FR2570167A1 - Automatic device for controlling the flue flap - Google Patents

Abstract

The invention relates to a device making it possible to automatically close a flue flap upon extinction of the fire and reduce the draught when the fire is too violent. It consists of a servomotor 1 consisting of a bimetallic strip wound into a spiral 6, enclosed in a casing and driving an arm 9 according to temperature variations. The arm 9 acts via a flexible tie rod 3 on the flue flap. The flap is opened manually and partially by operating the tie rod 5. The servomotor is placed between the heart of the hearth and the flap; as a function of the temperature, the arm describes 3 zones, progressive closure for low temperatures, almost full open for medium temperatures and progressive and limited closure for very hot temperatures.

Description

 The present invention relates to solid fuel fireplaces burning in open or closed fireplaces. It is particularly well suited to domestic fireplaces.

 the flues of domestic chimneys are equipped with a flap or a mobile hatch intended primarily to close the flue in the absence of fire, thus avoiding heat loss by ventilation and incidentally to regulate the draft of the chimney during operation.

 Regarding the closing of the shutter, the generally manual operation is done in poor conditions: In fact very often the fire finishes consuming itself at night, during the operator's sleep and the shutter can only be closed morning upon awakening, unless the hasty preparations which follow the awakening make forget this maneuver.

 An existing device uses a thermal bimetal spiral wound around the axis of the shutter. One end of the spiral is linked to the flap, the other to its fixed axis. A chain allows the partial manual opening-shutter, in a position held by an open hook. Manual action constrains the spiral. The heating - smoke fumes - relaxes the spiral, which relaxes the chain, which is released, and which opens the shutter. When the fire is extinguished, the spiral cools and contracts, causing the shutter to close.

Measurements show that at around 900C the shutter is fully open, and at 200C completely closed. The main drawbacks of this device are the direct contact of the fumes on the dt spiral (bimetallic strip which causes corrosion and fouling, and the absence of protection against excessive heating of the bimetallic strip; in fact from the temperature of full opening (about 900C), the bimetallic strip tends to continue its movement without being able to do so, the stroke of the flap being limited to the open position, thus more and more stresses are created, and, from around 150 C, these stresses cause permanent deformations by exceeding the threshold of the elastic limit of the material of the thermal bimetallic strip. These permanent deformations are such that during the lowering of the shutter will close much earlier, for a fairly high smoke temperature and characteristic of the presence of combustion in the hearth; It is very dangerous.

Another automatic closing device uses expansion
fluid in cylinders and very complex arming mechanisms.

The cylinders have seals which during wear and aging can leak
and the mechanisms are not accessible. In the event of an incident
tion is impossible without breaking part of the chimney.

The devices according to the present invention provide in the first place
automatic closing of the shutter after the combustion has stopped in the
foyer. In addition, they allow draft control such as the flap
patiently closes when the temperature rises too high
fumes, characteristic of too strong combustion and an excess of
draw.

The devices according to the invention are characterized by their cons
titration in separate elements easily accessible and removable
to know :
- a simple butterfly flap articulated around an axis and removable
for sweeping. This flap has two fixing elements, holes
or fasteners. These elements are generally on the shutter. In
special cases, they are external to the shutter and the duct of
smoke, being connected to the shutter by its axis.

- a thermal servo motor enclosed in a box and the element of which
active is a thermal bimetal wound in a spiral. From this box
pulls out a bearing axis of a movable arm. The case is in contact
with gases; hot or fumes. The box is simply attached
against a wall of the fireplace or the drain. The movable arm is in
the home or outside.

- A connecting element between the flap and the housing, at the
movable arm for the housing and at a fastening element,
hole or fastener, for the shutter.

- a manual control or manual arming element connected to the
flap by the second fixing element.

Other characteristics of the invention result from the design of the separate elements and their relative location.
- The flap on the flue is placed in a chosen location
regardless of the smoke temperature level, for
reasons for the construction of the chimney)
access facility. The shape of the flap and the flue is free: -, circular, rectangular However, the entire flap-connecting and manual control elements is such that there is an imbalance in weight in a chosen direction, opening or closing according to the embodiment of the device according to the invention. The shutter has its stroke limited by a stop in the closed position and a stop in the open position.

- the athermic servo motor has a dustproof housing. The
little clearance around the axis is enough to let out or
enter a little air or gas during temperature variations
internal and to balance pressures. This servo motor has a
large angular clearance significantly greater than that corresponding
during the stroke necessary for the complete opening of the flap. This
allows the thermal bimetal to expand after opening
from the souks component the effect of a rise in temperature; this allows
also reduce the opening of the shutter and the draft in case
significant increase in the flue gas temperature.
significant angular prevents bimetal deformation during
sslrheating by exceeding the elastic limit.

- The design of the servo motor allows an important choice in the
bimetallic strip at the level of variations in length, d width, thickness
and nuances; the servo motor having means for chocking the
arm position and bimetal preload.

- The connecting element between the servo motor and the flap is the most
often a flexible tie such as a cable, a rope, a chain which
only transmits stresses when tensioned. Some achievements
according to the invention may however have a connecting element
rigid transmitting tensile and compressive forces
ends of this element being articulated in this version.

- The manual control or manual locking element is fitted with a
holding element in partial open position. This element
is composed of a hook or a ring which hangs in a
fixed element such as a ring or a hook respectively.

The attachment is maintained as long as the stove is insufficient,
thanks to the action of return forces from the pre-tension servo motor and /
or the weight imbalance of the flap. The snap is released during
that ther, llique expansion of the bimetallic strip exceeds the threshold value
deolenclisient previously fixed on the servo-notor.

According to the embodiments the control element is> either a
flexible pulling like a chain, a cable transmitting only
tensile forces, i.e. a rigid tie rod articulated at the ends
e * -trat-Smettant tensile and compressive forces. The
fires- from I to 10 on the two plates in the appendices explain a
Preferrential embodiment of the present invention and a variant
Figure 1 is a section of a chimney equipped with a device
according to the present invention.

Figure 2 is a schematic perspective view of the device
Figure 1 mounted in the outlet of a chimney.

Figure 3 is a% section and a front view of the servo motor
thermal bimetal.

Figure 4 is a section along two% perpendicular axes of the
figure 3, one upwards the other to the right of this figure 3,
the arm being raised to the height of the Y2 axis "to the right".

Figure 5 is a schematic section of Figure 2, where the servo
motor is represented by the path of the attachment at the end
of his arm.

Figure 6 is a diagram relating temperature and displacement
in rotation of the bimetal strip according to FIG. 5.

Figure 7 is a section similar to that of Figure 5 concerning
an alternative embodiment of a device according to the invention.

Figure 8 is a diagram relating temperature and displacement
in rotation of the bimetal strip according to FIG. 7.

FIG. 9 is an enlarged detail of the device for maintaining the
manual command
Figure 10 is a section of Figure 9.

In a domestic chimney equipped with a device according to the invention a drain 4, connects to the flue 40 the hearth delimited by the harizontal hearth plate 41 and by the vertical walls-42.

In the connection zone between the drain 4 and the flue 40 is housed the closing flap 2 presented closed at 2 and open at 2 '.

The flap is articulated around an axis 22 and is removable for sweeping. The closed position 2 is delimited by the stop 24. A similar stop near the axis 22 delimits the open position 2 '.

The flap is mounted with a peripheral clearance in the upper part of the drain 4. In addition, two cut sides 8, are added to the peripheral clearance so that there remains a minimum passage section for safety. This minimum section is of the order of a few percent of the open shutter passage section. The additional advantage of the cut sides 8 is to allow the shutter to be placed at the base of a flue pipe 40 consisting of terracotta bushels with rounded corners inside.

The shutter is provided with two fasteners or fixings 20 and 21. The fastener 20 is located substantially in the median plane of the chimney. In the embodiment it consists of a long enough eye bolt, so that the connecting element 3 can exert a torque when the shutter is open in 2 ', being spaced from the axis 22 of the shutter. The connecting element 3 is a chain or cable located in a plane substantially perpendicular to the axis 22 of the flap so that the transmitted forces are translated by rotations. The connecting element 3 connects the flap 2 to the booster 1. A chain 5 is attached to the flap at 21 by an omega pin passed through a hole or by a simple bolt passed through the hole and in the last link of the chain. The chain 5 passes through a ring 33 fixed at the bottom and on the opposite face of the drain, the part between 21 and 33 being in a plane substantially perpendicular to the shutter axis.

The chain then passes into a holding device 7. The end of the chain 5 is equipped with a handle 32. By pulling on the handle 72, the ring or the hook 31- is brought into the holding device 7.

The shutter 2 is then held in a half-open position.

In its rotation, the flap 2 causes the attachment 20 which pulls on the chain 3. This chain is fixed by its other end to the rotary arm 9 of the booster 1. The partial opening of the flap 2 therefore causes the arm 9 to rotate.

The servomotor 1 consists of a box in two elements 60 and 61 containing a thermal bimetallic strip 6 wound in a spiral. The outer end 14 of the bimetallic strip is fixed by a rivet 15, made of stainless steel preferrenc to the housing 61.

The other end ll of the spiral is pinched in the center of the eccentric part 13 of an axis 10 and held in place by a bracket 12 fixed to the axis 12 by points of sofldure.; The axis 10-crosses the 2 opposite walls of the case. One end carries a slot 63 which makes it possible to rotate the axis using a screwdriver to relax or tighten the spiral 6. The other end carries the bearing 15 of the arm 9 This end is smooth, the relative fixing between the axis 10 and the means 16 being provided by a pressure screw 17. This connecting system makes it possible to fix the arm 9 on the axis 10, independently of the initial position of the axis 10, therefore of the angular position of the end 11 of the spiral 6, therefore independently of the length of the spiral 6 and the number of winding turns.

Holes 62 on the extension of a wall of the housing 60 allow the actuator 1 to be fixed against the drain 4.

The inertia of the box and the absence of direct contact between the burnt gases and the spiral mean that the response time of the actuator is relatively long. This will delay closing when the fire goes out. In addition, being fixed against the drain 4, the heat from the latter diffuses towards the housing and contributes to the delay of the closure, which increases operating safety. The housing 61 carries a stopper 18 which allows the arm 9 to be kept at rest, and for a given temperature, for example 200C, to prestress the bimetallic strip 6 before blocking the screw 17. This allows the assembly to adjust the flexible "pulling" 3 in closed shutter position 2.

In the embodiment presented, the opening driving force is first of all the manual action of the operator, the resistant action or reaction being given by the constraint of the bimetallic strip. This constraint is reduced with increasing temperature. The driving action to obtain greater opening results from an imbalance in weight. The weights tending to open being greater than the weights tending to close this imbalance is obtained by the offset of the axis 22 with respect to the median plane of the flap 2 and by hooked weights of chain 5 greater than those of tie rods 3. Furthermore, as in FIG. 5, it is possible to add a weight 23. If this weight is sufficient, the axis 22 can then be maintained in the median plane.
Figures 5 and 6 make it possible to follow the behavior of the dispo
-sitive according to the invention depending on the temperature of the spinnaker
-rale 6. The curve of figure 6 gives the evolution of the
free deformation as a function of temperature.

For TF = 300 C, the initial stress given to 200C has disappeared .; the
arm is ready to turn absence of external constraints.

For TA = o0 C, the arm is in A, the flap would be in A 'and A1 in
partial opening.

For TB = 1500C, the arm is in B, the flap would be in B 'and B1 in
total opening.

Towards TC = 3000C, the arm is in C, the flap remains in C 'and C, merged with B' and B1; when the arm goes from B to C, the chain 3 relaxes and the flap does not move.

Above 3000C, the arm goes towards D reached towards TD = 5000C, limit temperature which is not reached by the flue of a chimney. Beyond 3000C, the flap will again be driven by the arm going to Dl and DlJet while closing. The draft will be reduced and the intensity of the fire will decrease: there is a regulation of the draft
If the arm was locked at B, corresponding to the open positions
B 'and B1 of shutter 2', when the temperature T rises above
TB, there is creation of internal constraint (6 :: # = RE (T - TB)
For example for the bimetal AS of YMPHY R # 15. 10 -6 / C
E # 16 500 Kg / mm2 if (T - Tg) has # 610C then ## 15 kg / mm therefore beyond 211 C, the maximum admissible stress of 15kg / mm is exceeded and permanent deformations will be created; The device according to the invention avoids this phenomenon.

At cold start, the maximum admissible stress is 20 kg / mm corresponding to a difference of 800 C.

The prestressing of around 10C corresponds to the effort resulting from the weight imbalance on the flap-linkage assembly, so that at the start it is above 200C that there is a slight tendency to the opening. Conversely for automatic closing, possible as soon as manually the fastener 31 has been detached from the device 7, point B having been passed, the effect of the weight imbalance is opposed to closing. So it is not at 300C that the shutter will be closed but below 200C.

The present embodiment has some imperfections: The fastening element 31 must have a stop, so that the operator by pulling on the handle 32 limits the stroke of the arm 9, up to A.

Beyond and for full opening, the prestress thus created would be such that there would be a permanent deformation of the bimetallic strip, and the need to make adjustments by acting on the slot 63 and on the screw 17.

Another imperfection lies in the difficulty of automatically unhooking the element 31 from the device 7 as soon as the arm 9 has crossed threshold A and is heading towards B.

An alternative embodiment is presented using figures 7 - 8 - 9
and 10.

The actuator is held in a central position close to the previous one. I1 is returned by a Y2 turn so that the direction of rotation is reversed. The fastener 20 is on the other side of the flap, likewise the fastener 21 changes th face, remaining offset laterally. In addition, the fastener 21 is offset downwards by a long support 23i which serves as engine weight. This offset allows manual opening control by pushing on the pull tab 5.

This zipper passes through the holding device 7 ', in the shape of a capital A with parallel legs and fixed to the drain 4 at the level of the feet of the A. The zipper 5 slides with play in the light of the A, and it carries a hook 31 'which can be hooked in the crossbar of A; the width of the zipper 5 and the hook 31 'are such that together they pass into the lumen of A by sliding. By pushing on the handle 30 ', the articulated end 21-23' first moves from F1 to Ale the hook 31 'which can be hung on the support 7'. The differential weight of the flap 2 and the weight of the pull tab 5 tend to close the flap and keep the hook 31 'in contact with the part 7'. In the movement of the flap 2, the fastener 20 moves from F 'to A1, The flexible tie 3, connecting the attachment 2G to the arm 9 of the servomotor 1, is relaxed and relaxed: the point F moves slightly because the initial prestress is released, then there is no longer any transmission of stresses; the operator can even safely open the shutter completely.

This alternative embodiment therefore avoids the problems of permanent deformation by exceeding the elastic limit of the bimetallic strip during manual opening. This increases the possibilities of choosing the type of bimetallic strip, temperature thresholds, lengths, widths and thicknesses of the bimetallic strip. FIG. 8 presents a characteristic curve of a bimetallic strip different from that of FIG. 6.

When cold, manual interventions on the shutter are not transmitted to the bimetallic strip. When the temperature rises, and after the gradual release of the initial stress, the end of the arm 9 leaves the vicinity of point F and goes towards point A.

When this point begins to be exceeded, the flexible tie rod 3 is stretched and pulls on the flap at A '. The temperature rising arm 9 goes from A to M and the fastener 20 goes from A 'to M'.

The points I-t and M 'are such that the segment l-2I' passes through the center of the booster or through its geometric axis, in FIG. 7.

In practice, the element 3, consisting of a cable, a ciainette or a rope has its length greater than or equal to Mi4 ', the point M' corresponding to the opening at 90D .: of the shutter 2 Thus, the fastener 20, almost reaches the geometric point M ', while the end of the arm 9 can continue its race beyond N when the temperature rise becomes too great. The arm 9 can move up to the lifte value D defined by the characteristics of the bimetallic strip 1 by the temperature threshold and by a physical stop analogous to the stop 18. At this position corresponds a partial opening equivalent to that of A. When the end of arm 9 goes from M to
D there is a partial closure of the flap, the fastener 20 going from
M 'to D'.

the arm
During the first heating up when / 9 goes from A to M and, the fastener 20 from A 'to M', the fastener 21 goes from A1 to M1 by pulling on the pull tab 5 and by unhooking the hook 31 'from the holding 7 ', and the pull tab 5 falls to the bottom of the light 7', while being driven upwards. When the fire goes out, the hook 31 'passes into the 7V light without hanging and the shutter closes.

The motor force is given by the differences in weight1 the resistance or braking force by the dynamic characteristics of the servomotor. In the present alternative embodiment, the initial stress is in the direction of opening, so that the differences in weight acting on the flap bring the motor arm to 200C at position F. In the absence of differential motor weight1 the temperature should reach about 10 ° C so that the arm naturally reaches point F.

The devices produced according to the diagrams of FIGS. 1 - 5 and 7 allow not only in winter, in an open or closed hearth chimney, to automatically close the flap of the flue when the fire is stopped and to regulate the draft in fire in case of fire, but still in summer to provide automatic ventilation.

Indeed, if the hanging device 31 or 31 'is free, above 200C, or another temperature defined by modifying the initial setting, the shutter opens and lets hot air escape through the flue .

Cooler air, coming from outside taken in a gray area, is then introduced by natural draft to refresh the room.

It is obvious to those skilled in the art to make other devices according to the invention by modifying
- ltempla.svement of the servomotor
- 1d shape of the actuator housing
- the fixation systemsode the spiral
- the shapes of the axis and the servomotor arm
- the fixing points on the flap
- the flap joints
- the position of the flap in the chimney
- the nature of the connecting elements between the shutter and the
servo motor
- the attachment means of the manual control

Claims (8)

R E V E N D I C A T I O N S  1) Device for automatically controlling the flue flap characterized in that it comprises a servo-motor 1 with thermal bimetal enclosed in a box, connected to a flap 2 for closing the flue by means 3 of connection articulated at their end, said shutter being equipped with means 5 - 7 - 31 for partially opening it by manual action, and for keeping it partially open during the start-up phase of the fire.  2) Device according to claim 1 characterized in that the arrangement of the axis 22 of the shutter 2 and the possible addition of a weight 23, are such that the differential result of the weights of the elé: slow shutters, the weight of the addition 23, of the weights of the connecting elements 3 and of the means 5 for manual opening, causes the shutter in the same direction, either the opening or the closing.  3) Device according to claim.l or according to claim 2 characterized in that the stroke of the flap 2 is limited by a stop 24 in the closed position and by another stop in the open position and that the flap has notches 8 security.  4) Device according to any one of the preceding claims, characterized in that the box containing the thermal bimetallic strip is impermeable to dust and to smoke particles.  5) Device according to any one of the preceding claims, characterized in that the thermal bimetallic strip of the booster is wound in a spiral 6 around an axis 10 equipped with an arm 9 external to the housing, the end of the arm 9 being connected to the shutter 2 by a connecting means 3.  6) Device according to claim 5 characterized in that one end of the axis 10 is equipped with a means 63 for driving in rotation using a manual tool and that the other end or possibly ent the same is cylindrical and smooth so that the hub 15 of the arm 9 can be positioned freely at any angle independently of the spiral, then fixed: on the shaft 10 by a pressure screw 17,  7) Device according to any one of the dreams; ldications previous characterized in that the connecting means 3 is a flexible elé - slow, a cable, a wire, a rope or u: .e chain.  8) Device according to claim 7 characterized in that the manual opening means has an action opposite to that of the result of the different weights acting on the shutter 2 and tending to close it, and such that the means 3 of connection, flexible cannot transmit forces to the arm 9 or cause a significant displacement of the arm 9, the motor-drive being arranged so that the movements of the arm under the action of temperature variations / more or less limit the closing of the flap 2 without ever oppose the opening.  9Y Device according to any one of the preceding claims, characterized in that the location of the servomotor 1, the characteristics of the bimetallic strip and the geometric characteristics of the arm 9 and of the flap 2 are such that a first part of the stroke of the arm of the servo motor corresponds to an opening of the flap increasing with temperature, that at a second part of the stroke of the servo motor arm corresponding to a temperature range greater than that of the previous part, corresponds to keeping the flap in a position almost full opening and a third part of the stroke of the servo-iiioteur arm corresponding to a higher temperature range corresponds to a limited progressive closure of the flap increasing with temperature, and reducing the draft of the flue.