GB2147964A

GB2147964A - Liquid-tight compression joints for metal tubes

Info

Publication number: GB2147964A
Application number: GB08327550A
Authority: GB
Inventors: Walter Bennett
Original assignee: TRENT VALLEY ENGINEERING
Current assignee: TRENT VALLEY ENGINEERING
Priority date: 1983-10-14
Filing date: 1983-10-14
Publication date: 1985-05-22
Also published as: GB8327550D0; GB2147964B

Abstract

In forming a compression joint between two copper tubes 10 and 12 an end portion 27 of one tube 12 is expanded to a tight fit within a brass bush 18, and an endmost portion of the tube is flared outwardly to present an annular end face 28. An end portion 29 of the other tube 10 is inserted into the expanded end portion 27 of the one tube 12, and a nut 14 thereon is secured on to the bush 18 to trap an olive 16 against the end face 28 of the tube 12. A liquid-tight joint is so formed without requiring the bush 18 to be soldered to the tube 12. <IMAGE>

Description

SPECIFICATION Liquid-tight compression joints for metal tubes This invention is concerned with improve ments in or relating to the formation of liquid tight compression joints, in particular com pression joints for metal (e.g. copper) tubes.

In a well known conventional method of forming a liquid-tight compression joint be tween two lengths of copper tube in plumb ing, a brass olive becomes compressed between a nut on one tube and an externally threaded tubular sleeve (which can be referred to as a bush) secured on the other tube. The compressed olive forms a seal with one tube and with the bush at one end of the bush, and the bush is usually soldered at its other end to the other tube, both to secure the bush to the tube and to form a liquid-tight joint between the bush and the tube at that end of the bush.

We believe it would improve manufacturing efficiency if that soldering step could be elimi nated. The soldering process is generally time consuming and inefficient, and furthermore the soldered joint often has to be de-fluxed, chemically cleaned, and then pressure tested to check for leaks. There can also be a risk, certainly in soldering copper tube, that the tube will become locally annealed due to the soldering heat and consequently weakened.

At least for factory-assembled joints, we be lieve that the conventional joint-forming method can be improved.

In one of its aspects the invention provides a method of forming a light-tight compression joint between two metal tubes in which an olive on one of said tubes becomes compressed by screwing a nut on to a threaded bush mounted on the other of said tubes, said other tube being expanded to a tight fit within said bush to secure said bush on said tube, and an end most portion of said other tube being flared outwardly to present an annular end face, an end portion of said one tube being introduced into said expanded other tube and said olive becoming compressed by said nut against said end face.

By this method the soldering and cleaning steps of the conventional method (as hereinbefore referred to) are eliminated, as also is the risk of locally annealing the tube to which the bush is secured. Since the olive seals against the tube itself rather than against the bush, there is no need for the bush to be secured in a liquid-tight manner to the tube.

There now follows a detailed description, to be read with reference to the accompanying drawings, of a joint-forming method which illustrates the invention by way of example.

In the accompanying drawings: Figure 1 is a sectional view illustrating two tubes and associated fittings immediately prior to final assembly; and Figure 2 is a view similar to Fig. 1 showing the finished joint.

First and second copper tubes 10 and 12 which are to be joined together are shown in Fig. 1 bearing, respectively, a brass nut 14 and olive 16 and a tubular brass bush 18.

The nut 14 is of a conventional kind comprising an internally screw-threaded larger internal diameter portion 20, and a smaller internal diameter portion 22, which is a loose sliding fit on the first tube 10. The olive 16 can be received within the larger diameter portion 20 to abut a frusto-conical face 24 of the smaller diameter portion 22.

The bush 18 is externally screw-threaded from one end up to a hexagon head flange 26. When the bush is first assembled on to the second tube 12 it is an easy fit on the tube. An end portion 27 of the tube 12 is then expanded to a tight-fit within the bush, and further expanded to expand the bush, resulting in the bush being firmly secured to the tube. An end most portion of the tube 12 is flared outwardly to present a frusto-conical annular end face 28 of the tube. The expanded end portion 27 is of a suitable diameter to receive an end portion 29 of the first tube 10 in a sliding fit.

To assemble the tubes and fittings together, to provide a liquid-tight compression joint, the end portion 29 of the first tube 10 is inserted into the expanded portion 27 of the second tube 12 and the nut 14 screwed on to the bush 18 until tight; the olive 16 so becomes compressed between the oppositely inclined faces 24 and 28, respectively, of the nut and the flared portion of the second tube 12 (see Fig. 2).

1. A method of forming a liquid-tight compression joint between two metal tubes in which an olive on one of said tubes becomes compressed by screwing a nut on to a threaded bush mounted on the other of said tubes, said other tube being expanded to a tight fit within said bush to secure said bush on said tube, and an endmost portion of said other tube being flared outwardly to present an annular end face, an end portion of said one tube being introduced into said expanded other tube and said olive becoming compressed by said nut against said end face.

2. A method of forming a liquid-tight compression joint between two metal tubes substantially as hereinbefore described with reference to the accompanying drawings.

3. Apparatus comprising two metal tubes connected together by a method according to either of claims 1 and 2.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Liquid-tight compression joints for metal tubes This invention is concerned with improve ments in or relating to the formation of liquid tight compression joints, in particular com pression joints for metal (e.g. copper) tubes. In a well known conventional method of forming a liquid-tight compression joint be tween two lengths of copper tube in plumb ing, a brass olive becomes compressed between a nut on one tube and an externally threaded tubular sleeve (which can be referred to as a bush) secured on the other tube. The compressed olive forms a seal with one tube and with the bush at one end of the bush, and the bush is usually soldered at its other end to the other tube, both to secure the bush to the tube and to form a liquid-tight joint between the bush and the tube at that end of the bush. We believe it would improve manufacturing efficiency if that soldering step could be elimi nated. The soldering process is generally time consuming and inefficient, and furthermore the soldered joint often has to be de-fluxed, chemically cleaned, and then pressure tested to check for leaks. There can also be a risk, certainly in soldering copper tube, that the tube will become locally annealed due to the soldering heat and consequently weakened. At least for factory-assembled joints, we be lieve that the conventional joint-forming method can be improved. In one of its aspects the invention provides a method of forming a light-tight compression joint between two metal tubes in which an olive on one of said tubes becomes compressed by screwing a nut on to a threaded bush mounted on the other of said tubes, said other tube being expanded to a tight fit within said bush to secure said bush on said tube, and an end most portion of said other tube being flared outwardly to present an annular end face, an end portion of said one tube being introduced into said expanded other tube and said olive becoming compressed by said nut against said end face. By this method the soldering and cleaning steps of the conventional method (as hereinbefore referred to) are eliminated, as also is the risk of locally annealing the tube to which the bush is secured. Since the olive seals against the tube itself rather than against the bush, there is no need for the bush to be secured in a liquid-tight manner to the tube. There now follows a detailed description, to be read with reference to the accompanying drawings, of a joint-forming method which illustrates the invention by way of example. In the accompanying drawings: Figure 1 is a sectional view illustrating two tubes and associated fittings immediately prior to final assembly; and Figure 2 is a view similar to Fig. 1 showing the finished joint. First and second copper tubes 10 and 12 which are to be joined together are shown in Fig. 1 bearing, respectively, a brass nut 14 and olive 16 and a tubular brass bush 18. The nut 14 is of a conventional kind comprising an internally screw-threaded larger internal diameter portion 20, and a smaller internal diameter portion 22, which is a loose sliding fit on the first tube 10. The olive 16 can be received within the larger diameter portion 20 to abut a frusto-conical face 24 of the smaller diameter portion 22. The bush 18 is externally screw-threaded from one end up to a hexagon head flange 26. When the bush is first assembled on to the second tube 12 it is an easy fit on the tube. An end portion 27 of the tube 12 is then expanded to a tight-fit within the bush, and further expanded to expand the bush, resulting in the bush being firmly secured to the tube. An end most portion of the tube 12 is flared outwardly to present a frusto-conical annular end face 28 of the tube. The expanded end portion 27 is of a suitable diameter to receive an end portion 29 of the first tube 10 in a sliding fit. To assemble the tubes and fittings together, to provide a liquid-tight compression joint, the end portion 29 of the first tube 10 is inserted into the expanded portion 27 of the second tube 12 and the nut 14 screwed on to the bush 18 until tight; the olive 16 so becomes compressed between the oppositely inclined faces 24 and 28, respectively, of the nut and the flared portion of the second tube 12 (see Fig. 2). CLAIMS