U.S. patent number 3,823,285 [Application Number 05/318,735] was granted by the patent office on 1974-07-09 for pneumatically actuated switching device with ball contact means.
Invention is credited to Philip W. Dwyer.
United States Patent |
3,823,285 |
Dwyer |
July 9, 1974 |
PNEUMATICALLY ACTUATED SWITCHING DEVICE WITH BALL CONTACT MEANS
Abstract
An electrically conductive sleeve having a bore therethrough is
connected to a first conductor that is adapted to be connected to
one side of an electrical circuit. A second conductor is mounted in
an opening in the sleeve and is adapted to be connected to the
other side of the electrical circuit. An electrically conductive
ball is mounted in the bore and is movable by applying pneumatic
pressure thereto betwen a circuit open position out of electrical
communication with the second conductor and a circuit closed
position in electrical communication with the second conductor and
the sleeve. A cam surface extends into the bore and cams the ball
into electrical communication with the second conductor and the
sleeve in the circuit closed position. In a preferred embodiment,
the cam surface is defined by a spring which flexes as the ball
moves into and out of the circuit closed position so that the
surface of the ball wipes against the surfaces of the bore and the
spring, to clean such surfaces and thereby promote effective
electrical communication therebetween. The bore is carefully
dimensioned to very close tolerances so that the device is
responsive to the application of a minimum pneumatic pressure. The
pneumatic pressure is supplied by a deformable bulb manufactured in
one piece by an injection molding technique to preclude
leakage.
Inventors: |
Dwyer; Philip W. (Jacksonville
Beach, FL) |
Family
ID: |
23239399 |
Appl.
No.: |
05/318,735 |
Filed: |
December 27, 1972 |
Current U.S.
Class: |
200/81H;
200/DIG.29; 60/533; 200/277 |
Current CPC
Class: |
H01H
3/24 (20130101); H01H 1/16 (20130101); Y10S
200/29 (20130101) |
Current International
Class: |
H01H
1/12 (20060101); H01H 1/16 (20060101); H01H
3/00 (20060101); H01H 3/24 (20060101); H01h
035/24 () |
Field of
Search: |
;200/81H,83Z,82R,164R,DIG.29,86A,166BE,166BF,166BH,166CT,16D,61.52
;222/206,209 ;128/231 ;60/533 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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|
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411,154 |
|
Jan 1966 |
|
JA |
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554,793 |
|
Feb 1957 |
|
BE |
|
Primary Examiner: Schaefer; Robert K.
Assistant Examiner: Tolin; Gerald P.
Claims
I claim:
1. A pneumatically actuated switching device comprising:
a sleeve having a cylindrical bore extending therethrough and an
opening therein extending into said bore, at least the portion of
the surface of said bore opposite said opening being electrically
conductive;
a first electrical conductor means in electrical communication with
said conductive portion and adapted to be connected to a first side
of an electrical circuit;
a second electrical conductor means mounted in said opening and
adapted to be connected to a second side of said electrical
circuit;
an electrically conductive ball movably mounted in said bore, said
ball being movable between a circuit open position out of
electrical communication with said second electrical conductor
means and a circuit closed position in electrical communication
with said second electrical conductor means and said conductive
portion, whereby said the ball is in said circuit closed position
said first and second electrical conductor means are placed in
electrical communication with one another, said ball normally being
in one of said positions;
a cam surface attached to said second electrical conductor means
and extending into said bore and into the path of movement of said
ball adjacent said circuit closed position for camming said ball
into electrical communication with said second electrical conductor
means and said conductive portion, said cam surface comprising an
electrically conductive generally U-shaped spring having a contact
leg and a mounting leg, said legs being connected by a hinge
portion, said contact leg extending into said bore and said
mounting leg being attached to said second electrical conductor
means with said hinge portion free from contact with said second
electrical conductor means, whereby flexing of said spring is
unimpaired, said contact leg extending along said bore toward said
circuit open position so that said contact leg engages said ball
during movement of the ball to and from said circuit closed
position, said ball flexing said spring during movement of the ball
to and from said circuit closed position, whereby the surface of
said ball wipes against the surfaces of said bore and said spring
during movement of the ball to and from said circuit closed
position, to thereby clean said surfaces and thus promote effective
electrical communication therebetween, and
pneumatic actuating means connected to said sleeve and
communicating with one end of said bore, said actuating means being
selectively operable to move said ball from said one position to
the other of said positions by applying pneumatic pressure
thereto.
2. A pneumatically actuated switching device comprising:
a sleeve having a cylindrical bore extending therethrough and an
opening therein extending into said bore, at least the portion of
the surface of said bore opposite said opening being electrically
conductive;
a first electrical conductor means in electrical communication with
said conductive portion and adapted to be connected to a first side
of an electrical circuit;
a second electrical conductor means mounted in said opening and
adapted to be connected to a second side of said electrical
circuit;
an electrically conductive ball movably mounted in said bore, said
ball being movable between a circuit open position out of
electrical communication with said second electrical conductor
means and a circuit closed position in electrical communication
with said second electrical conductor means and said conductive
portion, whereby when the ball is in said circuit closed position
said first and second electrical conductor means are placed in
electrical communication with one another, said ball normally being
in one of said positions;
a cam surface extending into said bore and into the path of
movement of said ball adjacent said circuit closed position for
camming said ball into electrical communication with said second
electrical conductor means and said conductive portion;
pneumatic actuating means connected to said sleeve for
communicating with one end of said bore, said actuating means being
selectively operable to move said ball from said one position to
the other of said positions by applying pneumatic pressure
thereto;
means for locking said ball adjacent said other position; and
reset means for releasing said ball from said locking means, said
reset means comprising a reset rod mounted substantially coaxially
of said bore and movable into said bore through the other end
thereof, said reset rod engaging said ball upon movement thereof
into said bore, whereby movement of the reset rod into said bore
releases the ball from said locking means and moves the ball toward
said one position.
3. A pneumatically actuated switching device comprising:
a sleeve having a cylindrical bore extending therethrough and an
opening therein extending into said bore, at least the portion of
the surface of said bore opposite said opening being electrically
conductive;
a first electrical conductor means in electrical communication with
said conductive portion and adapted to be connected to a first side
of an electrical circuit;
a second electrical conductor means mounted in said opening and
adapted to be connected to a second side of said electrical
circuit;
an electrically conductive ball movably mounted in said bore, said
ball being movable between a circuit open position out of
electrical communication with said second electrical conductor
means and a circuit closed position in electrical communication
with said second electrical conductor means and said conductive
portion, whereby when the ball is in said circuit closed position
said first and second electrical conductor means are placed in
electrical communication with one another, said ball normally being
in one of said positions;
an electrically conductive spring means in electrical communication
with one of said conductors and positioned in said bore
substantially opposite the other of said conductors, said spring
means protruding into the path of movement of said ball at said
circuit closed position and extending therefrom toward said circuit
open position to intercept said ball in advance of said circuit
closed position, said ball thereby flexing said spring so that the
surface of said ball wipes against the surface of said bore and
said spring means during the final portion of movement into said
circuit closed position and the initial portion of movement out of
said circuit closed position to thereby clean said surfaces and
thus promote effective electrical communication therebetween;
and
pneumatic actuating means connected to said sleeve and
communicating with one end of said bore, said actuating means being
selectively operable to move said ball from said one position to
the other of said positions by applying pneumatic pressure
thereto.
4. The pneumatically actuated switching device of claim 3, wherein
said sleeve is oriented at an angle to the horizontal and said
pneumatic actuating means communicates with the lower end of said
bore, said ball being mounted in the portion of said bore extending
above said spring means and being normally in said circuit closed
position, said pneumatic actuating means moving said ball to said
circuit open position.
5. The pneumatically actuated switching device of claim 3, wherein
said sleeve is oriented at an angle to the horizontal and said
pneumatic actuating means communicates with the lower end of said
bore, said ball being mounted in the portion of said bore extending
below said spring means and being normally in said circuit open
position, said pneumatic actuating means moving said ball to said
circuit closed position.
6. The pneumatically actuated switching device of claim 3, further
comprising air filter means mounted adjacent the other end of said
bore.
7. The pneumatically actuated switching device of claim 3, wherein
said spring means is attached to said second electrical conductor
means.
8. The pneumatically actuated switching device of claim 7, wherein
said second electrical conductor means also extends into said bore
and into the path of movement of said ball and arrests the movement
of the ball in said circuit closed position.
9. The pneumatically actuated switching device of claim 3, wherein
said spring means comprises a leaf spring having a leg extending
into said bore, said leg having a free end oriented in the
direction of said circuit open position.
10. The pneumatically actuated switching device of claim 3, wherein
said spring means comprises a generally U-shaped spring having a
contact leg and a mounting leg, said legs being connected by a
hinge portion, said contact leg extending into said bore and said
mounting leg being attached to said second electrical conductor
means with said hinge portion free from contact with said second
electrical conductor means, whereby flexing of said spring is
unimpaired.
11. The pneumatically actuated switching device of claim 3, further
comprising a housing and a plug means, said sleeve being mounted in
said housing and said plug means being mounted in said housing in
alignment with said opening, said plug means including an
externally disposed tubular element comprising said first
electrical conductor means and an internally disposed rod element
comprising said second electrical conductor means, said plug means
being adapted to be received by a receptacle connected to said
electrical circuit.
12. The pneumatically actuated switching device of claim 11,
wherein said pneumatic actuating means comprises a deformable bulb
and a tube, one end of said tube being connected to said bulb and
the other end of said tube being connected to said housing adjacent
said one end of said bore, whereby when said plug means is received
by a generally horizontal receptacle the weight of said tube tends
to orient said sleeve generally vertically with said one end of
said bore oriented downwardly.
13. The pneumatically actuated switching device of claim 3, wherein
said pneumatic actuating means comprises a deformable bulb and a
tube, one end of said tube being connected to said bulb and the
other end of said tube communicating with said one end of said
bore.
14. The pneumatically actuated switching device of claim 3, wherein
said pneumatic actuating means comprises a manifold communicating
with said one end of said bore, and a plurality of deformable bulbs
connected in parallel to said manifold, whereby pneumatic pressure
may be applied to said ball by any one of said bulbs.
15. The pneumatically actuated switching device of claim 3, further
comprising means for locking said ball adjacent said other
position, and reset means for releasing said ball from said locking
means.
16. The pneumatically actuated switching device of claim 15,
wherein said locking means comprises a magnet means mounted
adjacent the other end of said bore.
17. The pneumatically actuated switching device of claim 13,
wherein said cam surface is defined by an electrically conductive
spring means attached to said second electrical conductor
means.
18. The pneumatically actuated switching device of claim 15,
wherein said reset means comprises a reset rod mounted
substantially coaxially of said bore and movable into said bore
through the other end thereof, said reset rod engaging said ball
upon movement thereof into said bore, whereby movement of the reset
rod into said bore releases the ball from said locking means and
moves the ball toward said one position.
19. The pneumatically actuated switching device of claim 18,
wherein said locking means comprises a magnetic means mounted
adjacent the other end of said first-mentioned bore and having a
second bore therethrough, said reset rod being movable through said
second bore into said first bore.
20. The pneumatically actuated switching device of claim 3, wherein
said pneumatic actuating means comprises a deformable bulb having a
pair of opposed, slightly convex actuating sides of relatively
large area.
21. The pneumatically actuated switching device of claim 20,
wherein said actuating sides are of generally circular
configuration.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to pneumatically operated devices
for switching electrical circuits, and is particularly well suited
for use in environments where it is undesirable to use a
conventional electrical switch, such as in atmospheres containing a
high concentration of potentially explosive gas. A good example of
such an environment is in hospital rooms and the like, where oxygen
commonly is used. Also, since the device is operated by only slight
pressure on an actuating bulb, it is well suited for use by
geriatric and other patients in a weakened or disabled condition.
However, use of the invention is not limited to hospitals and like
institutions, although a description of the invention as used in
such an institution facilitates an understanding thereof
Hospitals and like institutions usually have a signalling system by
which each patient may signal a central station, such as a nurse's
station, to summon assistance. Such systems are normally electrical
in nature, and frequently each patient is provided with a
conventional electrical switch which opens and closes a signal
circuit.
Under certain situations, notably when oxygen is being used,
electrical switches cannot be utilized in close proximity to the
patient because of the possibility of arcing within the switch,
which could cause ignition of combustibles in an atmosphere
containing a high concentration of oxygen, with catastrophic
results. Therefore, there have been developed a number of switching
devices for opening or closing a signal circuit by pneumatic means.
While this basic theory is sound, the prior art pneumatically
actuated switching devices have not been entirely satisfactory. For
example, a patient in a weakened or disabled condition must be able
to operate the device, and thus the device should be responsive to
the application of a minimum pneumatic pressure. Also, the device
must operate reliably over long periods of time without
maintenance, often in an atmosphere that is deleterious to the
components thereof.
SUMMARY OF THE INVENTION
It is the object of this invention to provide an improved
pneumatically actuated switching device that is extremely
responsive and reliable.
The pneumatically actuated switching device of the invention
comprises an electrically conductive sleeve having a bore
therethrough. An electrically conductive ball is mounted in the
bore and is movable in response to the application of pneumatic
pressure thereto. A porous air filter is mounted adjacent one end
of the bore to allow the passage of low pressure air in and out of
the bore to facilitate movement of the ball, and to prevent dust
and dirt from gaining entrance into the bore. The other end of the
bore is in communication with a tube to which is connected a source
of pneumatic pressure, such as a deformable bulb.
The device includes two conductors respectively adapted to be
connected to two sides of an electrical circuit, such as a signal
circuit. The first conductor is in electrical communication with
the sleeve. The second conductor is mounted in an opening in the
sleeve which extends into the bore. The ball is movable between a
circuit open position out of electrical communication with the
second conductor, and a circuit closed position in electrical
communication with the second conductor and the sleeve. A cam
surface extends into the bore and into the path of the ball, and
cams the ball into electrical communication with the second
conductor and the sleeve in the circuit closed position. The sleeve
normally is oriented generally vertically, although the device
operates satisfactorily when the sleeve is oriented almost
horizontally because the ball moves in the bore with very little,
if any, friction. The ball can be positioned above the cam surface,
wherein the circuit normally is closed and the ball is moved to
open the circuit, or below the cam surface, wherein the circuit is
normally open and the ball is moved to close the circuit.
In a preferred embodiment, the cam surface is defined by a spring
having a leg which flexes during movement of the ball to and from
the circuit closed position, so that during the last portion of
travel of the ball toward the circuit closed position and the first
portion of travel of the ball away from the circuit closed
position, the surface of the ball wipes against the surfaces of the
bore and the spring, cleaning such surfaces upon each actuation of
the device. Such wiping precludes the deposition of foreign matter
on the surfaces which may tend to cause the ball to stick and
adversely affect the sensitivity of the device. Particularly, such
wiping prevents the deposition of sulfides on the surfaces which
would adversely affect the conducting properties of the surfaces
and cause arcing. Since the conductive surfaces usually are plated,
arcing is particularly harmful, because it can erode the plating
away entirely. The spring also cushions and thereby minimizes
bouncing of the ball as the ball moves into the circuit closed
positioned, thus fostering a smooth, precise switching action.
In a preferred embodiment, the second conductor also extends into
the bore and arrests the movement of the ball in the circuit closed
position. The cam surface may be defined by the second conductor or
a spring attached to the second conductor.
Significantly, while the device responds to the application of a
very small amount of pressure on the deformable bulb, it is not
easily actuated by quick, sharp blows to the bulb, such as would be
applied when the bulb is dropped. This is because actuation of the
device requires displacement of a certain minimum volume of air
from the bulb, which volume is not displaced by quick, sharp blows
to the bulb.
The basic principles of this invention are applicable to electrical
circuits in which only a momentary opening or closing of the
switching device is necessary, as well as circuits in which opening
or closing of the switching device must be maintained until the
device is reset. In the latter instance, a locking means, such as a
magnet, locks the ball in the position to which it is moved
pneumatically. The device is reset by means, such as a plunger, for
releasing the ball from the locking means and moving it back to the
normal position.
The clearance between the ball and the surface of the bore in any
of the embodiments of the invention must be extremely small in
order to provide a device that is sensitive to the application of a
minimum of pneumatic pressure. Proper dimensioning of the bore is
difficult, especially when the sleeve is placed, and a novel method
of dimensioning the bore has been developed. The bore is first
reamed, and then is initially sized by ballizing with a ball of
hard material, such as tungsten carbide. The diameter of the
initial sizing ball is approximately equal to the desired final
diameter of the bore plus twice the thickness of the plating. The
bore is then plated with an electrical conductive material, such as
silver. The bore is then finally sized by ballizing with a ball of
hard material having a diameter slightly greater than the desired
final diameter of the bore to compensate for slight elastic
deformation of the plating during the final sizing.
The deformable bulb which is used to supply the pneumatic pressure
for operating the device must be leak-proof. Typically, the bulb
consists of a chamber and a neck. The chamber has a transverse
cross-section that is substantially wider than the transverse
cross-section of the neck. The bulb is best manufactured in one
piece, and a new method of doing so has been developed. The bulb is
made in one piece by injection molding an elastometric material in
a mold cavity defined between an outer mold and an inner mandrel.
Immediately after the injection molding, the bulb, with the mandrel
remaining inside, is removed from the mold cavity. The bulb is then
cooled to an elevated temperature below the temperature at which
the elastomeric material acquires elastic memory. A pressurized
fluid, such as air, is then injected into the bulb through a
passage in the mandrel, ejecting the bulb from the mandrel. During
the ejection of the bulb from the mandrel, the neck stretches to
accommodate the mandrel, but because the material has acquired
elastic memory, the bulb returns to the original molded shape.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of a first embodiment of the
pneumatically actuated switching device of the invention, with the
ball in the circuit open position;
FIG. 2 is a sectional view of the device of FIG. 1, with the ball
in the circuit closed position;
FIG. 3 is a sectional view of a second embodiment of the
pneumatically actuated switching device of the invention, with the
ball in the circuit open position;
FIG. 4 is a sectional view of the device of FIG. 3, with the ball
at a position intermediate the circuit open and circuit closed
positions;
FIG. 5 is a sectional view of the device of FIG. 3, with the ball
in the circuit closed position;
FIG. 6 is a sectional view of a third embodiment of the
pneumatically actuated switching device of the invention, with the
ball in the circuit closed position;
FIG. 7 is a perspective view of a pneumatically actuated switching
device of the invention to which a plurality of actuator bulbs are
connected; and
FIG. 8 is an elevational view, partially in section, showing
ejection of the bulb from the mandrel.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The pneumatically actuated switching device of the invention can be
used in a variety of systems and environments in which it is
desirable to switch an electrical circuit on or off by remote
means. The device is particularly well suited for use with
conventional nurse call signal systems and, since in this context
the features of the invention are highlighted, the invention is
described herein in combination with such a system. However, it
should be understood that the invention is not limited to such
use.
The pneumatically actuated switching device of the invention
comprises five basic components: a sleeve 10, a ball 11, a housing
12, an electrical plug 13, and a pneumatic actuating means, such as
a tube 14 and a deformable bulb 15.
A first embodiment of the invention is shown in FIGS. 1 and 2.
Sleeve 10 is of cylindrical configuration and has a cylindrical
bore 22 extending therethrough and a pair of open ends 20 and 21.
An opening 23 is provided in sleeve 10 intermediate ends 20 and 21
and extending into bore 22. This arrangement allows sleeve 10 to be
utilized without modification for both normally open circuit and
normally closed circuit electrical systems, as will be explained
below. At least the portion of the surface of bore 22 opposite
opening 23 is electrically conductive, or sleeve 10 may be
manufactured entirely of a conductive material, or sleeve 10,
including the surface of bore 22, may be plated or otherwise coated
with a conductive material. To provide maximum sensitivity, a
material having excellent conductivity, such as silver, should be
used, and it is therefore economically expedient to manufacture
sleeve 10 from a conductive material, such as brass, and then plate
the sleeve, including the surface of bore 22, with silver.
Alternatively, only a narrow annular band 24, shown in phantom in
FIG. 1, adjacent opening 23, need be plated or otherwise formed
from a conductive material.
Movably mounted in bore 22 is an electrically conductive ball 11.
Similarly to sleeve 10, ball 11 may be manufactured entirely of a
conductive material, or may be plated with such material. Again, to
provide maximum sensitivity, a material having excellent
conductivity, such as silver, should be used. Ball 11 is movable in
bore 22 in response to the application of pneumatic pressure
thereto. It is quite important that ball 11 be freely movable in
bore 22, and it is equally important that the clearance between the
outer surface of the ball and the surface of the bore be as small
as possible, so that the ball functions as a piston in response to
the application of a very small amount of pneumatic pressure. The
clearance between bore 22 and ball 11 should be of the magnitude of
0.0015 inch or less. This necessitates dimensioning bore 22 very
accurately. A novel process for accomplishing such dimensioning is
set forth below.
Sleeve 10 is mounted in a bore 25 of housing 12. The housing is
made from a non-conductive material and includes a stem 26 at one
end thereof. A passage 27 extends through stem 26 and communicates
at the interior end thereof with open end 21 of sleeve 10. The
outer surface of stem 26 is provided with a number of annular
ridges 28. Stem 26 is inserted into the end of pneumatic tube 14.
An annular collar 29, which may be made from an elastic material,
in installed around tube 14 and cooperates with ridges 28 to clamp
tube 14 securely to stem 26 in a leak-free connection. While this
is a preferred manner of connecting tube 14 to housing 12, other
means may be used, as long as the connection is leak-free.
A porous air filter 16 is press-fit into bore 25 at the other end
of housing 12. Filter 16 abuts open end 20 of sleeve 10 and allows
low pressure air to flow freely into and out of bore 22 while
preventing dirt and moisture from entering the bore which could
interfere with the proper operation of the device. Filter 16 can be
made from any suitable material such as metal, refractory or
plastic.
Housing 12 also is provided with a passage 30 communicating with
opening 23 and substantially perpendicular to bore 25. Plug 13 is
mounted in passage 30, and comprises an externally disposed tubular
element conductor 33 and an internally disposed rod element
conductor 32. Conductors 32 and 33 are electrically insulated from
one another by insulation means 34. A conductive cap 35 is
connected to the outer end of conductor 32. Plug 13 fits into a
conventional receptacle (not shown) in the conventional manner.
Within the receptacle, external conductor 33 is connected to one
side of a signal circuit, and internal conductor 32 is connected to
the other side of such circuit via cap 35.
Internal conductor 32 may be a conventional machine screw and
terminates at the inner end thereof in a hemispherical head 37.
Head 37 extends through opening 23 into bore 22 and into the path
of ball 11, but is spaced from the edges of opening 23 so that
there is no direct electrical communication between head 37 and
sleeve 10. If desired, insulating material may be placed in the
space between head 37 and the edges of opening 23. Head 37 is
provided with a cam surface 38, which may be the surface of the
head. Cam surface 38 preferably is plated with a material having
excellent conductivity, such as silver. Cam surface 38 is inclined
in such a manner to cam ball 11 into positive contact with the
surface of bore 22 and the cam surface, and thereby insure good
electrical communication therebetween in the circuit closed
position of the ball. This arrangement also compensates for any
looseness in fit between ball 11 and bore 22 because the ball is,
in a sense, arrested by head 37 in a wedge-like action.
External conductor 33 is in electrical communication with sleeve 10
via a conductive pin 40 that is inserted through a small bore 41 in
housing 12 contiguous with conductor 33. Pin 40 is received in a
recess 42 in sleeve 10. However, if only the surface of bore 22 is
plated or otherwise formed from a conductive material, pin 40 must
communicate directly with the surface of the bore.
The responsiveness of the device is enhanced by the particular
shape of bulb 15. As illustrated in FIGS. 3 and 7, bulb 15 has a
chamber 105 which includes opposed sides 120; such sides being
substantially flattened, slightly convex and of generally circular
configuration. Sides 120 have a relatively large surface area and
define the major portion of the surface area of chamber 105. Thus,
slight compressive deformation of one or both of sides 120 causes a
substantial volumetric chamber in chamber 105, thereby displacing a
relatively large volume of air from within the chamber. This
advantage is not achieved with bulbs of other shapes, especially
those of round cross-section employed in many prior art devices.
Bulb 15 also includes a neck 106 and is connected to tube 14 by a
connector 107.
The operation of this embodiment is as follows: Plug 13 is inserted
into the receptacle of an electrical system, such as a nurse call
signal system. While it is desirable that sleeve 10 be
substantially vertically oriented, the device will operate properly
with the sleeve inclined only two degrees from the horizontal. In
practice, the weight of tube 14 tends to orient housing 12, and
thus sleeve 10, substantially vertically. In FIGS. 1 and 2 the
device is illustrated in the context of a system in which the
circuit normally is open; a signal being initiated by closing the
circuit. In such a system. ball 11 is positioned in the lower
portion of bore 22, and normally rests against the bottom of bore
25. To close the electrical circuit, conductors 32 and 33 must be
placed in electrical communication with one another. This is
accomplished by moving ball 11 upwardly from the normal circuit
open position shown in FIG. 1 to the circuit closed position shown
in FIG. 2. To move ball 11 upwardly, the user squeezes bulb 15,
forcing air through tube 14 and passage 27. Due to the close
tolerance between ball 11 and bore 22, the ball reacts as a piston,
and moves upwardly in the bore to the position shown in FIG. 2. In
this position, ball 11 contacts cam surface 38 and is arrested in a
wedge-like action between cam surface 38 and bore 22. This
arrangement promotes effective electrical communication between the
surfaces of ball 11, bore 22 and cam surface 38.
In the circuit closed position shown in FIG. 2, ball 11 is in
electrical communication with conductor 32 via head 37, and with
conductor 33 via pin 40 and sleeve 10. Therefore, the electrical
circuit is closed. Upon relaxation of the pneumatic pressure in the
system, ball 11 will drop or roll to the lower portion of bore 22,
thus again opening the circuit. In the usual signal system, only a
momentary closing (or opening) of the circuit is sufficient to
initiate the desired signal, which will be maintained until reset
from a central station, notwithstanding the subsequent opening (or
closing) of the switching device.
The second preferred embodiment of the invention is shown in FIGS.
3-5 and in many respects is identical to the embodiment previously
described. However, the second embodiment incorporates an
additional novel feature which provides a number of additional
advantages.
In the second embodiment of the invention, internal conductor 32
terminates at the inner end thereo in a hemispherical head 50. A
generally U-shaped leaf spring 51 made from a copper alloy is
attached to head 50. Spring 51 has a contact leg 52 and a mounting
leg 53, such legs being connected by a hinge portion 54. While
spring 51 can be attached to head 50 in a number of manners, there
is a preferred manner, as follows: Head 50 is provided with a slot,
indicated generally at 55. The base of slot 55 is defined by a
first inclined portion 56 and a second inclined portion 57.
Mounting leg 53 is attached to base portion 56 by conventional
means, such as by soldering, so that hinge portion 54 will not be
coated with solder, which would detrimentally affect the flexure
characteristics of spring 51.
Head 50 extends into bore 22 and into the path of ball 11 so that
the movement of ball 11 is arrested by the head. However, contact
leg 52 extends slightly inwardly beyond head 50 and has the free
end thereof oriented in the direction of the circuit open position
of ball 11. Such free end defines a cam surface 58 which preferably
is plated with silver. Cam surface 58 engages ball 11 during
movement of the ball into and out of the circuit closed position.
During such engagement, spring 51 flexes and contact leg 52 moves
inwardly and outwardly of slot 55. Thus, the circuit can actually
be closed upon contact between ball 11 and cam surface 58 slightly
before and after the ball is in the circuit closed position.
The operation of the embodiment shown in FIGS. 3-5 is described in
the context of a system in which the signal circuit normally is
closed, and is opened to initiate a signal. In FIG. 3, ball 11 is
shown in the upper portion of bore 22, where it has been moved by
the application of pneumatic pressure thereto by bulb 15 through
tube 14. In FIG. 3, the electrical circuit is open. Upon release of
the pneumatic pressure ball 11, under the action of gravity and the
suction of bulb 15, drops downwardly to the position shown in FIG.
4, which is the moment of first contact between the ball and cam
surface 58. Under optimum conditions, the electrical circuit will
close at this moment. Ball 11 continues through the position shown
in FIG. 4, however, causing contact leg 52 to flex inwardly,
finally being arrested by head 50 in the circuit closed position
shown in FIG. 5. During the movement of ball 11 between the
position shown in FIG. 4 to that shown in FIG. 5, and vica versa,
cam surface 58 engages ball 11 and cams the ball into contact with
the surface of bore 22. Thus, the surface of ball is pressed into
intimate wiping contact with the surfaces of bore 22 and cam
surface 58. This is a key feature of the invention, and eliminates
some heretofore unsolved problems of the prior art devices. Wiping
of the various surfaces against one another cleans the surfaces and
prevents the deposition of sulfides or other contaminants thereon
which would deteriously affect the conducting properties of the
surfaces and result in arcing. Arcing would quickly erode the
surfaces, particularly plated surfaces, thereby destroying the
sensitivity and reliability of the device. For example, when silver
plated surfaces are wiped clean, a pneumatic pressure of only about
two inches of water is required to raise ball 11 from the circuit
closed position shown in FIG. 5 to the circuit open position shown
in FIG. 3. but if the silver plating is eroded away, a pneumatic
pressure of as much as about twelve inches of water is required,
because ball 11 tends to stick in the circuit closed position. The
extent to which contact leg 52 extends beyond head 50 is kept to a
minimum, commensurate with the desired wiping of the surface of
ball 11 against the surfaces of bore 22 and cam surface 58.
While spring 51 has been shown as U-shaped, other spring
configurations may be employed, within the limitation of providing
a biased cam surface to interact with the ball in the novel manner
described above.
It should be noted that in both of the embodiments described above,
the position of the ball can be reversed so that the circuit is
actuated in the manner opposite to that described. In such
instance, the cam surface, either on head 37 or on spring 51, is
reoriented to engage and cam ball 11 in the desired manner.
The above two embodiments illustrate the invention for use with
circuits where a momentary opening (or closing) of the circuit is
sufficient to initiate and maintain the signal. However, in some
signal circuits, the signal will be maintained only as long as the
circuit is switched open (or closed). In this type of circuit, the
ball must be held in the position to which it is moved, and
returned to its normal position by reset means.
The third embodiment of the invention shown in FIG. 6 embodies such
a structure. As in the previously described embodiments, a sleeve
10 having a bore 22 therethrough is mounted in a housing 12. A
conductive ball 11 made from a magnetically susceptible material is
movably mounted in bore 22. A plug 13 having an external conductor
33 and an internal conductor 13 is mounted in a bore 30 in housing
12. Internal conductor 32 terminates at the inner end thereof in a
hemispherical head 50 which has a slot 55 therein, as described
above. In this embodiment, head 50 does not extend through opening
23 into bore 22 and into the path of ball 11. However, a spring 51
is attached to head 50, as described above, with the contact leg 52
thereof extending into bore 22 and into the path of ball 11.
A reset assembly, including a porous air filter, is mounted in bore
25 at the end of housing 12 opposite stem 26. Also, a locking
means, comprising a cylindrical magnet 70, is mounted in bore 25 at
the same end of housing 12. Magnet 70 has a diameter less than the
diameter of bore 25 and is inserted into such bore against open end
20 of sleeve 10. An annular air passage 71 is defined between the
outer periphery of magnet 70 and the inner surface of bore 25.
Magnet 70 has a dished recess 73 for engaging ball 11, an axial
bore 76 therethrough, and a transverse air passage 74 communicating
between bore 76 and air passage 71. When ball 11 moves upwardly
into engagement with recess 73, the air above the ball flows into
bore 76 and through passages 74 and 71 upwardly around magnet 70.
Mounted on the outer end of magnet 70 is an insulator disc 77,
having an opening 78 therein. A porous air filter 80 is press-fit
into bore 25 against disc 77. Filter 80 has a first axial bore 81
partially therethrough and a second axial bore 82 having a diameter
less than the diameter of bore 81 through the remainder thereof. An
insulated sleeve 84 having a flange 85 extends through bores 81,
82, opening 78 and into bore 76, and aligns magnet 70 and insulator
disc 77 coaxially of filter 80 and bore 25.
A reset plunger 87 having a head 88 extends through sleeve 84. An
O-ring 89 and a locking ring 90 seal plunger in sleeve 84. A return
spring 92 is coiled about plunger 87 and acts against locking ring
90 and head 88. A non-conductive cap screw 94 having a head of
greater diameter than plunger 87 is screwed into the end of the
plunger and engages the end of sleeve 84 to properly position the
plunger.
The operation of this embodiment is as follows: In response to
pneumatic pressure applied by squeezing bulb 15, ball 11 begins to
move upwardly from the position shown in phantom in FIG. 5. The
pneumatic pressure need move ball 11 only into the magnetic field
of magnet 70. When the ball is in such field, it is drawn upwardly
toward magnet 70 until it is engaged in recess 73, as shown in
solid lines in FIG. 6. Ball 11 is thus locked in position by magnet
70. At a point slightly in advance of the locked position, ball 11
contacts cam surface 58 which cams the ball into contact with the
surface of bore 22 so that the surface of the ball wipes against
the surfaces of the bore and cam surface, as described above. The
movement of ball 11, however, is not arrested by head 50. The
electrical circuit is closed through spring 51. Ball 11 remains
engaged in recess 73 until reset plunger 87 is manually depressed
sufficiently to move the ball out of the magnetic field of magnet
70.
Since ball 11 and sleeve 10 are in the electrical circuit while the
ball is in recess 73, magnet 70 also becomes charged. However,
magnet 70 is insulated from filter 80 and reset plunger 87 by disc
77, sleeve 84 and screw 94 so that no external elements of the
device become charged. If desired, reset plunger 87 also may be
made from a non-conductive material.
Several alternative arrangements of the components of the device
illustrated in FIG. 6 are possible. While the device is shown for
use with a normally open circuit system, the device is equally
suitable for use with a normally closed circuit system, in which
instance opening 23 would be positioned in the lower portion of
sleeve 10. Thus, spring 51 would normally engage ball 11, and
upward movement of the ball toward magnet 70 would open the
circuit.
The pneumatically actuated switching device of the invention may be
operated from several stations. As shown in FIG. 7, a pair of bulbs
15a and 15b may be connected in parallel to a common tube 14 by
means of a manifold 64. The device will then be operated by
squeezing either bulb.
In view of the close fit required between ball 11 and the surface
of bore 22, the bore must be dimensioned in a very precise manner.
This is particularly difficult when sleeve 10 is plated with a
conductive material, such as silver, because the plating operation
by nature is not accurate. A particularly efficient method has been
developed for dimensioning the bore to the exacting measurements
required.
A plurality of balls 11 are manufactured, including plating, by
known techniques. The balls will have slight variations in
diameter, and are separated by diameter into lots. This allows the
bore of the sleeve associated with a particular ball to be very
accurately dimensioned. The bore is first reamed to roughly
establish the dimension thereof, and is then initially sized by
ballizing with a ball of hard material, such as tungsten carbide.
The diameter of the initial sizing ball is approximately equal to
the desired final diameter of the bore, plus twice the desired
thickness of the plating.
Bore 22 is then plated, usually by plating the entire sleeve. The
thickness of the plating on the surface of the bore is about 0.0005
inch. The plating material usually is silver, but may be another
conductive material. The bore is then finally sized by ballizing
with a ball of hard material having a diameter slightly greater
than the desired final diameter to compensate for slight elastic
deformation of the plating during the final sizing.
The manufacture of the pneumatic squeeze bulb also poses some
special problems. The bulb must have no leaks and should not have a
propensity for developing leaks during use. It is therefore
advantageous to manufacture chamber 105 and neck 106 in one piece,
and a new method for doing so has been discovered.
The transverse cross-section of chamber 105 is substantially wider
than the transverse cross-section of neck 106. Bulb 15 is
manufactured from vinyl or a similar elastomeric material by an
injection molding process in a mold cavity formed between an outer
mold (not shown) and an inner mandrel 110. Mandrel 110 comprises a
chamber forming portion 111 and a neck forming portion 112. Mandrel
110 further comprises an injection gas passage 113 communicating at
one end with a source of pressurized fluid, such as air (not shown)
and at the outer end with the interior of a bulb 15 formed thereon.
A check valve 115 is installed in passage 113 so that the
elastomeric material will not enter passage 113 when the material
is injected into the mold cavity. The outer mold is of the type
that can be opened to remove the mandrel from the mold cavity.
First, the elastomeric material in a high temperature, liquid state
is injected under pressure into the mold cavity in a conventional
manner, and changer 105 and neck 106 are formed to the desired size
and shape on mandrel 110. Then, while the material is still at an
elevated temperature, mandrel 110, with the formed bulb thereon, is
removed from the mold cavity. The bulb is then allowed to cool to
an elevated temperature below the temperature at which the
elastomeric material acquires elastic memory. A jet of high
pressure fluid is then injected via passage 113 into the interior
of the bulb, ejecting the bulb from mandrel 110. Neck 106 must
stretch to the width of chamber forming portion 111 during this
ejection, as shown in FIG. 8, but it has been found that such
stretching is accomplished without damage, and the bulb quickly
returns to its molded shape.
It is to be understood that while specific preferred embodiments of
the invention are herein illustrated and described, and the
invention has been disclosed for use with a particular type of
electrical system, the invention is not to be limited to such
embodiments or for use with such systems, but is defined solely by
the scope of the appended claims.
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