4 typical Elastomeric Couplings problems

Elastomeric Couplings replacement Twin Spring coupling TSC500 flexible coupling replaces universal joints, servo, beam, bellows and elastomeric couplings

Elastomeric couplings, used in a number of industries  mainly the Industrial sector in areas like food and beverage etc. are primarily used because of their makeup, a non metallic center made up of a tough polymer. In other industries bronze, hytrel and Buna N are other ma

The polymer helps to make the coupling flexible to a small degree (less than 5 degrees or less) and it also allows the coupling to absorb shock and vibration, some great qualities. These kinds of couplings apply to number of different types of elastomeric, dependent on their use. They are either compression or shear. Compression types include jaw, donut, the shear types include tire and sleeve.

Different commonly known couplings include both L type jaw and CJ type jaw couplings, donut, tire, nylon sleeve. Each have their uses but also their downsides as well.

Jaw couplings – Jaw couplings design allows for a angular misalignment of up to 5 degrees, the coupling has a insert or spider that fits in the middle between the two hubs. This spider insert absorbs vibration and as it is flexible (dependent on the insert used as there are 4 choices Bronze (no misalignment, higher torque) Hytrel from Lovejoy, Rubber/XFCR or Polyurethane, Nitrile Butadiene (Buna N).They can run at high speed and are cheap to buy and components are very common. Lovejoy L090- L276, Boston Gear FC25-FC45, Ruland JC and JS, SKF FRC150, FRC230 ,Tsubaki are all manufacturers of jaw couplings.

These inserts vary with the coupling and the equipment, the bronze insert is restricted to only 250rpm and high torque loads, as the material gets more flexible the speed increases up to 7000 RPM but with lower torque output. As the material gets more flexible so does the ability for the jaw coupling to work at increased levels of angular misalignment.

This increase comes at a price. The price is the spider inserts wear more rapidly and need to be replaced. The “legs” of the spider start to fray as they are pinched between the jaws of the coupling, adding to that the torque of daily use also compresses the insert reducing its ability to absorb vibration. In the end this means these spiders need to be replaced.

Donut couplings – Donut couplings are very similar to jaw couplings but have a rounded or donut shape, they can work at 5 degrees of misalignment much like the jaw but have the ability to stretch to 10 degrees momentarily, they have less torque and speed capability and traditionally are seen in Automotive. SKF Flex 90 – 140 and Lovejoy Saga 22 or Saga 26 are examples of donut coupling manufacturers.

Tire couplings – Are a molded 2 piece design that can run at mid level speed but low torque output. It like the jaw coupling is limited to 2 degrees of angular misalignment and 1 degree parallel misalignment, tire couplings are made up of 4 pieces , the 2 tire halves and each side has to have input and output hubs, to attach it to both the shafts and the coupling itself

Sleeve coupling – Very similar to a jaw coupling but is wider which means the design again is for lower speed  and or lower torque applications. The sleeve itself is made out of EPDM Rubber, Neoprene or Hytrel. ABB D Flex, TB Woods Sure Flex and Dura flex are examples of sleeve coupling manufacturers.

Other couplings like spring couplings are another option as well

The common ingredient is almost all of these couplings is a flexible insert, this gives it a small amount of flexibility and to be able to run at anywhere from low to high speeds. To change these inserts is normally a relatively straight forward and simple task which is why they are so common.

Adding to that this insert also means it can be used in applications where environment plays a huge factor in maintenance, factors like moisture, heat and fine particles which would destroy a coupling such as a universal joint and their internal bearings. The constant greasing and maintenance to ensure the bearings either friction or needle can stay working is a big factor in their usability in environments like this.

This is why these couplings have their place.

Downsides – As shown these couplings fall down in a number of key areas and force mechanical engineers and designers to have to work around these short falls

Lack of flexibility – With the insert, whether is be spider insert in jaw couplings, sleeve in sleeve coupling, the rubber insert in both the tire and donut coupling, while it does a great job of absorbing vibration it also limits its flexibility as the more the coupling flexs the more the edges of the couplings wear out.

Other couplings like the Twin Spring range of couplings have a flexibility of 25 to 45 degrees.

Constant replacement of internal components – With the insert, sleeve, donut, tire etc the part that takes the brunt of the work, it wears out. Compression from use makes it less flexible, the angle of misalignment it is used at dictates how much wear the edges of the inserts faces. The bigger the angle the quicker the wear. While replacing it is relatively straight forward, the actual costs of replacing the insert comes at a price. The insert itself is cheap but the cost of labor replacing it and machinery downtime is where the costs really add up.

Couplings like Twin Spring Coupling doesn’t have inserts so the coupling has a maintenance schedule that fits in with the other maintenance on the machinery, saving labor and unnecessary machinery downtime.

Speed – Elastomeric couplings vary with the speed they can handle, some can run over 7000 rpm, where others can only run at 250 rpm. A big contributing factor is the angle of misalignment, bigger the angle the lower the speed. Twin Spring Coupling’s central ball teamed with the twin springs means it can run at a higher speed with a larger angle than a typical coupling regardless of its type.

Multiple pieces make up  – Elastomeric couplings have a number of pieces, normally 3 (input and output hub, plus insert) the donut has 4. More pieces means more that can go wrong either elastomeric or the hubs, which can crack and if used in high torque situations split.

Twin Spring Coupling is the only 1 piece coupling, so integrated input and output hubs, no elastomeric insert, which means less chance of anything going wrong.

What Twin Spring Couplings offers

We can give you

High speed couplings – Can be used up to 7000 rpm

High flexibility – Some of our couplings can be used at 45 degrees

High Torque – The Twin torsion springs means high torque, up to 6000 in lbs. of torque, depending on the model chosen.

Best of all, NO ELASTOMERIC INSERTS. This means a higher ROI from your machinery, less maintenance and less downtime.

Twin Spring Coupling offers 3 models, TSC150 (150 Ft lbs of static torque) TSC300 (300Ft lbs. of static torque) and TSC500 (500 Ft lbs. of static torque)

Each of these couplings are available in spline types like Keyway (different key sizes are available) Square, Hex and plain shaft.

Please go to our product page and find out more about them and if you have any questions please go our contact page and we will happy to help you.

Twin Spring Coupling Products

 

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