Field of the Invention

The present invention relates to the field of pipe fittings. More particularly, the invention relates to an insertion fitting for pipes that have an inner surface made of plastic, not requiring a gasket.

Background of the Invention

When coupling devices to pipes or pipes to one another, a fitting is required to be efficiently attached to the pipe and to the coupled device. An efficient attachment requires, inter alia, that the fitting is firmly in place and doesn't get undesirably disengaged (whereas in some cases the fitting is required to be disengaged only on demand), that no substance leaks from the attachment points between the fitting and the pipe or between the fitting and the coupled device, and that minimum deformation is caused to the pipe in order to attach a fitting thereto.

Insertion fittings comprise an insertion member configured to be inserted with pressure into a pipe's extremity. Several insertion fittings and attachment schemes are commercially available. In the field of insertion fittings for plastic pipes (or pipes that comprise a plastic inner-surface), the variety of fittings and attachment schemes is relatively narrow and limited. The most popular scheme for connecting, for instance, a metal fitting to a plastic pipe comprises presenting an elastomeric (e.g. rubber) gasket or another sealant solution to the insertion member (e.g. to grooves in the insertion member) and forcing the insertion member into the pipe. Other insertion fittings (e.g. plastic fittings) are connected similarly.

In order to ensure firm attachment and prevent leaks in the above connecting scheme, the gasket is required to apply high pressure against the pipe's inner surface. Ideally a gasket with an external diameter that is slightly larger than the pipe's inner diameter is used. This, however, presents a drawback requiring very high force in order to insert the insertion member into the pipe. In fact, the more the gasket meets the above requirements, the more difficult it is to insert the fitting into a pipe and the more force is required. Inserting with such high force may cause deformation to the pipe. Moreover, this connection scheme requires a sealing member (e.g. a gasket) that isn't an integral part of the fitting. Such gaskets have limited reliability and may start to leak after a long period of time. Moreover, because connecting the pipe using such arrangements requires force, the fitting may sometime be inserted improperly, thus resulting in a leaky connection. Water leakage will, in turn, cause metal corrosion and subsequent pipe failure.

It is therefore an object of the present invention to provide an insertion fitting for plastic pipes (which term is meant to encompass also metal pipes with a plastic inner and outer surface) that doesn't require a gasket or another sealant solution.

Other objects and advantages of this invention will become apparent as the description proceeds.

Summary of the Invention

The present invention relates to an insertion fitting for coupling devices to pipes comprising: a. an elongated tubular insertion member at the distal end of the insertion fitting, comprising one or more circumferential grooves with a sealing member in each of said one or more circumferential grooves, the diameter of the insertion member being smaller than a diameter of an internal surface of a pipe;

b. a coupling member at the proximal end of the insertion fitting, which may comprise any suitable coupling element, and for instance comprises helical grooves suitable for coupling devices to the fitting; and

c. a restricting member, the diameter of which is larger than an external diameter of a pipe;

wherein the sealing member is a composite polymer material such that when heat is applied thereto it expands and fills gaps between the insertion member and the internal surface of the pipes, and adheres to the circumferential grooves and to the internal surface of the pipes, and thereby prevents the passage of fluids through said sealing members.

According to an embodiment of the invention, the fitting is metal. According to another embodiment of the invention, the fitting is made of brass. According to still another embodiment of the invention, the fitting is made of plastic material. According to yet another embodiment of the invention, the fitting further comprises a metal implanted within the sealing member, thereby allowing heat to be inducted from one point along said sheet to the whole circumference of said sealing member. According to another embodiment of the invention, the sealing member comprises a basic polymer compound, a chemical foaming agent and an adhesive compound. According to still another embodiment of the invention, the basic polymer compound is a polyolefin which, in a further embodiment of the invention, is selected from high density polyethylene; low density polyethylene; or polypropylene.

According to yet another embodiment of the invention, the foaming agent expands when heated beyond a predefined temperature; resists liquid over time; withstands temperature of 95 degrees Celsius; withstands pressure over time; resists mechanical withdrawing forces over time; and conserves adhesion properties of the adhesive compound.

According to still an embodiment of the invention, the adhesive compound strongly adheres metal and plastic to pipe materials; resists liquid over time; withstands temperature of 95 degrees Celsius; withstands pressure over time; and conserves the adhesion properties over time.

According to a further embodiment of the invention, heat is applied to the sealing member by heating the pipe's exterior; and/or by induction;

Brief Description of the Drawings

In the drawings:

Figs. 1A and IB show perspective views of an insertion fitting, according to an embodiment of the invention;

Fig. 2 shows a perspective view of the fitting of Fig. 1A, illustrating circumferential grooves, according to an embodiment of the present invention;

Figs. 3A and 3B show perspective cross section views of the fitting of Fig. 1A, according to an embodiment of the present invention;

Figs. 4A and 4B show perspective views of an insertion fitting according to another embodiment of the invention; and

Fig. 5 illustrates the elements of the fitting with an external coupling reinforcement sleeve. Detailed Description of the Invention

Reference will now be made to an embodiment of the present invention, examples of which are illustrated in the accompanying figures for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed, mutatis mutandis, without departing from the principles of the claimed invention.

Fig. 1A shows a perspective views from the front of an insertion fitting 101 according to an embodiment of the invention, and Fig. lb shows a perspective view from the back of insertion fitting 101, comprising an elongated tubular insertion member 103 and coupling member 106 on each side of a restricting member 105. Sealing members 102a and 102b are introduced at circumferential grooves (not shown in Fig. 1) in insertion member 103. The distal side 103a of insertion member 103 terminates at an opening 104 through which substance flows, when fitting 101 is attached to a pipe. The proximal side 103b of the insertion member terminates at hexagonal restricting member 105 that has a diameter that is larger than the external diameter of a pipe to which the fitting 101 is connected. The distance from distal side 103a to the distal side of restricting member 105 defines the depth that insertion member 103 can be inserted into a pipe. The exterior of coupling member 106 can be provided with helical grooves (not shown in the figures) suitable for coupling (i.e. screwing) various commercial devices to fitting 101, and therefore to a pipe into which the fitting is inserted. According to an embodiment of the present invention, the exterior distal side 103a of insertion member 103 is truncated cone-shaped, thereby aiding insertion of the fitting into a pipe.

Fig. 2 shows a perspective view of fitting 101 with sealing members 102a and 102b removed, illustrating circumferential grooves 107a and 107b. The diameter of insertion member 103 generally corresponds to the inner diameter of a pipe into which it is inserted. Grooves 107a and 107b relate to portions along insertion member 103 where the diameter is smaller than this aforementioned diameter. Figs. 3A and 3B show perspective cross section views from the front and back of fitting 101, respectively, demonstrating sealing members 102 and 102b filling grooves 107a and 107b, respectively, according to an embodiment of the invention.

It is noted that the present invention is not limited to a specific number, configuration, or size of sealing members and corresponding grooves. The number configuration, and size of sealing members and corresponding grooves illustrated in the Figs, is exemplary in nature, and more or less sealing members and grooves may be present. Fig. 4A illustrates a fitting 401 according to another embodiment of the present invention, with grooves 407a and 407b that are configured differently than grooves 107a and 107b (e.g. of Fig. 2), and Fig. 4B illustrates fitting 401 with a sealing member 402 of a size (i.e. length relative to insertion member 403) different than sealing members 102a and 102b (e.g. of Fig. 1A).

Sealing members 102a and 102b are comprised of a composite polymer material that when heated expands and fills any gap between the insertion member 103 and a pipe's internal surface into which it is inserted. In this particular embodiment two sealing members are shown, but the invention is not limited to any specific number of sealing members, and as long as the sealing surface is satisfactory for the indicated purpose one or three or more sealing members can be used. The composite material of sealing members 102a and 102b further has adhering properties that also are activated when the material is heated. Finally the composite material comprises sealing properties suitable to prevent passage of fluids through the sealing member, thereby preventing leaks. Accordingly, when insertion member 101 is inserted into a pipe and the sealing member is heated beyond a predefined temperature, the material expands radially. When the insertion member is cooled to below the predefined temperature, the now expanded material has adhered to both the inner surface of the pipe and to the outer surface of the insertion member 103 (e.g. to the grooves thereof).

According to an embodiment of the invention, the composite polymer material comprises three compounds. The first compound is a basic polyolefin polymer, e.g. polypropilene or high (HDP) or low density polyethylene (LDP), which grants the sealing properties. The second compound is a chemical foaming agent that causes the expansion of the sealing members when heated beyond the decomposition temperature of the foaming agent. The third compound is an adhesive agent that causes the adhering of the sealing members to the grooves and to the pipe's inner surface when heated beyond and then cooled below its melt temperature.

According to an embodiment of the present invention, the chemical foaming agent is long term liquid and pressure resistant, withstands temperature of 95 degrees Celsius, resists mechanical withdrawing forces of the insertion fitting and conserves adhesion properties of the adhesive compound. Illustrative examples of a chemical foaming agent include TRACEL IM 3170 MS or TRACEL PO 3180, both available from Trameco ^® , which have a decomposition temperature of 170° and 180°, respectively, for the above Trameco ^® product.

According to an embodiment of the present invention, the adhesive agent is capable of strongly adhering metal and plastic to pipe materials, requiring a minimum disassembly force of at least 250 kg., is long term liquid and pressure resistant, withstands temperature of 95 degrees Celsius, and conserves its adhesion properties for a long time. An illustrative example of adhesive agent is Polyglue ^® GE461P available from HDC ^® , having a melt temperature of 190°.

Heat can be applied to a sealing member in any common method known in the art. For instance heat can be applied to the pipe's exterior causing heat to be distributed to the whole circumference of the sealing material; however it is important to keep the temperature below the melting temperature of the pipe, which in some cases should not exceed 110 Celsius degrees. Another method that can be used is induction, in which heat is applied to a location of a metal fitting 101 causing the heat to be transferred to the insertion member 103 and to the sealing members. Internal heating, done by introducing a heating member inside the fitting, can also be used.

According to an embodiment of the invention the fitting is metallic and made of brass. According to another embodiment of the invention, the fitting is plastic and made of Polyvinylidene fluoride or Polyphenylsulfone, (such as Radel ^® PPSU from SOLVAY)

In case of a plastic fitting, in order to enable full circumferential heating and melting of sealing members, a metal sheet can be implanted within the sealing member, thereby causing heat to be inducted from one point along the sheet to the whole circumference of the sealing members. Alternatively or additionally, the sealing member can be heated by a remote heating method, e.g. using ultrasound waves. Furthermore, a fitting can be heated from its inside by, for instance, threading a heating element from the fitting's proximal side (i.e. from the coupling member through the restricting member and to the insertion member). Any other heating method that is capable of heating the sealing member beyond the melting and activation temperatures of its compounds without causing damage to the fitting or to the pipe into which it is inserted can be used. Fig. 5 illustrates the use of a further coupling reinforcement sleeve. Once rings 501 are put in place (as shown, for instance, with respect to rings 407 a and b in Fig. 4A) the fitting can be coupled with the pipe (not shown in the figure). Once the coupling is completed, an additional external sleeve 502 can be added, according to some embodiments of the invention. Sleeve 502 may be made of a variety of materials but, in one embodiment of the invention it is made of metal that can be easily compressed to apply a pressure on the pipe, thus obtaining a stronger coupling thereof with the fitting. Of course, other additional materials can be used and pressure can be applied, using sleeve 502 by any other method, such as by thermal expansion or any other method known in the art.

According to an embodiment of the invention, a fitting 101 can be disengaged from a pipe by applying heat to the sealing member, thereby causing a softening of the sealing material, and extracting the fitting therefrom. It is noted that in such a case the sealing member may not be reused inasmuch as the foaming process of the abovementioned foaming agent is irreversible.

Although embodiments of the invention have been described by way of illustration, it will be understood that the invention may be carried out with many variations, modifications, and adaptations, without exceeding the scope of the claims.