Seal and corresponding manufacturing method

The present invention relates to a seal and a method for manufacture thereof, in particular it relates to a seal to be interposed between a movable element and a fixed element to prevent the transfer between two contiguous zones of fluid and solid substances such as lubricating and/or refrigerating liquids, impurities, waste, residues and the like. Seals are known that are arranged for being mounted on an end neck of a lamination cylinder so as to rotate therewith, that are interposed between a front surface of said roller and a corresponding supporting bearing.

A seal of this type, disclosed, for example, in US patent US 4165881, comprises a first annular portion, suitable for being mounted on a tapered or conical side surface of said end neck to make a static seal, and a second annular portion suitable for abutting on a friction surface of a fixed abutting means, typically a flange, in order to make a dynamic seal . The second annular portion generally includes a pair of radial protrusions or flanges that are parallel to and spaced apart from one another, provided with respective end sealing lips configured for abutting on the sliding surface. The two radial protrusions form an annular gap inside which there is inserted, in a mounting condition, a separating baffle of the abutting means .

The annular portions of the seal are made of rubber or another elastomer material the composition of which depends on the chemical features of the fluids to be intercepted, on the mechanical features of the connected members and on the operating conditions (temperature, speed, etc) .

The seal separates an internal zone, in which the supporting bearing is mounted, from an external environment, in which the laminating cylinder is located. In this manner, the seal prevents, in use, both the exit into the external environment of lubricating oil coming from the internal zone of the bearing (oil side) , and the entry into the latter of

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refrigerating liquids (water) , impurities, waste, residues, etc that are externally (water side) .

The annular portions of the seals can be made in one piece or, as disclosed in US patent US 4099731, separately as distinct and subsequently assembled elements. In this case, the two portions can be moulded from different materials and/or enable one of the two portions to be replaced in the event of wear. Apart from the one-piece or two-piece embodiment, a drawback of the known seals disclosed above lies in the plastic deformation to which over time the sealing lips of the radial protrusions are subject, due to the relaxation of the elastomer materials of the seal. This plastic deformation in fact causes a decrease in the preload, i.e. of the contact pressure exercised by the lips on the friction surface of the abutting flange, with a consequent loss of time and passage of fluid and solid substances.

If it is the sealing lip on the oil side that is deformed, the corresponding loss of seal causes the oil to leak into the outside environment, which may compromise the operation of the supporting bearing and of the lamination cylinder. In order to avoid this drawback, it is therefore necessary periodically to replace these seals, with consequent interruption to production and increased operating costs. An object of the invention is to improve known seals, in particular the seals for laminating cylinders, and the corresponding manufacturing methods, increasing the reliability, resistance and working life thereof. Another object is to obtain a seal and a corresponding manufacturing method, so as to ensure, even in unfavourable operating conditions, a dynamic seal that is optimal, constant and effective over a period of time that is significantly greater than that of known seals. A further object is to make a seal that has a great life and resistance to wear and can be manufactured with a relatively simple, cheap and reliable procedure.

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In a first aspect of the invention there is provided a seal suitable for being interposed at least between a first element and a second element, comprising first sealing means couplable with said first element and second sealing means removably connected to said first sealing means and provided with lip means arranged for abutting on a friction surface of said second element, characterised in that it comprises elastic means fixed to said lip means to maintain the latter abutting on said friction surface . Owing to this aspect of the invention it is possible to manufacture a seal, the sealing means of which, in particular the lip means, provided with spring means, ensures, even in unfavourable operating conditions, a dynamic seal that is optimum, constant and effective over a period of time that is noticeably greater than that of known seals. This enables the reliability, resistance and working life of the seal to be increased.

Applying to the lip means ribbon means having greater resistance to wear and a low friction coefficient further enables a seal to be obtained of that has great life and resistance to wear.

The second sealing means, provided with lip means that ensures the dynamic seal, is further easily removable from the first sealing means in the event of excessive wear. A second aspect of the invention provides a method for manufacturing the seal of the first aspect and comprising compression moulding first sealing means and second sealing means respectively by first heated moulding means and second heated moulding means . The invention can be better understood and implemented with reference to the attached drawings, which illustrate an embodiment thereof by way of non-limiting example, in which: Figure 1 is a partial section of a seal according to the invention in an assembled condition; Figure IA is an enlarged view of a detail in Figure 1;

Figure 2 is a simplified partial section of the seal in

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Figure 1 in a dismantled condition;

Figure 3 is a section of the seal in Figure 1 interposed between a laminating cylinder and a corresponding support bearing, in an operating condition; Figure 4 is a partial section of first moulding means for making first sealing means of the seal in Figure 1, in a respective open condition;

Figure 5 is a partial section of the first moulding means in Figure 4 in a respective closed moulding condition; Figure 6 is a partial section of second moulding means for manufacturing second sealing means of the seal in Figure 1, in a respective open position;

Figure 7 is a partial section of the second moulding means in Figure 6 in a respective closed moulding condition; Figure 8 is a partial section of a version of the second moulding means in Figure 6 to make a version of the seal in Figure 1 ;

Figure 9 is a partial section of another version of the seal in Figure 1, in an assembled condition; Figure 10 is a partial section of a version of the first moulding means for manufacturing the first sealing means of the seal in Figure 9, in a respective open condition; Figure 11 is a partial section of a version of the second moulding means for making the second sealing means of the seal in Figure 9 in a respective open condition.

With reference to Figures 1 to 3 , there is illustrated a seal 1 that can be interposed between a first movable element 30 such as, for example, an end neck of a rotating laminating cylinder 31, and a second fixed element 40 for example an abutting flange provided with a friction surface 40a.

The seal 1 comprises first sealing means 2 arranged for being coupled with and fixed to the first rotating element 30 so as to rotate therewith, and second sealing means 3 connected to the first sealing means 2, in an assembled condition A, and arranged for abutting on the friction surface 40a in ^' a mounting operating condition C of the seal 1.

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The first sealing means 2 makes a static seal whereas the second sealing means 3 makes a dynamic seal.

The first sealing means 2 and the second sealing means 3 are made with the same elastomer, for example a thermosetting polymer that has been suitably cross-linked or vulcanised. Alternatively, the sealing means 2, 3 can be made of different elastomeric materials, for example a material that is more flexible and suitable for mounting on the neck 30 for the first sealing means 2 and a more hardwearing material for the second sealing means 3 intended for abutting slidably on the friction surface 40a.

The second sealing means 3 comprises a body 4 with an annular shape provided with lip means 11, 12 with a circular shape suitable for abutting on the friction surface 40a of the second element 40. In particular, the body 4 comprises a first radial protrusion 5 provided at one end with a first sealing lip 11 and a second radial protrusion 6 provided at a respective end of a second sealing lip 12. The radial protrusions 5, 6, are substantially parallel to and spaced apart from one another, and form an annular gap 7 inside which, in the operating condition C of the seal 1, a separating baffle 40b of the second element 40 can be inserted. The sealing lips 11, 12 are divergent, tilted outside in relation to said annular gap 7 and have respective contact portions 11a, 12a arranged for abutting on the friction surface 40a.

The first radial protrusion 5 and the first lip 11 are arranged substantially facing supporting means 42 of the first element 30, for example a bearing, whilst the second radial protrusion 6 and the second lip 12 are arranged facing a front wall 31a of the laminating cylinder 31. In this way, the first radial protrusion 5 and the first lip 11 prevent lubricating oil coming from an internal zone 9 in which the bearing 41 (oil side) is located from escaping into an external environment 8.

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The second radial protrusion 6 and the second lip 12 on the other hand prevent refrigerating liquids, impurities, waste, residues etc entering the internal zone 9 from the external environment 8. The seal 1 comprises elastic means 10 fixed to at least one of the lips 11, 12 to maintain the latter abutting on the friction surface 40a. In particular, the elastic means comprises a leaf spring or finger spring 10 with an annular shape, fixed to the first sealing lip 11 facing the oil side, and in particular vulcanised directly on said first lip 11.

The leaf spring 10, which is made, for example, of stainless steel, has a first end part 10a that adheres to an end portion 5a of the first protrusion 5, and a second end part 10b that adheres to an external portion lib of the first lip 11, opposite the contact portion 11a.

Alternatively, the second end part 10b may not be fixed to the external portion lib of the first lip 11 to make the latter more flexible. Between the two end parts 10a, 10b of the spring there is interposed a suitably shaped, substantially "S"-shaped central part 10c. The shape of the finger spring 10 is such as to maintain the first lip 11 abutting on the friction surface 40a in the operating condition C of the seal 1 at a preset contact pressure. By acting suitably on the thickness of the leaf spring 10 and/or on the shape of the shaped central part 10c, it is possible to obtain a desired contact pressure value. In an embodiment of the seal 1 which is not illustrated in the figures, the elastic means comprises a second leaf spring fixed to the second sealing lip 12. to maintain the latter abutting on the friction surface 40a at a respective defined contact pressure.

Stiff supporting means 15a, 15b typically comprising a rubberised fabric ring, is incorporated into the body 4 of the second sealing means to stiffen the latter.

The seal 1 further comprises ribbon means 13 , 14 made of a

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material having great resistance to wear and a low friction coefficient and fixed to the sealing lips 11, 12 so as to cover at least the contact portions 11a, 12a.

The ribbon means 13, 14 has a flat and elongated shape with a thickness comprised between 0.3 and 1 mm, preferably 0.5 mm, and a width that is variable according to the dimensions of the sealing lips. The ribbon means 4 is made, for example, with a fluoropolymer, in particular virgin or filled polytetrafluoroethylene (PTFE), i.e. containing fillers or elements of different type such as glass fibre, carbon, graphite, stainless steel, bronze, nickel, ceramics, etc. The choice of the type and quantities of fillers to be introduced depends on the mechanical and chemical features that are desired in the PTFE, and on the features of the materials with which said PTFE will come into contact during use.

The ribbon means 13 , 14 forms one piece with the second sealing means 3 as it is fixed cross-linking the latter during the seal 1 vulcanising step. The first sealing means 2 comprises .a central annular portion 20 to which flexible side seal appendages 21, 22 are fixed. The central portion 20 and the side appendages 21, 22 form a flexible wall 26 arranged for abutting on, and adhering to, a substantially conical coupling surface 30a of the first element 30. Further elastic means 24, 25 is fixed and in particular included in the first sealing means 2 to maintain the latter abutting on the coupling surface 30a.

The further elastic means 24, 25 comprises a first garter spring 24 closed in a ring and inserted inside the central portion 20, and a second garter spring 25 closed in a loop and inserted inside a first seal appendage 21 facing the supporting means 42.

The first garter spring 24 is included in the first sealing means 2 during the hot moulding process explained in detail further on in the description. The second garter spring 25 is inserted and sealed after the seal 1 has been moulded.

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The first sealing means 2 further comprises an end portion 27, connected to the central portion 20 at the first side appendage 21. The end portion 27 is arranged for abutting in the mounting operating condition C on the supporting bearing 42. A plurality of radial grooves 28 are provided on the periphery of the end portion 27 to enable the passage of the oil from the support bearing 41. An annular deviating element 29 is fixed to the end portion 27 to divert to the internal zone 9 the oil coming from the supporting bearing 42. The central portion 20 comprises an annular seat 20a arranged for receiving at least partially the body 4 of the second sealing means 3 (Figure 2) .

Connecting means 16 is provided for removably locking together the first sealing means 2 and the second sealing means 3 in the assembling condition A. The connecting means

16 enables the second sealing means 3 to be dismantled and replaced easily, for example in the event of wear and/or damage .

The connecting means 16 comprises one or more cylindrical plugs 18 inserted into the body 20 of the first sealing means 2 and arranged for engaging with respective bushes 17 inserted into the central portion 4 of the second sealing means 3. The reversible coupling between plugs 18 and bushes

17 determines the connection between the first sealing means 2 and the second sealing means 3.

As explained more precisely below in the description, the cylindrical plugs 18 also act as anti-rotation elements during the moulding process. Plugs 18 and bushes 17 are fixed to the respective sealing means 2, 3 by vulcanisation.

The connecting means 16 further comprises a ring 19 of steel ribbon, wound around the body 4 of the second sealing means 3 so as to lock the plugs 18 inside the respective bushes 17. The ring 19 can be mounted and dismantled, by deforming locally a portion of the second sealing means 3 towards the inside.

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With, reference to figures 4 to 7, the process for making a seal 1 according to the invention by compression moulding involves using first moulding means 50 and second moulding means 60 arranged for separately forming the first sealing means 2 and the second sealing means 3, by melting, compression and vulcanisation of respective charging means appropriately inserted and positioned inside said moulding means 50, 60. The charging means includes a plurality of elements of elastomer material that have been suitable sized and shaped.

The first moulding means 50, which is heatable to about 150°, comprises a first lower element 51 provided with a shaped housing 51a, a first upper element 52, provided with a respective compression portion 52a, and a first intermediate element 53 provided with a shaped portion 53a and with a shaped side wall 53b. On said shaped side wall 53b, having an annular shape, the cylindrical plugs 18 of the connecting means 16 are removably mounted. The first upper element 52 and the first intermediate element 53 are movable along a first movement direction Vl to enable the first moulding means 50 to be partially or completely opened or closed, respectively in the first opening condition Bl (Figure 4) and in the first operating closing condition Dl (Figure 5) . In the first opening condition Bl of the first moulding means 50, the first elements 51, 52, 53 are spaced apart from one another along the first movement direction Vl to enable not only the plugs 18 but first charging means 35, 36, 37 to be positioned that are necessary for forming respectively the central portion 20, the side sealing appendages 21, 22 and the deflecting element 29 of the first sealing means 2. With the charging means 35, 36, 37 the further elastic means 24 is also inserted that is to be comprised and vulcanised inside the first sealing means 2. The second moulding means 60, which is also heated to approximately 150°, comprises a second lower element 61 that

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forms a shaped housing 64, a second upper element 62, provided with a respective compression portion 62a, and a second intermediate element 63 provided with a first shaped portion 63a and a second shaped portion 63b, that are 5 opposite and substantially mirror one another.

The second upper element 62 and the second intermediate element 63 are movable along a second movement direction V2 to enable the second moulding means 60 to be partially or completely opened or closed respectively in a second opening0 condition B2 (Figure 6) and in a second operating closing condition D2 (Figure 7) .

In the second opening condition B2 , the second lower element 61, the second upper element 62 and the second intermediate element 63 are spaced apart from one another along the second5 movement direction V2 to enable second charging means 45, 46, 47, 48 necessary for forming the first radial appendage 5, the first lip 11 and part of the body 4 to be positioned inside the shaped housing 64. On a side wall 64a of the

^{• ■} shaped housing 64 the ^■ bushes 17 of the connecting means !& ^■ 0 are positioned that are kept in position by locking pivots 65 that are partially threaded and screwed on the second lower element 61.

During the step of extracting the second sealing means 3, at the end of the compression moulding process, after lifting of5 the second upper element 62 and before lifting of the second intermediate element 63, the locking pivots 65 are disengaged from the respective bushes 17.

On the side wall 64a supporting means 15a is further rested, comprising a preformed ring made of rubberised fabric. 0 On the first portion 63a of the second intermediate element 63 there is arranged third charging means 55, 56, 57 necessary for forming the second radial appendage 6, the second lip 12 and the remaining part of the body 4. Charging the second moulding means 60 provides the following 5 steps .

Initially, the leaf spring 10 is inserted into a suitable

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protrusion 64b of the shaped housing 64. Subsequently, the second charging means 45, 46, 47 is introduced progressively, which comprises strips with a rectangular section of elastomer material having different dimensions, shapes and hardness. A strip 45 is positioned above the leaf spring 10 so as to lock the leaf spring 10 partially on the protrusion 64b.

The first ribbon means 13 is then inserted, which is arranged above said strip 45 and said leaf spring 10, so as to be closed in a loop.

A further strip 48 of charging material is extended along a peripheral flap of the first ribbon means 13.

At this point it is possible to close the shaped housing 64 by means of the second intermediate element 63, which is lowered so as to form a first forming cavity. Closing is formed so that during centring of the second intermediate element 63 with the second lower element 61, the charged components do not move from the positions thereof. In a gap defined by th.e< second lower element 6T and by the- second intermediate element 63 in a partial closing condition of the second moulding means 60 it is possible to insert further supporting means 15b comprising a preformed ring made of rubberised fabric. On the first shaped portion 63a of the second intermediate element 63 the third charging means 55, 56, -57 can thus be positioned, comprising thin strips of elastomer with different hardnesses with a rectangular section. The second ribbon means 14 is inserted in particular between two strips 55, 57. At this point the second upper element 62 is lowered so that the compression portion 62a abuts on the third charging elements 55, 56, 57 and forms with the first shaped portion 63a a second forming cavity. The second moulding means 60 is then completely closed, in the second operating closing condition D2, so as to compress the second charging means 45-48 and the third charging means

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55-57 enclosed between the second lower element 61 and the second intermediate element 63 and between the latter and the second upper element 62 for a time that is necessary for the melting and subsequent vulcanisation thereof. Before positioning the ribbon means 13, 14 in the second moulding means 60, applying suitable adhesion promoters to a face of said ribbon means 13, 14 is provided that is intended for contacting the respective charging elements. The adhesion promoting means enables the latter to adhere firmly to the ribbon means 13, 14 during vulcanisation.

The ribbon- means 13, 14 must in addition be curved beforehand, for example, by a calendering operation. The charging means 45, 46, 47, 48, 55, 56, 57 is inserted and positioned inside the second moulding means 60 so as to fill completely, once melted, the exact volume of the forming cavities so as to be fixed between one another or at least to relate to one another definitively, above all to lock or maintain in position the leaf spring 10 and the ribbon means

^• 13, 14; •-. .- - . In Figure 8 there is illustrated a version of the second moulding means 60 that enables second sealing means 3 to be made having lightened sealing lips 211, 212 and ribbon means 213, 214 of moderate dimensions, in order to reduce the inertia and preloading forces of the sealing lips 211, 212 in applications in which the rotation speed is high.

In order to position correctly the first ribbon means 213, during charging of the second heated moulding means 60, the shaped housing of the second lower element 261 comprises an abutting step 264a. With reference to Figure 9, there is illustrated an embodiment of the seal 1 that differs from the previously disclosed embodiment through the fact that the connecting means 116 in this case comprises one or more teeth 117, made in the central portion 120 of the first sealing means 2 and arranged for engaging in one or more respective grooves 118 made on a peripheral portion 104a of the body 104 of the

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second sealing means 3.

The coupling between teeth 117 and grooves 118 determines the connection between the first sealing means 2 and the second sealing means 3. The teeth 117 also act as anti-rotation elements during the moulding process .

The further connecting means 19 comprising a steel ribbon ring wound around the body 104, enables the teeth 117 to be locked inside the respective grooves 118. The teeth 117 and the grooves 118 are made in the sealing means 2, 3 compression moulding process. For this purpose, the first intermediate element 153 of the first moulding means 50 comprises at the shaped side wall 153b one or more recesses 153c arranged for forming on said central portion 120 of the first sealing means 2 respective teeth 117 (Figure 10) .

Similarly, the second lower element 161 of the second moulding means 60 comprises at the side wall 164a of the shaped housing 164 one or more further recesses 164c arranged for forming on said body 104 of the first • sealing means 2 _: respective grooves 118 (Figure 11) .

The method for making by compression-moulding this version of the seal 1 of the invention is substantially identical to the previously disclosed method. It is further provided that the connecting means 16 may comprise a plurality of self-tapping screws or equivalent elements, the application of which nevertheless requires a certain attention to prevent said sealing means 2, 3 being damaged.

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