Note: Descriptions are shown in the official language in which they were submitted.
4~7a
This invention relates to a method of and apparatus for
cooling blocks of hot porous material and more particularly but
not exclusively for the rapid cooling of bread and the like food
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While the invention will be hereinafter described in terms
of the rapid cooling of bread and like food products, it will be
' apparent that the apparatus and the method herein described are
'~ suitable for the rapid cooling of blocks of porous material other
than food stuffs.
When bread is removed from a baking oven, it is necessary
for the bread to be cooled before any further operation such as
slicing and wrapping can take place. All the presently known
methods of cooling freshly baked bread are variations of con-
ventional fan cooling in which loaves of bread are racked either
manually or automatically and air is blown over their external
surfaces. The time taken to cool bread by these conventional
fan cooling methods varies from 90 minutes to 3 hours and requires
the installation of space consuming and expensive racking equipment
in the bakery. In addition the labour costs necessitated by the
presently known cooling methods is high in relation to the profibs.
Attempts have been made to cool bread rapidly by adopting
processes such as that utilised for cooling produce such as
lettuce. Such a process utilises the principle that when water
i8 subjected to reduced pressure it evaporates more readily with
attendant lowering of the temperature of the object from which the
water evaporates. Thus it is known to endeavour to cool bread by
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subjecting the bread to pressure lower than atmospheric pressure
during the cooling process. A hot loaf of bread subject to a
controlled reduction in air pressure down to a maximum vacuum
which is normally obtainable by commercially available vacuum
pumps will undergo a decrease in temperature from about 400F
to about 100F in a period of about 30 to 50 seconds. However
before this cooling process, it is necessary to rack the bread or
place it in compartments which must then be subjected to reduced
air pressure, In any event such fall in temperature is still
not sufficient to permit slicing and/or wrapping of the bread and
it is still necessary to allow the bread to cool naturally even
further before slicing and/or wrapping takes place so that the
benefits through such cooling are largely negated. In addition
a disadvantage is introduced by such known cooling processes in
that the bread suffers dehydration with a consequent loss in
quality.
Accordingly the invention consists of a method of cooling a
block of porous material comprising inserting said block into a
chamber, subjecting the chamber to air pressur less than that of
the ambient air and inserting means into the said block to induce
a flow of air through the interiar of the block to the said chamber.
I n another form the invention may also be said to consist
of means to induce a flow of air from the interior to the exterior
of a block of porous material comprising a chamber adapted to
house said block and to be maintained during an operative cycle
at an air pressure less than ambient air pressure means to
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locate and to grip the block within said chamber; an injector ~:
needle assembly including an injector needle adapted to enter
the said block after it has been located by the said gripping
means; and means to move the injector needle into said block
- 5 to allow air to flow through the said needles into and through
the said porous block.
A preferred form of the invention will now be described
with the aid of the accompanying drawings wherein:-
Fig. l is a side elevation of one form of the apparatus
and
Fig. 2 an end view partly in section of the apparatus
shown in Fig. 1.
Fig. 3 is a sectional view through a vacuum chamber.
Fig. 4 is a view to a larger scale of a detail of Fig. 1.
Referring to the drawings, a chamber wheel 1 is journalled
on bearings 2 suitably supported on a stand 3. The chamber
wheel is adapted to be rotated by means of a motor 4 driving
a reduction gear-box 5 through an air operated clutch 6. The
gearing is so arranged that the speed of revolution of the chamber
wheel is preferably one revolution every 50 seconds, but this can
be varied as required. The chamber wheel is of a size that it
can carry a number of vacuum chambers7 (see also Fig. 3) on its
periphery~ Each chamber, which is of a size that it will accept
the largest loaf of bread that it is desired to be cooled by the
apparatus, includes a loaf gripping means indicated in Fig. 3 and
which will be hereinafter further described. The number of
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chambers 7 on the periphery of the wheel and hence the
diameter and size of the wheel is set by the number of
chambers required and by the speed of rotation of the
wheel. In the preferred embodiment, sixty vacuum chambers
7 are arranged around the periphery of the chamber wheel.
Each vacuum chamber can be formed for instance from glass
reinforced, plastics material or the like and has a base 10,
si~wallsll and end walls 12 to form a box like structure.
The perimeter of the chamber wheel is provided with a cold
air duct 13 which extends on either side of the vacuum
chamber and which communicates with the interior of each
chamber as will be hereinafter described. t
The loaf gripper means are adapted to grip and retain
a loaf of bread after it has been inserted into the chamber
and are arranged so as to be automatically triggered to retain
the loaf within the chamber. The gripper means may consist of
two plates 14 which oppose each other and which are spaced
apart as indicated in Fig. 3. The plates are attached to
staunchions 15 which have sleeves 16 so that they can have a
sliding movement towards and away from each other on a support
rod 17. The sleeves 16 are spring loaded by means of coil
springs 18 so that the two plates will normally tend to move
together, The plates 14 are attached to the staunchions 15 by
means of springs 19 and bolts 20 in order that the plates can
be self aligning when they grip the sides or ends of the loaf.
In addition, studs 22 protrude from the opposing face
of each plate so as to assist in retaining the loaf after it has
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been gripped. A hydraulic ram 23 is arranged so that when
air under pressure is let into the ram, the plates 14 will
be held apart to the furthest extent. When a loaf has been
inserted into the chamber as will be hereinafter described
an air switch 27 is triggered so that the air under pressure
within the ram is exhausted, whereupon the springs 18 will pull
the plates 14 together to contact and grip the loaf of bread. !
Means are also provided so that when the plates 14 have
gripped the loaf of bread, further inward movement of the
plates is prevented. Such further inward movement would
otherwise damage the loaves which until cooled can be easily
crushed. One preferred means as indicated in Fig. 3 comprises
a ratchet and a pawl arrangement. The ratchet is preferably
in the form of a saw tooth rack 30 formed into or as part of
the support rod 17 while the pawl consists of a rod 31 slideable
within a cylinder 32 and spring loaded in an upwardly direction
by means of the spring 33. The lower end 34 of the pawl is so
formed that when it is in its lowered position the pawl will
engage the rack 30 and so prevent further inward movement of
the plate. A pawl actuating lever 35 extends from the plate
and terminates in a cam shaped enlargement 36 so that when
the plate is pushed in the directio- of the arrow III in Fig. 3
the pawl will be moved downwardly into a locking position.
Thus when a loaf of bread is inserted into the chamber the
hydraulic ram is actuatec to spread the plates 14 and the ram
then released so that the springs will act to bring the plates
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together so that the loaf will be gripped by the plates.
When the bias of the spring 19 is overcome, the pawl will be
actuated to engage the rack 30 and so prevent further inward
movement of the plates.
Each vacuum chamber includes at leastOne and preferably
two injector needle devices 40 for penetration of the loaf and
for admission of the cooling air and conveniently such devices
may be formed as part of the gripper means indicated in Fig. 3.
Each injector needle device includes a cyclinder 41 in which an
injector needle assembly can have sliding movement. An air seal
is formed by a gland 42 within the cylinder so that when air
; under pressure is let into the forward part of the cylinder, the
needle assembly will move in the direction of the arrow IV and
the air within the rearward part of the cylinder will exhaust
through the port 43 into the cold air duct 13. The air within
the cold air duct will normally be pressurised and can if desired
be refrigerated. The injector needle cylinder is fixed to a
gland 44 attached to the side wall 11 of the vacuum chamber so
as to form an airtight seal between the vacuum chamber and the
- cold air duct. Such gland 44 will also support the injector
needle cylinder 41 so as to correctly orientate it. When the
air in the forward part of the cylinder is exhausted to atmosphere,
then air under pressure within the cold air duct will pass through
the port 43 and enter the rearward part of the cylinder 41 and
will exert pressure on the gland 42 so as to force the injector
needle assembly to the position indicated in Fig. 3 i.e. in its
fully inserted position. The injector needle assembly consists
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of a tube 45 which is attached at one end to the gland 42 and at
its other end to a hollow hypodermic needle 46 the bore of which ;
can communicate with the bore 47 of the rod so that air can pass
from the cold air duct 13 through the port 43 into the rear part
of the cylinder, through the bore of the tube 45 and needle 46
and exit through the holes 48 formed in the cannula of the needle.
As shown in Fig. 3 two injector needles 46 are employed and both
injector needles can share a common longitudinal axis or can be
offset one from the other in order to accommodate different size
loaves and so as to provide a necessary form of adjustment in the I
cooling rate of different types of loaves. The needle 46 is
therefore of a length that it can be fully retracted from the loaf
of bread as required and can be inserted at least approximately
half the length of the loaf held between the plates 14.
Means are also provided so that the vacuum chambers 7 can be
selectively sealed as the chamber wheel rotates. As shown in the
drawings this is arranged by means of an endless belt 50 which
runs on the periphery 51 of the chamber wheel in recesses 52 (See
Fig. 3) formed in such perimeter. The belt is constructed so that
at the required degrees of rotation of the chamber wheel it will
positively seal one chamber 7 from the next and will also seal
each chamber 7 from ambient air pressure. The belt is an endless
belt and is guided by means of a framework 54 which is fixed to
the support frame 3 of the chamber wheel and which is provided with
rollers 55 so that the portion of the belt which is not contacting
the chamber wheel can be continuously returned and such return
rund will hot contact the chamber wheel. Thus is will be apparent
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that as the chamber wheel rotates, each chamber 7 will be success- -
ively covered by the belt and will remain covered until it reaches
the portion of the arc wherein the belt loses contact with the
chamber wheel to open the chamber. Preferably spring tension (not
shown in the drawings) or other means as known in the art is
utilised to maintain tension on the belt so as to ensure sealing
between the belt and the periphery of the chamber wheel. The
belt is preferably a rubberised nylon reinforced fabric and
has sufficient strength that when each vacuum chamber 7 is sub-
jected to vacuum as will be hereinafter described, a minimum -~
deformation of the belt will occur, so as to minimise the
possibility of the belt contacting the loaf of ~readwithin
the vacuum chamber. Means are provided so that each chamber
will be subjected to vacuum when the chamber wheel has rotated
to its correct station. This is arranged by means of a vacuum
pump connected to a rotary valve 57 (see Fig 2.) of a conventional
form with the valve being connected by vacuum lines 58 to the
respective vacuum chambers.
Means are also provided to insert a loaf of bread to be
cooled into each vacuum chamber 7 as appropriate. One preferred
method of obtaining this is shown in Fig 1. wherein a conveyor
belt 60 receives loaves 61 of bread direct ~rom a conventional
depanning machine (not shown in the drawings). The conveyor
comprises a number of bars 62 attached between a pair of endless
chains. Such conveyors are widely used in bread wrapping instal-
lations and are constructed so that each loaf rests against a
bar 62 to ensure a predetermined distance between each loaf. When
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the loaf reaches the discharge end 64 of the conveyor, it is
passed onto a carrier table 65 bf an insertion mechanism 66.
The insertion mechanism 66 is adapted to have movement in a
radial direction towards the axis of the chamber wheel and this
can be arranged by means of a rack 67 and pinion 68 so as to
have the required radial movement. The movement of the insertion
mechanism is time , for instance by the photocell uni~ 70, so that
when the chamber wheel reaches its correct station then the
photocell unit will activate either a clutch or electric switch
(not shown in the drawings) so as to move the carrier table in
a radiàl direction and to insert the loaf into the aligned
,S,, chamber 7 at station A of Fig. 1. At this point the air switch
27 (see Fig.2) will operate so that air under pressure is let
into the ram 23 so as to move the plates 14 apart. When the loaf
is correctly positioned within the chamber, the air switch 27
will again operate to open the ram to atmospheric pressure where-
upon the plates 14 will be spring urged together by the springs
18 so that the plates will grip the loaf of bread. The carrier
table 65 of the insertion mechanism is then retracted and an
impulse sent to the air clutch 6 so as to engage the clutch to
allow the chamber wheel to move to the next station. At the
station B of Fig. 1 the belt is commencing to seal the chamber
and when the chamber wheel proceeds to the next station C the
belt will completely seal the chamber. At this station the
chamber is subjected to vacuum by reason of the vacuum line 58
being connected through the valve 57 to the pump 56. The cold
air duct will normally contain air at atmospheric or above
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atmospheric pressure and the difference in pressure within the *
cyclinder 41 will act on the gland 42 of the insertion needle
assembly so that the insertion needles 46 will move and enter
fully into the loaf of bread. As the chamber wheel rotates, the
loaf of bread will be subjected to continuous vacuum in the
chamber and cool air will flow through the loaf from the cold
air duct 13 thus cooling the loaf from the inside out. When
the loaf reaches station D the gripping mechanism is released
and the loaf will drop onto the table 75 of the withdrawal
mechanism 76 which will be in the advanced position~ that is
with the table adjacent to the perimeter of the chamber wheel.
The table 75 is in the form of bars which cooperate with
fingers 77 which project from a frame work 78 on which a
discharge conveyor belt 79 is supported. When the withdrawal
mechanism is retracted to the position indicated in Fig. 1 the
fingers 77 will lift the loaf off the table 75 and the loaf will
~lide by gravity onto the discharge conveyor belt 79 where it
will be conveyed to the slicing and/or packing operations.
The injector needle assemblies are so constructed that the
injector needles 46 will enter either end of the loaf and will
penetrate the loaf for the required distance. Thus the len~th
of the nedles will normally be selected so as to correlate with
the length of loaf to be cooled. In some cases it might be
desirable for the injector needles to penetrate more than half
the length of loaf to be cooled and in such a case the injector
needles can be suitably offset so that when they enter the loaf
at either end no clashing of the needles will occur.
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The vacuum which obtains within the chamber and in addition
when the cold air duct is pressurised, will assist the action
; of the springs l~ so that the movement of the injector needles
;..
",J, . 46 into the loaf is rapid~. While the preferred form of the
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,~ 5 invention utilises cold air ducts to enable air to enter through
the needles into the loaf, nevertheless the bores of the injector
needles can be open to atmosphere in certain circumstances. It
is however desirable that the fresh air supply be as clean and
as cool as possible and preferably the air should be dry although
' 10 it may contain moisture in certain circumstances and it may also
include other additives such as flavouring, colouring,
preservatives and the like.
Because the pressure within the loaf and within the vacuum
chamber is kept reasonably constant by the vacuum pump, the
expansion of air as it flows through the orifices in the
needle will service to further cool the air and the movement
of the cool air through the pores of the loaf will quickly
and rapidly cool the loaf. The amount of cooling of the loaf
can be determined by the amount of time the injector needles
remain within the loaf, although normally the injector needles
will remain within the loaf for the full distance between
stations C and D.
