GB2263053A - Walk-in incubator. - Google Patents

Abstract

A walk-in incubator is formed of wall and roof panels, each panel comprising an inner polyurethane foam insulating material, the major surfaces of which are covered with wooden material having a plastics outer surface. The insulating material, the wooden material and the plastics outer surface are vacuum bonded together. In another aspect of the invention an incubator has a housing within which is located a plurality of stacked egg trays 40 on each side of a longitudinal passageway 51 and motor driven fans 53 are located above the longitudinal passageway with an air duct located between the ceiling and the roof. The air duct has an external air inlet 56 so that the fans blow air substantially vertically toward the floor of the housing and then rises past a heat controller 80 whereupon the air is recirculated 2. A pair of humidity air interchange trunkings 54, 55 each extend on an opposite side of the longitudinal passageway so that a substantially horizontal for and aft interchange of air is combined with the substantially vertical air flow. An aperture is located at a mid point of the housing so that air passes upwardly into the passageway and thence for and aft to provide extra impetus to the lower velocity external air. <IMAGE>

Description

WALK-IN INCUBATOR This invention relates to a walk-in incubator for eggs having a multi-stage tray suspension system and a mechanism for turning the eggs.

A known incubator has a housing in which is located a plurality of trays on each side of a central passageway extending the length of the housing and the eggs are located in the trays. The trays are stacked one above the other and are positioned along the length of the incubator on each side of the passageway.

The trays are arranged to be tilted at predetermined intervals by a turning mechanism comprising motors, cranks and cams and an air circulation system is provided for maintaining the eggs at a required temperature and humidity.

Over the past thirty years, progress has been directed toward obtaining the maximum egg capacity from any one incubator within a given floor space. As the size of the trays and the maximum number of trays that can be accommodated vertically is eighteen, the tendency has been to lengthen the incubator housing to increase capacity.

With careful design a longer machine will provide better results, be more cost-effective and efficient and require less maintenance. The necessity to maintain careful hygiene and disease-free surfaces devoid of numerous joints has become extremely important in view of the recent outbreaks of salmonella in hatcheries. Known incubators are formed of standard modules of 2.5m x 1.25m, dictated by material sheet sizes which results in numerous joints being required, for example a traditionally constructed incubator of lim x 3m x 2.lm typically uses thirty-three panels.The sides of the incubator have sometimes been made of wood but these, of course, are extremely difficult to clean. Some ,manufacturers have used composite panels of polystyrene with a very thin metal cladding and while insulation is good, the metal panels can corrode and problems are encountered with making secure screw fastenings into the thin metal sheet. If bolts are used, the panels tend to crush around the fastening and the soft core and thin cladding tends to be easily damaged by trolleys which are wheeled up and down the passageway to carry eggs into the out of the incubator.

It is an object of this invention to overcome the foregoing difficulty.

In an incubator, to obtain the highest possible incubation of eggs it is required that the eggs are subject to constant temperature and humidity throughout the whole volume of the incubator and it is a further object of this invention to provide an incubator that is more closely able to maintain the optimum parameters than hitherto.

According to a first aspect of this invention there is provided a walk-in incubator formed by a plurality of wall and roof panels, each panel comprising an inner polyurethane foam insulating material, the major surfaces of which are covered with wooden material and wherein the wooden material is applied with a plastics outer surface.

Conveniently, the wooden material is plywood.

Preferably, a wooden frame encompasses the minor edges of the insulating material.

Advantageously, the plastics outer surface is a GRP sheet material.

Preferably, the insulating material, the plywood, and the GRP sheet material are vacuum bonded together.

Advantageously, the wall panels have a density of 32kG/m2. In a preferred embodiment, the wall panels are 10.8m x 2.5m.

In a currently preferred embodiment, there is provided a framework comprising two longitudinally extending beams each supported by six equi-spaced floor engaging struts, said framework forming a load bearing structure for the wall and roof panels.

Preferably, the roof panels are interconnected by a rebate joint and are secured together by a polyurethane adhesive.

Advantageously, the wall and roof panels are interconnected by an orthogonal angle member and a silicone sealant is provided between the member and the panels.

Conveniently, the wall panels are secured to a floor through the intermediary of an orthogonal member and a polysulphide rubber is located between the bottom of the panels and the floor.

According to a further aspect of this invention there is provided a walk-in incubator having a housing within which is located a plurality of stacked egg trays, said stacks being on opposing sides of a longitudinal passageway, said housing having a roof and a ceiling spaced from the roof and above the longitudinal passageway, a plurality of motor drivable fans located in said ceiling substantially above the longitudinal passageway of said housing, and air duct means located in the space between said ceiling and said roof, said air duct means comprising:: A. an external air inlet means arranged to provide air fore and aft to each of said fans, whereby said fans each blow the air substantially vertically toward the floor of the housing where, with reducing pressure, the air moves laterally outwardly passing under then vertically upwardly through the egg trays and, on reaching the roof, passes heat control means to an area of maximum negative pressure above the fans, whereupon said air is recirculated.

B. a pair of humidity air interchange trunkings each extending on an opposite side of the longitudinal passageway of said housing and extending at least partially along the length of the housing across a mid-point thereof, each trunking having an air inlet located opposite a plurality of air outlets, each air outlet being adjacent a respective fan, the inlet of each trunking being positioned at an opposite side of said mid-point from one another, whereby a substantially horizontal fore and aft interchange of air is combined with the substantially vertical air flow, and C. an aperture located at said mid-point into said air inlet means, whereby air passes upwardly thereinto and thence fore and aft to provide extra impetus to the relatively lower velocity external air.

Advantageously, the passageway is located on a longitudinal axis of said housing.

Preferably, said external air inlet means is located centrally of said housing and includes ducting to provide said air fore and aft of said housing to said fans.

Advantageously, the ducting adjacent each fan has an opening which progressively increases in size towards the extremities of the housing.

Advantageously, a primary or low huinidity system is provided which comprises a nozzle at the inlet of each of said pair of humidity interchange trunkings and means for controlling a water supply to said nozzles.

Advantageously, there is also provided a secondary or high humidity system which comprises a steam generator arranged to introduce steam into said external air inlet means.

Preferably, an air exhaust means is provided through an opening in an end wall of said housing or through an opening at one end of the roof.

Advantageously, cooling means are provided above the air interchange trunkings for preventing overheating of the incubator.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: - Figure 1 shows a wall and roof panel for use in an incubator in accordance with the first aspect of this invention, Figure 2 shows a partially sectioned perspective view of an incubator in accordance with this invention, Figure 3 shows a side view in partial section of a roof panel joint and floor engaging strut support, Figure 4 shows a side wall and roof joint, Figure 5 shows a wall corner joint, Figure 6 shows a wall panel/floor joint, Figure 7 shows a detail of a door used in the incubator of this invention, Figure 8 shows a longitudinal cross-section of an incubator in accordance with the further aspect of this invention showing the air flow trunking, Figure 9 shows a cross-section along double arrowheaded line IX - IX of Figure 8, Figure 10 shows a partial longitudinal side view in cross-section of an alternative embodiment, and Figure 11 shows a cross-sectional end view of the alternative embodiment of Figure 10.

In the Figures like reference numerals denote like parts.

The wall and roof panels of the incubator shown in Figure 1 have a polyurethane foam insulation 1 having major surfaces covered with WBP plywood 2 and the outer surfaces of the plywood are covered with a white glass resin plastic (GRP) sheet 3. So as to enshroud the insulation 1, a wooden frame 4 is supplied around the minor surfaces thereof. The assembly thus far described is vacuum bonded together. Such a panel has the ability to be made in relatively large sheets, for example 10.8m x 2.5m, although the panels may be produced up to 12.8m in length.This means that whereas the traditionally constructed incubator of similar size would use thirty-three panels, an incubator made using panels of the present invention would only use eleven panels, i.e. six vertical panels and five roof panels, or if two incubators are connected side by side two adjacent side panels could be omitted so that one incubator would have eleven panels and the other incubator would have nine panels.

Typically, the polyurethane foam has a thickness of 35mm, the water and boil-proof (WBP) plywood has a thickness of 6.5mm and the GRP material has a thickness of linin. The wooden frame 4 may have a thickness of 35mm and a width of 95mm. Such a panel has a density of 32kG/m2.

The panels have excellent insulation properties enabling maximum heat retention in the incubator with subsequent energy saving. Being of high density and tough outer surfaces, the panels are resistant to damage by trolleys wheeled inside the incubator. Because the outer surfaces are of smooth plastics material, so they can be readily cleaned and maintained bacteria-free.

Referring to Figure 2, the incubator is formed on a concrete base 11 inside a building (not shown) and the incubator, shown in Figure 2, is a double incubator, each incubator having its own door 31. Each incubator has a framework of load-bearing beams connected by bolts so as to ensure that the structure is generally self-supporting.

This is in contrast to prior art incubators where the side walls were required to give lateral rigidity to the structure. The framework has floor engaging struts 12 having a plate 13 to which is bolted longitudinally extending beams 14 and the upper end of the respective plates 13 is L-shaped to support roof panels 15 through the intermediary of a clamp plate 16 and bolts 17 held in position by nuts 18.

The main function of the longitudinal beams 14 is to support the forward ends of 1,080 tray carrier frames (the rear end of the frames being supported on perforated wall bars attached to the side panels) via an overhead turning linkage (not shown) comprising sixty cam plates. Each of the cam plates, thirty per side, supports a column of eighteen tray carriers. All cams are linked with nylon bushed steel link bars. Four heavy master cams, one pair at each end, receive their motion via connecting rods coupled to four cranks on the ends of two lay shafts passing through sealed flanged bearings at each end of the beam structure. A further function of the beam assembly is to support the ten (in the present embodiment) fan boards and the pair of humidity air interchange ducts to be described hereinafter.

The roof panels are connected together by a rebate joint 18 and secured together by polyurethane adhesive (not shown) and screw 19.

The incubator has side panels 21 and, if made in a multiple, a common partitioning panel 22 between the two incubators. The incubator has rear panels 23 which fit between the sides to allow for exact length location inside the cabinet and front panels 25. The roof panels 15 also fit inside the side panels but overlap the rear panels.

A roof joint, as shown in Figure 4, is effected by joining the roof panel 15 to the side panel 21 through the intermediary of an orthogonal aluminium support member 24, the support member being screwed to the panels 15 and 21.

Similarly, the corners of the side panels 21 and rear panel 23, and the front panel 25 are connected by vertically extending orthogonal angle support members 26. Prior to positioning, the support members 24, 26 are coated with silicone sealant to provide a hermetic seal between the panels. The side panels 21 are secured to the floor 11 also by an orthogonal angle supporting member 27 and held in position by a screw 28 being connected to, the wall panel and an anchor bolt 29 being secured to the floor. The joint between the panels and the concrete floor is sealed with polysulphide rubber. The outer joint between the wall and the floor is provided with a rubber skirting 30.

The framework supports the carriers for the trays, and also the fans, cooling coils, gear boxes and humidity ducts. Having less weight to support, the housing panels can be reduced in thickness and weight in distinction to the prior art timber-framed, plywood clad sections. The resultant weight saving and manufacturing techniques enables larger panels than hitherto envisaged to be used, e.g. up to l2.8m in length.

The supporting member 27 may be a continous member along the length of the wall or may be a number of discrete members. The member or members 27 may be accurately positioned and fastened before bringing the wall panels into contact therewith.

A great advantage of the design of the present incubator housing is that elongation of the housing due to the number of joints is reduced to almost nil, making for quick and accurate assembly.

A further benefit is that when an uneven floor is encountered, the very long panels will span any irregularities with the floor without the need for packing and continual correction as work proceeds.

The housing can be built almost entirely from the inside which means that the side and back panels can be positioned immediately against the walls of a customer's building, if required. This is an important feature since, with very large incubators, floor space is at a premium.

All screw fixing is from inside, joints being additionally strengthened and sealed by adhesive sealant coated in the mating surfaces.

Each half of the incubator has a door 31 of the same construction as the cabinet panels. The door and the mating recess in the front panel 25 has stainless steel cappings 32 and the mating portions of the door and the recess have an intermediate foam gasket 33. A rubber seal 34 is secured to the bottom of the door to seal the door with the floor 11. The outer edges of the incubator housing are provided with anodised aluminium trim 35.

The use of a stable composite panel for the door avoids problems encountered in the prior art doors which tend to bow due to differential heat on the inner and outer sides of the incubator. The use of a foam gasket 33 provides an improvement in sealing over the previously used double rebated design of door.

A novel air flow system in accordance with a further aspect of this invention will now be described with reference to Figures 8 - 11.

The incubator is mounted on a floor 11 and has side walls 12 and a roof 15 with a door 31. The incubator has a longitudinal passageway 51 on a longitudinal axis of the incubator and on each side of which are a plurality of stacks of egg trays 40 operated by a turning mechanism (not shown).

Due to the weight of 142,560 eggs in the incubator, it is necessary to use two separate, but synchronised, turning units for the trays 40 supporting the eggs. Two heavy transverse mounting plates, one at each end of the incubator, are fitted between the beams and carry two gearboxes with a 3,900:1 reduction and are driven by electric motors. The output from each gearbox is transmitted via a duplex roller chain with a further 2:1 reduction to a lay shaft passing through the beams and carrying a crank at each end. Each lay shaft carries a set of three cams, one to control the angle of turn in each direction, another to give an impulse to the turning recorder, or hourly counter, and the third to control the level position for loading the trays 40. The gearboxes are sealed and adjustment is provided between the gearbox and lay shaft sprockets.Hourly turning is stimulated by a timer clock inside a control panel.

Located above the passageway and between the stacks of egg trays 40 is a ceiling 52 and equispaced along the ceiling, on the longitudinal axis, are a plurality of fans 53, there being ten fans in the presently described embodiment. Trunking 54, 55 is provided on each side of the longitudinal axis and extends partially along the length of the housing across a mid-point of the housing.

Each trunking forms a humidity air interchange trunking 54, 55 having an air inlet 541, 551 respectively, and air outlets 552, 553 respectively, the outlets being positioned adjacent a respective fan 53. In the present embodiment, three outlets are provided for each trunking 54, 55.

An air inlet duct 56 extends on the top of and from the front of the incubator along the longitudinal axis thereof to above a mid-point 57 of the incubator where an opening 58 is provided to permit air to pass into ducting 59 which extends fore and aft of the incubator. The ducting 59 has openings 60 of progressively increasing size towards the extremities of the housing to allow for the reducing pull of the fans. The inlet of the duct 56 is provided with a flow regulating valve 61. A primary or low humidity system is provided which is formed by a nozzle (not shown) at the inlet 541, 551 of the trunkings 54, 55 and the nozzles are operated by a single solenoid valve (not shown). The solenoid valve is controlled by a wet bulb thermometer up to a level of 82.50F wet bulb reading, at which level the valve closes.The waste water from the nozzle spray is carried away from the trunking by piping (not shown). Because the nozzles are located at the entry of the trunking, the moistened air is carried at high velocity to the far end of the duct where it is drawn into the fans. By placing the nozzles at opposing sides of the mid-point and at opposite sides of the longitudinal axis, both ends of the incubator receive moisture by the fans.

A secondary or high humidity system is formed by a steam generator 65 having a steam discharge pipe 66 which is at the entrance of the opening 58. Steam entering at this point travels with the inlet air along the distribution duct 59 and is blown into the incubator by the fans 53. The control level for the secondary or high humidity system is a 83.50F wet bulb and the steam generator is formed by a 3kW heater. The function of the secondary humidity system is to provide a topping-up service to keep the moisture level between 82.50F to 83.50F.

Three clusters of control thermometers 70 are located at each side of the longitudinal axis and on the longitudinal axis at the end wall 23 of the incubator.

Hot, humidified air is exhausted from the incubator through an opening 71 located in the end wall 23 and upwardly along a pipe 72. Alternatively, as shown in Figures 10 and 11, the exhaust may be provided by a pair of pipes 81 located on each side of the longitudinal axis and adjacent to the rear wall 23.

A cooling coil 80 is provided on the underside of the roof above the trunkings 54, 55 at the front, centre and rear of the incubator. Water cooling is used at a pressure of approximately 4bar. The cooling coils are positioned at a point where they are most effective in the return air flow and are only required to operate for a short period of time should an overheat situation arise. Any condensation from the coils is caught by drip pans (not shown) and in the tops of the humidity ducts which also fall on continuous pans. Each of the cooling coils is operated by separate solenoid valves with regulating gate valves and a flow indicator, the inlet water being passed through a fine screened filter. The solenoid valves are operated from the cooling contact thermometers, functioning via relays.

By the present invention, a highly efficient air circulating system is provided which ensures that the internal temperature and humidity of the incubator are closely controlled. The circulating air provides a transport medium for heat, cooling, humidity and CO2 within the incubator.

In operation, air is drawn by the action of the fans into the incubator via the flow regulating valve 61 and passes along the inlet duct 56 through opening 58 where it passes into the interior of the incubator and into the space between the roof and the ceiling. The air is then drawn fore and aft by the fans 53 and, as mentioned above, upon entering through opening 58 the air is humidified.

The air as it enters the incubator is shown by arrow-headed line . The primary air flow is downwards through the fans and blown substantially vertically towards the floor where, with reducing pressure, it fans outwardly, passing under, then substantially vertically upwardly through the trays of eggs. On reaching the roof the air passes through the three clusters of thermometers 70, thence passes through openings between the ceiling and the roof and in such passage passes beneath the cooling coils 80. The air thus passes into the area of maximum negative pressure immediately above the fans whereupon it is recirculated.

Such air flow is denoted by arrow-headed lines .

A secondary air circulation takes place as air passes up into the two humidity, air interchange trunkings 54, 55.

This air flow denoted by arrow-headed lines z and &commat; shows air being taken in at opposed inlets 541, 551 and being drawn out of openings at the distal ends of each trunking by the fans. Hence, a horizontal, fore and aft interchange is combined with the aforementioned vertical air flow.

Another air circulation pattern is achieved by air shown by arrow-headed lines passing upwardly through an aperture 90 located at the mid-point of the incubator and into the air inlet duct 59. As the relatively high pressure air passes up into the duct 59 it divides substantially equally fore and aft to pass along the front and rear sections of the distribution duct giving extra impetus to the relatively lower velocity air entering through the roof opening. The centre section of the distribution duct 59 is made of stainless steel and acts as a sump for collecting condensation from the steam discharge pipe 66.

Finally, the air is expelled, as shown by arrow-headed lines through the exhaust 71 or 81. The air below the ceiling where the exhaust is located is at maximum pressure and, therefore, driven into the exhaust.

By the subject invention, very thorough air mixing throughout the very large incubator results in a very low temperature differential at any point with no cold or hot spots. All eggs, therefore, receive an equal distribution of heat, cooling, humidity and CO2. Thus, substantially spontaneous incubation with minimal use of artificial energy is required. The six-way air circulation system coupled with the "total heat system" of the present invention utilises the natural heat given off by the developing embryos to maximum effect. The total "heat" is the sum of a multiplicity of uncontrolled sources of heat related to a large number of incubating embryos and their environment, namely: 1. Animal heat positive and negative.

2. Radiant heat from the eggs.

3. Surplus heat from fan motors.

4. Latent heat of egg evaporation.

5. Latent heat of vaporisation.

6. Latent heat of condensation.

7. Sensible heat of air supply and its moisture content.

8. Sensible heat of exhaust air and its moisture content.

9. Latent and sensible heat of water atomisation, etc.

At any time this arithmetical sum will be positive, zero or negative. The present invention has a total heat system close to zero most of the time, thereby producing the forementioned spontaneous incubation.

Claims (26)

CLAIMS:

1. A walk-in incubator formed by a plurality of wall and roof panels, each panel comprising an inner polyurethane foam insulating material, the major surfaces of which are covered with wooden material and wherein the wooden material is applied with a plastics outer surface.

2. An incubator as claimed in claim 1 wherein the wooden material is plywood.

3. An incubator as claimed in claim 1 or 2 wherein a wooden frame encompasses the minor edges of the insulating material.

4. An incubator as claimed in claim 3 wherein the plastics outer surface is a GRP sheet material.

5. An incubator as claimed in claim 4 wherein the insulating material, the plywood, and the GRP sheet material are vacuum bonded together.

6. An incubator as claimed in claim 5 wherein the wall panels have a density of 32kg/m2.

7. An incubator as claimed in any preceding claim wherein the wall panels are 10.8m x 2.5m.

8. An incubator as claimed in any preceding claim wherein there is provided a framework comprising two longitudinally extending beams each supported by six equi-spaced floor engaging struts, said framework forming a load bearing structure for the wall and roof panels.

9. An incubator as claimed in any preceding claim wherein the roof panels are interconnected by a rebate joint and are secured together by a polyurethane adhesive.

10. An incubator as claimed in any preceding claim wherein the wall and roof panels are interconnected by an orthogonal angle member and a silicone sealant is provided between the member and the panels.

11. An incubator as claimed in any preceding claim wherein the wall panels are secured to a floor through the intermediary of an orthogonal member and a polysulphide rubber is located between the bottom of the panels and the floor.

12. An incubator as claimed in claim 1 and substantially as herein described with reference to and as çown in Figures 1 - 7 of the accompanying drawings.

13. A walk-in incubator having a housing within which is located a plurality of stacked egg trays, said stacks being on opposing sides of a longitudinal passageway, said housing having a roof and a ceiling spaced from the roof and above the longitudinal passageway, a plurality of motor drivable fans located in said ceiling substantially above the longitudinal passageway of said housing, and air duct means located in the space between said ceiling and said roof, said air duct means comprising:: A. an external air inlet means arranged to provide air fore and aft to each of said fans, whereby said fans each blow the air substantially vertically toward the floor of the housing where, with reducing pressure, the air moves laterally outwardly passing under then vertically upwardly through the egg trays and, on reaching the roof, passes heat control means to an area of maximum negative pressure above the fans, whereupon said air is recirculated.

B. a pair of humidity air interchange trunkings each extending on an opposite side of the longitudinal passageway of said housing and extending at least partially along the length of the housing across a mid-point thereof, each trunking having an air inlet located opposite a plurality of air outlets, each air outlet being adjacent a respective fan, the inlet of each trunking being positioned at an opposite side of said mid-point from one another, whereby a substantially horizontal fore and aft interchange of air is combined with the substantially vertical air flow, and C. an aperture located at said mid-point into said air inlet means, whereby air passes upwardly thereinto and thence fore and aft to provide extra impetus to the relatively lower velocity external air.

14. An incubator as claimed in claim 13 wherein the passageway is located on a longitudinal axis of said housing.

15. An incubator as claimed in claim 14 wherein said external air inlet means is located centrally of said housing and includes ducting to provide said air fore and aft of said housing to said fans.

16. An incubator as claimed in claim 13 or 14 wherein a primary or low humidity system is provided which comprises a nozzle at the inlet of each of said pair of humidity interchange trunkings and means for controlling a water supply to said nozzles.

17. An incubator as claimed in any of claims 13 to 16 wherein there is also provided a secondary or high humidity system which comprises a steam generator arranged to introduce steam into said external air inlet means.

18. An incubator as claimed in any of claims 13 to 17 wherein an air exhaust means is provided through an opening in an end wall of said housing or through an opening at one end of the roof.

19. An incubator as claimed in any of claims 13 to 18 wherein cooling means are provided above the air interchange trunkings for preventing overheating of the incubator.

20. An incubator as claimed in claim 13 and substantially as herein described with reference to and as shown in the accompanying drawings.

Amendments to the claims have been filed as follows 1. A walk-in incubator formed by a plurality of wall and roof panels, each panel comprising an inner polyurethane foam insulating material, the major surfaces of which are covered with wooden material having la plastics outer surface, wherein the insulating material, the wooden material and the plastics outer surface are vacuum bonded together.

2. An incubator as claimed in claim 1 wherein the wooden material is plywood.

3. An incubator as claimed in claim 1 or 2 wherein a wooden frame encompasses the minor edges of the insulating material.

4. An incubator as claimed in claim 3 wherein the plastics outer surface is a GRP sheet material.

5. An incubator as claimed in any preceding claim wherein the wall panels have a density of 32kg/m2.

6. An incubator as claimed in any preceding claim wherein the wall panels are 10.8m x 2.5m.

7. An incubator as claimed in any preceding claim wherein there is provided a framework comprising two longitudinally extending beams each supported by six equi-spaced floor engaging struts, said framework forming a load bearing structure for the wall and roof panels.

8. An incubator as claimed in any preceding claim wherein the roof panels are interconnected by a rebate joint and are secured together by a polyurethane adhesive.

9. An incubator as claimed in any preceding claim wherein the wall and roof panels are interconnected by an orthogonal angle member and a silicone sealant is provided between the member and the panels.

10. An incubator as claimed in any preceding claim wherein the wall panels are secured to a floor through the intermediary of an orthogonal member and a polysulphide rubber is located between the bottom of the panels and the floor.

11. An incubator as claimed in claim 1 and substantially as herein described with reference to and as shown in Figures 1 - 7 of the accompanying drawings.

12. A walk-in incubator having a housing, said housing including a framework of load bearing beams connected together to form a self-supporting structure having exterior housing panels attached thereto, a plurality of stacked egg trays supported by said framework within said housing, said stacks being on opposing sides of a longitudinal passageway, said housing having a roof and a ceiling spaced from the roof and above the longitudinal passageway, a plurality of motor drivable fans located in said ceiling substantially above the longitudinal passageway of said housing, and air duct means located in the space between said ceiling and said roof, said air duct means comprising: : A. an external air inlet means arranged to provide air fore and aft to each of said fans, whereby said fans each blow the air substantially vertically toward the floor of the housing where, with reducing pressure, the air moves laterally outwardly passing under then vertically upwardly through the egg trays and, on reaching the roof, passes heat control means to an area of maximum negative pressure above the fans, whereupon said air is recirculated.

B. a pair of humidity air interchange trunkings each extending on an opposite side of the longitudinal passageway of said housing and extending at least partially along the length of the housing across a mid-point thereof, each trunking having an air inlet located opposite a plurality of air outlets, each air outlet being adjacent a respective fan, the inlet of each trunking being positioned at an opposite side of said mid-point from one another, whereby a substantially horizontal fore and aft interchange of air is combined with the substantially vertical air flow, and C. an aperture located at said mid-point into said air inlet means, whereby air passes upwardly thereinto and thence fore and aft to provide extra impetus to the relatively lower velocity external air.

13. An incubator as claimed in claim 12 wherein the passageway is located on a longitudinal axis of said housing.

14. An incubator as claimed in claim 13 wherein said external air inlet means is located centrally of said housing and includes ducting to provide said air fore and aft of said housing to said fans.

15. An incubator as claimed in claim 12 or 13 wherein a primary or low humidity system is provided which comprises a nozzle at the inlet of each of said pair of humidity interchange trunkings and means for controlling a water supply to said nozzles.

16. An incubator as claimed in any of claims 12 to 15 wherein there is also provided a secondary or high humidity system which comprises a steam generator arranged to introduce steam into said external air inlet means.

17. An incubator as claimed in any of claims 12 to 16 wherein an air exhaust means is provided through an opening in an end wall of said housing or through an opening at one end of the roof.

18. An incubator as claimed in any of claims 12 to 17 wherein cooling means are provided above the air interchange trunkings for preventing overheating of the incubator.

19. An incubator as claimed in claim 12 and substantially as herein described with reference to and as shown in the accompanying drawings.

20. A walk-in incubator comprising a floor on which is formed a framework of loadbearing beams connected together to form a self-supporting structure, said framework supporting a plurality of panels forming a housing.

21. An incubator as claimed in claim 20 wherein said framework includes floor-engaging struts each having, at the opposite end thereof from the floor, a plate to which is secured a longitudinally extending beam, whereby a beam is supported by a plurality of struts.

22. An incubator as claimed in claim 21 wherein an upper end of said plate is L-shaped to support a roof panel.

23. An incubator as claimed in claim 22 wherein said roof panel comprises an inner polyurethane foam insulating material, the major surfaces of which are covered with wooden material having a plastics outer surface, wherein the insulating material, the wooden material and the plastics outer surface are vacuum bonded together.

24. An incubator as claimed in claim 23 wherein said roof panel rests on said plate and a further plate is located on the opposite side of said roof panel to said plate and an assembly formed by said plate, said roof panel and said further plate is secured together by a nut and bolt, said bolt passing through said assembly.

25. An incubator as claimed in claim 20 wherein said framework has attached thereto wall and roof panels to form said housing, each panel comprising an inner polyurethane foam insulating material, the major surfaces of which are covered with wooden material having a plastics outer surface, wherein the insulating material, the wooden material and the plastics outer surface are vacuum bonded together.

26. A walk-in incubator as claimed in claim 20 and substantially as herein described with reference to, and as shown in, the accompanying drawings.