US3476234A - Self-balancing vibrating structures - Google Patents

Description

Nov. 4, 1969 Filed March 18, 1968 FIG. l

K. M. ALLEN ETAL SELF-BALANCING VIBRATING STRUCTURES 5 Sheets-Sheet l BUC/(HORN, @L ORE, KLROU/ST a SPAR/(MAN ATTORNEYS Nov. 4, 1969 K. M. ALLEN ETAL SELF-BALANCING VIRATING STRUCTURES 3 Sheets-Sheet 2 Filed March 18, 1968 FIG. 3

FIG. 4

KENNETH M. ALLEN CHESTER H. HARPER INVENTORS BUC/(HORN, 51.0195, KLROU/S 7' SPAR/(MAN ATTORNEYS NOV- 4, 1959 K. M. ALLEN ETAL.

SELF-'"BALANCING VIBRATING` STRUCTURES 3 Sheets-Sheet F Filed March 18, 1968 NNY- KENNETH M. ALLEN CHESTER H. HARPER INVENTORS OON OOM

BUCKHORN, BLORE, KLARQUIST 8. SPARKMAN ATTORNEYSv Unted States Patent O U.S. Cl. 198-220 19 Claims ABSTRACT OF THE DISCLOSURE A oating eccentric drive (FIGS. 1 to 3) drives connecting rods 180 out of phase to drive two conveyor beds through resilient coupler means permitting lost motion of the conveyor beds longitudinally relative to the connecting rods. The conveyor beds are supported by resilient struts, and the coupler means permit the conveyor beds to balance each other over a wide range of difference in loading of the two conveyor beds. The drive is operated at from 50 to 90% of resonant speed, and the ratio of the coupler spring constant of each coupler means to the total spring constant of the struts is at least 1:3. In FIG. 4, a single conveyor bed mounted on resilient struts is driven through a resilient coupler by a crank drive mounted on a counterweight carried below the conveyor bed -by resilient struts.

This is a continuation-in-part of our application Ser. No. 568,616, filed July 28, 1966, now abandoned.

This invention relates to self-balancing vibrating structures, and more particularly to conveyor structures having opposed, resiliently mounted, counter-balancing vibrating mechanisms.

An object of the invention is to provide self-balancing vibrating conveyor structures.

Another object of the invention is to provide conveyor structures having opposed, resiliently mounted, counter-balancing vibrating mechanisms.

A further object of the invention is to provide a selfbalancing vibrating structure in which opposed outputs of a vibrating drive are coupled 'by means including a resilient coupling to a pair of independently and resiliently mounted vibrating systems,

Another object of the invention is to provide a selfbalancing conveyor structure in which a pair of conveyor mechanisms are vibrated oppositely 4by a drive including a resilient drive coupling which permits the conveyor members to shift in amplitude and phase relative to each other to balance each other and loads thereon. y

A still further object of the invention is to provide a conveyor structure in which a pair of vibrating conveyor systems balance each other over a wide range of speeds.

Another object of the invention is to provide a conveyor structure in which the throw of an eccentric drive to a conveyor bed is amplified at speeds below resonance by resilient coupling means connecting the drive to the conveyor bed.

The invention provides a vibrating structure in which a conveyor bed supported by resilient support means opposing oscillation thereof is driven -by resilient drive means at a speed between 50% and 90% of resonance lCC and the spring constant of the drive means is at least one-third that of the resilient support means. A vibrating structure forming one specific embodiment of the invention includes a pair of independently and resiliently mounted vibrating mechanisms vibrated in opposite directions through drive means including at least one resilient, driven coupling. One or both of the vibrating mechanisms may be a conveyor mechanism. Each vibrating structure includes means for driving at frequencies less than the resonant frequency thereof. A vibrating structure forming one embodiment of the invention includes a pair of conveyor members mounted independently and resiliently and driven by opposed outputs of a drive including a pair of resilient couplings, the resilient couplings having effective spring strengths of the same order of magnitude as those of the resilient mounts of the conveyor members. The couplings permit the conveyor members to shift in phase and amplitude relative to each other to maintain a balance `between the conveyor mem-bers, and preferably the drive is free to shift to aid in maintaining the balance. Preferably the conveyor members are rigidly connected to flexible glass fiber reinforced plastic struts and are supported by the struts. The speed of the drive preferably is of a type with a wide range of speed adjustment adapted to drive the conveyor members at any selected speed below resonance in a wide range from a low speed at which material on the members is not advanced therealong to a high speed at which the material is advanced rapidly therealong. In a vibrating structure forming an alternate embodiment of the invention, an elongated first conveyor mem-ber is mounted resiliently for back and forth movement and an eccentric vibrating drive drives the conveyor member through a resilient coupling and also drives a counterbalancing member oppositely to the drive of the conveyor member, the counter-balancing member being mounted resiliently for back and forth movement opposite to that of the rst conveyor member.

A complete understanding of the invention may be obtained from the following detailed description of selfbalancing vibrating structures forming specific embodiments thereof, when read in conjunction with the appended drawings, in which:

FIG. 1 is a side elevation view of a self-balancing Vibrating structure forming one embodiment of the invention;

FIG. 2 is an enlarged, horizontal sectional View taken substantially along line 2 2 of FIG. 1;

FIG. 3 is an enlarged, vertical sectional view taken substantially along line 3-3 of FIG. 2;

FIG. 4 is a side elevation view of a self-balancing vibrating structure forming an alternate embodiment of the invention; and

FIG. 5 is a graph illustrating conveyor throw for different frequencies of operation.

Referring now in detail to the drawings, there is shown in FIGS. 1 to 3 a self-balancing vibrating structure forming one embodiment of the invention and including a pair of tandem arranged, generally horizontal, trough-like conveyor members 10 and 12, preferably of substantially equal lengths. The conveyor member 10 is resiliently supported by pairs of parallel, strap-like resilient struts 14, which are preferably composed of glass reinforced plastic material. The struts 14 slope downwardly and slightly forwardly relative to direction of feed and extend primarily vertically, and the upper end portions thereof are rigidly secured to the conveyor member 12 by brackets 16 and bolts 18. The lower end portions of the struts 14 are rigidly secured by brackets 20 and bolts 22 to an elongated base or frame 24 supported by cross members 25, which may be suitably mounted by resilient supports 27 on a floor or suspended from a ceiling. The conveyor member and the struts 14 comprise an independent vibrating mechanism or system.

The conveyor member 12 is resiliently supported, similarly to the supporting of the conveyor member 10, by pairs of resilient struts 26 identical to and parallel to the struts 14 and connected rigidly to the conveyor member 12 and the base 24 by brackets 28 and 30. Thus, each of the conveyor members 10 and 12 is resiliently mounted for independent reciprocating movement 'relative to the base 24, and each is a part of an independent vibrating mechanism or system. When each of the conveyor members is reciprocated longitudinally, the struts supporting it are liexed so that, as the conveyor member is moved to the left from its normal position, as viewed in FIG. 1, the conveyor member is moved downwardly, and, as the conveyor member is moved to the right from its normal or at rest position, the conveyor member is moved upwardly and feeds material thereon toward the right.

The conveyor member 12 is resiliently supported, similarly to the supporting of the conveyor member 10, by pairs of resilient struts 26 identical to and parallel to the struts 14 and connected rigidly to the conveyor member 12 and the base 24 by brackets 28 and 30. Thus, each of the conveyor members 10 and 12 is resiliently mounted for independent reciprocating movement relative to the base 24, and each is a part of an independent vibrating mechanism or system. When each of the conveyor members is reciprocated longitudinally, the struts supporting it are flexed so that, as the conveyor member is moved to the left from its normal position, as viewed in FIG. l, the conveyor member is moved downwardly, and, as the conveyor member is moved to the right from its normal or at rest position, the conveyor member is moved upwardly and feeds material thereon toward the right.

A floating drive 38 drives the conveyor members 10 and 12 oppositely and at the same frequency through pairs of resilient drive couplings 40 and 42 receiving outputs of the drive 38 from connecting rods 44 and 46, which are 180 out of phase relative to each other, and the couplings keep the frequencies of the conveyor members the same while permitting the phase and amplitude of one of the conveyor members to so vary relative to the phase and amplitude of the other conveyor member as to perfectly balance the vibration of the other conveyor member even though the load on one of the conveyor members may be several times greater than the load on the other conveyor member. The couplings provide for substantial lost motion between the drive 38 and the conveyor members.

There are two connecting rods 44 connected by selfaligning bearings 48 to two, in phase, eccentrics or crank portions 50 of a crankshaft 52 mounted rotatably in bearings 54 carried by parallel arms 56 of a floating mounting frame 57 pivotally mounted by a shaft 60 on the base 24. There are also two of the connecting rods 46 connected by self-aligning bearings 5S to eccentrics or crank portions 59, which are 180 out of phase from the eccentrics 50. The crankshaft carries small ywheels 62. The shaft 60 is driven at any selected rate of speed by a variable pulley 64, a belt 66 and a variable pulley 68 driven by an electric motor 70. These elements constitute an adjustable frequency drive. To change the speed, pressure of air in a control cylinder unit 72 is varied by a bleeder valve 74 in an air line 75 to shift a mount 76 to move the motor and pulley 68 farther from or closer to the pulley 64. This inversely changes the effective diameters of the pulleys 64 and 68 to change the speed 4 of the shaft 60. A fixed ratio belt and pulley drive 78 drivingly connects the shaft 60 to the crankshaft 52.

The drive couplings 40 and the drive couplings 42 are substantially identical, and only the drive couplings 40 will be described in detail. Each drive coupling 40 (FIGS. 1 and 3) includes a pair of rather long helical compression springs 80 of substantially equal lengths and of substantially equal spring constants mounted in seats on opposite sides of a vertical abutment plate 82 of a channellike bracket member 84 xed to the bottom of the conveyor member 10 and including suitable cross bracing. The conveyor members 10 and 12 have longitudinal stiffeners 88 and 90, which are substantially T-shaped in transverse cross-section. The connecting rods 44 extend quite loosely through notches or slots 92 in the abutment plate 82 and through the pairs of springs 80. Nuts 94 and 96 screwed onto threaded end portions 98 of the connecting rods 44 and spring seats 100 and 102 on the rods conne the pairs of springs under some preloading compression therebetween. The combined or effective strength of the springs 80 is substantially of the same order of magnitude as the combined strength of the struts 14. That is, upon the application of a given static force to the connecting rods to produce a given length of compression of the springs 80, the upper ends of the struts 14 will be moved a lesser length. For effective operation of the conveyor structure, the spring constant of the coupling should be at least about one-third that of the combined spring constant of the struts, and should not be greater than about three times. The connecting rods 46 are similarly connected to the conveyor member 12 by the drive couplings 42, which include pairs of compression springs 111 on opposite sides of an abutment plate 113 of a bracket member 11's secured to the conveyor member 12. Longitudinal stii'feners 117 are secured to the bottom of the conveyor member 12. The drive couplings 40 and 42 supply energy in generally opposed directions at the same frequency to the two independent vibratory systems comprising the conveyor members 10 and 12 and resilient struts 14 and 26. However, the phase relationship and amplitudes of reciprocation of the two vibratory systems are permitted by the resilient couplings to change so that the reaction force of each of the conveyor systems balances that of the other. As a result, no vibrations are transmitted to the base, no shocks are imparted to the drive, and very little power is required to drive the conveyor members.

In one constructed conveyor structure forming a specific embodiment of the invention, the throw of each connecting rod was three-eighths of an inch, and, for rotation of the crankshaft 52 at about fifty revolutions per minute, the amplitude or throw of each conveyor member Was about one-quarter of an inch. For rotation of the crankshaft at about eight hundred revolutions per minute, the amplitude of each conveyor member was about three-fourths of an inch. The drive was smooth, free of shock and quiet at all speeds throughout this range from fifty to eight hundred revolutions per minute. Each conveyor member 10 and 12 was about thirty feet long and was supported by eight pairs of struts, and, While under load, the power required to drive the conveyor members at eight hundred oscillations per minute was about one-quarter horsepower. The speed at which products were fed was from zero to one-hundred fifty feet per minute, about one and one-half tons being fed per minute.

In the operation of the above-described self-balancing vibrating structure, material is supplied to the lefthand end portion of the conveyor member 10. The motor 70 drives the crankshaft at a speed below the resonant frequency of the vibrating structure and determined by -the selected adjustment of the cylinder unit 72. The crankshaft reciprocates the connecting rods 44 and 46, the connecting rods 44 being in phase with each other and the connecting rods 46 also being in phase with each other 'but 180 out of phase relative to the connectingrods 44. The resilient drive couplings 40 and 42 impart the opposed forces to the conveyor members 10 and 12 to flex each of the struts 14 and 26 substantially equidistantly on opposite sides of the normal or unflexed position of that strut. At low frequencies of vibration, the material is not moved along the trough. When the frequency is increased, the amplitude or throw of the troughs is increased and the material is advanced by the troughs to the right. When the loads on the two conveyor members are equal, their phase relationships to the drive are substantially the same and their amplitudes are substantially equal. However, when their loads are quite different from each other, the phase relationship of the conveyor members and their amplitudes so shift as to balance their reaction forces on the drive, this -being permitted by the resilient drive couplings 40 and 42.

While the conveyor members 10 and 12 in the disclosed embodiment are lmounted by the struts 14 and 26 for feeding material in the same direction, it will 'be obvious that the struts 26, instead of being parallel to the struts 14, may be sloped opposite to the slope of the struts 14 so that the conveyor member 12 advances material oppositely to the direction of advancement by the conveyor member 10. Thus, the conveyor members can be mounted to both feed to a receiving means at the adjacent ends of the conveyor member. Also, the conveyor members 10 and 12 may be so mounted as to both feed material away from their adjacent ends. The conveyor members 10 and 12, while being shown as positioned in substantial alignment, may, of course, be offset from each other, and may, if desired, be placed one above the other. However, to achieve the self-balancing condition the conveyor members should Ibe mounted in substantially parallel positions and be driven substantially fully out of phase with one another. lf desired, the couplings 42 may be rigid, with the couplings 40 being resilient and providing all the necessary resilient lost motion for balancing.

In FIG. there are shown typical curves of the conveyor member in which the amplitude or throw of the conveyor is plotted against the frequency of the drive 38. The amplitude is given in percent of the throw of the eccentric drive and the frequency is given in percent of resonant frequency. Curve 1 is that in which the struts 14 supporting the conveyor mem-ber 10 are of no spring strength, and, in effect, are freely pivotal arms, with the entire spring structure being in the couplings 40 which have a spring constant such as to give the vibratory system which consists of the member 10, the struts 14 and the couplings 40 a resonant frequency between 400 and 1500 cycles per minute. A curve 2 shows the amplitude of the conveyor member 10 where the spring constant or strength of the couplings 40 is three times that of the struts 14 with the resonant frequency of the system being between 400 and 1500 cycles per minute. Curve 3 gives the amplitude of movement of the conveyor member 10 where the spring constants of the couplings 40 and the struts 14 are equal with the resonant frequency of the system consisting of the conveyor member 10, the couplings 40 and the struts 14 being between 400 and 1500 cycles per minute, for example. For the curve 4, the spring constant of the couplings 40 is one-half that of the struts 14 and the resonant frequency of the system consisting of the member 10, the struts 14 and the couplings 40 is between 400 and 1500 cycles per minute. The curve 5 represents the conditions where the spring rate or strength of the couplings 40 is one-third that of the struts 14 with the resonant frequency of the vibratory system made up of the member 10, the struts 14 and the couplings 40 being between 400 and 1500 cycles per minute. In the above examples K1 represents the spring constant of the couplings 40 and K2 is the total spring constant of the struts 14. In each of vthese examples, the conveyor is best operated below resonant frequency and at a frequency in the range of from 50% to 90% of the resonant frequency and has a Wide operating range wherein an appreciable change in amplitude results from a moderate change in frequency and in which there is an amplification of greater than one over a large portion of the operating range. This permits the throw of the eccentric drive 38 to be quite small and still obtain a large throw of the conveyor member 10, the throw of the eccentric drive lbeing not greater than 3A of an inch and preferably about 17s of an inch.

The ratio of the spring constant =of the couplings 40 to the total spring constant of the struts 14 should not be substantially less than 1:3 to provide efficient movement of the conveyor member 10 while operated below resonant frequency with a short throw of the eccentric drive 38 and amplification of the throw of the eccentric drive so that the throw or amplitude of the conveyor member is sufficiently long for excellent movement of material. The ratio of the spring contsant of the coupling 40 to that 4of the struts 14 may be indefinitely high so long as it is not substantially below the above-mentioned minimum of 1:3 while keeping the total spring constant of the system (the sum of the spring constant of the couplings 40 and that of the struts 14) at such a value that the resonant frequency of the system is not substantially lower than 400 cycles per minute and is not substantially higher than 1500 cycles per minute. However, it is desirable that the spring constant of the struts 14 be suicient to enable support of the conveyor member 10 and the material thereon by the struts with-out excess deflection, though, of course, pivotal arms or other supporting means could be used in place of the struts 14 if the spring constant of the coupling is made sufficiently great. The preferred range of the ratio of the spring constant of the coupling to that of the struts is from 1:2 to 3:1, a ratio of 1:1 being optimum. The conveyor bed should have suicient weight to cause amplification of the throw of the conveyor over that of the eccentric drive at drive frequencies within the range at which the conveyor efficiently moves material thereon. The preferred weight of the conveyor is from 4% to 10% that -of the spring constant of the system with an optimum being about 7 pounds of weight of the bed for a spring constant of pounds per inch. With the conveyor structure within the above-outlined limits and operated at a frequency not substantially lower than 50% and not substantially higher than 90% ofthe resonant frequency, a short crank throw can be used while imparting an amplified conveyor bed throw. Such amplification will, of course, begin lower in the operating frequency range for a higher ratio of coupler spring constant to the total spring rate of the supporting struts than for a lower ratio. The throw of the eccentric drive may be from 1A; inch to 3A inch for most applications.

A very close mathematical approximation of the various values of the conveyor comprising the conveyor member 11), the struts 14 and the coupling 40 is given by the following formula:

where K2=Total static spring constant or sum of spring constants of struts 14 in pounds per inch C=Viscous damping factor (resistance to movement of conveyor struts 14) 7 f=Frequency of conveyor in cycles per second=r.p.m./ 60 M=Mass of conveyor-:W/ 386; where W=weight in pounds, and 386=acceleration due to gravity in inches per second per second.

The factor C is suiciently small that it is negligible within the operating range :of frequency of the conveyor so that the above formula reduces to:

quency of the vibrating system made up of the conveyor member 10, the struts 14 and the couplings 40 is:

fR=Cycles per second at resonance where In a conveyor forming one constructed embodiment of the invention, only the conveyor member 10 with the base 24, `the supporting struts 14, the resilient couplings 40, the drive 57, the motor 70 and the coupling structure between the motor 70 and the drive 57 were used with the drive 57 held against floating. That is, the conveyor was a single conveyor. The member 10 was a channel having a weight about 7% of the spring force of the resilient elements, struts 14 mounted in pairs were used, the spring constant of the couplings 40 was about one-half that of the total spring constant of the struts 14, and the resonant frequency of the vibrating system thus formed was substantially higher than 700 cycles per minute. At 450 cycles per minute, the throw of the member 10 was 1A; inch; at 500 cycles per minute the throw was slightly less than lrV16 inch; at 550 cycles per minute the throw was slightly over A@ inch; `at 600 cycles per minute the throw was 1/2 inch; at 650 cycles per minute the throw was 5ft; inch; and at 700 cycles per minute the throw was 11A inches. In the same constructed single conveyor but with the spring constant of the couplings 40 increased to about one and one-half times the total spring constant of the struts 14 while leaving the spring constant of the struts the same, the resonant frequency of the system increased to substantially higher than 750 cycles per minute, and the throw at 500 cycles per minute was slightly less than 5%; inch; at 550 cycles per minute was slightly less than 3A; inch; at 600 cycles per minute was slightly over inch; at 650 cycles per minute was 1/z inch; at 700 cycles per minute was 5A: inch; and at 75() cycles per minute Was 3A inch. In another constructed single conveyor embodying the invention the conveyor member 10 weighed 56() pounds, there were 10 struts 14, which were 1A: inch inch fiber glass arms 2 inches by 8 inches, the ratio of the spring constant of the exciter couplings 40 to the total spring constant of the struts was 1:1, the resonant frequency was substantially above 800 cycles per minute, and the throws of the conveyor member were 1A inch at 550 cycles per minute, 5/16 inch at 600 cycles per minute, 3/3 inch at 65() cycles per minute, 7/16 inch at 700 cycles per minute, *M6 inch at 750 cycles per minute and 3/4 inch at 800 cycles per minute. With the same conveyor as that just described but with the couplings 40- being weaker to provide a 7 :8 ratio of couplings spring constant to total support struts spring constant, the throw varied from 1A inch at 500 cycles per minute to ll/s inches at 800 cycles per minute, the resonant frequency being lower than the immediately preceding described conveyor system and being somewhat over 800 cycles per minute.

EMBODIMENT OF FIG. 4

A self-balancing vibrating structure shown in FIG. 4 forming an alternate embodiment of the invention includes a conveyor member 110 and a counterbalancing member 112 forming parts of two independent, opposed vibrating systems or mechanisms. The conveyor member is mounted on a iirst pair of resilient, slightly inclined struts 114 and a second pair of parallel struts 116, brackets 118 and 120 connecting the member 110 rigidly to the upper end portions of the struts and brackets 122 and 124 connecting a base 126 rigidly to the lower end portions of the struts. The member 110 is adapted, when moved back and forth, to advance material to the left, as viewed in FIG. 4.

A resilient coupling of substantially the same construction as the previously described couplings 40 serves to resiliently connect the conveyor member 110y to an eccentric type vibrating drive 142. The coupling 140 includes a pair of elonagted coil springs 141 and 143 on the end portion of a connecting rod 144 and held by spring seats 148 and under preloaded compression abutting opposite sides of a rigid abutment plate 152 xed rigidly to the bottom of the conveyor member 110. The coupling 140 provides resilient lost motion between the connecting rod and the conveyor member.

The connecting rod 144 forms a part of the vibrating drive 142, and is driven -by an eccentric or crank portion of a crankshaft 162 journaled in bearings 164 mounted rigidly on counterbalancing member 112. Flywheels 166 are mounted on the crankshaft 162, which is driven by a belt and pulley drive 168 driven through a variable speed pulley drive 170 by an electric motor 172 mounted slidably on the base 126 and held in selected position by a spring 174 and a pneumatic cylinder unit 176 controlled by a remotely controlled bleeder valve 178 in a line 179 carrying air under a constant pressure.

The counterbalancing member 112 forms, with resilient pairs of slightly inclined struts 180 and 182 fixed to the member 112 and the base 126, an independent vibrating system or mechanism which is substantially matched to the vibrating system including the conveyor member 110 and struts 114 and 116. A counterweight 186 forms an integral part of the counterbalancing member 112. A shaft 188 journaled on the base is driven by output pulley 190 of the variable speed pulley drive 170, and has keyed thereto driving pulley 192 of the belt and pulley drive 168. A belt 194 of the drive 168 extends substantially parallel to the struts 180 and 182. The drive 142 has two outputs 180 out of phase or directly opposed, one output being nonresliently connected to the counterbalancing member 112 and the other output being connected for resilient, lost motion to the conveyor member 110.

When the crankshaft 162 is rotated, it drives the connecting rod 144 and the counterbalancing member 112 oppositely or 180 out of phase. The conveyor member 110 is driven by the connecting rod through the resilient coupling 140, whose resiliency is greater than the resiliency of either the vibrating system including the conveyor member 110 or the vibrating system including the counterbalancing member 112. That is, the spring constant of the springs 141 or 143 is substantially less than the total spring constant of the struts 114 and 116 or the total spring constant of the struts 180 and 182. This permits the member 110 to shift in phase and amplitude or throw relative to the member 112 so that the two vibrating systems are kept well balanced.

The above described conveyor structures have very high capacities, while being very light in weight and requiring very little power. The conveyor structures operate very well with short crank throws and amplified conveyor bed throw, and do so at frequencies below resonance so that it is not necessary to go up to or through resonance in their operation. The above-described conveyor systems balance so well that substantially no vibration is imparted to the bases thereof.

It is to be understood that the above-described arrangements are simply illustrative of the application of the principles of the invention. Numerous other arrangements may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

1. In combination,

a pair of vibrating members,

base means,

a plurality of resilient struts mounting the vibrating members independently on the ybase means for independent longitudinal back and forth movements and urging the vibrating members toward predetermined positions,

a drive mechanism having a pair of output drive means driven substantially 180 out of phase with respect to each other,

means mounting the drive mechanism oatingly relative to the base means,

means connecting one of the members to one of the output drive means, and

a resilient coupler connecting the other vibrating member to the other output drive means for relative longitudinal movement between one of the vibrating members and the last-mentioned output drive means.

Z. The combination of claim 1 wherein the amplitude of each output drive means is a predetermined distance,

the resilient coupler having a maximum movement at least as great as said predetermined distance.

3. The combination of claim 2 wherein the resilient coupler has a maximum movement substantially greater than said predetermined distance,

the drive means serving to drive the vibrating members at a frequency less than the resonant frequency of the combination to provide a throw greater than said predetermined distance.

4. In combination,

a pair of elongated conveyor members,

a base,

first resilient mounting means mounting one of the conveyor members in a generally horizontal position extending in a predetermined direction for movement back and forth on the base,

second resilient mounting means mounting the other conveyor in a generally horizontal position extending in said direction for movement back and forth on the base,

crank means having a pair of eccentric drive portions 180 out of phase,

a mounting structure mounting the crank means for floating movement in said direction,

a pair of connecting rods driven -by the eccentric drive portions,

power means for rotating the crank means, and

means connecting the connecting rods to the conveyor members and including at least one resilient coupler permitting limited longitudinal movement of one of the connecting rods relative to one of the conveyor members.

S. The combination of claim 4 wherein the coupler includes an abutment plate mounted rigidly on one of the conveyor members and having a clearance openlng through which one of the connecting rods extends, a pair of compression springs mounted on the last-mentioned connecting rod and a pair of spring seat means on the last-mentioned connecting rod holding the compression springs in engagement with the abutment plate.

6. The combination of claim 4 wherein each of the mounting means includes a plurality of parallel, stiif slats mounting one of the conveyor means on the base.

7. The combination of claim 4 wherein each of the mounting means includes means connecting the end portions of the slats rigidly to said one of the conveyor members and the base.

8. The combination of claim 4 wherein the power means comprises a variable speed drive and means coupling the drive to the crank means.

9. The combination of claim 4 wherein the mounting structure includes a U-shaped frame member pivotally mounted on the "base, and a pair of bearing means carried in aligned positions by the arms of the U-shaped frame member and journaling the crank means.

10. In combination,

a pair of elongated conveyor members,

a base,

a plurality of resilient lirst struts mounting one of the conveyor members in a generally horizontal position extending in a predetermined direction for movement back and forth on the base,

a plurality of resilient second struts mounting the other conveyor in a generally horizontal position extending in said direction for movement back and forth on the base,

floating crank means having a pair of eccentric drive portions out of phase,

a pair of connecting rods driven :by the eccentric drive portions,

power means for rotating the crank means, and

a pair of resilient couplers connecting the connecting rods to the conveyor members for longitudinal floating movement therebetween.

11. In a conveyor,

a conveyor member,

resilient means mounting the conveyor member for oscillatory movement and having a predetermined spring strength,

oscillating drive means having a predetermined throw,

and

resilient coupling means connecting the drive means to the conveyor member for oscillating the conveyor member, the spring constant of the resilient coupling means being sufficiently high relative to that of the resilient means that the throw of the conveyor mem- Iber is greater than said throw of the drive means when the drive means is operated at a frequency less than nine-tenths of the resonant frequency of the system including the conveyor member, the resilient means and the coupling means.

12. The conveyor of claim 11 wherein the spring constant of the resilient coupling means is sufficiently high relative to that of the resilient means that the throw of the conveyor member is greater than said throw of the drive means when the drive means is operated at a frequency within a substantial portion of a range of frequency from about one-half to about nine-tenths of the resonant frequency of the system including the conveyor member, the resilient means and the coupling means.

13. The conveyor of claim 11 wherein the spring constant of the coupling means is not substantially less than one-third of that of the resilient means.

14. The conveyor of the claim 11 wherein the spring constant of the coupling means is from one-half to twice that of the resilient means.

15. The conveyor of claim 11 wherein the spring constant of the coupling means is substantially equal to that of the resilient means.

16. In a conveyor,

a conveyor member,

resilient means including support means supporting the conveyor member for oscillatory movement and resilient coupling means for oscillating the conveyor member,

the resilient means and the conveyor member forming a vibrating system having a resonant frequency within a range of from 400 cycles per minute to 1500 cycles per minute,

drive means coupled to the conveyor member by the coupling means serving to oscillate the conveyor member at a frequency of from 50% to 90% of said range,

the resilient means having a predetermined spring constant,

the conveyor member having a weight of from 4% to the conveyor member is about 7% of said predetermined 10% of said predetermined spring constant, spring constant.

the spring constant of the resilient coupling means References Cited Ibeing not. substantially less than one-third of said UNITED STATES PATENTS predetermined spring constant. 5 2,669,344 2/1954 Flint.

17. The conveyor of claim 16 wherein the spring constant of the resilient coupling means is from one-half to 312161557 11/1965 Morrs twice that of the resilient means. FOREIGN PATENTS 1-8. The conveyor of claim 16 wherein the spring con- 7 495 1900 Great Britain stant of the resilient coupling means is substantially One- 10 half that Of the resilient means. EDWARD A SROKA, Primary Examiner 19. The conveyor of claim 17 wherein the weight of gg UNTTED STATES PATENT OFFICE CERTIFICATE OF CORRECTION aten: No. 3,476,234 Dated November 4, 1969 InT/entods) Kenneth M. Allen and Chester H- Harper It :ls certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, lines 26 to 42, are duplicates of the preceding paragraph and should be omitted.

Column 7, line 55, "inch" should be canceled.

bil...;D inkl) SEALED FEB 1 71970 r i lSEAL) Edward M-Flewm'" WILLIAM n. somma. JR.

Attesting Officer Commissioner of Patents

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