Optical pressure switch, door operating system and method

A door having a pneumatic sensing edge is operated automatically to open when an object and the edge make contact An optical pressure switch (10) in fluid communication with gas forced from the edge on contact with the object initiates the operation of a door opener The optical pressure switch (10) includes a membrane (16) having a portion that interrupts a light beam (LB) when the membrane (16) flexes due to the increase gas pressure over ambient pressure as gas is forced from the edge.

INCORPORATION BY REFERENCE

The inventors incorporate herein by reference any and all U.S. patents, U.S. patent applications, and other documents, hard copy or electronic, cited or referred to in this application.

DEFINITIONS

BACKGROUND OF INVENTION

Automatic door operating systems are commonly used in vehicles such as passenger transit buses and rail cars, for example. The door or doors of such systems have a pneumatic sensing edge connected by a gas conduit or hose to a pressure wave switch included in an electrical control circuit for the door operating system. When the sensing edge makes momentary contact with an object on closure of the door, a pressure pulse or wave is produced that propagates through the gas conduit to actuate the switch. The switch then provides a control signal energizing an operator of a door opening mechanism to open the door automatically.

Mechanical pressure wave switches are currently being used for passenger door obstruction sensing. Such conventional mechanical pressure wave switches typically use two mechanical metallic contacts that are subject to oxidation and other environmental contamination that can reduce the reliability or sensitivity of the switches, as well as creating a failure condition. The mechanical contact components of mechanical pressure wave switches have no self-cleaning capabilities such as contact wiping. Moreover, the mechanical contacts pass very low current (approximately 12-18 milliamps) which is not enough to keep these mechanical contacts clean.

SUMMARY OF INVENTION

This invention has one or more features as discussed subsequently herein. After reading the following section entitled “DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THIS INVENTION,” one will understand how the features of this invention provide its benefits. The benefits of this invention include, but are not limited to providing: an optical pressure wave switch having greater stability and reliability under environmental contaminating conditions; an optical pressure wave switch that is easy to calibrate or re-calibrate; an optical pressure wave switch that is less sensitive to environmental contamination, and therefore, will remain calibrated longer creating a longer life; and an optical pressure wave switch that is electronic rather than a mechanical type, and optionally, may have the ability for self annunciation for purposes of diagnostic testing.

Without limiting the scope of this invention as expressed by the claims that follow, some, but not necessarily all, of its features are:

One, the optical pressure switch of this invention includes a body having a passageway therein, a flexible membrane in fluid communication with the passageway, and an optically activated control device having a light beam projected along an optical path within the body. The light beam is interrupted upon the membrane flexing.

Two, the membrane may comprise an elastic diaphragm having a perimeter in a fixed position and a central portion from which an elongated portion extends that moves into the path of the light beam when the membrane flexes. The elastic diaphragm may be a rubbery sheet material and be circular and disk shaped. The elongated portion may be integral with the membrane and comprise a stem element projecting outward from a side of the membrane substantially at a right angle prior to the membrane flexing. There may be a guide member within the body aligned with the stem element to guide the stem element as it moves in response to the flexing of the membrane. For example, the guide member may comprise a tubular structure in which the stem element is seated.

Three, the body may comprises a plurality of components. For example, the components may be molded of plastic. In one embodiment of this invention, one component may include the passageway which has an inlet into which enters the pressure wave. This wave, being at a pressure above ambient pressure to flex the membrane, propagates along the passageway, exiting at an outlet of the passageway. Although referred to as an inlet and outlet, the inlet and outlet function as ports that allow air to flow in both directions. As discussed subsequently in greater detail, this enables the door operating system of this invention to be self-equilibrating.

Four, the components are assembled to create at least two chambers with the membrane providing a common wall for the chambers. The chambers normally are each at ambient pressure, however, the membrane flexes when there is a differential in pressure across the membrane as a pressure wave propagates through the switch. The membrane returns to an un-flexed condition when the differential in pressure is removed as the pressure wave dissipates. In other words, the pressure across the membrane is equalized. For example, one chamber may include a port normally in communication with ambient pressure but also in fluid communication with a pneumatic sensing edge.

Five, in one embodiment of this invention, one chamber includes the optically activated control device and is open to ambient pressure through a restricted opening that substantially reduces contamination of the optically activated control device that would interfere with the functioning of the light beam. This chamber is substantially closed to the atmosphere and houses or encloses essentially the entire optically activated control device, or at least the optical elements of the device. This protects the optical elements to reduce significantly environmental contamination.

Six, the components may be connected together in a manner that enables one component to be moved relative to the other component to adjust the distance the elongated portion must move before it interrupts the light beam. This feature enables the pressure switch to be calibrated. After calibration the components are fixedly connected together, for example, using a removable adhesive that is applied in a manner to maintain the two components fixedly connected together until the adhesive is removed.

Seven, the switch may have a control circuit and a first light-emitting device mounted on the exterior of the body that indicates when power is applied to the control circuit and a second light-emitting device mounted on the exterior of the body that indicates when pressurized gas flows into the switch. These light-emitting devices are used for testing of the switch as discussed subsequently.

In one embodiment, the body has a longitudinal reference line has first, second, and third housing components. The first housing component includes a threaded surface, and the second housing component includes a threaded surface. The third housing component includes the optically activated control device. The optical path intersects the longitudinal reference line. The first housing component is disposed between the second and third housing components. The membrane is a flexible and resilient circular disk having a circular perimeter and a center that the longitudinal reference line intersects. The disk is positioned between the first and second housing components to form within the first housing component a first chamber and within the second housing component a second chamber with the membrane providing a common wall for the chambers. A portion of the disk moves a predetermined distance into the optical path when the membrane flexes. Opposed sides of the membrane are each normally at ambient pressure so the membrane is in an un-flexed condition prior to the pressure wave entering one chamber.

This invention also includes a door operating system. This system includes a door mounted to open and close and having a pneumatic sensing edge holding a gas and the optical pressure switch discussed above in fluid communication with the gas so the switch is activated when it receives a pressure wave from the edge. Activation of the switch provides an operational control signal to operate a door opener mechanism. According to this feature, the pneumatic sensing edge upon connection to the switch is placed in fluid communication with ambient pressure and concurrently one side of the membrane, which normally has both its sides at ambient pressure. When the pressure wave propagates through the switch, the membrane flexes, but only momentarily. Shortly after the pressure wave dissipates, both the pressure within the edge and the pressures on both sides of the membrane are at ambient pressure because they are always in fluid communication with the atmosphere. Ambient pressure, however, constantly changes due to changing weather and the vehicle traveling to different elevations. Nevertheless, the door operating system of this invention self-equilibrates to readjust continually and compensate for changing ambient pressure. Consequently, the edge and the switch are always at ambient pressure except when the edge contacts an object or is squeezed during testing as discussed subsequently.

These features are not listed in any rank order nor is this list intended to be exhaustive.

This invention also includes a method of diagnosing problems with a door operating system. The embodiment of this invention that employs a light-emitting device is especially designed to be self-annunciating because it provides light signals indicating problems. A technician squeezes and holds the door sensing edge and the light-emitting device is illuminated. After a brief time period the light is automatically discontinued when the pressure differential across the membrane equalizes.

DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THIS INVENTION

As illustrated inFIGS. 1 through 7, one embodiment of the optical pressure switch of this invention designated by the numeral10comprises a body12, an optically activated control device14(FIG. 7), and a membrane16(FIGS. 4,5and6) within the body. A suitable optically activated control device14may be purchased from Bircher, distributed through JMT Automation and Controls, Inc., of Gastonia, N.C. When pressurized gas flows as a pressure wave through a passageway18(FIG. 6) in the body12, the membrane16flexes. An elongated portion16aextending from one side S1(FIG. 5) of the membrane16moves a predetermined distance, typically substantially from 0.02 to 0.12 inch, to interrupt a light beam LB (FIG. 1B) in the optically activated control device14when the membrane16flexes in response to the pressure wave. As discussed subsequently in greater detail, the optical pressure switch10is calibrated to respond to gas pressures substantially from 0.01 to 0.16 pounds per square inch (psi).

The optical pressure switch10may be utilized advantageously in a door operating system20such as depicted inFIG. 1A. The door operating system20is commonly employed in vehicles or other structures that require a door or doors22to open automatically when, for example, a passenger's hand, or other object, contacts the door, thereby avoiding accidents and injuries. The door22is mounted to open and close and has a pneumatic sensing edge22aholding a gas, typically air at ambient pressure. The pneumatic sensing edge22ais a well-known device comprising a balloon like, resilient vessel23having a hose22bwith one end E1in fluid communication with the gas in the vessel and its other end E2(FIGS. 1 and 6) connected to an inlet24of the optical pressure switch10. The resilient vessel23, upon being compressed when the edge22acontacts an object, forces gas to flow at a predetermined pressure to flow as a pressure wave from the vessel23through the hose22band into the switch10to flex the membrane16and move the elongated portion16ainto the optical path of the light beam LB. This actuates the switch10that provides a control signal CS (FIG. 1B) to a conventional door opener mechanism28. The door opener mechanism28opens in response to the control signal CS.

As best shown inFIGS. 4,5and6, the membrane16is an elastic diaphragm made of rubber or other suitable material and may be a circular disk having a recessed central portion16b(FIG. 5) and a center16cthat a longitudinal reference line X intersects at a right angle upon mounting the disk in the body12. The central portion16bis substantially flat and planar when not flexed. Although it is flexible and resilient, the central portion16bmaintains a substantially flat condition until a greater pressure is applied to the side S2(FIG. 6) than to the side S1. The perimeter16dof the membrane16may include a stiffening ring17. The elongated portion16ais formed during molding of the membrane16and is integral therewith. It may be in the form of a substantially rigid, elongated stem of sufficient length to extend through a tubular guide member19into the optical path of the light beam LB when the membrane16is flexed. The elongated portion16ais substantially at a right angle to the side S1prior to the membrane16flexing. For most applications the membrane16is designed so the elongated portion16amoves only a short distance to interrupt the light beam LB (FIG. 1B). Typically, this distance ranges substantially from 0.02 to 0.12 inch and is adjusted during calibration as discussed subsequently.

As depicted inFIGS. 4,5and6, the body12includes a plurality of housing components30,32, and34. The housing component30is disposed between the housing components32and34. These housing components30,32and34each have a generally hollow cylindrical portion with predetermined diameters enabling them to be nested together with the longitudinal reference line X being co-extensive with the axes of these cylindrical portions. The housing components30,32, and34may be molded from a plastic material such as, for example, ABS resin, and are connected together upon assembly to form three chambers C1, C2, and C3as depicted inFIG. 6. The membrane16provides a common wall for the chambers C1and C2.

The housing component30has a cylindrical wall30aopen at opposed ends with a threaded interior surface and an annular rim30bat a right angle to the wall. A pair of spaced apart cut-a-way sections30c(FIG. 5) are formed in the rim30b. There are a number of openings31passing through the rim30bthat, upon assembly of the components30,32and34, place the chambers C2and C3in communication with ambient air pressure as discussed subsequently in greater detail.

The housing component32has an upper block segment32athat includes an outlet25. Opposed to the inlet24is an enlarged, stepped, cylindrical recess created by aligned bores B3and B4as depicted inFIG. 6. The bore B4has a diameter slightly larger than the bore B3and its internal surface S3is threaded. A flow control member42and a threaded tubular cap44are seated in the stepped recess with the flow control member in the bore B3and the cap threaded into the bore B4to hold the flow control member in position. The flow control member42impedes gas flow through the passageway18so back pressure is created within the passageway when the pressure wave enters the passageway. The flow control member42may comprise a porous plug with a plurality of torturous paths therein. This flow control member42also serves as a filter to eliminate particulate contaminates from air flowing into the chamber C1through this flow control member. A suitable flow control member42in the form of a porous plug may be purchased from Applied Porous Technologies, Inc. The threaded tubular cap44is hollow to provide the outlet25.

The inlet24, which is integral with the block segment32a, is in the form of a tubular member projecting from the block segment32aand may be directly opposite and aligned with the outlet25. The passageway18connects the inlet24and the outlet25so gas may flow into the inlet, through the passageway, and out the outlet25. Under some conditions as discussed subsequently, gas may flow into the chamber C1through the outlet25. Between the inlet24and outlet25is a branch passageway18aextending along the longitudinal reference line X. This branch passageway18ahas an open end E3(FIG. 6) terminating in the chamber C1. The branch passageway18amerges at another end E4about mid-way between the inlet24and the outlet25to provide a generally T-shape configuration. Pressurized gas will flow from the open end E3when the pneumatic sensing edge22acontacts an object to produce a pressure wave that is at a pressure above ambient pressure.

A cylindrical wall40projects from an underside of the block segment32athat has a threaded exterior surface40a. A stepped cavity33(FIG. 6) within the housing component32is formed by cylindrical bores B1and B2, aligned so their axes are coextensive with the longitudinal reference line X. The bore B1has a diameter smaller than the bore B2, thereby forming a landing L1on which rests the perimeter16dof the membrane16. Along the wall of the bore B2is an annular groove35at a right angle to the longitudinal reference line X. The distance between the top of the groove35and the landing L1is approximately equal to the thickness of the perimeter16dof the membrane16. The diameter of the groove35is greater than the diameter of the membrane16and a C-ring38is snapped into the groove35to hold the perimeter16dof the membrane16snug against the landing L1in a fixed position, maintaining the membrane within the chamber C2with the elongated stem portion16aaligned with the longitudinal reference line X and extending into the chamber C3.

As best shown inFIG. 7, the housing component34holds a substantially flat circuit board36on which is mounted the optically activated control device14and other electrical and electronic devices of a control circuit46(FIG. 1A). As best shown inFIG. 7, a pair of cut-a-away sections36bof the circuit board36are aligned with the openings31to place the chambers C2and C3in fluid communication with ambient air pressure. Note, an inner portion of each of the cut-a-away sections36bextends inward to create access openings placing the chamber C3in fluid communication with chamber C2. The housing component34includes a cylindrical wall48open at its circular topside TS and preferably closed at its bottom side BS. (The dosed bottom side is shown removed inFIG. 7). The cylindrical wall48has a pair of slits49therein (FIG. 4) and a pair of spaced apart indentations50, each terminating as a base landing51integral with the wall's bottom side BS. Each base landing51includes a hole53through which a screw (not shown) passes when mounting the switch10. The interior of the cylindrical wall has an annular ledge54(FIG. 4) near the open topside TS upon which the circuit board36rests when the housing components30,32and34are assembled. Conductive metal prongs52extend outward from an edge of the circuit board36. The circuit board36provides a common wall for the chambers C2and C3. The tubular guide member19has a reduced diameter end19a(FIG. 6) that fits snugly into a central hole36ain the circuit board36.

As depicted inFIGS. 1 and 1B, the optical pressure switch10may have visual indicators such as light emitting diodes (LED), for example, a green light emitting diode LED G and a red light emitting diode LED R used to diagnose problems with the switch10or the door operating system20. The indicator LED R when lit indicates that power is being applied to the switch, and the indicator LED G when lit indicates that pressurized gas is flowing into the switch10. The indicators LED G and LED R are mounted on the exterior of the body12.

Assembly and Calibration

The parts of the optical pressure switch10are assembled in a conventional manner. The circuit board36with its components mounted thereon may first be positioned in the housing component34with the prongs52extending through the slits49and the circuit board resting on the ledge54. The surface of the circuit board36to which the electrical and electronic components are mounted faces the chamber C3so these electrical and electronic components, including the optically activated control device14, are in the chamber C3. The diameter of the rim30bis substantially equal to the diameter of the topside TS of the housing component34. The housing component30is next placed on top of the circuit board36with its rim30bresting on the top of the circuit board. The diameter of the rim30bis substantially equal to the inside diameter of the housing component34. Next, the housing component30is connected to the housing component32with membrane16and the flow control member42and threaded cap44attached thereto as discussed above.

Initially the membrane16is in an un-flexed condition, and the pressure on both sides S1and S2of the membrane is the same, i.e., ambient pressure. This is a state of equilibrium. When the pneumatic sensing edge22acontacts an object, air is forced to propagate along the passageway18and the branch passageway18aas a pressure wave above ambient pressure, causing the membrane16to flex to move the elongated portion16aa selected distance to interrupt the light beam LB of the optically activated control device14. This provides the control signal CS to which the door opener mechanism28responds to open the door22. The air pressure across the membrane16subsequently rapidly equalizes because the pressure wave dissipates due to air escaping from chamber C1through the outlet25. Consequently, the elastic membrane16again returns to its un-flexed condition almost immediately after the pressure wave actuates the switch10, thereby withdrawing the elongated portion16afrom the control device14, moving the same selected distance it moved to interrupt the light beam LB but in the opposite direction. The light beam is now uninterrupted by the elongated portion16a. In the un-flexed condition the membrane16is substantially at a right angle to the longitudinal reference line X.

As mentioned above, the optical pressure switch10is calibrated prior to being used in the door operating system20by adjusting the distance the elongated portion16amoves in order to interrupt the light beam LB. This adjustment is made by screwing the threaded surfaces of the housing components30and32together, rotating these housing components until the outer tip of the elongated portion16apasses through the tubular guide member19and is positioned next to the light beam LB at the selected distance. This distance depends on whether the user desires the membrane16to flex greatly before the light beam LB is interrupted or only to flex slightly. A slight flexing of the membrane16moves the elongated portion16aonly a short distance, making the switch10very sensitive. In other words, only a slight pressure increase in the passageway18and the branch passageway18awill cause the elongated portion16ato interrupt the light beam LB.

The housing components30and32are fixedly connected together after calibration. This may be accomplished by applying to adjacent exterior portions of the housing components30and32an adhesive after adjusting the relative positions of these components. A silicone type of adhesive may be used, which may be removable, to allow re-calibration. A suitable adhesive is sold by Dow-Corning under the identifying number 832.

An alternate embodiment of the switch of this invention is generally designed by the numeral10ainFIG. 8. This switch10ais essentially identical to the switch10, except an orifice plate60with a central aperture60atherein is used instead of the porous flow control member42. Typically, the aperture60ahas a diameter substantially from 0.008 to 0.016 inches. The orifice plate60is seated in the bore B4on a ledge between the bores B3(shallower than in the switch10) and B4and the aperture60ais aligned with the outlet25provided in the threaded tubular cap44. The cap44is screwed in position to hold the plate60in position in the bore B3.

Another alternate embodiment of the switch of this invention is generally designed by the numeral10binFIG. 9. The optical pressure switch10buses a membrane15that includes a tiny orifice15atherein to establish initially ambient pressure on each side S1and S2of the membrane15. The passageway18is also different in that it has a generally L-shape, with its one leg18chaving an outlet end E5terminating adjacent the side S2of the membrane15. This end E5serves as the only outlet of the passageway15. In the switch10, there are in effect two outlets: the outlet25provided in the threaded tubular cap44and the end E3in the branched passageway18a. In both the switches10and10a, a back pressure, respectively provided by the flow control member42and the orifice plate60, is sufficient so that most of the pressurized gas flows through the branched passageway18ato flex the membrane16. In the switch10b, there is only a single outlet, namely, the end E5in the one leg18c.

In all the embodiments, the pressurized gas flowing into the optical pressure switches10,10a, and10bis above ambient pressure and is a transitory phenomenon occurring only momentarily when the pneumatic sensing edge22amakes initial contact with an object. The switches10,10a, and10b, each essentially immediately provides the control signal CS on contact of the edge22awith an object so the door22is opened automatically. Thus, the door22and object disengage to discontinue forcing gas at an elevated pressure to flow into the operable switch10,10a, or10b, as the case may be. Because of the openings31in the rim30bof the housing component, the inner portion of the cut-a-away sections36bcreating access openings in the circuit board36, and the outlet25placing the chambers C1, C2and C3in fluid communication with the atmosphere, both sides S1and S2of the membrane16are initially subjected to ambient pressure and are again, essentially immediately, subjected to ambient pressure when the pressure wave dissipates, returning the membrane16to its normal un-flexed, equilibrated condition.

Because of the tiny orifice15ain the membrane15both its sides S1and S2are initially at ambient pressure. The diameter of the orifice15aonly about 0.012 inch. Consequently, a pressure wave entering the switch10still flexes the membrane15since only a very small faction of pressurized gas is forced through the tiny orifice15a. As soon as pressure wave dissipates, the membrane15returns to its normal un-flexed condition.

Diagnostic Method

The optical pressure switch10has the ability for self-annunciation for purposes of diagnosing or testing its operability. This is achieved by the means of the light indicators LED R and LED G. For example, the indicator LED R, when lit, is indicating that the switch10is electrically connected to a 12V or 24V power source P.S. (FIGS. 1A and 1B) from an electrical system of, for example, a vehicle such as a bus employing the doors22. The indicator LED G, when lit, is indicating that the switch10has been activated by the pneumatic sensing edge22amaking contact with an object as the door is being closed. This illuminated indicator LED G provides to, for example, a technician trouble shooting a visual “Door Obstruction” signal. A typical diagnostic test procedure is as follows:1. Open an access panel over the door opening to access a compartment holding the switch10.2. Activate the vehicle's run/key switch to provide power to the vehicle's onboard electronics including the switch10.3. Visually check the indicator LED R to confirm it is lit.An illuminated indicator LED R shows that the switch10is connected to the vehicle's wiring and that power and ground is present. This will eliminate further diagnosing of the vehicle's power circuit to the switch10and the technician may proceed to Step 4 below.If the indicator LED R is OFF (not illuminated), this is an indication that:1. There is a problem with vehicle's wiring to the switch10, or.2. There is a problem with the vehicle's power circuit, or.3. The switch10has failed
There is no need to further diagnose the rest of the components that comprise of the door operating system20until this problem is resolved. This will eliminate unnecessary troubleshooting of the remaining components such as the pneumatic sensing edge22aand the hose22bconnected to the inlet24.4. Observe the indicator LED G: While observing the indicator LED G, the technician conducts a test using his or her hand to squeeze and hold the pneumatic sensing edge22a. The indicator LED G should be illuminated each time the technician squeezes the pneumatic sensing edge22aand go out after releasing this pneumatic sensing edge. If the technician squeezes the pneumatic sensing edge22aand holds it, the indicator LED G will go out within a short time interval, for example about 30 seconds, because the air pressure in the chambers C1and C2equalizes.
The illumination of the indicator LED G when the pneumatic sensing edge22ais squeezed and held by the technician is an indication that the switch10is operating correctly and that it is receiving a signal from the logic circuit LC, indicating that the pneumatic sensing edge22aand the switch are working properly. If the indicator LED G does not light up at all when the technician squeezes and holds the pneumatic sensing edge22a, this is an indication that there may be a problem with the door edge22aand that it is not sending a pressure pulse wave to the switch10. It would then be necessary to troubleshoot the door edge22aor the hose22bconnecting the edge to the switch10. If the indicator LED G does not go out after the technician squeezes and holds the pneumatic sensing edge22a, this is an indication that the switch10is plugged and the pressure on the opposite sides S1and S2of the membrane16is not equalizing. If this cannot be remedied then the switch10should be replaced or repaired.

Some Advantages of this Invention

The stem16areplaces metallic contacts and improves the switch's operating characteristics when subjected to shock and vibration. This is because the stem16ais lighter in weight than metallic contacts. In addition, the stem16ais less affected by its mounting orientation, vertically or horizontal or otherwise. The prior art mechanical switch requires pressure between the two metallic contacts for the necessary electrical continuity. This makes calibration more difficult. This is not the case with the switches10,10aor10b. Calibration adjustments of these switches are much easier to make and they also has the capability of working at a very low air pressure (down to 2 millimeters of water column, or 0.003 psi). The switch10may use the porous flow control member42for an ambient air orifice which acts as a filter. Removing the cap44allows for replacement of the flow control member42if it becomes contaminated. This is a cost savings to the vehicle operators. The calibration adjustment allows for a visual tamper proof indicator, because the removal of the adhesive from the exterior of the housing components30and32is readily observable. This feature is desired by the vehicle manufactures to insure that unauthorized individuals have not changed the pressure setting.

SCOPE OF THE INVENTION

The above presents a description of the best mode contemplated of carrying out the present invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains to make and use this invention. This invention is, however, susceptible to modifications and alternate constructions from that discussed above which are fully equivalent. Consequently, it is not the intention to limit this invention to the particular embodiments disclosed. On the contrary, the intention is to cover all modifications and alternate constructions coming within the spirit and scope of the invention as generally expressed by the following claims, which particularly point out and distinctly claim the subject matter of the invention: