Process and equipment for veneer press to glue a thin layer on a variously shaped panel surface

Process and apparatus (10) for veneering a thin layer "T" on a support panel "P" by means of an upper plate (2) and lower plate (6). The upper plate (2) supports a support frame (1) for an elastic rubber sheet "G" stretched perimetrically by a stretching system (5) to form an airtight upper chamber "A". Upper chamber "A" and lower chamber "B" are connected with vacuum and pressure means that co-operate with respective inlets/outlets (4,7) between the plates (2,6) to shape under pressure the rubber sheet "G" to the contour of the panel "P" and effect the gluing of veneer "T" thereto.

TECHNICAL FIELD 
The invention relates to a veneer process and press equipment for veneering 
thin layers on curved and/or flat surfaces, particularly for the 
production of panels, as for instance the panels for small doors used in 
furniture production. 
The equipment could be more particularly utilized by well known veneer 
presses for funiture panel production or be the main apparatus of a 
specific press for non-flat surfaces. 
Therfore, an object of the present invention is the provision of a press 
having such equipment or system designed to accomplish the novel aspects 
of the present invention. 
BACKGROUND ART 
The methods of veneer pressing for effecting a gluing of thin layers, as 
for instance valuable wood layers, on curve surfaced panels, are well 
known in the prior art, as for instance the process of pressing with an 
oil-cushion, as disclosed in Italian patent application No. 83412 A/80, 
filed on July 28, 1980, entitled: "FLEXIBLE PRESSING PLATE DEVICE AND 
PRESS TICULARLY FOR THE VENEERING OF NON-FLAT PANELS". The use of such 
a system allows the veneer or layer, through the utilization of a cushion 
containing a fluid (normally hydraulic oil), to fit perfectly to the shape 
of the panel and thereby producing the shaping of the veneer on the panel 
surface, with gluing; but this is a specific solution. 
Other well known method of pneumatic veneering are very expensive because 
the pressing plates have a cushion that is usually heated by using a 
diathermic oil that requires a long time to get hot. Also, the utilization 
of pneumatic presses with electric resistance heating plates is not energy 
efficient, so that several industries are looking for an alternative, 
simpler, more profitable and efficient method of gluing. 
DISCLOSURE OF THE INVENTION 
The purpose of the present invention is the realization of a new process of 
veneering or gluing thin layers on panels having variously shaped surfaces 
including a flat surface, and furthermore accomplishes the gluing not only 
on the larger external surface of the panel but also on the perimetrical 
surfaces by using low-cost equipment in a very efficient, profitable 
process. 
The invention solves the above described problems by utilizing a veneering 
method combining the effects of fluid pressure and/or a vacuum exerted on 
a rubber sheet with the pneumatic action of compressed air on one side and 
the vacuum caused by a vacuum pump on the other side. 
In order to accelerate the gluing process, heat is transmitted to the work 
pieces through the rubber sheet which has been previously heated by 
contact with the hot surfaces of the pressing plates and the provision of 
heated compressed air. 
The intervention times of the pressures through the available temperatures 
and materials used (layer thickness, type of rubber, etc.) are regulated 
by preferably a previously set automatic cycle. 
In accordance with the invention, the standard equipment is more 
particularly constituted by: 
a metal frame of a pre-established size, with connecting means to be 
connected to the upper pressing plates; 
a rubber sheet of an adequate thickness and preferably of about 3 mm., heat 
resistant, whose size is slightly larger than that of the frame to which 
it has to be hung; 
an insulated air bag, with heat-exchanger to be connected to the net of 
compressed air or to a compressor; 
a volumetric vacuum pump; 
an electro-valve set; 
an electric-pneumatic control board with cycle computer. 
The embodiment is to be utilized in a press system as above-described, to 
carry out the pressing of a panel whose surface is to be covered, after 
being smeared with glue, with a thin covering, like a valuable wood layer 
or veneer and pressed between the lower pressing plate and the upper 
pressing plate of the press with the overhanging interposition of said 
rubber sheet in co-operation with the action of two opposed chambers. An 
upper chamber "A" and a lower chamber "B" experience first a vacuum action 
in the upper chamber "A" in order to retract upwardly and heat the rubber 
sheet, and by a pressing action and either a vacuum action in the lower 
chamber "B" or pressure action in the upper chamber "A", portions of the 
rubber sheet are displaced downwardly to make the rubber sheet conform 
perfectly to the shape of the panel being covered, simultaneously shaping 
under pressure the veneer, with the pressure action of the rubber sheet 
and the heat treatment gluing together the veneer and panel surface. 
The main advantages offered by the invention are: 
on the standard presses of furniture-makers having a large working area, it 
is possible to set up several of these apparatuses and thereby effect and 
increase in production by processing many panels in each plane; 
a very low operating cost can be realized because it is possible to heat 
the press plates sooner with heat sources already existing in the factory 
(water, oil, etc.), thus eliminating all the negative consequences caused 
by the use of diathermic oil in the hydraulic cushions, specifically the 
breaking of cushions which causes the leakage of oil, as it is well known 
that the breakage of said cusions occurs frequently; 
maintenance is reduced to a minimum; 
possible breakages of the rubber sheets do not compromise the continuation 
of work, as it is possible to stop the leak (temporarily) with the 
application of any patching such as a pad, including, when the breakage 
concerns the central plane of the sheet, the utilization of an overhanging 
particle board panel; 
it is not necessary to protect the wood layer against the effects of 
stretching because this does not occur, thereby precluding the necessity 
of using valuable strengthened wood layers, etc.; furthermore, obvious 
free movements facilitate the work process and allow the elimination of 
the preparation of the wood layer; 
it is possible to press surfaces in undercut, reaching very high limits, by 
changing the plate or rubber sheet elasticity; 
the finished panels, having been pressed under vacuum, come out completely 
dry thanks to the removal of the dampness from the steam of the glue 
caused during the gluing process, with the consequent advantage that 
pieces produced in this way do not undergo deformations and the painting 
is enhanced. Also, the work environment is free from pollution by noxious 
gas produced by the chemical reaction of the glue because the fumes are 
sucked in by the vacuum pumping system and ejected to the outside. 
The above mentioned characteristics, contained in the annexed claims, will 
be understood better with the aid of the following detailed description of 
a preferred embodiment of the invention and in accordance with the 
illustrative representations of the three enclosed sheets of drawings.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring now to FIG. 1, press 10 comprises an airtight frame 1 having the 
shape of a box with an open bottom, and supplied with at least one piping 
4 effecting a connection of the inner chamber "A" with exterior equipment 
for the passage of a fluid which can be put into or taken out of the 
chamber "A", either under pressure or vacuum with suitable means of 
pressure and vacuum formation (not shown). 
Through fixing and elastic stretching system 5, the perimeter of a flexible 
and elastic rubber sheet "G" is stretched over the bottom of the frame 1. 
Under a vacuum action effecting withdrawal of the air contained in chamber 
"A", the sheet "G" can be deformed as represented in FIG. 2 so that it 
elastically expands into perfect contact with the surface of the upper 
plate 2 of the press 10. The movable lower plate 6 of the press 10, which 
moves up and down for the pressing operation of FIG. 6, is supplied with a 
piping 7 communicating with the inner perimeter of chamber "A" defined by 
the inner perimeter of frame 1. On the movable lower plate 6 is a support 
"D" for panel "P". The upper and lateral external surfaces of panel "P" 
are to be covered with glue and a wood layer of flexible type "T" as 
represented in FIGS. 3 and 4. The piping 7 of the lower plate 6 is 
connected to well known pump means in order to create a vacuum in the 
lower chamber "B" after the pressing step of FIG. 5. The vacuum is created 
between the flexible rubber sheet "G" and the lower plate 6 as represented 
in FIG. 5 and through the vacuum action, the rubber sheet "G" is formed as 
represented in FIG. 6. The vacuum means is also suitable for operating in 
conjunction with the piping 4 of upper plate 2 as follows: creation of a 
vacuum in the lower chamber "B" by vacuum action in the piping 7 of lower 
plate 6 with free atmospheric pressure entering the upper chamber "A" or 
supra-atmospheric pressure in chamber "A" by means of inlet 4, 
accomplishing with such an operation the gluing of layer "T" to panel "P" 
under the temperature and pressure action as represented in FIG. 6. 
More particularly, to obtain quick gluing and complete polymerization, the 
upper plate 2 of the press 10 is brought to a temperature of 
95.degree.-120.degree. C. and in the same way the lower plate 6 of the 
press 10 is brought to the same or about the same temperature, more or 
less according to the specific requirements of an application. 
With such a system, the heating of rubber sheet "G" is accomplished and the 
sheet will transmit heat to the wood layer "T" to be pressed, and lower 
plate 6 will transmit heat to the panel "P" to be glued. 
A further system to accelerate the gluing is attained through the 
utilization of preheated air introduced through an inlet in a manner that 
accelerates the gluing and polymerzation system. The process steps are 
essentially: 
when the apparatus is not operating, the press 10 is as represented in FIG. 
1. The frame 1 fixed on upper plate 2 of the press 10 will hold the rubber 
sheet "G" well stretched through means of a packing 8 of lesser density; 
before starting the production cycle, the vacuum in chamber "A" is created 
so that the rubber sheet "G" expands to contact the lower surface of upper 
plate 2 of the press, the plate 2 being heated to 95.degree.-120.degree. 
C. and thereby heating, through conduction due to direct contact, the 
rubber sheet "G"; 
in the meantime, the parts to be glued will be prepared as represented in 
FIGS. 3 and 4. Glue is smeared on the panel "P" or applied on the wood 
layer "T" with possible further smearing of glue also on the free lateral 
surfaces thereof, keeping in mind that the glue can be applied both to the 
rough panel to be covered and to the wood layer according to the specific 
requirements and the available equipment; 
then the panel "P" with veneer "T" and their support "D" are placed on the 
lower plate 6 of the press system 10; 
the lower pressing plate 6 is lifted to press and glue the two pieces "P" 
and "T" as represented in FIG. 5; 
this portion of the pressing operation completed, atmosphere is introduced 
into the upper chamber "A" and a vacuum is created in the lower chamber 
"B", the atmosphere introduced being the inlet of hot fluid under pressure 
in upper chamber "A" as represented in FIG. 6, thus completing the 
pressing operation and gluing; 
then the pressures are reversed to create again the vacuum in upper chamber 
"A", and the plates are separated so that the panel "P" with veneer layer 
"T" glued thereto can be removed with support "D". 
It stands to reason that with the closing of the press 10, the two pieces 
to be glued (panel "P" and layer "T") are compressed between the two hot 
plates 2 and 6 of press 10 which is being heated. The pressure of machine 
10 presses the wood layer "T" under the rubber sheet in such a way that 
the layer "T" cannot undergo stretching during the extension of rubber 
sheet "G" in areas other than the flat surfaces and consequently breakages 
cannot occur. This mechanical pressure will increase further the specific 
pressure on the flat surfaces of the pieces without increasing the 
necessary pneumatic pressures on the curved surfaces, thus allowing a 
reduction of the resistant moments of the frame. This also develops a 
leveling action on the flat surface of the panel "P", eliminating possible 
stagnations of glue, etc. After the closing of the press, the valves 
arranged and preprogrammed for the cycle will reverse the flow of the 
fluids in the chambers "A" and "B", thereby starting the steps of the 
gluing process which, as already mentioned above, is accomplished by the 
combined action of the pneumatic supra-atmospheric pressure in the upper 
chamber "A" and pneumatic vacuum in the lower chamber "B" together with 
the mechanical pressure on the flat part of the piece as shown in FIG. 6. 
The rubber sheet "G", preheated by contact with the hot parts of the press, 
lies over the curved surfaces of the panel piece and conducts and 
transmits heat to the gluing surfaces of the piece through the overlying 
wood layer. At the same time, the compressed and preheated air in the 
upper chamber "A" contributes heat through the rubber sheet to the curved 
parts that do not receive heat from the heated upper plate 2, thereby 
reducing to a minimum the drying and hardening times of the glue. 
The pressure of the compressed air will be regulated in accordance with the 
shape of the pieces and their number; nevertheless the value cannot exceed 
that of the setting of the highest pressure valve installed on the bag and 
which value will be calculated on the basis of the mechanical resistances 
offered by the frame. 
For the step of opening the press, the automatically piloted electro-valves 
(not represented but of a well known type) will obviously intervene after 
a predetermined time to reverse the flow of the fluids in chambers "A" and 
"B" of the frame, and thereby retracting the rubber sheet to its starting 
position as above described for the condition preceding the pressing step. 
The step of preheating the rubber sheet will last the time necessary for 
discharging the glued pieces and smearing and introducing the new ones. 
After pressing the new pieces and resettling the pressure balances between 
chambers "A" and "B", another automatic control impulse will cause the 
opening of the press and thus conclude the pressing cycle, obviously to be 
followed by the discharge of the work pieces. Of course, all the execution 
details can be modified but without altering the innovative substance of 
the invention as described, illustrated and essentially claimed below. 
INDUSTRIAL APPLICABILITY 
The present invention can be utilized with veneering presses for adhering a 
thin layer to a variously shaped or flat surface.