Abstract:
A gate ( 50 ) for a vibratory conveyor ( 10 ) is provided. The conveyor includes a conveyor bed ( 26 ) that has a surface portion defining an aperture ( 52 ). The gate includes a cover plate ( 54 ) which is in contact with the conveyor bed and arranged for movement between a first position covering a first portion of the aperture and a second position covering a second portion of the aperture (e.g., between an open position and a closed position). The gate further includes a loading system ( 57, 72 ) coupled to the cover plate to exert a force urging the cover plate into contact with the surface portion of the conveyor bed. The gate still further includes a carriage assembly ( 55 ) coupled to the loading system for moving the cover plate between the first and second positions. Material conveyed on the conveyor bed can fall through the uncovered portion of the aperture to be thereby diverted from the conveyor bed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 60/261,128, filed Jan. 11, 2001. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to vibratory conveyors and, more particularly, to a gate for diverting conveyed material from a vibratory conveyor. 
     BACKGROUND OF THE INVENTION 
     An excited frame vibratory conveying system is disclosed by Gilman in U.S. Pat. Nos. 6,079,550 and 6,253,908, which are incorporated by reference herein. A vibratory conveying system consists of a conveying member that is spring mounted on a frame. A vibratory actuator on the frame causes the conveying member to vibrate in a substantially longitudinal direction along the conveying member at its natural frequency. The conveying member is trough-shaped, and material to be conveyed is introduced at one end of the conveying member and moves to the other end as the result of the vibration of the conveying member. Excited frame vibratory conveying systems are particularly suited for conveying particulate bulk material such as powdered, granulated, or comminuted material; small parts such as nuts, bolts, or washers; and other solids comprising relatively small pieces such as various food products. 
     The utility of a conveying system is greatly enhanced if some or all of the conveyed material can be selectively diverted from the conveyor at a point or points intermediate to the ends of the conveyor. This permits selective diversion of the material to other conveyors, containers, or processes. One method of diverting material from the elongated conveying member of a vibratory conveying system is to provide a gate in the bottom or bed of the conveying member. Generally, the gate comprises an aperture in the bed of the conveying member that is selectively covered by a cover plate. Typically, the cover plate is arranged to slide in a pair of channels defined by guides affixed to the underside of the bed of the conveying member. An actuator attached to the cover plate is arranged to slide the cover plate in the channels to selectively expose more or less of the aperture, controlling the amount of the conveyed material falling vertically through the aperture in the bed of the conveying member. This gate arrangement has several disadvantages, particularly when used with a vibratory conveyor. 
     First, it is desirable to minimize the mass of the conveying member to reduce the magnitude of the vibratory forces necessary to operate the conveyor. Therefore, the conveying member is characteristically constructed of relatively light-gauge material. However, affixing the guide channels, cover plate, and cover plate actuator to the conveying member increases its mass. Additional mass may also be required to stiffen the conveying member sufficiently to withstand the forces generated by the cover plate actuator. To reduce the mass of the conveying member, the cover plate actuator may be anchored instead to the excited frame or other stationary structure. However, such configuration requires a sophisticated isolation mechanism to ensure that the actuation force to be exerted on the cover plate will not interfere with the vibratory motion of the conveying member caused by the excited frame. Such a mechanism is complex and expensive. 
     Second, the channels in the guides for slidably supporting the cover plate must have sufficient clearance to permit the cover plate to slide easily therein. Consequently, when the conveying member is vibrating, the cover plate may move in the channels, producing noise and also causing the channels and the cover plate to wear in the areas of contact. The loose fit of the cover plate in the channels, which is exacerbated by wear, permits dust and other fines in the conveyed material to infiltrate into the interface between the channels and the cover plate. The buildup of material in the channels may make the gate difficult to operate in some cases and, in the case of handling food products, may pose sanitary problems. Further, if the cover plate loosens sufficiently in the guide channels, it can move independently of the cover plate actuator merely in response to the vibratory excitation of the conveying member. Uncontrolled motion of the cover plate interferes with the movement of the conveyed material and can substantially degrade the performance of the conveyor. For these reasons, gates of this construction require substantial maintenance, including frequent adjustment of the cover plate relative to the guide channels and removal of the cover plate to permit cleaning of the guide channels. Such gate maintenance is costly and requires that the operation of the conveyor and related processes be suspended for a significant period. 
     What is desired, therefore, is a gate for a vibratory conveyor that is compatible with the operation and structure of the vibratory conveyor, minimizes wear, is impervious to the effects of infiltration of dust and fines, and requires minimal maintenance. 
     SUMMARY OF THE INVENTION 
     The present invention provides a gate for a conveyor, for example a vibratory conveyor, that achieves all of the desired characteristics described above. The conveyor for incorporating a gate of the present invention includes a conveyor bed that has a surface portion defining an aperture. The gate includes a cover plate in contact with the conveyor bed but not otherwise constrained to move with the conveyor bed. The cover plate is arranged for movement between a first position covering a first portion of the aperture and a second position covering a second portion of the aperture (e.g., between an open position and a closed position). The gate further includes a loading system (e.g., a combination of elastic elements) coupled to the cover plate and exerting a force urging the cover plate into contact with the surface portion of the conveyor bed defining the aperture. The gate still further includes a carriage assembly coupled to the loading system for moving the cover plate between the first and second positions. 
     In one aspect of the present invention, the gate is particularly suited for use with a vibratory conveyor. A vibratory conveyor includes a conveyor bed and an excited frame that vibrates the conveyor bed. The carriage assembly of the gate of the present invention includes a base element coupled to the excited frame of the vibratory conveyor and a movable element coupled to the loading system. More specifically, the base element may be formed of a mounting block having a portion defining a bore, and the movable element may be formed of a support rod slidably arranged in the bore to be moveable in a direction substantially parallel to the surface portion of the conveyor bed defining the aperture. 
     In another aspect of the present invention, the carriage assembly generally prohibits movement of the cover plate in a direction normal to the surface portion of the conveyor defining the aperture bed but permits movement of the cover plate in a direction parallel to the surface portion. To this end, the movable element of the carriage assembly may further include a linear actuator to cause linear movement of the movable element in a direction parallel to the surface portion, such as a pneumatic actuator, an electric actuator, and a hydraulic actuator. 
     In yet another aspect of the present invention, the loading system may be formed of a plurality of elastic elements, for example a spring plate and an elastomer mount, which are arranged in series to exert a force to maintain the contact between the cover plate and the conveyor bed. 
     As will be apparent from the foregoing, the gate of the present invention provides several advantages. Because the cover plate is not connected to the conveyor bed of a conveying member, the mass of the conveying member is not altered (increased) by the provision of the gate or any reinforcement required to withstand the forces produced by actuation of the gate. Likewise, because the cover plate and its actuator are not connected to the conveying member, a complex mechanism is not required to isolate the mechanism for actuating the cover plate from the vibratory motion of the conveying member. Furthermore, since no sliding channels are required to support a cover plate, the source of significant wear and noise is eliminated. Still further, because the gate of the present invention is not constrained to the conveying member, any dust or fines that may infiltrate into the interface between the cover plate and the conveying member will migrate out of the interface during relative movement of the cover plate and the conveying member, and thus the gate is self-cleaning. Accordingly, with the gate of the present invention, deterioration of conveyor performance, noise, need for frequent maintenance, and conveyor downtime are substantially reduced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a pictorial representation of an excited frame vibratory conveyor system; 
     FIG. 2 is a side elevational view of an excited frame vibratory conveyor incorporating a gate of the present invention; 
     FIG. 3 is a plan (top) view of the vibratory conveyor incorporating the gate of FIG. 2; 
     FIG. 4 is an exploded view of the gate of FIGS. 2 and 3, including a cover plate and a carriage assembly; 
     FIG. 5 is a partial cross-sectional view of the vibratory conveyor incorporating the gate of FIG. 2 taken along line  5 — 5 , illustrating the gate in a closed position; 
     FIG. 6 is a partial cross-sectional view of the vibratory conveyor incorporating the gate of FIG. 2, illustrating the gate in an open position; and 
     FIG. 7 is a partial cross-sectional view of a gate including a vertically adjustable spring arrangement, formed in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates an excited frame vibratory conveying system  10 , suitable for incorporating a gate of the present invention. The conveying system  10  is supported by a pair of stationary supports  12 . The stationary supports  12  include pillars that are attached at one end to the floor and at the other end to the conveying system  10 . Alternatively, the conveying system  10  may be mounted to (or suspended from) an upper support, such as a ceiling. Referring additionally to FIG. 2, the stationary supports  12  typically include elastic isolation elements, such as springs  13 , to isolate the structure  15  to which the conveying system  10  is attached (e.g., the floor) from vibration transmitted through the stationary supports  12 . 
     Referring back to FIG. 1, the conveying system  10  includes an elongate excited frame  14  including a rear end  16  and a front end  18 . In the present description, the terms “rear” and “front” or “rearward” and “forward” are used with respect to the intended direction of movement of material to be conveyed on the conveying system  10 . 
     The conveying system  10  also includes an elongate conveying member  20  that extends between a rear end  22  and a front end  24 . The conveying member  20  includes a conveyor bed  26  for receiving the conveyed material (e.g., particulate matter). The conveying member  20  further includes a pair of side walls  28  and  30  that extend between the front and rear ends  24 ,  22  of the conveying member  20 . The conveying member  20  is preferably a lightweight, generally rigid structure. 
     The conveying system  10  further includes a support structure that resiliently supports the conveying member  20  on the excited frame  14 . The support structure includes leaf or beam springs  38  that interconnect the conveyor member  20  and the excited frame  14 . The springs  38  are spaced apart longitudinally along both sides of the conveying member  20  to enable the conveying member  20  to undergo vibrational motion in a generally forward and rearward reciprocating motion with respect to the excited frame  14 . 
     Each of the springs  38  are attached, with bolts or other suitable fasteners, at a slight inclined angle with respect to the longitudinal direction of the conveying system  10 . The springs  38  may be mounted on the outside of the conveyor as illustrated in FIG. 1 or on the inside of the side walls of the conveying member  20  and excited frame  14  as illustrated in FIG.  2 . The springs  38  prevent transverse movement of the conveying member  20  with respect to the excited frame  14 . The actual path of the reciprocating movement between the conveying member  20  and the excited frame  14  is in the nature of parallelogram, but for small displacements or vibrations, the path may be approximated as a straight line that is generally perpendicular to the direction of the springs  38  in their undeflected position. The size and number of the springs  38  may be varied to adjust the spring constants. 
     Still referring to FIG. 1, the conveying system  10  finally includes a vibratory drive  40 , which is directly connected to the excited frame  14  to vibrate the excited frame  14  in the intended direction of conveying. The vibratory drive  40  is preferably an electromagnetic drive that produces a vibratory motion along a linear force axis, but may be a rotating mass or other drive capable of generating vibratory force. The drive  40  exerts its force to the excited frame  14  along a linear force axis  42 , which is generally perpendicular to the set of springs  38 . Additionally, the force axis  42  extends through a center of mass of the conveying system  10 . The vibratory drive  40  is controlled by a drive controller  44 . 
     Referring additionally to FIG. 2, the vibratory conveying system  10  described above is suited for incorporating one or more gates  50  of the present invention, to facilitate diversion of the conveyed material from the conveyor bed  26  at points intermediate to the rear and front ends  22 ,  24  of the conveying member  20 . While FIG. 2 depicts the conveying system  10  that is substantially shorter in longitudinal length than that illustrated in FIG. 1 for ease of illustration, the construction and operation of the conveying system  10  in FIG. 2 are substantially the same as described above. Referring further additionally to FIG. 3, the gate  50  is used with a portion of the conveyor bed  26  defining an aperture  52 . The gate  50  includes generally two elements: a cover plate  54  in contact with a surface of the conveyor bed  26  and arranged for movement relative to the surface to selectively expose the aperture  52 ; and a carriage assembly  55  coupled to the cover plate  54  to move the cover plate  54 . 
     Referring further additionally to FIGS. 4 and 5, the construction of the gate  50  is described in detail. As illustrated, the aperture  52  defined through the conveyor bed  26  is typically rectangular, but apertures of other shapes may be used. 
     As described in the background section above, heretofore, gates for conveying systems have been slidably mounted to the conveying member using guide channels, which are subject to substantial wear, noise, and dust accumulation and require frequent maintenance. The inventors of the present invention realized that attachment of the cover plate to the conveying member was a significant cause of the maintenance and performance problems with these gates. The inventors further realized that constraining the cover plate to the light-weight vibrating conveying member undesirably increased the overall mass of the conveying member and also undesirably created a need to isolate the mechanism for actuating the cover plate from the vibratory motion of the conveying member relative to the excited frame. 
     Accordingly, in the gate  50  of the present invention, the aperture  52  in the conveyor bed  26  is sealed by contact between the cover plate  54  and a surface of the conveyor bed  26  when the gate is closed, but the cover plate  54  is not attached to the conveying member  20  or otherwise restrained thereto. The cover plate  54  includes a bearing plate  56  and a support plate  58 , and is held in contact with the bottom surface of the conveyor bed  26  preferably by a spring force exerted by a spring plate  57  attached to the carriage assembly  55 . The carriage assembly  55  is mounted to the excited frame  14  by a support block  59 , which is typically affixed to a side plate  17  of the excited frame  14  with bolts. Referring specifically to FIG. 4, the carriage assembly  55  includes a mounting block  60 , which defines a pair of bores  61  through which a pair of support rods  62  are slidably mounted via bushings  64 . Each of the support rods  62  includes a stop collar  68  at one end to prevent disengagement of the support rod  62  from the mounting block  60  when the support rod  62  is extended as shown in FIG.  4 . The other ends of the support rods  62  are attached to and support a carriage block  66 . 
     The cover plate  54  is held against the bottom surface of the conveyor bed  26  preferably by a spring force. The spring force is generated by the spring plate  57 , which is bolted to the carriage block  66  and includes an elastomer mount  72 . The elastomer mounts  72  intervene between the spring plates  57  and the cover plate  54  (or more specifically the support plate  58 ). The amount of spring force applied to the cover plate  54  can be adjusted by various means, such as by varying the distance between the carriage assembly  55  and the surface of the conveyor bed  26  against which the cover plate  54  is held, by compressing the elastomer mounts  72 , or by bending the cantilevered elements of the spring plate  57 . Typically, a modest spring force is required to support the cover plate  54  and a quantity of conveyed material on the upper surface of the cover plate  54 . 
     The spring plate  57  and the elastomer mount  72  together form a loading (or biasing) system for elastically supporting the cover plate  54 . Specifically, contact between the cover plate  54  and the conveyor bed  26  surface is maintained during the limited vertical displacements of the vibrating excited frame  14  by the elastic compliance of the elastomer mounts  72  and the spring plates  57 . Generally, the cover plate  54  vibrates transversely with the conveyor bed  26  as a result of friction therebetween although the cover plate  54  is not constrained to move with the conveyor bed  26 . The elastic mounts  72  and the spring plates  57  serve to isolate the carriage assembly  55  from vibration of the cover plate  54  with the conveyor bed  26 . At the same time, the series arrangement of the elastic mount  72  and the spring plate  57  optimizes the isolation of the cover plate  54  from the vibratory movement of the excited frame  14 . It should be understood by those skilled in the art that other arrangements may be used to achieve the same or similar effects achieved by the loading system including the spring plate  57  and the elastomer mount  72  of the illustrated embodiment. 
     While the gate  50  might be designed to be partially open at all times, the cover plate  54  is typically larger than the aperture  52  in the conveyor bed  26  (see FIG. 3) to completely seal the aperture  52  when the gate  50  is closed. Therefore, when the gate  50  is closed, only a generally annular area along the periphery of the bearing plate  56  is in contact with the conveyor bed  26  around the aperture  52 . However, when the cover plate  54  is withdrawn from the aperture  52  to open the gate  50 , an increasing portion of the total surface area of the bearing plate  56  comes in contact with the conveyor bed  26 . Thus, even while the cover plate  54  is moved relative to the conveyor bed  26 , the contact pressure at their interface is limited because of the combination of the use of modest spring force and increase in the contact area between the cover plate  54  and the conveyor bed  26 . The limited contact pressure reduces wear and abrasion of any contacting surfaces between the cover plate  54  and the conveyor bed  26 . The bearing plate  56  may be formed of plastic or other material suitable for minimizing abrasion from contact with the conveyor bed  26  and also for coming in contact with a particular material to be conveyed. 
     Referring specifically to FIGS. 3 and 4, the carriage assembly  55  includes an actuator  80  for moving the cover plate  54  transversely on the surface of the conveyor bed  26  for selectively altering exposure of the aperture  52 . A typical actuator  80  is a double-acting linear actuator having a shell  82  attached to a surface of the mounting block  60 . Pressurized fluid introduced at one end of the shell  82  causes a piston (not illustrated) within the shell  82  to be displaced toward the opposite end of the shell  82 . A movable element, for example an actuator rod  84 , is attached to the piston at one end and to the carriage block  66  at the other end. When the actuator rod  84  is extended or retracted, the support rods  62  are drawn through the bores  61  in the mounting block  60  by motion of the carriage block  66 . Corresponding movement of the spring plates  57 , extending from the carriage block  66  to support the cover plate  54  with bolts  86  (see FIG.  5 ), displaces the cover plate  54  to expose a lesser or greater portion of the aperture  52 . FIGS. 5 and 6 illustrate the gate  50  of the present invention, wherein the actuator rod  84  is fully extended and retracted, respectively, to thereby close and open the gate  50 . The gate actuator  80  is typically a pneumatic actuator for applications in which compressed air is readily available and fluid contamination is problematic. However, any appropriate actuator, including electric and hydraulic actuators, may be used. 
     Since both the cover plate  54  and the actuator  80  are not connected to the conveying member  20 , the mass of the conveying member  20  is not altered (increased) by the provision of the gate  50  or any reinforcement required to withstand the forces produced by actuation of the gate  50 . Likewise, because the cover plate  54  and the actuator  80  are not connected to the conveying member  20 , a complex mechanism is not required to isolate the mechanism for actuating the cover plate  54  from the vibratory motion of the conveying member  20 . 
     Because the gate of the present invention is not constrained to the conveying member  20 , the gate  50  is self-cleaning. Infiltration of dust and fines in the interface of the cover plate  54  and conveyor bed  26  is limited because the cover plate  54  fits tightly against the conveyor bed  26  and generally moves with the conveyor bed  26 . At the same time, since the gate  50  is not attached to the conveyor bed  26 , there is some relative movement, and any infiltrate would migrate out of the interface during such relative movement. Dust or fines migrating to edges of the cover plate  54  is free to disperse, since the gate  50  is free of any barriers that might trap the dust or fines. Accordingly, with the gate  50  of the present invention, deterioration of conveyor performance, noise, need for frequent maintenance, and conveyor downtime are substantially reduced. 
     In some applications, it may be desirable to adjust the vertical position of the cover plate  54  relative to the conveyor bed  26  after the carriage assembly  55  is mounted to the frame  14  of the conveying system  10 . FIG. 7 illustrates an alternative spring arrangement in accordance with the present invention, suitable for effecting such vertical adjustment. In FIG. 7, the same components as described above are referred to by the same reference numbers. In this arrangement, the cover plate  54  including the bearing plate  56  and the support plate  58  is supported by a flat leaf spring  57 ′. As before, an elastic mount  72  is interposed between the cover plate  54  and one end of the leaf spring  57 ′ and all components are secured by a bolt  86 . The other end of the flat leaf spring  57 ′ is secured to an adjustable bracket  90  with a bolt  86 . The adjustable bracket  90  includes a vertically extending slot (not shown), and is generally sandwiched between a clamping plate  92  and the carriage block  66  of the carriage assembly  55 . One or more clamp bolts  94  extend through the clamping plate  92  and the vertically extending slot of the adjustable bracket  90  into the carriage block  66 . Therefore, the adjustable bracket  90  is vertically slidable along its slot relative to the clamping plate  92  and the carriage block  66 . Further, one or more adjusting screws  96  are threaded through one or more nuts  98  and the clamping plate  92  against the adjusting bracket  90 . Thus constructed, when the adjusting screw(s)  96  are rotated clockwise or counterclockwise, the adjustable bracket  90  supporting the flat leaf spring  57 ′ and the cover plate  54  is vertically displaced relative to the carriage block  66  of the carriage assembly  55  that is mounted to the frame  14  of the conveying system  10 . Therefore, even after the carriage assembly  55  is mounted onto the frame  14 , a user may adjust the vertical position of the cover plate  54  relative to the conveying member  20  using this arrangement. 
     While the preferred embodiments of the invention have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.