US3343483A

US3343483A - Electrostatic printing with stencils mounted on a drum

Info

Publication number: US3343483A
Application number: US439720A
Authority: US
Inventors: Marlin A Schueler
Original assignee: UNIMARK CORP
Current assignee: UNIMARK CORP
Priority date: 1965-03-15
Filing date: 1965-03-15
Publication date: 1967-09-26
Anticipated expiration: 1984-09-26
Also published as: DE1486867B1; IL25348A; GB1106872A

Description

Sept. 26, 1967 M. A. SCHUELER 3,343,433

ELECTROSTATIC PRINTING WITH STENCILS MOUNTED ON A DRUM 4 Sheets-Sheet 1 Filed March 15, 1965 nN W: H MIHIHHWIH wu ch IW l HIH .mIH

mum mm wn no MHUHmHH m INVENTOR- MARLIN A. SCHUELER E a [ff/law ATTORNEYS p 26, 1967 M. A. SCHUELER 3,343,483

ELECTROSTATIC PRINTING WITH STENCILS MOUNTED ON A DRUM Filed March 15, 1965 4 SheetsSheet 2 (was? mnxaxmaxi-axmxmx 5 IE'IIEFLA l I I 1 131cm? Dim DXG-JIQIQIGL INVENTOR. MARLIN A. SCH UELER 'fw /rwmwo AT TORNEYS Sept. 1967 M. A. SCHUELER 3,343,483

ELECTROSTATIC PRINTING WITH STENCILS MOUNTED ON A DRUM Filed March 15, 1965 4 Sheets-Sheet I5 INVENTOR.

MARLIN A. SCHUELER ATTORNEYS p 26, 1967 M. A. SCHUELER 3,343,483

ELECTROSTATIC PRINTING WITH STENCILS MOUNTED ON A DRUM Filed March 15, 1965 4 Sheets-Sheet 4 INVENTOR.

MRLEN A. SCHUELER BY 7 y m Y ATTORNEYS United States Patent ()fifice 3,343,483 Patented Sept. 26, 1967 3,343,483 ELECTROSTATIC PRINTING WITH STENCILS MOUNTED ON A DRUM Marlin A. Schueler, Danville, Calif., assignor to Unimark Corporation, a corporation of California Filed Mar. 15, 1965, Ser. No. 439,720 8 Claims. (Cl. 101-114) This invention relates to electrostatic printing generally along the lines described in US. Patent No. 3,081,698, issued Mar. 19, 1963, to C. O. Childress et -al., in that a surface-dry powder is employed as the printing medium, and such powder is conducted across an air gap from a supply thereof onto the subject to be printed upon. The transfer of the powder is effected by establishing an electrostatic field between the powder and the said object.

One of the objects of this invention is the provision of improved apparatus for printing by the above system, in which a substantially uniform air gap is maintained between the powder and the article irrespective of variations in the size of the articles.

Another object of the invention is the provision of an improved printing system for printing on articles or material, and which system includes improved conveyor means for carrying the articles.

An added object of the invention is the provision of improved means for supporting the screen stencils that, in turn, support the powder to be transferred onto the articles or material to be imprinted.

A still further object is the provision of improved means for distributing the powder onto the screen stencils that support the powder for transfer onto the objects to be printed upon, and for moving a substantially uniform :layer of said powder through the screen openings for said transfer thereof.

An additional object is the provision of improved means for successively transferring symbols, designs, etc. onto material or objects passing below the screen.

Another object is the provision of improved means and method for rapidly and clearly electrostatically printing on objects of irregular shape and size, such as potatoes, avocados, cucumbers, etc., by the system broadly described in the aforesaid patent in that the printing medium is powder that is transferred, electrostatically, across an air gap onto the articles.

A further object is the provision of structure whereby multicolor electrostatic printing is enabled.

Other objects and advantages will appear in the description and drawings.

FIG. 1 is a side elevational view of apparatus illustrative of a printing system embodying the present invention and the method.

FIG. 2 is a semi-diagrammatic top plan view of the apparatus of FIG. 1.

FIG. 3 is a fragmentary cross-sectional view taken along line 3-3 of FIG. 2 showing drive means.

FIG. 4 is an enlarged fragmentary side elevational view of the drum and associated mechanism at the printing station.

FIG. 5 is a cross-sectional view generally as viewed from line 5-5 of FIG. 4.

FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 5 with portions cut away for purposes of clarity.

FIG. 7 is an enlarged cross-sectional view taken along line 7-7 of FIG. 4.

FIG. 8 is a cross-sectional view taken along line 8-8 of FIG. 7.

FIG. 9 is a fragmentary cross-sectional view taken along line 9-9 of FIG. 8.

FIG. 10 is a fragmentary bottom plan view of part of the printing drum as seen from line 10-14 of FIG. 8.

FIG. 11 is a fragmentary side elevational view of the portion of the machine shown in FIG. 8 showing in broken lines interior parts in a different position from those shown in full line in FIG. 8.

FIG. 12 is a fragmentary cross-sectional view taken along line 12-12 of FIG. 11.

FIG. 13 is a fragmentary cross-sectional view showing a modification of part of the printing drum, partly in elevation.

In detail, refer-ring to FIGS. 1, 2, the apparatus illustrated for carrying out the invention comprises a feed hopper 1 or any other suitable feed device, at one end of an endless, horizontally elongated conveyor, generally designated 2. Articles or material to be imprinted are fed from the hopper or feeder 1 onto the feed end of conveyor 2, which may also be called the rear end of the apparatus, for being carried forwardly to and past the printing station generally designated 3 to the discharge or forward end 4 of the apparatus where the printed articles or material are discharged.

The use of the words rear, rearward, forward and forwardly are used with respect to the direction of movement of the articles or conveyor 2, the latter carrying the articles forwardly.

Conveyor 2 comprises a pair of endless chains 5 (FIGS. 4, 5), opposed links of which carry shafts 6 that respectively support adjacent pairs of rollers 7 between said chains for rotation of said rollers about the respective axes of said shafts.

The chains 5 extend over pairs of sprocket wheels 9, 10 (FIG. 1) respectively at the rear and forward ends of the apparatus, which pairs of wheels are carried by shafts supported for rotation in bearings carried by frame 1.

The rear end portion 11 (FIG. 1) of conveyor 2 extends slantingly upwardly from the feeder 1, the upper runs of said chains being slidably supported on the upper edges of guide strips 12 (FIG. 5) that, in turn, are rigid with the frame 1 and are upwardly inclined in a forward direction from feeder 1 for slantingly supporting said portion 11.

The lower runs of conveyor 2 are similarly supported on the upper edges of guide strips 13 (FIG. 5) that are also rigid on frame 1.

At the upper end of portion 11, the upper and lower runs of the chains 5 respectively extend over rollers or sprocket wheels 14, 15 (FIG. 1) or any other suitable means and from said rollers or wheels the upper and lower runs of the chains 5 extend horizontally to and over the end pair of sprocket wheels 10.

The guide strips 12, 13 support the conveyor against sagging, and this is articularly important with the upper run, inasmuch as it carries the articles to be printed upon past and below the printing device at the printing station 3.

The means for driving the chains and other portions of the apparatus comprises a motor 18 (FIG. 1) in driving relation with a sprocket wheel 19. Sprocket wheel 19 is connected with a sprocket wheel 20 by a chain 21, said wheel 29 being secured on. a shaft 22 that, in turn, is rotatably supported at its ends in bearings 23 (FIG. 3) carried by frame 1, said shaft extending transversely of the conveyor below the upper run of chains 5 at a point adjacent to the printing station 3.

The shaft 22 has a bevel gear 24 (FIG. 3) secured thereto in a position between the opposed side frame members 25 of frame 1, and gear 24 is in mesh with a bevel gear 26 on a shaft 27 that extends parallel with conveyor 2 between said frame members 25. This shaft 27 is rotatably supported at its ends in bearings carried by said frame members, and gear 26 is secured on one end of said shaft while a bevel gear 28 is secured on its opposite end. The gear 28 is in mesh with a bevel gear 29 that is sewith the said chains through suitable gaps (not shown) in the guide tracks 11 for driving the chains.

The shafts 6 of rollers 7 are equally spaced along chains 5, and the rollers themselves are the same, each being circular in cross-sectional contour and the central portions 34 (FIG. of each roller may be cylindrical and of reduced diameter while the opposite end portions 35 are of progressively increasing diameter from said central portion in opposite outward directions to provide surfaces that are slightly concave lengthwise of the rollers. These end portions commence at their adjacent ends at said central portion, to be of slightly larger diameter than the central portion.

By this arrangement'each adjacent pair of rollers will provide a cradle for supporting a vegetable, such as a potato, avocado or other fruit or vegetables. The rollers shown are suitable for potatoes, each of which centers itself in the cradle formed by an adjacent pair of rollers, and the rollers, being rotatable, facilitate such centering,

' and also facilitate proper printing on each article, as will be described later.

The rollers 7 are spaced apart. and their diameters are such that an object cradled orsupported by one pair will not contact the articles supported by the adjacent pairs that include one of the rollers of said one pair. Such articles are generally indicated at 73 (FIGS. 4, 5).

Frame 1 is provided with a pair of upwardly projecting posts 37 (FIGS. 4, 7) that extend a substantial distance above the conveyor 2. Posts 37 are in spaced opposed relation at opposite sides of the conveyor and are rigid with frame 1.

A horizontal shaft 39 is rotatably supported at its ends in hearings carried by the posts 37 at their upper ends.

Two pairs of arms 40, 41 (FIGS. 4, 5, 7) are respectively supported at one of their ends on the opposite ends of shaft 39 (FIG. 4). These arms extend generally horizontally from shaft 39 (FIG. 1) in the direction of movement of the upper run of conveyor 2, and arms 40 may be called the inner arms, since they are adjacent to each other, while arms 41 are the outer arms, or the ones outside the arms 40.

Supported between the forward ends of

arms

40, 41 is a polysided printing drum generally designated 42 (FIGS. 1, 4) which drum is 'at printing station 3.

Before going into complete detail as to drum 42, it is sufficient at this point to say that it comprises a pair of spaced opposed side plates 43, 44 (FIGS. 5, 7) connected around their outer peripheral edges by flat plates 45 (FIG. 8) that carry the screens, as will be described later more in detail.

Sides plates

43, 44 of drum or wheel 42 are respectively centrally secured on coaxial sleeves 46, 47 (FIG. 7) through which a horizontal shaft 48 extends, and outwardly of side plate 44 and sleeve 47 is a timing pulley 49, the hub of which is coaxial and rigid with sleeve 47. Shaft 48 also extends through the hub of pulley 49 and through another sleeve 50 outwardly of and coaxial and rigid with said hub.

The bores of the

sleeves

46, 47, 59 and the hub of pulley 49 are substantially greater in diameter than the outside diameter of shaft 48 (FIG. 7). Thus the shaft 48 and the drum or wheel 42 are adapted to move relatively in a direction transversely of said shaft. FIG. 7 shows space 51 between the bores of said sleeves and shaft 48.

Ball bearings 54 (FIGS. 6, 7) respectively on

sleeves

46, 50 support said sleeves for rotation in the outer ends of arms 40, hence the drum or wheel 42 is rotatably supported in the outer ends of said arms 40.

The

sleeves

46, 47, 50, and the hub of pulley 49 may,

Y 4 insofar as function is concerned, he considered as a hollow shaft through which the shaft 48 freely extends and on which hollow shaft the drum or wheel 42 is supported for rotation therewith.

Referring back to FIGS. 3, 4, the shaft 22 that carries the sprocket wheel 20 and which shaft has a timing pulley 55 secured thereon at the side of the apparatus opposite to the side shown in FIG. 1 (FIG. 4) and a timing belt 56 connects pulley 55 with a timing pulley 57 on shaft 39.

Shaft 39 also has a timing pulley 58 thereon that is connected by a timing belt 59 with pulley 49 on sleeve 47 (FIG. 7) that is secured to the printing wheel or drum 42. Since the latter as well as the hollow

shaft comprising sleeves

46, 47, 50 and the hub of wheel 42 are rotatable as a unit in bearings 54, it is seen that the train of timing belts and pulleys to the pulley 47 will elfect rotation of the wheel 42 in timed relation to conveyor 2 upon actuation of motor 18.

The words timing belt, and timing pulley and the plural thereof, refer to conventional belts and pulleys that are connected for movement together in substantially the same manner as sprocket chains and sprocket wheels.

Shaft 48 that extends through the sleeves forming the hollow shaft is rigidly secured at its opposite ends to the forward or outer ends of outer arms 41 (FIG. 7) through which the outer ends of shaft 48 extend, said last mentioned outer ends being of reduced diameter to provide axially outwardly facing shoulders against which the inner or opposedly facing surfaces of the outer ends ofarms 40 are clamped by nuts 62.

Radially outwardly projecting

flanges

63, 64 respectively on

sleeves

46, 50 may function to space bearings 54 from side plate 43 of the printing drum and from the pulley 49.

Carried by and rigid with side frame members 25 are upstanding members 65 (FIG. 5) having opposedly extending arms 66 (FIG. 5), each of which, in turn, carries a resilient bumper 60 (FIG. 6) at their adjacent ends. These bumpers are adjacent to the outer ends of outer arms 41 and support said outer ends of arm 41 thereon.

Secured to the outer end of each arm 40 is a pair of laterally outwardly projecting, vertically spaced

stop elements

67, 68, the elements 67 being the upper stop elements and elements 68 being the lower ones, and the elements of their pairs ext-end across the upper and lower edges or sides of the outer arms 41. Vertical adjusting screws 69 are threadedly secured on the outer ends of arms 41 and project downwardly and upwardly from the upper and lower sides of said arms for engagement with

stop elements

67, 68 respectively for adjustahly limiting the degree of up and down movement of the outer ends of arms 41 relative to the outer ends of arm 40.

By the foregoing construction it is seen that drum 42 and the outer ends of arms 40 will move upwardly from a lowermost position relative to the shaft 48, before the.

outer ends of arms 41v and shaft 48 move upwardly, but as soon as the lower screws 69 on the outer ends of arms 41 are engaged by lower stop members 68, the outer ends of

arms

40, 41 will move upwardly together.

When arms 41 are in their lowermost position, the 7 upper adjusting screws 69 on the outer ends of arms 41 will support the upper stop members 67 thereon and the outer ends of arm 41 will be supported on stationary resilient bumpers 60.

As has been explained, the

side plates

43, 44 of drum 42 are connected by stencil or screw supporting plates 45. These plates 45 are of the same size and are flat and the outer peripheral edges of the

side plates

43, 44 are polygonal in outline so that the said flat screen or stencil carrying plates 45 may be secured along two of their opposite edges from end to end of each pair of opposed parallel straight outer peripheral edges of

side plates

43, 44 and may be secured thereto by any suitable means such as screws 70. Said plates 45 and the screws thereon enclose the space between the

side plates

43, 44 and form the .peripheral outer sides of the drum 42, the screen being described below.

Each plate 45 is formed with an aperture 71 (FIG. 13) and a flat stencil screen 72 (FIGS. 8, 13) extends across the opening, being positioned at the radially inwardly facing side of each aperture so that the thickness of the plate 45 will be between the screen 72 and the article, such as potato 73, to space the outer surface of the potato that is opposed to said screen from the screen, thereby providing a relatively uniform air gap between the screen and the potato.

Each screen 72 may be of woven nylon or any other suitable electrically chargeable material, and the openings of the area defining the design to be printed on article or material 73 are of a uniform size for passing the particles of the powder therethrough as described in the hereinabove mentioned patent. The stencil screen 72 may also be formed in any suitable manner, one being as described in said patent.

A printing mechanism 77 (FIG. 8) is disposed within the drum 42, which mechanism, as an assembly, is carried by shaft 48. A supporting member 78 for said printing mechanism, is keyed to said shaft 48 against rotation relative to the latter.

A rotary brush generally designated 80 has a cover, preferably of mohair or the like, providing the short, radially outward bristles of such brush, and a horizontal shaft 82 rotatable at its ends in hearings on support 78 support the brush for rotation. Shaft 82 is parallel with the shaft 48, and the latter is parallel with the shaft supporting the drum 42.

When the drum 42 is in its lowermost position with the upper stop members 67 supported on upper screws 69, the brush 80 will be out of engagement with the inner surface of the outer side of the drum, or the lowermost screen 72, and in this position the brush is free from driving engagement with a drive means of any kind.

Also carried by the supporting member or body 78 is a magazine or holder 83 for the printing powder, which may be in loose powder form or compressed into the form of a block or stick 84 extending generally radially of the axis of brush 80 with one end frictionally engaging the outer surface of said brush over the area of the latter that is adapted to wipe or brush across the openings in screen 72. This stick preferably is located above the brush 80 and is of a texture or consistency whereby adequate powder from the stick will abrade onto the bristles or outer periphery of the brush to be carried by said bristles onto the screen 72 when the bristles move downwardly to the screen and also said powder so deposited on to the upper or inner surface of the screen will be moved through the screen openings upon rotation of the brush while in engagement with the screen, as will later be described more in detail.

The holder 83 for stick 84 is generally tubular with an open end directed toward the brush 80 out of which the lower end of the stick 84 extends into said engagement with the brush, and one or more weights 85 may be slidably supported in the upper end of the holder 83 against the upper end of the stick to maintain the lower ends of said sticks against the brush under suitable uniform pressure under the gravitational force of the weights.

Secured to brush 81) coaxial therewith is a ratchet wheel 86 (FIG. 8). As seen in FIG. 8, wheel 86 is rotatable counterclockwise, or in a direction opposite to the direction of rotation of drum 42, and a spring leaf 87 secured to any stationary part of or attached to support 78 engages the teeth of wheel 86 to prevent rotation of the latter and brush 80 in the same direction of rotation as that of the drum.

One side of the member 78 is formed with a recess 89 (FIGS. 8, 9) into which a shaft 90 projects, and on the projecting end of said shaft and in said recess are a pair of

bearings

93, 94. Bearing 93 supports one end of a crank arm 95 while bearing 94 supports an arm 96 at a point intermediate the ends of the latter for rotation of

arms

95, 96 relative to each other about the axis of shaft 90.

One side of arm 95 faces arm 96 (FIG. 8) and said side is relieved at the surface so engaging arm 96 to provide a shoulder 97 adapted to engage an edge of arm 96 to form a stop to prevent the

arms

95, 96 from swinging relative to each other to a more acute angular relationship than is shown in FIG. 8.

A stop pin 98 stationary on the stationary supporting member or body 78 is adapted to be engaged by the upper end portion of arm 96 above shaft to limit the counterclockwise rotation of arm 96 as seen in FIG. 8, and a spring 99 connected with said upper end of arm 96 and the body 78 yieldably holds said upper end against said stop pin 98.

A spring 108 connects the portion of arm 96 below shaft 90 with the arm to yieldably hold the arm 96 against the shoulder 97 on arm 95.

Pivotally mounted on the outer end of arm 95 by pivot 192 is a pawl 103 having a tooth at one end that is yieldably held into engagement with the teeth of ratchet wheel 86 by means of a spring 104 that connects an arm on the other end of the pawl with an arm 106 rigid with and projecting from arm 95.

When the roller or brush 80 is in the position for printing, as seen in FIG. 8, the lower end of arm 96 is in what may be termed its rear and lowermost position directed substantially vertically, and can be moved only forwardly or clockwise.

Rigid with the side plate 44 of drum 42 that is adjacent and opposed to arm 96 are a plurality of lugs 107 that are rigid with said side plate and equally spaced from the axis of the drum with one lug for each screen circumferentially spaced equal distances from each other. The lower end of arm 96 is in the path of said lugs, and the latter are positioned so as to engage the lower end of each arm at a point when each screen is substantially in printing position. As the drum is driven clockwise in FIG. 8 substantially a distance at least equal to the distance circumferentially of the drum of the printing area of the screen, the brush 86 will be rotated counterclockwise due to the ratchet-pawl engagement between ratchet wheel 86 and pawl 103, and at the end of such movement the lower end of arm 96 will be'disengaged from the lug 197 that is in engagement therewith and the pawl 183 and arm 96 will spring back to starting position until the next lug 197 in the annular row thereof engages the lower end of arm 96 and again rotates the brush 80.

An electrical DC. power source 168 (FIG. 1) of the desired voltage may electrically connect with the rollers of conveyor 2 at the printing station and with the brush 80 or each screen 72 when the latter moves past the printing station to thereby establish an electrical potential between the screen and the article, such as potato 73 when they are in the position shown in FIG. 8, and the bristles of the roller 89 will move the discrete powder particles through the screen openings and into the electrostatic field in the air gap between the screen and each potato for conduction onto each potato in the pattern corresponding to the pattern of the screen openings. Conductor 199 may extend from the voltage source to the brush 89 or screen 72 and conductor 118 to the rollers 7 through member 114, or any other suitable and conventional circuit may be provided to establish the desired electrical potential.

Also, referring to FIG. 2, an air jet or nozzle 111 may be supported by any suitable portion of the stationary frame that supports the operating elements of the machine, in a position for blowing air against the outer sides of the screens after each printing operation for cleaning the outer surfaces of the outer periphery of the printing drum and screens of any printing powder that may adhere thereto. Such source of compressed air is 7 indicated in FIG. 2 at 112 and the line leading to the nozzle is indicated at 113.

After the articles have been carried beyond the printing station 3, they are moved past any suitable valve actuated fixing device 115 for spraying a fixative onto the powder and article for fixing the powder onto each article. Obviously a conventional heater may be used instead of a fixative, it being understood that either of these ways of fixing the powder is conventional, and each may be valve actuated.

In operation (FIG. 2) articles 73 are deposited on adjacent pairs of rollers 7 of the upper run of conveyor for automatic centering between or on each pair. The articles may be fed onto said upper run from hopper 1, or in any other suitable manner.

From hopper 1 said articles are carried by the conveyor 2 for movement to and past the printing station 3 and below the printing drum 42.

When there is no material, or no article in a printing position below the drum 42, the latter is nevertheless rotating in synchronism with the conveyor 2, but the outer ends of arms 40 support the drum in its lowermost position, with the abrading and powder applying brush 82 stationary and spaced above the printing screens or the walls forming the outer periphery of the drum 42. 7 Upon material, or an article, on conveyor 2 moving toward a position below the drum 42, the outer peripheral wall of the drum, during rotation of the latter, will engage the material or article, causing the drum to be elevated so that the radially inner surface of the screen will engage the abrading roller 80, and at the same time the lower end of arm 96 will move into the path of travel of the lugs 107 to be engaged thereby. This engagement occurs at the point just in advance of, or it may be at the point where the pattern of openings in screen 72 commence as the drum rotates, and when the screen is in spaced opposed relation to the material or article on the conveyor 2.

Continued rotation of the drum 42 after the outer end of arm 96 is engaged by a lug 107 results in rotating the powder abrading and distributing brush 80 relative to the inner surface of the screen through movement of arm 96 by lug 107 and consequent actuation of the ratchet wheel 86 by pawl 103.

The lug or projection 107 will clear the lower end of arm 96 after each printing operation and the roller actuating mechanism including arm 96 and pawl 103 will quickly be returned to starting position for another actuation of roller 80 by the next approaching lug or projection 107, but should there be no article or material on the conveyor in a position for printing the drum will automatically move downwardly and away from the roller 80 under the influence of gravity, and the lugs 107 will not engage the arm 96, hence there will be no rotation of the abrading roller 80.

The employment of the separately replaceable screens enables quick replacement if for any reason one of the screens is not printing properly due to the screen, or each screen may be formed for printing different information, usually in the latter case the material to be printed.

In FIG. 12 a modification of the powder feed is shown in which a holder 117, similar to holder 83, is shown in which there is a plurality of sticks or bodies 118 of compressed powder in a row, the said bodies being separated by partitions 119 dividing the housing or container into separate compartments in side by side relation for separating the bodies. The latter are respectively supported in engagement with separate brushes 120 rigid on a single shaft 121 corresponding to shaft 82 in FIG. 8 and actuated in the same manner as described for roller 80, the shaft having a ratchet wheel 122 secured to one end thereof for engagement with pawl 103 when used in the arrangement described in FIG. 8.

By the above structure, a multicolor printing may be 8 readily performed, each body of powder being a different color.

The employment of a compressed body of powder from which a uniform amount is abraded only when a printing operation is performed, enables the operator to reduce the amount of floating or surplus powder to a negligi-ble degree. Weights such as weights or any other suitable form of pressure are used in the housing or holder in FIG. 12, each of the bodies being urged into engagement with one of the brushes. Thus means is employed for varying the pressure of the bodies against the rollers by increasing or decreasing the number of weights, so that more or less powder is abraded from each block, stick or body of powder.

In connection with the foregoing, it may be emphasized that the character of the printing is to an appreciable degree dependent upon the uniformity of the amount of powder brushed through the openings in each printing screen.

I claim:

1. In an electrostatic printing machine, the combination comprising:

(a) a drum-like wheel supported for rotation about a horizontally disposed axis, and having radially outwardly outer peripheral walls that, in turn, include an annular row of screens coaxial with said axis, each having radially inwardly and radially outwardly facing sides relative to said axis, and each formed with a plurality of openings in a predetermined pattern corresponding to the designs to be printed;

(b) a conveyor including article supporting means for supporting articles to be printed upon for movement along a predetermined path of travel projecting from said article supporting means and means for actuating said conveyor for moving said article supporting mean-s to move the articles thereon along said path;

(c) wheel supporting means for supporting said wheel over said path at'a point therealong for movement of one of said screens into opposed printing relation to each of said articles when each article is closest to said wheel, and means connecting said conveyor with said'wheel rotating the latter to move screens to said opposed printing relation upon actuation of said conveyor;

(d) a supply of printing powder Within said wheel;

(e) powder distributing and moving means within said wheel between said supply and each screen when the latter is in printing relation to one of said articles for depositing powder from said supply onto the radially inwardly facing side of said screen, and for moving the powder so deposited through the openings in each screen to the radially outwardly side of each screen;

(f) means for establishing an electrostatic field between the screen and article in said printing relation for conducting the powder moved through said openings onto the article opposed thereto upon any one screen and article being moved to said printing relation;

(g) means on said wheel rigid therewith and around the plurality of openings in each screen projecting radially outwardly of each screen relative to the axis of said wheel for engaging the outer surface of an article on said conveyor around the portion to be printed upon when a screen is in said opposed printing relation to such article for spacing the screen from said article.

2. The combination as defined in claim 1, including:

(h) said conveyor being a row of adjacent pairs of equally spaced rotatable rollers connected for movement along said path, each of said rollers having generally conical end portions with their smaller diameter ends adjacent to each other for supporting and automatically centering each article adjacent tion comprising:

(a) a carrier for supporting material to be printed upon past a stationary printing station;

(b) a screen at said printing station formed with a plurality of openings in a predetermined pattern corresponding to the design to be printed on said material;

(c) screen supporting means for supporting said screen in a position opposed relative to material at said station adapted to be carried therepast by said carrier;

(d) said screen supporting means including a mechanism supporting said screen for movement toward and away from material on said carrier; and

(e) material engaging means connected with said screen movable therewith to a position for engagement with material on said carrier as it is carried therepast and for actuating thereof by movement of said material engaging means past said station for spacing said screen at said station a substantially uniform distance for such material;

(f) means connected with said carrier for moving it and material thereon past said printing station;

(g) powder depositing means for depositing printing powder on the side of said screen opposite to said carrier for passage through the openings in said screen and onto material in opposed relation to the latter at said printing station;

(h) means for establishing an electrostatic field between said screen and material at said station when said material is in said opposed relation only;

(i) and means adjacent to said station supported for movement to a position for engagement with said material on said carrier at said station during movement of the latter therepast actuatable by said engagement and movement for moving powder on said screen through said openings and into said electrostatic field, said last mentioned means being automatically movable to an inoperative position in the absence of material on said screen, whereby no powder will be deposited by said powder distributing means on said screen in the absence of a material at said station in a position to be printed upon.

4. In an electrostatic printing machine, the combination comprising:

(if) means connected with said carrier for moving it and material thereon past said printing station;

(g) powder depositing means for depositing printing powder on the side of said screen opposite to said carrier for passing through the openings in said screen and onto material in opposed relation to the latter at said printing station;

(h) a supply of printing powder spaced from said screen;

(i) movable powder-conducting means supported for movement from said supply of printing powder to said screen and operatively connected with said screen for conducting powder from said supply to said screen upon movement of said screen under the influence of movement of said material engaging means when said material engaging means is in engagement with material on said carrier.

5. An electrostatic printing machine, comprising:

(a) a horizontally disposed, drum-like wheel supported for rotation about a horizontal axis, and having an annular row of screens coaxial with said axis defining outer peripheral walls of said wheel, each screen formed with a group of openings is a pattern corresponding to a design to be printed, said screens having, radially inwardly and outwardly facing sides, relative to said axis;

(b) a conveyor including a horizontally extending row of article suporting means for supporting thereon articles of different vertical thicknesses to be printed upon, whereby said articles will project different distances above said row of article supporting means, said article supporting means being supported for movement longitudinally of said row thereof and con-veyor actuating means connected with said conveyor for so moving said article supporting means;

(c) wheel supporting means for supporting said wheel for rotation about its axis, and in a position over said row of article supporting means for moving said screen, in succession into opposed printing relation to articles on said article supporting means at the point along said row of article supporting means at which said screens are closest to articles on said article supporting means upon rotation of said wheel and upon actuation of said conveyor;

((1) wheel actuating means operably connected with said conveyor actuating means for simultaneously rotating said :wheel and for actuating said conveyor, for movement of the screens and articles on said article supporting means to said printing relation at said point;

(e) means for establishing an electrostatic field between said screens and articles on said article supporting means at said point for conducting printing powder moved through the group of openings in each screen onto an article on an article supporting means at said point;

(if) a powder supply within said wheel and powder distributing means for depositing powder therefrom onto the radially facing side of each screen at said point and for moving the powder so deposited through the group of openings in such screen and into said electrostatic field, during rotation of said wheel and actuation of said conveyor;

(g) article engaging means on said wheel adjacent to each screen for engaging an article on article supporting means at said point for spacing such screen and article a substantially uniform distance from each other during said rotation of said wheel and actuation of said conveyor;

(h) said wheel supporting means including means supporting said Wheel for bodily movement different distances toward and away from said article supporting means under the influence of articles engaged by said 11 article engaging means at said point, according to said different thicknesses of articles on said article supporting means for maintaining substantially uni form spacing between the screens and articles on said printing relation at said point.

6. In a printing machine as defined in claim (i) each of said screens being planar, and means for removably securing each of said screens to said wheel around the outer periphery thereof for selective replacement of said screens, and said screens, respectively, being tangential to a circle coaxial with the axis of said screen.

7. In a printing machine as defined in claim 5:

(i) means supporting said powder distributing means within said wheel for bodily movement of said wheel relative thereto in a direction toward an article supporting means and out of engagement with said powder distributing means, at said point, in the absence of an article on an article supporting means being in engagement with said article engaging means.

8. In a printing machine as defined in claim 7:

(j) said powder supply being a unitary body of compacted printing powder abradable upon movement of said powder distributing and moving means thereof; and

(k) said powder distributing means being a rotary brush having its radially outwardly facing surface in frictional engagement with said body;

12 (1) brush rotating means including meansrcspective- 1y on'said wheel and brush supported for movement into driving relation with each other for rotating said brush upon engagement of said article engaging means with an article on said article supporting means at said point, and movable out of said engagement with each other in the absence of an article on such article supporting means at said point.

References Cited UNITED STATES PATENTS 1,167,004 1/1916 Magna 101-38 1,501,817 7/1924 Sevigne 101-40 2,432,202 12/1947 Mason 101-227 2,473,729 6/ 1949 Salz 118-637 2,866,403 12/1958 Simmerman et al. 101-38 X 2,950,671 8/1960 Allen et a1. 101-40 2,974,632 3/1961 Westervelt et al. 118-637 2,987,037 6/1961 Bolton 118-637 3,081,698 3/1963 Childress et al. 101-129 3,115,091 12/1963 Hakogi 101-40 X 3,198,116 8/1965 Mikurak 101-40X 3,218,967 11/1965 Childress 101-114 3,218,968 11/1965 Childress et a1 101-115 3,228,326 1/ 1966 Childress et al.

ROBERT E. PULFREY, Primary Examiner.

E. S. BURR, Assistant Examiner.

Claims

1. IN AN ELECTROSTATIC PRINTING MACHINE, THE COMBINATION COMPRISING: (A) A DRUM-LIKE WHEEL SUPPORTED FOR ROTATION ABOUT A HORIZONTALLY DISPOSED AXIS, AND HAVING RADIALLY OUTWARDLY OUTER PERIPHERAL WALLS THAT, IN TURN, INCLUDE AND ANNULAR ROW OF SCREENS COAXIAL WITH SAID AXIS, EACH HAVING RADIALLY INWARDLY AND RADIALLY OUTWARDLY FACING SIDES RELATIVE TO SAID AXIS, AND EACH FORMED WITH A PLURALITY OF OPENINGS IN A PREDETERMINED PATTERN CORRESPONDING TO THE DESIGNS TO BE PRINTED; (B) A CONVEYOR INCLUDING ARTICLE SUPPORTING MEANS FOR SUPPORTING ARTICLES TO BE PRINTED UPON FOR MOVEMENT ALONG A PREDETERMINED PATH OF TRAVEL PROJECTING FROM SAID ARTICLE SUPPORTING MEANS AND MEANS FOR ACTUATING SAID CONVEYOR FOR MOVING SAID ARTICLE SUPPORTING MEANS TO MOVE THE ARTICLES THEREON ALONG SAID PATH; (C) WHEEL SUPPORTING MEANS FOR SUPPORTING SAID WHEEL OVER SAID PATH AT A POINT THEREALONG FOR MOVEMENT OF ONE OF SAID SCREENS INTO OPPOSED PRINTING RELATION TO EACH OF SAID ARTICLES WHEN EACH ARTICLE IS CLOSEST TO SAID WHEEL, AND MEANS CONNECTING SAID CONVEYOR WITH SAID WHEEL ROTATING THE LATTER TO MOVE SCREENS TO SAID OPPOSED PRINTING RELATION UPON ACTUATION OF SAID CONVEYOR; (D) A SUPPLY OF PRINTING POWDER WITHIN SAID WHEEL; (E) POWDER DISTRIBUTING AND MOVING MEANS WITHIN SAID WHEEL BETWEEN SAID SUPPLY AND EACH SCREEN WHEN THE LATTER IS IN PRINTING RELATION TO ONE OF SAID ARTICLES FOR DEPOSITING POWDER FROM SAID SUPPLY ONTO THE RADIALLY INWARDLY FACING SIDE OF SAID SCREEN, AND FOR MOVING THE POWDER SO DEPOSITED THROUGH THE OPENINGS IN EACH SCREEN TO THE RADIALLY OUTWARDLY SIDE OF EACH SCREEN; (F) MEANS FOR ESTABLISHING AN ELECTROSTATIC FIELD BETWEEN THE SCREEN AND ARTICLE IN SAID PRINTING RELATION FOR CONDUCTING THE POWDER MOVED THROUGH SAID OPENINGS ONTO THE ARTICLE OPPOSED THERETO UPON ANY ONE SCREEN AND ARTICLE BEING MOVED TO SAID PRINTING RELATION; (G) MEANS ON SAID WHEEL RIGID THEREWITH AND AROUND THE PLURALITY OF OPENINGS IN EACH SCREEN PROJECTING RADIALLY OUTWARDLY OF EACH SCREEN RELATIVE TO THE AXIS OF SAID WHEEL FOR ENGAGING THE OUTER SURFACE OF AN ARTICLE ON SAID CONVEYOR AROUND THE PORTION TO BE PRINTED UPON WHEN A SCREEN IS IN SAID OPPOSED PRINTING RELATION TO SUCH ARTICLE FOR SPACING THE SCREEN FROM SAID ARTICLE.