The need to mount parts so that they can move during the operation of the mechanism led to the invention of simple and complex swivel joints. In this article, we will talk about this in more detail.
What is a swivel joint?
A device by which two parts are connected to each other, while maintaining mobility around a common axis, is called a swivel joint. It consists of a pin and a clip. The device has received the widest development and modification. It is used in various areas of industry and the national economy.
In a cylindrical joint, the trunnion usually has the form of a rod. It is pressed into the holes of another part, which is called a clip. The simplest example of a hinged joint is door hinges. Looking at them carefully, it is easy to understand the principle of operation of the device. Both parts of the hinges are equipped with hollow cylinders, which are the clips of the connection. The pin (usually pressed tightly into one of them) is the finger.
Parts connected in this way move around a common axis. Cylindrical hinge is found in simple and complex mechanisms. It is present even in the usualstapler.
Complex articulations
A more complex swivel joint consists of a trunnion pressed into the inner race of a plain or rolling bearing, rotating in it. No electric motor can be assembled without the use of this assembly. The rotor is suspended in the stator by means of a cylindrical hinge using plain or rolling bearings. The wheels of railway cars are fixed to the bogies by means of a hinge, the cage of which is the axle box, the pin is the axle of the wheel sliding in it by means of a roller bearing.
Ball joint
There are other types of articulated joints that can provide more degrees of freedom for rotating structures. The connection of parts, in which they move around a common center, is called a ball joint. The pin in it is made in the form of a sphere.
Unlike a cylindrical one, the pin of a ball joint has all degrees of freedom. Being limited only in its position, it provides the parts articulated with it, the ability to move in different directions.
A ball joint is called a spherical kinematic pair. The body containing the spherical trunnion is usually made of cast iron. The parts assembled in such a node are able to take a position at different angles to each other. To reduce friction of the surfaces in the hinge, the trunnion is protected by special liners from contact with the housing filled with grease. Antherseals the hinge from dirt and prevents leakage of grease.
All existing mechanisms are initially seen in natural phenomena. As well as the ball joint, which is very reminiscent of the hip joints and spinal vertebrae of the human body.
Evolution of the cylindrical joint
A unit of two cylindrical joints with perpendicularly placed trunnions is used in cardan transmission. It is named after Gerolamo Cardano, who described it in the 16th century.
Cylindrical kinematic pair invented by English physicist Robert Hooke, used to transmit torque. The uninterrupted operation of the assembly is ensured by the obligatory fulfillment of the condition of alignment of the parts of the drive shaft. Otherwise, under certain loads, the swivel joint begins to collapse. In case of violation of the alignment of the movement of parts, it is advisable to use a cardan with two crosses. This method is used if the torque is transmitted along axes at an angle. Adding a cross increases the number of degrees of freedom, relieves stress on the trunnions and forks, and prevents their destruction.
Use
The use of the Hooke joint in the automotive industry made it possible to transmit rotational motion from the gearbox to the wheels, even in the presence of significant articulation angles of the elements. This unit subsequently formed the basis of the cam-disk hinge, consisting of a disk of forks and cams, which are used mainly intrucks.
CV joint
A peculiar mutant, obtained by crossing a ball joint with a Hooke cardan, represents a completely new type of connection of elements. It is a deformed ball bearing, where the inner race took the form of a sphere with slots, and the outer one - spheres with grooves on the inner surface. Both rings are splined to the drive shaft. The balls placed between them are held by the separator.
The CV joint at significant angles of rotation undergoes heavy loads. "Inverted wheels" at rated speeds are fraught with damage to the assembly.
CV joints are subject to mandatory sealing with anthers. Their place of operation contributes to the ingress of dust and moisture into the hinge, quickly disabling it. Abrasives and corrosion destroy the grooves, balls, kill the separator. On modern cars, a very reliable swivel joint is used, sealed in a casing that contributes to the full use of its resource.
The swivel requires periodic inspection of the rubber boot. Maintaining its integrity protects the assembly from contamination. If a violation of its tightness is detected, it is desirable to replace the entire hinge.
Unconventional hinges
Original application found a cylindrical connection in the manufacture of furniture products. Doors, blinds, decorative partitions, assembled from slats, became available with the advent of woodworking cutters on the market. Having a small machine will help easilymake a swivel with your own hands.
Passing the edge seam cutter forms a rough groove on one of the narrow edges of the wooden lath. Then it is passed with a grooving cutter to obtain a curly groove.
A spike is forming on the other side. It is obtained in two finishing passes. It will help to make a cylindrical swivel joint with an edge curly cutter. After rounding the edges, the rail takes on a finished look.
Alternately fixing the corresponding cutter on the milling machine and passing a wooden blank along it, the hinge joints are made. By assembling the spike-in-groove rails, a flexible sheet material is obtained that, depending on the width of the parts and the density of the joints, can be rolled up into a tube up to 15 cm in diameter.
Tube joints in their design have much in common with CV joints: two spherical clips, between which the balls held by the separator are located in the grooves. The use of a fluoroplastic ring ensures a radial seal of the joint. The inner ferrule is connected to one end of the pipeline, the outer one to the other.
Thus, both pipelines are free to rotate in all directions relative to each other. The mutual fixation of the clips is provided by the balls located between them.
Drain and fill elements of pipelines operate in conditions of frequent change in the direction of supply of the transported substance. To speed up the relocation on such highways, swivel pipes are used. Itcan be used in oil, petrochemical, food or gas industries.
Summarize
In today's world, everywhere you look, there are hinges everywhere: dolls and headphones, wheels and tower cranes, children's steerable cars and swinging beds - everything is made using them. Sometimes they are modified beyond recognition.
