US3834408A - Apparatus for cleaning small items - Google Patents

Abstract

Compact apparatus for cleaning electronic, and other small items of manufacture, of soils, such as those which result from prior manufacturing operations, includes a helical non-vibratory elevator track, which is wound upwardly about a cylindrical supporting stem, and an endless chain conveyor for pushing the items along the track. The soiled items are deposited into a load chute leading down to a lower flight of the track. This portion of the track is submerged, or partially submerged, in a cleaning solution which is flowing down the track into a lower sump. The immersed soiled items are pushed through the cleaning solution along the lower level of the track, and, after emerging therefrom, are pushed up the track through sprays of clean distillate solvent and a vapor zone located at intermediate flight levels, then through a drying zone at upper flight levels, after which the cleaned and dried items are discharged from the track down a discharge chute. The conveyor for conveying the items up the helical elevator track may preferably include an endless chain having fixtures or pushers extending laterally therefrom at spaced intervals for pushing the items along the track. The helical track and its chain conveyor occupy but a small amount of floor space and the entire cleaning system is housed in a compact housing.

Description

APPARATUS FOR CLEANING SMALL ITEMS [75] Inventor: Richard E. Thalacker, Bowling Green, Ky. [73] Assignee: Detrex Chemical Industries, Inc., Detroit, Mich.

[22] Filed: Sept. 13, 1972 [21] App]. No; 288,685

[52] US. Cl 134/83, 134/107, 134/108, 134/132, 198/136, 198/171 [51] Int. Cl. B08b 3/02, B08b 3/10, B65g 19/00 [58] Field of Search 134/83, 132, 65; 198/136 [56] References Cited UNITED STATES PATENTS 1,226,730 5/1917 Weston 198/136 1,758,994 5/1930 Yeomans 198/136 2,011,786 8/1935 Walker 134/132 X 2,119,191 5/1938 Wilkinson et al.... 134/132 2,204,011 6/1940 Cook 198/136 X 2,662,851 12/1953 Jones et a1. 134/132 X 2,746,468 5/1956 Desmond et al..... 134/132 X 3,216,431 11/1965 White 134/132 3,682,295 8/1972 Roinestad 198/136 X Primary Examiner-Daniel Blum 111 3,834,408 Sept. 10, 1974 [5 7] ABSTRACT Compact apparatus for cleaning electronic, and other small items of manufacture, of soils, such as those which result from prior manufacturing operations, includes a helical non-vibratory elevator track, which is wound upwardly about a cylindrical supporting stem, and an endless chain conveyor for pushing the items along the track. The soiled items are deposited into a load chute leading down to a lower flight of the track. This portion of the track is submerged, or partially submerged, in a cleaning solution which is flowing down the track into a lower sump. The immersed soiled items are pushed through the cleaning solution along the lower level of the track, and, after emerging therefrom, are pushed up the track through sprays of clean distillate'solvent and a vapor zone located at intermediate flight levels, then through a drying zone at upper flight levels, after which the cleaned and dried items are discharged from the track down a discharge chute. The conveyor for conveying the items up the helical elevator track may preferably include an endless chain having fixtures or pushers extending laterally therefrom at spaced intervals for pushing the items along the track. The helical track and its chain conveyor occupy but a small amount of floor space and the entire cleaning system is housed in a compact housing.

7 Claims, 15 Drawing Figures PAIENIEDsEP 1 0:914

SIEU Z0! 6 PAIENTED SEP 1 01924 SEEIJUG PATENIE SEP 1 01914 sumwe 1 APPARATUS FOR CLEANING SMALL ITEMS BACKGROUND OF THE INVENTION This invention relates to apparatus for cleaning small items of soils, such as small manufactured items having soils thereon resulting from prior manufacturing operatrons.

The apparatus of the present invention is particularly useful in the cleaning of electronic items, such as electronic circuit boards. In the production of such circuit boards, wave soldering processes are frequently employed. These processes leave contaminates, such as flux and/or oil on the circuit board. To improve the operating characteristics and life expectancy of the circuit boards, these contaminates must be removed. The present application describes apparatus which is particularly useful in the removal of such contaminates.

SUMMARY OF THE INVENTION A primary object of the present invention is to provide apparatus for cleaning electronic and other small items of manufacture of soils such as those which result from prior manufacturing operations.

A further object is to provide cleaning apparatus, as aforesaid, which is adapted for continuous operation, as on a production line.

A further and important object is to provide cleaning apparatus, as aforesaid, which requires substantially less floor space than has heretofore been required.

The foregoing objects are achieved, in accordance with the present invention, by providing an apparatus in which the items to be cleaned are conveyed upwardly along a helical track and transported successively through a cleaning solution in which the articles are immersed in the solution, then through a cleaning spray, and then through a drying zone, before being discharged from a discharge chute. In one embodiment, some forty feet of travel on the track is provided in a compact housing which occupies a rectangular floor space measuring 7 foot by 7 foot.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration of a cleaning system provided in accordance with an embodiment of the present invention.

FIG. 2 is an elevational view of one form of compact apparatus. This, however, is not the presently preferred form. The presently preferred form is illustrated in FIGS. -15.

FIG. 3 is a plan view looking down along the line 3-3 of FIG. 2.

FIG. 4 is a plan view looking down along the line 44 of FIG. 2.

FIG. 5 is a fragmentary perspective illustration of one form of chain and one of its fixtures used in the nonpreferred embodiment of FIGS. 2-4.

FIG. 6 is a view, in section, looking along the line 6-6 of FIG. 4.

FIG. 7 is a modified form of track having a corrugated floor which provides well for the cleaning solvent.

FIG. 8 is a view, in section, looking along the line 88 of FIG. 7.

FIG. 9 is similar to FIG. 7 but shows a mesh belt form of conveyor.

FIG. 10 is a plan view of a presently preferred form of apparatus.

FIG. 11 is an elevational view, partly schematic, looking along the line l1ll of FIG. 10.

FIG. 12 is an elevational view, enlarged and in section, of a portion of the drive for the endless chain.

FIG. 13 is a fragmentary view of the endless chain of FIGS. 10-12 and one of the pushers.

FIG. 14 is a view looking down along the line 14-14 of FIG. 12.

FIG. 15 is a plan fragmentary view of the endless chain of FIGS. 10-14.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 2, there is shown an eleva- .tional view of a presently non-preferred form of apparatus housed compactly within a housing 10. Housing 10, which is illustrated as being rectangular but need not be, has a cover 12 which is preferably removable.

Supported within housing 10 is a vertical stem or column 25. Surrounding column 25 and supported thereon is a track 20. Track 20 is wound helically about the column 25. FIG. 6 is a view in section of the track 20. As there shown, the inward edge of the track is secured, as by welding, to column 25. The outer edge of the helical track 20 is provided with an upwardlyextending flange 21. Vertical stiffeners may be used to tie together the multiple levels of the flange 21.

Supported on track 20 for sliding movement therealong, at the inward edge thereof, is an endless chain 35, which in FIGS. 2-9 is of a universal type. Chain 35 is shown to be trained over four sprockets 30 identified individually by the reference numerals 30-1, 30-2, 30-3, 30-4. Two of the sprockets, namely, 30-3 and 30-4, are idler sprockets. The other two sprockets 30-1 and 30-2 are driven.

While other suitable means may be used for driving the chain 35, the particular drive means illustrated in the embodiment of FIGS. 2, 3 and 4 includes a variable speed drive consisting of electric motor 80, an adjustable pulley 81, a belt 82 and a pulley 83 driving a speed reducer 84. These components, as well as others, are supported within cover 12. The output of reducer 84 drives a shaft 88 through a chain-and-sprocket drive consisting of sprocket 85, chain 86 and sprocket 87. Keyed or otherwise mounted on shaft 88 for rotation therewith is sprocket 30-2 which is one of two sprockets which drive endless chain 35. Also mounted on shaft 88 is a sprocket 89 which, by way of a chain 90, drives a sprocket 92 which drives a change-of-direction device 93, which may be a bevel gear device. Device 93 drives a sprocket 94 over which a chain 95 is trained. Chain 95 occupies a diagonal position. It extends diagonally downwardly from sprocket 94, which is mounted in the left front corner of the cover area, to a sprocket 96 in the lower left rear corner of the housing 10. The diagonal path of chain 95 carries it down through an opening 15 in the ceiling plate 14. Sprocket 96 drives a shaft 97 on which sprocket 30-1 is keyed or otherwise mounted for rotation. Sprocket 30-1 is the other of the two sprockets which drives chain 35.

The path of endless chain 35 may be traced from drive sprocket 30-1 which, as seen in FIGS. 2 and 4, is located opposite side of the lower flights of the spiral track 20. Chain 35 is guided by a guide rail 22 onto the lowermost flight -1 of track 20 where the chain 35 occupies a position adjacent the column or stem 25, as seen in FIG. 6. Chain 35 follows the same upward helical path defined by the track 20. At the upppermost flight 20-8, chain 35 leaves the track and passes through an L-shaped opening 16 in the ceiling plate 14 and then up and over the vertically-disposed drive sprocket -2, as seen in FIGS. 2 and 3. The chain then follows a horizontal path from right to left as viewed in FIGS. 3 and 4. It passes about horizontally-disposed idler sprocket 30-3, and then moves horizontally rearwardly, and over the vertically disposed idler sprocket 30-4 and then vertically downwardly through the opening 17 in the ceiling plate 14 to the drive sprocket 30-1 located in the rear lower left corner of the housing 10, as seen in FIGS. 2 and 4.

The construction of drive chain is shown in detail in FIG. 5. As there illustrated, alternate links 35-1 of the chain are similar and consist of a pair of U-shaped members the sides of which lie in vertical planes the two members being connected together by a central horizontally disposed pin. The other alternate links 35-2 are likewise similar to each other, although different from links 35-1. Links 35-2 consist of a pair of U- shaped elements the sides of which lie in horizontal planes, the two members being connected together by a vertically disposed pin. The teeth on the sprockets 30 are so spaced that adjacent teeth are adapted to enter into recesses in adjacent links of the same type. For example, the teeth of the vertically disposed sprockets 30-1, 30-2 and 30-4 are adapted to engage recesses in links 35-1, while the teeth of the horizontally disposed sprocket 30-3 are adapted to engage recesses in the chain links 35-2. It will be seen that the chain 35 is of a universal type adapted for movement along either a horizontal path or along a vertical path, and adapted to change from one to the other without any twisting of the chain.

Reference is now made to FIG. 1 which is a schematic illustration of a cleaning system provided by the compactly arranged apparatus contained in housing 10. A supply of cleaning solution or solvent,such as a chlorinated hydrocarbon, or a fluroinated hydrocarbon solvent, or an azeotrope mixture thereof including different types of alcohol azeotropes, is provided in a sump 51. Cleaning solvent from sump 51 is pumped by pump 55 through filters 54 and out of recirculating spray nozzles 56 positioned above track 20 at lower flights thereof. The recirculated solvent projected from nozzles 56 flows down the lower flights of track 20 and then out a straightway portion 120 back of the sump 51. The cleaning solvent returned to sump 51 is dirty, being contaminated by the soils of the items being cleaned. This dirty solvent overflows into a boil tank 52. Boil tank 52 is provided with a source of heat, illustrated as steam coils 57, and the dirty solvent in tank 52 is boiled and distilled. Other forms of heat may be used, such as electric or gas coils. The vapors rise from boil tank in the housing 10 to a level established by a water jacket 62 (FIG. 2). At this level, the vapors are condensed and the clean liquid distillate is collected in a trough 63 and pumped, as by pump 59, out spray nozzles 60 onto intermediate-level flights of the helical track 20. This spray distillate further cleans the items being pushed up this portion of the helical track. The distillate and the soils then flow back down track 20 and out the straightaway 120 to the sump 51.

The upper flights of track 20 carry the items upwardly through a drying zone. If heat is needed for the drying, it is provided by a steam jacket 61 along the upper flights of the track. The clean dirty items are then discharged from track 20 into a discharge chute.

All of the components depicted in the schematic of FIG. 1 are housed in the compact housing 10, and most but not all of these components are illustrated in FIGS. 2, 3 and 4. The recirculating sump 51,- and the boil sump 52 containing the steam coils 57, are seen at the bottom of FIG. 2. Several of the recirculating spray nozzles 56, and several of the distillate spray jets 60 are seen in FIG. 2 at flight level 20-3 and 20-4. Water jacket 62 and trough 63, and the steam jacket 61 are also illustrated in FIG. 2. Omitted from FIG. 2 are the filters 54 and the pumps 55 and 59.

In operation, the electronic circuit boards or other items to be cleaned are dropped down an inclined load chute 71 which leads to lower flight 20-1 of the helical track 20. If the items have oil soils and tend to be slippery, a flap 72 slows them down as they drop down the chute, preventing them from dropping at too rapid a rate. If, on the other hand, due to the nature of the soils, the parts dropping down the chute 71 would tend to stick, a jet of cleaning solution may be supplied as at 64 from one of the pumps to allow the parts to flow freely down the chute. At the point at which the items from load chute 71 enter track 20 there is a moderate depth of liquid cleaning solvent and the items become immersed therein. The items which drop from load chute 71 into the liquid solvent on track 20 are, as is seen in FIG. 4, engaged by one of the fixtures 38 of the endless chain 35 and are pushed along through the liquid solvent and then up the helical path of the track 20. The parts, in their upward helical travel pass in successiori through a second zone in which the items are sprayed by recirculated liquid solvent from spray jets 56, then through a third zone in which the items are sprayed by condensed distillate from spray jets 60, then through a vapor zone which extends up as far as water jacket 62, and finally through a drying zone in which the already warm items are further heated, and dried. The clean dry items are then discharged from the track, at flight 20-8, and drop down an inclined discharge chute 75. g

If the cleaning solution be of a non-solvent type, instead of a solvent, air may be forced through a heat exhchanger and applied to the parts in the drying zone to dry the parts.

In the system illustrated schematically in FIG. 1, the cleaning solution is assumed to be a solvent. TI-Ie solvent is boiled in boil sump 52 and the vapors rise to the water jacket condenser area defined by water jacket .62. These vapors are condensed and flow through trough 63 to the distillate receiver water separator 58 illustrated schematically in FIG. 1 but not shown in FIG. 2 to avoid confusion of lines. The distillate receiver water separator 58 serves as a means to remove water entrapped in the solvent and as a sump for the spray distillate. From the separator 58 the solvent overflows to the recirculating spray sump 51 which serves as a sump to supply solvent for the recirculating spray; solvent overflows the recirculating spray sump 51 back to the boil sump 52, to complete the solvent cycle. In the case of an aqueous wash system, the recirculating and boil sumps would be arranged to function as wash and rinse sumps with appropriate pumps applied.

An important feature of the present invention resides in the non-vibratory type of sprial elevator which is employed to convey the items through the system. One form, although not the currently preferred form, is that which has been described above. In the form already described in connection with FIGS. 1-6, as well as in the preferred form later to be described in connection with FIGS. -14, a fixed helical support track is employed in combination with a driven endless chain having pusher fixtures attached thereto at spaced intervals. In one particular form of compact machine according to the present invention, the cubical housing, including the hood or cover, measures 7 X 7 X 7'. The helical track inside the cube provides over 40 feet of travel. This compares with prior art machines wherein, the same floor space, only 10 to 12 feet of travel is provided inside the machine. The track 20 is 12 inches wide and has a 6-inch pitch about the tubular stem which has a diameter of 18 inches.

FIGS. '7, 8 and 9 depict modified forms of fixed helical track. In FIGS. '7 and 8, the floor of the track 220 is corrugated, thereby providing grooves or wells 221 down which the contaminated cleaning solution may flow. The pusher bars 238, in FIGS. 7 and 8, are shown as having depending fingers or legs which project down into the wells 221 to move along any small items which may drop therein and which would otherwise not be pushed along by the bar 238. In FIG. 9, in lieu of endless chain and pusher bars 38 or 238, an endless chain conveyor belt 201 is indicated supported on and movable along the fixed track 220 for carying the items to be cleaned indicated in phantom.

FIGS. 10-15 illustrate the presently preferred form of non-vibratory spiral elevator. Referring first to FIGS. 13-15, the preferred chain 40 is a roller chain comprising rollers 41, pins 44, roller-link plates 42 and pin links 43. The chain is constructed to have extra clearance for permitting side flexing and twisting. Side flexing is illus trated in FIG. 15. The pin links 43 are designed to allow greater clearance between the pins 44 and the bushings and also between the pin links 43 and the roller-link plates 42. Standard toothed sprockets may be used to drive the flexible chain 40.

The means for driving the drive sprockets to drive chain 40 will now be described with particular reference to FIGS. 10-12.

Similar to the embodiment of FIGS. 1-6 first described and illustrated, the drive of FIGS. 10-12 includes a motor 80 which drives a gear reducer 84 through a belt and pulley system 81-83, with the output sprocket 85 of the gear reducer 84 driving a chain 86 and a sprocket 87, the latter being fixed on a rotatable shaft 88 supported in a bracket 91. Also fixed on shaft 88 for rotation therewith is a sprocket 89 which in the embodiment of FIGS. 16-12 drives a chain 26 and a sprocket 27. Sprocket 27 is fixed to the upper end of a rotatable vertical shaft 45 which extends downwardly through the interior of the hollow stem 25 off the center axis thereof. The axis of vertical shaft 45 is relatively close to the perimeter of the hollow cylindrical stem 25, as is seen in FIG. 10, and fixed to shaft 45 at spaced-apart levels are a plurality of sprockets 47, three being shown in the illustrated embodiment. As seen in FIGS. 12 and 14, the teeth of sprockets 47 extend through slots in the peripheral wall of the stem 45 and engage the chain 40 at three levels as indicated schematically in FIG. 11, and as illustrated in section Chain 40 is also trained over two idler sprockets 48 and 49 as seen in FIGS. 10 and 11. Sprocket 48 is mounted on a shaft 78 in the upper part of the housing 10 and occupies an inclined position relative to he horizontally disposed drive sprocket 89. The other idler sprocket 49 is mounted on a shaft 79 in the lower left corner of the housing, as viewed in FIG. 11, and occupies a similar inclined position relative to the horizontal. The path of the flexible chain 40 is indicated in FIGS. 10 and 11 and may be traced as follows: After leaving idler sprocket 49, the chain 40 follows an arcuate guide rail on to the peripheral surface of the hollow vertical stem 25 at the level of the lower flight of the spiral track 211. As in the embodiment of FIGS. 1-6, the chain 40 is supported on the floor of the helical track 20 and is driven spirally upwardly, as indicated schematically in FIG. 11. At a plurality of levels, three being indicated in the illustrated embodiments of FIGS. 18-12, the chain 40 is engaged by the drive sprockets 47 which, being driven rotationally by the shaft 45, drive the chain 40 spirally upwardly. At the levels of the drive sprockets 47, the chain 40 is held against the teeth of the sprocket by arcuate guide members 31. At the uppermost flight, the chain leaves the track 20 and is engaged by drive sprocket 89. After leaving drive sprocket 89, chain 40 twists downwardly over the inclined idler sprocket 48 in the upper corner of the housing and then diagonally downwardly to the inclined idler sprocket 49 in the lower corner of the housing.

As the embodiment illustrated and described in FIGS. 1-6, the chain 40 of FIGS. 10-15 is provided at spaced intervals with pusher bars 65. These bars 65 may be generally similar to the bars 238 shown in FIG. 7. As seen best in FIG. 13, pusher bar 65 is pivotally mounted on the chain 40, as at connector 66, and is movable and downwardly to allow the bar 65 to follow the floor 220 of the track 20. In FIG. 12, the floor 220 of the track 20 is assumed to be of corrugated design, and is similar to floor 220 illustrated in FIGS. 7 and 9. The bar 65 is provided with elements 67 having depending legs 68. The elements 67 are adapted to ride on the crest of the corrugations of the floor 220, with the legs 68 projecting down into the troughs of the floor, so as to push along any small items which may fall into the troughs.

As indicated previously, chain 40 and its drive means, illustrated in FIGS. 10-15, constitute the currently preferred form of chain and drive. The advantages of this form of chain and drive over that depicted in FIGS. 1-6 includes the following: The large rollers 41 decrease the frictional resistance to the chain as it is pulled around the stem 25. The additional drive sprockets 47 at different levels along the stem 25 assist materially in driving the chain. While chain 40 is not adaptable without twisting to being driven by sprockets which are orthogonally related, whereas chain 35 is, nevertheless chain 40 has the ability to twist and to be trained over sprockets which are angularly disposed relative to other sprockets.

What is claimed is:

1. Apparatus for cleaning small items of manufacture comprising:

a. a housing; b. a vertical stem in said housing;

c. a helical track wound about said stem and supfrom said upper level flight of said helical track.

ported thereon, said track having at least one lower 2. Apparatus according to claim 1 wherein: level flight, at least one intermediate flight, and at a. said sprocket drive means is adapted to drive at least one upper level flight; least two of said sprockets; d. means for directing items to be cleaned to said b. means are provided for mounting one of said lower level flight of said track; 10 driven sprockets at the level of the uppermost flight e. means for supplying liquid cleaning-solution to said of said track.

lower level flight, including 3. Apparatus according to claim 2 wherein: i. a first sump for said cleaning solution, a. means are provided for mounting other of said ii. at least one jet spray at said lower level flight, driven sprockets at spaced apart levels along said iii. a first pump for pumping cleaning solution to stem;

said spray jet, and, iv. track means on the floor of said helical track defining parallel troughs in the longitudinal direcb. a vertical drive shaft is provided within said stem for driving said last-named sprockets. 4. Apparatus according to claim 1 characterized in tion of said track for carrying said cleaning solutions downwardly to said first sump; f. heat means for supplying a distillate cleaning soluthat said heat means for supplying a distillate cleaning solution to an intermediate-level flight of said track includes:

tion to said intermediate flight; g. heat means establishing a drying zone at said upper level flight; h. means for transporting said items to be cleaned spirally upwardly along said helical track through said cleaning solution at said lower level flight, through said distillate zone at said intermediate flight, and throubh said drying zone at said upper level flight, including i. an endless chain adapted to be driven spirally upwardly along said helical track, said chain being flexible and adapted to be moved in planes which are inclined at an angle to each other,

ii. pusher arms fixed to said endless chain at spaced intervals,

iii. a plurality of sprockets about which said chain is trained, at least one sprocket being mounted for rotation on an axis inclined at an angle to the that said pusher arms extend laterally from said endless chain.

6. Apparatus according to claim 3 characterized in that said track has at least six flights.

7. Apparatus according to claim 1 characterized in that said pusher arms are provided with depending legs extending down into said troughs.

Claims (7)

1. Apparatus for cleaning small items of manufacture comprising: a. a housing; b. a vertical stem in said housing; c. a helical track wound about said stem and supported thereon, said track having at least one lower level flight, at least one intermediate flight, and at least one upper level flight; d. means for directing items to be cleaned to said lower level flight of said track; e. means for supplying liquid cleaning solution to said lower level flight, including i. a first sump for said cleaning solution, ii. at least one jet spray at said lower level flight, iii. a first pump for pumping cleaning solution to said spray jet, and, iv. track means on the floor of said helical track defining parallel troughs in the longitudinal direction of said track for carrying said cleaning solutions downwardly to said first sump; f. heat means for supplying a distillate cleaning solution to said intermediate flight; g. heat means establishing a drying zone at said upper level flight; h. means for transporting said items to be cleaned spirally upwardly along said helical track through said cleaning solution at said lower level flight, through said distillate zone at said intermediate flight, and throubh said drying zone at said upper level flight, including i. an endless chain adapted to be driven spirally upwardly along said helical track, said chain being flexible and adapted to be moved in planes which are inclined at an angle to each other, ii. pusher arms fixed to said endless chain at spaced intervals, iii. a plurality of sprockets about which said chain is trained, at least one sprocket being mounted for rotation on an axis inclined at an angle to the axis of the others of said sprockets, and iv. drive means for driving at least one of said sprockets; and i. means for discharging the cleaned and dried items from said upper level flight of said helical track.

2. Apparatus according to claim 1 wherein: a. said sprocket drive means is adapted to drive at least two of said sprockets; b. means are provided for mounting one of said driven sprockets at the level of the uppermost flight of said track.

3. Apparatus according to claim 2 wherein: a. means are provided for mounting other of said driven sprockets at spaced apart levels along said stem; b. a vertical drive shaft is provided within said stem for driving said last-named sprockets.

4. Apparatus according to claim 1 characterized in that said heat means for supplying a distillate cleaning solution to an intermediate-level flight of said track includes: a. a boil sump receiving overflow from said first sump; b. a condenser and water separator for condensing vapors distilled from said boil sump and collecting the same; c. spray jets at an intermediate-level flight of said track; d. a second pump for pumping distillate to said spray jets at said intermediate-level flight.

5. Apparatus according to claim 1 characterized in that said pusher arms extend laterally from said endless chain.

6. Apparatus according to claim 3 characterized in that said track has at least six flights.

7. Apparatus according to claim 1 characterized in that said pusher arms are provided with depending legs extending down into said troughs.

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