Slat driven positive displacement sorter

An article sorter is made up of a web defined by a plurality of interconnected, laterally elongated, slats. An upper portion of the web defines a longitudinally extending conveying surface. Each of the slats has a generally planar upper surface forming a portion of the conveying surface. A plurality of pusher shoes travel laterally of the conveying surface to laterally displace articles on the conveying surface. A drive assembly is provided. The drive includes at least one sprocket and a motor. The motor is adapted to rotate the sprocket(s). The sprocket(s) engage the slats to propel the web.

BACKGROUND OF THE INVENTION

The present invention is directed to article sorters and, in particular, to positive displacement sorters in which pusher shoes traveling with the conveying surface selectively laterally displace articles on the conveying surface such as to a selected spur.

In one type of positive displacement sorter, such as disclosed in commonly assigned U.S. Pat. No. 5,127,510, the web defining the conveying surface is made up of a plurality of slats that are connected at opposite ends to endless chains. The pusher shoes travel laterally along one or more slats. Wheels mounted to the chain support the web. The chains are driven by motor driven chain sprockets which propel the web.

In another type of positive displacement sorter, such as disclosed in commonly assigned U.S. Pat. No. 6,814,216, the web defining the conveying surface is made up of a plurality of slats that are each supported by one or more wheels supporting each slat and members interconnecting adjacent slats. The pusher shoes travel laterally along one or more slats. The web is driven by a linear motor system made up of motor primaries distributed beneath the web and secondary plates attached to the slats.

SUMMARY OF THE INVENTION

An article sorter, according to an aspect of the invention, is made up of a web defined by a plurality of interconnected, laterally elongated, slats. An upper portion of the web defines a longitudinally extending conveying surface. Each of the slats has a generally planar upper surface forming a portion of the conveying surface. A plurality of pusher shoes travel laterally of the conveying surface to laterally displace articles on the conveying surface. A drive assembly is provided that includes a sprocket and a motor. The motor rotates the sprocket. The sprocket engages the slats to propel the web.

The sprocket may engage the slats between first and second lateral portions of the web. The first lateral portion of the web is where the pusher shoes are in a non-diverted state and the second opposite lateral portion of the web is where the shoes are in a diverted state after the pusher shoes have traveled across the web to divert an article.

Complementary surface portions may be defined between the sprocket and the slats to propel the web. The complementary surface portions may include an extension of the sprocket engaging a recess in the slats, or vice versa. The extension may be formed as a gear tooth. The extension may be made from an impact-absorbing material, such as a polymeric material.

The article sorter may include a track assembly having an upper track portion and an end track portion. The upper track portion is adapted to support the upper portion of the web. The end track portion is adapted to support a portion of the web at the sprocket. The article sorter may further include a wheel assembly supporting each lateral side of the web. The wheel assembly engages the track. The wheel assembly may include a plurality of wheels, with the sprocket engaging one of said slats between said plurality of wheels. The track assembly may be made up of a generally continuous track assembly.

The motor may be in the form of a motorized roller with the sprocket mounted to an outer surface of said motorized roller. Alternatively, the sprocket may be mounted to a shaft with the motor rotating the shaft.

These and other objects, advantages and features of this invention will become apparent upon review of the following specification in conjunction with the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings and the illustrative embodiments depicted therein, an article sorter20is made up of an endless web22that is moveably supported by a frame assembly23(FIG. 1). Web22is made up of a plurality of laterally elongated slats24. An upper portion of web22defines a conveying surface26moving in a longitudinal direction. Each slat24has an upper surface28and a lower surface30. Upper surface28is generally flat, or planar, such that article sorter20is known as a flat-top sorter. It should be understood that considerable variation in the shape of upper surface28from a true plane can be accommodated without negating it being generally flat or planer. Article sorter20additionally includes a plurality of pusher shoes32which travel with the web in the longitudinal direction and can be diverted laterally in order to displace an article traveling on conveying surface26. Pusher shoes32travel along one or more slats and can be of any configuration known in the art. Examples of pusher shoes32are disclosed in commonly assigned U.S. Pat. Nos. 5,127,510; 6,814,216; and 6,860,383; and U.S. Patent Application Publication No. 2005/0023108, the disclosures of which are hereby collectively incorporated herein by reference. Also, a lateral stabilizer33is defined between each pusher shoe32and slat24as described in the preceding patents.

A divert switch assembly80selectively diverts one or more pusher shoes32to a diverting rail82to divert the pusher shoe(s) from a non-diverted state, represented by lateral portion50of the conveying surface, to a diverted state, represented by lateral portion52of the conveying surface. This lateral movement of the pusher shoe(s) displaces an article, such as to a take-away spur (not shown), for sortation. Diverted pusher shoes are returned to a non-diverted state by a return rail84. In the illustrated embodiments, article sorter20is shown with a single divert switch assembly and diverting rail to provide the ability to divert an article to a single spur. However, multiple such divert switch and diverting rail combinations can be provided for article sorter20to allow sortation to multiple spurs.

Web22is supported on frame assembly23by a wheel assembly34. Wheel assembly34includes a series of wheels36and links38(FIG. 10). In the illustrated embodiment, two wheels are mounted to each end of each slat24and adjacent wheels of adjacent slats are joined by links38. Links38pivot about the axles37of the joined wheels to accommodate rotation between slats as they move around the ends of the web, as illustrated inFIGS. 5 and 5a. Wheels36are rotatably mounted to their respective slats by the fixed positioning of their respective axle37in an opening39in their slat. The axle may be fixed to the slat by press-fit, by fasteners, or the like. Other arrangements for interconnecting and supporting slats24, such as chains, are known in the art and may be used without deviating from the spirit of the present invention.

Web22is driven by a drive assembly40. Drive assembly40includes at least one sprocket42, although two are used in the illustrated embodiment, and an electric motor44for rotating the sprocket(s). Motor44may be in the form of a motorized roller in which the motor windings are internal to the roller and drive an outer shell46to which the sprocket(s) are attached. Such motorized rollers are well known in the art and come in various configurations, including alternating current, direct current, gear driven, direct driven, and the like. In the illustrated embodiment, motor44is a direct driven motorized roller having a 110 millimeter diameter outer shell46and a motor that is operated at 48 volts direct current. Alternatively, sprocket(s)42may be shaft mounted and driven by an external motor rotating the shaft. The use of an external motor may be especially effective for longer conveying surfaces, such as ones which provide sortation to multiple spurs because it is capable of a wide range of output power.

Each sprocket is positioned laterally between lateral portion50of conveying surface26, where non-diverted pusher shoes are located, and lateral portion52of the conveying surface, where diverted pusher shoes are located (FIG. 1). This placement of sprocket(s)42avoids interference with the pusher shoes while allowing the pusher shoes to be closer to the lateral edge of the conveying surface than if the sprocket(s) were to be located at extreme ends of shell46. This reduces the overall width of the conveying surface without restricting the article conveying area and ensures a more reliable divert by providing guidance of the article until it is essentially fully off of the conveying surface.

Each sprocket42has portions54that engage a slat in order to propel the web. Portions54are made from an impact-absorbing material. This has the effect of significantly reducing noise generated by the driving of the web. In the illustrated embodiment, the material of portions54is a polymeric material, specifically polyurethane. Other impact absorbing material may be used. Web-engaging portions54are provided in the illustrated embodiment by a series of bands, such as O-rings58, that are stretched across the face55of a core57. O-rings58are stretched around pins60that protrude laterally from opposite sides of core57. This divides each O-ring into a first lobe62and a second lobe64stretched across the face55of core57. When viewed from the side, as illustrated inFIG. 6, first lobe62is a greater distance from the center of rotation of core57than is second lobe64. First lobe62is positioned in this manner by a first land66and second lobe64is positioned in this manner by a second land68, with first land66being elevated with respect to the second land. First lobe62is also supported by a first adjacent surface70, extending perpendicular to first land66. Second lobe64is also supported by a second adjacent surface71extending perpendicular to second land68. As will be explained in more detail below, first lobe62both supports and propels a slat24while second lobe64supports the slat.

Each slat24includes a first protrusion72and a second protrusion74defined in lower surface30. First and second lobes62,64support and propel the slat by acting upon protrusions72and74. In the illustrated embodiment, protrusions72,74also define openings39for mounting of wheels36. As can best be seen by reference toFIGS. 5 and 5a, each protrusion72,74is cradled between a slat-engaging portion54of first lobe62of one O-ring58and a slat-engaging portion54of second lobe64of an adjacent O-ring. The slat-engaging portion54of first lobe62engages higher on the protrusion to ensure that rotational force of the sprocket is transferred to the slat and, hence, to the web.

The use of urethane O-rings has several advantages. The core of sprocket42can be made of a more durable material, such as steel, aluminum, or the like, while still providing an impact absorbent interface to the slats. Also, the O-rings can be readily assembled and readily replaced for maintenance purposes. Also, this configuration is more economical than making the entire sprocket from urethane. O-rings are less expensive than an entire urethane sprocket.

An end of web22opposite drive assembly40includes an idler pulley assembly76. Idler pulley assembly76includes a pair of pulleys75rotatably mounted by a shaft77. A take-up assembly78is provided to idler pulley assembly76to remove any slack from the web and accommodate expansion and contraction of the web, such as due to temperature. In the illustrated embodiment, take-up assembly78includes a spring-biasing member, as best illustrated inFIG. 2. Transition members92provide transition from a feed conveyor (not shown) feeding articles to conveying surface26and between conveying surface26and a take-away conveyor (not shown) taking away articles exiting the end of conveying surface26.

Diverting switch assembly80includes an upstream facing divert arm86and a rotary solenoid88for selectively rotating arm86between a divert position and a non-divert position (FIG. 11). In the divert position illustrated inFIG. 11, the divert arm intercepts the pin of a diverting pin and bearing assembly90extending beneath the associated pusher shoe and directs the pin and bearing assembly to diverting rail82. When not in a divert position, the divert arm is retracted and allows the pin and bearing assembly90to continue along in a longitudinal direction. An advantage of such a divert switch assembly is that rotary solenoid88can be controlled to move arm86to a divert position before the diverting pin and bearing assembly of the prior pusher shoe has fully cleared the divert switch assembly. This increases the speed of the divert cycle. A faster divert speed cycle allows the length of slats24in the direction of movement of web22to be shorter without sacrificing speed of the conveying surface. It should be understood that other types of divert switch assemblies can be used such as vertical diverters of the type disclosed in commonly assigned U.S. Pat. No. 5,038,912 or magnetically actuated diverters of the type disclosed in commonly assigned U.S. Pat. No. 6,615,972, the disclosures of which are both incorporated herein by reference.

An alternative embodiment of an article sorter, designated120is made up of an endless web122that is moveably supported by a frame assembly123(FIGS. 12 through 15.). Web122is made up of a plurality of laterally elongated slats124. An upper portion of web122defines a conveying surface126moving in a longitudinal direction. Each slat124may have an upper surface128and a lower surface130. Upper surface128is generally flat, or planar, such that article sorter120is known as a flat-top sorter. It should be understood that considerable variation in the shape of upper surface128from a true plane can be accommodated without negating it being generally flat or planer. Article sorter120additionally includes a plurality of pusher shoes132which travel with the web in the longitudinal direction and can be diverted laterally in order to displace an article traveling on conveying surface126. Pusher shoes132travel along one or more slats and can be of any configuration known in the art. Examples of pusher shoes132are disclosed in commonly assigned U.S. Pat. Nos. 5,127,510; 6,814,216; and 6,860,383; and U.S. Patent Application Publication No. 2005/0023108, the disclosures of which are hereby collectively incorporated herein by reference. Also, a lateral stabilizer133is defined between each pusher shoe132and slat124as described in the preceding patents.

Frame assembly123includes a track assembly125that supports web122for movement throughout its endless path. Track assembly125includes an upper track portion125athat supports the upper portion of web122that defines the conveying surface. Track assembly125further includes an end track portion125bthat supports web122as it transitions from the conveying surface to a lower return portion of the web. Although track assembly125is illustrated for supporting the web at one lateral end of the slats, it should be understood that another track assembly is provided on the opposite lateral side of the frame assembly to support the web at the opposite lateral end of the slats.

Web122is propelled by a drive assembly140which engages the web at end track portion125b. Drive assembly140includes at least one sprocket142, although two are used in the illustrated embodiment, and an electric motor144for rotating the sprocket(s). In the illustrative embodiment, motor144drives a shaft145which rotatably supports sprocket(s)142. Connection between the motor and shaft may be by cog belt and sheaves, direct coupling, or the like. In the illustrative embodiment, the motor is electrically actuated by a variable frequency drive which allows conveying surface126to be driven within a range of speeds. However, fixed speed or other forms of variable speed drives may be used. Alternatively, the motor may be in the form of a motorized roller in which the motor windings are internal to the roller and drive an outer shell to which the sprocket(s) are attached. As previously set forth, such motorized rollers are well known in the art and come in various configurations including alternating current, direct current, gear driven, direct driven, and the like.

Each sprocket142may be positioned laterally between a lateral portion150of conveying surface126, where non-diverted pusher shoes are located, and a lateral portion of the conveying surface (not shown), opposite to portion150, where diverted pusher shoes are located. This placement of sprocket(s)142avoids interference with the pusher shoes while allowing the pusher shoes to be closer to the lateral edge of the conveying surface at the end of the divert than if the sprocket(s) were to be located at extreme ends of shaft145. This reduces the overall width of the conveying surface without restricting the article conveying area and ensures a more reliable divert by providing guidance of the article until it is essentially fully off of the conveying surface.

Web122may be supported on track assembly125by a wheel assembly134. Wheel assembly134includes a series of wheels136and links138(FIG. 10). In the illustrated embodiment, two wheels are mounted to each end of each slat124and adjacent slats are joined by links138. Links138may pivot about bushings135which may also rotatably support a wheel136, all of which may be retained by a fastener137to accommodate rotation between slats as they move around the ends of the web, as illustrated inFIGS. 5 and 5a. Fastener137engages an opening139in the slat, such as by threads, press fit, or the like. Alternatively the link and wheel may be rotatably mounted on a common axle, by separate axles, or the like. The axle may be fixed to the slat by press-fit, by fasteners, or the like. Other arrangements for interconnecting and supporting slats24, such as chains, links, or the like, are known in the art and may also be used.

Sprocket(s)142and slats124have engaging surface portions defined between the sprocket(s) and the slats that propel the web. These complementary surface portions may include an extension194of the sprocket which engages a depression, or slot,195of the slat, although the extension could be on the slat and the slot on the sprocket. Extension194and slot195may have generally the same, but complementary, surface configurations. In the illustrative embodiment, extension194is configured as a gear tooth having sloped leading surface196aand sloped trailing surface196b. Leading surface196ahas a slope, such as approximately 15 degrees, that is steeper than trailing surface196bto impart a propelling force to the slat, but is sloped to allow smooth engagement with the slat according to gear design parameters.

As is conventional, slats124may be made of metal, such as extruded aluminum. In the illustrated embodiment, extensions194are made from an impact-absorbing material, such as a polymeric material. Examples of such material include polyurethane, nylon, Delran, and others, which are known to the skilled artisan. However, extensions may be made of other materials, including metals, and the like. The entire sprocket142including extensions194may be formed as a unitary piece from one material. Alternatively, extensions194may be mounted as inserts in a hub of sprocket142that may thus be made from a different material. This would allow the hub to be made from a material, such as metal, that may be stronger and less costly than the material of the extensions. Also, this may allow worn or broken extensions to be replaced without the necessity to replace the entire sprocket.

As is conventional, each pusher shoe132may include a pin198for diverting of the pusher shoe to a diverting rail by a diverter switch and a bearing199for engagement of the diagonal diverting rail (not shown inFIG. 15) to laterally propel the pusher shoe to divert an article. Pusher shoe132may include a fastener200that is an extension of guide pin198and which rotatably supports bearing199. In the illustrative embodiment, the upper end of fastener200is allowed to extend into slot195. This may reduce the vertical footprint of the pusher shoe and slat.

Referring now toFIG. 13, it can be seen how the slats may be guided around the driven end of the web by the combination of sprocket(s)142and track assembly125. As a slat124, supported by its wheels136on track assembly125, approaches the transition from the planar upper track portion125ato the curved end track portion125b, the slat is in the position illustrated as “A” inFIG. 13. In this position, one extension194of sprocket142is entering slot195. It can be seen that the extension has not yet fully entered the slot and that there is a space between the end of the extension and the bottom of the slot. This is a result of the geometry of the slat and the sprocket including the positioning of the slot between the wheels. In particular, because the wheels136of a slat is position “A” are on a relatively planar surface extension194only extends partially into slot195. However, as the slat moves toward position “B” inFIG. 13, the wheels136are fully on the curved surface of end track portion125b. This results in relative movement of extension194and slot195to fully seat the extension in the slot. This is because the slot is between the wheels. When the wheels sit on a curved surface, the distance between the slot and the sprocket is less than when the wheels sit on a flat surface, as would be understood by the skilled artisan.

Thus, when an extension enters a slot of a slat in position “A,” there is only partial engagement between the extension and the slot. As the slat then moves onto the curved track portion, full engagement is achieved between the sprocket and the slat but at a relatively gradual rate. This may facilitate a reduction in vibration and noise. Moreover, motion of the slats as they travel past the drive assembly is guided by end track portion125b, not the outer surface of sprocket142. This results in a smoother motion of the web at the drive assembly which may also facilitate a reduction in vibration and noise.

Track assembly125may include one or more bottom track sections125cto guide the return portion of the web. It may also include another curved end track portion (not shown) that is opposite to the driven end of the web. In this manner, the track assembly may be a generally continuous track to guide motion of the web throughout its endless travel. While bottom section125cis shown guiding the web from above as the web comes out of engagement with the sprocket, it may include a portion that supports the web from below against the force of gravity. The bottom track section may also include one or more sections to modify the motion of the lower run of the web including a take-up assembly, if desired.