DK149408B - DRILL AND CHEESE HAMMER WITH COMBUSTION ENGINE DRIVE - Google Patents

Description

149403 i

The invention relates to a drill and chisel hammer driven by a combustion engine arranged in a housing and comprises a flywheel connected to the crankshaft of the engine.

5 Hand tools of the type mentioned are especially used for major demolition work as well as in remote, non-powered construction sites. Compared to electrically powered appliances, these tools have the advantage of being more mobile. On the other hand, prior art devices 10, driven by an internal combustion engine, have a significantly greater weight, significantly greater noise generation, as well as stronger vibrations than the electrically powered appliances.

Work on the previously known appliances is therefore very tiring over time. Partly to equalize the drive motor's asymmetrical shape and partly to offset the temporal shift between the combustion engine's power output and the impact absorption of the impact tool, the known drill and chisel hammers have a flywheel connected to the engine crankshaft. The energy stored in the flywheel must be sufficiently large to cover the pulse-like percussion required by the percussion and the combustion engine's compression work without 20 major speed reductions. In order to prevent the tool from being removed from the subsoil to be processed, an increase in the engine speed and at the same time an undesirable, excessive noise development, known tools have a throttle mechanism by which the engine speed can be lowered to an idle speed. This throttle-latching mechanism is activated manually or automatically. For now during these working breaks, as well as above all at the reinsertion, to avoid the engine "drying out" at a lower idle speed, the flywheel must have a certain flywheel torque.

It is e.g. it is possible to provide, by means of a heavily dimensioned flywheel, which, however, limits the size of the flywheel for weight and space reasons.

2 U9408

At present, known hand tools, which comprise an internal combustion engine drive, are mostly the so-called fast runners, at which the required performance is first obtained at a relatively high speed. However, this results in a very high noise level and strong vibrations, which is why the apparatus over time is dangerous to health and can hardly be used anymore. So-called slow runners, on the other hand, use a larger and heavier flywheel, so that these are not suitable as portable appliances.

The object of the invention is to provide a hand tool which enables a low engine rpm and a low weight.

According to the invention this is achieved by placing a transmission gear between the crankshaft and the flywheel which is adapted to increase the speed of the flywheel relative to the crankshaft speed. Since the energy content of a flywheel increases square with the speed, despite the additional transmission gear, it is possible to reduce the weight of the whole device and a reduction in the engine speed.

For smaller appliances, the flywheel usually takes on other tasks as well. Thus, it is known to provide the flywheel as a fan blade to provide an air flow which cools the engine. The increase of the flywheel rpm by means of the transmission gear also now leads to a significantly greater air flow, so that even with longer use of the working tool a sufficient cooling of the motor is achieved despite the smaller flywheel diameter.

Since the flywheel mostly also serves as a generator for providing spark ignition, the ignition voltage, even at lower rpm of the drive motor, can be kept approximately 30 constant. In addition, a transmission gear that increases the flywheel rpm relative to the crankshaft speed also provides the additional benefit gained by a bearing stabilization of the entire apparatus due to the flywheel gyroscopic effect. This largely avoids unintended tilting movements of the entire apparatus during use # due to eccentric attacking forces. The device thus also works with considerably weaker vibrations.

For spatial and weight reasons, it is advantageous to design the transmission as compact as possible. To achieve this, the transmission gear may conveniently be formed as planetary gear. In addition, a planetary gear can be positioned coaxially with respect to the crankshaft so that the outer shape of the hand tool is thereby practically not adversely affected.

In order to obtain a favorable transmission of power and for dimensional reasons, it has proved advantageous if the planetary gear connection part is driven by the crankshaft, the hole wheel is firmly connected to the housing and the sun gear is coupled to the flywheel. With suitably designed gears, two or more planetary wheels may be provided to achieve a uniform distribution of force.

The gear ratio between the crankshaft and the flywheel is limited for practical reasons. By means of the additional transmission drive, part of the possible weight saving at the flywheel is eliminated. The flywheel rpm should therefore be significantly above the crankshaft speed. On the other hand, the speed of the flywheel must also not be too high at normal speed at the drive motor, since otherwise the gyroscopic effect of the flywheel becomes so strong that the apparatus can hardly be handled. Therefore, to obtain a favorable mean value, it is appropriate if the transmission ratio of the transmission is 1: 3. The gear ratio must be an integer multi-plum as the flywheel absorbs the ignition magnets that cause the induction of the tooth coil.

The invention is explained below with reference to the drawing, in which FIG. 1 is a partial cross-sectional view of a drill and chisel saw in accordance with the invention; and FIG. 2 is a section through the embodiment of FIG. 1 in line with line II-II, seen in larger target conditions.

5 The embodiment of FIG. 1 drill and chisel hammer essentially consists of a housing which is provided with the general reference numeral 1. On the rear end of the housing 1 is provided a handle 2. On the opposite handle 2 located on the side of the housing 1 a tool holder 3. Inside the housing 10 1 is rotatably mounted a crankshaft for a drive motor, designated by the general reference number 4. On a crankshaft 4a of the crankshaft 4, a connecting rod 5 is attached. This connecting rod 5 is itself connected to a drive piston 6 in the drive motor. At the upper end of the crankshaft 4 15 is provided a crank which is provided with the general reference numeral 7 and which is connected to the crankshaft 4 by means of a thread 4b. connecting rod 8, which is part of the percussion. This connecting rod 8 is connected to 20 a percussion piston 9 in the percussion. This drive piston 9 is inserted into a cylinder liner 10.

The opposite end of the thread 4b of the crankshaft 4 is surrounded by a planetary gear. A connecting part 11 of the planetary gear is rotatably connected to the crankshaft 25 4. On this connecting part 11 a planetary wheel 13 is mounted on this shaft 12. This planetary wheel 13 is partly engaged with a fixed hole 11 and is connected to the housing 1 and partly with a sun gear 15a arranged on a flywheel provided with the general reference numeral 30 15. This flywheel as well as the associated sun gear 15a is pivotally mounted on the crankshaft 4 via a bearing bushing 16. By means of the planetary gear which consists of the connecting portion 11, the planetary wheel 13, as well as the hole wheel 14 and the sun wheel 15a increase the speed of the flywheel 15 in proportion