King Industrial Limited.

7/F., Allied Kajima Building,

138 Gloucester Road,

Wanchai,

Hong Kong

Press fitting and joint assembly with such a press fitting

Description

The present invention refers to a press fitting comprising a socket defining at one end an opening for the insertion of an end of a tube, a sealing ring within the socket and a gripping ring within the socket, arranged in front of the sealing ring in the direction of insertion of the tube; and a joint assembly with such a press fitting having a tube inserted therein.

EP 1 756 462 Bl discloses a pipe fitting for use in coupling metallic pipes and comprising a housing having therein a grip-ring, pipe support means downstream of the grip-ring in the direction of pipe insertion, sealing means downstream of the pipe support means and means limiting movement of the sealing means in said pipe insertion direction, with the pipe support means as well as the limiting means being formed integral with the housing.

A press fitting is known from EP 1 593 899 Bl with a socket housing in addition to a gripping ring and a sealing ring a spacer or separating ring.

The drawback of the known press fitting is the necessity of a spacer.

It is an object of the present invention to further develop the known press fitting to save costs by omitting a spacer.

This object is achieved in that the gripping ring is provided with at least two weakening features, in particular in form of notches, being reducible in size by deforming the gripping ring when applying a pressing action on the socket such that the inner diameter of the gripping ring is reduced. 2 Jones Day

According to the invention it is preferred that the weakening features extend, preferably equally spaced, around the inner diameter and/or the outer diameter of the gripping ring, in particular in pairs of two opposing weakening features.

In addition, the weakening features extend substantially, axially and the invention proposes that the inner diameter of the gripping ring is chosen to be larger than the outer diameter of the tube prior to reducing the size of the weakening features when applying a pressing action.

With the invention it is proposed that the weakening features comprise notches which are at least partially closed when applying a pressing reaction.

It is also beneficial that the weakening features of the gripping ring around the inner diameter are provided with chamfer angles at their tube facing side, with the chamfer angle Al preferably being at most 45°.

With the invention it is also proposed that gripping edges of the gripping ring are provided by teeth of the gripping ring around the inner diameter D2 of the gripping ring and each tooth being defined between two neighbouring weakening features provided around the inner diameter D2 of the gripping ring, with a gripping angle of each gripping edge preferably being greater than 45°.

It is proposed by the invention that the gripping ring is arranged within a recess of the socket together with the sealing ring or within a recess of the socket separate from the recess of the socket for the sealing ring or within a broadened mouth of the socket separate from the recess of the sealing ring.

According to the invention it is preferred that the gripping ring and the sealing ring are arranged next to each other within the same recess with the face of the gripping ring facing towards the sealing ring forming a sealing ring abutment with an abutment angle A3 relative to the inner surface of the socket within the recess of 90° ± 10°, preferably substantially 90°.

It is also proposed that the sealing ring is arranged within a cavity defined by the recess and the gripping ring. 3 Jones Day

Embodiments of the invention can be characterized in that the gripping ring is provided with at least one projection for engaging a groove within the socket, and/or the gripping ring is provided with a split.

It is preferred that the sealing ring of the invention has an outside diameter which is chosen to be larger than the inside diameter of the recess and/or an inside diameter which is chosen to be smaller than the tube outer diameter.

Further embodiments of the invention are characterized in that the sealing ring has a first face facing towards the recess which is defined by a substantially rectangular cross section, preferably with smoothened edges, and/or the sealing ring has a second face facing towards the tube which is defined by a substantially triangular cross section with smoothened edges and/or forming a projection, and/or the cross section of the sealing ring is symmetrical to a plane perpendicular to its axis.

With the invention also a joint assembly with a press fitting according to the invention and a tube inserted into the press fitting is provided.

The invention will now be described by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a longitudinal cross-sectional view of a press fitting of the invention;

Figure 2 is a perspective view of the gripping ring shown in fig. 1;

Figures 3 a, 4a and 5 a show front elevation views of different weakening features of a gripping ring to be used in a press fitting of the invention;

Figures 3b, 4b and 5b show isometric details of the weakening features of figs. 3a, 4a and 5a respectively;

Figure 6a is a front elevation view of the gripping ring of fig. 2; Figure 6b shows a projected section through A-A of fig. 6a; Figure 7 is an enlarged view of fig. 6b in the region of circle C; 4 Jones Day

Figure 8 a is showing two opposing notches of the gripping ring of fig. 2 prior to the application of pressure;

Figure 8b is showing the two notches of fig. 8a after the application of pressure when forming a tight joint assembly of the invention;

Figure 9 is a part view of fig. 1 ;

Figure 10a is a front elevation view of the sealing ring shown in fig. 1;

Figure 10b shows a projected section through A-A of fig. 10a;

Figure 11 is a cross-sectional view of the sealing ring of figs. 10a and 10b; and

Figures 12 to 15 are part cross sections of different joint arrangements of the invention.

Fig. 1 illustrates a cross section through a press fitting 1 of the invention prior to the application of a pressing action. The press fitting 1 comprises a socket 10 designed to accept a tube (not shown) and latterly by means of diametric reduction by a pressing tool (not shown) provide a gas/water tight joint with said tube having a sealing ring 20 as well as a gripping ring 30 arranged between the socket 10 and the tube.

The socket 10, preferably being a metal socket 10 of known structure, may be incorporated into fittings as to provide directional variation, diameter reduction of tube or jointing to threaded connections. It is provided with a step 11 for stopping the introduction of the tube, a taper 12 to facilitate the introduction of the tube, which will be at least partly diminished when applying a pressing action for closing the joint assembly, and a recess 13 for housing, in the direction of the tube insertion, at first the gripping ring 30 and behind the gripping ring 30 the sealing ring 20, with a flange 14 of the socket 10 at the open mouth thereof securing the gripping ring 30 as well as the sealing ring 20 within the recess 13.

No spacer as is utilised in known technology is required. An explanation of the technical reasoning behind the omission of a spacer is described later. The use of two parts only between the socket 10 and the tube of a fitting of this type is novel. 5 Jones Day

The gripping ring 30 is more clearly illustrated in fig. 2. A plurality of deliberately weakened sections, provided in form of notches 31, 32, preferentially equally spaced, extend around the diameter of the gripping ring 30 and are provided to reduce the force needed during the pressing action to reduce the diameter of the joint assembly. During pressing the gripping ring 30 the notches 31, 32 are deformed allowing diameter reduction. This diameter reduction induces engagement of the inner edge of the gripping ring 30 and the inserted tube. The design maintains even distribution of the engagement between tube and the gripping edge around its diameter.

The illustrated version of fig. 2 shows a specific form of weakening sections. There could be other variations that are effective to varying degrees. The use of such forms to provide an effective diameter reduction without the use of forces beyond the capabilities of a readily available pressing tool is principle to the invention.

Variations of the notches 31 to 3 Γ are illustrated in figs. 3a, 4a, 5a and their related isometric details in figs. 3b, 4b, and 5b. In these instances the notches of no particularly specified shape are used to create weak points in the gripping ring 30. In instances of figs. 3a, 4a and 5a the notches 3 Γ, 31 ^" and 3 Γ ^" are shown on one edge of the gripping ring 30. It is also possible that notches are provided by opposed pairs or arranged as shown in fig. 2.

The material of the gripping ring 30 chosen for its hardness qualities and corrosion resistance is stainless steel although other materials with suitable hardness and corrosion resistance either inherent or added via coatings may be usable. The hardness of the material is critical to provide sufficient penetration of the gripping edge into the inserted tube and also provide resistance to deformation of the edge when tensile forces are applied due to pressurization of the completed joint.

It is also conceivable that such a configuration could be split at a chosen point around the diameter of the gripping ring 30 and still function effectively.

The gripping mechanism is now explained in further detail with reference to fig. 6a to 8b:

Fig. 6a is a front elevation view of the gripping ring 30 of fig. 2, and fig. 6b illustrates a projected section through A-A of fig. 6a. The gripping ring 30 is designed as follows: Jones Day

Dl and D2 are the outer and inner diameters of the gripping ring 30, respectively. Dl is chosen to fit within the socket recess 13, whereas D2 is chosen to be smaller than the outer diameter of an incoming tube to ensure a tight joint as explained later.

LI is the length of the gripping ring 30 in the tube insertion direction and is chosen to be of sufficient length to prevent section rotation when tensile forces are applied to the joint assembly.

Al are chamfer angles provided to reduce circumferential engagement with the tube during pressing and thus reduce forces required. The chamfer angle can be around 20° and should not exceed 45°.

Rectangle B in fig. 6b highlights a section through the main part of the gripping ring 30 and shows a gripping edge or rather tooth 33 facing the tube in a joint assembly. The tooth 33 is shown enlarged in fig. 7 with its gripping angle A2. The gripping angle A2 has proven to be advantageous to be greater than 45°. At 45° or less the interior gripping edge can be distorted to cause joint failure when tensile forces induced by pre-determined test pressures are applied. It is of course possible to use smaller angles A2 if harder materials were used but would imply greater costs. Also where lesser tensile forces are encountered the necessity for a greater degree of inclusive angle A2 is reduced.

The gripping ring is provided with a face 35 best shown in figure 5 next to the sealing ring 20. This face 35 together with the recess 13 defines a cavity for holding the sealing ring 20 in position. In order to avoid a migration of sealing ring material outside that cavity, in particular within the region of the gripping ring 30, the face 35 extends substantially radially, being in the vertical direction in the figs. Thus, the face 35 forms an abutment face with an angle A3 to the recess 13 of around 90°.

Circle C in fig. 6b highlights a weakening section in form of the notches 31 and 32.

L is the gap between neighbouring teeth 33 on the gripping or seal side of the gripping ring 30. 7 Jones Day

The lengths L5 to L9 defining the opposing notches 31 and 32 of the gripping ring 30 and shown in fig. 8a encourages collapse of the gripping ring diameter. The one notch 31 has a radial length L7 and an axial length L8 and the other notch 31 has a radial length L5 and an axial length L6, with the two notches being separated by a length L9 in axial direction. During a pressing operation the forces implied on the joint assembly cause the notches 31 and 32 to collapse to adopt a form as shown in fig. 8b with axial length L10 and Ll l being smaller than L8 and L6, respectively. The reduction of the length L6 (L8) to a lesser value Ll l (L10) is also beneficial for preventing any possible high pressure extrusion of the sealing means through any of the gaps L.

The radial alignment of the inner gripping edges of the teeth 33 and the outer edges of the gripping ring 30 facing the socket 10 is maintained during the distortion. This is beneficial to both the seal and the engagement of the tube. The space in which the seal needs to operate is not violated and the maintenance of the radial alignment of the teeth 33 provides a consistent force to retain the tube under pressure induced tension.

Next, the special design of the sealing ring 20 of the invention is described with reference to figs. 9 to 11.

The use of an O ring is known in press fittings. But the socket shape with a substantially rectangular recess 13 is not ideally suited to such an O ring. Although the radial inner length L12 of the recess 13 shown in fig. 9 is chosen to provide desired compression of the sealing ring, it is not sufficient to prevent potential for an O ring displacement during tube insertion if an O ring of a diameter equivalent to (or greater than) LI 4 is used, with L14 > LI 2. This has led in the past to development and inclusion of particular spacer parts to prevent O ring displacement.

For seals to function correctly the cross sectional area of the recess 13 must provide at least an equivalent area of the sealing ring 20, and it has to be taken into consideration that the gripping ring 30 has some limited linear movement in the un-pressed joint condition and therefore could move to a position where, if an O ring was utilised, the necessary cross sectional area is encroached upon. Previous designs have answered this problem with special spacers.

The arrangement of fig. 9 dispenses with the need for such spacers. 8 Jones Day

Localised distortion in the form of tube diameter reduction may occur in the immediate vicinity of the gripping edges. In the instance of an O ring being used the O ring could migrate either before pressing or via pressure induced movement after pressing migrate to the reduced tube area adjacent to the gripping edges. This could result in joint failure via leakage of the interior medium. With the seal shape of the invention this is avoided.

The shape of the sealing ring 20 utilised according to the invention and shown best in figs. 10a to 11 is self regulating to provide sufficient area for seal function after pressing and is designed as follows:

The sealing ring 20 has an outside diameter D3 which is chosen to be in all instances of tolerance larger than the inside diameter of the recess 13. This ensures the provision of an outwardly radial force that encourages the sealing ring 20 to remain in its location. The inside diameter D4 of the sealing ring 20 depends on D3 and L14 but in all instances is smaller than the tube outer diameter.

The sealing ring 20 has two different faces, a first face 21 facing towards the recess 13 and a second face 22 facing towards the tube. The face 21 is defined by a substantially rectangular cross section with smoothened edges, see lengths L15 and LI 6 as well as radii Rl and R2 in fig. 11, to fit within the recess 13. The face 22 is chosen to assist in the prevention of seal displacement and has a substantially triangular cross section with smoothened edges, see radii R2 and R3 in fig. 1 1, forming a projection with a length L14- L 15. If a tube upon insertion is inserted at angle to the main axis of the socket 10 the effect of tube edge contact with face 22 is to urge the sealing ring 20 radially outwards thus preventing seal displacement. In this instance the sealing ring 20 is symmetrical to prevent accidental incorrect assembly losing this facility.

Length LI 3 in fig. 9 or L16 in fig. 11 defines the width of the sealing ring 20 or rather of its first face 21 and is chosen to provide sufficient distance between the teeth 33 or rather its gripping edges of the gripping ring 30 and the sealing ring 20 or rather its central radius R3 within the recess 13. 9 Jones Day

Furthermore the shape of the seal described above provides greater seal to tube and seal to socket contact areas than would be the case in the instance of an O ring being used. This provides a more secure sealing means. In parallel operating conditions the seal would provide greater longevity due to the greater sealing area employed. Particularly in larger size fittings where the cost of replacement is considerably higher than that of smaller diameter fittings this is a considerable advantage.

Figs. 12 to 15 illustrate joint assembling of the invention with a tube 5 inserted. Fig. 12 shows the usage of press fitting of fig. 1. Within a joint assembly fig. 13 illustrates the usage of the gripping ring 30 of a form shown in fig. 2 in a differing socket configuration having two recesses 13a and 13b and making usage of a common O ring 20\ Fig. 14 illustrates the usage of a gripping ring 30" differing from the one of fig. 2 by the addition of an outwardly raised portion or projection 34" to engage in an internal circumferential groove 15" of the socket 10" to provide engagement and location. It is possible that the inherent spring of the gripping ring due to the weakening features may be urged into this location during assembly. The socket 10 ^" does not need a flange. Fig. 15 illustrates the use of a similar gripping ring 30 ^' as fig. 14 within a differing press socket profile having a recess 13 ^{" "} for an O ring 20 ^" and opened mouth 16 ^{" "} without a flange.

The features disclosed in the claims, the specification and the figures may be important for the claimed invention, taken separately or in any combination, for the invention in the respective different embodiments.

10 Jones Day

Reference sign list

I press fitting

5 tube

10, 10', 10", 10"' socket

I I step

12 taper

13, 13a, 13b, 13", 13" ' recess

14 flange

15", 15" ' groove

16"' mouth

20, 20' sealing ring

21 first face

22 second face

30, 30' gripping ring

31, 31 ', 31 ", 31 "' notch

32 notch

33 tooth

34' projection

35 face

Al, A2, A3 angle

D1-D4 diameter

L1-L16 length

L gap

R1-R3 radius