Abstract:
A vibratory conveying apparatus includes a trough operatively associated with a vibratory drive assembly for conveying pieces along the trough. The vibratory drive assembly includes a base member and a vibratory drive mounted to the base member. The trough is operatively associated with the vibratory drive to be driven into vibration substantially longitudinally with respect to the base member. First and second flexure members or bars extend longitudinally of the base member on opposite lateral sides of the base member, the bars connected at base ends to the base member. At least one leaf spring extends laterally across the base member, the leaf spring connected at opposite ends to distal ends of the bars and operatively connected at a center thereof to the trough. The flexure members provide increased flexibility at the leaf spring connections to increase useful spring life.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The invention relates to a vibratory feeder or conveyor that employs leaf springs. Particularly, the invention relates to an improved leaf spring connection for a vibratory feeder or conveyor, the feeder or conveyor having a base member and relatively reciprocating trough connected to the base member by the leaf springs. 
     BACKGROUND OF THE INVENTION 
     Vibratory feeders and conveyors are known which employ bar shaped leaf springs connecting a trough to a base member. The leaf springs in these feeders or conveyors may be mounted individually, or in banks of multiple leaf springs to meet the spring rate required by the design of the vibratory equipment. The leaf springs are known to be arranged such that one end of the bank of leaf springs is clamped to the conveying member, for example, the trough of the vibratory feeder, and the other end is clamped to the base member, or to the stationary member in the case of a single mass feeder design. In some designs, a center region of the bank of springs is clamped to structure of the conveying member of the feeder or conveyor, while the ends of the bank of leaf springs are clamped to structure of the base member, forming two spring bank sections. 
     A problem associated with these prior art designs is that as the spring bank is deflected, the leaf springs are required to elongate due to the geometry of the spring bank configuration. This elongation subjects the leaf springs to very high tensile stress as the leaf springs try to stretch. Also, as the feeder operates in each vibration cycle, the leaf springs are required to first deflect, in a characteristic “S” shaped form, in one direction, then to return to pass through a neutral position, and then to deflect in the opposite direction, and then to return to the neutral position once again to complete the cycle. Thus, with each cycle, the leaf springs experience a fully reversing stress which is detrimental to the useful life of the leaf springs. 
     The generated forces acting along a spring axis are directed to urge the leaf springs in the spring bank to slip in their clamped connection during some stage of deflection. If the clamping force at the clamped connection is increased to prevent such slippage at this stage of deflection, the resulting tensile stress, combined with the increased bending stress of the spring, particularly at the stress riser location formed where the spring is clamped, is often sufficient to cause a premature failure of a leaf spring as it is deflected back and forth. 
     There have been some prior art attempts to alleviate the design problem discussed in the previous paragraph, by fixing one end of the leaf springs, say to the base member of the conveyor or feeder, and allowing the other end of the spring to rotate. U.S. Pat. No. 3,845,857 discloses an arrangement of a single mass vibratory feeder wherein one end of a spring bank is connected to a rod mounted in an elastomer bushing such that as the spring element are deflected, the bushing yields, allowing the spring ends to move to provide a substantially simple deflection of the spring. This connection avoids the “S” shape form characteristic of deflecting a leaf spring that is fixed at both ends. While this spring mounting means may reduce the spring stresses involved in the deflection, the resultant spring rate would be reduced to an extent that would make the system impractical for large feeders. 
     SUMMARY OF THE INVENTION 
     The present invention contemplates a vibratory conveying apparatus, such as a conveyor or feeder, having a vibratory drive assembly and a trough. The trough is connected to a base member of the vibratory drive assembly via a leaf spring assembly. The leaf spring assembly has an improved spring connection configuration located between the trough and the base member to decrease stress on a leaf spring or springs of the leaf spring assembly to increase the useful life of the leaf spring assembly, while still providing an effective spring rate. 
     The apparatus includes a vibratory drive arranged between the base member and the trough. The vibratory drive can be an electromagnetic driver, a rotating eccentric weight driver, a rotating crank arm driver, or other type of drive which acts directly on the trough, or acts to indirectly induce vibration through the spring assembly, such as in a base excited conveyor. 
     The leaf spring assembly preferably includes a plurality of leaf springs stacked together in a spring bank, although a leaf spring assembly having a single leaf spring is also encompassed by the invention. Where a plurality of leaf springs are employed, the springs can be separated by spacers. 
     In a preferred embodiment, the leaf springs are arranged in a bank and extend substantially perpendicularly to a first direction of vibratory movement of the trough. The leaf springs are connected at a first region to a flexure member and at a second region to structure of the trough. The flexure member is elongated in the first direction, having a base end fastened to the base member and a distal end connected to the leaf springs. The flexure member can flex laterally at its distal end in response to flexing force from the leaf springs. 
     Preferably, the first region is one end of the leaf springs and the second region is a center region of double length leaf springs. The leaf springs can also include a third region at an opposite end of the double length leaf springs. A second flexure member is connected at its base end to the base member and at its distal end to the third region. The first and second flexure members are configured and arranged in mirror image fashion on opposite lateral sides of the base member. 
     Each flexure member includes a substantially plate shaped bar member extending substantially along its length from the base end to the distal end. The flexure member includes a clamp element or clamp block connected to the distal end of the bar member. The bar member and the clamp element include openings in registry for accepting one or more leaf spring elements. A fastener proceeds into the distal end of the clamp element to be advanced along the first direction to abut the leaf spring(s) and press the leaf spring(s) against an end surface of the opening to clamp the spring(s) into the clamp element. 
     The spring attachment mechanism of the present invention is an improvement over the prior known arrangement in that it lowers the spring stresses while maintaining high spring rates for practical designs of large two mass vibratory feeders and conveyors. According to the preferred embodiments of the invention, the characteristic “S” shape form of the deflected leaf spring is retained. 
     The invention provides an improved means to mount and connect leaf springs used in vibratory feeders and conveyors such that combined tension and bending stresses are minimized. These lower stresses prevent premature spring failure which allows higher vibration strokes than feeders and conveyors using conventional spring clamping methods. The attachment mechanism accommodates a high system spring rate to keep the number and the size of the springs within practical limits. 
    
    
     Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a vibratory conveying apparatus utilizing a vibratory drive assembly of the present invention; 
     FIG. 2 is an enlarged elevational view of the vibratory drive assembly shown in FIG. 1; 
     FIG. 3 is an elevational view of the drive assembly of FIG. 2; 
     FIG. 4A is a plan view of a base member of the assembly of FIG. 2; 
     FIG. 4B is an elevational view of the base member of FIG. 4A; 
     FIG. 4C is an end view of the base member of FIG. 4A; 
     FIG. 5A is a plan view of vibratory components of the assembly of FIG. 2; 
     FIG. 5B is an elevational view of the vibratory components of FIG. 5A; 
     FIG. 6A is a plan view of a flexure member of the assembly of FIG. 2; 
     FIG. 6B is an elevational view of the flexure member of FIG. 6A; 
     FIG. 7 is a schematic plan view of the assembly of FIG. 2; and 
     FIG. 8 is a schematic view of an alternate embodiment of the invention. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While this invention is susceptible of embodiment in many different forms, there are shown in the drawing and will be described herein in detail specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
     FIG. 1 illustrates a conveying apparatus  10  of the present invention. The apparatus  10  can be a vibratory conveyor or feeder. The apparatus includes a trough  20  for holding pieces to be conveyed in the direction X. A vibratory drive assembly  14  (described below) is connected to the trough  20  and can be hung via one or more rods  13  from a support structure  17 , for example, in the case of a single mass feeder or conveyor. The trough  20  can also be supported from the support structure  17  via one or more rods  13   a.  Power is supplied to a vibratory drive  34  (described below) located within the drive assembly  14 , via an electric power cord  44 , to drive the trough into vibration along the axis A. 
     The trough  20  is connected to the drive assembly  14  by means of one or more trough brackets  21  connected by fasteners  19  to one or more connector brackets  22  (shown in FIG.  2 ). The connector brackets  22  are connected to the vibratory drive assembly  14 . 
     FIG. 2 illustrates the vibratory drive assembly  14 . The assembly includes a base member in the form of a base assembly  16 . The base assembly  16  is supported from the structure  17  by the rod(s)  13 , as shown in FIG.  1 . The connector brackets  22  are connected to a trough frame or chassis  24  via four extending arms  24   a  (two shown in FIG.  2 ). The trough chassis  24  is supported by a bank  25  of leaf springs  26 . 
     The electric power cord  44  is passed through a rubber strain relief bushing  33 , fastened to the base assembly  16 , to protect the cord from pulling loose or fraying. 
     The base assembly  16  is described below with respect to FIGS. 4A through 4C. The base assembly  16  forms a substantially enclosed space for the chassis  24  and the vibratory drive  34 . The enclosure is formed by a cover plate  92 , a top plate  100 , a base plate  108 , a back plate  102  and two flexure members  54  (described below). The connector brackets  22  are each welded or otherwise connected to two of the four extending arms  24   a  of the chassis. The brackets  22  each include six threaded holes  120  for receiving the fasteners  19 , to connect each of the trough brackets  21  to one of the connector brackets  22 . 
     FIG. 3 illustrates the vibratory drive assembly  14 . The cover plate  92  and the top plate  100  are removed for clarity of description. The vibratory drive  34  is mounted to the base assembly  16  and operates to impart vibration between the base assembly  16  and the trough  20 . The vibratory drive  34  includes an electromagnet  38  having an electromagnetic coil  48 . The trough chassis  24  includes an armature  40  in close proximity to the electromagnetic coil  48  such that an oscillating magnetic field in the coil  48  causes the armature  40  to be repetitively drawn toward and then released from the coil  48 . The electric power cord  44  conducts electric power to the coil  48 . The electromagnet  38  is mounted to the base assembly  16  via a mounting bracket  50  and fasteners  52 . 
     The leaf springs  26  are connected at opposite ends to respective flexure members  54 . Each flexure member  54  includes an elongated bar element  56  having a base end  57  and a distal end  59 . The base end  57  of the bar element  56  is fastened by fasteners  69  to respective side members  106  (described below) of the base assembly  16 . Connected at the distal end  59  is a block-shaped clamp element  60 . The bar element  56  includes a bar window or opening  58  adjacent to its distal end  59 . The clamp element  60  extends in a direction from the distal end  59  of the bar element  56  back toward the base end  57  of the bar element  56 . The clamp element  60  includes a clamp window or opening  62  which is in registry with the bar window  58  of the bar element  56 . 
     A clamp fastener  64  extends through a front wall portion  66  of the clamp element  60 , threaded into a threaded bore  71 . The clamp fastener  64  extends into the window  62  when the clamp fastener  64  is advanced in the element  60 . The fastener  64  has a protrusion  64   a  that presses against a clamp block  63  which presses against the plurality of springs  26 . The springs  26  can be spaced apart by interleaved spacers  65 . The bank of springs  25  is clamped tightly within the window  62  against a stop block  67  which is pressed to an end surface  68  of the clamp window  62 . The bank of springs  25  passes loosely through the bar window  58 . 
     The chassis  24  includes a transverse slot or opening  80 . The springs  26  extend through the opening  80 . A stop block  67 , a clamp block  63  and spacers  65  between adjacent springs  26 , are arranged within the opening  80 . A further clamp fastener  64  extends through a front wall portion  86  of the chassis  24 . Advancement of the further clamp fastener  64  through the front wall portion  86  presses the clamp block  63  into the bank of springs  25  against the clamp block  67  which itself abuts an end surface  84  of the chassis  24 . Thus, the springs are tightly clamped at each of the flexure members  54  and at a center region thereof within the chassis  24 . 
     FIGS. 4A and 4B illustrate the base assembly  16  of the apparatus. The base assembly includes the top plate  100  supported from the base plate  108  by the back plate member  102 , the two side members  106  and two front support members  116 . The top plate  100  includes an access opening  101  above the vibratory drive  34 , for maintenance access. The access opening  101  is closed by the cover plate  92 , as shown in FIG.  2 . The side members  106  include threaded holes  107  for receiving the fasteners  69 , as shown in FIG.  2 . Extending upwardly from the base plate  108  are two electromagnet support blocks  112 , which support the mounting bracket  50 , each of which contain bracket mounting holes  126  which are threaded to receive the fasteners  52 . 
     FIGS. 5A and 5B illustrate the vibratory driver  34  arranged adjacent to the armature  40 . The electromagnet mounting plate  50  includes four fasteners holes  126  which are elongated longitudinally in order to precisely set the distance of the electromagnetic coil  48  to the armature  40 . 
     FIGS. 6A and 6B illustrate the flexure member  54  in more detail including the rectangular clamp window  62  which is open to the threaded bore  71 . The flexure member mounting holes  130  are used to receive the fasteners  69 . 
     FIG. 7 illustrates the vibrational behavior of the trough chassis  24 , the spring bank  25  and the flexure members  54  during operation of the apparatus. Although only one double length spring  26  is shown for simplicity, the behavior of all of the leaf springs  26  of the bank  25  would be similar. As the apparatus operates, in each vibration cycle each of the springs  26  first deflects from a neutral position to its characteristic “S” shaped form, in one direction, returns to pass through the same neutral position, and then deflects in the opposite direction, and then returns to the neutral position to complete the cycle. As the spring bank  25  is deflected, the tension, due to the spring elements trying to elongate, and the axial bending strain, produce a force whereby the elongated bar element  56  of the flexure member  54  deflects along its own “S” shaped path in the direction defined by the arrows  144 . The selected spring rate of the flexure member  54  limits the combined stress level in the spring system  26  to be within safe design values for long spring life, but at the same time is sufficiently stiff to provide a resultant spring rate to handle the trough weights of the largest of vibratory feeders or conveyors, without the spring system slipping in the spring clamp elements  60 . 
     The dashed lines on the right side of FIG. 7 indicate the displacement of the chassis  24  and the deflection of the spring  26  as the armature  40  is being attracted to the core of the electromagnet  38  when electric power is applied to the magnetic coil  48 . The dashed lines on the left side of FIG. 7 indicate the displacement of the chassis and the deflection of the spring  26  after the armature  40  is released by the electromagnet  38  and has moved by spring force. The arrows  140  indicate the direction of the displacement of the armature  40  and the trough chassis  24  during operation. The arrows  144  indicate the direction of the displacement of the spring and clamping flexure member  54  as the spring  26  is deflected in the characteristic “S” shaped form, as indicated by the dashed lines. 
     In the illustrated embodiment, the conveying apparatus is powered by an electromagnet. It is not intended to limit the invention to single mass or two mass electromagnetic feeders as it will be readily understood by those skilled in the art that the invention would be useful over a broad range of vibratory feeders and conveyor designs employing leaf springs. Any drive means that can cause the trough  20  to reciprocate back and forth in the direction of the arrows  140 , such as rotating eccentric weights, rotating crank arms, and the like, may also be employed and are encompassed by the invention, regardless of any geometry differences and in the placement or arrangement of the component parts. The geometry of the flexure members  54  might also be varied to suit individual feeder or conveyor designs without departing from the principles of the invention. 
     FIG. 8 illustrates the principles of the invention schematically. A first structure  200 , such as a trough, is connected at a connection  204  to a leaf spring  208 . The connection  204  is preferably a stack of spring bars. The spring is connected at a connection  212  to a flexure member  216 . The connection is preferably a clamped connection. The flexure member  216  is preferably a bar member. The flexure member  216  is connected at a connection  220  to a second structure  226  such as a base. The connection  220  can be a bolted connection. The length of the spring  208  is preferably arranged at about 90° to the longitudinal axis of the flexure member  216 , although the invention is not limited to that angle as other angles would be operational and are encompassed by the invention. The apparatus shown in FIG. 8 could be turned upside down with the second structure  226  being the trough and the first structure  200  being the base. The first structure  200  and the second structure  226  are reciprocated relative to each other along the direction W. 
     From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.