US3302564A

US3302564A - Stencil-printing machine

Info

Publication number: US3302564A
Application number: US383775A
Authority: US
Inventors: Wilford Ernest
Original assignee: Bradford Dyers Association Ltd
Current assignee: Bradford Dyers Association Ltd
Priority date: 1963-07-19
Filing date: 1964-07-20
Publication date: 1967-02-07
Anticipated expiration: 1984-02-07
Also published as: DE1264380B; GB1009740A; AT254816B; NL6408117A

Description

Feb. 7, 1967 E. WILFORD 3,3@2,554

STENCILPRINTING MACHINE Filed July 20, 1964 3 Sheets-Sheet 1 Feb. 7, 1967 E. WILFORD STENCIL-PRINTING MACHINE Filed July 20, 1964 3 SheetsSheet 2 3 Sheets-Sheet 3 Filed July 20, 1964 United States Patent 3,302,564 STENCIL-PRINTING MACHINE Ernest Wilford, Crossflatts, Bingley, England, assignor to The Bradford Dyers Association Limited, Bradford, England, a British company Filed July 20, 1964, Ser. No. 383,775 Claims priority, application Great Britain, July 19, 1963, 28,727 63 4 Claims. (Cl. 101123) In machines for the stencil-printing of textile fabrics in more than one colour, there is a support over which the material is moved in step-by-step fashion, a stencil which lies immediately above the material on the support and which has imperforated ends and a central perforated part, and an applicator for the colouring matter. This applicator usually reciprocates over the stencil in each printing stroke, and at the end of each stroke comes to rest on an imperforate part of the stencil. In order to allow the fabric to be moved through one step into position for the next printing stroke, the applicator and stencil are lifted off it by lifting mechanism. In the perforated part of the stencil the openings may be completely void or may be partly occupied by the meshes of a screen.

The applicator may be a botttomless container, the lower edges of which are formed by flexible lips of rubbet or similar material and thus act as squeegees in that on each stroke the trailing rubber strip forces the colouring matter before it over the stencil and through the openings in it. No great difficulty arises so long as the colouring matter is a fairly viscous paste. When, however, pile fabrics and particularly pile carpets are to be printed, I have found it necessary to use a free-flowing liquid as the colouring matter, in a bottomless container, to apply suction to the underside of the stencil and to maintain substantially constant the pressure difference set up across the stencil and fabric by the head of the liquid and the suction, all as described in our US. Patent 3,129,- 442.

Now although the process and apparatus described in US. Patent 3,129,442 are wholly satisfactory when the openings in the stencil are fairly large, it is found that there is difliculty when fine lines must be printed and in consequence the openings in the stencil are very narrow. It then becomes desirable to apply positive pressure to the liquid. If such pressure is to be applied, it is also desirable to use another form of applicator, namely one comprising a container with a narrow bottom outlet which lies between two squeegees that are fixed to the underside of the bottom of the container, these squeegees acting in the same way as those formed by flexible lips on a bottomless container. With the use of pressure in such an applicator it is possible to force the colouring liquid right through the material. However, while printing is not taking place the pressure of the colouring liquid on the imperforate end of the stencil forces the stencil away from the bottom outlet, so that there is leakage of colouring liquid on to the stencil outside the area occupied by the container. This drawback can be avoided by cutting off the supply of colouring liquid at the end of each printing stroke under the control of a timing device, but then the printing is uneven, as at the beginning of each stroke the fresh application of pressure on the colouring liquid causes the liquid to surge downwards and in consequence the printing is heavier at the beginning of the stroke. If a timing device is employed it is impossble to control the pressure at a constant value. Fluctuatons in pressure of as little as lb./sq. in. cause uneven printing on the carpet.

The greater the pressure on the colouring liquid in the container, the greater is the risk of leakage of colouring Patented Feb. '7, 1967 'ice liquid under the edge of the squeegees while the applicator is on the imperforate portion of the stencil at the end of the stroke. If leakage occurs the colouring liquid may pass beyond the imperforate part of the stencil, and onto the screen or other perforate part, where it will be sucked into the carpet by capillary action. The effect of this is that part of the carpet receives a preliminary quantity of colour before the printing stroke begins, and is thus more heavily printed during the first portion of the printing stroke than the remainder. If the leakage becomes really serious, it is necessary to stop the machine to prevent colouring liquid splashing over the stencil frame onto the adjacent part of the carpet.

Because of this leakage when pressure is used, as is found necessary when fine lines are to be printed, as operator must watch the stencil continuously and remove the colouring liquid by a hand scoop.

According to the invention means are provided for applying suction along and outside each squeegee to draw away colouring liquid leaking under it.

The use of such suction is advantageous in that colouring liquid that has leaked beneath the edges of the squeegees is removed by the suction.

Two apparatus according to the invention will now be described by way of example with reference to the accompanying drawings, in which:

FIGURE 1 is a diagrammatic elevation of the first apparatus;

FIGURE 2 is a diagram of an applicator above a stencil;

FIGURE 3 is a diagrammatic vertical section through the applicator;

FIGURE 4 is a longitudinal vertical section through part of a modified applicator; and

FIGURES 5 and 6 are cross-sections in the lines VV and VIVI respectively in FIGURE 4.

FIGURE 1 shows part of a machine for printing carpets, comprising a main frame 1 that includes a support 2 over which the carpet is moved in step-by-step fashion during printing in a series of printing stations. At each printing station there is a stencil 3 and a colour applicator 4. The stencil 3, as shown in FIGURE 2, is formed by a central screen 50 which has imperforate ends 51 lying within a frame 52, and in operation the applicator 4 comes to rest at the end of each stroke on one of the imperforate ends 51 and on the next stroke reciprocates across the stencil as shown by arrows A and comes to rest on the other imperforate end. At the end of each stroke the stencil and applicator are lifted as a whole to allow the carpet to move.

The applicator shown in FIGURE 3 has a central pressure chamber 5 for colouring liquid lying within a suction chamber 6 both chambers being mounted on a block 8. The block 8 carries two rubber members 9 of inverted U-shape which extend over the whole length of the applicator, that is to say over the whole width of the machine. The inner walls 10 of these members 9 constitutes squeegees lying on each side of a space 11 to which passages 12 in the base of the chamber 5 and the block 8 lead. Passages 13 are formed through the members 9 and the block 8 to put the suction chamber in communication with. the spaces within the members 9.

The applicator is closed at the top except for openings to which pipes 14 and 15 are connected. The pipes 14 branch from a pipe 16 which is connected to the pressure side of a pump 17 by which colouring matter is drawn from a container 18 and supplied to the central chamber 5 through tubes 7 which extend upwards through the top of the suction chamber 6. The pipes 15 branch from a suction pipe 19 which is connected to a suction pump 20, the pressure side of which delivers to the container 18.

In operation both the

pumps

17 and 20 runs continuously so that colouring liquid is supplied to the central chamber 5 and suction is applied through the suction chamber 6 to the interiors of the members 9. In consequence, colouring matter that leaks beneath the squeegee 10 and builds up in the spaces between the members 9 to the level of the bottom of the passage 13 is drawn away and returned to the container 18. The outer walls of the members 9 'act as outer squeegees, and in effect bound chambers outside the squeegees constituted by the squeegees 10, the suction being applied to these chambers.

One advantage obtained is that when a wide material, for example broadloom carpeting, is being printed, sagging of the stencil towards the centre is overcome by the upward suction. In addition, if the suction is maintained at the end of each printing stroke it exerts an upward lift of the stencil which causes this to remain in firm contact with the squeegees and thus to prevent leakage when the stencil and applicator are lifted.

The applicator shown in FIGURE 3 may be used with advantage whenever positive pressure on the liquid is desirable.

When a deep pile carpet is being printed in a pattern that includes fine lines, it is found that neither the use of the combined gravity head and suction nor of positive pressure alone gives the best results. Rather it is desirable to effect the printing in two stages. In the first of these stages free-flowing colouring liquid is applied to the stencil under gravity while suction is applied to the underside of the fabric and in the second stage further colouring liquid is applied to the stencil under positive pressure. If the line is very narrow, the printing in the first stage will adequately colour the top of the pile, but the colouring liquid will tend not to colour the base of the pile uniformly. Rather, the colour extends downwards in decreasing width. When the further colouring liquid is applied under pressure in a second stage, the pile becomes substantially uniformly coloured throughout its whole depth over the desired narrow line.

A pattern to be printed on a carpet often is formed by relatively large areas of different colours, for example of seven different colours, and fine lines of another colour. In order to print such a carpet there may be eight printing stations, one for each colour, and at each at which the areas are relatively large the printing may be effected with the liquid under a gravity head and the application of suction below the perforated support over which the carpet moves. In the remaining station the printing may be effected in two stages with the use of an applicator as shown in FIGURES 4 to 6 and with the application of suction to the underside of the carpet.

The applicator of FIGS. 46 is a box-like structure having end walls 21 and side walls 22. An assembly 23 extends from one end wall to the other within the side walls and is composed of a top header section 24, a middle chamber section 25 and a bottom printing section 26. The top header section 24 is bounded at the underside by a horizontal partition 27 and is divided longitudinally by vertical partitions 47 into alternating suction and

supply pipes

30 and 31 are connected. There 'are three suction chambers 28 and two pressure chambers 29. Below the partition 27 the middle section 25 is divided by vertical partitions 48 into a further pressure chamber 54 and two

lateral suction chambers

32 and 33. Passages 34 are made through the partition 27 to put both the pressure chambers 29 in communication with the chamber 54, and passages 49 are made in the same partition to put all the suction chambers .28 in communication with both the

suction chambers

32 and 33. A nozzle 35 lies beneath the bottom of the chamber 54 and receives colouring liquid from this chamber through opening 36. This nozzle 35 lies in a space 37 between two longitudinal members 38, on the undersides of which there are doublelipped squeegees 39.

The assembly 23 is spaced away from the long side walls 22 to form

chambers

41 and 42 which communicate with the atmosphere through passages 43. Squeegees 44 are clamped to the side walls 22 by plates 50 and form the lower boundaries of the

chambers

41 and 42, which communicate with the

chambers

32 and 33 through passages 45. The squeegees 44 are suitably shaped by bevelling the lips to ensure the best possible contact with the stencil at the end of each stroke, and while the stencil is lifted. In this applicator, it will be seen, the suction is applied to the

chambers

41 and 42, which are bounded by squeegees but which are also open to atmosphere, with the result that colouring liquid can build up in them to the level of the bottoms of the passages 43 when printing is not taking place.

Trunnions 46 are provided on the end walls for engagement by lifting mechanism not shown.

In operation, suction is applied to the underside of the perforated support 2 through a suction box 53, the top of which is formed by the support 2, as shown in FIG- URE 1. This suction is continuously applied throughout the whole of each printing stroke, but is destroyed and replaced by positive pressure at the end of each stroke to enable the carpet or other fabric easily to be moved through one step to bring a fresh length into each printing station.

The pressure on the colouring liquid in the chamber 54 forces it beneath the squeegees 39 into the

chambers

41 and 42, but as these are not under pressure but actually are under suction there is little or no tendency for the colouring liquid to leak past the squeegees 44. In fact during the printing the suction exerted through the passages 45 is largely satisfied by air entering through the passages 43. At the end of each printing stroke colouring liquid passes into and tends to build up in the

chambers

41 and 42, but the extent to which it can build up is limited, since when it reaches the level of the bottoms of the passages 45, the suction ceases to be satisfied by air and is wholly exerted on the colouring liquid. This liquid is thus drawn up into the suction chambers above it, and at the beginning of each printing stroke there is a constant head of colouring liquid in each of the

chambers

41 and 42. As the printing stroke proceeds, colouring liquid flows from the leading

chamber

41 or 42 as the case may be through the openings in the stencil into the carpet. Simultaneously the amount of suction exerted on each opening of the stencil is reduced, as explained in US. Patent 3,129,442, and initial printing therefore takes place under a substantially constant pressure difference. Printing further takes place in a second stage as the space 37 comes over each opening in the stencil, and as explained above this is found to produce more uniform printing through very narrow openings in the stencil than if printing takes place in a single stage.

If desired, printing by an applicator as shown in FIG- URES 46 may be carried out without the use of suction under the fabric. In this case, printing is effected by the colouring liquid in the

outer chambers

41 and 42 under gravity alone, and continued by the liquid in the centre space 37 under pressure.

The invention enables uniform printing to be effected, without the use of timing devices for cutting off the supply of colouring liquid.

I claim:

1. A stencil-printing machine for pile fabric comprising a stencil having imperforate ends and a central perforated part, a support for the fabric passing beneath said stencil, and applicator means mounted for reciprocating movement over said stencil and having a bottom opening extending over the entire length of said applicator means for the supply of free-flowing coloring liquid under pressure to said stencil, a pair of inner squeegees secured to said applicators means on opposite sides of said opening and adapted to bear on said stencil, a pair of outer Squeegees secured to said applicator means and spaced from said inner squeegees on opposite sides thereof to define bounding chambers extending over the entire length of said applicator means outside said inner Squeegees, and means for applying suction to said chambers to draw away coloring liquid leaking under said inner squeegees into said chambers.

2. A stencil-printing machine according to claim 1 wherein said applicator means further comprises a central pressure chamber flanked by two suction chambers and flexible means connected to the tops of said chambers for supplying liquid to the pressure chambers and suction to the suction chambers.

3. A stencil-printing machine according to claim 1 wherein said applicator means further comprises a central pressure chamber lying within a suction chamber and flexible means connected to the tops of said chambers for supporting liquid to the pressure chamber and suction to the suction chambers.

4. A stencil-printing machine according to claim 1 in which each outer bounding chamber is open to atmosphere to allow colouring liquid to build up in it when printing is not taking place.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 9/ 1956 Belgium. 5/ 193 2 Great Britain. 4/ 195 2 Germany.

ROBERT E. PULFR EY, Primary Examiner.

H. P. EWELL, Assistant Examiner.

Claims

1. A STENCIL-PRINTING MACHINE FOR PILE FABRIC COMPRISING A STENCIL HAVING IMPERFORATE ENDS AND A CENTRAL PERFORATED PART, A SUPPORT FOR THE FABRIC PASSING BENEATH SAID STENCIL, AND APPLICATOR MEANS MOUNTED FOR RECIPROCATING MOVEMENT OVER SAID STENCIL AND HAVING A BOTTOM OPENING EXTENDING OVER THE ENTIRE LENGTH OF SAID APPLICATOR MEANS FOR THE SUPPLY OF FREE-FLOWING COLORING LIQUID UNDER PRESSURE TO SAID STENCIL, A PAIR OF INNER SQUEEGEES SECURED TO SAID APPLICATORS MEANS ON OPPOSITE SIDES OF SAID OPENING AND ADAPTED TO BEAR ON SAID STENCIL, A PAIR OF OUTER SQUEEGEES SECURED TO SAID APPLICATOR MEANS AND SPACED FROM SAID INNER SQUEEGEES ON OPPOSITE SIDES THEREOF TO DEFINE BOUNDING CHAMBERS EXTENDING OVER THE ENTIRE LENGTH OF SAID APPLICATOR MEANS OUTSIDE SAID INNER SQUEEGEES, AND MEANS FOR APPLYING SUCTION TO SAID INNER SQUEEGEES, AND AWAY COLORING LIQUID LEAKING UNDER SAID INNER SQUEEGEES INTO SAID CHAMBERS.