Pneumatic switch for patient call system having multiple-position housing assembly

A pneumatically actuated switching device is disclosed for forming a momentary electrical signal circuit with a receptacle of a patient call system utilizing a conductive plunger which slides in response to a pulse of pressurized air delivered to an internal chamber through a housing connection which provides for optional assembly orientations. A spring is used to maintain separation between a conductive plunger and the electrical components when the pneumatic switching device is not activated by a patient.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a pneumatically actuated switching device for a 
patient call system, and more particularly to a switching device having a 
conductive plunger responsive to pressurized air delivered from a 
hose/housing connection which allows for multiple assembly orientations. 
2. Description of the Prior Art 
Hospitals, and other patient-care institutions, frequently provide patient 
call systems wherein a patient may activate a signal to a central station, 
such as nurse's station, to summon assistance. The use of conventional 
electrical switches to generate the signal in such environments is 
undesirable given the potentially combustible levels of oxygen that will 
likely be present near the patient. 
As an alternative to conventional electrical switches, the use of a 
pneumatically actuated switch, which utilizes a pulse of pressurized air 
to actuate a signal circuit, avoided the safety concerns associated with a 
conventional switch. Such a device, however, should have the ability to 
complete a signal circuit in response to a relatively weak pneumatic pulse 
in order to accommodate patients who may be in a debilitated state and 
therefore unable to generate a large pressure pulse. 
Examples of prior art pneumatically actuated switching devices for patient 
call systems can be found in U.S. Pat. No. 3,823,285 and U.S. Pat. No. 
5,113,048 to Lafferty. While the '285 Patent provided an entirely 
satisfactory solution to the need for a pneumatically actuated switch for 
a patient call system, the design of the switch left room for improvement. 
The use of the conductive ball slidable in an air tight relation along a 
sleeve according to the '285 patent depends on gravity forces to reset the 
switch components once the pressure pulse has made the contact necessary 
to complete the signal circuit. Therefore, optimum functioning of the 
device requires that the device be positioned so that the sleeve is in a 
generally vertical orientation. 
U.S. Pat. No. 5,113,048 to Lafferty incorporates a tightly sealed chamber 
for the pressure pulse in order to compress a deformable diaphragm 
confronting the chamber. The compression of the diaphragm results in the 
contact of conductive elements required to complete the signal circuit. 
The relatively large size of the diaphragm in relation to the chamber 
requires maximal use of the available pressure pulse in order to ensure 
that the volume of air that is required to compress the diaphragm is 
present in the chamber. This design is therefore unforgiving of pressure 
losses and necessitates the tightly sealed volume which includes the bulb, 
tubing and the chamber. 
SUMMARY OF THE INVENTION 
According to the present invention, there is provided a pneumatically 
actuated switch for a patient call system, the switch including means for 
generating and discharging a quantity of pressurized air, tubing having a 
first end connected to the means for generating and an opposite second 
end, a connector having a first end connected to the second end of the 
tubing and an opposite second end having a surface, the connector having 
an internal passage extending through the connector between the ends, a 
housing having a first end with a cavity for enclosing at least a portion 
of the second end of the connector and an opposite second end, the first 
end of the housing having a surface which is capable of interfitting with 
the surface of the second end of the connector, the surface of the housing 
including a recessed portion for forming a chamber communicating with the 
internal passage of the connector upon interfacing contact between the 
surfaces, the housing further including an internal opening having a first 
end communicating with the recessed portion and an opposite second end, 
means at least partially contained within the internal opening in the 
housing for creating a momentary electrical connection in response to the 
pressurized air, and means connecting the connector to the housing for 
maintaining the interfacing contact between the surfaces, the means for 
maintaining providing for a plurality of assembly options each having a 
different angular orientation of the connector relative to the housing 
while maintaining communication between the internal passage of the 
connector and the recessed portion of the housing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIGS. 1 and 2, isometric views show a pneumatic switch assembly 10 for 
providing a signal in a patient call system according to the present 
invention. FIG. 1 shows an in-line assembly configuration for the switch 
housing and FIG. 2 shows a right angle configuration, the assembly options 
being described below. The switch responds to a relatively weak pressure 
pulse to create a momentary electrical connection. The pressure pulse may 
be generated by a squeeze bulb 12. Such bulbs are, per se, well known in 
the art, examples of which are described in U.S. Pat. No. 5,461,207 to Van 
Lear, and U.S. Pat. No. 5,155,309 to Dwyer. Typically, the bulb will 
include a deformable actuator confronting a pressure chamber. When a user 
of the device places pressure on the actuator, the deformation of the 
actuator causes compression of the pressure chamber resulting in the weak 
pressure pulse. 
The pressure pulse is conveyed from the bulb 12 by tubing, such as the 
pneumatic hose 14, to the connector 16. The connector allows for multiple 
assembly options each providing for a different angular orientation of the 
connector. The connector 16 is made of a nonconducting material, such as 
plastic, and includes a strain-relieving section 18, in the region of the 
connection of the hose 14 to the connector 16. 
Turning to FIG. 3 through 5, the construction of the switch components may 
be seen. The connector includes an internal passage 20 extending through 
the connector from a first end of the connector connected to the hose 14 
to an opposite second end of the connector. The second end of the 
connector 16 includes a curved surface 22. 
The connector 16 is partially enclosed within a cavity formed in an end of 
a housing 24. The cavity of the housing 24 includes opposing side walls 
26, as seen in FIG. 5, and a curved surface 28 located between the side 
walls. The contour of the curved surface 28 is compatible with the surface 
22 of the connector 16 such that the two components can be brought into 
interfacing contact with one another. Although the preferred embodiment 
involves continuously curving surfaces 22 and 28, other geometries could 
be employed as well, such as a surface including multiple planar segments. 
Curved surface 28 of the housing 24 also has a recessed portion 30 for 
forming a chamber 31 when the curved surfaces of the connector and the 
housing are brought into interfacing contact with one another. The 
recessed portion 30 is located so that the end of the passage 20 will 
confront the chamber 31 for each of the possible assembly options, which 
will be discussed below. The housing further includes an internal opening, 
such as central bore 32, which has an end communicating with the recessed 
portion 30. The housing is made from a nonconducting material, such as 
plastic. The construction described above provides a pathway for the pulse 
of pressurized air which extends from the bulb 12, through the tubing 14, 
to the internal passage 20 of the connector 16 and into the central bore 
32 of the housing 24 via the chamber 31. 
To maintain the interfacing contact between the connector and the housing, 
which provides sealing contact for the pressure pulse within the chamber 
31, pins 34 extend through the connector 16 and through the opposing side 
walls 26 of the housing 24 thereby locking the two components together in 
a preselected angular orientation of the connector relative to the 
housing. The pair of pins 34 shown, require two openings in the connector 
16 and in each of the side walls 26 of the housing 24. The inclusion of 
the additional openings in the side walls 26 provides for the different 
angular orientation options for the connector during the assembly of the 
switch. End caps 36 as seen in FIG. 5 form the final closure for 
maintaining the locked assembly orientation by retaining the pins within 
the openings in the connector and the housing. The pins may be integral 
with one of the end caps, as shown in FIG. 5, or alternatively may be 
separate components. One of the end caps 36 includes openings for seating 
of ends of the pins 34 extending from the openings in the side walls 26 of 
the housing 24. The end caps also include concave portions 37 on the 
external surfaces, as seen in FIGS. 1 and 2, for improved gripping of the 
assembled switch. 
A portion of the assembly which will make the temporary electrical 
connection is housed within the center bore 32 of the housing 24. This 
includes a conductive plunger 38 which is slidably contained within the 
central bore. As will be apparent to one skilled in the art, a relatively 
close tolerance fit will be required between the plunger 38 and the bore 
32 to ensure that the plunger will slide in response to a pressure pulse 
delivered to the chamber 31. If too great a gap exists between the plunger 
and the bore, the pulse of air might pass by the plunger instead of 
driving the plunger into the bore. 
The plunger 38 has a reduced diameter portion opposite from the end of the 
plunger which confronts the chamber 31 thereby creating a ledge for 
contact with a spring 40. The spring acts to maintain separation, in the 
absence of a pressure pulse, between the plunger 38 and a portion of the 
electrical connection components, as will be described in greater detail 
below. 
The switch assembly includes a jack extending from an end of the housing 
for electrical connection with the receptacle of a patient call system. 
The jack includes a conductive outer body 42 having an inner cavity 44 
extending along the entire elongated length of the outer body 42. As seen 
in FIG. 3, the outer body 42 is positioned within an opening in the 
housing such that an end of the outer body confronts the end of the 
central bore 32. The outer body 42 and the opening in the housing are 
toleranced so that a slight interference fit will exist to maintain the 
position of the outer body. The outer body 42 further includes a knurled 
portion in the region of the connection to the housing to enhance the 
gripping strength of the connection. Within the cavity 44, a conductive 
core 46 is housed, the core extending beyond both ends of the outer body 
42 thereby forming at one end an extension 48 which extends into the 
central bore 32 for contact with plunger 38. The core extends from the 
opposite end of the outer body 42 to connect to a conductive jack tip 50. 
The plunger 38 and the extension 48, as shown, have compatible 
interfitting surfaces providing for conductive contacting surfaces. 
Insulators 52 provide for electrical separation between the jack tip 50 
and the outer body 42 and between the core 46 and the outer body 42. 
An important feature in the functioning of the switch involves an 
additional purpose of the spring 40 beyond that of providing for the above 
described separation, which will exist in the absence of a pressure pulse, 
between the plunger 38 and the extension 48 of the jack core 46. The 
spring is made from a conductive material so that the spring also provides 
for an electrical pathway to exist between the plunger 38 and the end of 
the outer body 42 confronting the central bore 32 through the spring 40. 
The spring 40 has an end section with a reduced diameter spiral for 
seating of that portion of the spring between the outer body 42 and 
insulator 52 thereby ensuring good conductive contact between the spring 
and the outer body. 
The temporary electrical connection will result in the following manner. A 
first electrical pathway will exist between the receptacle and the plunger 
38 through the outer body 42 and the spring 40. A second pathway will 
extend from the receptacle to the extension 48 of the jack core 46 through 
the jack tip 50. The first and second pathways are kept electrically 
separated from one another by the insulators 52 between the core 46 and 
outer body 42 and between the jack tip 50 and the outer body 42. Upon the 
entrance of a pressure pulse into the chamber 31 and the central bore 32, 
the plunger will slide in the central bore resulting in contact between 
the interfitting surfaces of the plunger 38 and the core extension 48. 
This contact will unite the two electrical pathways resulting in an 
electrical signal, which may be monitored at a central location such as a 
nurse's station, indicating that the switch has been activated. 
The sliding of the plunger is facilitated by the inclusion of a bleed 
pathway 54 in the housing extending from the end of the central bore 32 
opposite the chamber 31 to the end of the housing. The pathway 54 allows 
for the escape of air present in the central bore 32 and adjacent to the 
spring 40 which would otherwise be pressurized in the absence of the bleed 
pathway. 
While the present invention has been described in connection with the 
preferred embodiments of the various figures, it is to be understood that 
other similar embodiments may be used or modifications and additions may 
be made to the described embodiment for performing the same function of 
the present invention without deviating therefrom. Therefore, the present 
invention should not be limited to any single embodiment, but rather 
construed in breadth and scope in accordance with the recitation of the 
appended claims.