US2362874A - Diaphragm switch - Google Patents

Description

Nqv. 14, 1944. G. G. WILEY 2,362,874

DIAPHRAGM SWITCH Original Filed Feb. 19, 1940 3e a I 26 Fig.2...

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H 31 17 30 n I3 5 Inventor George G. wi Key y C Attorney Patented Nov. 14, 1944 UNITED {STATES PATENT OFFICE George Gr.'Wiley, Chicago, Ill.,.assignor to 'Streeter 'Amet Company; Chicago, Ill.

"Original application February 19, 1940, Serial No.

319;667. vDivided and this application September 18, 1942, Serial No. 459,947

5 Claims. 01920043) This .inventionhrelates to switchesfor counting apparatus and the like used, for "example, in acountmg vehicular trafiic,:and among other 0bect :aimsto provide. an improved pneumatically roperatedswitch for controlling the operation of rthewcountervorsother mechanism.

i'Thez'nature "of the invention may be readily un'derstood by reference to one illustrative con- --struc.tion:tembodying the invention. and shown. in the accompanying drawing.

.In saidmdrawing: .Fig. 1 lie aplan 'view of the. switch device; Fig.2 is accross-isection thereof taken on the plane 2'2 of Fig.1; :Fig 3 is another cross-section taken on :the

plane 3-3 of Fig.1; -and I-Fig. 41s a fragmentary sectionon the :plane 4-;4 -.:of Fig. 1 showing 'on'an enlarged scale :a detail -:of the switch structure.

Automatic counting of vehicular traflicpresents problems not encountered in counting other things. :examplattraffic :counting apparatus, one example of which being illustrated .my co-pending application Serial 319,667,. now Patent No. 2,340,634, patented February 1,.1944, of which this application is .andivision; is :not under constant observation -or:attention itvis subject to a widerange of temperatures under all of .which it :must operate reliably; and the character of the traffic-created operating signals varies widely.

:Such variation occurspa'rticularly if the apparatus respond "to pneumatic'impulses created by vehicles crossinga pneumatic tubeor the like. Slowly :moving tra'ffic or traffic crossing the .re-

mote end .of the "detectortube, delivers a faint impulse. Heavy, wide.ormultiple-tread vehicle .tiresrand traiiic crossing the detector tube-"close ...to the .countercreate'strong impulses and zalso supplementary oscillationszin-the pneumatic :system whichzare difficult to :distinguish from trafiiccreated impulses. Rapidly traveling vehicles create impulses of veryrshort duration'whereas dense traflic characterized iby' vehicles traveling :nearly *abreast.createtimpulses having exceedingly-short zintervalsbetweenz'them.

The illustrative device is designed to respond reliably' to a wide variation in primary or traniccreatedimpulses and tho-differentiate these from secondary :or supplementary oscillations in the pneumatic system. It will :be understood, however, that thepresent switch device is notlimited in its use to control any particular form of count- "ing orother apparatus.

'Tlhestrafiic detector tube which may advantageously :be in the form'of "flexibletube 9 (only partly shown) :of rubber or similar material 'stretched transversely across the highway, is connectedzat one end to-a fitting 10 leading to the .switchmechanism and by means of "which the pneumatic impulses .iare 'rconducted thereto.

:thepresentcase-fitting H1 is screwedinto a diaphragm housing 11 in the form of a circular and generally. flat plate having a hollow threaded boss :12. The-boss: l2 advantageously-serves not only .desired; position. .Forthat purpose itis provided .asuthe'smeansxof connection with the roadtube but as --aameans of mountingthe switch in any with exterior .threads 13 on whicha clamping nut or the likeHmay-be screwed. :The opposite face of the housing is provided with an outer annulanseat l4.for themargin of diaphragm l5 and an inner'sseat 16 around the inlet passage 11. The diaphragm is'held against displacement iby an annular ring -|=8 attached by screws 19 or other appropriate fasteningzmeans to the margin 1-2-0wof thehousingbeyond the outer edge of the diaphragm. The inner edged! of the marginof the diaphragm housing is spaced beyond theedge .22 of the diaphragm and sis also substantially thicker than the ldiaphragmto provide clearance -both:bey.o-nd-the edge of the diaphragm and between .the'diaphragm and the seat l4 and the ring -l8. Thus while the diaphragm .is held "against substantial displacementit is otherwise free in the a housing.

:In the ,present case the clearance around th diaphragm .is about one sixty-fourth of :an inch.

Controlled by the diaphragm is a movable contact point .23 in the form of a rivet which serves to attach the contact pointto the diaphragm and to connect the flexible electric conductor 2 thereto. .Betweenz-t-he head of the contact point and the diaphragmisa relatively stiiT disc 25 talso'oonnectedby means of the conductor rivet to the diaphragm, :and whose function it .is to .prevent substantial local flexing of the diaphragm. -Opposite the movable contact 23 is an adjustable stationary contact 26 insulated from the movable contact as presently described. Electric conduits 21 and 28 lead to the movable ,and stationary contacts respectively.

- To enable the switch device-to differentiate :between faint traffic-created impulses and sec- :ondary pneumatic oscillations which produce only aslightl fainter impulses, the contact gap between 'T the :stationary and movable contacts is carefully 1 adjusted. gap under'normal operating conditions is quite small 1, -.e.,.from .004 to .009 inch,

*muchszsmaller'than customary contact gaps for other traffic operated switches. 'With a gap of this character faint traffic-created impulses are just sufficient to make contact, whereas the secondary oscillations are not quite strong enough to deflect the diaphragm sufficiently to close the gap. In ordinary switches the use of such a small gap would cause additional difficulty such as faulty operation due to distortion of the diaphragm and lack of uniform diaphragm deflection under impulses of a given strength. Diaphragm distortion has the effect of changing the effective contact gap and obviously distortion of as little as two or three thousandths of an inch might produce faulty operation. Both diaphragm distortion and temperature variation result in erratic or non-uniform deflection of the diaphragm.

Faulty operation of this character has been eliminated by the free mounting of the diaphragm as above described. This prevents stretching or distortion of the diaphragm under deflection by pneumatic impulses and by thermal expansion and contraction. Indeed with the free mounting and the clearances at the margin of the diaphragm, little actual diaphragm deflection is required. This avoids fatigue in the diaphragm. Strong pneumatic impulses are prevented from excessively deflecting the diaphragm by allowing such impulses to expand laterally below the diaphragm and to escape around the edges of the diaphragm. For this purpose the housing is undercut or recessed as at 30. Weak impulses on the other hand are not duly dissipated since they are initially confined against lateral expansion by the annular seat 16 adjacent the inlet passage l1. Lateral expansion or dissipation of the impulse cannot occur until the diaphragm has been raised beyond the annular seat l6 after which lateral expansion is not serious since the diaphragm and contact have been given sufficient momentum to complete closing of the contacts.

The annular seat l6 closely adjacent the inlet passage I! also advantageously prevents deflection of the diaphragm away from the stationary contact under periodic suction following an impulse and created by oscillation of the air column in the pneumatic system. This avoids oscillation of the diaphragm in response to oscillation of the air column and avoids any failure to close the contacts under a faint impulse such as would be the case if the contacts were permitted to separate (under reverse deflection of the diaphragm) beyond a predetermined maximum. In the present case the predetermined maximum contact gap (fixed by adjustment of the contact 26) cannot be exceeded since outward or reverse deflection is prevented by the annular seat l6.

Additional venting or escape for strong impulses may be provided if necessary by one or more passages 3| in the diaphragm housing itself and located beyond the annular seat I6. Also for the same purpose if desired one or more small openings 32 may be formed in the diaphragm itself at a point' beyond the seat 16. Openings such as 3| and 32 may be very small such as formed by a No. 60 drill.

Excessively strong impulses are thus partly dissipated without a corresponding effect on weak impulses and without damage to the diaphragm; and ensuing secondary oscillations are minimized or damped to intensities below that of the minimum traffic-created impulses. The close control of the contact gap as aforesaid makes it possible to eliminate the effect of false signals from secondary oscillations without making the device insensitive to the only slightly stronger trafllccreated impulses. The diaphragm is also protected from distortion and erratic deflection which would nullify the selective operation made possible by close contact gap adjustment.

The diaphragm is advantageously made of vinyl resin (which may be obtained on the market under the trade name Vinylite) or other appropriate material whose deflection characteristics are not substantially affected by variation in temperature as is the case with diaphragms made of rubber and similar materials. The thickness of the diaphragm may advantageously be about .005 inch. In the present instance the stationary contact is made adjustable by forming it with a screw-threaded shaft 35 threaded through a nut 36 mounted on a piece of electric insulation 31 which in turn is attached by one or more of the screws l9 to the diaphragm housing. The threaded shaft carries a fluted head 39 against which bears a spring 40 which serves both to hold the contact in adjusted position and as a conductor for making an electrical connection between wire 21 and the contact. For that purpose the shaft 35 and its head 38 are made of metal. The contact shaft is also advantageously provided with a pointer or index 4| which in conjunction with the scale 42 formed on the ring It indicates the contact gap in thousandths of an inch. Zero contact gap may then be accurately flxed with reference to the scale 42.

The flexible conductor 24 for the movable contact is also mounted on and connected to the insulator 31 by means of a terminal 43 to which the wire 28 is connected. Wires 2! and 28 are appropriately connected in the circuit to be controlled by the diaphragm switch,

Obviously the invention is not limited to the details of the illustrative device since these may be variously modified. Moreover, it is not indispensable that all features be used conjointly since various features may be used to advantage in different combinations and subcombinations.

Having described my invention, I claim;

1. In a high speed counter a switch device responsive to short pneumatic impulses of varying intensity comprising in combination a housing, a substantially flat diaphragm in said housing of such light weight as to be moved by faint impulses, a passage in said housing to direct said impulses against said diaphragm, stationary and movable electrical contacts having a small contact gap between 0.004 and 0.009 of an inch, the movable contact being moved by said diaphragm, said stationary contact being adjustable toward and away from said movable contact, a support in said housing to prevent deflection of said diaphragm away from said stationarycontact, said housing having a seat for loosely holding said diaphragm and leaving the margins thereof free so as not to cause permanent distortion of said diaphragm, thereby making it possible to maintain a uniform but small contact gap.

2. In a high speed switch the combination comprising, a diaphragm case, a thin diaphragm seated in said case, means for directing air impulses against said diaphragm, an electrical contact member spaced from said diaphragm, another contact on said diaphragm adapted upon a predetermined deflection of said diaphragm to engage the first named contact, and means for adjusting said first named contact to a predetermined spacing from said other contact to prevent closing of the circuit upon minor movements of said diaphragm, said case being provided with means for loosely holding the margins of said diaphragm to prevent distortion thereof which would interfere with the eifective spacing between said contact and said .diaphragm.

3. In vehicle counting apparatus responsive to air impulses of varying intensity, the combination comprising a switch having a relatively flat diaphragm moved by said impulses, a housing for said diaphragm having a passage for conducting the impulses thereto, said housing having a seat for engaging said diaphragm marginally and designed to permit leakage of strong impulses around said diaphragm thereby to minimize diaphragm distortion, said housing providing a' support for said diaphragm and having below said diaphragm a space adapted to be connected with said passage to permit lateral expansion of strong impulses, thereby to reduce the strength of secondary oscillations in said tube.

4. In vehicle counting apparatus responsive to pneumatic impulses of varying intensity, the combination comprising a diaphragm housing, a flexible diaphragm in said housing, a passage in said housing adapted to direct pneumatic impulses toward said diaphragm in close proximity to the center thereof, said housing loosely engaging the margins of said diaphragm so as to prevent permanent distortion thereof, and means including a rigid disc rigidly connected to said diaphragm opposite said passage to limit fiexure of the center of the diaphragm under the impact of said pneumatic impulses. v

5. In counting apparatus responsive to pneumatic impulses, the combination comprising a diaphragm housing having therein a passage for air impulses, a flexible relatively flat diaphragm in said housing adapted to be moved by said air impulses and lying transversely to the direction of said impulses and being bodily displaced by said impulses, a pair of normally open electrical contact members adapted to be closed by predetermined deflection of said diaphragm and having such small gap as substantially to afi'ect the amount of deflection necessary to close said contacts if the diaphragm be permanently distorted,

said housing loosely engaging the margins of said diaphragm so as to prevent permanent distortion thereof.

GEORGE G. WILEY.

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