DE19654702C1 - Pressure-generating system for transfer printing - Google Patents

Abstract

The system presses a transfer sheet against a support (11), having a heated press table (10) accommodated with a plate-type tappet (13) in a supporting frame. The sheet and support are between the table and the tappet and below the latter is an elastic bellows (14) connected to a pressure source and actuating it. The bellows is supported on the frame and is circular, with a peripheral annular bead enclosing an upwards-protruding pressure plate (17) acting against the tappet underside. The plate and bellows enclose the geometrical centre of gravity of the tappet, with which they are in contact over a large area. A mechanism (21) thrusts the tappet in the transverse direction from the working position opposite the table, to allow the sheet and support to be placed on it. To give even pressure between sheet and support, the tappet is movable vertically or on the Z-axis via a three-point guide-pin system. Both the table and the tappet have an elastic cushion (23) filled with heat-resistant gel or oil, so that even uneven supports are subjected to even pressure.

Description

The invention relates to a device for generating Contact forces, especially for color transfer printing Preamble of claim 1.

It has been known for some time, the individual pressure of One-offs or small series based on the so-called color carry out transfer procedure. With this procedure a template, for example a photo, a drawing or a 35mm slide on a laser color copier in one page wrong copy provided as a print template. In the Print template creation is a format change and the end form different colors according to common color charts possible.  

Then the one on a transfer film Print template using a color transfer press under On keep defined temperature, time and pressure conditions transfer the print medium.

So much is achieved through precise temperature and pressure control Energy supplied in the form of heat and pressing force that the Transfer of the image of the print template optimally to the Print media follows without affecting the whole different materials to be printed. The prints obtained are permanent and color stable. With the be written procedures can be extremely short pro Production times of just a few minutes and one particularly high flexibility with regard to the printable Reach materials so that additional uses are accessible.

A previously necessary lamination of the dimensions to be printed materials with plastic film or the like is omitted.

The constant temperature of known transfer presses must be above the entire area kept constant within a range of ± 0.5 ° C will. In addition, pressures are on the order of 7 -8 kg / cm².

Known transfer presses have an electrically heatable Press table and a movable plate-shaped press ram which moves towards the press table during operation becomes.

The press ram takes the pressure carrier and the one above sensitive transfer facing the heated press table film on.

After an appropriate preheating time of the press table he this one in coordination with the size to be printed material and the film used predetermined temperature.  

After the print carrier including transfer film on the be movable plunger is applied, this is analogous to a hydraulic press by an appropriate hydraulic pre towards the press table. Via a defined A predetermined pressure is set over time so that the transfer of the print image from the transfer film adjusts the print carrier.

The press ram is then retracted, in which the hydraulic device in a corresponding Be drive state is shifted.

The disadvantage of known transfer presses is that the hydraulic controls and the entire hydraulic system movement and pressure exerted between the press ram and press table extremely material and cost intensive and are subject to cyclical maintenance.

In the case where large format prints are to be made, it is structurally necessary to segment the press ram and to drive with several hydraulic cylinders.

The smooth, quasi movement and pressure synchronous control however, a large number of hydraulic cylinders are technical very complex. Ensure necessary gear quantity parts do not provide sufficient constant surface pressure over the entire dimensions of the print carrier or the upper area of the press table and press ram.

It has also been shown that when using the known hydraulic transfer presses not readily possible is, tabletop devices for mobile use with a mass to manufacture that easily by people without elaborate technical aids can be moved.

In the generic DE 23 13 006 A1 from a front direction for printing on textile materials, which according to the so-called vacuum transmission process is working. There is an embodiment shown below  of a press table arranged bellows. This Bellows are used to lower a lower plate, if one upper plate from the existing frame using a lever was removed without air entering the entire system.

Using the constructive measures described above DE 23 13 006 A1 is intended to undesirably compress Textile material can be prevented during the printing process, so that the transfer of the printed image improves.

DE 37 17 639 A1 describes a transfer press with a spring Compensating devices known. These equalizers can have bellows. The bellows serve that Uniform pressure force to apply. For this will the press table shown against a frame by means of the resilient compensation devices supported so that ver different spatial directions are adjustable, which in turn non-flat substrates can be printed.

The actual pressure force in the solution according to DE 37 17 639 A1 is operated by means of spindle drives and couplings with a Drive device are connected generated.

DE 32 12 309 A1 describes a transfer printing device known with the convex surface of an article can be printed. Pressure pads are provided for this, which are elastically deformable. In addition, there is Possibility of being made of elastic, heat-resistant material existing pressure pad to improve the quality of the To heat the transfer process.

It is therefore an object of the invention to develop a device for Er testify to contact forces, especially for color transfer printing to indicate from a transfer film on a print carrier, which che permits surface pressures of sufficient strength and Homogeneity with the greatest possible vertical adjustment between table and ram with as little material as possible and other expenses.

The object of the invention is achieved with a counter stood according to the features of claim 1.

The subclaims provide at least a practical design and further training.

According to an essential basic idea of the invention, a movable press ram, which over a three-point pin guide vertically to the press table can be moved.

The three-point pin guide is designed with play where with a printing plate in the geometric center of gravity or Attacks the center of the press ram from below. Through the game affected three-point pin guide and the defined Angrei The press ram can tilt the pressure plate Execute at a predetermined angle and it is safe represents that a uniform pressing of the print carrier and a transfer film, which is located on the press ram, is guaranteed. With the proposed measure, you can otherwise necessary exact parallel guides, the technolo gisch are very complex and especially with differ Chen print media can be problematic, who does not  the. In addition, the pressure plate with a rubber counter piece, which is arranged at the bottom of the press ram or what as a coating on the printing plate itself is included, realize a pressing process, which by a steady increase in pressure is marked. The be written effect is improved in that the Pres plunger facing surface of the press table an elastic layer, for example made of felt is.

The construction briefly described above can be considered Lich the actual pressure generation with both elastic bellows, which with a pneumatic printer ger is connected, cooperate as well as by a suitable Nete hydraulic device with compressive force in the Z direction be hit.

The basic concept of the invention on the device side exists in addition, the necessary movement in the Z direction between the plate-shaped press ram and the heated ren press table and a corresponding press force generation to bring about that below the press ram or an elastic bellows below the pressure plate, for example made of rubber, which is arranged with a pneumatic Print memory or a pressure generator such cooperates that the bellows in when pressurized Direction of the press table, i.e. in the Z direction below Carriage of the press ram expands and moves, which makes Stop of the press ram against the press table or the a transfer film and print carrier in between corresponding pressing force results.

As a result of that the elastic bellows has a circular cross section with a has corresponding ring bead and being quasi from the On the top of the bellows, the ring bead surrounds the mentioned preferably metallic pressure plate is arranged, the  in the event of an operation, i.e. when pressure is applied to the Bottom of the press table is even Power transmission with correspondingly not sudden pressure course guaranteed and on the other hand it is secured represents that by reducing the mass of the pressure plate of the excess pressure in the bellows a faster displacement of the pressure gases takes place, so that the cycle times between expansion shorten and relax the bellows.

The pressure plate can be used on an otherwise necessary Retraction spring can be dispensed with.

Through the formation of the bellows, which is mentioned above Pressure plate has, in conjunction with the guide, a End position of the opposing surfaces of presses table and press ram during the actual printing process ges ensured at which the contact pressure or adjusting surface pressure evenly over the entire Surface section between transfer film and print carrier are distributed.

The bellows is activated by means of a valve or a throttle Direction in a given manner with pressure below sensitive gas, for example compressed air, such that a sudden impact of pressure is avoided. This can also sensitive objects or Drucktra be treated without material damage.

In the invention is the Movable plunger for the transfer film and printing carrier on an insert that can be moved in the Y direction mounted, so that an easier arrangement and removal of Print carrier and film on the ram is possible. Therefor the movable plunger becomes a heatable one Press table opposite position, that is the Working position, changed to a shifted position, being in the position-changed position of the print carrier and  the transfer film can be arranged on the plunger. After Move the insert back with the three-point pin guide is in the working position for the press ram the movable plunger in turn above the pressure plate or of the bellows, so that, as described, pressure is exerted against the heated press table is possible.

The device according to the invention is according to a special Embodiment of the invention with a closed support frame made of profile steel, which the occurring Absorbs and dissipates forces without unwanted deformation tion, especially of the press table.

Accordingly, the support frame takes in the upper section Press table and forms the opening in the lower section bearing of the elastic bellows. By the chosen stable pro fil frame construction results in a further mass reduction ornamentation and easier interchangeability of the individual Components.

A further basic idea of the invention can thus be followed the heated press table has a flat shape have a different shape.

For example, the table can have a concave or convex top have surface shape, so that even non-planar print carriers with be provided with an appropriate decorative coating can.

According to the invention, for generating a uniform surface pressure when using non-level pressure carriers hit an elastic pillow to be arranged on the heated press table. On another elastic cushion is placed on the Press ram arranged. The elastic pillows are filled with a heat-resistant gel or an oil. The pillow attached to the heated press table takes in  essentially the temperature of the press table itself. If there is a non-even pressure medium on the bellows of the press pestle is placed and then by Relativbe movement of the press table and press ram the pressure medium is exerted, so by displacing the gel or oil inside the pillow the pillow the shape of the non-planar print carrier. In this way it is ensured that even sensitive print media almost any shape of a uniform surface pressure can be placed without the risk of destruction or deformation of the print carrier itself.

On the procedural side, this is necessary for color transfer printing contact pressure by applying an elastic bal ges, for example, the type of one from the motor vehicle Technically known air suspension with compressed air from one pressure gas storage or pressure generator realized, a ge desired expansion of the bellows in the Z direction towards pressing table is done. This expansion then leads to Interact with the press table to create an even Surface pressure between the transfer film and the print carrier, the are preferably arranged on the movable plunger.

Due to the pressure transfer having a defined mass supply plate, which is on the bellows and with this is releasably connected, if necessary, an acceleration the pressure reduction from the bellows is reached when a movement is desired in the Z direction of the table.

Because the bellows below and in the geometric heavy point of the movable plunger is arranged and over the Pressure plate in the center of gravity attacks even in the described, less complex mechanical constructive embodiment of the plunger a uniform Press the print carrier and the printing film against the rigid, heated press table guaranteed.  

Since in the described embodiment on a no parallel guidance ensuring positive guidance is, but only with play via appropriate stops and pins the movement in the Z direction is predetermined ensures that no tilting when moving the plunger occurs in the Z direction.

Through an appropriate valve control or the arrangement A throttle in the compressed gas supply line can change the pressure be controlled such that a sudden movement of the respective elastic bellows with the disadvantageous consequences for the print carrier is almost excluded.

A particular advantage of the device according to the invention and the associated method also consists in that Use of conventional, well-known elastic bellows play air vehicle springs, significant cost reductions possible are.

The invention is intended below with reference to exemplary embodiments len and explained with the help of figures the.

Here show:

Figure 1 is a schematic diagram for explaining the color transfer printing.

Fig. 2 is a front view of an apparatus according to an embodiment;

Fig. 3 is a side view of the device shown in Fig. 2;

Figure 4 is a top and side view of the press ram with three-point pin guide.

Fig. 5 top view and sectional view of a support frame portion; and

Fig. 6 is a side view of the press table and press ram, each with elastic cushions arranged there for printing on non-planar parts.

In the color transfer printing apparatus according to Figure 1 is a. Used, which has a for example electrically heatable press table 10.

On a plate-shaped press ram 13 which is movable in the Z direction, the print carrier 11 is located with the transfer film 12 arranged above it.

The transfer film 12 contains an upside down copy of the image to be printed. Toner is transferred to the print carrier 11 by means of the transfer film 12 .

The movement of the plate-shaped press ram 13 is carried out by an elastic bellows 14 which cooperates with a printer generating device (not shown).

The actual process of transferring images to print media ger is by adhering to the parameters pressure, temperature and time given.

The dimensions of the press table are, according to an Aus example, in a range from 300 × 250 to 500 × 500 mm.

The press table 10 itself is extremely stable and rigid and is provided with a surface grinding and / or a felt coating on its surface side facing the press ram.

The stroke or the working height of the device according to an off guide example is essentially 100 mm.

By means of an exchangeable press table 10 , for example the use of a concave press table, it is also possible to provide a coating with correspondingly shaped, for example convex, print carriers.

In the transfer press according to the exemplary embodiment, the elastic bellows 14 , which is arranged below the movable, plat-shaped press ram 13 , is subjected to pressure, for example compressed gas, which results in the desired movement in the Z direction.

The bellows is advantageously one from the motor vehicle Technically known air spring can be used.

In the front view shown in FIG. 2 of a principle of the device according to the invention, the heatable press table 10 can again be seen, which lies opposite the movable plate-shaped press ram 13 . To absorb the forces generated during the pressing process, the press table 10 is held by a support frame 15 (see also FIG. 5), which at the same time forms a support 16 for the elastic bellows 14 .

The elastic bellows 14 preferably has a circular cross section in its shape and is circumferentially surrounded by an annular bead. A pressure plate 17 with predetermined dimensions and dimensions is arranged almost centrally on the bellows 14 . When the bellows 14 moves, the pressure plate 17 comes into contact with the underside of the movable press ram 13 and moves with the latter towards the press table 10 . The underside of the press ram 13 and / or the corresponding side of the pressure plate 17 can NEN with an elastic layer, for. B. made of rubber. The print carrier 11 and the transfer film 12 already shown in FIG. 1 lie on the press ram 13 .

The movable press ram 13 has on its underside arranged guide pins or extensions 18 which engage in savings 19 ( Fig. 4).

The game between the pins or extensions 18 and the associated recesses 19 is chosen so large that a slight lateral tilt is possible without a Ver edge occurs during the movement of the press ram 13 in the Z direction.

Exact guide elements in the sense of a parallel movement of press ram 13 and press table 10 , as known in hydraulic devices or given by the hydraulic cylinder, are not required.

The elastic bellows 14 has a connection 20 which leads to a pressure generation or pressure storage device, not shown.

In addition, there are control valves or throttles not shown sel devices for pressure curve adjustment provided, which together via an electronic control device act with the temperature control for heating the presses table are suitable for the successful color trans Ferdruck necessary procedure with regard to the A setting of pressure, temperature and time parameters ben.

The pressure plate 17 of the bellows 14 secures by its own mass, possibly in cooperation with the mass of the movable, plate-shaped press ram 13, pushing back and moving back the bellows in the Z direction when the internal pressure of the bellows 14 is reduced or venting takes place via the connection 20 in cooperation with the control valve.

Additional means, such as a return spring or the like are not required.

Both the press table 10 and the support 16 together with the bellows 14 can be exchanged via fastening means on the support frame 15 .

From the basic constructions shown in FIGS . 2 and 3 it can be seen that, in contrast to known hydraulic devices in the exemplary embodiment, only a small overall height is taken up with sufficient working space or sufficient working height for accommodating printing media and transfer foils, so that in a simple manner Table devices can be created.

In the side view of the device shown in FIG. 3 according to the exemplary embodiment, the same reference numerals are used for the same elements as explained with reference to FIG. 2.

In particular, Fig. 3 shows the possibility of forming a movable press ram 13 , which is arranged on a slide 21, which is displaceable in the Y direction. The insert 21 is held on lateral guide rails and can be pulled out, for example manually, so that the printing carrier 11 and the transfer film 12 can be arranged on the press ram 13 which is then exposed.

After the insert has been moved back into its working position, the usual procedure begins, namely loading due to the press ram 13 to the press table 10 , with a defined pressure and temperature regime being maintained over a certain period of time.

For example, in a device according to one embodiment Example of pressure totaling 1.6t between table and Tappets effective, with temperatures ranging between 500. and 200 ° C for optimal molecular crosslinking of the toner materials are adjustable with the respective print media. The process time is in a range from 1 to approx. 1,000 Seconds.

Through the aforementioned valves and throttles related the electronic control device ensures that the desired final pressure is not sudden, but continuous is achieved so that glass or other sensitive materials can be printed without damage.

It is essential for the printing success to be a predetermined one to reach such a final pressure and over a predetermined time to keep.

In one embodiment, in a time of approximately 2 Seconds the required final pressure is reached so that it corresponds short cycle times during printing are guaranteed.

Characterized in that the bellows 14 is loaded with a pressure plate 17 , and in addition, when the press ram moves down in the Z direction, its mass acts, the fall time of the press ram is essentially equal to the start-up time, ie the time until the final pressure is reached.

FIG. 4 shows a plan view and a side view of the press ram with a three-point pen storage.

In turn, the press ram 13 , the guide pins or extensions 18 and the cutouts or bores 19 in the movable insert 21 can be seen .

Preferably 19 bushings 22 are inserted into the recesses, which have a friction-reducing PTFE coating or are even made of PTFE.

The distribution of the extensions or pins 18 on the surface of the press ram 13 takes place in a triangular shape, so that the desired three-point guidance or bearing is obtained. Preferably, the distance from the center line M to a pair of pins 18 X, the distance to the third pin 18 on the center longitudinal line L, starting from the center line M, X + essentially 10 units of the distance dimension, z. B. mm.

In the basic illustration of a supporting frame segment shown in FIG. 5, it can be seen that the same was made from a U-shaped profile or a closed square profile by means of a material connection, in particular welding. Two such support frame 15 form the receiving device for all other mechanical components such that the resulting forces can be absorbed. Of particular advantage is the fact that all wide ren elements of a housing of the device do not have to perform any carrying functions, so that the overall cost can be reduced and a maintenance-friendly construction is created.

The stable construction of the support frame with the task of Acquisition and the derivation of acting forces together connection with the structure and material selection of the heated press table sure that the latter does not follow partial deformations.

Compared to known hydraulic devices the device according to the exemplary embodiment is only exceptional Low maintenance activities, so that the effort in the use and maintenance of such transfer presses significantly reduced by the user.  

It has been shown that it is particularly advantageous if, during the actual transfer printing, a flexible base is arranged between the movable press ram 13 and the pressure carrier, as a result of which the force distribution and the surface pressure are further homogenized.

Further improvements in the printing of non-planar parts, ie the use of non-planar print carriers 11 , result if, as shown in FIG. 6, an elastic cushion 23 is provided on the press table 10 and on the press ram 13 . The pillows 23 are filled with a heat-resistant gel or an oil, so that when a non-planar print carrier 11 is to be printed, the corresponding pillow adopts the surface shape of the print carrier 11 by displacing the filling, so that a uniform surface pressure without damaging the part to be printed. The attached to the press table 10 pad 23 takes on the heat-resistant gel or oil due to the heating temperature required to carry out the color transfer printing.

The material for the pillows has elastic properties on, so that a due to the shape of the print medium Displacing the essentially incompressible gel or Oil becomes possible. For example, as a pillow material oil-resistant rubber or plastic used.

Claims (4)

1. Device for generating contact pressure, in particular for color transfer printing from a transfer film ( 12 ) on a print carrier ( 11 ), comprising
a heatable press table ( 10 ),
a movable, plate-shaped press ram ( 13 ) and a support frame ( 15 ) for receiving the press table ( 10 ) and ram ( 13 ), the transfer film and the print carrier being arranged between the press table ( 10 ) and the press ram ( 13 ) and below the press ram an elastic bellows ( 14 ) connected to a pressure accumulator or a pressure generating device is arranged, said bellows moving in the direction of the press table ( 10 ) while taking the press ram ( 13 ) when a pressure is present in the elastic bellows using the pressure accumulator or the pressure generating device adjustable overpressure is set, characterized in that

• - That the elastic bellows ( 14 ) is supported against the supporting frame ( 15 ) and has a circular cross-section with a circumferential annular bead, with the annular bead laterally enclosing an upwardly projecting pressure plate ( 17 ) which is arranged when the bellows is expanded with the Underside of the press ram ( 13 ) cooperates,
• - That the pressure plate ( 17 ) and the bellows ( 14 ) around the geome metric focus of the plate-shaped plunger is large with this in operative connection for transmitting the pressing force and that the movable plunger ( 13 ) on a movable in the y-direction insert ( 21st ) is arranged so that the plunger ( 13 ) from a working position opposite the heatable press table ( 10 ) can be changed in position to an offset position in order to place the transfer film ( 12 ) and the print carrier ( 11 ) on the plunger, and
• - That to generate a uniform surface pressure between rule's transfer film ( 12 ) and pressure carrier ( 11 ) of the plate-shaped press ram ( 13 ) via a three-point pin guide is mounted vertically or in the Z direction, and
• - That on the heatable press table ( 10 ) and on the press ram ( 13 ) an elastic cushion ( 23 ) is arranged, the cushion ( 23 ) being filled with a heat-resistant gel or oil, so that even non-planar pressure carriers ( 11 ) are uniform Surface pressure can be exposed.

2. Apparatus according to claim 1, characterized in that the three-point pin guide is formed with play such that, regardless of the flatness of the print carrier, the same is pressed onto the press table ( 10 ). 3. Device according to one of the preceding claims, characterized in that the opposite surfaces in the working position of the heatable press table ( 10 ) and the movable press ram ( 13 ) are the same size, or that the area of the heatable press table ( 10 ) is larger than the area of the movable press ram ( 13 ) is selected. 4. Device according to one of the preceding claims, characterized in that the heatable press table ( 10 ) is designed to be interchangeable for printing under different objects and has a rigid surface shape adapted to the respective objects to be printed.