Abstract:
A vibration mechanism ( 300 ) for shaking a tree trunk held between two clamps, for an efficient harvest of the tree-fruits and for preventing damage to the tree-roots and to the tree trunk. The vibration unit comprises two counter-rotating rotors (R) weighted by displaceable weights ( 18, 19 ) and powered, preferably, by at least one hydraulic motor (M). A transmission (T) coupled to the motor and to the rotors, counter-rotates the rotors.

Description:
This application is a U.S. National Phase Application Under 35 USC 371 of International Application PCT/IL00/00716 (published in English) filed Nov. 5, 2000. 
     TECHNICAL FIELD 
     The present invention relates to tree-shaking harvesting equipment, and in particular to the vibration generation unit which actuates such equipment. 
     BACKGROUND ART 
     Traditionally, picking fruit and nuts from trees was always done manually and was inherently labor intensive. With the rise of wages and the increase of competition in the food supply market, efforts were made to mechanize the harvesting of trees and to provide for methods that are more efficient. Because of this quest, tree-shaking machines were developed. Those tree shakers are equipped with a pair of two opposing clamps, which firmly engage a tree on two diametrical sides of the trunk. The tree shaker also comprises a vibration generation unit that is connected to the clamps of the tree-shaking machine. Once the clamps are engaged, the tree is shaken to remove the fruit, with the intent that the inertial forces that will develop on the fruit will exceed the bonding force between the fruit and the stem. 
     A vibration generation unit is typically driven by a dual oscillation mechanism, which operate substantially independently of one another. An example is provided in U.S. Pat. No. 3,338,040 which shakes the tree in a number of different random directions. Such action is undesirable, because some of these directions may cause damage to the tree. For example, those directions in which the clamps vibrate tangentially to the trunk cause transverse shear which can strip tree bark and abrade the stem. Furthermore, two randomly vibration generation units do sometimes oppose one another and cause energy dissipation; or excessively reinforce one another and thereby exert exaggerated compressive forces on the tree. 
     Efforts to coordinate the action of the two vibration generating units, such as modification of the moment of inertia of the spinning rotators resulted in U.S. Pat. Nos. 3,548,578 and 4,903,471. But even those improved devices wrench the trees across a range of directions at once, risking damage to the root system. Experiments were also conducted with the variation of the frequency of shaking, to reach the natural resonance frequency of the tree. It was thought that if it would be possible to reach the maximum amplitude of displacement, then the most efficient tree harvesting conditions would be s obtained. A limb shaker having a variable throttle arrangement that can be adjusted until the greatest displacement is observed is taught in U.S. Pat. No. 3,650,099. However, with a manual throttle setting device, the shaker was poorly suited for commercial harvesting. 
     In a paper of the American Society of Agricultural Engineers, by J. D. Whitney, G. H. Smerage and W. A. Block, No. 0001-2351/90/3304-1066, published in April 1990, there is mention of a shaking system with a three-shaft linear vibrator. As shown in FIG. 1, the elements of the system comprise a vibration unit A, a tree clamp C engaging a trunk B and part of the shaker machine D. The vibration unit A consists of three identical vertical sprocket wheels mounted side by side on a horizontal frame beam F inside a housing H. One sprocket wheel MS, the middle one for example, is driven by a motor M, not shown in FIG. 1 for the sake of clarity, and the other two sprocket wheels, on the sides of the driven sprocket wheel MS, are driven sprockets S. A chain CH couples the three sprocket wheels, with the slack side SS of the chain CH, running substantially in parallel and below the frame beam F. The slack side SS is tensioned by an idler ID. The two driven sprocket wheels S are engaged by the chain CH to rotate in the same direction while the middle driving sprocket MS counter-rotates. This is achieved by running the chain over both side sprocket wheels S but under the driven sprocket wheel MS. 
     To generate vibrations, the sprocket wheels carry eccentric weights. A single weight G is mounted eccentrically on each one of the sprocket wheels S while a double weight 2G is mounted with the same eccentricity on the driven sprocket wheel MS. With reference to FIG. 1, the single weights G and the double weight 2G are all aligned to the east, according to the directions of the compass card. A force vector equal to the sum of forces applied by the two single weights G and the one double weight 2G is thus applied eastwards. 
     Assuming that the driven sprocket wheel MS rotates anti-clockwise, then both sprocket wheels S will rotate clockwise. FIG. 2 now represents the s vibration unit A after a quarter of a turn of the sprocket wheels, according to the assumed direction of rotation. The single weights G on the sprocket wheels S now point northwards while the double weight 2G points southwards. The force vector of the sum of forces applied all the weights, namely, two single forces G pointing to the north and one double weight 2G directed to the south, now equals zero, and thereby, the upward and the downward forces cancel out. 
     Another quarter of turn of the sprocket wheels is depicted in FIG.  3 . This time all the weights are aligned westwards. The resultant force vector is thus the same as at the start, as shown in FIG. 1, but in the opposite direction. One more quarter of a turn, not illustrated in a drawing, would result in a rotation of 180 degrees of all the sprocket wheels relative to FIG. 2, whereby the force vector would again sum up to zero. It has thus been shown that the vibration unit A is a linear shaker: theoretically, forces appear only horizontally, in the east to west direction, while no forces are generated vertically, north-south. 
     In practice however, the results are quite different. First, the vibration unit A is limited to rather slow rotational velocities, due to the chain drive, which makes it unfit for the harvesting of smaller fruit. Second, the vibration unit A develops severe wear and tear, resulting in costly maintenance expenses. Third, the vibration unit A engages the tree trunks with its longitudinal axis in the direction of shaking, thus rendering it very awkward to operate. 
     Although tree shakers are readily available, their vibration generating units still suffer from various drawbacks such as slippage, loss of rotational synchronization which causes deviation from a single shaking direction, as well as damage to tree trunks and overall low harvesting efficiency. 
     For the above-mentioned reasons, there is obviously a need for better vibration generating units that keep their synchronization, are cheap to maintain and operate, and are easy to use. Moreover, there is definitely a need for equipment which features high efficiency harvesting and is inexpensive to manufacture. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a vibration generation mechanism for the high efficiency harvesting of trees. 
     It is another object of the present invention to provide a vibration generation mechanism, which is simple to use and operate. 
     It is a further object of the present invention to provide a vibration generation mechanism that will not harm the trees during shaking. 
     It is yet another object of the present invention to provide a unitary improved but simple vibration generation mechanism featuring low costs of production, of operation and of maintenance. 
     Still another object of the present invention is to provide a vibration generation mechanism, which is reliable and long lasting. 
     It is an object of the present invention to provide a linear vibration generation mechanism for a tree trunk shaker, the shaker comprising a pair of clamps for locking on the trunk on opposite sides thereof and the linear vibration generation mechanism comprising: 
     at least one motor for providing rotational motion at a predetermined angular velocity, 
     a transmission coupled to the at least one motor, the transmission for providing a counter-rotating motion, 
     a pair of identical eccentric rotators coupled to the provided counter-rotating motion, the pair of eccentric rotators rotating in parallel planes and at same angular velocity, and 
     an enclosure for containing the linear vibration generation mechanism, the enclosure being associated with one clamp of the pair of clamps. The enclosure is possibly an integral part of one clamp of the pair of clamps. 
     It is another object of the present invention to provide a linear vibration mechanism, where the pair of eccentric rotators further comprises: 
     at least one weight, and 
     an arm having for releasably but fixedly supporting the at least one weight in adjustable position thereon, and the arm accommodates for the support of different at least one weight(s) and allows adjustment of the at least one weight(s) to achieve different identical eccentricity of the pair of eccentric rotators. 
     Another object of the present invention is to provide a way to define the direction of linear vibration by alignment of the at least one weight of each one of the pair of eccentric rotators in the desired direction of vibration. 
     Yet another object of the present invention is to allow a choice of motor from hydraulic motors, electric motors, internal combustion motors and pneumatic motors, or the selection of a motor built as a hydraulic motor of the gear-on-gear type, either with spur gears or with helical gears. It is also possible to have the at least one motor also serves as the transmission for providing counter-rotating motion. Evidently, the predetermined angular velocity of the motor is controllable. 
     Moreover, another object of the present invention is to provide a linear vibration mechanism wherein the at least one hydraulic motor comprises a modification of a conventional gear-on-gear oil pump into a hydraulic motor, wherein 
     the conventional gear-on-gear oil pump comprises: 
     a housing having a first side in parallel and opposite to a second side, the housing also comprising a third side opposite to a fourth side, the first side being perpendicular to the third side, the housing being sealed close, and the housing defining an inside and an outside, 
     a first drive gear, 
     a driven gear of the same size as the first drive gear, the first drive gear and the driven gear meshing side-by-side in counter-rotation inside the housing, 
     a first driving shaft coextensive and coaxial with the first drive gear, the first driving shaft protruding outside of the first side of the housing in sealed engagement therewith, 
     an oil inlet port located amid the third side, and 
     an oil outlet port located amid the fourth side, and 
     the at least one hydraulic motor comprises: 
     the conventional gear-on-gear oil pump, 
     a second drive gear, 
     a second driving shaft, the second driving shaft and the second drive gear being of the same size as the first drive gear and the first driving shaft, the second drive gear meshing with the first drive gear in replacement of the driven gear, and the second driving shaft protruding outside of the second side of the housing in sealed engagement therewith, the first driving shaft and the second driving shaft being parallel to each other, 
     whereby supply of oil under pressure to the oil inlet port counter-rotates the first drive gear in mesh with the second drive gear to counter-rotate the first driving shaft and the second driving shaft and thereby creating a hydraulic motor which also serves as the transmission for providing counter-rotating motion. The gears of the first drive gear and of the second drive gear are selected from the group consisting of spur gears and helical gears. 
     Furthermore, it is another object of the present invention to provide a vibration generation mechanism where the at least one motor further comprises: 
     an output shaft, and 
     the transmission further comprises: 
     a housing comprising a first side and a second side, the second side being opposite to and in parallel with the first side, the housing defining an inside and an outside, the first side outside supporting the at least one motor with the output shalt thereof entering inside the housing through the first side and protruding outside of the second side, 
     a first gear coupled to the output shaft inside the housing, 
     a second gear of the same size as the first gear, the second gear and the first gear meshing side-by-side in counter-rotation inside the housing, and 
     a driven shaft coextensive and coaxial with the second gear, the driven shaft exiting the housing and protruding outside the first side of the housing, and the output shaft being parallel to the driven shaft, 
     the housing further accommodating bearings to support the output shaft, the first gear, the second gear and the driven shaft, 
     whereby rotation of the at least one motor counter-rotates the output shaft relative to the driven shaft. The housing may be selected from the group consisting of an open housing, a closed housing and a sealed housing. 
     In addition, it is another object of the present invention to provide a vibration generation mechanism where the at least one motor further comprises: 
     a first motor having a first output shaft and a second motor having a second output shaft, the first motor rotating in direction opposite to rotation direction of the second motor, and 
     the housing further comprising: 
     the first side outside supporting the first motor and the second side outside supporting the second motor, 
     the first output shaft and the second output shaft penetrating from the side of their respective motor to inside the housing and protruding to the opposite side outside, the first output shaft and the second output shaft being parallel, and 
     the first gear and the second gear being coupled, respectively, to the first output shaft and to the second output shaft. In this case, the first gear and the second gear synchronize rotation of the first motor and of the second motor. 
     It is another object of the present invention to provide that the at least one motor further comprises an output shaft, and the transmission comprises: 
     a housing of rectangular cross-section having a first side, a second side, a third side and a fourth side, the first side and the third side being opposite to and in parallel with, respectively, the second side and the fourth side, the sides of the housing defining a housing inside and a housing outside, with the first side outside supporting the at least one motor with the output shaft thereof penetrating inside the housing, 
     a drive pinion coupled to the output shaft inside the housing, the drive pinion being a rotatably mounted bevel gear, 
     a pair of coaxial parallel bevel gears meshing in perpendicular with the drive pinion, each one of the pair of bevel gears being rotatably located inside the housing, respectively on the third side and on the fourth side, 
     a pair of coaxial driven shafts protruding outside the housing, each one of the pair of driven shafts being coupled to each one of the pair of parallel bevel gears, the output shaft and the pair of driven shafts residing in the same plane, 
     whereby rotation of the output shaft drives the parallel bevel gears in counter-rotation, thereby counter-rotating the pair of driven shafts. The housing is selected from the group consisting of an open housing, a closed housing and a seated housing. 
     Still another object of the present invention is to provide a vibration generation mechanism where the at least one motor further comprises: 
     a first motor having a first output shaft and a second motor having a second output shaft, the first motor rotating in direction opposite to rotation direction of the second motor, 
     the housing further comprising: 
     the first side outside supporting the first motor and the second side outside supporting the second motor, 
     the first output shaft and the second output shaft penetrating from the side of their respective motor to inside the housing, 
     a first drive pinion and a second drive pinion located inside the housing and coupled respectively, to the first output shaft and to the second output shaft, the first drive pinion and the second drive pinion being a rotatably mounted bevel gear, 
     a pair of coaxial parallel bevel gears meshing in perpendicular with the first drive pinion and a second drive pinion, each one of the pair of bevel gears being rotatably located inside the housing, respectively on the third side and on the fourth side, 
     a pair of coaxial driven shafts protruding outside the housing, each one of the pair of driven shafts being coupled to each one of the pair of parallel bevel gears, the first output shaft and the second output shaft and the pair of driven shafts residing in the same plane, 
     whereby rotation of the output shaft drives the parallel bevel gears in counter-rotation, thereby counter-rotating the pair of driven shafts. In this case also, the first drive pinion and a second drive pinion and the pair of coaxial parallel bevel gears synchronize the rotation of the first motor and of the second motor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order to better understand and more fully appreciate the invention and to see how the same may be carried out in practice, some preferred embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawing in which: 
     FIG. 1 is a schematic view of a prior art shaking system with a three-shaft linear vibrator; 
     FIG. 2 is a detail of FIG. 1 after a quarter of turn rotation of a sprocket; 
     FIG. 3 shows the detail of FIG. 2 after another partial sprocket rotation; 
     FIG. 4 is a block diagram displaying the elements of the present invention; 
     FIG. 5 shows a schematic of first embodiment of a vibration generation mechanism; in relation to the elements detailed in FIG. 4; 
     FIG. 6 depicts a second schematic embodiment of the vibration generation mechanism also in accordance with the elements of FIG. 4; and 
     FIG. 7 illustrates a third schematic embodiment of the present invention, likewise based on FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Previous efforts of the present inventors have resulted in a past invention disclosed in U.S. Pat. No. 5,473,875, which is incorporated herewith by reference. There was presented a tree-shaking apparatus with a pair of two separate vibration generation units, each unit with an eccentric rotator and with sensors for sensing the instantaneous angular position of the eccentric rotator. In addition, the tree shaker comprised control means for rotating both eccentric rotators at a uniform rotational speed in opposite direction, which provided a predetermined shaking frequency. More control means coordinated the rotation of both eccentric rotators, in response to data provided by the position-sensing means, to keep the rotation in phase and thereby shake the tree along a single axis. 
     The intention was to provide for a tree shaker that would automatically select the optimal parameters of operation to maximize the efficiency of harvesting. This maximum efficiency was achieved by automatically matching of the frequency of tree shaker to the natural resonance of the tree, by choosing the best direction of shaking and by shaking the tree along a single axis. However, field tests proved that application of the procedure of automatic matching of parameters for tree after tree is too tedious and too time consuming. Test evidence further indicated that the trees of a same groove all exhibit approximately the same inherent characteristic response to shaking. It was thus concluded that it would be practical to provide for a shaker with one single linear vibration generation unit consisting of a sturdy, simple and reliable pair of counter-rotating eccentric rotators rotating at exactly the same rotation speed. Accordingly, details of the present invention will be supplied below. 
     FIG. 4 presents the main elements of a linear vibration generation mechanism for a tree trunk shaker. In general, the vibration generation mechanism is composed of a motor M, for the provision of rotary motion, of a transmission T to produce counter-rotation and of a pair of eccentric rotators R, to generate vibrations. The motor M derives energy from a power supply PS and the output of the eccentric rotators R is coupled to a pair of clamps C, which clamp the tree trunk and impart vibrations thereto. FIG. 4 thus depicts an autonomous linear vibration generation mechanism with counter-rotating eccentric rotators for shaking tree trunks held in clamps. The vibration generation mechanism comprises the motor M, the transmission T and the pair of eccentric rotators R designated by the numeral I in FIG.  4 . 
     Both clamps C transmit the vibrations from the vibration generation mechanism to the tree trunk. These clamps C are operated as a power system, which is separated from the vibration generation mechanism and will not be described, as they are not part of the present invention. The following description will be restricted to the vibration generation mechanism I of FIG.  4 . 
     A first embodiment  100  of the vibration generation mechanism is shown in FIG.  5 . The pair of eccentric rotators is designated as R, but the motor is indicated by MT, thus motor and transmission, because it serves the double purpose of providing for generation and transmission of rotation and also for outputting counter-rotation. The implementation of the motor and transmission MT will now be explained. 
     To build a motor and transmission element MT, it is easiest to convert a hydraulic pump and to turn it into a hydraulic motor. Hydraulic pumps are well known components, which will not to be described in detail. Citation is made of the Fluid Power Reference Issue of Machine Design, volume 47, number 22, of Sep. 11, 1975, published by the Penton Publishing Co., of Cleveland, Ohio, USA, that is incorporated herewith by reference. Hydraulic pumps are covered in Section 1, which starts on page 7 and ends on page 22 inclusive. Best suited for the task are gear-on-gear type pumps, consisting of two identical gears in mesh with each other, inside a sealed housing. It should be noted that helical gear motors are also suitable for the task. The first gear of the hydraulic pump, named drive gear or driving gear, is driven by a drive shaft that is an extension of the driving gear. The second gear, called the driven gear, is rotated by the drive gear. Both the drive gear and the driven gear are enclosed in a housing having an oil inlet and an oil outlet. When the drive shaft is rotated by an external motor, oil supplied to the oil inlet enters the hydraulic pump and is swept around the periphery of the meshing gears towards the oil outlet, where it exits under pressure. The pair of gears of the pump, which carry the full power load of the pump, are supported by appropriate bearings. The housing of the pump and the driving shaft are sealed to withstand high pressures. Hydraulic pumps are manufactured with either spur gears or helical gears, but the spur gear configuration, which is preferred, is the most common. 
     It will now be explained how a hydraulic pump, which uses the rotational input of a motor to generate hydraulic pressure, may be converted to a hydraulic motor that generates rotational motion, when provided with hydraulic pressure. Starting with the hydraulic pump, the driven spur gear is replaced by a drive spur gear of the same size. As both gears are of the same size, the housing fits. However, the drive gear has a drive shaft that is an extension thereof and therefore, the housing must be modified to comprise appropriate bearing support and seals. For the sake of clarity, the bearings and the seals, all well known to the art, are not shown in the drawings. 
     The result obtained comprises a housing with an inlet port and an outlet port and a pair of drive gears, inside the housing, which both extend in drive shafts protruding to the outside of the housing. Now, when hydraulic pressure is supplied to the oil inlet, hydraulic fluid flows through the periphery of the spur gears to the oil outlet, rotating both gears simultaneously, and thereby also rotating both shafts. As both gear are in mesh, they counter-rotate and their corresponding shafts follow suit. 
     The hydraulic pump has thus been modified into a hydraulic motor with an inherent counter-rotating capability. Evidently, a gear-on-gear hydraulic motor may be transformed in the same manner, to provide the same results. FIG. 5 is a schematic rendering of the first embodiment  100 , with a cross-section cut through the housing  10 , The oil inlet and the oil outlet are deleted for the sake of clarity. Two spur gears  12  and  13  extend into, respectively, drive shafts  14  and  15  forming rotator shafts. In the same symmetric fashion, two arms  16  and  17  are fixedly coupled, respectively, to the drive or rotator shafts  14  and  15 , by means well known to the art. The arms  16  and  17  are made to support fixedly, but releasably and adjustably, two weights, respectively,  18  and  19 , again, by means well known to the art. As the connection between the weights  18  and  19  is adjustable, the weights,  18 ,  19 , may be relocated along the length of the arms  16  and  17 . These weights  18  and  19  may also be replaced by other weights, either heavier or lighter. 
     The parameters controlling the output of the vibration generation mechanism may be varied in different ways. First, by controlling the volumetric flow of oil supplied to the motor MT, which will proportionally alter the delivered rotational velocity. Therefore, the higher the flow rate, the higher the frequency of the vibrations. Second, the distance between each weight  18  and  19 , and its respective drive or rotator shafts  14  and  15 , and third, the mass of each one of the weights  18  and  19 , mass which may be augmented or reduced. 
     A second embodiment  200  of the vibration generation mechanism will be described with the help of FIG.  6 . The three elements, namely, a motor M, a transmission T for generating counter-rotating motion, and a pair of eccentric rotators R are present, but as three separate entities. A motor M of any kind, but preferably a hydraulic motor, is mounted outside the housing  20  and is coupled to the transmission T. A pair of meshing gears  22  and  23 , either helical gears or preferably spur gears, extend each, respectively, in rotator shafts  24  and  25 . These gears  22  and  23  are supported by bearings and seals (not shown in FIG. 5) on the housing  20 . It should be noted that the rotator shaft  25  is shown as being the output shaft of the motor M. Another option would be to couple the output shaft of the motor M to the rotator shaft  24 . The two rotator shafts  24  and  25  are coupled to the two eccentric rotators R in the same manner as was described above for the embodiment  100 . Still another option would be to provide for two motors M, one for each rotator shaft  24  and  25  respectively. The task of the meshing gears  22  and  23  is now only one of synchronizing both motors M and not anymore to carry loads. 
     In contrast with the first embodiment  100 , the motor M of the second embodiment  200  is located outside of the housing  20 , whereby it is easier to perform motor maintenance and to replace the motor M. In addition, the transmission mechanism T may be sealed inside the housing  20  awhile the single or pair of motors M remain outside the housing  20 , for better cooling and ease of maintenance. 
     A third embodiment  300  of the linear vibration generation mechanism is shown in FIG.  7 . Here again, the three elements, motor M, transmission T and eccentric rotators R are separate elements, as opposed to the first embodiment  100 . 
     A motor M, preferably a hydraulic motor, although other motors are suitable, is mounted on a housing  30 . The output shaft  31  of the motor is coupled to a bevel gear drive pinion  32  and is supported by bearings (not shown in FIG. 7) on the housing  30 . A pair of coaxial parallel bevel gears  34  and  35  mesh in parallel planes perpendicular with the plane of the drive pinion  32 . Each one of the bevel gears  34  and  35  meshes on diametrically opposed sides of the drive pinion  32 . The bevel gears  34  and  35  further extend in, respectively, aligned driven or rotator shafts  36  and  37 . The rotator shafts  36  and  37  are each supported by bearings (not shown in FIG. 7) mounted on the housing  30 . The output shaft  31  is perpendicular to the driven rotator shafts  36  and  37 , but all the three shafts  31 ,  36  and  37  reside in the same horizontal plane. 
     Operation of the motor M rotates the output shaft  31 , which drives the drive pinion  32 . In turn, the pinion drive  32  rotates both coaxial parallel bevel gears  34  and  35 , but those parallel bevel gears counter-rotate as they are both driven by the same pinion drive  32 . As a result, the driven or rotator shafts  36  and  37  counter-rotate. Similar to the embodiment  200 , the pair of eccentric rotators R is coupled to the driven or rotator shafts  36  and  37 . Here too, a second motor M may be mounted on the housing  30 , opposite to the first motor M. such an option calls for the addition of a second drive pinion  32 , in opposite and in parallel with the first drive pinion  32 . The two drive pinions  32  and the two bevel gears  34  and  35  would form a rectangle. Still another option allows the gears to only synchronize the rotation of the two motors M without carrying loads, by coupling each motor M to one of the pair of parallel bevel gears  34  and  35  instead of to the pinion gears  32 . Evidently, a single pinion gears  32  would suffice for synchronization. 
     While preferred embodiments of the invention have been described shown and described in detail, it should be apparent that many modifications and variations thereto are possible, all of which fall within the true spirit and scope of the invention. For example, more than one motor may be used to provide for redundancy or greater output power. Also, other configurations are possible for the arms of the eccentric rotators, such being in the shape of a disk, of a sector, or in another shape. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described above. Rather the scope of the present invention is defined only by the claims, which follow.