GB2290844A - Grease filled hydraulic bolt - Google Patents

Abstract

A grease filled hydraulic bolt comprises a ring 32 slidably disposed on the bolt shank 24. Cylindrical openings 50 are formed through the bolt head 28 and are circumferentially connected by an annular passageway 52. A stressing screw 54 connected to a piston 56 is threadably engaged in each opening 50. The openings 50 and passageway 52 are filled with a suitable grease. During use, the screws 54 are rotated to drive the pistons 56 downwardly to pressurise the grease. The resulting forces will press the ring 32 against one of the plates (not shown) to which the bolt is attached so that the bolt shank 24 is stretched. The bolt tension is maintained by hand-screwing a collar 38 down the external screwthread on the head 28 into engagement with the ring; in Fig. 7 (not shown), the ring has an external screwthread on which the collar is screwed upwards to engage the head 28; in Figs 11 and 12 (not shown), skims are inserted in the gap between the head and the ring. <IMAGE>

Description

GREASE FILLED HYDRAULIC BOLT The present invention relates to bolts. More particularly, the present invention relates to grease filled hydraulic bolts.

Conventional bolts are well known and typically comprise a head and bolt shaft with at least the lower end of the shaft being threaded. Also, grease filled hydraulic nuts are known for attachment to threaded studs. By way of example, one such grease filled hydraulic nut is commerclally available from Raymond Engineering of Middletown, Connecticut under part number series BCHN. The benefits of the grease filled hydraulic technology are not available irl applications where space is severely limited.

In such situations conventional bolts are used since a bolt head requires less space than a grease filled hydraulic nut mounted on a threaded stud to achieve the same retaining force. In order to Increase the forces exerted by the grease filled hydraulic nut a wider nut Is required to accommodate the annular piston area, since nominal wall thicknesses are required to contain the pressurised grease, as is known. Further, the threads of such a stud are often damaged when a band wrench Is used to rotate the stud.

Accordingly, a need exists for a fastening device capable of achieving a high retaining force in a smaller space.

The present invention provides a hydraulic bolt comprising: a bolt shaft having a first shaft portion and a second shaft portion1 said second shaft portion having a plurality of holes passing therethrough, one end of said first shaft portion being threaded; a ring shaped body disposed about said bolt shaft for closing off one end of said holes in said second shaft portion, said holes having a liquid disposed therein; means for reducing tho volume of said holes which increases the pressure of said liquid in said holes to exert an axial force on said bolt shaft resulting in a displacement of said second shaft portion from said body; and means for maintaIning said displacoment of sald second shaft portion from said body.

In a first embodiment of the present inventlon, the grease filled hydraulic bolt comprises a head assembly with a shaft extending downwardly at about the centre of the bolt. This shaft comprises a lower shaft portion and an upper shaft portion. The lower end of this lower shaft portion is threaded. A ring shaped outer body is disposed about this shaft at the lower end of the upper shaft portion and the upper end of the lower shaft portion. A lower surface of the body defines the bearing surface of the head assembly.

A top load retention collar is attached to tho upper shaft portion by inner threads thereof which engage outer threads on the upper shaft portion. Lip seals are disposed within grooves of the head assembly to provide a seal between the body and the shaft. A plurality of spaced cylindrical openings are formed through the upper shaft portion with the upper portion of each opening being threaded. A lower portion of the openings extends circumferentially about the lower end of the upper shaft portion, which defines a passageway connecting all of the openings. This passageway is positioned between the aforementioned lip seals to provide a seal thereabout. A stressing screw is threadably engaged in each opening. A piston is attached at the lower end of each screw with a seal attached to each piston to provide a seal between the corresponding piston and the upper shaft portion.The openings and passageway are filled with a suitable grease.

During use, the bolt of this Invention may for example be used to fasten two plates together. The bolt is initially disposed in an opening of the plates and then rotated whereby the threads of the bolt engage the threads in the opening of one of the plates. The bolt Is rotated until hand tight. In its initial closed position the stressing screws are at a top position where virtually no pressure is exerted on the grease in the openings by the pistons, and the collar Is adjacent to the body. Then each stressing screw is individually rotated to drive the corresponding piston downwardly thereby reducing the overall volume of the openings whereby the grease therein is pressurised. Each screw is tightened until a desired pressure is obtained in the annular piston area. As the pressure on the grease increases the shaft is axially stretched, In other words tensioned.The resulting forces will hold the body against the upper surface of one of the plates while the shaft is stretched. Since the collar is attached to the upper shaft portion it will move upwardly with the shaft as It stretches resulting in a gap. Once the screws have been tightened to achieve the desired grease pressure, the collar is rotatcd downwardly closing this gap. The stressing screws are then loosened until the pressure returns to zero. The bolt is now accurately tensioned.

In accordance with an alternate embodiment an Inner ring shaped body is disposed about the shaft and a bottom load retention collar is attached to the body. During use, each stressing screw is individually rotated downwardly wlth the resulting forces holding the body against the upper surface of one of the plates while the shaft is stretched. Since the collar is attached to the body it will remain at its initial position while the shaft stretches resulting in a gap. Once the screws have been tightened to achieve the desired grease pressure, the collar is rotated upwardly closing this gap. The stressing screws are then loosened until the pressure returns to zero. The bolt is now accurately tensioned.

In still another alternate embodiment the collar is eliminated and a shim is used to fill the aforementioned gaps.

The grease filled bolts of the present invention provide a large tension force within a small space. Further, the grease filled bolts of the present Invention avoid many of problems of the prior art standard bolts, e.g., the need for hydraulic or pneumatic tools to torque the bolt to specified levels, and stresses induced on the bolt resulting from a torque requirement as opposed to a tension requirement, such as twisting of the bolt and others.

Certain preferred embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: FIGURE 1 is a perspective view of a top collar grease filled hydraulic bolt in accordance with the present invention; FIGURE 2 is a side elevation view partly in cross section of the grease filled hydraulic bolt of FIGURE 1; FIGURE 3A is a top view of the grease filled hydraulic bolt of FIGURE 1; FIGURE 3B Is a view taken along the line 3B-3B In FIGURE 2.

FIGURE 4 is a side elevation view partly in cross section of the grease filled hydraulic bolt of FIGURE 1 securing two members together with the grease filled hydraulic bolt in its initial closed position; FIGURE 5 is a partIal side elevation view partly in cross section of the grease filled hydraulIc bolt of FIGURE 1 securing two members together with the stressing screws of the grease filled hydraulic bolt tightened down thereby stretching the bolt; FIGURE 6 is a partial side elevation vlew partly in cross section of the grease filled hydraulic bolt of FIGURE 1 securing two members together with the collar of the grease fillcd hydraulic bolt tightened downwardly thereby malntaining the tension on the bolt; ; FIGURE 7 is a partlal side elevation view partly in cross section of a bottom collar grease filled hydraulic bolt in accordance with an alternate embodiment of the present invention securing two members together with the grease filled hydraulic bolt in its initial closed position; FIGURE 8 Is a partlal side elevation vlew partly in cross section of the grease filled hydraulIc bolt of FIGURE 7 securing two members together with the stressing screws of the grease filled hydraulic bolt tightened down thereby stretching the bolt; FIGURE 9 is a partlal side elevation vlew partly in cross section of the grease filled hydraulic bolt of FIGURE 7 securing two members together with the collar of the grease filled hydraulic bolt tlghtened upwardly thereby maintaining the tension on the bolt;; FIGURE 10 is a top view of a blow out cover for an oil well hole using the grease filled bolts of the present Invention; FIGURE 11 is a partial side elevation view partly in cross section of a top shim grease filled hydraulic bolt in accordance with still another embodiment of the present invention; and FIGURE 12 is a partial side elevation view partly in cross section of a bottom shim grease filled hydraulic both In accordance with yet another embodiment of the present invention.

Referring to FIGURES 1, 2, 3A and 3B, a grease filled hydraulic bolt is shown generally at 20 in its initial closed position. Hydraulic bolt 20 comprises a head assembly 22 with a shaft 24 extending downwardly at about the centre of bolt 20. Shaft 24 comprises a lower shaft portion 26 and an upper shaft portion 28. The lower end of shaft portion 26 is threaded. However, it will be appreciated that the entlre shaft portion 26 may be threaded as such is dictated by the particular application. As is clearly shown In FIGURE 2, shaft portion 28 has a greater diameter than shaft portion 26 whereby a stcpped surface 30 is deflned. A ring shaped outer body 32 is disposed about shaft 24 at the lower end of portion 28 and the upper end of portion 26.Body 32 includes an inner stepped surface 34 which aligns with stepped surface 30 of shaft 24. The lower end of body 32 is stepped inwardly by an outer stepped surface 35. A lower surface 36 of body 32 defines the bearing surface of head assembly 22.

A top load retention collar 38 is attached to portion 28 of shaft 24 by inner threads thereof which engage outer threads on portion 28. An outer surface 40 at the lower end of portion 28 is slidably disposed adjacent an inner surface 42 of body 32. A lip seal 44 is disposed within a groove around the lower end of surface 42 adjacent stepped surface 30 of shaft 24, whereby a high pressure liquid tight seal is formed between surface 42 of body 32 and surface 40 of shaft 24. Another lip seal 46 is disposed within a groove around the upper end of an inner surface 48 of body 32 adjacent stepped surface 34, whereby a high pressure liquid tight seal is formed between surface 48 of body 32 and the outer surface of shaft 24. Inner surface 48 is slidably disposed adjacent the outer surface of portion 26 of shaft 24.

A plurality of spaced cylindrical openings 50 are formed through portion 28 of shaft 24. The upper portion of each opening 50 is threaded.

Openings 50 are sufficlently spaced inwardly from the outer surface of portion 28 to assure that the material thickness between the outer surface of portion 28 and each opening 50 will withstand high pressures (e.g., pressures in excess of 22,000 Ibs.lin 2 (151.7 MPa)).

A lower portion 52 of opening 50 extends circumferentially about the lower end of portion 28 in surface 30. Portion 52 of opening 50 defines an annular passageway connecting all of the openings 50. This passageway 52 is positioned between lip seals 44 and 46 such that these lip seals form a seal about passageway 52 between body 32 and shaft 24.

A stressing screw 54 is threadably engaged in each opening 50. A piston 56 is attached at the lower end of each screw 54 with a seal 58 attached to each piston 56 to provide a hlgh pressure liquid tight seal between corresponding piston 56 and portion 26 of shaft 24. Accordingly, opening 50 Including passageway 52 are each completely sealed by corresponding seals 68 and lip seals 44 and 46. Openings 50 and passageway 52 are filled with a suitable grease (not shown In FIGURE 2), such as the type used the aforementioned prior art grease filled hydraulic nuts.

A hex head 60 Is disposed at the upper end of shaft 24 to aid in the installation of bolt 20 as is described more fully below.

Referring to FIGURE 4, a first member or plate 62 having an opening 64 Is attached to a second member or plate 66, which includes a threaded opening 68, by bolt 20. Bolt 20 is initially disposed in opening 64 and then rotated whereby the threads of bolt 20 engage the threads In opening 68.

Bolt 20 is preferably rotated with a wrench applied to hex head 60 until hand tight. Moreover, bolt 20 is shown in Its initial closed position with stressing screws 54 at a top position where virtually no pressure Is exerted on the grease in openings 50 and 52 by pistons 56, and collar 38 is adjacent body 32. When bolt 20 is hand tight, bearing surface 36 of bolt 20 will bear against an upper surface 70 of member 62.

Referring to FIGURE 5, each stmssing screw 54 is then individually rotated, using preferably a hand tool (e.g., an allen wrench) or pneumatics, to drive the corresponding piston 56 downwardly thereby reducing the overall volume of openings 50 and 52 whereby the grease therein is pressurised. Each screw 54 is tightened until a desired pressure is obtained.

The pressure is monitored by a pressure gauge 72 which is in communication with the grease chamber as is well known, e.g., as with the prior art grease filled hydraulic nuts. Further, it is not important that screws 54 be tightened In any particular order since the force applied by the grease will be uniform throughout openings 50 and 52. Moreover, all screws 54 are preferably not required to be completely tightened in order to obtain the desired pressure, whereby manufacturing tolerances can be accounted for. As the pressure on the grease increases shaft 24 is axially stretched, in other words tensioned. Tlle resulting forces will hold body 32, and more particularly surface 36 of body 32, against surface 70 of member 62 while shaft 24 is stretched.Since collar 38 is attached to portion 28 of shaft 24 it will move upwardly with shaft 24 as It stretches resulting in a gap 74.

Referring now to FIGURE 6, once screws 54 have been tightened to achieve the desired grease pressure and thereby the desired tension on the bolt, collar 38 is rotated downwardly closing the gap 74 (FIGURE 5). The outer surface of collar 38 Is knurled to facIlItate hand rotating of the collar.

The outer surface of collar 38 also includes a plurality of holes 76 to allow use of a tommy bar or spanner wrench when tIghtenIng collar 38 to a hand tight position, as shown In FIGURE 6. This results in collar 38 exposing a portion 78 of threads of portion 28 of shaft 24.

Bolt 20 is now accurately tensioned and screws 54 are loosened and preferably removed from the bolt 20 to avoid tampering with the bolt and to relieve the pressure on the grease which Is no longer required.

Referring to FIGURE 7, a grease filled hydraulic bolt in accordance with an alternate embodiment is shown generally at 80. Bolt 80 is shown In Its Initial closed position attached a first member or plate 82 having an opening 84 to a second member or plate (not shown) which includes a threaded opening.

Bolt 80 comprises a head assembly 90 with a shaft 92 extending downwardly at about the centre of bolt 80. Shaft 92 comprises a lower shaft portion 94 and an upper shaft portion 96. The lower end of shaft portion 94 Is threaded1 as In the prior embodiment. As is clearly shown in the FIGURES, shaft portion 96 has a greater diameter than shaft portion 94 whereby stepped surface 98 is defined. An inner ring shaped body 100 is disposed about shaft 92 at the lower end of portion 96 and the upper end of portion 94. Body 100 includes an inner stepped surface 102 which aligns with stepped surface 98 of shaft 92. The lower end of head assembly 90 is stepped inwardly by slightly extending body 100 downwardly. A lower surface 104 of body 100 defines the bearing surface for head assembly 90.

A bottom load retention collar 106 Is attached to body 100 by inner threads which engage outer threads of body 100. Inner and outer surfaces 108, 110 of body 100 are slidably disposed adjacent to corresponding surfaces of shaft 92. A lip seal 112 is disposed within a groove in portion 94 adjacent to the upper end of surface 110 of body 100, whereby a high pressure liquid tight seal Is formed between surface 110 of body 100 and shaft 92. Another lip seal 114 is disposed within a groove in portion 49 adjacent to the upper end of surface 108 of body 100, whereby a high pressure liquid tight seal Is formed between surface 108 of body 100 and shaft 92.

A plurality of spaced cylindrical openings 116 are formed through portion 96 of shaft 92. The upper portion of each opening 116 is threaded.

Openings 116 are sufficiently spaced inwardly from the outer surface of portion 96 to assure that the material thickness therebetween will withstand high pressures.

A lower portion 118 of opening 116 extends circumferentially about the lower end of portion 96 in surface 98. Portion 118 of opening 50 defines an annular passageway connecting all of the openings 116. This passageway 118 is aligned with body 100 such that lip seals 112 and 114 form a seal about the passage way 118 between body 100 and shaft 92.

A stressing screw 120 is threadably engaged in each opening 116.

A piston 122 is attached at the lower end of each screw 120 in opening 116. A seal 124 is attached to each piston 122 to provide a high pressure liquid tight seal between corresponding piston 122 and opening 116.

Accordingly, opening 116 including passageway 118 are each completely sealed by corresponding seals 124 and lip seals 112 and 114. Openings 116 and a portion of passageway 118 are filled with a suitable grease, as described hereinbefore.

Bolt 80 is initially disposed in opening 84 and then rotated whereby its threads engage the threads in the opening of the second plate. Bolt 80 is preferably rotated with a wrench applied to a hex head 121, disposed at the upper end of shaft 94, until hand tight. In the initial closed position stressing screws 120 are at a top position where vertically no pressure Is exerted on the grease In openings 116 and 118 by pistons 122, and collar 106 is adjacent surface 98 of portion 96. When bolt 80 is hand tight, bearing surface 104 of bolt 80 will bear against an upper surface 124 of member 87.

Referring to FIGURE 8, each stressing screw 120 Is then individually rotated, using a hand tool or pneumatics, to drive the corresponding pistons 122 downwardly thereby reducing the overall volume of openings 1 16 and 118 whereby the grease therein is pressurised. Each screw 120 is tightened until a desired pressure is obtained. The pressure is monitored by a pressure gauge as described hereinbefore. As in the prlor embodiment, it is not Important that the screws 120 be tightened in any particular order.

Further, as the pressure on the grease increases shaft 92 is axially stretched, in other words tensioned. The resulting forces will hold body 100, and more particularly surface 104 of body 100, against surface 124 of member 82 while shaft 92 is stretched. Since collar 106 is attached to body 100 it will remain at its initial position while shaft 92 stretches resulting in a gap 128.

Referring now to FIGURE 9, once screws 120 have been tightened to achieve the desired grease pressure and thereby the derived tension on the bolt, collar 106 is rotated upwardly closing gap 128 (FIGURE 8). The outer surface of collar 106 is knurled to facilitate hand rotating of the collar. The outer surface of collar 106 also includes a plurality of holes 130 to allow use of a tommy bar or spanner wrench when tightening collar 106 to a hand tight position as shown in FIGURE 9. This results in collar 106 exposing a portion 132 of threads on body 100.

Bolt 80 is now accurately tensioned and screws 120 are loosened and preferably removed from the bolt 80 to avoid tampering with the bolt and to relieve the pressure on the grease which is no longer required.

Referring to FIGURE 10, a blow out cover for an oil well hole is shown generally at 134. In the prior art, cover 134 was retained by four standard bolts meeting specific size requirements. These are now replaced by the bolts of the present invention. Further, while one of ordinary skill in the art may attempt to utilise the prior art grease filled nuts with studs for such an applicatlon, these prior art grease filled nuts are not suitable for such an application due to the aforementioned size limitations. If the prior art grease filled nut was mounted on a stud the overall diameter would be too large for this particular application, due In part to the high tension requirements. Further, the rotating of the stud with, for example a band wrench, often damages the threads.The grease filled bolts of the present invention resolves this problom whereby large tension requirements are met within a smaller space. The present invention is not only applicable to the oil well industry but many other applications will be readily apparent to one of ordinary skill In the art. Moreover, the grease filled bolts of the present Invention avoid many of the other well known problems of the prior art standard bolts, e.g., the need for hydraulic or pneumatic tools to torque the bolt to specified levels, and stresses induced on the bolt resulting from a torque requirement as opposed to a tension requirement, such as twisting of the bolt and others.

Referring to FIGURES 11 and 12, yet another alternate embodiment of the present invention Is shown. In FIGURE 11 the embodiment of FIGURE 2 is modified whereby the collar is eliminated and made part of the shaft. A shim 136 Is disposed in the gHp (I.e., between the body and the collar portion which Is now integral with the shaft) generated by the tightening of the stressing screws, whereby the tension is maintained. In FIGURE 12 the embodiment of FIGURE 7 Is modified whereby the collar is eliminated and made part of the body. A shim 138 is disposed in the gap (i.e., between the collar portion which is now integral with the body and the shaft) generated by the tightening of the stressing screws, whereby the tension is maintalned.

Claims (13)

1. A hydraulic bolt comprising: a bolt shaft having a first shaft portion and a second shaft portion, said second shaft portion having a plurality of holes passing therethrough, one end of said first shaft portion being threaded; a ring shaped body disposed about said bolt shaft for closing off one end of said holes in said second shaft portion, said holes having a liquid disposed therein; means for reducing the volume of said holes which increases the pressure of said liquid in said holes to exert an axial force on said bolt shaft resulting in a displacement of said second shaft portion from said body; and means for maintaining said displacement of said second shaft portion from said body.

2. A hydraulic bolt as claimed in claim 1 wherein said means for maintaining said displacement of said second shaft portion from said body comprises a collar rotatably disposed on said second shaft portion of said bolt shaft.

3. A hydraulic bolt as claimed in claim 1 wherein said means for maintaining said displacement of said second shaft portion from said body comprises a collar rotatably disposed on said body.

4. A hydraulic bolt as claimed in any preceding claim wherein said means for reducing the volume of said holes comprises: a piston disposed in each of said holes; and means for driving each of said pistons.

5. A hydraulic bolt as claimed in claim 4 wherein said means for driving each of said pistons comprises: a stressing screw threadably mounted in each of said holes, each of said stressing screws having one of said pistons attached at one end thereof.

6. A hydraulic bolt as claimed in claim 4 or 5 further comprising: means for sealing between said piston and said second shaft portion within said holes.

7. A hydraulic bolt as claimed in any preceding claim further comprising: means for sealing between said body and said second shaft portion at each of said holes.

8. A hydraulic bolt as claimed in any of claims 1 to 6 wherein: said second shaft portion further includes an annular opening interconnecting said holes; and, said body is disposed about said bolt shaft for closing off one end of said annular opening in said second shaft portion, said holes and said annular opening having said liquid disposed therein.

9. A hydraulic bolt as claimed in claim 8 further comprising: means for sealing between said body and said second shaft portion about said annular opening.

10. A hydraulic bolt as claimed in claim 9 wherein said means for sealing between said body and said second shaft portion about said annular opening comprises: a lip seal disposed at each side of said annular opening.

11. A hydraulic bolt as claimed in claim 1 wherein said means for maintaining said displacement of said second shaft portion from said body comprises a shim inserted between said second shaft portion of said bolt shaft and said body.

12. A hydraulic bolt as claimed in any preceding claim wherein said liquid is a grease.

13. A hydraulic bolt substantially as described hereinbefore with reference to the accompanying drawings.