WO1992011663A1

WO1992011663A1 - Apparatus and method for filling and sealing alkali metal electrode containers for alkali metal energy conversion devices

Info

Publication number: WO1992011663A1
Application number: PCT/GB1991/002296
Authority: WO
Inventors: David Joseph Riley
Original assignee: Chloride Silent Power Limited
Priority date: 1990-12-21
Filing date: 1991-12-20
Publication date: 1992-07-09
Also published as: GB9027814D0

Abstract

An apparatus for filling and sealing an alkali metal container (20) for an alkali metal energy conversion device includes a plurality of intercommunicating chambers (1, 2, 3, 4, 5), which are hermetically sealable. Transfer means are operable to transfer a plurality of alkali metal containers (20) to be filled and sealed successively from chamber to chamber. The atmosphere in each chamber is independently controlled by vacuum means to provide predetermined pressures of inert gas in the chambers (1, 2, 3, 4, 5). Means are also provided for independently controlling the temperature in each chamber. The apparatus further includes filling means arranged to fill said container (20) by delivering to each container (20) two predetermined amounts of an alkali metal. The filling means are located in one of the intercommunicating chambers being a first process chamber. Adjacent the filling means are located container de-pressurising means. The container (20) de-pressurising means comprises means for providing a direct sealed coupling to a container in said first process chamber to enable the de-pressurisation and subsequent re-pressurising of said coupled container between delivery of the two predetermined amounts of alkali metal to the container (20) whilst the first process chamber is maintained at a predetermined pressure. The apparatus further includes sealing means located in one of said intercommunicated chambers arranged to seal the containers (20) after filling.

Description

APPARATUS AND METHOD FOR FILLING AND SEALING ALKALI METAL ELECTRODE CONTAINERS FOR ALKALI METAL ENERGY CONVERSION DEVICES

The present invention is concerned with improved apparatus for filling and sealing alkali metal electrode containers for alkali metal energy conversion devices. This invention also relates to a method of filling alkali metal electrode containers, for alkali metal energy conversion devices, with alkali metal.

Such devices employ an alkali metal as one or sometimes both of the electrodes in a cell including a separator, or electrolyte, between the electrodes, formed of a solid ceramic material which is electronically insulating but conductive to cations of the alkali metal.

A particular example of such devices is the sodium sulphur cell which employs liquid sodium as the anode of the cell and liquid sulphur/sodium pol sulphide material as the cathode, the two being separated by a solid electrolyte of beta alumina.

Sodium sulphur cells for experimental purposes have been made in small quantities and it is very readily possible to fill the sodium reservoir or container of the cell by carrying out the filling operation in a closed chamber filled with a suitable inert gas or vacuum, the cell being sealed before removal from the chamber. The entire operation is carried out at a temperature substantially in excess of the melting point of sodium, typically 150°C.

However, such a technique is not suitable for quantity production of cells. Since the cells must be heated within the chamber prior to filling and then allowed to cool again. Furthermore, once the filled cells have cooled, the chamber must be broached to remove the cells and for the insertion of a fresh batch, whereupon the atmosphere in the chamber must be purged of any air before the next batch is heated and filled.

GB-A-2061598 describes a method and apparatus for filling sodium sulphur cells which avoids some of these difficulties. In the described arrangement, each sodium container or reservoir is provided with an open ended metal filler tube protruding from the container. Empty containers are heated progressively and presented to a sodium filling head whilst in air at atmospheric pressure. The filling head is specially designed to seal around the filler tube of the sodium container, evacuate air from within the sodium container before feeding sodium into the evacuated container. The filling head is then designed to pinch off the metal tube to seal the container before breaking the seal made with the filler tube. To facilitate this operation, it is usually necessary for the filler head to have a feed tube which can be inserted down through the filler tube of the cell into the interior of the sodium container so as to feed sodium directly into the container. The requirement for the filling head to seal to the filler tube of the sodium container also renders the design of the filling head relatively complicated as can be appreciated from the above referred specification.

In applicant's co-pending application WO 89/01244 there is disclosed apparatus and method for filling and sealing sodium sulphur cells which is an improvement over the prior art. The apparatus comprises intercommunicating entry, filling and exit chambers. Sodium cells are transferred into the entry chamber which is heated, evacuated and then flushed with argon gas. The cells are then transferred to the filling chamber which is maintained at a particular pressure of argon and filled in a two step process. To ensure that the cells are properly filled it is necessary to evacuate the filling chamber between the two filling steps. A current collector pin is then automatically inserted into the lid of the cell and welded in position before the cells leave the filling chamber to the exit chamber. In the exit chamber the cells cool down in argon and the pressure is equalised with atmospheric pressure before the completed cells are discharged. According to one aspect of the present invention there is provided apparatus for filling and sealing an alkali metal container for an alkali metal energy conversion device, comprising a plurality of intercommunicating chambers, which are hermetically sealable, transfer means operable to transfer a plurality of alkali metal containers to be filled and sealed successively from chamber to chamber, vacuum means arranged for independently controlling the atmosphere in each chamber to provide predetermined pressures of inert gas in said chambers, means for independently controlling the temperatures in said chambers, filling means arranged to fill said container, by delivering to each container two predetermined amounts of an alkali metal, the filling means being located in one of said intercommunicating chambers being a first process chamber, container de-pressurising means located adjacent said filling means and sealing means located in one of said intercommunicating chambers arranged to seal the containers after filling, wherein the container depressurising means comprise means for providing a direct sealed coupling to a container in said first process chamber to enable the de-pressurisation and subsequent re-pressurisation of said coupled container between delivery of the two predetermined amounts of alkali metal to the container whilst the first process chamber is maintained at a predetermined pressure.

By this arrangment the inefficiency of evacuating and re-purging the entire filling chamber is avoided in that the containers are individually evacuated without effecting the rest of the chamber. This enables other operations to take place simultaneously.

Preferably means are provided to simultaneously position at least a first cell for filling with an alkali metal and at least a second adjacent cell for de-pressurisation and subsequent re-pressurisation in the first process chamber.

There is considerable advantage in enabling the two operations to take place simultaneously in a commercial process such as this.

The preferred embodiment of the invention the filling means comprise at least a pair of filling heads, a first of which provides a first predetermined quality of alkali metal into the container before de-pressurisation and re-pressurisation and a second of which provides second predetermined quantity of alkali metal into the container after evacuation, and means are preferably provided to simultaneously position at least a third cell for a first filling, at least a second adjacent cell for evacuating and at least a first adjacent cell for a second filling.

By providing a two stage filling process this enables three sets of cells to be simultaneously operated on which again improves the effeciency of the process which is commercially advantageous.

The sealing means are preferably located in a second process chamber which is maintained at a predetermined pressure lower than that in the first process chamber during the sealing process.

The provision of two processing chambers enable easy access to the apparatus of the sealing means, e.g. welding heads and the like without disturbing or contaminating the atmosphere in the filling chamber and need arises for maintainanσe or a change of electrodes etc. It also allows for each operation, i.e. filling and sealing to be carried out at the optimium operating pressures and cycles and pass through rates. Preferably the second process chamber is hermetically sealable from the first process chamber and has at least one entry hatch to permit access to the sealing means.

In alternative embodiment of the invention there are provided first and second entry chambers in which containers are evacuated of air and flused with inert gas and heated to a predetermined temperature before being transferred to a process chamber for filling with sodium. The advantage of providing two entry chambers are that two sets of cells are permitted to be heated and evacuated at the same time to speed up the supply of cells to the filling chamber, which operates more quickly because of the previously mentioned advantages.

Preferably the containers are heated to a temperature in the region of 100°C to 140°C in the first entry chamber and to a temperature in the region of 150°C to 200°C in the second entry chamber, and more preferably to a temperature of 120°C in the first entry chamber and 180°C in the second entry chamber.

In a further embodiment of the invention there is provided an exit chamber in which the containers are cooled to a predetermined temperature before being removed from the apparatus.

In accordance with a further aspect of the invention a method of filling alkali metal electrode containers, for alkali metal energy conversion devices each container holding solid material, with alkali metal having a large wetting angle to the solid material, comprising the steps of filling said containers with gas which is inert to the alkali metal; pumping a first predetermined quantity of alkali metal into the container; reducing the pressure of said gas in the container and then raising the pressure of the gas to force into spaces in the container the alkali metal; pumping a second predetermined quantity of alkali metal into the container; positioning an electrode in the container and sealing the container wherein at least three cells are simultaneously operated upon respectively to receive the first quantity of alkali metal, to be de-pressurised and re-pressurised, and to receive the second quantity of alkali metal.

The method of this further aspect of the invention is applicable to the filling of alkali metal electrode containers comprising an electrolyte cup having a safety reservoir of mild steel. A narrow space between the outer wall of the reservoir and the inner wall of the electrolyte cup defines an active region for the alkali metal electrode. Wetting of the outer wall of the reservoir by the molten alkali metal is desirable to allow the molten alkali metal to fill the narrow space. As the molten alkali metal has a large wetting angle to the outer wall of the reservoir, the method of this further aspect of the invention allows efficient filling of the alkali metal electrode containers. A sodium sulphur cell having a sodium electrode container of this form is disclosed in WO89/05527 (Chloride Silent Power Limited).

The method of this further aspect of the present invention may also be applied to the filling of alkali metal electrode containers which include other solid materials to which the alkali metal has a large wetting angle. One example of such a solid material, as disclosed in the aforementioned WO89/01244, is an aluminium filler gettering agent which may be provided in the form of powder or flakes.

A preferred embodiment of the present invention is described in detail with reference to the following drawings in which:

Fig. 1 in the schematic diagram of filling and sealing apparatus embodying the invention and particularly adapted for filling the sodium container for a sodium sulphur cell;

Fig. 2 is a cross-sectional view of a typical sodium container for a sodium cell which has been filled and sealed by the apparatus of Figure 1;

Fig. 3 is a plan view partly in cross section of one version of a carriage for carrying the sodium

containers of Figure 2 for filling and sealing in the apparatus illustrated schematically in Figure 1;

Fig. 4 is an elevational view from one end, partially in cross section, of the carriage of Figure 3;

Fig. 5 is a side view and elevation of the first entry chamber of the apparatus illustrated in Figure 1, showing the drive means for guiding and propelling the carriage of Figures 3 and 4 within the first entry chamber;

Fig. 6 is a cross sectional view of the drive means of Figure 5 from one end taken along line A - A in Figure 5;

Fig. 7 is a side view in elevation illustrating the transfer of the carriage from the drive means of the second entry chamber to the drive means in the filling chamber;

Fig. 8 is an elevational view from one end, partially in cross section, of the drive means in the filling chamber;

Fig. 9 is a cross sectional side elevation of the filling chamber of the apparatus of Figure 1 illustrating in particular the filling evacuating stations; Fig. 10 is a part .cross-sectional side elevation of the evacuating station of figure 9.

Fig. 11 and 12 are views of the filling chamber from one side and end respectively and particularly illustrating the mechanism for lifting the guide railwithin the filling chamber to bring the sodium container and the carriage mounted thereon into engagement with the filling and evacuating heads in the chamber (some parts are omitted for clarity) ;

Fig. 13 is a detailed view in cross section of the carriage assembly illustrating the aperture for receiving the locating pin; Fig. 14 is a detailed view of the filling chamber from one end (with parts omitted for clarity) illustrating, partially in cross section, the mechanism for actuating the locating pins to locate the carriage within the filling chamber accurately relative to the filling and evacuating heads;

Fig. 15 and 16 are more detailed illustrations of an assembly for placing the current collector into the aperture in a sodium container prior to sealing of the container, and

Fig. 17 is a schematic diagram of the vacuum and argon supply system for the apparatus.

Referring to Fig. 1, the apparatus is formed of a five chamber pressure vessel. Each chamber of the vessel is generally cylindrical in shape and the five chambers are arranged co-axially, the three outer chambers being somewhat smaller in diameter and shorter than the central chambers. From left to right in Fig. 1, the chambers comprise a first entry chamber 1, a second entry chamber 2, a filling chamber 3, a sealing chamber 4 and an exit chamber 5. An entry hatch 6 provides access to the first entry chamber. Communicating doors 7,8,9 and 10 are provided between the first entry chamber 1 and second entry chamber 2, the second entry chamber 2 and filling chamber 3, the filling chamber 3 and sealing chamber 4 and the sealing chamber 4 and exit chamber 5. An exit hatch 11 provides access to the exit chamber 5. Each of the hatches 6, 11 and doors 7, 8,9, 10 allow the chambers to be sealed hermetically relative to the atmosphere and/or the neighbouring chamber or chambers.

Within each of the chambers 1, 2, 3, 4 and 5 there are provided respective drive means 12, 13, 14, 16 and 18 for guiding and propelling forward in the chambers a carriage 19 on which are mounted a number of sodium containers 20 to be filled and sealed by the apparatus.

Heating devices 25, 26, 27 and 28 are provided in the two entry chambers 1 and 2, the filling chamber 3 and the sealing chamber 4. These heaters 25, 26, 27 and 28 may be formed as electrically powered infrared heaters suitably positioned within each chamber to heat up and maintain the temperature of the containers 20 throughout the filling and sealing operations. It will be appreciated that the sodium is delivered to each sodium container 20 whilst in molten state and it is therefore essential to keep the container 20 substantially above the melting point of sodium metal to enable the filling operation to take place.

Metered filling stations 30 and 32 are provided at two locations within filling chamber 3, between which is located a cell evacuating station 31.

A current collector insertion station 33 is provided in sealing chamber 4 adjacent to a welding station 34 and cooling fans 35.

In the exit chamber 5, which is primarily a cooling chamber, there are provided cooling fans 36 to assist in the cooling of the completed cells 20. Argon and air supplies, vacuum pumping systems and valves are provided for separately evacuating and controlling the atmosphere within each of the chambers 1, 2, 3, 4 and 5 according to signals from a control unit (not shown) . The filling and sealing operations in the filling and sealing chambers 3, 4 are conducted in an atmosphere of inert gas, typically argon, and the vacuum pumps enable chambers 2, 3 and 4 to be purged of air and flushed with argon. All operations of the apparatus illustrated are controlled from a central control unit (not shown)

Each of the features mentioned above will now be further described in further detail.

The entry and exit hatches 6 and 11 and communicating doors 7, 8, 9 and 10 are independent gate valves of known type and are remotely actuated by the control unit 38 to open and close the doors. Each of the hatches 6 and 11 and doors 7, 8, 9 and 10 may be of the same design, or different.

The control unit is programmed such that the one gate cannot be released unless the adjacent gate is closed in place. In this way, the integrity of the atmosphere within each chamber is maintained irrespective of the occasional opening of the entry and exit hatches 6 and 11 for delivery and withdrawal of batches of sodium containers 20. Fig. 2 illustrates a typical form of sodium container which has been filled by the apparatus herein described. A sodium container 70 comprises a cup 71 of solid electrolyte material, typically beta alumina. A lid 72 of electrically insulating alpha alumina is glazed to the open end of the cup 71.

This unit, comprising the cup 71 and the glazed on lid 72 forms the container 70 to be filled with sodium 75 and subsequently sealed. The container 70 is supplied to the filling apparatus with a small aperture 73 through the centre of the lid 72. A metal washer 74 is fastened and sealed to the outer surface of the lid 72, typically by thermocompression bonding, so as to surround the aperture 73 as shown in the drawing. In the filled and sealed sodium container 70, a pin 76 forming a current collector for the sodium electrode, is inserted through the aperture 73 so as to make contact with sodium 75 within the container and is then welded to the washer 74 so as to form an hermetic seal completely closing the sodium container 70.

Another embodiment of the sodium sulphur cell is disclosed in applicant's International published patent application No. WO89/05527. This cell has a safety reservoir of mild steel within the electrolyte cup leaving only a narrow space between the walls of the reservoir and the cup. A gas tight seal is made to the reservoir so that an overpressure can be applied to force sodium through a hole in the base of the reservoir to wet the region around the reservoir. When the container 70 is supplied to the sodium filling apparatus for filling and sealing, the pin 76 is not inserted in the aperture 73 and the sodium metal is delivered through this aperture within the apparatus.

A plurality of sodium containers 70 is transported through the pressure vessel of Fig. 1 by means of a carriage 19, one example of which is illustrated in Figs. 3 and 4. One version of the carriage 19 holds 10 sodium containers 70 for processing as a single batch through the apparatus. A preferred version of the carriage holds 20 containers in 2 rows of 10. This enables pairs of containers 70 to be processed simultaneously. It should however be understood that any suitable number of containers may be held in a single carriage. The carriage 19 shown in Fig. 3 comprises an upper plate 77 in which there are circular apertures 78 for receiving the cups 71 of sodium containers 70 to be filled. The central aperture 79 is not used to receive a container 70 for filling but is a blank position having a dummy container used for temperature monitoring during the processing through the filling apparatus.

The upper plate 77 is held spaced from a lower platform 80 by means of a plurality of stanchions 81, 82. Along one side of the row of apertures 78, stanchions 81 are provided, one for each aperture as shown in Fig. 3, though only three of the stanchions 81 include threaded portions extending through the upper plate 77 and receiving nuts 83 securing the plate 77 to the stanchions 81, 82. Each of the stanchions 81 except that adjacent the central dummy aperture 79, are axially drilled from their upper ends, visible through holes in the upper plate 77, so as to receive the current collector pins 76 (Fig. 2) for the respective sodium container 70 located in the adjacent aperture 78 of the top plate 77. Thus, not only are a number of open sodium containers 70 mounted in the respective apertures 78 in the top plate of the carriage 19, but also current collector pins 76 for each of these containers 70 are located immediately adjacent the respective containers 70. The platform 80 of the carriage 19 carries rollers 84, 85, 86 and 87 for engaging on rails in the entry, filling sealing and exit chambers of the apparatus. Rollers 84, 85 which rotate about horizontal axes, are provided down both sides of the platform 80 and these rollers 84, 85 engage between pairs of vertically opposed rails provided in the entry and exit chambers l, 2, 5 as will be described later herein. Rollers 86, 87 rotating about vertical axes, are provided underneath the platform 80 to engage on opposite edges of an horizontally extending rail in the filling chamber 3 and sealing chamber 4. Three sets of horizontally opposed rollers 86, 87 are provided distributed along the length of the carriage 19.

An aperture 89 is provided extending upwards through the platform 80 immediately beneath each container position, i.e. each aperture 78, 79 in the upper plate 77. The aperture 89 through the platform 80 is adapted to receive a locating pin so as to locate the respective sodium container 70 accurately within the chambers 1, 2, 3, 4, 5.

It will be appreciated that the design of the container carriage 19 may be varied from that described above which is only one acceptable version. Referring to Figure 5, the carriage 19 of Figures 3 and 4 is illustrated mounted on the transfer or drive means 12 in the first entry chamber 1 of the apparatus. The carriage is indicated in Figure 5 by the reference number 19 (corresponding to the reference used in Figure 1) , although for clarity only the platform 80 of the carriage 19 is shown in Figure 5.

The entry hatch 6 to the first entry chamber 1 is shown to the left hand side in Figure 5. The left hand end of the carriage 19 is illustrated in Figure 5 in longitudinal section so that the rollers 86 on one side of the carriage 19 can be seen.

The manner in which the carriage 19 is mounted and guided within the first entry chamber 1 is better illustrated in Figure 6 which is a cross-sectional view taken along line A-A of Figure 5. It can be seen from Figure 6 that the carriage 19 is supported in the first entry chamber 1 by means of the laterally extending rollers 84 and 85. The rollers 86 and 87 (Fig. 4) are not employed in the first entry chamber 1 and are omitted from Fig. 6 for clarity. The rollers 84 and 85 are engaged between pairs of upper and lower rails 92 and 93, 94 and 95 respectively. The rollers 85 to one side of the carriage 19 are circumferentially grooved to engage around rails 94 and 95 to provide lateral support for the carriage 19. It will be appreciated that the spacing between the vertically opposed pairs of rails 92, 93 and 94, 95 is such as to enable the respective rollers 84, 85 to rotate when engaging either the upper or the lower rail. Thus there is a small amount of play to ensure that individual rollers do not engage both upper and lower rails simultaneously.

The carriage 19 is driven along the rails 92 to 95 by friction drive from a drive wheel 90. The drive wheel 90 is driven from an electric motor (not shown in Figure 6) via a drive train comprising a clutch and brake assembly 96, rotary vacuum seal 97, flexible drive coupling 98 and miter gears 99 and 100. A further friction drive wheel (not shown) corresponding to wheel 90 is provided towards the other end of the rails 92 to 95 at the position indicated by the axle bearing 91 in Figure 5. This second drive wheel is connected by a belt drive to the axle of the first drive wheel 90. Pulley 101 of one end of the belt drive is illustrated in Figure 6. It will be appreciated that any other suitable form of drive and transfer means may be employed in any of the chambers 1 to 5.

Position sensors are provided in the first entry chamber 1 for detecting the carriage 19 as it is first introduced into the tracks 92 to 95, to initiate forward drive once the carriage is fully engaged, and subsequently to slow down and halt the drive when the carriage is fully drawn into the chamber.

When the second entry chamber 2 is ready to receive the carriage 19, the communicating door 7 is opened and transfer of the carriage 19 from the first entry chamber 1 to the second entry chamber 2 can take place.

The second entry chamber 2 contains transfer and drive means 13 the same as the transfer and drive means 12 in entry chamber l. The distance between the end of the rails 92-95 in the first entry chεunber and the start of identical rails in the second entry chamber 2 is such that the carriage 19 is driven forward by the drive means 12 in the first entry chamber so as to extend through the bulkhead, still supported cantilever fashion by at least two sets of rollers 84, 85 at the rear end of the carriage 19 until a set of rollers 84, 85 at the front end of the carriage 19 engage on the rails 92 to 95 in the second entry chamber 2. During this transfer of the carriage 19 from first entry chamber 1 to second entry chamber 2, drive of the carriage 19 from the first entry chamber 1 is continued until the carriage 19 has engaged a further friction drive wheel 90 in the second entry chamber 2. Thus once the carriage 19 has been driven forward such that the last pair of rollers 84, 85 disengage rails 92 to 95 of the first entry chamber 1, the carriage 19 is supported cantilever fashion by the rollers 84 and 85 at the front of the carriage 19 and rails 92 to 95 of the second entry chamber 2 as it is drawn fully into the second entry chamber 2. Sensors detect that the carriage 19 is progressed far enough into the second entry chamber 2 to engage the friction drive wheel 90 to operate the drive to continue drawing the carriage 19 into the chamber 2. Further sensors are provided in the second entry chamber 2 to detect when the drive means should be slowed and halted.

Figures 7 and 8 illustrate the drive means within the filling chamber 3 which allow more accurate positioning that the system found in entry chambers 1 and 2. Figure 7 in particular is a cross-sectional view showing carriage 19 being transferred through the communicating door 8 to engage with the drive means of the filling chamber 3. In Figure 7 the second entry chamber 2 is shown on the right hand side and the filling chamber 3 on the left hand side. In transferring the carriage 19 from the second entry chamber 2 to the filing chamber 3 through the door 8, the carriage 19 is driven forward by the drive means 13 in the second entry chamber 2 so as to extend through the door from the drive means, still supported cantilever fashion by at least two sets of rollers 84, 85 until the rollers 86, 87 at the front end of the carriage 19 engage on opposite sides of an horizontally extending rail 102 in the filling chamber 3. The rail 102 can be seen in cross-section in Figure 8 and has bevelled edges engaging in the grooves in rollers 86 and 87 to provide both lateral and vertical guided support of the carriage 19.

In the transfer of the carriage 19 from chamber 2 to chamber 3, drive of the carriage 19 from chamber 2 is continued until the carriage 19 has engaged a first friction drive wheel 103 of the drive mechanism 14, 15 within the filling chamber. Further, the rail 102 in chamber 3 and tracks 92 to 95 in chamber 2 extend close enough to each other so that the carriage 19 is fully supported cantilever fashion while being driven forward from chamber 2 to engage the front rollers 86, 87 on rail 102 and subsequently is supported by at least one pair of rollers 84, 85 at the rear end of the carriage 19 in chamber 2 until a second set of rollers 86, 87 at the front end of the carriage 19 have engaged rail 102 in chamber 3, whereupon the carriage 19 is supported cantilever fashion from the rail 102 as it is drawn fully into chamber 3.

Position sensors detect that the carriage has progressed far enough into chamber 3 to engage the first friction drive wheel 103 to operate the drive to continue drawing the carriage 19 into the chamber 3. Further sensors control the drive means 14, 15 to bring the carriage 19 to the correct positions beneath the filling and evacuating stations 30, 31.

As seen in Figure 8 the drive in chamber 3 derives from an electric motor 104 via gear box 105, flexible coupling 106, clutch and brake unit 107, a second flexible coupling 108, a rotary vacuum seal 109 a further flexible coupling 110, and miter gears 111, 112.

Sufficient additional friction drive wheels corresponding to wheel 103 are provided along the length of the rail 102 in chamber 3 to ensure that the carriage 19 is engaged by at least one drive wheel throughout its journey through the chamber 3. The additional friction drive wheels are driven by belt drives via pulleys corresponding to pulley 113 in Figure 8.

The rail 102 described is a single rail. However, this can be replaced by a rail having more than one section if appropriate.

An identical transfer and drive means arrangement is provided in sealing chamber 4 which allows for the cantilever style transfer from chamber 3 to chamber 4. Again the rear rollers 86, 87 remain in contact with the rail 102 in chamber 3 until the front rollers 86, 87 are fully supported by the rail 102 in chamber 4.

The transfer and drive means in exit chamber 5 are identical to those in the entry chambers 1, 2. The arrangement allows for transfer from sealing chamber 4 to exit chamber 5 in the reverse manner to the transfer from entry chamber 2 to filling chamber 3.

Fig. 9 is a cross-sectional view of the filling chamber 3 showing the carriage 19 (platform 80 only shown for clarity) mounted and guided on the rail 102. Only three sodium containers 70a, 70b, 70c are illustrated as they will be supported on the carriage 19. The rest are omitted for clarity. As each of the filling stations 30, 32 and evacuating stations 31 have pairs of nozzles the containers 70a, 70b and 70c should be considered as pairs of containers. The filling chamber 3 includes a first filling station 30 of known type having a pair of filling heads 120 (only one of which is shown) arranged side by side for feeding accurately controlled quantities of molten sodium into the pairs of containers 70 in the 20 container carriage through the open apertures 73 (see Fig. 2) in the lid 72 of the containers 70. If the 10 container carriage 19 is used only a single filling head is required at each station.

Adjacent the first filling station 30 is an evacuating station 31 with a pair of evacuating nozzles 121. Again if the 10 container carriage is used only 1 evacuating nozzle 12 is required. Figure 10 illustrates the evacuating station 131 in more detail. When containers 70 are pressed against the nozzles lower sections 115 thereof move upwardly compressing bellows 116 against the action of compressed springs 117 which normally hold the lower sections 115 away from the upper sections 118 as shown in Figure 10. Brackets 119 attached to the lower and upper sections 115, 118 are slidable along pins 120 to enable this movement to take place.

Adjacent to the evacuating station 31 is a second filling station 32 having a pair of filling heads 122 providing the cells with a top up charge of sodium. The second filling station 32 is the same as the first filling station 30.

It should be noted that the filling stations 30 and 32 and evacuating station 31 can be provided singly or in plurality such that one or a plurality of adjacent (side-by-side) containers can be operated on at each stage, dependent on the layout of the carriage 19.

The rail 102 carrying the carriage 19 is itself mounted on the intermediate support frame 123 which is vertically movable relative to the frame 124 within chamber 3 which supports the filling and evacuating stations 30, 31 and 32. The intermediate support frame 123 carrying the rail 102 and the carriage 19 can be raised in its entirity by vertical axial movement of supporting shafts 125 which extend through axial seals in the outer wall 126 of the filling chamber 3.

The construction of this lifting mechanism is illustrated in more detail in Figs. 11 and 12. The two supporting shafts 125 are actuated by means of cams 127 acting on cam follower rollers 128 mounted on the lower ends of the shafts 125 extending outside the wall 126 of the pressure vessel. The cams 127 are mounted on a shaft 129 extending longitudinally underneath the cylindrical pressure vessel. Rotation of the shaft 129 by means of a pneumatic cylinder acting on a lever 130 rotates the cams 127 to raise and lower the supporting shafts 125, in turn raising and lowering the frame 124 with rail 102 carrying the carriage 19. The raising and lowering operation of the carriage 19 enables the sodium containers 70 to be brought into engagement with the filling heads 120, 122 and evacuating nozzles 121 as required.

Thus, when the carriage is to be driven along the rail 102 to bring a fresh pair of containers 70 into position under the heads 120 and 122 or nozzles 121, the carriage 19 is maintained in the lowered position. Once the containers 70 are correctly positioned relative to the heads or nozzles 120, 121 and 122, the carriage 19 is lifted by means of the cams 127 and shafts 125 to bring the relevant containers 70 into engagement with the heads or nozzles 120, 121 or 122 as required.

It will be appreciated that accurate positioning of the sodium containers 70 relative to the heads and nozzles 120, 121 and 122 is essential. For this purpose, locating pins 131 are provided in the filling chamber 3 which are axially movable to engage in the apertures 89 (Figure 4) in the platform 80 of the carriage 19. Thus, the carriage 19 is first driven to approximately the desired position presenting the intended container 70 immediately beneath the heads or nozzles 120, 121 and 122, and then the locating pins 131 are driven upwards to engage firmly in one or more of the apertures 89 of the carriage 19, thereby positively locating the carriage 19 in the correct position for engagement of the selected containers with the required heads.

Figures 13 and 14 illustrate the operating mechanism for the locating pins 131. Each index pin 131 is mounted for axial movement in a bearing 133 secured in a frame member 134 which is fixed within the chamber 3. The lower end of each pin 131 is journalled to one end of a lever arm 135 having its other end keyed to a shaft 136. The shaft 136 interconnects the levers 135 for the locating pins 131 and the shaft 136 is itself pivoted between bearings 137 fixed within the chamber 3. A further actuating lever 138 is keyed to the shaft 136 midway between the levers 135 and this lever 138 is connected via a piston rod 139 extending by means of an axial seal through the wall 126 of the chamber 3, to a pneumatic cylinder 140.

Thus, operation of the pneumatic cylinder 140 to move the piston red 139 upwards in Figure 14 rotates the shaft 136. thereby moving the locating pins 131 axially upwards also. - 22 -

Figure 13 illustrates in cross-section the platform 80 of the carriage 19 showing in particular the aperture 89 into which one of the locating pins 131, can be inserted. It should be noted that apertures 141 through the rail 102 are provided also immediately opposite each locating pin 131 to allow the pin 131 to pass through the rail before engaging in aperture 89.

A similar lifting mechanism and locating means are providing in sealing chamber 4 to enable the containers 70 to be raised and accurately placed with respect to the pin locating mechanism 33 and the adjacent welding station 34.

Figure 15 illustrates the pin locating station 33 in chamber 4. The pin insertion head 150 of pin locating station 33 operates to pick up the current collector pin 76 for the container 70 from its position on the carriage 19 immediately adjacent the container 70 as described earlier. The pin 76 is picked up from this location and inserted through the aperture 73 in the top of the container 70. The carriage 19 is then driven forward to bring the next container (or pairs of containers) into position for pin insertion. The insertion head 150 is mounted on a frame assembly 151 fixed within the sealing chamber 4. A pair of axially movable and rotatable shafts 152 and 153 extend down through a flange 154 of the sealing chamber 4 and also extend through the supporting frame 151. The two shafts 152 and 153 are disposed side by side across the width of the chamber, so that Figure 15 is a view of the insertion head looking along the length of the chamber 4 from the welding station 34. Supported in a fixed position from the frame 151 by means of a supporting rod 155 is a guide peg 156. This guide peg 156 is positioned so as to provide a guiding aperture immediately over the aperture 73 of the sodium container 70 into which the pin 76 is to be inserted.

Attached to the lower end of the shaft 152 is e pick and place arm 157. The arm 157 has at one end 158 spring loaded "jaws" by which the arm 157 can engage over the head of the current collector pin 76. In order to insert a pin 76 in a container 70 the shaft 152 is first rotated to the position as shown in dotted outline in Figure 16, with the jaws 158 precisely located over the head of the current collector pin 76 mounted in the carriage. The shaft

152 is then moved downwards axially so that the jaws mechanically engage the head of the pin 76, whereupon upward movement of the shaft 152 draws the pin 76 up free of the carriage 19. The arm 157 is then rotated, by means of the shaft 152, through 90° to bring the pin precisely over the aperture 73 in the lid of the container 70. Depression of the shaft 152 should then insert the pin 76 guided by means of the guide peg 156 into the aperture 73 in the container 70.

Attached to the lower end of the other shaft

153 is a second arm 159 carrying a stripper pin 160. During the above described operation of the pick and place arm 157, the stripper pin arm 159 is fully retracted and pivoted to the position shown in Figure 16 at 158* . When the pick and place arm 157 has inserted the pin 76 into the aperture 73 of the container 70, the stripper pin arm 159 is rotated by means of the shaft 153 to bring the stripper pin 160 into alignment with the head of the current collector pin 76 held in the jaws of the pick up arm 157. The stripper pin 160 is then depressed, by axial movement of the shaft 153 so as to engage the head of the current collector pin 76 and push the head out of the jaws of the pick and place arm 157, and firmly home to bear against the lid 72 of the sodium container 70. The stripper pin 160 is then withdrawn from the pick and place arm 157 and rotated away again to the position 158'.

Again the pin insertion station 33 may have a pair of heads 150, in which case a pair of containers 70a are located there beneath.

A little further along the sealing vessel 4 there is a welding station 34. When the third cell on the carriage 19 is brought into position for pin insertion under the insertion head 156, this also simultaneously brings the first container 70a into position under the welding station 34. Thus, when the pin is being inserted into the third sodium container, the pin 76 already inserted in the first container 70a is welded in place to the washer 74 (Figure 2) to seal the container 70. If the pin insertion station 33 has a pair of heads 150 the welding station 34 may also have two welding heads. Thus when the 3rd row of two containers in a 20 container carriage are receiving their pins, the first row of containers is being welded. The operation is continued until all ten rows of containers on the carriage 19 have had their pins inserted and subsequently welded to seal the container 70. The detailed design of the welding station 34 is of no concern to the invention.

Fans 35 are located adjacent the welding station 34 to start cooling of the containers 70 after welding.

A maintenance hatch (not shown) may be provided in sealing chamber 4 to provide access to the welding heads which enables them to be easily changed without disturbing and possibly contaminating the filling chamber. An operating procedure for use with the above apparatus will now be described referring to Figure 17 which is the schematic diagram of the vacuum system employed independently controlling the atmosphere in each of the chambers of the apparatus. All functions of the apparatus are controlled by a control unit (not shown) remotely or otherwise which may also include programmable control means for automating the procedure. The valves VI to V19 are generally solenoid valves although any other suitable valves may be used.

Firstly, a carriage 19 is loaded with the required number sodium containers 70 and current collector pins 76 as previously described. Valve VI is closed and the pressure in the first entry chamber 1 is brought to one atmosphere of air by opening valve Vll to allow air to be pumped into the chamber 1. When the correct pressure is achieved, and provided that the communicating door 7 to the second entry chamber 2 is closed, entry hatch 6 is opened. The carriage 19 carrying the sodium containers 70 is then introduced into the track system 12 in the first entry chamber 1 and drawn fully into the chamber 1 as described previously. As mentioned before, the central container position on the carriage 19 has a dummy sodium container fitted with temperature sensors and when the carriage 19 has been driven into position in the first entry chamber 19 a location pin is inserted into the carriage 19 and a thermocouple inserted into the dummy container 79. Thus correct positioning can be maintained and the temptation of the containers 70 monitored during processing.

When the hatch 6 is subsequently closed valves Vll and V13 are closed and the chamber is evacuated by pumping system 41, via valve VI which is opened, to a pressure of below 1 x 10"¹ mBarAbs. Obviously valves V2 and V3 must also be closed. When the vacuum is achieved valve VI is closed off. At the same time the heaters 25 in the first entry chamber are energised to begin bringing the temperature of the sodium containers up. The heaters 25 heat up at approximately 15°C per min for 7.3 minutes. This time period however is dictated by when the second entry chamber 2 is correctly evacuated and empty. The vacuum is maintained after valve VI is closed by opening valve V13 to connect pumping system 40 to chamber 1 which duly maintains the vacuum. This releases pumping system 41 to be used to evacuate chamber 2. When the second entry chamber 2 is available, it will have already discharged a previous batch of containers to the filling chamber 3 and will be at one atmosphere of Argon. The chamber 2 must be evacuated to the same pressure as chamber 1 using pumping system 41 via opened valve V2 before transfer of the carriage 19 can take place. Valves VI and V3 must be closed during pumping. When the correct vacuum is achieved communicating door 7 will be opened to allow transfer of the carriage 19 to the second entry chamber 2. This will only happen if the entry hatch 6 is closed. After the locating pin and thermocouple have been withdrawn the carriage 19 is then driven forward through the opened door 7 into the second entry chamber 2. When the carriage 19 is fully into the second entry chamber 2, the communicating door 7 is closed again.

In the first entry chamber 1 the pressure must be brought back up to atmospheric pressure. Valve V13 is therefore closed and valve Vll opened to allow air to flow into the chamber l. When atmospheric pressure has been achieved hatch 6 may be opened. Once the chamber 1 has been reloaded and hatch 6 closed, the chamber 1 is reconnected to pumping system 41 as previously described.

In the second entry chamber 2, the thermocouple is inserted so that the temperature of the containers 19 can be further monitored. The locating pin is also inserted to ensure correct positioning.

The second entry chamber 2 continues heating the containers 70 to a preset temperature of between 150°C and 180°C under vacuum. Once the correct vacuum has been achieved, pumping system 40 is used to maintain the vacuum. To do this valves V2, V13, V15 and V17 are closed and valves V14 and VI6 opened. This releases pumping system 41 for evacuating chamber 1.

When the filling chamber 3 is available, it will have already discharged a previous batch of filled containers to the sealing chamber 4 and will itself be at a pressure of approximately one atmosphere of argon. Before transfer can. take place the second entry chamber 2 is flushed with argon to a pressure of approximately one atmosphere to equalise it with the pressure in the filling chamber 3 which is constantly maintained at 1 barAbs Argon. To enable this to happen valve V14 is closed to disconnect the pumping system 40, valve V17 is closed and valves V15 and VI6 opened to connect the second entry chamber 2 to the argon supply.

The communicating door 8 can be opened provided that the communicating door 9 to the sealing chamber 4 and the communicating door 7 to the first entry chamber 1 are shut. If there is even a slight pressure differential on to door 8 it will not open. If this is the case, closing valve V15 and opening valves V16 and V17 will allow the pressure to balance. The heaters in the second entry chamber 2 are then switched off, the thermocouple and locating pin withdrawn and the carriage 19 driven forward through the door 8 into the filling chamber 3. Once the position sensors detect that the carriage 19 is fully in the filling chamber 3, door 8 is closed again.

Second entry chamber 2 must now be evacuated to allow it to receive new containers from first entry chamber 1. To do this valve V2 is opened and valve V13 closed and pumping system 41 is reconnect to evacuate the chamber 2.

In the filling chamber 3, the thermocouple is inserted in the dummy container so that the temperature of the containers can be monitored throughout. However, in the filling chamber 3, the thermocouple is mounted so as to be slidable along a rail within the chamber 3, parallel to the direction of movement of the carriage 19.

A coiled lead connects to the thermocouple to provide electrical lead outs and so connection can be retained to the thermocouple continuously as the carriage 19 is moved along the chamber 3.

The drive 13 in the second entry chamber 2 brings the carriage 19 to present the first pair of containers 70a to the first filling station 30 and the location pins 131, 132 are operated to correctly locate the carriage 19. The carriage 19 is then raised as previously described so that the filling nozzles 120 are inserted into the aperture 73 in the lid 72 of the first pair of containers 70a. The filling heads 120 then inject a first charge of liquid sodium into the first pair of cells 70. Thereafter, the carriage 19 is lowered, location pins 131, 132 are retracted, and the drive means 14 operate to move the carriage 19 forward so that the first pair of containers 70a are located under the evacuating station 31. The carriage 19 is then raised so that the evacuating nozzles 121 seal with the containers 70. The containers 70 are evacuated by a cell evacuation facility via valve V20 connected to pumping systems 42 (with valve V21 closed) to reduce the pressure therein to approximately 1 x 10"¹ mBarAbs. The containers 70 are then repressurised with the argon in chamber 3 via valve V21 (with valve V20 closed) to 1 barAbs. Simultaneously with this operation, the second pair of containers 70b will have been positioned and located correctly with respect to the first filling station 30 and will receive an initial charge of sodium from the filling nozzles 120. Drive means 14, 15 are then engaged to drive the carriage 19 forward until the first pair of cells 70a is located under the second filling station 32. The carriage 19 is then raised so that the second filling nozzles 122 are inserted into the aperture in the lid of the first pair of containers 70a and a second quantity of liquid sodium injected into first pair of containers 70a. Simultaneously, the second pair of containers 70b will be raised to the evacuating nozzles 121 for evacuating and repurging and the third pair of containers 70c will be receiving their first charge of sodium from the first filling nozzles 120. On completion of the final filling operation on the last pair of containers 70 in the carriage 19, the temperature sensor is disconnected and the heaters 27 in the filling chamber 3 are switched off.

When all the sodium containers are filled the carriage 19 is driven along the rail 102 and transferred to the sealing chamber 4. When the argon in the filling chamber 3 is getting depleted it is replenished by opening valves V18 and V10 (keeping valve V3 closed) .

When the sealing chamber 4 is ready, the thermocouple and locating pin withdrawn and the carriage is driven forward towards communicating door 9. Since the thermocouple will have been moved along the chamber 3 with the carriage 19, it must be returned to its initial position ready for the next carriage 19 by a suitable return conveyor or the like. The pressure in the sealing chamber 4 is usually maintained at 0.88 of an atmosphere of Argon but must be increased to the same pressure as in filling chamber 3 before transfer. To do this valve V7 and V10 are opened, with valves V4, V6, V8, V18 and V19 closed to effectively connect chambers 3 and 4. The chamber 4 must be empty before transfer can take place and provided that the communicating doors 10 and 8 are shut, the communicating door 9 can be opened. When the carriage is driven forward from the filling chamber 3 to engage in the drive 16 in the sealing chamber 4 which draws the carriage 19 fully into the sealing chamber 4. The communicating door 9 is then closed again and the filling chamber 3 is immediately ready to receive carriage 19 from the second entry chamber 2.

The cells in chamber 4 are heated such that the cells are maintained at a temperature of approximately 130°C and the pressure reduced back to 0.88 of an atmosphere before operations continue. This is achieved by closing valves V7 and V10 and opening valve V4 to connect chamber 4 to pumping system 43. It should be noted that the pressure is selected to be compatible with cell performance. The valve V4 is closed and the carriage is then driven to bring the first pair of container(s) 70a under the pin insertion head 150 of a pin insertion station 33 and again the locating pins 131, 132 are actuated so as to properly locate the carriage 19 in position and the thermocouple inserted to monitor the temperature of the container(s) 70. The carriage is then raised as before and the pin insertion head 150 actuated to insert the current collector pin 76 into the first pair of container(s) 70a on the carriage 19.

Subsequently the carriage 19 is lowered again and driven forward to repeat the process on the next container(s) 70b on the carriage 19.

When the pin is being inserted in the third pair of container(s) on the carriage 19, the first pair of container(s) 70a with pin 76 already inserted, will be directly beneath the welding head 34. Thus welding of the first pair of container(s) 70a can take place simultaneously with pin insertion on the third pair.

The welding and pin insertion actions continue for each pair of container(s) 70 in turn along the carriage 19, skipping the dummy container in the middle until the pin 76 has been inserted in the tenth pair of container(s) , simultaneously with welding the eighth pair. Thereafter the ninth and tenth pair of container(s) are in turn presented to the welding head 34 to complete the welding and sealing of the all containers. When the last containers have been welded, the pressure in chamber 4 is brought back up to one atmosphere Argon to assist cooling by opening valves V6 and V7 to connect chamber 4 to the argon supply. The fans 35 are then switched on.

When all the containers are completed, the thermocouple is disconnected, the locating pin withdrawn, the heater 28 and fan 35 are switched off and when the exit chamber 5 is ready, the carriage is driven forward towards the communicating door 10 and valves V6 and V7 are closed. Exit chamber 5 is prepared by balancing the pressure with that in chamber 4. This is achieved by opening valves V7 and V8 and closing valves V9, VI0, V19 and V6. The communicating door 10 can then be opened and the transfer takes place in one atmosphere of argon. Then the carriage 19 is driven forward from the sealing chamber 4 to engage in the drive 18 in the exit chamber 5 which draws the carriage 19 fully into the exit chamber 5. The communicating door 10 is then closed again and the sealing chamber 4 is immediately prepared to receive a fresh carriage 19 from the filling chamber 3.

In the exit chamber 5, the thermocouple sensor in the dummy container is again connected so that the temperature of the containers 70 can be monitored as they cool. Cooling is assisted by fans 36 which circulate the argon therein. Once the containers 70 are cooled down to a predetermined value, valve V9 is opened and air allowed into chamber 5. The thermocouple in the dummy container is then disconnected and the locks on exit hatch 11 may be released, provided that the communicating door 10 is shut. Exit hatch 11 may be opened when the pressures on either side are balanced and when the hatch 11 is open, the carriage with filled and sealed containers 70 thereon can be removed for unloading and further processing.

The exit chamber hatch 11 is then shut and locked, valve V9 closed and valve V5 re-opened to connect pumping system 43 to reduce the pressure in the exit chamber 5 to the required vacuum. When the exit chamber 5 is again ready to receive a fresher process batch of containers 70 from sealing chamber 4, valve V5 is closed and the process repeated.

Claims

CLAIMS :

1. Apparatus for filling and sealing an alkali metal container for an alkali metal energy conversion device, comprising a plurality of intercommunicating chambers, which are hermetically sealable, transfer means operable to transfer a plurality of alkali metal containers to be filled and sealed successively from chamber to chamber, vacuum means arranged for independently controlling the atmosphere in each chamber to provide predetermined pressures of inert gas in said chambers, means for independently controlling the temperatures in said chambers, filling means arranged to fill said container, by delivering to each container two predetermined amounts of an alkali metal, the filling means being located in one of said intercommunicating chambers being a first process chamber, container de-pressurising means located adjacent said filling means and sealing means located in one of said intercommunicating chambers arranged to seal the containers after filling, wherein the container depressurising means comprise means for providing a direct sealed coupling to a container in said first process chamber to enable the de-pressurisation and subsequent re-pressurisation of said coupled container between delivery of the two predetermined amounts of alkali metal to the container whilst the first process chamber is maintained at a predetermined pressure.

2. Apparatus as claimed in claim 1 in which means are provided to simultaneously position at least a first cell for filling with an alkali metal and at least a second adjacent cell for de-pressurisation and subsequent re-pressurisation in the first process chamber.

3. Apparatus as claimed in claim 1 or claim 2 in which the filling means comprise at least a pair of filling heads, a first of which provides a first predetermined guantity of alkali metal into the container before de-pressurisation and re-pressurisation and a second of which provides second predetermined quantity of alkali metal into the container after evacuation.

4. Apparatus as claimed in claim 3 in which means are provided to simultaneously position at least a third cell for a first filling, at least a second adjacent cell for evacuating and at least a first adjacent cell for a second filling.

5. Apparatus as claimed in any one of the preceding claims in which the sealing means are located in a second process chamber which is maintained at a predetermined pressure lower than that in the first process chamber during the sealing process.

6. Apparatus as claimed in claim 5 in which the second process chamber is hermetically sealable from the first process chamber and has at least one entry hatch to permit access to the sealing means.

7. Apparatus as claimed in any one of the preceding claims in which there are provided first and second entry chambers in which the containers are evacuated of air and flushed with inert gas and heated to a predetermined temperature before being transferred to a process chamber for filling with sodium.

8. Apparatus as claimed in claim 7 in which the containers are heated to a temperature in the regions of 100°C to 140°C in the first entry chamber and to a temperature in the region of 150°C to 200°C in the second entry chamber.

9. Apparatus as claimed in claim 8 in which the containers are heated to a temperature of 120°C in the first entry chamber and 180°C in the second entry chamber.

10. Apparatus as claimed in any one of the preceding claims in which there is provided an exit chamber in which the containers are cooled to a predetermined temperature before being removed from the apparatus.

11. A method of filling alkali metal electrode containers, for alkali metal energy conversion devices each container holding solid material with alkali metal having a large wetting angle to the solid material, comprising the steps of filling said containers with gas which is inert to the alkali metal; pumping a first predetermined quantity of alkali metal into the container; reducing the pressure of said gas in the container and then raising the pressure of the gas to force the alkali metal into spaces in the container; pumping a second predetermined quantity of alkali metal into the container; positioning an electrode in the container and sealing the container wherein at least three cells are simultaneously operated upon respectively to receive the first quantity of alkali metal, to be de-pressurised and re-pressurised, and to receive the second quantity of alkali metal.

12. A method as claimed in claim 11 in which the sealing operation is carried out simultaneously with the filling and de-pressurising operations.

13. Apparatus substantially as hereinbefore described with reference to or as shown in the accompanying drawings.