GB2156466A - Pipe coupling - Google Patents

Abstract

In a pipe coupling for smooth- end pipe, a middle ring 13 of spin- formed steel has a frustoconical outwardly spun portion (22, 23 Fig. 3) at each end. A pair of end rings 14, 15 of spin-forming steel each have a generally cylindrical portion with a circumferential series of slots therethrough, and a spin-formed radial flange at its outwardly facing end. An elastomeric O-ring 17 is compressed between each frustoconical seat and a radial flange. A J-bolt 19 for each slot has a hook-like end extending radially through the slot and a shank extending toward the opposite end ring and having a threaded end 43. A turnbuckle 20 is threaded to each of an axially aligned pair of J-bolts to tighten the coupling. <IMAGE>

Description

SPECIFICATION Improvements in or relating to a pipe coupling This invention relates to pipe coupling and more particularly to a pipe coupling for use in coupling together smooth-end pipe.

For over seventy-five years many pipe couplings have used the combination of a cylindrical steel middle ring with two steel follower rings, two resilient gaskets that fit between the middle ring and the follower rings, and a set of steel bolts or nuts. The middle ring has frustoconical ends, and usually the gasket has been shaped, although sometimes it has been a round O-ring.

These couplers have been somewhat expensive because they have generally been machined from steel, which also means that have been relatively heavy.

Furthermore, these couplers have necessarily had to be made in a large number of different sizes, and to make a coupler for each actual pipe size has required a separate set of deep draw punches and dies or some equivalent. These have been very expensive because the tolerance had to be kept close. The significance of this fact becomes more apparent when it is realized that one nominal pipe size may actually mean at least five different outside diameters, according to the type of pipe.Thus, for a pipe which is nominally known as six inch (15.24 cms) diameter pipe, steel tubing will actually be six inches (1 5.24 cms) in outer diameter, but the outer diameter of cruder steel pipe will be 6.625" (16.83 cms), polyvinylchoride pipe will be 6.3" (16.00 cms) in outside diameter, cast iron pipe will be 6.9" (17.52 cms) and asbestos cement 7.1" (18.03 cms) in outside diameter. Each one of these requires a different sized set of coupling elements;-a different size of middle ring, a different size of follower ring, and a different size gasket.

According to one aspect of this invention there is provided a pipe coupling for joining together two sections of smooth-end pipe in a substantially leak-tight manner, including in combination: a middle ring of thin steel having a middle portion, larger in diameter than the pipe sections being coupled, and a generally frustoconical end portion at each end having an outer end and providng a general frustoconical seat on its radially inner face, a pair of end rings of thin steel, each having a generally cylindrical portion larger in diameter than said outer end and having a circumferential series of slots-therethrough, and a radial flange at its outwardly facing end extending in to a diameter smaller than that of said middle portion though still larger than the diameter of said pipe sections, an elastomeric O-ring at each end between a said frustoconical seat and a said radial flange, a J-bolt for each slot, each having a hook-like end extending radially inwardly through its slot and a shank extending toward the opposite end ring and having a threaded end short of the axial midpoint of said middle ring, said end rings being aligned relatively to each other so that the J-bolt shanks from one end ring are axially aligned with those from the other end, resulting in axially aligned pairs of J-bolts, and a turnbuckle for each axially aligned pair of J-bolts threaded to their shanks, for tightening said coupling, bringing the end rings toward each other so as to compress the elastomeric O-rings between a radial flange and a frustoconical seat.

According to another aspect of this invention there is provided a method of making a middle ring for a pipe coupling, said ring having a middle portion between a pair of outwardly inclined generally frustoconical end portions, comprising rolling a mild steel flat band to a specific diameter cylindrical shape, welding the adjacent edges of the band together to produce a continuous ring having said specific diameter, and spinning first one end portion and then the other on a spinning mandrel with a cylindrical portion about half as long as said ring and an outwardly inclined generally frustoconical portion joined to said cylindrical portion.

According to a further aspect of this invention there is provided a method of making an end ring for a pipe coupling, said ring having an inwardly extending flange at one end of a generally cylindrical portion, comprising rolling a mild steel flat band to a specific diameter cylindrical shape, welding the adjacent edges of the band together to produce a continuous ring having said specific diameter, and spin-forming said ring on a spinning mandrel with a cylindrical portion about half as long as said ring and a radial end wall, forming an end portion of said ring inwardly against said radial end wall by a tool pressed against said ring's end portion.

A preferred pipe coupling of the present invention includes a middle ring of spin-formed mild steel having a middle portion which is larger in diameter than the pipe sections that are to be coupled, and generally frustoconical outwardly spun end portions. Each end portion has a generally frustoconical seat on its radially inner face.

There is a pair of followers or end rings, also spin-formed from mild steel. Each of these has a cylindrical portion that is larger in diameter than the outer ends of the middle ring, and has a circumferential series of slots extending through its wall. It also has a spin-formed radial flange with its outwardly facing end extending in to a diameter smaller that that of the middle portion, though still larger than the diameter of the pipe sections.

An elastomeric O-ring is compressed at each end between a frustoconical seat and a radial flange of an end ring.

Each slot through the end rings is equipped with a J-bolt, which is anchored in the slot at a hook-like end that extends radially inwardly through the slot. Each J-bolt has a shank that extends toward the opposite end ring, and the shank has a threaded end. The shanks are short enough so that they go less than half the distance to the opposite end ring. The J-bolts at one end are aligned with the J-bolts at the other end, so that there are axially aligned pairs of Jbolts.

Finally, there is a series of turnbuckles, one for each axially aligned pair of J-bolts. The turnbuckles are threaded to the shanks of the J-bolts and are used for tightening the coupling, bringing the end rings toward each other so as to compresss the elastomeric O-rings between the radial flange of the end ring and the generally frustoconical seat of the middle ring.

An important feature of the method of making the pipe coupling is that the middle ring and both follower rings are spun formed. Thus, the middle ring is made by rolling a flat piece of mild steel band to a cylindrical shape having a desired specific diameter. The adjacent edges of this band are then welded together to produce a continuous ring, having the desired specific diameter. Then, first one end portion and then the other are spin-formed on a spinning mandrel.

The mandrel has a cylindrical portion about half as long as the ring, and an outwardly inclined generally frustoconical portion that is joined to the cylindrical portion.

Similarly, the end ring also is made by rolling the mild steel band to a cylindrical shape and welding its adjacent edges together to produce a continuous ring of a desired specific diameter.

Then this cylindrical member is provided with a spin-formed flange with the aid of a suitable mandrel having a radial portion on which the spin-forming can take place.

The spin-forming enables the use of thin metals, such as ten gauge steel. Spin forming gives high yield strengths, and also minimises production costs because spinning is much less expensive than hot forming or deep drawing, or the manufacture of welded rings.

Since the mandrels are relatively inexpensive, as compared with deep draw punches and dies, it is possible to adapt the various external sizes much more easily, and to do this without having such expensive parts. The only part that needs to be changed for making such adjustment inside is the spinning mandrel itself, and, of course, the cutting to size of the steel strip from which the cylindrical band is formed.

In order that the invention may be more readily understood and so that further features thereof may be appreciated the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a view in side elevation of a coupling embodying the principles of the invention shown installed on two smooth end pipe sections; Figure 2 is an enlarged view in section taken along the line 2-2 in Fig. 1; Figure 3 is a view in section of a portion of a finished centre ring section; Figure 4 is a view partly in side elevation and partly in section showing how a cylindrical steel ring is placed on a mandrel for spinning to shape one of the ends; Figure 5 is a view in elevation and partly in section of a completed follower or end ring;; Figure 6 is a view in side elevation and partly in section of a plain cylindrical ring about to be placed on a spinning mandrel to form the radially extending flange; Figure 7 is a view like Fig. 6 showing the installation of the plain ring on the opening mandrel and the use of a forming tool; Figure 8 is a similar view showing the forming of the radial end flange; and Figure 9 is an enlarged view in side elevation of two retaining J-bolts and a turnbuckle joining them.

The drawings show an assembled pipe coupling 10 and also the elements from which it is assembled. Thus, Fig. 1 shows a complete coupling 10 for joining together two smooth-end pipe sections 11 and 12. The coupling 10 includes a middle ring 13 (shown by itself in Fig. 3), a pair of identical end rings 14 and 15 (one of which one is shown in Fig. 5), a pair of identical O-ring gaskets 16 and 17 (see also Fig. 2), and an assebly of J-bolts 18 and 19 and turnbuckles 20 (see also Fig. 9).

As can be seen in Fig. 3, the middle ring 13 comprises a long middle portion 21, and two generally frustoconical end portions 22 and 23. Instead of being truly frustoconical, these portions 22 and 23 may have a slight concavity, if desired.

As Fig. 4 shows, the middle ring 13 is made from a strip of thin, mild steel, e.g., 1 0-gauge steel, which is rolled into a cylindrical shape, with a specific diameter, and its adjacent edges are then welded together to make a precisely dimensioned cylindrical ring 25. A spinning mandrel 26 has a cylindrical portion 27 having approximately the same outer diameter as the inner diameter of the steel ring 25, and is about half as long as the ring 25. At its inner end, the mandrel 26 has a shaped substantially frustoconical portion 28, and an end flange 29. The ring is spun on the mandrel first at one end, and then at the other end. When the usual spinning technique is employed, it results in a very strong, though light, middle ring 13.

Similarly, Figs. 6-8 a show that each of the follower rings 14 and 15 is made in the same basic manner, by first forming a flat strip of thin mild steel into a cylindrical portion by rolling, then welding the adjacent edges together to form a cylindrical ring 30 and then spinning upon a spinning mandrel 31. The mandrel 31 has a cylindrical portion 32 between a radial end wall 33 and an outwardly flared portion 34. The ring 30 is installed on the mandrel 31 with the aid of a back-up plate 35 and a tool 36 is held againt the cylinder 30 to held in making an outward flare 37 and then to turn a flange 38 in inwardly at the end of a cylindrical portion 39.

Then a circumferential series of slots 40 is punched through the end ring 14 or 15. Typically the slots 37 are < " (1.27 cms) in diameter and may be as long as an inch in the axial direction.

Although shaped sealing gaskets 16 and 17 may be employed, round rubber rings are relatively inexpensive and are easy to obtain in the sizes needed. Any suitable elastomer can be used.

Each J-bolt 18, 19, (Figs. 2 and 7) includes a hook or J-section 41 used to extend in radially through one of the slots 40. The bolts 18 and 19 also each have a straight shank 42 at the outer end of which is a suitable threaded portion 43. The turnbuckle 20 is used to tighten each pair of J-bolts 18 and 19 together and thereby to pull the followers or end rings 14 and 15 in toward each other, thereby compressing the O-ring gaskets 16 and 17. The bolts 18 and 19 are made short enough so that a steel rod or screw driver can be inserted into the turnbuckle 20 and used to turn it for tightening or loosening the assembly.

The couplers 10 of this invention use fewer pairs of J-bolts 18 and 19 than the prior art used as long bolts: Coupler Present Invention Prior Art 4 inch (10.16 cms) 3 4 6 inch (15.24 cms) 3 6 8 inch (20.32 cms) 4 6 10 inch (25.40 cms) 5 8 16 inch (40.64 cms) 7 10 18 inch (45.70 cms) 8 12 20 inch (50.80 cms) 9 14 24 inch (60.96 cms) 10 14 From the foregoing it will be appreciated that the present invention provides an improved coupling which is able to use thinner steel than the prior art, is more easily kept within the desired tolerances, is less expensive to make, is more versatile, and hold water pressures up to 300 p.s.i. (2068KN/m2). Also, changes in actual pipe sizes are easier and less expensive to adapt to, for no expensive set of dies is required.

Also, this invention provides an improved method for manufacture of such couplers from flat steel stock by rolling the stock and welding it into a tube, and then spin forming the tube to desired shapes. This applies both to the middle ring with its frustoconical ends, and to the follower members which are cylindrical with a radial flange.

Claims (10)

1. A pipe coupling for joining together two sections of smooth-end pipe in substantially leaktight manner, including in combination: a middle ring of thin steel having a middle portion, larger in diameter than the pipe sections being coupled, and a generally frustoconical end portion at each end having an outer end and providng a generally frustoconical seat on its radially inner face, a pair of end rings of thin steel, each having a generally cylindrical portion larger in diameter than said outer end and having a circumferential series of slots-therethrough, and a radial flange at its outwardly facing end extending in to a diameter smaller than that of said middle portion though still larger than the diameter of said pipe sections, an elastomeric 0ring at each end between a said frustoconical seat and a said radial flange, a J-bolt for each slot, each having a hook-like end extending radially inwardly through its slot and a shank extending toward the opposite end ring and having a threaded end short of the axial midpoint of said middle ring, said end rings being aligned relatively to each other so that the J-bolt shanks from one end ring are axially aligned with those from the other end, resulting in axially aligned pairs of J-bolts, and a turnbuckle for each axially aligned pair of J-bolts threaded to their shanks, for tightening said coupling, bringing the end rings toward each other so as to compress the elastomeric O-rings between a radial flange and a frustoconical seat.

2. A pipe coupling according to Claim 1, wherein the middle ring is of spin-formed, thin, mild steel and the end rings are of spin-formed, thin mild steel, the inwardly extending radial flange at its outwardly facing end being spin formed.

3. A method of making a middle ring for a pipe coupling, said ring having a middle portion between a pair of outwardly inclined generally frustoconical end portions, comprising rolling a mild steel flat band to a specific diameter cylindrical shape, welding the adjacent edges of the band together to produce a continuous ring having said specific diameter, and spinning first one end portion and then the other on a spinning mandrel with a cylindrical portion about half as long as said ring and an outwardly inclined generally frustoconical portion joined to said cylindrical portion.

4. A method of making an end ring for a pipe coupling, said ring having an inwardly extending flange at one end of a generally cylindrical portion, comprising rolling a mild steel flat band to a specific diameter cylindrical shape, welding the adjacent edges of the band together to produce a continuous ring having said specific diameter, and spin-forming said ring on a spinning mandrel with a cylindrical portion about half as long as said ring and a radial end wall, forming an end portion of said ring inwardly against said radial end wall by a tool pressed against said ring's end portion.

5. A method according to Claim 4, including flaring the cylindrical portion of said end ring outwardly with a shaped mandrel portion at the opposite end from said flange.

6. A method according to Claim 4 or 5, including punching a circumferential series of slots through said cylindrical portion of the end ring.

7. A pipe coupling substantially as herein described with reference to and as shown in the accompanying drawings.

8. A method of making a middle ring for a pipe coupling substantially as herein described with reference to the accompanying drawings.

9. A method of making an end ring for a pipe coupling substantially as herein described with reference to the accompanying drawings.

10. Any novel feature or combination of features disclosed herein.