Improvement in Controlling the Temperature in Baking Ovens.
Year: 1896

page_text: Improvement in Controlling the Temperature in Baking Ovens.
I, PAUL FFLEIDERER of Throssel House West Norwood S.E. Engineer do
hereby declare the nature of my said invention to be as follows:-
In modern bakeries it is sometimes necessary to cool an oven down temporarily
but rapidly and it is equally important to raise the baking temperature again
without loss of time. Under my invention one way of doing this is to employ a
regular Perkins heating coil more or less widely spread out in the baking chamber
of the oven which in this case takes the place of the furnace and to connect it with
an expansion chamber and a short circulation pipe well bedded in non conducting
material to reduce the loss of hent while no cooling is wanted when this complete
hot water heating apparatus serves as a heat storage and equalizing system I add
or insert an ordinary line of outside circulation pipe which when I switch it in
instead of the short insulated circuit will draw heat from and cool the oven the
more rapidly the longer the circulation and the more receptive the medium or fluid
is to which the heat is given off the most convenient method being that of passing the
circulation pipe through water which when heated may be utilized for other purposes
and which water if kept circulating in radiators through pipes may serve as a
secondary or as a low pressure heating apparatus. Another way is to utilize heat
storage pipes such as are described in my Patent No. 1462 A.D. 1893 which may exist
in the oven or be put in for the purpose or in case of hot water or steam ovens the heat
carrying or fire pipes themselves may be so utilized by passing either or both kinds of
such pipes through larger pipes running crossways similar to or rather taking the
place of the equalizing block T. These cross pipes are of larger bore than the
utside diameter of the storage or fire pipes passing through them so that any
water or fluid in them can circulate or communicate around the sinaller pipes so far
as they are exposed inside the bore of the larger pipes the water circulated or
passed thro' thus equally cools all the small pipes and thereby the baking
chamber itself. Another way is to evaporate water in the baking chamber with or
without spray or sprinkler and with or without the addition of artificial draught.
My two first plans can be carried into practice in such a manner that they avoid
the disadvantages experienced by others who have tried to cool part of the oven
by applying thereto a coil or length or pipe through which they pass a cooling
current of water which often gradually deposits an incrustation inside the pipe
and scon prevent the working of the apparatus. The water which I circulate
either thro' a Perkins hot water heating coil or thro' the above mentioned
cress pipes I prefer to use over and over again thus avoiding incrustation and as
circumstances make it desirable I cool the thus circulating water by passing it
through a sufficient length of piping which will give off the heat to the surrounding
atmosphere as in an ordinary heating apparatus or to make a shorter line of pipes
do the work pass that line wholly or in part through a vessel or boiler and now
if necessary the water in such boiler may be constantly changed or renewed
without any danger of corroding the bore of the pipe built into the oven or of

page_text: causing any incrustation in it. This arrangement may be worked intermittently
and may serve as an approximate measurement of the quantity of heat withdrawn
from the baking chamber by having a closed boiler of given capacity filling the
same with cold water and running the water off as soon as it has reached a
certain temperature. The boiler may be well covered and insulated so that when
it contains air and vapour it absorbs hardly any heat while a given quantity of
cold water quickly run into it will rapidly remove a certain quantity of heat from
the circulating water and thereby cool the baking chamber rapidly although
indirectly. Even in this arrangement if a suitably constructed boiler be employed
the cooling water may be utilized over and over again in a closed system by
making the boiler communicate with a vessel or vessels of similar content so
arranged that air and water may be readily made to change places the air being
now in the boiler and the waiter in the outside vessels under ordinary conditions
while the water is caused to run into the boiler (receiving the heat from the baking
chamber through the circulating Perkins hot water current) and the air to take its
place in the outside vessels as soon as cooling the oven is required.
Where the nature of the water admits of it the cross pipe may be exactly fitted
with its row of storage or fire pipes either as a tight fit or without being quite
water tight and a current of fresh water passed through or a certain quantity of
fresh water filled into it with the object of becoming evaporated by means of the
heat it withdraws from the small pipes the steam so produced may escape in the
one case through au outlet from the large (cress or block) pipe to the outside or it
may partly leak away through the imperfect joints at the points where the small
pipes penetrate the large pipe and in the latter case the steam escapes into the
baking chamber so that where this is objectionable the former plan of steam-tight
joints must be adhered to.
Nevertheless the main principle and object of my invention is to produce the
cooling effect of a body of water which although it does not or need not come
in direct contact with the walls of or with the atmosphere in the baking chamber
yet rapidly draws and carries away a large amount of heat by exactly the same
means as those by which similarly confined bodies of water transfer heat on the
Perking principle ez. by circulating inside a system of hermetically sealed pipes
through the walls of which auch heat enters at the furance end and is thrown out
again at whatever parts of the pipes the surrounding outside temperature is lower
than that of the water and steam at the respective spot inside the pipes.
Alternately surrounding those parts of the cooling pipes or coil with water or air
ie, passing them through vessels or boilers which can be alternately chargel with
water or air gives me a ready means of rapidly creating a high pressure or head
of temperature for quickly drawing off the heat from the baking chamber or of
keeping it in with a minimum of loss when no cooling is required. All this being
done quite independently from the state of the fire in the furnace of the oven the
same is always ready to supply without loss of time the larger haking heat at a
higher temperature in the baking chamber, my method of cooking may be compared
to a train with the brakes on being propelled by a locomotive engine working at
and exerting its utmost power and yet not imparting the corresponding full speed
i.e. that speed which it would impart if there were no brake on. Taking off the
brake gives the full speed in a very short time equally as running the water off
which surrounds the cooling pipes brings lack the full baking temperature very
quickly. To avoid overheating I provide the baking or other chamber with a
safety plug alarm consisting of a Perkins pipe containing a quantity of fusible
metal instead of the water and being hermetically sealed. The pipe is set inclined
with the solid metal charge at the higher end and so balanced on a knife edge or
anti friction trunnion that as soon as the bulk of the fusing plug has melted and
the liquid metal has run to the lower end the pipe tips over and strikes an alarm at
the same time turning on the cooling water or opening a valve or damper or doing
all those things direct or by setting further motive power into operation to do what
is necessary for counteracting any dangerous or inconvenient consequences arising

page_text: from too high a temperature prevailing in the oven or drying closet or other heated
chambers
Dada 1 1 1900
GEO.
DOWNING,
8 Quality Court, London, W.C., Agent.
COMPLETE SPECIFICATION.
Improvement in Controlling the Temperature in Baking Ovens.
I PAUL PFLEIDERER of Throssel House West Norwood S. E. Engineer, do
hereby declare the nature of my said invention and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement, reference being hereby made to the accompanying drawings,
in which similar letters of reference indicate corresponding parts:-
In modern bakeries it is sometimes necessary to cool an oven down temporarily
but rapidly and it is equally important to raise the baking temperature again
without less of time. Under my invention one way of doing this is to employ a
regular Perkins heating coil (Fig. 1) more or less widely spread out in the
baking chamber of the oven, which in this case takes the place of the furnace
and to connect it with an expansion chamber and a short circulation pipe well
bedded in non-conducting material to reduce the loss of heat, while no cooling is
wanted, during which time this complete hot water heating apparatus serves as a
heat storage and equalizing system to the baking chamber. I add or insert an
ordinary line of outside circulation pipes C which, when I switch it in instead of
the short insulated circuit, will draw heat from and cool the atmosphere in the
oven the more rapidly the longer the circulation and the more receptive the
medium or fluid is to which the heat is given off, the most convenient method being
that of passing the return circulation pipe through water which when heated may
be utilized for other purposes and which water if kept circulating in radiators
through pipes may serve as a secondary or as a low pressure heating apparatus.
Another method is to utilize heat storage pipes such as are described in Figs. 10, 13,
14 and 15 of my Patent No. 1462 A.D. 1893, which may exist in the oven or be
put in for the purpose, or, in case of hot water or steam ovens, the heat carrying
or fire pipes themselves might be so utilized, by passing either or both kinds of
such pipes through larger pipes T (Figs. 2, 3 and 4) running crosswise, similar to
or rather taking the place of the equalizing block T. These cross pipes T are of
larger bore than the outside diameter of the storage or fire pipes S passing
through them, so that any water or fluid in them can circulate or communicate
around the smaller pipes S so far as they are exposed inside the bore of the larger
pipes T; the water circulated or passed through thus equally cools the small
pipes S and thereby the baking chamber itself. A common way is to evaporate
water in the baking chamber with or without spray or sprinkler, and with or
without the addition of artificial draught. My two first plans can be carried into
practice in such a manner that they avoid the disadvantages experienced by others
who have tried to cool certain hotter parts of ovens by applying thereto a coil or
length of pipe through which they pass a cooling current of water which often
gradually deposits an incrustation inside the pipe or coil which soon prevents the
working of the apparatus. The water which I circulate either through a Perkins
hot water heating coil C, or through the above mentioned cross pipes T, I prefer
to use over and over again, thus avoiding incrustation, and, as circumstances nake
it desirable, I cool the thus circulating water by passing it through a sufficient
length of piping which will give off the beat to the surrounding atmosphere, as in

page_text: an ordinary heating apparatus; or, to make a shorter line of pipes C do the work,
pas that line wholly ur in part through a vessel or boiler B, and, if necessary,
the water in auch hoiler B may he constantly changed or renewed without any
danger of corroding the bure of the pipe Iuilt into the oven, or of causing any
incrustation therein. This arrangement may be worked intermittently, and may
serve as a means of approximate measurement of the quantity of heat withdrawn
from the baking chamber O, by having a closed boiler B of given capacity, filling
the same with cold water, and running the water off as soon as it has reached a
certain temperature. The boiler 1 inay he well covered and insulated, to that,
when it contains nir and vapour, it absorbs hardly any heat, while a given quantity
of cold water quickly run into it will rapidly remove a certain quantity of heat
from the circulating water, passing down through the return pipe, and thereby
cooling the baking chamber O rapidly, although indirectly, seniling the heat up
through the flow pipe. Even in this arrangement, if a suitably constructed boiler
surrounding the return pipe be employed, the cooling water may be utilized over
and over again in a closed system, by inaking the boiler communicate with a vessel
or vessels of similar contents, so arranged that air and water may be really mule
to change places, the air leeing now in the boiler and the water in the outside
vessels under ordinary conditions, while the water is caused to run into the boiler
(receiving the heat from the baking chamber through the circulating Perkins
hot water current) and the air to take its place in the outside vessels as soon as
the oven is required to be conled.
Where the nature of the water admits of it the cross pipe T may be exactly
fitted with its row of storage or fire pipes S, either with a tight fit or without being
quite water tight, and a current of fresh water passe! through, or a certain
quantity of fresh water filled into it with the object of becoming evaporatel by
means of the heat it withdraws from the small pipes S; the steam so produced
may escape in the one case through an outlet from the large (cross or block) pipe T
to the outside, or it may partly leak away through the imperfect joints at the
points where the small pipes S penetrate the large pipe T, and in the latter rasu
the steam escapes into the baking chamber O. But where this steam and wat
vapore is objectionable the former plan of steam tight joints must ha adhere i to.
Nevertheless the main principle and object of my invention is to produce the
cooling effect of a body of water, which, although it does not, or need not, come
into direct contact with the walls of, or with the atmosphere in, the baking
chamber O, yet rapidly draws and carries away a large amount of heat from
inside such chamber by exactly the same means as those hy which similarly
confined bodies of water transfer heat on the Perkins principle, ri, by circulating
inside a system of hermetically sealed pipes, through the walls of which such best
enters at the furnace end, and is thrown out again at whatever part of the pipes
the surrounding outside temperature is lower than that of the water and steam or
other heat-absorbing fluid flowing past the sama. Alternately surrounding thuse
parts of the cooling pipes S, or coil C, with water or air fe.mising these pipes
ihrough vessels or boilera which can be alternately charged with water or air,
affords a ready means of rapidly creating a high pressure or head of temperature,
for quickly drawing off the heat from the baking chamber O, or of keeping it in
with a minimum of luss, when no cooling is required. All this being done quite
independently from the state of the fire in the furnace of the oven, the same is
always rondy, as is the heat retaining brickwork, to supply without loss of time
the larger baking heat which may he required immediately afterwards at a higher
temperature in the baking chamber. Running the water off which surrounds the
cooling pipes brings back the full baking temperature very quickly. I therefore
provide the baking or other chamber with a permanent. safety plug alarm as shown
in Fig. 5, to avoid over-heating. This appliance consists of a Perkins pipo P
containing a quantity of Fusible material, such as composition or metal M, instead
of water, and being also bernetically sealed. The pipe P is set at an inclination
with the solid metal charge M at the higher end, and so halanced on a knife edge,

page_text: or anti-friction trunnion, that, as soon as the bulk of the fusing plug M has:
melted, and the liquid metal has run to the lower end M', the pipe P tips over and
strikes an alarm A, at the same time turning on the cooling water or opening a
valve or damper V, or doing all these things either by direct action or by setting
further motive power into operation to do what is necessary for counteracting any
dangerous or inconvenient consequences arising from too high a temperature
prevailing or arising in the oven or drying closet, or other heated chambers, when
the cooling current is turned off, or the water in the boiler B is replaced by air, or
if for any other reason the temperature has risen above the required maximum,.
corresponding with the melting point of the fuse metal, or other meltable
material.
On hearing the alarm the attendant can take the safety fuse pipe P' out, and'
stand it upright in a cool place, or dip it into water, so as to re-solidify the fuse.
metal M in its proper place, when the pipe is ready to serve again; and so on for
an indefinite number of times. This simple alarm or automatic maximum indicator
may be usefully employed by itself for controlling high or low temperatures as for
instance in cold storage rooms, where the temperature should not rise for any
length of time above freezing point of water. For such purpose the simplest fuse
plug is ice, which, melting into water, causes the pipe to over balance, and,
besides raising the alarm, may be made to regulate the refrigerator. Certain fats.
or tallows, such as cocoa butter or similar mixtures which readily melt and solidify,
may thus be used for controlling temperatures in rooms. The infinite number of
tinies and the absolute cleanliness with which the fusing material may be used
over and over again, is a valuable commercial feature in this part of my invention,.
which is not confined to ovens only.
The Perkins system of rapid heat transferring and conducting by means of
ready-heat-absorbing and heat-transmitting liquids or fluids, which are enclosed
and allowed to change their aggregate state, and to flow freely inside a system of
hermetically sealed pipes from the one end of such system, where higher
temperature surrounds it, to other parts or ends of it, where the surroundings are
cooler, returning again after having lost i.e. :-transmitted its heat to those cooler
surroundings, to the hotter end by gravitntion, without ever coming into direct
contact with the bodies or surroundings from and to which it carries the heat, is
now well understood, but what I claim as my invention is
1. The combination with and application in the manner described to the cooling.
of baking chambers of externally heated baking or other ovens of a system of
Perkins coils C and C or pipes T and S with a boiler B alteruately chargeable
with water or air by themselves or controlled by the safety fuse pipe P as and for
the purpose set forth.
2. The combinations with so cooled baking or drying chambers or other hot or
cold rooms heated or cooled artificially by the Perkins or similar system of pipes
of a hermetically sealed safety pipe P, so balanced and supported and filled with a
small quantity of matter, which while in the solid aggregate state remains at the
higher end motionless, but which when melted runs by gravitation to the lower
end whereby it upsets the equilibrium of the pipe soon after the temperature to
which the pipe is exposed has risen above the melting point of the matter, as and.
for the purpose described.
Dated 2nd L. 1907
GEO.
DOWNING,
8 Quality Court, London, W.C., Agent.