Lock Nut / Locking Nut

In the spare parts system of cone crushers, the lock nut (also commonly referred to as the locking nut or lock ring) is a critical fastener used to secure the mantle (movable cone liner) and the bowl liner (fixed cone liner).

1. Core Functions: What Exactly Does It Do?

Securing Wear Liners

The lock nut is typically installed at the top of the main shaft or on the adjustment ring. Its primary function is to firmly press the mantle onto the movable cone or secure the bowl liner to the adjustment ring, preventing the liners from sliding relative to each other or falling off during the crushing process.

Withstanding Massive Impact Loads

When crushing hard ores, the liners are subjected to enormous axial and radial impact forces. The lock nut must possess extremely high tensile strength and yield strength to prevent thread deformation or nut fracture.

Maintaining the Discharge Opening Size

For the lock nut on the fixed cone, it also serves to maintain the relative position of the adjustment ring, ensuring that the discharge opening gap of the crushing chamber remains unchanged under severe vibration.

2. Anti-loosening Principles: Why Doesn't It Come Loose?

To prevent it from loosening under severe vibration, the lock nut typically employs one or more of the following anti-loosening mechanisms:

Hydraulic Locking

This is currently the most mainstream method for large cone crushers (such as multi-cylinder hydraulic cone crushers). An annular chamber (or rubber bladder) is built into the nut or its base. A high-pressure hydraulic pump injects oil into this chamber. The oil pressure pushes a piston or causes a slight elastic deformation of the nut itself, generating massive axial preload that tightly "bites" the threads together.

Mechanical Locking

This restricts the nut's rotation through physical structures. For example, set screws are installed on the outside or bottom of the nut. Once the nut is tightened, these set screws are threaded in to press against the main shaft or thread block, forming a rigid mechanical block. Other mechanical locking methods include using lock washers and cotter pins.

Self-locking Design

Some designs utilize the actual rotational direction of the main shaft to achieve self-locking. For instance, the tightening direction of the lock nut's threads is set opposite to the main shaft's actual rotation. During operation, friction naturally forces the nut to tighten further.

Sawtooth Thread Engagement

In spring cone crushers, the contact surfaces between the lock nut, support ring, and adjustment ring are typically machined with sawtooth threads. During operation, hydraulic cylinders apply pressure to force these sawtooth slopes into tight contact, achieving a secure lock through massive friction.

3. Common Structural and Material Characteristics

Material Requirements: Lock nuts are usually forged or cast from high-strength alloy steel and undergo quenching and tempering heat treatment. This ensures a "hard exterior and tough interior," preventing brittle fracture under impact.

Split Design: To facilitate replacement and reduce costs, some lock nuts feature a split design (e.g., the nut body and the bottom thread block are separated). Fixed bolts are used to lock the two threaded sections together, which not only ensures the locking effect but also reduces the weight and machining difficulty of individual components.

Protective Cover Design: To prevent dust and mud/water from entering the thread mating surfaces (which can cause wear or seizing), some lock nuts are equipped with an external protective cover (or feed distributor plate) that completely encloses them, thereby extending their service life.