SCREWS

The invention relates to a pin assembly comprising a pin which, in a first end portion, is provided with a pin head and, in a second end portion, is provided with a threaded portion arranged to receive a nut, the pin head and the nut being provided with coni- cal circumferential surfaces falling towards respective first, outward -facing end faces on the pin head and the nut; internally conical, radially expandable bearing sleeves which are axially displaceable on the conical circumferential surfaces of the pin head and the nut, respectively, and are provided with cylindrical, external sleeve surfaces. The invention also relates to a flange joint comprising a first flange and a second flange, each including a set of pin holes corresponding with each other, and wherein each pin hole is provided with a recessed pin-hole end portion facing away from a flange abutment surface, the recessed pin-hole end portions being defined by cylindri cal wall surfaces and bottom surfaces which are perpendicular to centre axes of the pin holes; and a pin assembly comprising a pin which, in a first end portion, is provid- ed with a pin head and, in a second end portion, is provided with a threaded portion arranged to receive a nut, the pin head and the nut being provided with conical cir- cumferential surfaces falling towards respective first, outward -facing end faces on the pin head and the nut; internally conical, radially expandable bearing sleeves which are axially displaceable on the conical circumferential surfaces of the pin head and the nut, respectively, and are provided with cylindrical, external sleeve surfaces arranged to rest supportingly against the cylindrical wall surfaces of the recessed pin-hole end por- tions.

When joining large structures, for example pipe flanges, by means of screws extend- ing through pin holes, the screw diameter will, as a rule, be so large that the frictional forces between a screw head and the abutment of the screw head, possibly between a nut and the abutment of the nut, will prevent or complicate precise and even tighten- ing of the screws to a desired level. At the same time, it is important to centre the

P28147PC00 description and claims screws in the pin holes to achieve even stressing of the screws and accurate relative positioning of the structures to be joined.

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art. The object is achieved through the features that are specified in the description below and in the claims that follow.

In what follows, the terms "flange", "flange connection", "flange joint" and the like are not restricted to referring only to flanges on pipes, but also cover corresponding ele- ments forming joining details on machine components, frame structures, etc. The invention provides a pin assembly for joining flange connections by means of at least one pin, the at least one pin being provided, in a first end portion, with a pin head and being provided, in a second end portion, with a nut that engages with the screw via a threaded portion. The pin head has a circumferential surface which is coni- cally tapering towards an outward-facing end of the pin head. Correspondingly, the nut has a circumferential surface which is conically tapering towards an end of the nut.

In an alternative embodiment, the pin head may be formed of a second conical nut which engages with the pin in a second threaded portion. In what follows, the term "pin head" will be used for this embodiment as well.

At least one of the pin head and the nut is provided with a set of first threaded holes which are arranged in the axial direction of the pin head and the nut, respectively, and extend through the pin head and the nut, respectively, from a first end portion to a second end portion of the pin head and the nut, respectively. Said first threaded holes are preferably evenly distributed along a first pitch circle. Said set of first threaded holes are arranged to receive a set of first clamping bolts. The pin head and the nut are also provided with sets of second threaded holes which are arranged in the axial directions of the pin head and the nut, respectively, and extend through the pin head and the nut, respectively, from first end portions to second end portions of the pin head and the nut, respectively. Said second threaded holes are preferably evenly dis- tributed along said first pitch circle, possibly along a second pitch circle. Said second threaded holes are arranged to receive a set of second clamping bolts. The set of first threaded holes may have the same diameter and thread pitch as the set of second threaded holes or be different.

The pin assembly includes bearing sleeves which are arranged to be moved in on the

P28147PC00 description and claims conical pin head and the conical nut, respectively. The bearing sleeves are internally conical and radially expandable and have substantially cylindrical external surfaces.

Each end of the pin assembly is provided with a clamping plate which is arranged to rest against an end face on the respective bearing sleeve. The clamping plate is pro- vided with a set of through bolt holes corresponding with the set of second threaded holes arranged in the pin head and the nut, respectively. Said set of second clamping bolts extend from the clamping plate and into the set of second bolt holes of the pin head and the nut, respectively.

Each of the flanges that form part of a flange connection which is to be joined is pro- vided with corresponding sets of pin holes arranged to receive the pin assembly. Pin- hole end portions facing away from an abutment surface on each flange are cylindri- cally recessed with bottom surfaces which are preferably perpendicular to the centre axes of the pin holes and are arranged to receive the bearing sleeves of the pin as- sembly. When the flanges are positioned with corresponding pin holes in line and joined by pins having been passed through the flanges and the nut having been screwed in on each of the pins so that the pin head and the nut are resting against bottom surfaces in the respective recessed pin-hole end portions, the bearing sleeves are slipped over each pin head and each nut, respectively, so that the pins are centred in the pin holes by the radial expansion of the bearing sleeves until the cylindrical, external bearing-sleeve surfaces are resting against the widened end portions of the respective pin holes. Then the pins are tightened by the first clamping bolts being screwed into the respective pin heads and nuts with a desired torque into abutment against the bottom surfaces of the recessed end portions of the respective pin holes. With that, the pins of the flange connection are subjected to a desired tensioning.

Then the clamping plates are fitted as they are being placed in abutment against the end faces of the bearing sleeves, which project from the recessed pin-hole end por- tions in the flanges. The second clamping bolts are passed through the bolt holes of the clamping plates and screwed into the second threaded holes of the pin head and the nut, respectively, and are tightened so that the bearing sleeves are displaced fur- ther in over the conical circumferential surfaces of the pin head and the nut, respec- tively, and expand further into abutment against the walls of the surrounding pin-hole end portions. Thereby the pin assembly has also provided a radial clamping of the flange connection.

The pin assembly may include a washer which is placed between the one of the pin head and the nut that is provided with the set of first clamping bolts and the bottom

P28147PC00 description and claims surface of the respective recessed pin-hole end portion of the flange. The washer may be formed from a material of greater hardness than the flange, for example by the washer being formed from hardened steel, so that the first clamping bolts will not de- form the bottom surface against which they are resting. It may also be an advantage if the first clamping bolts are formed with greater tensile and compressive strengths than the second clamping bolts, since, as a rule, the first clamping bolts will have to be tightened to a greater torque than the second clamping bolts.

The first threaded holes and the second threaded holes may be distributed on a com- mon pitch circle or on separate pitch circles. It is an advantage if the threaded holes of each set of first and second threaded holes are evenly spaced angularly.

The invention is defined by the independent claims. The dependent claims define ad- vantageous embodiments of the invention.

In a first aspect, the invention relates, more specifically, to a pin assembly comprising a pin which, in a first end portion, is provided with a pin head and, in a second end portion, is provided with a threaded portion arranged to receive a nut, the pin head and the nut being provided with conical circumferential surfaces falling towards respective first, outward -facing end faces on the pin head and the nut;

internally conical, radially expandable bearing sleeves which are axially dis- placeable on the conical circumferential surfaces of the pin head and nut, respectively, and are provided with cylindrical, external sleeve surfaces;

characterized by

at least one of the pin head and the nut being provided with a set of first, threaded holes extending through the pin head and the nut, respectively, substantially parallel to centre axes through the pin head and the nut, respectively and a set of second, threaded holes extending into the pin head and the nut, respectively, from the respective first, outward -facing end faces of the pin head and the nut, substantially parallel to the centre axes through the pin head and the nut, respectively;

a set of first clamping bolts being arranged in the first threaded holes;

clamping plates being arranged to rest against an end face on each of the bear- ing sleeves, as sets of second clamping bolts extend through bolt holes in the clamp- ing plates and into the sets of second threaded holes in the pin head and the nut, re- spectively.

A washer may be arranged at a second, inward-facing end face of the one of the pin

P28147PC00 description and claims head and the nut that is provided with the set of first clamping bolts.

The washer may be formed from a hardened material.

The first threaded holes and the second threaded holes may be distributed on a com- mon pitch circle. Alternatively, the first threaded holes and the second threaded holes may be distributed on separate pitch circles.

The threaded holes of each set of first and second threaded holes may be evenly spaced angularly.

The pin head may be formed of a second nut arranged on a second threaded portion on the pin. In a second aspect, the invention relates, more specifically, to a flange joint compris- ing

a first flange and a second flange, each comprising a set of corresponding pin holes provided with recessed pin-hole end portions facing away from a flange abut- ment surface, the recessed pin-hole end portions being defined by cylindrical wall sur- faces and bottom surfaces that are perpendicular to centre axes of the pin holes; and a pin assembly comprising

a pin which, in a first end portion, is provided with a pin head and, in a second end portion, is provided with a threaded portion arranged to receive a nut, the pin head and the nut being provided with conical circumferential surfaces falling towards respective first, outward -facing end faces of the pin head and the nut;

internally conical, radially expandable bearing sleeves which are axially dis placeable on the conical circumferential surfaces of the pin head and the nut, respec- tively, and are provided with cylindrical, external sleeve surfaces arranged to rest supportingly against the cylindrical wall surfaces of the recessed pin-hole end portions, characterized by

at least one of the pin head and the nut being provided with a set of first threaded holes extending through the pin head and the nut, respectively, substantially parallel to centre axes through the pin head and the nut, respectively, and a set of second threaded holes extending into the pin head and the nut, respectively, from the respective first, outward -facing end faces of the pin head and the nut, substantially parallel to the centre axes through the pin head and the nut, respectively;

a set of first clamping bolts being arranged in the first threaded holes and be- ing arranged to rest supportingly with bolt end faces against the bottom surfaces of the recessed pin-hole end portions;

P28147PC00 description and claims clamping plates being arranged to rest against an end face on each of the bear- ing sleeves, as sets of second clamping bolts extend through bolt holes in the clamp- ing plates and into the sets of second threaded holes of the pin head and the nut, re- spectively. A washer may be arranged at a second, inward-facing end face on the one of the pin head and the nut that is provided with the set of first clamping bolts.

The washer may be formed from a hardened material.

The pin head may be formed of a second nut arranged on a second threaded portion on the pin. In what follows, examples of preferred embodiments are described, which are visual- ized in the accompanying drawings, in which:

Figure 1 shows, in perspective, a pin assembly according to the invention;

Figure 2 shows, in perspective, the pin assembly partially assembled; Figure 3 shows the pin assembly, partly in a side view, partly in an axial section, as a connection between two flanges, and

Figure 4 shows a portion of a pin, in which a pin head has been replaced by a second nut.

Reference is first made to figures 1, 2 and especially figure 3. A pin assembly 1 corn- prises a pin 11 provided with a pin head 12. An end portion of the pin 11 is provided with a threaded portion 111 for receiving a nut 13 (see figure 3). The pin head 12 and the nut 13 are provided with conical circumferential surfaces 121 and 131, respective- ly, and are arranged to supportingly receive respective bearing sleeves 15, each bear- ing sleeve 15 being provided with a conical internal sleeve surface 151 which is com- plementary to the circumferential surfaces 121 and 131 of the pin head 12 and the nut 13, respectively. Clamping plates 16 are arranged to rest supportingly against an end face 154 on each of the bearing sleeves 15. Placed on the pin 11, within the pin head 12 and the nut 13, there are washers 18.

The pin head 12 and the nut 13 are provided with several first threaded holes 124 and 134, respectively, directed axially, extending through the pin head 12 and the nut 13, respectively, from a first head end face 122 and a first nut end face 132, respectively, to a second head end face 123 and a nut end face 133, respectively, for receiving sets

P28147PC00 description and claims of first clamping bolts 14 which can rest with bolt end faces 141 against the respective washers 18.

The pin head 12 and the nut 13 are additionally provided with several second threaded holes 125 directed axially, extending into the pin head 12 and the nut 13, respective- ly, from a first head end face 122 and a first nut end face 132, respectively, and being arranged to receive sets of second clamping bolts 17. The second threaded holes 125 are arranged on a pitch circle and with an angular distance corresponding to that of threaded bolt holes 161 extending through the clamping plates 16.

Each of the bearing sleeves 15 is provided with a cylindrical external sleeve surface 152 which is penetrated by several slits 155. A salient end portion of the bearing sleeve 15 is penetrated by an end-portion slit 155a forming an extension of one of the slits 155 penetrating the sleeve surfaces 151, 152. The salient end portion 153 forms an outward-facing end face 154.

Reference is now made to figure 3, in which the pin assembly 1 is shown in a joint of a first flange 2 and a second flange 2a, in which respective flange abutment surfaces 22 are resting supportingly against each other. Each of the flanges 2, 2a is provided with a pin hole 21 in which a pin-hole end portion 211 facing away from the flange abut- ment surface 22 is recessed, the recessed pin-hole end portion 211 forming a bottom surface 212 and a cylindrical wall surface 213. The bottom surface 212 forms an axial clamping face for the pin assembly 1, and the wall surface 213 forms a radial clamping face for the pin assembly 1 when the flanges 2, 2a are being joined.

Before installing the pin assembly 1 in a pair of corresponding pin holes 21 in opposite flanges 2, 2a, the nut 13 and the respective second clamping bolts 17, clamping plate 16, bearing sleeve 15 and washer 18 are removed. The first clamping bolts 14 of the pin head 12 are unscrewed sufficiently so that the clamping bolts 14 do not project from the inward-facing second head end face 123 of the pin head 12. The pin 11 is inserted into the corresponding pin holes 21, and the nut 13 with the respective wash- er 18 and bearing sleeve 15 is connected to the pin 11 and tightened by light rotation of the nut 13. The bearing sleeves 15 are slipped onto the conical circumferential sur- faces 121 and 131, respectively, of the pin head 12 and the nut 13, respectively, so that the bearing sleeves 15 centre the pin 11 in the pin holes 21. The pin 11 is then clamped axially by the first clamping bolts 14 being screwed into the pin head 12 and the nut 13, respectively, until abutment by the bolt end faces 141 against the respec- tive washers 18 with the desired torque. Then the clamping plates 16 are tightened against the end faces 154 of the bearing sleeves 15 by means of the second clamping

P28147PC00 description and claims bolts 17 in order thereby to give the pin assembly 1 a radial clamping in the flanges 2, 2a.

If the flanges 2, 2a are formed from a sufficiently hard material, the pin assembly 1 may be used without washers 18. But under normal circumstances, providing washers 18 of a preferred material hardness will be easier and more cost-effective than provid- ing flanges 2, 2a of a sufficient material hardness.

Reference is now made to figure 4. In an alternative embodiment, the pin head 12 is replaced by a second nut 13a, the pin 11 being provided with a second threaded por- tion 111a which is arranged to receive the second nut 13a. The second nut 13a has a design which is identical to the design of the first nut 13, with respect to both thread- ed holes 134, 135, the circumferential surface 131 and nut end faces 132, 133.

It should be noted that all the above-mentioned embodiments illustrate the invention, but do not limit it, and persons skilled in the art may construct many alternative em- bodiments without departing from the scope of the attached claims. In the claims, reference numbers in brackets are not to be regarded as restrictive.

The use of the verb "to comprise" and its different forms does not exclude the pres- ence of elements or steps that are not mentioned in the claims. The indefinite article "a" or "an" before an element does not exclude the presence of several such elements.

The fact that some features are indicated in mutually different dependent claims does not indicate that a combination of these features cannot be used with advantage.

P28147PC00 description and claims