IE43479B1 - A liquid-sealed pump - Google Patents

Description

This invention relates to a liquid sealed pump in which air is sucked and exhausted by suction and discharge actions of liquid in a tank.

Vacuum pumps which have heretofore been used in vacuum drying apparatus include vapour ejector pumps, oil rotating vacuum pumps, and liquid-sealed type vacuum pumps. In the case of the vapour ejector pump, a multi-stage ejector must be used to obtain the desired ultimate pressure and a great amount of vapour is used up, naturally resulting in high drying costs. In the case of the oil rotating pump the vapour is sucked and hence the performance is materially lowered by such factors as deterioration of oil and decrease in exhaust velocity. In order to eliminate these drawbacks, the pump and oil tank are heated by vapour or electrical heat to heat the vapour above its condensation temperature into a non-condensed gas, which is discharged to prevent water from being mixed with the oil. In the conventional liquid-sealed type vacuum pumps, the ultimate pressure desired cannot be obtained even if the circulating liquid temperature is decreased to about 5°C, with the result that low temperature vacuum drying 2. cannot be accomplished. Further, conventional vacuum pumps suffer from various disadvantages. For example, due to the mechanical clearances which are inevitably present in the pump, some of the gas sucked into the pump is retained in the clearances and cannot be completely discharged so that it is very difi'cult to achieve a high degree of vacuum. Also lubricating oil is emulsified with the liquid content under suction to hamper the lubricating action. Also if entry of a large amount of liquid is made during suction phenomena such as liquid hammer and knocking occur and a cumbersome starting operation is involved.

It is therefore an object of this invention to provide a liquidsealed pump in which the above-mentioned disadvantages are overcome or alleviated.

According to the invention, a liquid-sealed pump includes at least one liquid containing chamber, a mechanism for alternately increasing and decreasing the pressure of liquid in said liquid containing chamber, a suction chamber into which air can be drawn and which is connectable to the liquid containing chamber, valve means operable to admit air to said liquid containing chamber from the suction chamber when the liquid pressure in said liquid containing chamber is low and to allow air and said liquid to be discharged from said liquid containing chamber when said liquid pressure is high, an outlet for at least air discharged from said liquid containing chamber, means for returning at least part of the discharged liquid to the liquid containing chamber, and means for cooling the air drawn into the pump via the suction chamber.

The present invention provides an arrangement wherein liquid within the liquid containing chamber is alternately increased and decreased in pressure by said mechanism and utilization of the operation of sucking and discharging of the liquid is made to suck air from the suction chamber so 3. that for example, a substantially complete vacuum may easily be obtained.

In addition, the only mechanism required is the mechanism for increasing and decreasing the liquid pressure and consequently no complicated mechanism is required as in the prior art. Moreover, the construction is very simple so that large sized pumps can be easily designed. In addition, in the pump of the present invention, it is not necessary to use lubricating oil as is required in the prior art and hence the present invention provides various advantages, which cannot be achieved by prior art vacuum pumps e.g. the operation is not hampered by emulsification of the oil with the liquid; liquid hammer and knocking due to entry of a quantity of liquid cannot possibly occur; smooth and accurate operation may be secured; starting can be achieved without difficulty; and the utilization range is extremely wide.

In the accompanying drawings: Figure 1 is a partially cut-away front elevation showing a vacuum pump according to one embodiment of the present invention; Figure 2 is a sectional view showing a principal part of Figure 1; Figure 3 is a partially cut-away front elevation showing another embodiment according to the invention; Figure 4 is a sectional view showing a principal part of Figure 3; Figure 5 is.a partially cut-away front elevation showing a further embodiment according to the invention; Figure 6 is a transverse cross-sectional top plane view of Figure 5 Figure 7 is a longitudinal sectional side view showing a principal part of Figure 5; Figure 8 illustrates a modification of the embodiment of Figure 5; and Figures 9 to 15 illustrate respective vacuum treatment systems for food or the like to which the present invention can be applied. 4.

Referring to Figures 1 and 2, which illustrate one embodiment according to the present invention, there are shown a pair of left and right liquid containing cylinders 1 and 1^ the upper ends of which are placed in communication with each other while the lower ends are placed in communication through a cylinder 2. A piston 3 is closely fitted in the cylinder 2 to isolate the pair of left and right liquid containing cylinders 1 and 1^ and is provided with a piston rod 16 which is reciprocated by a suitable mechanism (not shown). The communicating portion at the upper end is provided with an air exhaust port 4 at the top thereof and a water discharge port 5 at the side thereof.

Slightly below the communicating portion between the liquid containing cylinders 1 and 1^ are mounted partition walls 7, each being formed with a discharge port 6 provided with a narrow, liquid return pipe 8 and fitted with a discharge valve 9. Each valve 9 is arranged to be open only when liquid within its associated liquid containing cylinder is discharged. A suction pipe 12 is connected to each liquid containing cylinder 1 and 1^ just below the associated partition wall 7. Each suction pipe 12 communicates with a smaller chamber 11 located within a suction chamber 10. The smaller chamber 11 communicates with the suction chamber 10 through a port 14 formed at the lower end thereof and having an intake valve 13 fitted therein.

The suction chamber 10 is designed so that the upper end portion thereof may be cohnected with a desired vacuum chamber, for example, such as a vacuum drying chamber for food, and a helical cooling water pipe 15 is interiorly provided at the upper part of the suction chamber to condense the water vapour in the air drawn into the suction chamber.

With the above-mentioned construction of the present invention, when the upper part of the suction chamber 10 is connected, for example, . with the vacuum drying chamber for food and the piston 3 is reciprocated within the cylinder 2, the liquids within the left and right liquid containing cylinders 1 and I1 are discharged alternately through the respective discharge valve 9 and air and liquid from the chamber 10 is simultaneously drawn into the cylinders P and 1 through the intake valves 13.

That is, when the piston 3 is moved to the right as shown in the drawing the liquid within the left-hand liquid containing cylinder is sucked into the cylinder 2 thereby forming a vacuum in the upper portion of the cylinder 1. At the same time the liquid and air within the suction chamber 10 is sucked into the liquid containing cylinder past the intake valve 13 and through the suction pipe 12.

Also as the piston is moved to the right a part of the liquid in the right hand liquid containing cylinder P along with the air contained therein, causes the discharge valve 9 of the cylinder 1^ to open. As a result, liquid and air are discharged through the discharge port 6, whereafter the air escapes through the exhaust port 4. Liquid thereby collects above the partition wall 7 and when this reaches the level of the water discharge port 5, it flows off through the port 5. When the piston 3 is subsequently moved to the left, the liquid and air previously sucked into the left-hand liquid containing cylinder 1 are expelled through the discharge valve 9. A vacuum forms just below partition 7 in liquid containing cylinder 1^ and at the same time the suction pipe 12 of the cylinder 1^ sucks the liquid and air within the suction chamber 10 through the appropriate intake valve 13. This cycle of operation may be repeated so that the food vacuum chamber is gradually deaerated.

In the above embodiment, the liquid return pipe 8 positioned at the discharge valve 9 serves when the liquid is expelled under pressure from 6. one of cylinders 1, l\ to return part of the liquid to said one cylinder so as to maintain the interior of said one cylinder in a vacuum condition.

While the pair of left and right liquid containing cylinders 5 have been provided in the above-mentioned embodiment in order to fully utilise the reciprocating motion of the piston, it will be understood that a single cylinder may of course be provided. In addition, it is to be understood that other mechanisms than a piston could be used to alternately increase and decrease the pressure of liquid in the liquid containing cylinders and liquids used may include water, oil, sulfuric acid, etc, in accordance with the purpose of use.

Referring now to Figures 3 and 4, which illustrate another embodiment, there are shown a pair of left and right liquid containing internal cylinders 17 and 17^ having upper ends which are open and lower ends which are in communication through a cylinder 18. Extending around the exterior of the upper parts of the liquid containing internal cylinders are cooling coils 19 connected to a supply of a cooling medium. Fitted within the cylinder 18 is a piston 20 to be reciprocated by a suitable mechanism so that the liquid within the cylinder 18 may be sucked and discharged alter20 nately to withdraw liquid from and supply liquid to the liquid containing internal cylinders 17 and 17^.

Liquid containing external cylinders 21 and 2p are positioned externally of the upper portions of the aforementioned liquid containing internal cylinders 17 and The upper ends of the external cylinders communicate with each other through a communicating cylinder 22. A liquid discharge valve 24 with a small opening 23 is mounted at the connection of each outer cylinder 21 and 211 with the communicating cylinder 22. Suction valves 25 are provided at the lower ends of the external cylinders, and heat 7. 3479 «changing spiral fins 26 formed of aluminium are affixed to the outer leripheral surfaces of the external cylinders.

The liquid containing external cylinders 21 and 211 are placed n suction chamber cylinders 28, 28^ each covered with a layer of insulating laterial 27, 27^ respectively. The suction chamber cylinders 28 and 28^ ire formed with suction ports 29 at the upper ends thereof.

Further, the aforementioned communicating cylinder 22 is formed /ith an air and liquid discharge port 30, and at the upper part of the (iquid discharge valve 24 there is provided a plate 32 having a stopper 31 /rejecting from the lower surface thereof for limiting movement of the valve ’4. A through hole 33 formed in the upper part of the liquid containing jxternal cylinders 21 and 2p is provided to decrease the height of water lead, and the suction valve 25 has an associated stopper 34.

With the above-mentioned construction of the present invention, ’/hen the suction ports 29 are connected, for example, with the food vacuum drying chamber to be evacuated and the piston 20 is reciprocated within the cylinder 18, the liquids within the pair of left and right liquid containing internal cylinders 17,17^ and liquid containing external cylinders 21, 21^ are oscillated. This causes air to be sucked in through the respective suction valve 25 from the respective suction chamber and liquid with air to be discharged through the respective discharge valve 24.

This is, for example, when the piston 20 is slidably moved rightwards as shown in Figure 3, the liquid within the left-hand liquid containing internal cylinder 17 is sucked into the cylinder 18 thereby forming a vacuum in the upper portions of the liquid containing internal cylinder 17 and liquid containing external cylinder 21. At the same time the air sucked through the suction port 29 is cooled by the heat exchanging spiral fins 26 of the suction chamber cylinder 28 to partially condense the water vapour in 8. the air, the condensed water vapour then being sucked into the liquid containing external cylinder 21 through the suction valve 25.

Also a part of the liquid in the liquid containing internal cylinder 17 and liquid containing external cylinder 21 along with air contained therein causes the discharge valve 24 to open when the piston 20 is slidably moved rightwards. As a result, the liquid and air are discharged into the communicating cylinder 22 from which they are discharged through the air and liquid discharge port 30. When the piston 20 is subsequently slidably moved leftwards, the operation of the two sides reverses.

This cycle of operation may be repeated so that the food drying chamber is gradually evacuated. The small opening 23 provided in each liquid discharge valve 24 allows part of the liquid discharged through the valve 24 to return to its associated liquid containing internal cylinder 17(17^ and liquid containing external cylinder 21, 21^ to retain the cylinders in a vacuum condition. The cooling coils 19 positioned around ι the liquid containing internal cylinders 17 and 17 may serve to cool the liquid temperature down to 5-10°C to enhance the degree of vacuum to about 0.008 to 0.16 Kg/cnA Further referring to Figures 5, 6 and 7, which illustrate another embodiment according to the present invention, there is shown a pair of external cylinders 35 each defining a suction chamber and having an outer peripheral surface covered with an insulating material 351 and formed with an air intake opening 36 at one side upwardly thereof. At the bottom of each external cylinder 35 there is formed an intake opening 37, which communicates with opposite sides of a liquid tank 39 having a cylinder 38 therein. The liquid tank 39 is divided into two sections by means of a piston 40 slidable within the cylinder 38. 9.

Liquid containing internal cylinders 41, each having exterior exchanging spiral fins 41^ are placed within the aforementioned rnal cylinders 35. A number of exhaust ports 42 extend between the im of each internal cylinder and the liquid tank 39 and are positioned nd the intake opening 37. A guide cylinder 45 with a flange 44 nding above the exhaust ports 42 is secured to cylinder cover 43 tioned centrally on the bottom of each internal cylinder. An annular ust valve 46 slidably mounted around the guide cylinder 45 is movable nd down under liquid pressure to open and close the exhaust ports 42. Ive control member 48 mounted on the upper end of an intake valve 47 opening and closing the intake opening 37, is upwardly biased by means spring 49, and is slidable within the cylinder cover 43. The intake e 47 is formed of a hollow or other buoyant material, and the bottom eof has a pressure plate 50 attached thereto.

Air separating chambers 51 have their lower portions placed iriorly of the liquid containing internal cylinders 41 respectively e their upper portions extend into a cooling water chamber 52 placed •e the pair of liquid containing internal cylinders 41. The upper ends ;he chambers 51 are provided with an air discharge opening 55 that may ipened and closed by a valve 54 having a float 53. A middle portion of ι chamber 51 has an overflow opening 56 in communication with the liquid ;aining internal cylinder 41, and a lower end is provided with a disced liquid pipe 57, the opposite end of which is open to the cooling ir chamber 52. A cooling coil 58 connected to a supply of a cooling ium is provided in the central portion of the cooling water chamber 52 :oo1 the liquid within the cooling water chamber 52. Above the pipe there is provided an air exhaust port 59 and at the side thereof there provided an overflow liquid discharge pipe 60. The opposite lower . portions of the cooling water chamber 52 and the opposite lower portions of the liquid tank 39 are connected by circulating pipes 62, each having a check valve 61 to prevent back-flow of liquid from the liquid tank 39.

In the drawings, the reference numeral 63 designates an air cushion chamber located above the overflow opening 56 in the liquid containing internal cylinder 41, numeral 64 represents a piston rod reciprocable by a suitable mechanism to move the piston 40, numeral 65 represents a flow control valve mounted in the circulating pipe 62, numeral 66 represents a separating plate mounted on the cooling water chamber 52, numeral 67 indicates an insulating material for the cooling water chamber 52 and liquid tank 39, and numeral 68 indicates a support frame for the intake valve 47.

With the above-mentioned construction of the present invention, when the air intake ports 36 are connected, for example, with the food vacuum drying chamber to be evacuated and the piston rod 64 is driven to cause the piston rod 40 to reciprocate, any condensed liquid within the pair of left and right external cylinders 35 is drawn alternately through the respective intake valves 47, into the liquid tank 39 for subsequent discharge through the respective exhaust valves 46.

That is, for example, when the piston 40 is slidably moved from the position shown in Figure 5 to the left, the condensed liquid in the right-hand external cylinder 35 is sucked into the liquid tank 39 by the opening of the intake valve 47 due to the suction pressure created by the piston 40 thereby to produce a vacuum in the upper portion of the right hand external cylinder 35. Air (saturated with vapor) is thus sucked through the right hand air intake port 36 and into the tank 39, the air being cooled by the heat exchanging spiral fins 41^ to cause partial condensation of water vapour in the air. At the same time, the exhaust 11. 4347© valve 46 of the right hand liquid containing internal cylinder 41 is maintained in a closed condition due to the suction pressure created by the piston 40.

In the left-hand external cylinder 35, the exhaust valve 46 of the exhaust ports 42 is opened at the same time as the intake valve 47 is closed due to the increase in liquid pressure within the liquid tank 39 to cause the liquid and air in the liquid tank 39 to the left of the piston 40 to be discharged into the left hand liquid containing internal cylinder 41. The air discharged into this cylinder 41 enters the separating chamber 51 through the overflow opening 56 and passes through the cooling water chamber 52 by way of the air discharge opening 55, and is thence discharged through the air exhaust port 59. This cycle of operation may be repeated to suck air alternately through the left and right air intake ports 36 and to exhaust this air through the exhaust port 59. The liquid which over-flows into the separating chamber 51 stays at the bottom of the separating chamber 51 and raises the valve 54 via the float 53, thus closing the air discharge opening 55 and elevating the pressure within the separating chamber 51. This elevated pressure forces the liquid at the bottom of chamber 51 to be returned to the cooling chamber 52 through the discharge liquid pipe 57. When the level of the liquid is lowered, the valve 54 causes tha air discharge opening 55 to open thereby discharging air through the exhaust port 59 by way of chamber 52. During the suction strokes of the piston 40, the circulating pipe 62 allows the cooled liquid in the cooling water chamber 52 to flow into the liquid tank 39 via one of the check valves 61 so as to cool the liquid in the tank 39. During the exhaust strokes of the piston 40, the check valves 61 serve to prevent a backflow from the tank 39, while the air cushion chamber 63 located above each liquid containing internal cylinder 41 serves to prevent liquid hammer.

Figure 8 shows a modification of the pump shown in Figure 5 and 12. 34 7ο includes a modified separating chamber 69 open at its upper and lower ends. Preferably, a cooling water spraying chamber is provided upstream of the air intake port 36 in order rapidly to cool by heat-exchange the suction air (saturated vapour).

While the operation of the pump according to the present invention has been explained in the case where the pump is used as a vacuum used pump, it is to be understood that the pump may of course be/as a compression pump by using the former in a reversed manner.

Liquids which may be used with the pump according to the present invention include water, a mixture of water and ethylene glycol, ethylene glycol, and oil. In the case of water, the water temperature is 3 to 5°C and the vacuum is 6 to 5mm of mercury column residual pressure; in the case of a liquid comprising 10 to 20% of ethylene glycol mixed with water, the liquid temperature may be decreased to -5 to -15°C to thereby elevate the degree of the vacuum; and in the case of using ethylene glycol or oil, the circulating liquid may be reduced to a temperature of from -20 to -30°C to produce an even higher vacuum.

In the following an example of the pump according to the present invention, which is applied to the vacuum treatment of food, will be discussed.

Turning now to Figure 9, which illustrates one embodiment incorporating the pump according to the present invention, there is shown a treating container 101 having an upper portion connected through a pipe 102 to a suction port 104 of a pump 103 according to the present invention. A heat exchanger 105 is provided at the bottom of the container 101 and refrigerator 106 is circulatively connected by a pipe 107 to the heat exchanger 105 so that heat from the refrigerator 106 can be transmitted to the treating container 101. 13.

When the vacuum pump 103 and refrigerator 106 are operating with food A to be dried or condensed received within the treating container 101, air within the treating container 101 is sucked and exhausted by the suction and exhaust action of liquid in the vacuum pump 103, while the liquid in the vacuum pump is cooled and circulated through the refrigerator 106. The waste heat from the refrigerator 106 is transmitted to the heat exchanger 105 and used as a heat source of the treating container 101.

Figure 10 shows an embodiment, in which the present invention is applied to the treatment of defreezing food, wherein a heat exchanger 105, in the form of a heating coil, is immersed in water provided at the bottom of a treating container 101. A frozen product A is placed on a shelf 108 located in the container 101 above the level of the water therein, after which the treating container 101 is interiorly evacuated, thereby resulting in rapid evaporation of the water. The water vapour then condenses at the surface of the frozen product A and, due to the heat generated as the vapours condenses, the required defreezing may be achieved at a low temperature under vacuum.

Further, an additional heating device may be incorporated in the treating container 101 as necessary.

In Figure 11, a cylindrical treating container 101, which is closed at its ends and which is inclined to the horizontal is provided with a raw material supply pipe 109 at the upper part of its lower end and a discharge pipe 110 at its other end. The raw material supply pipe 109 is connected to a raw material supply device (not shown), and the discharge cylinder 110 is connected to a product containing tank 111. 14. 43473 Within the treating container 101, an endless conveyor belt 115 of about 0.1 to 0.05 mm in thickness made of a heat conductive material such as stainless steel or aluminium extends over a drive roll 112, a follower roll 113, and a tension roll 114 whereby, when the drive roll 112 is driven, the raw material sprayed or coated on the belt 115 from the raw material supply pipe 109 is continuously transported toward the discharge cylinder 110. A hollow heat exchanger 116 is mounted in contact with the undersurface of the endless conveyor belt 115.

The heat exchanger 116 is connected to a heating medium supply device 119 by means of a heating medium supply pipe 117 and a discharge pipe 118 so that the raw material on the conveyor belt 115 may be heatexchanged by heat conduction of the heating media such as heated water or vapour. The supply device 119 forms part of a refrigerator 194 associated with the vacuum pump 103 such that waste heat from the refrigerator is utilized as the heat source for heating the fluid in the supply device 119.

At the bottom portion of the treating container 101 is mounted a layer of insulating material 120, on which a cooling heat exchanger 121 composed of finned pipes is mounted. This cooling heat exchanger 121 is connected by a transport pipe 124 with a cooling water tank 122. A pump 123 is used to feed the cooling water to the cooling heat exchanger 121 so cooling and recondensing the vapour emitted from the raw material, the cooling liquid being returned to the cooling tank 122 via a return pipe 125 from the cooling heat exchanger 121 to allow the return of heated cooling water for recirculation.

The lower portion of said lower end of the treating container 101 is connected by a suction pipe 126 to the vacuum pump 103 for removal of the liquid vapourized and condensed from the raw material and at the . 43473 same time to subject the treating container 101 to deaeration and suction.

In Figure 11 (and Figures 12 and 14), the numeral 152 or 195 denotes a compressor, the numeral 166 indicates a suction port, the numeral 187 denotes a cooling coil, the numeral 189 indicates an air exhaust port, the numeral 192 denotes a circulating pipe, the numeral 196 indicates an expansion valve, the numeral 197 denotes a fluid receiving device, the numeral 198 indicates a drier and the numeral 199 indicates an auxiliary cooling device.

Referring to Figures 12 and 13, a closed cylindrical treating container 101 is interiorly provided with a heat exchanger drum 127 of which opposite ends are closed by side plates 12?\ and wall surfaces are in the form of a double hollow configuration. The heat exchanger drum 127 has a vapour and gas emitting port 128 in the upper peripheral surface thereof, a raw material supply port 129 at the upper part of the one end thereof, and a raw material discharge port 130 at the other end thereof. Flow of material through the port 130 is controlled by an opening-andclosing cover 130^ operated by a lever 100 and provided in one side plate 127^, the raw material discharge port 130 being connected to product receiving tank 131, Rotatably supported by the plate 127^ is a rotary shaft 133 of a stirrer 132 in sliding contact with the inner peripheral surface of the heat exchange drum 127. The rotary shaft 133 extends outwardly of the treating container 101 and is connected by a belt to a drive motor 134.

The heat exchanger drum 127 has a space between the walls a thereof connected to/heating medium supply pipe 135 located at the central portion of the drum. The space is also connected to a discharge pipe 136 16. in the lower central portion of the drum walls. The heating medium supply pipe 135 and the discharge pipe 136 are connected to a heating medium supply device 137 so that a heating medium such as heating water or vapour may be circulated through the container 101 to heat articles to be treated within the heat exchanger drum. The waste heat from a refrigerator associated with the vacuum pump 103 may be utilized as the heat source of the heating medium supply device 137 of the vacuum vessel.

At the bottom portion of the treating container 101 is mounted a layer of insulating material 138, on which a cooling heat exchanger 139 composed of finned pipes is mounted. This cooling heat exchanger 139 is connected by an inlet pipe 124 with a cooling liquid supply device 140 in the form of a cooling water tank cooled by the evaporator of the refrigerator. A pump 141 feeds the cooling water through the pipe 124 to one end of the cooling heat exchanger 139 thereby cooling and recondensing the vapour emitted from the raw materials. The cooling liquid is returned to the cooling tank 140 via a return pipe 143 provided at the other end of the cooling heat exchanger 139 to allow the heated cooling water to be cooled and circulated.

The lower portion of the end of the treating container 101 remote from port 129 is connected by a suction pipe 144 with the vacuum pump 103 to suck the liquid vaporized and condensed from the raw material and at the same time to subject the interior of the treating container 101 to deaeration and suction. In Figure 12, the numeral 195 denotes a compressor.

In Figures 14 and 15, a closed treating container 101, having an upper cylindrical portion and a lower conical portion, has a raw material discharge outlet 145 located at the lower conical end connected to a product 17. containing tank (not shown). A partly hollow rotary shaft 147 driven by a motor 146 is provided at the centre of the cylindrical portion. To the upper end of the hollow portion of the rotary shaft 147 is connected a liquid-state raw material supplying pipe 148 whereas to the lower portion thereof is extended a spray nozzle 149. A scraper plate 150 is mounted on the rotary shaft 147 with a displacement of 180° from the spray nozzle 149, as can be seen from the drawing.

A heat exchanger drum 151, which is formed with inner and outer hollow portions separated by a partition plate positioned so that the portions are connected at their upper ends, is mounted in the treating container 101 with a scraper plate 150 in sliding contact therewith. The lower ends of the outer and inner hollow portions of the drum 151 are connected to a heating medium supply device 155 by a heating medium supply pipe 153 and a discharge pipe 154 through annular connection pipes 152, 1521, respectively, whereby the raw material sprayed against the inner peripheral surface of the heat exchanger drum 151 may be heated by heat exchange with a heating medium such as heated water or vapour.

The waste heat from the heat exchanger of a refrigerator acts as the heat source of the heating medium supply device 155.

On the inner peripheral surface of the treating container 101 there is mounted a layer of insulating material 156, and within the container there is mounted a cooling heat exchanger 157 composed of finned pipes located adjacent the heat exchanger drum 151. This cooling heat exchanger 157 is connected by an inlet pipe 160 to a cooling liquid supply device 158. The latter may be a cooling water tank cooled by the evaporator of the refrigerator. A pump 159 feeds the cooling water to the lower portion of the cooling heat exchanger 157 thereby cooling and recondensing the vapour 18. emitted from the raw material. The vapour is returned to the cooling liquid supply device 158 or cooling tank via a return pipe 161 connected to the upper end of the cooling heat exchanger 157 to allow the heated cooling water to be returned for cooling and recirculation.

The treating container 101 is connected by a suction pipe 163 with the vacuum pipe i66to remove the liquid released from the raw material and at the same time to subject the treating container 101 to deaeration and suction.

Claims (11)

1. A liquid-sealed pump including at least one liquid containing chamber, a mechanism for alternately increasing and decreasing the pressure of liquid in said liquid containing chamber, a suction chamber into which air can be drawn and which is connectable to the liquid containing chamber, valve means operable to admit air to said liquid containing chamber from the suction chamber when the liquid pressure in said liquid containing chamber is low and to allow air and said liquid to be discharged from said liquid containing chamber when said liquid pressure is high, ah outlet for at least the air discharged from said liquid containing chamber, means for returning at least part of the discharge liquid to the liquid containing chamber, and means for cooling the air drawn into the pump via the suction chamber.

2. A pump as claimed in Claim 1, wherein said liquid containing chamber is located within an external chamber which defines said suction chamber, and said valve means includes an intake valve which allows passage of liquid and air from said external chamber to said liquid containing chamber. 19.

3. A pump as claimed in Claim 2, wherein said intake valve is formed of a buoyant material and has a flow pressure plate mounted at an end thereof extending into the liquid containing chamber so as to control operation of the valve in accordance with the liquid flow pressure on the plate.

4. A pump as claimed in Claim 1 wherein said valve means includes a discharge valve located at the upper part of said liquid containing chamber and operable, in use, to allow liquid and air to be discharged from said liquid containing chamber, and said means for returning at least part of the liquid discharged from the liquid containing chamber includes a pipe defined by said discharge valve and extending between the interior and exterior of the liquid containing chamber.

5. A pump as claimed in Claim 2, wherein said valve means includes a discharge valve located at the upper part of the external chamber and operable to allow liquid and air to be discharged from said liquid containing chamber, the discharge valve being formed with an opening through which at least part of the discharged liquid can return to the liquid containing chamber.

6. A pump as claimed in any one of Claims 1 to 3 wherein said valve means includes an air separation chamber connected to the upper part of the said liquid containing chamber for receiving air and overflow liquid therefrom, a normally open, air discharge valve at the top of said air separation chamber, a buoyant member connected to the air discharge valve and extending to the lower end of said chamber for closing said valve when the liquid in the air separation chamber rises above a certain level, a pipe connected at its lower end to the lower part of the air separation chamber and being open at its upper end so that, when said air discharge 20. valve is closed, the increased air pressure in said air separation chamber causes liquid therein to be expelled through said pipe.

7. A pump as claimed in any one of Claims 1 to 3 or Claim 6 wherein said means for returning at least part of the discharged liquid 5 to the liquid containing cylinder includes a cooling chamber for receiving said discharged liquid and a conduit connecting said cooling member with said liquid containing chamber by way of a check valve to prevent back flow of liquid from the liquid containing chamber.

8. A pump as claimed in Claim 2 or any Claim appendant to Claim 2, 10 wherein said cooling means includes heat exchanging spiral fins provided in or on the external chamber.

9. A pump as claimed in any preceding Claim, wherein said cooling means includes a cooling coil mounted in the liquid containing chamber.

10. A liquid-sealed pump comprising the combination and arrangement 15 of parts substantially as hereinbefore described with reference to and as shown in Figures 1 and 2, or Figures 3 and 4, or Figures 5, 6 and 7, or Figure 8 of the accompanying drawings.

11. Apparatus for the vacuum drying of food including a pump as claimed in any one of the preceding Claims.