Knocker Gland

Details Common Models and Types of Knocker Gland

Typical Structural Features (Taking the DJ4 hydraulic shock jack as an example)

• Connection Characteristics: The upper end cap of this shock jack uses a reverse-threaded connection with the spline sleeve, while all other components use a normal-threaded connection. This special thread design prevents loosening at the connection points under high pressure and impact conditions downhole. The male and female threads of the end cap need to be coated with thread lubricant (except for the DJ4-475 model, which requires Loctite262) to enhance sealing and connection strength.

• Sealing and Internal Assembly: The upper end cap is equipped with a Poly-Pak seal and an O-ring. A pre-cut beveled bearing is installed between the two Poly-Pak seals (the bevel is a necessary structure for assembly; otherwise, installation is impossible). The upper end cap is equipped with an oil hole, sealed with a threaded plug. The oil hole is used for oil injection and pressure relief, while the threaded plug prevents downhole mud and impurities from entering the internal oil chamber.

• Inspection Standard Structure: The upper end cap has clearly defined dimensional inspection standards, requiring inspection with a Cougar gauge. If the gauge can penetrate the end cap, it indicates excessive wear and replacement is necessary. This structural design ensures the assembly accuracy and reliability of the end cap.

  
  

Core Functions

• Sealing and Protection: The upper end cap, in conjunction with the sealing ring and threaded plug, forms a sealed space. This prevents downhole mud, sand, and other debris from entering the shock absorber, avoiding wear and blockage of core components such as the splined shaft, piston, and hydraulic valves. Furthermore, it prevents internal hydraulic oil leakage, ensuring the energy transmission efficiency of the hydraulic shock absorber, which is crucial for equipment that relies on hydraulic oil damping for its shock function.

• Component Fixing and Positioning: It secures internal components such as bearings and seals, and provides a stable assembly reference for moving parts like the splined shaft. This ensures the splined shaft maintains a precise trajectory during movement, guaranteeing the relative stability of all internal components and preventing displacement due to severe downhole vibrations, which could affect the accuracy of the impact.

• Load Bearing and Impact Resistance: The downhole environment is high-pressure, and the impact load generated during operation is intense. The impact cover (upper cover) is made of high-strength metal material, directly bearing these loads and protecting the fragile internal transmission and hydraulic components from deformation and damage due to external impacts.

  
  

Similar Component Functions in Other Types of Impacters:

• Mechanical Drilling Impactors: Although not explicitly named "impact cover," the combination of its top connector and upper control sleeve serves a similar function. The top connector seals the upper control sleeve, protecting internal splined sleeves, locking mechanisms, etc., while also connecting to the drill string via threads to transmit torque and impact force. This highly complements the protective and connecting functions of the upper cover in hydraulic impactors.

• Lubricated lower impactor: The sealing end cap at the end of its cylinder can also be regarded as a similar component to the impact cover. This end cap is connected to the upper, middle and lower cylinders as one unit, and together with the sealing device, it forms a sealed annular space to contain lubricating oil, while protecting the internal upper impact hammer, guide tube and other components, preventing lubricating oil leakage and impurity intrusion, and ensuring that the components move smoothly in the oil bath environment.