Abstract:
A fastener feeder for feeding fasteners that have a head and a shaft including: a substantially stationary bin, an inline feeder, with a feed track located higher than an upper level of fasteners in the bin and sloped downwardly and operably connected to a vibrator such that the vibrator vibrates the feed track to cause the fasteners to drop into the feed track so that the head is supported by the feed track and the shaft dangles below the head and to cause fasteners to travel down a slope in a queue; a lift gate to elevate a small number of fasteners from the plurality of fasteners in the bin to the feed track; and an escapement at a lower end of the in line feeder capable of isolating a single fastener from the lower end of the queue.

Description:
CLAIM TO PRIORITY  
       [0001]     This application claims priority to U.S. Provisional Application 60/654,314 filed Feb. 18, 2005 entitled “Screw Feeder.” 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to devices for collating and feeding of screws, nails and other like fasteners. More particularly, the invention relates to devices for collating and feeding screws to automated screwdrivers.  
       BACKGROUND OF THE INVENTION  
       [0003]     Automated screwdrivers are commonly used in manufacturing facilities. An automated screwdrivers typically includes a pair of jaws for receiving and holding a screw while a screwdriver bit is advanced to engage the screw head and simultaneously rotate the screw while advancing it into a pre-drilled hole. Automated screwdrivers are commonly used to secure hardware to manufactured goods.  
         [0004]     Automated screwdrivers are commonly fed with screws via tubing made of polyethylene or another durable, flexible material. Prior to sending screws to an automated screwdriver down a tube, the screws must be collated and aligned so that all the heads and/or tips are facing the same direction.  
         [0005]     Automated screw feeders have existed in the industry for some time. One type of automated screw feeder is described in U.S. Pat. No. 5,480,087 to Young et al. This style of automated screw feeder includes a generally cylindrical vibratory hopper that has a spiral ramp along its outer perimeter. The hopper is vibrated in such a way that screws align themselves along the spiral ramp, which is wide enough to support only one screw at a time. As the hopper vibrates, the screws slowly climb the spiral ramp until they fall into a feeding line, which comprises a deep slot of sufficient width to receive the shaft and threaded portion of the screw therein, but narrow enough so that the head of the screw is supported at the top. Screws that do not fall into the feeder slot tumble back into the vibratory bin and are cycled through the process again. This type of screw feeder tends to be somewhat fussy to operate, as it requires a great deal of tuning and adjustment to prepare the vibratory hopper to handle screws correctly. Furthermore, this type of screw feeder must be designed to accommodate a specific size and design of screw in order to operate properly.  
         [0006]     Another type of screw feeder is a so-called “blade” type feeder. Such a feeder is described in U.S. Pat. No. 4,222,495 to Kaneko. In a blade feeder, a blade is cycled repeatedly up and down in a hopper. The hopper is filled with screws, and as the blade cycles up, some screws will fall into a slot on the blade such that their shaft and threaded portion is in the slot and the head is supported at the top. As the blade reaches its apogee, the slot assumes a tilted orientation so that the picked-up screws can slide, by gravity, downhill into a slot that continues into an in line feeder and be fed to an escapement mechanism for further processing.  
         [0007]     More and more commonly, screw heads are pre-finished to match a manufactured product. Unfortunately, the reciprocation of the blade within the hopper of a blade type feeder has a tendency to abrade and chip the screw heads as they picked up by the blade. The vibration of vibratory hopper screw feeders also tends to damage the finished portions of prefinished screws. The chips or abrasions on the finished heads create an unacceptable cosmetic appearance.  
         [0008]     Sometimes, as screws are sent through a tubular line to an automated screwdriver, the screw will stop short of being delivered to the automated screwdriver. In this case, it is desirable to purge the line prior to dropping another screw. In other words, it is desirable to be able to send a blast of compressed air down the line to carry the screw already in the line to its destination prior to placing another screw in the line, which otherwise may result in jamming of the automated screwdriver. Many current systems are not capable of performing this act, and therefore must be disassembled and manually unclogged if a screw does not travel all the way to its destination through the tubular feed line.  
         [0009]     Another problem with screw feeders arises from the fact that, commonly when screws are received from the manufacturer, various undesirable materials may accompany the screws in their package. The undesirable material may include shavings created in the screw manufacturing process, screws that are damaged in the manufacturing process, and fragments of various packing material that may end up in with the screws during manufacture or shipping.  
         [0010]     All of the above-described prior art screw feeders will tend to be clogged or otherwise disrupted in their operation by the presence of the various foreign material in the fasteners that are utilized.  
         [0011]     An additional shortcoming of currently available screw feeders is that they are commonly designed only to work with a manufacturer&#39;s specific screw driving equipment. Many facilities that manufacture other products would like to be able to utilize a screw feeder with different items of equipment and to handle different sizes and specifications of screws.  
         [0012]     Another limitation of existing screw feeders is that those that utilize a vibrating hopper tend to abrade the pre-finished portions of pre-finished screws, thus resulting in screws that have an unacceptable cosmetic appearance.  
         [0013]     Another limitation of existing screw feeders is that they often require that the screw feeder be specifically designed for a specific size and configuration of screw; or, that the entire in line feed track be changed to accommodate a different-sized screw.  
         [0014]     Finally, many existing vibratory hopper screw feeders are limited to a relatively small-capacity hopper, and therefore the hopper must be refilled with screws more often than would be desirable in a manufacturing process. Ideally, the hopper would need to be filled only one time for a manufacturing shift.  
         [0015]     Thus, the screw feeder art would benefit from the availability of a screw feeder that accommodates a large capacity of many sizes of screws, with minimal clogging of screws or with shavings or debris. In addition, it would be desirable if the screw feeder would require minimal tuning for reliable operation. Further, it would be desirable to have an automated screw feeder that is easily adjusted to accommodate a wide variety of different sizes and configurations of screws. In addition, it would be desirable to minimize the damage to pre-finished screws that might be fed through the system. Finally, it would be helpful to the screw feeders arts if the screw feeder had the ability to drop a screw; purge the line; or do either independently, or both together.  
       SUMMARY OF THE INVENTION  
       [0016]     The present invention overcomes many of the above-described limitations of prior art screw feeders. The present invention accommodates many different sizes and configurations of screws, and is easily adjusted to do so. In addition, the present invention minimizes clogging with shavings and other debris that may be mixed in with screws, and requires minimal tuning to operate efficiently. The present invention minimizes damage to pre-finished screws and has the ability to drop a screw, purge the line, or both independently or simultaneously.  
         [0017]     The screw feeder generally includes a hopper with a lift gate, an in line feeder and an escapement. The hopper may be a generally box-shaped structure that tapers toward the bottom so that accumulated fasteners are directed by gravity toward the lift gate. The lift gate is aligned near a back wall of the hopper, preferably in one corner of the hopper. The lift gate is arranged to cycle up and down immediately adjacent the back wall of the hopper. The lift gate cycles so that it extends to the lowest part of the hopper and then elevates along the back wall until a portion of the lift gate is slightly higher than the back wall of the hopper.  
         [0018]     The in line feeder is positioned adjacent and directly behind the hopper so that the lift gate can discharge screws onto a platform slide, which leads into the track portion of the in line feeder. The in line feeder is operably connected to a linear vibrator that oscillates the in line feeder generally parallel to its long axis.  
         [0019]     The in line feeder track includes a waterfall portion where the track drops a short distance. The waterfall portion is adjacent to a return chute through which screws that do not achieve proper alignment in the track are returned to the hopper. In addition, the screw feeder may include an air blast to dislodge any misaligned screws resting on the track and return them to the hopper. The in line feeder track continues on to a drop chute that leads to the escapement. The drop chute may angle downward at a substantially steeper angle than does the in line feeder track. This allows screw heads to shingle on the drop chute as it leads to the escapement.  
         [0020]     The escapement may be a linear acting escapement. In this embodiment, the linear acting escapement has a slide that cycles horizontally back and forth, preferably by pneumatic operation. As the escapement cycles back, it receives a single screw into a screw holder portion. As the escapement cycles forward, it separates that single screw from other screws that are aligned in a shingled fashion in the drop chute. As the escapement slide cycles forward, the screw in the screw receiver encounters a ramped stripper, which then strips the screw from the screw-receiving portion. Once the screw is stripped free of the screw-receiving portion, it drops into a shaft via gravity, which allows the screw to enter an alignment funnel. An air blast is then used to force the screw through the alignment funnel and into a tubular line, which leads to the automated screw driving device.  
         [0021]     In another embodiment, a two stage escapement may be employed.  
         [0022]     In one embodiment the invention includes a fastener feeder for feeding fasteners that have a head and a shaft, the fastener feeder comprising: a substantially stationary bin to contain a plurality of fasteners; an inline feeder, comprising a feed track located higher than an upper level of fasteners in the bin and sloped downwardly and operably connected to a vibrator such that the vibrator vibrates the feed track to cause the fasteners to drop into the feed track so that the head is supported by the feed track and the shaft dangles below the head and to cause fasteners to travel down a slope in a queue; a lift gate to elevate a small number of fasteners from the plurality of fasteners in the bin to the feed track; and an escapement at a lower end of the in line feeder capable of isolating a single fastener from the lower end of the queue. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]      FIG. 1  is a perspective view of a screw feeder in accordance with the present invention;  
         [0024]      FIG. 2  is a detailed perspective view of a screw feeder in accordance with the present invention;  
         [0025]      FIG. 3  is a side elevational view of the screw feeder;  
         [0026]      FIG. 4  is a perspective view of an in line feeder in accordance with the present invention;  
         [0027]      FIG. 5  is an side elevational view of the in line feeder;  
         [0028]      FIG. 6  is a sectional view of a drop chute in accordance with the present invention;  
         [0029]      FIG. 7  is a perspective view of an escapement in accordance with the present invention;  
         [0030]      FIG. 8  is a side elevational view of the escapement with internal parts shown in phantom;  
         [0031]      FIG. 9  is a sectional view taken along section line  9 - 9  of  FIG. 8 ;  
         [0032]      FIG. 10  is a sectional view taken along section line  10 - 10  of  FIG. 8 ;  
         [0033]      FIG. 11  is a sectional view taken along section line  11 - 11  of  FIG. 8 ; and  
         [0034]      FIG. 12  is a perspective view of a hopper and lift gate assembly in accordance with the present invention with the lift gate lowered;  
         [0035]      FIG. 13  is a perspective view of another embodiment of a screw feeder in accordance with the present invention;  
         [0036]      FIG. 14  is a another perspective view of the screw feeder of  FIG. 13 ;  
         [0037]      FIG. 15  is a perspective view of another embodiment of a hopper and lift gate assembly in accordance with the present invention with the lift gate lowered;  
         [0038]      FIG. 16  is a perspective view of the hopper and lift gate assembly of  FIG. 15  with the lift gate partially raised;  
         [0039]      FIG. 17  is a plan view of the hopper and lift gate assembly;  
         [0040]      FIG. 18 . is a perspective view of a two stage escapement in accordance with the present invention with some parts removed for clarity;  
         [0041]      FIG. 19  is a plan view of the two stage escapement with the shuttle out and the screw eject open;  
         [0042]      FIG. 20  is plan view of the two stage escapement with the shuttle in and the screw eject open; and  
         [0043]      FIG. 21  is a plan view of the two stage escapement with the shuttle in and the screw eject sealed  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0044]     Referring to  FIGS. 1 and 2 , screw feeder  20  generally includes support frame  22 , hopper  24 , lift gate  26 , in line feeder  28 , and escapement  30 . Support frame  22  supports hopper  24  and lift gate  26  together so that hopper  24  and lift gate  26  may be tiltably adjusted. Support frame  22  also supports in line feeder  28  and escapement  30  such that they may be adjusted in tilt to ensure proper gravity operation.  
         [0045]     Hopper  24  generally includes backplate  32 , frontplate  34 , sides  36 , and sloped bottom  38 . Sloped bottom  38  is sloped to direct the contents of hopper  24  toward lift gate  26 . Backplate  32  may be pierced by return aperture  40 . Return aperture allows for the passage of return chute  41  through backplate  32 . Sloped bottom  38  includes a cut out lift gate opening  42 . Lift gate opening  42  is sized to allow close sliding passage of lift gate  26  therethrough. Hopper  24  is desirably formed of a durable abrasion resistant material such as sheet steel. Hopper  24  can be adjusted to slope from about zero to six degrees from the vertical.  
         [0046]     Backplate  32  extends below sloped bottom  38  of hopper  24 . Backplate  32  supports slide tracks  44 . Slide tracks  44  are structured and positioned to slidably support lift gate  26  so that lift gate  26  may reciprocate in a generally vertical direction. Backplate  32  may also support wear plate  46 . Wear plate  46  may be formed from stainless steel, polyethylene, or another smooth, wear-resistant material.  
         [0047]     Lift gate  26  is generally a plate  48  having tapered shoulders  50  and defining lifting notch  52 . Plate  48  is, for example, 1 to 1½ centimeters in thickness. Tapered shoulders  50  define a sloped top edge  54 . Sloped top edge  54  is at an angle sufficient to deter fasteners from resting on shoulders  50  of plate  48 . Lifting notch  52  has a top surface substantially perpendicular to the face of plate  48 . The width  56  of lifting notch  52  may be adjusted to be slightly larger than the maximum length of a screw that is to be handled by screw feeder  20 . Lift gate  26  should be smoothly finished on all surfaces, to facilitate easy sliding against hopper  24  or fasteners that are found in hopper  24 . Smooth finishing minimizes abrasion damage to prefinished fasteners. Lift gate  26  is operably connected to and reciprocated by lift gate cylinder  57 .  
         [0048]     Referring to  FIGS. 4 and 5 , in line feeder  28  generally includes feeder backbone  58 , screw back fence  60 , screw slide  62 , screw feed track  64 , vibrator  66 , and vibrator mount  68 . Feeder backbone  58  supports screw back fence  60 , screw slide  62 , and screw feed track  64 . Feeder backbone  58  is mounted to vibrator  66 . Screw back fence  60  is mounted behind and generally parallel to screw feed track  64 . Screw slide  62  is mounted adjacent to and in front of screw feed track  64 . Screw back fence  60  extends upwardly above screw feed track  64 . Screw slide  62  provides a substantially flat table that is sloped slightly downward toward screw feed track  64 .  
         [0049]     Vibrator  66  is preferably a linear vibrator such as a magnetically actuated linear vibrator. For example, an RM Series in line vibrator from Service Engineering of Greenfield, Ind., is one suitable linear vibrator.  
         [0050]     Vibrator mount  68  generally includes vibrator base  70  pivotably secured to vibrator base end mounts  72  and vibrator base adjustor  74 . Vibrator adjuster  74  actuates pivotable movement of vibrator base  70  relative to vibrator base end mounts  72 .  
         [0051]     Screw feed track  64  includes front support  76 , rear support  78 , and shims  80 . Front support  76  and rear support  78  are aligned substantially parallel and are held separated by a fixed distance by shims  80 . Shims  80  may be changed, added or removed as necessary to adjust the spacing between front support  76  and rear support  78 . Front support  76  and rear support  78  define waterfall  82 . Waterfall  82  includes an abrupt drop in the height of front support  76  and rear support  78 .  
         [0052]     Referring to  FIG. 6 , screw feed track  64  further includes drop chute  84 . Drop chute  84  includes front chute plate  86 , rear chute plate  88 , drop chute cover  90 , and screw holddown  92 . Front chute plate  86  and rear chute plate  88  are substantially parallel to one another and held separated by shims  94 . Drop chute cover  90  covers the upper portion of drop chute  84  and includes adjustable screw holddown  92 . Drop chute  84  descends at a substantially steeper angle than the portion of screw feed track  64  formed by front support  76  and rear support  78 . Drop chute  84  terminates at escapement  30 .  
         [0053]     Referring to  FIGS. 6-11 , escapement  30  generally includes pneumatic cylinder  96 , body  98 , and slide  100 . Pneumatic cylinder  96  is operably connected to slide  100  and adapted to oscillate slide  100  relative to body  98 .  
         [0054]     Body  98  generally includes base  102 , cover  104 , stripper  106 , manifold  108 , and cylinder mount  110 . Referring to  FIG. 11 , base  102  is bored out to define funnel  112 , shaft  114 , and tubular fitting  116 .  
         [0055]     Referring to  FIGS. 9, 10 , and  11 , cover  104  is machined to define screw trough  118  and drop shaft  120 . Screw trough  118  is dimensioned to support the head of a screw. Drop shaft  120  is dimensioned to allow a screw and head to drop vertically through cover  104  to funnel  112 .  
         [0056]     Stripper  106  is secured between slide  100  and cover  104 . Stripper  106  may be secured by bolts or machine screws. Stripper  106  includes a ramped portion which is located substantially parallel to screw trough  118 .  
         [0057]     Manifold  108  fits on top of cover  104  and slide  100 . Manifold  108  slidably supports slide  100  along with base  102 . Both manifold  108  and base  102  are machined to slidably support slide  100  therebetween. Manifold  108  defines compressed air inlet  122 . Compressed air inlet  122  is threaded or otherwise adapted to receive a fitting (not shown) to supply compressed air to manifold  108 . Compressed air inlet  122  may be supplied with compressed from an air line (not shown) that is controlled by a valve (not shown) that is independent of the valve (not shown) that controls pneumatic cylinder  96 .  
         [0058]     Referring particularly to  FIGS. 9 and 11 , slide  100  is operably connected to pneumatic cylinder  106  and may oscillate supported by base  102  and manifold  108 . Slide  100  is formed to obtain a close sliding fit with cover  104 . Slide  100  defines screw receiving recess  124 . Screw receiving recess is shaped to receive a screw or screws of various sizes and lengths. Screw receiving recess  124  includes head portion  126  and shaft portion  128 . Head portion  126  is dimensioned to receive the head of a screw. Shaft portion  128  is dimensioned to receive the shaft and threaded portion of a screw. Shaft portion  128  is dimensioned to be significantly longer than the longest screw that is intended to be handled by escapement  30 . In operation, A tubular line is attached to screw feeder  20  at tubular fitting  116 . The tubular line then runs to an automated screwdriver or other device to which it is desired to feed the fasteners.  
         [0059]     Referring to  FIGS. 13 and 14 , in another embodiment, screw feeder  20  includes support frame  22 , hopper  24 , lift gate  26 , inline feeder  28 , and escapement  30 . In this embodiment support frame  22  and inline feeder  28  are substantially similar to that described above and will not be further described. Hopper  24 , lift gate  26 , and escapement  30  vary from the above described embodiment and will be described in greater detail below.  
         [0060]     In this embodiment, hopper  24  generally includes back plate  130 , front plate  132 , sides  134 , sloped bottom  136  and removable panel  138 . Slope bottom  136  is sloped to direct the contents of hopper  24  toward lift gate  26 . Removable panel  138  can be removed to facilitate emptying of hopper  24 .  
         [0061]     Return chute  140  is located adjacent to hopper  24  and inline feeder  28  and is sloped to direct its contents back to hopper  24 . Return chute  140  is positioned to capture fasteners that fall from inline feeder  28 .  
         [0062]     Referring particularly to  FIG. 17 , in this embodiment lift gate  26  is located in a corner  142  of hopper  24  and is recessed adjacent to back plate  130 . Lift gate  26  is located in close apposition to back plates  130 . Lift gate  26  is operably connected to lift gate cylinder  144 .  
         [0063]     In this embodiment lift gate  26  includes flat upper surface  146 . Flat upper surface  146  and the remainder of lift gate  26  are smoothly finished to present a nonabrasive surface toward the interior of hopper  24 .  
         [0064]     Referring particularly to  FIG. 17 , lift gate  26  is surrounded by gap  148 . Gap  148  is sized to permit debris that may accumulates in hopper  24  to fall out the bottom thereof while being small enough to contain fasteners within hopper  24 . Lift gate  26  may reciprocate vertically in close proximity to back plate  130 .  
         [0065]     Referring to  FIGS. 13, 14 , and  18 - 21  in this embodiment escapement  30  includes two-stage escapement  150 .  
         [0066]     Two-stage escapement  150  is depicted in  FIGS. 18-21  with certain parts removed for clarity of viewing the internal mechanism. Two-stage escapement  150  is located at the lower end of drop chute  84 .  
         [0067]     Two-stage escapement  150  generally includes shuttle assembly  152 , screw eject assembly  154 , and escapement body  156 .  
         [0068]     Shuttle assembly  152  generally includes shuttle plate  158  and shuttle actuator  160 . Shuttle plate  158  may be substantially flat and defines receiving groove  162 . Receiving groove  162  is sized and shaped to receive the shaft and threaded portion of a fastener. Receiving groove  162  may be located at a substantially right angle to the direction of motion of shuttle actuator  160 .  
         [0069]     Shuttle actuator  160  is depicted here as a pneumatic cylinder  164 . Pneumatic cylinder  164  may be a double acting pneumatic cylinder. Shuttle actuator  160  may also be a hydraulic cylinder, electromechanical actuator, electrical actuator or another linear actuator.  
         [0070]     Screw eject assembly  154  generally includes screw eject plate  166  and screw eject actuator  168 .  
         [0071]     Screw eject plate  166  is a substantially rectangular plate defining first air passage  170 , second air passage  172 , step  174 , and fastener head recess  176 . Screw eject plate  166  has a substantially flat upper surface  178 . Step  174  is located on lower surface  180 . Fastener head recess  176  may be cut into step  174 .  
         [0072]     Escapement body  156  is located adjacent to shuttle plate  158  and to screw eject plate  156 . Shuttle plate  158  abuts escapement body  156  on a side thereof. Screw eject plate  166  abuts the top of escapement body  156 .  
         [0073]     Escapement body  156  defines discharge groove  182 . Discharge groove is in fluid communication with discharge passage (not shown). Discharge passage (not shown) leads to a tubular structure through which fasteners are directed to an automated screwdriver.  
         [0074]     In operation, an operator fills hopper  24  with fasteners of a desired size and configuration. When screw feeder  20  is placed into operation, lift gate  26  oscillates upwardly and downwardly within hopper  24 .  
         [0075]     Referring to  FIGS. 1-12 , as lift gate  26  oscillates downward into hopper  24 , a number of fasteners will be engaged by lifting notch  52 . Desirably, lifting notch  52  lifts between 1 and 6 fasteners per cycle. Lifting notch  52  may be varied in size to adjust and limit the number of screws picked up to minimize jamming caused by an excessive number of screws reaching screw feed track  64 . Lift gate  26  then oscillates upwardly until lifting notch  52  is even with, or slightly above, screw slide  62 . At this point, fasteners drop by gravity from lifting notch  52  to the surface of screw slide  62 . Screw slide  62 , along with screw feed track  64 , is vibrated by vibrator  66 . Thus, assisted by gravity, screws or other fasteners on screw slide  62  slide downwardly toward screw feed track  64 .  
         [0076]     Fasteners on screw feed track  64  are vibrated until the shaft and threaded portion of the screw drop into the space between front support  76  and rear support  78 . The head of screws remains on top of front support  76  and rear support  78 . The vibratory motion of screw feed track  64  causes screws to travel toward waterfall  82 . When screws reach waterfall  82 , those that are within screw feed track  64  drop to the lower level and travel onward toward drop chute  84 . Screws that have failed to become received into screw feed track  64  fall from waterfall onto return chute  41  and are returned to hopper  24 . In addition, foreign objects or debris that may accompany screws in the hopper  24  are returned to hopper  24  with jamming the operation of screw feeder  20 .  
         [0077]     Screw feed track  64  is of a depth great enough to accommodate screws of greatly variable length. This permits the operation of screw feeder  20  with many different size screws without tooling changes. Also, if an incorrect size screw appears in the hopper it will feed through screw feeder  20  without jamming.  
         [0078]     To adjust screw feeder  20  to accommodate fasteners of differing diameters shim  80  may be added or shims  80  may be exchanged for shims  80  of differing thickness. The angle of screw slide  62  may be adjusted via vibrator base adjuster  74  to allow screws to slide down to screw feed track  64  more or less steeply.  
         [0079]     If an excessive number of screws accumulate on screw slide  62  or screw feed track  64 , the excess weight causes vibrator  66  to cause the excess screws to travel backward relative to their normal trajectory until the excess screws drop off of the open end of screw feed track  64 . Thus, screw feed track  64  is partially self-clearing if an excessive number of screws accumulate thereon.  
         [0080]     Having passed waterfall  82 , screws on screw feed track  64  continue until they reach drop chute  84 . Screws that line up on drop chute  84  tend to shingle so that their heads are partially nested, one overlapping another.  
         [0081]     The bottommost screw on drop chute  84  rests against slide  100  of escapement  30 . Drop chute  84  is covered by drop chute cover  90 , which supports screw holddown  92 . Screw holddown  92  may be adjusted to provide minimal clearance between the screw heads that are shingled in drop chute  84  so as to prevent screws becoming misaligned.  
         [0082]     At escapement  30 , slide  100  is oscillated by pneumatic cylinder  96  based on a demand signal from the automated screwdriver or other device that is fed fasteners. Slide  100  oscillates toward drop chute  84  and a screw from drop chute  84  engages into screw receiving recess  124 . A screw is received into screw receiving recess  124  so that the head of the screw is supported by head portion  126 , and the shaft of the screw is aligned in shaft portion  128 . Slide  100  is then oscillated away from drop chute  84 . As slide  100  moves alongside cover  104 , stripper  106  forces the screw toward cover  104  and into screw trough  118 . The screw travels along screw trough  118  to drop shaft  120 .  
         [0083]     When the screw enters drop shaft  120 , compressed air may be directed into manifold  108  via compressed air inlet  122 . This compressed air then forces the screw down drop shaft  120  into funnel  112  through shaft  114  and tubular fitting  116  into a tubular line (not shown), which directs the screw to the automated screw driving machine or other device. It also should be noted that manifold  108  allows a blast of compressed air to drive the fastener through drop shaft  120  from behind thus applying a stronger propulsive force than prior art screw feeders that apply a compressed air flow to fasteners downstream from the location at which they are dropped via a branch wye or tee fitting. Further, slide  100  is in a closed position when the compressed air pulse is applied this preventing leakage of compressed air upstream through the system which wastes the force of the compressed air and does not propel the fastener through the tubular line as effectively.  
         [0084]     In the event that a signal is not received from the automated screwdriver indicating that the screw has been received there, another blast of compressed air may be directed through compressed air inlet  122  to purge the tubular line of the screw which did not make it to the end destination. In case the previous screw has made it to its end destination, the screw feeder  20  may be instructed to initiate another screw feed cycle and to purge simultaneously so as to send the screw down the tubular line to the receiving device. The screw feeder  20  may utilize a programmable logic controller (PLC) to control the feeding of fasteners based on demand signals from an automated screwdriver.  
         [0085]     The use of lift gate  26  allows the use of a large capacity hopper  24  thus minimizing the need to refill hopper  24 . The fact that hopper  24  is nonvibrating prevents abrasion or other damage to prefinished screws. In addition, screw feeder  20  has few moving parts relative to prior art feeders minimizing maintenance, adjustment and wear to screw feeder  20 .  
         [0086]     Referring to  FIGS. 13-21  in operation of the embodiment disclosed there, an operator fills hopper  24  with fasteners. Lift gate  26  is cycled up and down by lift gate cylinder  144 . Screws or other fasteners are picked up by lift gate  26  from hopper  24 . It is notable that because of the location of lift gate  24  in corner  142  of hopper  24  and because of the recessed location of lift gate  26  along back plate  130  the likelihood of screws jamming lift gate  26  is substantially reduced as compared to some prior art screw feeders. In addition, screws or fasteners returning to hopper  24  via return chute  140  are less likely to accumulate in return chute  140 .  
         [0087]     The transfer of screws or other fasteners from lift gate  26  to inline feeder  28  on the way to escapement  30  is substantially the same in this embodiment as in the prior described embodiment above.  
         [0088]     Referring now to  FIGS. 18-21 , screws are received at two-stage escapement  150  via drop chute  84 . At the bottom of drop chute  84  screws rest against shuttle plate  58 . Shuttle plate  158  is translated by shuttle actuator  160  to the position seen in  FIG. 19 . In this position, receiving groove  162  is aligned with drop chute  84 . One screw or other fastener is thus engaged in receiving groove  162 . Shuttle actuator  160  then translates shuttle plate  158  to a position seen in  FIG. 20 . Here the screw is substantially aligned with discharge groove  182  in escapement body  156 . Screw eject assembly  154  is then actuated so that screw eject plate  166  is moved from the position seen in  FIG. 20  to the position seen in  FIG. 21 . Once screw eject plate is in the position seen in  FIG. 21  compressed air is directed through second air passage  172  to direct the screw or other fastener through tubing to an automated screwdriver or other tool. It is notable that when screw eject plate  166  is in this position the screw is removed from receiving groove  162  and into discharge groove  182 .  
         [0089]     It is further notable that when screw eject plate  166  is in the retracted position as seen in  FIG. 20  first air passage  170  is aligned with discharge groove  182  so that a surge of compressed air may be directed through first air passage  170  to purge a screw that may have become lodged in the tubing between screw feeder  20  and an automated screwdriver or other tool.  
         [0090]     Another point of note is that the fit of screw eject plate  166  and shuttle plate  158  against escapement body  166  is such that a small amount of compressed air can escape. The benefit of this escape of compressed air is that items of debris that may get into the mechanism along with screws or other fasteners can be dislodged thus presenting wear and damage to the escapement mechanism.  
         [0091]     The present invention may be embodied in other specific forms without departing from the spirit of the essential attributes thereof; therefore, the illustrated embodiments should be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.