GB2203695A

GB2203695A - Turret machine for screen printing onto articles

Info

Publication number: GB2203695A
Application number: GB08730024A
Authority: GB
Inventors: Takahide Satoh
Original assignee: SASAKI GLASS KK; Sasaki Glass Co Ltd
Current assignee: SASAKI GLASS KK; Sasaki Glass Co Ltd
Priority date: 1987-04-24
Filing date: 1987-12-23
Publication date: 1988-10-26
Anticipated expiration: 2007-12-23
Also published as: IT1223547B; DE3744361C2; GB2203695B; IT8723107A0; FR2614235B1; DE3744361A1; GB8730024D0; FR2614235A1

Description

i 22036,95 1 PRINTING MACHINE The present invention relate.s to a printing

machine suitable for making prints, which may be multi coloured, on objects or workpieces of various shapes, such as polygonal pillar shapes (for example the circumferential surfaces of cups) or on plane surfaces.

A printing machine of the above kind generally comprises: a work table disk which intermittently rotates about the vertical axis; a plurality of cup holders secured to the periphery of the work table disk to hold one end of objects to be printed (in the following description cups are taken as an example) and to hold them horizontally and radially outwardly; a plurality of printing stations arranged around the work table having a horizontal printing screen; a cup supply station for supplying cups to the cup holders; and a cup delivery station for taking the printed cups from the cup holders and transferring them onto the conveyor; whereby the work table is intermittently rotated to transfer the cups held by the cup holders to the printing stations successively where they are printed on their circumferential surfaces with various pictures, patterns or numbers in different colors. The printing screen moves horizontally while.in contact with the outer surface of the cup and is pressed by a stationary squeeze to print a pattern on the surface. The cup holder has a chuck mounted at the end of the horizontally rotatable shaft to grip one end of the cup. To synchronize the moving speed of the printing screen with the cup rotating speed, a rack is provided to the printing screen and also a pinion in mesh with the rack is mounted on the horizontal rotating shaft of the cup holder.

The printing screen as a whole is made vertically movable so that at the end of the printing process it moves up to disengage the rack and the pinion to allow the Cup to be transferred to the next printing station.

Such a printing machine, however, has some drawbacks.

The first drawback is that since the printing screen rack is engaged with the.pinion of the cup holder each time the cup holder moves to each printing station, any deviation in the initial meshing position between the rack and the pinion will results in a deviated superimposition of printed images. It is thus necessary to make an initial engagement position adjustment for all printing screens and this adjustment requires skills and experience on the part of an operator and also takes time.

Secondary, since the cup print start position in each printing station must be set to the same position each time the cup holder moves to the printing station in order to prevent deviated superimposition of printed 3 images, it is necessary to provide the holders with a return mechanism for setting the cup print start position exactly to a specified position. The adjustment of this mechanism also takes time.

The third problem is that because the cup holder pinion is in mesh with the printing screen rack to synchronize the printing screen moving speed and the cup rotating speed in such a way that one complete rotation of the pinion will cause the cup to make one turn for printing, it is necessary to make the pinion diameter equal to the cup diameter. This requires a number of pinions to be prepared for various cup diameters. Furthermore, each time the cup diameter is changed, the conventional printing machine requires pinion replacement with the one of corresponding diameter.

The present invention has been achieved with the view to overcoming the above problems of the conventional printing machine. It is therefore an object of this invention to provide a printing machine which, when the diameter of an object to be printed such as a cup is changed, can perform printing by making a simple adjustment without having to change the pinion and which can keep the print start position at each printing station always in the same position without any adjustment, and which can perform multiple color printing on many kinds of objects.

4 The printing machine to achieve the above object in which, at the stop position of an object or work to be printed that is intermittently rotated on a horizontal plane, the printing screen disposed above the object is pressed by a vertically movable squeeze against the object to obtain a desired print on the object, comprises:

three rotating members, upper, middle and lower,.

_vertically spaced from each other and having a common vertical axis; a drive means for reciprocally rotating the upper and lower rotating members in synchronism with each other, the.amount of rotation of each rotating member being variable; an intermittent rotation drive means for intermittently rotate the middle rotating member through a dividing angle corresponding to a specified division number in one direction after the printing process is completed; first transmission means provided one for each printing screen to convey the reciprocal rotation of the upper rotating member to the printing screen and thereby reciprocally move the printing screen on a horizontal plane; and second transmission means each having an object holding means and adapted to transmit the reciprocal rotation of the lower rotating member to reciprocally rotate the object, the second transmission means being provided along the circumference of the middle rotating member at positions spaced the division angle part; whereby the first and second transmission means are so set as to make the moving speed of the printing screen equal to the circumferential speed of the object, and the second transmission means is also set so as to return the object to the initial turning position after the middle rotating member has been intermittently rotated.

By way of example only, certain specific embodiments of the present invention will now be described with reference to the accompanying drawings, wherein:

Fig. 1 is a schematic drawing showing the fundamental construction of a printing machine as one embodiment of this invention; Fig. 2 is a perspective view showing details of the printing machine of the embodiment as shown in Fig. 1; Fig. 3 is a cruss-sectional view of an essential part of Fig. 2; Fig. 4 shows a work holder with Fig. 4(a) representing a side cross-sectional elevation, Fig. 4(b) a cross section taken along the line A-A of Fig. 4(a) and Fig. 4(c) a side view of the work holder of Fig. 4(a); Fig. 5 is a perspective view of another embodiment of the printing station; Fig. 6(a) is a perspective view of an object 6 to be printed on, showing a partial printing area on it, Fig. 6(b) is a simplified view showing how the printing is done on a mug cup and Fig. 6(c) is a perspective view of an object to be printed on, showing the case where one side of the object is printed; Fig. 7 is a schematic diagram for a pneumatic unit; Figs. 8(a) and 8(b) are a rough layout of the printing stations; Fig. 9 is an explanatory drawing showing the process of printing different patterns on the objects successively supplied; and' Fig. 10 is an outline drawing showing a still another embodiment of this invention.

The present invention will be described in detail taking as examples preferred embodiments shown in the attached drawings.

Fig. 1 is a schematic drawing showing the basic construction of the first embodiment of this invention.

In the figure, denoted 1 is a linear reciprocal motion mechanism which has a first crank 1-1 with a variable rotation radius and connected to an output shaft 1-0 and a second crank 1-2 also with a variable rotation radius, the second crank being 180 out of phase with the first crank. The reciprocal linear motion mechanism 1 converts the rotating motion of the first 7 crank 1-1 into the linear reciprocal motion through a first linearly movable slide plate 1-3 and also converts the rotary motion of the second crank 1-2 through a second linearly movable slide plate 1-4 into the linear reciprocal motion which is in reverse relationship to that of the first slide plate 1-3.

Reference numeral 2 represents a first free rotating member rotatable about its vertical center axis L. The free rotating member 2 has a first large bevel gear 2-1 secured thereto along the entire periphery at its lower part and also a first large gear 2-2 secured thereto along the entire periphery at its upper part.

The first free rotating member 2 has its first large gear 2-2 engaged with a first rack 3-2 mounted at the end of the first connecting shaft 3-1 extending from the first slide plate 1-3 to ut;ilize the linear reciprocating motion of the first connecting shaft 3-1 as the driving force in performing the reciprocal rotary motion.

Designated 4 is a second free rotating member disposed below the first free rotating member 2 and rotatable about the axis L. The second free rotating member 4 has a second large bevel gear 4-1 secured thereto along the entire periphery of its upper part and a second large gear 4-2 secured thereto along the entire periphery of this lower part. The second free rotating member 4 has the second large gear 4-2 engaged with a second rack 3-4 mounted at the end of the second connecting 8 shaft 3-3 extending from the second slide plate 1-4 to use the linear reciprocating motion of the second connecting shaft 3-3 as the driving force in performing the reciprocal rotary motion in synchronism with and in the same direction as the first free rotating member 2.

Number 5 represents an index device to intermittently rotate the output shaft 5-1 through an angle of 3600/n (hereinafter referred to as a division angle) in the direction of arrow where n is the division number n (n > 2). The index device 5 stops the output shaft 5-1 while the first and second cranks 1-1 and 1 2 are undergoing the first half of one turn and rotates the output shaft 5-1 by the division angle when the cranks are rotating during the second half turn.

An index table 6 is disposed between the first free rotating member 2 and the pecond free rotating member 4 and is secured to the output shaft 5-1 of the index device 5 for intermittent rotation in the direction of arrow through the division angle at a time.

The index table 6 has secured thereto the same number of work holders 7 as the division number of n spaced from each other at an angle equal to the division angle.

The work holders 7 each have a horizontal, radially extending, rotatable shaft 7-1 which in turn has at its end a second small bevel gear 7-2 in mesh with the second large bevel gear 4-1 of the second free rotating member 4. The horizontal rotatable shaft 7-1 9 also has a holding means at the other end for horizontally holding the object 8 in such a way that the object can be removed.

Denoted 9 is a printing station and such printing stations 9 which number m are arranged along the circle about the center axis L. In this station a printing screen 9-1 is disposed above the object 8.

The printing station 9 is located at the stop position of the object 8 which is halted when the index table 6 stops after intermittent'rotation. Since it is necessary to provide the printing object supply station for supplying the object to the work holder 7 and the printed object delivery station for taking the object 8 from the work holder 7 and transferring it onto the conveyor (it is possible to make a single station serve these two functions), the printing station is made installable in-the range of 1 < m < n-l considering the positions of the supply and delivery stations. The printing screen 9-1 of the printing station 9 is supported in such a manner that it is horizontally movable in the direction perpendicular to the horizontal rotating shaft 7-1 of the work holder 7. The screen 9-1 is horizontally moved while pressed against the object or work 8 by a squeeze 9-1 which is supported vertically movable by the stationary table 10.

Designated 11 is printing screen driving mechanisms secured to the stationary table 10 which have radially extending, horizontal, rotatable shafts 11-1.

- The horizontal rotating shaft 11-1 has at one end a first small bevel gear 11-2 engaged with the first large bevel gear 2-1 of the first free rotating member 2 and, at the other end, has a third small gear 11-3.

The third small gear 11-3 is in mesh with the rack 9-3 integrally secured to the printing screen 9-1 and which extends in the direction of movement of the screen 9-1 so that the printing screen 9-1 is reciprocally' moved.

In the foregoing the construction of the printing machine of this invention was described. Now, the operation of the printing machine will be explained.

As the linear reciprocal motion mechanism 1 is driven and the output shaft 1-0 is rotated in the direction of arrow (+), the first slide plate 1-3 and the second slide plate 1-4 start linear movement simultaneously in the direction (+), turning the first and second free rotating members 2 and 4 in the same direction (+).

As the first free rotating member 2 rotates in the direction (+), the printing screen 9-1 starts moving horizontally in the direction (+). The rotation of the second free rotating member 4 toward the direction (+) causes the work or object 8 to turn in the direction (+) or the same direction as the movement of the screen 9-1. As a result, the rotating object 8 is printed on its surface by the squeeze 9-2. The printing ink may be organic coloring materials, ceramic color or thermoplastic paint which harden at normal temperatures, or ultraviolet ray hardening paint which, after being spread over the work, hardens when radiated with ultraviolet ray.

Now, we will consider the amount of displacement of the printing screen 9-1 when the output shaft 1-0 turns from 0 to 180in the direction Let us assume that:

R 1 stands for the radius of the first crank 1-1; S 1 stands for the stroke of the first slide plate 1-3; D 10 stands for P.C.D.'of the first large gear 2-2 of the first free rotating member 2; D 11 stands for P.C.D. of the first large bevel gear 2-1 of the first free rotating member 2; D 12 stands for P.C.D. of the first small bevel gear 11-2 of the printing screen driving mechanism 11; and D 13 stand.s for P.C.D. of the third small gear 11-3 of the printing screen driving mechanism 11.

Then S 1 = 2 x R 1. (1) If we let the rotating angle of the first large gear 2-2 produced by the stroke S 1 of the first slide plate 1-3 be 9 1 (rad), the formula (1) can be rewritten as S 1/2 x D 10 X 9 1 (2) If we let 0 1 ' (rad) stand for the rotating 12 angle of the first small bevel gear 11-2, we get the following formula since the rotating angle of the first large bevel gear 2-1 is equal to that of the first large gear 2-2.

1/2 x D 12 X 9 1 112 x D 11 X 9 D 1 1 D 12 Suppose St is the amount of displacement of the printing screen 9-1. Since the third small gear 11-3 and the first small bevel gear 11-2 are secured coaxially to the horizontal rotating shaft 11-1 and the third small gear 11-3 also rotates through 9 1 1, st 1 is given by St 1 = 112 x D 13 X 9, (4) from (1), (2), (3) and (4), St 1 is rewritten as D,, X D 13 St = 2 x x R (5) D 10 x D 1 1 The amount of rotation (displacement) of the object 8 when the output shaft 1-0 rotates from 00 to 1800 in the direction (+) is considered in the following.

Let us assume that:

R 2 stands for the radius of the second crank 1-2; S 2 stands for the stroke of the second slide plate 1-4; D 20 stands for P.C.D. of the second large gear 4-2 of the second free rotating member 4; D 21 stands for P.C.D. of the second large bevel gear 4-1 of the second free rotating member 4; n stands for the number of division of the index 13 device; D 21 stands for P.C.D. of the second small bevel n gear 7-2 of the work holder 7; and D stands for the outer diameter of the object to be printed.

Then, we obtain S 2 _ 2 x R 2 (6) If we let 9 2 (rad) stand for the rotating angle of the second large gear 4-2 produced by the stroke S 2 of the second slide plate 1-4, S 2 is expressed as S 2 = 1/2 x D 20 X 9 2 (7) Suppose 9 2 ' (rad) is the rotating angle of the second small bevel gear 7-2. 'Since the rotating angle of the second large bevel gear 4-1 is equal to that of the second large gear 4-2, we obtain 1 D 21 x - x x D X 9 2 n 2 2 21 2 9 2 n X 9 2..... (8) Now, let St 2 stand for the circumferential displacement of the object 8 caused by the rotation of the horizontal rotating shaft 7-1 of the work holder 7.

Since the object holding means and the object 8 which are coaxial with the second small bevel gear 7-2 and secured to the horizontal rotating shaft 7-1 rotate through 9 2 1, we get st 2 1/2 x D x 0 2 (9) From (6), (7), (8) and (9), st 2 2 x D n x D x R 2'..... (10) It follows therefore that during the first half turn of the output shaft 1-0 in the direction the printing screen 9-1 and the work or object 8 each move in the direction (+). The rotating radii of the first and second cranks 1-1 and 1-2 are so set that the displacement St 1 of the printing screen 9-1 is equal to the circumferential displacement St 2 of the object 8.

That is, st 1 = St 2 (11) Substituting the expressions (5) and (10) into the equation (11), we obtain D 11 X D 13 2 x n x D 2 - D 10 X j12 x R, D 20 x R 2 D 10 X D 12 x n x D R R (12) 2 D D D 11 x 13 x In the expression (12), "n, D 101 D ill D 121 D 131 D 2J are constants determined during design, so that once the outer diameter D of the object 8 is determined, the ratio of R 1 and R 2 is also determined.

The outer diameter D of the object 8 and the stroke St of the screen with a particular pattern determine R from the expression (5) and also R 2 from the expression (12). Thus, the circumferential displacement of the object 8 and the amount of displacement of the printing screen 9-1 are equal and since the first and second cranks 1-1 and 1-2 are on the same shaft and have the same displacement time, the circumferential (rotation) speed of the object 8 becomes equal to the moving speed is - of the screen 9-1, permitting correct printing. This means that even when the diameter of the object 8 should be changed, correct printing can be performed with only the adjustment on.the radii of the first and second cranks.

When the output shaft 1-0 of the linear reciprocal motion mechanism 1 turns from 1800 to 360 in the direction (+), the first slide plate 1-3 and the second slide plate 1-4 each start moving in the direction (-) and at the same time the output shaft 5-1 of the index device 5 begins to rotate in the direction of arrow by the specified division angle.

As the first slide plate 1-3 moves in the direction (-), the first free rotating member 2 reverses and turns in the direction (-) causing the printing screen 9-1 to move a distance St 1 in the direction and return to the initial position.

As the second slide plate 1-4 moves in the direction (-), the second free rotating member 4 also rotates in the direction (-) as with the first free rotating member 2, so that object 8 rotates in the direction (-) through an angle of 9 2' (rad) and its circumferential displacement is St 2 toward the direction.

Rotation of the index shaft 5-1 causes the index table 6 to turn about the index shaft 5-1 and therefore the object 8 on the work holder 7 to move horizontally corresponding to the specified division 16 - angle.

At the time, the second small bevel gear 7-2 of the work holder 7 which is in mesh with the second large bevel gear 4-1 of the second free rotating member 4 turns in the direction (+) and the object 8 also rotates through the.same angle in the direction (+).

In other words, as the index shaft 5-1 rotates,.

the second small bevel gear 7-2 moves about the second large bevel gear 4-1 while rotating through the angle of 2n/n (rad). The rotating angle 9 3 (rad) is given by D 21 1 !Tr x X X 9 3 2 x D 21 n 2 n 9 3 = 21T (13) That is, as the result of the rotation of the index shaft 5-1, the object 8 undergoes one complete turn in the direction Therefore, the object 8 is driven simultaneously by the displacement of the second slide plate 1-4 toward the (-) direction and also by the rotation of the index shaft 5-1. If we let 0 4 (rad) stand for the object's rotating angle for the.second half rotation of the output shaft 1-0, we obtain 4 2 + 0 3 2 + 21r (14) Since the rotating angle of the object 8 for the output shaft's first half rotation is 9 2 the overall rotating angle 9 5 (rad) is given by 17 2 1 + 0 4 2 Tr (15) It follows that the second half rotation of the output shaft 1-0 of the linear reciprocal mechanism 1 causes the printing screen 9-1 to return to the print start position and the object 8 to move to the next section while completing one turn. As a result, the print start position on the object is the same as that in the previous section. This process, when repeated successively, enables multiple color printing with the number of colors equal to that of the printing stations employed.

Fig. 2 shows a more concrete illustration of the embodiment of Fig. 1.

In this embodiment, the linear reciprocal motion mechanism 1 and the index device 5 are driven by the same driving source. The rotation of the variable speed motor 12 is transmitted through the timing belt 13a to the clutch and.brake unit 14 equipped with the clutch and brake mechanism. The clutch and brake unit 14 has pulleys 14a, 14b secured to each end of its output shaft.

One of the pulleys 14a-is connected through the timing belt 13b to the reduction gear 1-5 of the linear reciprocal motion mechanism 1. The other pulley 14b is connected through the timing belts 13c, 13d to the reduction gear 5-2 of the index device 5.

The reduction gear 1-5 of the linear reciprocal motion mechanism 1 has a pair of output shafts 1-0 on 18 the same axis. Mounted at the other ends of these output shafts 1-0 are a first crank 1-1 and a second crank 1-2 with their crank length adjustable. The first and second crank 1-1 and 1-2 have cam followers 1-1a and 1-2a attached to the end thereof which are slidably engaged with cam slots 1-3a and 1-4a formed vertically longitudinal in slide plates 1-3 and 1-4.

The first and second slide plates 1-3 and 1-4 are each slidably mounted on a pair of horizontally extending slide rails 1-6 so that the slide plates can move linearly along the length of the slide rails.

A first connecting shaft 3-1 that transmits the linear reciprocal motion of the first slide plate 1-3 to the first free rotating member 2 has one end secured to the first slide plate 1-3 and the other end to a slide rail 3-12 of the linear bearing 3-11. The linear bearing 3-11 is rigidly secured to the bracket 3-13 which in turn is fixed to the stationary table 10. A first rack 3-2 secuied to the slide rail 3-12 is engaged with the first large gear 2-2 of,the first free rotating member 2 so that the linear reciprocal motion of the first connecting shaft 3-1 is converted into a smooth reciprocal rotating motion of the first free rotating member 2.

A second connecting shaft 3-3 that transmits the linear reciprocal motion of the second slide plate 1-4 to the second free rotating member 4 has one end secured to the second slide plate 1-4 and the other end to the 19 second rack 3-4.which, like the first connecting shaft 3-1, is engaged with the second large gear 4-2 of the second free rotating member 4. A bracket 3-131 on which a linear bearing 3-11' is rigidly mounted is secured to the equipment body.

The index device 5 has a doughnut-shaped output shaft (or index shaft) 5-1 which rotates about the vertical axis L. Inside the index shaft 5-1 is installed a stationary hollow shaft 5-3. Secured to the index shaft 5-1 is a hollow cylindrical index stay 20 which is fixed to the index table 6. Inside the index stay 20 is installed a hollow cylindrical stationary stay 21 which is secured to the stationary table 10. - The stationary table 10, first free rotating member 2, index table 6 and the second free rotating member 4 are assembled as shown.in Fig. 3.

The stationary table 10 is securely bolted to the upper end of the stationary stay 21. The first free rotating member 2 is rotata bly but axially not slidably (in vertical direction) mounted on the outer periphery of the sleeve 10a of the stationary table 10 through a bearing member 22.

The index stay 20 is sleeved over the stationary stay 21 with a gap therebetween and has its upper end bolted to the index table 6. The free rotating member 4 is rotatably but axially not slidably mounted on the outer periphery of the index stay 20 through a bearing member 23.

- 20 Mounted on the stationary stay 21 between the first free rotating member 2 and the index table 6 is an air distributor 24 which supplies vacuum and air to the suction chuck (described later) for holding the object 8 on the work holder 7. The air distributor 24 consists of a ring-shaped upper distributor 25 and a stepped ring-shaped lower distributor 26 which is rotatably fitted into the upper distributor 25. The upper distributor is secured to the stationary stay 21 by a push-down mechanism 27 using a downward spring force.

The lower distributor is secured to the index table 6.

Each of these upper and lower distributors 25, 26 is provided with bottomed air distribution holes 28, 29 which are equal in number to the division number n and which extend from the side of the distributors toward their axis. The upper air distribution holes 28 are each formed with a downwardly extending communication passage 28a located along a circle. The lower air distribution holes 29 are also formed with upwardly extending communication passages 29a located along the same circle as with the downwardly extending communication passages 28a. When the index table 6 stops at each dividing position, the communication passage 28a of the upper air distribution hole 28 is aligned with the communication passage 29a of the lower air distribution hole 29 bringing the upper and lower air distribution holes 28 and 29 into communication with each other.

The upper distribution 25 is formed at the 21 - lower side with a horse's hoof-shaped groove or recess (not shown) which communicates with the upper air distribution holes except for the one corresponding to the delivery station, so that when the index table 6 is rotating, the lower distributor 26 is continuously supplied with vacuum. The groove eliminates the need for providing the upper air distribution holes 28 to all stations. However, since there is a possibility that when an object comes off from the work holder breaking the vacuum, other objects may also come off, the upper air distribution holes 28 are provided to all the sections to prevent a possible vacuum leakage.

The upper air distribution holes 28 are connected with air pipes 30 which are led to an air unit (described later) and the lower air distribution holes 29 are also connected with air pipes 31 which are further led to the work holder.

The air pipes 30 connected to the air unit are introduced into the stationary stay 21, passed through small holes 21a cut in the side wall of the stationary stay 21 and then led to the upper air distribution holes 28. The air pipe 30 that is connected to the upper air distribution hole 28 corresponding to the printed object delivery station is supplied with pressurized air or is open to an atmosphere. And the remaining air pipes 30 are given vacuum.

Now, we will explain the air unit that supplies vacuum and pressurized air to the upper distributor 25 22 - by referring to Fig. 7. The vacuum produced by the vacuum pump 100 is stored in the reserve tank 101 to stabilize the vacuum pressure. The reserve tank 101 is connected through air pipes 30 with the upper air distribution holes 28-2 to 28-8 except for the one 28-1 that corresponds.to the delivery station. A manual valve 102 and a speed controller 103 for regulating the pressurized.

air flow in breaking the vacuum are installed on the air pipe 30 connected to the reserve tank 101.

The manual valve 102 is connected with an air source that supplies pressurized air. When the object 8 stops at the delivery or take-out position, the manual valve 102 is operated to supply the pressurized air from the air source to the upper air distribution hole 28-1 to remove theobject 8 from the suction chuck of the work holder 7.

The reason that the vacuum is supplied through the manual valve 102 to the upper air distribution hole 28-1 is to keep in the work holder 7 the object 8 that was moved to the delivery position while adjustment is made of the printing machine. If the manual valve 102 is replaced with a solenoid valve and the vacuum is supplied after the pressurized air is supplied, it is then possible to take the object into and out of the printing machine at a positioncorresponding to the upper air distribution hole 28-1. In that case, if the halt time of the index table 6 is-short, there is a possibility that the operation or removing the printed object 8 from 23 - the work holder 7 and putting a new object 8 in the work holder.7 may not be completed in that short period of time. To avoid this, the clutch and brake unit 14 is operated to temporarily stop the linear reciprocal motion mechanism 1 and the index device 5. The operation of the clutch and brake unit 14 and the solenoid valve can be controlled by a microcomputer. The simple method of detecting the object arriving at the supply and delivery position and outputting the detection signal to the microcomputer may be achieved, for instance, by mounting to the index device 5 a rotary encoder 5-4 which rotates in synchronism with the index shaft 5-1 and outputting the encoder signal to the microcomputer.

The work holder 7 is structured as shown in Fig. 4, and has a bearing 7-4 of the horizontal rotating shaft 7-1 and an air box 7-5 to which the air pipe 31 leading to the lower air distribution hole 29 of the lower distributor 26 in the air distributor 24 is connected. Thp bearing 7-4 and the air box 7-5 are mounted to the bracket 7-3 extending downwardly from the index table 6. The air box 7-5, as shown in Fig. 4(c), can be inclined vertically relative to the horizontal direction.

The horizontal shaft 7-1 consists of a first shaft 7-7 and a second shaft 7-8, coupled together by a helical coupling which.enables a large deflection between the shafts while making the two shafts rotate at an equal speed. The first shaft 7-7 is rotatably 24 - supported on the bearing 7-4 and the second shaft 7-8 passes through the air box 7-5 in a hermetically sealed condition. The first and second shafts 7-7 and 7-8 are coupled together between the bearing 7-4 and the air box 7-5 by the helical coupling in such a way that the two shafts can be deflected at the coupling to make the outer peripheral surface of the objects 8', 8" horizontal irrespective of the shape of the objects.

The first shaft 7-7 of the horizontal rotating shaft 7-1 has mounted thereon a friction clutch consisting of a pair of friction members 7-9, 7-10. One of the friction members 7-9 is rotatably mounted on the first shaft 7-7 through a bearing 7-11. The other friction member 7-10 is splined axially slidable on the first shaft 7-7 and is pressed by the coil spring 7-12 against the former friction member 7-9 so that the two friction members 7 9, 7-10 are always in a frictional engagement with each other. The friction member 7-9 is secured with the second small bevel gear 7-2 that engages with the second large bevel gear 4-1 of the second free rotating member 4 to transmit the reciprocal rotation of the second free rotating member 4 through the other friction member 7-10 to the first shaft 7-7 and further, through the helical coupling 7-6, to the second shaft 7-8 which rotates in the same direction and at the same speed as those of the first shaft 7-7.

The friction clutch is engaged or disengaged by moving the latter friction member 7-10 toward the - bearing 7-4 against the force of the coil spring 7-12.

The ON/OFF mechanism of the friction clutch, as shown in Fig. 4(b), consists of: a pair of studs 7-14 with bearings 7-13 attached to their ends which engage with the groove 7-10a formed along the circumference of the friction member 7-10; a U-shaped frame 7-16 which is pivotably supported at fulcrums 7-15 on the end of the horizontal bar 7-4a extending horizontally from the bearing 7-4 and which is secured with the pair of studs 7-14; and a cam follower 7-17 mounted at the lower end of the frame 7-16. As the index table 6 is rotated and the cam follower 7-17 is guided on a cam plate provided to the equipment body, the frame 7-16 is oscillated toward the direction (-) as shown in Fig. 4(a) and the studs 7-14 move the friction member 7-10 toward the bearing 7-4, thereby preventing the rotation of the second small bevel gear 7-2 from being transmitted to the horizontal rotating shaft 7-1. The cam plate is provided as necessary to stop the shaft rotation when printing is done along the axis from a particular position on the object 8 (described later), or installed at a position corresponding to the object supply station and the printed object delivery station to stop the object rotation and thereby facilitate its supply and delivery.

The second shaft 7-8 of the horizontal rotating shaft 7-1 has a suction check 7-18 removably mounted at its end for horizontally holding the object 8 by suction. The second shaft 7-8 is formed with an axial 26 hole 7-8a that extends axially from the front end toward the rear to communicate with the air box 7-5.

The suction chuck 7-18, in the case of a cup as the object 8, consists of an engagement disk 7-19 engaging with the open end of the cup and a mounting shaft 7-20 which is passed into and secured to the engagement disk 7-19. The mounting shaft 7-20 is screwed over the second shaft 7-8, and has an axial hole 7-20a opening at each end thereof. The air in the cup 8 is drawn out through the axial hole 7-20a, another axial hole 7-8a and the air box 7-5 into the air pipe 31.

This produces a vacuum in the cup attracting and holding it to the engagement disk 7-19.

The object 8 is printed on with one end supported. Since the pressure of the squeeze 9-2 during printing may cause axis deflection of the shaft 7-1, it is Preferable to rotatably support the object 8 on the support roller 32 as shown in Fig. 2. The support roller 32 is moved up or down by the cylinder 33 in such a way that the roller movement will not hinder the smooth horizontal movement of the object 8 by the index table 6.

The cylinder 33 mounted on the cylinder base 34 is secured to the mount 35. In this embodiment the object is supported from under, but it is also possible to support the object from its axial direction.

The mount 35 is provided with an object sensor 37 consisting of a microswitch 36 that is brought into contact with the object 8 to check whether the object 27 - is held by the suction chuck 7-18 when the chuck is moved toward the mount 35. When the sensor 37 detects that no object is held in the chuck 7-18, the squeeze 9-2 stops lowering to prevent the ink from seeping through the printing screen 9-1.

In this embodiment, the object 8, which is a cup, is supported at the open end by the suction chuck 7-18. It is also possible to check the object from the bottom of the cup depending on the object shape and printing conditions. In such a case, the chuck may be formed into a bowl and also the object may be held by a mechanism such as air cylinder.

The printing screen driving mechanism 11 has a horizontal rotating shaft 11-1 rotatably supported on the bearing 11-4 secured to the stationary table 10.

The horizontal rotating shaft 11-1 has a first small bevel gear 11-2 secured at one end which is in mesh with the first large bevel gear 2-1 of the first free rotating member 2. The shaft also has a third small gear 11-3 secured to the other end which is in mesh with the rack 9-3 of the printing station 9.

The printing station 9 consists of the printing screen section and the squeeze head. The printing screen section further consists of: a screen holder 9-6 having a frame 9-4 with a virtually square plane and an extension bar 9-5 integrally secured to the frame 9-4; a printing screen 9-1 which is suspended from the frame 9-4 of the screen holder 9-6 through a pair of suspension 28 - fittings 9-7 that permit positional adjustment on the screen 9-1 in any arbitrary directions, vertical or lengthwise; a linear rack 9-3 which is secured to the front member 9-4a of the frame 9-4 and is engaged with the third small gear 11-3; and a slide stand 9-8 that slidably supports the extension bar 9-5 and thereby guides the screen holder 9-6 for horizontal movement and which is secured to the mount 35.The squeeze head consists of: a position adjust fitting 9-10 which adjusts the vertical position of the squeeze rod 9-9 extending vertically upward from the squeeze 9-2 and also adjusts the direction of the squeeze 9-2; a first cylinder 9-11 which has a vertically extending rod secured to the position adjust fitting 9-10; and a second cylinder 9-12 which has a radially extending rod fixed on the stationary table 10 and secured with the first cylinder 9-11.

When the object 8 is turned and printed over its entire circumferential surface, the second cylinder 9-12 is stopped and the first cylinder 9-11 is operated to press the squeeze 9-2 against -the printing screen 9-1 with an appropriate pressure and thereby press the printing screen 9-1 against the outer surface of the object 8.

The printing screen 9-1 is adjusted by the suspension fitting 9-7 so as to be positioned 2 to 3 mm above the outer circumferential surface of the object 8.

This prevents the ink on the screen 9-1 from being 29 - inadvertently applied to the object 8 when the object is moved.

When the object 8 has a uniform diameter along its length, correct printing can be performed by horizontally moving the printing screen 9-1 in the rotating direction of the object 8. However, when the object 8 is shaped like a truncated cone, there is a difference in speed between the ends of the object, which will result in incorrect printing. To avoid this, the following measures are taken. The air box 7-5 of the work holder 7 is inclined, as shown in Fig. 4(c), to make the outer circumferential surface of the object 8 horizontal. Further, as shown in Fig. 5, the rack 9-3' secured to the front member 9-4a of the frame 9-4 is curved and the extension bar 9-5 is supported on the stand 9-8' in such a way that the bar 9-5 can be oscillated about the fulcrum P. The printing screen 9-1 is then oscillated about the fulcrum P by the meshing engagement bet.ween the second small gear 11-3 and the rack 9-31 thereby permitting correct printing on the truncated cone object. If the rack 9-3' is curved, the engagement with the third small gear 11-3 is theoretically not correct. However, by making the thickness of the rack 9-31 smaller, the engagement can be made substantially smooth allowing the smooth oscillating movement of the printing screen 9-1. When the printing screen 9-1 is to be oscillated with higher accuracy.

the third small gear 11-3 and the rack 9-3' may be changed - to bevel gears.

The above description concerns the case where the object 8 which need not be specified with a print start Position is rotated to be color-printed on its entire circumferential surface. As shown in Fig. 6(a), it is also possible to print only on a shaded part of the outer surface by turning the object.

That is, the amount of displacement of the 4 printing screen 9-1 and the amount of rotation of the object 8 can be changed continuously by adjusting the turning radii of the first crank 1-1 and the second crank 1-2. Further, the print start position on the object 8 at each printing station is always the same even when the turning radius of the second crank 1-2 is changed, because the reciprocal movement stroke from the second crank 1-2 is so set as to reciprocally rotate the object 8. Thus, by adjusting the first and second cranks 1-1 and 1-2 so that the printing screen 9-1 and the object 8 dre moved by an amount equal to the circumferential length (L) of the part print section, it is possible to color-print only a desired part of the object 8. At that time, if at the object supply position the print start point is determined and the object 8 is held by the work holder 7, a color print can be obtained at a desired location on the object 8.

When, for example, a large mug cup 8a with a grip is to be printed as shown in Fig. 6(b), the outer circumferential surface excluding the grip section can 31 - be color-printed by using the printing screen 9-11 whose cross section isa reversed trapezoid. This configuration is possible because the object is not given a complete turn.

Also, if the vertical movement of the squeeze 9-2 at each printing station is controlled by microcomputer, different patterns can be printed in many colors on the objects supplied one after the other.

That is, as shown in Fig. 9, the two-color pattern A is printed at the first printing station 9A and the second printing station 9B. Similarly, at the third printing station 9C and the fourth printing station 9D, a color pattern B is printed; and at the fifth and sixth printing stations 9E and 9F, a color pattern C is printed. When the first object 8 arrives and stops at the first and second printing stations 9A and 9B, the squeeze 9-2 is lowered. When the object 8 stops at the third through sixth printing station 9C to 9F, the squeeze is blocked from coming down. For the second object, the printing is done only at the third and fourth printing stations 9C and 9D. For the third object, it is printed at the fifth and sixth printing station 9E and 9F. In this way, different patterns are printed on each object which is successively taken out from the delivery station.

The use of this kind of printing system enables successive packaging of a plurality of cups,-say three cups, with different patterns printed on.

32 - In addition to the function of color-printing a pattern on the outer peripheral surface of the object while turning the object, the printing machine of this embodiment can also print on the side surface of a polygonal cylinder-shaped object 8b, as shown in Fig. 6(c). The printing process for the object 8b is explained below.

The rotating radii of the first and second cranks 1-1 and 1-2 are set to zero; and the first and second free rotating members 2 and 4 are fixed immovable to stop the movement of the printing screen 9-1 and also the rotation of the object 8b. At this time, the object 8 is so positioned that its printing surface faces up and then mounted on the chuck of the work holder 7. Then, the squeeze head is operated for printing during the first half of one turn of the output shaft 1-0 in the linear reciprocal motion mechanism 1. The squeeze operation is performed as follows. The squeeze 9-2 is rotated beforehand through 90 from the position shown in Fig. 2 and then fixed. The first cylinder 9-11 is lowered to press against the printing screen 9-1. Then the second cylinder 9-12 is operated to move the squeeze 9-12 radially outwardly, applying a pattern onto one side surface of the object 8b.

When printing is finished, the index table 6 is rotated to give the object 8b one complete turn and transfer it to the next section. At that time, if the angle between the lines normal to the adjacent surfaces 33 - of the object 8b is large, the object will contact the frame of the printing screen 9-1. To prevent this, a ring-shaped cam plate is provided to the machine body to guide the cam follower 7-17 of the friction clutch in such a way that the friction clutch in the work holder 7 is.disengaged stopping the rotation of the horizontal rotating shaft 7-1 and the object 8b. This permits the object to be transferred to the next station without being rotated and therefore enables the color printing on one side of the object 8b.

In the embodiment, when one of the side surfaces of the object 8b-shown in Fig. 6(c) is printed, the friction clutch of the work holder 7 is disengaged by the ring-shaped cam. Instead of using the ring-shaped cam, it is possible to provide at the stop position of each work holder 7 a cylinder device which pushes the cam follower 7-17 of the friction clutch. The friction clutch is disengaged during printing and engaged when the index table 6 is intermittently rotated to allow the object 8b to be rotated. At the same time, the rotating radius of the second crank 1-2 is set to a certain length. This construction also permits printing of different patterns on two or more side surfaces of the object 8b shown in Fig. 6(c).

In other words, during printing the object 8b is not rotated because the friction clutch of the work holder 7 is disengaged, but when the index table 6 is rotated intermittently the friction clutch is engaged 34 - and the object is turned. At this time, if the rotation radius of the second crank 1-2 is zero, the object 8b is rotated by one complete turn. However, since the second crank rotation radius is set to a certain length, the object 8b is turned by a certain angle () before it rests at-each work holder stop position. Thus, by setting this angle (4;) corresponding to the angle between' the print surfaces, it is possible to perform printing on all the side surfaces of polygonal cylinder or nay opposing surfaces.

That is, if we let 0 2 ' stand for the rotating angle of the second small bevel gear 7-2 during printing, the second small bevel gear 7-2 rotates by an angle of -9 2' +2w from the end of printing until the object 8b moves to and rests at the next work holder stop position.

Thus, the second crank 1-2 should be set so that its rotating angle will be -() 2 1 + 2w (rad) Fig. 8 shows the outline of the printing machine of this invention when the division number (n) is set to eight.

Referring-to'Fig. 8(a), a work supply device 38 for feeding the object 8 to the work holder is provided next to the linear reciprocal motion mechanism 1. Next to the work supply device 38 is installed a work delivery device 46 to take the printed object 8 from the work holder. In other sections are installed printing stations 9a through 9e each of which has different - printing ink on the printing screen. The index table 6 is rotated counterclockwise to transfer the object 8 from the printing station 9a to the next stations successively until it reaches the last printing station 9e.

In still another example of Fig. 8(b), the work supply device 38 and the work delivery device 46 are installed in positions different from those of Fig. 8(a) and the index table 6 is rotated clockwise.

To facilitate the supply and delivery of the object 8, the friction clutch of the work holder 7 is made to disengage to stop the rotation of the chuck 7-18 as the work holder 7 approaches the work supply device 38 and the work delivery device 46. However, where there is a possibility of the horizontal rotating shaft 7-1 rotating slightly off center causing a deviation in the print start position when the friction clutch is again engaged after the object 8 is held by the chuck 7-18, an alternative method may be taken. That is, the friction clutch is engaged at all times and when the work holder 7 arrives at the stop position (the squeeze head and associated components a. re not yet activated) the linear reciprocal motion mechanism 1 and the index device 5 are stopped by the clutch and brake unit 14 for a specified period of time, during-which time the object 8 is supplied. This eliminates axis deviation due to friction clutch and assures higher accuracy in positioning the object.

36 Fig. 10 s a rough perspective view showing other embodiment of the printing machine according to this invention.

In this embodiment, the first large gear 2-2 of the first free rotating member 2 is in mesh with the motor gear 201 secured to the motor shaft 200a of the first servo motor 200; the second large gear 4-2 of the second free rotating member 4 is engaged with the motor gear 203 secured to the motor shaft 202a of the second serve motor 202; the first and second servo motors 200 and 202 are synchronized with each other by a controller using microcomputer and perform reciprocal rotation; and the third servo motor 204 having a hollow motor shaft 204a intermittently rotates the index table 6.

Thus, this embodiment requires to mechanical driving mechanism such as cam or clutch in rotating the first and second free rotating members 2 and 4. In other words, the amount of rotation and the rotation speed of the first dnd second free rotating members 2 and 4 can be electrically controlled. Also, setting of the dividing angle, rotating speed and halt time of the index table 6 can be done with ease, which in turn contributes to reduction in the job change time and increased variation in printing.

To summarize, the printing machine of this invention has a variety of features. Some of them are listed below:

that even when the diameter of the object is 37 - changed, a desired and correct multiple-color printing is obtained simply by-adjusting the amount of rotation of the upper and lower rotating members; that the multiple-color print is obtained also on a desired part of the circumferential surface of the object or on any arbitrary side surface of polygonal cylindrical object; and that these printing functions can be performed by a single machine.

38 4

Claims

Z CLAIMS.

1. In a printing machine in which, at the stop position of an object or work to be printed that is intermittently rotated on a horizontal plane, a printing screen disposed above the object is pressed by a vertically movable squeeze against the object to obtain a desired print on the object, the printing machine comprising:

three rotating members, upper, middle and lower, vertically spaced from each other and having a common vertical axis; a drive means for reciprocally rotating the upper and lower rotating members in synchronism with each other, the amount of rotation of each rotating member being variable; an intermittent rotation drive means for intermittently rotate the middle rotating member through a dividing angle corresponding to a specified division number in one direction after the printing process is completed; first transmission means provided one for each printing screen to convey the reciprocal rotation of the upper rotating member to the printing screen and thereby reciprocally move the printing screen on a horizontal plane; and second transmission means each having an object holding means and adapted to transmit the reciprocal 39 rotation of the lower rotating member to reciprocally rotate the object, the second transmission means being provided along the circumference of the middle rotating member at positions spaced the division angle part; whereby the first and second transmission means are so set as to make the moving speed of the printing screen equal to the circumferential speed of the object, and the second transmission means is also set so as to return the object to the initial turning-position after the middle rotating member has been intermittently rotated.

2. A printing machine as set forth in claim 1, wherein the drive means consists of a first linear moving member and a second linear moving member, the first and second linear moving member are adapted to perform linear reciprocal movements in synchronism with each other, and their strokes are variable.

3. A printing machine as set forth in claim 1, wherein the drive means consists of motors provided for the upper rotating member and the lower rotating member.

4. A printing machine as set forth in any of claims 1 to 3, wherein the printing screen is shaped like a fan and is made reciprocally movable.

5. A printing machine as set forth in any of claims 1 to 4, wherein the second transmitting means has its-object holding means vertically inclinable.

6. A printing machine as set forth in any of claims 1 to 5, wherein the squeeze is made variable in its direction relative to.the printing screen and is also movable along the length of the object.

7. A printing machine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

41 publibhed 1988 at The Patent Ofnee, State House, 8&71 High Holborn, London WC1R 4TP. Further copies may be obtained from The Patent OMea, Wes Branch, St Mary Cray, Orpington, Kent BRS 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Con. 1/87.