Portable Propane Gas Hand Torch

The present invention relates in general to piezoelectric-type portable propane gas hand torches, and more particularly to such piezoelectric igniter-type gas hand torches having finger actuated mechanical structure for activating the piezoelectric spark-producing device solely responsive to mechanical hand pressure and valving the gas to flow into the burner tube immediately prior to spark generation to insure proper ignition.

Piezoelectric spark-producing devices for use in igniting combustible fuels such as propane gas and similar fuels which can be stored in portable containers have been known for a number of years. Such devices typically have a hammer which is moved into force impact with an anvil structure of a piezoelectric crystal assembly forming part of an electrical circuit having a spark gap. When the crystal is deformed by the hammer blow, a voltage is generated in the circuit of sufficient magnitude to create a spark in the gap area of the circuit. Typical of such piezoelectric spark-producing devices are those shown in prior U.S. Pat. Nos. 3,509,388 dated Apr. 28, 1970 and 4,139,792 dated Feb. 13, 1979, both assigned to Matsushita Electric Industrial Co., Ltd. In those devices, the hammer is actuated by moving a slidable finger-piece or plunger slidably supported in telescoping relation projecting into the outer housing, which during an initial portion of its inward stroke arms a spring while restraining the hammer against movement towards the crystal, and then suddenly releases the hammer to be driven by the spring into spark generating impact with the crystal stack. Other mechanical arrangements have also been devised in prior art piezoelectric-type spark-producing devices for driving the hammer into spark generating impact with the crystal structure.

Other similar devices have been proposed, as U.S. Pat. No. 3,802,828 granted Apr. 9, 1974 to Mercer et al, wherein the hammer is driven by a piston which responds to fluid pressure from the combustible fuel source, in a manner which ensures that the gaseous fuel has reached the combustion chamber portion of the burner by the time the hammer is allowed to impact against the crystal and produce the spark for igniting the fuel in the burner.

An object of the present invention is the provision of a novel portable finger-activated gas hand torch with a piezoelectric igniter, wherein the igniter is associated with a finger-operated control knob in a novel manner facilitating manufacure and reliable operation of the torch, and which provides improved safety features insuring igniting of the gaseous fuel from the attached container and operation only while safely in the hands of the user maintaining the control knob in depressed condition by finger-pressure, thus ensuring automatic extinguishing of the torch if it is dropped or finger-pressure is released from the control knob for any reason.

Another object of the present invention is the provision of a novel portable gas hand torch of the piezoelectric igniter-type, as described in the immediately preceding paragraph, wherein the action of the igniter and the valve controlling release of gaseous fuel to the combustion chamber of the burner tube reliably operate in a manner such that gaseous fuel reaches the combustion zone of the burner tube immediately prior to spark generation.

Yet another object of the present invention is the provision of a novel portable gas hand torch of the piezoelectric igniter-type, constructed in such manner that the torch may be used upside down or in any position without flare-out of flame or significant changes in flame pattern and wherein the control knob which in its ON position must be maintained depressed to continue the burning condition the burning condition is spring biased to cause shut off of gas fuel supply so that the torch will not be accidentally maintained in burning condition when accidentally overturned or rolling on surfaces onto which it may be dropped.

Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.

FIG. 1 is a perspective view of a portable hand-held propane torch of the piezoelectric igniter-type, assembled with a propane tank, embodying the present invention;

FIG. 2 is a side elevation view of the portable hand torch handgrip control head and burner tube assembly portion of the torch;

FIG. 3 is a front elevation view of the portion shown in FIG. 2;

FIG. 4 is a vertical section view, to enlarged scale, of the control head and burner tube assembly, taken predominantly along the line 4--4 of FIG. 3;

FIG. 5 is an exploded elevation view of the hand torch;

FIG. 6 is a longitudinal section view of the orifice member; and

FIG. 7 is an end elevation view of the helix member.

Referring to the drawings, wherein like reference characters designate corresponding parts throughout the several figures, the portable propane gas hand torch of the piezoelectric-type embodying the present invention is indicated generally by the reference character 8, and is generally made-up of a handgrip control head and burner tube assembly forming the upper portion thereof, indicated generally by the reference character 9, assembled onto a conventional liquified propane tank or cylinder 10. The upper control head and burner tube assembly 9 comprises a handgrip-shaped main body 11 having an internally threaded entrance portion 11a to a cavity 11b opening downwardly through the lower handgrip-shaped portion 11c of the body 11, to be threaded onto the conventional neck of the propane gas container or tank 10 to form a changeable tank assembly therewith. The body 11 is preferably a metal molded body, and includes a plurality of interconnected passages and cavities, formed generally by the gas passage 11d communicating with the cavity 11b and with a manually activated control valve cavity 11e, which in turn communicates with gaseous fuel passage 11f which extends to a main orifice housing cavity 11g opening through the top surface 11h of the enlarged upper portion 11i of the body 11. The cavity 11g houses the orifice member 13 defining the exit orifice for the fuel from the container or tank 10, having, for example, the cross-sectional shape shown in FIG. 6, providing a pair of external circumferential grooves concentric with the axis of the passage through the orifice member 13 in which are seated a pair of O-rings 14 to form seals about the exterior of the orifice member 13 in the smaller diameter lower portion of the cavity 11g and against the walls of the central bore of the orifice adapter member 15 which is releasibly held by screw 15a in the enlarged upper portion of the cavity 11g in the body 11. Surmounted on the orifice adapter 15 is the shaped tubular venturi member 16 having a large diameter portion 16a encircling the truncated conical upper nozzle portion 13a of the orifice member 13 with laterally facing openings therein as shown, and having a smaller diameter upper, substantially cylindrical portion 16b tightly fitted in the lower end portion of the burn tube 17 having a bend 17a near its midregion and providing a straight exit end section 17b as shown apertured at 17c near the uppermost end thereof.

Removably held on the upper end portion 17b of the burn tube 17 by threaded collar 17d is a tubular cylindrical burn tip 18 positioned with its downstream or inlet end tightly against the outlet end of the burn tube 17 and having a helix or flame divider structure 19 near the midregion of the bore 18a of the cross-sectional configuration shown in FIG. 7, to impart some helical swirl to the flame passing through the burn tip 18.

The enlarged upper portion 11i of the body 11 includes another upwardly opening, frusto-conical cavity 11j, communicating with an enlarged cavity portion 11k for a control knob, later described, joining with the valve chamber 11e, in which is tightly fitted an insulator 20. The insulator 20 houses and supports the lower end portion of a conduit 22 for the igniter wire 21. The wire 21 at the upper end of the curved conduit 22 extends into an electrode housing 23 of insulating material having an electrode 24 therein connected to and projecting at right angles from the upper end portion of the wire 21 and extending into exposed position in the burner tube 17 near its outlet end as shown. The lower end of the wire 21 below the lower end of the conduit 22 within the bore of the insulator 20 is in electrical contact with a contact cap 44 which engages and is in electrical communciation with the ignition electrode 33a of the piezoelectric-type igniter 33, which in the preferred embodiment is an igniter having the construction shown in previously mentioned U.S. Pat. Nos. 3,509,388 or 4,139,792.

The piezoelectric spark generating device or igniter 33, as will be apparent from a review of either U.S. Pat. Nos. 3,509,388 or 4,139,792, includes a stationary housing portion indicated at 33b, (the left-hand portion of the igniter shown in FIG. 4) which houses the piezoelectric crystal stack and in which the finger-actuated slide plunger member 33c slides. A transverse pin 33d in the hammer portion rides in what appears as a substantially T-shaped slot 33e in FIG. 4, projecting laterally from the hammer through a cam slot in one or both sides of the plunger 33c. The lower portion of the T-shaped slot 33e as viewed in FIG. 4, in which the pin initially is located, restrains the pin and thus the hammer against movement during initial inward movement of the plunger (to the left as viewed in FIG. 4) while a spring within the plunger is compressed. At a predetermined position during the inward or leftward stroke of the plunger, inclined surfaces of the cam slot in the plunger sidewalls cam the pin upwardly to the horizontal portion of the T-slot 33 e as viewed in FIG. 4, releasing the hammer to impact against the crystal and produce the momentary high-voltage which is conducted through the electrode 33a and wire 21 to the electrode tip 24 within and near the discharge end of the burn tube 17. The inwardmost end, or left end portion as viewed in FIG. 4, of the piezoelectric spark igniter device bears against an actuator 32 surrounded by an O-ring 32a to form a seal against the surrounding wall of the cavity in which the actuator resides, and the actuator bears against a spring 28 whose other end engages the plunger pin of valve core 31 controlling the emission of gaseous fuel from the passage 11d to the passage 11f and into the region of the venturi formed at the outlet of the orifice device 13.

The plunger end portion of the igniter device 33 is surrounded by a rotatably adjustable and axially movable control knob 34 which projects from the right-hand end of the enlarged portion 11i of the body 11. The control knob 34 has an index mark 34a on its surface as viewed in FIG. 2 and is rotatably adjustable about its axis between an OFF position, an ON position and a CLEAN position. In the ON position, a slot 34b paralleling the center axis of the control knob and located in its periphery in upwardly facing position at the ON position of the knob, aligns with the lower end portion of a lock button assembly formed of a vertically movable lock button 30 in a suitably shaped cavity in the body 11 projecting from the top of the body 11, and having a bore in which are seated a lock button spring 46 and a shaft 27 surrounded by a spring 26 compressed between the lower end of the lock button 30 and the top of the control knob 34. The lock button is normally restrained within its cavity with the lower end portion of the shaft 27 extending into the slot 34b by a lock button screw 25 threaded into the body 11.

A regulator valve and piston assembly is housed in the downwardly opening bottom cavity 11b of the body 11 and, as illustrated, comprises a regulator piston 37 having a substantially cylindrical smaller diameter upper portion which is movable axially within the uppermost portion of the cavity 11b substantially conforming in diameter to the smaller diameter piston portion, while the lower portion of the regulator piston is of larger diameter as indicated at 37b and corresponds substantially to the diameter of the portion of cavity 11b in which it moves. O-rings 39 are provided in grooves in the regulator piston portions 37a and 37b as shown to seal against the confronting wall portions of the cavity 11b. A center bore passes axially through the regulator piston 37, and is shaped at the lower end portion of the center bore to receive a spider-like contact plate 40 having, for example, three outwardly extending legs to engage in the shaped portions of the center passage through the regulator piston 37 in which it is seated, while its center portion engages the plunger pin of the regulator valve core 31a. For example, a valve core such as the 5344 valve core made by Schrader Automotive Products Division of Scovill Manufacturing Co., of the type used with refrigerants such as R-12 and R-22, having an internal spring biasing the plunger pin to resiliently maintain the valve core in closed condition, may be used for both valves 31 and 31a.

The regulator valve core 31a is threaded into and carried by a regulator valve body insert 41a carried within a regulator valve body member 41 as shown, and having a gasket 42 against the lower face thereof. The regulator valve body 41 has external threads for threading it into the internal threaded portion 11a of the cavity 11b and also has an O-ring 39 to form a seal near the upper end of the regulator valve body member 41. After positioning of the regulator valve body member 41 and its associated valve body insert 41a within the cavity 11b, the lower end portion of the body 11 can then be assembled onto the threaded neck of the conventional propane container or tank with the gasket 42 forming a seal against the rim of the container neck and the regulator valve body insert 41a engaging and depressing the customary control valve pin internally incorporated in the container neck to open the internal propane container valve and communicate the propane gas through slot passages in the lower end portion of the valve body insert 41a communicating with the center bore of the insert to admit the propane gas to the regulator valve core 41a. The pressure regulator assembly in the cavity 11b including the regulator valve core 41a with its plunger pin bearing against the center portion of the contact plate 40 in the piston 37 which is spring-biased by the piston spring 35, is constructed so as to change the higher pressure in the propane cylinder or container to a lower consistent approximately 36 p.s.i. (+ or -3 pounds) for operation of the torch.

When the control knob 34 is in the OFF position, the lower end portion of the spring-biased shaft 27 assembled with the lock button 30 lies in a portion of the control knob groove 34b which restrains the control knob in its outermost position illustrated in FIG. 4. When the control knob 34 is rotated to the ON position, the portion 34b' of the control knob slot which extends parallel to the center axis of the control knob aligns with the lock button shaft 27, permitting the control knob to be depressed inwardly against the spring bias of the internal spring in the igniter 33 and against the bias of the actuator spring 28. Inward axial movement of the control knob 34 in the ON position moves the igniter 33, actuator 32 and the plunger pin of the control valve core 31 just enough to release the propane gas for travel through the orifice 13a and burn tube 17 to the location of the electrode 24 before the piezo-crystal igniter 33 is depressed enough to produce the electric current for generating the spark. When the hammer of the piezoelectric igniter 33 releases by camming of its pin to alignment with its release slot, the impact of the hammer against the piezo-crystal portion produces an electric current that travels up through the wire 21 in the conduit 22 to the electrode 24 and jumps from the end of the electrode to the inside of the burn tube, causing a spark that ignites the gas.

To torch is designed to facilitate cleaning to remove any clogging of the orifice in a novel manner. If the orifice becomes blocked due to contamination, burner tube 17 and venturi structure 16 and orifice adapter 15 can be removed by loosening the orifice adapter screw shown at 15a, the orifice member 13 can then be removed and reversed, and the burner tube, venturi and orifice adapter reassembled. The control knob 34 may then be shifted to the CLEAN position, wherein a short axial portion 34b" of the slot 34b aligns with the lock button shaft 27 which will permit a slight amount of inward movement of the control knob 34, igniter 33 and actuator 32 sufficient to depress the plunger pin of valve core 31 and admit some gas pressure to the passage 11f, but the control knob stroke is insufficient to activate the igniter to produce a spark. When the control knob is pressed to the extent allowed by the slot 11b at the CLEAN position, gas pressure is admitted through the orifice member in the reverse direction to achieve cleaning of the orifice by the pressurized gas. The components can then be reassembled to the original positions to resume normal operation.