GB2129268A - Rack oven and rack system - Google Patents

Abstract

A rack oven comprises a chamber defined by one or more heat insulated walls and a closure member. The chamber is arranged to accommodate an array of trays disposed one above the other in a rack system, and includes a plurality of compartments, each individually heated from its base. Each compartment also can accommodate at least one tray of the rack system. In the rack system, a wheeled trolley chassis has a pair of upright members rising vertically from opposite ends of one edge, each upright member carrying a multiplicity of arms arranged in opposed pairs extending over the chassis. The arms provide a series of rack positions disposed one above the other in a system which can accommodate at least one tray for each pair of opposed arms.

Description

SPECIFICATION Rack oven The present invention relates to a rack oven, in particular a rack oven suitable for use in baking dough, for example, as loaves of bread, bread rolls and the like.

In its present widely used form, a rack oven comprises a baking chamber in which one or more wheeled trolleys carrying a multiplicity of racked trays can be accommodated. The chamber is heated from the rear by hot air fed via a blower system from a heat exchanger disposed outside the chamber and access to the chamber is provided through a single door at the front.

In the production of quality baked goods, a number of difficulties are experienced in the use of a rack oven of the above-known design. Thus, for example, because heat is provided via a blower system from a heat exchanger disposed outside the baking chamber, the chamber in its empty state filled only with air has a low thermai capacity, with the result that the temperature of the chamber falls rapidity to a low level each time the door is opened, and one or more hot trolleys with racks bearing baked goods are exchanged for cold troileys with racks bearing unbaked goods.

This temperature fluctuation, with the temperature in the initially filled oven being at a relatively low level, with subsequent rapid reheating from the rear, results in very uneven lift.

Consequently shaped goods can become misshapen as they cook, their quality thereby effectively being damaged.

Furthermore, because the baking chamber has such a low thermal capacity, that is because it lacks so-called "solid" heat, the goods first have to be effectively over-proved to achieve a reasonable finished size. In accordance with standard procedure, prior to baking goods formed of dough once moulded to the desired shape of the finished goods are "proved" by standing for a given time (determined by the individual baker according to his skill and experience) in a proving chamber.

As an alternative to providing over-proved goods, the problem of uneven lift and badly shaped goods can be overcome by including a larger than normal amount of improver in the dough. This however, results in large goods lacking in taste.

In addition, because heat is supplied to the rear of the baking chamber, and because circulation by means of hot air through an array of racks in practice is not good, complicated mechanisms with consequent increase in cost have been devised to rotate or otherwise move each rack system to improve circulation.

We have now found that the above-mentioned disadvantages can be overcome by providing an oven which can accommodate a trolley having a multiplicity of racks, and which provides a plurality of compartments, each individually heated from its base, each of which can accommodate at least one tray of goods for baking in a rack system.

Accordingly, the present invention provides a rack oven suitable for producing baked goods from proved dough, which oven comprises a chamber defined by one or more heat insulated walls and a closure member, the chamber being arranged to accommodate an array of trays disposed one above the other in a rack system, and including a plurality of compartments, each individually heated, and each of which can accommodate at least one tray of the rack system.

In a rack oven according to the invention, each compartment preferably comprises a base member including a heating element, the heating element preferably being one which is electrically heated. In one such arrangement, which is especially preferred, each base member comprises a pair of plates between which the heating element is sandwiched, the lower piate of the base member forming the roof of any next lower compartment. Preferably, such base member plates are metal, more preferably stainless steel.

For normal density baking, that is say for baking loaves of bread, it is preferred that the heated base members are arranged so that when a rack system is parked in the baking chamber an individually heated base mamber is disposed immediately beneath each tray carried in the system. Even with such an arrangement, the oven can be used to process a higher density of goods, say when baking buns, by providing twice as many trays disposed in the system, of which no more than two share each compartment so that pairs of trays are heated by a heated base member disposed immediately beneath the pair.

In a rack oven according to the invention at least the side walls of the oven preferably comprise heat-insulating bricks. However, it is more preferred that the rear wall and roof should also comprise heat-insulating bricks. By using such materials the oven can be pre-heated say on cheap rate electricity for use later with relatively minimum energy input at a higher tariff rate.

Preferably, the baking chamber is sub-divided into an upper set of compartments and a lower set of compartments, each of which includes a thermostat to control the overall temperature of the set. Preferably also, the upper and lower sets of compartments are separated by a dividing wall comprising an upper and a lower member, between which are sandwiched a layer of insulating material adjacent the lower wall member and a heating element adjacent the upper wall member. As in the case of the compartment base members, of which the dividing wall is a special case, the dividing wall members are preferably metal plates, typically stainless steel plates.

In a sub-divided arrangement as described above, the closure member is preferably operable to expose either or both of the upper or lower sets of compartments. With such an arrangement the whole baking chamber can be used to bake a load of goods disposed on racked trays carried on a trolley, with upper and lower sets of goods being cooked under different temperature conditions, if necessary. Furthermore, part of such an oven once used to bake one or more loads of say bread in a morning, and thereby pre-heated, can be used for more specialised baking throughout an afternoon, without the need to continue to heat both sets of compartments.

Preferably, each individual heating element of the baking chamber includes its own heat control to enable the temperature of each compartment to be individually varied.

In order to keep heat losses to a minimum during changeover time, each compartment preferably includes a flap member operable to close the open mouth of the compartment when the chamber is open. Preferably, a flap may be associated with each base member and may be pivoted about an axis in the plane of the member.

The series of flaps thus provided may be driven by a common drive system operable by movement of a trolley as it moves into and out of the oven.

The oven of the invention preferably also includes means to supply steam to the baking chamber in order to afford any necessary crust on loaves. Preferably, such steam supply means is arranged to supply steam to each compartment of the chamber.

The rack oven of the invention is suitable for use in producing baked goods from proved dough, the dough pieces from which the goods are baked being disposed on trays which in turn are arranged on racks in a system based on a trolley arrangement. In that connection the invention also provides a rack system comprising a wheeled trolley chassis having a flair of upright members rising vertically from opposite ends of one edge, each upright member-carrying a multiplicity of arms arranged in opposed pairs extending over the chassis and providing a series of rack positions disposed one above the other in a rack system which can accommodate at least one tray for each pair of opposed arms.

Preferably, each arm comprises a portion providing a horizontal surface on which at least an edge of a tray can be supported. Thus, for example, the arms may be formed having an "L"shaped cross section with the lower limbs of the "L" of each arm forming the necessary support, and opposed arms having their said lower limbs facing inwards towards each other.

Preferably, each arm is supported by a strut member fixed to the adjacent upright member, the gap between any strut and an adjacent next arm being such as to accommodate the thickness of a base member of a rack oven in accordance with the invention. Preferably also the chassis is rectanguiar and has a wheel at each corner.

The invention also includes the combination of a rack oven as defined herein, together with a rack system as defined herein.

The present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a perspective view from the front of one form of rack oven according to the invention; Figure 2 shows a view from one side of a rack system for use with a rack oven as shown in Figure 1; and Figure 3 is a diagrammatic cross section showing details of a preferred oven construction.

Referring to the drawings, the rack oven shown in Figure 1 comprises side walls 11 and 12, a rear wall 13 and a top wall 14 defining a baking chamber. The walls 11 to 14 comprise heatinsulating bricks 75 (Figure 3) sandwiched between metal sheets 76 and 77, at least the inner sheets 76 comprising stainless steel. At least the side walls 11 and 12 are supported on struts 15 and 16.

The baking chamber defined by walls 11 to 14 is sub-divided into a series of individually heated compartments by base members 17 to 24. Each base member 1 7 to 24 comprises an electrically operable heating element 78 (Figure 3) sandwiched between upper and lower metal plates 79 and 80 respectively, preferably of stainless steel. Furthermore, in the case of base members 17 and 21, these also include disposed beneath the heating element and above the lower plate 80 a layer of heat-insulating material 81.

The baking chamber is divided into two sets of compartments by base member 21. The insulating layer 81 of base member 21 effectively serves thermally to isolate the lower set of compartments defined by base members 17 to 21, when the upper compartments defined by base members 21 to 24 only are in use and vice versa. The baking chamber is closed by closure member 25 comprising a pair of doors 26 and 27 which can be operated together or separately. Each door respectively includes a window 28 and 29 and a catch 31 and 32.

Each heating element of each compartment includes its own heat control 33 to 42 respectively. Furthermore, each set of compartments includes its own on/off switch 43 and 44 respectively, as well as its own thermostatic control 45 and 46 respectively.

At the centre of the top edge of the oven there is a handle 82 to operate the oven damper system (not shown). As mentioned above the oven preferably includes means to supply steam to each compartment of the baking chamber and handle 82 serves to control that supply. As is known steam is supplied at the end of the baking cycle to give a crust on loaves etc.

Referring to Figure 2, the oven shown in Figure 1 is used with a trolley 47 comprising a pair of upright members 48 carrying a number of pairs of opposed arms 49 to 56. The arms 49 to 56 have an "L"-shaped cross section and are mounted so that pairs of arms provide opposed horizontal surfaces on which the edges of a tray can be supported when the tray is slid between an opposed pair of arms. The arms are supported by struts 57 to 64 respectively and the upright members 48 with their associated arms 49 to 56 are carried on a rectangular chassis 65 having a wheel 66 at each corner. Typically, the arms may be say 1 8 inches in length with a horizontal spacing of 184 inches.

In use, a series of trays bearing a suitable number of proved loaves or the like is each mounted at a rack position effectively provided by one of the pairs or arms 49 to 56, and the rack system bearing loaded trays is fed into the open oven of Figure 1. The arrangement of racks, trays and compartment base members is such that when the rack system trolley is parked with the chassis 65 below the base member 1 7 (subject to the inclusion of a suitable ramp arrangement, either if the floor is uneven or to achieve any necessary clearance), the various pairs of arms 49 to 56 with their associated trays are disposed with one tray immediately above each of the base member 17 to 24, with a typical clearance of about 2 inch (about 1.3 cms).The pair of doors 26 and 27 are arranged so that the trolley can be pushed into the chamber and the doors closed on the trolley when parked in the chamber.

Referring specifically to Figure 3, as can be seen there is preferably a gap 74 between the rear edge of each of base members 1 8 to 20 and 22 to 24, and the inner sheet 76 of the rear wall 13. The gap 74 improves circulation within each of the sets of compartments defined by the base member 21 sub-dividing the baking chamber.

Also, as can be seen, each base member includes a flap (the flaps 67, 68 and 69 of base members 20 to 22 only being shown), the flaps being movable about a pivot 83, 84 and 85 respectively by a drive arrangement operable by a microswitch whereby, as the rack system leaves the baking chamber, the flaps are brought to a vertical position as shown in dashed lines, from a position where they each lie fiat on a base member as shown in unbroken lines, so that each compartment of the overall baking chamber arrangement is effectively closed to retain heat during any time the chamber remains open between the leaving of one trolley and the entering of another. The micro-switch can be arranged to operate a motor which drives the series of flaps via a wire, downwards as the trays enter, and upwards as they leave. Additionally or alternatively, there may be a manual switch to activate the flaps.

In the arrangement shown above there is provided a rack oven which gives a very solid heat.

Moreover, the heat-insulating bricks enable the oven to be pre-heated on cheap rate electricity at night, resulting in minimal energy expenditure at peak rate during baking in a morning or afternoon session. Also, goods are heated from below, which is very useful with fermented goods and the above-described flap arrangement prevents unnecessary heat loss.

Furthermore, because the oven has two doors, the whole oven can be used for baking a series of loads of goods having a high demand such as loaves of bread, and part of the oven later can be used, during times of lower demand, for more specialised baking not requiring the use of a rack system. Furthermore, since there is solid heat supplied where it is required, there is no necessity to rotate or manoeuvre the racks once in situ, and accordingly the floor area of the oven can be relatively small, typically say 36 inches (about 91 cms) x 43 inches (about 109 cms).

In the case of the heating elements, these are readily accessible from the front of the oven and can be serviced and renewed with relative ease.

As will be appreciated the invention is not limited to the details described above. For example, a higher or lower number of heated base members may be provided, and the base members may be fitted in an arrangement whereby the number and spacing of base members may be varied according to the type of baking required.

Claims (23)

1. A rack oven suitable for producing baked goods from proved dough, which oven comprises a chamber defined by one or more heat insulated walls and a closure member, the chamber being arranged to accommodate an array of trays disposed one above the other in a rack system, and including a plurality of compartments, each individually heated from its base, and each of which can accommodate at least one tray of the rack system.

2. A rack oven according to claim 1, wherein each compartment comprises a base member including a heating element.

3. A rack oven according to claim 2, wherein the base member comprises a pair of metal plates between which the heating element is sandwiched.

4. A rack oven according to claim 2 or claim 3, wherein the heating element is electrically heated.

5. A rack oven according to any one of claims 2 to 4, wherein the base members are arranged so that when a rack system loaded for baking loaves of bread is parked in the chamber, an individually heated shelf is disposed immediately beneath each tray carried in the system.

6. A rack oven according to any one of the preceding claims, wherein at least the side walls of the oven comprise heat-insulating bricks.

7. A rack oven according to any one of the preceding claims, wherein the chamber is subdivided into an upper set of compartments and a lower set of compartments, each of which includes a thermostat to control the overall temperature of the set.

8. A rack oven according to claim 7, wherein the upper and lower sets of compartments are separated by a dividing wall comprising an upper and a lower member, between which are sandwiched a layer of insulating material adjacent the lower wall member and a heating element adjacent the upper wall member.

9. A rack oven according to claim 8, wherein the wall members are metal plates.

10. A rack oven according to any one of claims 7 to 9, wherein the closure member is operable to expose either or both of the upper or lower set of compartments.

11. A rack oven according to any one of the preceding claims, wherein each compartment includes a flap member operable to close the open mouth of the compartment when the chamber is open.

12. A rack oven according to claim 11 , wherein a flap member is associated with each base member.

13. A rack oven according to claim 11 or claim 12, wherein the flaps are driven by a common drive system operable by movement of a rack system trolley into and out of the oven.

14. A rack oven according to any one of the preceding claims which includes means to supply steam to the chamber.

1 5. A rack oven according to claim 14, wherein the steam supply means is arranged to supply steam to each compartment of the chamber.

16. A rack oven substantially as hereinbefore described, with reference to and as iliustrated in the accompanying drawings.

17. A rack system, which system comprises a wheeled trolley chassis having a pair of upright members rising vertically from opposite ends of one edge, each upright member carrying a multiplicity of arms arranged in opposed pairs extending over the chassis and providing a series of rack positions disposed one above the other in a rack system which can accommodate at least one tray for each pair of opposed arms.

1 8. A rack system according to claim 17, wherein each arm comprises a portion providing a horizontal surface on which at least an edge of a tray can be supported.

19. A rack system according to claim 18, wherein the arms are formed having an "L"shaped cross section, with the lower limbs of the "L" of each arm forming the necessary support, and opposed arms having their said lower limbs facing inwards towards each other.

20. a rack system according to any one of claims 17 to 19, wherein each arm is supported by a strut member fixed to the adjacent upright member, the gap between any strut and an adjacent next arm being such as to accommodate the thickness of a base member of a rack oven according to any one of claims 1 to 1 6.

21. A rack system according to any one of claims 1 7 to 20, wherein the chassis is rectangular and has a wheel at each corner.

22. A rack system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

23. The combination of a rack oven according to any one of claims 1 to 16, together with a rack system according to any one of claims 17 to 22.