TECHNICAL FIELD

The present invention relates primarily to a machine for manufacturing a base-unit intended for an illuminated sign and provided with a plurality of photodiodes. The machine comprises a frame or a support structure against which the base-unit is fixedly related, and further includes an aperture-forming device located on one side of the base-unit and a counterforce device located on the other side of said base-unit.

The machine also includes means for moving the aperture- forming device and the counterforce device relative to one another and to the base-unit, and control means which function to stop said relative movement at pre ^¬ determined coordinate values in a right-angle two-dimensional coordinate system.

The invention also relates to an illuminated sign pro- vided with a plurality of photodiodes, which are wired electrically the sign, and a base-unit manufactured in a machine and having formed therein apertures and recesses in which photodiodes are placed, and a control system which is operative to apply a voltage to one or more photodiodes, via electrical conductors, in a time- dependent manner and in accordance with a pre-determined configuration.

BACKGROUND PRIOR ART

Machines for manufacturing a base-unit provided with a plurality of photodiodes and intended for use in an illuminated sign are previously known to the art, and in order to illustrate the state of the art from which the present invention can be considered to have developed, reference is made here to the machine and arrangement illustrated and described in European Patent Publication 0 127 598.

This publication describes and illustrates a method for manufacturing signs which comprise light-emitting diodes or photodiodes which are positioned so as to form a pre¬ determined pattern and in which reflectors are arranged in the base-unit and configured partially to embrace respective photodiodes.

According to this publication, the coordinates in which the photodiodes are positioned shall be evaluated and established in a manner to form the pattern desired, and the coordinates thus evaluated are utilized for dis¬ placing a device which functions to form light- reflecting depressions in an aluminium plate forming the base-unit, such as to press-shape said reflectors, and also to form apertures or openings in said depressions or hollows with the aid of a punch, these apertures being used to accommodate the photodiodes.

When practicing the method described in this publi¬ cation, the diodes are secured in the apertures formed in the reflector depressions by means of a mechanical binding agent.

With regard to the significant features of the present invention, reference is also made to the alpha numerical sign assembly described and illustrated in US Patent

Specification 4,336,580, in which the reflector-recess formed comprises pre-deter ined surface configurations which function to deflect light waves parallel with the centre axis of the reflector.

According to this publication, the axial dimension of a central through-passing aperture, adapted to hold a photodiode, has a length of 1.5 mm and a diameter of 3.4 mm, and the reflector has a continuously curved shape, so as to be able to reflect light from a punctiform light source.

SUMMARY OF THE PRESENT INVENTION

TECHNICAL PROBLEMS

With reference to the prior state of the art, as des¬ cribed above with respect to a machine for manufacturing a base-unit intended for an illuminated sign provided with a plurality of photodiodes, it will be seen that a technical problem is one of simplifying the manufacture of the base-unit, by using a material which is totally different from aluminium sheet and which can be machined readily and with precision with the aid of a rotatable milling tool or like cutting tool, and by giving the base-unit a thickness which will enable said unit to accommodate a simple reflector surface.

It will also be seen that a technical problem resides in realizing the advantages that are afforded by replacing an aluminium base-unit, in which stress-concentrations are engendered when forming the aperture-recesses therein, with a thick base-unit in the form of a slab of material having properties equal to or substantially equal to the properties of extruded expanded polystyrene

or a somewhat harder material, and to also realize that a previously known, reciprocatingly moveable counter- force device, adapted to withstand the pressure exerted by a tool used to emboss the reflector surface can now be arranged to take a forwardly displaced position in which the outer surface of the counterforce device solely rests against the rear surface of the base-unit and takes a forwardly displaced position such that the counterforce device will locate the base-unit in a central position allotted to the base-unit.

It will also be seen that when using a milling tool, a technical problem resides in realizing that the milling tool, as it rotates in said forwardly displaced posi- tion, will form a circular aperture-recess configuration which is capable of retaining a photodiode and, at the same time, will also form in the base-unit a reflection surface of conical configuration having two mutually different cone angles, of which the one cone-form is intended to reflect light from a cylindrical surface and the other cone-form is intended to reflect light from a hemispherical surface, therewith providing good reflec¬ tion even when the photodiode is not precisely centred and takes an exact position.

It will also be seen that a technical problem is one of realizing the simplifications which the control means coacting with the machine can provide when the foremost setting-position of the counterforce device and the foremost setting-position of the milling tool are depen¬ dent on one another in an unequivocal manner, particu¬ larly when the length or depth extension of the circular aperture, calculated from the rear side, shall be con¬ stant, or substantially constant, irrespective of the thickness of the base-unit.

It will also be seen that a technical problem is one of realizing that the use of a milling tool will result in a circular aperture whose shape will conform with the conical shape of the photodiode, therewith improving and simplifying the mounting and subsequent adjustment of the photodiodes used.

It will also be seen that a technical problem is one of realizing that the aperture-forming device or milling tool and the counterforce device can be manoeuvred by two drive motors and mounted for movement in two right- angle coordinates and adapted for synchronous movement so as to be able to establish each of the positions in which a light-reflector and photodiode shall be placed.

It will also be seen that a technical problem is one of realizing the advantages that are afforded when the milling tool has a three-part configuration, such that when seen from the tip of the milling tool the respec¬ tive photodiode-accoramodating recesses will have a circular aperture-part, a first light-reflecting section inclined at an angle of 45°, or substantially 45°, and a second light-reflecting section inclined at an angle of 55°, or substantially 55°, where the first and the second light-reflecting sections merge discontinuously with one another and are intended to form together a reflective surface such as to be able to direct the light rays emitted from the photodiode readily to a parallel or substantially parallel light beam, without needing to adopt costly measures for forming the curva¬ ture of the reflectors more precisely to a punσtiform light source.

It will also be seen that a further technical problem is one of realizing the advantages that are afforded when the base-unit is given a thickness such that the upper surface of a photodiode, or the uppermost part of said photodiode, located in respective apertures and recesses will be located in the proximity of the front surface of the base-unit, so that the photodiode will be protected by the base-unit while simultaneously producing a light¬ ing effect which is in strong contrast to surrounding parts.

It will also be understood that a further technical problem is one of reducing the effect of stray light in a simple and practical manner, i.e. direct radiating light from photodiodes, angled away from the desired parallel light beam.

It will also be understood that a technical problem is one of realizing the advantages that are afforded by a sign, an illuminated sign, comprising a base-unit with which one or more of the aforesaid technical problems has been solved and in which photodiode-receiving apertures and recesses have been formed, and by pro¬ viding control means which apply voltage via connecting conductors to one or more photodiodes in a time- dependent manner and in accordance with a pre-determined configuration, and that a further technical problem is one of realizing that respective apertures shall have a particular length of 2-5 mm and shall include two coni- cal light-reflecting surfaces located adjacent said apertures such as to concentrate the light rays emitted from the photodiode to a parallel light beam, without needing to place excessively high demands on the posi¬ tion of the photodiode in the light reflector.

It will also be seen that a technical problem resides in the ability to adapt solely two relevent cone angles to the configuration of the photodiode, so that the maximum of light is reflected.

It will also be seen that a further technical problem is one of realizing the possibility of creating with one and the same tool or one and the same machine conditions which will cause a shaped light-reflector to produce a higher light-intensity, by providing a smaller outer diameter and a lower light-intensity with a larger outer diameter, so as to be able to adapt the number of photo¬ diodes requires to a selected outer diameter, where a smaller outer diameter requires more photodiodes than a larger outer diameter.

SOLUTION

According to one aspect, the present invention relates to a machine for manufacturing a base-unit intended for an illuminated sign provided with a plurality of photo¬ diodes, said machine comprising a frame or a support structure against which the base-unit is fixedly re¬ lated, a aperture-forming device located on one side of the base-unit, a counterforce device located on the other side of the base-unit, means for moving the aper¬ ture-forming device and the counterforce device relative to the base-unit, and control means for stopping said relative movement at pre-determined coordinate values in a right-angle two-dimensional coordinate system.

In accordance with the invention, the aperture-forming device has the form of a rotatable milling tool or like device which is mounted for reciprocating movement along the front surface of the base-unit; in that the

counterforce device, which extends perpendicular to the rear surface of the base-unit, is mounted for recipro¬ cating movement along said base-unit such as to lie (without pressure) against the rear surface of the base- unit in its forwardly displaced position and there function as a counterforce or anvil, and to take a forwardly displaced position such that the counterforce device will locate the base-unit in a centred position during a machining operation.

It is also proposed that the milling tool shall be capable of moving reciprocatingly, at right angles to the front surface of the base-unit and, as it rotates in a forwardly displaced position, to form a circular aper- ture, adapted to receive and to hold a photodiode, and a reflection surface in the base-unit; and that the mill¬ ing tool can be displaced forwards and towards the counterforce device to an extent and to a position such that the length or depth extension of the circular aperture, calculated from the rear sideof the base-unit, will be constant, or substantially constant, irrespec¬ tive of the thickness of the base-unit.

In accordance with one preferred embodiment which lies within the scope of the present invention, it is pro¬ posed that the circular aperture shall be utilized for coaction with the conical form of the photodiode, with the larger diameter located on the rear side of the base-unit, such as to simplify mounting and retention of the photodiode, suitably with the aid of an adhesive or the like.

It is also proposed that the aperture-forming device or milling tool and the counterforce device are driveable by two drive motors in the direction of two right-angle

coordinates and adapted for synchronous movement.

According to one particularly preferred embodiment of the invention, movement of the counterforce device at right angles to the base-unit is controlled so as to stop said device in a position in which its anvil sur¬ face is located at a distance of half the thickness of the base-unit related to a central plane of the base-unit.

The movement of the milling tool perpendicular to the base-unit and to the counterforce device is also con¬ trolled so as to stop said movement at a location in which the length or depth extension of the circular aperture exceeds 2 mm and is less than 5 mm, preferably about 3 mm.

When the aforesaid control means include processors, the processor and the control means may advantageously be programmed and controlled such that when a value relat¬ ing to the thickness of the base-unit is fed to the processor, this value will control the movement of the counterforce device and milling tool at right angles to the horizontal surface of the base-unit, so that said milling tool and counterforce device can be stopped in respective positions corresponding to said thickness value.

The configuration of the milling tool is of particular significance, and the head is configured such that, calculated from its tip, the respective photodiode- receiving apetured recesses will comprise a circular aperture-part, a first light-reflecting section inclined at an angle of 45°, or substantially 45°, and a second light-reflecting section inclined at an angle of 55°, or

substantially 55°, where the first and the second light- reflecting sections merge discontinuously with one another and are intended to form one reflective surface.

The material from which the base-unit is made and the thickness of the base-unit are preferably so selected that the uppermost part of a photodiode placed in respe¬ ctive apertures and light-reflecting recesses will lie in the proximity of the front surface of the base-unit.

Furthermore, it is proposed that the recess-diameter at the front surface of the base-unit is adapted to provide the degree of reflectivity and light-intensity desired, and that a larger diameter is obtained either by in- creasing the diameter of the first and the second sec¬ tion of the apertures or by increasing the thickness of the base-unit.

The invention also relates to a base-unit intended for use in a sign, an illuminated sign, and manufactured in a machine of the aforesaid kind, said base-unit com¬ prising photodiodes placed in apertures and light- reflecting recesses formed in said unit, and further comprising a control means which applies voltage to one or more photodiodes in a time-dependent manner, via electrical conductors.

It is proposed in accordance with the invention that respective apertures have a length or depth extension of

2-5 mm and that said aperture adjoins a first conical light-reflecting surface having a first cone angle and a second conical light-reflecting surface having a second cone angle.

According to one preferred embodiment, one cone angle is smaller than the other cone angle and the difference between said cone angles is from 7 to 15°, preferably about 10° .

It is also proposed that the uppermost part, or front part of the photodiode is located in the proximity of the front surface of the base-unit.

Finally, it is proposed that the junction or transition between the aperture and the first conical light- reflecting surface is formed abruptly, in those instances when the recess has a large diameter adjacent the front surface of said unit and when the base-unit has a small thickness.

ADVANTAGES

Those advantages primarily associated with a machine constructed in accordance with the present invention reside in the provision of conditions which enable a base-unit suitably adapted for use in an illuminated sign which can be machined with the aid of a rotatable milling tool in a manner to form the requisite light- reflectors or reflection surfaces in the base-unit without creating stresses therein as a result of press¬ ing recesses in the surface thereof, while enabling the milling tool to be configured in a manner such that said head can work against a stationary counterforce device whose position is determined and which will locate the base-unit in relation to a centre plane of said unit, and also in enabling respective photodiode-receiving recesses to be given a circular aperture-part, a conical first light-reflecting section and a conical second light-reflecting section, where the first and the second

sections merge with one another such as to form a common reflecting surface for reflecting the light emitted by the photodiode.

The advantages primarily associated with a sign con¬ structed in accordance with the present invention reside in the possiblity of readily treating the material from which the base-unit is made, normally by spraying var¬ nish thereon, such as to form bright reflecting sur- faces, and thereafter enabling photodiodes to be mounted in the circular aperture-parts, which have a length or depth adapted within narrow limits, irre¬ spective of the thickness of the base-unit, and having a first conical light-reflecting surface and a second conical light-reflecting surface located adjacent one another, and where one cone angle is smaller than the other cone angle so as to concentrate the light emitted from the photodiode into a more or less parallel light beam. Furthermore, the possibility is afforded whereby the light-intensity from the photodiodes in a sign comprising a plurality of diodes can be increased or decreased, by providing for lower intensity at recesses of larger diameter and by using a smaller number of diodes.

Furthermore, a base-unit made of a plastics material and machined by cutting tools will be more flexurely rigid and contain less stress concentrations than a base-unit made from aluminium material and will also be lighter in weight than the aluminium base-unit.

The main characteristic features of a machine con- structed in accordance with the present invention are

set forth in the characterising clause of Claim 1, and the primary characteristic features of a sign con¬ structed in accordance with the present invention are set forth in the characterising clause of the following Claim 10.

BRIEF DESCRIPTION OF THE DRAWING

A preferred embodiment of a machine having the charac¬ teristic features significant of the present invention will now be described in more detail with reference to the accompanying drawings, in which

Figure 1 is a perspective view of a known machine which has been modified in accordance with the present inven¬ tion; Figure 2 is a sectional view of the machine taken on the line II-II in Figure 1;

Figure 3 illustrates in larger scale a base-unit posi¬ tioned in the machine, and shows a counterforce device in abutment with the rear side of the base-unit, immediately prior to the formation of requisite reflec- tion surfaces with the aid of a milling tool;

Figure 4 is a side view, in section, of a photodiode positioned in a base-unit manufactured by a machine illustrated in Figures 1-3; Figure 5 is a sectional view of a reflection surface formed by a milling tool in a plastic material having a thickness of 8 mm with a smaller recess; ^' Figure 6 is a sectional view of a reflection surface formed by a milling tool in a plastic material having a thickness of 8 mm, with a larger recess;

Figure 7 is a sectional view of a reflection surface formed by a milling tool in a plastic material having a thickness of 10 mm, with a still larger recess; and Figure 8 is a perspective view of an illuminated sign comprising a matrix of photodiodes, each of which is energized by means of control apparatus.

DESCRIPTION OF A PREFERRED EMBODIMENT

Figure 1 illustrates a known machine for manufacturing a base-unit intended for use in an illuminated sign provi¬ ded with a plurality of photodiodes, said machine being modified in accordance with the present invention.

The machine comprises a stand structure 3 which supports a base-unit 4 and stands on a foundation surface 2.

In accordance with the present invention, the base-unit 4 is stationary in relation to the frame 3. Located on one side of the base-unit 4 is a aperture-forming device 5, while a counterforce or anvil device 6 is located on the other side of the base-unit, said aperture-forming device 5 and counterforce device 6 being driven by two drive motors 7 , 8 for movement in a right-angle two-dimensional coordinate system and are adapted for precise synchronous movement. It will be understood, however, that the aperture-forming device 5 and the counterforce device 6 may be stationarily mounted and the base-unit 4 arranged for movement in said right- angle two-dimensional coordinate system.

As will be seen from Figure 2, the base-unit 4 of the illustrated embodiment is held stationary in relation to the frame 3 by means of a clamping arrangement 10.

The aperture-forming device 5 and the counterforce device 6 located on respective sides of the base-unit 4 are illustrated schematically in Figure 1 in a pre-determined position in which a reflection surface for coaction with a photodiode is formed in the base- unit 4.

In order to produce a complete base-unit containing a plurality of photodiodes and reflection surfaces, it is necessary for the device 5 and the device 6 to be moved in accordance with a pre-determined movement pattern.

This movement pattern is stored in a control unit 11, in a known manner.

The control unit 11 of the illustrated embodiment in¬ cludes a data-processing device, and the drive motor 7, 8 and the control unit 11 function to control the move- ment of the aperture-forming device 5 and the counter- force device 6 in relation to the base-unit 4. With the aid of control means incorporated in the control unit 11, it is possible to stop this relative movement at pre- determined coordinate values in a right-angle two- dimensional coordinate system.

As will be seen from Figure 3, the aperture-forming device 5 of the illustrated embodiment comprises a rotatable milling tool or like device, this tool being driven in a known manner not shown.

The forward and backward movement of the counterforce device 6 at right angles to the rear surface 4b of the base-unit 4 is controlled by the control unit 11, which

also evaluates the instantaneous positional values of the counterforce device, which is arranged for displace¬ ment to a position in which it functions as a counter- force device or anvil surface and in which it only lightly abuts the rear surface 4b of said base-unit and takes a position such as to locate the base-unit in a central position.

Accordingly, the distance between a central plane 4 ' of the base-unit 4 and the front surface 6a of the counter- force device 6 will correspond to half the thickness of the base-unit, and when the value of 8 mm is inserted into the control unit 11, the counterforce device 6 will consequently be displaced to a position which is located 4 mm from the aforesaid centre plane 4' .

The milling tool 5 extends perpendicular to the front surface 4a of the base-unit and is arranged for recipro¬ cating movement, wherein the movement of the milling tool and its instantaneous positional value can be evaluated in the control unit 11. As the milling tool is advanced, while rotating, to a determined, forwardly displaced position, it will form a circular aperture 40 and a first reflection surface 41 which will be located immediately adjacent the diode, when fitted, the dia¬ meter of which aperture is adapted to receive and hold a photodiode 12, (See Figure 4).

The milling tool 5 is intended to be advanced towards the counterforce device 6 through a distance such that the length or depth extension of the circular aperture 40, calculated from the rear side 4b of the base-unit, will be constant, or substantially constant, irre¬ spective of the thickness of the base-unit concerned.

The circular aperture 40 is configured for coaction with the slightly conical part of the photodiode, with the larger diameter located on the rear side 4b of the base- unit, such as to form a press-fit with the bottom part of the diode.

Forward movement of the milling tool at right angles to the base-unit 4 and towards the counterforce device 6 is controlled such that the axial length of the circular aperture will have a value greater than 2 mm and less than 5 mm, preferably a value between 2.5 and 4 mm, i.e. about 3 mm.

It lies within the scope of standard technology to provide a control unit and control means including a data processor, and to insert values relating to the thickness of the base-unit or the material from which the base-unit is made, and to control the movement of the milling tool 5 and the counterforce device 6 at right angles to the surfaces of the base-unit on the basis of said values, in order to stop said devices 5 and 6 in their respective positions corresponding to the said thickness value.

Figures 5, 6 and 7 illustrate schematically and in side view mutually different base-units 4 of mutually dif¬ ferent thickness. Each of the base-units has provided therein mutually different apertured-recesses which function as light-reflecting surfaces.

The present invention also pertains to a milling tool of particular configuration which is adapted to form a photodiode-receiving aperture 40 from which a reflecting surface of particular configuration diverges.

The apertured-recess widens from a location immediately adjacent the circular aperture-part 40 into a first section 41 which inclines at an angle of 45° , or sub¬ stantially 45°, and a second section 42 which inclines at an angle ot 55°, or substantially 55°, said first and second sections merging either continuously or discon- tinuously with one another and being intended to form a common reflecting surface .

Figure 5 illustrates an embodiment in which there is formed in the front surface 4a of the base-unit a cir¬ cular reflecting surface having an external diameter of 12 mm. In this case, the length extension "a" is 3.5 mm, the length extension "b" of the first section is 1.5 mm, whereas the length extension "c" of the second section is 3 mm.

Figure 6 is a section view of an embodiment in which a large circular aperture having a diameter of 16 mm is formed in the front surface 4a of the base-unit, said base-unit having a thickness of 8 mm.

In this case, the surfaces 41 and 42 are displaced outwards, whereas the distance "a" is 3 mm, the distance "b" is 1.5 mm, the distance "c" is 3.0 mm, and a dis¬ tance "d" is 0.5 mm.

It will be seen clearly from Figure 6 that between the aperture 40 and the first section 41 there is a bridging part between the aperture and the first conical light- reflecting surface 41, this bridging part 43 forming an abrupt transition. The size of the bridging part may vary, although it should not be so large as to give a "black" impression. It is proposed that this bridging part 43 is at most from 2 to 3 mm.

The illustration of Figure 7 shows that when the length "a" is 2.5 mm, the length "b" will be 2 mm, the length "c" will be 5 mm, and the length "d" will be 0.5 mm.

The part 43 bridging the aperture 40 and the first conical light-reflecting surface 41 forms an abrupt transition also in this instance, whereas the conical surface 42 has a length which exceeds the length of the corresponding surface of the embodiments illustrated in Figures 5 and 6.

An important feature of the present invention is that the circular aperture-part or the aperture 40 has a length "a" of approximately 3 mm, so as to be able to hold a photodiode 12 effectively.

Consequently, the first conical light-reflecting section 41 will have an extension such that its uppermost part will lie approximately 5 mm from the rear side 4b of the base-unit.

The remaining part, the extent of which depends upon the thickness of the base-unit 4, will form the second section or second conical light-reflecting surface 42.

The thickness of the base-unit 4 is preferably such that the uppermost part 12a of a photodiode 12 placed in a respective aperture and recess will lie in the proximity of the front surface 4a of the base-unit.

The diameter of the apertύred-recess (12 mm, 16 mm or 20 mm) is adapted to the degree of reflectivity and light-intensity desire, and a larger diameter can be obtained by increasing the diameter of the first and the

second sections 41, 42. It should be observed that a narrower opening results in greater light-intensity combined with the fact that a larger number of photo¬ diodes are required herefore, whereas a larger diameter will produce lower light-intensity combined with the fact that a smaller number of photodiodes are used.

It will be understood, however, that both higher and lower light-intensities can be achieved in one and the same illuminated sign, depending upon the diameter of the apertured recesses in accordance with Figures 5, 6 or 7.

Figure 8 illustrates in perspective part of an illumi- nated sign incorporating a base-unit manufactured in a machine of the aforedescribed kind. The base-unit is provided with apertures and recesses in which photo¬ diodes are placed and is connected to a control unit 80 which applies a voltage to one or more diodes 12 in a time-dependent manner and in a pre-determined configuration.

Thus, the illustrated base-unit has a circular aperture having a length or depth extension of 2-5 mm, and a first conical light-reflecting surface 41 having a first cone angle and a second conical light-reflecting surface 42 having a second cone angle, said surfaces lying adjacent said circular aperture. It is assumed that the base-unit of the Figure 8 embodiment has a thickness of 10 mm, in accordance with the Figure 7 illustration, and has connected to the rear side thereof a back part 82, with electrical conductors 81 located between the base part 4 and the back part 82.

One of the cone angles is smaller than the other of said angles, and in the illustrated embodiment the surface 41 has a cone angle of 43.5° whereas the surface 42 has a cone angle of 54.5°, these angles being referenced "v" and "w" in Figure 7.

In the case of the Figure 8 embodiment, the top part 12a of the photodiode 12 will be located in the proximity of the front surface 4a of the base-unit, although at a small distance beneath said front surface.

The abrupt transition between the aperture 40 and the conical light-reflecting surface 41 cannot be seen in the illustration of Figure 8, since this transition is obstructed by the photodiodes.

It will be understood that the invention is not restric¬ ted to the described and illustrated embodiment, and that modifications can be made within the scope of the following claims.