US3877525A

US3877525A - Flame-guard device for isolating and stepping of premises

Info

Publication number: US3877525A
Application number: US381609A
Authority: US
Inventors: Jean Henri Husson; Marie Simonel
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-08-03
Filing date: 1973-07-23
Publication date: 1975-04-15
Anticipated expiration: 1992-04-15
Also published as: DE2339352B2; CH573756A5; DE2339352C3; FR2212759A6; GB1439865A; DE2339352A1; FR2195162A5

Abstract

The flame-guard device comprises at least one liquid-porous screen which is maintained near the ceiling, weights are fixed to the bottom of the screen to cause unrolling of the screen upon outbreak of a fire, and spraying nozzles are provided to cause impregnation of the screen and flow of a liquid on the whole surface thereof as the screen is unrolling.

Description

United States Patent Husson et a1.

[ Apr. 15, 1975 803,618 11/1905 Mumford 160/1 998,065 7/1911 Wilson 1,092,243 4/1914 C016 169/1 R 1,369,518 2/1921 Bumbarger 160/1 3,687,185 8/1972 Singer 160/1 Primary ExaminerM. Henson Wood, Jr. Assistant ExaminerAndres Kashnikow Attorney, Agent, or Firm-Browdy and Neimark 57 ABSTRACT of the screen and flow of a liquid on the whole surface thereof as the screen is unrolling.

27 Claims, 20 Drawing Figures 1 FLAME-GUARD DEVICE FOR ISOLATING AND STEPPING OF PREMISES [76] Inventors: Jean Henri Husson, 34 Avenue du President Franklin Roosevelt, Fontainebleau-Avon; Marie Simone], 9 Rue des Pervenches, 92 Bagneux, both of France [22] Filed: July 23, 1973 [2]] Appl. No.: 381,609

[30] Foreign Application Priority Data Aug. 3, 1972 France 72.28074 Dec. 28, 1972 France 72.46787 [52] US. Cl. 169/48; 160/1; 169/57 [51] Int. Cl. E06b 5/16 [58] Field of Search 169/1 R, l A, 2 R, 48, 169/54, 56-58; 160/1-10, 25, 35, 126

[56] References Cited UNlTED STATES PATENTS 259,063 6/1882 Von Falkenhausen 169/1 R ""lllllii PATENIEBAPR 2 Sims SHEET 2 95 g Om M 3 87 7. 52 5 PATENTEBAPR 1 519. 5 v I FIG. 4

PATENTEU APR 1 5W5 3. 877. 525

SHEET s 95 gs FIG. 7

'PATENTEUAPR 1 1915 3, 877. 525

snmvggg FLAME-GUARD DEVICE FOR ISOLATING AND STEPPING OF PREMISES The present invention relates to a new flame-guard device designed to be placed in various premises. It is well known that it is required, in case of fire, to divide the premises as well as their clearances into as many compartments as possible to prevent or at least to minimize the spreading of a fire and its indirect effects: combustion gas and smoke. This requirement appears up to now very difficult to realize in public premises and in large size premises such as commercial centers, halls of large buildings, large underground parking places, etc,... It has already been thought to use metallic screens which could come down from the ceiling to separate into various compartments premises of large sizes, but this arrangement is not satisfactory because, besides being extremely difficult to practically realize, it requires that doors be designed into the screens to provide an escape for the people who would be enclosed in a compartment.

Besides, the efficiency of such metallic screens can be completely annihilated if there is an obstacle in their way, for example in commercial premises a counter, a bench or other objects which could obstruct the complete coming down of the screen. It is also to be taken into consideration that to make sure of the efficiency of a flame-guard device, it is necessary to proceed to periodical operating tests, and that without proceeding to complex operations.

The present invention completely solves said problems by creating a new flame'guard device with a small bulkiness which can consequently be easily placed in various premises and, if required, be kept out of sight.

The device of the invention is also very light, of a very quick operation without any risk of bad working and cannot cause any injury even if it is operated while there are still people moving on. In fact people can, at any moment, pass through it anywhere, without having to look for a special exit and without its function as a flame-guard device being annihilated, even if there is one or a plurality of obstacles in the way it has to follow during its unfurling. Besides, it provides a reduction of the temperature increase due to a fire and can be adapted to any form of premises.

According to the invention, the device comprises at least one liquid-porous flexible screen which is wound close to the ceiling of a premises, means to operate the unrolling of said screen at the outbreak of a fire, and means to ensure impregnation of the screen with a liquid and flow of said liquid on the whole surface of the screen when said screen is unrolled.

Various other characteristics of the invention are moreover shown in the following detailed description.

Embodiments of the invention are shown by way of non-restrictive examples in the accompanying drawing, in which:

FIG. 1 is a partial perspective view of a first embodiment of the flame-guard device of the invention.

FIG. 2 is an explicative diagrammatic partly sectional view.

FIG. 3 is a diagrammatic plan view showing an assembling of various devices according to the invention.

FIG. 4 is a diagrammatic sectional view showing a modification of. the invention.

FIGS. 5 to 7 are partial perspective views showing different ways for mounting the device of the invention.

FIGS. 8 and 9 are diagrammatic sectional views of a first variant.

FIGS. 10 and 11 are diagrammatic elevation views showing a modification of the invention.

FIGS. 12a and 12b are a partial perspective view of a variant of the modification of the present invention illustrated in FIGS. 10 and 11.

FIG. 13 is a diagrammatic perspective view showing a further variant.

FIG. 14 is a diagrammatic perspective view similar to FIG. 13 showing another embodiment.

FIGS. 15 and 16 are perspective views of other variants.

FIG. 17 is a perspective view of another embodiment of the flame-guard device of the invention.

FIGS. 18a and 18b show the front view and cross view of the curtain.

FIGS. 1- 3 show an embodiment of the invention wherein the device is contained in a housing generally designated by reference numeral 1, which housing is, for example, made of sheet metal and has a substantially parallelepipedic shape with notched ends, as shown in 2 and 3 in FIG. 3.

The housing supports by means of lugs 4,

4a drums

5, 5a placed on spindles 6, 6a.

The

drums

5, 5a respectively support, rolled up on each of them, at least one

screen

7, 7a, respectively. Preferably, as shown in FIG. 3, each screen is divided in several breadths 7 7 7 and respectively 7a,, 711 7a,, which are set off by half a pitch. Thus, still considering FIG. 3, the breadth 7 is overlapping the

breadths

7a,, 7a,; the breadth 7 is overlapping the breadths 7u 7%; etc...

The

screens

7, 7a can be made of different materials, for example of genuine or synthetic cloth which may or not be fireproofed. Woven or not, and possible combustible vegetable materials, can also be used, said materials being fireproofed or not.

Preferably, the material of the screens is selected so that they have capillary structures enabling the regular supply of water from ramps 12, 12a on the whole height and on the whole width of each breadth. The materials are besides selected among those enabling water running down their thickness to exude towards the surface of the breadths.

Such materials can, typically, be constituted by means of directed fibers, especially glass fibers or fibers of other materials, comprising for example a core delimiting channels, ducts or passages extending from top to bottom, said core being encompassed by layers of coating whose fibers are directed diagonally to the fibers of the core, thus water which has to impregnate the screens tends this to be well distributed on the whole surface of said screens.-

The

screens

7, 7a are preferably rolled up in an opposite direction on their

respective drums

5, 5a to enable said screens, when unrolled from the two drums, to be brought one against each other, or at least to an immediate proximity. To take in consideration the radius decrease as the

screens

7, 7a are unrolling, said decrease being represented in a slotted line in FIG. 2,

guides

8, 8a are placed beneath the drums at a short distance from each other and on which pass said screens formed by the plurality of breadths. The

guides

8, 8a can be made in various ways, for example as represented, they can be constituted by means of rolls placed on spindles 9, being themselves placed at the end of arms and struts 11 (FIG. 1) to be connected to the housing 1.

The

guides

8, 8a can also be constituted by mere fixed bars, or it is also possible that the struts 11 be fixed to a resilient element tending to push the rolls or bars against each other to provide the

screens

7, 7a to be brought together in contact or practically in contact. Said

guides

8, 8a can also be constituted by tubes and, in such a case, said tubes are advantageously provided with holes to constitute suppliers for water or other liquids provided to impregnate the screens 7 7a, when said screens are unrolled from the

drums

5, 5a to form a fire-guard screen.

When the water, designed to impregnate the screens and possibly to run down on said screens, is not brought by the

guides

8, 8a then, as previously stated, supply ramps 12 are designed to throw the water or to spray the same on said screens.

To ensure unrolling of the screens, it is advantageous to provide them, near their end, with weights 13 for example constituted by a metal bar extending on the whole width of each breadth, said metal bar being fixed on the side of each breadth which is opposite to the side in front of another breadth.

Besides, the weights 13 provide, at the end of the screens, a free segment 14 designed to bear on the ground when the screens are completely unrolled, and then to form a tight joint, whatever be the pressures applied on the screen itself.

To release the screens, i.e. to enable the weights 13 to unroll said screens from the

drums

5, 5a, various means can be utilized. For example the spindles 6, 6a of the drums, or the drums themselves, can be retained by a melting element whose melting is caused by an abnormal increase of the temperature; it is also possible that a smoke detector be holding the drums; a hand brake can also be designed as well as any other required devices.

Of course, several detecting devices of different nature can be utilized simultaneously in view of enabling the screens to be unrolled, with no difference, either from a hand control, or if smokes are detected, or still in the absence of smoke but if the temperature increases beyond a determined threshold, or yet if any ambient perturbation caused by an outbreak of fire is detected.

FIG. 3 shows that various devices can be associated to each other. Actually, it is to be noticed that the device contained in the housing 1 can be assembled with a device contained in an housing la and placed in its extension thereof. In such a case, the breadths of the screens of the two assembled devices mutually overlap each other in the same way as the breadths of a single device.

Besides, it is also possible to place the devices for them to form an angle (one in relation with the other) which is illustrated by housing 1b. In such a case it can be seen that the breadth 7-,, is brought against the breadth 7 or at least in the close vicinity of the latter, when all the screens are unrolled.

FIG. 4 shows a modification of the invention which takes into consideration the fact that in case of a fire in the premises, the temperature, in a first step, tends to increase more at the upper portion of the premises. According to this modification, at the lower portion of the housing 1, a tank 15 is placed in recess respectively to the water projection ramps 12, and the lower portion of the tank or its lateral side is connected to a baffle plate 16 leading to the area of the screen 7 having passed upon the guide 8. Each ramp 12 is then pro vided with

projection nozzles

17 and 18, the nozzles 17 being directed, as represented, towards the drum 5, while the nozzles 18 are directed towards the screen 7. From the above disclosure, it is to be noted that upon unrolling the screen 7, the nozzles 18 impregnate said screen with Water as it is coming down, while the nozzles l7 perform a preimpregnation of the part of the screen which is still rolled up on the drum 5. A portion of the water projected towards the drum 5 falls down and is recovered into the tank 15 which is progressively filled up and which finally overflows, the water being directed by the baffle-plate 16 onto the upper portion of the screen 7 when the same is completely unrolled; this procedure increases the quantity of running water when the fire continues for a noticeable time and while the temperature caused by said fire is substantially increasing. The flow of water or of another liquid can be:

either calculated prima facie in order to compensate for the calorific effects of a fire, said fire being considered in function of the calorific potential of the premises to be protected and of the time deemed necessary for the protection:

or servoed to a heat flux control (hydrothermostatic regulation).

The lower part of the tank 15 as well as the baffleplate 16 can be construed in an aesthetic way to constitute hiding places which are not prejudicial to the appearance of a ceiling above which the device of the invention is placed.

FIGS. 5 to 7 show that the device of the invention can be adapted to the shape of a building.

According to FIG. 5, the housing 1 of each device is fixed by angle-irons 19 at the sub-side ofa floor pavingstone 20.

In FIG. 6, the housing 1 is fixed, through its lateral wings 21, directly into a ceiling 22 hung for example by means of ties 23 to the paving-stone 20.

In FIG. 7, the housing 1 is fixed, on one hand, or a girder or a rail 24 and, on the other hand, to the floor paving-stone 20 by means of ties 25. i

To prevent water vapor or smoke from accumulating in the housing 1, it is advantageous, as shown in FIGS. 1 and 3, that the top of each housing be bored with ventilating holes 26.

Besides, to make easier the setting together of various housings 1, they must advantageously comprise, at their ends, flanged edges 27 having holes 28 for placing bolts or fixation clamps. Also the ends of the spindles 6, 6a supporting the drums of each housing are advantageously provided with additional coupling elements 29, 29a, represented in FIG. 1 as being of the tenon and mortise type but the same can, of course, be constituted in many other ways. Thus when several devices are assembled together, their spindles 6, 6a are also connected together and a single control assembly can be utilized.

In the above described embodiment, the different breadths constituting the screens are represented and described as rolled up around drums; however, this is only an advantageous arrangement, the rolling-up way could be different. For example FIG. 8 shows an arrangement wherein the device is placed between the floor paving-stone 20 and the ceiling 22 which can be at a short distance one another. In that case, the guides 8 are supported either by the paving stone 20, or by the ceiling 22 wherein is designed a slot 30. Anchorages 31 are then designed on the top of the ceiling 22 to retain an end of the

screens

7, 7a which are respectively rolled up around a bar or a roll 32, 32a, respectively, retained by a cable, a rod or other maintaining component 33 on which can be placed fire or smoke detectors 34, 34a.

In case of fire or smoke, the detectors 34, 34a release the retaining rolls 32, 32a, and the weights 13 drive the screens to the ground.

The watering ramps 12 are, in that case, placed either on the top of ceiling 22, or beneath the floor pavingstone, or in the guides 8.

FIG. 9 shows another simplified embodiment which is particularly efficient where premises of small volume are concerned because it enables, if required, to utilize only one screen. In that case, said screen'is rolled up, as represented with the weights 13 thereof advantageously placed at the central portion of the constituted roll; then the whole screen is retained by a flap 35 hinged on one side around hinge 36 and maintained on its other side by the detector 34. In case of fire, the flap is opened due to the breaking of the detector 34 and the screen unrolls by itself. At least one watering ramp 12 is designed for the impregnation of the screen with water and, if required,to make the water to run down.

In all the embodiments described in the above disclosure and as better shown in FIG. 1, the free segment 14 ensures to the breadths an excess of length when they are down, which provides a tightness with the ground, even if said breadths are submitted to possible motions caused by pressures or depressions applied to the screen. v

FIG. shows that it is further advantageous to provide at least the lateral side of the end breadths directed towards a wall or a partition 38 with lateral fringes 37 which ensure, when they are impregnated, a very good tightness between the screen, the wall or partition, and even if the sheet is moved with respect to the wall. The fringes 37 can have various shapes and especially be designed to mutually overlap each other.

FIG. 11 shows lateral fringes 37 constituted in a finger-stalls type with their end 37a closed and their end 3717 open, in order to recuperate the water which has been sprayed and which is running down on the breadth, thus ensuring an excellent tightness with the wall 38, in that the water contained by the fringes tends to incline the same as is represented.

FIG. 12a illustrates another embodiment wherein the lateral edge of at least the end breadths, 7, 7a are each provided with a sleeve 39, for example made of thin cloth in order not to constitute an overthickness when the breadth is rolled up on the drum or otherwise folded. The sleeve 39 is connected to the water or other liquid supplying device, thus after unrolling the breadth, said sleeve is inflated as shown in 39a in FIG. 12a and maintained in slight over pressure by the water passing in the cloth. Upon bearing against the wall 38, the sleeve 39a which then forms a pad, ensures an excellent tightness and some water runs also down the wall.

According to the variant shown in FIG. 13, the breadths 7 7 constituting the screen 7 are provided, on one or on the two sides thereof, or in the portion forming a core when the breadths are made of multiple layers, with

small ducts

37, 38 which can be more or less porous and which run at different heights as represented, in order to bring water coming from the ramp 12 at different levels of the screen.

FIG. 14 shows another arrangement wherein horizontally extending pads 39 are placed, on each breadth transversely to them. Preferably, the pads 39 are fixed, for example through sewing, on the side of each breadth which is directed towards the area to be protected. Due to the existence of the pads 39, water running down in the direction of the arrow f tends to accumulate above each of said pads thus constituting a storage area which impregnates the breadth.

According to FIG. 15 the breadths are made like

strips

40, 40a and 41, 41a exactly as the previously mentioned breadths, but said strips are then very narrow by comparison with said previously considered breadths. Said arrangement enables to constitute said

strips

40, 41 by means of braided fibers which can delimit an inner duct, or by means of overlapped strips providing ducts 42 between them.

The

strips

40, 41 are of course porous to let the water exuding on the whole surface in a substantially regular way.

According to FIG. 16 the breadths are replaced by

tubular cords

43, 43a, 43b and 44, 44a which mutually overlap each other as are doing the breadths of the

screens

7, 7a.

Also in such an embodiment, the ducts, delimited by the tubular cords, are utilized to supply' the whole height of the so formed screens with water, by driving water which is brought to the inside of the cords or strips through the ramp or ramps 12.

It is obvious that when the screens are constituted of strips as shown in FIG. 15 or of cords as shown in FIG. 16, then each strip or each cord is provided, near its lower end, with a weight having the same width as that of the strip or cord and leaving beneath the same a free segment designed to bear on the ground. Besides, the drums 4, 4a are arranged in taking into consideration the shape of the screens. In the case of strips as in FIG. 15, or cords as in FIG. 16, then the drums are constituted by a succession of pulleys.

FIG. 17 shows a variant making possible to roll up the successive breadths 7, 7' 7' on a single drum 5,.

The drawing shows that the breadths 7 partly cover, for example on half of their width, the breadths 7' 7 and that the breadths 7' cover in the same way the breadths 7' and Ta. Weights 13 are placed on the outer side of the successive breadths 7, 7'a. and weights 13a are in the same way on the outer side of the breadths 7' 7' thus said weights. The weights ensure unrolling of the breadths from the drum 5, and the maintaining thereof under stress while the segments 14 and 14a form tight joints with the ground, and they apply also the breadths 7, 7 'a-against the

breadths

7,, 7 2.

In such a structure it is advantageous to constitute the housing 1, in such a way that it will form a guide, by means of a rib 45, for the successive breadths. The rib 45 and an upwards edge 46 delimit then retaining elements for a certain amount of water 47 in the bottom of the housing, said water accumulates when the projection ramps 12, 12a placed into the housing are themselves supplied to impregnate the breadths. Besides the rib 45 forms a baffle-plate to regularly distribute the water on the whole length of the breadths when they are unrolled and the water contained in the bottom of the housing prevents deterioration of said housing even if it is reached by flames.

We claim:

1. A fire-protecting device comprising:

at least one liquid porous, flexible screen, said screen being stocked at the top of an area to be fireprotected;

means to cause one end of said screen to go downward upon outbreak of fire; and

means provided at the top of the area to be fireprotected and outside the stock of the screen for impregnating said screen with an aqueous liquid from bottom to top of said screen as said screen is travelling downward and continuously impregnating said screen thereafter;

whereby said screen is simultaneously going downward and being impregnated with said aqueous liquid.

2. Device, as set forth in claim 1, wherein the screen is constituted by a succession of various mutually overlapping vertically extending breadths of screens maintained together in close contact.

3. Device, as set forth in claim 2, further including two parallel drums placed in a housing and on which are rolled up the at least one breadth, said drums being off set by a distance substantially corresponding to a half width of the breadth.

4. Device, as set forth in claim 3, wherein the housing containing the two drums whereupon are placed the breadths is notched at two ends thereof and comprises assembling means to be connected to at least one additional housing, whereby the drums of the successive housings are respectively lined up and the breadths supported thereby are placed in an alternate arrangement.

5. Device, as set forth in claim 3, comprising parallel horizontal guides against which pass the breadths unrolled from the drums, whereby the screens formed by said breadths and coming from parallel drums are brought to an immediate vicinity of each other to form a fire-proof partition when they are impregnated with a liquid.

6. Device, as set forth in claim 3, wherein said means for impregnating include spraying ramps placed in the vicinity of the screens unrolled from the drums.

7. Device as set forth in claim 2, wherein weights are fixed to each breadth, at some distance from the free end thereof to provide a free segment of screen beneath said weights whereby said weights cause unrolling of the breadths, said free segment resting on the ground forming a tight joint therewith.

8. Device as set forth in claim 1, wherein the liquid is water and a tank is provided for the recovery of water, said tank being placed in the vicinity of said impregnating means, said impregnating means comprising spraying ramps provided with nozzles, said nozzles throwing water on one hand directly onto the at least one screen and on the other hand towards the drums on which are rolled the at least one screen to preimpregnate portions of screen still rolled up thereon, the excess water being sprayed falling into said tank to progressively fill said tank, a baffle-plate extending from said tank directing the water overflowing from the tank towards the top of the unrolled screens.

9. Device, as set forth in claim 8, wherein the tank and the baffle-plate act to conceal the device included in a ceiling.

10. Device, as set forth in claim 3, wherein the drums are placed on spindles provided with coupling means, whereby the spindles of various devices connected to each other are automatically coupled.

11. Device as set forth in claim 2, wherein the breadths are placed between a ceiling and a floor paving-stone thereabove in forming a loop between a fixed anchorage point controlled by a fire outbreak detector and guides, holding the breadths at a suitable distance to be unrolled and liquid impregnated at the outbreak of a fire.

12. Device, as set forth in claim 1, wherein each screen is anchored to a floor paving-stone at the underside thereof by one end and held rolled up on a flap being part of a ceiling placed beneath said pavingstone.

13. Device, as set forth in claim 1, wherein the screens are made of cloth.

14. Device, as set forth in claim 1, further comprising detecting elements sensitive to a temperature threshold, to the presence of smoke or other data related to a fire, said detectors causing locking of the screens in folded position.

15. Device, as set forth in claim 2, wherein the screens comprise end breadths, at least said end breadths being provided with fringes to constitute tightness joints with a wall or with another screen.

16. Device, as set forth in claim 15, wherein the fringes are constituted as finger-stalls.

17. Device, as set forth in claim 16, wherein permeable sleeves are provided at least on end edge of the end breadths, said sleeves being connected to the liquid supplying means.

18. Device, as set forth in claim 1, wherein means are designed in said screen to distribute the impregnation water at different levels.

19. Device, as set forth in claim 1, wherein the screen is constituted of a succession of breadths comprising substantially vertical ducts opening at the upper portion thereof close to liquid supplying means and opening at the lower portion thereof at different levels.

20. Device, as set forth in claim 2, wherein the breadths include transverse pads forming barriers to retain water at different levels.

21. Device, as set forth in claim 2, wherein the breadths include a succession of narrow strips delimiting longitudinal channels.

22. Device, as set forth in claim 2, wherein the screen is constituted of a succession of tubular cords.

23. Device, as set forth in claim 1, wherein the screens are woven to provide longitudinal ducts extending substantially vertically when the screen is unrolled.

24. Device, as set forth in claim 1, wherein the screen is constituted of fibers comprising a core made of directed fibers to provide water to run down through said web in a vertical direction, said core being covered on each side thereof by coating fibers diagonally directed to said core whereby causing water to exude towards the surface.

25. Device, as set forth in claim 1, wherein .the screens are rolled up on drums and pulleys.

26. Device, as set forth in claim 2, wherein the breadths are mutually overlapping each other and are rolled up on a common drum, weights being designed near the lower end of each breadth on the outer side thereof.

3 ,8 77 ,5 25 9 10 27. Device, as set forth in claim 26, wherein the drum breadths from distributors placed in said housing, said common the FF m is i in a guiding rib forming distribution means for the water housing having a bottom delimiting a r b for guiding the breadths and an upward edge protruding inside the housing in delimiting a tank for water supplied on the 5 running down from the tank.

Claims

1. A fire-protecting device comprising: at least one liquid porous, flexible screen, said screen being stocked at the top of an area to be fire-protected; means to cause one end of said screen to go downward upon outbreak of fire; and means provided at the top of the area to be fire-protected and outside the stock of the screen for impregnating said screen with an aqueous liquid from bottom to top of said screen as said screen is travelling downward and continuously impregnating said screen thereafter; whereby said screen is simultaneously going downward and being impregnated with said aqueous liquid.

8. Device as set forth in claim 1, wherein the liquid is water and a tank is provided for the recovery of water, said tank being placed in the vicinity of said impregnating means, said impregnating means comprising spraying ramps provided with nozzles, said nozzles throwing water on one hand directly onto the at least one screen and on the other hand towards the drums on which are rolled the at least one screen to pre-impregnate portions of screen still rolled up thereon, the excess water being sprayed falling into said tank to progressively fill said tank, a baffle-plate extending from said tank directing the water overflowing from the tank towards the top of the unrolled screens.

12. Device, as set forth in claim 1, wherein each screen is anchored to a floor paving-stone at the underside thereof by one end and held rolled up on a flap being part of a ceiling placed beneath said paving-stone.

13. Device, as set forth in claim 1, wherein the screens are made of cloth.

25. Device, as set forth in claim 1, wherein the screens are rolled up on drums and pulleys.

27. Device, as set forth in claim 26, wherein the drum common to the overlapping breadths is placed in a housing having a bottom delimiting a rib for guiding the breadths and an upward edge protruding inside the housing in delimiting a tank for water supplied on the breadths from distributors placed in said housing, said guiding rib forming distribution means for the water running down from the tank.