Squeegee mount for independent pressure and angle adjustments

Abstract

An adjustable squeegee supporting device of a rotating screen in a sheet material printing machine of the type wherein the squeegee is supported by a bar, the two ends of which are connected respectively to two exterior fixed points through two links and is subjected to the action of position adjusting means. One of the ends of the links is rigidly connected to the bar and the other is pivotally mounted on an axis along the line of contact of the screen with the material. The inclination of the links may be adjusted through two rods connected to two simultaneously adjustable disk-cranks. The free edge of the squeegee is applied against the screen by means of an inflatable tube interposed between the squeegee and its supporting bar.

Description

BACKGROUND OF THE INVENTION

This invention relates to adjustable supporting devices for a squeegee inside a rotating screen in a machine for printing sheet materials such as, for example, cloth.

The invention concerns more particularly the devices of the type in which the flexible squeegee is supported by a bar two ends of which are connected, respectively, to two fixed points exterior to the screen through two links, and is subjected to the action of position adjusting means, for example such as those described in French Pat. publication No. 2006 887.

PRIOR TECHNIQUES

In a known embodiment of this type, the two ends of the bar through which the squeegee is supported are connected to the moving parts of two vertical screw jacks and they are rigidly connected to one end of the two links, the other end of which may horizontally slide in guiding members disposed substantially at the same level as the screen axis. This arrangement has the disadvantage of providing only a single adjusting means, i.e., a height adjustment of the two screw jacks, so that, for each position of said screw jacks there is not only a definite angle of the edge portion of the squeegee against the screen, but also a definite pressure which cannot be varied without modifying the inclination angle of said squeegee. Moreover, the position of the operative edge of the squeegee against the screen cannot be accurately adjusted as desired, said position resulting from the inherent bending of the flexible squeegee in response to the position given to its supporting bar. In other words, the only adjusting means available does not permit individually adjusting the pressure of the squeegee operative edge, the angle of the squeegee edge portion with the screen, and the accurate position of the squeegee edge.

In a further known embodiment of the aforesaid type, each end of the bar which supports the squeegee is no longer rigidly connected to one end of the link, but is rigidly connected to one end of the moving part of the corresponding vertical screw jack, the other end of which, i.e. its upper end, is pivotally mounted about a horizontal axis, while each end of said bar is pivotally mounted on one end of the corresponding link, the other end of which is also pivotally mounted on the exterior fixed point, the length of said link being adjustable. Two adjusting means are thus available, i.e. a height adjustment through vertical screw jacks and a horizontal adjustment through the length adjustable link. However, the squeegee is widely distorted and thus assumes an inherent bending resulting from the combination of said two above noted adjustments. Due to the fact that the two adjustments react upon each other, it is very difficult to impart to the squeegee a predetermined angle at the same time as a predetermined pressure, independently from each other and, moreover, to accurately position the operative edge of the squeegee, since in any case, three parameters have to be determined whereas only two adjusting means are available.

OBJECT AND SUMMARY OF THE INVENTION

The present invention has for its object the provision of a reliable device of simple construction which, however, permits an individual accurate adjustment of the squeegee pressure against the screen and of the angle of the operative edge thereof with the screen surface, all by distinct and easily operable means.

For this purpose, the device is designed in such a way that the operative edge of the squeegee is always automatically located substantially along the desired line of contact of the screen with the material, i.e. always the same, at the location where printing must take place, while through two very simple means, not reacting upon each other, the angular position of the squeegee and its pressure against the screen may be individually adjusted.

Therefore, according to the present invention, the two ends of the squeegee supporting are rigidly connected to one end of each link, of fixed length, the other end of which is pivotally mounted about an axis which coincides with the horizontal plane along which said screen is intended to engage with the sheet material to be printed, the operative edge of the squeegee being disposed adjacent the line of contact of the screen and the material, the adjusting means for the position of the bar consisting of simultaneous adjusting means for the angular position of the two links relative to the horizontal plane of the screen containing said line of contact, said device further comprising means for resiliently flexing the squeegee so that its operative edge is in engagement with the inner surface of the cylindrical screen coinciding with said line of contact.

With such a device, there is no need to care for the position of the squeegee edge, since said edge is always at the right place. The inclination angle of the squeegee may be conveniently adjusted by giving to the links a corresponding inclination and this without any interference with the squeegee pressure, which is adjusted through independent adjusting means.

According to a preferred embodiment of the invention, the adjusting means for the squeegee pressure against the screen is in the form of an inflatable air tube arranged so as to be connected to an air supply at a suitable pressure, and interposed between the squeegee and its supporting bar.

The invention will be more clearly understood from the following description with reference to the accompanying drawings, which represent, by way of example only, one embodiment of a squeegee supporting device according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a side view of the device according to the invention,

FIG. 2 is a top view of the device of FIG. 1,

FIGS. 3 and 4 show on an enlarged scale the maximum and minimum limit inclination positions of the squeegee relative to the screen, with the edge of the squeegee being not applied against said screen, and

FIG. 5 shows the squeegee in operative position, with the same inclination as in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

The device illustrated in FIGS. 1 and 2 is intended for adjustably supporting a squeegee 1 (see FIG. 3) inside a rotating cylindrical screen 2 for printing on sheet materials such as for example a cloth 3. The location of the rotating screen 2 is immovable with respect to the machine frame 21.

The squeegee 1 is secured, for example, through a clamp 5 to a portion of a rectangular cross-section bar 6 disposed inside the screen and the ends of which comprise two sockets 7, 8 secured to a round bar 9 extending axially through the screen and protruding outwardly of said screen at each end thereof.

The two ends of bar 9 are supported in the same manner so that only the supporting means for one of said ends will be described, with the supporting means for the other end of said bar being designated by the same reference numerals bearing the suffix A.

The two ends of bar 9 are thus supported by the upper ends of two links 12, 12A. The lower end of link 12 is pivotally mounted about an axis 13 on the upper portion of a leg 14, the lower end of which is carried by a plate 15 secured in turn in a horizontal arm 16 of a bracket 17 integral with a tube 18 which is secured to two supports 19, 19A, fixed on frame 21 of the printing machine.

The reference numeral 22 indicates for illustration purposes, a supporting roller for the sheet 3 to be printed on. The pivoting axis 13 for the link 12 on the leg 14 is situated substantially in alignment with the nip of roller 22 with the cylindrical screen 2. The accurate positioning of said axis is facilitated by the fact that leg 14 is vertically adjustable through means schematically illustrated in the drawings in the form of a bolt 24 which extends through a hole in the leg 14 and a vertical slot 25 in the plate 15, with the latter being also horizontally adjustable through similar means, for example, in the form of a bolt 26 which extends through a hole in said plate and a horizontal slot 27 in the arm 16.

In FIG. 1, the direction of link 12 is the same as that of the rectangular bar 6 so that the latter is not visible on said figure.

The inclination of links 12 and 12 A may be adjusted by means of two also identical devices, one of which comprises a rod 31, one end of which carries two bent fingers 32, 33 which grip the corresponding end of the round bar 9 and the other end of which is pivotally mounted on a crank pin 34 of a crank disk 35 rigidly secured to one end of a transverse shaft 36 rotatably mounted within tube 18. The other end of shaft 36 carries a crank-disk 35A having a crank pin 34A for driving a rod 31A connected to the other end of the round bar 9. The angular position of the crank-disk 35 may be conveniently adjusted through a worm 41 rotatably vertically mounted in bracket 17 and meshing with a tangential toothed wheel consisting of a toothing 42, cut for example in the edge of crank-disk 35. The upper end of the worm shaft carries a knurled control knob 43 through actuation of which, the worm 41 may be selectively rotated in either direction, so as to cause rotation of the two crank-disks 35 and 35A in a corresponding direction, thus modifying the inclination of links 12 and 12A and thereafter that of squeegee supporting bar 6.

The above described construction is so arranged that, when the squeegee 1 is disengaged from the cylindrical screen 2, whatever may be the inclination of links 12 and 12A and therefore that of supporting bar 6, the operative edge of the squeegee 1 is always substantially along the nip of cylindrical screen 2 with the pressure roller 22, i.e. the line designated A in FIGS. 3 to 5.

FIG. 3 shows the squeegee in one of its limit angular positions in which it defines with the inner surface of screen 2 a maximum angle B, while in FIG. 4, said squeegee has reached its other limit angular position in which it defines with the inner surface of screen 2 a minimum angle C. In FIGS. 1 and 2, the squeegee forms an angle of intermediate value between that of angles B and C of FIGS. 3 and 4, respectively.

The squeegee 1 which is a flexible strip secured only along its upper edge, may be applied at the desired pressure by its opposite edge against the inner surface of the screen by any suitable means which consists, in the embodiment illustrated, of an air tube 51 housed in a longitudinal groove 52 formed in the side of the rectangular bar 6 facing the squeegee. When no compressed air is supplied to tube 51, the squeegee assumes a natural planar configuration due to its inherent resiliency, whereas when air under a suitable pressure is supplied to tube 51, a deformation of the portion of the squeegee which is not squeezed between the clamp 5 and bar 6 is obtained, so that the free edge of said squeegee will bear against the inner surface of cylindrical screen 2, as shown in FIG. 5. The pressure of the squeegee may be adjusted as desired by varying the value of air pressure discharged into tube 51 through a hose 53 (FIG. 2).

Therefore, the adjustment of the inclination of the squeegee by means of the knurled control knob 43 and the adjustment of the pressure of said squeegee against the screen by means of compressed air directed into air tube 51 are completely independent from each other, which permits to impart to said two adjustments optimum individual values. Whatever the selected adjustments may be, there is no need to care for the position of the squeegee edge since the latter is always substantially adjacent the nip A due to the structure of the device, with the squeegee support pivoting about axis 13 which is precisely situated in alignment with nip A.

While only one embodiment of the invention has been shown and described it is to be understood that modifications can be made without departing from the scope of the appended claims.

The squeegee strip may be made of an elastomer, particularly of a plastic material, and preferably polyurethane; its Shore A hardness is preferably between about 70 and 92 and its thickness is in the range of 1.5 to 5 % of the free width between its free edge and the edge of clamp 5.

Claims

What is claimed is:

1. A device for adjustably supporting a flexible squeegee within a rotating horizontal cylindrical screen of a sheet material printing machine, said screen engaging the material to be printed along a nip, said squeegee having a securing edge and a free operative edge, said device comprising: a supporting bar extending axially through said cylindrical screen and longer than the axial length of said screen, said supporting bar having end portions, said securing edge of said squeegee being secured to said supporting bar, fixed support means, two links located at either end of said screen, the end portions of said supporting bar being respectively rigidly secured to one end of one of said links, the other end of each of said links being pivotally mounted to said fixed support means on an axis which is in alignment with said nip, supporting bar adjusting means connected to said fixed support means for adjusting the angular position of said two links relative to the radial plane containing said nip, said operative edge of said squeegee always being located substantially along said nip, and means for biasing said squeegee to cause said operative edge of said squeegee to press the inner surface of said screen at said nip with a predetermined pressure.

2. A device as defined in claim 1, wherein said supporting bar adjusting means comprises: two crank-disks each having a crank-pin, two further links, each further link having one end pivotally connected to the crank-pin of one of said crank-disks and the other end pivotally connected to one end of said supporting bar, a horizontal shaft parallel with said squeegee rotatably mounted on said fixed support means, said crank-disks being rigidly secured to said pivoting shaft, and means for adjusting the angular position of said shaft.

3. The device as defined in claim 1, wherein said biasing means comprises an inflatable air tube extending lengthwise between said supporting bar and said squeegee, said inflatable air tube engaging said supporting bar and a longitudinal area of said squeegee located between said securing edge and said operative edge of said squeegee.