The outer and inner circulation of the THK Ball Screw

There are two commonly used circulation methods for THK Ball Screw: outer circulation and inner circulation. The ball that sometimes disengages from the screw during the cycle is called the outer loop; the ball that always keeps in contact with the screw is called the inner loop. Each closed loop of the ball is called a row, and the number of leads contained in each closed loop of the ball is called the number of turns. Next, we will specifically introduce the outer loop and inner loop of the THK Ball Screw. Here are some answers.

Here is the content list:

The outer loop of THK Ball Screw.

The inner loop of the THK Ball Screw.

The outer loop of THK Ball Screw.

The outer circulation means that the balls return to the THK Ball Screw through the spiral groove or intubation on the outer surface of the nut after the circulation process is over. The return method of the outer circulation THK Ball Screw pair according to the ball circulation mainly includes the end cap type, the intubation type, and the spiral groove type. Commonly used external circulation methods include end cap type, intubation type, and spiral groove type.

In the end cap type, a longitudinal hole is machined on the nut as a return passage for the balls. The cover plates at both ends of the nut have return ports for the balls, and the balls enter the return pipe to form a cycle. The intubation type uses the elbow as the return pipe. This structure has good manufacturability, but because the pipe protrudes from the nut body, the radial dimension is relatively large. The spiral groove type is to mill a spiral groove on the outer circle of the nut. The two ends of the groove are drilled with through holes and are tangent to the threaded raceway to form a return channel. This structure has a smaller radial size than the cannula structure, but it is more manufactured.

complex. The outer circulation structure and manufacturing process of the THK Ball Screw is simple and widely used. The disadvantage is that it is difficult to smooth the joints of the raceways, which affects the stability of the ball raceways.

The inner loop of the THK Ball Screw.

The inner circulation of the THK Ball Screw adopts a reverser to realize ball circulation. There are two types of inverters. The cylindrical part of the cylindrical convex key reverser is embedded in the nut, and the end is provided with a reverse groove. The reverse groove is positioned by the cylindrical outer surface and the round key on the upper end to ensure the alignment of the thread raceway direction. Oblate insert reverser, the reverser is a general round head flat key insert, the insert is embedded in the slot of the nut, and the end is opened with a reverse groove, which is positioned by the outer contour of the insert. Comparing the two inverters, the latter has a smaller size, which reduces the radial size of the nut and shortens the axial size. However, the outer contour of this kind of reverser and the dimensional accuracy of the slot on the nut is required to be high.

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