Patent Description:
This invention relates to mechanical pipe couplings for joining pipe elements.

Mechanical couplings for joining pipe elements together end-to-end comprise interconnectable segments that are positionable circumferentially surrounding the end portions of co-axially aligned pipe elements. The term "pipe element" is used herein to describe any pipe-like item or component having a pipe-like form. Pipe elements include pipe stock, pipe fittings such as elbows, caps and tees as well as fluid control components such as valves, reducers, strainers, restrictors, pressure regulators and the like. Couplings like that can be found, for example, in <CIT>, <CIT> and <CIT>.

Each mechanical coupling segment comprises a housing having projections which extend inwardly from the housing and engage, for example, the outer surfaces of pipe elements of various configurations including, for example, pipe elements having circumferential grooves. Engagement between the projections and the pipe elements provides mechanical restraint to the joint and ensures that the pipe elements remain coupled even under high internal pressure and external forces. The housings define an annular channel that receives a ring gasket or seal, typically an elastomeric ring which engages the ends of each pipe element and cooperates with the segments and the pipe elements to provide a fluid tight seal. The segments have connection members, typically in the form of lugs which project outwardly from the housings. The lugs are adapted to receive fasteners, such as nuts and bolts, which are adjustably tightenable to draw the segments toward one another.

Mechanical couplings for grooved pipe elements according to the prior art have continuous arcuate projections on the segments that engage the outer surfaces of the pipe elements which they are joining end to end. These arcuate projections are part of the segment structure commonly referred to as the "keys" of the coupling. The keys may engage the outer surface of pipe element in various configurations including, for example, pipe element having circumferential grooves.

The arcuate projections on prior art couplings for grooved pipe elements typically have arcuate surfaces with a radius of curvature that is marginally larger than the radius of curvature of the outer surface of the pipe element within the groove that it is intended to engage. For couplings used with grooved pipe elements, the radii of curvature of the arcuate surfaces are smaller than the radii of curvature of the outer surfaces of the pipe elements outside of the grooves so that the projections fit within and engage the grooves.

Methods of securing pipe elements in end to end relation comprise a sequential installation process when mechanical couplings according to the prior art are used. Typically, the coupling is received by the technician with the segments bolted together and the ring gasket captured within the segments' channels. The technician first disassembles the coupling by unbolting it, removes the ring gasket, lubricates it (if not pre-lubricated) and places it around the ends of the pipe elements to be joined. Installation of the ring gasket often requires that it be lubricated and stretched to accommodate the pipe elements. With the ring gasket in place on both pipe elements, the segments are then placed one at a time straddling the ends of the pipe elements and capturing the ring gasket against them. During placement, the segments engage the gasket, the projections are aligned with the grooves, the bolts are inserted through the lugs, the nuts are threaded onto the bolts and tightened, drawing the coupling segments toward one another, compressing the gasket and engaging the projections within the grooves.

As evident from the previous description, installation of mechanical pipe couplings according to the prior art requires that the technician typically handle at least seven individual piece parts (and more when the coupling has more than two segments), and must totally disassemble and reassemble the coupling. Significant time, effort and expense would be saved if the technician could install a mechanical pipe coupling without first totally disassembling it and then reassembling it, piece by piece.

The invention concerns a coupling for joining pipe elements according to the technical features of independent claim <NUM>. Advantageous embodiments of the invention are disclosed in the dependent claims. An example according to the invention may comprise a plurality of tabs.

In one example embodiment, the spring assembly comprises a first boss projecting from the first end of the first segment and a second boss projecting from the first end of the second segment. The second boss is positioned adjacent to the first boss. A first fulcrum is positioned on the first boss and contacts the second boss. The segments pivot about the first fulcrum. A link extends between and capturing the first and second bosses.

An example embodiment may further comprise a second fulcrum positioned on the second boss. The second fulcrum contacts the first fulcrum.

Another example embodiment comprises a first land positioned contiguous with the first fulcrum on the first boss and a second land positioned contiguous with the second fulcrum on the second boss. The first and second lands are oriented angularly with respect to a plane defining an interface between the first and second segments.

Further by way of example, the coupling may comprise a first head projecting from the first boss and a second head projecting from the second boss. The link engages the first and second heads for retaining the link to the bosses. In an example embodiment the link comprises a ring encircling the first and second bosses.

By way of example the adjustable attachment assembly may comprises a first lug attached to the second end of the first segment. A second lug is attached to the second end of the second segment and is positioned in facing relation with the first lug. Each lug defines a respective hole. A fastener extends between the first and second lugs. The fastener is received within the respective holes. The fastener is adjustable for drawing the segments toward one another against the biasing of the spring assembly.

By way of example, a third channel is positioned between the first and second channels in each of the segments. The third channels extend between the ends of the segments and facing the central space.

In an example embodiment, the teeth are oriented angularly with respect to a line extending radially from an axis arranged coaxially with the central space. In a further example, the at least one tab is oriented perpendicularly to a line extending radially from an axis arranged coaxially with the central space. Further by way of example, the at least one tab is offset from the band toward an axis arranged coaxially with the central space. In a specific example embodiment, the at least one tab projects toward the third channel.

In an example embodiment, a first aperture is positioned in at least one of the segments. The first aperture may be aligned with the first channel and provide a line of sight toward the central space. In an example embodiment the first aperture is positioned between the first and second segments. The first aperture may comprise a trough positioned at an interface between the first and second segments by way of example. A further example comprises a second aperture in at least one of the segments. The second aperture may be aligned with the second channel and provide a line of sight toward the central space. The second aperture may be positioned between the first and second segments and may comprise a trough positioned at an interface between the two segments for example.

In an example embodiment a ring seal is positioned within the third channels. The ring seal has an inner surface sized to receive the pipe elements and an outer surface sized to support the segments in spaced apart relation sufficient to permit insertion of the pipe elements into the central space while the segments are attached to one another. Further by way of example, the retainer bands may be sized to cooperate with the ring seals to support the housing portions in the spaced apart relation.

In another example embodiment, each of the first and second segments comprises first and second shoulders positioned on opposite sides of each of the segments. The shoulders extend lengthwise along the segments and project toward the central space. The shoulders define a channel therebetween. A first arcuate surface is positioned on the first shoulder, and a second arcuate surface is positioned on the second shoulder. The arcuate surfaces face the central space in this example. A plurality of projections may be positioned on each of the first and second arcuate surfaces. The projections project toward the central space. In an example embodiment, the first arcuate surface may have a first radius of curvature and the second arcuate surface may have a second radius of curvature wherein the second radius of curvature is less than the first radius of curvature.

In an example embodiment a ring seal is positioned within the channel. The ring seal has an inner surface sized to receive the pipe elements and an outer surface sized to support the segments in spaced apart relation sufficient to permit insertion of the pipe elements into the central space while the segments are attached to one another.

The invention further encompasses a combination of a preassembled coupling and a first element according to the technical features of claim <NUM>.

In an example embodiment, the coupling comprises first and second segments positioned end to end surrounding a central space for receiving the pipe elements. First and second shoulders are positioned on opposite sides of each of the segments. The shoulders extend lengthwise along the segments and project toward the central space. A first arcuate surface is positioned on the first shoulder. A second arcuate surface is positioned on the second shoulder. The arcuate surfaces face the central space. A spring assembly joins a first end of the first segment to a first end of the second segment. The spring assembly biases the segments away from one another. An adjustable attachment assembly joins a second end of the first segment to a second end of the second segment. The adjustable attachment assembly is adapted to draw the first and second segments toward one another and into engagement with the pipe elements. The first pipe element comprises a rim projecting outwardly from the first pipe element and extending circumferentially. The rim is positioned in spaced relation to an end of the first pipe element. The rim engages the first shoulder and is captured within the central space.

In an example embodiment the rim is defined by a circumferential groove in the first pipe element. In another example embodiment the rim is defined by a circumferential bead which projects radially outwardly from the first pipe element.

In an example embodiment the spring assembly comprises a first boss projecting from the first end of the first segment. A second boss projects from the first end of the second segment and is positioned adjacent to the first boss. A first fulcrum is positioned on the first boss and contacts the second boss. The segments pivot about the first fulcrum. A link extends between and capturing the first and second bosses.

An example embodiment may further comprise a second fulcrum positioned on the second boss. The second fulcrum contacts the first fulcrum. A first land may be positioned contiguous with the first fulcrum on the first boss, and a second land may be positioned contiguous with the second fulcrum on the second boss. The first and second lands are oriented angularly with respect to a plane defining an interface between the first and second segments. In another example embodiment of a combination according to the invention, a first head projects from the first boss, and a second head projects from the second boss. The link engages the first and second heads for retaining the link to the bosses. In an example embodiment the link comprises a ring encircling the first and second bosses.

In an example embodiment of the combination, the adjustable attachment assembly comprises a first lug attached to the second end of the first segment. A second lug is attached to the second end of the second segment and is positioned in facing relation with the first lug. Each lug defines a respective hole. A fastener extends between the first and second lugs. The fastener is received within the respective holes. The fastener is adjustable for drawing the segments toward one another against the biasing of the spring assembly.

In a further example embodiment the combination comprises a channel positioned between the first and second shoulders in each of the segments. The channels extend between the ends of the segments and face the central space. Further by way of example, a ring seal is positioned within the channels. The ring seal has an inner surface sized to receive the pipe elements and an outer surface sized to support the segments in spaced apart relation sufficient to permit insertion of the second pipe element into the central space while the segments are attached to one another and the first pipe element is captured within the central space.

A plurality of projections may be positioned on each of the first and second arcuate surfaces in an example embodiment of the combination. The projections project toward the central space. An example embodiment may further comprise at least one aperture in at least one of the segments. The at least one aperture may be positioned between the first and second segments. In an example embodiment, the at least one aperture comprises a trough positioned at an interface between the first and second segments.

The invention also encompasses a method, according to the method steps of independent claim <NUM>, of assembling the combination of a preassembled coupling and pipe element.

Further by way of example, the method may comprise:.

By way of example, the method may further include supporting the first and second segments in spaced apart relation sufficient to permit insertion of the second pipe element into the central space while capturing the first pipe element within the central space comprises support the segments on a ring seal positioned within a channel positioned between the first and second shoulders in each of the segments.

In an example embodiment, engaging the first end of the first segment with the first end of the second segment to form the spring assembly may comprise:.

Further by way of example, joining the first boss projecting from the first end of the first segment with a second boss projecting from the first end of the second segment using the link may comprise inserting the projections within a ring such that the ring surrounds the bosses.

In another example, attaching the second end of the first segment to the second end of the second segment using the adjustable attachment assembly may comprise attaching a first lug mounted on the second end of the first segment to a second lug mounted on the second end of the second segment using a fastener extending between the first and second lugs.

In an example embodiment for joining the second pipe element to the first pipe element, the example method comprises:.

An example method may further comprise engaging the first and second arcuate surfaces with the first and second pipe elements respectively upon drawing the segments toward one another. An example method may further comprise engaging projections on the first and second arcuate surfaces with the first and second pipe elements respectively upon drawing the segments toward one another.

In an example embodiment, the drawing the segments toward one another using the adjustable attachment assembly may comprise:
tightening a fastener extending between first and second lugs, the first lug being attached to the second end of the first segment, the second lug being attached to the second end of the second segment and positioned in facing relation with the first lug, the fastener being adjustable for drawing the segments toward one another against the biasing of the spring assembly.

By way of example, a method further comprises:.

An example embodiment of a coupling <NUM> according to the invention is shown in <FIG> and <FIG>. Coupling <NUM> is for joining pipe elements and comprises first and second segments <NUM> and <NUM> positioned end to end surrounding a central space <NUM> for receiving the pipe elements. A spring assembly <NUM> joins a first end <NUM> of first segment <NUM> to a first end <NUM> of the second segment <NUM>. The spring assembly <NUM> biases the segments <NUM> and <NUM> away from one another toward or into an open, pre-assembled state shown. When in this open or pre-assembled state, pipe elements can be inserted into the central space <NUM> without disassembling the coupling <NUM> as described below.

The example spring assembly <NUM> shown in <FIG> and <FIG> comprises a first boss <NUM> projecting from the first end <NUM> of the first segment <NUM>, and a second boss <NUM> projecting from the second end <NUM> of the second segment <NUM>. The second boss <NUM> is positioned adjacent to the first boss <NUM>. Bosses <NUM> and <NUM> are cantilevers and thus are substantially responsible for the biasing force of the spring assembly <NUM> as described below. A first fulcrum <NUM> is positioned on the first boss <NUM>, the first fulcrum <NUM> contacting the second boss <NUM> and providing an axis <NUM> about which the segments <NUM> and <NUM> may pivot. In this example embodiment a second fulcrum <NUM> is positioned on the second boss <NUM>. The second fulcrum <NUM> contacts the first fulcrum <NUM> to further define the pivot axis <NUM> about which the segments <NUM> and <NUM> pivot. First and second fulcrums <NUM> and <NUM> are defined in this example embodiment by first and second lands <NUM> and <NUM>. The first and second lands <NUM> and <NUM> are respectively positioned on the first and second bosses <NUM> and <NUM>, the first land <NUM> being contiguous with the first fulcrum <NUM>, and the second land <NUM> being contiguous with the second fulcrum <NUM> (when present). At least the first land <NUM> is oriented angularly with respect to a plane <NUM> comprising the interface between the first and second segments <NUM> and <NUM>. In this example embodiment both the first and second lands <NUM> and <NUM> are angularly oriented with respective orientation angles <NUM>.

A link <NUM> extends between the first and second bosses <NUM> and <NUM>. Link <NUM> captures the bosses, while permitting pivoting motion of the segments <NUM> and <NUM>. In this example the link <NUM> comprises a ring <NUM> which encircles the first and second bosses <NUM> and <NUM>. Ring <NUM> is retained on the bosses <NUM> and <NUM> by engagement with first and second heads <NUM> and <NUM> respectively projecting from the first and second bosses <NUM> and <NUM>. Ring <NUM> and the bosses <NUM> and <NUM> cooperate to provide the spring biasing action of the spring assembly <NUM>. The thickness <NUM> of the ring <NUM>, the distance <NUM> between the fulcrums <NUM> and <NUM> and the point where the bosses <NUM> and <NUM> engage the ring <NUM>, along with the area moment of inertia of the bosses, are parameters which will establish the spring constant of the spring assembly <NUM> and thus determine the amount of force necessary to close the coupling <NUM> and effect a joint. The angular orientation <NUM> of the lands <NUM> and <NUM> and the distance the fastener <NUM> has been tightened each act to set the maximum limit of separation between the segments <NUM> and <NUM>, and the inner diameter <NUM> of the ring <NUM> determines the minimum separation of the segments when supported by an undeformed spring assembly <NUM> as shown in <FIG> and <FIG>. In one embodiment, the angular orientation <NUM> is such that, if the fastener <NUM> is not present (such as during the assembly of the coupling by the manufacturer) bosses <NUM>, <NUM> may be brought near enough together that the inner diameter <NUM> of ring <NUM> will clear heads <NUM>, <NUM>, allowing ring <NUM> to be easily assembled over bosses <NUM>, <NUM>. Subsequent assembly and tightening of fastener <NUM> to a pre-determined distance <NUM> (see <FIG>) acts to separate heads <NUM>, <NUM> sufficient to retain ring <NUM> behind heads <NUM> and <NUM> as described above. The ring inner diameter <NUM> may be sized to hold the segments <NUM> and <NUM> in the open or pre-assembled state sufficient to permit insertion of pipe elements into the central space <NUM>, or the diameter <NUM> may be larger, and permit the segments <NUM> and <NUM> to be supported in the open or pre-assembled state by other elements of the coupling as described below. In this situation the segments <NUM> and <NUM> will have some angular free play as the segments are drawn toward one another to close the coupling, the spring assembly <NUM> not immediately coming into effect upon pivoting of the segments.

Segments <NUM> and <NUM> are drawn toward one another by an adjustable attachment assembly <NUM>. Attachment assembly <NUM> joins the second end <NUM> of the first segment <NUM> to the second end <NUM> of the second segment <NUM>. Attachment assembly <NUM> is adapted to draw the segments <NUM> and <NUM> toward one another and into engagement with the pipe elements as described below. In this example the adjustable attachment assembly <NUM> comprises a first lug <NUM> attached to the second end <NUM> of the first segment <NUM>, and a second lug <NUM> attached to the second end <NUM> of the second segment <NUM>. Each lug <NUM>, <NUM> defines a respective hole <NUM>, <NUM> which receive a fastener <NUM> that extends between the lugs. In this example fastener <NUM> comprises a bolt <NUM> and a nut <NUM>, which, when tightened, draw the segments <NUM> and <NUM> toward one another against the biasing force of the spring assembly <NUM>.

As shown in cross section in <FIG>, each segment <NUM> and <NUM> comprises first and second channels <NUM> and <NUM> respectively positioned on opposite sides <NUM> and <NUM> of each segment. The first and second channels <NUM> and <NUM> extend between the first and second ends <NUM> and <NUM> of the first segment <NUM>, and the first and second ends <NUM> and <NUM> of the second segment <NUM> (see also <FIG>). Channels <NUM> and <NUM> face the central space <NUM>. As shown in detail in <FIG>, each channel <NUM>, <NUM> (channel <NUM> in segment <NUM> being shown) is defined by sidewalls <NUM> and <NUM> positioned in spaced relation to one another. Each channel <NUM>, <NUM> furthermore has first and second floors <NUM> and <NUM> located between sidewalls <NUM> and <NUM>. Floors <NUM> and <NUM> face the central space <NUM> and are arcuate in shape as they extend between the ends <NUM> and <NUM> and <NUM> and <NUM> of the segments <NUM> and <NUM>. As shown in <FIG>, first floor <NUM> is positioned closer to the side <NUM> of segment <NUM> and has a greater radius of curvature <NUM> than the second floor <NUM>, which has a radius of curvature <NUM>. As shown in <FIG>, the channels <NUM> and <NUM> and the arrangement of their floors <NUM> and <NUM> are symmetric about an axis <NUM> extending transversely through the coupling <NUM>.

As further shown in <FIG> and <FIG>, the channels <NUM> and <NUM> each receive a respective retainer <NUM>. Retainer <NUM> is shown in detail in <FIG> and comprises an arcuate band <NUM> having oppositely disposed ends <NUM> and <NUM>. Band <NUM> thus forms a "split ring" which, when compressed radially will deform to a smaller radius of curvature (see <FIG>). In some embodiments, each band <NUM> is sized such that contact between bands <NUM> and the respective segments <NUM> and <NUM> within channels <NUM> and <NUM> allow one or both bands <NUM> to support segments <NUM> and <NUM> in spaced apart relation as shown in <FIG>. A plurality of teeth <NUM> are positioned along one edge <NUM> of band <NUM>. Teeth <NUM> project from band <NUM> toward the central space <NUM>. As shown in <FIG> and <FIG>, teeth <NUM> are oriented angularly toward axis <NUM> with respect to a line <NUM> extending radially from an axis <NUM> arranged coaxially with the central space <NUM>. The angular orientation is advantageous for retaining pipe elements as described below.

As shown in <FIG>, at least one, but in this example embodiment, a plurality of tabs <NUM> are positioned along an edge <NUM> oppositely disposed from edge <NUM>. As shown in <FIG>, the one or more tabs <NUM> are oriented substantially perpendicular to the line <NUM> and are offset from the band <NUM> toward axis <NUM> arranged coaxially with the central space <NUM>. This offset of tabs <NUM> permits them to overlie the second floor <NUM>, and the band <NUM> to overlie the first floor <NUM>, when retainers <NUM> are properly received within respective channels <NUM> and <NUM> as shown in <FIG> and <FIG>. Proper assembly of the retainers <NUM> within the channels <NUM> and <NUM> permits pipe elements to be inserted into a pre-assembled coupling <NUM> as described below. However, as shown in <FIG>, the channels <NUM> and <NUM> (<NUM> shown) and the retainers <NUM> are sized such that if the coupling <NUM> is improperly assembled with the band <NUM> overlying the second floor <NUM> and the tab or tabs <NUM> overlying the first floor <NUM>, the retainer's radius of curvature is smaller and teeth <NUM> effectively prevent insertion of the pipe element into the central space <NUM> with the segments <NUM> and <NUM> in spaced apart relation in the pre-assembled state. This cooperation between the retainer <NUM>, its tabs <NUM>, teeth <NUM>, and the first and second floors <NUM> and <NUM> of channels <NUM> and <NUM> prevent improper assembly of a pipe joint using coupling <NUM>. If the pipe elements could be inserted with the retainer teeth <NUM> facing in the wrong direction (<FIG>) then the teeth will not be self-actuating against forces which would draw or push the pipe element out of the coupling. Thus the retainer would provide reduced mechanical restraint.

As shown in <FIG>, segments <NUM> and <NUM> further comprise a third channel <NUM>. Channel <NUM> is positioned between the first and second channels <NUM> and <NUM> and faces the central space <NUM>. Channel <NUM> receives a ring seal <NUM> which ensures a fluid tight joint. Ring seal <NUM> is formed of a flexible, resilient material such as EPDM or other rubber compounds and has inner surfaces <NUM> sized to receive pipe elements when they are inserted into the central space <NUM> as described below. A pipe stop <NUM> is positioned between inner surfaces <NUM>. The pipe stop projects into the central space <NUM> and limits insertion of pipe elements by engaging the pipe elements when they are inserted into coupling <NUM> to the desired depth. Ring seal <NUM> also has an outer surface <NUM> that may be sized to engage and support the segments <NUM> and <NUM> in spaced apart relation as shown in <FIG> and <FIG>. One or more of the bands <NUM> may also cooperate with the ring seal <NUM> to support the segments <NUM> and <NUM> in spaced apart relation. The separation of the segments <NUM> and <NUM>, when supported by the ring seal <NUM> and/or band or bands <NUM>, is sufficient to permit pipe elements to be inserted into the coupling when it is in its pre-assembled state (<FIG>, <FIG> and <FIG> shows an example channel configuration wherein the second floors <NUM> are positioned between the first floors <NUM> and the third channel <NUM>. In this example the tabs <NUM> project toward the third channel <NUM> when the retainers <NUM> are properly oriented within the coupling <NUM>.

As shown in <FIG>, coupling <NUM> further comprises a first aperture <NUM> in segment <NUM>. In this example embodiment aperture <NUM> is aligned with the first channel <NUM> and provides a line of sight <NUM> toward the central space <NUM>. In this example embodiment, aperture <NUM> is positioned at the interface <NUM> between segments <NUM> and <NUM> and is formed as a trough <NUM> in both segments <NUM> and <NUM>. The troughs <NUM> in each of the segments <NUM> and <NUM> are aligned so that when the segments are drawn into engagement they provide a view toward the central space <NUM> to permit visual confirmation that the retainer is present and that a pipe element is present within the central space and seated at least past the retainer. As shown in <FIG>, a second aperture <NUM> is also positioned in at least one of the segments <NUM> and <NUM>. The second aperture <NUM> is aligned with the second channel <NUM> in this embodiment (see <FIG>) and also provides a line of sight toward central space <NUM>. Again, in the example embodiment <NUM> illustrated, the second aperture <NUM> is positioned between the segments <NUM> and <NUM>. Aperture <NUM> is also formed by troughs <NUM> at the interface <NUM> between the segments <NUM> and <NUM>. The second aperture also permits visual confirmation that a pipe element is present within the central space <NUM>.

As shown in <FIG> and <FIG>, each segment <NUM> and <NUM> also comprises first and second arcuate surfaces <NUM> and <NUM> respectively positioned on sidewalls <NUM> and <NUM>. Arcuate surfaces <NUM> and <NUM> face the central space <NUM> and a plurality of projections <NUM> may be positioned on each arcuate surface <NUM>, <NUM>. Projections <NUM> are arranged in spaced relation to one another along the arcuate surfaces <NUM> and <NUM> and project toward the central space <NUM>. As described below, projections <NUM> engage the pipe elements and increase joint stiffness and accommodate a wider tolerance range on the pipe outer diameter.

When projections <NUM> are forced into engagement with the pipe elements as the segments <NUM> and <NUM> are drawn toward one another they add stiffness to the joint between the coupling <NUM> and the pipe elements upon their engagement with the outer surfaces of the pipe elements. Additionally, the projections <NUM> allow the coupling <NUM> to accommodate a larger pipe outer diameter tolerance in combination with known manufacturing tolerances for coupling <NUM>. When the outer diameter of pipe elements is near the small end of the tolerance range the presence of the projections <NUM> ensures mechanical engagement between the coupling <NUM> and the pipe elements. However, when the pipe diameter is at the large end of the tolerance range the projections will tend to deform the outer surface of the pipe elements locally, and projections <NUM> may also deform. For couplings <NUM> used with plain end pipe elements this is particularly advantageous as plain end couplings are typically designed so that the arcuate surfaces <NUM>, <NUM> (see <FIG>) do not engage the outer surfaces of the pipe elements. This arrangement ensures that the clamping force provided by the fastener <NUM> (see <FIG>) is fully applied to the retainers <NUM>. Were the arcuate surfaces <NUM>, <NUM> of the coupling <NUM> to engage the pipe outer surface directly, the clamping force would be divided between contact of the arcuate surfaces with the pipe and contact between the retainers <NUM> and the pipe elements. Because the surface areas of projections <NUM> are small relative to the arcuate surfaces <NUM>, <NUM>, and contact the pipe element outer surface only at discrete points, only minimal clamping force from the fastener <NUM> needs to be diverted into contact between the projections <NUM> and the pipe elements to provide enhanced stiffness without compromising the axial retention provided by the retainers <NUM>. Projections <NUM> are advantageous in that they achieve greater rigidity even with the lesser clamping force available with the single fastener design of the coupling <NUM>. The single fastener <NUM> acts in conjunction with the spring assembly <NUM> to ensure that adequate clamping force is applied to the pipe elements.

Operation of coupling <NUM> is illustrated in <FIG>, <FIG>, <FIG> and <FIG>. With the coupling <NUM> in the pre-assembled state as shown in <FIG> and <FIG>, pipe elements <NUM> and <NUM> are inserted into the central space <NUM>. The pipe elements clear the teeth <NUM> of retainers <NUM>, engage and the inner surfaces <NUM> of ring seal <NUM>, and engage the pipe stop <NUM>. Next, the fastener <NUM> is tightened (see also <FIG>) drawing the segments <NUM> and <NUM> toward one another. As shown in <FIG> the ring seal <NUM> and the teeth <NUM> are compressed between the segments <NUM> and <NUM> and the pipe elements <NUM> and <NUM>. Pivoting motion of the segments about fulcrums <NUM> and <NUM> (see <FIG>) is resisted by the biasing force of the spring assembly <NUM>. As shown in <FIG>, the elements comprising the spring assembly, in this example, the bosses <NUM> and <NUM> and the ring <NUM>, deform in proportion to the spring force, with the ring <NUM> extending into an oval shape and the bosses <NUM> and <NUM> bending as cantilevers (deformed shapes shown in solid line, undeformed in broken line). Apertures <NUM>, <NUM> may be used to visually confirm that the pipe elements are present in the coupling <NUM>.

<FIG> shows an exploded view, and <FIG> shows an assembled view, of a preassembled combination coupling and pipe element <NUM> according to the invention. The combination coupling and pipe element <NUM> comprises a coupling <NUM> and a first pipe element <NUM>, and is used to couple a second pipe element <NUM> to the first pipe element (see <FIG> and <FIG>). The second pipe element <NUM> may, for example, be part of a piping network (not shown), and the first pipe element <NUM> may be part of another assembly, such as a flexible hose for a fire suppression sprinkler, or an inlet or and outlet of a pump or a valve to cite a few examples.

The coupling <NUM> comprises first and second segments <NUM> and <NUM> positioned end to end surrounding a central space <NUM> for receiving pipe elements. A spring assembly <NUM> and an adjustable attachment assembly <NUM>, as described above for coupling <NUM>, join the ends of the segments. Coupling <NUM> further comprises first and second shoulders <NUM> and <NUM> (see also <FIG>) positioned on opposite sides <NUM>, <NUM> of each segment <NUM> and <NUM>. Shoulders <NUM> and <NUM> extend lengthwise along the segments <NUM> and <NUM> and project toward the central space <NUM>. Shoulders <NUM> and <NUM> define a channel <NUM> which extends between the ends of the segments <NUM> and <NUM> and faces central space <NUM>. Channel <NUM> receives a ring seal <NUM> for a fluid tight joint. Ring seal <NUM> has an inner surface <NUM> sized to receive pipe elements (see also <FIG>) and an outer surface <NUM> which may be sized to support the segments <NUM> and <NUM> in the preassembled state, i.e., in spaced relation sufficient to insert the second pipe element <NUM> into the central space <NUM> without disassembling the combination <NUM>. <FIG> shows the coupling in the preassembled state with the segments <NUM> and <NUM> in spaced relation. As described above for coupling <NUM>, the spring assembly <NUM> may also be used to bias the segments <NUM> and <NUM> into the open, preassembled state shown in <FIG>. Ring seal <NUM> may also comprise a pipe stop <NUM> positioned between the inner surfaces <NUM>. Pipe elements inserted into the central space engage the pipe stop <NUM> when properly seated (see <FIG>).

As shown in <FIG> and <FIG>, each segment <NUM> and <NUM> further comprises a first arcuate surface <NUM> positioned on the first shoulder <NUM> and a second arcuate surface <NUM> positioned on the second shoulder <NUM>. Arcuate surfaces <NUM> and <NUM> face the central space <NUM>. A plurality of projections <NUM> may be positioned on the arcuate surfaces <NUM> and <NUM>. Projections <NUM> are arranged in spaced relation to one another along the arcuate surfaces <NUM> and <NUM> and project toward the central space <NUM>. Projections <NUM> engage the pipe elements and increase joint stiffness and accommodate a wider tolerance range on the pipe outer diameter. As shown in <FIG>, the coupling <NUM> may have at least one aperture <NUM> in one of the segments <NUM>, <NUM>. In this example the aperture <NUM> comprises a trough <NUM> positioned at an interface between the first and second segments <NUM> and <NUM>.

As shown in <FIG>, the first pipe element <NUM> comprises a rim <NUM> which projects outwardly from the first pipe element and extends circumferentially around. Rim <NUM> is positioned in spaced relation to an end <NUM> of the first pipe element <NUM>, and as shown in <FIG> and <FIG>, is captured within the central space <NUM> by engagement with the shoulder <NUM>.

Rim <NUM> may be defined by a circumferential groove <NUM> in the first pipe element <NUM>, or a circumferential bead <NUM> which projects radially outwardly from the first pipe element <NUM>. In the example embodiment shown in <FIG>, the rim <NUM> is defined by both the groove <NUM> and the bead <NUM>.

The preassembled combination coupling and pipe element <NUM> shown in <FIG> in its preassembled state is assembled as illustrated in <FIG> and <FIG>. The first pipe element <NUM> is engaged with the ring seal <NUM>. The ring seal <NUM> is then positioned within the channel <NUM> of the first segment <NUM> while the rim <NUM> is engaged with the first shoulder <NUM> within what will become the central space <NUM>. Next the spring assembly <NUM> is formed by engaging the first end <NUM> of the first segment <NUM> with the first end <NUM> of the second segment <NUM>. In the example shown, engagement of the first ends <NUM> and <NUM> is effected by joining a first boss <NUM> projecting from the first end <NUM> of the first segment <NUM> with a second boss <NUM> projecting from the first end <NUM> of the second segment <NUM> and pivotably linking them together using a link <NUM>. In this example the link <NUM> comprises a ring <NUM> into which the bosses <NUM> and <NUM> are inserted, each boss having a respective head <NUM>, <NUM> which retain the bosses within the ring <NUM> when the segments are pivoted into the preassembled state. As shown in <FIG>, the second boss <NUM> is contacted by a fulcrum <NUM> on the first boss <NUM>, and the first boss <NUM> is contacted by a fulcrum <NUM> on the second boss <NUM>. The bosses <NUM> and <NUM> joined by the ring <NUM> act as cantilever springs which bias the segments <NUM> and <NUM> away from one another and can also be used to support the segments in spaced apart relation, either alone or in combination with the ring seal <NUM> as described above. Next the second end <NUM> of the first segment <NUM> is attached to the second end <NUM> of the second segment <NUM> using the adjustable attachment assembly <NUM>. In this example embodiment the adjustable attachment assembly comprises a first lug <NUM> mounted on the second end <NUM> of the first segment <NUM>, a second lug <NUM> mounted on the second end <NUM> of the second segment <NUM>, and a fastener <NUM> extending between the first and second lugs.

Working together with the spring assembly <NUM> (and/or the ring seal <NUM>), initial tightening of the fastener <NUM> holds the segments <NUM> and <NUM> in the preassembled state shown in <FIG> and <FIG>. In this configuration the segments <NUM>, <NUM> are supported in spaced apart relation sufficient to permit the second pipe element <NUM> to be inserted into the central space <NUM> (see <FIG>) while also capturing the first pipe element <NUM> by engagement between the shoulder <NUM> and the rim <NUM>. As shown in <FIG>, the projections <NUM> increase the ability of the segments <NUM>, <NUM> to retain the first pipe element <NUM> when the combination <NUM> is in the preassembled state.

<FIG> and <FIG> illustrate use of the combination <NUM> to join pipe elements <NUM> and <NUM>. As shown in <FIG>, with the combination <NUM> in the preassembled state the second pipe element <NUM> is inserted into the central space <NUM>. Upon insertion the second pipe element <NUM> engages with surface <NUM> on the ring seal <NUM> (the first pipe element <NUM> is similarly engaged with the ring seal). As shown in <FIG>, the segments are then drawn toward one another using the adjustable attachment assembly <NUM>. In this example the fastener <NUM> is tightened, drawing the segments <NUM> and <NUM> against the biasing force of the spring assembly <NUM> (see <FIG>) and compressing the ring seal <NUM> to form a fluid tight joint. If projections <NUM> are present they engage the pipe elements <NUM>, <NUM>, otherwise, the arcuate surfaces <NUM> and <NUM> engage the pipe elements. <FIG> shows the arcuate surface <NUM> engaging a groove <NUM> in the second pipe element <NUM>.

<FIG> shows an embodiment of the preassembled combination <NUM> wherein the first arcuate surface <NUM> has a first radius of curvature <NUM> and the second arcuate surface <NUM> has a second radius of curvature <NUM>. In this example embodiment the second radius of curvature <NUM> is less than the first radius of curvature <NUM>. This configuration of radii is appropriate when rim <NUM> of the first pipe element is defined by a groove <NUM> because it permits the first pipe element <NUM> to be captured by coupling <NUM> when it is in the preassembled state, while allowing the second pipe element <NUM> to be inserted into the central space <NUM> without disassembling the coupling. The groove <NUM> in the first pipe element <NUM> may be deeper than the groove <NUM> in the second pipe element <NUM> to accommodate this embodiment.

The use of the combination <NUM> having a single fastener <NUM> and a captured pipe element <NUM> provides significant advantage by increasing the stability of the coupling on the pipe elements through engagement between the coupling shoulder and the rim of the pipe element. The presence of the spring assembly and single fastener significantly inhibit the ability to manipulate the coupling by rocking it, making it much more difficult to separate the pipe element from the coupling. The single fastener also simplifies the tightening step, as only one fastener need be tightened, as opposed to two fasteners, which must be tightened in an alternating sequence to avoid damage to the ring seal.

Claim 1:
A coupling (<NUM>) for joining pipe elements, said coupling comprising:
• first and second segments (<NUM>, <NUM>) positioned end to end surrounding a central space (<NUM>) for receiving said pipe elements;
• a spring assembly (<NUM>) joining a first end of said first segment to a first end of said second segment (<NUM>), said spring assembly biasing said segments (<NUM>,<NUM>) away from one another; and
• an adjustable attachment assembly (<NUM>) joining a second end (<NUM>) of said first segment (<NUM>) to a second end (<NUM>) of said second segment (<NUM>), said adjustable attachment assembly (<NUM>) adapted to draw said first and second segments (<NUM>,<NUM>) toward one another and into engagement with said pipe elements,
• wherein each of said first and second segments comprises:
first and second channels (<NUM>, <NUM>) positioned on opposite sides of said segments, each of said channels extending between said ends of said segments and having a first floor (<NUM>) and a second floor (<NUM>) facing said central space, said first floor having a greater radius of curvature than said second floor;
first and second retainers (<NUM>) positioned respectively in said first and second channels, each of said retainers comprising a band (<NUM>) having oppositely disposed ends, a plurality of teeth (<NUM>) being positioned along one edge of said band and projecting toward said central space, at least one tab being positioned along an opposite edge of said band, said band overlying said first floor, said at least one tab overlying said second floor when said retainers are positioned within said channels [claim <NUM>].