US3823285A

US3823285A - Pneumatically actuated switching device with ball contact means

Info

Publication number: US3823285A
Application number: US00318735A
Authority: US
Inventors: P Dwyer
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-12-27
Filing date: 1972-12-27
Publication date: 1974-07-09
Anticipated expiration: 1991-07-09

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.

Description

United States Patent [191 Dwyer I PNEUMATICALLY ACTUATED SWITCHING DEVICE WITH BAlLlL CONTACT MEANS [76] Inventor: Philip W. ll wyer, PO, Box 51182,

Jacksonville Beach, Fla. 32250 22 Filed: Dec. 27, 1972 21 Appl. No.: 318,735

[52] US. Cl..... 2011/81 11, 200/164 R, ZOO/DIG. 29, 200/166 BE, 60/533 [51] Int. Cl. 1101111 35/241 [58] ll ieltl of Search. 200/81 11, 83 Z, 82 R, 164 R, ZOO/DIG. 29, 86 A, 166 BE, 166 BF, 166

B11, 166 CT, 16 D, 61.52, 61.45 M; 222/206,

Primary Examiner-Robert K. Schaefer Assistant ExaminerGerald P. Tolin [5 7] 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 ballinto electrical communication with the second conductor and the sleeve in the circuit closed position. In a preferred embodiment, the cam su'rfaceis 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.

21 Claims, 8 Drawingllfigures PATENTEU JUL SHEET 1 OF 3 FIG.1

FATENTED L 9W 31.820285 SHEET 0F 3 COMPRESSED 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 nurses 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 circurt.

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 pres sure, 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 appli cation 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 crosssection 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. Im-

mediately 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 ballin 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 applicationof 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 moismm 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 perpendicularto 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. Conductors32 and 33 are'electrically insulated from one another by insulation means 34. A

conductive cap 35 is connected to the outer end of con-' ductor 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 via a conductive pin 40 that is inserted through a small bore 11 in housing 12 contiguous with conductor 33. Pin 40 is received in a recess 42 in sleeve 111. However, if only the surface of bore 22 is platedor 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 13. As illustrated in FIGS. 3 and 7, bulb 13 has a chamber 103 which includes opposed sides 1211; 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 103. Thus, slight compressive deformation of one or both of sides .120 causes a substantial volumetric chamber in chamber 105, thereby displacing a relatively largevolume 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 13 also includes a neck 1% and is connected to tube 14 by a connector 1117.

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 23. 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.

I The second preferred embodiment of the invention is shown in FIGS. 3-3 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 30. A generally U-shaped leaf spring 31 made from a'copper alloy is attached to head 30. Spring 31 has a contact leg 32 and a mounting leg 33, such legs being connected by a hinge portion 34. While spring 31 can be attached to head 30 in a number of manners, there is a preferred manner, as follows: Head 311 is provided with a slot, indicated generally at 33. The base of slot 33 is defined by a first inclined portion 36 and a second inclined portion 37. Mounting leg 33 is attached to base portion 36 by conventional means, such as by soldering, so that hinge portion 341 will not be coated with solder, which would detrimentally affect the tlexure characteristics of spring 31.

Head 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 32 extends slightly inwardly beyond head 51) 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 33 which preferably is plated with silver. Cam surface 38 engages ball 11 during movement of the ball into and out of the circuit closed position. During such engagement, spring 31 flexes and contact leg 32 moves inwardly and outwardly of slot 33. Thus, the circuit can actually be closed upon contact between ball 11 and cam surface -7 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 inFlG. 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 thedevice. 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 inchesof water is required, because ball 11 tends to stick in the circuit closed position. The extent to which contact leg 52 extendsbeyond 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 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 hecome 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 ll 1, 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 H6. '7, a pair of bulbs 15a and 151) may be connected in parallel to a common tube 14 by means of a manifold dd. The device will then be operated by squeezing either bulb.

In view of the close fit required between ball ill and the surface of bore 22, the bore must be dimensioned in a very precise manner. This is particularly difficult when sleeve T 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 llll 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 istherefore advantageous to manufacture chamber 1105 and neck 1106 in one piece, and a new method for doing so has been discovered.

The transverse cross-section of chamber T is substantially wider than the transverse cross-section of neck 1106. Bulb 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 ill and a neck forming portion 112. Mandrel 110 further comprises an injection gas passage H3 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 11115 is installed in passage M3 so that the elastomeric material will not enter passage M3 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 1105 and neck 106 are formed to the desired size and shape on mandrel llltl. 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 ll1l0. Neck 106 must stretch to the width of chamber forming portion llll 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.

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 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 first electrical conductor means in electrical communication with said conductive portion and adapted to be connected to a first side of an electrical circuit; I

a second electrical conductor means mounted in said opening and adapted to be connected to a second side of said electrical circuit; 7

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 electricalconductor 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 n0rmally-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;

prising: f

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 sleeveis 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.

it'll-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.

111. 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.

ill-The pneumatically actuated switching device of claim ll, wherein said pneumatic actuating means comprises a deformable bulb and a tube, one endof 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 115, 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.

13. 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.

circular configuration.

l= l= =i

Claims

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 Ushaped 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.

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.

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.

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.

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.

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.

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.