Threadless Coupling Report3

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1. Introduction To Couplings

A coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power. Couplings do not normally allow disconnection of shafts during operation, however there are torque limiting couplings which can slip or disconnect when some torque limit is exceeded.[3]

The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end movement or both. By careful selection, installation and maintenance of couplings, substantial savings can be made in reduced maintenance costs and downtime. [3]

Couplings are fittings used to join two or more lengths of pipe in a straight run. If the material and size of the pipes being joined are not the same, the fitting may be called a 'reducing coupling' or reducer, or an adapter. The term 'expander' is not used for a coupling that increases pipe size; instead 'reducer' is used. [3]

Couplings for copper pipe are available either with or without a stop. The stop is in the center of the coupling and is useful for ensuring that the coupling is centered between the two pipes being connected. The disadvantage of a stopped coupling is that in some repair situations it may be necessary to slide the coupling completely on to one pipe and then slide it back when the pipes being joined are in position. The type of coupling that doesn't have a stop is referred to as a repair coupling. Repair couplings are available in longer than standard lengths to facilitate the repair of a short length of pipe. [3]

The primary purpose of couplings is to join two pieces of rotating/not equipment while permitting some degree of misalignment or end movement or both. By careful selection, installation and maintenance of couplings, substantial savings can be made in reduced maintenance costs and downtime. [3]

Fig. 1-Simple Threaded Coupling[3]

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1.1 Uses of Couplings:

Shaft couplings are used in machinery for several purposes, the most common of which are the following. [3]

To provide for the connection of shafts of units that are manufactured separately such as a motor and generator and to provide for disconnection for repairs or alterations.

To provide for misalignment of the shafts or to introduce mechanical flexibility. To reduce the transmission of shock loads from one shaft to another. To introduce protection against overloads. To alter the vibration characteristics of rotating units.

1.2 Requirements of good shaft alignment / good coupling setup: [3]

It should be easy to connect or disconnect the coupling. It does allow some misalignment between the two adjacent shaft rotation axes. It is the goal to minimize the remaining misalignment in running operation to

maximize power transmission and to maximize machine runtime (coupling and bearing and sealing lifetime).

It should have no projecting parts. It is recommended to use manufacturer's alignment target values to set up the

machine train to a defined non-zero alignment, due to the fact that later when the machine is at operation temperature the alignment condition is perfect.

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2. Types Of Couplings

In the industrial field types of couplings used. Some of them are described below:

a) Threadless Coupling:A threadless coupling for pipes has a cylindrical coupling body having longitudinally-extending slots or sections along the entire length thereof, a pair of grip sections forming grooves facing oppositely from each other on the outside of the edges of both ends of the opening section of the coupling body, and a grip case which is slidable fitted for coupling on the pair of grip sections.[2]

Fig. 2-Threadless Couplings[2]

b) Diaphragm Coupling:Diaphragm couplings transmit torque from the outside diameter of a flexible plate to the inside diameter, across the spool or spacer piece, and then from inside to outside diameter. The deforming of a plate or series of plates from I.D. to O.D accomplishes the misalignment.[4]

Fig. 3-Diaphragm Coupling[4]

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c) Flexible Coupling:Flexible couplings are used to transmit torque from one shaft to another when the two shafts are slightly misaligned. Flexible couplings can accommodate varying degrees of misalignment up to 3°. In addition to allowing for misalignment, flexible couplings can also be used for vibration damping or noise reduction. Flexible couplings are designed to transmit torque while permitting some radial, axial, and angular misalignment. Flexible couplings can accommodate angular misalignment up to a few degrees and some parallel misalignment. [4]

Fig. 4-Flexible Coupling[4]

d) Beam Coupling:A beam coupling, also known as helical coupling, is a flexible coupling for transmitting torque between two shafts while allowing for angular misalignment, parallel offset and even axial motion, of one shaft relative to the other. This design utilizes a single piece of material and becomes flexible by removal of material along a spiral path resulting in a curved flexible beam of helical shape. Since it is made from a single piece of material, the Beam Style coupling does not exhibit the backlash found in some multi-piece couplings. Another advantage of being an all machined coupling is the possibility to incorporate features into the final product while still keep the single piece integrity. [3]

Fig. 5-Beam Coupling[3]

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e) Disc Coupling:Disc couplings transmit torque from a driving to a driven bolt tangentially on a common bolt circle. Torque is transmitted between the bolts through a series of thin, stainless steel discs assembled in a pack. Misalignment is accomplished by deforming of the material between the bolts.

f) Gear Coupling:A gear coupling is a mechanical device for transmitting that are not collinearjoints are connected by a third shaft, called the spindle.

Fig.

Disc couplings transmit torque from a driving to a driven bolt tangentially on a common bolt circle. Torque is transmitted between the bolts through a series of thin, stainless steel discs assembled in a pack. Misalignment is accomplished by deforming of the material between the bolts. [4]

Fig. 6-Disc Coupling[4]

is a mechanical device for transmitting torque between two shafts collinear. It consists of a flexible joint fixed to each shaft. The two

oints are connected by a third shaft, called the spindle. [4]

Fig. 7-Gear Coupling[4]

Disc couplings transmit torque from a driving to a driven bolt tangentially on a common bolt circle. Torque is transmitted between the bolts through a series of thin, stainless steel discs assembled in a pack. Misalignment is accomplished by

between two shafts . It consists of a flexible joint fixed to each shaft. The two

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g) Oldham Coupling:An Oldham coupling has three discs, one coupled to the input, one coupled to the output, and a middle disc that is joined to the first two by tongue and groove. The tongue and groove on one side is perpendicular to the tongue and groove on the other. The middle disc rotates around its center at the same speed as the input and output shafts. Its center traces a circular orbit, twice per rotation, around the midpoint between input and output shafts. Often springs are used to reduce backlash of the mechanism. An advantage to this type of coupling, as compared to two universal joints, is its compact size. The coupler is named for John Oldhamwho invented it in Ireland, in 1821, to solve a paddle placement problem in a paddle steamer design. [3]

Fig. 8-Oldham Coupling[3]

h) Rag-Joint Coupling:Rag joint Couplings are commonly used on automotive steering linkages and drive trains. When used on a drive train they are sometimes known as giubos. [3]

Fig. 9-Rag Joint Coupling[3]

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i) Rigid Coupling:A rigid coupling is a unit of hardware used to join two shafts within a motor or mechanical system. It may be used to connect two separate systems, such as a motor and a generator, or to repair a connection within a single system. A rigid coupling may also be added between shafts to reduce shock and wear at the point where the shafts meet. [3]

Fig. 10-Rigid Coupling[3]

j) Universal-Joint Coupling:

An universal joint is named after the style of coupler used to create the joint. Shafts involved are fitting with a "U" style of coupler that is connected by an "X" member (U joint) with bearing on each of the four ends. These bearings allow the "U" joint to operate under extreme load. Grease is used to lubricate the joint they can either be installed by a pressurized grease gun or by the manufacturer when the universal joint is assembled. This joint allows the shafts to be connected while axis's pivots change, for example: when suspension operation occurs. A typical "U" joint has grease seals on each bearing cap so a boot is not needed like a CV joint. A "U" joint is much like the CV joint in that it doesn't require service unless fitted with a zirk fitting meant to allow grease to be inserted. Universal joints are also known as Cardan joints. [4]

Fig. 11-Universal Joint Coupling[4]

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k) Bellows Coupling:Bellows couplings have been a mainstay for efficient motion systems because they offer high torsional stiffness, low moment of inertia, and minimal restoring forces under misalignment. They may help maintain tight control over loads, which is especially critical when considering that the flexible coupling often represents the point of least stiffness in an electromechanical system. In this way, couplings have a significant effect on the stability of the entire system, as well as the positional accuracy of the load. Bellows couplings benefits include misalignment compensation paired with precise transmission of velocity, angular positioning, and torque. [3]

Fig. 12-Bellows Coupling[3]

l) Elastomeric Coupling:An elastomeric coupling for a rotating shaft includes a driving yoke, a driven yoke, and a substantially circular elastomeric body having a circumferential face and first and second sets of bushings within the elastomeric body. The bushings have threaded openings exposed at the circumferential face. A plurality of fasteners secures the driving yoke to the first set of bushings and secures the driven yoke to the second set of bushings. A plurality of tensile members are located within the elastomeric body, with the tensile members connecting the first set of bushings to the second set of bushings. [4]

Fig. 13-Elastomeric Coupling[4]

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m) Bushed Pin Coupling:These are designed for lower stresses on the rubber bushes and pins. Greater flexibility and life compared to other types of pin bush couplings is assured. The standard range covers torque rating upto 1000 kg. M. [4]

Fig. 14-Bushed Pin Coupling[4]

n) Donut Coupling:These couplings rely on two mechanically independent coupling components to compensate for shaft misalignment. The design does not depend on a material flexible element or a mechanically flexible connection between driver and load shafts; instead, shaft misalignment is accommodated by an air gap that separates both shafts. [3]

Fig. 15-Donut Coupling[3]

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o) Spider or jaw coupling (or lovejoy coupling): [4]

Flexible insert caters for incidental angular, parallel and axial misalignment. Absorbs shock loads and damps small amplitude vibration. Insert design presets correct distance between hubs, using raised pads on each leg of the insert. Available in a range of stock bore sizes. Can also be supplied with finished bore & key way. Unaffected by moisture, grease and oils-including non-aromatic and non-ketone solvents and temperatures with in range – 40°C to +100° C. Spacer coupling with spacer size depending upon the distance between two shaft ends (DBSE).

Fig. 16-Spider Coupling[4]

p) Geislinger Coupling:The Carbotorq is a torsional elastic coupling, that combines advanced composite and silicone elastomer. It is an extremely lightweight coupling which not only dampens the torsional vibrations of the drive line, but also compensates for axial, angular and radial misalignments. The patented Carbotorq consists of an elastic silicone element and two advanced composite membranes. [4]

Fig. 17-Geislinger Coupling[4]

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q) Resilient Coupling:Hi–torque type resilient couplings are in use in all types of industrial applications over many years with success. Such a resilient coupling comprises mainly two hubs, grid spring and covers to protect the spring. The grid spring element is so designed that it provides required resiliency for variable flexibility of a coupling and considerable damping properties making the coupling very suitable for drives involving high shock loads to the extent of 80%. Misalignment that inevitably occurs between rotating shafts, which are independently supported, is also taken care of by the spring element within allowable limits. [4]

Fig. 18-Resilient Coupling[4]

r) Roller Chain And Sprocjet Coupling:A sprocket is defined to include added chordal pitch reduction when in a new or “as-manufactured” condition. The sprocket chordal pitch Ps′ is purposefully reduced as compared to the as-built chain pitch Pc (or a theoretical maximum sprocket chordal pitch) a select amount referred to herein as “added chordal pitch reduction.” This added chordal pitch reduction is in addition to the inherent chordal pitch reduction that exists owing to manufacturing tolerances. [4]

Fig. 19-Roller Chain & Sprocjet Coupling[4]

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3. Threadless Coupling

A threadless coupling for pipes has a cylindrical coupling body having longitudinally-extending slots or sections along the entire length thereof, a pair of grip sections forming grooves facing oppositely from each other on the outside of the edges of both ends of the opening section of the coupling body, and a grip case which is slidable fitted for coupling on the pair of grip sections. The grip case is tapped with a hammer of the like to slide onto the pair of grip sections, thereby compressing the coupling body around the conduits to be coupled by decreasing the gap between the pair of grip sections and accordingly reducing the diameter of the coupling body. [2]

3.1 Background Of The Invention: [2]

1. Field of the Invention

The present invention relates to improvements in threadless couplings for pipes for connecting steel or plastic pipes such as electrical conduits, water-service pipes, steam pipes, and plant pipes.

2. Description of the Prior Art

In so-called electrical conduit laying operations for laying conduits in which insulated electrical wires or cables are placed, couplings are used to connect conduits of a fixed length, the number of which is determined by the length of piping to be laid. A coupling in conventional use comprises a tubular coupling provided with internal threads which is connected by screwing on to an externally threaded end of a conduit. This type of screw-on coupling is unusable when a pair of curved or bent conduits need to be connected. This is due to the fact that the connecting operation must be typically held in a narrow place and at least one of the conduits to be connected must have sufficient room to allow it to be rotated and screwed onto the other conduit.

Fig. 20: Compression on Coupling[2]

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To obviate this inconvenience, threadless couplings capable of connection without rotating the conduit have been in use. A prior-art threadless coupling for thin-steel conduits which is specified in the Japanese Industrial Standards (JIS). This coupling gives rise to the following problems: the tightening of the tightening screws is time consuming, resulting in a poor operation efficiency; threads of the tightening screws are often likely to be stripped or crushed; and the conduits, being fastened at two points by the tightening screws, cannot be maintained straight.

A threadless coupling has also been used for connection of gas pipes, water-service pipes, and conduits. This threadless coupling has a cylindrical coupling body, a pipe stopper at the center of its inner periphery and external threads on the outer periphery of both of its ends, a pair of rubber rings, a pair of metal cut rings, and a pair of cap nuts for pressing the rubber rings and the cut rings against the end of the couplingbody.

When this threadless coupling is used to connect electrical conduits, first the cap nuts, the cut rings and the rubber rings are inserted (in the order recited) over the ends of both of the conduits. Then the ends of the conduits are inserted into the coupling body such that these ends will be butted. Finally, the cap nuts 8 are tightened such that the cut rings and the rubber rings are pressed against both ends of the coupling body and deflected inwardly into contact with the conduits.

However, this type of coupling has a complicated construction and, therefore, requires a high manufacturing cost. Also, the connection of this coupling requires the assembling and tightening of many parts by specific procedures, which is also time consuming, thus resulting in a low operational efficiency.

Furthermore, a prior-art threadless coupling has been proposed in a Japanese utility model application. This threadless coupling has a cylindrical body formed in a cylindrical shape from a flat square metal-plate having opposite edge sections which can be brought close to each other. In these opposite edge sections of the cylindrical body are formed hook-like engaging sections and which are engageable with each other. In the inner peripheral surface of this cylindrical body, two projections are formed to bite the conduits to effect fastening.

When the conduits are connected, the conduits are inserted as deep into the central section of the cylindrical body from the opposite ends thereof. Then the cylindrical body is closed until the engaging sections are engaged with each other.

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3.2 Summary Of The Invention:

It is, therefore, an object of the present invention to provide a pipe coupling which solves the above-mentioned problems. [2]

It is a particular object of the present invention to provide threadless coupling for pipes capable of improving pipe connecting operational efficiency. [2]

It is a more particular object of the present invention to provide an air-tight sealed inner cylinder for a threadless coupling capable of improving air tightness and capable of easy and facile installation in the threadless coupling. [2]

According to the present invention, the threadless coupling comprises a coupling body having an opening which is open throughout its full length parallel to the axis of the coupling body and formed into a cylindrical form; a pair of groove-like grips face opposite one another, outwardly of both ends of the opening of the coupling body; and a grip case which is slidable fitted for connection in the pair of grip sections. The grip case is slid to be fitted to the pair of grip sections by tapping with a hammer, reducing the distance between the grip sections and, in turn, decreasing the diameter of the coupling body to compress the coupling body to the pipes, and thereby improving the work efficiency of pipe connection. [1]

Furthermore, according to a further embodiment of the present invention, an air-tight inner cylinder for a threadless coupling if provided which is formed into a cylindrical shape and is made of resilient material. The inner cylinder is intended to be installed in close fitting contact with the inner surface of the coupling body of the threadless coupling. Annular projections which serve as stoppers are integrally formed at both outer end surfaces of the inner cylinder. A linear projection defining an engaging portion is disposed parallel to the longitudinal axis of the inner cylinder and is integrally formed on its outer surface. An annular central stopper or projection is integrally formed on a central part of the inner surface of the cylinder. Air-tight reinforcing portions of annular projections are integrally formed on the inner surface at both sides of the center stopper, respectively, and a reinforcing plate is encased within the engaging portion. With this arrangement, the outer surface of the air-tight inner cylinder is press-contacted with the inner surface of the coupling body and the air-tight reinforcing part at the inner surface is press-contacted with the outer surface of the pipe to keep an air tight fit. Furthermore, the stopper portions are engaged with both ends of the coupling body and the engaging portion is engaged with an opening of the coupling body. As a result, the air-tight inner cylinder is closely contacted with the inner surface of the coupling body. With this arrangement, it is possible to increase air tightness and easily perform an installing operation for the threadless coupling. [1]

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3.3 Characteristics And Features: [1]

A threadless coupling for pipes, comprising:

A generally cylindrical coupling body having a longitudinally-extending slot extending the entire length thereof disposed parallel to the longitudinal axis of said coupling body, said body having a pair of opposite ends having edges which cooperate to define said slot, which, in turn, defines an opening section;

A pair of groove-like grip sections formed on the outside of said edges of said ends;

A grip case slidable fitted over said groove-like grip sections for effecting coupling of said pair of grip sections and, in turn, the pipes to be coupled by said coupling;

An inner cylinder received within said coupling body including a generally cylindrical inner cylinder body having opposite ends which, in turn, have outer end surfaces;

Annular, raised stopper portions integrally-formed at both outer end surfaces of said ends;

A raised coupling body-engaging portion integrally-formed on the outer surface of said inner cylinder body, extending linearly between said annular stopper portions, generally parallel to the longitudinal axis of said inner cylinder body;

A raised, radially-inwardly extending, annular center stopper portion, integrally-formed on the inside surface of said inner cylindrical body centrally thereof;

A plurality of raised-radially, inwardly extending, annular, auxiliary stopper portions, integrally-formed on the inside surface of said inner cylinder body on both sides of said center stopper portion;

A reinforcing plate disposed with said cylindrical body beneath said engaging portion;

Wherein said stopper portions are engaged with both ends of said coupling and the coupling body-engaging portion is engaged with the opening of said coupling body.

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An inner cylinder for a threadless coupling of the type including a generally cylindrical coupling body, wherein said inner cylinder made of a resilient material is dimensioned to closely contact the inner surface of said threadless coupling when installed therein, said inner cylinder comprising:

A generally cylindrical inner cylinder body having opposite ends which, in turn, have outer end surfaces;

Annular, raised stopper portions integrally-formed at both outer end surfaces of said ends;

A raised coupling body-engaging portion integrally-formed on the outer surface of said inner cylinder body, extending linearly between said annular stopper portions, generally parallel to the longitudinal axis of said inner cylinder body;

A raised, radially-inwardly extending, annular center stopper portion, integrally-formed on the inside surface of said inner cylindrical body centrally thereof;

A plurality of raised-radially, inwardly extending, annular, auxiliary stopper portions, integrally-formed on the inside surface of said inner cylinder body on both sides of said center stopper portion;

A reinforcing plate disposed within said cylindrical body beneath said engaging portion.

Fig. 21-Water Coupling [1]

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An inner cylinder for a threadless coupling of the type including a generally cylindrical coupling body, wherein said inner cylinder made of a resilient material is dimensioned to closely contact the inner surface of said threadless coupling when installed therein, said inner cylinder comprising:

A generally cylindrical inner cylinder body having opposite ends which, in turn, have outer end surfaces;

annular, raised stopper portions integrally-formed at both outer end surfaces of said ends;

A raised coupling body-engaging portion integrally-formed on the outer surface of said inner cylinder body, extending linearly between said annular stopper portions, generally parallel to the longitudinal axis of said inner cylinder body;

A raised, radially-inwardly extending, annular center stopper portion, integrally-formed on the inside surface of said inner cylindrical body centrally thereof;

A plurality of raised-radially, inwardly extending annular, air-tight holding portions, integrally-formed on the inside surface of said inner cylinder body on both sides of said center stopper portions for press-contact with outer surfaces of pipes;

A reinforcing plate disposed within said cylindrical body beneath said engaging portion.

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A threadless coupling for pipes having an inner cylinder to be received within a coupling body comprising:

A generally cylindrical coupling body having a longitudinally-extending slot extending the entire length thereof disposed parallel to the longitudinal axis of said coupling body, said body having a main cylindrical body portion and pair of opposite ends having edges which cooperate to define said slot, which, in turn, defines an opening section; said edges of both of said ends being folded outwardly, said body additionally including a relatively narrow neck section and adjacent to said main cylindrical body portion and said pair of outwardly folded ends, said neck section defining a pair of groove-like grip sections;

A grip case having inwardly folded edges which define fastening sections which engage said groove-like grip sections of said narrow neck section to couple said pair of grip sections and, in turn, the pipes to be coupled by said coupling;

A generally cylindrical inner cylinder body having opposite ends which, in turn, have outer end surfaces;

Annular, raised stopper portions integrally-formed at both outer end surfaces of said ends; [1]

A raised coupling body-engaging portion integrally-formed on the outer surface of said inner cylinder body, extending linearly between said annular stopper portions, generally parallel to the longitudinal axis of said inner cylinder body;

A raised, radially-inwardly extending, annular center stopper portion, integrally-formed on the inside surface of said inner cylindrical body centrally thereof;

A plurality of raised-radially, inwardly extending, annular, air-tight holding portions, integrally-formed on the inside surface of said inner cylinder body on both sides of said center stopper portion for contacting the outer surfaces of pipes;

A reinforcing plate disposed within said cylindrical body beneath said engaging portion;

Wherein said stopper portions are engaged with both ends of said coupling body and the coupling body-engaging portion is engaged with the opening of said coupling body.

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Connectors:Quick-Lok connectors eliminate hydraulic leaks, thus reducing maintenance, downtime, and warranty claims. The threadless couplers include a hardened-steel stem machined to tight tolerances, along with a double O-ring stem-to-adapter interface.(As in Fig.22) A snap ring in the adapter helps eliminate manifold and port leaks that can be common in other connectors. Once the coupling is connected, it cannot be inadvertently disconnected. Nor will it release under pressure. It also resists side loading and impulse shocks. Standard ports do not need to be modified to accept Quick-Lok connectors, which are available in all common coupling and adapter configurations. The connectors can be used on hydraulic equipment using one and two-wire hoses, as well as industry-standard SAE 100R1 and 100R2 hoses. [6]

Fig. 22- Quick lock Connector[6]

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3.4 Applications: [2]

Seamless Compression Couplings are used in dry locations to connect the ends of two unthreaded rigid or IMC conduits together.

Steel compression couplings provide concrete tight connections.

These couplings eliminate the need to thread bald conduits to couple them together.

Seamless Compression couplings are zinc electroplated for excellent corrosion protection in damp locations.

Threadless Coupling eliminate leaks and emissions, exceeding today’s environmental standards the world over.

Also used as combination coupling, as shown in Fig. 23.[5]

Fig. 23

Fig. 23-Combination Coupling [5]

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3.5 Some Of Threadless Couplings:[5]

Fig. 24

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3.6 Coupling maintenance and failure: [3]

Coupling maintenance is generally a simple matter, requiring a regularly scheduled inspection of each coupling. It consists of:

Performing visual inspections, checking for signs of wear or fatigue, and cleaning couplings regularly.

Checking and changing lubricant regularly if the coupling is lubricated. This maintenance is required annually for most couplings and more frequently for couplings in adverse environments or in demanding operating conditions.

The only way to improve coupling life is to understand what caused the failure and to correct it prior to installing a new coupling. Some external signs that indicate potential coupling failure include:

Abnormal noise, such as screeching, squealing or chattering. Excessive vibration or wobble. Failed seals indicated by lubricant leakage or contamination.

3.7 Checking the coupling balance: [3]

Couplings are normally balanced at the factory prior to being shipped, but they occasionally go out of balance in operation. Balancing can be difficult and expensive, and is normally done only when operating tolerances are such that the effort and the expense are justified. The amount of coupling unbalance that can be tolerated by any system is dictated by the characteristics of the specific connected machines and can be determined by detailed analysis or experience. [3]

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4. Conclusion

So by studying the topic threadless coupling, we reached to a conclusion that it is error-proof installation, no torque required, visually confirms connection and quickconnection that holds under pressure. Threadless Couplings go together fast and they stay together-with no leaks. That means higher productivity and less warranty claims for leakers.

Threadless Couplings, remains leak-proof even under impulse shocks and side loads. Components ports needs no modification and available in all common coupling and adapter configuration.

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5. References

1. http://www.google.com/patents/US20040070207.html

2. http://www.gates.com/brochure.cfm?brochure=2938&location_id=3490.html

3. http://en.wikipedia.org/wiki/Couplings.html

4. http://www.totalpumps.co.nz/products/couplings/.html

5. http://shop200911101091294537.en.china.cn/sellingleads/detail,1094027118,Conduit-Fitting-Threadless-Combination-Coupling-P2101.html

6. http://machinedesign.com/article/threadless-coupling-for-leak-free-connections-0223.html