US3040803A - Oil-firing apparatus - Google Patents

Description

June 26, 1962 c. MALMsTRM ETAL 3,040,803 I OIL-FIRING APPARATUS Filed Feb. 24. 1959 United States Patent O 3,040,803 01L-FIRING APIARATUS Carl Malmstrm and Bjrn Slot Magnus Paint, both of R0. Box 157, Norrkoping, Sweden Filed Feb. 24, 1959, Ser. No. 794,910 Claims priority, application Sweden Mar. 13, 1958 7 Claims. (Ci. 15S- 28) lt is known from Swedish Patent No. 142,470 to fit a throttle into au oil-firing apparatus consisting of a fan connected to a burner tube in which an oil atomizing nozzle is fixed, which throttle, by means of a springloaded piston servo-motor influenced by the oil pressure of the supply pipe to the burner nozzle, is caused to shut olf the air supply as soon as lthe oil pump stops, and to open the air supply as soon as the oil pump starts.

Our U.S. patent application No. 695,609 describes such an apparatus in which this piston servomotor is constructed in such a way that it closes the oil supply pipe leading to the burner nozzle as soon as the air throttle is not fully open.

The present invention relates to an arrangement in which, when the pump stops a piston servo-motor simul- -staneously shuts the oil supply to the burner nozzle, shuts the air supply to the burner and draws the burner nozzle backwards in the burner tube so that any oil present in the burner nozzle is not affected by the heat in the furnace combustion chamber causing it to become locked; and when the pump starts iirst pushes the burner nozzle forward and opens the air throttle and then opens the oil supply when the throttle is fully open and the nozzle is in the most favourable position for combustion.

According to this invention the apparatus comprises a cylindrical burner tube which is closed at its rear end, and at this rear end is fitted with a transversely directed air inlet from a fan.

In the rear end of the burner tube there is concentrically fitted a piston servo-motor the piston-rod of which points toward the mouth of the burner tube and acts upon a throttle for the combustion air so that this throttle is closed when the piston of the servo-motor is at its end position furthest from the mouth of the burner tube, and so that it is quite open when the piston is at its opposite end position. The piston-rod of the servomotor, at its free end, carries a burner nozzle and is provided with a longitudinal passage for the supply of oil to the nozzle, which passage via a transversely directed passage in the piston opens into an annular recess in the surface of the piston jacket. This recess is arranged `so that when the piston is at its end `position nearest the mouth of the burner tube it communicates with a longitudinal channel in the jacket of the servo-motor cylinder, which channel through a passage` close to the cylinder head furthest from the mouth of the burner tube is in communication with the interior of the cylinder, which through a passage in the head named, is in communication with the pressure pipe of the oil pump. The aforementioned annular recess is arranged so that as soon as the piston is not in the last-named end position the recess is kept closed by the surface of the cylinder jacket. The piston is forced back towards the feed head of the cylinder by a spring. The space at the feed head in the cylinder is in communication with the space at the piston-rod side by a meals of a channel that is closed by the piston when the latter is at its end position nearest the mouth of the burner tube, but is opened as soon as the piston leaves this position. The piston`rod side of the cylinder, by means of a passage, is in constant communication with the return pipe leading to the oil tank.

The invention is illustrated by the accompanying drawing, the only FIGURE of which shows, in longitudinal sec- 3,040,803 Patented June 26, 1962 rs. Ce

tion, one form of construction in accordance with the invention.

'A mainly cylindrical burner tube 1 is open at one end, this end being suitably contracted at the mouth 2. At the opposite end of the burner tube there is fitted a head 3 in which there is a round opening 4. On one side of the burner tube 1 close to the head 3 there is an opening` the oil pump l12.

A piston 13 is slidiably fitted inside the cylinder 7. At the end opposite to the passage 10 the piston isvtted with a sliding, sealing, piston rod 15 through the opposite cylinder head 14, which rod 15 has ya shoulder 16 to limit the movement of the piston 13 in the direction of the piston-rod.

Between the cylinder head 14 and the piston 13 there is fitted la spring 1'7 which is arranged to force the piston 13 against the feed head 9 of the cylinder 7.- In the jacket of the cylinder 7 there is a passage 18 which during the whole piston stroke connects the piston-rod side `of the cylinder 7 with the oil tank 19 via the return pipe 20. In the jacket of the cylinder 7 th/ere is also a longitudinal passage 21, which at least in part of its length has Va considerably smaller area than the feed pipe 11. Through a passage 22 close to the feed head 9 this passage Z1 is in communication with the feed side or working chamber '7a of the cylinder 7, and through another passage 23 the channel 21 is in communication with the piston-rod chamber 7b of the cylinder 7. The passage 23 is situated at such a distance from the feed head 9 that it is open during the greater part of the piston stroke,

but is closed by the piston 13 just before the shoulder 16 on the piston-rod 15 limits the movement of the piston 13 in the direction of the pistonrod 15.

In the jacket of the cylinder 7 there is another longitudinal channel 24 which, through a passage 25 close to the feed head 9, is in communication with the feed side of the `cylinder 7, and has another passage 26 towards the interior of the cylinder '7. Passage 2.16 is situated at such a distance from the feed head 9 that it is closed during the greater part of the piston stroke, 'but just before the shoulder 1d limits the movement lof the piston 13 yin the direction of the piston-rod it is caused to communicate with an annular recess 27 in the piston 13.

Through a passage 28 the recess 27 is in communication with the free end of the pistonaod 15 by means of a central longitudinal passage 29 inside the piston-rod 15.

The piston-rod 15 is so long that when the shoulder 16 has stopped the movement of the piston 13 its free end is so near the mouth of the burner tube 1 that the burner nozzle 30 fixed to the free end of the piston-rod 15, and in communication with the passage 29, is in the most favourable position for combustion. The position of the burner nozzle can be adjusted inwards or outwards by means of the 'adjusting nuts 40. l

On the piston-rod head of the cylinder 7 there 'is slidably fitted ya cylindrical collar 31.

with `an extended collar 32, which in the direction towards the last-named mouth merges into a cylindrical part 1331 which in the same direction'merges into a truncated At its end facingV the mouthof the burner tube 1 the collar 31 is providedL the lburner tube 1. This ring 37 is so arranged that with its outer edge it is mainly in contact with and sealing the inside of the burner tube 1, and its inner side can be made mainly to slidably seal the cylindrical part 33 :of lthe collar 31. The inside of the rlng 37 is made suitably streamlined so as to cause the least possible res-i-stance to the combustion `air owing through the slit between the ring 37 and the 4conical part 34 of the collar 31. The hub 3S is secured on to the piston-*od 15 at such a distance from the piston 13 that the ring 37 completely closes the air suppiy to the mouth of ti e burner ltube 1 when the piston 13 is 'at its end position nearest the feed end 9 of the cylinder7 and opens the air supply named when the piston 13 is at its opposite end position.

The maximum size of the inlet for the `air supply can be adjusted by a displacement of the collar 31, aected by means of an adjusting rod 38 which is fixed to the collar 431, passes through the cylinder part S, is threaded on the part passing through the part 8 and fitted with an adjusting nut 41 on the rear side of the part 8. The adjusting rod is provided with a fixed liange 42 .and between this iiange and the cylinder part 8 there is placed a helical Ispring 43 arranged to press the rod 3S towards the burner mouth 2. Between the burner nozzle 3521 and the hub 3S, suitably fixed on the piston-rod 15, there is a turbulator 39 which is free to slide within the burner tube 1. The turbulrator may also be fixed inside the burner tube 1, in which case the piston-rod 15 is free to slide through the hub of the turbul-ator 39. The spokes 36 can )also be m-ade in the form of turbulator blades.

The arrangement functions as follows:

When the pump 12 is not working the piston 13 under pressure from the spring 17 is pressed against the feed head 9 of the cylinder 7. The ring 37 completely closes the yair supply tothe mouth ofthe burner tube 1 and the burner nozzle 3i) is withdrawn inside the burner tube 1 so that it is `not affected by the heat from the furnace combustion chamber.

When the pump 12 starts it forces oil into the cylinder 7 through the passage .19. Part of this oil flows through the passage 22, the channel 21 and the passage 23 into the space on the piston-rod side of the cylinder 7, and from there through the passage 18 and the return pipe 20 to the oil tan-k 19. The greater part of the oil howing through the passage 16 forces the piston 13 in t-he direction towards the piston-rod head 14 of the cylinder 7. This movement forces the oil in the space at the piston-rod side of the cylinder 7 out th-rough the passage 1'8 and via the return pipe 20 to the oil tank 19. Simultaneously the ring 37 successively opens the supply of air to the mouth of the burner tube 1 so that any ex plosive gases present in the furnace combustion chamber are blown out. Immediately before the shoulder 116 limits the movement of the piston 1.3 towards the piston-rod head 14 of the cylinder 7 the piston 13 closes the passage 23. Simultaneously or immediately after that Ithe piston 13 causes the recess 2.7 to communicate with the passage 26 so that the oil can iiow from the space on the feed side of the cylinder 7 through the passage 25, the channel 24, the passage 216, the recess 27, the passage 28 and the passage 29 to the burner nozzle 30 which has now been pushed forward to a position most favourable -for combustion, where the oil is atomized and lighted in the usual way, for example by an electric spark.

When the pump 12 stops the piston =13 is forced in the direction of the feed head 9. This movement first closes the passage 26 simultaneously opening the passage 23 so that the oil in the feed space of the cylinder 7 can ilow through the passage 22, the passage 21 and the passage 23 to the spaceatthe piston-rod head of the cylinder 7. IOn account of the constriction afforded by this passage the movement of the piston `13 is slowed down so that the ring 37 only slowly closes the sup-ply of air to the mouth of the burner tube 1 and because of the natural draught from the chimney the furnace combustion chamber is freed from any explosive gases that may be present there before the air supply is completely cu-t off. Simultaneously the burner nozzle 30 is drawn into the burner tube 1 so that i-t is protected from the influence of the heat in the furnace combustion chamber.

Although the above shows and describes only one form of construction other forms within the scope of the' invention may occur. For example, the arrangement for shutting off the supply of combustion air may be differently constructed and placed.

We claim:

l. In an oil-iiring apparatus having a burner tube, a fuel oil pump, and an air supply means connected to the burner tube; a piston servo-motor comprising a cylinder and a servo-piston having a piston rod carrying a burner nozzle, the cylinder being located within the burner tube and having one end thereof in communication with the outlet of the fuel oil pump so that the servo-piston is exposed to outlet pressure of the pump to carry the nozzle to an advanced position within the burner tube when the pump is operating, resilient means biasing the servo-piston towards a retracted position of the nozzle, a throttle valve member carried by the piston rod so as to allow air to pass from the air supply means to the region of the burner tube containing the' nozzle when the piston is advanced, means for limiting the speed of retraction of the servo-piston and throttle valve member by the biasing resilient means when the pump is inoperative, and means for supplying fue-l from the pump outlet to the nozzle only when the nozzle is in the advanced position.

2. A structure as claimed in claim il in which the means for supplying fuel Ifrom the pump outlet to the burner nozzle comprises a duct in the 'piston rod communicating with the oil supply when the piston is in the advanced position.

3. The structure as claimed in claim l in which there is a threaded section on the rear part of the cylinder of the piston servomotor having adjusting nuts screwed on to it which enable an axial adjustment of the servomotor.

4. An oil tiring apparatus as claimed in claim 1 in which the throttle valve consists of a collar provided with a cylindrical extension mounted on the cylinder of the piston servomotor, and of a ring secured to the piston rod, the outer edge of this ring forming a movable seal with the inner ywall of the burner tube, and the inner edge being spaced from the collar, the space being variable according to the position of the piston rod and t-hus regulating the supply of combustion air.

5. An oi-l tiring apparatus as claimed in claim 4 in which the cylindrical extension is slidably secured to the cylinder of the piston servomotor and the collar bears an adjustment -rod which passes through an aperture in a threaded section on the rear part of the cylinder of the piston servomotor and has secured to it mea-ns to prevent its advance beyond a desired position.

6. An oil-firing apparatus comprising a burner tube open at one end, air supply means connected to said burner tube, an oil supply circuit including an oil tank, an oil pump, a piston servo-motor, an oil supply passage to the servo-motor, and an oil return pipe from said piston servo-motor, said piston servo-motor being situated inside said burner tube and consisting of a cylinder, a piston slidable Within said cylinder, and a piston rod connected to said piston, said piston defining a working chamber and a piston rod chamber within said cylinder, resilient means in said piston rod chamber biasing said piston towards a retracted position, a burner nozzle situated on the end of said piston rod, the piston rod having a longitudinal internal `passage extending from said burner nozzle, the piston having an annular recess communicating with said longitudinal passage, the cylinder having rst, second and third passages defined in the wall thereof, the said iirst passage communicating with the working chamber being in register with said annular recess only when the piston is in a forward position nearest the open end of the burner tube, the second passage providing a constricted connection between the working chamber and the piston rod chamber and being open at all piston positions except said forward position, the third passage connecting the piston rod chamber to the oil return pipe and being open at all piston positions; a throttle valve for combustion air within said burner tube and having a movable member operatively connected to said piston servo-motor, so that when the oil pump starts the throttle valve is opened for combustion air and the burner nozzle is simultaneously pushed forward, fuel only passing through said burner nozzle after these operations are completed, and when the oil pump stops the fuel ceases to pass through the burner nozzle and said burner nozzle is drawn back from the combustion zone, the throttle valve for combustion air being slowly closed while this happens.

7. In an oil-firing apparatus having a burner tube, a fuel oil pump, and an air supply means connected to the burner tube; a servo-motor located within the burner tube and having a stationary member and a movable member, the said movable member carrying a burner nozzle, a working chamber of the servo-motor being in communication with the outlet of the fuel pump so that the movable member may carry the nozzle to an operative advanced position within the burner tube when the pump is in operation, resilient means biasing the movable member towards a retracted position of the nozzle, a throttle valve member carried by the movable member allowing air to pass from the air supply means to the zone of the burner tube containing the nozzle when the" movable member is advanced, means vfor limiting the speed of retraction of the movable member and the throttle valve member by the biasing resilient means when the pump is inoperative, and means for supplying fuel from the pump outlet to the nozzle only when the nozzle is in advanced position.

References Cited inthe file of this patent UNITED STATES PATENTS 2,047,523 Scranton et al July 14, 1936 2,134,471 Coulter et al Oct. 25, 1938 2,540,416 Asscher Feb. 6, 1951 2,661,794 Shorrock Dec. 8, 1953 2,689,001 JLeysen Sept. 14, 1954 2,832,401 Lail Apr. 29, 1958 FOREIGN PATENTSv 497,119. Great Britain Dec. 13, 1938

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