GB2205858A

GB2205858A - Generating a mixture of oxygen and hydrogen electrolytically

Info

Publication number: GB2205858A
Application number: GB08713659A
Authority: GB
Inventors: Douglas Diepa Williams
Original assignee: UNIT DESIGNERS Ltd
Current assignee: UNIT DESIGNERS Ltd
Priority date: 1987-06-11
Filing date: 1987-06-11
Publication date: 1988-12-21
Also published as: GB8713659D0

Abstract

An oxygen/hydrogen gas generator includes an electrolytic cell, the electrical supply circuit of which includes a transformer 20 Fig. 2 and a pair of rectifier diodes 21, 22, wherein the electrolytic cell has a fin or flange 29 on which the rectifier diodes are mounted. By mounting the diodes onto the cell, heat generated in the diodes is conducted to the cell to increase the temperature of the electrolyte. An oxygen/hydrogen gas generator includes an electrolytic cell and means whereby the mixture of gases issuing from the electrolytic cell is caused to pass through a condensation trap 37 prior to its passage to a container within which a volatile inflammable liquid (e.g. methylethylketone) is contained. The inflammable liquid is entrained in the mixture of oxygen and hydrogen and results in the risk of "burn-back" being avoided when the flow of the gas mixture is interrupted e.g. when used in a welding process. An oxygen/hydrogen gas generator includes an electrolytic cell and a pipe connecting the cell to a chamber 41 having an inlet 40 and an outlet 45. A flexible diaphragm 43 prevents the flow of fluid from the inlet 41 to the outlet 45, the inlet 41 communicating with the interior of the cell and the outlet being 45 connected to a pressure switch controlling operation of the electrical circuit of the cell. <IMAGE>

Description

GAS GENERATORS Field of the Invention This invention relates to oxygen/hydrogen gas generators of the kind which include an electrolytic cell which, in operation, generates a combustible gas mixture which can be used for, for example, welding purposes.

Description of the Prior Art It is known to provide a gas generator which includes an aluminium housing in the form of a tray or trolley within which the different components of the generator are mounted. The electrolyte is normally aqueous potassium hydroxide and the cell circuit includes a pair of rectifier diodes and a transformer, all mounted within the housing.

It is' an object of the present invention to provide a gas generator which operates more efficiently than the gas generators presently available. Further objects of the invention are to improve the reliability and the safety of a gas generator.

Summary of the Invention According to a first aspect of the present invention there is provided an oxygen/hydrogen gas generator which includes an electrolytic cell, the electrical supply circuit of which includes a transformer and a pair of rectifier diodes, characterised in that the electrolytic cell has a fin or flange on which the rectifier diodes are mounted.

The cell may have a single fin or flange on which both rectifier diodes are mounted. Alternatively, the cell may have two separate fins or flanges with a rectifier diode mounted on each fin or flange.

The or each fin or flange is preferably formed of mild or stainless steel to avoid problems caused by corrosion and mounting of the diodes is preferably effected by the use of screw threaded fasteners.

By mounting the diodes directly onto the cell, instead of mounting them on the base or side walls of the housing, the majority of the heat generated by electrical losses in the rectifier diodes is conducted to the cell to increase the temperature of the electrolyte.

This serves to stabilise the cell operating temperature and, at the commencement of operation of the cell, a shorter warm up time is obtained. As the temperature of the electrolyte is increased, the resistance thereof is decreased. The applied voltage can, therefore, be reduced. A lower transformer power rating can be employed effecting a reduction in the power consumption and hence in the cost of operation of the generator.

In previous gas generators in which the rectifier diodes have been mounted directly on to the aluminium housing, the spillage of potassium hydroxide has resulted in the formation of an oxide coating on the aluminium. This oxide coating has acted as an insulator increasing the overall resistance of the supply circuit of the electrolytic cell. This reduction in power losses by making the or each fin or flange from steel also contributes to the overall improvement .in efficiency which is obtained in accordance with this aspect of the present invention.

By removing the liquid condensate from the gas mixture prior to flow of the mixture into the container of, for example, methylethylketone, dilution of the methylethylketone is reduced or substantially avoided and, as a result, the length of time for which the generator can be used without replacement of the methylethylketone is increased.

Oxygen/hydrogen gas generators as at present in use are normally controlled by a pressure switch which is operated by the oxygen/hydrogen gas mixture so that, in the event of leakage of the pressure switch diaphragm, the explosive oxygen/hydrogen gas mixture can enter the switching compartment of the pressure switch and the gas mixture can be ignited by a spark from the pressure switch contact. This will result in a blow-back which, at the least, will result in damage to the switch and malfunction of the generator.

It is accordingly a further object of the present invention to provide an arrangement in which the pressure switch of an oxygen/hydrogen gas generator is not exposed to the oxygen/ hydrogen gas mixture.

According to this aspect of the invention there is provided an oxygen/hydrogen gas generator in which there is a pipe connecting the cell to a chamber having an inlet and an outlet and in which a flexible diaphragm prevents the flow of fluid from the inlet to the outlet, the inlet communicating with the interior of the cell and the outlet being connected by a line to a pressure switch controlling operation of the electrical circuit of the cell.

The pipe leading from the cell to the chamber preferably has an end portion which projects into the chamber to provide the chamber inlet and the diaphragm is preferably in the form of a flexible bellows which fits over and is clipped to said end portion of the pipe.

The oxygen/hydrogen gas mixture generated by the cell preferably passes through a container within which a volatile inflammable liquid is contained, the inflammable vapour being entrained in the flow of the mixture of oxygen and hydrogen and serving to assist in the prevention of wburn-back".

Oxygen/hydrogen gas generators are most efficient at elevated temperatures at which steam is generated so that the gas mixture issuing from the generator thus contains a high proportion of water vapour. When the water condenses in the container containing the volatile liquid, the contents of the container gradually become a mixture of water and the volatile liquid which may be, for example, methylethylketone. As the percentage of water in the mixture increases, the vapour pressure of the methylethylketone is reduced. This results in a higher flame temperature which in turn results in an increased flame propagation rate and increases the danger of "burn-back".

It is accordingly a further object of the present invention to reduce the danger of wburn-back".

According to this aspect of the present invention there is provided an oxygen/hydrogen gas generator in which the mixture of gases issuing from the electrolytic cell is caused to pass through a condensation trap prior to its passage to a container within which a volatile inflammable liquid is contained.

The condensation trap preferably comprises a helical tube wound round a condensation chamber with the arrangement such that the gas mixture passes through the helical tube before entering the condensation chamber. The arrangement is preferably such that the condensation chamber communicates with the base of the electrolytic cell so that liquid which is condensed within the helical tube or condensation chamber is returned to the cell.

This arrangement will ensure that, although the pressure switch will respond to the pressure within the diaphragm, and hence the pressure within the cell, there can be no flow of electrolyte or of oxygen/hydrogen gas mixture to the pressure switch. The danger of corrosion of the pressure switch or of explosion of the oxygen/hydrogen gas mixture on operation of the pressure switch contacts is thus avoided.

In order to further increase the reliability and safety of operation of the oxygen/hydrogen gas generator, the pressure switch preferably has two sets of contacts, one set of contacts being set to operate at the normal operating pressure which is required and the other set of contacts being set to respond to over pressure conditions.

The electrical circuitry of the cell preferably includes a start switch or push button which, when energised, serves to operate a relay or hold-on device which is maintained in an energised condition via normally closed contacts of the over pressure switch. The arrangement is such that, in the event of the lower level switch contacts of the pressure switch failing to open upon an increase in pressure over and above that at which they are set to open, the over pressure switch contacts will open to de-energise the relay or hold-on device to shut down the generator. At the same time,a warning light or buzzer is preferably operated to indicate that an over pressure condition has been obtained. This warning light is preferably then the only part of the electrical circuit of the generator which is operative, every other part of the circuit will have been de-energised.

Brief Description of the Drawings Figure 1 of the drawings shows, somewhat diagramatically, the electrolytic cell of an oxygen/hydrogen gas generator, and Figure 2 shows the electrical circuit of the gas generator.

Description of the Preferred Embodiment Referring first to Figure 2 which shows the electrical circuit of the oxygen/hydrogen gas generator, there are live, earth and neutral terminals 10, 11 and 12 which are connected by a line which contains a start switch or push button 13 and a stop switch or push button 14 and a relay 15. The contact of the start switch 13 is normally open whereas the contact of the stop switch 14 is normally closed. When the relay 15 is energised, contacts 16 and 17 are moved from the positions shown in Figure 2. Contact 16 is a holding switch so that, when the start switch 13 is released, the relay 15 is maintained in its energised condition via the holding contact 16. Contact 17, when closed, serves to energise a fan 18 and an indicator lamp 19 whilst at the same time completing the electrical circuit of a transformer 20.The ends of the secondary coil of the transformer 20 are connected by lines containing rectifier diodes 21 and 22 to the outer electrode 23 of the electrolytic cell whereas the centre of the secondary coil of the transformer 20 is connected to the inner electrode 24 of the electrolytic cell.

The indicator lamp 19 and the primary coil of the transformer 20 are disposed in parallel and are connected to one side of a first pressure switch 25. There is a second or over pressure switch 26, the contact of which is normally in the position shown in Figure 2 but which moves from the position shown in Figure 2 when an over pressure condition is sensed.

In this over pressure condition, an over pressure lamp or indicator 27 is lit. At the same time, the circuit to the relay holding contact 16 is interrupted and relay 15 is deenergised. De-energisation of relay 15 results in opening of contact 17 and thus the interruption of the electrical circuit to the fan 18 and transformer 20.

The mechanical features of the oxygen/hydrogen gas generator are illustrated in Figure 1 and the various components are mounted within an aluminium housing in the form of a tray or trolley (not shown). The outer electrode 23 forms the casing of the electrolytic cell and the electrolyte of the cell is aqueous potassium hydroxide which is normally fiiled to the level indicated at 28. The inner and outer electrodes are both non consumable and the outer electrode 23 carries, at a position spaced from its base, a mounting fin 29 which is formed of mild or stainless steel. The mounting fin 29 is formed with a pair of spaced apertures which receive threaded shanks each of which forms part of the body of one of the rectifier diodes 21, 22. The rectifier diodes are held in position on the mounting fin by means of nuts 30 which are tightened onto the threaded shanks of the diode bodies.In operation, substantial heat is generated by the rectifier diodes 21, 22 each of which may be provided with twisted aluminium cooling fins to facilitate heat dissipation and to avoid over heating of the rectifier diodes 21, 22.

At its upper end, the electrolytic cell is closed by means of a top plate 31 and an impermeable rubber seal 32. There is a central filler tube 33 carried by the top plate 31 and the filler tube 33 is closed by means of an internally threaded filler cap which screws over the top of the filler tube 33.

There is a branch line 35 which leads from the filler tube 33 so that, in operation of the cell, the evolved gas mixture flows outwardly through this branch line 35.

Operation of the cell is carried out at an elevated temperature such that the gas mixture flowing along the branch line 35 consists of a mixture of oxygen, hydrogen and water vapour.

The branch line 35 is connected to a helical pipe 36 which forms part of a condensation trap 37. The condensation trap 37 also includes a chamber 38 and the arrangement is such that, in operation of the generator, a cooling air flow is produced by the fan 18 to flow over the helical tube 36 so that, during passage of the gas mixture through the tube 36, the majority of the water vapour is condensed. This condensate drips from the free end of the tube 36, which is contained within the chamber 37, and the condensate then returns to the cell via a connecting tube 39. An outlet pipe 40 extends from the upper end of the condensation chamber 38 and this leads to a container within which methylethylketone is disposed.As the mixture of oxygen and hydrogen passes through this container, methylethylketone vapour is entrained in the mixture of oxygen and hydrogen so that the gas mixture which is then used for, for example, welding or for other similar processes, consists of methylethylketone, oxygen and hydrogen. When, therefore, the flow of the gas mixture is interrupted, the risk of "burn-back" is avoided.

By arranging for the gas mixture issuing from the cell to pass first through the condensation trap 37, the amount of water vapour entrained in the gas flow is substantially reduced and dilution and degradation of the methylethylketone is avoided.

The connecting tube 39 is connected to the cell adjacent the base thereof and there is a second line 40 also extending from adjacent the base of the cell. This line 40 comprises a pipe, the upper end of which is contained within an air chamber 41. The pipe of line 40 passes through an aperture in a screw cap 42 with a seal surrounding the pipe 40 and fitting in the aperture in the cap 42. On the end of the pipe 40 there is a flexible rubber diaphragm 43 which is in the form of a corrugated cover held in position on the pipe 40 by means of a retaining clip 44.

The pipe 40 provides an inlet of the chamber 41 and there is an outlet 45 extending from the chamber 41, the outlet 45 leading to a pressure switch arrangement which includes the pressure switch contacts 25 and 26 shown in Figure 2.

The diaphragm 43 serves as an impermeable membrane preventing the flow of fluid from the inlet pipe 40 to the outlet pipe 45. The diaphragm 43 provides, however, for the transmission of pressure from the inlet pipe 40 to the outlet 45 so that, when the pressure within the cell increases there is a corresponding increase in pressure in the outlet pipe leading to the pressure switch. If, therefore, during normal operation of the generator, the pressure Increases to reach the pressure at which contact 25 is set to operate, the contact will then open to interrupt the supply to the transformer 20 so that the rate of gas evolution will fall abruptly and there will be a reduction in pressure which will then allow the contact 25 to return to its closed position to reconnect the transformer 20 to the power supply.

If, as explained above, the contact 25 should fail to open and the pressure within the cell should increase such that over pressure conditions are obtained, the contact 26 will then open to de-energise the relay 15 and switch off the power supply to the cell. When this over pressure condition is obtained, it is only the lamp 27 which remains on; everything else is shut down.

Although, as mentioned above, the components of the generator can be mounted within an aluminium tray, they can alternatively be mounted within a housing of fibreglass or any other material capable of withstanding the operating conditions.

Claims

CLAIMS:

1. An oxygen/hydrogen gas generator which includes an electrolytic cell, the electrical supply circuit of which includes a transformer and a pair of rectifier diodes, characterised in that the electrolytic cell has a fin or flange on which the rectifier diodes are mounted.

2. A generator according to claim 1, in which the cell has a single fin or flange on which both rectifier diodes are mounted.

3. A generator according to claim 1, in which the cell has two separate fins or flanges with a rectifier diode mounted on each fin or flange.

4. A generator according to claim 2 or claim 3, in which the or each fin or flange is formed of mild or stainless steel.

5. An oxygen/hydrogen gas generator which includes an electrolytic cell and means whereby the mixture of gases issuing from the electrolytic cell is caused to pass through a condensation trap prior to its passage to a container within which a volatile inflammable liquid is contained.

6. A generator according to claim 5, in which the condensation trap comprises a helical tube wound round a condensation chamber with the arrangement such that the gas mixture passes through the helical tube before entering the condensation chamber.

7. A generator according to claim 6, in which the condensation chamber communicates with the base of the electrolytic cell so that liquid which is condensed within the helical tube or condensation chamber is returned to the cell.

8. An oxygen/hydrogen gas generator which includes an electrolytic cell and in which there is a pipe connecting the cell to a chamber having an inlet and an outlet and in which a flexible diaphragm prevents the flow of fluid from the inlet to the outlet, the inlet communicating with the interior of the cell and the outlet being connected by a line to a pressure switch controlling operation ocf the electrical circuit of the cell.

9. A generator according to claim 8, in which the pipe leading from the cell to the chamber has an end portion which projects into the chamber to provide the chamber inlet and the diaphragm is in the form of a flexible bellows which fits over and is clipped to said end portion of the pipe.

10. A generator according to claim 8, in which the pressure switch has two sets of contacts, one set of contacts being set to operate at the normal operating pressure and the other set of contacts being set to respond to over pressure conditions.

11. A generator according to claim 10, in which the electrical circuitry of the cell includes a start switch or push button which, when energised, serves to operate a relay or holdon device which is maintained in an energised condition via normally closed contacts of the over pressure switch.

12. An oxygen/hydrogen gas generator according to claim 1 and substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

13. An oxygen/hydrogen gas generator according to claim 5, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

14. An oxygen/hydrogen gas generator according to claim 8, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.