CA1189559A - Electromagnetic vibrating system operable at high amplitudes - Google Patents
Electromagnetic vibrating system operable at high amplitudesInfo
- Publication number
- CA1189559A CA1189559A CA000374267A CA374267A CA1189559A CA 1189559 A CA1189559 A CA 1189559A CA 000374267 A CA000374267 A CA 000374267A CA 374267 A CA374267 A CA 374267A CA 1189559 A CA1189559 A CA 1189559A
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- CA
- Canada
- Prior art keywords
- linear
- spring means
- linear spring
- vibrated
- spring
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
- B06B1/04—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with electromagnetism
- B06B1/045—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with electromagnetism using vibrating magnet, armature or coil system
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
- B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
- B07B1/00—Sieving, screening, sifting, or sorting solid materials using networks, gratings, grids, or the like
- B07B1/42—Drive mechanisms, regulating or controlling devices, or balancing devices, specially adapted for screens
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
- B65G27/00—Jigging conveyors
- B65G27/10—Applications of devices for generating or transmitting jigging movements
- B65G27/16—Applications of devices for generating or transmitting jigging movements of vibrators, i.e. devices for producing movements of high frequency and small amplitude
- B65G27/24—Electromagnetic devices
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- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Apparatuses For Generation Of Mechanical Vibrations (AREA)
- Reciprocating, Oscillating Or Vibrating Motors (AREA)
- Vibration Prevention Devices (AREA)
- Electromagnets (AREA)
Abstract
A B S T R A C T
An electromagnetic vibrating system comprising an electromagnet-armature combination producing vibration and including at least first and second elements defining a gap therebetween, a base member supporting the first element, a member to be vibrated which is connected to the second element, and non-linear spring apparatus associated with the base and the member to be vibrated including apparatus for storing substantial energy of the electromagnet-armature combination as it approaches its minimum gap and converting it to kinetic energy of the member to be vibrated.
An electromagnetic vibrating system comprising an electromagnet-armature combination producing vibration and including at least first and second elements defining a gap therebetween, a base member supporting the first element, a member to be vibrated which is connected to the second element, and non-linear spring apparatus associated with the base and the member to be vibrated including apparatus for storing substantial energy of the electromagnet-armature combination as it approaches its minimum gap and converting it to kinetic energy of the member to be vibrated.
Description
~ he present invention relates to vibrating systems generally and more particularly to electrolr,agnetic vibrating systems.
Vibrating systems are known and used in a great variety of forms for various functions such as feeding, conveying, screen-ng, sorting, shaking and discharging bulk materials. The ,ource of vi~ration For such systems rr,ay be mechanical, such as an electric rllotol^ rotating eccentric masses, hydraulic, pneumatic or electromagnetic. Electromagnetic systems are favored in most vibrating systems since they enable relatively simple and inexpensive constructions to be employed, requiring neither bearings in the case of electric motors, nor seals or valves as in hydraulic and pneumatic systems, and enable simplified amplitude monitoring and control.
Despite these advantages, electromagnetic vibrating systems have a serious inherent deficiency, which will now be described:
T~/o types of electromagnetic vibrating structures are in common use.
One employs a moving permanent magnet which passes through an AC-e!lergi~ed coil. This structure, which is normally used in loud-speakers is inefficient from an energy standpoint, since it wastes magnetic flux.
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The second commonly employed structure employs an armature plate which is attracted head-on by a wound core. This structure avoids the erlergy inef~iciency of the above-described moving magnet structure and is capable of producing relatively large forces. This structure~
which is commonly used in materials handling applications, has the inherent limitation that its amplitude is limited by the maximum gap permitted bet~een the armature and coil. The gap is limited by the amount of current that can be carr;ed by the coils oF the electromagnet.
If the gap is increased, the current is increased correspondingly.
Thus for a given gap, even though relatively high currents could be employed and magnet energies could be drawn from the magnet, the operating current and thus the magnet's energy output is deliberately kept low to prevent knocking of the armature against the core when the amplitude reaches the gap dirnensions. It may thus be appreciated that electromagnetic systems are significantly limited in their operation due to the physical limitations of ~he gap.
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5~
In order to overcome this problem it has been proposed to employ an electronic system for reducing the current supplied to the electromagnet as the gap between the electromagnet and the armature decreases. This is not desirable since it decreases the maglletic force and energy available to maintain the system in motion.
It has also been suggested to employ damping springs in association with electromagnetic systems to control the vibration thereof. The provision of damping springs negates the purposes of the present invention since it inhibits the reaching of high amplitudes and reduces the force and energy available for operating the vibrating system. Therefore, insofar as possible~ in accordance with the present invention springs with relatively small damping are employed. I
I
It is known from U.S. Patent 2,187,717 to employ a non-linear spring in association with an electromagnetic vibrating system.
The purpose of this spring in the disclosed system is to control the natural frequency of the system and to maintain the system close to resonance notwit~istanding variations in the load.
The frequency of such a system is given by the expression Frequency = 21 c = f ~1) where c = spring rate (2) and c is the ratio between change in force and change in displacement at any given point along the force/displacement curve of a spring.
It may thus be appreciated that the frequency can be maintained constant by suitable selection of the amplitude range of a non-linear spring at which desired force/displacement characteristics for a given mass are present. U.S. Patent 2,187,717 suggests the provision of selectable pretensioning means operative in response to a changing mass so as to match the force/displacement characteristics to thQ chanying mass in order to keep the natural frequency constant in accordance with equation (1). Variations in the frequency o~ such vibrating systems are undesirable.
~ 5 5~3 It is also appreciated that in order to match the ~oree/displacell;PIlt characteristics lo a changing mass as sugsested in U.S. Patent 2,187,717, the non linearity of the spring must be moderate enough to enable a constant spring rate c to be maintained within the range of amplitude of the system for any given mass.
As ~i~ill be described hereinafter, in accordance with the prcsent invention, the spring rate c is not held constant within the alllpli~ude range of the system. In accordance with an embodilllent of the present invention, the spring rate c changes by at least twice its magnitude at rest (zero amplitude) and only in the direction of increasing rate with decreasing gap. If the electrom3gnet acts on only one side of the armature, the non-linearity is only along a portion of the parthway of the armature. In contrast, the aforesaid U.S. Patent 2,187,717 provides non-linearity along the entire range of motion of the armature.
It is also noted that the non-linear spring of the system in U.S. Patent 2,187,717 is a highly damping spring due to its high internal friction as a result of rubbing between its leaves.
In contrast, the present invention calls ~or springs having low damping characteristics.
U.S. Patent 4,235,153 shows a linear motion, electromagnetic force motor employing a non linear spring to oppose a rising magnetic force in order to stabilize the system. This patent does not disclose a vibratory system but instead deals with positioning apparatus which operates in a D.C. mode. As such, it does not address the problem described hereinabove, the physical iopacting between a vibrating member driven by an electromagnet and ar,other member under high amplitude conditions.
It is noted in this connection that in a D.C. system, reduction in the yap greatly increases the magnetic force. In an AC vibratory system, it has been ~ound that this force increase is not present, since as the gap is closed, the inductance, which opposes current flow, increases. A generally constant magnetic force is thus displayed by vibratory electromagnetic systems.
5S~ ~
There is provided in accordance with an embodiment of the present invention apparatus which overcomes the above~described di~ficulties and which provides high amplitude operation at relatively low power.
There is thus provided in accordance with an embodiment of the present invention an electromagnetic vibrating system comprising an electromagnet-armature combination producing vibration and including at least first and second elements defining a gap therebetween, I
a base member supporting the first element, a member to be vibrated which is connnected to the second element, and non-linear spring apparatus associated with the base and the member to be vibrated including apparatus for storing substantial energy of the electromagnet-armature combination as it approaches its minimum gap and converting it to kinet;c energy of the member to be vibrated.
Further in accordance with an embodiment of the present invention there is also provided linear spring apparatus associated with the base and the member to be vibrated and the electromagnet-armature combination is operative to provide vibration of the member to be vibrated close to rescnance of the linear spring apparatus.
Additionally in accordance with the invention, the energy of the electromagnet-armature combination that it stored by the non-linear spring apparatus includes kinetic energy of the member to be vibrated.
I
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BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more fully understood and appreciated ~rom the following detailed description taken in conjunction with the drawings in which:
Figs. lA, lB and lC are displacement versus time curves illustrating the operation of apparatus constructed and operative in accordance with an embodiment of the present invention;
Figs. 2A and 2B are pictorial illustrations of a vibrating system constructed and operative in accordance with an embodiment of the present invention;
Figs. 3A , 33, 3C, 3D and 3E are illustrations of variations of a vibrating tray type system constructed and operative in accordance with an embodiment of the present invention;
Figs. 4, 5, 6, 7, 8, 9, 10 and 11 illustrate examples of types of non-linear spring constructions useful in vibrating systems constructed and operative in accordance ~ith the present invention;
Fig. 12 illustrates a vibrating tray type system constructed and operative in accordance with an embodiment of the present invention and employing a non-linear Kappa spring;
Fig. 13 illustrates another embodiment of vibrating system constructed and operative in accordance ~ith an embodiment of the invention and employing a Kappa spring;
Fig. 14 is an illustration of a Kappa spring useful in the invention;
Figs. 15A and 15B are illustrations of a modified Kappa spring useful in the invention; and Fig. 16 is an illustration of a non-linear spring construction useful in vibrating systems constructed and operative in accordance with the present invention.
a553 DETAILED DESCRIPTION OF THE INVENTION
Be~ore proceeding to a detailed description of the invention~ a hrief explanation of the problem of knocking in moving arrna~ure type electromagnetic systems will be presented, witn reference to Figs. IA, lB and lC Fig. lA shows a displacement curve o~ a moving armature electromagnetic system in which the displacement amplitude is equal to the maximum gap separat;on, Fig lB shows a theoretical amplitude that could be realized with the electromagnetic system of F;g lA were it not for the physical limitation imposed by impacting of the armature against the electromagnet. Fig. lC shows the amplitude of an electromagnetic system constructed and operat;ve in accordance with the present invent;on wherein the ampl;tude of the electromagnetic system during the far half cycle of the armature is increased beyond the gap limits.
The tecllniques for producing this desired result will be described hereinaFter.
The present invention will now be described with particular reference to the drawings. It is noted that while most of the drawings relate to a particular type of v~hrating system, the vibrating tray or screen type, the invention is no~ limited to such types and is applicable to all suitable electromagnetic vibrating systems.
Fig.2A illustrates a vibrating system of general construction comprising a base 10. A mass to be vibrated 12 is mounted onto base 10 as by leaf springs 11. An armature 14 is fixedly mounted onto mass 12. Also mounted onto base 10 is an electronagnet 16, disposed in facing relationship to armature 14 and defining a gap 18 therebetween. A pair of 10w-damping coil springs 20 are mounted onto base 10 facing mass 12 but separated therefrom by a distance L at rest.
The distance L is typically one-third of the gap distance at rest.
It is a particular feature of the present invention that sprinss 20 do not contact mass 12 except when mass 12 approaches ~he electromagnet 16, i.e. when the gap 18 is at a minimum Thus it may be appreciated that springs 20 may be linear springs which in this construction constitute a non-linear spring system or spring means due to the fact that they are engaged only during part of the relative displacement o~ the members .
In the embodiment of Fig. 2~ both springs 20 are of the sam2 length and contact mass 12 at approximately the same point.
An alternative embodiment is illustrated in Fig. 2B where instead of a pair of identical springs 20, there are provided springs 21 and 23 of differing length, such that spring 21 is longer than spring 23 and contacts mass 12 at an earlier point along its d1splacement path than does spring 23. It may thus be appreciated that by using a plurality of springs which engage thè
~ibrating system along different portions of the displacement path, a desired forceldisplacement characteristic can be constructed. Alternatively or additionally combinations of springs having different characteristics may be ernployed.
lhe operat;on of the apparatus illustrated in Fig. 2A will be better understood by considering the displacement curve of Fig. lC
which, as noted above, indicates that the amplitude is l;mited in one direction but not in the other. This limitation is achieved by the action o~ a non-linear spring system embodied in springs 20 of the embodiment of Fig. 2A. The non-linear spring system prevents armature knocking against the magnet and is operative to store the high speed kinetic energy of the moving elements as well as the electromagnetic energy of the magnet, until the armature comes to a standstill momentarily at its minimum gap. Immediately thereafter the armature is repelled 'rom the electromagnet while the non-linear spring system releases the stored energy such that the armature ;s thrown forcefully towards the opposite direction with a high amplitude.
The linear springs 11 bring the armature back to its zero position and the next cycle begins.
~ q3 ~ 5~ ' It is appreciated that the force produced by the j;
linear springs 11 increases rather slowly with displacement, while the force produced by springs 20, which is applied only after a displacement L from the zero position upon contact between the springs 20 and mass 12, increases quickly with ~`
displacement. It is thus apparent that the resultant spring .
Force of the spring system comprising springs 11 and 20 corresponds subst~ntially to the force required to absorb j the kinetic energy of the moving parts and the magnetic ~'~
energy of the electromagnet-armature combination before the ~i gap reaches zero.
In the illustrated embodiment of the present invention a Ç
non-linear spring system is produced by a combination of two linear springs. Alternatively one or more non-linear springs may be ' employed, alone or in combination with linear springs.
It is a general requirement that throughout the E
displacement cycle of the system the natural frequency of the vibrating systerm inclu,lin~ tne s~rings and rasses corresponds generally to the required frequency of the electromagnet.
The provision of the spring system comprising `
springs 20 is a primary feature of the invention, since these springs act to prevent "knocking" of the apparatus at high amplitudes and to store the electromagnetic and kinetic energy as the gap approaches zero and to accelerate the vibrating mass in the ,;
other direction at high speed.
For the purposes of clarity and distinction from the prior art, the terms " non-linear spring system" and "non-linear ~`
spring means" will be employed throughout the sperification and ~!
claims to refer to a spring system or spring means wherein the spring rate c changes within the operative amplitude range of the springs at any given time. This definition thus excludes the structure disclosed in U.S. Patent 2,187,717 wherein c remains su~stantially constant within any given operative amplitude range.
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It is a primary feature of the invention that the spring system displays low internal dampiny or friction in order that the spring system is operative to convert substantially all of the ~agnetic energy absorbed thereby to kinetic energy of the mass to be vibrated. Thus the spring system must not act as a damper, resulting in energy wastage.
In practice it is seen that in order to correspond to the force required to decelerate the mass to zero speed without impacting against the magnet, the spring system must be non-linear.
It is noted for the sake of clarity that although the above discussion has been concerned with a system in which an electromagnet is stationary and an armature moves with respect thereto, the invention is equally applicable to the converse system wherein the armature is stationary and the electromagnet moves.
Generally stated, the invention as described above is applicable to relative motion between the electromagnet and its armature including motion of either or both the armature and electromagnet.
Reference is now made to Figs. 3A - 3E which illustrate various constructions of a vibrating table type electromagnetic vibrating system. For the sake of clarity and conciseness, the elements common to all of the various constructions will be described only in connection with Fig. 3A and the same reference numerals will be used for identical parts in all of Figs. 3A - 3E .
The illustrated vibrating table type electroma~netic vibrating system comprises a vibrating base 22, which is mounted by means of soft springs 24 onto a fixed support 26, such as a floor. A tray 28 which it is desired to vibrate along an axis 30 is mounted onto vibrating base 22 by means of leaf springs 32 and 34 which generally satisfy equation (1).
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An electromagnet 36 is mounted onto vibrating base 22 and an armature 38 is mounted on tray 28 in facing relationship to electromagnet 36 across a gap 39. A non- linear spring system 40, shown schematically, is associated with vibrating base 22 and tray 28 for substantially storing the magnetic energy produced as the gap decreases to its minimum separation. Various embodiments of non-linear spring systems 40 will be described in detail hereinafter in connection with Figs.
4 ~
The embodiment illustrated in Fig. 3A is characteri~ed in that the magnet 36 and armature 38 are arranged along an axis which is parallel to the ax;s of motion 30 of the vibrating tray 28.
In con~rast, the embodiment of Fig.3B is characterized in that the magnet and armature are aligned horizontally and thus at an angle ~ with respect to axis 30. This construction has the advantage of simplicity in manufacture as well as the additional important advantage that the gap is maintained relatively small.
This may be appreciated by noting that for a maximal displacement of tray 28 of 2A, the maximal gap between the magnet and the armature in the embodiment of Fig. 3B will be 2Acos ~ as compared with a maximal gap of 2A for the embodiment of Fig. 3A.
The embodiment of Fig. 3C is similar to that of Fig. 3B
except in that a pair of electromagnets 42 and 44 are employed and disposed on opposite sides of armature 38 across respective gaps 4~ and 48. An electronic control 50 is provided for directing current to either one of the electromagnets, where a soft iron armature is employed. Alternatively, where the armature is a permanent magnet, the electronic control successively changes the polarity of the electromagnets.
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The embodiment of Fig. 3D is similar to that of Fig. 3A
and illustrates one example of a substant;ally non-damping spring system constructed and operative in accordance with an embodiment of the invention. Here a leaf spring ~2 is mounted onto base 22 Spring 52 may be assumed to be linear and to have very low internal ~riction.
An impacting member 54 is associated with tray 28 and arranged to engage spring 52 only during that portion of the displacement cycle of the apparatus when gap 39 is approaching its minimum separation. During this portion of the cycle, spring 52 absorbs substantially all of the magnetic and kinetic energy produced and converts substantially all of it to kinetic energy of the vibrating elements in accordance with the invention. It is specifically noted that in this embodiment, a linear spring is employed to provide a non-linear, discontinuous spring system.
It is noted also that impact member 54 may be formed of an elastomer such as rubber in order to reduce impact noise.
The embodiment of Fig. 3E is in e~fect a combination of the embodi~ents of Fig. 3D and Fig. 3C in that a pair o~ magnets 42 and 44 are employed. In this embodiment the analogy to the spring system of Fig. 3D is a two sided substantially non damping spring system 56? typically comprising low internal friction rubber pads assoc;ated with first and second impacting members 58 and 60 mounted onto tray 28.
It is noted that the employment of a pair of magnets as in the embodiments of Figs. 3C and 3~ effectively limits the amplitude of armature vibration to the overall distance between the two magnets. This arrangement does, however, have the advantage that one of the magnets, remote from the zero line may be energized only to assist the other magnet for high amplitude operation without requiring ~he provision of an additional armature. A highly symmetric oscillation may be provided in this manner, which is particularly desirable for certain operations, such as screening.
_ 12 ~ ~3~ 5 5~
It should be appreciated in connection with all of the embodiments illustrated in Figs. 3A - 3E that tray 28 may be alternatively a screen or any other desired element and that the springs employed may be alternatively any other type of spring such as coil springs, elastomer springs or leaf springs. All of these various constructions are exemplary a1so of other types of vibrating systems in which the invention may be employed.
Reference is now made to Figs. 4 - 11 which illustrate various exernplary embodiments of spring systems useful in the present invention. Fig. 4 shows a conventional leaf spring 60 associated with a curved support 62. When the tray 28 is deflected in the direction of the solid arrow 64, the leaf spring 60 leans against the curved support 62, thus decreasing its free length by a distance "s" as illustrated in Fig. 6 with the result that the spring is effectively stiffened. Deflection of tray 28 in the opposite direction produces no such stiffening. Thus a non-linear spring system operative as a linear spring in one direction is provided.
Fig. 5 illustrates a variation on the embodiment of Fig.
4 wherein first and second curved supports 66 and 68 are provided, both of which engage the leaf spring 60 during its deflection in the direction of the solid arrow 64 and neither of which engages the 1eaf spring 60 when it is deflected in the opposite direction.
Figs. 7 and B illustrate a non-linear coil spring 67 in respective compressed and at rest orientations. As seen in Fig. 8 the spring 6g is a variable pitch spring. Under compression the lower pitch coils initially are compressed solid reduc;ng the active spring length9 and thus increasing the spring stiffness along a portion of its deflection cycle.
Fig. 9 illustrates a conical spring which is also a variable pitch spr;ng. Here the larger and thus softer coils are initially compressed and lean against a support 70, leaving the smaller coils which define a stiffer spring.
5~
Fig. 10 illustrates a further embodiment of non-linear spring system com,prising an elasto~leric pillow 72, formed of rubber, poly-urethane, or any uther suitable material. The pillow 72 is seated in a senerally conical cup 74. The elastomeric materials e,nployed in pillow 72 have the property that they are resilient in one direction so long as they can expand in another perpendicular direction.
When the pillow is not compressed, it sits loosely within the cup 74. ~Ihen a compressive force is applied to the pillo~
along an axis 76, the pillow i5 forced up against the inner walls of the cup, effectively stiffening the spring system.
The spring system illustrated in Fig. 10 has advantages o~ si~plicity of construction and very high energy storage capacity for a relatively small spring volume. It suffers from the disadvantage that its rate depends on temperature and ag;ng of the elastomeric material.
Fig. il illustrates a non-linear spring system which is the analog of the embodiment of Fig. 4 for use with a two magnet vibrating system as illustrated, for example in Fig. 3C~ The spring sysiem employs first and second curved supports 78 and 80 mounted on opp~site sides of a leaf spring 82, for reducing the effective length thereof as a function of displacement in either direction.
Fig. 12 i 11 ustrates an electromagnetic vibrating system of the vibrating tray type in which the non-damping non-linear spring sys~em comprises a Kappa spring. The construction of Kappa springs is described in applicant's U.S. Patent 4,129,290. This particular Kappa spring is constructed as illustrated generally in Fig. 14, having a cen~ral leaf 85 and a pair of side leaves 87 and 89 connected to the central leaf 85 by connecting members 91 and 93. L1 denotes the free length of each of the side leaves ~7 and 89 as illustrated and L2 denotes one-half of the free length of central leaf 85. B illustrates the free length of the connecting member 91 or 93, which are typically identical, measured as sho~m. When L1 ~ L2 = 3B, a linear spring is produced.
~ S 5~
In accordance with the present invention 3B is selected to be greater than L1 + L2. There is thus produced a Kappa spring whose ~pring rate increases with displacement under compression and decreases with displacement under tension.
Reference is now made to Fig. 13 which shows a vibrator com~rising a ~ibrating base ~4 mounted on a supporting surface by neans of soft springs 86 and supporting an electromagnet 88. A first ~ibrating mass 90 is supported by a plurality of non-lir,ear Kappa springs 92 of the type described hereinabove on base 84. A plurality o~ linear coil springs 94 are also mounted on base 84 and extend towards mass 90 and are spaced therefrom by a separation 96 which is equal at rest to approximately one-third of the electromagnet-armature gap 98 defined bet~een electromagnet 88 and a facing annature supported on mass 9Q.
A further vibrating mass 99 is mounted on mass 90 by means of springs i00. ~he illustrated vibrator may have many possible uses for example in settling poured concretP and serves as an example of various uses for embodiments of the invention.
It is noted that the non-linear spring means illustrated in Figs. 4-6 and 11 constitute a preferred embodiment of non-linear spring means for use in accordance with the invention. These constructions may be characterized in that they comprise a curved support surface defining a circular section. The force/displacement characteristics of such systems provide a linear range which enables them to sâtisfy equation (l) and a non-linear range at greater displacements ~hich enable them to correspond to the force/
displacement characteristics required herein.
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g~iS~
~ t is appreciated that the introduction of a non-linear spring having the performance characteristics seen in Fig. lC
provides a system whose natural frequency is amplitude dependent.
This is not the case with linear springs. In practice, however, the amplitude dependence does not affect performance since in most applications there is a constant variation in mass which contributes a non-lirlear element in any event which has the same amplitude dependency of the frequency as its result.
It may be desired in certain applications to provide an electronic trigger circuit for providing electrical impulses to the magnet such that the system automatically operates at resonance with maximum amplitude at a minimum current. The addition of suitable feedback circuitry can enable this apparatus to be used to control the amplitude.
Reference is now made to Figs. 15A and 15B which illustrate a modified version of the Kappa spring of Fig. 14 in respective at rest and compressed orientations. For convenience, common numbering is used for common elements ~ppearing also in Fig. 14. The modification illustrated in Figs. 15A and 15B is the provision of elastomer impacting pads 102 and 104 in facing orientation onto connecting members 91 and 93. These impacting pads provide an additional energy storage and conversion device which comes into play only at a predetermined compression level, when the pads initially contact.
If the springs of Figs. l~A and 15B were used to replace the springs 92 in the vibrating system of Fig. 13, for example, the elastomer pads would provide kinetic and magnetic energy storage during only the portion of the travel cycle at which the electromagnet gap is at a minimum. In such a way they provide desired non-linearity for the system.
It is appreciated that instead of a pair of elastomer pads as shown, only one may be employed for impact against a rigid member.
The elastomer pads may be formed of rubber or any other suitable material.
As a further alternative they may be replaced by other types of springs which are characterized in that they achieve compressive contact only along a portion of the travel range of the vibrating system.
_ 16 ~ ~3~ 5 S~
Reference is now made to Fig, 16 which illustrates an embodiment of non-linear spring system which comprises a linear coil spring 110 which is attached at one end to a rubber pad 112 and at a second end to a supporting surfdce 114, A generally cylindrical rubber pad 116 is located interiorly of coil spring 110 and is selectably positioned onto an adjustable supporting bolt 118 which threadably engages a counter nut 120 for selectable mounting of the pad 116 with respect to the pad 112. The rubber pad 116 may be retained in place by means of a locating projection 122 extending outwardly from bolt 118.
It may be appreciated that the structure of Fig, 16 provides an adjustable non-linear spring system. By suitable adjustment of the position of bolt 118 the portion of the range of travel of pad 112 over which pad 116 acts as an energy absorber can be selected. Thus the non-linear spring system of Fig. 16 can be considered as a mechanically programmable non-linear spring system. It may also be appreciated that a plurality of elastomer pads, each mounted on an adjustably positionable support may be used to provide a multi-step adjustable non-linear spring system. Such a system is particularly useful in the apparatus of the present invention but is not limited to such applications, It will be appreciated by persons skilled in the art that the invention is not limited to what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined only by the claims which follow:
Vibrating systems are known and used in a great variety of forms for various functions such as feeding, conveying, screen-ng, sorting, shaking and discharging bulk materials. The ,ource of vi~ration For such systems rr,ay be mechanical, such as an electric rllotol^ rotating eccentric masses, hydraulic, pneumatic or electromagnetic. Electromagnetic systems are favored in most vibrating systems since they enable relatively simple and inexpensive constructions to be employed, requiring neither bearings in the case of electric motors, nor seals or valves as in hydraulic and pneumatic systems, and enable simplified amplitude monitoring and control.
Despite these advantages, electromagnetic vibrating systems have a serious inherent deficiency, which will now be described:
T~/o types of electromagnetic vibrating structures are in common use.
One employs a moving permanent magnet which passes through an AC-e!lergi~ed coil. This structure, which is normally used in loud-speakers is inefficient from an energy standpoint, since it wastes magnetic flux.
.
The second commonly employed structure employs an armature plate which is attracted head-on by a wound core. This structure avoids the erlergy inef~iciency of the above-described moving magnet structure and is capable of producing relatively large forces. This structure~
which is commonly used in materials handling applications, has the inherent limitation that its amplitude is limited by the maximum gap permitted bet~een the armature and coil. The gap is limited by the amount of current that can be carr;ed by the coils oF the electromagnet.
If the gap is increased, the current is increased correspondingly.
Thus for a given gap, even though relatively high currents could be employed and magnet energies could be drawn from the magnet, the operating current and thus the magnet's energy output is deliberately kept low to prevent knocking of the armature against the core when the amplitude reaches the gap dirnensions. It may thus be appreciated that electromagnetic systems are significantly limited in their operation due to the physical limitations of ~he gap.
.
5~
In order to overcome this problem it has been proposed to employ an electronic system for reducing the current supplied to the electromagnet as the gap between the electromagnet and the armature decreases. This is not desirable since it decreases the maglletic force and energy available to maintain the system in motion.
It has also been suggested to employ damping springs in association with electromagnetic systems to control the vibration thereof. The provision of damping springs negates the purposes of the present invention since it inhibits the reaching of high amplitudes and reduces the force and energy available for operating the vibrating system. Therefore, insofar as possible~ in accordance with the present invention springs with relatively small damping are employed. I
I
It is known from U.S. Patent 2,187,717 to employ a non-linear spring in association with an electromagnetic vibrating system.
The purpose of this spring in the disclosed system is to control the natural frequency of the system and to maintain the system close to resonance notwit~istanding variations in the load.
The frequency of such a system is given by the expression Frequency = 21 c = f ~1) where c = spring rate (2) and c is the ratio between change in force and change in displacement at any given point along the force/displacement curve of a spring.
It may thus be appreciated that the frequency can be maintained constant by suitable selection of the amplitude range of a non-linear spring at which desired force/displacement characteristics for a given mass are present. U.S. Patent 2,187,717 suggests the provision of selectable pretensioning means operative in response to a changing mass so as to match the force/displacement characteristics to thQ chanying mass in order to keep the natural frequency constant in accordance with equation (1). Variations in the frequency o~ such vibrating systems are undesirable.
~ 5 5~3 It is also appreciated that in order to match the ~oree/displacell;PIlt characteristics lo a changing mass as sugsested in U.S. Patent 2,187,717, the non linearity of the spring must be moderate enough to enable a constant spring rate c to be maintained within the range of amplitude of the system for any given mass.
As ~i~ill be described hereinafter, in accordance with the prcsent invention, the spring rate c is not held constant within the alllpli~ude range of the system. In accordance with an embodilllent of the present invention, the spring rate c changes by at least twice its magnitude at rest (zero amplitude) and only in the direction of increasing rate with decreasing gap. If the electrom3gnet acts on only one side of the armature, the non-linearity is only along a portion of the parthway of the armature. In contrast, the aforesaid U.S. Patent 2,187,717 provides non-linearity along the entire range of motion of the armature.
It is also noted that the non-linear spring of the system in U.S. Patent 2,187,717 is a highly damping spring due to its high internal friction as a result of rubbing between its leaves.
In contrast, the present invention calls ~or springs having low damping characteristics.
U.S. Patent 4,235,153 shows a linear motion, electromagnetic force motor employing a non linear spring to oppose a rising magnetic force in order to stabilize the system. This patent does not disclose a vibratory system but instead deals with positioning apparatus which operates in a D.C. mode. As such, it does not address the problem described hereinabove, the physical iopacting between a vibrating member driven by an electromagnet and ar,other member under high amplitude conditions.
It is noted in this connection that in a D.C. system, reduction in the yap greatly increases the magnetic force. In an AC vibratory system, it has been ~ound that this force increase is not present, since as the gap is closed, the inductance, which opposes current flow, increases. A generally constant magnetic force is thus displayed by vibratory electromagnetic systems.
5S~ ~
There is provided in accordance with an embodiment of the present invention apparatus which overcomes the above~described di~ficulties and which provides high amplitude operation at relatively low power.
There is thus provided in accordance with an embodiment of the present invention an electromagnetic vibrating system comprising an electromagnet-armature combination producing vibration and including at least first and second elements defining a gap therebetween, I
a base member supporting the first element, a member to be vibrated which is connnected to the second element, and non-linear spring apparatus associated with the base and the member to be vibrated including apparatus for storing substantial energy of the electromagnet-armature combination as it approaches its minimum gap and converting it to kinet;c energy of the member to be vibrated.
Further in accordance with an embodiment of the present invention there is also provided linear spring apparatus associated with the base and the member to be vibrated and the electromagnet-armature combination is operative to provide vibration of the member to be vibrated close to rescnance of the linear spring apparatus.
Additionally in accordance with the invention, the energy of the electromagnet-armature combination that it stored by the non-linear spring apparatus includes kinetic energy of the member to be vibrated.
I
ss~
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more fully understood and appreciated ~rom the following detailed description taken in conjunction with the drawings in which:
Figs. lA, lB and lC are displacement versus time curves illustrating the operation of apparatus constructed and operative in accordance with an embodiment of the present invention;
Figs. 2A and 2B are pictorial illustrations of a vibrating system constructed and operative in accordance with an embodiment of the present invention;
Figs. 3A , 33, 3C, 3D and 3E are illustrations of variations of a vibrating tray type system constructed and operative in accordance with an embodiment of the present invention;
Figs. 4, 5, 6, 7, 8, 9, 10 and 11 illustrate examples of types of non-linear spring constructions useful in vibrating systems constructed and operative in accordance ~ith the present invention;
Fig. 12 illustrates a vibrating tray type system constructed and operative in accordance with an embodiment of the present invention and employing a non-linear Kappa spring;
Fig. 13 illustrates another embodiment of vibrating system constructed and operative in accordance ~ith an embodiment of the invention and employing a Kappa spring;
Fig. 14 is an illustration of a Kappa spring useful in the invention;
Figs. 15A and 15B are illustrations of a modified Kappa spring useful in the invention; and Fig. 16 is an illustration of a non-linear spring construction useful in vibrating systems constructed and operative in accordance with the present invention.
a553 DETAILED DESCRIPTION OF THE INVENTION
Be~ore proceeding to a detailed description of the invention~ a hrief explanation of the problem of knocking in moving arrna~ure type electromagnetic systems will be presented, witn reference to Figs. IA, lB and lC Fig. lA shows a displacement curve o~ a moving armature electromagnetic system in which the displacement amplitude is equal to the maximum gap separat;on, Fig lB shows a theoretical amplitude that could be realized with the electromagnetic system of F;g lA were it not for the physical limitation imposed by impacting of the armature against the electromagnet. Fig. lC shows the amplitude of an electromagnetic system constructed and operat;ve in accordance with the present invent;on wherein the ampl;tude of the electromagnetic system during the far half cycle of the armature is increased beyond the gap limits.
The tecllniques for producing this desired result will be described hereinaFter.
The present invention will now be described with particular reference to the drawings. It is noted that while most of the drawings relate to a particular type of v~hrating system, the vibrating tray or screen type, the invention is no~ limited to such types and is applicable to all suitable electromagnetic vibrating systems.
Fig.2A illustrates a vibrating system of general construction comprising a base 10. A mass to be vibrated 12 is mounted onto base 10 as by leaf springs 11. An armature 14 is fixedly mounted onto mass 12. Also mounted onto base 10 is an electronagnet 16, disposed in facing relationship to armature 14 and defining a gap 18 therebetween. A pair of 10w-damping coil springs 20 are mounted onto base 10 facing mass 12 but separated therefrom by a distance L at rest.
The distance L is typically one-third of the gap distance at rest.
It is a particular feature of the present invention that sprinss 20 do not contact mass 12 except when mass 12 approaches ~he electromagnet 16, i.e. when the gap 18 is at a minimum Thus it may be appreciated that springs 20 may be linear springs which in this construction constitute a non-linear spring system or spring means due to the fact that they are engaged only during part of the relative displacement o~ the members .
In the embodiment of Fig. 2~ both springs 20 are of the sam2 length and contact mass 12 at approximately the same point.
An alternative embodiment is illustrated in Fig. 2B where instead of a pair of identical springs 20, there are provided springs 21 and 23 of differing length, such that spring 21 is longer than spring 23 and contacts mass 12 at an earlier point along its d1splacement path than does spring 23. It may thus be appreciated that by using a plurality of springs which engage thè
~ibrating system along different portions of the displacement path, a desired forceldisplacement characteristic can be constructed. Alternatively or additionally combinations of springs having different characteristics may be ernployed.
lhe operat;on of the apparatus illustrated in Fig. 2A will be better understood by considering the displacement curve of Fig. lC
which, as noted above, indicates that the amplitude is l;mited in one direction but not in the other. This limitation is achieved by the action o~ a non-linear spring system embodied in springs 20 of the embodiment of Fig. 2A. The non-linear spring system prevents armature knocking against the magnet and is operative to store the high speed kinetic energy of the moving elements as well as the electromagnetic energy of the magnet, until the armature comes to a standstill momentarily at its minimum gap. Immediately thereafter the armature is repelled 'rom the electromagnet while the non-linear spring system releases the stored energy such that the armature ;s thrown forcefully towards the opposite direction with a high amplitude.
The linear springs 11 bring the armature back to its zero position and the next cycle begins.
~ q3 ~ 5~ ' It is appreciated that the force produced by the j;
linear springs 11 increases rather slowly with displacement, while the force produced by springs 20, which is applied only after a displacement L from the zero position upon contact between the springs 20 and mass 12, increases quickly with ~`
displacement. It is thus apparent that the resultant spring .
Force of the spring system comprising springs 11 and 20 corresponds subst~ntially to the force required to absorb j the kinetic energy of the moving parts and the magnetic ~'~
energy of the electromagnet-armature combination before the ~i gap reaches zero.
In the illustrated embodiment of the present invention a Ç
non-linear spring system is produced by a combination of two linear springs. Alternatively one or more non-linear springs may be ' employed, alone or in combination with linear springs.
It is a general requirement that throughout the E
displacement cycle of the system the natural frequency of the vibrating systerm inclu,lin~ tne s~rings and rasses corresponds generally to the required frequency of the electromagnet.
The provision of the spring system comprising `
springs 20 is a primary feature of the invention, since these springs act to prevent "knocking" of the apparatus at high amplitudes and to store the electromagnetic and kinetic energy as the gap approaches zero and to accelerate the vibrating mass in the ,;
other direction at high speed.
For the purposes of clarity and distinction from the prior art, the terms " non-linear spring system" and "non-linear ~`
spring means" will be employed throughout the sperification and ~!
claims to refer to a spring system or spring means wherein the spring rate c changes within the operative amplitude range of the springs at any given time. This definition thus excludes the structure disclosed in U.S. Patent 2,187,717 wherein c remains su~stantially constant within any given operative amplitude range.
_ 9 _ i~
s~
It is a primary feature of the invention that the spring system displays low internal dampiny or friction in order that the spring system is operative to convert substantially all of the ~agnetic energy absorbed thereby to kinetic energy of the mass to be vibrated. Thus the spring system must not act as a damper, resulting in energy wastage.
In practice it is seen that in order to correspond to the force required to decelerate the mass to zero speed without impacting against the magnet, the spring system must be non-linear.
It is noted for the sake of clarity that although the above discussion has been concerned with a system in which an electromagnet is stationary and an armature moves with respect thereto, the invention is equally applicable to the converse system wherein the armature is stationary and the electromagnet moves.
Generally stated, the invention as described above is applicable to relative motion between the electromagnet and its armature including motion of either or both the armature and electromagnet.
Reference is now made to Figs. 3A - 3E which illustrate various constructions of a vibrating table type electromagnetic vibrating system. For the sake of clarity and conciseness, the elements common to all of the various constructions will be described only in connection with Fig. 3A and the same reference numerals will be used for identical parts in all of Figs. 3A - 3E .
The illustrated vibrating table type electroma~netic vibrating system comprises a vibrating base 22, which is mounted by means of soft springs 24 onto a fixed support 26, such as a floor. A tray 28 which it is desired to vibrate along an axis 30 is mounted onto vibrating base 22 by means of leaf springs 32 and 34 which generally satisfy equation (1).
~ 5 5~
An electromagnet 36 is mounted onto vibrating base 22 and an armature 38 is mounted on tray 28 in facing relationship to electromagnet 36 across a gap 39. A non- linear spring system 40, shown schematically, is associated with vibrating base 22 and tray 28 for substantially storing the magnetic energy produced as the gap decreases to its minimum separation. Various embodiments of non-linear spring systems 40 will be described in detail hereinafter in connection with Figs.
4 ~
The embodiment illustrated in Fig. 3A is characteri~ed in that the magnet 36 and armature 38 are arranged along an axis which is parallel to the ax;s of motion 30 of the vibrating tray 28.
In con~rast, the embodiment of Fig.3B is characterized in that the magnet and armature are aligned horizontally and thus at an angle ~ with respect to axis 30. This construction has the advantage of simplicity in manufacture as well as the additional important advantage that the gap is maintained relatively small.
This may be appreciated by noting that for a maximal displacement of tray 28 of 2A, the maximal gap between the magnet and the armature in the embodiment of Fig. 3B will be 2Acos ~ as compared with a maximal gap of 2A for the embodiment of Fig. 3A.
The embodiment of Fig. 3C is similar to that of Fig. 3B
except in that a pair of electromagnets 42 and 44 are employed and disposed on opposite sides of armature 38 across respective gaps 4~ and 48. An electronic control 50 is provided for directing current to either one of the electromagnets, where a soft iron armature is employed. Alternatively, where the armature is a permanent magnet, the electronic control successively changes the polarity of the electromagnets.
55~
The embodiment of Fig. 3D is similar to that of Fig. 3A
and illustrates one example of a substant;ally non-damping spring system constructed and operative in accordance with an embodiment of the invention. Here a leaf spring ~2 is mounted onto base 22 Spring 52 may be assumed to be linear and to have very low internal ~riction.
An impacting member 54 is associated with tray 28 and arranged to engage spring 52 only during that portion of the displacement cycle of the apparatus when gap 39 is approaching its minimum separation. During this portion of the cycle, spring 52 absorbs substantially all of the magnetic and kinetic energy produced and converts substantially all of it to kinetic energy of the vibrating elements in accordance with the invention. It is specifically noted that in this embodiment, a linear spring is employed to provide a non-linear, discontinuous spring system.
It is noted also that impact member 54 may be formed of an elastomer such as rubber in order to reduce impact noise.
The embodiment of Fig. 3E is in e~fect a combination of the embodi~ents of Fig. 3D and Fig. 3C in that a pair o~ magnets 42 and 44 are employed. In this embodiment the analogy to the spring system of Fig. 3D is a two sided substantially non damping spring system 56? typically comprising low internal friction rubber pads assoc;ated with first and second impacting members 58 and 60 mounted onto tray 28.
It is noted that the employment of a pair of magnets as in the embodiments of Figs. 3C and 3~ effectively limits the amplitude of armature vibration to the overall distance between the two magnets. This arrangement does, however, have the advantage that one of the magnets, remote from the zero line may be energized only to assist the other magnet for high amplitude operation without requiring ~he provision of an additional armature. A highly symmetric oscillation may be provided in this manner, which is particularly desirable for certain operations, such as screening.
_ 12 ~ ~3~ 5 5~
It should be appreciated in connection with all of the embodiments illustrated in Figs. 3A - 3E that tray 28 may be alternatively a screen or any other desired element and that the springs employed may be alternatively any other type of spring such as coil springs, elastomer springs or leaf springs. All of these various constructions are exemplary a1so of other types of vibrating systems in which the invention may be employed.
Reference is now made to Figs. 4 - 11 which illustrate various exernplary embodiments of spring systems useful in the present invention. Fig. 4 shows a conventional leaf spring 60 associated with a curved support 62. When the tray 28 is deflected in the direction of the solid arrow 64, the leaf spring 60 leans against the curved support 62, thus decreasing its free length by a distance "s" as illustrated in Fig. 6 with the result that the spring is effectively stiffened. Deflection of tray 28 in the opposite direction produces no such stiffening. Thus a non-linear spring system operative as a linear spring in one direction is provided.
Fig. 5 illustrates a variation on the embodiment of Fig.
4 wherein first and second curved supports 66 and 68 are provided, both of which engage the leaf spring 60 during its deflection in the direction of the solid arrow 64 and neither of which engages the 1eaf spring 60 when it is deflected in the opposite direction.
Figs. 7 and B illustrate a non-linear coil spring 67 in respective compressed and at rest orientations. As seen in Fig. 8 the spring 6g is a variable pitch spring. Under compression the lower pitch coils initially are compressed solid reduc;ng the active spring length9 and thus increasing the spring stiffness along a portion of its deflection cycle.
Fig. 9 illustrates a conical spring which is also a variable pitch spr;ng. Here the larger and thus softer coils are initially compressed and lean against a support 70, leaving the smaller coils which define a stiffer spring.
5~
Fig. 10 illustrates a further embodiment of non-linear spring system com,prising an elasto~leric pillow 72, formed of rubber, poly-urethane, or any uther suitable material. The pillow 72 is seated in a senerally conical cup 74. The elastomeric materials e,nployed in pillow 72 have the property that they are resilient in one direction so long as they can expand in another perpendicular direction.
When the pillow is not compressed, it sits loosely within the cup 74. ~Ihen a compressive force is applied to the pillo~
along an axis 76, the pillow i5 forced up against the inner walls of the cup, effectively stiffening the spring system.
The spring system illustrated in Fig. 10 has advantages o~ si~plicity of construction and very high energy storage capacity for a relatively small spring volume. It suffers from the disadvantage that its rate depends on temperature and ag;ng of the elastomeric material.
Fig. il illustrates a non-linear spring system which is the analog of the embodiment of Fig. 4 for use with a two magnet vibrating system as illustrated, for example in Fig. 3C~ The spring sysiem employs first and second curved supports 78 and 80 mounted on opp~site sides of a leaf spring 82, for reducing the effective length thereof as a function of displacement in either direction.
Fig. 12 i 11 ustrates an electromagnetic vibrating system of the vibrating tray type in which the non-damping non-linear spring sys~em comprises a Kappa spring. The construction of Kappa springs is described in applicant's U.S. Patent 4,129,290. This particular Kappa spring is constructed as illustrated generally in Fig. 14, having a cen~ral leaf 85 and a pair of side leaves 87 and 89 connected to the central leaf 85 by connecting members 91 and 93. L1 denotes the free length of each of the side leaves ~7 and 89 as illustrated and L2 denotes one-half of the free length of central leaf 85. B illustrates the free length of the connecting member 91 or 93, which are typically identical, measured as sho~m. When L1 ~ L2 = 3B, a linear spring is produced.
~ S 5~
In accordance with the present invention 3B is selected to be greater than L1 + L2. There is thus produced a Kappa spring whose ~pring rate increases with displacement under compression and decreases with displacement under tension.
Reference is now made to Fig. 13 which shows a vibrator com~rising a ~ibrating base ~4 mounted on a supporting surface by neans of soft springs 86 and supporting an electromagnet 88. A first ~ibrating mass 90 is supported by a plurality of non-lir,ear Kappa springs 92 of the type described hereinabove on base 84. A plurality o~ linear coil springs 94 are also mounted on base 84 and extend towards mass 90 and are spaced therefrom by a separation 96 which is equal at rest to approximately one-third of the electromagnet-armature gap 98 defined bet~een electromagnet 88 and a facing annature supported on mass 9Q.
A further vibrating mass 99 is mounted on mass 90 by means of springs i00. ~he illustrated vibrator may have many possible uses for example in settling poured concretP and serves as an example of various uses for embodiments of the invention.
It is noted that the non-linear spring means illustrated in Figs. 4-6 and 11 constitute a preferred embodiment of non-linear spring means for use in accordance with the invention. These constructions may be characterized in that they comprise a curved support surface defining a circular section. The force/displacement characteristics of such systems provide a linear range which enables them to sâtisfy equation (l) and a non-linear range at greater displacements ~hich enable them to correspond to the force/
displacement characteristics required herein.
!
g~iS~
~ t is appreciated that the introduction of a non-linear spring having the performance characteristics seen in Fig. lC
provides a system whose natural frequency is amplitude dependent.
This is not the case with linear springs. In practice, however, the amplitude dependence does not affect performance since in most applications there is a constant variation in mass which contributes a non-lirlear element in any event which has the same amplitude dependency of the frequency as its result.
It may be desired in certain applications to provide an electronic trigger circuit for providing electrical impulses to the magnet such that the system automatically operates at resonance with maximum amplitude at a minimum current. The addition of suitable feedback circuitry can enable this apparatus to be used to control the amplitude.
Reference is now made to Figs. 15A and 15B which illustrate a modified version of the Kappa spring of Fig. 14 in respective at rest and compressed orientations. For convenience, common numbering is used for common elements ~ppearing also in Fig. 14. The modification illustrated in Figs. 15A and 15B is the provision of elastomer impacting pads 102 and 104 in facing orientation onto connecting members 91 and 93. These impacting pads provide an additional energy storage and conversion device which comes into play only at a predetermined compression level, when the pads initially contact.
If the springs of Figs. l~A and 15B were used to replace the springs 92 in the vibrating system of Fig. 13, for example, the elastomer pads would provide kinetic and magnetic energy storage during only the portion of the travel cycle at which the electromagnet gap is at a minimum. In such a way they provide desired non-linearity for the system.
It is appreciated that instead of a pair of elastomer pads as shown, only one may be employed for impact against a rigid member.
The elastomer pads may be formed of rubber or any other suitable material.
As a further alternative they may be replaced by other types of springs which are characterized in that they achieve compressive contact only along a portion of the travel range of the vibrating system.
_ 16 ~ ~3~ 5 S~
Reference is now made to Fig, 16 which illustrates an embodiment of non-linear spring system which comprises a linear coil spring 110 which is attached at one end to a rubber pad 112 and at a second end to a supporting surfdce 114, A generally cylindrical rubber pad 116 is located interiorly of coil spring 110 and is selectably positioned onto an adjustable supporting bolt 118 which threadably engages a counter nut 120 for selectable mounting of the pad 116 with respect to the pad 112. The rubber pad 116 may be retained in place by means of a locating projection 122 extending outwardly from bolt 118.
It may be appreciated that the structure of Fig, 16 provides an adjustable non-linear spring system. By suitable adjustment of the position of bolt 118 the portion of the range of travel of pad 112 over which pad 116 acts as an energy absorber can be selected. Thus the non-linear spring system of Fig. 16 can be considered as a mechanically programmable non-linear spring system. It may also be appreciated that a plurality of elastomer pads, each mounted on an adjustably positionable support may be used to provide a multi-step adjustable non-linear spring system. Such a system is particularly useful in the apparatus of the present invention but is not limited to such applications, It will be appreciated by persons skilled in the art that the invention is not limited to what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined only by the claims which follow:
Claims (24)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electromagnetic vibrating system comprising:
an electromagnet-armature combination producing vibration and including at least first and second elements arranged in head-on facing relationship and defining a gap therebetween having a predetermined gap separation, the vibration being characterized by having amplitudes An and Af for the near and far half cycles of vibration when the first and second elements are respectively near and far from each other;
a base member supporting said first element;
a member to be vibrated, said member connected to said second element; and non-linear spring means associated with said base and said member to be vibrated including means for storing substantial energy of said electromagnetic armature combination as it approaches its minimum gap and converting it to enhanced amplitude of the member to be vibrated, said non-linear spring means being arranged with respect to said gap for providing an amplitude Af which exceeds said gap separation;
wherein said non-linear spring means are arranged to define a linear range of motion extending over at least part of said amplitudes An and Af.
an electromagnet-armature combination producing vibration and including at least first and second elements arranged in head-on facing relationship and defining a gap therebetween having a predetermined gap separation, the vibration being characterized by having amplitudes An and Af for the near and far half cycles of vibration when the first and second elements are respectively near and far from each other;
a base member supporting said first element;
a member to be vibrated, said member connected to said second element; and non-linear spring means associated with said base and said member to be vibrated including means for storing substantial energy of said electromagnetic armature combination as it approaches its minimum gap and converting it to enhanced amplitude of the member to be vibrated, said non-linear spring means being arranged with respect to said gap for providing an amplitude Af which exceeds said gap separation;
wherein said non-linear spring means are arranged to define a linear range of motion extending over at least part of said amplitudes An and Af.
2. A system according to claim 1 and wherein said non-linear spring means displays increasing stiffness as a function of increasing deflection amplitude.
3. A system according to claim 1 and wherein said non-linear spring means is operative over a non-linear range thereof.
4. A system according to claim 1, claim 2 or claim 3 and wherein said member to be vibrated comprises a vibrating tray.
5. A system according to claim 1, claim 2 or claim 3 and wherein said member to be vibrated comprises a screen.
6. A system according to claim 1, claim 2 or claim 3 and wherein said non-linear spring means interconnects said base and said member to be vibrated.
7. A system according to claim 1, claim 2 or claim 3 and wherein said non-linear spring means does not interconnect said base and said member to be vibrated, and makes contact therebetween only as said combination approaches its minimum gap.
8. A system according to claim 1, claim 2 or claim 3 and wherein said non-linear spring means comprises a plurality of linear springs which are engaged successively with increasing deflection amplitude.
9. A system according to claim 1, claim 2 or claim 3 and wherein said non-linear spring means comprises a non-linear spring.
10. A system according to claim 1, claim 2 or claim 3 and wherein said non-linear spring means comprises spring means having a linear characteristic around its rest position and a non-linear characteristic at high amplitude deflection in at least one direction.
11. A system according to claim 1, claim 2 or claim 3 and wherein said non-linear spring means has a non-linear characteristic at high amplitude deflection in a single direction.
12. A system according to claim 1, claim 2 or claim 3 and wherein said non linear spring means comprises a leaf spring associated with a curved supporting surface for engagement therewith at a predetermined deflection amplitude in at least one direction.
13. A system according to any of claims 1 to 3, wherein said non linear spring means comprises a leaf spring associated with a plurality of curved supporting surfaces for engagement therewith at a predetermined deflection amplitude in at least one direction.
14. A system according to any of claims 1 to 3, wherein said non linear spring means comprises a leaf spring associated with at least one curved supporting surface for engagement therewith at a predetermined deflection amplitude in a single direction.
15. A system according to any of claims 1 to 3, wherein said combination includes a single electromagnet and a single armature.
16. A system according to any of claims 1 to 3, wherein said combination includes a pair of electromagnets and a single armature.
17. A system according to any of claims 1 to 3, wherein said combination is arranged along an axis parallel to the axis of vibration of the system.
18. A system according to any of claims 1 to 3, wherein said combination is arranged along an axis angled with respect to the axis of vibration of the system.
19. A system according to claim 1, wherein said non-linear spring means comprises a non-linear Kappa spring.
20. A system according to claim 1, claim 2 or claim 3, wherein said non-linear spring means comprises a pneumatic spring.
21. A system according to claim 1, claim 2 or claim 3 wherein said non-linear spring means comprises an elastomer spring.
22. A system according to claim 19, wherein said Kappa spring comprises an elastomer spring.
23. A system according to claim 1, wherein said non-linear spring means is operative to store substantially all of the magnetic and kinetic energy of the vibrating system.
24. A system according to claim 1, also comprising linear spring means associated with said base and said member to be vibrated, said electromagnet-armature combination being operative to provide vibration of said member to be vibrated close to resonance of said spring means.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IL59740A IL59740A0 (en) | 1980-03-31 | 1980-03-31 | Electromagnetic vibrating system operable at high amplitudes |
| IL59740 | 1980-03-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1189559A true CA1189559A (en) | 1985-06-25 |
Family
ID=11051725
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000374267A Expired CA1189559A (en) | 1980-03-31 | 1981-03-31 | Electromagnetic vibrating system operable at high amplitudes |
Country Status (13)
| Country | Link |
|---|---|
| JP (1) | JPS56155512A (en) |
| AR (1) | AR226886A1 (en) |
| AU (1) | AU6890981A (en) |
| BE (1) | BE888187A (en) |
| BR (1) | BR8101887A (en) |
| CA (1) | CA1189559A (en) |
| DE (1) | DE3112569A1 (en) |
| ES (1) | ES8204214A1 (en) |
| FR (1) | FR2479034A1 (en) |
| GB (1) | GB2081026B (en) |
| IL (1) | IL59740A0 (en) |
| IT (1) | IT1137106B (en) |
| ZA (1) | ZA811945B (en) |
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| JPH0763674B2 (en) * | 1986-04-25 | 1995-07-12 | 大和製衡株式会社 | Shaker |
| IL89983A (en) * | 1989-04-17 | 1992-08-18 | Ricor Ltd Cryogenic & Vacuum S | Electromagnetic vibrating system |
| US5293987A (en) * | 1992-02-21 | 1994-03-15 | Fmc Corporation | Feeder drive |
| GB2307024B (en) * | 1995-11-06 | 2000-03-01 | Yamamura Churchill Limited | A method of mounting a loudspeaker |
| US5967294A (en) * | 1997-04-23 | 1999-10-19 | Fmc Corporation | High stroke, highly damped spring system for use with vibratory feeders |
| US7571817B2 (en) * | 2002-11-06 | 2009-08-11 | Varco I/P, Inc. | Automatic separator or shaker with electromagnetic vibrator apparatus |
| CN113990156B (en) * | 2021-11-05 | 2022-07-08 | 中国矿业大学(北京) | Double-plastid gap nonlinear dynamics experimental device |
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| DE1130631B (en) * | 1960-01-22 | 1962-05-30 | Schenck Gmbh Carl | Oscillating system with continuously variable frequency and amplitude, especially for vibrating tables, dynamic material testing machines and the like like |
| US3778697A (en) * | 1971-04-26 | 1973-12-11 | Arkon Scient Labor | Solenoid actuators and generators and method of using same |
| DE2617779C2 (en) * | 1976-04-23 | 1982-02-11 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V., 8000 München | Percussion instrument for diagnostic and testing purposes |
| DE2623855C3 (en) * | 1976-05-28 | 1980-11-20 | Licentia Gmbh | Electromagnetic shock vibrator |
-
1980
- 1980-03-31 IL IL59740A patent/IL59740A0/en unknown
-
1981
- 1981-03-24 ZA ZA00811945A patent/ZA811945B/en unknown
- 1981-03-27 GB GB8109711A patent/GB2081026B/en not_active Expired
- 1981-03-30 JP JP4832681A patent/JPS56155512A/en active Pending
- 1981-03-30 DE DE19813112569 patent/DE3112569A1/en not_active Withdrawn
- 1981-03-30 IT IT20820/81A patent/IT1137106B/en active
- 1981-03-30 BR BR8101887A patent/BR8101887A/en unknown
- 1981-03-30 ES ES500837A patent/ES8204214A1/en not_active Expired
- 1981-03-30 BE BE0/204304A patent/BE888187A/en not_active IP Right Cessation
- 1981-03-30 AU AU68909/81A patent/AU6890981A/en not_active Abandoned
- 1981-03-31 FR FR8106463A patent/FR2479034A1/en active Pending
- 1981-03-31 CA CA000374267A patent/CA1189559A/en not_active Expired
- 1981-03-31 AR AR284810A patent/AR226886A1/en active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111790497A (en) * | 2020-07-27 | 2020-10-20 | 杭州曾份科技有限公司 | Tealeaves processing is with stirring breaker based on light sense control |
Also Published As
| Publication number | Publication date |
|---|---|
| BR8101887A (en) | 1981-10-06 |
| IT8120820A0 (en) | 1981-03-30 |
| GB2081026B (en) | 1984-07-04 |
| DE3112569A1 (en) | 1982-03-18 |
| GB2081026A (en) | 1982-02-10 |
| BE888187A (en) | 1981-07-16 |
| FR2479034A1 (en) | 1981-10-02 |
| IT1137106B (en) | 1986-09-03 |
| AU6890981A (en) | 1981-10-08 |
| ZA811945B (en) | 1982-04-28 |
| ES500837A0 (en) | 1982-04-01 |
| AR226886A1 (en) | 1982-08-31 |
| JPS56155512A (en) | 1981-12-01 |
| ES8204214A1 (en) | 1982-04-01 |
| IL59740A0 (en) | 1980-06-30 |
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