US3152703A

US3152703A - Blast furnace sealing apparatus

Info

Publication number: US3152703A
Application number: US125540A
Authority: US
Inventors: Jr William E Slagley
Original assignee: Inland Steel Co
Current assignee: Inland Steel Co
Priority date: 1961-07-20
Filing date: 1961-07-20
Publication date: 1964-10-13
Anticipated expiration: 1981-10-13

Description

Oct. 13, 1964 5 Sheets-Sheet 1 Filed July 20, 196] 4 N2 1 n ma mm m n m m a g 2 a, v 4 w a KN @N J |l|l|.|. Wk 1\ kw MN gw WW /I Y W\ k Km NW u Q H \ww UN WNW j w @NN wwl QNN N m o. w W MN Nw NN\.W Sn \m W K o N NW QR mw Oct. 1 3,- 1964 w. E. SLAGLEY, JR 7 BLAST FURNACE SEALING APPARATUS 5 Sheets-Sheet 2 Filed July 20, 1961 Oct. 1.3, 1964 w. E. SLAGLEY, JR 3,152,703

BLAST FURNACE SEALING APPARATUS IN VEN TOR.

MM TJvg Jx I Oct. 13, 1964 w. E. SLAGLEY, .JR I 3, ,7

BLAST FURNACE SEALING APPARATUS Filed July 20. 1961 5 Sheets -Sheet 4 W. E. SLAGLEY, JR

BLAST FURNACE SEALING APPARATUS Oct. 13, 1964 Fiied July 20. 1961 5 Sheets-Sheet 5 United States Patent 3,152,703 BLAST FAQE EALING APPARATUS William E. Slagley, .lr., East Chicago, Ind, assignor to- This invention relates to blast furnaces and deals primarily with seals therefor and a method of operation which are particularly useful in blast furnaces operating at high top pressures.

Blast furnaces have for many years been operated at what is called in the art as normal pressures. These pressures are in the order of two to three pounds per square inch (gauge). This is the normal back-pressure caused by the piping in the take-offs, distribution mains, and the gas cleaning facilities. Prior art types of seals usable for these normal pressures are not satisfactory as pressures increase. A development in blast furnace practice in recent years is high top-pressure operation. Here a restriction is placed in the gas line leaving the furnace, and a back-pressure is deliberately imposed on the furnace. This increases the average furnace pressure and results in higher furnace production, lower dust rates, better coke rates, and so forth. In practice, at the present time, it is desired to achieve ten to fifteen pounds per square inch (gauge) top-pressure. Indications are that improved operations will result at top pressures up to forty pounds per square inch (gauge). Numerous furnace improvements have been made to increase the top pressure. For example, furnace and gas cleaning facilities can be reinforced, blowers of greater capacities can be installed and equalizing and relief systems can be added so that the pressure between the bells can be equalized and the bells operated. In spite of these improvements, continued operation at these pressures has not been practical under normal conditions and primarily because of excessive leakage of blast furnace gases at the bell seats and at the distributor seal. A bell seat that has an expected life of six to seven years at two to three pounds per square inch (gauge) pressure is reduced to only about two years at ten to twelve pounds per square inch (gauge) pressure, not to speak of the extremely short life of the seats at the proposed higher pressures of thirty to forty pounds per square inch (gauge).

The basis of this invention is the provision of an elastic or resilient seal that is disposed between the surfaces to be sealed, namely, the surfaces between the conventional hopper and its associated conventional bell, and between the hopper which can be of the distributing type and other blast furnace structure. It is an important feature of the invention that conventional blast furnaces can be easily and economically equipped with the seals of the present invention.

It is a feature of the invention that when the blast furnace charge is being discharged from the hopper that the seal is retracted out of the path of the blast furnace charge. The seal always contacts the bell surface in a normal direction when in the sealing position and the bell never scuffs or rubs the surface of the seal to cause wear.

The elastomer seal should be heat-resistant and water- .and-air-impervious at normal operating temperatures.

Elastomers such as vinylidene fluoride-hexafluoropropylene type copolymers are usable, such as described in Industrial and Engineering Chemistry, vol. 49, page 1687, October 1957; and Report No. 58-3, May 1958, by Moran and Eubank, entitled Viton A and Viton A-HV, E. I. du Pont de Nemours & Co., Inc.

Particularly outstanding results are obtainable with a heat-stable elastomer product of the foregoing type and "ice composition which is produced by E. I. du Pont de Nemours & Co., Inc., and sold under the names Viton A-HV and Viton A.

The elastomer seal in use is always being cooled by a circulating medium which also functions to activate and deactivate the seal into and out of sealing contact between the hopper and the bell, and between the structure of the blast furnace and the distributing hopper.

The seal here described is one which is usable at all normal furnace operating temperatures and even higher without damage to the elastomer. Cooling fluid, preferably oil, is supplied internally to activate and deactivate the seal. This keeps the outside of the elastomer seal at a reduced temperature, which normally does not exceed degrees F. The furnace temperature at the location of the seal is controlled, according to preferred present operating practice, to hold its optimum temperature below that at which the elastomer is usable. This is done by either keeping the furnace charged or by wetting the blast furnace charge, for example with water.

The seal is a strip-like, flexible, resiliently deformable member having one large-area surface disposed toward the hopper and another large-area surface, opposite the one large-area surface, disposed toward the bell.

Although seals are illustrated herein as disposed between both the upper hopper and upper bell and the lower hopper and the lower bell, satisfactory results are obtainable with a seal only between the lower hopper and the lower bell.

In the diagrammatic drawings:

FIGURE 1 is an elevational view shown mainly in cross-section of the upper portion of a blast furnace equipped with the seals of the invention;

FIGURE 2 is a cross-sectional elevational view of the novel seal disposed between the lower hopper and the lower bell;

FIGURE 3 is a cross-sectional elevational view of a portion of the lower hopper and the lower bell showing the seal in sealing contact therebetween;

FIGURE 4 is an elevational view, partly in cross-section, showing the seal extending circumferentially around the lower portion of the lower hopper;

FIGURE 5 is a cross-sectional view of a modified form of the invention shown in FIGURES 2, 3 and 4;

FIGURE 6 is a cross-sectional elevational view of a portion of the distributor seal of the invention;

FIGURE 7 is a schematic view of the fluid system of the invention; and

- FIGURE 8 is a detailed elevational view of the upper hopper and upper bell, and associated structure.

In the illustrative embodiment shown in FIGURE 1 of the drawings, there is shown the upper portion of a blast furnace 10, which in the present embodiment is of the double bell and hopper type. The blast furnace It) includes closure means in the form of a small upper bell 11 which is adapted to move vertically into and out of seating contact with its associated distributing upper hopper 12, the form of which will later be discussed in further detail. The small bell 11 is suitably mounted for vertical movement and is supported by a bell rod 13 which is connected at its upper end to a bell beam 14 having a counter-weight 15.

The large lower bell 16 is adapted to move into and out of seating contact with its associated large lower hopper 17. The large lower bell 16 is mounted for vertical movement and is supported by a bell rod 18 which travels within bell rod 13 and which is connected to a bell beam 19 having a counterweight 20. Both bell beam 14 and bell beam 19 are mounted for pivotal movement on a common support member 21. The blast furnace charge is received into a chute 21a which permits the same to 3 fall into the small hopper 12. When the small bell 11 is moved out of seating contact with the hopper 12, the

charge is permitted to fall into the large hopper 17. From the large hopper 17 the material is subsequently caused to fall directly into the remainder of the blast furnace when the bell 16 is moved out of seating contact with the hopper 17. A drive mechanism 22 is employed to rotate the upper hopper 12 to position the charge therein for even distribution on the lower bell before dumping the lower hopper 17.

The seals of the present invention include a seal 23 between the upper closure structure 24 of the blast furnace 10 and the hopper 12, a seal diagrammatically indicated at 25 disposed between the small upper bell 11 and the upper hopper 12, and a seal 26 between the lower bell 16 and the lower hopper 17. These seals function to prevent the blast furnace gases from escaping from the inside of the blast furnace to the outside thereof. The

seals

25 and 26 can take the forms shown in FIGURES 2, 3, 4 and 5, while the seal 24 can take the form the details of which are shown in FIGURE 6.

Although in the description of FIGURES 2, 3, 4 and the lower hopper 17 and the structure with which it is associated are referred to, the description applies equally to the structure of the small upper hopper 12 and the structure with which it is associated, that is, the seal indicated generally at 25 and the seal indicated generally at 26 are constructed alike.

Referring now to FIGURE 2 of the drawings, there is shown a conduit 27 and a conduit 28, which respectively lead into and out of a chamber 29 defined by the lower portion of the hopper 17 and by the elastomer seal 30. As an alternative construction, conduits 27a and 28a are shown as forming a part of the hopper in place of

conduits

27 and 28. The lower portion of the hopper 17 is provided with a seat 31 which permits the bell 16 to move into and out of seating contact with the hopper 17 when the bell 16 is moved vertically upward and downward. The seat 31 has a recess 32 formed therein which extends around the circumference of the hopper 17. The elastomer seal 30 is retained at its marginal edges within the recess 32 by an adhesive material 33 between the seal 30 and the hopper 17, as well as by a pair of opposed retaining rings 34. Threaded fasteners 35 pass through each of the opposed retaining rings 34 and the elastomer seal at is marginal edges and are threaded into the hopper 17. Upon tightening the threaded fasteners 35 the re taining rings 34 are urged into ever tighter contact with the marginal edges of the elastomer seal 30. A weldment 34a is provided between each of the retaining rings 34 and the hopper 17. i

It is noted in FIGURE 3 that the seal 30 is shown in its sealing position by solid lines and in its unsealing position by broken lines, while in FIGURE 5, the seal 30 is shown in its sealing position by broken lines and in its unsealing position by solid lines. The fluid which is used in the system shown in FIGURE 7, to be described later, upon being forced into the conduit 27 and in turn into the chamber 29, causes the elastomer seal 30 to move out of the recess and into sealing contact with the bell 16 after the bell has been moved into seating contact with the hopper 17. When it is desired to release the blast furnace charge contained in the hopper 17, the fluid pressure is first removed by causing more of the fluid to pass out of the chamber 29 into the conduit 28. The seal then, due to its inherent resilient character, is caused thereby to move into the position shown in FIG- URE 5. When the bell 16 is lowered vertically, the blast furnace charge passes between the seat 31 of the hopper 17 and the bell 16. Since the seal 30 is out of the path of the blast furnace charge, no scufling or rubbing of the seal results.

It should be noted that due to the construction of the seal of the invention, the surface to be sealed need not be clean or smooth. The wide coverage of the seal due to the large-area surfaces thereof and the even seal pressure which is exerted by the fluid cause the seal 30 to surround and engulf any materials lodged between the seal 3d and the surface of the bell 16. The flexing of the elastomer seal at each cycle will serve to make it selfcleaning.

A seal generally indicated at 23 in FIGURE 6 of the drawings has been devised in order to prevent the blast furnace gases in the chamber between the upper hopper 12 and the lower hopper 17 from passing between the structure 24 of the blast furnace and the distributing hopper 12 to the outside of the blast furnace. The upper hopper 12 is of the revolving or distributing type which is caused to be rotated at definite intervals by conventional structure indicated schematically at 22. The hopper 12 has a rib 37 suitably sealed and secured thereto as by welding. The rib 37 contains a seat 38 which extends around the circumference of the hopper 12. A seal 39 is secured to a ring 41) which likewise extends circumferentially around the upper hopper 12. A manifold 41 is defined by the ring 4-11 and by the elastomer seal 39. A conduit 411a conducts the seal activating fluid from a system like and in parallel with the system shown in FIGURE 7 into the manifold 41}. An adhesive 42 and retaining rings 43 retain the elastomer seal 39 at its marginal edges. A plurality of threaded fasteners 44 pass through the retaining rings 43 and the marginal edges of the seal 39 and are threaded into the ring 41). The fluid under pressure enters the chamber 41 and causes the elastomer seal 39 to be moved into seating contact with the web 38. It is to be understood, of course, that although a rib 37 having a seat 38 is illustrated, the seal 39 can be made to be moved into sealing contact with the hopper 12 directly, if desired. A plurality of seals 45 form part of conventional sealing structure in use today. They need not be eliminated in order to practice the invention.

In the modification of FIGURE 5, one of the retaining rings 43a is disposed at the extreme lower end of the hopper 17. This embodiment is especially useful where a very wide seal is required. Weldments 34b are provided between the retaining rings 43 and 43a and the hopper 17. An adhesive 42a aids in sealing the elastomer seal 30a to the hopper.

Referring now to FIGURE 8 of the drawings, the drive mechanism 22 for driving the upper hopper 12 is shown as containing a motor 22a and a gear reducer 22b suitably mounted on the upper portion of the blast furnace 10 by brackets 220. A drive shaft 22d extending from the rear reducer 22b has fixedly mounted thereon a pinion gear 46 which meshes with a gear 4.6a which is fixedly attached to the outer portion of the hopper 12. The motor 22a is operated intermittently to position the charge in hopper 17 for even distribution on the lower bell.

A conduit 47 conducts the seal activating fluid from a system like and in parallel with the system shown in FIG- URE 7 into a manifold 48 formed in a collar 49 in the upper portion of the blast furnace 10. The manifold 48 extends circumferentially around the hopper 12 and leads into a conduit 47a, through which the fluid is discharged. The collar 49 is tapered to form a bearing seat for the hopper 12. Suitable fluid seals 49a are provided between the collar 4-9 and the hopper 12 to prevent the escape of the seal activating fluid.

Where the upper hopper is of a fixed or non-rotatable type, the small upper bell and hopper are a duplicate of the lower bell and hopper shown in FIGURES 2-5, inclusive.

The fluid system, designated generally at 50 in FIG- URE 7, can activate and deactivate the seal 30 of the invention. The hopper and the seal, for example, the lower hopper 17 and the lower bell 16 are shown schematically in conjunction with the fluid system 50'. The system comprises a fluid pump 51 having electrical leads 52 leading thereto from a suitable source. The pump 51 draws the fluid which it is adapted to pump from a sump 53 through a conduit 54. A conduit 55 leads from the pump 51 into the chamber 32 which extends around the circumference of the hopper. A conduit 56 leads from the opposite side of the passage 32 into both of conduits 57 and 58. A valve 59, preferably of the solenoid type, is disposed along the conduit 57. Electrical leads 60 lead to the solenoid valve from a switch 61 which is contacted by the end of the bell beam 19. When the bell beam 19 is in the position shown in FIGURE 1, then the valve 59 is in its closed position. When the bell beam 19 is pivoted counter-clockwise from the position shown in FIGURE 1, the switch 61 is operated to energize the valve 59 into its opened position.

Similar switches 61a and 6112 are associated with the upper bell 11 and the revolving distributor hopper 12, respectively. A cam 610 on the revolving hopper 12 actuates the switch 61b. A switch 62 is provided in leads 62a to provide for manual operation of the solenoid valve 59. In the event the system is manually operated, no electrical energy is supplied to the valve 59 through the leads 60. Each of these switches 61a and 61b is provided with a system (not shown) like and in parallel with the system of FIGURE 7. Parallel systems are required since, for example, the lower bell 16 is not operated at the same time as is the upper bell 11.

The conduit 58 contains restriction orifices 63 which maintain the pressure in the system when the valve 59 is in the closed position. The orifices can be exchanged for orifices of different sizes (not shown) so that the fluid pressure in the chamber 32 can be adjusted. The conduits 57 and 58 lead into a conduit 64- Which leads into a cooling apparatus 65. The cooling apparatus 65 serves to cool the fluid which has passed thereto from the passage 32 in the blast furnace hopper 17. A conduit 66 leads from the cooling apparatus 65 into the sump 53, wherefrom it is constantly being drawn by the pump 51. It is seen that the sump 53 always contains cool fluid. The cool fluid takes on heat energy from the seal when it comes into contact therewith and hence extends itslife.

In order that the cooled fluid of the system will not be unduly warmed by the heat in the blast furnace,

refractory material

70 and 71 is cast around the ends of the hopper and the bell, respectively.

Anchor wires

72 and 73 in the

refractory materials

70 and 71 reinforce the same.

For the sake of clarity, the operation of the system illustrated in FIGURE 7 and the method of the invention will be described. Assuming that the hopper 17 has just discharged its blast furnace charge, the bell 16 is moved vertically upward until it comes into seating contact with the hopper 17. The valve 59 is then closed either automatically or manually so that the fluid is caused to flow through the conduit 53. Due to the restriction orifices 63 in the conduit 58, until suflicient pressure is built up in conduit 55, the passage 32, conduit 56, and so forth, less fluid will pass through orifices 63 than is being pumped by the pump 51. When equilibrium is reached between the amount of fluid pumped by the pump 51 and that which passes through the orifices 63, the pressure is constant and at a maximum. The components of the system are so sized that the pressure is built up rapidly so that sealing is effective between the hopper and the bell a short time after the valve 59 is closed. The hopper then receives a blast furnace charge and when it is desired to drop the charge the valve 59 is opened whereupon fluid flow through the system increases and the pressure in the chamber 32 falls rapidly. When the pressure drops, the seal, due to its resiliency and higher furnace pressure, assumes the unsealing position shown, for example, in FIGURE 5 by the solid lines. The bell 16 is then lowered out of seating contact with the hopper 17, whereupon the charge is discharged. It will be noted that in the unsealing position the seal is out of the path of the blast furnace charge when the charge is discharged from the hopper. Increased flow of cooling fluid through the seal and the rest of the system of FIG. 7 is important when the bell is open because this is the time when the seal is exposed to the most heat and to the highest temperatures. After the charge has been discharged, the bell 16 is again moved into seating contact with the hopper 17, and the method is repeated. The seal can be flexed one or more times at the end of each cycle in order to clean it. This is accomplished by opening and closing the valve 59 one or more times, either by a suitable timer (not shown) along leads 69 or manually by the operation of the switch 62.

The method is similar with respect to the seal indicated at 23. The only difference is that instead of the CIQSHIC structure 24 moving toward and away from the hopper 12 as does the bell 11, the hopper 12 rotates with respect to the closure structure 24. When the hopper 12 has been rotated into the seating position, the rotation of which has caused distribution of the charge around its circumference, the seal can be activated into the position shown by the broken lines in FIGURE 6. Shortly before the hopper is to be rotated out of the seating position, the seal is deactivated.

The fluid employed by the system can be either a liquid or a gas. Liquid is preferable, because, due to its incompressibility, fast pressure changes are made possible, and a liquid provides better cooling of the elastomer seal. The liquid preferably employed is a fire-resistant oil, or, in some cases, water.

The above-described embodiments being exemplary only, it will be understood that the present invention comprehends organizations differing in form or detail from the presently described embodiments. Accordingly, the invention is not to be considered as limited save as is consonant with the scope of the following claims.

What is claimed is:

1. In a blast furnace:

hopper means, located at the top of said furnace, for

containing a blast furnace charge, said hopper means having a lower opening;

closure means at the bottom of said hopper means;

means mounting said closure means for vertical movement between an open lower position, in which said hopper means is in communication with a lower portion of said furnace and said charge is permitted to descend from said hopper means toward said lower furnace portion, and an upper position for closing said lower opening of the hopper means;

means for moving said closure means between said lower and upper positions thereof;

flexible, resiliently deformable sealing means located between said hopper means and said closure means when the latter is in an upper position;

said sealing means having a first surface, with at least a portion thereof facing said closure means, and a second surface with at least a portion thereof facing said hopper means;

means mounting said sealing means to said hopper means for flexing movement of said sealing means between a sealing first position, in which the sealing means extends toward the path of said descending charge and said portion of said first surface sealingly engages an adjacent surface of said closure means, and a non-sealing, retracted second position located outside said path of the descending charge;

means for flowing a fluid along said second surface;

and means for pressurizing said fluid, to move said sealing means from said second position to said first position thereof, and for depressurizing said fluid to increase the flow of fluid and retract said sealing means to its second position.

2. In a blast furnace as recited in claim 1 wherein said last-recited means comprises:

means for pressurizing said fluid when said closure means is in an upper closed position, and for depressurizing said fluid when the closure means moves toward its open lower position.

3. In a blast furnace as recited in claim 1 wherein:

said closure means comprises a bell movable between a lower first position and an upper second position;

said hopper means comprising means for seating said bell when the latter is in its second position;

said seating means including a surface recess encircling said bell and having an opening facing the interior of said hopper means; 1

said sealing means comprising a strip-like member with said second surface being a large-area surface overlying the entire recess opening when the sealing means is in both of its positions to close the recess opening and define, together with said recess, a fluid-tight chamber;

said first surface on the sealing means being a largearea surface, opposite said second large-area surface for engaging an adjacent surface of said bell;

said means for moving and retracting the sealing means including means for introducing a fluid into said chamber and means for withdrawing a fluid from said chamber.

4. In a blast furnace as recited in claim 1 wherein:

said sealing means comprises a strip-like member composed of a non-metallic material which is heatresistant and impervious to water and gas at the normal operating temperatures in that part of the furnace in which said sealing means is located.

5. In a blast furnace as recited in claim 1 and cornprising:

structure surrounding and enclosing said hopper means;

means mounting said hopper means for rotation about a vertical axis;

means actuable for imparting rotation to said hopper means;

flexible, resiliently deformable second sealing means located between said structure and said hopper means;

said second sealing means having a first surface, with at least a portion thereof facing said hopper means, and a second surface with at least a portion thereof facing said structure;

means mounting said second sealing means to said structure for flexing movement of said second sealing means between a first position in which said portion of said first surface is in sealing engagement with said hopper, and a disengaged second position;

means for flowing a fluid along said second surface of the second sealing means;

and means for pressurizing said fluid to move said second sealing means from said second position to said first position thereof, and for depressurizing said fluid to increase the flow of fluid and retract said second sealing means to its second position.

6. In a blast furnace:

hopper means;

structure surrounding and enclosing said hopper means;

means mounting said hopper means for rotation about a vertical axis;

means actuable for imparting rotation to said hopper mean-s;

flexible, resiliently deformable sealing means located between said structure and said hopper means;

said sealing means having a first surface, with at least a portion thereof facing said hopper means, and a second surface with at least a portion thereof facing said structure;

means mounting said sealing means to said structure for flexing movement of said sealing means between a first position, which said portion of said first surface is in sealing engagement with said hopper means, and a disengaged second position;

means for flowing a fluid along said second surface;

and means for pressurizing said fluid to move said sealing means from said second position to said first position thereof, and for depressurizing s-aid fluid to increase the flow of fluid and retract said sealing means to its second position.

7. In a blast furnace as recited in claim 6 wherein:

said structure has an interior surface recess facing the hopper;

said sealing means comprises a strip-like member with said second surface being a large-area surface overlying the entire recess opening when the sealing means is in both of its locations to close the recess opening and define, together with said recess, a fluid-tight chamber;

said first surface on the sealing means being a largearea surface, opposite said second large-area surface, for engaging an adjacent surface of said hopper means;

said means for moving and retracting the sealing means including means for introducing a fluid intosaid chamber and means for withdrawing a fluid from said chamber.

8. In a blast furnace as recited inclaim 6 wherein said last-recited means comprises:

means for pressurizing said fluid when the hopper means is stationary, and for depressurizing said fluid when said rotation-imparting means is actuated.

References Cited in the file of this patent UNITED STATES PATENTS 2,486,312 Mohr et al. Oct. 25, 1949 2,516,190 Dougherty et al. July 25, 1950 2,599,334 Latham June 3, 1952 3,042,360 Sneddon July 3, 1962 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N0. 3 152 703 October 13 1964 William E, Slagley Jr.

It is hereby certified. that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3 line 46 for "is" read its column 4L line 49 for "rear" read gear column 8 line 16 before "which" insert in Signed and sealed this 26th day of January 1965.,

(SEAL) Attest:

I ERNEST W. SWIDER' EDWARD J. BRENNER eating Officer Commissioner of Patents

Claims

1. IN A BLAST FURNACE: HOPPER MEANS, LOCATED AT THE TOP OF SAID FURNACE, FOR CONTAINING A BLAST FURNACE CHARGE, SAID HOPPER MEANS HAVING A LOWER OPENING; CLOSURE MEANS AT THE BOTTOM OF SAID HOPPER MEANS; MEANS MOUNTING SAID CLOSURE MEANS FOR VERTICAL MOVEMENT BETWEEN AN OPEN LOWER POSITION, IN WHICH SAID HOPPER MEANS IS IN COMMUNICATION WITH A LOWER PORTION OF SAID FURNACE AND SAID CHARGE IS PERMITTED TO DESCEND FROM SAID HOPPER MEANS TOWARD SAID LOWER FURNACE PORTION, AND AN UPPER POSITION FOR CLOSING SAID LOWER OPENING OF THE HOPPER MEANS; MEANS FOR MOVING SAID CLOSURE MEANS BETWEEN SAID LOWER AND UPPER POSITIONS THEREOF; FLEXIBLE, RESILIENTLY DEFORMABLE SEALING MEANS LOCATED BETWEEN SAID HOPPER MEANS AND SAID CLOSURE MEANS WHEN THE LATTER IS IN AN UPPER POSITION; SAID SEALING MEANS HAVING A FIRST SURFACE, WITH AT LEAST A PORTION THEREOF FACING SAID CLOSURE MEANS, AND A SECOND SURFACE WITH AT LEAST A PORTION THEREOF FACING SAID HOPPER MEANS;