GB2153026A - Clamping for flanged ducts - Google Patents

Abstract

A clamping and sealing system comprising plastics clamping ring (10) for securing and sealing the joint between adjoining peripherally flanged ducts (12, 16 and 14, 18) has a generally V-shaped cross-section provided with a moulded in place or bonded seal (30) which engages the flange rims. A latching feature (36,42) permits the ends of the clamp to be temporarily latched in position to frictionally limit, without preventing, adjustment of the relative angular position of the two adjoining coaxial ducts (12, 14) prior to application of the full clamping force. <IMAGE>

Description

SPECIFICATION Improved clamping and sealing system for flanged ducts and the like The present invention involves the art of connecting and clamping together adjoining lengths of flanged pipes, tubes and ducts, hereafter and in the claiming clauses hereof generally referred to as "ducts". Such connections are commonly employed in a variety of hydraulic and pneumatic systems. The system disclosed herein is particularly well suited for applications where an assured seal is essential, notwithstanding large pressure differentials between the duct interior and exterior, and where preliminary adjustment of the relative angular position of the adjoining ducts about their common axis is desired, even after an initial connection of the ducts.

Duct ends have in the past been commonly formed with peripheral flanges having conical surfaces which taper outwardly toward the end of the duct. O-rings or gaskets have been employed between the abutting flanges of the ducts to be joined, so that when a V-type retainer ring is tightened around the joined ducts, the flanges are wedged and urged toward each other to compress the seal.

An example of this type of prior art connection is the V-retainer coupling manufactured by Voss Industries, Inc. of Cleveland, Ohio. This coupling generally consists of a ring having a V-shaped cross-section, with the legs of the V engaging the conical surfaces of the duct flanges, the V-ring being supplemented by an additional flat band secured to the outer circumference of the ring, that is, to the base of the V-shaped portion. A threaded connection at the ends of the coupling draws the ends together to establish the clamping force. The coupling is fabricated of metal, and the side walls or legs of the V-shaped portion must therefore be interrupted at one or more points around the perimeter to permit the ring to be spread apart during assembly over the duct flanges without buckling or tearing of these legs.This interruption in the continuity of the clamping ring reduces the effectiveness of the clamping pressure against the sealing means in the area of the gap.

The present invention seeks to provide an improved clamping system for flanged ducts which provides an effective and continuous seal around the full periphery of the duct joint, and which provides multiple stages or lines of sealing engagement. It further seeks to provide such a clamping system which can be initially positioned over the adjoining ducts to maintain the ducts in their joined condition prior to final clamping while permitting the ducts to be rotated about their common axis to a desired angular position.

According to the present invention in a system for removably clamping and sealing together the ends of a pair of connecting ducts of circular cross- section wherein each duct end is provided with a peripheral flange which is engageable by a clamping ring adapted to surround the flanges of the ducts to be joined, the ring being shaped and dimensioned to engage the flanges and force them together upon tightening of the clamping ring, the ring being formed with a short circumferential opening to enable it to be resiliently spread apart for assembly over the duct flanges and provided with adjustable securing means to draw together the two ends of the ring at the ring opening to tighten the ring upon the duct flanges to thereby clamp and seal the joint between the pair of ducts, the clamping ring comprising a first end having an undercut recess to receive an integral non-adjustable projection on the second end of the ring, the recess and projection being shaped and positioned so that the projection can be inserted into the recess only by the temporary resilient relative displacement of the first and second ends of the ring in a radial direction, release of the displacement force permitting the first and second ends to return to a position wherein the recess and projection cooperate to form a temporary latch which holds the ends of the ring in a predetermined relative position and prevents the ends from separating in a circumferential direction; the predetermined relative position being selected to provide sufficient clamping force to retain the connected ducts in an unclamped but loosely connected condition while permitting the ducts to be rotated about their common axis for final position adjustment prior to application of full clamping force by the adjustable securing means, which is adapted to draw the two ends of the ring together after the projection and recess have established the temporary latch, thereby to tighten and clamp the ring onto the duct flanges and tightly draw the connecting ducts together.

The clamping ring may be injection moulded from a plastics material such as polyurethane, pheyelene oxide, or polyphenylene sulfide. The clamping ring may be formed with a relatively soft compressible seal which is either moulded in place or bonded to the full inner perimeter of the ring and positioned to engage the outer rim of the duct flanges and, in an alternative embodiment, to additionally engage the conical surfaces of the duct flanges.

One end of the clamping ring may be additionally provided with an undercut recess which receives a projection from the other end to establish a temporary latching position. The seal is turned radially outwardly in such recess and is positioned to be abutted and compressed by the latching projection, to establish a complete uninterrupted seal around the full periphery of the joint.

The invention will now be further described, by way of examples, with reference to the accompanying drawings, in which: Figure 1 is a fragmentary elevational view of two assembled flanged ducts, with a portion of the clamping ring broken away to reveal the flanges; Figure 2 is an enlarged cross-sectional view of the duct flanges and clamping ring, viewed along the direction of line 2-2 of Figure 1; Figure 3 is an enlarged cross-sectional view of the ends of the clamping ring in their latched posi tion, viewed along the direction of line 3-3 of Figure 1; Figure 4 is a fragmentary elevational view, similar to Figure 3, but showing the relationship of the ends of the clamping ring in their as-moulded position; Figure 5 is a fragmentary perspective view of one end of the clamping ring;; Figure 6 is a greatly enlarged cross-sectional view of the latching portion of the clamping ring, similar to part of the view in Figure 3, and Figure 7 is a cross-sectional view of the clamping ring of a modified form of the present invention.

Referring to Figures 1 and 2 of the drawings, clamping ring 10 is shown in assembled position over two adjoining ducts 12 and 14 having periph eral flanges 16, 18 respectively. In the illustrated ducts, the end configuration includes a tapered recess 20 on the end of duct 12 which receives a similarly tapered extension 22 on the end of duct 14. This optional feature provides an additional line of sealing contact, but is not essential to the claimed features of the present invention. Additionally, a seal 24 is shown between the abutting flanges, which seal may be moulded in place on, or bonded to, the flange of one of the ducts.Seal 24 is also an optional feature, to provide an additional line of sealing engagement, which is not essential to the novel clamping ring of the present invention As best shown in Figures 2 and 3, clamping ring 10 is generally in the form of an inverted V, including a base portion 26 and two legs 28. A peripheral seal 30 is located in the root or groove portion of ring 10, and extends around the full perimeter thereof.

One end 32 of ring 10 is formed with an extension 34 (see Figures 3-6) having a radially outwardly projecting lip 36. The other end 38 of clamping ring 10 has a similarly shaped recess 40 to receive extension 34. Recess 40 is formed with an undercut behind latching lip 42, so that a latching function is established when lip 36 is positioned behind lip 42 as shown in Figures 3 and 6.

Extension 34 also has a seal engagement face 44 which is positioned to abut an outwardly turned portion of seal 30 in recess 40 of ring end 38, as will be described hereafter.

A clearance gap 46 (see Figure 6) is maintained between the opposed faces of ring ends 32 and 38, to assure that the two ends do not prematurely "bottom out" prior to the desired compression of the seals.

Chamfers 48 and 50 are provided on the leading edge of latching lip 36 and 42 for a purpose to be explained below.

Clamping ring 10 is preferably formed by injection moulding of a thermoplastic material having physical properties which permit it to resiliently flex in a radial direction as required for assembly over the flanges, while having sufficient tensile strength to resist creep resulting from high clamping forces over an extended period of time. As will be appreciated by those skilled in the art, the specific environment and desired physical properties of a particular application will dictate the final selection of ingredients. Among suitable materials are polyurethane, pheyelene oxide, and polyphenylene sulfide.

Seal 30 may be injection moulded onto the already formed clamping ring 10, or alternatively, may be adhesively or solvent bonded to the ring after separate fabrication of these two components, depending upon the desired physical properties for the intended environment. Suitable materials include those previously listed as appropriate for the clamping ring, plus butyl rubber. As will be appreciated by those skilled in the art, the particular formulation of material for the seal will depend upon the physical properties required in the intended environment.

Referring now to Figure 4, there is fragmentarily shown the end portions of the clamping ring in their as moulded position. By way of example, for an approximately six inch diameter duct, the mould for the ring would be formed so that the end faces of the left and right halves of the ring (as viewed in Figure 4) are inclined at a three degree angle relative to each other, as measured from arc centre 52. This particular configuration permits the ring to be resiliently flexed apart for assembly over the duct flanges, and also to be resiliently latched together in a position (such as shown in Figure 3 and 6) in which the resiliency will tend to retain the clamp in its latched position.

Ring ends 32, 38 are provided with clearance holes 54, 56 respectively (as shown in Figures 3 and 5) to receive a clamping bolt (not illustrated) which will draw the ends together to establish the desired clamping pressure when threaded into steel nut 58 which may be moulded in place.

In use, the clamping ring is resiliently spread apart a sufficient distance to permit it to clear flanges 16 and 18 of the pre-positioned ducts 12, 14. Ring ends 32 and 38 may then be manually pressed together to engage the latch. That is, as the ends 32 and 38 approach each other, chamfer 48 on latching lip 36 will engage chamfer 50 to cam lip 42 radially outwardly to permit lip 36 to pass behind lip 42 to establish the latch, as shown in Figure 6. It will be noted that in the latched position, there is still clearance between seal-engaging face 44 of ring end 32 and the outwardly turned portion of seal 30 in recess 40 of ring end 38. The purpose of the latch and of this clearance is to enable the ducts to be rotated about their common axis after they are preliminarily positioned and retained by clamping ring 10, in the event that it is necessary to establish a predetermined angular relationship between one of the ducts and another connection to be made at the remote end of the illustrated ducts. Once that angular relationship had been established, clamping ring 10 may be tightened by means of a bolt inserted in holes 54, 56 to establish the desired clamping pressure. As shown in Figure 6, clearance gap 46 is greater than the gap between engagement face 44 and seal 30, to assure that sufficient compression of the seal is established prior to a bottoming out condition which would result from premature elimination of gap 46.

The particular dimensions are preferably selected so that with the latch engaged, but prior to tighten- ing of the bolt, enough friction will be established between the two ends of the ducts to normally maintain a pre-selected position of the ducts, while permitting angular adjustment about their common axis, until the bolt is tightened. However, the frictional force is not so great as to cause damage to the seals during such adjustment.

As the clamping bolt is tightened, seal 30 will compress against the cylindrical outer rims of flanges 16, 18 thereby establishing a seal across the gap between the flanges. Another line of sealing contact is established along the engaging conical surfaces of legs 28 and flanges 16, 18. This engagement also serves to wedge the two flanges toward each other. The effectiveness of this action can be enhanced by forming the slope of the inner faces of legs 28 at an angle of approximately onehalf degree closer to vertical than the slope of the conical faces on the duct flanges, thereby increasing the lateral wedging action.

The flexibility and resilience of the disclosed plastic ring materials enables the legs 28 to be continuous, without the relieving gap generally necessary to prevent tearing or buckling of metal rings. This feature permits continuous wedging and sealing pressure around the full flange perimeter.

A modified embodiment of the present invention is illustrated in Figure 7, wherein like parts are identified with prime notations on the reference numerals. Comparing Figure 7 with Figure 2, it will be seen that seal 30' is formed with depending legs positioned to engage the conical surfaces of the abutting ducts. Thus, like seal 30 of the embodiment of Figures 1 to 6, tightening of the clamping ring will tighten the seal against the cylindrical outer rim of flanges 16 and 18, but the seal 30' of the Figure 7 embodiment will additionally engage and seal against the conical surfaces of the flanges.

This invention may be further developed within the scope of the appended claims.

Claims (7)

1. A system for removably clamping and sealing together the ends of a pair of connecting ducts of circular cross-section wherein each duct end is provided with a peripheral flange which is engageable by a clamping ring adapted to surround the flanges of the ducts to be joined, the ring being shaped and dimensioned to engage the flanges and force them together upon tightening of the clamping ring, the ring being formed with a short circumferential opening to enable it to be resiliently spread apart for assembly over the duct flanges and provided with adjustable securing means to draw together the two ends of the ring at the ring opening to tighten the ring upon the duct flanges to thereby clamp and seal the joint between the pair of ducts, wherein the clamping ring comprises a first end having an undercut recess to receive an integral non-adjustable projection on the second end of the ring, the recess and projection being shaped and positioned so that the projection can be inserted into the recess only by the temporary resilient relative displacement of the first and second ends of the ring in a radial direction, release of the displacement force permitting the first and second ends to return to a position wherein the recess and projection co-operate to form a temporary latch which holds the ends of the ring in a predetermined relative position and prevents the ends from separating in a circumferential direction; the predetermined relative position being selected to provide sufficient clamping force to retain the connected ducts in an unclamped but loosely connected condition while permitting the ducts to be rotated about their common axis for final position adjustment prior to application of full clamping force by the adjustable securing means, which is adapted to draw the two ends of the ring together after the projection and recess have established the temporary latch, thereby to tighten and clamp the ring onto the duct flanges and tightly draw the connecting ducts together.

2. A clamping and sealing system as claimed in claim 1, which further comprises a seal formed of relatively resilient compressible material secured to the entire inner circumference of the ring, a terminal portion of the seal at one end of the ring being turned radially outwardly to a position where it is engaged and compressed by the other end of the ring when the ring ends are drawn together by the securing means thereby uninterruptingly to engage the full periphery of the duct flanges.

3. A clamping and sealing system as claimed in claim 1 or 2, wherein the clamping ring has a cross-section of generally V-shaped configuration defining a pair of radially inwardly diverging legs joined at their radially outer ends by a generally cylindrically-shaped base, the clamping ring being shaped and dimensioned so that the legs engage conical surfaces on the duct flanges which slope radially outwardly toward the duct ends, so that tightening of the clamping ring by the adjustable securing means wedges the duct ends toward each other, the legs of the clamping ring being continuous except for the short circumferential opening in the ring.

4. A clamping and sealing system as claimed in claim 1, 2 or 3, which further comprises a seal formed of relatively resilient compressible material secured to the entire inner circumference of the ring and positioned to uninterruptingly engage the full periphery of the duct flanges to seal the duct joint when the clamping ring ends are drawn together by the securing means.

5. A clamping and sealing system as claimed in any one of claims 1 to 4, wherein the clamping ring is injection moulded from a plastics material.

6. A clamping and sealing system as claimed in claim 5, wherein the plastics material is polyurethane, pheyelene oxide or polyphenylene sulfide.

7. Clamping and sealing systems substantially and herein described with reference to and as illustrated in the accompanying drawings.