Abstract:
A vibratory feeder apparatus includes a bed, a base, a plurality of elastic amplifiers having a first end connected to the bed and a second end connected to the base, and a plurality of elastic isolators coupled to the base to support the base above surrounding terrain. The feeder apparatus also includes a pneumatically operated linear actuator mounted on the base and having a housing and a reciprocating mass slidably disposed inside the housing. The reciprocating mass is isolated from mechanical connection to any component outside of the housing.

Description:
[0001]     The present application is a continuation of U.S. application Ser. No. 10/338,316, filed on Jan. 8, 2003, issued as U.S. Pat. No. 7,322,569, which is hereby incorporated by reference in its entirety in the present application. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention generally relates to vibratory process equipment and, more particularly, to drives for generating vibratory motion in such equipment.  
       BACKGROUND OF THE INVENTION  
       [0003]     Vibratory process equipment is used in a wide variety of industrial applications. Vibratory feeders and conveyors, for example, may be used to transport granular material, foundry castings, or other objects. Such feeders and conveyors typically include a bed on which the objects are transported and a drive for producing a vibratory motion of the bed which advances the objects in the desired direction. The drive typically includes an electric motor with eccentric weights mounted on the output shaft. In operation, the output shaft with eccentric weights is rotated to generate vibratory force that is transferred to the bed.  
         [0004]     Vibratory process equipment may generally be classified as single mass or two mass systems. In single mass systems, the drive is rigidly connected to the bed and the drive/bed combination is isolated from surrounding terrain by an elastic member. In two mass systems, the drive is elastically coupled to the bed, and either the drive or the bed is isolated from surrounding terrain by an elastic member. Two mass systems are preferable in many applications since they are capable of more efficiently producing vibratory movement. Consequently, a smaller motor may used be used in a two-mass system to produce a force having the same amplitude as that of a single-mass system having a larger motor.  
         [0005]     The conventional rotating motors produce a rotational force having an unnecessary and undesired force component. Most vibratory process equipment drives the bed in a desired motion. The rotational force produced by rotating eccentric weights, however, generates a force component that is perpendicular to the desired motion. In two mass systems, the drive is coupled to the bed by an elastic member. The elastic member is typically supported so that it has several degrees of freedom in which to move. A spring, for example, has six primary degrees of freedom (i.e., movement along the X, Y, and Z axes and rotation about the X, Y, and Z axes). As a result, the elastic member may be excited in any number of ways other than in the desired motion. The perpendicular force component may therefore excite the elastic member in undesired directions, thereby detracting from the desired motion and reducing efficiency of the system.  
         [0006]     In addition, vibratory process equipment using conventional rotating motors have a rotational inertia that delays stopping and starting of the equipment. As the rotating motors are accelerated from rest to the operating speed, the resulting vibratory force passes through various undesirable frequencies that may excite the connecting or isolation elastic members in undesirable directions. The vibratory force passes through the same undesirable frequencies as the motors decelerate from operating speed to rest. For example, specific frequencies may cause isolation bounce, isolation rock, and rocking between the drive and the bed, among others. These undesirable motions cause extraneous movement of the bed, which may be particularly undesirable for applications requiring quick starting and stopping, such as precision feeders.  
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0007]      FIG. 1  is a side elevation of vibratory process apparatus constructed in accordance with the teachings of the present invention;  
         [0008]      FIG. 2  is a side elevation of an alternative vibratory process apparatus constructed in accordance with the teachings of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0009]     The embodiments described herein are not intended to be exhaustive or to limit the scope of the invention to the precise form or forms disclosed. The following embodiments have been chosen and described in order to best explain the principles of the invention and to enable others skilled in the art to follow its teachings. While the embodiments of vibratory process apparatus illustrated herein are commonly referred to as feeders or conveyors, it will be appreciated that the teachings of the present invention may be used in other applications, such as compaction tables, grinding mills, or other vibratory processing equipment.  
         [0010]     Referring now to the drawing,  FIG. 1  illustrates a feeder  10  of the type generally well known in the art. The feeder  10  includes a bed such as trough  12 , which defines a work surface for receiving the work material to be processed. The trough  12  has a receiving end  18  and a discharge end  20 , and is supported on elastic members such as springs  14  which isolate the bed from the surrounding terrain.  
         [0011]     A vibratory drive  22  is elastically coupled to the trough  12  for generating a vibratory motion of the bed. In the embodiment illustrated at  FIG. 1 , the drive  22  is connected to the trough  12  by an elastic member such as spring  24 . The drive  22  includes a base  26  supporting a linear actuator  28  and a tuning weight  30 . While the linear actuator  28  is illustrated in  FIG. 1  as being positioned inside the spring  24 , it will be appreciated that the actuator may be positioned at other points on the base  26 . Furthermore, while a single spring  24  is illustrated, the apparatus may include multiple springs extending between the base  26  and trough  12 . Still further, the tuning weights  30  may be attached at any point on the base  26  without departing from the teachings of the present invention.  
         [0012]     In operation, the linear actuator  28  generates a linear force that may be sinusoidal or non-sinusoidal over time. The linear force is amplified by the spring  24  and transferred to the trough  12 , resulting in vibratory motion of the trough. Material placed on the work surface of the trough  12  will move in response to the vibratory motion of the trough  12 . Because of the elastic connection between the trough  12  and drive  22 , the illustrated embodiment would be considered two-mass system, defined herein as a vibratory apparatus having a working mass elastically coupled to an exciter mass.  
         [0013]     In the apparatus of  FIG. 1 , the linear actuator  28  and spring  24  are angled to produce a bed motion that raises and translates the work material to the right, so that the work material will move from the receiving end  18  to the discharge end  20  of the trough  12 . The orientation of the drive and or springs may be modified to move the work material in different manners. For example, the drive and springs may be oriented so that work material placed on the work surface is compacted. In general, the springs are aligned with the line of motion generated by the linear actuator  28  so that, when the actuator is at an operating frequency, the spring will be excited at a natural frequency in the desired direction, thereby to move the trough  12  in the desired motion.  
         [0014]     The linear actuator  28  may be operated pneumatically, hydraulically, or otherwise. In the illustrated embodiment, the linear actuator  28  includes a reciprocating piston  29  inside the actuator to generate the vibratory force; however it will be appreciated that other sources of linear force in addition to the piston may be used, such as a pair of counter-rotating shafts carrying eccentric weights. When the linear actuator  28  is pneumatic or hydraulic, the fluid pressure to the actuator  28  may be controlled to adjust not only the frequency at which the piston  29  reciprocates but also to adjust the force output of the actuator  28 . Accordingly, both the frequency and amplitude of the vibratory force produced by the drive  22  may be adjusted. Furthermore, when fluid pressure is used to actuate the piston  29 , the frequency and force output of the linear actuator  28  are infinitely adjustable.  
         [0015]      FIG. 2  illustrates an alternative embodiment of a vibratory apparatus  50  constructed in accordance with the teachings of the present invention. The vibratory apparatus  50  includes a base  52  supported by isolation springs  54  above the surrounding terrain. Amplifying springs  56  have first ends attached to the base  52  and second ends attached to a bed  58 . The bed  58  defines a work surface for receiving a work material.  
         [0016]     A linear actuator  60  is attached to the base  52  for generating a vibratory force. The linear actuator  60  may include a reciprocating piston  62  that is operated using pneumatic or hydraulic pressure. In operation, the reciprocating piston generates a force that is amplified by the springs  56  to create a vibratory motion of the bed  52 .  
         [0017]     The primary difference between the embodiments of  FIGS. 1 and 2  is the location of the isolation springs. In the  FIG. 1  embodiment, the isolation springs are coupled directly to the trough  12 , while in the embodiment of  FIG. 2 , the isolation springs are coupled to the base  52 . Apart from the isolation springs, the construction and operation of the two embodiments are quite similar.  
         [0018]     The above embodiments use a linear actuator to produce a vibratory force in a two mass system. The force produced by the linear actuator acts in a single direction, and therefore the perpendicular force component (and the resulting detrimental effect on the desired vibratory motion) generated by conventional drives having rotating motors is minimized or eliminated. In addition, linear actuators weigh significantly less than electric motors and therefore the weight of the drive may be reduced. This is significant for applications in which the material to be processed is light, since the bed must weigh more than the drive for the apparatus to operate efficiently. Still further, when the linear actuator is operated by pressurized fluid, it is more finely adjustable than electric motors, thereby allowing greater control of the rate at which the objects are transported. Finally, the use of the linear actuator in a two mass system not only allows adjustment of frequency but also amplitude, thereby allowing further adjustment of the vibratory drive in a simple and inexpensive manner.  
         [0019]     Numerous modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teachings those skilled in the art the best mode of carrying out the invention. The details of the structure may be varied substantially without departing from the spirit of the invention, and the exclusive use of all modifications which come within the scope of the appended claims is reserved.