Background of the Invention

1. Field of the Invention

The present invention relates to couplings for ventilation conduits, and, more particularly, the present invention relates to couplings for mine ventilation conduits that provide a substantially air tight joint between the conduits.

2. Description of the Prior Art

It has long been recognized that it is desirable to provide a substantially air tight coupling between tubular conduits used for mine ventilation. One type

10 of prior art substantially air tight coupling comprises two_ steel tubular conduits each having a flanged end with a gasket positioned between the flanges. Bolts secured through both flanges and the gasket connect the conduits. This type of coupling is heavy, cumbersome ,e to install, is expensive, requires precise alignment between the conduits, and comprises many pieces including a gasket and bolts which may be misplaced.

A coupling of fiberglass reinforced plastic conduits for mine ventilation is also known. This

20 coupling comprises a tubular conduit having a flared end portion which mates with the end portion of a second tubular conduit. The end portion of the second conduit is force fitted into the flared end portion of

the first conduit. Although this coupling is less expensive and easier to install than the steel tubular type coupling discussed above, this coupling results in substantial air leakage due, at least in part, to irregularities in the conduit and the tendency of the coupled conduits to separate.

Summary of the Invention

The present invention provides a coupling for mine ventilation conduits which provides a substantially air tight seal between conduits. A coupling in accordance with the present invention includes a first tubular conduit having a flared end portion for receiving an end portion of a second tubular conduit.

A resilient compressible seal is secured circum- ferentially around the outer surface- of the second tubular conduit. The .conduits are positioned in ati-ng relation with respect- ^' to each other and are drawn together to compress the seal between the inner surface of the flared-end portion of the first tubular conduit in the outer surface of the end portion of the second tubular conduit.

Although various mechanisms for drawing the conduits together to compress the seal may be used, it is preferred that at least one and preferably two or more elongate straps be used. Each strap has one end attached to one conduit and another end attached to the other tubular conduit. Various types of straps may be used to draw the conduits together. One type of strap comprises and elongate resiliently extensible strap that is typically made of natural or synthetic rubber. The strap, which has an unextended length that is shorter than the distance between the points of attachment on the respective conduits, is stretched and attached to the conduits to draw them together. Alternatively, a non-extensible type strap may be used,

such as for example a nylon strap. In the case of non-extensible strap, the coupling device would include a mechanism, such as a buckle, for tightening the strap to draw the conduits together. In a preferred embodiment of the invention, the seal is seated in a groove which extends around the circumference of the outer surface of the second conduit. The groove confines the seal against any substantial longitudinal movement in either direction when the conduits are mated or separated. The groove is preferably defined by two spaced-apart ridges located on and extending circumferentially around the outer surface of the tubular conduit. The seal, which preferably comprises an O-ring, is positioned in the groove defined by the ridges and has an outer portion which protrudes from the groove. When the tubular conduits are mated and drawn together by one or jnore straps, the protruding outer portion of the O-ring contacts the interior surface of the flared end of the first conduit and is compressed to provide a substantially air tight seal between the conduits.

The conduits are preferably made of a reinforced plastic material, such as fiberglass reinforced plastic, as is used for mine ventilation conduits. Such conduits are typically made by winding reinforcing rovings impregnated with a thermosetting resin in a helical pattern around a cylindrical mandrel to form the conduit. Thereafter, the thermosetting resin is cured to form a rigid conduit. In accordance with the present invention wherein it is desirable to provide two ridges having therebetween ^a groove in which the O-ring seats, such ridges may be provided by first forming an uncured reinforced plastic conduit and then positioning the O-ring at the desired location on the uncured conduit. Thereafter, while the conduit is still in an uncured state, the ridges are built up on

both sides of the O-ring by repeatedly winding the impregnated rovings in a circular pattern adjacent to the sides of the O-ring. Thereafter, the conduit with the ridges thereon is cured to form a conduit with integral ridges.

In accordance with another embodiment of the invention, the seal comprises a resilient compressible strip, preferable made of a foam material, that is secured circumferentially around the second conduit. The resilient foam material is preferably made of polyvinyl chloride foam although other types of foams such as polyurethanes, polyesters and polyethers may be used. The strip of foam material may be faced with a thin film which provides integrity to the foam and increases the useful life of the sealing strip. A coupling in accordance with the present invention provides not only a substantially air tight seal, but also, provides an inexpensive, easy to install coupling that is less prone to failure because of misalignment °f the conduits. These advantages and others will be apparent from the following detailed description of the invention with reference to the drawings.

Brief Description of the Drawings

FIG. 1 is a perspective view of a coupling for mine ventilation conduits prior to assembly of the

Coupling;

FIG. 2 is a sectional view of the coupling shown in FIG. 1 after it has been assembled; FIG. 3 is an enlarged sectional view of the coupling and the device for tightening and holding the strap;

FIG. 4 is an enlarged sectional view of the resilient foam material adhered to the tubular conduit;

FIG. 5 is a perspective view of the device for tightening and holding the strap shown in FIG. 3;

FIG. 6 is a sectional view of the strap tighten¬ ing device along the plane 6-6 of FIG. 5; FIG. 7 is a side plan view of another embodiment of a coupling in accordance with the present invention with a portion sectioned away to show the seal;

FIG. 8 is an enlarged sectional view of the seal of the coupling shown in FIG. 7 just prior to assembly of the coupling;

FIG. 9 is an enlarged se°ctional view of the seal of the coupling as shown in FIG. 8, except that the coupling has been assembled;

FIG. 10 is an enlarged prospective view of the resilient extensible strap for drawing the conduits together as shown in FIG. 7;

FIG. 11 shrows in sectional view one of the tubular conduits in an uncured state with a seal placed in the desired position; FIG. 12 shows in sectional view the tubular conduit shown in FIG. 11 after one of two ridges has been built up thereon; and

FIG. 13 shows in sectional view the tubular conduit shown in Figs. 11 and 12 after two ridges have been built thereon.

Description of the Prefereed Embodiments

Referring to FIGS. 1, 2 and 3, a coupling for joining a first tubular conduit 10 and a second tubular conduit 12 is shown. Conduits 10 and 12 have a generally cylindrical shape and are made from fiberglass reinforced plastic which is preferably filament wound. Cylindrical conduits are shown by way of example and conduits having other shapes such as oval may be used. The conduits may also be made of various materials and may be

unreinforced or reinforced by methods other than filament winding. Tubular conduit 10 includes a flared or diverging end portion 14 for receiving the end portion 16 of tubular conduit 12. An elongate flexible strap 18 is attached at one end thereof to either tubular conduit 10 or tubular conduit 12. In the case of the coupling shown in FIGS. 1-3, strap 18 is anchored to conduit 10 and is preferably attached to conduit 10 during fabrication. A resilient compressible strip, preferably of foamed plastic, is adhered around the periphery of the end portion 16 of tubular conduit 12. The resilient strip 24 has small portion 26 extending beyond the lip 28 of conduit 12 so that when conduit 12 is inserted into the diverging portion 14 of conduit 10, the overlapping portion 26 of resilient strip 24 is free to wrap around end_ lip 28 of conduit 12.

Th'e device 30 for tightening «and holding the strap is attached to tubular conduit 12 and tightens flexible strap 18 to draw tubular conduits 10 and 12 together. The detail of the structure and operation of tightening device 30 will be described in detail below. As the device 30 tightens strap 18, end portion 16 of conduit 12 is drawn within flared end portion 14 of conduit 10. As conduits 10 and 12 are moved together, resilient strip 24 is compressed between inner surface 72 of flared end portion 14 and the outer surface 74 of end portion 16 of conduit 12 to provide a substantially air tight seal between conduits 10 and 12. As shown in FIG. 3, the resilient strip 24 is compressed in the region of end lip 28 of conduit 12. By- using a resilient compressible material, and irregularities which exist in surfaces 72 and 74 of conduits 10 and 12 are accomo- dated. The tightening device 30 also holds the tightened strap in position to maintain the seal.

The resilient foam material of strip 24 and the

manner by which the foam material is adhered to conduit 10 will be described with respect to FIG. 4. The resilient foam material 24 has a body 32 which is preferably polyvinyl chloride foam although other types of foam such as polyurethanes, polyesters and polyethers may be used. Body 32 is faced at one side thereof with a thin film 34 which is preferably a polyester film such as Mylar. Film 34 may be made of various materials other than polyester such as polyvinyl chloride, polyethylene and aluminum foil. Film 34 provides integrity ot foam 32 and increases the useful life of foam body 32 which would otherwise be worn after repeated insertions of tubular conduit 12 into the flared end portion 14 of tubular conduit 10. Foam body 32 is preferably adhered to the periphery of conduit 10 by a conventional adhesive 36. The foam ^" material including the body portion 32, the 'film 34 and the adhesive 36 may be formed as a single unit. It is preferred that the foam material 24 be adhered to the inner surface 72 of the flared portion 14 of conduit 10.

Referring to FIGS. 3, 5 and 6, the strap tight¬ ening device used in coupling in accordance with'-t e present invention will now be described in detail. It should be understood that this device is being shown as a preferred embodiment and that other mechanisms for tightening and holding the tightened strap in position may be used. Tightening device 30 includes a body 38 comprising a floor 40 and two walls 42 and 44 extending upwardly from the floor. Walls 42 and 44 include apertures 46 and 48 for receiving a spool rotatable with respect to walls 42 and 44. Spool 50 has a central portion 52 extending between walls 42 and 44 and extending upwardly from the floor. Walls 42 and 44 include apretures 46 and 48 for receiving a spool rotatable with respect to walls 42 and 44. Spool 50 has a central portion 52

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extending between walls 42 and 44 and end portions 54 and 56 extending through the apertures 46 and 48. The central portion 52 of spool 50 includes an elongated slot 61 which extends through spool 50. Strap 18 may be threaded through slot 61 which retains the strap (see FIG. 3) .

End portions 54 and 56 of spool 50 include holes 59 and 60 which extend transversely to the longitudinal access of spool 50 and which receive - elongate lever arms 62 and 64 which are slidable with, respect to spool 50 in holes 58 and 60. A hook 66, extends from one side of floor 40 and provides for releasable attachment of buckle 30 to a ring 68 attached to conduit 12 by strap 70. The operation of the strap tightening device will now be described with respect to FIGS. 1, 2, 3 and 5 _ As shown in FIG. 1, the. conduits 10 and'12 are in a position ^' just prior to joining thereof. -The conduits 10 and 12 are then moved into mating relation, that is, end portion 16 of conduit 12 is inserted into flared end portion 14 of conduit 10. The end 60 of strap 18 is threaded through slot 61 of tightening device 30. As shown in FIGS. 1 and 3, lever arms 62 and 64 are grasped and rotated to tighten strap 18 to the position shown in FIG. 3 (several turns have occurred on spool 50) . As conduit 12 moves within the flared portion 14 of conduit 10, the resilient compressible foam strip 24 contacts the interior surface of the flared portion 14 and is compressed to provide a seal between the two conduit rs as shown in FIG. 3.

When the strap has been tightened, both levers 62 and 64 are slid in holes 59 and 60 to a position to maintain strap 18 in a tightened condition. Referring to FIG. 2, lever 64, under the urging of the tensional force on strap 18 transmitted to spool 50, urges the lever arm 64 (and also lever arm 62 not shown in FIG. 2)

in a counterclockwise direction to lock the lever arm against conduit 12.

Only one strap and tightening device set is shown in FIG. 1. It is preferable to have at least two sets of straps and tightening devices to provide for balanced application of forces on the coupling. As shown in FIG. 2, a second set of tightening devices and straps is provided and since this set is identical to the set described above, the same reference characters are used in the drawings.

Strap 18 is preferably a flexible flat nylon strap. It should be understood that materials other than nylon may be used and belts, cords, ropes and other means for drawing the conduits together may be used.

Referring to FIGS. 7-13, another embodiment of a coupling in accordance with the present invention is shown. Tubular. conduit 70 includes a flared end portion 74 which is sized to receive the end portion 76 of the second tubular conduit 72. The second conduit includes an outer surface 78 having a seal 80 secured circu ferentially thereon. As shown particularly well in FIGS. 8 and 9, a groove 82 that extends circumferen¬ tially around the outer surface 78 provides a seat for seal 80. The groove 82 confines the seal .80 against any substantial longitudinal movement which may otherwise occur when the conduits are being mated or when the conduits are being separated. The groove 82 is defined by ridges 84 and 86, which extend circumferentially around conduit 72 and are sized so that the seal 80, which is preferably an O-ring, has an outer portion 88 which protrudes from groove 82.

FIG. 8 shows the conduits 70 and 72 just prior to assembly of the coupling. During assembly of the coupling, end portion 76 of conduit 72 is inserted as shown by arrow 90 into the diverging end portion 74 of

conduit 70. As shown in FIG. 9, upon insertion, the outer portion 88 of the O-ring 80 contacts the interior surface 92 of conduit 70 and is compressed to form an air tight seal. Ridge 86 prevents the O-ring 80 from being forced rearwardly upon insertion, and ridge 84 prevents the O-ring from being forced forwardly when the conduits are disassembled.

Various mechanisms for drawing the tubular conduits 70 and 72 together may be used. Referring to FIG. 7 the coupling includes one or more sets of straps for drawing the conduits together. Since each set of straps is substantially identical to the other set or sets of straps, only one will be described. As shown in FIGS. 7 and 10, securement straps 94 and 96 are anchored respectively to conduits 70 and 72, and are preferably attached to their respective conduits during manufacture of the conduits ^' wherein one or more- layers of fiberglass rovings, impregnated with thermosetting resin are wound over the ends 98 and 99 of the straps to attach them to their respective conduits. As best shown in FIG. 10, each strap includes a D-shaped ring 100 secured at the end thereof. The strap 102, which is used to draw the conduits together, comprises a resilient extensible material such as synthetic or natural rubber and includes at its respective ends 104 and 106 "S-clamps" 108 and 110. S-clamp 110 includes an opening 112 to enable the clamp to be attached to and detached from D-shaped ring 100. The strap 102, which has an unextended length that is shorter than the distance between the points of attachment on the respective conduits (the distance between the D-shaped rings) , is stretched and attached to the conduits to draw them together. The strap 102 shown in FIgS. 7 and 10, may be replaced by other mechanisms for drawing the conduits together, and, more specifically, the device for drawing conduits together shown and

described with respect to FIGS 1 through 6 may be used.

Referring to FIGS 11, 12 and 13, the method of manufacture of tubular conduit 72 will now be described. Conduit 72 is formed in a conventional manner by winding fiberglass rovings impregnated with thermosetting resin on a cylindrical mandrel to form an uncured conduit. The O-ring seal 80 is positioned on the exterior surface 78 of the uncured conduit 72 at the desired position as shown in FIG. 11. Thereafter, and while the thermosetting resin of conduit 72 is in an uncured state, ridge 84 is formed by repeatedly winding impregnated rovings in a circular pattern adjacent one side of the O-ring 80 as shown in FIG. 12. The impregnated rovings are built-up to a height that is substantially less than the diameter (d) of the O-ring. Thereafter, a second ridge 86 is built up adjacent on the other side of o-ring 80 in a similar manner. Once both ridges have been built up, the conduit 72 and ridges 84 and 86 are cured to form a conduit wherein ridges integral with the conduit.

It should be understood that although specific embodiments of the invention have been described herein in detail, such description is for purposes of illustration only and modifications may be made thereto by those skilled in the art within the scope of the invention.