U.S. patent application number 12/944829 was filed with the patent office on 2011-03-17 for shielded position sensor for translationally moving parts.
This patent application is currently assigned to PILZ AUSLANDSBETEILIGUNGEN GMBH. Invention is credited to Fouad MAHDI, Max SCHMID.
Application Number | 20110062949 12/944829 |
Document ID | / |
Family ID | 38562927 |
Filed Date | 2011-03-17 |
United States Patent
Application |
20110062949 |
Kind Code |
A1 |
SCHMID; Max ; et
al. |
March 17, 2011 |
SHIELDED POSITION SENSOR FOR TRANSLATIONALLY MOVING PARTS
Abstract
A sensor is disclosed for monitoring a part which can move
translationally relative to a sensor with reference to its position
on the axis of motion. This part is for example a piston in a
cylinder which is equipped with a sensor. The sensor can be
actuated by means of a magnet which is oriented in the direction of
motion with respect to the north and south pole and which is
located on the movable part. The sensor has three reed contacts
which are aligned in parallel and of which the first and the second
reed contact are located in one plane and parallel next to one
another with their lengthwise axes, by which they can be actuated
almost at the same time by the magnetic field of the magnet which
is located on the movable part. The third reed contact is located
at a distance to the plane of the first and the second reed
contact. This sensor with the first two reed contacts is mounted
facing the actuating magnet. This arrangement has the advantage
that an external magnetic field always actuated the third reed
contact as well, if it can actuate the first two reed contacts.
Then the sensor indicates an error report or an unsafe position,
but never a safe position of the movable part.
Inventors: |
SCHMID; Max; (Wangs, CH)
; MAHDI; Fouad; (Bonaduz, CH) |
Assignee: |
PILZ AUSLANDSBETEILIGUNGEN
GMBH
Ostfildern
DE
|
Family ID: |
38562927 |
Appl. No.: |
12/944829 |
Filed: |
November 12, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11806414 |
May 31, 2007 |
7852067 |
|
|
12944829 |
|
|
|
|
Current U.S.
Class: |
324/207.24 |
Current CPC
Class: |
G01D 5/2515 20130101;
G01D 5/06 20130101 |
Class at
Publication: |
324/207.24 |
International
Class: |
G01B 7/14 20060101
G01B007/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 1, 2006 |
CH |
00882/06 |
Claims
1. Sensor for monitoring a part which can move translationally
relative to the sensor with reference to a position on an axis of
motion, comprising: a magnet which is located on the movable part;
and a fastening means which prevents shifting of the sensor in a
direction of motion of the part, which fastening means connects the
sensor to a carrier for the sensor, and wherein there is a spring
means for maintaining a form-fit of the fastening means.
2. Sensor as claimed in claim 1, wherein the sensor on opposing
ends is provided with one mounting tail each, and wherein there are
two catch heads, the mounting tail being provided with teeth and
each catch head being provided with a catch mechanism which engages
the teeth, such that in interaction the two catch heads are slipped
onto one mounting tail at a time, but the catch heads are prevented
from being pulled off.
3. Sensor as claimed in claim 1, wherein the sensor is equipped
with two catch mechanisms which work in opposition, and wherein
there are two fixing parts with one mounting tail each and a stop
head, the mounting tail being provided with teeth, such that in
interaction with one of the catch mechanisms on the sensor the two
fixing parts are slipped onto the sensor, but the fixing parts are
prevented from being pulled off.
4. Sensor as claimed in claim 3, wherein the fastening means
encompasses a sensor body.
5. Sensor as claimed in claim 4, wherein the fastening means is a
spring element which has been released from the sensor.
6. Sensor as claimed in claim 1, comprising: a fastening means
which has at least one tooth which can be pressed into a surface of
a groove which holds the sensor.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 11/806,414 filed on May 31, 2007, which claims priority under
35 U.S.C. .sctn.119 to Swiss Application 00882/06 filed in
Switzerland on Jun. 1, 2006, the entire contents of which are
hereby incorporated by reference in their entireties.
TECHNICAL FIELD
[0002] The disclosure relates to a sensor for monitoring a part
which can move translationally relative to a sensor with reference
to its position on the axis of motion, and to a cylinder with such
a sensor for monitoring the position of the piston with respect to
its axis of motion. The disclosure relates especially to a safety
position sensor for a pneumatic or hydraulic cylinder and such a
cylinder with the position sensor.
BACKGROUND INFORMATION
[0003] Monitoring the position of a piston which is provided with a
magnet using a reed contact which can be influenced by the magnet
is known. This is often achieved with magnetic rings around the
piston and one or two reed switches which act in parallel on the
cylinder. The cylinder consists of nonmagnetic material for this
purpose.
[0004] These reed contacts can moreover be caused to close by
magnets attached from the outside when they should be open due to
the position of the cylinder. This should be avoided for safety
reasons. Moreover unintended movement of the sensor along the axis
of motion of the cylinder should be prevented to allow calibration
of the position of the sensor.
SUMMARY
[0005] A safety sensor is disclosed which indicates a safe position
of a movable part only when this part is in the safe position. It
should not be able to be influenced by external magnet fields to
indicate a safe position of the cylinder when it is in an unsafe
position. Thereby, the sensor can be positioned and safe fixing of
the sensor is possible for example on a cylinder in this position
using technically simple means.
[0006] A sensor for monitoring a part which can move
translationally relative to a sensor with reference to its position
on the axis of motion can be actuated by means of a magnet which is
oriented in the direction of motion with respect to the north and
south pole and which is located on the movable part. An exemplary
embodiment has three reed contacts which are arranged in parallel
and of which the first and the second reed contact are located in
one plane. They are located parallel next to one another with their
lengthwise axes. By this arrangement they can be actuated almost at
the same time by the magnetic field of the magnet which is located
on the movable part. The third reed contact is located at a
distance to the plane of the first and the second reed contact.
This sensor, with the third reed contact located at a greater
distance to the actuating magnet than the other two reed contacts,
is safe against manipulation by external magnetic fields. An
external magnetic field applied from the outside will always first
actuate the third reed switch which is nearer the magnet which has
been applied from outside. It is almost impossible not to actuate
the third reed contact located near the first two reed contacts
when the first and second reed contact are actuated with an outside
magnetic field. In order to actuate the first two reed contacts
without actuating the third reed contact, it is necessary to
achieve a drop in the magnetic field as large as possible between
the position of the first two and the position of the third reed
contact. This is essentially only possible when the field magnet is
near the first two reed contacts, and therefore at the position
which is already intended for the field magnet. Moreover fine
tuning of the sensitivities of the reed contacts and of the
strength of the magnetic field which has been generated by the
magnet on the movable part is necessary.
[0007] This sensor is especially suited to detecting the position
of a piston in a cylinder. In this connection the sensor is located
on the cylinder which consists of nonmagnetic material, for example
aluminum, and the piston bears a magnet, e.g., a magnetic ring
around the piston.
[0008] The third reed contact is advantageously at most as
sensitive as the two identically switching reed contacts which are
arranged in parallel, so that it does not respond only at a
stronger magnetic field than this. Thus the distance to the field
magnet is the deciding factor.
[0009] In order to make the range for a sensor signal more precise
and to make the boundary region between the position of the magnet
which excites the sensor signal and the position which does not
excite a sensor signal as short as possible, on one end of the two
identically switching reed contacts, e.g., on both ends of the reed
contacts, the sensor is provided with a shield, especially an iron
part. This shield distorts the magnetic field of the field magnet
so that the magnetic field is deflected by the material of the
shield away from the region of the reed contacts. Starting from a
certain position of the magnet the magnetic field jumps with one
pole out of the shield and with the other pole into the shield,
i.e. when mainly the field lines in the north have been deformed by
the shield until then and the field lines in the south have
remained essentially undeformed, the deformation jumps suddenly
onto the field lines of the south pole, while the field lines of
the north pole remain largely undeformed. In this way a more
distinct signal is achieved.
[0010] This jumping can also be achieved with bilateral shielding,
all the field lines being deformed. The field lines which have been
acquired by the first shield are however suddenly acquired by the
other shield, the first shield immediately acquiring the field
lines of the other pole.
[0011] The bilateral shielding has especially the advantage that
backward installation of the sensor is precluded. Alternatively
there can be unambiguous identification of the sensor and the
position of the shield.
[0012] For simple installation of the sensors which cannot be moved
by vibrations and unintentional manipulation, the sensor is
provided on opposing ends with a mounting tail. This mounting tail
prevents movement of the sensor away from the end of the tail so
that with two opposing mounting tails movement in both directions
is prevented.
[0013] In order to easily attach the mounting tails there are
advantageously two catch heads. The mounting tail is provided with
teeth and the catch head is provided with a catch mechanism which
engages the teeth. The teeth and the catch mechanism in interaction
allow the catch heads to be slipped on, but prevent the catch head
from being pulled off once it has been slipped on. These teeth and
catch mechanisms are known from cable links.
[0014] It can be provided that the catch mechanism can be released
from active connection with the mounting tail by means of a
tool.
[0015] Simple and reliably immovable positioning of the sensor for
monitoring a part which can move translationally relative to the
sensor with reference to its position on the axis of motion which
can be actuated by means of a magnet located on the movable part
can be achieved in that the sensor is provided on the opposing ends
with a mounting tail and that there are two catch heads. Each
mounting tail is provided with teeth and each catch head is
provided with a catch mechanism which engages the teeth, which in
interaction allow the catch heads to be slipped on the mounting
tail, but prevent the catch heads from being pulled off once a
catch head has been slipped on. The catch heads have a stop which
after mounting of the sensor, for example on a cylinder, presses
against the stop surface of the cylinder so that the sensor is
prevented by one mounting tail from moving in one direction, and
with the other mounting tail from moving in the opposite
direction.
[0016] For fine calibration, a stop of the catch heads can be
connected via a thread to the catch mechanism of the catch heads,
which thread extends in the lengthwise direction of the mounting
tail. For the sake of safety the stops can be captively connected
to the catch mechanism. Twisting of the stops around the thread
axis should not be able to lead to release of the catch head from
the mounting tail.
[0017] Alternatively to the version with two mounting tails on the
sensor and two catch heads which interact with them, the sensor can
also be made with two catch mechanisms which engage oppositely, and
fixing of the sensor can take place by insertion of the mounting
tails which are provided with stops and teeth. They are inserted
into the two catch mechanisms from both sides. Advantageously the
mounting tails are made such that they have room next to one
another in a groove which is made for example on the cylinder and
can therefore overlap in the lengthwise direction.
[0018] Formulated somewhat more generally, the sensor is
characterized by a fastening means which is made interacting with
the sensor or connected to the latter. It prevents shifting of the
sensor, especially in the direction of motion of the piston. The
fastening means connects the sensor via, e.g., a detachable
form-fit to a carrier for the sensor. The carrier is mainly the
wall of the cylinder. There can be a spring means for maintaining
the form-fit. The spring means are captive and reliably maintain
the form-fit, for example between the mounting tail and catch lip,
or between a tooth and a recess which has been pressed into the
surface of the carrier.
[0019] The sensor can be provided with a fastening means which has
at least one tooth which can be pressed into the surface of a
groove which holds the sensor. A depression for the form-fit with
the tooth can be achieved by this pressing in. But alternatively
there can also be for example edging in the surface of the carrier
which has a series of recesses. In this case the tooth engages one
of these recesses of the edging.
[0020] The fastening means advantageously encompasses the sensor
body. In this way it is likewise positively connected to the
fastening means.
[0021] The fastening means can thus be a spring element which has
been detached from the sensor. This has the advantage that the
fastening means can be produced in one piece from for example a
spring steel strip which is made to surround the sensor body.
Advantageously there are at least two teeth which can be caused to
engage the surface of the groove in the carrier. On this spring
element moreover a flange 69 is advantageously formed and fits into
the undercut of a groove which has been undercut in a T-shape. Thus
the spring element simply together with the sensor can be pushed in
the lengthwise direction into and out of the groove.
[0022] The disclosure also relates to a cylinder with a piston in
which on the piston there is a magnet which is pointed with the
polarity in the direction of motion of the piston. On the cylinder
there is a sensor for monitoring the position of the piston in the
cylinder. The sensor can make the monitoring of the piston position
reliable. It ensures safety in that the two reed contacts have to
respond at the same time to the magnetic field of the magnet and in
that the third reed contact should not respond. The third reed
contact due to its greater distance from the magnet and piston is
in a closer position to the external magnetic field acting from the
outside. It therefore always switches before the two inner reed
contacts when an external magnetic field which is acting from the
outside is strong enough to influence the sensor. Since the third
reed contact opens when the other two close (or vice versa), a safe
position of the piston cannot be simulated by the external magnetic
field.
[0023] On the cylinder a groove is advantageously formed in which
the sensor is movably supported in the direction of motion of the
piston. The sensor can be inserted into this groove from the
outside and can be moved into the desired position along the
direction of displacement which is possible in it.
[0024] The sensor is advantageously made as a cylindrical part (but
a non-axially symmetrical and therefore non-circularly cylindrical
part, but can be as a right parallelepiped which is made
symmetrical to the mirror plane), with a cylinder axis which is
parallel to the lengthwise direction of the reed contacts.
[0025] Due to the deviation from axial symmetry the cross section
of the sensor perpendicular to its cylinder axis is made such that
the sensor can be pushed into the groove in the cylinder only in a
single rotary position with respect to its cylinder axis. Thus
insertion of the cylinder in an incorrectly aligned position can be
made impossible. Alternatively (or additionally) marking of the
sensor is possible which makes incorrect insertion of the sensor
into the groove obviously detectable.
[0026] In the known manner a magnetic ring is formed around the
piston so that the position always has the same effect on the
sensor regardless of its rotary position around the piston
axis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The invention is detailed below using the examples shown in
the figures.
[0028] FIG. 1 shows in a perspective and schematic the basic module
of an exemplary sensor,
[0029] FIG. 2 shows a view of a sensor which has been potted in a
sensor body,
[0030] FIG. 3 shows a perspective sketch of a first exemplary
embodiment of the sensor with two mounting tails,
[0031] FIG. 4 shows a perspective sketch of a catch head for
locking interaction with a mounting tail,
[0032] FIG. 5 shows a lengthwise section through a cylinder with an
exemplary sensor and a field magnet on the piston, in which the
piston is in an unsafe position,
[0033] FIG. 6 shows a cross section through the cylinder as shown
in FIG. 5,
[0034] FIG. 7 shows a lengthwise section through the cylinder in
which the piston is in a safe position,
[0035] FIG. 8 shows an extract from a lengthwise section through a
cylinder with a second exemplary embodiment of a sensor without a
mounting tail, with the piston in a safe and in an unsafe position,
one field line at a time being shown which is deformed by the
shielding which is present in the sensor.
[0036] FIG. 9 shows a view of a cylinder in the direction of the
cylinder axis of the sensor and the axis of motion of the piston,
with a T-shaped groove and an exemplary sensor in it.
[0037] FIG. 10 shows an extract from FIG. 9 with the sensor
provided with a locking means in the groove.
[0038] FIG. 11 shows a perspective sketch of a sensor and a spring
element for attaching the sensor in a groove which has been
undercut in a T-shape.
[0039] FIG. 12 shows a top view of another exemplary embodiment of
such a spring element.
[0040] FIG. 13 shows four circuit diagrams which enable detection
of the sensor state with two electrical lines.
DETAILED DESCRIPTION
[0041] The heart of the sensor 11 shown in FIG. 1 is comprised of a
printed board 13 and the first two reed contacts 15, 16 and a third
reed contact 17. The first two reed contacts 15 and 16 are make
contacts which are arranged in parallel. The third reed contact 17
is connected in series to the first reed contact 15 and is a break
contact.
[0042] The first two reed contacts are located next to one another
underneath the printed board 13 in a common plane such that the
terminal points for the reed contacts are arranged in a rectangle.
The third reed contact 17 is located above the printed board 13 and
parallel to it. Its terminal points lie on the two sides of the
rectangle formed by the terminal points of the first two reed
contacts 15, 16.
[0043] In the plane of the first two reed contacts 15 and 16 there
is a metal rod as magnetic shielding 19. The three-dimensional
execution of the metal rod in the example is aligned perpendicular
to the lengthwise direction of the reed contacts 15 and 16. The
width of the metal rod is pointed in the lengthwise direction of
the reed contacts 15 and 16. In this way the shielding is located
as much as possible at a distance to the third reed contact and
effectively shields the first two reed contacts.
[0044] These aforementioned parts are potted in the plastic sensor
body 21 which is shown in FIG. 2. This sensor body 21 has a
T-shaped cross section. Within the upright of the T is the third
reed contact 17, in the crosspiece of the T are the printed board
and the first two reed contacts 15 and 16, and if present, the
shielding 19. The sensor body 21 is matched in its shape to the
receiving means which is designed to hold the sensor. The
illustrated cylindrical shape with the T-shaped cross section is
suited to arranging the sensor to be able to move lengthwise in a
groove which is made undercut in a T shape.
[0045] The sensor 11 which is shown in FIG. 3 with two of the catch
heads 23 shown in FIG. 4 on the two mounting tails 25 can be fixed
in different positions in this groove which has been undercut in a
T shape. The sensor 11 on the central sensor body 21 has one
mounting tail 25 each on the opposing T-shaped end sides which lie
perpendicular to the lengthwise direction of the reed contacts.
They are cast in one piece with the sensor body 21. Connecting
cables 27 for the sensor emerge from one of these end sides. These
cables can also emerge on the two end sides, in contrast to the
figures. The connecting cables 27 can be routed through the
openings 29 in the catch head 23.
[0046] On the catch head 23 a catch opening 31 for routing through
the mounting tail 25 is formed. In this catch opening 21 there is a
catch lip 33 which can engage the teeth 35 on the mounting tails
25. On the catch head a stop surface 37 is formed which can
interact with one end side of the wall which forms the groove.
[0047] In FIG. 5 this sensor 11 is located in a groove 41 in the
wall of a cylinder 43. The piston 45 is supported to be able to
move linearly in the cylinder space 47. It can be pushed back and
forth by air, hydraulic fluid, or another medium, or it moves this
medium by its position change which is caused for example by a
motor. For entry and exit of the medium in the piston wall there
are openings 46. This motion of the piston is transferred with a
plunger 48 from the motor to the piston or from the piston to a
tool, for example. On the periphery of the piston 45 there is a
ring magnet 49. A field line 51 represents the local magnetic field
of the magnet 49 schematically simplified.
[0048] In FIG. 5 the piston is in the unsafe region B. In FIG. 7
the piston 45 is shown in the safe region A. When the piston 45 is
in the unsafe region B, the magnetic field of the magnet 49 is not
strong enough to switch the reed contacts in the sensor 11. Only in
the position in which the field lines extend through the reed
contacts can the magnet switch them. The first two reed contacts 15
and 16 are nearer the magnet. They therefore shield the outer,
third reed contact in addition. The magnet lines extend, as soon as
they reach the region of the contact elements of the reed switch,
concentrated through them and thus excite the force which closes
the contact in them.
[0049] In FIG. 8 the same situations as in FIGS. 5 and 7 are shown.
But the sensor is provided with two shields 19. The field lines 51
are therefore distorted in both positions of the piston 45.
Therefore in the region of the sensor 11 there is a safe position
A. Outside of this region the piston 45 is in an unsafe position.
The transition region between these regions with the shield 19 is
more precise than without this shield.
[0050] Furthermore in FIG. 8, in contrast to FIGS. 1 to 7, the
sensor 11 is not made with two mounting tails 25, but with two
catch mechanisms, especially two catch lips 33, for locking
engagement with the teeth 35 of the fixing parts 53. These fixing
parts 53 have a mounting tail 25 with teeth 35 and a stop head 55.
The teeth of the mounting tail 25 engage the catch lips on the
sensor body 21. Since the mounting tails which engage them can no
longer be pulled back, in this way the sensor body is fixed in its
position as soon as the two stop heads of the fixing parts 53 are
in contact with the cylinder 43. So that the stop heads do not
project over the length of the cylinder 43, the groove on its end
is widened and the stop heads 55 fit into the widened groove.
Advantageously the two lateral flanges 59 of the groove wall which
form the undercut are cut out on their end.
[0051] The engagement can be releasable with a tool. For this
purpose either the catch lip 33 can be pressed away from the
mounting tail 25, or the mounting tail 25 can be raised off the
catch lip 33. In the former case the catch lip 33 is elastically
connected to the sensor body 21 or is made on a part which is
elastically connected to the sensor body 21. In the latter case the
mounting tails 25 are elastically supported against the groove 41.
In any case the engagement is maintained by spring means.
[0052] Another example for safe attachment of the sensor 11 in the
groove 41 of a cylinder 43 is shown in FIGS. 9 and 10. On the
sensor 11 a fastening disk 61 is attached which consists of a
harder material than the jacket of the cylinder in which the groove
41 which has been undercut in a T-shape is made. This disk 61 is
provided with a thread into which a screw 65 is screwed. On the
edge or on the four corners of the disk 61 teeth 63 are formed. By
tightening the screw 65 these teeth can be pressed into the
material of the flange 59 which forms the undercut of the groove
41. The teeth are thus engaged with the flange 59. In this way a
form-fit is established. This disk is held by a spring 67 in this
engagement position. The spring 67 can, as shown, be a helical
spring, or also a leaf spring. There can be resilience between the
sensor with the fastening disk and the groove, or between the
sensor body 21 and the fastening disk 61. By turning back the screw
65 and pressing the screw in against the spring force of the spring
67 the disk 61 can be disengaged from the groove wall so that the
sensor can be moved. The sensor however is not unintentionally
moved since engagement is ensured by the spring force.
[0053] Instead of the disk 61 a leaf spring can also be provided
with teeth 63 and a thread and therefore can assume the function of
the disk and spring at the same time. To press the teeth into the
groove wall a tool which is independent of the sensor can also be
used instead of the screw 65.
[0054] The spring element which is shown in the FIG. 11 for
attaching the sensor 11 in a groove 41 which has been undercut in a
T shape is produced in one piece from spring steel. It has a part
which surrounds the sensor body 21 and a spring part with two teeth
63 which can be caused to engage a recess in the side wall of the
groove, especially of the narrower and outer part of the T-shaped
groove. These recesses can be attained by pressing a tooth 63 into
the aluminum of the piston jacket.
[0055] The parts which surround the sensor body 21 in the mounted
position are between the sensor body and the flange 59. They can
additionally apply a spring force to the sensor which presses it
against the base of the groove. The teeth 63 in the elastic part
are pressed to the outside by the spring force of this part. In the
relieved state of the spring element they are at a greater distance
from one another than the width of the groove. In this way when the
spring element is inserted into the groove with deformation of the
spring parts against one another, they must be caused to approach.
With a screwdriver or a special tool the teeth 63 which have been
folded and punched out of spring steel can be pressed directly
against one another into the aluminum of the flange 59 and
therefore hold positively.
[0056] One version of this spring element is shown in FIG. 12. It
likewise has flanges 69, a part which surrounds the sensor body and
two spring parts with teeth 63. But here they are in front of and
behind the sensor.
[0057] FIG. 13 shows four circuit diagrams in which the three reed
contacts 15, 16, 17 are combined into two printed conductors and
can have three distinguishable switching patterns. Aside from these
circuit diagrams, it is also possible to tap the three reed
contacts individually and to analyze the operating state of the
sensor with downstream logic.
[0058] In FIGS. 13a and 13b the first reed contact 15 and the third
reed contact 17 are connected in series. In the series connection
it is necessary for the first reed contact to be a make contact and
for the third to be a break contact in order to obtain a distinct
sensor signal. The second reed contact can be a break contact (FIG.
13b) or a make contact (FIG. 13a).
[0059] In FIGS. 13c and 13d the first reed contact 15 and the third
reed contact 17 are connected in parallel. This requires that the
first reed contact 15 is a break contact and the third reed contact
17 is a make contact so that distinct sensor signals are generated.
The second reed contact can again be a break contact or a make
contact.
[0060] The state of the reed contacts is analyzed with a logic
circuit (e.g., with an electronic component). The following applies
for the cited circuits:
TABLE-US-00001 Diagram 13a 13b 13c 13d Reed contacts 15/17 16 15/17
16 15/17 16 15/17 16 Activated by the 1 1 1 0 0 1 0 0 exciter part
Not activated 0 0 0 1 1 0 1 1 Activated by the external 0 1 0 0 1 1
1 0 magnetic field
[0061] If the reed contacts are tapped individually, each reed
contact independently of one another can be a make contact or a
break contact. The logic circuit can be configured accordingly such
that the open position and closed position of the individual reed
contacts are correctly interpreted.
[0062] It will be appreciated by those skilled in the art that the
present invention can be embodied in other specific forms without
departing from the spirit or essential characteristics thereof. The
presently disclosed embodiments are therefore considered in all
respects to be illustrative and not restricted. The scope of the
invention is indicated by the appended claims rather than the
foregoing description and all changes that come within the meaning
and range and equivalence thereof are intended to be embraced
therein.
* * * * *