Method and apparatus for making a branch collar in a pipe

Abstract

 The invention relates to a method and an apparatus for bending the rims of a hole for a hole-enclosing collar or neck. The collar is produced by means of a forming die (3) adapted for substantially radial movement from inside the pipe outwards. A calibration mandrel (11) is pressed by means of an external drive unit from outside inwards into a collar established by the forming die (3). The calibration mandrel stretches the collar to match its own size and rectifies the undersized transverse dimension and the oversized lengthwise dimension of the forming die. Upon its penetration into the collar, the calibration mandrel (11) pushes the forming die (3) back to its initial position for a new collaring operation.

Description

[0001] The invention relates to a method as defined in the preamble of claim 1 and an apparatus as defined in the preamble of claim 3 for making a branch collar or a neck in a pipe.

[0002] This type of method and device are prior known from the Applicant's earlier patent publication US 5,515,710.

[0003] When a tubular metal casing or mantle is formed with a branching, cylindrical collar or neck by stretching the casing material, its final size is determined by elasticity of the pipe and internal residual stresses of the material. As a rule, the collar size in a cross-pipe direction D₂ is less than in a lengthwise direction D₁. Moreover, in a majority of relevant materials, for instance in a stainless steel, the collar size in a crosswise direction is less than a dimension D₂' of the tool used for forming the collar.

[0004] This problem has been addressed in the prior patent publication US-5,515,710 by giving the forming die a diameter larger than that of the pipe. This oversized forming die is delivered inside a pipe by squeezing the pipe to ellipticity, whereby its diameter increases in the oversize direction of the forming die. This arrangement is possible with large pipes and thin walls, which possess a required elasticity. With regard to smaller pipes, wherein the ratio of a diameter to a wall thickness alters the pipe elasticity in such a way that said utilization of elasticity and pipe ellipticity is not functional, the shaping and dimensioning of a neck or collar can be implemented as described in this invention.

[0005] It is an object of the invention to provide a method and an apparatus, which can be used for correcting the roundness and diametrical dimensions of a neck or collar formed by the collaring device disclosed in patent publication US-5,515,710.

[0006] This object is accomplished by means of a method set forth in the appended claim 1 and an apparatus set forth in claim 3. The non-independent claims disclose preferred embodiments of the invention.

[0007] The invention will now be described in more detail by way of a working example with reference to the accompanying drawings, in which

fig. 1

shows an apparatus of the invention in side and plan views, respectively;

fig. 2

shows in a perspective view a collared pipe and relative dimensions of its collar and a forming tool in relation to a pipe diameter D;

fig. 3

shows the apparatus of fig. 1 in the initial position of a forming die, in compliance with the device disclosed in patent publication US-5,515,710 except for the dimensioning of a forming die (a calibration mandrel of the invention is not shown);

figs. 3A and 3B

illustrate the forming die and its dimensioning in various diametrical directions;

fig. 4

shows a section taken along a line IV-IV in fig. 1; and

fig. 5

shows the dimensioning of a calibration mandrel in various diametrical directions.

[0008] Referring to the illustrated embodiment, a body 1 of the apparatus comprises a cylindrical element provided with a lengthwise hole of rectangular cross-section, which is fitted with an elongated wedge 2 and its base member 5 whose end 4 can be engaged by a drive unit for operating the wedge 2 lengthwise of the body 1.

[0009] The body 1 has its cylindrical surface formed with a substantially radial hole or recess 9. The hole or recess 9 can also be set at a desired angle within the range of 90°-45° with respect to the center axis of the body 1. However, the most common pipe branches are perpendicular and the most common collars or necks are perpendicular, whereby the angle is 90°. The bottom of a forming die 3 is in contact with a wedge surface 14 of the wedge 2 as the forming die 3 is positioned in the hole or recess 9. In the illustrated case, the wedge 2 is operated by pulling, but it can also be operated by pushing. It is also conceivable to employ two wedges which are movable in directions opposite to each other.

[0010] A pipe to be collared is pushed over the body 1, such that a preformed hole in the pipe sets in alignment above the hole or recess 9 and the forming die 3 present in the latter. As the wedge 2 is forced to travel with its larger or thicker end moving towards the forming die 3, said forming die 3 is driven upwards to force the pipe wall outward from around the preformed hole. The pipe wall stretches around the rim of the preformed hole and forms a branching neck or collar, having its shape and direction consistent with those of the emerging forming die 3.

[0011] The diameter of a tool depicted in fig. 3 is dimensioned for a loose fit in a pipe so as not to leave abrasion marks on the inside wall of the pipe. The forming die 3 fitted in the recess or hole 9 may not be of the size to cause marks on the inside wall of the pipe. This problem, which is about a die causing a mark or a scratch, is particularly evident when making a branch whose size is equal to the pipe itself.

[0012] This problem is resolved with a method and an apparatus of the invention by designing the collar-forming die 3 to be elliptical in such a way that its diameter D₂' transverse to the pipe is smaller than the inner diameter of the pipe and smaller than a diameter D₁' of the forming die 3 in the longitudinal direction of the pipe.

[0013] The neck or collar produced by means of the above-described forming die 3 is elliptical or oval. The collar diameter D₂ is smaller than the inner pipe diameter D as a result of the dimension D₂' of the forming die 3, as well as smaller than the diameter D₂' of the forming die 3 as a result of internal shaping stresses and elasticity of the material.

[0014] This ellipticity of a collar can be rectified by using a special calibration mandrel 11 for finishing the collar. The calibration mandrel 11 is designed for axial movement co-directionally with the center line of the hole 9 present in the collaring tool and it can be pressed against the forming die 3 with a force sufficient for pushing the forming die 3 in front of it back into the hole 9 and stretching the collar to the dimensions of its own size.

[0015] Diameters D₃ (crosswise) and D₄ (lengthwise) of the calibration mandrel 11, as well as those D₁' (lengthwise) and D₂' (crosswise) of the forming die 3 are interrelated, depending on the dimensions and qualities (elasticity) of a pipe to be worked and a desired final result, particularly whether it is desirable to have the inner diameter D₂ of a collar comply with the inner pipe diameter or whether it is desirable to provide the collar and the pipe with equal outer diameters. If the outer diameters are to be equal, the lengthwise diameter D₁' of the forming die 3 is dimensioned to provide the collar with a diametrical size D₁ which is so large that the corresponding outer diameter of the collar is slightly oversized. In this case, the calibration mandrel 11 is dimensioned in such a way that its crosswise diameter D₃ stretches the sides of the collar to a size matching the outer pipe diameter and its lengthwise diameter D₄ supports the collar in the longitudinal direction D₁, allowing the diameter co-directional therewith to be reduced by the extent of an oversize produced by the die 3. A reduction of size occurring co-directionally with the diameter D₁' during the calibration process facilitates essentially a lateral stretching of the crosswise diameter D₂.

[0016] The calibration mandrel 11 has its pipe-entering end 12 designed in an arched shape for pushing its flanks 13 substantially closer to the center line of a pipe than the final position of the top end of the forming die 3. As pointed out above, the calibration mandrel 11 has a crosswise diameter D₃ which exceeds its lengthwise diameter D₄. The mandrel 11 has an outer surface which is slightly conical.

[0017] Thus, the calibration mandrel 11 has a dual function. It pushes the forming die 3 back to the bottom of the hole or recess 9 and at the same time its crosswise measurement disparity rectifies the dimensional error of the forming die 3, which results from the fact that a forming die, which fits inside a pipe, is not capable of producing a diametrical size sufficiently large in crosswise direction.

Claims

1. A method for bending the rims of a pipe hole for a hole-enclosing collar or neck by using a forming die (3), which is movable radially relative to the pipe and which is displaced from inside the pipe outwards for shaping the collar, characterized in that the rectification of a collar produced by the forming die (3) in terms of its roundness and/or diametrical sizes is effected by means of a calibration mandrel (11) movable from outside the pipe inwards, which is pressed by means of an external drive unit into a collar produced by the forming die (3), the calibration mandrel (11) stretching the collar to comply with its own size and, upon its penetration into the neck, the calibration mandrel (11) pushes the forming die back to its initial position for a new collaring operation.

2. A method as set forth in claim 1, characterized in that the forming die (3) is used to produce a collar diameter larger than a desired final size in the lengthwise direction and a collar diameter smaller than a desired final size in the crosswise direction of a pipe, and that the dimensioning of the collar diameters is rectified by a crosswise measurement of the calibration mandrel (11), wherein the calibration mandrel (11) has a diameter which is larger in a transverse direction (D₂) than in a lengthwise direction (D₁).

3. A collaring apparatus for bending the rims of a hole for a hole-enclosing collar or neck, said apparatus comprising a body element (1) insertable inside a pipe to be collared and a forming die (3) adapted for substantially radial movement relative to the pipe and having an outer diameter which is substantially equal to a desired inner diameter for the collar, a hole or recess (9) present in the body element (1), which is dimensioned to receive the forming die (3), said forming die (3) being operable under the guidance of said hole or recess (9), as well as elements (2, 4, 5, 14) engageable with a drive unit for displacing the forming die (3) from inside the pipe outwards, characterized in that the hole or recess (9) has its center line aligned with a calibration mandrel (11) movable co-directionally therewith, which is pressable by means of an external drive unit from outside the pipe inwards into a collar produced by the forming die (3), the calibration mandrel (11) stretching the collar to comply with its own size and, upon its penetration into the collar, the calibration mandrel (11) pushes the forming die (3) back to its initial position for a new collaring operation.

4. An apparatus as set forth in claim 3, characterized in that the calibration mandrel (11) has its pipe-entering end (12) designed in an arched shape for pushing flanks (13) of the mandrel end substantially closer to the center line of a pipe than the final position of the top end of the forming die (3).

5. An apparatus as set forth in claim 3 or 4, characterized in that the calibration mandrel (11) has a diameter which is larger in a transverse direction (D₂) than in a lengthwise direction (D₁) of the pipe.

6. An apparatus as set forth in any of claims 3-5, characterized in that the calibration mandrel (11) has an outer surface which is slightly conical.

7. An apparatus as set forth in any of claims 3-6, characterized in that the forming die (3) is dimensioned to produce a collar diameter (D₁) larger than a desired final size in the lengthwise direction and a collar diameter (D₂) smaller than a desired final size in the crosswise direction of a pipe, the calibration mandrel (11) having a crosswise measurement disparity which rectifies the final size as desired.

Drawing