Differential impulse conveyor with improved drive

A differential impulse conveyor (10) includes a tray (12) laterally moveable in a forward direction at a first speed and in a backward direction at a second speed greater than the first speed, thereby moving goods along the tray. A plurality of legs (18, 20) support the tray during lateral movement, and a motor (30) powers a drive pulley (30). A driven pulley (36) is powered by the drive pulley, and a flexible member (34) interconnects the driven pulley and the drive pulley. At least the driven pulley has an eccentric pulley axis, thereby imparting lateral movement to the tray. A tension mechanism (38, 40) is provided to take up slack in the flexible member.

FIELD OF THE INVENTION

The present invention relates to conveyors of the type that utilize an elongate tray to move goods along the tray. More particularly, this invention relates to a differential impulse conveyor wherein a drive unit or drive assembly moves the tray forward at a first speed, then backward at a greater speed such that goods slide relative to the tray and thus move forward along the tray. The improved conveyor drive has high reliability and relatively low cost by avoiding the use of a conventional crank and associated bearings.

BACKGROUND OF THE INVENTION

Various types of conveyors have been devised which employ an elongate tray or pan having a planar surface for transporting goods thereon. These trays conventionally have sides projecting upwardly from the planar floor of the tray, such that the tray has a generally U-shaped cross-sectional configuration. Conveyors with these types of trays are preferred for various applications since the goods transported along the tray need only engage the tray during the conveying operation, and since the tray may be easily cleaned.

One type of conveyor which utilizes such a tray is a vibratory conveyor or shaker conveyor. These types of conveyors utilize a drive mechanism which essentially vibrates the tray, so that goods move along a slightly inclined or horizontal tray floor due to the forward direction imparted to the goods while raised off the floor. An earlier version of a conveyor drive is disclosed in U.S. Pat. No. 2,374,663, which utilizes a pair of crank arms. The crank arm causes a change in the rotational speed of a driven pulley. Other drives for a vibratory conveyor system are disclosed in U.S. Pat. Nos. 4,260,052, 4,913,281, 5,404,996, 6,019,216, 6,230,875, 6,276,518, 6,415,912, and 6,435,337. More recent drives for vibratory conveyors are disclosed in U.S. Pat. Nos. 6,719,124 and 6,868,960. U.S. Pat. No. 4,917,655 is directed to a timing belt tensioner.

Differential impulse conveyors have significant advantage over vibratory conveyors for many applications. Differential impulse conveyors slide goods along a tray, but do not require vertical movement of the goods with respect to the tray. Goods conveyed with a differential impulse conveyor are thus generally subject to less damage than goods transported by a vibratory conveyor. Moreover, the drive mechanism itself may operate in a quieter manner and may be less susceptible to maintenance problems. An early version of a drive for an inertial conveyor is disclosed in U.S. Pat. No. 5,178,278. Drives for differential impulse conveyors are disclosed in U.S. Pat. Nos. 5,794,757, 6,079,548, 6,189,683, 6,398,013, 6,415,911 and 6,527,104. Another type of differential impulse conveyor drive is disclosed in U.S. Pat. No. 7,216,757.

The disadvantages of the prior art are overcome by the present invention, and an improved differential impulse conveyor and a drive for such a conveyor are hereinafter disclosed.

SUMMARY OF THE INVENTION

In one embodiment, a conveyor assembly comprises a tray laterally moveable in a forward direction at a first speed, and a backward direction at a second speed greater than the first speed, thereby moving goods along the tray. This embodiment may employ a plurality of legs pivotally connected to the tray and supporting the tray during lateral movement. A motor is provided for powering a drive pulley about a drive pulley axis, and the driven pulley is powered by the drive pulley. A belt or other flexible member interconnects the driven pulley and the drive pulley, with the driven pulley mounted to one of the plurality of legs and the tray and rotatable about a driven pulley axis. At least one of the drive pulley and the driven pulley have an eccentric pulley axis, thereby imparting lateral movement to the one of the leg and the tray. The conveyor assembly further includes a tension mechanism to take up slack in the flexible member, which may be a biasing member or a tensioning pulley.

According to another embodiment of the invention, a method of conveying goods includes providing the tray and the motor discussed above, and powering a driven pulley by the drive pulley and a flexible member interconnecting these pulleys. The driven pulley may be mounted to one of a plurality of legs or the tray. One or both of the drive pulley and the driven pulley are rotated about an eccentric pulley axis, thereby imparting lateral movement to the tray.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1illustrates one embodiment of a differential impulse conveyor10according to the present invention. The conveyor includes a tray12which moves laterally in the forward direction (to the right inFIG. 1) at a first speed, and in a backward direction at a second speed greater than the first speed, such that goods slide relative to the tray floor during the backward movement and thereby move forward with the tray as it moves forward. The tray12as shown inFIG. 1may have a pair of opposing sides14which determine the maximum depth of the goods in the tray, such that the tray itself in cross-section has a general U-shaped configuration.

As shown inFIG. 1, a plurality of legs18,20(two rearward legs18and two forward legs20) are pivotally connected at26to the tray, and are pivotally connected at24to a base22, with travel of goods along the tray inFIG. 1being to the right. The legs18,20thus support the tray during lateral movement in the forward and backward directions. Various other mechanisms may be provided for supporting the trays as discussed subsequently. The conveyor is driven by a drive motor30which is positioned on motor base28supported on the conveyor base22. The motor30is conventionally powered electrically but could be powered hydraulically or pneumatically. The motor rotates a drive shaft31, which as shown inFIG. 1is concentrically mounted on the motor base28. Although not shown inFIG. 1, those skilled in the art will appreciate that a speed reducer or other gear box may be positioned between the drive motor30and the pulley32, so that the motor powers the speed reducer, and the output of the speed reducer rotates the pulley32.

FIG. 1also shows a driven pulley36which is eccentrically mounted on one of the plurality of legs20, and is powered by the drive pulley32and a flexible member34, such as the timing belt or a timing chain, which interconnects the drive pulley and the driven pulley. Since the driven pulley is eccentrically mounted, its rotation during a full cycle pivots the arm20in a forward direction at a relatively slow speed, and in a backward direction at a relatively fast speed, thereby moving goods along the tray. The distance of travel for the tray during the full forward cycle or backward cycle is relatively short, and normally in the range of from 1 to 3 inches. The vertical movement of the tray during this cycle is very limited and does not contribute to or detract from movement of goods along the tray. The timing belt34may pull the pulley36in a direction so that it rotates closer to the pulley32, but cannot push the pulley36in an opposing direction to take up the slack in the timing belt. Accordingly, a tension mechanism consisting of another timing belt38and pulley40concentrically mounted on tensioning pulley base42are provided. The shaft on which the pulley36is mounted may thus effectively have two pulleys, or a single pulley with two belt grooves, so that the tensioning mechanism38and40act to pull the driven pulley36in a direction away from the drive pulley32.

In order to reduce vibration in the system and contribute to a long life, as well as to reduce the noise of the conveyor drive, the drive pulley32driven by the motor30is also connected to an eccentrically mounted counterweight pulley46, with timing belt44connecting the pulley32and the pulley46. The pulley46is eccentrically mounted on arm48which is secured to counterweight50, which in turn is pivotally supported on leg52which rotates about pivot54on the base22. Another tensioning mechanism is provided by the timing belt56and the concentrically mounted pulley58, which is supported on pivot base60secured to the base22. Rotation of the pulley32thus simultaneously rotates both the eccentrically mounted pulleys36and46, with the appropriate tensioning mechanisms provided for each pulley to take up the slack in the respective flexible member. Pulley36thus imparts the desired differential impulse movement to the tray12, while the pulley46moves the counterweight50in a manner which opposes the momentum of the tray movement, thereby reducing vibration problems. More particularly, the eccentric mounting of the driven pulley36causes it to tighten and loosen belt34, thereby moving arm20forward and backward. The eccentric mounting of pulley36also causes belt34to pull on a short radius, causing it to rotate fast and after 180° of rotation, and to pull on a long radius, causing it to rotate slow. The combined effect causes arm20to move rearward at a fast speed and forward at a slow speed, thereby causing goods to move along the tray. The counterweight and associated counterweight mechanism may not be required for all applications, i.e. small, light pans, or slow speed conveyors.

A significant advantage of theFIG. 1embodiment is the simplicity of the drive mechanism. Various types of crank arms are not employed, thereby avoiding the costs associated with both the crank arm and the bearings which control the crank arm movement. A further significant feature of the above conveyor is that the rotational speed and thus the stroke of the tray may be easily controlled by the eccentricity of each pulley, which may be adjustable. In the present design, the pulleys change both the speed and stroke of the pan or tray.

Subsequent drawings illustrate portions of a conveyor shown inFIG. 1, andFIGS. 2 and 3only the front or forward supports20are depicted, with no pan12. Also, the pulleys for driving a counterweight are not shown inFIG. 2for clarity of the depicted components, although in general a counterweight and pulleys for driving the counterweight as discussed inFIG. 1would be used for both theFIG. 2andFIG. 3embodiments. InFIG. 2, the drive pulley120is concentrically mounted with respect to motor base28, and the timing belt34rotates a driven pulley122which is eccentrically mounted on the arm20. This arrangement achieves the same result as the drive mechanism shown in theFIG. 1embodiment, resulting in backward and forward movement of the tray support20and thus the tray. In theFIG. 2embodiment, a spring, such as spring128, acts between the leg20and the spring base130, thus exerting a continual force to bias the leg20away from the drive pulley120. InFIG. 2, the concentric pulley is mounted on the motor and the eccentric pulley on the arm20. Belt tension and the slow forward movement is provided by the spring in lieu of pulley40and belt38as shown inFIG. 1.

Fine tuning between the stroke and the fast/slow ratio may be achieved by varying the height of the driven pulley122in relation to the height of the driving pulley120. Eccentric pulley122is thus adjustably positionable along curved slot144in guide plate142, which is secured to arm20. The pulley122may be locked in a selected position to adjust the stroke length and the slow forward/fast backward ratio. Moving the pulley122upward within the slot144changes the angle of the belt34, which shows inclines substantially when the pulley122is positioned as shown inFIG. 2. Increasing the belt angle from horizontal changes the timing between the slow forward/fast backward movement of the tray and the cranking mechanism involved in that motion. Adjustment of this timing by selectively varying the angle of the driven pulley relative to the drive pulley thus allows for optimization to travel over specific product moving along the tray, so that the selected belt angle is a part of function of the product being conveyed.

In theFIG. 3embodiment, both the drive pulley124and the driven pulley126are eccentrically mounted, with the spring132acting as the tension mechanism to take up slack in the flexible member132in a manner similar to that achieved with the compensating pulley40and the belt38shown inFIG. 1. TheFIG. 3embodiment allows the eccentricity of the pulley to be half of the pulley used in theFIG. 1andFIG. 2embodiments, thereby allowing the timed pulleys to be smaller in diameter with reduced out-of-balance forces. For all the embodiments, substantial stops to limit travel in the forward and backward directions may be provided to minimize over travel of the arms and tray in the event of a belt breakage. A similar mechanism is shown inFIG. 3for fine-tuning the conveyor performance by varying the angle of the driven pulley with respect to the drive pulley. In other embodiments, either the drive pulley or both the drive pulley and the driven pulley may be selectively adjustable, since a change in their relative position is important. Other mechanisms may be used for facilitating that adjustment and then selectively locking the position of the adjustable pulley in place.

FIG. 4is a side view of the conveyor10with a tray12as discussed above. The drive pulley32driven by motor30powers a driven pulley36which is interconnected with the drive pulley via a timing belt34. Pulley36eccentrically rotates about axis80, which is laterally fixed by plate assembly82directly to the pan12. Another pulley84rotates about the same axis80, with the belt38connecting pulley84with compensating pulley86, which eccentrically rotates about the shaft88and is rotatably about support90secured to the base22. As with theFIG. 1embodiment, the motor also rotates pulley92, which acts through the belt44to rotate pulley46, which is in turn moves counterweight50slidably supported on pad94. Pulley96is also rotated by the drive motor and belt44, with belt56driving pulley58which is eccentrically supported on base post98. A plurality of support legs102,104may support the tray12on the base22, with bearing slide packages106and108providing for sliding movement of the tray relative to the base in both the forward and backward directions.

FIG. 5is a top view of the assembly shown inFIG. 4, with a portion of the tray12cutaway to shown the orientation of the primary components of the drive mechanism. An advantage over the previous embodiments is that the space between the floor of the tray and the base in theFIG. 5embodiment may be relatively short because the axes of the pulleys are each substantially vertical in theFIGS. 4 and 5embodiment, rather than being substantially horizontal as shown in theFIGS. 1-3embodiments. Also, this embodiment shows the option of interconnecting the driven pulley directly to the tray, with the legs102,104only supporting the tray during lateral movement. In alternate embodiments, the tray could be otherwise supported so that it slid back and forth during operation of the drive. In some applications, the tray may be supported from rods or arms extending upward from the tray to a roof or other overhead structure.

The embodiment as shown inFIGS. 4 and 5has significant advantages in that the vertical spacing between base22and the tray12may be relatively short. This allows for the possibility of the conveyor to fit within a relatively small vertical spacing, and also allows the possibility of a plurality of conveyors to be vertically stacked in a desired arrangement.

The conveyor assembly includes a driven pulley mounted to one of the plurality of legs or the tray, with the driven pulley rotatable about a driven pulley axis. At least one of the drive pulley and the driven pulley have an eccentric pulley axis, thereby imparting movement in either the forward direction or the backward direction to the tray. A tension mechanism takes up slack in the flexible member so that the flexible member returns the tray back to its starting position by moving the tray in the other of the forward direction or the backward direction. The belt or other flexible member may pull the tray in either the forward direction at a first slow speed, or may pull the tray in a backward direction at a second speed greater than the first speed, thereby moving goods forward along the tray. The tension mechanism thus acts to return the tray in the opposite direction, which may correspond to travel of the tray at either a slow forward speed or faster return speed.

Two embodiments of a tension mechanism to take up the slack in the flexible member are disclosed. In one embodiment, a spring or other biasing member exerts a biasing force to bias the tray or one of the legs away from the drive pulley, and this biasing force may result in either a slow forward or faster return motion for the tray. In another embodiment, the tension mechanism comprises a tension pulley mounted to a stationary base, with a flexible tensioning member interconnecting the driven pulley and the tensioning pulley. Either tension mechanism may cause either the slow forward or faster return motion of the tray, with the drive pulley and the driven pulley causing the other tray motion.

FIG. 1illustrates a feature of the invention wherein each of the shafts for the pulleys32and36, and optionally also shaft40, shaft46, and shaft58, if used, are at the same horizontal level, i.e., within a plane parallel to the floor. This design simplifies the operation of the system, so that fine tuning the system can be commenced with this starting point. More particularly, lowering the drive shaft31from this starting point provides a selective change in timing between the rotation of the drive shaft and the lateral movement of the tray. In some applications, it may be desirable to vertically change the height of shaft31relative to the shaft drive for pulley36, as effectively shown inFIGS. 2 and 3. Even for this embodiment, all shafts other than shaft31preferably may be at the same horizontal level.

Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.