US1756793A - Head for gas detectors - Google Patents

Description

J. K. MABBS ET .AL

HEAD FOR GAS DETEGTORS Filed Aug. ll, 1928 INVENTORS ATTORNEYS.

Apl 29, 1930.

Patented `Apr. v2,9, 19:30.

y v UNITED STATES? PATENT ori-ica JOHN K. MABBS, OF BAYSIDE, AND HERMANN C. STELLING, F ORANGEBURG, NEW

YORK, AS'SIG'NOIKIS T0 OXWELD ACETYLENE COMPANY, A CORPQRATION OF WEST l VIRGINIA HEAD non eas nn'rnc'roas Application linea august 1, 192s'. aerial No. 296,857.

This invention relates to an improved head for detectors of combustible gases of the type in which a heated lament is exposed to the latmospherewhich is to be tested. If the fila-' ment be heated to such a temperature that' erably by noting lthe change in electrical resistance vof the filament. While we have found that a platinum filament is suitable, the inventon is not limited to the' use of platinum for'filament material.

An object of our invention is to provide a head surrounding the filament which shall be so constructed and arranged that the heated iilament can never be heated except when surrounded by protective gauze. '.Ihis prevents the propagation of ame from within the gauze to the surrounding` atmosphere with consequent danger `of an explosion. To this end we provide a series of auze jackets around the filament. These jackets when @5 forced into place engage a switch closing' mechanism and permit the current to flow to the lament. When-the gauze jackets are removed or merely loosely held in lace, the switch is forced open by 'any suita le means 30 and the circuit to the filament is broken. An-

other object of our invention is to lprovide ymeans for ivingr an indication of the'position of the lament that shall be visible, and sensible to the touch, even though the fila-` ,ment 'be concealed within the protective screens. 4 These and other objects of our invention will be evident from the following description having reference to `the accompanying @0 drawings in/which:

Fig. 1 is a vertical section through a gas detector head illustrating one embodimentof our invention, y

Fig. 2 is a` horizontal cross section taken on line II--II of Fig. 1, and

Fig. 3 is a similar sectionon line III-III.' 1n thisl drawing we show a gasy detector head comprising a base 10 which is mounted on a pole 11 ina manner to be described here-L W after. vThe mounting of the head on the pole permits the detector head to be inserted into crevices or the like or into high places where it would be difficult, it not impossible, for an operator to carry the head if un rovided with this pole. This pole may be o any convenient length. Within the base 10 is an insulating block 12 which rests upon a shoulder 13 in the base. rlhe insulating block 12 is held against rotation with respect to the base 10 by ridges 15--15' and a suitable screw'lA. Within the insulating block 12 is a cylindrical shell 16 which is provided with J-shaped slots 17 lwhich engage pins 14 on the base oa lament holdin unit which will be described below. n 1f .desired the insulating block may be cut away oppositethe slots, but itfthe 'shell be of sulicient thickness this will not be necessary. On the under side of the insulating block are fouroconductors 18, 19, 21 and 22.

The insulating block is provided with holes 26--26 each having a restricted portion 27-27. Plungers are provided in these holes for closing the circuit to the filament. .1n

order that lthe plungers may be inserted past the constricted portion 27 of the holes, these are conveniently made in two piecesL 28 Vand 29. At least yone of these pieces should be made of insulating material in order to pre- 'vent' short circuiting through the screens which engage the upper portion of the plun ers. When only oneof said portions is ma e of insulating material we prefer that it shall 'be the lowerone. The two pieces are held "together `by threaded portion otvp528 tting into the lower portion 29. insulating part 29 is provided with 'a depressionin the lower portion so that the bottom of the screw does not come in contact with contact meinbers 33 and 35 on the conductors 22 and 21 respectivel The conducting pieces 21 and 33 and 34 and 35 .are norma y separated.`

The conductor 1 8 is electrically connected to the shell 16 and the conductor 19 terminates in a contact member 36 which is spaced be- 90 22 are vresi ient and tend to force the plung- Y v low the opening in the shell and adapted to engage the lower portion of the filament holding unit. Conductor members 21 and 22 are connected to wires 37 and 38 of a cable 5 39 which is attached to a Wheatstone bridge or other apparatus for measuring the resistance in the filament. The cable 39 is led through the base and the pole 11. At the junction of the base and the pole an annulus 10 is formed in which may be disposed suitable packing 41 for the purpose ofrendering the joint as ktight and thus preventing propagation o flame through the handle. This packing is preferably trapezoidal in cross section and also serves to grip the cable, vthus preventing strain from being put on the wires 37 and 38.

The filament holding unit .consists of a base 42 upon which are mounted supports 43 `and 44. The filament 45 is mounted on the supports in any suitable manner and a link 46 prevents these supports from changing their relativepositions. The support 43 is electrically connected to the base and the support 44 is connected to a bottom contact 48. The base 42 is adapted to be placed in electrical contact with the shell 16 and the bottom contact 48 is adapted to engage the contact 36. The pins 14, heretofore referred to, are

l 3o mounted on the base 42 of the filament holding unit and engage the J-shaped slots 17 forming a bayonet joint for holding the lal ment-holding unit in place against the pressure of the conductor 19. For the purpose of preventing propagation offlame of gas ignited by the heated filament to asurrounding combustible atmosphere and at the same time permitting the atmosphere to be tested to have ready access to the filament we provide a series of gauze jackets 51, 52 and 53. These jackets are assembled in coaxial relation and are provided with anges `54, 55 and 56. The flange 56 is adapted to engage the` top members 28 of the plungers to force them downwardly and to complete the circuit between the contacts 34 and 35 and 32 and 33. However, the weight of these screens and flanges is not suicient to close this circuit, but the flanges are forced downwardly and held in position by a locking ring 57 Which engages with the outer portion of the base 10. In case both the base 10 and the locking ring 57 are made of aluminum for the sake of lightness we prefer to vinterp'ose an intermediate member 58 of some other material to prevent any danger of binding between the asel and the locking ring. y Surrounding the gauze jacketsl, 52 and 53 and preferably mounted upon .the locking ring 57 is a protective .bonnet 59 which `is provided with a number of apertures 61 topermit the passage of atmosphere to the filament. If it is desired to provide means for supporting the head other than by the pole ci a hook 62 may be secured tothe bonnet.

A"the pins 14 an 'and 35 and renders it possible to heat thge filatial to maintain the longitudinal axis of the filament in a horizontal position as deviations from this position will indicate a higher percentage of'combustible gas than is registered in the horizontal position and thus a safety factor is insured. However, it is desired that the readings, shall be as accurate as possible and for this reason we desire that some indication vshall be available as to the direction of the lament even when the screen jackets andthe protective bonnet are in place. lf this is knownthe filment can be maintained horizontally .not only when the device as awhole is vertical, but when it is rotated about an axis parallel with the axis of the filament. Moreover, it is. desirable that this indication Shall be tangible as well as visible, a tangible indication is provided by suitable ridges or other means 63 on the side of the pole. While we have shown these ridges as separate strips attached to the pole they may be integral therewith. Moreover, we do not wish to limit ourselves to any particular shape but contemplate the use of any cross sectlonal shape which shall give a distinct indication as to the direction of the filament. ln order to insure that the strips and filament are in predetermined relation, webs 64 are provided on the base 10, these webs having redetermined relation to the screw 15A for ocking the insulating block which in turn is in predetermined relation to vthe d-shaped slots 17. These slots establish the position 105 of the filament'holding unit and accordingly the lament is Yalways in a predetermined position with respect to the webs 64. l lin attaching the pole l1 to the base 10 care 1s' taken to align the strip 63 with the webs 64 thus insuring the correct relative position of the filament 45 and the strip 63.

The operation of our device is as follows. The pole and base being assembled and the insulating block in position in the base, the .115 filament holdin unit is inserted into the center of the insu ating block and located and held by thel ba onet joint formed between the J-shaped slot 17. The 53 are then put in place gauze jackets j51, 52, :.120

and the locking ring 57 screwedon which' forces the flanges 54, 55 .and 56 downwardly toward the insulatingv block. This closes the circuit between the lcontacts 32 and 33 and 34 mi ment when current from an external source is supplied when yproperly assembled. But if any one of the ganzes is not in place screwin down the ring to the limit of its travel ndt depress plungers 28 .suliciently to close f 'j eo the above contacts. The circuit remains open and therefore no current can iiow through the filament. The device is then taken. into the atmosphere to be tested and observations made of the temperature of the filament in any suitable manner but preferably by noting the change in electrical resistance of said filament. i

l. In ahead for gas detectors of the class described, the combination of a supporting member, a filament mounted, on said supporting member, gauze jackets surrounding said filament, means for holding said ackets against said supporting member, conductors for supplyingcurrentA to said iilament, said conductors including a resilient portion normally in a position to open the circuit, and

means actuated by said jackets when held against said supporting member to force the resilient portion of said conductor to a position to close said circuit.

2. In a head for gas detectors of the class described, the combination of a supporting member of insulating material, means for mounting a filament holding unit on said supporting member, a lurality of gauze jackets surrounding said lament, means tor hold# ingsaid jackets against one side of'said supporting member, conductors for supplying current to said filament, said conductors including a switch normally in a position to open said circuit and means cooperating with said jackets to close said switch when said jackets are held against said supporting 3. A device as claimed in claim 2 in which the switch is formed by a vresilient portion of said conductors and an adjacent portion of said conductors and said switch closing means comprises a plunger extending through said supporting means.

. said filament, said jacket havinla dange 4f. lna head for as detectors of the class described, the combination of a base, an in-` sulating block mounted on said base, a filament holding unit secured to said insulating block, a cylindrical gauze jacket surroundin base, a locking ring engaging e base of said head and the base of said jacket to force the 'base of the jacket against said insulating j block, conductors on said insulating block for supplying current to said lalnent, said conductors including a switch, and switch actuating means engaging said jacket base to close said switch when said 'acket base is forced' against said. 'insulating lock.

5..In a gas detector head, an insulating supporting block, a shell of conducting ma'- terial extending through said block and adapted to receive a filament holding unit, plungers extending through said ,block and adapted to be engaged by gauze jackets surrounding'said Vilament,'two pairs of conduc'- tors, *the* conductors of each pair. extending past the lower end of each of said plungersin i normally spaced relation, one conductor of each .pair being adapted to be connected to an. external circuit, the otherl conductor of. one pair being connected to said shell and the 7; A device as claimed in claim 5 in which the conductors are provided with enlarged contacts opposite the lower ends of the-plungers and the 'lower ends of the plungers are of insulating material and provided with recesses opposite the enlarged contacts.

8. A device as claimed in claim 5 in which the shell is provided with J-shaped slots extending downwardly from the upper edge, the filament holding unit is' provided wlth pins adapted to engage said slots and the con-l ductor opposite the opening in said shell is resilient whereby said pins are held in engagement with said. slots. Y

9. A. gas detector head comprising a base provided with a socket to receive a pole and an opening within said socket, means for supporting a filament on said base, screens surrounding said lilamentand engaging the base with a gas tight fit, a pole tting in said socket, said pole being provided with an,

aperture in communication with an aperture in the base, a conductor extending through mounted on said block, a gauze jacket surroundino1 said filament, said jacket being provided with a Hanged base adapted to engage said block, means yfor holding .said baseagainst said block, said block beingprovided with an openingextending therethrough and having a restricted intermediate portion, a

two part plunger extending through said opening and having enlargements above and below said restricted portion and conductors for supplying current to said ilament on the lower portion of said block, said conductors including a. switch, said plunger being in operativeenga ement with the base of saidv screen and said switch.

11. A gas detector head including a horizontal filament and a protective covering surrounding said iilament, a handle for said head and means on said handle sensible to touch '-.in lixed relation to said filament for indiroundingsaid lilament and in gas tight engagement with said base for preventing the propagation of flame from said filament, a socket on' said" hase for receiving a handle, said base being provided with an aperture within said socket, a handle having an aperture engaging said socket, said socket and said handle helngprovidedwith recesses surrounding said aperture, la conductor extending through said apertures, and a packing member in said recesses.

. 14. A gas detector head comprising a block, a shell in said block to receive a filament holding unit, a plunger extending through said block and insulated'from said shell, a screen having a a'nged base adapted to surround the filament of said filament holding unit,

said base engaging said plunger, conductors, including a switch in operative relation to said plunger, on said block, and means for holding the base of said screen against said plunger and block.

tures.

JOHN K. Mfr-BBS.

HERMANN C. STELLNG.

In testimony whereoffvve ax our signa-

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