contact and having an elongated columnar housing which has, perpendicular to its principal axis, a cross-sectional shape with two orthogonal axes of symmetry. The housing is divided into at least two parts and the parts are joined at three abutting surfaces. One of the abutting surfaces extends in the plane of the principal axis and the others intersect the first surface, extending at angles of 90.degree. thereto. The greatest length of the first abutting surface, measured in the direction of the principal axis, is the same as the distance between the principal axis and the outer surface of the housing. With this arrangement, it is possible to arrange the sensor head carrying the sensor operating surface so that the operating surface lies on the longitudinal axis or at 90.degree. to the longitudinal axis in such a manner that the sensor surface does not extend beyond a generatrix of the outer surface.

BACKGROUND OF THE INVENTION 
This invention relates to a proximity switch which can be operated without 
physical contact. The switch has an elongated columnar housing with a 
cross section having orthogonal axes of symmetry which are perpendicular 
to its principal axis. The housing is divided into at least two housing 
parts joined at abutting surfaces which lie at an angle to the principal 
axis. 
In a proximity switch of the above-mentioned general type known from 
British Pat. No. 1,566,089, the housing parts are bounded by surfaces 
which face each other and which extend at a sharp angle, preferably 
45.degree., to the longitudinal axis of the housing. In a proximity switch 
of this kind it is possible to align the operating axis of the sensing 
head with the longitudinal axis of the prismatic housing as well as 
transversely thereto. However, when the sensing head is arranged with its 
operating axis transverse to the longitudinal axis of the housing, the 
sensor surface extends beyond the lateral outside surface of the housing. 
This is necessary so that the cup core of the sensor, which has a 
predetermined height, can be accommodated in the cross section of the 
columnar housing. This is particularly true when the housing has a 
circular cross section. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a proximity switch of 
the above-mentioned type in which the sensor surface lies in the extension 
of at least one generatrix of the outside lateral surface of the housing 
when the chosen operating direction of the sensor is transverse to the 
longitudinal axis of the housing. This is achieved by providing each 
housing part with a mating end having three abutting surfaces. One of the 
abutting surfaces extends in the plane of the principal axis and the 
others extend at an angle of 90.degree.to the first surface as measured at 
the respective intersection with the first named surface. The greatest 
length of the abutting surface which extends in the direction of the 
principal axis is made equal to the distance between the principal axis 
and the outside surface of the housing. In this way, when the position of 
the active surface of the switch is shifted from the end of the housing to 
the side of the housing, the full cross section of the proximity switch 
housing is also available in half the width of the proximity switch. As a 
result, a cup core can easily be accommodated in the circular end housing 
of the proximity switch for use in either position without the impairment 
of response which results from reducing the height of the cup core to make 
it fit. 
The principles of the invention can also be applied to advantage in a 
proximity switch operable without physical contact having a circular cross 
section such as is shown in British Pat. No. 1,566,089. When this is done, 
the abutting surface which lies in the direction of the principal axis is 
defined by a straight boundary line where that surface meets the endmost 
lateral abutting surface and by an inwardly extending semicircle of the 
same radius as the housing. The abutment surface so defined has an area 
equal to one-half of the cross-sectional area of the housing. This 
arrangement of abutting surfaces can also be used to advantage when the 
housing is divided into three parts, with three abutting surfaces provided 
at each of the separating points.

DETAILED DESCRIPTION OF THE INVENTION 
The proximity switch shown in the drawings consists of center part 1 which 
contains the circuit, connecting part 2, and sensor part 3 constituting 
the sensor. In the illustrative embodiment shown in FIGS. 1 and 2, which 
has a generally quadrilateral or square cross section, only center part 1 
and sensor part 3 are shown. Center part 1 and sensor part 3 meet at a 
joint defined by intersecting abutting surfaces 4, 5 and 6. As seen from 
the side, the intersecting surfaces look like a Z. The height of 
longitudinal abutting surface 5 is indicated by the arrow 7 (FIG. 2) and 
corresponds to half the width of the square dimension of the housing. This 
provides a symmetry which makes it possible to connect sensor part 3 to 
center part 1, for axial activation, in the manner indicated in FIG. 1, 
or, for transverse activation, in the manner shown in FIG. 2. The boundary 
line between abutting surfaces 5 and 6 is designated 8, and that between 
abutting surfaces 4 and 5 is designated 9. The sensing surface of sensor 
part 3 bears the reference symbol 10. 
The abutting surfaces in the housing of square cross section, of FIGS. 1 
and 2, are relatively symmetrical with respect to each other. However, 
when the proximity switch housing has a circular cross section, similarly 
placed abutting surfaces take different shapes, as can be seen in FIGS. 
3-7. In the circular structure, longitudinal surface 5 of center part 1 
extends, as before, from one end of center part 1 towards the middle. 
Lateral abutting surface 6 is again the endmost surface of center part 1 
and meets longitudinal surface 5 in a straight line intersection 8. This 
surface is now semi-circular instead of rectangular. Lateral abutment 
surface 4, on the other hand, is a concave surface which intersects 
longitudinal surface 5 at curved boundary line 9 and, being perpendicular 
to longitudinal surface 5, intersects outer surface 12 of the housing in a 
curve. Sensor part 3 has, in addition to longitudinal surface 5 which 
corresponds in shape and size to longitudinal surface 5 of center part 1, 
projecting, convex abutting surface 4 which conforms to the concave 
surface of abutting surface 4 on center part 1. Similarly, transverse 
surface 6 center part 1 is abutted by transverse surface 6 on sensor part 
3. When sensor part 3 is assembled to center part 1 with the axis of 
center part 3 and the axis of center part 1 in alignment as shown by the 
direction of the arrow, it will be seen that the parts are mated end to 
end, forming a continuous cylinder with abutting surfaces 4, abutting 
surfaces 5, and abutting surfaces 6 in juxtaposition (see FIGS. 4 and 5). 
The second position of sensor part 3, which provides for lateral operation, 
can be seen at FIG. 3, right, where the sensing surface of part 3 has been 
shifted 90.degree.. Now, abutting surface 4 of part 3 will form, when 
assembled with center part 1, a continuing part of outer surface 12; also, 
a portion of outer surface 13 of part 3 now rests against abutment 
surfaces 4 of center part 1. Sensor surface 10 now includes a generatrix 
of outer surface 12. 
Connecting part 2 can be connected to central part 1 in the same way as 
just described. It is also capable of both longitudinal or lateral 
orientation, e.g. of change of position by 90.degree.. 
It is clear, especially from FIGS. 3 and 7, that in sensor part 3 half of 
the diameter of the housing is available for receiving the ring-shaped cup 
core without need to extend sensor surface 10 beyond the most outward 
generatrix of the housing's outer surface; i.e., departure of passing 
articles from the surface of the housing is impossible. Also, this means 
that the proximity switch can be accommodated in a very small space. 
Electrical connections between center part 1 and sensor part 3 or 
connecting part 2 can be made, in a manner not shown via flexible 
connecting lines which can be accommodated in recesses, not shown, in the 
vicinity of the longitudinal axes of center part 1, connecting part 2, and 
sensor part 3. The parts can be fastened to each other by means of screw 
clamps or snap in connections. In the exploded view of FIG. 3 screws 14 
are shown which can be screwed in in different directions to connect the 
parts. Interconnection via cables has the advantage that no sealing 
problems such as otherwise can occur with cuts at an angle, arise and that 
terminations in connecting part 2 can be made via plug-in and screw 
connections in the cylindrical part.