Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal for a pipe – conduit – or cable
Reexamination Certificate
2002-05-29
2004-02-10
Knight, Anthony (Department: 3676)
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal for a pipe, conduit, or cable
C277S650000, C277S652000, C277S627000, C428S375000
Reexamination Certificate
active
06688607
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to material for sealing threaded pipe joints, particularly for use in the plumbing industry for making joints in pipes for water-supply, water-discharge, heating and the like, but also having utility for other types of pipework, e.g., in industrial plants. The invention also relates to a dispenser for the material.
2. Brief Description of the Related Technology
It is well known for plumbers to use a two-part system of hemp fibre and paste for sealing threaded pipe fittings. Dry hemp fibre is usually supplied in loose unwoven form, and a quantity is taken and drawn out into a length. Hemp is also available in the form of a hank wound on a spool which can be held in a dispenser with a tubular dispensing guide for the hemp. In either case, a length of hemp is wrapped around the threaded area of a male pipe fitting. The paste may be applied to the fitting first, in which case the hemp is drawn through the paste as it is wrapped around the fitting, or alternatively (or in addition) the paste is applied over the hemp. The paste keeps the hemp in place on the male threaded fitting. The female threaded fitting is then applied and completes the joint. The joint can be adjusted later, if desired.
While this two-part system is widely used, it is not acceptable for pipes intended to carry drinking water because hemp does not meet the standards for materials in contact with potable water. Hemp is capable of supporting microbiological growth.
An alternative two-part system is available using polypropylene fibre instead of hemp, which system is approved for contact with potable water. However any two-part system has disadvantages because it is cumbersome to use and requires a high degree of skill and takes time to apply.
Another commercially available sealing material is a polytetrafluoroethylene (“PTFE”) tape which is non-fibrous in nature. It is typically about 10 mm wide and 0.25-0.5 mm thick. In use, the tape is wound around the threaded area of a male fitting, with a number of overlaps used to build up a thickness as desired. The female threaded part is then applied to complete the assembly. This system also requires skill in application and it suffers the disadvantage that it cannot be used in a joint where readjustment may be necessary without loss in seal.
Georg Fischer Rohrverbindungstechnik GmbH of D-78224 Singen, Germany, offers for sale a range of the cap materials including pastes for use with hemp and also including a product called PARALIQ PM 35 VLIES which comprises a tape in the form of a synthetic special web, fleece or gauze saturated with a thread sealing paste. It is fibrous in nature like hemp and can be used without either hemp or a separate paste. The tape is 16 mm wide and is available in a roll of tape 10 m or 25 m long. The 25 m tape is said to be sufficient for 100 1 inch (25 mm) threads (i.e. threads on pipe of 1 inch (25 mm) outside diameter). The broad tape is less convenient for the plumber to handle than fibrous hemp or a yarn. It is applied across a number of threads in a band 16 mm wide rather than being wound into individual threads. It is supplied on a roll but not in a dispenser which can be handled by the plumber in one hand.
In a different technical field, dental floss is available in the form of a multifilament yarn, optionally waxed, which is wound on a spool and held in a dispenser with a dispensing aperture. A blade for cutting the yarn is located on the exterior of the dispenser, adjacent to the dispensing aperture, for cutting the yarn into desired lengths. Dental floss is not (1) a sealing material or (2) coated with a composition suitable for sealing pipe joints. Accordingly, dental floss does not provide teaching relevant to the field of threaded pipe joints.
SUMMARY OF THE INVENTION
The present invention provides, as an article of manufacture, a material for sealing threaded pipe joints comprising a multifilament yarn ready-coated with a joint sealing composition and packaged in a dispenser from which the coated yarn may be supplied for direct application to a screw-threaded area of a pipe.
The material according to the invention is more convenient to use than prior art systems. The yarn is easy to wind on to the threaded area of a pipe and it enters into the well of the screw-thread. The material can be handled by a plumber in one hand.
The term “yarn” as used in this description and the following claims includes a “thread”.
The dispenser may suitably be hermetically sealed prior to its initial use, e.g., by use of a hermetic envelope around it. Desirably also the dispenser has an aperture for dispensing the coated yarn and closure means for closing over the aperture when the dispenser is not in use; such closure means should re-seal the dispenser in a sufficiently airtight manner to allow a shelf life of at least one week, preferably at least one month, after initial opening of the package, without substantial deterioration of the sealing composition.
In one aspect of the invention, the sealing composition may suitably be a non-curing paste composition, for example of the type known for use with hemp in a two-part system for pipe sealing, or an oleoresinous caulk or putty similar to a glazing putty. Such compositions are packaged in sealed conditions to prevent contamination and to minimize exposure to air which could cause deterioration of the composition, for example by drying out (volatilization) or oxidation. The packaging should desirably be air-impermeable and suitably may be such that the sealing composition coated onto the yarn has a shelf life of more than 2 years without significant loss of quality.
Suitable non-curing paste compositions comprise a mixture of oil and particulate filler. The oil may suitably be an unsaturated oil (e.g., linseed oil). The particulate filler may suitably be selected from one or more of mineral fillers (e.g., calcium carbonate), powdered polymer fillers (e.g., polyethylene powder or polytetrafluoroethylene powder) and chopped fibre fillers (e.g., chopped aramid fibres, polyethylene fibres or carbon fibres, particularly aramid fibre pulp as described in U.S. Pat. No. 5,068,265 assigned to Loctite, the contents of which are incorporated herein by reference). Mixtures of two or more types of filler may be used. The filler gives the oil body to form the paste. Increased amounts of filler are used to increase the viscosity of the composition. Typical compositions comprise oil and filler in proportions of 20-40 parts by weight oil and 80-60 parts by weight filler. The composition may also contain other resins or plasticizers to aid the composition to adhere to the yarn.
However, a joint sealing composition based on linseed oil has some disadvantages including limited shelf stability due to the tendency of linseed oil to oxidize. This results in drying-out of the composition. As already described, sealed packaging can be used to minimize this problem, but special packaging increases the cost of the final product. Also the composition may dry out too quickly after the package has been opened for use. In addition, linseed oil has been found to leave a residual taste in potable water as result of leaching of oil from the joint sealing composition.
It is desirable therefore in some circumstances to use a non-curing oil other than linseed oil. Silicone oils and minerals oils are two groups of suitable non-curing oils. Silicone oils may in particular be liquid polydimethyl siloxanes such as are listed under CAS Registry Number 63148-62-9. They may suitably have a viscosity in the range from 1,000 mPas to 100,000 mPas and a molecular weight in the range from 10,000 to 500,000. Examples of suitable silicone oils include hydroxyl-terminated polydimethyl siloxane such as Silopren E2 from Bayer A. G. or methyl-terminated polydimethyl siloxane such as Silopren W1000, also from Bayer A. G.
Mineral oils may also be used instead of linseed oil. Mineral oils are generally high molecular weight liquid hydrocarbons and are listed under CAS Registry
Casey Tadgh Eisirt
Cullen Ellen Patricia
Martin Francis Richard
Regan Philip Malcolm
Bauman Steven C.
Henkel Loctite Corporation
Knight Anthony
Patel Vishal
LandOfFree
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