GB2208315A

GB2208315A - Conditioned air egg incubator and method of operation

Info

Publication number: GB2208315A
Application number: GB8817471A
Authority: GB
Inventors: Yves Lemonnier
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-07-24
Filing date: 1988-07-22
Publication date: 1989-03-22
Anticipated expiration: 2008-07-22
Also published as: GB8817471D0; IT8821358A0; IT1226791B; FR2618300A1; FR2618300B1; GB2208315B

Abstract

The incubator has at least one incubation chamber 2 mounted at the side of an air-conditioning chamber 17. A centrifugal fan 11 conveys a flow of sucked air into the central zone and delivers it towards the peripheral zones. The direction of rotation of the fan 11 for conveying air into the suction chamber 2 from the air-conditioning chamber 7 is periodically reversed. The air flows F returning to the central zone from the incubation chamber 2 along the axis of the centrifugal fan are accelerated by a helical fan 16 to give them the same speeds as the peripheral flows. A programmer 14 controls the speed of the fan 16 and the operation of water sprayers 18 to ensure uniform thermal and hygrometric conditions for all the eggs. <IMAGE>

Description

Egg Incubator and Method of Operation In FR-A-2 450 056, the applicant describes an incubator comprising two substantially parallelepipedal cavities adapted to receive slides bearing trays containing eggs, and an intermediate chamber between the two cavities and having a cross-section corresponding to that of the two cavities and containing a centrifugal fan which takes air halfway up and at the centre of the incubator and propels it towards the periphery and distributes it into the cavities around the slides and returns it via the slides.

An incubator constructed in this manner is better than earlier designs in ensuring the required conditions for incubating large batches of eggs, the main conditions being uniform ambient temperature and'humidity for all the eggs, to prevent them hatching at widely different times.

To obtain this uniformity it had previously been proposed, in FR-A-2 265 269, to guide the flows of conditioned air generated by a central chamber through the stacks of egg-trays in the incubation chambers by disposing guide deflectors up the outer wall so as horizontally to deflect the flow of descending air between the egg trays and near the wall, the flow resulting from the flow of conditioned air delivered upwards from the central chamber and separated into two side flows which in turn are divided into flows descending around the egg boxes before being sucked at the base of the central conditioning chamber. Clearly, the flows are distributed at random and,above all, the speeds of the air flows in contact with the eggs suffer considerable variations shown by temperature differences which can reach or exceed a degree centigrade.

In an effort to obtain yet more uniform flow characteristics of conditioned air in contact with the eggs, DE-A-9 11 790 proposes an incubator construction in which the air conditioned in the lateral or central conditioning chamber is extracted by fans disposed at its top and bottom to produce flows returning from the periphery towards the conditioning chamber, in the top and bottom respectively of the stacks of trays. This construction can give a more uniform environment, but the limited-diameter helical fans used in this incubator inevitably produce concentrated flows which are unevenly divided over the width of the stacks, resulting likewise in excessive temperature differences.

FR-A-2 450 056, which proposes a centrifugal fan mounted axially halfway up and at the centre of the airconditioning chamber, has the advantage of producing a peripheral excess-pressure zone in contact with the side, top and bottom walls of the chamber or in general with the two incubation chambers containing the egg trays.

The air therefore flows from the conditioning chamber towards the opposite wall of the incubation chamber or chambers and occupies the top, bottom and side passages around the stacks of trays and returns to the centre towards the suction zone of the fan.

A careful study of the ambient temperature distribution and the flow speeds has shown much greater homogeneity than in prior-art incubators but has shown that temperat'Jre differences between some points may reach several tenths of a degree.

The inventor, after a critical study, has discovered that this lack of uniformity is mainly due to the rotation imparted to the air flow by the centrifugal fan rotating in the conditioning chamber, and because the diffusion at the fan outlet inevitably occurs in a rectangular crosssection.

To solve this problem, it is proposed in US-A3 654 345 to periodically reverse the direction of rotation of the central centrifugal fan for conveying air to the incubation chambers from the conditioning chamber. During the reversal, a simultaneous adjustment is made in the slope of the platens of the trays carrying the eggs.

However, it has been found that when the incubation chambers are empty, the flow speeds along the axis, from the incubation chamber to the suction zone of the centrifugal fan, are substantially twice the speeds in the peripheral zones, from the incubation chamber to the outer wall of the incubation chambers. When incubation chambers contain slides carrying egg-trays, the flow speeds in the peripheral parts are only slightly reduced and are more turbulent owing to the presence of the trays, but the flow speeds in the central part for return towards the centrifugal fan suction zone are only about a third of the peripheral speeds.

To remedy this situation, as per a first feature of the method according to the invention, the air flows returning from the central zone of the incubation chambers along the axis of the centrifugal fan are accelerated so as to give them the same speed as the peripheral flows. This acceleration can be brought about by injectors associated with venturis taking air from the wall and propelling it towards the trays in the incubation chamber. Helical fans blowing towards the chamber interior are mounted at or near the side wall, for economic reasons and to facilitate monitoring the speed given to the central flows in dependence on the temperatures detected at various places in the incubation chamber.The helical fans are preferably driven by variable- speed electric motors monitored in dependence from the temperatures recorded at a number of places in the incubation chamber.

Uniform and adequate humidity, at the end of incubation and inter alia at the moment of hatching, are important for success. In DE-A-911 710, FR-A-1 204 007, FR-A-1 491 779, etc. the humidity in the flow of conditioned air leaving the conditioning chamber or the device for propelling it is adjusted before distributing the air oer the eggs. The result, owing to the prviously-discssed non-uniform distribution of air flows, is a lack of uniformity In the amount of water vapour brought into contact with the eggs, and a lack of uniformity in condensation of water on the eggs in the various zones in the incubation chamber.Condensation, as a result of exchange through the shell, supplies the embryo during the last phase of incubation with the water necessary for periodically lowering its temperature and increasing the fragility of the shell.

The aforementioned characteristics which increase the uniformity of the ambient atmosphere in the incubation chambers also increase the uniformity of humidity. It has been found, however, that it is difficult to control humidity by adjusting the humidity of the air leaving the conditioning chamber, owing to condensation on the walls.

Consequently, according to a preferred feature of the method of the invention, the humidity in the immediate neighbourhood of the eggs is monitored and the embryos at the end of the incubation process are cooled by spraying water laterally on to the stacks of trays, the spray being produced intermittently in dependence on the temperatures recorded in the incubation chamber.

The invention also provides an incubator comprising at least one air-conditioning chamber and an incubation chamber alongside at least one side of the air-conditioning chamber, air being circulated in the conditioning chamber and the incubation chamber by a centrifugal fan mounted for rotation with its axis horizontal and at the centre of the air-conditioning chamber and driven by an electric motor, the aforementioned electric motor being of reversible type and controlled by a programmer, in which at least one helical fan is mounted on the wall of the incubation chamber remote from the air-conditioning chamber and near the centre of the wall, the air flowing in contact with the wall being sucked at the periphery and delivered towards the incubation chamber.The fan is driven by a variable-speed motor, the speed of which is controlled by a programmer whose input receives the temperatures measured by thermometer probes distributed in the chamber.

According to another feature, sprayers having jets directed towards the interior of the incubation chamber are provided between the air-conditioning chamber and the incubation chamber and on the opposite side of the incubation chamber. The supply to the sprayers is controlled by a programmer whose input receives the temperatures recorded by thermometric probes and/or the degrees of humidity recorded by hygrometric probes.

According to another feature, electric resistors for heating the air are disposed in a circle concentric with the centrifugal fan in the surface between the conditioning chamber and the incubation chamber, screens being disposed between the resistors and the incubation chamber and forming deflectors for preventing heat exchange by radiation towards the interior of the chamber.

According to another feature, fresh air is admitted into the incubator via ducts opening into the central cavity between the blades of the centrifugal fan. Preferably and owing to the. rotation imparted to the air in the central cavity, the direction of rotation being periodically reversed, at least two ducts are provided and open tangentially into the cavity and their orifices are in opposite directions.

The result is to suck fresh-air into the incubator.

The features of the invention will be clearly understood from the following detailed description of an embodiment of the invention with reference to the accompanying drawings. in which: Fig. 1 is a view in section through the central longitudinal plane of a prior-art incubator, so as to explain the problems solved by the invention; Fig. 2 is a view in section corresponding to Fig. 1, showing an incubator according to the invention; and Fig. 3 is a detailed view in section through a vertical plane of a heating element.

In the drawings, reference 1 denotes the outer wall of an incubator of the kind described in FR-A-2 450 056, the incubator comprising two incubation chambers 2 adapted to receive slides 3 bearing trays 4 carrying eggs. Trays 4 are mounted in known manner so as to oscillate around an axis 5 under the action of a motor 6 which varies their slope periodically, e.g. every hour. Reference 7 denotes an air-conditioning chamber inserted between the other two chambers. In the air-conditioning chamber 7 a centrifugal fan is mounted for rotation around a shaft 9 and comprises a driving pulley 10 and radial blades 11, e.g. eight blades and four on each side of the pulley, the fan being driven by motor 12 and belt 13.

In the aforementioned incubator, when fan 11 is in operation and the incubation chamber 2 is empty (on the left of Fig. 1) the speed V1 of the air flows blown into the top and bottom of the chamber is e.g. 1.5m/s whereas the speed V2 of the air flows returning to the central part is about 3m/s. When slides 3 are in position in the incubation chambers and trays 4 carry eggs and are inclined (on the right side of Fig. 1), the flow speeds V3 of blown air are still about 1.2 to 1.3m/s whereas the speed V4 of the returning air flows fall to about 0.4m/s. This lack of uniform speeds results in considerable variations in temperature depending on the position of the eggs in the incubation chamber.

The incubator according to the invention comprises a programmer 14 whose input receives measurements made by thermometric and hygrometricprobes 15 distributed in the chambers. Motor 12 is a reversible motor and programmer 14 adjusts the slope of egg trays 4 at a given frequency, once every hour in practice, via motors 6, and reverses the direction of rotation of the fan 11 at the same frequency but halfway through the inclination period of the trays.

The incubator according to the invention also comprises a helical fan 16 on the end wall of each incubation chamber 2, the fan being driven by a variable-speed electric motor 17; this sucks the layer adjacent the wall and delivers it in a central flow F, at a speed varying from 1.5 to 3 m/s when the chamber contains slides 3.

Programmer 14 regulates the speed of fans 16 in independence on the temperatures recorded by the probes 15 in the central part.

In order to adjust the thermal and humidity conditions of the eggs in the incubation chambers, sprayers 18 are provided between the air-conditioning chamber and the incubation chambers and parallel to the end walls thereof. The spray jets are directed towards slides 3 and consequently towards the eggs in trays 4. The sprayers 18 are controlled by electromagnetic valves 19 which in turn are actuated by programmer 14.

The air is heated by coiled electrical resistors 20 disposed coaxially with axis 9 on both sides of chamber 7 and occupying the central part so as to heat the flow of air sucked by the centrifugal fan 10, 11. To prevent heating the eggs by direct radiation from resistors 20, a deflector 21 made up of a ring of concentric blades is mounted between the incubation chamber and the surface of each resistor. The flow of air sucked through deflector 21 exchanges heat therewith and the blades have a frustoconical shape so as to concentrate the air flows towards the centre and prevent any direct radiation. The supply to resistors 20 is also controlled by programmer 14.

Finally, fresh air is admitted into the incubator via ducts 22 which cpen at 23 into the central cavity of the an blades 11, tne cavity being at negative pressure with vcrtex currents.The mouths 23 of two ducts extend in opposite directions to increase the sucton flow The incubator according to the invention can be usec to maintain substantially uniform temperature ana humidity throughout the incubation chambers, oth curing the endothermic phase at the beginning of incubation and during the exothermic phase before hatching. Any remaining diferences, which are extremely small, will 5 compensated by the periodical reversing of the centrifugal fan 10, 11 and the periodical adjustments of the slope or egg trays 4.

Claims

Claims:

1. A method of operating an egg incubator comprising at least one incubation chamber mounted at the side of an airconditioning chamber and a centrifugal fan for producing a flow of air sucked into the central zone and delivered towards the peripheral zones, the direction of rotation of the central centrifugal fan being periodically reversed in order to convey air into the incubation chambers from the conditioning chamber, in which the air flows returning from the central zone of the incubation chamber along the axis of the centrifugal fan are accelerated so as to give them substantially the same speed as the peripheral flows.

2. A method as claimed in claim 1, in which the humidity of the immediate neighbourhood of the eggs is monitored and the embryos at the end of the incubation process are cooled by spraying water laterally on to the stacks of trays. the spray being produced intermittently in dependence on the temperatures recorded in the incubation chamber.

3. An incubator comprising at least one air-conditioning chamber and an incubation chamber alongside at least one side of the air-conditioning chamber, a centrifugal fan for circulating air in the conditioning chamber and the incubation chamber. the centrifugal fan being mounted for rotation with its axis horizontal and at the centre of the airconditioning chamber and being driven by an electric motor which is reversible and is controlled by a programmer, and at least one helical fan is mounted adjacent the wall of the incubation chamber remote from the air-conditioning chamber and in the region of the centre of the wall, the air flowing in contact with the wall being sucked in at the periphery and delivered towards the incubation chamber.

4. An incubator as claimed in claim 3, in which the helical fan is driven by a variable-speed motor whose speed is controlled by the programmer, whose input receives temperatures measured by thermometric probes distributed in the incubation chamber.

5. An incubator as claimed in claim 3 or 4, including sprayers having jets directed towards the interior of the incubation chamber between the air-conditioning chamber and the incubation chamber and on the opposite side of the incubation chamber.

the supply to the sprayers being controlled by the programmer.

6. An incubator as claimed in any of claims 3 to 5, including electrical resistors for heating the air disposed around the fan axis between the conditioning chamber and the incubation chamber, and screens disposed between the resistors and the incubation chamber and forming deflectors for preventing heat exchange by radiation towards the interior of the chamber.

7. An incubator as claimed in any of claims 3 to 6, including ducts for admitting fresh air into the incubator, the ducts opening into a central cavity of the centrifugal fan.

8. A method of operating an incubator, substantially as described with reference to Figures 2 and 3 of the accompanying drawings.

9. An incubator substantially as described with reference to. and as shown in, Figures 2 and 3 of the accompanying drawings.