GB2153943A

GB2153943A - Compression pipe fitting

Info

Publication number: GB2153943A
Application number: GB08501544A
Authority: GB
Inventors: Danny Bryan Sutton; Lester Bruno Wright
Original assignee: Bundy Corp
Current assignee: Bundy Corp
Priority date: 1984-02-02
Filing date: 1985-01-22
Publication date: 1985-08-29
Also published as: JPS60179590A; DE3503265A1; GB8501544D0; IN163849B; IN163781B

Abstract

A spring washer compression fitting 10 employes a conical frustum shaped spring washer 46 which, when axially compressed within the fitting, causes radial deformation of the associated tube 28 thereby sealingly connecting the fitting to the tube. The internal bore portion 24 of the fitting has a dimension greater than that of the external diameter of the associated tube, so that a limited extent of off- axis orientation between the internal bore and the longitudinal axis of the tube is permitted. A second embodiment of this invention is described wherein a pair of identical spring washers are employed in opposed relationship. <IMAGE>

Description

SPECIFICATION Spring washer compression fitting assembly Background and summary of the invention This invention relates to a tube connection fitting and more particularly, to an improved compression type tube fitting assembly utilizing an internal compressible spring washer element which seals against the associated tube and fitting.

Numerous types of stationary machinery and mobile apparatus include internal fluid flow systems employing tubes which conduct gases or liquids. Separate components of such systems are typically interconnected by one or more tubes which are connected to these components by tube fittings. An example of use of such tubes is found in motor vehicles wherein tubes are employed to conduct fuels, lubricants, coolants and gases. Due to design and operation parameters, and cost concerns, tubes made from a relatively ductile metal material or alloy are frequently employed.

Due to production and manufacturing tolerance variations which occur during mass production of a particular device employing fluid conduction tubing, the orientation and distance between tube fittings varies from one device to another. Therefore, it is often necessary to custom fit the interconnecting tubes such that the ends properly engage the tube fittings. Such custom fitting requires that the tube be cut to the proper length and properly bent so that the longitudinal axes of the tube at its ends coincide closely with the axes of the fitting bores so that the tube ends may be easily inserted within the fittings. This problem is normally aggravated where the respective ends are not parallel to one another. This requirement of custom tailoring the tube for a particular application leads to cost penalties and production time constraints.Absent precise dimensioning and alignment of an interconnecting tube with the associated fitting, residual stresses are imposed on the tube structure because the tube must be deformed to engage the fittings. Such residual stresses can lead to fatigue fracture development when the tube is exposed to constant vibration or other stress which, for example, occurs when the system is employed in a motor vehicle.

Alternatives include the use of corrugated tubing or tubing made from elastomeric materials. Such types of tubing, however, have their own drawbacks, such as cost, strength, etc. It is, therefore, desirable to provide a tube fitting which can sealingly interengage a connecting tube without the free length of the tube being critically dimensioned and, also without alignment of the longitudinal axes of the terminal ends of the tube being critical. It is a principal object of this invention to provide such a fitting assembly.

It is further desirable to provide a tube fitting assembly which employs a minimum number of components and which is easily assembled. It is therefore another object of this invention to provide a tube fitting assembly which employs a minimum number of components and which may be used by inexperienced personnel to produce a reliable, inexpensive tube connection.

The above principal objects of this invention are achieved in a novel manner through the provision of an improved compression type fitting which employs a conical frustum shaped spring washer which, when axially compressed between threadingly engaged members, is caused to contract radially against the wall surface of tube within the fitting so that fluid-tight engagement is caused therebetween. The fitting is provided with an internal bore having a diameter which exceeds that of the associated tube so that a limited extent of off-axis orientation between the longitudinal axis of the tube and the axis of the fitting bore is permitted. Additionally, the fitting is provided with an axially elongated internal bore which permits the tube length to vary within the fitting, so that the tube length is non-critical.

Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments invention and the appended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a longitudinal cross-sectional view illustrating the spring washer compression fitting assembly according to this invention with the spring washer in an undeformed state and further illustrating in phantom lines the extent of off-axis orientation between the fitting and associated tube which is accommodated by the fitting.

Figure 2 is a longitudinal cross-sectional view illustrating the spring washer compression fitting assembly of Fig. 1 after the fitting is tightened and the spring washer is axially compressed thereby causing sealing engagement between the fitting and associated tube.

Figure 3 is a perspective view of the spring washer according to this invention.

Figure 4 is an alternate embodiment of the spring washer compression fitting assembly according to this invention wherein a pair of spring washers are employed in an opposed relationship.

DETAILED DESCRIPTION OF THE INVEN TION A spring washer compression fitting assembly according to this invention is illustrated in Figs. 1 and 2, being generally designated by reference character 10. Fitting 10 includes a first fitting element body 12 having a male pipe threaded portion 14 so that the fitting can be employed where conventional fittings are currently used. Body 12 further has a second exteriorally threaded portion 16.

Interposed between threaded portions 14 and 16 is a radially projecting flange 18 preferably having a hexagonally shaped external perimeter, thereby permitting body 12 to be installed using conventional tools. Body 12 has an internal bore 20 comprising a first internal diameter portion 22, a second internal diameter portion 24, and a radially extending shoulder 26 therebetween.

One of the significant features of the invention is that the diameter of bore portion 24 is chosen such that it exceeds the external diameter of the tube 28 being connected, indicated by reference character 28, thereby permitting off-axis orientation between the longitudinal axis of the tube and the central longitudinal axis 30 of bore 20. The diameter of bore portion 24 is preferably sufficiently greater than the diameter of tube 28 to permit approximately a 5 off-axis orientation to occur therebetween. Angle A shown in Fig. 1 illustrates such off-axis orientation.

Another significant aspect of the invention resides in the axial length of bore portion 24 which is formed with a sufficient axial extent to accommodate a significant range of insertion distances of tube 28 within body 12. For example, for a one-half inch diameter tube 28, it is desirable to accommodate a range of insertion distances of at least one-eighth of an inch and preferably approximately one-half inch (i.e. plus or minus one-quarter inch).

Body 12 also has a planar end surface 32 adjacent threaded portion 16, and disposed perpendicular to axis 30 of internal bore 20.

Other configurations for body 12 can be employed and are within the scope of this invention. For example, threaded portion 14 can be eliminated where the fitting is formed integrally with another component. Further, a fitting could be constructed in accordance with the teachings of this invention which would be useful for connecting two tube ends together.

Tube 28 is preferably a conventional thinwalled tube which is formed from one of the conventionally used ductile metals. Other materials for tube 28, such as a polymeric plastic substance can also be used. It is necessary only that the material used to form tube 28 be capable of undergoing radially inward circumferential deformation, as will be detailed below.

Fitting assembly 10 also includes a second fitting element nut 34 having an internally threaded portion 36 adapted to threadingly engage threaded portion 16 of body 12. Nut 34 preferably has a hexagonally shaped external perimeter 38 permitting tightening by conventional tools, and a radially inwardly extending flange 40 having an internal planar shoulder surface 42 which, like end surface 32, is disposed in a planar perpendicular to axis 30. Flange 40 has a bore 44 therethrough which is larger than the external diameter of tube 28. In order to accommodate off-axis orientation between tube 28 and bore portion 24, bore 44 may be tapered as shown in the Figures.

Fitting assembly 10 further comprises a spring washer 46 disposed between nut 34 and body 12. Spring washer 46 is best illustrated in its normal undeformed state in Fig.

3. As can be seen, it has a conical frustum configuration having an external peripheral edge 48 and an internal peripheral edge 50.

The cross-sectional configuration of edge 48 is not critical; however, edge 50 is preferably machined so that it is cyclindrical with respect to the axis of the washer. Angle B is the conical included angle of washer 46 measured between lines 56 and 58, which are drawn along the surface of the washer and lie in a plane passing through the central axis 60 of the washer. The diameter of edge 48 is such that washer 46 may be inserted within nut 34 without interference with threaded portion 36 thereof in any condition of the fitting assembly. Internal edge 50 of washer 46 is dimensioned such that it may receive tube 28 without interference, but preferably such that the clearance between tube 28 and edge 50 is very small; for example, in the range of three one-thousandths of an inch to five one-thousandths of an inch.Large clearances limit the extent of compression of tube 28 by spring washer 46, thereby reducing the effectiveness of the seal therebetween, particularly in off-axis alignment situations. Spring washer 46 is preferably formed from a spring type steel or stainless steel (if corrosion problems are anticipated) having a high yield limit.

Nut 34 is formed so that it can threadingly engage body 12 to the extent that surfaces 42 and 32 may contact one another, or at most be separated by a dimension less than the thickness of washer 46.

Fitting assembly 10 is shown assembled in Fig. 1 wherein washer 46 is interposed between end surfaces 32 and 42. Fig. 1 illustrates fitting 10 in a condition in which spring washer 46 is in an undeformed state. In this condition, tube 28 may be introduced into bore 20 of body 12. The extent of insertion of tube 28 into bore 20 is noncritical in that end 52 of tube 28 may vary anywhere within the range shown generally at X in Figs. 1 and 2.

Because a range of insertion depth is permitted, the length of tube 28 is noncritical. Also, because of the clearance between the tube and fitting body, off-axis orientation of the tube and the axis of the fitting is accommodated, so that alignment and spacing of the components being connecting is similarly noncritical. The position of tube 28 shown in phantom lines in Fig. 1 illustrates off-axis orientation between the tube and fitting axis.

With specific reference to Fig. 2, a fitting connection is shown wherein fitting assembly 10 is in a fully tightened condition. By tighthening nut 34 onto fitting body 12, spring washer 46 is caused to be axially compressed between end surface 32 and internal shoulder surface 42. Such axial compression causes inner edge 50 to contract in a radial direction, which in turn causes local circumferential compression of tube 28. Deformation of tube 28 caused by spring washer 46 results in a fluid tight connection being formed therebetween. Angle B of spring washer 46 is chosen such that the desired degree of radial contraction of inner edge 50 results.During the course of development of this invention, it was discovered that excellent results were achieved when angle B is approximately 110 . Nut 34 is tightened onto fitting body 12 until washer 46 assumes a flat or nearly flat configuration (i.e., angle B approaches 1 80'), whereby the washer is sealingly compressed between surfaces 32 and 42. Since an annular clearance is provided around spring washer 46, the washer may be compressed when it is located off axis with respect to body 12. When tightening nut 34 onto body 12, the torque applied to nut 34 necessary to cause rotation increases dramatically once the position shown in Fig. 2 is achieved, therefore giving the operator a positive ''feel'' for the proper extent of tightening of nut 34.

Although Fig. 1 illustrates washer 46 being installed within fitting 10 so that external edge 48 contacts end surface 32 prior to deformation, the washer could also be installed in a reverse orientation in which external edge 48 initially contacts shoulder surface 42 of nut 34. Accommodation for both orientations results since both fitting body end surface 32 and nut internal shoulder surface are flat. In order to accommodate such reversed orientation, the bore diameters of the fitting elements are chosen so that, in any orientation of spring washer 46, axial compression of the washer results as the fitting is tightened.In those applications wherein it is desired to minimize the tortional stresses exerted on tube 28 imposed during rotation of nut 34, the orientation of washer 46 as shown in Figs. 1 and 2 is believed preferable because of the greater radius of contact between washer 46 and a non-rotating part (fitting body 20), as compared to the radius of contact between the washer and a rotating part (nut 34).

A second embodiment of this invention is illustrated in Fig. 4 and is generally designated by reference character 1 0'. This embodiment varies from that illustrated in Figs. 1 and 2 only in that a pair of spring washers 46 are employed, rather than a single washer. As is shown in Fig. 4, spring washers 46 are installed within fitting 10' such that they are in an opposed relationship, i.e. with their internal edges 50 contacting one another.

When tightened, the fitting illustrated in Fig.

4 provides a greater extent of sealing engagement on the periphery of the tube. This embodiment might be preferable in instances where greater sealing is necessary or where a greater radial compression force is necessary to cause compression of tube 28. The invention of the second embodiment could also be practiced by installing a pair of spring washers 46 with external edges 48 contacting one another. In construction of the second embodiment, it may be necessary to increase the axial length of internal threaded portion 36 of nut 34 so that the nut can accommodate the additional part.

While the preferred embodiments of the present invention are described above, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.

Claims

1. A compression fitting adapted to be sealingly connected to a tube, comprising: (a) a first fitting element having a first substantially planar end face and an internal first bore terminating at said first end face, said first bore being of a diameter sufficient to receive said tube; (b) a second fitting element having a second substantially planar end face and an internal second bore terminating at said second end face, said second bore being of a diameter sufficient to receive said tube; (c) a conical washer disposed between said first and second end faces, said washer having an outer peripheral edge and an inner peripheral edge defining a central opening having a diameter slightly greater than the outside diameter of said tube; and (d) means operative between said first and second fitting elements to tightly and sealingly compress said washer between said first and second end faces when actuated whereby said outer peripheral edge will be expanded and said inner peripheral edge will contact into sealing engagement with said tube.

2. A compression fitting according to Claim 1 wherein said means operative between said first and second fitting elements comprises a threaded connection.

3. A compression fitting according to Claim 1 wherein said washer has a conical included angle of approximately 11 0,.

4. A compression fitting according to Claim 1 wherein said washer is made from spring steel.

5. A compression fitting according to Claim 1 wherein said washer is made from stainless steel.

6. A compression fitting adapted to be sealingly connected to a tube of a given outside diameter, comprising: (a) a first fitting element having a first end face and an internal first bore terminating at said first end face, said first bore being of a diameter sufficiently greater than the outside diameter of said tube to permit substantial relative angular misalignment therebetween; (b) a second fitting element having a second end face and an internal second bore terminating at said second end face, said second bore being of a diameter sufficiently greater than the outside diameter of said tube to permit substantial relative angular misalignment therebetween; (c) a conical washer disposed between said first and second end faces, said washer an inner peripheral edge defining a central opening therethrough having a diameter slightly greater than the outside diameter of said tube; and (d) means operative between said first and second fitting elements to tightly and sealingly compress said washer between first and second end faces when actuated whereby said inner peripheral edge will contract into sealing engagement with a tube of said given diameter disposed therein even though said tube is angularly misaligned with said first bore.

7. A compression fitting according to Claim 6 wherein said first and second bores have diameters sufficiently greater than the diameter of said tube to permit 5 angular misalignment between said bores and said tube.

8. A compression fitting according to Claim 6 wherein said means operative between said first and second fitting elements comprises a threaded connection.

9. A compression fitting according to Claim 6 wherein said washer has a conical included angle of approximately 110 .

10. A compression fitting according to Claim 6 wherein said washer is made from spring steel.

11. A compression fitting according to Claim 6 wherein said washer is made from stainless steel.

12. A compression fitting adapted to be sealingly connected to a tube, comprising: (a) a first fitting element having a first end face and an internal first bore terminating at said first end face, said first bore being of a diameter sufficient to receive said tube; said first bore being of a length from said end face sufficient to accommodate a range of insertion distances of said tube within said first bore, (b) a second fitting element having a second end face and an internal second bore terminating at said second end face, said second bore being of a diameter sufficient to receive said tube; (c) a conical washer disposed between said first and second end faces, said washer having an inner peripheral edge defining a central opening therethrough having a diameter slightly greater than the outside diameter of said tube; and (d) means operative between said first and second fitting elements to tightly and sealingly compress said washer between first and second end faces when actuated whereby said inner peripheral edge will contract into sealing engagement with a tube of said given diameter disposed therein at all distances of insertion of said tube within said first bore within said range of insertion.

13. A compression fitting according to Claim 12 wherein said means operative between said first and second fitting elements comprises a threaded connection.

14. A compression fitting according to Claim 12 wherein said washer has a conical included angle of approximately 1105.

15. A compression fitting according to Claim 12 wherein said washer is made from spring steel.

16. A compression fitting according to Claim 12 wherein said washer is made from stainless steel.

17. A compression fitting according to Claim 12 wherein the length of said first bore from said first end face is at least one-eighth of one inch.

18. A compression fitting according to Claim 12 wherein said range of insertion distance is at least one-eighth of one inch.

19. A compression fitting according to Claim 12 wherein the opposite end of said first bore terminates at a shoulder, said shoulder being spaced from said first end face a distance of at least one eighth of one inch.

20. A compression fitting adapted to be sealingly connected to a tube, comprising: (a) a first fitting element having a first end face and an internal first bore terminating at said first end face, said first bore being of a diameter sufficient to receive said tube; (b) a second fitting element having a second end face and an internal second bore terminating at said second end face, said second bore being of a diameter suffici ent to receive said tube; (c) a pair of conical washers disposed be tween said first and second end faces, each of said washers having an inner peripheral edge defining a central opening therethrough hav ing a diameter slightly greater than the out side diameter of said tube, said washers en gaging one another adjacent said inner per ipheral edges thereof; and (d) means operative between said first and second fitting elements to tightly and sealin gly compress said washers between first and second end faces when actuated whereby said inner peripheral edges will contract into sealing engagement with said tube.

21. A compression fitting according to Claim 20 wherein said means operative between said first and second fitting elements comprises a threaded connection.

22. A compression fitting according to Claim 20 wherein said washers each have a conical included angle of approximately 110 .

23. A tubing connection, comprising in combination: (a) a tube, (b) a first fitting element having a first end face and an internal first bore terminating at said first end face, the opposite end of said first bore terminating at a shoulder, said tube disposed within said first bore, the end of said tube being spaced from said shoulder; (c) a second fitting element having a second end face and an internal second bore terminating at said second end face, said second bore being of a diameter sufficient to receive said tube; (d) a conical washer disposed between said first and second end faces, said washer having an inner peripheral edge in sealing engagement with said tube.

24. A compression fitting adapted to be sealingly connected to a tube, such fitting being constructed and arraged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.