Hammer drill

A hammer drill is a machine for drilling holes in mineral material, such as stone or concrete. Due to the impact pulse of the drill, the material is worn down. The rotational movement of the cutting edge of the drill is implemented and thereby erupted material. The operation and the feed are usually carried out by hand without mechanical aids. Depending on the type of drive energy differentiates pneumatic rotary hammers and electric drills.

• 4.1 Principle of operation
• 4.2 history
• 4.3 Miscellaneous

Pneumatic hammer drill

Pneumatic hammer drills are operated with compressed air. A by compressed air, which is controlled by a ball or flutter valve driven piston strikes a blow piece which in turn strikes the shank of the boring bar. The striking piece is provided with a transfer device which causes a rotation of the striker piece and the inserted boring bar at the rebound. Thus, a reaction of the drill bit is achieved in each unloaded condition. The weight of a pneumatic hammer drill is, according to the use, between 10 and 50 kg, typically at about 42 kg mining. Add to this the weight of the drill column or a gun carriage.

History

First pneumatic rotary hammers have been developed in the 1860s for tunneling, later for the mining industry. The most important companies in the production of rotary hammers were the Flottmann - works in Herne.

A drill

Hydraulic hammer drills correspond in their function essentially the pneumatic rotary hammers, except that as a drive medium hydraulic fluid is used. Hydraulic hammers are consistently higher in weight and performance classes (150 kg or more ) settled as the pneumatic hammers and are exclusively gun carriage out.

The first hydraulic hammer drill has been designed and developed in 1973 by Vigg Romell, an operating engineer at Atlas Copco.

Removal of drilling dust

The dust is removed dry or wet from the well. The dry air purge is applied mainly in mining. Compressed air is fed through the hollow drill string to the bit and carries the cuttings in the annulus between drill string and the borehole wall to the outside. In some cases, the dust is sucked away through the hollow drill rod. ( Königsborn device in the German coal industry, to reduce dust pollution in the neighborhood. ) The wet water rinse offers the benefits of effective chisel cooling and an effective dust control, because of the risk of stone dust, it is used below ground almost exclusively. Above ground is often used no water rinse for economic reasons, since in addition to a compressed air supply, a supply of fresh water would be necessary and, if the muddy rinse water must be disposed of. Self-contained diesel-powered construction equipment with rotary hammers produce their compressed air usually with its own compressor, the use of air conditioner can be dispensed with a water supply.

Electric Hammer Drill

Electric rotary hammers are used in all applications where compressed air is not available. Compared with the pneumatic hammer, the electric variant on a lower power. Compared with the also electrically powered hammer drill, the hammer drill is mainly characterized by a lower impact rate at much higher impact energy.

Principle of operation

In contrast to impact drills rotary hammers have a movable in the axial direction drills. The need for drilling in hard materials impact energy is generated by the so-called percussion. The types most commonly used in rotary hammers are spring hammer works or pneumatic hammer mechanisms. Both a movable mass is passed to the drill bit, transmitting the energy to the drilling material.

The pneumatic hammer mechanism consists of drive bearing or cam gear, piston, clubs and firing pin. The drive bearing or the eccentric setting the rotational movement of the electric motor into a reciprocating motion of the piston. In the backward movement of the piston, a negative pressure which pulls the club backwards formed. During the forward movement of the piston a positive pressure between the piston and stick ( compression), which accelerates the club forward is formed. The flying forward racket strikes the firing pin and releases its kinetic energy ( impact energy ) from. The momentum of the racket is transferred from the firing pin on the tool shank of the drill or chisel. The firing pin is essentially a precision turned part made of hardened steel, which also protects in addition to the momentum transfer inside the machine with a sealing ring against dust and dirt. To prevent damage to the mechanism and a dangerous for the user, especially to the machine torque in blocking of the drill, hammer drills are usually equipped with a safety coupling.

The drill must simultaneously perform a rotational and axial movement. While impact drills, the drill and the chuck are firmly connected, so the food must join the axial movement, this concept is not suitable for rotary hammers. Firstly, the non-positive voltage of the drill would be loosened by the vibration in the feed, on the other hand was going through the relatively large mass of the chuck much kinetic energy is lost. Therefore, it was in 1975 with an SDS-Plus bit reception system developed in which the drill bit is freely movable along the axis of rotation by about 1 cm. For large drilling or chipping hammers SDS -Max system is available. The promotion of the drilling dust is carried by the helical grooves of the drill.

History

The first " drill with electro- pneumatic hammer mechanism " was built in 1914 by the company fine and applied for a patent.

In 1932 the first " Bosch Hammer" series was built from Bosch. He had an impact mechanism for drilling and chiseling, and already had a safety clutch. In 1967 the company built Hilti electric hammer drills, which helped the company to a high level of awareness for this product.

Others

The operation of rotary hammers is associated with intense noise. Only in the past 20 years it has managed to reduce the noise level to about 108 dB ( A); previously had levels of more than 125 dB ( A) usual.

Many rotary hammers can not just hammer drill, but also chisel or without impact drill (for example, tile, steel or wood) by different gear ratios (speed control ) and application of a change chuck.

Cordless rotary hammers are from the mains independent, but by the battery heavier than equally strong network devices. Furthermore, the operating time is usually very limited due to the high energy consumption.

Hammers or chisels hammers have no rotary drive and are therefore only for chiselling or remove tiles, break through walls, etc. suitable. As a rule, chisel hammers are beating stronger and lighter than rotary hammers with comparable power consumption and cheaper than comparable rotary hammers with impact energy.