The need to mount parts so that they can move during operation of the mechanism has led to the invention of simple and complex articulated 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. It consists of a pin and a holder. The device has received the broadest development and modification. It is used in various fields of industry and national economy.
In a cylindrical hinge, 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 hinge is door hinges. Having looked at them carefully, it is easy to understand the principle of the device. Both parts of the loops are equipped with hollow cylinders, which are the clips of the connection. A pin (usually tightly pressed into one of them) is a finger.
The parts connected in this way move around a common axis. The cylindrical hinge is found in simple and complex mechanisms. It is present even in the usual clerical stapler.
Complex swivel joints
A more complex hinged joint consists of a pin pressed into the inner race of a sliding 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 joint using sliding or rolling bearings. The wheels of railway cars are fixed to the bogies by means of a hinge, the casing of which is the axle box, with the finger the axis 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 trunnion in it is made in the form of a sphere.
Unlike a cylindrical spigot, the ball joint has all degrees of freedom. Being limited only in its position, it provides the parts articulated with its help, the ability to move in different directions.
The ball joint is called a spherical kinematic pair. A housing containing a spherical trunnion is usually made of cast iron. Parts assembled in such a node are able to take a position at different angles to each other. To reduce the friction of the surfaces in the hinge, the trunnion with special inserts is protected from contact with the housing filled with grease. The boot covers the hinge from dirt and prevents the leakage of grease.
All existing mechanisms were initially seen in natural phenomena. As well as the ball joint, very reminiscent of the hip joints and spinal vertebrae of the human body.
The evolution of the cylindrical joint
A unit of two cylindrical hinges with perpendicularly placed trunnions is used in the universal joint transmission. It is named after Gerolamo Cardano, who described her in the 16th century.
The cylindrical kinematic pair was invented by the English physicist Robert Hooke and is used to transmit torque. Uninterrupted operation of the assembly ensures that the condition of alignment of parts of the drive shaft is fulfilled. Otherwise, at certain loads, the articulated joint begins to break. In case of misalignment 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 that are at an angle. Adding a cross increases the number of degrees of freedom, relieves stress on the trunnions and forks, prevents their destruction.
Using
The use of the Hooke hinge 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. This unit subsequently formed the basis of the cam-disk hinge, consisting of a disk of forks and cams, used mainly in trucks.
SHRUS
A kind of 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 cage took the form of a sphere with slots, and the outer cage looked like spheres with grooves on the inner surface. Both rings are splined to the drive shaft. Balls placed between them holds the separator.
The hinge of equal angular velocities at significant angles of rotation undergoes large loads. “Inverted wheels” at rated speeds are fraught with damage to the site.
SHRUS are subject to obligatory sealing by anthers. Their place of operation contributes to the ingress of dust and moisture into the hinge, quickly destroying it. Abrasives and corrosion destroy grooves, balls, kill the separator. On modern cars, a very reliable joint is used, sealed in a casing, contributing to the full use of its resource.
Swivel joints require periodic inspection of the rubber cover. Maintaining its integrity protects the unit from contamination. If a leak is detected, the replacement of the entire joint is desirable.
Unconventional hinges
The cylindrical connection in the manufacture of furniture products found their original application. Doors, shutters, decorative partitions, assembled from slats, became available with the advent of woodworking mills on the market. Having a small machine will make it easy to make a swivel joint with your own hands.
The passage of the edge seam cutter forms a rough groove on one of the narrow faces of the wooden battens. Then it is grooved shaped cutter to obtain a curly groove.
On the other hand, a spike is formed. It is received in two finishing passes. It will help to make a cylindrical swivel edge edged mill . After rounding the edges of the rail takes a finished look.
By sequentially securing the corresponding cutter on the milling machine and passing a wooden blank along it, the production of articulated joints is performed. Having assembled the thorn-in-groove slats, a flexible sheet material is obtained, capable of folding up to 15 cm in diameter depending on the width of the parts and the density of the joints.
Pipe hinges in their design have much in common with CV joints: two spherical cages, between which in the grooves are balls held by a separator. The use of a fluoroplastic ring provides a radial seal of the joint. The inner sleeve is connected to one end of the pipeline, the outer to the other.
Thus, both pipelines are able to freely rotate in all directions relative to each other. The mutual fixation of the cages is ensured by the balls located between them.
Drainage and filling elements of pipelines operate in conditions of frequent changes in the direction of supply of the transported substance. To accelerate the relocation on such highways, swivel pipes are used. It can be used in the oil, petrochemical, food or gas industries.
Summarize
In the modern world, wherever you look, hinges are everywhere : dolls and headphones, wheels and tower cranes, children's controlled cars and swinging little beds - everything is made using them. Sometimes they are modified beyond recognition.