DE3809558A1 - Damping device for reducing the transmission of oscillations produced by vibrating apparatuses to the hand-arm system - Google Patents

Abstract

The subject of the invention is a damping device for reducing the transmission of oscillations produced by vibrating apparatuses to the hand-arm system. The invention is to be allocated to the area of "damping devices for mechanical oscillations", in particular in the case of intensely vibrating hand-held apparatuses. For the loading of the hands and hand-arm system, oscillation components in the frequency range below 60 Hz are particularly damaging to health. The damping devices disclosed hitherto display only inadequate damping properties in this particularly important frequency range. The subject of the invention is a device which also heavily damps the oscillations in the frequency range below 60 Hz. This is achieved in that gripping surfaces made of dimensionally stable material are coupled to the apparatus via a viscoelastic material layer over as large an area as possible (composite system). The good damping behaviour in the low-frequency oscillation range results by using a soft, viscoelastic material as coupling layer. The main area of application for the subject of the invention is the oscillation damping of hand-held apparatuses and tools.

Description

The invention relates to a vibration damping principle that ins special the hand-held tools in the hand-arm System initiated vibrations even in the low frequency range should dampen without causing a significant loss in Füh precision comes.

1 Task

When working with strongly vibrating handheld devices after several years of continued vibration exposure, the Ent are from bone and joint damage or from blood circulation and nerve dysfunction in the hand-arm elbow rich cannot be excluded [1, 2]. Here are for the burden of the hands and the hand-arm system frequency range below 60 Hz of particular importance [8].

The invention has for its object vibrations by hand-held vibrating devices are generated, also outdoors dampen the frequency range below 60 Hz without causing a significant loss of leadership precision comes.

2. State of the art

To reduce vibration transmission on hand-held Devices are far from using vibration-dampened handles common [3, 4]. Studies [1] on the effectiveness of these Handles revealed that their damping effect in particular Frequencies above 60 Hz is pronounced, while it is in Fre frequency range below 60 Hz may lead to an ampl acceleration of vibration comes.

Also recent developments, according to which damper elements between  Handle and implement are arranged in the frequency display rich below 60 Hz practically no effect.

The elastic handle covers for Handles or gripping points of vibrating devices also have High frequency range good damping properties, while in lower frequency range no vibration damping, sometimes even a vibration amplification can be observed [5].

Comparable conditions were when using Antivi protective gloves found [6, 7].

3. Description of the subject matter of the invention

The task is solved in that from dimensionally stable Material-made gripping surfaces over a viscoelastic Material layer coupled to the device over as large an area as possible are (network system). The good damping behavior in low frequency quent vibration range results from using a soft, viscoelastic material as a coupling layer.

An optimal damping effect is achieved with this principle under the following conditions:

To ensure precise guidance of the work equipment, the layer thickness of the elastic material is as low as possible hold. But with that the soft, viscoelastic damping material rial by the holding forces occurring during the work process is compressed so much that it's vibration-damping Loss of properties is caused by training as large as possible of the gripping surfaces that acting on the coupling layer Distribution of pressure over a large area. In individual cases, the size the coupling surface, the layer thickness and the elasticity of the viscoelastic material according to the given vibration range of the device, which under practical conditions conditions occurring holding forces and the required guidance coordination precision.  

An embodiment is shown in drawing Fig. 1 and is described in more detail below:

A forging pliers are shown with which workpieces are held with both hands during drop forging. To dampen the introduction of vibrations to the hand-arm system, the pliers handles ( 1 ) are provided with a large area with brass tube sleeves ( 2 ), which are non-positively coupled to the handles of the forging tongs via a foam layer ( 3 ).

In the exemplary embodiment, the foam layer was made of 3 mm strong foam sheets made of PORON 4701 (Rogers Corporation, East Woodstock, CT 06244 USA). The length of the brass Handle sleeves is 300 mm, the outer diameter 14 mm, the Inner diameter 13 mm and the outer diameter of the pliers handles 8 mm.

With this arrangement, the evaluated vibration strength K _e for a specific job (forging knife blades with a 500 kg hammer) could be reduced from K _eq = 60 to K _eq = 29, which means that according to VDI 2057, Sheet 3 (May 1987 edition) permissible daily load duration could be extended from 0.6 hours to 2.5 hours.

Another embodiment is shown in FIG. 2. It is a schematic representation of an electric impact drill ( 4 ), in which large-area gripping surfaces ( 5 , 6 ) are coupled to the implement via a soft, visco-elastic intermediate layer ( 7 , 8 ). In this embodiment, the viscoelastic material is introduced through a foaming process.

literature

[1] Christ, E .:
Reduction of the effects of vibration on vibrating hand-held tools
The BG, (1986), No. 1, pp. 15-20
[2] Dupuis, H .:
Effect of mechanical vibrations on the hand-arm system - literature analysis
Research Reports No. 308 and 348, Wirtschaftsverlag NW, Bremerhaven 1982 u. 1983
[3] Bitsch, J. et al .:
Fouloirs pneumatiques a "some allonge". Etude de la reduction des vibrations et du bruit.
Cahiers de notes documentaires No. 114. 1 ^er trimestre 1984, pp. 35-45
[4] Miwa, T .:
Vibration Isolation Systems for Hand-Held Vibrating Tools.
In: Vibration Effects on the Hand and Arm in Industry. Ed. by AJ Brammer and W. Taylor. John Wiley and Sons, New York 1982, pp. 303-310
[5] Suggs, CW and JH Hanks:
Resilient handgrips.
In: Vibration Effects on the Hand and Arm in Industry. Ed. by AJ Brammer and W. Taylor. John Wiley and Sons, New York 1982, pp. 333-337
[6] Griffin, MJ and others:
The Transmission of Vibration to the Hand and the Influence of Gloves.
In: Vibration Effects on the Hand and Arm in Industry. Ed. by AJ Brammer and W. Taylor. John Wiley and Sons, New York 1982, pp. 103-116
[7] Voss, P .:
Problems Concerning the Construction of an Effective Vibration Isolation Glove.
Internoise '83. Proceedings Vol. I, pp. 523-526.
Ed. Inst. Of Acoustics Edinburgh, UK, 1983
[8] VDI 2057, sheet 2:
Effects of mechanical vibrations on humans - evaluation.
Section 6: Assessment of exposure via the hand-arm system. May 1987 edition.

Claims (2)

1. Damping device for reducing the transmission of vibrations generated by vibrating devices to the hand-arm system, characterized in that the gripping surfaces and, in addition, the largest possible adjoining areas of a device are designed as dimensionally stable formwork, which over a large area of soft, vibration-damping material to the Device are coupled, the layer thickness of the vibration-damping material depending on the size of the coupling surfaces and the softness of the vibration-damping material is to be determined in such a way that the vibration-damping effect is retained at every point of the coupling layer even under the effect of the maximum possible device holding forces. 2. Damping device according to claim 1, characterized in net that the vibration damping intermediate layer from turned foamed or preformed viscoelastic material stands, especially under vibration frequencies 60 Hz has good vibration damping properties.