VACUUM TRANSFER CONVEYOR

Abstract: Vacuum transfer apparatus for transferring flat-ended articles such as aluminum cans (16), selecting only those cans which are upright and which are correctly orientated, comprises a movable, foraminous transfer belt (54) which extends between a first station (10) horizontally to a second station (not shown). A vacuum plenum (38) having a bottom wall (50) draws only upright cans (16) upwards onto a pick-up surface on the transfer belt (54), and is capable of holding only correctly orientated cans. Incorrectly orientated cans, which obscure fewer apertures of the foraminous transfer belt (54), are rejected during transfer from the first station (10). The improvement lies in substantially reducing the sizes of the apertures either in the transfer belt (54) or in the bottom wall (50) of the plenum, substantially reducing the volume rate of air transfer into the plenum. The narrower, more rapid, air jets through the apertures then provide a finer control and selec­ tivity, while allowing the use of a lower-powered vacuum drawing fan.

Description: VACUUM TRASFER CONVEYOR This invention relates to apparatus for vacuum transfer of articles having at least one flat surface, such as cans, bottle caps and cartons. It is especially useful for the separation of misaligned containers from properly aligned containers by transferring only the properly aligned containers. More and more operations in the manufacture and packaging of goods require a sensitive means of detecting and removing out-of-specification cans, containers, cartons, packages and the like. The items to be removed may not be within certain weight limits, size, position, or shape to pass a particular test. With the rapidity that the modern machines have to run to satisfy production requirements, the usual visual methods of screening is not satisfactory. In the past, vacuum devices have been used to automatically detect and reject downed (fallen) cans. With devices of this type, a vacuum is applied to the open upper end of upright cans to hold the cans against a moving conveyor, while the downed cans will not be held against the vacuum mechanism and are rejected to a collection station. One such device is disclosed in U.S. Patent No. 4,146,467 wherein a pair of endless belt conveyors are spaced apart longitudinally to convey cans in an upright position. The upright c ans are transferred from one conveyor to the other by a vacuum transfer mechanism which is located above the adjacent ends of the conveyors. The transfer mechanism includes an endless perforated belt that travels across the open bottom of a plenum housing which is divided into a series of chambers. The chambers are subjected to a vacuum w hich acts to attract and hold the upright cans against the perforated belt so that the cans can be transferred by movement of the belt from one conveyor to the other, while downed cans are rejected from the conveyor system. A central chamber is subjected to a lesser vacuum than the remaining chambers, and as the cans move across this central chamber, cans with damaged upper flanges will fall from the belt to a collection site Since they do not have a sufficient effective contact are to be supported by the lesser vacuum. Another device is dislcosed in U.S. Patent No. 4,136,767, which is directed to the use of a vacuum transfer apparatus to move cans from a feed-in can conveyor in an inverted position to an upper conveyor in upright position by means of a perforated endless can-carrying and can-uprighting conveyor belt which works over the peripheral surface of a rotary foraminous metal cylinder or drum. Vacuum is applied from a vacuum chamber or housing and a first vacuum control device to the perforated endless conveyor belt which lifts the cans off the feed-in can conveyor belt, whereupon the perforated endless conveyor belt grabs and holds the cans with the closed bottoms of the cans disposed against the perforated endless conveyor belt, around approxim ately half of the peripheral surface or circumference of an air-permeable, rotary, foraminous, metal drum or cylinder. When the cans reach the top of the drum or cylinder, the vacuum from the vacuum chamber or housing, acting through a second and upper vacuum control devicle and the perforated endless conveyor belt, is cut off and the cans are delivered in upright position to a take-away or delivery conveyor by which the cans may be transported to a second work station. Although these known devices have been suitable for their intended purposes, they have certain shortcomings which heretofore have not been overcome. In every instance, the size of the openings through the plenum and the transfer belt is quite large so that the volumetric rate of transfer of air through the belt is quite high. At the beginning of a cycle when no cans are on the belt, the openings in the belt are all open so that air is drawn through the belt at a very high rate, whereas the pressure difference between the ambient air and the plenum is relatively low. As cans are picked up by the belt, an increasing number of holes becomes closed by the ends of the cans or containers over the belt. As this occurs, the volumetric rate decreases and the air speed increases as the static pressure within the plenum increases. Since the pressure differential is relatively little at the beginning of the cycle, the rate must be extremely high in order to attract the cans to the belt. Later when a large number of cans are on the belt, the static pressure differential is so great that sometimes canS which are tipped over will be drawn up against the belt rather than being separated frtom the other cans. Also, the greater air speed created by the much higher pressure differential will cause the air flowing through the space between adjacent cans to create a low pressure between the cans in accordance with Bernoulli's Principle. This can be undesirable where one of these cans is defective or improperly oriented. For example, the bottom of conventional aluminum can has a chine or taper at the bottom end so that the closed bottom end has a smaller surface area than the openueper top. Thus, a vacuum transfer device can be adjusted so that only cans in the upright position will be attracted to the belt, whereas if the bottom of the can is up the surface area is too small to be held up by the vacuum and therefore is separated at the transfer station from the other cans. On the other hand, where three cans are together, one of them being inverted, if the volumetric rate is sufficiently great, low pressure will be created in the space between the cans in accordance with the Bernoulli Principle so that the inverted can is carried along with the other two. Thus, effective separation of the cans with the desired orientation from those which are not, is difficult and sometimes almost impossible to obtain. Additional disadvantages with known devices is that the size of the fan must be very great in order to draw air at a sufficient rate through the transfer belt when the system starts up in order to attract a can to the belt. Thus, the power requirements for the transfer conveyor are excessive. Additionally, it is often necessary to provide suitable venting devices or pressure regulator devices within the plenum so that the static pressure does not become so great as to collapse the ducting. Thus, in the known devices, the pressure within the plenum is constantly changing, depending on the number of cans on the transfer belt, creating wide variations not only in static pressure within the plenum, but also in the volumetric rate of air transfer through the belt, resulting in difficult regulation and control problems. The invention consists in a vacuum transfer conveyor apparatus for transferring only those flat-ended articles having a predetermined, desired orientation from a first station to a second station spaced from the first station, the apparatus comprising: a foraminous transfer belt having a reach extending from the first station to the second station and movable for transferring those articles that are flat end uppermost from the first conveyor to the second conveyor, the transfer belt having an outer pick-up surface spaced above the first station a distance just slightly greater than the height of the upright articles; a vacuum plenum extending along an inner surface of the transfer belt; and means for drawing a vacuum in the plenum; and characterised in that a predetermined pattern of air jet openings is defined from the vacuum plenum to the pick-up surface of the transfer belt such that the vacuum drawing means draws the maximum vacuum in the plenum of which it is capable when all the air jet openings are uncovered and which vacuum is just sufficient to pick-up only properly orientated ones of the said articles at the first station. According to a further aspect, the invention consists in a method of transferring upright flat-ended articles from a first station to a second station spaced from the first station, the method comprising: moving a foraminous transfer belt from a position spaced above the first station a distance slightly greater than the height of the upright articles, to the second station and, with a vacuum plenum, drawing a vacuum over the transfer belt, thereby picking up on to a pick-up surface, articles from the first station and conveying them to the second station, characterised in that a predetermined pattern of air jet openings is defined from the vacuum plenum to the pick-up surface of the transfer belt, and in that the vacuum drawn is the maximum vacuum which the plenum is capable of producing when all the said openings are uncovered, and which vacuum is just sufficient to pick-up only properly orientated articles at the first station. In order that the invention may be better understood, various embodiments will now be described, by way of example, with reference to the accompanying schematic drawings, in which: Figure 1 is a side view in elevation of a preferred embodiment of the vacuum transfer conveyor of this invention; Figure 2 is an enlarged, horizontal section, taken along line 2-2 of Figure 1, showing details of this invention; Figure 3 is an enlarged, fragmentary section, taken along line 3-3 of Figure 2, showing how the containers are lifted up to the transfer belt; Figure 4 is an enlarged, fragmentary perspective view, in accordance with the prior art, showing how an improperly aligned container can be held and carried along with two properly aligned containers; ; Figure 5 is a fragmentary perspective view, showing an alternative plenum and belt arranghement wherein the plenum has spaced parallel rows of jet openings and the belt is provided with corresponding rows of slots for sequentially exposing and covering the jet openings; Figure 6 is an enlarged, horizontal section, taken along line 6-6 of Figure 5, showing further details of the plenum and vacuum belt construction and showing a container being supported by the belt; Figure 7 is a fragmentary top plan-view of a corner portion of the plenum wall of Figure 5 showing the relationship between the jet openings and the belt slots; Figure 8 is a greatly enlarged, fragmentary top view of the transfer belt showing, in phantom lines, an alternative arrangement for the jet openings and their co-operation with the belt splice to retain a container over the splice; ; Figure 9 is a horizontal section, taken along line 9-9 of Figure 8, further showing the positioning of a container under the splice; Figure 10 is a fragmentary perspective view, similar to Figure 5, but showing a further alternative plenum and belt arrangement wherein the plenum has spaced parallel pick-up and transfer slots and the belt is provided with corresponding rows of jet openings aligned with those slots; Figure 11 is an enlarged, horizontal section, taken along line 11-11 of Figure 10, showing further details of the plenum and vacuum belt construction and showing a container being supported by the belt; Figure 12 is a fragmentary, enlarged, top plan view of a portion of the plenum wall of Figure 10 showing the relationship between the jet openings in the belt and the plenum wall slots; ; Figure 13 is a horizontal section, taken along line 1313 of Figure 12, showing how containers are transferred and selectively separated by the transfer belt; and Figure 14 is a perspective view of a vacuum transfer device according to a further embodiment in which it is used in conjunction with a vertical single filer. Referring to Figure 1, there is shown one illustration of how a preferred embodiment of the present invention is implemented. The conveying system includes an upstream conveyor 10 and a downstream conveyor 12. The upstream conveyor and the downstream conveyor are longitudinally spaced apart in the direction of travel of the conveyors. A vacuum transfer conveyor apparatus is positioned above the adjacent ends of the conveyors 10 and 12 and functions to transfer a plurality of upright cans 16 from the first upstream conveyor 10 to the second downstream conveyor 12. Downed cans 18 and inverted cans 20 will fall off conveyor 10 to be coll¯ected and recycled or discarded. Conveyor 10 may be a conventional link belt conveyor and includes a porous endless link belt 22. The belt 22 travels over a plurality of spaced rollers, including end roller 24, as shown, which is journalled on shaft 26. One of the rollers can be driven by suitable means, not shown, to move the belt 22 in EMI11.1 /endless path to deliver the cans to a first station where the properly orientated cans are picked up by transfer apparatus 14, as explained below. The second, downstream conveyor 12 is of similar construction to conveyor 10 and includes an endless link belt 28 which is supported by rollers, such as roller 30, journalled on shaft 32 for conveying the cans from a second station, where the cans are dropped off the transfer apparatus to be carried to the next work station. Although conveyors 10 and 12 are illustrated as belt conveyors, either or both could be of the air conveyor or air table type as disclosed in U.S. Patent No.4,347,022. The transfer mechanism 14 includes a frame 36 supporting a closed chamber or plenum 38 including a top wall 40, shown in Figure 1, and a pair of side walls 42 and 44, a pair of end walls 46 and 48 and a bottom wall 50 provided with a plurality of apertures 52 therethrough which serve as vacuum jets, as seen in Figure 2. Advantageously, a sloping wall 53 joins top wall 40 and end wall 48, as shown in Figure 1. The side wall 44 is provided with an outlet opening 58 to which is connected a blower 57, shown in dotted lines in Figure 1. It will be understood that blower 57 may be mounted at any suitable location outside plenum 38 and connected thereto through opening 58. The transfer mechanism 14 includes a porous foraminous belt, such as link belt 54, extending between the upstream and downstream conveyors 10,12 and mounted for movement across and adjacent to plenum wall 50 between an idler roller 55 and a drive roller 56. The drive roller is driven by motor 59 through a gear box 60 and a belt or chain 62. The transfer belt 54 also rides on idler pulleys 64,66,68 and take-up pulley 70 having means, such as a screw 72, to move the pulley 70 up or down to shorten or lengthen the belt 54 to provide the desired tension thereon. shown in Figure 3, air moves over the top edges 72 of the containers 16 at the first station at the discharge end of conveyor 10 at a high face velocity in the direction of arrows 73. This results in a lowered pressure being developed between the top edges 72 of the containers 16 and bottom wall 50 of plenum 38 to lift the container in the direction of arrow 74 as a result of the Bernoulli Principle, whereby an increase in velocity of a gas results in a lower pressure, and of the Coanda Effect, whereby a jet of gas tends to follow a wall contour when discharged adjacent to a surface, even when that surface curves away from the jet discharge axis, so that air surrounding the wall is drawn in and thus reduces the pressure above the wall. By utilizing these principles to lift the cans onto the transfer belt, the vacuum drawn by the plenum, need be only sufficient to hold the cans on the belt during transfer and not sufficient to also provide all of the lifting force to lift the cans off belt 22. The apertures are sized and spaced so as to support the cans when blower 57 draws maximum vacuum in plenum 38. In this way, the amount of air passing through vacuum jets or apertures 52 is the same whether no apertures are covered by cans or whether all of the apertures are covered by cans because the differential pressure between the ambient air and the plenum remains the same. It can be understood from viewing Figure 3 that in a conventional aluminum or steel container or can, the bottom surface 76 has a diameter hl which is less than the diameter ffi of the top edge 72 of the can because of the taper or chine 80. Thus, by adjusting the number of apertures in wall 50 with respect to the vacuum within plenum 38 so that an upright can will just be supported by the belt, it will be apparent that if a can should be supplied to the transfer belt in an inverted position with the bottom 76 up, the amount of openings available to draw a vacuum on this area will be less and therefore, the inverted cans cannot be supported by the transfer belt 54 thereby separating them from the properly orientated cans. Referring to Figure 4, a common problem with the prior devices having large openings 52' in bottom wall 50 is that when two cans 16 are in side to side contact and a third inverted can 16' is positioned near the intersection of cans 16 so as to generally form a triangle, the Bernoulli Principle and Coanda Effect will act to create a partial vacuum in the space between the three cans so that can 16' will be drawn toward the other two cans in the direction of arrow 78 and held thereagainst and supported by these cans so as to be carried along by transfer belt 54. In other words, the vacuum from the plenum together with the supporting force caused by the partial vacuum between the cans will hold inverted can 16' so that i t is carried along with cans 16 across the transfer mechanism when, in fact, the can should have been discarded. This occurs when large openings 52' are used so that a high volume of air pass es through the holes tending to draw the cans up against the transfer belt in the prior devices. Thus, when the opening to the plenum is substantially unobstructed this mass flow of air will create a partial vacuum in accordance with the Bernoulli Principle and Coanda Effect. On the other hand, with the embodiments of the invention described, the flow of air is substantially less and therefore a finer sensitivity concerning the support of containers by the transfer belt 54 is obtained so that the chance of carrying an improperly orientated can across the transfer station is minimized. In one preferred embodiment of the present invention, the belt 54 of the transfer mechanism is run at a substantially faster speed, as much as twice the speed of belt 22 of upstream conveyor 10. This is to provid e longitudinal spacing between the containers picked up by the transfer belt 54 to further minimize the difficulties described with respect to Figure 4. Furthermore, if a fallen (downed) container 18 is present, by the faster running of belt 54, the longitudinal spacing of containers 16 will allow the downed container 18 to fall free and drop as shown. The discharge conveyor 12 can be run at the same speed as, or a different speed from, the transfer unit. If the outlet conveyor is set to travel at the same speed as the inlet conveyor, the containers will be returned to the same pattern as when they left the upstream conveyor. Furthermore, since the system always operates at a constant vacuum and at maximum static pressure rather than having to accommodate a wide range of air flow and static pressure as in the prior art, a much smaller blower and motor may be used. This can be exemplified by reference to Table I below in conjunction with the following description. This table is for a fan having a 12.25 inch (31cm) diameter and a fan outlet area of 0.86 square feet (800 cm2). Static Pressure (SP) at the plenum openings is given in inches (and cm) of water. Corresponding fan speeds are given in RPM (revolutions per minute) and fan powers BHP (brake horse power). TABLE I (dm3 per minute) Volumetric 1/2" (1.3cm) 1.5" (3.8cm) 4" (10 cm) 5" (17 cm) Air Transfer SP SP SP SP Rate: CFM RPM BHP RPM BHP RPM BHP RPM BHP (Cubic Feet per minute) 34.1 1203 1652 0.19 2071 0.44 2885 1.16 3175 1.51 36.5 1289 1735 0.22 2142 0.48 2925 1.23 3206 1.58 38.9 1375 1821 0.25 2216 0.52 2970 1.31 3237 1.65 43.8 1547 1989 0.32 2367 0.62 3075 1.46 3327 1.84 48.7 1719 2164 0.41 2520 0.73 3193 1.63 3430 2.03 53.5 1891 2342 0.51 2680 0.86 3323 1.83 3545 2.24 58.4 2063 2520 0.62 2842 1.01 3466 2.05 3680 2.49 63.3 2235 2701 0.76 3009 1.17 3608 2.28 3814 2.75 68.1 2407 2885 0.91 3175 1.36 3755 2.53 3959 3.03 With the known conveyors, if one determined that a particular design required 2407 cubic feet of air (CFM) to operate the system and that a 1/2 inch (1.3cm) static pressure (SP) was required at the plenum openings, the chart determined that the fan was to be operated at 2885 revolut iow per minute (RPM) with all the plenum openings clear, i.e. when none was covered by a can. If the openings were restricted to about one-half, by loading the belt with containers, the air transfer rate would be halved to 1203 (CFM), which with a fan speed of 2885 RPM means that, according to the chart, the static pressure (SP) would have increased from 1/2 inch (1.3cm) to 4 inches (10cm), or by a factor of eight. By way of a second example, if a static pressure of 1.5 inches (3.8cm) were desired with air flow of 2407 CFM the fan would have had to operate at 3175 RPM. Again, if cans covered approximately half of the holes so that the CFM dropped to 1203, then 5 inches (17cm) of static pressure would have been drawn in plenum 38. The result of this would have been a dramatic increase in the face velocity of the air passing through the vacuum jet openings 52. As a r ç t, misaligned cans would have been carried by the transfer belt across the transfer station defeating the purpose of the machine. Another way of viewing this same problem and the dramatic differences between the apparatus of the preferred embodiment of the present invention and the prior art is to consider the air transfer rate required to operate the system of the preferred embodiment as compared to that of the prior art. In the system of this embodiment, if a vacuum of 3.5 inches (8.9cm) of water is drawn in the plenum through 1/8 inch (.32cm) holes having a spacing of 1/2 inch (1.3cm) between centres, each hole will draw 0.6723 CFM (0.019 dm3 per minute) at a face velocity of 7,900 feet (2400m) per minute. This hole spacing provides 576 holes per square foot (0.62 hole per square cm) arranged in parallel rows. If the plenum wall is 19 inches (48cm) by 14 inches (36cm), i.e. 1.85 square feet (1720cm2), it will have a total of 1,131 holes and will drawn .760 CFM (21.5 dm3 per minute). Because of the relatively small size of the holes, even if the belt 50 has onlky 50% open mesh, virtually all of the holes will be open unless they are covered by a can. If a can is a standard 211/413 12 oz. aluminum can, it weighs 145.2 grams. When the can is in the upright position as shown in Figure 3, the top edge 72 of the can will cover an average of 23.7 holes. Byh providing a spacing of 3/16 inch (0.48cm) between the upper edge 72 of the cans and the belt 54, the Bernoulli Principle and Coanda Effect will be effective to at least partially lift the cans from belt 22 to belt 54. By comparison, if larger holes ' and lower static pressure is provided as in the prior art, such as 1/2 inch (1.3cm) holes at a static pressure of 1/2 inch (1.3cm water), it can be determined that the face velocity is 2,828 feet (862m) per minute. This is calculated by muitiplying the square root of 1/2 by 4,000 feet (1220m) per minute, the face velocity of a 1 inch (2.5cm) hole. With a 50% open mesh belt, it could be assumed that the effective area is half of 1.85 square feet (1720cm2), i.e. 0.925 square feet (860cm,2). Thus, by multiplying 2,828 feet (862m) per minute x 0.925 square feet (860cm2) the air flow is 2,616 CFM (74.1 dm3 per minute) as compared to 760 CFM (21.5 cm3 per minute) with the preferrd embodiment of the invention. One of the things that this additional flow of air means, is that the Bernoulli Principle and the Coanda Effect will create the situation shown in Figure 4 with respect to three adjacent cans, where one is in an inverted position. Additionally, cans which are lying sideways on the belt, such as can 18 of Figure 1, can also be picked up due to the high CFM (volumetric rate of flow) generated. Furthermore, because of the chine near the lower end of the can, the bottom diameter of the can is approximnately 2 inches (5.1cm), whereas the top is 2 3/4 inches (7cm). In this regard, the area of a 2 inch (5.2cm) diameter can bottom is 3.1416 square inches (25.8cm2) and the area of a 2 3/4 inch (7cm) diameter can top is 5.9396 square inches (48.8cm2), an increase in area of 89 percent. With the preferred embodiment having a hole size as described, the average number of holes holding the top of the can is over 23, comapred with 12 holes holding the bottom of the can if an inverted can is in position. In other words, there are almost twice as many active jet openings working on the top of the can as compared to the bottom of the can. On the other hand, in the example given of a prior known conveyor with 1 inch (2.5cm) holes, the differential number of holes with respect to the top of the can and the bottom of the can is considerably lower. An alternative construction is shown in Figures 5-7 wherein a plenum 80 is provided having side walls 82 and 84 interconnected by end walls 86 and 88. The plenum also includes a bottom wall 90 which is provided with longitudinal spaced parallel rows of jet openings 92. Somewhat larger jet openings 94 are provided at the upstream end of bottom wall 90 in each row, as will be more fully discussed below. An endless vacuum belt 96 is provided which moves from the upstream end to the downstream end across bottom wall 90 and plenum 80 and has parallel spaced rows of longitudinal apertures in the form of slots 98 which are aligned with jet openings 92 and 94 to sequentially cover and expose them. Conveniently, when a vacuum is drawn on plenum 80, the openings 92 and 94 which are covered by the belt 96 will cause it to be drawn up tightly against the plenum, whereas the openings which are uncovered by virtue of being above the slots will draw a vacuum to lift and support cans to be moved with the reach of belt 96 from the upstream end to the downstream end. The belt is pulled across plenum wall 90 by a drive roller 100 at the downstream end of the plenum and also runs over an upstream idler roller 102. Conveniently, vacuum belt 96 is provided with a longitudinal rib 104 adjacent each edge which is received in a corresponding groove, such as groove 106 in wall 90, as best seen in Figure 6. Conveniently, drive roller 100 is provided with spaced grooves 108 for receiving ribs 104 to enhance the pulling power of the drive roller. Also, idler roller 102 is provided with grooves 110 also corresponding in spacing to ribs 104. By this arrangement, the belt will be positively guided along the proper path. The rib 104 and groove 106 in plenum wall 90 provide the dual or secondary function of serving as an air seal so that air does not leak in between the sides of the plenum wall and the belt. By way of example, assuming that the cans to be conveyed are aluminium cans weighing approximately 14 grams and having an upper end diameter of 2 1/2 inches (6.4cm) and are to be conveyed across a vacuum plenum plate 90 which is 14 1/2 inches (37cm) wide and 20 inches (50cm) long. The first four holes 94 in each row will be 13/64 inch (0.52cm) on 3/8 inch (0.95cm) centres and the rest of the holes in each row will be 5/64 inch (0.2cm) holes on 1/2 inch (1.3cm) centres, the rows of slots being spaced 1 1/4 inches (3.2cm) apart so as to correspond with the spacing of the holes and travel over the respective rows of holes. By this arrangement, no matter where a container is picked up by the belt, at least one hole will be exposed through a slot to the can and will provide sufficient vacuum for lifting a container if it is under holes 94 and to support a container if it is under one of holes 92. With the dimensions given, there will be eleven rows of holes and, thus, 44 larger holes 94 and 396 smaller holes 92. If a 4 inch (10cm water) vacuum is drawn, each larger hole will pass 1.80 CFM (0.05 dm3 per minute) of air, giving a total of 79.2 CFM (2.2 dm3 per minute) for all holes. Similarly, these smaller holes 92 will each draw 0.1627 CFM (.0046dm3) giving a total of 64.4 CFM (1,8dim3 per minute). Thus, the total CFM for the entire system with all holes open would be 143.6 CFM (4.1 dm3 per minute). However, because the belt covers the holes, only a maximum of approximately 60% of the holes can be open when the belt is completely empty of cans. Thus, the most air that can be drawn at one time is 60% of 143.6 CF (4.1in3) or 86.16 CFM (2.4 dm3 per minute). Thus, the air usage is very small which in turn makes the power requirements very low. It is contemplated that a onethird horse power (BHP) motor used with a Grainger 2C820 fan, capable of producing 160 CFM (4.5dm3 per minute) at 5.0 inches (17cm) static pressure, is adequate for the operation of this apparatus as previously described. Additional features of this embodiment are shown in Figures 8 and 9 wherein the ends of belt 96 are joined,as by a splice 112 in the form of a piano hinge, to form the endless belt. Splice 112 includes first hinge plate member 114 extending across one end of the belt and attached thereto, as by spaced cleats 116. A plurality of knuckles 118 extend from the opposite side of hinge plate 114. Splice 112 includes a second hinge plate 120 having cleats 122 connected to the other end of belt 96 and also having knuckles 124 extending from the other side which interlace with knuckles 118 and have an opening therethrough for receiving a hinge rod 126. As can clearly be seen in Figure 8, there are air spaces between the knuckles 118 and 124 which will permit extra air to be drawn through the plenum at the location of the hinge as it moves across the surface of the plenum. In other words, any air jet openings 94 which align with the splice will draw air. As shown in Figure 9, a can 16 will not be drawn flush against the belt at splice 112 because the splice is thicker than the belt. Thus, the container will tend to wobble and additional air can be drawn in around the base created between the upper edge of the can and the belt. Thus, if the vacuum is not sufficient, the can will not be retained, but will fall from the belt. In order to be sure that enough air is drawn through the spaces between knuckles 118 and 124 along splice 112, an additional row of jet openings 94' is provided between each row of holes 94. As previously pointed out, jet openings 94 in each alternate row are staggered. Similarly, jet openings 94' are staggered in the same relationship as the rows containing jet openings 94. The jet openings 94' serve to draw the belt up against the bottom of platen 90 and normally are never exposed to atmosphere. However, when splice 112 passes over them, they will draw air through the openings between knuckles 118 and 124 and therefore will provide additional air flow and vacuum for supporting a container 16 which is positioned over the hinge in addition to the air provided through the opening or openings 94 that are exposed through one of slots 98. Thus, the openings in the hinge actually provide means for drawing additional air through additional openings to assure that the container 16 is carried along with the belt even though it is positioned under the hinge and can tilt back and forth as illustrated in Figure 9. Also, additional air can be drawn in and around the lip of the can bringing into effect Bernoulli's Principle which will cause the can to tend to be drawn up against the belt. The air may follow the path indicated by either arrow 128 or 130, depending upon the tilt of the container. It will be understood that although the apertures in the transfer belt in the embodiments of Figures 5-9 have been illustrated and described as slots, they may be of any conveniently and suitable shape, such as circular. A still further alternative embodiment is shown in Figures 10-13 wherein a plenum 32 has spaced side walls 132 and 136 interconnected by end walls 138 and 140. A bottom wall 142 is provided which has spaced parallel transfer slots 144 extending from one end thereof to the other, as best seen in Figures 10 and 12. Spaced between, or interleaved with, each pair of transfer slots 144 are pick-up slots 146 which are adjacent the upstream end of wall 142. Conveniently, a vacuum transfer belt 148, having parallel spaced rows of jet openings 150, extends across plenum wall 142 between a drive roller 152 and an idler roller 154. The rows of jet openings 150 are spaced so that one coincides with each transfer slot 144 and each pick-up slot 146. One advantage of this arrangement is that the jet openings on the vacuum belt can be spaced closely together so that rather small articles 156, such as bottle cans, can be conveyed by this system. It is important that during the transfer operation at least one jet opening be available to each article being conveyed so as to hold it against the surface of belt 148. At the upstream end, the pick-up slots 146 effectively double the air flow thereby increasing the flow of air so that the Bernoulli Principle and Coanda Effect will be effective to at least partially lift the articles from the upstream belt, such as belt 22 of Figure 1. As will be apparent, at the upstream end of belt 148, 100% of the openings will be exposed since there is either a transfer slot 144 or a pick-up slot 146 over every row of openings. However, beyond the downstream ends of pick-up slots 146, the number of openings will decrease by 50% which is sufficient to hold articles which are properly formed. However, any malformed articles will drop off the belt, as best seen in Figure 13. Thus, this vacuum transfer device can be used to transport rather small light-weight articles, where any malformed articles can be eliminated. Also, if the belt speed is increased above that of the upstream belt, the articles can be separated longitudinally to reduce any bridging effect wherein the malformed article would be carried by two adjacent articles, as previously discussed with respect to Figure 4. As in the embodiment of Figures 5-7, belt 148 can be provided with ribs 158 adjacent each edge which are received in grooves 160 adjacent each end of drive roller 152 and grooves 162 adjacent each end of idler roller 154 as well as grooves 164 in plenum wall 142, best seen in Figure 11. This provides a tight air seal so that air is pulled into the plenum only through jet openings 150. As an alternative to the embodiment of Figures 10-13, the bottom of the plenum can be omitted entirely so long as suitable means are provided for creating an effective seal between the edges of the transfer belt and the plenum to maintain the relatively high subambient static pressure required for the operation of this conveyor. Additionally, plenum wall 50 can be provided with a large opening for receiving a removable plate having vacuum jets therein. This will facilitate providing different size and spacing of jet openings for different size and weight containers. An alternative embodiment is shown in Figure 14 wherein the vacuum transfer device of Figures 10-12 is utilized in connection with other apparatus, as described below, for transferring a mass of cans from an upstream location to a downstream location wherein they are arranged in single file. It will be understood that the vacuum transfer devices of the other embodiments could also be utilized for this purpose, the embodiment shown being for illustrative purposes only. Containers 166 can be supplied en masse at an upstream location, as by means of an air table 168 of the type having a jet board 170 through which air is applied by means of a plenum 172 to convey the containers in a large mass to transfer conveyor 132. The containers 166 will be carried by the transfer belt 148 to a downstream conveyor 176. Conveniently, transfer belt 148 operates at sufficient speed to provide longitudinal separation of the containers as shown. Also, any containers which are bent or misshapen, such as container 166', will be dropped from the transfer belt, as previously described with respect to the other embodiments. Advantageously, downstream conveyor 176 has converging sidewalls 178 and 180 which cause the longitudinally separated containers 166 to be moved towards each other so as to be brought into single file between parallel walls 182 and 184. Conveyor 176 has also been illustrated as an air table having a jet board 186, but other types of conveying apparatus could be used. Because of the longitudinal separation of the containers by vacuum transfer belt 148, the angle of sidewalls 178 and 180 can be much sharper than other single file conveying devices. Thus, the total length of the single filing apparatus which includes the vacuum transfer portion can be significantly shorter. Of course, the angle of sidewalls 178 and 180 will be designed so as to bring the containers into an isosceles triangular configuration so that they will advance smoothly and can be accelerated into single file arrangement. Although the transfer belt has been illustrated as transferring containers along a horizontal path from a first station to a second station, it will be understood that the principles of this invention can be applied to the transporting of the cans along an incline, such as in an elevator or around a curved surface, such as a plenum in the form of a drum. A very low volume rate of air transfer is then required for supporting the containers and thus the power requirements are very low. In some uses of the present invention it will be desirable to transfer cans which are in an inverted rather than upright position, such as cans being transferred from a washing station to a drying station. In that situation, should one of the cans be upright, it will undoubtedly contain some amount of water which will cause it to be too heavy to be held by the belt and thus will be separated from the inverted cans even though the larger end of the can will be adjacent the transfer belt.

Claims: CLAIMS 1. A vacuum transfer conveyor apparatus for transferring only those flat-ended articles (16) having a predetermined, desired orientation from a first station (10) to a second station (12) spaced from the first station, the apparatus comprising: a foraminous transfer belt (54) having a reach extending from the first station (10) to the second station (12) and movable for transferring those articles that are flat end uppermost from the first conveyor (10) to the second conveyor (12), the transfer belt having an outer pick-up surface spaced above the first station (10) a distance just slightly greater than the height of the upright articles (16); a vacuum plenum (38) extending along an inner surface of the transfer belt (54); and means (57) for drawing a vacuum in the plenum; and characterised in that a predetermined pattern of air jet openings (52,54; 144,150) is defined from the vacuum plenum (38) to the pick-up surface of the transfer belt (54) such that the vacuum drawing means draws the maximum vacuum in the plenum of which it is capable when all the air jet openings are uncovered and which vacuum is just sufficient to pick up only properly orientated ones of the said articles (16) at the first station (10). 2. Apparatus according to claim 1, wherein the vacuum plenum (38) has a bottom wall (50) against whose outer surface slides the inner surface of the transfer belt (54), and wherein the said air jet openings (52,54) are defined by air jet openings (52) through the plenum wall (50) and by open areas (54) in the transfer belt having a substantially greater total open area than the total open area of the said air jet openings (52), so that the open areas (54) in the transfer belt (54) have no appreciable effect on the amount and velocity of air passing through to the plenum (38). 3. Apparatus according to claim 1, wherein the vacuum plenum (38) has a bottom wall (50) against whose outer surface slides the inner surface of the transfer belt (54), and wherein the saiud air jet openings (144,150) are defined by a plurality of parallel slot means (144) through the plenum wall (50) and extending from above the first station (10) to the second station (12); and a plurality of spaced jet openings (150) arranged in parallel rows corresponding to and overlying at least some of the said slots, the said jet openings being of such a size that the vacuum drawing means (57) draws the maximum vacuum in the plenum of which it is capable when all of the said jet openings are uncovered and which vacuum is just sufficient to pick-up properly orientated articles at the first station (10), and the said slot means having no appreciable effect on the amount or velocity of air passing through to the plenum (38). 4. Apparatus according to claim 3, wherein the said slot means comprise: a first set of parallel transfer slots (144) extending from an upstream end to a downstream end of the plenum wall (50); and a second set of shorter pick-up slots (146) interleaved between the said transfer slots and extending from the upstream end a short incremental distance along the plenum wall (50) towards the downstream end so that a greater number of jet openings are effective to lift and hold articles against the transfer belt (54) at the first station (10) than elsewhere. 5. Apparatus according to claim 4, wherein: a row of jet openings is provided in the transfer belt (54) which is aligned with each of the said transfer slots (144) and with each of the said pick-up slots (146). 6. Apparatus according to any preceding claim, comprising a first conveyor (22) for moving at a first predetermined speed to transport the articles (16) to the first station (10); and a second conveyor (28) for moving at the first predetermined speed to transport the articles (16) away from the second station (12). 7. Apparatus according to claim 6, comprising means for moving the transfer belt (54) at a second predetermined speed which is greater than the first predetermined speed to space the articles longitudinally along the transfer belt (54) so that misaligned articles (16',Fig.4) cannot be picked-up and carried by adjacent properly orientated articles (76). 8. Apparatus according to any preceding claim, wherein the spacing between the first station (10) and the transfer belt (54) is such that the said flat end of an upright article (16) is positioned witb respect to the pick-up surface of the transfer belt (54) so that air flow therebetween increases in velocity to reduce pressure between the flat end and the pick-up surface in accordance with the Bernoulli Principle and the Coanda Effect to assist in lifting the article off the first station (10) and on to the pick-up surface where it is held by the vacuum in the plenum. 9. Apparatus according to any preceding claim, wherein the said air jet openings are such, in relation to the power of the vacuum drawing means, that in use the flow of air in the space between three mutually touching cylindrical containers (16,16',Fig.4), one of which is inverted, is of insufficient velocity to create a reduced pressure area in the space therebetween to draw the inverted container (16') against the other two and hold it by the plenum vacuum alone against the transfer belt (54). 10. Apparatus according to claim 9, wherein the said jet openings (94,Fig.5) near the first station (10) are larger than the rest (92) of the jet openings to provide increased air flow at the first station (10) to lift the articles from the first station to the transfer belt (54). 11. Apparatus according to any preceding claim, comprising a longitudinal rib (104,Fig.5) on the inside surface of the transfer belt (54) adjacent each side edge thereof; and a longitudinal groove on the outer surface of the plenum wall (50) adjacent each side edge thereof for receiving the respective ribs (104) to form an air seal between the said edge of the transfer belt and the plenum wall. 12. Apparatus according to claim 9 or any claim appendent thereto, wherein the rows of spaced apertures overlie every alternate one of the said rows of air jet openings. 13. Apparatus according to any preceding claim, wherein the transfer belt (54) has first and second ends, the apparatus comprising splicing means (112) extending laterally across the transfer belt to join the first and second ends together to form an endless belt, the splicing means having a lateral opening through which air is drawn into the vacuum plenum when the splicing means is over the said air jet openings, in order to assist the retention of articles at the joint of the belt. 14. Apparatus according to claim 2 or any claim appendent thereto, wherein the said open areas in the transfer belt are elongate slots (98). 15. Apparatus according to claim 1, for the transport of vertically-arranged cylindrical articles in a wide mass at an upstream location (168,Fig.14) into a smaller width at a downstream location (184), wherein the first station is a conveyor station (168) supplying articles in bulk at a predetermined speed; and the second station is a conveyor station (176) having side walls (180) converging in the downstream direction for merging the articles into a lesser width; and comprising means for moving the transfer belt (54) at a higher speed than the movement of articles to the first station (10) to space longitudinally the articles at the second station (12) to facilitate the merger of the articles upon engagement with the said converging side walls (180). 16. A method of transferring upright flat-ended articles from a first station (10) to a second station (12) spaced from the first station, the method comprising: moving a foraminous transfer belt (54) from a position spaced above the first station (10) a distance slightly greater than the height of the upright articles (16), to the second station and, with a vacuum plenum, drawing a vacuum over the transfer belt (54), thereby picking-up on to a pick-up surface, articles from the first station and conveying them to the second station, characterised in that a predetermined pattern of air jet openings (52,54; 144,150) is defined from the vacuum plenum (38) to the pick-up surface of the transfer belt (54), and in that the vacuum drawn is the maximum vacuum which the plenum is capable of producing when all the said openings are uncovered, and which vacuum is just sufficient to pickup only properly orientated articles at the first station (10). 17. A method according to claim 16, of conveying a wide mass of articles from the first station to a smaller width at the second station, the method comprising the steps of: picking-up articles on to the transfer belt (54) at the first station; longitudinally separating the articles as they are picked-up at the first station; conveying the articles to the second station; depositing the articles at the second station in longitudinally separated condition; moving the articles away from the second station; and laterally converging the articles into single file as they move away from the second station.

Inventors: LENHART, RONALD A.
Applicants: PRECISION METAL FABRICATORS, INC.
Application year: 1984
Main classification: B65G47
IPC codes: B65G21