Spring (device)

As spring is referred to in the art components, the yield under stress and return to relief in the original form, so behave elastically resetting.

• 6.7.1 volute
• 6.7.2 Ring spring
• 6.7.3 screw

History

Simple ungewundene springs, such as the arch, have been used by humans in prehistoric days. In the Bronze Age more sophisticated spring mechanisms came on, as it can be shown in many cultures based on the distribution of the tweezers. Ctesibius of Alexandria developed a method for making bronze with spring-elastic properties by after casting the bronze he cured to form an alloy with an increased proportion of tin processed and this by hammering.

Spiral springs are found since the early fifteenth century in watches; this evolved from spring-driven clocks with the transition to the sixteenth century to the first pocket watches. The coil spring in the balance of pocket watches was first built from 1673 by Salomon Coster, according to a patent by Christiaan Huygens. The change from the torsion pendulum to the coil spring had previously been proposed by Jean de Hautefeuille.

In 1676 the British physicist Robert Hooke discovered the principle of the spring mechanism underlying the under the force exerted by a spring force proportional to its length, and this is known as Hooke's law today.

Designs

There are as many different types of construction machinery element: wire helically or spirally wound or rod-shaped stretched or bent parts. Bouncy can also be a trapped gas cushion.

Application

Springs are often used as storage for potential energy ( door closers, watches drives, valve springs). Furthermore, they can create a positive connection between components, such as elastic clutches, brakes and valves. With spring balances forces are measured and limited by slip clutches forces. Machine parts by means of springs to be moved or opened and closed switching contacts (contact springs relay). Here, the springs generate the desired spring force.

Another important possible application is the decoupling of shock and vibration ( rubber mount ), with additional components usually have a dampening effect. Often this will be a division of the force on several parallel springs ( upholstery, wheel loading of vehicles ). Ultimately springs can also take the form of changes to other components in thermal length changes, wear and mechanical deformations.

Materials

The material preferably special spring steel or copper -beryllium alloys ( beryllium copper ) are used. Other possible materials for springs are rubber or gases. In recent years, are also more common fiber composites, especially glass-fiber reinforced plastic are used.

Parameters

For the characterization of springs, the spring constant ( spring stiffness ) or the spring characteristic is specified as a technical factor, which describe the relationship between deformation ( distance or angle ) and force or torque. This characteristic is often a linear and thus behaves according to Hooke's law. Other important parameters are efficiency, damping factor and damping value, defined via the spring labor.

Types of springs

Springs are divided principally by their internal stress in torsion, bending, train and gas springs. The most famous spring, coil spring ( used eg in pens ), belongs to the group of torsion springs. For her, the spring wire is hardly bent or compressed, but mainly twisted. After the cause of the resilience of springs, a distinction form or fabric feathers.

Coil spring

Torsion spring or torsion bar

Bending spring

Spiral spring with torque load

Spiral spring with torque load ( not to be confused with the coil spring ) is a newly coiled spiral spring. Spiral springs are made ​​as helically wound metal strip in a plane. They are, for example, in children's toys that can be put on, and used in the model, where they serve as a mechanical energy storage ( spring engine ). In mechanical watches they had for a long time as a drive and as part of the balance is essential.

Diaphragm spring

Diaphragm springs are thin flexible plates, usually circular, are mounted circumferentially on the rim. Typical applications in clutches of motor vehicles with internal combustion engines.

Leaf spring

It consists mostly of flat - rectangular profile of spring steel, which is biased arc-shaped, and is used primarily in commercial vehicle and in wagons. Rectangular leaf springs of constant thickness, however, would not exploit well the material; better suited would be a triangular or trapezoidal shape, the bending stresses over the spring length to remain constant at the. Such springs are rare because they are expensive to manufacture and require much space, so several equally broad leaves ( spring layers ) can be used with different lengths and biases rather than a wide, trapezoidal spring, which are laminated to a spring package by a common heart stud and spring clips held together. The friction between the sheet ends of the plies by means of the change in length during compression causing internal damping; by inserted plastic flakes or lubrication with fat, this can be reduced. Parabolic springs are leaf springs ( usually also made ​​of steel) with only one spring location, decreases in thickness towards the ends. You use the material a little better than layered leaf springs. Springs made of glass fiber reinforced plastic are performed with a constant cross- sectional area than Hyperbelfedern: to the ends, the width and the height from. Even so, can a uniform material stress over the length of the spring reach.

Disc spring

With a plate spring is defined as a conical ring shell that is resilient in axial direction and can be stressed in both resting and swinging. The force is usually on the upper inner edge and the lower outer edge.

The plate spring can be used as a single spring, or a spring column. In a column, either single plate springs or consisting of several springs spring assemblies may be stacked in alternate directions.

• The plate spring, in comparison with other types of springs, a number of advantageous properties It can absorb very large forces with small installation space.
• Your spring characteristic can (rising) be designed according to the measure relations be linear or degressive, and by a suitable arrangement also progressive.
• By the way, almost any combination of individual disc springs, the characteristic can be varied by the column length within broad limits.
• Long service life at dynamic load when the spring is correctly dimensioned.

• Group 1 disc springs with plate thickness <1.25 mm: punched or finely cut from strip material
• Group 2 disc springs with plate thickness of 1.25 to 6mm: punched or cut fine. With punched plate springs inner and outer diameter to be rotated after the die-cutting, in order to remove cutting marks ( Kerbempfindlichkeit! ).
• Group 3 disc springs with plate thickness 6 mm: of thermoformed boards, the surface is completely rotated.

• DIN 2092 Disc Springs, calculation
• DIN 2093 Disc springs, dimensions and quality requirements

Air spring

Air springs mainly found in trucks, buses and rail vehicles application. They allow, among other things, a level of regulation, ie that the vehicle maintains the same ground clearance even with different loading conditions. It can also be set specifically a change in the level position of the vehicles to facilitate the entry of buses or to enable driving over obstacles ( ATVs ).

In rail vehicles are air springs for vehicles with high comfort and acoustic requirements such as high-speed services, local transport ( S-Bahn ), used for locomotives and subway trains that must withstand high payloads. The air suspension systems are controlled by a mechanical lever level control so that, for each load level of the same transition from a vehicle can be secured to the platform.

Chance of air springs have been used already in the 1960s in passenger cars, for example, Borgward and Mercedes, the costs and problems with the pressure tightness but could not prevail on the basis of the time. Just today, air springs are also increasingly used in the upper and middle class of car, with the advantage of a higher driving comfort. Due to the properties of the air suspension the structure natural frequency of a vehicle is largely load- independent.

Air springs in road vehicles are built in two forms.

Gas pressure spring

Gas springs are usually as an opening mechanism is used for example on the luggage compartment door of automobiles. For them, the internal gas pressure pushes the piston rod with a nearly constant force from the cylinder.

Elastomer spring

Rubber springs are used in a wide range of applications of the technology. They have next spring and damping properties. They are used for example as bearings for vibratory machine parts, or in the chassis of motor vehicles ( earlier generations of the Mini Cooper ). Rubber springs are incompressible, ie their volume does not reduce itself during compression. It is therefore necessary to provide space for a lateral deflection.

In motor vehicles, in addition to the actual suspension in the end stops of the axes helper springs made ​​of polyurethane ( PUR) or Micro Cellular Urethane (MCU ) can be used. This is a plastic foam which is compressed under load. The characteristics of such a spring is largely determined by the shape, as well as additional support elements such as plastic rings.

Other types of springs

Volute

The volute spring, also called clock spring or pot spring is wound from a standing upright flat material and was used among others in the rail vehicle technology for the mitigation of hook, buffers and bogies. It was invented in 1846 by John Baillie as Bailliesche helical spring.

Ring spring

In railway construction ( crash cushion ) of the wagons ring springs are used in the buffers that are deposited as a horizontally positioned stack in two sizes alternately into each other. When driving a wagon to another large spring rings are stretched and compressed the small spring rings. The springs slide partially into each other and also dampen the motion by friction. Due to the additional damping, a ring spring achieve Artnutzungsgrad (? A ) of more than one.

Screw

Expansion bolts are designed in such a manner that a controlled tightened screw behaves like a prestressed spring. This can be achieved by a long slender screw: The longer and thinner the screw, the flatter the spring characteristic. Such screw requires no screws securing. Applications: as cylinder head bolts.

Spring constant and spring characteristics

The spring characteristic curve describes the dependence of the spring force F on the spring travel s In addition to the spring design with a linear spring characteristic or a spring constant (see in Fig: characteristic 2 ) there are constructive ways to adjust the spring design to the requirements of the design.

Examples of non-linear characteristics:

• With rubber springs progressive characteristics are often achieved (see Figure: Characteristic curve 1).
• Modern sports bows have a degressive spring characteristic (see Figure in point 3). The area under the curve corresponding to the stored energy. This is the same holding force greater than with a linear characteristic.
• In a car - coupling, it is desirable to require a constant pedal force for the entire pedal travel (see Figure in point 4 ), for which an annular spring is suitable.
• The suspension in motor vehicle often used a progressive characteristic curve (point 1) to prevent strike-through at high load, while the normal load a soft, comfortable suspension is desired. The hardening of the spring then enters the fact that the larger coils form a first shock, thereby shortening the effective length of the spring. The same purpose a two-stage coil ( point 5), which is somewhat simpler to manufacture. Such a spring characteristic can also be achieved by two different springs can be set one after the other.
• Discontinuous transitions are also at special leaf springs as the clicker.