Lovejoy CJ 42/55 Curved Jaw Coupling, Urethane Spider

Lovejoy CJ 42/55 is the size 42/55 curved jaw coupling of the Lovejoy CJ Series: two hubs and a crowned polyurethane spider, rated 265 Nm (2,345 in-lb) nominal and 530 Nm maximum with the standard 92 Shore A spider, to 6,000 RPM. A-style hubs accept bores up to 42 mm and B-style hubs up to 55 mm.

Curved jaw design for pump and gearbox drives

The curved jaw design adds radial and axial curvature to the elastomer spider, which Lovejoy lists with three benefits: easy three-piece assembly, no lubrication, and fail-safe operation because the jaw design in compression keeps working after the elastomer fails. The CJ Series covers 67 to 221,260 in-lb across fourteen sizes, with hubs in sintered iron, steel, aluminium, cast iron and nodular iron depending on size. The standard spider has a hole in the centre to accommodate small shaft-end distances.

The spider is urethane, offering high abrasion resistance, elasticity and good damping, and it resists oil, dirt, sand, grease, moisture, many solvents and ozone, according to the catalogue.

Technical specifications

Spider options for size 42/55

CJ Series sizes

Nominal torque with the 92A spider, maximum speed and spider diameter:

Selecting a curved jaw size

Work out nominal torque (HP x 63,025 / RPM), then the total service factor K = K1 x K2 x K3. K1 is 1.0 for uniform loads such as centrifugal pumps, blowers, fans and belt or screw conveyors, 1.2 for mills, mixers and textile machines, 1.3 for irregular loads such as generators, shredders and printing presses, and 1.4 for shock-loaded duty such as concrete mixers, compression pumps and centrifuges. K2 rises from 1.0 at 100 starts per hour to 1.6 at 800, and K3 from 1.0 at -30 to 30 C ambient to 1.6 at 80 C. Compare design torque with the maximum torque column, then check bore against the hub table.

Installation and operation notes

Follow the catalogue warnings: do not exceed catalogue ratings, avoid sudden shock loads, and never run with improper alignment or a damaged spider. Inspect shortly after initial operation and periodically; a coupling that vibrates or makes a beating sound should be shut down and realigned. A Lovejoy installation guide for the curved jaw is available on the Lovejoy site.

Where it is used

Hydraulic pump drives, centrifugal pumps, fans and general motor-to-gearbox couplings are the catalogue’s first-group examples, with the red or green spider where torque demands are higher. Compare with the KTR ROTEX jaw coupling, whose spiders are different and not interchangeable.

Operating notes for Oman and the GCC

Curved jaw couplings are a common choice for pump, compressor and gearbox drives in water, HVAC and process plants in the region. They need no lubrication, and the jaws continue to drive if the spider fails, which keeps a pump running until a planned stop. The spider is the wear part, so its material and hardness should match the duty. Urethane spiders are sensitive to high temperature, so check the spider limit against the real operating temperature near the motor and pump in hot plant rooms or outdoor installations, and select another spider grade where needed.

Check alignment at installation and again after the first weeks of running. Keep a spare spider for each critical drive, and inspect it at routine maintenance for cracks, hardening or wear.

Information to send with an enquiry

• Motor power and speed, and the driven machine
• Shaft diameters and keyways for both hubs, A or B style
• Spider hardness and material
• Shaft separation and installation space
• Quantity, and any spare spiders needed
• Whether the hubs should be supplied bored and keyed or as rough-bore stock

Frequently asked questions

What does CJ 42/55 mean?

Size 42/55 of the Curved Jaw series: A-style hubs bore up to 42 mm and B-style hubs up to 55 mm, with a spider 95 mm in diameter.

Which spider is standard?

The 92 Shore A yellow polyurethane spider is the standard, with 80A blue, 95/98A red and 64D green as alternatives.

What is the benefit of the curved jaw?

The spider has radial and axial crowning, and the jaws work in compression with no metal-to-metal contact; the coupling still transmits torque if the spider fails.

What temperature can the spider take?

The 92A spider is rated -40 to 212 F normal and up to 248 F maximum; the 64D green spider is rated -30 to 230 F normal and 266 F maximum.

How many pieces make up the coupling?

Three: two hubs and one spider, assembled without lubrication or special tools.

Documents and quotation

The Lovejoy curved jaw catalogue section (May 2026) is hosted on this page. See Couplings and Shaft Locking Devices. Seven Star LLC is an independent supplier in Muscat; send size, hub style, bores and spider hardness for a quotation.