GB2225825A

GB2225825A - Swing bolt assembly for a pressure vessel

Info

Publication number: GB2225825A
Application number: GB8828794A
Authority: GB
Inventors: Ian Wilson
Original assignee: Fort Valve Engineering Ltd
Current assignee: Fort Valve Engineering Ltd
Priority date: 1988-12-09
Filing date: 1988-12-09
Publication date: 1990-06-13
Anticipated expiration: 2008-12-09
Also published as: GB2225825B; GB8828794D0

Abstract

A swing bolt (30) is pivotally mounted at 32 on a pressure vessel so that the swing bolt (30) may be engaged in the slot (38) between two lugs (36) on a lid of a pressure vessel, and a hand nut (40) may be screwed along the bolt to secure the lid, the hand nut (40) itself being provided with a captive washer (44) which is rotatably mounted on the hand nut (40), and which is made of a harder material than the hand nut material. The washer (44) bears against the lugs (36) in use, allowing the hand nut (40) to rotate inside the washer (44) with full face contact on a complementarily shaped internal seat. <IMAGE>

Description

DESCRIPTION SWING BOLT ASSEMBLY FOR A PRESSURE VESSEL The present invention relates to swing bolt assemblies for pressure vessels, and to securing nuts used in such assemblies.

Pressure vessels and tanks in general are provided with lids which typically are circular and are pivotally attached to a neck ring which is attached to the vessel.

Swing bolt assemblies secured to the neck ring at pivot brackets engage with lugs secured to the lid so as to clamp the lid in sealing engagement with the neck ring.

Such swing bolt assemblies typically comprise a bolt which is pivotally mounted about a horizontal axis which is also tangential to the exterior of the pressure vessel or tank. A hand nut is threadedly mounted on the swing bolt which may be pivoted upwardly into the slot of a lug bracket attached to the lid. By screwing the hand nut towards the pivotal axis of the swing bolt, the hand nut can be made to bear upon the slotted lug bracket, thereby securing the lid of the vessel to the vessel itself. Usually a plurality of swing bolt assemblies is used to provide a secure attachment.

The standard swing bolt assembly is formed from a stainless steel swing bolt and a stainless steel slotted lug bracket, whereas the hand nut is made of Naval brass. As the hand nut is tightened against the stainless steel bracket, considerable wear takes place on the seat of the nut. Very often, the seat of the nut is part-spherical, and is adapted to engage with partspherical recesses in the lug bracket, in order to produce a secure fixing. The wearing of the seat of the brass hand nut has a detrimental effect on the engagement of the nut and the lug bracket, thereby reducing the effectiveness of the fixing. A typical known arrangement is shown in the specification of United Kingdom Patent No. 2098302.

It is an object of the present invention to provide a swing bolt assembly, and a securing nut for a swing bolt assembly, which overcomes or alleviates the above disadvantages.

In accordance with the present invention, a swing bolt assembly for a pressure vessel comprises a swing bolt pivotally mounted to one of the pressure vessel and a lid of the pressure vessel, a lug on the other of the pressure vessel and the lid, and a securing nut threadedly mounted on the bolt and adapted to engage with the lug to secure the lid to the pressure vessel, the securing nut having an annular bearing member mounted on the securing nut for rotation about the axis of rotation of the nut, which bearing member, in a securing position of the securing nut, is disposed between the material of the securing nut and the lug.

In this way, the hand nut can rotate inside the bearing member, with contact over its full bearing face on the bearing member, in contrast to the previous design where the contact on the bearing face of the securing nut is intermittent as a result of the necessary slot in the lug bracket.

In a preferred embodiment, the co-operating portions of the securing nut and the annular bearing member are complementarily shaped, for example part spherical, allowing the securing nut to be rotated easily with respect to the bearing member. In one embodiment, the co-operating portions of the bearing member and the lug are complementari ly shaped, for example part spherical, in order to provide a secure clamping action.

Preferably, the material from which the annular bearing member is formed is harder and/or more wearresistant than the material from which the securing nut is formed. Advantageously, the material of the annular bearing member is of the same hardness and/or wear resistance, as the lug. This may be carried out conveniently by forming the bearing member and the lug from the same material.

The securing nut may be in the form of a hand operable nut, and preferably there are stop means on the swing bolt for preventing the inadvertent removal of the nut from the swing bolt.

The present invention also includes a securing nut adapted to be threadedly mounted on a swing bolt of a swing bolt assembly, and having an annular bearing member mounted on the nut for rotation about the axis of rotation of the nut.

Preferably, the co-operating portions of the bearing member and the securing nut are complementarily shaped, and advantageously are part spherical. The external surface of the bearing member may also be complementarily shaped with the article against which it is adapted to bear.

Preferably, the material of the bearing member is of a harder and/or more wear resistant material than the material from which the nut is made. Preferably, the material of the annular bearing member is of the same hardness and/or wear resistance as the member against which it is to bear, and may advantageously be made of the same material as the member.

The present invention also includes a container fitted with a swing bolt assembly or a securing nut of the present invention.

By way of example only, a specific embodiment of the present invention will now be described, with reference to the accompanying drawings, in which: Fig. 1 is a side view of a pressure vessel and lid fitted with a swing bolt assembly in accordance with the present invention; Fig. 2 is a side elevational cross section through an embodiment of swing bolt assembly in accordance with the present invention; and Figs. 3 and 4 are a cross sectional side elevation and plan view respectively of an annular bearing member forming part of the swing bolt assembly of Fig. 2, before attachment to the assembly.

A pressure vessel comprises a tubular drum 10 (part of which is illustrated in Fig. 1) and a lid 12. The lid is pivotally attached at pivot 14 to the vessel 10, and comprises an inner skin 16 and an outer skin 18.

The central portion of the inner skin is in the form of a flat disc, and is of pressed construction, having a seal groove 20 formed about its circumference, the seal groove 20 accommodating an annular seal 22 which, in use, engages with the upper edge of the vessel. The seal groove 7 has a tapered cross section with its mouth being narrower than the base, and this serves to retain the seal in position.

The outer skin 18 serves as a reinforcing member and is of thicker material than the inner skin. The outer skin is generally domed, but has an outer rim or flange 24 which is disposed generally parallel to the flat circular portion of the inner skin 16. The flange 24 has an annular tubular portion 26 extending perpendicularly to the flange portion 24. The outer skin is also formed by pressing.

The inner skin 16 is spaced from the inner concave surface of the outer skin 18 so as to provide an air space 28 which serves to afford insulating properties to the lid. A threaded swing bolt 30 is pivotally mounted about pivot 32 to the pressure vessel. In practice, there will normally be more than one swing bolt, at equally spaced positions around the periphery, but the pressure vessel and lid described herein is provided with only a single swing bolt. The pivotal axis of the swing bolt is substantially parallel to the flat portion of the inner skin 16 of the lid, and extends almost tangentially to the exterior surface of the vessel. The swing bolt may be pivoted through a right angle, from the vertical position shown in Fig. 1 to a horizontal position in which it extends substantially radially with respect to the longitudinal axis of the pressure vessel 10.

The lid is provided with a securing bracket diametrically opposed to the lid pivot 14. The bracket 34 is in the form of two lugs 36 separated by a slot 38 which is opened radially outwardly. The width of the slot is such that it allows the swing bolt to be pivoted into and out of the vertical position illustrated in Fig. 1 when the lid is in its generally horizontal, closed position. Only a single securing bracket is provided, corresponding to the single swing bolt, but if more swing bolts were provided, a corresponding number of securing brackets would be located on the lid.

The swing bolt is provided with a hand nut 40 which is threadedly mounted on the bolt. When the lid is in its closed position, by pivoting the swing bolt upwardly such that it lies in the slot 38 in between the two lugs 36, the hand nut 40 may then be turned such that the base of the hand nut engages with the lugs, thus keeping the lid securely closed. The hand nut is normally prevented from screwing right off the bolt by means of a washer 41 which is releasably securable to one end of the bolt. The construction of the vessel, apart from the swing bolt assembly, is conventional, and a full description may be found in the specification of United Kingdom Patent No. 2098302.

The construction of the swing bolt assembly is illustrated in more detail in Fig. 2, in which it can be seen that the hand nut is provided with a lower, part spherical engagement portion 42 which is engageable with a complementarily shaped (i.e. part spherical) receiving portion of each of the securing lugs 36. The hand nut, which is made of Naval brass, does not bear directly on the lugs 36, but by means of a bearing member which is disposed between the nut and the lugs.

The bearing member is in the form of a stainless steel annular cup 44 which is rotatably mounted on the part spherical portion of the hand nut 40 about an axis which is coincidental with the rotational axis of the handle. The bearing member is in the form of a captivated cup which actually abuts the lugs 36 of the lug bracket 34, and which is complementarily shaped (i.e. part spherical) to reduce wear and to produce a good locating and securing action.

Referring to Figs. 3 and 4, the construction of the captivated washer is illustrated before attachment to the hand nut. The washer comprises an annular, part spherical portion 46 of internal radius of 1" (2.54 cm) and a tubular, upstanding portion 48 of 0.12" (0.30 cm) extending from the wider end of the part spherical portion 46. A circular aperture 50 of 0.8" (2.03 cm) diameter is formed in the opposite end of the washer.

The washer itself is 0.036" (0.091 cm) thick.

As best seen in Fig. 2, the spherical portion 42 of the hand nut 40 has a maximum diameter which is greater than the diameter of the hand nut in a direction away from the part spherical portion 42, such that an annular recess 52 is formed behind the part spherical portion 42. The undeformed washer is placed around the part spherical portion 42, and the upstanding tubular portion 48 is deformed to lie in the annular recess 52, such that the co-operating spherical surfaces of the hand nut and the washer engage, and the washer and hand nut are relatively rotatable.

The lug bracket 34 and the lugs 36 are commonly made of stainless steel, and when the hand nut is screwed down to close the lid tightly, the part spherical surface 42 of the hand nut rotates inside the cup 44, which is shaped complementarily (i.e. part spherically) with the part spherical portion, thus allowing full face contact on the spherical seat of the hand nut. It should be appreciated that, without the cup 44, the hand nut would bear directly on the stainless steel lugs, and since the hand nut is made of brass, and since the contact of the part spherical seat with the lugs would not be continuous (as a result of the slots 38 between the lugs 36) considerable wear would occur. With the construction of the present invention, the co-operating part spherical seats of the hand nut 40 and the washer 44 allow rotation of the hand nut with respect to the washer when the washer is in fixed contact with respect to the lugs 36. Since there is full contact on the whole of the periphery of the part spherical portion, the wear is greatly reduced as compared with the prior art construction.

The invention is not restricted to the details of the foregoing embodiment. For example, although the swing bolts are shown as being located on the vessel 10 and the securing brackets are on the lid 12, it is possible for the swing bolts to be located on the lid 12 and for the securing brackets to be located on the vessel 10.

Claims

1. A swing bolt assembly for a pressure vessel comprising a swing bolt pivotally mounted to one of the pressure vessel and a lid of the pressure vessel, a lug on the other of the pressure vessel and the lid, and a securing nut threadedly mounted on the bolt and adapted to engage with the lug to secure the lid to the pressure vessel, the securing nut having an annular bearing member mounted on the nut for rotation about the axis of rotation of the nut, which bearing member, in a securing position of the nut, is disposed between the material of the nut and the lug.

2. A swing bolt assembly as claimed in claim 1, wherein the co-operating portions of the bearing member and the securing nut are complementari ly shaped.

3. A swing bolt assembly as claimed in claim 2, wherein the said co-operating portions are part spherical.

4. A swing bolt assembly as claimed in any of claims 1 to 3, wherein the co-operating portions of the bearing member and the lug are complementarily shaped.

5. A swing bolt assembly as claimed in claim 4, wherein the said co-operating portions are part spherical.

6. A swing bolt assembly as claimed in any of claims 1 to 5, wherein the material of the annular bearing member is harder and/or more wear resistant than the material from which the nut is made.

7. A swing bolt assembly as claimed in any of claims 1 to 6, wherein the bearing member is made from material which is of substantially the same hardness and/or wear resistance as the material of the lug.

8. A swing bolt assembly as claimed in claim 7, wherein the bearing member and the lug are of the same material.

9. A swing bolt assembly as claimed in any of the preceding claims, wherein the securing nut comprises a hand-operable nut.

10. A swing bolt assembly as claimed in any of claims 1 to 9, further comprising stop means cn the bolt for preventing inadvertent removal of the nut from the bolt.

11. A securing nut adapted to be threadedly mounted on a bolt of a swing bolt assembly, and having an annular bearing member mounted on the nut for rotation about the axis of the rotation of the nut.

12. A securing nut as claimed in claim 11, wherein the co-operating portions of the bearing member and the securing nut are complementari ly shaped.

13. A securing nut as claimed in claim 12, wherein the said co-operating portions are part spherical.

14. A securing nut as claimed in any of claims 10 to 13, wherein the material from which the bearing member is made is harder and/or more wear resistant than the material from which the nut is made.

15. A securing nut as claimed in any of claims 11 to 14, wherein the material from which the bearing member is made is of the same hardness and/or wear resistance as the member against which it is to bear.

16. A securing nut as claimed in claim 15, wherein the bearing member and the member against which it is to bear are formed from the same material.

17. A securing nut substantially as herein described, with reference to, and as illustrated in, the accompanying drawings.

18. A swing bolt assembly comprising a securing nut as claimed in any of claims 11 to 17.

19. A swing bolt assembly substantially as herein described, with reference to, and as illustrated in, the accompanying drawings.

20. A container comprising a swing bolt assembly as claimed in any of claims 1 to 10, 18 or 19, or comprising a securing nut as claimed in any of claims 11 to 17.