Abstract:
In a parts feeder driven by an electromagnet driver, the magnet core and the armature are rotationally misaligned either to adjust the lines of direct magnetic force between the electromagnet and the armature or, where the armature is magnetically charged, such that the magnetic force will exert both an attractive force between the magnet core and the armature and a relative torque between the magnet core and the armature which tends to align the poles of the armature and the magnetic core. A round baseplate design allows the unit to be simply enclosed for aesthetic or for potential air purging applications. Counterweights for tuning the parts feeder natural frequency can be bolted to the round baseplate, the counterweights having a ring segment shape to compactly fit on the round baseplate.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The invention relates to a vibratory parts feeder utilizing an electromagnetic vibratory drive. Particularly, the invention relates to an improvement in the electromagnetic drive and an improvement in the base assembly which supports the electromagnet of the drive. 
     BACKGROUND OF THE INVENTION 
     A typical vibratory parts feeder is shown in U.S. Pat. No. 3,258,111. The feeder includes a base mass that is supported upon vibration isolators and a frame mass that is mounted above the base mass by four inclined leaf spring sets which enable rotational oscillatory movement of the frame mass in response to an exciter motor. The frame mass includes a bowl for receiving parts. 
     The exciter motor is of an electromagnetic type that includes a field core and a coil mounted on the base mass. An armature is mounted on the underside of the frame mass with an air gap between opposing facing of the field core legs and the armature. When an alternating current is supplied to the coil, the armature and frame mass are alternately drawn toward the coil and released, flexing the leaf spring sets. Thus, the frame mass oscillates rotationally about a central vertical axis at a predetermined frequency that is established by the frequency of the current supplied to the coil. 
     As described for example in U.S. Pat. No. 4,007,825, a helical track originates in the bottom of the bowl and extends upwardly along an inner periphery of the bowl wall to an exit station at the top of the bowl. Parts can be progressively fed from the lower portion of the bowl along the helical track to the exit station as a given feed rate by vibratory energy. 
     Many manufacturers in the industry operate the vibratory bowl units at their resonant frequency to minimize electrical power consumption and to achieve maximum vibratory stroke. The pitfall of this approach is that the bowls and drives are then sensitized to mass changes, caused by more or fewer parts contained in the bowl, which creates increases and decreases in the vibratory stroke corresponding to the mass changes. A known solution to this pitfall has been to design sophisticated, and somewhat expensive, controls which monitor the resonant frequency and amplitude of stroke, and using these parameters, to change the control output dynamically to maintain the desired amplitude of vibration. This also has been a relatively expensive solution. 
     SUMMARY OF THE INVENTION 
     The present invention provides an electromagnet and armature mounting configuration that allows for optimization of the electromagnetic flux field density created by the electromagnetic coil. The configuration of the mounting allows for enhanced power conversion from electromagnetic power to physical bowl movement in the vibratory direction desired. Because of this approach, heavier vibratory bowls can be excited with less required electrical energy than units currently available. 
     According to one aspect of the invention, the electromagnet and armature are intentionally misaligned across the magnetic gap. By mis-aligning the armature to the electromagnet across the magnetic gap, the direct lines of magnetic force can be adjusted to fine tune the driving force of the vibratory drive and the natural frequency of the drive to adjust vibratory amplitude. The common industry practice is to align the magnet core and armature faces, in a direct alignment, to capitalize on the straight line of force attraction between the magnet core and the armature. 
     According to another aspect of the invention, the magnet core and a magnetic armature are rotationally misaligned such that the magnetic force will exert both an attractive force between the magnet core and the armature and a relative torque between the magnet core and the armature tending to align the poles of the armature and the magnetic core. This torque is arranged to be additive to the rotary force caused by the deflection of the inclined springs caused by the attractive force between the magnet core and the armature. 
     The invention allows for the adjustability of magnet core and armature alignment to modify bowl vibration amplitude. The unit may be aligned directly or can be misaligned dependent on the application desired. By intentionally mis-aligning the magnet core and the armature, advantages can be achieved such as the use of a single magnet on larger drive units, the “drive unit” being the parts feeder less the bowl; the use of only three spring stacks on larger units where such units typically have four or more spring stacks; significantly decreased power consumption while maintaining vibrational power. In some cases, a reduction by a factor of five for similar performance can be achieved. The invention allows for simple control technology to maintain higher strokes, such as by using variable voltage with no amplitude feedback. 
     The invention allows a single drive unit to handle a wide range of bowl weights such that one drive unit can be adjusted to carry a range of bowl sizes. Significantly lower inventory and manufacturing costs can be achieved. 
     The achievement of maximum stroke and minimization of electrical power consumption are achieved by operating the unit, not at resonance, but at a point above or below resonance to allow for mass changes in the bowl load which will then not affect the amplitude of the vibratory stroke. 
     According to another aspect of the invention, amplitude adjustment can be controlled by adding counterweight to the drive unit versus changing the springs to tune the resonant frequency of the unit. The manufacturing time to tune a parts feeder is greatly reduced. The invention utilizes a round baseplate design which allows the unit to be simply enclosed for aesthetic or for potential air purging applications. The counterweights have a ring segment shape to compactly fit on the round baseplate. The desired mass  1  (base assembly and electromagnet) to mass  2  (bowl, frame and armature) ratio can be maintained by increasing the mass  1  using incremental weight counterweights bolted to a common baseplate design. Manufacturing economies of scale can thus be achieved. The invention allows for the manufacture of one size of base assembly to replace a product mix of five sizes. 
     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 an exploded, fragmentary perspective view of a parts feeder according to the present invention; 
     FIG. 1A is a fragmentary, enlarged perspective view of a portion of the parts feeder of FIG. 1; 
     FIG. 2 is an diagrammatical, elevational view of the parts feeder of FIG. 1, shown with the bowl removed; 
     FIG. 2A is a fragmentary, sectional view taken generally along line  2 A— 2 A of FIG. 2; 
     FIG. 3 is a diagrammatical, plan view of the parts feeder of FIG. 2; 
     FIG. 4A is a schematic sectional view of the electromagnet and armature showing the lines of magnetic force therebetween; 
     FIG. 4B illustrates a top view of the magnet and armature shown in FIG. 4A; 
     FIG. 5 is a diagrammatical, sectional view of an alternate embodiment electromagnet and armature arrangement; 
     FIG. 6 is a diagrammatical plan view of the arrangement of FIG. 5; and 
     FIG. 7 is a schematic sectional view of an alternate arrangement electromagnet and armature. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, 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 parts feeder  5  including a bowl  8  supported on a drive unit  11 . The drive unit  11  is supported on isolators  12  (shown in FIG.  2 ). The drive unit  11  includes a frame  13  supported by three spring units  14  from a base assembly  15 , and driven by a vibratory exciter  16 . The frame  13  includes a bowl support  17  to which the bowl  8  is attached by fasteners (not shown). The base assembly  15  is preferably more massive by greater weight and rotational inertia than that of the frame so that the principal vibratory motion will be realized by the frame  13 . The weight and rotational inertia characteristics of the feeder bowl  8  are additive to the weight and rotational inertia characteristics of the frame  13 . The vibration of this two mass system, and the spring units  14  that couple the frame  13  and the base assembly  15 , is powered by the vibratory exciter  16 . 
     Everything attached to or carried by the frame  13  constitutes a certain mass, which coupled to the base assembly  15 , results in a combined inertial mass which provides a natural frequency depending upon the tuning of the spring units  14 . 
     The spring units  14  each include one or more leaf springs  14   a , stacked and interleaved by spacers  18  at ends thereof, and held by bolts  20  and block washers  24  to upper and lower spring blocks  21  and  22 . Each spring block  21 ,  22  has an inclined face or “spring seat”  23  on which the spring units are held by the bolt  20  and washer  24 . The blocks  21 ,  22  are welded to a spring mounting plate  30  of the frame  13  and a baseplate  32  of the base assembly  15 , respectively. The bowl support  17  is fastened to the upper spring blocks  21  by stud and nut assemblies  17   a.    
     The baseplate  32  preferably has a round perimeter which allows for an effective cylindrical enclosure thereof, aesthetically pleasing and more compatible for air purging. A cylindrical shape has a greater pressure retaining capacity without distorting, given a selected wall thickness, than a cubical shape. 
     An isolator adjustment disk  36  and arcuate counterweights  38   a,    38   b  are mounted around a perimeter of, and on, the baseplate  32 , between each adjacent pair of spring blocks  22 . The disks  36  are welded to the baseplate  32 . Each pair of counterweights  38   a,    38   b  is fastened to the baseplate  32  by a single bolt  39 , penetrating a centralized hole of the counterweights and threaded into a threaded hole (not shown) of the baseplate  32 . 
     The counterweights are selectively added to tune the natural frequency of the parts feeder. The counterweights are segments of a flat ring that has the outside diameter equal to the baseplate  32 . The shape of the counterweights enhances a compact, overall design of the baseplate and minimizes floor space for the parts feeder. The counterweights serve to provide a cost effective, and time conserving, manufacturing method of tuning a parts feeder compared to the known method of adding, subtracting or changing leaf springs of the spring units. 
     As illustrated in FIG. 1A, a threaded stud  42 , having an Allen wrench or hex drive head  43 , penetrates the disk  36 , and is connected below the baseplate  32  to a foot  12   a  of the isolator  12  that is supported on the floor, as shown in FIG.  2 . The stud  42  is threaded into a hole  44  through the disk  36 . By advancing or retracting the threaded stud  42 , by turning the head  43  with a tool, the elevation of the baseplate at each isolator can be adjusted. The invention thus allows convenient leveling adjustment from a top side of the baseplate. 
     Referring to FIGS. 2 and 4A, the vibratory exciter  16  includes an armature  49  and an electromagnet  50 . The electromagnet  50  comprises a field core  51  having a prone E-shape, the central leg of which carries a coil winding  52 . Three pole faces  53  of the E-shape provide a uniform air gap  54  between the pole faces  53  and an underside of the armature  49 , the latter being secured to the underside of the spring mounting plate  30 . The core  51  of the electromagnet is secured through a mounting block  56  and counterweights  57 , as applicable, to the top of the baseplate  32 . 
     For reasons explained below, one or both of the core  51  and the armature  49  can be fastened in a manner to be rotationally relatively adjustable about a vertical axis to set a degree of mis-alignment between the electromagnet pole faces  53  and the armature. The adjustability can be provided by set screws penetrating arcuate slots or oversized holes in the mounting block  56  and/or the armature  49 , wherein the set screws can be loosened and the respective armature  49  or core  51  can be rotationally adjusted and the set screws re-tightened. 
     As illustrated in FIGS. 2 and 2A, preferably, the armature  49  is fixedly carried on an armature mounting plate  49   a.  The mounting plate  49   a  is attached to the overlying spring mounting plate  30  by a plurality of set screws  49   b  penetrating oversized holes in the spring mounting plate  30  and either threaded into the armature mounting plate  49   a  or into nuts located below the armature mounting plate  49   a.  The armature mounting plate  49   a  is rotationally guided on the support plate  30  at its center by a bolt or pin  51 . To adjust the rotary position of the armature, the set screws  49   b  are loosened and a rotational fine adjustment screw  4   c  is selectively turned. The rotational fine adjustment screw  49   c  is located at a radial distance from the center of the mounting plate  49   a  and is threaded into a hole through the spring mounting plate  30 . The adjustment screw  49   c  has a tapered end which abuts a side of an oversized tapered hole or other abutment of the armature mounting plate  49   a  such that advancement of the adjustment screw  49   c  into the spring mounting plate  30  progressively rotates the armature mounting plate  49   a  about the pin  51  with respect to the spring mounting plate  30 . After rotational adjustment, the set screws  49   b  can be re-tightened. Alternately, or additionally, a similar rotary adjustment arrangement can be applied between the electromagnet mounting block  56  and the base plate  32 , or the intervening counterweight  57  as applicable, wherein the electromagnet  50  is secured to the mounting block  56  and the mounting block is rotationally adjustable with respect to the base plate  32 . 
     According to the common practice in the industry, the electromagnet  50  can be aligned vertically with the armature  49 . The electromagnet is aligned pole face to pole face with all corners corresponding. This alignment allows for rotation motion of the bowl to be created as the electromagnetic coil is energized and de-energized. This direct alignment approach only captures the attraction power in the perpendicular direction of the electromagnetic pole face. 
     According to the invention, and as illustrated in FIG. 4B, the armature and electromagnet are intentionally, selectively misaligned to adjust the number of lines of direct magnetic force to adjust the vibratory drive force and the resultant parts feeder amplitude of vibration. 
     FIG. 5 illustrates an alternate embodiment vibratory exciter  16 ′ that includes the electromagnet  50  as previously described, and additionally includes an electromagnetic armature  60  that includes a prone, inverted E-shaped armature core  61  having poles  62  with pole faces  63  and a winding or coil  64  wound around the center one of the poles  62 . The winding  64  is electrically charged at the vibrational frequency of the electromagnet  50  with an opposite voltage polarity, relative to the electromagnet  50 , to attract the armature pole faces  63  periodically to the electromagnet pole faces  53 . This arrangement increases the attractive force across the gap  66  and also increases the available torque T (FIG. 6) caused by the intentional misalignment between the armature  60  and electromagnet  50 . As described above, the intentional misalignment can be selectively adjusted to tune the parts feeder, depending on the relative masses of the base assembly  15  and the frame  13  and feeder bowl  8 , and the overall spring constants of the spring units  14 . 
     The alignment illustrated in FIG. 6 not only capitalizes on the perpendicular lines of force but also on the non-perpendicular lines at the magnets end poles causing a torque T which urges the armature to align itself rotationally with the electromagnet. This approach energizes rotation not only due to spring deflections due to the direct alignment force, but also due to additional torque caused by the magnet and armature aligning themselves in the direction of vibratory rotation. This approach allows for better efficiency of transformation of the electrical energy driving the electromagnet to physical movement energy in the use of vibration to move products or parts in the feeder bowl. 
     Alternatively, rather than an armature having an electromagnetic winding, a permanent magnet armature can be used, having magnetic poles that correspond to the electromagnet pole faces, to periodically attract the armature to the electromagnet at the frequency of the charging of the electromagnet. As described above, the intentional misalignment of the electromagnet pole faces and the permanent magnet poles can be selectively adjusted to tune the parts feeder, depending on the relative masses of the base assembly  15  and the frame  13  and feeder bowl  8 , and the overall spring constants of the spring units  14 . 
     FIG. 7 illustrates an alternate configuration electromagnet  150  and armature  149  configuration of the type shown in FIG. 5, utilizing U-shaped electromagnet and armature cores. The U-shaped cores can also be used with any of the previously described embodiments to replace respective E shaped cores. 
     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.