WO2000061469A1

WO2000061469A1 - Balanced vibrator with flat springs

Info

Publication number: WO2000061469A1
Application number: PCT/DK2000/000165
Authority: WO
Inventors: Morten Skak
Original assignee: Valdemar Skak Dansk Svingningsteknik AS
Current assignee: Valdemar Skak Dansk Svingningsteknik AS
Priority date: 1999-04-09
Filing date: 2000-04-05
Publication date: 2000-10-19
Anticipated expiration: 2001-10-09
Also published as: DK199900471A; AU3551500A

Abstract

Balanced vibrator with two oscillating masses (M1, M2), where the one consists of a machine or an apparatus, i.e. the so-called effective mass (M1), and the other consists of a counter-oscillating mass (M2) for balancing, in that both masses are individually supported by at least one leaf spring (3, 3', 3', 3'', 4, 4', 4', 4'') said leaf springs opposite the oscillating masses being secured in a common base (5, 5', 5', 17), that by a drive motor (1) the two oscillating masses are brought into movement with their deflections in opposite directions, but with their centres of gravity in a defined direction of oscillation (L1), that the securing points for the leaf springs are disposed in a substantially straight securing line (L2) or in a number of securing lines (L2) parallel with each other, and which moreover are dimensioned in such a manner that the sum of the leaf springs' securing moments is substantially zero. The ratio between the weight of the two oscillating masses (M1, M2) can be different from 1, and the securing line or lines (L2) are substantially parallel with the direction of oscillation (L1) of the oscillation masses, and the leaf springs (3, 4) and the base (5, 5') for said masses are configured as a one-piece unit and of the same material. Hereby is achieved a vibrator which is balanced in such a way that no vibrations are transferred to the base on which the vibrator is placed.

Description

BALANCED VIBRATOR WITH FLAT SPRINGS

The invention concerns a balanced vibrator of the kind disclosed in the preamble to claim 1. Such vibrators are used to a great extent when there is need for a controlled vibration, e.g. in the operation of vibration feeding chutes, vibrating conveyors and vibration screens etc.

For the generation of vibrations, it is commonly known to make use of e.g. a motor-vibrator, i.e. an electric motor with imbalance weights mounted on the axle journals, a mechanical vibrator i.e. an apparatus with axles coupled together with imbalance masses, where the axles are driven by an external motor, or electromagnetic vibrators where an electromagnet constitutes the driving means in an oscillation system. If such systems are not configured in a suitably balanced manner, forces and herewith vibrations are trans- ferred from the apparatus as a whole to the base on which this is mounted, e.g. a concrete floor in a building, which gives rise to many known disadvantages such as undesired vibrations and tremors in the base and herewith in the building, possibly with damage as a consequence, undesired noise and vibration effects on the personnel and disproportionately high energy consumption etc. In order to reduce these disadvantages, the connecting link between the vibrating machine and the base often consists of rubber elements, helical springs, leaf springs etc.

From the applicant's Danish patent no. 170,517 there is known a balanced vibrator with a resonance system with helical springs between two counter- oscillating masses, where the vibrator can be set by the setting of the helical springs so that no vibrations are transferred to the base.

From USA patent no. 3,786,912 there is known a linear vibrator driven by an electromagnet, where the effective mass is a conveyor chute. The vibrator is balanced partly by a counter-oscillating mass by means of leaf springs secured in a base in which the leaf springs which support the conveyor chute are also secured. To a certain extent, it should be possible hereby to avoid the transfer of vibrations to an under layer or base on which the apparatus is mounted. However, vibrators which have electromagnetic driving means have several known disadvantages. They have poor efficiency and are thus very uneconomical in comparison with the use of electric motors. As a rule, magnetic vibrators must be provided with current from the mains network, i.e. with 50 or 60 Hz mains voltage, which means that a relatively precise oscillatory balancing of the mechanical system is neces- sary if resonant oscillations are to be achieved and herewith the desired length of stroke. An unintentional change in the natural frequency of the vibrator has great influence on the actual length of stroke. If it is desired to be able to regulate an electromagnetic vibrator, expensive regulation plant is required for reasons of the high current consumption.

Electromagnetic driven vibrators are suitable only for small stroke lengths, whereas the users desire greater stroke lengths and low frequencies. This is possible by making use of electric motors, where several simple and inexpensive circuits are known for the regulation of the speed of rotation.

From USA patent no. 3,817,370 there is known a vibration system where chutes are supported by leaf springs, and where the vibrations are generated by means of an electric motor which drives an eccentric mechanism with drive rods to the chutes. The drive motor is placed under an inter- mediate base to which the leaf springs are secured, and where this base or table is supported with legs which rest on the under layer or the building fundament. The intermediate base must be of a very rigid and robust configuration, the reason being that it is exposed to bending influences due to the lack of balance, because the centres of gravity of the counter-oscillating masses are moved in directions which, even though they are parallel, extend in a direction other than the intermediate base. The intermediate base, moreover, is also further anchored by means of beams etc., so that the rigidity of the construction is increased, but herewith also the weight and the extent hereof, so that vibrations which are not balanced out can be absorbed in the construction.

By configuring a balanced vibrator according to the invention as characterised in claim 1 , it is hereby possible to construct a vibrator which can be balanced more or less completely, so that no vibrations are transferred to the base. The ratio between the weight of the two oscillating masses is preferably different from 1 , and in practice is often configured so that the ratio between the weight of the oscillating masses is inversely proportional to the ratio between their respective oscillations. The vibrator according to the invention is particularly simple and uncomplicated in construction, and can be produced for an especially competitive price in comparison with other complicated mechanisms. That no vibrations are transferred to the base or the under layer on which the vibrator is mounted is due to the special geometry of the construction. The vibrator according to the invention can thus be used on normal factory floors without reinforcement. The configuration according to the invention is particularly advantageous for small and medium-sized vibrators. Moreover, at one and the same time there is achieved a configuration where the securing line(s) for the leaf springs and the line for the centres of gravity of the oscillating masses are always parallel, and a very competitive product with very few individual parts. In addition hereto, an advantageous production method is achieved for the production of the unit, i.e. advantageously by water or laser cutting e.g. in a thermoplastic material, or by moulding, powder-pressing, stamping-out or in another manner in or of a suitable material which has the necessary characteristics. Moreover, in this manner it is possible to configure the transitions between springs and base so that a better distribution of the bending stresses is achieved in this/these areas. Particularly great advantages are achieved when also the mounting element for the effective mass, e.g. a chute, is configured as characterised in claim 2.

When the vibrator according to the invention is configured as characterised in claim 3, the possibility is provided of achieving a particularly compact construction, and without any sacrifice whatsoever with regard to the balancing. Such compact vibrator mechanisms have very, very great practical advantages and therefore a very large area of application.

The vibrator according to the invention is preferably configured as characterised in claim 4, i.e. where the drive unit comprises an electric motor with the many advantages this affords from the point of view of energy and regulation. However, for certain special applications or for placing in special factory premises or geographic areas, use can also be made of an electromagnetic drive unit, or alternatively a drive system based on compressed air in piston or bellows or hydraulic operation in a corresponding manner. The configuration according to claim 4 provides the many advantages which are achieved with a vibrator driven by an electric motor. Depending on how great a stroke length is desired, the same vibrator is driven either by forced vibration or by resonance-reinforced operation, whereby strokes of maximum length are achieved. In practice, resonance- reinforced operation is understood to be when the applied vibration frequency lies between 90% and 100% of the natural frequency of the me- chanical system.

For many applications, it is advantageous to configure the vibrator according to the invention as disclosed and characterised in claim 5. It is hereby possible to construct a vibrator with a counter-oscillating mass which is considerably less than the effective mass, while still completely avoiding that the vibrator transfers vibrations to the base. If the counter-oscillation mass is e.g. three or four times smaller than the effective mass, the oscillation of the effective mass must be three or four times less than the oscillation of the counter-oscillating mass. This is achieved quite simply by corresponding differences in the radius on the crank drive or the eccentric drive mechanism, and by effecting corresponding changes in the spring constants, so that the leaf springs which support the effective mass are three of four times more stiff than the leaf springs which support the counter-oscillating mass. In practice, the latter changes in the springs can be effected by use of a corresponding number of leaf springs coupled in parallel.

Claims 6-8 disclose in more detail a practical embodiment of a balanced vibrator according to the invention which has many practical applications within the industry.

Particularly in the case of small or medium-sized vibrators, it can be an advantage to configure the balanced vibrator according to the invention as disclosed in more detail and characterised in claim 7. The result is a particularly advantageous configuration which is simple and inexpensive to produce, and which does not include any mutually movable wearing parts, in that the movement is absorbed in bending and displacement in the material. This results in a very long lifetime. In addition to this, it is possible to select a material which makes the connecting rod(s) insensitive to conditions of temperature, moisture and corrosion. It can be an advantage for the connecting rod(s) to be configured as one independent unit formed in one piece from a piece of material in the same manner as the unit which is comprised of springs, base etc., and as disclosed in connection with claim 2.

Finally, as disclosed and characterised in claim 9, the vibrator according to the invention can be equipped with one or more elements for measuring the spring deflection. The voltage or current which is delivered by the element, e.g. a crystal, increases with the magnitude of the deflection, and can be used as a signal in a control circuit for controlling the drive unit. The possibility is hereby provided for different methods of control, e.g. control for fixed length of stroke, even though the loading of the vibrator varies.

The drawing

In the following, the invention will be explained in more detail with reference to the drawing, in that

fig. 1 is a principle diagram which shows a vibrator according to the invention,

fig. 2 shows a side view of a first embodiment of the invention, where the vibrator drives a chute, and where the effective mass has the same mass as the counter-oscillating mass,

fig. 3 shows a side view of a second embodiment of the invention, where the effective mass is three times greater than the counter-oscillating mass,

fig. 4 shows a side view of a third and particularly advantageous embodiment of the invention,

fig. 5 shows the vibrator unit alone, and

fig. 6 shows an example of the mounting of a crystal element on one of the vibrator unit's springs. In fig. 1 , the drive unit 1 is an electric motor which by means of an angle bracket 2, e.g. bent flat steel, is secured to a base 5, e.g. in the form of a solid iron or steel part.

On the motor shaft there is mounted an eccentric bearing with hub 6 and drive rods 12 which couple the eccentric bearing to the masses M1 and M2. The drive rods 12 comprise elastic elements 8,9, so that the drive rods can be deflected in order to follow the eccentric drive, and so that the masses M1 and M2 which are fastened on leaf springs 3 and 4 respectively can move outwards and inwards in relation to the centreline of the motor shaft during operation. A stiff element 7 is placed between the elastic element 8 and the leaf spring 3. The centres of gravity for the masses M1 and M2 lie on the shown line L1 , which line constitutes the direction of oscillation. When the motor 1 rotates, the masses M1 and M2 will be brought into movement and will move opposite to each other, whereby the leaf springs 3,4 are bent and apply forces to the base 5 which can result in the base being deflected in the vertical direction, i.e. in the direction of the motor shaft. Through the base 5 there is shown the securing line L2 in which the leaf springs 3,4 are secured. In the principle drawing shown in fig. 1 , the securing line L2 is parallel with the direction of oscillation L1. If the masses M1 and M2 are of equal size, and the springs 3,4 have identical characteristics, the sum of the leaf springs' securing moments will be zero, in that the securing moments of the two springs are constantly equal and oppositely directed. If the base 5 is configured in a suitably rigid manner, so that substantially no deflection takes place, the forces will be mutually equalised so that the base 5 can be mounted on an under layer, e.g. a concrete floor in a building or another fundament, without vibrating forces being transferred hereto. At the same time, since the oscillating elements follow the direction of oscillation L1 , and the masses M1 and M2 are counter-os- ciilating, the vibrator is completely balanced and the resulting forces to the fundament, e.g. the concrete floor on which the vibrator is placed, will be quite minimal. Consequently, no vibrations are transmitted from the vibrator to the surroundings via the base 5 and the building fundament.

Fig. 2 shows a practical embodiment where the counter-oscillating masses are still of equally great mass. The one mass M1 comprises a chute 10, e.g. a conveyor chute, and a securing bracket 11. Together, the parts 10 and 11 constitute the mass M1. The counter-oscillating mass consists of a counter- oscillating block M2 with the same mass as M1. M1 and M2 are configured in such a manner that the centre of gravity line L1 is moved in relation to the points of application of the drive system, but still so that L1 is a straight line. Moreover, the vibrator is provided with two further leaf springs 3', 4' which control the movement of the oscillating masses, but which also form a part of the spring element in the overall oscillation system. The base 5' is placed on a frame 15 which constitutes the connection between the ma- chine base 5' and the surrounding fundament 16, e.g. the concrete floor in a building. In addition, the reference figures used here are the same as those used for corresponding parts in fig. 1. Also here, the masses M1 and M2 and the leaf springs 3,3' and 4,4' are configured so that the sum of the securing moments in the securing line L2 cancel each other out when the vibrator is working.

It is seen clearly in fig. 1 and fig. 2 that it is possible by use of the invention to configure a completely balanced vibrator, so that the vibrating mechanism itself occupies a minimum of space.

Fig. 3 shows an embodiment of the invention where M1 has a mass which is three times greater than M2, i.e. the effective mass is three times greater than the counter-oscillating mass.

The oscillating masses M1 and M2 are secured by spring systems in a common machine base 17, where each securing area comprises a smaller base part 5". M2 is supported by the leaf springs 4",4'", and M1 is supported by spring packs. In the example shown, the spring packs 3", 3'" each comprise three leaf springs, corresponding to the relationship between the two oscillating masses.

The system is driven by a drive motor 1 with an eccentric drive arrangement, or by a crank-drive arrangement 6 which via stiff drive rods 12 and elastic elements 8,9, e.g. of rubber, transfers the vibration energy to the masses M1 and M2. The drive motor 1 is shown mounted on a column 17' on the common base 17, but will also be able to be mounted in other places on the base 17. The motor will also be able to be placed, as is otherwise known, on the one of the masses with eccentric or crank and with drive rod extending to the other mass.

From fig. 3 it will be seen that the points of gravity for the masses M1 and M2 move along a line L1 which is parallel with the lines L1 through the securing points, and which is also parallel with the lines L2 through the securing points for the stationary end of the leaf springs. The securing points hereby become neutral, in that the sum of the moments in each base part 5" becomes zero, so that vibrations are not transferred to the common machine base 17 which, in a manner corresponding to that described in connection with fig. 1 and fig. 2, will therefore be able to be placed directly on a floor in a building.

Hereafter, the system will oscillate so that the stroke length for the mass M2 is three times greater than the stroke length of the mass M1.

It will also be seen from fig. 3 that the lines L1 are parallel with the stiff drive rods 12. The drive rods 12 and the drive arrangement 6 can also be configured as disclosed in Danish patent application no. 245/97, i.e. as a connecting-rod system with connecting rods which are resilient or can be elastically deformed.

Figs. 4 and 5 show the principles involved in the configuration of parts of the balanced vibrator as a one-piece unit of the same material. In figs. 4 and 5 it is seen how the base 5, springs 3,3' for a mounting element 13 for the effective mass M1 and springs 4,4' for a counter-oscillating mass M2 can be configured as one integrated unit 20. On the springs 4,4' there can be mounted a counter-oscillating mass M2, and an effective mass can be secured in a suitable manner on the mounting element 13, which effective mass as shown can be a conveyor chute 10, but which naturally can also be any other form of effective mass which is made to vibrate as desired. In the embodiment shown, the leaf spring 3' serves mainly to control the oscillating movement of the chute 10 in the desired direction, while the leaf spring 3 provides the desired spring constant for the co-oscillating mass M1.

The drive unit 1 , which is shown placed between the springs, drives an eccentric mechanism or a crank mechanism 6 which, via drive rods with elastic elements 8,9, activates the effective mass and the counter-oscillating mass M2.

In fig. 6 is shown an example of how an electrical control of the stroke length can be established. On one of the springs there is mounted an element 18, e.g. a crystal element (e.g. a piezoelectric crystal) which, since the element is glued firmly on the spring 4 and follows its deflection, delivers a voltage or a current which is a function of the deflection,. It will be obvious to an expert in the field that the element 18 will be able to be mounted on any of the springs in the element 20 for the measurement of the deflection, and herewith for controlling the length of stroke. The current or the voltage is used to control the supply of energy to the drive unit 1 which, e.g., is an electric motor, e.g. a DC motor.

By configuring the vibrator according to the invention as shown in fig. 4, i.e. with an inclined, asymmetrical base 5, the possibility is provided for the chute 10 to extend horizontally or in a substantially horizontal manner. Moreover, a configuration can be achieved whereby all of the springs are parallel, so that total balancing is achieved.

Claims

1. Balanced vibrator with two oscillating masses (M1.M2), where the one consists of a machine or an apparatus, i.e. the so-called effective mass (M1), and the other consists of a counter-oscillating mass (M2) for balancing, in that both masses are individually supported by at least one leaf spring (3, 3', 3", 3'", 4, 4',4",4'") said leaf springs opposite the oscillating masses being secured in a common base (5,5',5",17), that by a drive motor (1) the two oscillating masses are brought into movement with their de- flections in opposite directions, but with their centres of gravity in a defined direction of oscillation (L1), that the securing points for the leaf springs are disposed in a substantially straight securing line (L2) or in a number of securing lines (L2) parallel with each other, and which moreover are dimensioned in such a manner that the sum of the leaf springs' securing moments is substantially zero, ch a racte ri sed in that the ratio between the weight of the two oscillating masses (M1,M2) can be different from 1, that the securing line or lines (L2) are substantially parallel with the direction of oscillation (L1 ) of the oscillating masses, and that the leaf springs (3,4) and the base (5,5') for the masses are configured as a one-piece unit and of the same material.

2. Balanced vibrator according to claim 1, characterised in that the unit also comprises a mounting element (13) for the effective mass (M1) or a part hereof, which mounting element is configured as a one-piece unit together with leaf springs and base.

3. Balanced vibrator according to claim 1 or 2, characterised in that the drive unit (1) is placed between the leaf springs for the effective mass, so that counter-oscillating springs (3,3',4,4') are disposed on each their sides of the drive unit.

4. Balanced vibrator according to any of the claims 1-3, and where the drive unit comprises an electric motor (2) with crank/eccentric mechanism (6) and drive rods (12) or the like which are coupled to the two oscillating masses, and where the drive unit is secured to the common base (5,5', 17), characterised in that the motor (1 ) is controlled to drive the vibrator either at a desired frequency, i.e. so-called forced vibration, or at a frequency close to the natural frequency of the system, i.e. so-called resonance-reinforced operation.

5. Balanced vibrator according to claim 1, and where the effective mass (M1) is of a greater weight than the counter-oscillating mass (M2), characterised in that the drive unit is an electric motor (1 ) which is secured to the common base (17), and that it comprises a crank/eccentric mechanism (6) with actuating rods or the like (12) coupled to the oscillating masses (M1,M2).

6. Balanced vibrator according to any of the claims 1-5, ch a racterised in that the effective mass (M1) consists wholly or partly of a conveyor chute (10), a screen or another machine or apparatus which is sup- ported by a number of leaf springs (3,3') or by a set of leaf springs (3",3'") coupled in parallel.

7. Balanced vibrator according to claim 6, characterised in that the counter-oscillating mass (M2) also consists of a conveyor chute, a screen or another machine or apparatus.

8. Balanced vibrator according to any of the claims 1-7, c a racte rised in that the drive unit (7,8,9,12) comprises the use of one or more connecting rods which are resilient or can be deformed elastically.

9. Balanced vibrator according to any of the claims 1-7, characterised in that on at least one of the springs (3,3',4,4') in the vibrator there is mounted at least one element (18), e.g. a crystal element, for the measurement of the extent of the deflection.