FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to a pallet registration apparatus and method and, more particularly, but not exclusively, to such registration for the purposes of printing a textile at multiple stations.

Textile printing using digital printers at multiple stations requires accurate registration of the pallet at each station so that the different operations at the different stations are aligned. Registration is generally required to be fast and accurate, and the alignment system should be easy to calibrate, rarely need recalibration, and not be prone to part failure. In particular when using digital printers, the registration needs to be within the accuracy level of the individual printed pixel.

An existing system for a multi-station printer uses a pallet which is placed on a trolley. At each station, registration sockets on the pallet are engaged by cones and the pallet comes to rest at the location defined by the points of at least two cones in corresponding registration sockets.

Aligning the pallet in this way has disadvantages. First of all, calibration requires alignment of the sockets over the different stations. Secondly, the cones may blunt over time, making accurate registration more difficult. Thirdly, settling time is relatively large, as the pallet has to settle in the position defined by two different cones in two different sockets. SUMMARY OF THE INVENTION

The present embodiments provide the pallet with a cam follower that works against tension on the pallet to guide the pallet into a stop position which is defined by a single stationary roller.

The pallet and trolley may have three degrees of freedom, two linear and one rotary, and sources of tension may pull the pallet into the stop position so that the pallet is held into the roller in a defined position in the cam follower, against all three degrees of freedom. A second roller may work with an exit track added to the cam to provide a disengagement path for the pallet and also hold the pallet against movement in the three degrees of freedom.

According to an aspect of some embodiments of the present invention there is provided a pallet registration apparatus for a pallet and a multiple station printing machine, the pallet configured to carry a printing substrate for printing operations at a plurality of stations of the printing machine, each one of the stations requiring corresponding registration of the printing substrate, each station providing a stop position for the pallet, the pallet comprising a cam follower on a first side to guide the pallet into each of the stop positions, wherein each stop position is defined by a stationary roller on the printing machine, and the cam follower comprises a track for engaging the roller, the track comprising an inclusion for receiving the roller and stopping the roller at the stop position defined by the stationary roller.

In an embodiment, the pallet is carried by a trolley and the pallet and trolley have a first linear degree of freedom parallel to the cam follower, a second linear degree of freedom perpendicularly towards the cam follower, and a rotary degree of freedom in a plane whose axis is perpendicular to the cam follower.

In an embodiment, sources of tension are located to act on the pallet from the trolley to pull the pallet into the stop position against all three degrees of freedom.

In an embodiment, the cam follower has an upper cam track and a lower cam track.

In an embodiment, each first stationary roller is aligned with the upper cam track and a respective second stationary roller, associated with each first stationary roller, is aligned with the lower cam track.

In an embodiment, one of the cam tracks defines the stopping position and the other of the cam tracks defines a release path for the pallet for onward travel after treatment at a given one of the stations.

In an embodiment, the inclusion comprises a concave inclusion sized for the first stationary roller.

In an embodiment, the other cam track defines a flat section against the second roller when the first roller is located in the concave inclusion and a sharp curve having a predefined depth, the sharp curve being in front of the second roller in a pallet travel direction when the first roller is located in the concave inclusion.

In an embodiment, the sharp curve defines successive depths to push against the second roller as the pallet leaves for onward travel, to cause the cam follower to disengage the first roller and release the pallet.

In an embodiment, the concave inclusion defines a pressure angle of between 45 and 65 degrees, and the pressure angle is the angle defined between the direction of motion of the cam follower and the direction of an axis of motion transmission.

In an embodiment, the stationary rollers are located on a plate, the plate having at least two adjustment holes, thereby to allow calibration to provide alignment at each station.

An embodiment may involve a machined X rail surface to provide a reference.

In an embodiment, calibration for a rotation of the trolley is defined according to a rotation print file.

According to a further aspect of the present invention there is provided a pallet for a multiple station printing machine, the pallet configured to carry a printing substrate for printing operations at a plurality of stations of the printing machine, each one of the stations requiring corresponding registration of the printing substrate, each station providing a stop position for the pallet, the pallet comprising a cam follower on a first side to guide the pallet into each of the stop positions, wherein each stop position is defined by a stationary roller on the printing machine, and the cam follower comprises a first track for engaging the roller, the track comprising an inclusion for receiving the roller and stopping the roller at the stop position defined by the stationary roller.

The pallet may be carried by a trolley, wherein the pallet has a first linear degree of freedom parallel to the cam follower, a second linear degree of freedom perpendicularly towards the cam follower, and a rotary degree of freedom in a plane whose axis is perpendicular to the cam follower.

In an embodiment, sources of tension are located to act on the pallet from the trolley to pull the pallet into the stop position against all three degrees of freedom.

According to a further aspect of the present invention there is provided a textile printing machine having a plurality of stations for carrying out respective print operations on textiles carried on a series of pallets, the textile printing machine comprising stationary positioning rollers at each station configured to engage cams on the pallets and stop pallets at predefined stop positions at each station, the positioning rollers being located on adjustable plates, thereby to allow corresponding calibration at each station to provide mutual alignment of the stop positions.

The machine may include a release roller associated with each positioning roller on each plate, the release roller configured to engage second cam tracks on the pallets to release the pallets from the predefined stop positions.

According to a yet further aspect of the present invention there is provided a method for aligning pallets at successive stations on a station-based printing machine, the pallets carrying textiles for printing, the method comprising:

at each station providing a stationary roller;

on each pallet providing a cam track, the cam track having an inclusion for locating on respective stationary rollers to define a stop position of the respective pallet at each station;

calibrating each roller so that different stop positions at different stations provide references to allow for correspondence of pixels printed at the different stations;

driving the pallets between each station;

at each station allowing engagement between the pallet and the roller to arrest respective pallets.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

In the drawings:

Fig. 1 is a simplified schematic diagram showing a pallet in a stop position defined by a registration apparatus made up of a cam track and a roller according to embodiments of the present invention;

Fig. 2 is a simplified schematic view showing the degrees of freedom of a pallet on a trolley of the embodiments of Fig. 1;

Fig. 3 is a view from above of the cam track and roller and showing the pallet approaching the stop position shown in Fig. 1;

Figs. 4.1 to 4.4 are four figures showing successive positions of a pallet as it approaches a stop position, engages the stop position, begins departure from the stop position and leaves the stop position;

Fig. 5 is a view of the registration apparatus of Fig. 1 where the pallet has just left the stop position;

Fig. 6 is a view from above of the pallet on a trolley according to the present embodiments wherein tensioning means are used to hold the trolley in three degrees of freedom when pressed against the first and/or second position rollers;

Figs. 7 A and 7B are schematic diagrams illustrating the use of a pressure angle in constructing the cam of the present embodiments; and

Fig. 8 is a simplified diagram showing a machined rail on a multi-station printer that may be used as a reference for calibrating the registration apparatus of the present embodiments. DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to a pallet registration apparatus and method, a pallet, and a multiple station textile printing machine and, more particularly, but not exclusively, to such registration for the purposes of printing a textile at multiple stations.

The pallet carries a printing substrate for printing operations at the successive stations on the printing machine, requiring corresponding registration at each station. Each station has a positioning roller that defines a stop position for the pallets. The pallets in turn have a cam follower that tracks the positioning rollers to guide the pallet into each stop position. The track engages the positioning roller, and has an inclusion which receives the roller and stops the pallet as the roller enters the inclusion.

The printing operations are typically digital printing operations, say using ink jet printing and nozzles to print pixels.

In greater detail, a stationary positioning roller is provided at each station. A pallet rides on a trolley and has a cam follower attached on one side. The cam follower has a track aligned for the roller and a concave inclusion along the track that receives the roller at a given position that defines the stop position. Springs or other tension means between the trolley and the pallet serve to push the pallet into the roller and prevent motion in any of three degrees of freedom including rotation of the pallet from a flat position on the trolley.

A second roller and a second cam track may be provided to allow the pallet to exit the stop position following the particular operation of the given station. The second roller may also hold the pallet in the stationary position against motion in all three degrees of freedom.

The pallet typically carries an item of textile to be printed, and arrives at a first station, where the registration mechanism ensures that the roller and cam track meet and the pallet stops at the position defined by the concave inclusion. A pre-printing or printing operation is carried out, and then forward motion on the trolley engages the second roller which travels up a step or sharply upward curve part on the second track and pushes the pallet away from the rollers, thus disengaging the first roller and allowing the trolley to exist the first station. The trolley then continues on to a second station where the registration process is repeated. A calibration will have been carried out to ensure that the registrations at the two stations correspond so that the printing operation carried out at the second station properly corresponds with the operation carried out at the first station. For example the textile may be a black tee shirt and the first station may print an undercoat of white. The second station may print an image over the undercoat. It is not intended that any of the white should be visible, but rather every last pixel should be overprinted by the image, and the present embodiments may provide an accuracy of registration that allows such a feat to be achieved.

The same is repeated at third and subsequent stations as necessary.

A significant parameter of a registration system is settling time, and the present embodiments may achieve improved settling time since location is based on a single point in space.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

Referring now to the drawings, Figure 1 illustrates a pallet registration apparatus 10 for a trolley 12 that carries a pallet 13, and where the pallet carries a printing substrate such as a textile. Printing is carried out as a series of operations at different stations, in which each one of the stations requires a corresponding registration of the printing substrate, so that the different operations may be aligned. One operation may be to print a white background and then subsequent stations may print the primary colors, and corresponding registration at each station allows the various operations to be aligned. The pallet according to the present embodiments includes a cam follower 14 built in on one of its sides. The cam follower 14 may guide the pallet 13 into a stop position which is defined between the cam follower 14 and a first 16 stationary roller at each station. A second roller 18 is raised with respect to roller 16. The rollers are provided at each station and are fixed in position after calibration. For example the rollers may be placed on a plate or ledge 24 alongside the pallet stopping position at the station. The cam follower may include upper and lower tracks 20 and 22 that ride along the rollers, and consequently the pallet, against tension from the trolley, is guided by the cam follower 14 into a stop position in which the first roller 16 engages with a concave inclusion in the upper track 20. The pallet is subsequently guided out of the stop position by the lower roller travelling along lower track 22, to release the pallet, after the operation is complete, as will be explained in greater detail below.

Thus when stationary, the pallet is pressed by the trolley into the cam track and the rollers by tensioning springs of which two, 36 and 38 are shown in Fig. 1, as will be explained in greater detail below, to provide registration. The pressure against the two rollers holds the pallet against the three degrees of freedom, rendering the pallet stationary at a clearly defined position.

Ledge or plate 24 may be provided with adjustment lugs and holes 26 allowing for the alignment of the ledge to be altered during calibration. In the embodiment illustrated, three adjustment holes and lugs 26 are provided. The ability to align the ledge allows for calibration of the position of corresponding rollers at different stations so that the stop positions at the different stations provide references to allow for correspondence of pixels printed at the different stations.

Reference is now made to Fig. 2, which illustrates the degrees of freedom of the pallet on the trolley. The pallet 13 is carried by the trolley 12, and the pallet and trolley have three degrees of freedom, a first linear degree of freedom - arrow 30 - in the direction parallel to the cam follower and which is the direction of motion of the trolley. A second linear degree of freedom - arrow 32 - is in the direction which is perpendicular to the cam follower. A third degree of freedom - arrow 34 - is a rotary degree of freedom in a plane whose axis is perpendicular to the cam follower.

Returning to Fig. 1, sources of tension in the form of springs 36 and 38, are located on the trolley to pull the pallet into the stop position and immobilize the pallet against all three degrees of freedom.

Reference is now made to Fig. 3, which is a simplified diagram illustrating a view from above of the registration apparatus when the pallet approaches the stop position.

Cam follower 14 is located on the edge of pallet 13, which is located on trolley 12. First and second stationary rollers 16 and 18 are on ledge 24 which belongs to the stationary part of the printer. As the cam follower approaches the rollers, the rollers are engaged and the pallet stops at a stop position defined between first or upper roller 16 and concave inclusion or indentation 42 on the upper track of the cam. The sources of tension push the pallet into the cam follower, via the rollers, to take away the pallet's degrees of freedom so that the stop position is clearly defined. Adjustment mechanism 44 at the side of ledge 24 allows for minor adjustments to the ledge so that the ledges at all stations are aligned. Thus the pallet at the stop position is held between springs and the first roller at a position clearly defined by the cam track.

Thus, as discussed, the cam follower in fact consists of two tracks, an upper and a lower track, wherein the upper track defines the stop position against the upper roller and the lower track defines an exit path for the pallet against the second roller so that the pallet can be released after printing etc. at the given station. The skilled person will appreciate that the roles of the tracks could be reversed.

The cam track defining the stopping position, in the present example the upper track, includes concave inclusion or indentation 42 as discussed above, which may be sized for the first stationary roller and aligned to meet the first stationary roller.

The other cam track may define a flat part for the stationary stage followed by a steep curve or a step having a predefined depth. The other cam track is aligned to be opposite the second roller so that the second roller slides along the cam track as the first roller becomes located in the concave inclusion. The curve on the lower track may define successive depths to push the pallet away from the second roller as the pallet is released for onward travel. The slope pushes the cam follower to disengage the pallet from the upper roller and thus release the pallet.

Reference is now made to Figs 4.1 to 4.4 which illustrate four successive stages of engagement and disengagement of the pallet with the rollers as the trolley advances. Fig. 4.1 illustrates engagement of the cam follower 50 upper track with the first roller 52 as the trolley and pallet 54 approach the stop position.

Fig. 4.2 illustrates the pallet in the stop position. The first roller 52 is in the concave indentation 56 or "V" groove, in the upper track and the pallet 54 is jammed into a very defined position by tension from the trolley acting on the pallet as it pushes via the cam follower 50 against the first roller 52. The second roller 58 is engaged on the lower track.

Fig. 4.3 illustrates the start of motion to leave the stop position. The lower roller 58 rides the lower cam track along a rising exit curve which disengages the upper or first roller 52 from the concave indentation 56.

Fig. 4.4 illustrates the trolley and pallet 54 after disengaging from the rollers 52 and 58.

Reference is now made to Fig. 5 which is a simplified schematic diagram showing in greater detail the upper the and lower cam tracks in relation to the rollers. Cam follower 60 is bolted or otherwise attached to the side of the pallet 62 and has an upper track 64 with a concave inclusion or indentation or "v" groove 66. The upper track is generally straight apart from the inclusion 66. The lower track is curved, and the curve includes a rapid rise or step 69, just after the stop position to push the pallet away and thus disengage the first roller 70. As illustrated, the pallet is shown just before arriving at the stop position.

Reference is now made to Fig. 6, which illustrates a pallet 82 anchored to the frame of a trolley 80. The pallet includes cam follower 84 which is bolted or otherwise attached to the side of the pallet 82. The pallet is anchored by tension from first 86, second 88 and third 90 springs. The springs together ensure that when the pallet is in the stop position against the first roller it is immobilized in three degrees of freedom as discussed above.

Reference is now made to Figs. 7A and 7B which illustrate in greater detail the construction of the cam follower. The cam follower is constructed in order to provide a clearly defined stop position and also allows for easy release of the pallet from the stop position. Upper cam track 92 includes concave inclusion 94 and lower cam track 96 includes a flat section followed by a sharp curved portion or step 98. The release from the stop position, defined by the first roller being located in concave inclusion 94, involves lower roller 100 approaching curve 102. Meanwhile the upper roller 103 has a pressure angle, defined as the angle between the tangent 104 drawn at the contact of the roller with the cam, and the travel direction 106. At a pressure angle of zero there is no stop position and the pallet is free to travel. At a pressure angle of 90 degrees, forward motion will not succeed in getting the pallet to move away from the stop position. Instead an angle between 45 and 60 degrees is preferred for a pressure angle that allows for release from the stop position. As shown the lower roller 100 may just clear the lower track 96 at the stop position in front of the step 98.

Reference is now made to Fig. 8, which is a simplified diagram showing a section 110 of a multi-station printing apparatus in which a machined X rail surface 112 provides a reference that extends along the device to each of the stations to allow for a corresponding alignment at each station. Subsequently, registration may be carried out to align the plate or ledge and then test the alignment using a print file. Separate print files may be used for aligning each degree of freedom so that there would be a separate rotation print file etc.

It is expected that during the life of a patent maturing from this application many relevant textile printers, station-type printers and inkjet printers will be developed and the scopes of the corresponding terms are intended to include all such new technologies a priori.

The terms "comprises", "comprising", "includes", "including", "having" and their conjugates mean "including but not limited to".

The term "consisting of means "including and limited to".

The term "consisting essentially of" means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment and the present text is to be construed as if such a single embodiment is clearly and explicitly described. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention, and the present text is to be construed as if such separate embodiments and subcombinations are clearly and explicitly described. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements. Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.