Product category:
Gears, brakes, couplings and engines
News Release from: Lovejoy | Subject: LF, LK and LM torsional couplings
Edited by the Engineeringtalk Editorial
Team on 24 April 2002
Torsional couplings handle rough diesel
outputs
A broad line of shaft- or flywheel-mounted couplings from Lovejoy solves virtually all types of torsional vibration problems common to internal combustion engine driven applications.
A broad line of shaft- or flywheel-mounted couplings from Lovejoy solves virtually all types of torsional vibration problems common to internal combustion engine driven applications such as pumps, compressors and gensets These three basic designs, with a variety of configurations, offer alternatives for absorbing shock loads, accommodating misalignment and/or shifting critical speeds safely above/below normal operating speed ranges
This article was originally published on Engineeringtalk on 24 Apr 2002 at 8.00am (UK)
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All are nonlubricated, maintenance-free designs featuring easy assembly and rugged construction.
Lovejoy's LF family offers the group's most versatile coupling design, built around a doughnut-shaped elastomeric element alternately bolted to a cylindrical centre shaft hub and a flange-type shaft hub.
The alternating radial and axial mounting bolts assure "failsafe" service that continues transmitting torque in the unlikely event of elastomer failure.
Fifteen sizes accommodate nominal torque up to 5000Nm (12,500Nm max), and continuous vibratory torque up to 2000 Nm.
Elastomers are offered in a choice of natural rubber or Neoprene - both in four durometer hardness ratings for a wide range of torsional vibration requirements - plus Hytrel for greater torsional stiffness and temperature tolerance, and Zytel for ultimate torsional stiffness, temperature tolerance and chemical resistance.
Further reading
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CD-ROM has full details of couplings
A new full-line international catalogue in CD-ROM format from Lovejoy details 11 categories of shaft-to-shaft power transmission couplings, with separate metric sections.
Configurator aids coupling specification
Lovejoy reckons it has transformed the highly technical experience of sizing and selecting couplings into a simple and comprehensive series of questions.
Elastomer doughnuts from the LF family are available separately for mounting on user-designed hubs, or with centre hub only for mounting directly to engine flywheels, pulleys, brake discs, friction clutches, U-Joints or gears.
Additional models are provided with flywheel mounting plates in all standard SAE flywheel sizes, and shaft hubs in a variety of ANSI (SAE) DIN, and JIS splined bores as well as straight or tapered bores.
Splined hubs feature the L-Loc design, which applies clamping force evenly around the entire shaft profile to eliminate spline distortion and fretting.
A special thin-profile LF family model serves close engine housing/pump applications, with a disc-shaped Hytrel element pilot-mounted to a cast alloy SAE flywheel adapter plate machined to SAE J620 specifications.
In addition, floating-shaft models are available in buyer-specified lengths, with special corrosion- and heat-resistant materials, and special designs to allow free endplay or accommodate long spans.
Lovejoy LK Family flywheel couplings offer a simple, robust two-piece unit with nearly rigid torsional stiffness.
Intended for diesel, gasoline or natural gas engines in the low- to mid-power ranges, LK couplings raise critical speeds well above the operating RPM of low-inertia equipment such as hydraulic pumps and hydrostatic drives.
Five sizes accommodate nominal torque up to 2400Nm (6000Nm max).
The LK design features a molded Polyamid flange strengthened with glass fibre to produce a high-impact material that withstands temperatures of -40 to +150C.
Moulded into the flange is a socket shaped to receive a "hubstar" consisting of a shaft-mounting hub fitted with four, six or eight radial dogs.
The coupling installs in less time and at lower cost than conventional diesel/pump flywheel couplings by bolting the coupling's flange to the engine flywheel, mounting the hubstar on the pump shaft, advancing the pump to seat the hubstar into the flange socket, then bolting the pump to the pump mounting plate or housing.
Standard LK flanges are one-piece units sized to fit standard flywheels ranging from SAE 6.5 through 14 using SAE J620 mounting measurements, as well as to fit metric flywheels.
For other nonstandard flywheels, a special two-piece mounting combines a universal flange with a steel adapter.
Hubstars, using the L-Loc system, can be mounted anywhere along the splined shaft at the ideal axial location to mate properly with the flange socket.
Although very stiff radially as well as torsionally, LK family flanges are able to compensate for small radial and angular misalignments normal with flange-mounted drives.
Hubstar dogs have slight crowns along their lateral flanks to avoid edge pressure at angular misalignment.
Lovejoy LM family flywheel couplings are made expressly for diesel engines driving relatively small inertia loads such as splitter-gear multiple pump drives, two-bearing generator sets, centrifugal pumps, compressors and marine propulsion, designed to shift critical speeds low enough to avoid torsional resonance across the entire operating range from low idle to full speed.
Eight sizes with nominal torque ratings from 250 to 3800Nm cover applications ranging from small single-cylinder to large multi-cylinder engines.
Very soft torsionally, the LM coupling features a disc-shaped elastomeric element with cogs or teeth moulded around its perimeter.
These cogs mate in a no-backlash fit with internal cogs cast into an aluminium ring mounted on the engine flywheel.
Elastomeric elements are offered in natural rubber with a variety of Shore hardness ratings and temperature tolerance of -45 to +90C, or special silicone rubber that extends temperature tolerance up to +120C.
The element's shape is designed to allow a large angle of twist (6 to 12 degrees), while reducing stress at its thicker portions around the centre and around the perimeter at the cogs.
A steel ring bonded into the centre of the elastomeric disc assembles to a steel hub that is machined to fit the user's keyed or splined driven shaft, and mounted by set screws, tapered split hub or the L-Loc clamping system.
A special radial assembly/disassembly (drop-out) type LM coupling allows the elastomeric element to be changed quickly and easily without disturbing the coupling shaft.
The Lovejoy torsional coupling line also includes pump mounting plates, plus light-weight cast aluminium pump-mounting housings for engines lacking an SAE flywheel housing, in styles designed to fit a variety of Cummins, Ford, Kubota, Deutz, GM and Perkins engines.
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