SE504437C2 - Device for vibrating rotary grinder with self-centering grinding wheel - Google Patents

Abstract

An arrangement to devibrate a hand-held, compressed air-driven rotary grinding machine with vertical spindle. A grinding machine equipped with an unbalanced and unequally worn grinding wheel vibrates severely and will injure the operator. To avoid vibration reaching the hands of the operator, the drive unit (2) with its integral spindle (13) is supported by shock and vibration-absorbing elements (3, 4, 4', 16) in the outer case (1) where it is able to move in three dimensions. The working movement (compression-elongation as well as sideways) of the elements is never exceeded by the amplitude of the vibration that occurs when the machine runs at a normal working rotational speed, which is much higher than the critical resonance speed. The drive unit (2) is very lightweight in relation to the outer case (1) and to the grinding wheel (5, 6, 7). As a result of this, the grinding wheel will centre itself automatically when the critical resonance speed is passed. Compressed air is supplied to the motor through a flexible hose (10).

Description

504 457 2 grinding machine is equipped with vibratory handles, which is usually done by mounting a rubber block between the machine and the handles, the vibration becomes very marginal. This is partly because the handles are very light in relation to the machine, which is why vibrations in the machine also cause the handles to vibrate, and partly because the rubber must be relatively hard to be able to absorb the large bending moments to which the handles are subjected. the machine. At the same time, the machine becomes more uncomfortable and more strenuous to hold as the handles come out further, which gives a higher bending moment on the operator's wrists together with the machine having to be held tighter.

In a rotary grinder, the frequency and amplitude of the vibrations change during the work as the grinding / cutting disc is sucked.

Unevenness in the wear means that the grinding wheel deviates from its original rotational symmetry and can become eccentric, oval, triangular, square, etc. This, together with different employment angles and forces, results in grinding machines with weaned handles similar to e.g. chainsaws at certain speeds easily come into self-oscillation. The same thing occurs with grinding machines where the dexubation-damping elements consist of rubber rings such as e.g. Eyes, whose effective working / suspension path is well below the amplitude.

When a machine comes into self-oscillation, the vibrations are amplified and these are transmitted to the operator's hands.

Object of the invention and most important features. The object of the invention is to insulate the vibrations directly and as close as possible where they occur on a hand-held, compressed air-driven grinding machine, ie. at the grinding wheel, and as far as possible prevent them from spreading to the handles and thus to the operator's hands. The machine, which is equipped with a speed controller, operates at supercritical speeds. In order to keep the resonance-critical speed as low as possible, the drive unit, ie. the compressed air motor with associated drive shaft, grinding spindle shaft, as light as possible. This is achieved through several parts, e.g. the engine's bearing cap, is made of aluminum and that the rotor is equipped with axial light holes. The motor housing is then suspended suspended in soft shock and vibration damping elements in the outer casing. The shock and vibration damping elements are positioned in such a way that imbalance and process vibrations continue. 3,504,437 as well as the motor power pulses are attenuated in three dimensions. In case of imbalance, the grinding wheel becomes self-centering where the movement pattern, centric or oscillating depending on the grinding wheel's design, weight and mass moment of inertia, while the movements relative to the outer casing are absorbed by the shock and vibration damping elements. However, the drive unit is suspended so stably that the grinding wheel can be firmly attached to the workpiece without the drive unit hitting the outer casing. Inclined loads when angled when the grinding wheel is applied are taken up by highly placed shock and vibration damping elements, lying in line with the board's point of contact. Control and support handles are dumbly attached to the outer casing, while the compressed air motor with the associated grinding spindle shaft and thus also the grinding wheel, remains completely "floating".

Description_of the drawings.

Fig. 1 shows a vertical section through the grinding machine with a hub pad mounted. This shows the free suspension of the drive unit, with associated spindle shaft, in the upper and lower shock and vibration damping elements. At the same time, the air supply to the compressed air motor is shown as well as the movable diaphragm which serves as a seal between the lower part of the drive unit and the outer housing.

Fig. 2 shows a vertical section of the lower part of the machine with a cutting disc mounted. In both Fig. 1 and Fig. 2, the machine is provided with a so-called explosion protection.

Fig. 3 shows a vertical section of the lower part of the machine with a shell grinding wheel mounted.

Fig. 4 shows a vertical section through the machine where the lower shock and vibration damping element consists of a e.g. between two sleeves vulcanized rubber ring. Fig. 4 is an alternative to Fig. 1 and Fig. 5.

Fig. 5 shows a section along the line A-A in Fig. 1 where the location of the lower shock and vibration damping elements is shown.

Two of these are mounted radially and one tangentially to thereby dampen vibrations in all directions.

Fig. 6 shows a section along the line B-B in Fig. 1 where the location of the upper shock and vibration damping elements is shown. This figure also applies to embodiments in accordance with Fig. 4. cont.

Claims (3)

504 437 4 Description of the working example. In the drawing, 1 denotes the outer casing, 2 the drive unit equipped with a compressed air motor, where 13 marks the spindle shaft. The upper shock and vibration damping elements are denoted by 3 and the lower ones by 4 and 4 '. The grinding machine can be equipped with different types of grinding wheels where 5 shows a hub disc, 6 a cutting disc and 7 a bowl grinding wheel. When working with hub disc and cutting disc, the machine must be equipped with explosion protection, 14. The control handle, 9 contains a pneumatic valve, 15, which is actuated by the actuating handle 11. The compressed air is transferred from the valve to the compressed air motor via a flexible hose, 10. During grinding operations in the control handle, 9, and in the support handle, 8. A bellows-shaped, flexible mother, 12, causes an expansion chamber to be formed between the drive unit 2 and the outer housing 1, which reduces the noise level from the exhaust air of the compressed air motor. The lower shock and vibration damping elements, 4 and 4 ', as well as the mother 12, can be replaced with e.g. one between two sleeves invu fl æd gmmüring, l6. PATENT REQUIREMENTS Device for hand-held, pneumatic rotary grinding machines with vertical axis where the pneumatic motor unit (2) with the grinding spindle shaft (13) is freely suspended in the machine's outer casing (1), k-marked d-ä of the compressed air motor unit (2 ), by means of one or more series of shock and vibration damping elements (3) and lower either series of shock and vibration damping elements (4, 4 ') or a recessed rubber ring (16), with a suspension path greater than the amplitude of the vibrations, sits in three dimensions freely suspended in the outer casing (1), which at the supercritical working speed of the grinding machine results in the grinding wheel (5,6,7) becoming unbalanced in the event of imbalance without vibrations being transmitted to a greater extent to the outer casing (1) and handles (8,9) and that the grinding pressure is absorbed by the upper shock and vibration damping elements (3). Device according to claim 1 k-ä-n-n-e-t-e-c-k-n-a-d d-ä-r-a-v that the freely suspended compressed air motor unit (2) is allowed to continue. 504 437 the air via a three-dimensionally flexible hose (10) which at its other end is connected to a hand-operated control valve (15) and that the compressed air motor unit (2) is sealed to the outer means by means of a three-dimensionally movable diaphragm (12). the housing (1) and thereby forms a sound-absorbing expansion chamber. Device according to claims 1 and 2 k-ä-n-n-e-t-e-c-k-n-a-d d-ä-r-a-v that the grinding machine is intended to be used for both flat grinding wheels, so-called hub discs (5), for cutting discs (6) as well as for bowl grinding discs (7) and that the compressed air motor, with bearing cover of aluminum and the rotor fitted with light holes, is very light in relation to the outer casing.