US3063930A - Valveless pump, particularly for fused salts or metals - Google Patents

Description

I Nov. 13, 1962 A. v. DE? PAVA 3,063,930 I VALVELESS PUMP, PARTICULARLY FOR FUSED SALTS 0R METALS Filed Dec. 26, 1957 z Sheets-Sheet 1 F g. 3 INVENTOR.

3 Sheets-Sheet 2 A. V. DE" PAVA VALVELESS PUMP, PARTICULARLY FOR FUSED SALTS 0R METALS FIG. 4

Nov. 13, 1962 Filed Dec. 26, 1957 FIG. 8

Nov. 13, 1962 A. v. DE' PAvA VALVELESS PUMP, PARTICULARLY FOR FUSED SALTS OR METALS Filed Dec. 26, 1957 3 Sheets-Sheet 3 FIGS FIG.6

r m L r FIG .7

3,063,930 Patented Nov 13, 1962 3,0fi3,930 VALVELESS PUMP, PARTICULARLY FOR FUSED SALTS R METALS Alberto Vajna de Pava, Milan, Italy, assignor to Montecatini, Societal Generale per ilndustria Mineraria e Cnimica, Milan, Italy, a corporation of Italy Filed Dec. 26, 1957, Ser. No. 705,373

Claims priority, application Italy Dec. 27, 1956 15 Claims. (Cl. 204244) The present invention relates to a system comprising a force pump particularly suited for lifting and conveying, through conduits, (liquid substances which due to their chemical aggressivity or elevated temperature (e.g. 1000 C.) do not permit utilization of pumps of a conventional kind, provided with valves or other mobile closing members. The latter would not be suited for correct operation, whether employed in continuous or discontinuous contact, with such substances, since there would occur frequent blocking, due to partial cooling down of the molten substance, or corrosion of the pump elements.

From the above it follows that a pump for lifting metals or salts in the molten state should be characterized by maximum simplicity. In the majority of cases the purpose is to overcome heads and to provide deliveries of modest magnitude only, with the greatest possible safety in operation. Good volumetric efficiency of the pump becomes of relatively lesser importance.

It is an object of the present invention to provide a force pump which is essentially constituted by only two elements: a cylinder or pump body, and a piston, valves or other mobile elements being dispensed with.

Without limiting the scope of the present invention there will now be described in detail the structure and principle of operation of a pump constructed according to a preferred embodiment of the present invention. In the drawing:

FIG. 1 is a vertical section taken at line A A of FIG. 3. The piston is at the upper end of its stroke;

FIG. 2 is a vertical section on the same plane as in FIG. 1. In FIG. 2 the piston is at the lower end of its downward stroke;

FIG. 3 is a composite of two left and right horizontal sections, the left being taken at AA' in FIG. 1, and the right being at BB in FIG. 1.

FIGS. 4 to 8 illustrate the assembly of the valveless pump in the necklace type multicell alumina electrolysis furnace described in the copending applications of De Varda and Calabria mentioned below;

FIG. 4 is a transverse section taken at the left end portion of FIG. 7, but with the modification that only one pump is employed;

FIG. 5 is a longitudinal section taken at 55 of FIG. 7 (unmodified);

FIG. 6 is a longitudinal section taken at 66 of FIG. 7 (unmodified);

FIG. 7 is a plan view of the multicell furnace; and

FIG. 8 is a transverse section taken at the left end of FIG. 7.

The pump comprises an elongated cylindrical housing or chamber C arranged with its longer axis vertical, or if desired, inclined. The chamber is closed at bottom. The vertical part of the cylinder is provided, at convenient height, with one or more ports 1 for admission of liquid.

During operation the pump should be placed with its bottom submerged in the liquid to be lifted and the latter should have a level L higher than said admission port or ports.

In chamber C is a reciprocating piston S driven by means of conventional connecting rod and crank members, not shown in the drawing, for simplicity. The

solid piston S is of cylindrical shape and has formed in its lateral surface one or more grooves 2 parallel to the axis. The length of groove 2 should be equal to the intended head of the pump, preferably.

Between the pump body and the piston there should be a slight play, to be determined in accordance with the nature of the material of which the pump is made and with the kind of liquid that is to be lifted.

When the reciprocating piston has reached the upper dead point (see FIG. 1), its bottom end is at a level higher than the port or ports 1 employed for admission of the liquid to be lifted. The liquid can thus enter the lower part of the pump body and fill it.

As soon as the piston starts its downward stroke, the admission port or ports for the liquid in the cylindrical chamber are closed by said piston. Hence the liquid is pushed towards the sole outlet available, constituted by the vertical groove or grooves 2 provided in the piston will, up to the upper end of said groove or grooves.

When the piston is at the lower dead point, the upper end of the groove or grooves 2 will be at a certain height of the pump body. At that height (see FIG. 2) the cylindrical chamber is provided with a circular channel 3 for collecting the liquid, the channel being connected to an outlet member 4 having a discharge orifice. The channel prevents further rise of the liquid between the cylinder C and the piston.

The circular channel 3 functions as a collector, enabling the pumped liquid to be collected without rising further between the cylindrical chamber and the piston.

The chamber containing the liquid to be lifted is indicated at D. It is to be understood that chamber D of FIG. 1 is representative only, since in many applications (see FIGS. 4 to 8) the pump is used to raise molten liquid from a lower level in a sealed chamber such as D to a higher level in a second chamber also sealed from the atmosphere. The second chamber may have a bottom higher than that of the first chamber, to serve as the supply vessel for a gravity feed system. The molten liquid can spill from the outlet 4 onto inclined surface E from which it passes to the second chamber (not shown in FIG. 1, but described below with reference to FIGS. 4 to 8).

Employing the same principle of operation, thegroove or grooves 2 in the longitudinal surface of the piston may be dispensed with in some cases. To supply the liquid to be lifted with the necessary path for'rising, free play may be provided between the piston and cylinder ampler than would be necessary for the hydraulic seal between the two members. The path or play may be provided by suitably profiling the piston over a height equal to the head desired. The play itself serves as a space permitting the rising of a film or thin flowing layer of the liquid to the desired level. The centering between piston and pump body is ensured by the minimum play existing between the two members in the upper zone of the piston.

In similar cases however the piston will be provided along its longitudinal axis, in correspondence with the port or ports for liquid admission, with as many ribs or projecting reliefs as there are ports, destined to provide the closing of said ports at the predetermined time, and which aid said centering.

To attain the best operative efficiency, the reciprocating movement to be imparted to the piston, should not be synchronous in the two stages of rising and descent of the piston. That is, periods of stay of the latter at the-two dead points, the upper and lower, should not be equal and should not be instantaneous. The movement instea should have the following characteristics:

(a) The rising of the piston should be comparatively slow and of longer duration, as compared with the movement of descent. For instance, the rising should be with a speed equal to 20-30% of the total duration of one cycle of the piston.

(b) There should be a comparatively long stay of the piston at the upper dead point, to enable the liquid to enter through the admission ports and to fill the lower circular chamber. This stay should have a duration generally equal to 50-70% of the total duration of one cycle of the piston.

(c) The descent of the piston should be with a comparatively rapid velocity as compared with the afore-said rising movement, with a duration equal, for example, to about 10% of the total duration of one piston cycle.

In practice a reciprocating movement having the aforesaid characteristics is readily provided through control cams of conventional design (not shown).

The theoretical delivery of the pump at each stroke is determined by the volume of the cylindrical chamber, up to the leve of the admission port 1, less the volume of the vertical groove or grooves provided in the piston wall.

To make the principle of construction and operation of the pump of the invention more readily understandable, FIG. 3 of the appended drawings indicates two horizontal sections of the pump. The left half section (taken along A A of the pump body is at the height of the inlet ports for the liquid. The right half is a section (taken along BB) of the pump body at the height of the collecting channel and of the discharge port for the liquid.

Due to its extreme constructive simplicity the pump can be built of any material selected to fulfill special operating requirements.

The liquids to be lifted, the temperatures and the surronndings in which the pump is to be employed determine the nature of the materials to be used. The carbon steels permit operation at a temperature of 450-500 C. Some stainless steels, such as a strongly alloyed steel having an austenitic structure, such as type A181 310 standards (25% Cr, 20% Ni), may be employed to advantage, up to temperatures of the order of 800900' C., for lifting liquids which do not display chemical aggressivity against the said steels.

Among the special steels having a high content of non-ferrous elements there may be selected, to advantage, alloys of the type of commercial Hastelloy (60% Ni, 20% Mo. 18-20% Fe), or alloys of the Multimet type (N-155) based on Cr, Ni, Co, Fe, and others.

Among the non-metallic materials which due to resistance to high temperatures and chemical inertness to the liquids to be lifted, for instance fused salts, are suited for the making of the pumps, are carbonaceous materials such as compact carbon agglomerates, and above all graphite.

In the field of utilizable materials defined as refractories proper are the silico-aluminous materials having a structure as compact as possible, as well as refractories of special type, such as metal oxides treated at high temperatures, for example sinterized A1 sinterized MgO, etc.

In the case of pumps built with said non-metallic materials it is obvious that said materials will be employed only for the making of the pump body and piston. The latter then will be rigidly connected with a suitable metallic rod which serves for the purpose of connecting said piston mechanically with the drive members enabling to actuate the pump. In the accompanying drawings, which are only diagrammatical, said rod has not been represented.

If the liquid to be lifted is to be maintained at an elevated temperature for the purpose of avoiding solidification, the pump may be provided with or coated with a suitable heating jacket within which an appropriate fluid is circulated, or it may contain, incorporated with the thickness of the body, a system of electric resistors conveniently insulated, or said resistors may be merely wound up externally around the pump body, if the latter is made of a material which is a good heat conductor. For the sake of simplicity, the heating systems here mentioned have not been indicated in the accompanying drawings.

According to a further embodiment of the invention, the pump which itself has no heating members, may be accommodated in and be operated in the vessel or chamber containing the liquid at high temperature (for example 1000 C.) to be lifted. In such case, the stiff metallic rod controlling the piston will be conveniently extended outside said chamber, which of course is provided with a heat-insulating coating or lining, to enable connection with suitable mechanical drive members placed outside.

Merely by way of example, but without limitative intent, there are given, with numerical data, some applications of pumps constructed in accordance with the invention, for lifting molten metals or salts of various kinds.

Example 1 The liquid to be lifted comprised a fused fluorinated bath, with suitable additions, and containing dissolved therein from 3 to 9% of aluminum oxide. Said bath was similar to those conventionally used with furnaces for the production of aluminum metal by fused salt electrolysis. The operating temperature was about 940 C., that is, a temperature quite higher than the critical temperature at which the bath attains such a viscosity as to render its passage diflicult through channels or pipings. Said bath, in the specific case of the present example, was to be lifted from the lower chamber to the higher chamber in a necklace type multicell furnace substantially as described in G. De Varda U.S. application Serial No. 587,985, filed May 29, 1956 (now Patent 2,952,592), and G. Calabria U.S. application 670,785, filed July 9, 1957 (now Patent 2,991,240). The total level difference to be overcome was cm. To ensure bath circulation with a maximum of 200 ml./sec. in the circuit of the furnace now mentioned, there were directly installed in the interior of the lower chamber, in which was maintained an atmosphere substantially deprived of 0 two twin pumps in accordance with the constructional and operational principles set forth hereinbefore, each of which possessed dimensions and characteristics as hereinafter defined: The material was graphite. The inner diameter of the lower cylindrical chamber was 62 mm. The piston stroke was 200 mm., which signifies a total volume of the lower cylindrical chamber equal to 600 ml. The piston moving in the interior of the pump was provided with two vertical grooves 2, diametrically opposed, of 800 mm. length and 0.5 sq. cm. cross-section, each having a total volume of 80 ml. With these specifications, the theoretical delivery of one single pump was 520 ml. per pump shot. Considering the clearance volume and the minor losses due to the play between piston and cylinder, there was in practice a useful delivery of about 450 ml. per pump shot, with a volumetric efiiciency of Each of the two pumps was driven with a timing of 12 to 13 pump shots per minute, thus providing an effective delivery unit of ml. per second, which proved to be sufficient for the desired purpose. The mechanical power absorbed for the operation of each individual pump proved to be very low and, at any rate, such as not to cause any worry with respect to possible, vibrations and, therefore, the mechanical resistance of the material of which the pump was made, was not prejudiced or lowered under the severe operating conditions required. Owing to the characteristics of the necklace type multicell furnace, continuous operation of the pumps was not needed, and in the various intervals of rest and starting no disturbances or troubles arose, such as would have been due to blocking or other reasons. The twin pumps can be operated so as to raise liquid alternatively or at the same time.

assass n Example 2 A pump quite analogous in its constructional and operational principle, to the pump of Example 1, was built of carbon steel and was designed to lift molten lead that had to be fed at the temperature of 350 C. to a reactor, for the production of a lead-and-sodium alloy. A level difference of 140 cm. was to be overcome. The pump was accommodated with its bottom submerged in an ample crucible, wherein the lead was held at the desired temperature, and sheltered from air. The pump body was heated in this case by an electric resistor externally wound around said body and conveniently insulated, which ensured for the whole pump a uniform temperature of 350 C.

The internal surfaces designed to contact each other, the piston and internal surface of the pump body, had been ground so as to be able to slide easily with a play of the order of 0.2 mm. With a volume of the lower cylindrical chamber equal to 1000 ml. and a volume of the two grooves provided at diametrically opposed regions in the piston, of 280 ml. (cross-section 1 sq. cm. each), the theoretical delivery was 720 ml. per pump shot. With a frequency of 20 shots per minute, considering the clearance volume, the actual lift of molten lead was about 13 liters, which is equal to 130-140 kg. per minute. The pump proved able to work under such conditions continuously, even for 5 to 6 hours, without the slightest inconvenience.

Example 3 A pump analogous to that mentioned in Example 1 was made of graphite, but the volume of its lower cylindrical chamber was 700 ml. It was used to lift molten aluminum coming from the collecting pocket of a furnace for fused salt electrolysis and destined to be conveyed to an ingot mould. In this case the whole pump body was kept at a temperature of 700 -C., which is necessary to enable easy lifting of the aluminum in the molten state. The heating was by means of a system of electric resistors, housed with suitable heatand electricinsulation within special grooves provided in the thickness of the pump body. As a matter of fact, in this case it was not possible to house the whole pump, as in Example 1, in a closed chamber, and the contrivance now described had to be resorted to, to obtain the desired temperature. The difference in level to be overcome was 120 cm. The piston of the pump was provided with a single groove of 1 sq. cm. cross-section. The theoretical delivery was 580 ml. per pump shot. The actual delivery was 500 ml. per shot, that is, the volumetric efliciency was of the order of 86%. The pump was driven in discontinuous manner, that is, with periods of rest, at a frequency of shots per minute. Thereby quite regular lifting of molten aluminum at a rate of 8 litres (i. e. about kg.) per minute was attained, which is considered satisfactory, considering the technological requirements of transfer of molten metal from a furnace to an ingot mould.

It is to be understood that, in its specific application as part of a transfer means for a gravity system of a molten bath electrolyte circulatory system in multicell electrolytic furnaces, the piston and pump cylinder can be used in place of the liquid transfer means described in the application Serial No. 670,785 mentioned above. The orifice 4 can supply the molten material directly to the upper chamber or to a conveying conduit or sloped surface E connecting the lower-bottomed chamber to the upper-bottomed chamber of the gravity system.

This transfer system is illustrated in FIGS. 4 to 8, which are now described. Like numerals and letters designate the same elements as in FIG. 1 to 3.

Referring to FIG. 4, the pump piston S is provided with an operating mechanism B, including an eccentric drive g. The pump cylinder C has two lower liquid intakes at 1 and 5. The molten liquid raised from liquid 6 body 8 is fed by spout 4' to the sloping ledge surface 41; At 4 2 is a return conduit for overflow from upper chamber 7 to lower chamber 6. Chambers 6 and '7 are provided with overflow outlets 60 and 70. FIG. 8 is substantially like FIG. 4, the difference being that two pumps are employed in FlG. 8, as mentioned above. The two pumps are also shown in F168. 6 and 7.

FIG. 7 is a plan view of the furnace. The pumps shown in chamber 6, at the left end, raise the molten cryolite bath from which the liquid flows through passages 11 provided in the upper parts of each of the terminal electrodes 131 and 132 (FIG. 5) and of each of the intermediate bipolar electrodes 130. The bath liquid circulates through the necklace of cells, through passages 11 and 11 (FIGS. 6 and 7), being replenished with alumina introduced at 111 and 112. The larger fixed covers for the furnace are indicated in FIG. 7, but removable covers ususally used for electrolysis gaps 10 are not shown. carbonaceous anode 131 is provided with embedded electric conductors 14. Carbonaceous cathode electrode 132 is likewise provided with embedded conductors 12.

I claim:

1. A valve-less force pump system for raising corrosive, hot, molten liquids, comprising means providing an outer chamber for liquid, a piston force pump device in the chamber, said device comprising a housing having a closed bottom end, said device further comprising an upwardly-downwardly extending recirprocating piston loosely fitted in said housing with play sutficient to permit the rising of a thin flowing layer of said liquid between said piston and said housing during downward movement of said piston, an inlet port for the liquid in the lower side portion of the housing at a distance above the bottom end thereof, the piston opening and closing the inlet port in its stroke cycle, said piston device having an upwardly extending open surface groove for upward flow of liquid from a chamber formed in the lower portion of the housing when the piston is moved downwardly to force the liquid upwardly, said housing being provided with outlet means for flow of the raised liquid therefrom and having in its upper portion a peripheral passageway communicating with said groove and with said outlet means for reception of the raised liquid and for passing it to said outlet means.

2. A valve-less force pump system for raising corrosive, hot, molten substances, comprising means providing an outer chamber for liquid, a piston force pump device in the chamber, said device comprising a housing having a closed bottom end, said device further comprising an upwardly-downwardly extending reciprocating piston loosely fitted in said housing with play sufficient to permit the rising of a thin flowing layer of said liquid between piston and said housing during downward movement of said piston, an inlet port for the liquid in the lower side portion of the housing at a distance above the bottom end thereof, the piston opening and closing the inlet port in its stroke cycle, said piston device having an upwardly extending open surface groove for upward flow of liquid from a chamber formed in the lower portion of the housing when the piston is moved downwardly to force the liquid upwardly, said housing being provided with outlet means for flow of the raised liquid therefrom and having in its upper portion a peripheral passageway communieating with said groove and with said outlet means for reception of the raised liquid and for passing it to said outlet means, said passageway comprising an inner peripheral channel formed in the housing wall at a height equal to the proposed head of the raised liquid above the level in the said outer chamber.

3. A valve-less force pump system for raising hot, corrosive, molten substances, comprising means providing an outer chamber for liquid, a piston force pump device in the chamber, said device comprising a housing having a closed bottom end, said device further comprising an upwardly-downwardly extending reciprocating piston loosely fitted in said housing with play sufficient to permit the rising of a thin flowing layer of said liquid between said piston and said housing during downward movement of said piston, an inlet port for the liquid in the lower side portion of the housing at a distance above the bottom end thereof, the piston opening and closing the inlet port in its stroke cycle, said piston device providing therein an upwardly extending passage for upward flow of liquid from a chamber formed in the lower portion of the housing when the piston is moved downwardly, said passage comprising an open groove formed in the lateral surface of the piston, said housing providing in its upper portion a passageway communicating with said passage for reception of liquid from the latter, the passageway comprising an inner peripheral channel formed in the housing wall at a height equal to the proposed head of the raised liquid above the level in the said outer chamber, said passageway having an exit means for passage of the raised liquid therefrom, the upper end of the groove being substantially at the level of the channel when the piston is at lower dead end position.

4. The system defined in claim 1, the housing and piston being of graphite, the system being suitable for use at 700 C. for lifting molten aluminum.

5. The system defined in claim 1, the housing and piston being of carbon steel, the system being suitable for use up to 450 C.

6. The system defined in claim 1, for use at high temperatures for pumping corrosive liquids, the housing and the piston being of stainless steel.

7. A valve-less force pump system for raising hot, corrosive, molten substances, comprising means providing an outer chamber for liquid, a piston force pump device in the chamber, said device comprising a housing, said device further comprising an upwardly-downwardly extending reciprocating piston loosely fitted in said housing with play sumcient to permit the rising of a thin flowing layer of said liquid between said piston and said housing during downward movement of said piston, an inlet port for the liquid in the lower side portion of the housing at a distance above the bottom end thereof, said housing being closed below said inlet port, said piston device providing therein an upwardly extending passage for upward flow of liquid from a chamber formed in the lower portion of the housing when the piston is moved downwardly, said passage comprising an open groove formed in the lateral surface of the piston, the groove being off-set peripherally from the inlet port, said housing providing in its upper portion a passageway communicating with said groove for reception of liquid from the latter, the passageway comprising an inner peripheral channel formed in the housing wall at a height equal to the proposed head of the raised liquid above the level in the said outer chamber, said passageway having an exit means for passage of the raised liquid therefrom, the upper end of the groove being substantially at the level of the channel when the piston is at lower dead end position, said inlet port being below but closely adjacent to the lower end of the piston when the latter is at the end of its upper stroke, whereby when the piston arrives at its upper end position the inlet port is opened and when it starts its downward stroke it closes the inlet port.

8. The apparatus defined in claim 1, said means providing an outer chamber for liquid comprising enclosure means in which the housing and piston are enclosed and isolated from the atmosphere, the enclosure means having temperature maintenance means to prevent solidification of the liquid, drive means for reciprocating the piston outside the enclosure means, and a metal rod connected to the piston and extending outside the enclosure means in operative connection with the drive means.

9. A high temperature apparatus comprising a structure providing a processing zone containing a hot, corrosive, molten material, and providing two chambers for the molten material, a first one of the chambers communicating with the processing zone to receive the molten material therefrom, and the second communicating with the processing zone to return molten material thereto, each having a liquid head, the liquid head of the second chamber being higher than that of the first chamber, said molten material being caused to circulate by gravity from said second chamber, through the processing zone and back to said first chamber, by differences in liquid head between the processing zone and the said two chambers, a valve-less apparatus to transfer molten material from the first chamber to the second, comprising a piston force pump device disposed in said first chamber, said device comprising a piston housing and an upwardly-downwardly reciprocating piston loosely fitted in said housing, an inlet port for the molten material in the lower portion of the housing, said piston housing having a closed bottom end below said inlet port, the piston opening and closing the inlet port during its operating cycle, said piston device having an upwardly extending surface groove for upward flow of molten material from a chamber formed in the lower portion of the housing when the piston is moved downwardly to push the material up wardly, said piston housing providing in its upper portion a passageway communicating with said groove for reception of molten material from the latter, said passageway having an exit means for passage of the raised molten material to the second chamber.

10. An apparatus comprising a structure providing a processing zone containing a molten liquid, and providing two chambers for liquid, a first one of the chambers communicating with the processing zone to receive molten liquid therefrom, and the second communicating with the processing zone to return liquid thereto, means for maintaining a liquid head in the second chamber higher than that in the first chamber, said bath being caused to circulate by gravity from said second chamber, through the processing Zone and back to said first chamber, by differences in liquid head between the processing zone and the said two chambers, a valve-less apparatus to transfer liquid from the first chamber to the second, comprising a piston force pump device disposed in said first chamber, said device comprising a piston housing in said chamber, an upwardly-downwardly reciprocating piston loosely fitted in said housing with play sufficient to permit the rising of a thin flowing layer of said liquid between said piston and said housing during downward movement of said piston, an inlet port for the liquid in the lower side portion of the housing, said piston housing having a closed bottom end below said inlet port, said piston having an upwardly extending open surface groove for upward flow of liquid from a chamber formed in the lower portion of the housing when the piston is moved downwardly to force the liquid in the chamber upwardly, said groove being offset peripherally with respect to the inlet port, said housing providing in its upper portion a passageway communicating with said groove for reception of liquid from the latter, the passageway comprising an inner peripheral channel formed in the housing wall, said passageway having an exit means for passage of the raised liquid to the second chamber, said inlet port being below but closely adjacent to the lower end of the piston when the latter is at the end of its upper stroke, whereby when the piston arrives at its upper dead end position the inlet port is opened and when it starts its downward stroke it closes the inlet port, the upper end of the groove of the piston being substantially at the level of the peripheral channel when the piston is at lower dead end position.

11. A valveless force pump system for lifting molten fluorine compounds, comprising means providing a closed outer chamber for the molten liquid, a piston force pump device in the chamber, said device comprising a housing of graphite having a closed bottom end, said device further comprising an upwardly-downwardly extending reciprocating, graphite piston loosely fitted in said housing with play sufficient to permit the rising of a thin flowing layer of said liquid between said piston and said housing during downward movement of said piston, an inlet port for the liquid in the lower side portion of the housing at a distance above the bottom end thereof, said housing being closed below said port, the piston opening and closing the inlet port in its operating cycle, said piston device having an upwardly extending surface groove for upward fiow of liquid from within the lower portion of the housing when the piston is moved downwardy to force liquid upwardly, said housing being provided in its upper portion with a peripheral passageway communicating with said groove for reception of liquid from the latter, said passageway having an exit means for passage of the lifted liquid therefrom.

12. An electrolysis furnace comprising a heat-insulated structure containing a plurality of electrolytic cells, the cells containing a molten bath to be electrolyzed and opposed cathodes and anodes, the insulated structure providing two adjacent chambers therein, a first one of said chambers communicating with a cell to receive molten bath liquid therefrom, and the second communicating with another cell to return molten bath liquid thereto, each chamber having a liquid head, the liquid head of the second chamber being higher than that of the first chamber, said bath being caused to circulate by gravity among the cells during the electrolysis, from said second chamber, through the cells, and back to said first chamber, by difierences in head between the various cells and the said two chambers, a communicating duct in said insulated structure between the two chambers, the duct communi cating with the first chamber above the liquid level of the latter, an apparatus in said insulated structure to transfer molten bath liquid from the first chamber to the second, comprising a piston pressure pump device in the first chamber, said device comprising a housing and further comprising an upwardly-downwardly extending reciprocating piston loosely fitted in said housing with play sufiicient to permit the rising of a thin flowing layer of said liquid between said piston and said housing during downward movement of said piston, an inlet port for the liquid in the lower side portion of the housing at a distance above the bottom end thereof, said housing being closed below said port, said piston having a groove formed in its lateral surface providing an upwardly extending passage for upward flow of liquid from the lower portion of the housing when the piston is moved downwardly, the groove being peripherally offset from the inlet port, said housing being provided in its upper portion with a passageway communicating with said groove for reception of liquid from the latter, said passageway comprising an inner peripheral channel formed in the housing wall at a height equal to the proposed head of the raised liquid above the level in the said chamber, said passageway having an exit means for passage of the raised liquid therefrom to the second chamber.

13. A valve-less force pump system for lifting molten lead, comprising means providing an outer chamber for molten lead, a piston force pump device in the chamber, said device comprising a housing, said device further comprising an upwardly-downwardly extending reciprocating piston loosely fitted in said housing with play sufficient to permit the rising of a thin flowing layer of said liquid between said piston and said housing during downward movement of said piston, an inlet port for the molten lead in the lower side portion of the housing at a distance above the bottom end thereof, said housing being closed below said inlet port, said piston having formed therein an upwardly extending open surface groove for upward flow of molten lead from within the lower portion of the housing when the piston is moved downwardly to force lead upwardly, said groove being displaced with respect to the inlet port, said housing being provided in its upper portion with a passageway communicating with said groove for reception of liquid from the latter, said passageway comprising an inner peripheral channel formed in the housing wall at a height equal to the proposed head of the raised liquid above the level in the said chamber, said passageway having an exit means for passage of the raised liquid therefrom.

14. The apparatus defined in claim 12, the pump housing and piston being of graphite.

15. The apparatus defined in claim 12, the pump housing and piston being of stainless steel.

References Cited in the file of this patent UNITED STATES PATENTS 732,169 Chapman June 30, 1903 2,250,164 Minden July 22, 1941 2,451,492 Johnson Oct. 19, 1948 2,528,210 Stewart Oct. 3.1, 1950 FOREIGN PATENTS 319,487 Germany Mar. 9, 1920

Claims (1)

1. A VALVE-LESS FORCE PUMP SYSTEM FOR RAISING CORROSIVE, HOT, MOLTEN LIQUIDS, COMPRISING MEANS PROVIDING AN OUTER CHAMBER FOR LIQUID, A PISTON FORCE PUMP DEVICE IN THE CHAMBER, SAID DEVICE COMPRISING A HOUSING HAVING A CLOSED BOTTOM END, SAID DEVICE FURTHER COMPRISING AN UPWARDLY-DOWNWARDLY EXTENDING RECIRPROCATING PISTON LOOSELY FITTED IN SAID HOUSING WITH PLAY SUFFICIENT TO PERMIT THE RISING OF A THIN FLOWING LAYER OF SAID LIQUID BETWEEN SAID PISTON AND SAID HOUSING DURING DOWNWARDLY MOVEMENT OF SAID PISTON, AN INLET PORT FOR THE LIQUID IN THE LOWER SIDE PORTION OF THE HOUSING AT A DISTANCE ABOVE THE BOTTOM END THEREOF, THE PISTON OPENING AND CLOSING THE IN-

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