AU637325B2 - Screen printing - Google Patents

Description

COMMONWEA6TH AL 7,3A2 C 0 M M 0 N W E A L T H PATENT ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE CLASS INT. CLASS Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority: Related Art-: NAME OF APPLICANT: ADDRESS OF APPLICANT: NAME(S) OF INVENTOR(S) ADDRESS FOR SERVICE: REEFDALE PTY. LTD.

20-22 Braeside Drive, Braeside 3195 Victoria

AUSTRALIA

DAVIES COLLISON, Patent Attorneys 1 Little Collins Street, Melboorne, 3-JO.

COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: "SCREEN PRINTING" The following statemient is a full description of this invention, including the best method of performing it known to us -la- "SCREEN PRINTING" This invention relates to screen printing machines of the general type which may typically comprise a multiple armed fixed frame and a multiple armed movable frame -nounted to rotate above or below the fixed frame through a series of operative positions or operating stations. Print heads may be operatively connected to the fixed frame and screen platens operatively connected to the movable frame or vice versa. In at least some of the operative positions, the movable frame can be axially moved towards or away from the fixed frame between a non-print position and a print position so that a printing operation can be effected.

The present invention is more particularly concerned with the provision of means for causing the axial movement of the movable frame relative to the fixed frame.

In one arrangement currently in use, the axial movement of the movable frame is effected through a plurality of pneumatic cylinders which operate on yokes guided on guide means and which in turn raise a plurality of rods adapted to engage on a thrust plate mounted to the movable frame. This arrangement is mechanically complicated and is prone to binding and can result in an equal lifting force as being applied to one side of the frame as compared to another side.

The present invention seeks to provide an improved manner of axially mov-ing the movable frame relative to the fixed frame in a screen printing machine.

According to a first aspect of the present invention there is provided a screen printing machine comprising i) an upright post having a longitudinal axis, and a hollow generally cylindrical portion; ii) a fixed frame which is fixed relative to said post, said fixed frame including a plurality of arms which extend generally radially with respect to the longitudinal axis of said post; iii) a movable frame mounted for rotational movement about the longitudinal axis of the post and for axial movement in the direction of the longitudinal axis of said post between a print pcsition and a Il 930305,p: \oper\kay,41788.ca,1 -2non-print position; iv) drive means for causing said axial movement of said movable frame; v) transmission means operatively connecting said drive means to said movable frame said transmission means including a connecting rod operatively connected to said drive means and at least partially disposed within said hollow portion of said post said connecting rod extending generally in the direction of the longitudinal axis of the post, and a support member having support arms which extend generally laterally with respect to the longitudinal axis of the post, said support arms extending through openings in the wall of the hollow portion of the said support arms having support sections operatively connected to said movable frame.

In one form, the drive means may comprise a pneumatic piston/cylinder assembly which is preferably pneumatically operated and which is at least partially disposed within or axially aligned with the hollow portion of the post and operatively connected to the transmission means. In another arrangement, the drive means may comprise an air bag operatively connected to the movable frame and being adapted to be inflated or deflated to cause the actual movement of the movable frame section. The drive means may be located above or below the movable frame and the latter is presently preferred.

The post preferably includes a hollow generally cylindrical portion and the air bag is operatively connected to the movable frame by transmission means. The transmission means may include a connecting rod operatively connected to the air bag and at least partially disposed within the hollow portion of the post, the connecting rod extending generally in the direction of the longitudinal axis of the post. The transmission means may further include a support member having support arms which extend generally laterally with respect to the longitudinal axis of the post, these arms extending through openings in the wall of the hollow portion of the post and having support sections thereon operatively connected to the movable frame.

In this particular form of the invention, the drive means may comprise piston/cylinder assembly which is preferably pneumatically operated and which is at least partially disposed within or axially aligned with the hollow portion of the post 930305,p:\opr\kay,4178.cla.2 -3and operatively connected to the transmission means. Preferably the drive means is disposed towards one end of the post and the counter balancing means is disposed towards the other end of the post.

In alternative arrangement, the drive means may comprise a pair of fluid controlled fluid powered linear actuators such as for example, pneumatic or hydraulic piston/cylinder assemblies operatively connected to the movable frame and disposed externally of the post but preferably adjacent thereto.

The movable frame may be rotatable through a plurality of operating positions in which the movable frame arms are disposed relative to the fixed frame arms such that a printing operation can be effected by axial movement of the movable frame to the print position. The screen printing machine may include primary stop means for inhibiting axial movement of the movable frame unless it is in one of the operating positions.

The apparatus may further include preliminary locating means operable to locate the frames relative to one another prior to axial movement of the movable frame.

Preferred embodiments of a screen printing machine in accordance with this invention will now be described with reference to the accompanying invention in which: Figure 1 is a perspective view of a screen printing machine illustrating the general features of the machine; Figure 2 is a schematic cross-sectional view of part of 930305p:\oper\kay,4 1788.a,3

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1 a screen printing machine in accordance with one aspect of 2 the invention; 3 Figure 3 is a schematic partly sectional view of part 4 of a screen printing machine according to the invention; Figure 4 is a view approximately corresponding to part 6 of the machine shown in figure 2 showing a control mechanism 7 for use with the machine; 8 Figure 5 is a schematic perspective view of an end of 9 one of the arms of the screen printing machine shown in figure 1; Figure 6 is a schematic perspective view of 11 part of a screen printing machine in accordance with this 12 invention; 13 Figure 7 is a schematic sectional side elevation of 14 screen printing machine according to another aspect of the invention incorporating a counter balancing means; 16 Figure 8 is a sectional side elevation of a screen 17 printing machine showing a variation on the embodiment shown 18 in figure 7; 19 Figure 9 is a schematic view of part of a screen printing machine according to the present invention; 21 Figure 10 is a schematic side elevation of preliminary 22 locating means for a screen printing machine according to 23 another aspect of %he invention; and 24 Figure 11 is a schematic perspective view of the preliminary locating means shown in figure 26 The screen printing machine 10 shown in figure 1 27 includes a fixed frame 12 and a rotatable frame 20. Fixed 28 fraine 12 has multiple arms 13 that project radially from a 29 central disk 14 which is secured to an upstanding post or column 15. At their outer ends, arms 12 may be supported on 31 rectangular frame stands 16 which are themselves braced from 32 fixed angle section ring 17 by respective radial struts 18.

33 The movable frame 20 likewise comprises of multiple 34 radially projecting arms 21 fixed to a second disk 22 which forms part of a structure rotatable on post 15. Arms 21 36 extend in cantilever fashion and are braced by respective 37 uprights 23 and adjustable diagonal struts 24 to underlying 38 ,plates 25 which form a further part of the rotatable 890922,ARSSPE. 022. screen.

6 1 structure and are themselves rigidified by an inner angle 2 section ring 26.

3 Post 15 is supported on broad pedestal box 28 that 4 itself rests upon spaced elongate stabilizing feet 29. In a complete installation, arms 13 carry respective print heads 6 and the arms 21 support platens for the substrate to be 7 printed. The movable frame is axially movable to that the 8 arms 21 come into close proximity with arms 13 to effect a 9 print operation.

Box pedestal 28 may be arranged to house a rotary 11 indexing mechanism for rotating moving frame 20 about post 12 15. An example of a suitable rotary indexing mechanism is 13 described in International patent application 14 PCT/AU88/00232. Arms 21 are equiangularly spaced by an angle equal to the angular spacing of arms 13. It will be 16 seen that two of the arms 12 are missing and it is in this 17 gap that the material or substrate to be printed is 18 positioned on the printing platens on the cantilever arms 19 and retrieved therefrom after having executed a complete circuit.

21 Each screen must stop at each station defined by arms 22 12 whereupon the movable frame is raised towards the arms of 23 the fixed frame so that a printing operation can be 24 effected.

Figures 2 and 4 illustrate arrangements by which the 26 movable frame is axially movable. As shown there is 27 provided drive means 30 in the form of an air bag 31 which 28 can be inflated with compressed air and also allowed to 29 deflate. The bag 31 is disposed within box pedestal 28 and in axially aligned with post 15. A plate 32 bears on the 31 bag and is lifted thereby upon inflation. Stop 33 is 32 provided to limit the lifting of plate 32.

33 Transmission means 39 operatively connects bag 31 to 34 the movable frame 20. The transmission means 39 comprises a vertically disposed connecting rod 34 which extends from the 36 bag 31 upwardly into a hollow portion 19 of post or column 37 15. At the end of connecting rod 34 there is a mounting 38 head 36 which receives a support member 37 which has 890922. ARSSPE.022. screen.

1 sections which extend througi slots or apertures 38 in the 2 cylindrical portion 19 of post 15. This is best seen in 3 figure 3. The support member 37 has support sections 4 thereon which are adapted to carry a thrust bearing 42. A further bearing 41 permits rotation and vertical sliding of 6 the movable frame 20 on post 15. It will be readily 7 apparent that by inflating and deflating bag 31 that the 8 movable frame 20 can be raised and lowered.

9 As shown in figure 4, the plate 32 is connected to an arm 43 which on lifting of the plate 32 engages a shutoff 11 arm 44 of an air valve 45 for supplying air to the bag 31.

12 Thus in use the lifting should come to a smooth stop.

13 In an alternative construction the air bag 31 may be 14 replaced by a pneumatic or hydraulic ram. In another alternative, a pneumatic or hydraulic ram may be located 16 above the frame 20 from above rather than from beneath as 17 shown in figures 2 and 3.

18 Operation of the drive means 30 is usually part of an 19 automatic cycle can also be through push buttons 53 mounted conveniently at the free ends of the arms of the fixed frame 21 12. (Figures 1 and 5) This manual override provides a most 22 advantageous arrangement where for example one of the 23 printing operations at one of the stations as to be 24 repeated.

According to another aspect of the present invention, a 26 counter balancing mechanism is provided to assist in the 27 axial movement of the movable frame. This arrangement is 28 shown in figures 7 and 8. As shown/ the counter balancing 29 means 70 is comprised by an air bag 71 operatively connected to the drive means 75 by way of transmission mechanism 31 The transmission mechanism 80 is in essence the same as that 32 described earlier and includes a connecting rod 81, mounting 33 head 82, support member 83 having support sections 85 for 34 carrying a thrust bearing 42.

In figure 7 the drive means 75 comprises a pneumatic 36 piston/cylinder assembly 76 operatively connected to 37 mounting head 82 via coupling member 78. As shown, the 38 major part of the transmission between drive means 75 and 75an 890922, ARSSPE. 022. screen, -7counter balancing means 70 is disposed within hollow cylindrical portion 19 of post In Figure 8 the drive means 75 comprises a pair of actuators 77 and again the air bag 31 acts as a counter balancing device.

The counter balancing air bag 71 is arranged so as to provide a substantially constant counter balancing force to the weight (or at least part of the weight) of the movable frame. For example, the air bag 71 may be connected to a pressurised fluid source via a pressure regulator which can maintain the pressure within the bag substantially constant. In another arrangement, it may be possible to connect the bags 71 to a reseroir of much larger volume or of sufficient volume that the pressure in the bag remains substantially unchanged.

In the various embodiments described there may be provided primary stop means 90 which prevents the movable frame 20 from being raised unless it is correctly registered with the fixed frame 12. That is unless the arms of the movable frame are correctly aligned with those of the fixed frame the arms will contact the stop means 90 to prevent the movable frame from being raised. Two embodiments of stop means 90 are shown in Figures 6 and 9.

As shown in Figure 6 the stop means 90 comprises a perimetric skirt 62 which forms part of the top 61 of the fixed frame. It will be noted in this schematic drawing the arms of the fixed frame are not shown. The skirt 62 has a series of slots 63 therein along which the arms of the movable frame 20 can travel when correctly or near correctly registered with respect to the arms of the fixed frame 12. When the movable frame is in its lower position the arms are disposed below the skirt 62 and thus the movable frame 20 is free to rotate. Should for some reason the arms of the movable frame come to rest in a position where they are not in alignment with the arms of the fixed frame, the arms of the movable frame will engage skirt 62 upon lifting and prevent the movable frame being raised further.

In the embodiment shown in Figure 9, the primary stop means 90 comprises series of circumferentially spaced stop bars 91 which are mounted to ring 17 of the fixed frame. These bars 91 are engaged by register arms or plates 25 on 93a305,p:\opcr\kay,41788&da,7 I, 1 the movable frame if these arms (and therefore the main 2 arms) are not correctly positioned.

3 Figures 10 and 11 relate to a preliminary locating 4 device 100 which brings the fixed and movable frames into correct register position prior to the movable frame being 6 raised. The preliminary locating means comprises a movable 7 member which is actuatable by actuation of the drive member 8 30 or 75 for causing axial movement of the movable frame, 9 this movable member being operable to commence moving before the drive member commences to move and being adapted to 11 engage a Gdo~a-t-i-ng-member 25 on the other parts so as to 12 correctly align the two parts together.

13 The movable member 100 includes a pair of spaced apart 14 rollers 101 operatively connected to a pneumatic piston/cylinder assembly 105 which is operatively connected 16 to the fixed frame or a fixed support, the rollers/ l-15 being 17 adapted to locate within an alignment block 25 on the 18 movable frame. Piston/cylinder assembly 105 is connected to 19 bridge 108 and raises rods 107. Crash bars 103 are disposed on both sides of the rollers 101 and stop operation of the 21 device is too far out of alignment. The pneumatic 22 piston/cylinder assembly 105 is operatively connected to the 23 same power source as the drive means but is smaller in size 24 so that it will activate more quickly.

Thus in operation when one of the movable arms 21 is 26 positioned correctly relative to one of the fixed arms 12 at 27 one of the operating positions, the pneumatic power source 28 which moves the movable frame axially is activated. Because 29 assembly 105 is smaller than the assembly used to move the frame it is activated first and member 100 is moved so as to 31 correctly locate the two frames with respect to one another.

32 The frame 20 then commences to left with the arms of 33 the two frames being held by member 100. After frame 20 has 34 moved a selected axial distance a further registration device may come into effect. Such advice is shown in figure 36 3 and comprises a pair of rollers 56 mounted to frame 37 engageable with block 54 operatively connected to the fixed RA4/\ 38 frame 12.

890922.ARSSPE.022, screen.

1 Finally, it is tn be understood that various 2 alterations, modifications and or additions may be 3 incorporated into the various constructions and arrangements 4 of parts without departing from the spirit and ambit of the invention.

r 0 /890922.ARSSPE.022. screen,

Claims (6)

1. A screen printing machine comprising i) an upright post having a longitudinal axis, and a hollow generally cylindrical portion; ii) a fixed frame which is fixed relative to said post, said fixed frame including a plurality of arms which extend generally radially with respect to the longitudinal axis of said post; iii) a movable frame mounted for rotational movement about the longitudinal axis of the post and for axial movement in the direction of the longitudinal axis of said post between a print position and a non-print position; iv) drive means for causing said axial movement of said movable frame; v) transmission means operatively connecting said drive means to said movable frame said transmission meanr including a connecting rod operatively connected to said drive m.ans and at least partially disposed within said hollow portion of said post said connecting rod extending generally in the direction of the longitudinal axis of the post, and a support member having support arms which extend generally laterally with respect to the longitudinal axis of the post, said support arms extending through openings in the wall of the hollow portion of the said support arms having support sections operatively connected to said movable frame.

2. A screen printing machine according to claim 1 wherein said drive means comprises a pneumatic piston/cylinder assembly at least partially disposed ,vithin said hollow portion of said post and operatively connected to said transmission means.

3. A screen printing machine according to claim 1 or claim 2 wherein said support sections of said arms are adapced to engage a thrust bearing arranged to support said movable frame. 930305,p:\ocr\ kay,41788cla,10 X _I -i C ~s~i CYIY)-I

11- 4. A screen printing machine according to any preceding claim wherein said movable frame is rotatable through a plurality of register positions in which arms of the movable frame are disposed relative to the fixed frame arms such that a printing operation can be effected by axial movement of the movable frame to said print position, the screen printing machine further including primary stop means for inhibiting axial movement of the movable frame unless it is in one of said register positions. A screen printing machine according to any preceding claim further including locating means operable to locate the frames relative to one another prior to axial movement of the movable frame. 6. A screen printing machine according to any one of claims 5 to 9 wherein said drive means comprises an air bag operatively connected to said movable frame and being adapted to be inflated or deflated to cause the axial movement of the movable frame section. 7. A screen printing machire according to claim 1 further comprising counter balancing means operatively connected to the movable frame and being arranged to provide a counter balancing force to at least part of the weight of the movable frame during said axial movement thereof, said counter balancing means being adapted to maintain a substantially constant counter balancing force during said axial movement of said movable frame. 8. A screen printing machine according to claim 7 wherein said counter balancing means comprises an air bag operatively connected to said movable frame and being adapted to be inflated or deflated to control the counter balancing force on the movable frame. 9. A screen printing machine according to claim 8 wherein said air bag is cperatively connected to said movable frame by transmission means, said transmission means including a connecting rod operatively connected to said air bag 930305,p:\oper\kay,41788.chia11 12 and at least partially disposed within said hollow portion of said post, said connecting rod extending generally in the direction of the longitudinal axis of the post, and a support member having support arms which extend generally laterally with respect to the longitudinal axis of said post, said support arms extending through openings in the wall of the hollow portion of the post, said support arms having support sections operatively connected to said movable frame. A screen printing machine according to claim 9 wherein said drive means comprises a pair of pneumatic piston/cylinder assemblies operatively connected to said movable frame, said piston/cylinder assemblies being disposed externally of said post. 11. A screen printing machine according to claim 1 wherein said movable frame is rotatable through a plurality of register positions n which arms of the movable frame are disposed relative to the fixed frame arms such that a printing operation can be effected by axial movement of the movable frame to said print position, the screen printing machine further including locating means operable to locate the frames relative to one another prior to axial movement of the movable frame.

12. A screen printing machine according to claim 11 wherein said preliminary locating means comprises a movable member having spaced apart rollers thereon operatively connected to a linear actuator fixedly mounted relative to the movable frame, and an alignment block on said movable frame capable of being received between said pair of rollers. 930305,p: \oper\kay,41788.cla,12 13

13. A screen printing machine substantially as herein described with reference to the accompanying drawings. DATED this 5th day of March 1993 Reefdale Pty Ltd. By Its Patent Attorneys DAVIES COLLISON CAVE 930305,p:\oper\kay,41788.cla,13