Plastic pipe branch fitting with reinforcing ribs

Details Plastic pipe branch fitting with reinforcing ribs Plastic pipe branch fitting with reinforcing ribs

1995-01-12

1996-09-03

Arola, Dave W.

Pipe joints or couplings

Connector for conduit housing electromagnetic line:

Having box and connector

285286, 285156, 138172, F16L 4102

Patent

active

055517331

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF INVENTION

The present invention relates to plastics material pipe tees. The invention is particularly suited for application to pipe tees for joining pipes of 80 mm diameter or more, and particularly for use in pressure pipe installations.
Plastics material pipes and fittings have widespread application, but are not widely used for applications in which they are subjected to relatively high pressures. A major reason for this is the short life of plastics pipe tees when subjected to cyclic variations in pressure such as those which occur in a pipeline when a valve is opened or closed or which occur in the region downstream of a pump. In these situations, plastic pipe tees have a tendency to develop cracks at the crutch points which lie at the junction of the branch and the straight body of the tee in the centre plane which contains the axes of both the branch and the body. This problem is peculiar to plastics tees and does not affect cast iron tees, and thus cast iron tees are often preferred for these situations.
Attempts have been made to overcome this defect by stiffening the tee at the crutch points by thickening at those points or by the provision of ramps moulded with the tee to extend between the body and the branch in the region of the crutch. However, these modifications have been found to give no significant increase to the life of the tee. Furthermore, thickening in the region of the crutch promotes unequal heat transfer during the cooling process after moulding, resulting in cooling stresses which weaken the tee.


SUMMARY OF THE INVENTION

The present invention seeks to reduce the tendency of plastics tees and other branched fittings to crack at the crutch.
Surprisingly, the applicant has discovered that this may be achieved by stiffening the tee in the side region of the intersection between the surfaces of the branch and body, rather than at the crutch point as has previously been proposed. As used herein, crutch point and crutch points refer to the region as understood in the art.
The present invention thus provides a branched pipe fitting of plastics material, characterised in the provision of preferential stiffening means for preferentially stiffening the side regions of the fitting.
Preferably, the preferential stiffening means comprises localised thickening in the side region compared to the crutch points. In one preferred embodiment, the thickening comprises ribs each of which extends substantially along a locus defined by the intersection of the outer surface of the fitting and a plane which:
(a) passes through a crutch point,
(b) is perpendicular to the plane containing the axes of both the branch and the body of the fitting and
(c) is convergent with the axis of the branch in the direction away from said branch.
In one particularly preferred form, the thickening comprises one pair of ribs on each side of the tee, essentially following the lines of intersection of the surfaces of the body and the branch, with each pair crossing essentially at the apex point of the respective side.
In a further preferred form of the invention, the side apex points are preferentially stiffened compared to the crutch points. Preferably, there is no thickening of the pipe tee at the crutch points.


BRIEF DESCRIPTION OF THE DRAWINGS

Further preferred embodiments of the present invention shall now be described with reference to the accompanying drawings:
FIG. 1 is a side view of a standard plastics pipe tee;
FIG. 2 is a side view of a first pipe tee according to the present invention;
FIGS. 3 to 5 are inverted plan, perspective and plan views of the pipe tee of FIG. 2;
FIG. 6 is an approximate cross-section along line 6--6 of FIG. 2; and
FIG. 7 and 8 are side views of second and third pipe tees according to the invention.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, a standard pipe tee comprises a straight body 11 with oppositely extending sockets 12, 13 and a branch portion 14 with socket 15. The tee has substantially uniform wall thickness. The intersecti

REFERENCES:
patent: 1755898 (1930-04-01), Root
patent: 3279500 (1966-10-01), Feder
patent: 3497245 (1970-02-01), Metzger
patent: 4971307 (1990-11-01), Killerud et al.

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