GB2111895A - Moulding bricks of dry ice - Google Patents

Abstract

Liquid CO2 from cylinder 21 is blown by nozzles 13 to form dry ice snow 14 in a charging mould. A block 15 pre-compressed by piston 8 is transferred to a pressing mould when shutter 6 is fully retracted. With shutter 6 in the closed position shown, piston 10 compresses block 15 to a brick 16. Upon partial withdrawal of the shutter brick 16 is lifted into the space below the auxiliary shutter 7, the latter keeping the charging mould closed. The brick is then pushed out onto a rack 29 by the advance of the shutter 6 and a new block 15 is pre-compressed to start the next cycle. Hydraulic actuators 9, 11 and 25 are preferably heat-insulated from pistons 8, 10 and shutter 6. Shutter 6 is made of porous sintered metal to allow CO2 gas to escape into discharge passages 30. This material can also be used for the lower part of the charging mould. The pressing mould has external strengthening fins 24 which also serve to absorb heat and reduce sticking of the brick 16. <IMAGE>

Description

SPECIFICATION An apparatus for producing bricks of dry ice from liquid carbon dioxide This invention relates to an apparatus for producing bricks of dry ice from liquid carbon dioxide. More particularly, the invention relates to an apparatus which enables dry ice makers to produce much brick-shaped dry ice speedily for restaurants, icecream shops and confectioners.

Among various apparatus for producing bricks of dry ice, the most similar conventional apparatus to the one of the present invention is shown in the U.K.

patent specification No. 433018 "Improvements in Presses for Producing Solid Carbon Dioxide".

In the apparatus described in that specification, liquid carbon dioxide is sprayed through a nozzle into a charging cylinder, and changes to dry ice snow through adiabatic expansion. After generating dry ice snow in the charging cylinder, a shutter between the charging cylinder and a press cylinder is opened by an actuator, and dry ice snow drops into the press cylinder by its own weight. Then, after the shutter has been closed, a press plunger is elevated by a hydraulic actuator and a block of solid dry ice is produced from the dry ice snow.

During the above pressing, dry ice snow for next cycle is supplied as described above. Then, by lowering the press cylinder hydraulically, the solid dry ice on the press plunger is extruded outside the press cylinder, and is taken out.

However, the following defects remain unsolved in the above conventional apparatus.

(1) In order to take out the solid dry ice the press cylinder has to be driven up and down vertically. The driving mechanism of the press cylinder is complicated, and expensive, and the durability is reduced.

(2) In case of automatic operation, the solid dry ice on the press plunger has to be taken out by some transferring means which works automatically without any interference with the press cylinder. Therefore, the mechanism becomes more compiicated.

(3) As the dry ice snow supplied into the press cylinder has quite low density, in order to produce large blocks of solid carbon dioxide, it is necessary to increase the height of the press cylinder and also to increase the stroke of the hydraulic actuator having a large pressing capacity. Therefore, the apparatus is necessarily increased in height and becomes very expensive.

(4) During pressing of the dry ice snow in the press cylinder, the gaseous carbon dioxide contained in the dry ice snow is shut in the solid carbon dioxide.

This gaseous carbon dioxide reduces the speed of pressing, and the solid dry ice is easy to break or to crack due to the pressurized gaseous carbon dioxide in it.

In case of installing two shutters for keeping constant quantity, some of the dry ice snow remains sticking on the inside surface of the charging cylinder, so it is difficult to make blocks of solid carbon dioxide having a constant weight.

The features of the embodiment of the present invention to be described below will now be summarized.

A pressing mould for pressing brick-shaped dry ice is located right under a charging mould with the interposition of a shutter space. An outlet opening for dry ice snow is formed at the lower end face of the charging mould, and an inlet opening is formed at the upper end face of the pressing mould. The shutter space is provided with a shutter which shuts or opens simultaneously both said outlet opening and said inlet opening.

A nozzle for jetting liquid carbon dioxide is installed facing into the upper part of said charging mould. Said shutter is formed so as to be slidable forward and backward with a shutter actuator.

A pressing block slidable in the pressing mould is driven vertically by a pressing actuator. After generating dry ice snow in the charging mould by spraying liquid carbon dioxide from the nozzle, the shutter is driven to open the outlet opening and the inlet opening, whereby dry ice snow is dropped and charged into the pressing mould through the outlet opening, the shutter space and the inlet opening.

Then, after driving the shutter to shut both openings, the pressing block is driven upward by the pressing actuator, whereby dry ice snow in the pressing mould is pressed to be a brick-shaped block of solid carbon dioxide.

However, the apparatus in accordance with the present invention comprises the above-described known features in combination with the following characteristic features.

An Auxiliary shutter extends forward from the upper front end of the shutter, and the front end face of the shutter is formed as a push face of greater height than the bricks of dry ice for ejecting the products. Ataking out rack is formed adjacent the lower side of said shutter space to receive the ejected bricks.

The shutter and the auxiliary shutter are driven forward and backward by the shutter actuator to move between 3 positions - a shutdown position, an inlet open position and a full open position.

In said shut down position, both the outlet opening and the inlet opening are closed completely. In said inlet open position, as the shutter is retracted, the inlet opening is opened to the shutter space, and the outlet opening is closed by the auxiliary shutter.

In said full open position, as the auxiliary shutter and the shutter retreat further, both the outlet and the inlet openings are opened to the shutter space.

Now, the apparatus in accordance with the present invention comprises the above described fundamental features and it is preferable to add the following additional features in order to obtain better results.

A precompressing block slidable in the charging mould is driven vertically by a precompressing actuator. Said precompressing block is driven to move between three positions:- a rest position, a pre-compression position, and an ejection or transfer position. In said rest position, the precompressing block is elevated higher than the charging inlet which the inlet nozzle faces. In said precompression position, the precompressing block is driven lower than said charging inlet so as to precompress dry ice snow in the charging mould. In said transfer posi tion, the precompressing block is driven lower than said precompressing position to transfer a precompressed block of dry ice snow into the pressing mould.

In order to exhaust the gaseous carbon dioxide in dry ice snow, the shutter is preferably formed from such a breathing porous material as sintered metal.

With this apparatus the following advantages can be attained: (1) When taking out the brick-shaped dry ice from inside the pressing mould, after elevating the solid dry ice into the shutter space by means of the pressing block, the solid dry ice is transferred onto the taking out rack by the shutter.

Therefore, the pressing mould can be fixed to the supporting frame, and the hydraulic actuator for the pressing mould can be saved. Moreover, without any special taking out device for the solid dry ice, it can be transferred by means of the shutter. Consequently, the whole construction of the apparatus can be simplified and compacted, and the construction cost can be reduced.

(2) In case of prepressing dry ice snow in the charging mould with the precompressing block and this precompressed dry ice snow being dropped into the pressing mould, the following advantages can be attained.

(a) After precompressing the dry ice snow and reducing its height, the dry ice is dropped into the pressing mould, whereby the pressing mould can be decreased in its height and consequently the stroke of the pressing actuator of large capacity can be shortened. Therefore, the apparatus is reduced in its total height and structural weight, and therefore can be cheapened.

(b) By injecting a certain quantity of liquid carbon dioxide for each pressing cycle, dry ice snow of constant weight is produced in the charging mould, and the whole of said snow is precompressed and supplied into the pressing mould. Therefore, the bricks of dry ice of constant weight can be produced reliably.

(c) During dropping of the compressed dry ice snow into the pressing mould from the charging mould and waiting until starting of pressing, some gaseous carbon dioxide escapes from the precompressed dry ice snow without being shut in, whereby the quantity of CO2 gas in the solid carbon dioxide can be decreased. Therefore, the pressing actuator can be made more compact and working efficiency and the quality of the produce are improved.

(3) In case of constructing the shutter from a breathing porous material, some of the CO2 gas in the dry ice snow escapes through the shutter during pressing, whereby pressurized CO2 gas does not prevent pressing. Therefore, the capacity of the pressing actuator can be reduced, and the efficiency is improved and solid dry ice of high quality can be produced.

The invention will now be described in more detail with the aid of an example illustrated in the accompanying drawings, in which: Figure 1 is a perspective view of the basic constituent parts of an apparatus embodying the present invention, Figure 2 is a side view, partially in section, of the complete apparatus, Figures is a front view of the apparatus, Figure 4 is an explanatory schematic drawing showing five stages in the process of production of bricks of dry ice with the apparatus of Figures 1 to 3, Figure 5 is a detail of Figure 2, showing a modification, and Figure 6 is a table showing a driving sequence of the pressing block, the precompressing block, the shutter and the auxiliary shutter, controlled through detecting signals from limit switches.

As shown in Figure 1, a charging mould 1 and a pressing mould 2 are disposed respectively, above and below, to define a shutter space 3. An outlet opening 4 at the lower end face of the charging mould 1 and an inlet opening 5 at the upper end face of the pressing mould 2 are open to the shutter space 3. A shutter 6 movable forward and backward in the shutter space 3 is disposed in the shutter space 3 so as to open or close both the outlet 4 and the inlet openings 5 simultaneously.

A precompressing block 8 arranged to slide vertically inside the charging mould 1 is driven by a precompressing actuator9 comprising a hydraulic cylinder. A pressing block 10 arranged to slide vertically inside the pressing mould 2 is driven by a pressing actuator 11 comprising a hydraulic cylinder.

Charging ducts 12 are connected obliquely at the upper part of the charging mould 1, and each duct 12 has a nozzle 13 attached so as to blow dry ice snow into the charging duct 12 by injecting liquid carbon dioxide.

This dry ice snow is blown into the charging mould 1 through the charging inlet 14, and thus the charging mould 1 is filled with the dry ice snow.

After the dry ice snow has been precompressed by the precompressing block 8, this soft block of dry ice snow 15 drops into the pressing mould 2 by gravity.

In the pressing mould 2, said precompressed dry ice snow 15 is pressed to a brick 16 of high density by means of the pressing block 10. During generation of dry ice snow for the next cycle and precompression of this in the charging mould 1, and precompressed dry ice snow is pressed in the pressing mould 2 and then the brick 16 is pushed out into the shutter space 3 from the pressing mould 2.

Now, the detailed structure of the apparatus for producing brick-shaped dry ice will be explained with reference to Figures 2 and 3. The charging mould 1 and the pressing mould 2 each comprise a vertical metallic drum with a rectangular transverse section, and these drums are fixed between supportins frames 17 comprising a pair of thick steel plates.

The charging mould 1 constructed with the stainless steel plates is provided with CO2 gas vent holes 18 at its upper end part, and the outside of the drum in the region of these vent holes 18 is enclosed with a duct 19 for gathering CO2 gas. The CO2 gas leaked from the charging mould 1 into the duct 19 is discharged through a gas outlet opening 20 into the atmosphere.

The nozzle 13 is formed so as to produce dry ice snow by adiabatic expansion of the injected liquid carbon djoxide, and is disposed at the inside top of the charging duct 12. The nozzle 13 communicates with the liquid carbon dioxide cylinder 21 through a flow passage 22. The charging duct 22 comprises a divergent channel gradually expanding its cross sectional area from its top, and its charging inlet 14 communicates with the inside of the charging mould 1 below the gas vent holes 18.

The pressing mould 2 is also constructed with stainless steel plates and is provided with reinforcing stiffeners 24 serving as heat absorbing fins on the outside upper part of the pressing mould 2. As toward the end of pressing, dry ice snow is pressed with high pressure of approximately 150kg/cm2, the upper part of the pressing mould 2 should be constructed to have the requisite structural strength.

When the outer peripheral surface of the brick of solid dry ice 16 sticks to the inner surface of the mould by freezing, the brick 16 can not be pushed out into the shutter space 3. Therefore, the reinforcing stiffeners 24 are formed so as to have a large external surface area to serve as heat absorbing fins.

Also, it is preferable for the pressing mould 2 to have a smooth internal peripheral surface.

An auxiliary shutter 7 like a horizontal plate extends forward from the upper front edge of the shutter 6, and when the outlet opening 4 is closed with this auxiliary shutter 7, the inlet opening 5 is opened to the shutter space 3. When the shutter 6 is driven backward by full stroke of the shutter actuator 25, both the outlet opening 4 and the inlet opening 5 are opened.

As described above, the shutter 6 and the auxiliary shutter 7 are driven by the shutter actuator 25 so as to move between the shutdown position, the inlet open position and the full open position. In shutdown position, both the outlet opening 4 and the inlet opening 5 are closed by the shutter 6. In inlet open position, the outlet opening 4 is closed by the auxiliary shutter7 and the inlet opening 5 is opened by the retraction of the shutter 6. In the fully open position, both the auxiliary shutter 7 and the shutter 6 are withdrawn, whereby both the outlet opening 4 and the inlet opening 5 are opened to the shutter space 3. The shutter 6 movable in the shutter space 3 between the charging mould 1 and the pressing mould 2 is driven forward and backward by a shutter actuator 25 comprising a small horizontal hydraulic cylinder.

Now, with reference to Figure 4, the explanation relates to changing of shutter positions in producing bricks of dry ice.

Upon starting, as shown in (I), the shutter 6 is set to said shutdown position, and the precompressing block 8 is set at its rest position higher than the charging outlet 14, whereby dry ice snow is produced in the charging mould 1.

Then, as shown in (II), by lowering the precompressing block 8 from the rest position to the precompressing position below the charging inlet 14, dry ice snow is precompressed. Then, as shown in (III), after changing the shutter 6 and the auxiliary shutter 7 to the fully open position, the precompressed dry ice snow 15 is dropped into the pressing mould 2 by lowering the precompressing block 8 from the precompressing position to the transfer position. Then, as shown in (IV), after moving the shutter 6 back to said shutdown position, the precompressed dry ice 15 is pressed to form a brick 16 of solid dry ice in the press mould 2.

In parallel with above process, the charging mould 1 is supplied with dry ice snow. Then, as shown in (V), after moving the shutter 6 and the auxiliary shutter 7 to said inlet open position, the brick of dry ice 16 is pushed into the shutter space 3 by the pressing block 10, and thus this brick 16 is pushed forward by a push face 28 formed on the front end face of the shutter 6 as the shutter 6 is moved to said shutdown position, whereby the brick 16 is transferred speedily onto a taking out rack 29 in front of the shutter space 3. In parallel with above, dry ice snow is generated continuously and the charging mould 1 is filled with dry ice snow. Then, the process is repeated cyclically from (V) to (11), (III) and (IV), whereby the bricks of solid dry ice 16 are produced automatically at intervals of a few minutes.

Now, according to Figure 2 and Figure 3 again, explanation will be continued. When precompressing dry ice snow and pressing precompressed dry ice snow, it is preferable to vent CO2 gas in dry ice snow. Therefore, the shutter 6 is constructed of sintered metal as a breathing porous material and is provided with internal gas vent passages 30. Because of this structure, without being prevented by the pressure of CO2 gas, precompressed dry ice snow 15 can be pressed efficiently in the pressng mould 2, and bricks 16 of dry ice having high density and high quality can be produced. From the same technical viewpoint, it is further preferable to form the lower part 51 of the charging mould 1 from sintered metal, as shown in Figure 5. And it is also preferable to form the upper part of the pressing mould 2 with sintered metal.

Now, explanation relates to the heat-insulating structure between the pressing actuator 11 and the pressing block 10 and between the precompressing actuator 9 and the precompressing block 8. As the pressing block 10 and the precompressing block 8 are in contact almost all the time with dry ice snow at approximately -70 C, hydraulic oil would be cooled heavily, whereby its viscosity would increase and the hydraulic power device 31 would lose some of its output power. Moreover, because of thermal transmission from the hydraulic cylinders to the pressing block 10 and/or to the precompressing block 8, some of the dry ice snow may sublimate into CO2 gas.

To prevent these defects, the pressing block 10 and the precompressing block 8 are connected to the piston rod of the pressing actuator 11 and the precompressing actuator 9 respectively, so as to shut off the heat transmission by means of heatinsulating material. A plate (8b.1 0b) formed from some heat-insulating FRP material is attached between the pressing plate (8c.10c) and the base plate (8a.1 Oa).

Also, it is preferable to provide some heat insulation (not shown in the Figures) between the shutter actuator 25 and the shutter 6 or the auxiliary shutter 7. The hydraulic power device 31 for supplying pressurized oil to hydraulic cylinders (9.11.25) com prises an oil tank, an hydraulic pump, an electric motor, directional control solenoid valves, pressure switches, etc. Said hydraulic power device 31 is installed on the base supporting frame 17A behind the pressing mould 2.

A control box 32 is provided with sequence control circuits for controlling actuators (9.11.25) by operating said directional control solenoid valves for the hydraulic flow passages 33 and operating flow control solenoid valve 23 on the liquid carbon dioxide flow passage 22. This control box 32 is attached on the front side of the supporting frame 17. The apparatus of the invention is worked automatically with said sequence control circuits, or may be worked manually through push buttons on the control box 32. Hereinafter, detailed explanations on the constitutions of said control circuits will be omitted, however, the following descriptions relates to one cycle of actuating sequences of the pressing block 10, the precompressing block 8, the shutter 6 and the auxiliary shutter 7, according to Figure 6 and Figure 2.The pressing actuator 11 is provided with limit switches LS1, LS2, LS3 for detecting the upper position, the pressing limit position and the lower position of the pressing block 10, respectively.

The precompressing actuator 9 is provided with limit switches LS7, LS8 for detecting said rest position and said transfer position of the precompressing block 8, respectively. The shutter actuator 25 is provided with limit switches LS4, LS5, LS6 for detecting said fully open position, said inlet open position and said shut down position of the shutter 6 and the auxiliary shutter 7. When the auto starting button is operated, the flow control solenoid valve 23 on the liquid carbon dioxide flow passage 22 opens and dry ice snow is supplied into the charging mould 1 from the nozzle 13, and the sequence control circuits control actuators (9.11.25) and solenoid valves according to detecting signals from limit switches LS1, LS2.... LS8.

First of all, the precompressing block 8 is lowered in the charging mould 1, whereby dry ice snow is precompressed (as shown at (a) in Figure 6). After the shutter 6 and the auxiliary shutter 7 have been moved the said open position (as shown at b), said precompressed dry ice snow is dropped into the pressing mould 2 (as shown at C).

Then, after the shutter 6 has been moved to said shutdown position (as shown at d), said precompressed dry ice 15 is pressed to brick-shaped solid dry ice 16 by elevating the pressing block 10 in the pressing mould 2 (as shown at e). Then, while the said solid dry ice 16 is held in stand-by condition (as shown atf), the shutter 6 and the auxiliary shutter 7 are moved to said inlet open position (as shown at g), and then the solid dry ice 16 is elevated into the shutter space 3 (as shown at h) with the pressing block 10. As the shutter 6 is moved to said shutdown position by driving forward, the solid dry ice 16 is pushed forward with the push face 28, whereby the solid dry ice 16 is transferred into the taking out rack 29 (as shown at i).

In parallel with the above process e.f.. i, as shown atj, the dry ice snow for the next cycle is supplied into the charging mould 1 by keeping open the solenoid valve 23 of the liquid carbon dioxide flow passage 22.

Claims (12)

1. Apparatus for producing bricks of dry ice from liquid carbon dioxide comprising a charging mould disposed over a pressing mould with a shutter interposed between an outlet opening at the bottom of the charging mould and an inlet opening at the top of the pressing mould and capable of shutting both openings simultaneously, the charging mould having an injection nozzle for spraying liquid carbon dioxide into its upper part to form dry ice snow, and the pressing mould having a pressing block drivable upwardly to compress the dry ice into a brick, wherein the shutter has a forward face for pushing out a formed brick and an auxiliary shutter extending beyond the forward space from the upper edge thereof and the shutter is movable between three positions in the first of which both the inlet and outlet openings are closed and a brick can be compressed in the pressing mould while dry ice is being formed in the charging mould, in the second of which the outlet is closed by the auxiliary shutter while the inlet is open for ejection of a brick from the pressing mould, and in the third of which the outlet and inlet are open for the transfer of dry ice from the charging mould to the pressing mould.

2. Apparatus as claimed in claim 1 in which the charging mould has a vertically slidable precompressing block drivable from a rest position above the dry ice inlet to a pre-compressing position below the said inlet and thence to an ejection position to transfer a pre-compressed block to the pressing mould.

3. Apparatus as claimed in claim 2, in which the pressing block and the pre-compressing block are driven by respective hydraulic actuators, that for the pressing block being directly below the pressing mould and that for the pre-compressing block being directly above the charging mould.

4. Apparatus as claimed in claim 3 in which the actuators are connected to the respective blocks by way of heat-insulating material.

5. Apparatus as claimed in claim 4 in which the shutter is driven by a hydraulic actuator coupled to the shutter by way of heat insulating material.

6. Apparatus as claimed in any of the preceding claims in which the pressing mould and the charging mould are each in the form of a vertical drum of rectangular transverse section.

7. Apparatus as claimed in any of the preceding claims in which the pressing mould has external reinforcing stiffness at its upper end which serve also as heat-absorbing fins.

8. Apparatus as claimed in any of the preceding claims in which the upper part of the internal surface of the pressing mould is formed of smooth stainless steel.

9. Apparatus as claimed in any of the preceding claims in which the shutter is constructed of porous material.

10. Apparatus as claimed in claim 9 in which the material of the shutter is sintered metal.

11. Apparatus as claimed in any of the preceding claims in which the lower peripheral wall of the charging mould is constructed of porous material.

12. Apparatus as claimed in any of the preceding claims in which the charging mould has two injection nozzles communicating with respective inlet passages, the inlet passages being symmetrically arranged about the vertical centre line of the mould.