GB2083583A

GB2083583A - Pipe Fitting

Info

Publication number: GB2083583A
Application number: GB8125968A
Authority: GB
Original assignee: Massey Ferguson Perkins Ltd
Current assignee: Perkins Engines Group Ltd
Priority date: 1980-09-06
Filing date: 1981-08-26
Publication date: 1982-03-24

Abstract

A pipe fitting (10) for securing a pipe (11) within a screw-threaded bore (12) in a component (13) includes a nut (14) with an externally threaded portion (17) for screw- threaded engagement with a threaded portion (20) of the component bore (12), and a pipe-gripping ferrule (15). The nut and ferrule have cooperating first (18) and second (21) abutment surfaces which extend in planes perpendicular to the longitudinal axis (19) of the component bore (12) so that when the nut is tightened into the threaded bore, a nose portion (22) of the ferrule (15) cooperates with an inwardly tapering portion (23) of the component bore to form a seal between the pipe (11), ferrule (15) and component bore (12) and to hold the nose portion of the ferrule captive in an indentation (24) in the pipe. <IMAGE>

Description

SPECIFICATION Pipe Fitting This invention relates to a fitting for connecting a pipe with a bore in a component.

There is a requirement for a pipe fittingfor use with presurised fluid, such as hydraulic fluid, which is simple in construction, compact, and capable of ensuring that the pipe remains connected with the bore in the component at high pressures of say 2,000 to 3,000 p.s.i.

It is an object of the invention to provide an improved form of pipe fitting which meets the above requirements.

According to the present invention there is provided a pipe fitting for securing a pipe into a screw-threaded bore in a component, said fitting comprising a nut with an externally threaded portion for screw-threaded engagement with a threaded portion of the component bore, the nut having an internal bore which allows the passage therethrough of the pipe and a first abutment surface extending in a plane perpendicular to the longitudinal axis of the component bore, and a pipe-gripping ferrule having a second abutment surface on its outer end extending in a plane perpendicular to said component bore axis for cooperation with the first abutment surface, the ferrule also having a nose portion on its inner end arranged, when the nut is tightened into the threaded portion of the component bore, to cooperate with an inwardly tapering portion of the component bore on the inner side of the threaded portion to form a seal between the pipe, ferrule and component bore and to ensure that the nose portion of the ferrule is held in an indentation in the pipe thus securing the pipe relative to the ferrule.

References throughout this specification to "inner end", "outer end", "inner side" etc., refer to the disposition of the components in their operational position relative to the component bore. Thus, for example, the term "outer end" refers to the end nearest the end of the component bore through which the pipe and other parts are introduced.

When the material of the component is sufficiently hard the tapering portion of the component can be arranged to actually cause the nose of the ferrule to indent the pipe as the nut is tightened into the component bore. Where softer materials are used for the component, the ferrule indentation is best achieved as a preliminary separate step in the assembly of the fitting using a hardened swaging tool which includes a bore which is essentially a duplicate of the component bore. This prevents damage to the tapering portion of the component bore which might otherwise occur when the component is made of softer material.

When the ferrule indentation is made as a separate preliminary step, the ferrule becomes captive on the pipe and when the fitting is assembled into the bore the nut simply applies sufficient pressure to the ferrule to provide the sealing effect and also ensure that the nose portion of the ferrule remains in the indentation.

In a pipe fitting in accordance with the present invention the disposition of both the first and second abutment surfaces in planes perpendicular to the axis of the component bore results in purely axial loads acting between the nut and ferrule thus eliminating the possibility of any radial forces acting between these components which might cause, for example, the nut to bind in the threaded portion of the component bore thus reducing the ability of the nut to cause the required axial movement of the ferrule and resulting in inadequate indentation into the pipe.

The invention also provides a method of securing a pipe in a bore in a component comprising the steps of forming the bore in the component with an internally threaded portion adjacent the outer end of the bore and an inwardly tapering portion on the inner side of the threaded portion; providing a pipe fitting nut having a head portion, an externally threaded portion for cooperation with the threaded portion of the component bore, and a first abutment surface at the opposite end from the head portion and which extends in a plane perpendicular to the longitudinal axis of the nut; providing a pipe gripping ferrule with a second abutment surface at one end which is perpendicular to the longitudinal axis of the ferrule for cooperation with the first abutment surface and a nose portion at the other end for gripping the pipe; introducing an end portion of the pipe into the bore with the nut and ferrule on said end portion orientated to allow contact between the first and second abutment surfaces; and tightening the nut in the threaded portion of the bore so that the first and second abutment surfaces cooperate and force the nose portion of the ferrule into sealing contact with the pipe and the tapering portion of the component bore, and cause the nose portion of the ferrule to grip the pipe.

As explained above, the act of tightening the nut in the threaded portion of the bore may be arranged to actually cause the nose portion of the ferrule to indent and thus grip the pipe.

Alternatively, if the component is of soft material, this indentation can be effected as a preliminary separate operation using a hardened swaging tool.

As will be appreciated, by suitable design of the shape of the nut, the projection of the nut from the bore when the nut is fully tightened can be made small. This makes the fitting particularly suitable for use on installations where space is limited.

Such fitting details as the bore and nut threads, the general dimensions of the ferrule, the proportions of the tapering portion of the bore, and the material specifications of the various fitting parts are all preferably in accordance with SAE standard SAE J 51 4h on flareless tube fittings.

One example of the present invention will now be described, by way of example only, with reference to the accompanying drawing which shows a vertical section through one form of pipe fitting embodying the present invention.

Referring to the drawing a fitting 10 for securing a hydraulic pipe 11 into a bore 12 in a component 13 comprises a nut 14 and a pipegripping ferrule 15.

The nut 14 has a head portion 16 of conventional hexagonal form, an externally threaded portion 16 and a first abutment surface 18 at the end remote from the head portion. As can be seen, the first abutment surface 18 extends generally perpendicularly relative to the longitudinal axis 1 9 of the bore 12 and the threaded portion 17 of the nut is arranged to engage an internal threaded portion 20 of the bore.

The pipe-gripping ferrule 15 is made of hardened material in accordance with SAE standard J 514h and has at its outer end a second abutment surface 21 for cooperation with the first abutment surface 18. Again, as can be seen, the abutment surface 21 is generally perpendicular to the axis 19. The other end of the ferrule terminates in a nose portion 22 which cooperates with a tapering portion 23 of the bore 12 to indent the pipe 11 at 24 and thus retain the pipe in the position shown in the drawing.

The fitting can be assembled in two ways.

If the component 13 is made from sufficiently hard material the nut 16 and ferrule 1 5 are placed on the end portion of pipe 11 and the pipe is then introduced into the bore 12 until its end 25 contacts a step 26 in the bore. The nut 16 is then tightened into the screw-threaded portion 20 of the bore and forces the nose portion 22 of the ferrule between the outside of pipe 11 and the tapering portion 23 of the bore, causing the nose portion to be driven into the outside of the pipe thus producing the gripping indentation 24.

As will be appreciated, when the nut 16 is fully tightened home a fluid-tight seal is provided between the tapering portion 23 of the bore and the ferrule 15 and between the pipe 11 and the ferrule.

It has been found that since both the cooperating abutment surfaces 18 and 21 on the nut and ferrule respectively are disposed in planes perpendicular to the axis 1 9 of the bore 12, this results in purely axial forces being applied to the ferrule when the nut is tightened. This eliminates any possibility of the nut and/or ferrule binding in the bore and ensures that the necessary axial displacement of the ferrule takes place to produce an adequate indentation of the pipe. Experience has shown that this type of fitting is capable of reliably retaining hydraulic piping in position when subjected to pressure of 2,000 to 3,000 p.s.i.

If the material of the component 13 is not sufficiently hard to be capable of causing the nose portion 22 of the ferrule 1 5 to indent the pipe without damage to the tapering surface 23 this indentation can easily be effected as a preliminary operation in a hardened swaging tool which is essentially a duplicate of the bore 12 shown in the accompanying drawing. Thus if this method of assembly is used the nut and ferrule will be placed on the pipe which will then be introduced into the swaging tool in exactly the same manner as described above in relation to the component 13.After the nut has been tightened down to force the nose portion 22 of the ferrule into the pipe using a tapering portion of the swaging tool corresponding to the tapering portion 23 of the component 13, the nut will be released so that the pipe can be removed from the swaging tool and subsequently inserted into the bore in the component 13. When the nut 16 is tightened into the component bore the tapering surface 23 of the bore is not called upon to actually drive the nose portion 22 into the wall of the pipe but to simply ensure that the nose portion remains in the indentation 24 which has been previously produced in the hardened swaging tool.

Again, as will be appreciated, the nut 16 applies sufficient pressure to provide a seal.

If the swaging of the nose portion into the pipe is effected as a preliminary operation, as described above, it is desirable that the depth Y of the bore in the swaging tool should be fractionally less than the corresponding depth of the bore in the component 13 in order to ensure that when the nut is tightened into the component bore contact between the end 25 of the pipe and the step 26 does not prevent the ferrule making sealing contact with the component and pipe.

As will be appreciated by appropriate design of the head portion 16 of the nut the head room X of the fitting can be kept to a minimum. This is an important feature of the fitting which makes it particularly suitable for installations where space is limited. In particular it is possible for the pipe 11 to execute sharp bends, as indicated by the dotted detail 11' in the accompanying drawing, soon after emerging from the head end of the fitting. The present invention thus provides a simple and efficient pipe fitting which is of a compact construction and also capable of withstanding high pressures and reliably holding an associated pipe in a component bore.

An example of one application for which the present invention has been found particularly suitable is the securing of a pipe into an outlet bore in a hydraulic pump block mounted within a tractor chassis. It has been found that the pipe fitting when used in this application can withstand high pump outlet pressures (say 2,000 to 3,000 p.s.i.) without the pipe blowing out of the block which could necessitate the expensive operation of splitting the tractor chassis in two in order to gain access to the disconnected pipe.

Claims

1. A pipe fitting for securing a pipe into a screw-threaded bore in a component, said fitting being characterised by comprising a nut (14) with an externally threaded portion (17) for screwthreaded engagement with a threaded portion (20) of the component bore (12), the nut having an internal bore which allows the passage therethrough of the pipe (11) and a first abutment surface (18) extending in a plane perpendicular to the longitudinal axis (19) of the component bore (12), and a pipe-gripping ferrule (15) having a second abutment surface (21) on its outer end extending in a plane perpendicular to said component bore axis (19) for cooperation with the first abutment surface (18), the ferrule also having a nose portion (22) on its inner end arranged, when the nut is tightened into the threaded portion of the component bore, to cooperate with an inwardly tapering portion (23) of the component bore (12), on the inner side of the threaded portion to form a seal between the pipe, ferrule and component bore and toensure that the nose portion of the ferrule is held in an indentation (24) in the pipe thus securing the pipe relative to the ferrule.

2. A method of securing a pipe in a bore in a component said method being characterised by comprising the steps of forming the bore (12) in the component (13) with an internally threaded portion (20) adjacent the outer end of the bore and an inwardly tapering portion (23) on the inner side of the threaded portion; providing a pipe fitting nut (14) having a head portion (16), an externally threaded portion (17) for cooperation with the threaded portion (20) of the component bore (12) and a first abutment surface (18) at the opposite end from the head portion and which extends in a plane perpendicular to the longitudinal axis (19) of the nut; providing a pipe gripping ferrule (1 5) with a second abutment surface (21) at one end which is perpendicular to the longitudinal axis (19) of the ferrule for cooperation with the first abutment surface and a nose portion (22) at the other end for gripping the pipe; introducing an end portion of the pipe (11) into the bore (12) with the nut (14) and ferrule (15) on said end portion orientated to allow contact between the first (18) and second (21) abutment surfaces; and tightening the nut in the threaded portion (20) of the bore so that the first and second abutment surfaces cooperate and force the nose portion (22) of the ferrule into sealing contact with the pipe (11) and the tapering portion (23) of the component bore (12), and cause the nose portion (22) of the ferrule (1 5) to grip the pipe (11).

3. A method according to claim 2 characterised in that the act of tightening the nut (14) in the threaded portion (20) of the bore (12) causes the nose portion (22) of the ferrule (1 5) to indent and thus give the pipes (11).

4. A method according to claim 2 characterised by the inclusion of an additional preliminary and separate step in which the nose portion (22) of the ferrule (1 5) is caused to indent the pipe (11) by tightening the nut ( 14) into a bore in a swaging tool which represents the bore in the component so that the ferrule is held captive on the pipe.