DEVICE FOR GENERATING MECHANICAL VIBRATION

Abstract: The invention concerns a device where creation of mechanical vibration is made with a system (1) of two or more rotating eccentrics (10). Each eccentric (10) is rotated by an individually controlled motor (11) and the angle position of each eccentric (10) is read by an angle sensor (12). With a control and monitoring system (5), the rotation frequency, direction of rotation and phase position of each eccentric (10) can be controlled. By choosing a number of eccentrics, mass of the eccentrics, rotation frequency, direction of rotation and phase position, a force vector diagram of suitable form, in space and time, can be generated. The invention is intended primarily for use in appliances for dynamic compaction of various materials.

Description: DEVICE FOR GENERATING MECHANICAL VIBRATION. The invention presented concerns a device for generating mechanical vibration, intended primarily for dynamic compaction of various sorts of material. For compacting various materials, e.g., in the construction of roads, airfields, vibratory compaction equipment is used to increase the compaction capacity and optimise the result of the compaction work. Optimisation can consist, for example, of increasing the density of the material, increasing its bearing capacity, achieving a certain density profile with regard to depth and of obtaining a particular surface structure. The equipment used can, for example, be rollers that have one or more vibrating drums, self-propelled vibratory plates, vibratory pokers and tampers. To create the vibration, various types of mechanical systems having rotating eccentrics that utilise centrifugal force are used. This gives in space a rotating circular force vector and in time a sine shaped force vector in a certain direction. To optimise compaction with regard to properties of the compacted material it is necessary that the vibration be given varying frequency, amplitude and direction. Known vibratory devices with rotating eccentrics alter parameters of the force vector in the following way: Examples of systems with one eccentric for achieving a circular force vector with variable amplitude: See, US-patent 5,618,133 Vibrating mechanism and apparatus for generating ... US-patent 4,342,523 High-low force amplitude device US-patent 4,221,499 Vibratory device US-patent 3,966,344 Adjustable vibratory roller Amplitude of the vibration is changed in that the centre of mass for the eccentric weight is displaced in relation to the rotation centre of the eccentric. The vibration frequency is set with the speed of rotation of the rotating eccentric. This is achieved at present by some type of mechanical system. Systems with two eccentrics: See US-patent 5,797,699 Process and apparatus for dynamic soil compaction. A linear force vector is obtained by the two eccentrics rotating in different directions of rotation and fully synchronised, ie, at the same speed of rotation. By phase displacement of the eccentrics so that the direction is changed as the eccentrics pass each other, the force vector can be controlled to act in varying directions. Phase displacement of the eccentrics is made by a mechanical system. Vibration frequency is set with the speed of rotation of the rotating eccentrics. Characteristic for present vibration systems is that they only permit some specific form of vibration and that complicated mechanical devices are required. The object of the invention presented is to optimise compaction with consideration to many different types of material being compacted using one and the same device. Figure 1 and 2 are schematic drawings of the device and figure 3 is a form of execution. The invention is characterised thereby, in that the generation of vibration is made by a system 1 of two or more so-called force vector cells 2 and where a rotating eccentric 10 in each force vector cell generates a circular rotating force vector. All force vector cells 2 generate a force vector that acts in the form of a resulting force vector on the common mass 3. Each eccentric 10 is rotated by a separate electrically controlled drive 11, e.g., electric motor, hydraulic motor, and where the angular position of each eccentric in relation to a reference direction is measured by an angle sensor 12 with electric output signal 9. Rotation of each eccentric with regard to rotation frequency, direction of rotation and phase position is controlled by a control and monitoring system 5 by a control signal 8 to the drive 11. With control signal 6, a superior control device 4 determines signal 7, containing a rotation frequency, a direction of rotation and a phase position for each force vector cell 2 to achieve a determined resulting force vector diagram. The control devices 4 and 5 are at present based on microcomputers for advanced control and monitoring and simple re-programming of the vibration characteristics. By choosing a suitable number of eccentrics 10, centrifugal force of the eccentrics, frequency, direction of rotation and phase position, it is possible to generate a force vector diagram of suitable form, in space and time. With one and the same configuration of force vector cells 2, many different types of force vector diagrams can be obtained. The form of the resulting dynamic force vector diagram can easily be optimised with regard to factors such as the degree of compaction, direction of movement of the compacting appliance and the static force vector from the mass of the appliance. The invention also allows the force vector diagram to be "modulated" by varying the speed of rotation and phase position of the eccentrics in time. For the compacting of certain types of material, optimisation can be achieved since the vibration is composed of several different frequencies (multi-frequency vibration). The invention described also allows an existing apparatus to be easily "re-programmed" to conform to force vector diagrams that have been tested and to new types of material that need to be compacted. See figure 4-7 for some typical force vector diagrams that can be achieved: Figure 4: Circular force vector diagram with adjustable amplitude: 105 The vibration system consists of two force vector cells, where the eccentrics rotate in the same direction and at the same rotational speed and where the phase difference can be regulated. This results in a circular force vector with amplitude that is adjustable between 0 and maximum depending on the phase difference between the eccentrics. 110 The figure shows amplitude of the rotating force vector for the phase differences 0, 135 and 180°. Figure 5: Force vector with adjustable direction and fixed amplitude, 115 The vibration system consists of two force vector cells, where the eccentrics rotate in opposite directions and at the same rotational speed and where their phase position can be regulated. This results in a linear force vector that acts in one direction only (+/-) and at fixed amplitude. Direction of the force vector depends on when the centrifugal forces of both 120 eccentrics interact in one direction for each revolution. The figure shows how displacing the phase position 0, 90 and 45° in relation to the reference direction can turn the force vector. Figure 6: Force vector with adjustable direction and fixed amplitude, 125 The vibration system consists of two force vector cells, where the eccentrics rotate in opposite directions and where eccentric 2 rotates at double the rotational speed compared to eccentric 1. By giving eccentric 2 different phase positions a force vector diagram with different combinations of depth and surface effect can be obtained. 130 Figure 7A: The vibration system consists of three force vector cells, where the eccentrics 1 and 3 rotate in the same direction and eccentric 2 in the opposite direction Speed of rotation for eccentric 1 = 4 Hz, eccentric 2 = 8 Hz, eccentric 3 = 12 Hz. Amplitude of eccentric 1 = 0.5, eccentric 2 = 0.41, eccentric 3 = 0J8. With these settings a force vector that acts in depth for a short period is obtained. 140 Changing the phase position of the eccentrics turns the direction. Figure 7B: The vibration system consists of three force vector cells, where the eccentrics 1 and 3 rotate in the same direction and eccentric 2 in the opposite direction. 145 Speed of rotation for eccentric 1 = 4 Hz, eccentric 2 = 8 Hz, eccentric 3 = 12 Hz. Amplitude of eccentric 1 = 0.5, eccentric 2 = 0.5, eccentric 3 = 0.5. With these settings a force vector is obtained that has combined surface and depth effect. Changing the phase position of the eccentrics turns the direction. 150 The execution form according to figure 3 is a device with two force vector cells 2a, 2b, where the eccentrics have coaxial location. This implies that the outer eccentric 10a rotates round the inner eccentric 10b. This location means that the mass centre (centre of gravity) of the eccentrics has the same axis of rotation 17 and the same rotation plane 18, which is of significance for the resulting force vector for both of the eccentrics. 155 The axles 14a and 14b are carried by a number of bearings 16 so that they can rotate freely in relation to one another and to the holder 15. The principle of coaxial located eccentrics can also be used for 3 or more eccentrics. The cells are mounted on a common plate 3 the mass of which shall vibrate to compact the underlying material. 160 The eccentrics 10a, 10b rotate with the respective axle 14a and 14b, which are common for the respective electric motor 11a, l ib and respective angle sensor 12a, 12b. The motor 1 la, 1 lb is fed from the control device 5a, 5b by a voltage 8a, 8b that determines the direction and speed of rotation for the axle 14a, 14b. From angle sensor 12a, 12b a signal 9a, 9b is given that is the angle value of the eccentric 165 10a, 10b in relation to a reference direction which, for example, can be in the horizontal plane. The signal 7a, 7b from the control device 4 is the desired value for the direction of rotation, speed of rotation and phase position for the eccentric 10a, 10b. 170 From the signal 9a, 9b from the angle sensor 12a, 12b the control device 5 a, 5b calculates the value of the real direction of rotation, speed of rotation and phase position for the eccentric 10a, 10b. Consequently, these values form the actual value of the control 175 system. The control device 5a, 5b regulates with the voltage 8a, 8b the electric motor 11a, 1 lb so that the desired value and the actual value are the same. 180 The signal 6 gives the parameters for the operational case to the control device 4. The parameters can for example be the frequencies for the vibration, form of the force vector diagram and modulation.

Claims: 185 PATENT REQUIREMENTS 190 1. Device for generating mechanical vibration with rotating eccentrics (10) characterised by a system (1) with two or more force cells (2) with rotating force vectors, where the resulting force vector of all force cells acts on a mass (3) and where each force cell (2) consists of a rotating eccentric (10) driven by a separate electrically controlled drive (11) that is mechanically coupled to an angle sensor (12) for 195 measuring the angular position of the respective eccentric in relation to a reference direction. 2. Device according to requirement 1 characterised by a superior control device (4) giving a signal (7) to a separate control and monitoring system (5) for each 200 force cell for setting of fixed or variable direction of rotation, rotational speed and phase position in relation to a reference eccentric for each respective eccentric. The control and monitoring system (5) receives, via an output signal (9) from the angle sensor (12), information about the angle position of the eccentric and calculates the direction of rotation, speed of rotation and phase position of the eccentric and by means of the signal 205 (7) regulates the correct direction of rotation, speed of rotation and phase position through a signal (8) to the drive device (11) of the respective eccentric. 3. Device according to requirement 1 and 2 characterised by the superior control device (4) receiving information about the parameters for a specific force vector 210 diagram through a control signal (6) and determining the direction of rotation, speed of rotation and phase position of the eccentrics, the values of which are transmitted to all of the control and monitoring systems (5) through the signal (7). 4. Device according to requirements 1-3 characterised by the mass centre of 215 the eccentrics (10) having approximately the same geometric axis of rotation (17) and that the mass centre of the eccentrics (10) rotates in approximately the same geometric plane (18).

Inventors: ANDERSSON ULF BERTIL, ANDERSSON, ULF, BERTIL
Applicants: ANDERSSON ULF BERTIL, ANDERSSON, ULF, BERTIL
Application year: 2000
Main classification: E01C19
IPC codes: B06B1, E01C19, E02D3