CA1181781A - Band seal clamp - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An improved band seal clamp for clamping of tubular members is disclosed which features a band-like clamping member having slots formed in its ends for interaction with bolts held rigidly in holes formed in a spacing member disposed between the ends of the clamp. The ends of the band are shaped to define surfaces at an angle with respect to the surface of the tubular members which coact with force bars having corresponding shapes.
Throughbolts fit through the slots in the band, holes in the force bars and the holes in the spacing member, so that upon tightening of the bolts the ends of the band clamp are forced outward, thus exerting a compressive stress on the tubular member.

Description

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This ap~lication rela~es generally to tlle field of clamps for clamping of tubular sections. ~ore particularl~, the invention relates -to a band seal clamp wherein a generally c~lindrical straplike band is clamped around two portions of pipe o$ generall~ circular cross-sectlon, which may be either butted against one another or be sized so that one fits wi-thin the other. Upon tighkening of the clamp a rigid and mechanically strong connection is formed which exerts a radially inward, subtantially uniform force completely aro~lnd the circumference of the tubes.
The prior art is replete with various attempts at solving the problem of clamping two generally cylindrical members, for example tubes or pipes, together. The problem is to provide a clamp which exerts a radially inward force uniformly around the entire circumference of the tubes to be fastened together. ~hile it is relatively straightfor~ard to exert the force over the greater portion of the circumference of the tubes, it is important if a mechanically strong and leak-free connection is to be formed that the force be exerted over the entire circumference of the pipe. To this end, numerous attempts have been made in the prior art to provide rigid pipe couplings; see, far example, United States Patent 494,996 to Dwelle in ~hich rigid hinged members are clamped together to grip the pipe. See also United States Patent

2,227,551 to ~orris which shows clamps having interlocking fingers to be clamped together to exert the force QVer the entire circumference of the tube.
Later ~atentees realized that it would be preerable to use a somewhat flexible band wh~ch would be slightly deformed ~o more closel~ match the contaurs of the pipe to be clamped, thus being more likely to exert the orce uniforml~
araund the entire circumference of the pipe. Into this class fall the patents tQ Cassel et al United States 4,056,273 and United States 3,9Q5,623, as well as

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that to ~oti United States 4,165,109. All these show provision of cla~ps which use a plurality of bolts connecting two ends of a band wrapped around a pair of pipes to be joined and havlng a connection piece i.nterposed therebetween.
Typicall~, the connection piece ls formed wich an axially extending recess formed between the bolt ho].es on both its sides so that upon tightening of the bolts the ends of the band will be deforlned to fit more closely together within the recesses; force bars may be used to spread the orce exerted by tightening the bolts uniformly across the wldth of the clampO In some cases, particularly United States Patent 4,056,273 to Cassel, the shaping member may also be shaped to coact with the outer circumference of the tube so as to exert a radially lnward force thereon by being pulled into the surface of the pipe by the tightening of the bolt~s) simultaneously with deormation of the ends of the band. However, the fact th,at this deformation is required means that the orce exerted upon tightening the bolts is at least partiall~ directed towards this deformation ancl is not useful in achieving the primary object o~ the clamp, that is, to e:xert a generally radiall~ inw.ard force substantially uniformly around the circumference of the tubeO
As ~ill be discussed in further detail below, the present invention is directed at solving this need of the art in that it has as its primar~
ob~ective the provision of an improved band seal clamp for the clamping of tubes together.
The improved band seal cla~p should preferahly provide a substant-ially uniform clamping force exerted radially inwardly about subs~an*ially the entire circumference of the tube, Substantial deformation of the ends of the band is to be avoided upon tightening of the clamp. The band seal clamp can be readily assembled in a "band aid" mode, that is~ ~ithou~ disassembly of pairs of tubes to be clamped; instead, the clamp can be slipped around the tubes ~2~

without their disassembly or without requiring free access from the joint to be clampec~ to one end of the tube.
Summary of the Invention The inventlon provides a band clamp for clamping of one or more tubular memberc;, comprising: an elongated flat strip oE
material adapted to be circumferentially wrapped around said tubu-lar members to be coup].ed and having outwardly extending end por-tions, said end portions having slots extending in the direction of elongation of said strip for interaction with clamping means inserted therethrough; a central shaping and spacing member adapted to be disposed between the end portions of said strip and having holes formed therein for insertion of said clamping means, said holes being so sized as to fit relatively closely with said clamp-ing means, and shaped t:o fit said tubular members to be clamped;
and first and second fc,rce transmitting members adapted to be dis-posed on opposite sidec of said centxal shaping member and of said end portions of said ba~nd, said force transmitting members having holes formed therein fc,r insertion of said clamping means and hav-: ing outwardly extending reaction surfaces formed thereon to inter-act with inwardly exten.ding reaction surfaces formed on the end portions of said band, whereby the slots permit the end portions of said band -to move generally radially outwardly with respect to said tubular members when clamped by said clamping means.
The invention also provides a band seal clamp for clamp-ing one or more tubular members, comprising: a spacing member hav-ing one or more holes formed therein for the inser-tion of generally cylindrical bolts and adapted to space the axes of said bolts a predetermined distance from said tubular members; at least one force har having holes ormed therein for the inse:rtion of said bolts, and having a generally planar surface extending generally axially with respect to said -tubular members and disposed at an angle between about 30'' and about 60 with respect to a plane on a diameter of said tuhular members passing through the center of said spacing member; and a generally strap-like band having Eirst and second end portions having slots formed therein for insertion of said bolts, at least one of said end portions being shaped so as to coact with said surface formed on said force bar, so that upon assembly of said band i.ts end portions are disposed on opposite sides of said spacing member, said force bar is disposed on the same side of said shaped end portion of said bands from said spac-ing member, said shapecl end portion separating said force bar from said spacing member, and said bolts are inserted through said holes in said spacing member, through said force bar and through said slots in said band, such that upon tightening of said bolts, the slots permit the end portions of said band to move in a direction generally radially outwardly from said tubular member, whereby a substantially uniform compressive force is exerted at all points around the circumference of said tubular members covered by said band.
The invention will be better understood if reference is made to the accompanying drawings, in which:
Figure 1 represents an overall perspective view of a exemplary preferred embodiment of a complete connector according to the invention;
Figures 2a-2c represent cross-sectional views of successive stages in the clamping of a tube by the coupling of the ~' '7~;~

invention, taken along the line 2c-2c of Figure l; and Flgures 3a-3c represent comparable cross-sections of a second embodiment of the invention shown at various stages of assembly.
As described above, this invention re:Lates to the pro-vlsion of a -4a-~, band seal clamp for clamping two tubcs togetherO A completed assembly of such a clamp according to the invention is depicted generally in Figure 1 clamping two tubes shown in phantom. The two ~ubes may be butted together or one may slide within the otherO In either case, the objective of the clamp is to exert a substantially uniform compressional force directed radially inwardly on the tubes~ This is done by tightening two bolts 12 which cause the band 10 to tighten generally upon the tubes. The bolts 12 operating in concert with shaped members or force bars 14 cause the overall circumference of the band 10 which is in contact with the tubes to decreasel thus exerting a compressional 10 force on the tubeO This movement is effected by the relative shaping of the force bars 14 with respect to a central shaping member 16 in a manner which will be discussed more fully belowO
Referring now to ~igures 2a through 2c, the sequence of operations leading to clamping of *he tubes by the clamp of the invention is shown. In Figure 2a, a portion of a tube 20 and a section of the band seal clamp 10 of the invention are shown. As wilL be apparentJ the first step in assembly of the clamp is to bring the two ends 22 and 24 of the band together. These ends have down-turned portions 22a and 24a respectively which fit within a groove 26 formed wi~hin the central shaping and spacing member 16. They are retained 20 there by the "spring" of thl3 band, typically formed of formable steel. As noted, the central shaping and spacing member 16 comprises an upper portion 16a and a lower portion 16b which are connected by a thin tongue of material 16c;
one or more holes indicated by dotted lines at 16d are formed in the spacing member 16 for insertion of through bolts 12 (Figure 2b). These holes 16d are shaped to fit bolts 12 relatively closely, as compared with the corresponding holes formed in the band 10 which are instead slotted, to permit movement of the band 10 with respect to the bolts 12 for reasons l~lich will be discussed below.
Referring now to ~'igure 2b, the bolts 12 are shown assembled toget-her ~th the force bars 1~ disposed on either side of the shaping member 16.
A nut 28 is used on the opposite side of the bolt 12 from its head; however, it ~ill be understood that one o the orce bars 14 could b~ threadedl although this would then mean that the~ could not be identical. Similarly, the force bars could be individually fitted ~o the bolts. They could be circular in outline, or elongated as sho~n. Whatever, the shape of these force trans-mitting members, the bolt holes must fit the bolts well enough that the reaction surfaces cannot be rotated out of contact with the band 10. The force bars 1~ are formed to comprise a generall~ semi-circular cross-section which ma~ have a substantially flat face shaped to interact with recesses formed in the cross sectional outline o~ either side of the central shaping and spacing nember 16 and with the band 10 fitting therewithin. As shown in Figure 2b, the initial hole 16d formed for the insertion of the bolt 12 in the shaping and spaclng member 16 is positioned so as that upon assembly of the force bars 14 their semi-circular outline shape does not fit within the semi-circular recesses in the shaping member 16, but instead is disposed some dlstance outwardly along a radial line with respect to the tube 20. The bolts are thus ~0 fixedl~ spaced c.ut~ardly from the tube 20 b~ the shaping member 16. Therefore, upon tightening of the nut 28 ~ith respect to the bolt 12 an unbalanced force ~ill be exerted on the band 10 by the force bars; since the hole 16d in the shaping mem~er 16 fits the bolt 12 closel~ as explalned above, the resultant force exerted tends to separate the upper portion of the shaping member 16a ~rom the lower portion 16bu Since the ends 22 and 24 of the band are held b~
the shaping and spacing member 16~ the upward movement of the upper portion 16a ~6~

with respect to the lower portion 16b o$ the shaping member tends to *ighten the band 10 on the tube 20, Eventually the tongue 16c breaks$ which permits further uplif~ing of the ends of the band; concomitantly, of course, the band is tightened by the relative outwarcl movement of the rigidly fixed end sections indicated generall~ at 22 and 24. A shaping rnember having such a frangible tongue could be made by a process such as ex~rusion, or perhaps by molding.
~owder metallurgy techniques might also be employed.
As shown in Pigure 2c the net effect of tightening the bolts is to move the upper portion 16a ~f the shaping member 16 outwardly with respect to lQ the lower portion 16b; as the ends of the band 22 and 24 are attached to the owter portion 16a, the band 10 is tightened about the tube 20 upon tigh~ening of the nut 28 with respect to the bolt 12.
It will be appreciated by those skilled in the art that this method of tightening the band prov:ldes a relatively limited range of adjustment, which means merely that a given b~md seal clamp will only be use~ul to clamp tubes of a relatively limited range of sizes. Since, however, tubing is manufaGtured only to specific and well-known sizes, this poses no difficul~y but instead provides the advantage of a]lowing the underside of the lower portion of the shaping member 16 to be curved as at 16e so as to fit the tube 20 very closely.
In this ua~ the net force exerted on the tube is relatively uniform around its circumference, being merel~ a function ~f the total force exerted by tightening the nuts 28 on the bolts 12 divided by the area of the band 10 combined with that of the curved surface 16e. By making the wldth of the band equal to the length of the shaping member~ the force exerted ~ill be uniform all the way around the circumference of the clampO
Figures 3a through 3c sho~a second preferred embodiment of the invention. These three figures are all cross-sections taken through one of ~he plurality of bolt holes ~oxmed in the band 10 and in the central spacing member 30 and show how the tightening of the bolt results in relative compression of the tube by the band, ~or exaD~ple, in ~igure 3a the band 10 is shown generally assembled about a central ~lember 30 having one or more holes 32 formed therein.
The hole 32 is sized so as to fit relatively closely with a bolt 34 (Figure 3b) inserted therethrough, while a somewhat wider slot lOa is formed in the band 10. As noted from Figure 3a, the ends of the band 10 may be formed ~o comprise surfaces lOf and making an angle--typically bet~een about 30 and about 60, l~ith respect to a plane on a diameter of the tube and going through the center af the spacing member 30--simply by folding over of its ends, and may thus double the thickness of the band in ~he region of the holes lOa. As noted, the hole lOa is a slot being larger than the hole 32 formed in the central member, so that relative movement of the band with respect to the bolts 34 is posslble~ Referring no~ ~o ~igure 3b, a bolt 34 is shown having been assembled through the slQt lOa and through the hole 32 in the central spacing member 30.
~atching force bars 36 are dispased on opposite sides of the central spacing member and are held in place by the bolt 34 on which is threaded a nut 38. As discussed above, the ends of the band 10 are formed to comprise angled reaction surfaces lOf disposed on either side and awa~ from the central shaping member 3~. These reaction surfaces lOf are adap~ed ~o interact with shaped surfaces on the force bars 36 and are disposed with respect to the slot lQa so that upon assembly of the force bars 36 together with bolt 34 and nut 38 the force bars 36 will only touch the ends of the band 10 at the reaction surfaces lOf~
so that when the nut 38 is tightened on the bolt 34 thus exerting an axial stress on the bolt, the force exerted on the band 10 by the force bars 36 will 3~

be exerted only on the shaping surfaces lOf. Since these surfaces are on the side of the bolt 34 opposite the tube 30, the net effec~ of tightening the bolt 34 will be to pull thls ends of the band 10 together and force them to slide out~ardly past the force bars, thus tightening the band 10 on a tube or pair of tubes about ~hich it is encircled. Clearl~, the interacting surfaces of the band lOf ~nd of the force bars 36, as in the case o~ the embodiment of Figures 1 and 2a-2c need not be simple planes or semicylindersl so long as they form a tangent surface throughout their relative movement. It will furthermore be understood that a plurality of bolts and nuts could be used by axial extensions o the force bars and spacing members, widening the band, and multiplying the holes and slots. Another possibilit~ would be to fill the loop-like structure formed on the ends of the band with an incompressible member such as a rod, to preclude c~llapsing of the loop~ though the passage o the bolt 34 through the slots formed in both the bod~ of the band and in the folded over loop end would largel~ eliminate this possibility.
Further t:ighteni~ng of the nut 38 upon the bolt 3~ results in ~he condition shown in F:igure ;c, where the force bars 36 have bottomed in ~he recesses formed in the end of the band 10 by its bending over to form its ends.
~t ~111 b~ noted that in this embodiment the ends of the band are shaped to provide a reaction surface lOf to interact with the force bars, as opposed t~ the embodiment of Figures 2a-2c, in which the central shaping and spacing member provides the reactian surface. In the embodiment of Figures 3a-3c, the function of member 30 is ch,iefl~ therefore spacing the bolts 34 from the sur-~ace of the tube to be clamlped, and providing shaped surfaces 30a and 30b tFigure 3~ to exert force uniforml~ on the tube and to provide a ~ide radius bend to the band upon tightening of bolts 34 respectivel~. As noted, the shaft `7~

of the bolt 3~ no~ abuts the bottom of the slot lOa formed in the ends of the band lO, as opposed to the position sho~n in ~igure 3b. ~rrows drawn in Figure 3c show the movement o~ the various parts of the clamp according -to -tlle invention, upon tightening of the nut 38 with respect to the bolt 3~.
As discussed abl~ve in connection with Figures 2a through 2c, the amount of tightening provided by the clamp according to the invention is rel-atively limited, which requires that the clamp be chosen to it relatively closely upon the tube prior to assembly. In turn this results in the advantage that the underside 30a of 1he central shaping member 30 can likewise be chosen to fit the tube relativel~ accurately, whereby substantially uniform compres-sional forces are exerted at all points around the circumference of the band on the tube~
It will be appreciated that there has been described a band seal clamp for the clamping of 1:ubes to one another which meets the needs of the art and objects of the inve~ntion described above, although it might also be useful in clamplng a single~ tube, e.g. to clamp a plug over a leak. ~he clamp of the invention is simple and readily and inexpensively manufacturable~ yet exerts a substantially unif`orm compressional force upon tubes clamped thereby.
Moreover, the fact that it relies upon relative movement of the band with respect to the clamping bolts, the positions of whlch are fixed by the central spacing member, as permitte~d by the formation of slots in the ends of the band, rather than upon simple deformation of the band to fit a recess formed in a central shaping member, as shown in the prior art, results in more of the total f'orce being applied to cla~ing and less lost to deformation. Finally, it will be appreciated that while two preferred embodiments of the invention have been descrlbed, numerous other modi~ications and improvements are possible. In particular, the clamp of the invention need not be symmetric; only one en~ of the band need have an angled reaction surface, and only one forcebar need be providedO In some circumstances this might simplify manufacture and/or assembly of the clamp of t:he invention. Therefore, the scope of -the inven-tion should not be measured by the above disclosure) which :is exemplary only, but rather by the following claims.

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Claims (15)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A band clamp for clamping of one or more tubular members, comprising:
an elongated flat strip of material adapted to be circum-ferentially wrapped around said tubular members to be coupled and having outwardly extending end portions, said end portions having slots extending in the direction of elongation of said strip for interaction with clamping means inserted therethrough;
a central shaping and spacing member adapted to be dis-posed between the end portions of said strip and having holes formed therein for insertion of said clamping means, said holes being so sized as to fit relatively closely with said clamping means, and shaped to fit said tubular members to be clamped; and first and second force transmitting members adapted to be disposed on opposite sides of said central shaping member and of said end portions of said band, said force transmitting members having holes formed therein for insertion of said clamping means and having outwardly extending reaction surfaces formed thereon to interact with inwardly extending reaction surfaces formed on the end portions of said band, whereby the slots permit the end por-tions of said band to move generally radially outwardly with respect to said tubular members when clamped by said clamping means.

2. The clamp of claim 1 wherein the material of which said strip is formed is metallic.

3. The clamp of claim 1 wherein said clamping means com-prise a threaded bolt and a nut mating therewith.

4. The clamp of claim 1 wherein the reaction surfaces on the ends of said band are formed by bending the ends of said strip to form a generally loop-like end on said band, whereby reaction surfaces at an angle to the surface of said tubular members are formed.

5. The clamp of claim 1 wherein said reaction surfaces on the ends of said band are defined by shapes formed in said central shaping and spacing member.

6. A band seal clamp for clamping one or more tubular members, comprising:
a spacing member having one or more holes formed therein for the insertion of generally cylindrical bolts and adapted to space the axes of said bolts a predetermined distance from said tubular members;
at least one force bar having holes formed therein for the insertion of said bolts, and having a generally planar surface extending generally axially with respect to said tubular members and disposed at an angle between about 30° and about 60° with respect to a plane on a diameter of said tubular members passing through the center of said spacing member; and a generally strap-like band having first and second end portions having slots formed therein for insertion of said bolts, at least one of said end portions being shaped so as to coact with said surface formed on said force bar, so that upon assembly of said band its end portions are disposed on opposite sides of said spacing member, said force bar is disposed on the same side of said shaped end portion of said bands from said spacing member, said shaped end portion separating said force bar from said spac-ing member, and said bolts are inserted through said holes in said spacing member, through said force bar and through said slots in said band, such that upon tightening of said bolts, the slots per-mit the end portions of said band to move in a direction generally radially outwardly from said tubular member, whereby a substantial-ly uniform compressive force is exerted at all points around the circumference of said tubular members covered by said band.

7. The clamp of claim 6 wherein said slots extend generally radially outwardly with respect to the axis of said tubular members.

8. The clamp of claim 6 wherein said band is formed of a metallic material.

9. The clamp of claim 6 wherein said end of said band shaped to coact with said force bar is formed by bending over the end of said band to define a generally loop-like structure.

10. The clamp of claim 6 wherein the shape of said end of said band shaped to coact with said surface formed on said force bar is defined by a shape formed in said spacing member.

11. A band clamp for clamping of one or more tubular members, comprising:
an elongated flat strip of material adapted to be cir-cumferentially wrapped around said tubular members to be coupled and having slots extending in the direction of elongation of said strip formed in the end portions thereof for interaction with clamping means inserted therethrough;
a central shaping and spacing member adapted to be disposed between the ends of said strip and having holes formed therein for insertion of said clamping means, said holes being so sized as to fit relatively closely with said clamping means, and shaped to fit said tubular members to be clamped; and first and second force transmitting members adapted to be disposed on opposite sides of said central shaping member and of said ends of said band, having holes formed therein for inser-tion of said clamping means and having reaction surfaces extending generally outwardly formed thereon to interact with reaction sur-faces extending generally inwardly formed on the ends of said band, whereby said slots permit the ends of said strip to move generally radially outwardly with respect to said tubular members when clamped by said clamping means.

12. The clamp of claim 11 wherein the material of which said strip is formed is metallic.

13. The clamp of claim 11 wherein said clamping means com-prise a threaded bolt and a nut mating therewith.

14. The clamp of claim 11 wherein the reaction surfaces on the ends of said band are formed by bending the ends of said strip to form a generally loop-like end on said band, whereby reaction surfaces at an angle to the surface of said tubular members are formed.

15. The clamp of claim 11 wherein said reaction surfaces on the ends of said band are defined by shapes formed in said central shaping and spacing member.