AU479552B2 - Mandrels for supporting containers - Google Patents

Description

7 8 .1 4 This invention relates to mandrels for supporting open-

topped containers of circular cross-section, for example cylindrical or frusto-conical containers, and is concerned more particularly, but not exclusively, to mandrels suitable for use in a multi-cylinder printing machine as described and illustrated In British Patent Specification No. 1,316,272.

In the printing of containers mounted on rotary mandrels, it is essential for satisfactory results that the containers be accurately centered relative to the rotational axis of the mandrel, since otherwise the pressure between the printing plate and the container would vary during rotation of the mandrel. Various constructions of expandable mandrels comprising col lars slidable along tapered cores have been proposed for holding and centering containers in printing- machines, but such mandrels are not suitable for use with thin walled containers having little resistanmce to transverse deformation, since the rressure between the printing plate and a part of the container sL'pported by a collar of the mandrel tends to be greater than the pressure between the printing plate and a part of the container not so supported.

According to the present invention there Is provided a mandrel for holding and centering an open-topped container of circular cross section, comprising a rotatable body having an outer end which is adapted to extend Into the interior of the container through the open top thereof, two axially spaced centering rings secured to or integral with said body, the two rings being adapted to engage the walls of the container and centralize the container relative to the axis of the mandrel upon axial movement of the container on the mandrel towards the innier end thereof, and said rings subdividing the space enclosed between the container and the mandrel body therein into an end chamber between the outer end of the mandrel and the base of the container and an annular chamber between

-2 479552

78,141 the mandrel body and the side wall of the container, suction conduit

means for extracting air from said end chamber, and pressure conduit

means for supplying air or other fluid under pressure to said annular

chamber whereby, in operation, the difference between the pressure

in the end chamber and atmospheric pressure exerts a force on the base of the container holding the container against the centering

rings, and the pressure of the fluid in the annular chamber supports

the part of the container wall between the centering rings. The mandrel of the invention is particularly suitable for

use in printing on thin-walled containers in multi-cylinder printing

machines since the pressure of air in the annular chamber ensures

substantially even contact between the printing cylinders and the

part of the container supported by the air pressure, despite any

small irregularities in the shape of the container or in the printing cylinders.

Moreover, the mandrel of the invention can be of simple

construction and light ±n weight so that a turret of a printing

machine holding a plurality of mandrels can be indexed at greater

speed, resulting in a higher output of the machine, than would be

the case if the turret were fitted with mandrels of heavier construction.. Embodiments of the invention will now be described, by way

of example, with reference to the accompanying drawings, in which- Fig. 1 Is a sectional elevation view of a multi-cylinder

flexographic printing machine fitted with mandrels for supporting

cylindrical containers in accordance with the invention, Fig. 2 is a sectional elevation view, on a larger scale,

of part of the machine of Fig. 1, showing one of the mandrels and

its supporting and drive mechanism,

Fig. 3 is a plan view of an air distribution ring which

controls the supply of air under pressure and the application of

vacuum to conduits in the mandrels on the turret in accordance with rotation of the turret

78,141 Fig. 4 is a detail view of a modified construction of centering ring between the mandrel and the closed end of a

container on the mandrel,

Fig. 5 is a detail view of a modified construction of centering ring between the mandrel and the open end of a container

on the manidrel, and

Fig. 6 illustrates a mandrel according to the Invention suitable for use with a frusto-conical container shown mounted in

position on the mandrel.

The multi-cylinder flexographic printing machine shown in Fig. 1 is substantially the same as the printing machine shown and

described in British Patent Specification No. 1,316,272 except

that the turret is fitted with mandrels in accordance with the present invention. A brief description of the construction and operatior of the printing machine is given hereinafter to facilitate

understanding of the operation of the mandrels illiistrated in the

drawings, but the same reference numerals have been used to identify

similar parts of the two printing machines and reference may be made to specification 1,316,272 for a fuller description of the parts

of the machine not connected with the mandrels.

Referring now to the drawings of the present application, the machine shown in Fig. 1 comprises a base 10 having a peripheral wall

11, several printing cylinders 12 mounted one at each of separate

printing stations B spaced apart around the outside of the wall 11,

a turret 13 rotatably mounted on a vertical spindle 14 on the base

the turret having a plurality of mandrels 15 spaced at equal

angular intervals around the periphery of the turret, a master gear

unit 16 rotatably mounted on the turret and adapted to rotate the

printing cylinders 12 and mrandrels 15 in synchronism, and a Geneva

indexing mechanism 17 operable to index the turret in one direction

of rotation to register each mandrel in turn at a loading station A

7 8.141 (Fig. 3,each of the- above mentioned p)rinting stations B, each of several dryin~g stations C disposed one between each adjacent pair

of printing stations, a final drying station X, and then at an

unloading station Y. The containers to be printed are mounted on

the mandrels. An air distribution ring 100 fixed to the frame of

the machine controls supply of air under pressure and the application

of vacuum to conduits leading to the mandrels to hold and support

containers mounted on the mandrels in accordance with rotation of the turret as hereinafter described.

As shown in Fig. 2, each mandrel 15 is fitted on the outer

end of a spindle 101 rotatably mounted in the turret 13 by bearings

102, 103 spaced apart by two annular spacers 104, the axis of the

spindle being radial relative to the rotational axis of the turret.

The inner end portion of the spindle is fitted with a bevel gear 29

which meshes with a bevel gear 41 forming part of the master gear

unit 16 rotata~iy mounted on the turret, whereby rotation of gear 41

rotates all the spindles 101 and mandrels 15 in sync~hronism.

Each mandrel 15 comprises a tubular cylindrical body 110

secured to -the outer end of the associated spindle 101, the tubular

body 110 being open at its outer end, a centering ring 111 fitted

in the outer end of the body and forming a frusto-conical seat 112

on the outer end of the mandrel, and a further centering ring 113

secured to the in~ner end of the body 110 and forming a frusto-conical

shoulder 114 larger in diameter than the body 110, the taper on the

frusto-conical seat and the frusto-conical shoulder being in the

radial outwdards direction. The container shown on the mandrel in

Fig. 2 has a cylindrical wall 116, a'circular base 117, and a frusto-

conical raill 118 forming the junction between the wall 116 and base

117, the container being of a size such that its cylindrical wall

116 is a loose fit on the body 110 of the mandrel, its frusto-conical wall 118 engages flat against the frusto-conical seat 112 on the

7 8.1 4 1 mandrel, and the mouth of' the container engages on the frusto-conical

shoulder 114 on the mandrel. The centering rings 111, 113 thi's

center the container on the axis of' the mandrel and moreover the

seat 112 and shoulder 114 on these rings make sealing engagement

with the container so that the space between the mandrel and the

contairer' is subdivided by the centering rings into two chambers,

namely an end chamber 120 between the base 117 of' the container and

the body 110 of' the mandrel and an annular chamber 121 between the

cylindrical wall 116 of' the container and the body 110 of' the mandrel.

Each of' the spindles 101 supporting the mandrels has its

inner end formed with a nipple 125 which extends through an air

seal 126 into a separate chamber 127 in the turret, and an axial

duct 128 in the spindle connects the chamber 127 with the chamber

120 formed between the mandrel and the base of' a container thereon.

An air duct 129 in the turret connects the chamber 127 to a port

130 In the wall of' the turret which mates with the stationary c'.r

distribution ring 100.

Each spindle 101 is also f'orme~d with a f'urther axial duct 131,

the outer end of' which is connected by a transverse duct 132 to the

annular chamber 121 formed between the mandrel and a container

thereon, and tl'~inner end of' which is connected by a transverse

duct to the annular cavity 134 formed between rotating air seals

135 fitted to the annular spacers 104 for the bearings 102, 103.

The cavity 134 is connected by a duct 136 in the spacers 104I and by

a duct 138 in the turret to a pipe 139 which leads to a port 140 in

the wall of' the turret which mates with the stationary air

distribution ring 100.

The stationary air distribution ring 100 (Fig. 3) is formed

with an arcuate groove 145 which registers with each of' the ports

130 in the turret during movement of' the associated mandrel from the

loading station A to the final printing station B, and the ring 100

is also f'ormed with a further arcuate groove 146 which registers with

6 479552

7 8,141 each of the ports 1410 in the turret durfng movement of. the associated

mandrel from the first printing station B to the final printing

station B. 7he Groove 1415 is connected by a pipe 1417 to a source

of vacuu.ri and the groove 1416 Is cornected by a pipe 1118 to a source

of air under pressure. The ring 100 is also provided with two ports

1119, 150 connected to atmosphere and arranged to register with each

pair of ports 130, 1410 respectively in the turret when the mandrel

associated with these parts is at the final drying station X. A

further port 151 in the ring 100 is connected to a timed supply of

compressed air and arranged to register with each part 130 in the turret when the associated mandrel is at the unloading station Y.

The operation of the printing machine is as follows:

A container is placed loosely on each mandrel 15 when the

mandrel is indexed at the loading station A (Fig. 3) and at this

position the arcuate groove 11451in ring 100 is in register with port

130 and a vacuum is being drawn through the pipe 1417. The vacuum

in ducts 129, 128 and chamber 120 then draws the container onto the

mandrel until a seal is formed between the frusto-conical seat 112

on the centering ring 111 and the frstol.conical wall 118 at the

base of the container. In this position the open end of the container

engages the conical shoulder 1141 on the mandrel to close off the annular chanber 121.

When the turret turns to index the mandrel and container at

the first prin ting station B the port 1410 comes into register with

the arcuate groove 1146 so that compressed air is supplied through

the pipe 139 and ducts 131, 132 to the annular chamber 121. The

air under pressure in the annular chamber 121 supports the wall of

the container during printing at the various printing stations.

The difference between the high air pressure in the annular

chamber 121 and atmospheric pressure exerts a force on the container

tending to move the container radially outwards on the mandrel, and

the difference between the vacuum pressure in chamber 120 and

7 8.1 4 1 atmospheric pressure exerts a counter foice on the container tending to m~ove the container radially inwards on the mandrel. The cross sectional area of chamber 120 is however considerably greater than the cross sectional area of chamber 121, so that the force due to the vacuumn in chamber 120 is considerably greater than the force

due to the compressed air in chamber 121 and the container Is thus

held securely on the mandrel.

When the mandrel and container are indexed into the final drying station X, the associated ports 130, 140 in the turret are

In register with ports 149, 150 connected to atmosphere so that

the vacuum In chamber 120 is relieved and the pressure in the annular chamber 121 is released. At the unloading station Y port 130 is in register with the pcrt 151 in the ring 100 and a timed

blast of compressed air from port 151 enters the chamber 120 and

ejects the co itainer from the mandrel at the appropriate inatant in

the machine cycle. As shown in Fig. 4. the centering ring on the outer end of

the mandrel may comprise a resilient sealing ring 160 of rubber

or rubber-like material mounted in an annular groove in a frusto-

conical end wall of the mandrel, the ring 160 being arranged to

engage the frusto-conical wall 118 around the base of the container.

As shown in Fig. 5, the centering ring on the inner end of the mandrel may comprise a collar 165 secured to an inner end wall

of the mandrel, the collar having an internally projecting annular

ridge 166 adapted to engage the outside of a container mounted on

the body of the mandrel. This construction has the advantage that the wall of the container is forced against the ridge 166 upon

expansion of the container under the influence of fluid pressure in

the annular chamber 121 formed between the mandrel and the.

corntain~er, thereby increasing the effectiveness of the seal between

the ridge 166 and the container.

78,141 The mandrel sho'-n in Fig. 6 for use with frusto-conical

containers comprises a frusto-conical body 170 formed at its ends

with raised frusto-conical shoulders 171, 172 adapted to mate with

the inter.al surfaces of the container and thereby center the

container on the mandrel, the space enclosed between the frusto-

conical wall of the container and the two shoulders forming the

annular char.ber 121 to be supplied with fluid under pressure to

support the wall of the container in accordance with the invention,

and the space enclosed between the base of the container and the

outer end wall of the mandrel forming the chamber 120 to be

evacuated to hold the container on the mandrel.

Containers for use with the mandrels of the invention need

not necessarily have straight walls as shown in the drawings. For

example, the open ends of the containers may be necked, that is

the internal diameter of the open end may be less than the internal

diameter of the remainder of the container, or the base of the

container may be concave as viewed from outside the container.

Claims (1)

1. 7 8,14 1

   The claim-s defining the invention are as follows:

   1. A mandrel for holding and centerinG an open-topped container

   of circular cross section, comprising a rotatable body having an

   outer end which is adapted to extend into the Interior of the

   container through the open top thereof, two axially spaced centering

   rings secured to or integral with said body, the two rings being

   adapted to engage the walls of the container and centralize the

   container relative to the axis of the mandrel upon axial movement of

   the container on the mandrel towards the inner end thereof, and said

   rings subdividing the space enclosed between the container and the

   mandrel body therein into an end chamber between the outer end of the

   mandrel and the base of the container and an annular chanmber between

   the mandrel b3dy and the side wall of the container, suctiorn conduit

   means for extracting air from said eiid chamber, and pressure conduit,

   means for supplying air or other fluaid under pressure to said annular

   chamber whereby, in operation, t-he difference between the pressure

   in the end chamber and atmospheric pressure exerts a force on the

   base of the container holding the container against the centering

   rings, and the pressure of the fluid in the annular chamber supports

   the part of the container wall between the centering rings.

   2. A mandrel as claimed in claim 1, wherein the centering ring

   at the outer end of the mandrel Is frusto-conical and adapted to

   engage a corresponding frusto-conical part of the container surrounding

   the base thereof.

   3. A mandrel as claimed in claim 1, wherein the centering ring

   at the outer end of the mandrel is resilient and adapted to make

   sealing engagement with a frusto-conical part of the container

   surrounding the base thereof.

   47955 2

   78,141 41. A randrel as claimed in any one of claims I 3, wherein the centering ring at the Inner end of the mandrel is frusto-conical

   ar adapted to engage the inside of the open end of the container.

   A 7.andrel as claimed in any one of claims 1 3, wherein the centering ring at the inner end of the mandrel has an

   internally-projecting annular ridge adapted to engage the outside

   of the container mounted on the body of the mandrel.

   6. A mandrel as claimed in claim 1 and suitable for holding

   -and centering a frusto-conical container, wherein the mandrel body

   is frusto-conical and formed at its ends with raised frusto-conical

   shoulders constituting said centering rings, the space enclosed

   between the shoulders, the container and the mandrel body forming

   said a-nular chamber, and the space enclosed between the base of

   the container and the outer end wall of the mandrel body forming

   said end chamber. 7. A multi-cylinder printing machine having a plu-ality of

   mandrels as claimed in any of the preceding claims, the maadrels

   being rotatably morntzd on a turret angularly movable to index each

   mandrel in succession at a loading station, a plurality of printing

   stations, and an unloading station, wherein valve means are operable

   upon rotation of the turret to connect the suction conduit means

   of each randrel to vacuum during passage of the mandrel through the loading station and the printing stations and to connect the pressure conduit means of each mandrel to a source of fluid under pressure

   during passage of the mandrel through the printing stations. 7 8. A multi-cylinder printing machine as claimed in claim wherein said valve means are operable to connect the suction conduit

   means and the pressure conduit means of each mandrel to atmosphere

   during passage of the mandrel between the final printing station and

   the unloading station.

   47 9 5 5 2

   78,141 rn 9. A multi-cylinder printirn machine as claimed in claim 8, wherein said valve means are operable to connect the suction conduit

   means of each mandrel to a timed blast of compressed air upon

   indexing of the mandrel at the unloading station to thereby eject

   a container from the mandrel.

   D A T E D this 11th day of February, 1 9 7

   CHROUIAX LIMITED

   By its Patent Attorneys:

   CALLINAN AMD ASSOCIATES

   78,141

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   78,14 1

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