EP0057964A1

EP0057964A1 - A method and apparatus for producing individual transfer signs

Info

Publication number: EP0057964A1
Application number: EP82200148A
Authority: EP
Inventors: Ole Nonbye; Erland Falk Hansen
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-02-06
Filing date: 1982-02-08
Publication date: 1982-08-18
Also published as: FI820401L; NO820367L; WO1982002688A1; DK48982A

Abstract

For production of a transfer sign member (52) having letter members of sheet material a sandwich tape (8) is stepwise indexed to and through a punching station (10), to which is successively supplied individual punching tool plates (3) from an indexing tool plate magazine (28). The tool plates (30) successively punch the contours of the letters in one layer of the sandwich tape (8), such that the surplus area portions of this layer (46) may later be pulled off from the remaining second carrier layer (44) of the tape (8), whereafter the sign letters are transferable to a final mounting surface with unchanged mutual positioning. The tape indexing means are controlled by memory means, which are prepared so as to define the necessary individual spacing between the letters in all relevant pairs of letters, whereby a high graphical quality of the product is automatically achieved.

Description

A method and apparatus for producing individual transfer signs.
This invention relates to methods and means for producing individual sign members of the type comprising a row of letter members made of flexible sheet material and adapted to be secured to a surface, preferably by way of a pressure sensitive adhesive, e.g. as a name sign on the outside of a commercial motor car. Conventionally such a marking of cars or vans and many other types of surfaces has been carried out by a direct painting of the letters on the respective surface, but several attempts have been made to simplify this troublesome and highly skilled work. A first approach is to provide the letter members as punched out sheet members, whereby the painting word is replaced by a correct mounting of the letter members, one by one, on the receiver surface, but even this work requires skill,_' because in professional sign writing (or letter mounting) it should be observed that the spacing between two consecutive letters should not generally be the same for all pairs of letters; thus, for example, the letter combination AV requires a letter spacing which is smaller than in the combination AJ, and for each pair of letters the designer or "painter" should select the correct spacing.
Now, the job of selecting correct spacing between consecutive letters is rather different from the job of mounting the letter members on a receiver surface, and the latest development is that the signs - or individual text lines - are prepared in a sign making enterprise, where the required letter members are premounted on a carrier sheet with correct spacings as determined by graphically educated personnel, whereafter the carrier sheet units are delivered to the "painting" firm undertaking to transfer the letter members from the carrier sheet to the relevant surface to be marked. In this manner the personnel of the latter firm or department need not be graphically skilled, while on the other hand the persons preparing the sign units need not be trained in the art of selecting the optimal sign mounting place on a given surface and mounting the sign under the conditions as required for a durable adhesion of the sign to the surface.
In the sign making enterprise it is necessary to have at disposal a vast number of letter members of different shapes and sizes for meeting the requirements as to various texts on various types of signs (sizes, typography), this in addition to the requirement as to graphically skilled personnel.
It is the purpose of this invention to provide a novel sign making method and apparatus, whereby the signs in question are produceable in a labour saving manner and in a preferred embodiment of the invention even with reduced total skill requirements.
According to the invention the making of the letter members is carried out in direct connection with the production of the prepared sign members as provided on said carrier sheet, a sandwich sheet length comprising the carrier sheet and the letter material sheet being advanced through a letter forming station in which tool means are provided for selectively and consecutively precutting the letter material sheet to define the required consecutive letters, such that these letters remain on the carrier sheet when the remainder of the letter material sheet is pulled off therefrom (or inversely, if a "negative" sign is wanted).
The said tool means should comprise die members corresponding to all the letters of the alphabet, each die member being individually operable to cut through the letter material sheet or tape along lines according to the contours of the respective letter. As far as the single die members are concerned these may correspond to the known die members for producing the said single or separate letter members, and basically the die members may even be actuated in the same manner, viz. by being forced against the letter tape typically in a heated condition, whereby protruding ridge portions on the die member as defining the contour lines of the letter will cut and/or melt their way through the letter tape without cutting through the carrier sheet.
In the production of single letter members the single die members may be selected from a stationary magazine such that consecutive series of individual letters are produceable, but in connection with the invention it is essential that the various die members can be readily and rapidly brought into an operative position in a punching station, in or through which the tape is indexed in steps corresponding to the individual widths of the letters,.since in sign writing it is normally necessary to operate with such individual widths. Already known are some types of lettering machines for small sign strips in which the single letters are relief printed in the tape by means of individually operable die plate members arranged in a circular row constituting a self-contained die member magazine, which is rotatable relative the punching station to enable the user to bring any desired die member into registry with suitable actuator means in the punching station. In these machines the means for effecting the punching operation are normally operatively connected with the means for indexing the tape such that between two punching operations the tape is advanced through a predetermined fixed length with no possibility of a length adjustment according to special width requirements of the single letters. As in ordinary typewriters, therefore, the letters should be designed so as to appear in a graphically acceptable manner despite the uniform spacing between each pair of letters or rather between the middle of the consecutive letters.
Such a uniform letter spacing, however, is intolerable in the writing of larger signs, and the problem is automatically overcome with the said manual mounting of prefabricated letter members, since each of these are of course made with their natural individual width. For the invention it is correspondingly necessary to provide for individual letter widths, and this is obtained by causing the indexing of the letter tape to correspond selectively to each single letter as "written" on the tape.
In modern typewriters it is known to provide for variable letter width by causing the written surface to get displaced relative the writer head corresponding to the requirements of the written "type" of letter, the various letters being accorded one of a few standard widths, but in professional sign writing it is not sufficient to operate with just a few standard widths, and ideally each single letter should have its own width, though of course several letters will require identical widths. None of the known arrangements, therefore, would be usable for the purpose of the invention, and it is a special feature of the invention that each single letter or die member is accorded an individual width requirement expressed by an associated control function or code marking operable to cause the tape indexing means to respond consecutively to the individual letter width requirements.
Another essential feature of the invention is that the said die member magazine is a carrier magazine for the necessary plurality of individual die members disposed generally in a row parallel with each other and closely juxtaposed instead of in planar prolongation of each other. In the latter case the row of die members for larger sign letters would be very long, whether dis-" posed in a rectilinear or circular manner, and a shift between two consecutive letters, therefore, could require a considerable time, just as the entire magazine would show pronounced space requirements. According to the invention, therefore, the die member magazine is preferably made as a movable rack, in which the die members as thin plate members are placed with small spacing face to face in a row so as to be readily individually retractable from the rack, the rack being movable or indexable so as to be operable to bring any selected die plate member into a position, from which it is temporarily retractable to an operative position just outside the rack in a punching station, where means are provided for forcing the die member against the sign tape as indexed through the punching station. Thereafter the die member is moved back into the rack, and the rack is indexed to bring the next selected die member to the position in registry with the punching station while the tape is indexed corresponding to the width requirement of the next letter or rather - as more detailed described below - with the width requirement as defined by both the preceding and the following letter.
The die member rack or magazine is preferably a cylindrical unit in which the die plate members are arranged in radial pockets, whereby the indexing of the rack is achievable in a simple and advantageous manner by rotation of the rack unit. One such unit-may hold all the die members belonging to at least one alphabetic system as defined by the shape and the size of the letters, and the means for supporting and indexing the rack unit may be designed to enable the rack unit to be easily changeable with another similar rack unit se- _lected from several such units representing different typographical systems.
The means for displacing the successively selected die members to and from the operative position in the punching station during stillstand of the rack unit may be constituted by simple pushing or pulling means cooperating with the leading and/or the opposite edge of the die plate members. A possible solution would be the use of means for gripping about the edge of the die plate member and then moving it both out of and back into its rack pocket, but there will not be much space left for such a gripping operation when the die plates are reasonably closely juxtaposed in the rack. According to the invention a preferred displacement system comprises a double acting push/pull member having end portions which are of the same small thickness as the die plates and are provided with widened outer head portions engaging loosely within correspondingly undercut recesses or notches in the edge area of the die plates, whereby the push/pull member will not prevent a free rotation or indexing motion of the rack unit, while on the other hand it will be in inherent operative retraction engagement with the selected die plate when the indexing motion stops.
The necessary and sufficient punching pressure on the various die plates in the punching station will not be the same for all letters, not even of the same typographical system. According to the invention means are provided for adapting the pressure individually to the single consecutive letters.
A very important aspect of the invention relates to the control of the indexing of the sign tape. As already mentioned, means are provided for causing the tape to be displaced corresponding to the individual width requirements of the single letters, but as also discussed above this will not be sufficient for producing a graphically correct sign text, because a visually correct spacing between one letter and the preceding or following letter will depend of the character of the particular letters. According to the invention this problem is overcome in the manner that for each relevant typographical system the visually correct spacing between the letters of each possible pair of letters as found empirically is fed into a memory or expressed otherwise as a control constant which is automatically consultable every time the respective letter pair occurs, such that in operation the tape indexing system will be automatically controllable to cause exactly the required individual spacings for making the sign text appear as written with all graphical skill.
It will be appreciated that a control task of this kind is easily solved based on electric computer technology, but it should be emphasized that the various said control constants are in no way bound to be expressed and used solely with this type of technology.
Thus, each selected die member as displaced into the punching station may carry an identification code marking which is read and identified by a reader unit in the punching station, whereby a letter width memory unit is actuated to cause the tape indexing means to displace the tape as required for the particular letter width preparatory to the punching of the first letter. This letter is now memorized by a memo unit, and when the next selected letter is received in the punching station and is identified, then the identification signal is applied to a further unit for identifying the specific combination of the preceding letter as memorized by said memo unit and the newly arrived letter; once the specific combination has been identified the said memory unit for correct visual spacing between the letters is actuated to respond to the particular letter combination, and the response signal is utilized for causing the sign tape indexing means to effect the required indexing corresponding generally to the width of the second letter, but corrected according to the special requirement of the particular letter combination.
In the following the invention is described in more detail with reference to the accompanying drawings, in which:-

Fig. 1 is a perspective general view of an apparatus for producing sign members according to the invention,
Fig. 2 is a schematic side view of the apparatus,
Fig. 3 is a perspective view of a sign member as produced by the apparatus,
Fig. 4 is a similar view illustrating the further handling of the sign member,
Fig. 5 is a perspective view of a tool magazine of the apparatus,
Fig. 6 is a sectional top view of the magazine,
Fig. 7 is a view of a pair of letters to appear on the sign,
Fig. 8 is a further view of sign letters,
Fig. 9 is a perspective view of another sign producing machine according to the invention,
Fig. 10 is an enlarged view of one end thereof,
Fig. 11 is a sectional view of a detail thereof,
Fig. 12 is a perspective view of another detail,
Fig. 13 is a perspective view of the punching station of this machine,
Fig. 14 is an exploded view of a detail of this station,
Fig. 15 is a top view of the punching station, and
Fig. 16 is a schematic view of a modified control system for the indexing of the sign tape.

The apparatus as shown in Figs. 1 and 2 comprises a base structure or chassis 2 having a table top portion 4 to which is secured a roll holder 6 for rotatably supporting a supply roll 8 for a sandwich sheet material, the free end of this material being drawn through treating stations 10,12 and 14 and delivered onto a flat chute portion 16. The station 14 is a sheet station in which a prepared sign sheet member is cut so as to thereafter be removable from the chute 16. Adjacent the delivery end of the chute 16 the table top 4 is provided with a data monitor screen 18.
The staion 12 is a sheet advancing station comprising roller means 20,22 (Fig. 2) engaging the opposite sides of the sheet end length, designated 24, and of which at least one, e.g. the lower roller 22, is drivingly connected with a motor 26 of some suitable indexing type.
The station 10 is a letter forming station in which the sheet or rather the carrier sheet backed letter sheet layer thereof is subjected to a cutting or punching treatment by letter forming tools supplied in a consecutive manner from a tool magazine 28 so as to pre- punch the sheet according to the desired sequence of various letters.
The letter punching tools are constituted by plate members 30 housed in individual compartments 32 in a rotary magazine structure 28 and each provided at one side with outstanding punching ridges 34 (Fig. 2) defining the contours of a letter. The rotary magazine 28 is driven by an indexing motor 36 operable to position any desired compartment 32 just outside the station 10, an3 means to be described below are provided for pullinc. the tool plate 30 of the respective compartment into the station 10, viz. into a position in which the tool plate is located just above the sheet 24 and in top side contact with an overhead stationary heater element 38; the tool plates are made of a material of good heat conductivity, such that the punching ridges 34 are heated very soon after the introduction of the tool plate underneath the heater element.
In the punching station 10, underneath the sheet or tape 24, is arranged a pressing piston block 40 mounted on the piston rod of a working cylinder 42 so as to be operable to urge the sheet 24 upwardly against the cutting ridges 34.
The sheet 24 is laminated from a lower layer 44 of relatively good strength and heat resistivity and an upper layer 46 also of good strength (e.g. PVC), but generally less heat resistant compared with the lower layer 44. Therefore, when the punching ridges 34 are suitably heated and the sheet is forced thereagainst by the operation of the cylinder 42, the ridges will cut or rather melt their way through the top sheet layer 46 without cutting or melting into the bottom sheet layer, thus also without welding the layers together. This cutting technique,is well known from the production of series of similar letters.
At the end of the punching operation the piston block 40 is lowered, the tool plate 30 is returned into its compartment 32, the magazine is rotated to bring a desired consecutive letter or character punching plate 30 to register with the punching station, and upon the rollers 22,20 having caused the sheet to advance to one stop the next letter is "printed" by repeated operation as described above. Once the sign is completed the cutting station 14 is actuated, whereby a cutter knife 48 mounted e.g. on a working cylinder 50 is caused to cut entirely through the sheet and thus produce a loose sign member 52 resting on the chute portion 16.
The top sheet material 46 outside and between the prepared letters may later on be pulled off from the bottom sheet layer 44, as illustrated in Fig. 3, whereafter the "clean" letters or characters are left on the bottom sheet, adhering slightly to the surface thereof, though by way of a strongly adhering pressure sensitive adhesive against a prepared slip surface of the carrier sheet 44. The sign letters should later be transferable onto a final receiver surface, without any risk of displacement between the letters mutually, and this may be obtained according to any known method as used for the transfer of letters having been manually mounted on a carrier sheet. A preferred method is illustrated in Fig. 4.
The sign members as prepared by removal of the surplus sheet 46 is subsequently covered by a film 45 sticking to the surface of the single letters so as to be operable to later on lift off the letters from the carrier sheet 44. The top portion of the carrier sheet is cut through along a line 47, cut from the rear side so as to leave the film 45 uncut, and thereafter the edge strip 49 of the sheet above the cut line is removed, leaving uncovered the corresponding sticky rear .strip area of the film 45. Then the sign member is placed in the desired mounting position on the final receiver surface and the said sticky rear portion of the film is pressed against the surface to thereby fix the sign member thereon, outwardly foldable about the line 47. Thereafter the remainder of the carrier sheet 44 is removed from the film 45 and from the rear of the single letters, which now stick to the film 45, and then the letter carrying film portion below the line 47 is folded back against the receiver surface and forced against it with a high pressure exerted e.g. in a successive local manner, whereby the letters will stick firmly to the carrier surface. Finally the film 45 is removed entirely, leaving the letters on the receiver surface in their finally mounted positions.
The main feature or function of the invention is the manner in which the sign members themselves are produced, not by lying up the single letter members in a manual manner, but by controlling the operation of the tool magazine 38 to obtain the desired sequence of the various sign letters or characters and by controlling the sheet advancing or indexing mechanism to obtain correct mutual positioning of the letters on the sheet length, as explained below in more detail.
An arrangement for transferring the letter die tool members 30 between the magazine 28 and the station 10 is illustrated in Figs. 5 and 6.
It comprises a horizontal plate member 54 secured to the piston rod of a working cylinder 56 (Figs. 1 and 6) so as to be shiftable crosswise to the moving direction of the sheet 24 between a shift position, in which it is located inside the station 10, and a retracted position outside the station 10. Opposite its connection with the piston rod the plate member 54 is provided with a pair of protruding plate arm portions 58 each having a wider head portion 60, these arm and heat portions in the said shift position of the plate member 54 extending into the magazine 28 and being received in T-shaped recesses 62 in each.of the die plates 30, such that in this position of the plate member the magazine structure 28 may be freely rotated, with the die plate arms 58,60 engaged within the circular grooves as defined by the said recesses 62 of all the die plates as located in the compartments 32 between radial wall members 33.
When the magazine is stopped, with a predetermined die plate 30 located flush with the letter forming station 10, the cylinder 56 is operated to pull the plate member 54 towards its retracted position, whereby the head portions 60 of the plate arms 58 serve to pull the selected die plate into its operative position in the station 10 as shown in dotted lines in Fig. 6. When the die plate has served its purpose in the sta- t_ion the cylinder 56 is actuated to push back the plate member 54 and therewith push the die plate 30 into the magazine 28, whereafter this may be further rotated for selection of the following die plate member.
A very important aspect of the invention is the use of special control means which is shown as a unit _C in _Fig. 2, but otherwise not illustrated in the draw- i_ng. A major task of this control unit is to control the operation of the sheet driving station 12 in such a manner that each single letter or character, accord- i_ng to the nature thereof, e.g. whether being-an "_I" or a "_W", will be accorded the sheet length as indivi- _dually required (variable letter width), and furthermore such that the spacing between any pair of consecutive letters will be adapted to the requirements as existing between the letters of the particular letter combination (variable spacing). Thus, the combination _"HE" will require a spacing which is larger than for "_IW" or "KE" or "AV". Of course,, it could be sufficient to make use of a relatively low number of different spacings, but nevertheless the control unit should be adapted not only to provide the necessary space for the single characters, but also to control the interspacing in accordance with the type of both the preceding and the following character. Such a control unit should not by necessity be constituted by a device as named "a computer" in modern terminology, as it is readily appreciated that basically it will be possible to design a non-electronic control unit prepared so as to produce the required interspacing between any two of the finite number of letters or characters. On the other hand it will be just as evident that a modern electronic computer or data processing machine will be extremely well suited for the purpose in question, because of its ability to handle a relatively high number of data combinations in a simple manner.
Thus, the preferred control unit as used in connection with the invention is an electronic computer programmed so as to respond to the read-in of various letters or characters by supplying relevant control information to the sheet driving station 12 in order to provide for correct letter width and interspacing.
Once a computer is selected as the control unit of the sign "printing" device according to the invention it will of course be possible to "computerize" practically all other control functions of the device, including the indexing operation of the magazine 28, the operation of the working cylinder 56 (or any equivalent reciprocation system) and the cylinder 42 or other means for operating the pressing block 40, as well as the operation of the sheet cutting means 48,50.
The said computer (not shown) may be adapted to receive all relevant date relating to the required sign member production during e.g. one working day. Normally the various orders will deal with individual signs of different colours and sizes and perhaps even diffe-. rent typographies. When all orders are read into the computer the orders will be automatically rearranged and grouped most conveniently in similar types of orders as far as colour, size or typography is concerned, and the data screen 18 will tell the operator when it is time to change out the sheet supply roll 8 with another supply roll of another colour or another width. As far as the typography is concerned this relates to both the size and the shape of the letters or characters, and though of course the magazine 28 may hold a vast number of die plates belonging to several different typographical size or shape systems, it is nevertheless to be preferred in practice that the magazine 28 holds but one or a few systems, while the magazine 28 as an entity is easily exchangeable with one or more similar structures holding character die plates 30 belonging to other typographical systems, by size or shape.
It should be mentioned that the means for heating the die plate members may comprise a heater system for keeping the entire magazine heated to the required temperature or at least preheated at a temperature not far from the required operational temperature of the die plate members, whereafter the final heating in the station 10 is rapidly obtainable. Besides, the means for heating the plate member in this station should not necessarily be a separate heater element 38, since the heating may be effected otherwise, e.g. by virtue of direct electrical resistance or high frequency heating of the metallic plate members. Alternatively hot air may be blown onto these members.
As far as smaller size typographical systems are concerned each of the die plate members 30 may be provided with two or even more similar characters belonging to different systems, when the respective different characters are placed on the plate members so as to be operable to cooperate with a sheet strip of a corresponding width and guided so as to pass the various plate members just underneath the location of the characters of the selected type or size. Hereby a desired change to a new typographical system may be effected merely by repositioning the sheet supply roll 8 on its carrier shaft or changing it by another supply roll of a different width and located in the respective correct position on said carrier shaft or other carrier structure.
The tool magazine 28 should not necessarily be a rotatable or revolving structure, since any compartment divided structure will be usable, when it is operable by indexing means, e.g. in a rectilinear reciprocable manner, so as to bring any of its compartments into register with the station 10 in a well defined manner. Thus, it is indicated by dotted lines in Fig. 1 that the magazine could be a vertical box structure 29, which should then be vertically indexable.
Especially when the operations are controlled by a computer it will be possible and indeed within the scope of the invention to arrange for an auxiliary tool magazine at the opposite side of the station 10 and to arrange for the various die plates to be transferred, upon use, from the station 10 into a vacant compartment of the auxiliary tool magazine, whereby the magazine 28 may be operated for selection of the following die plate member as soon as the preceding die plate members has been transferred into the station 10. Thus, when said preceding die plate has fulfilled its purpose in the station 10 it is transferred to the auxiliary magazine, but in the meantime the following die plate of the main magazine has already been brought into its "ready" position and is transferable to the station 10 immediately upon the preceding die plate being removed therefrom, i.e. with a minimum waste of time. The computer will memorize the position of the die plate as transferred to the auxiliary magazine, and when this particular die plate is selected for renewed use the computer will cause the auxiliary magazine to be moved into the required position in which the die plate is re-transferable to the station 10 from the other side thereof. In this manner the two opposed tool magazines will be operable to supply and receive, respectively and invertedly, the various individual tool plate members 30 such that the sign making operation may be carried out at maximum speed.
The station 10 may be designed in such a manner that the various consecutive die or tool plate members 30 are operated to accomplish their letter forming purpose while they are moved along with the advancing movement of the sheet strip material 24, whereby the sheet strip is continuously movable while the various die or tool plates are engagebale with the strip material and are hereby transferable to a receiver tool magazine at the end of their operative movement, while in the meantime the computer has already effected the supply of the required following tool plate to the start operation end of the station 10.
In practice, however, it will normally be sufficient and preferable that the sheet length 24 is advanced stepwise and that the die or tool plates are delivered from and returned into a single magazine structure 28, though this may be exhangeable with other similar structures.
Instead of being placed as die or tool plate units in the compartments of a rotary or displaceable tool magazine the various die or tool plate members may be hinged together to form a chain structure generally extending crosswise of the sheet strip 24 such that any desired or selected die or tool plate member is positionable relatively to the sheet strip by way of the computer controlling the drive mechanism of the said chain structure.
For controlling the operation of the tape indexing means 26 in the required correct manner it is of course necessary to select a specific geometric reference, to which also the location of the letter masters on the die plates 30 should refer. Thus, it may be chosen to select either the left or the right hand end point or line of the single letters (front side or rear side, respectively), whereby the letter masters on the die plates should all be located with specific reference to the respective side edge of the die plates, i.e. small letters would then normally occur pronounced closer to one side edge than to the other side edge. With such a system it is possible to control the indexing of the tape in close accordance with the width requirements of the single letters, because based on the simply memorized width of the single letters the indexing means should index the tape either such that the last printed letter is moved sufficiently, according to its-own width, to just get out of the punching area before the next letter is printed, or such that just before the next letter is printed the tape will be indexed sufficiently, according to the sensed or memorized width of that next letter, to again bring the previously printed letter just out of the punching area.
For enabling a memory unit to memorize the correct individual width of a given letter it is of course necessary to define this "correct width", which in sign writing is not simply the geometrical width of the letter, because the width should of course include the necessary spacing between the letters in order to effect correct indexing of the sign tape. Generally a letter side consisting of a vertical full height line will require a larger spacing from its neighbouring letter than other letter side configurations, and as shown in Fig. 7 it is possible to determine for each letter the so-called spatial point at both sides of the letter, these points or vertical lines as designated A and B representing the graphical sides of the letter including the spacing to be observed from the particular letter to a neighbouring letter or rather to the relevant spatial point of that letter. It will be noted that the spatial point B of the "k" shown lies even inside the geometric side of the letter. If the "k" was followed by another "k" correct spacing would be obtained when the spatial point A of the last "k" coincided with point B of the first "k", In the example shown the "k" is followed by an "n", which could well be positioned with its spatial point A_N coinciding with point B of the "k", but for illustration it is shown that it may be desired to work with a certain correction Δd of the spacing.
Now, if as mentioned above, the letter printing and indexing of the tape is based on a letter side reference it would be natural to select either the right or the left spatial line A or B as the reference, whereby at least an approximately correct spacing between the letters would be achievable, and the printing system could operate based on an instantaneous knowledge or measurement of the width of the one letter being processed, without paying any regard to the width of the preceding or following letter.
When the printing is controlled by a computer it will be a special possibility that the indexing of the tape is controllable based on a memory knowledge of the width of both the letter being processed and the following lettter, and in that case, therefore, i it will be possible to use other reference lines, because the computer may calculate the correct spacing anyway. In a preferred arrangement the reference line is chosen to be the middle line.M between the two spatial points or lines A and B. This will involve in practice that all the symmetrical letters (A,M,u,v etc.) can be positioned symmetrically about the middle line of the punching plates 30 and generally that all letters are placed midways on these plates rather than adjacent a reference side thereof. For providing correct indexing of the sign tape it is then sufficient to provide a control signal corresponding to half the width of the first letter plus half the width of the following letter (d_k ⁺ d_n), whichever is printed first.
An important circumstance is that it is not generally possible to count on the coincidence of the spatial points for the provision of a fully correct spacing between the letters. In many letter conbinations it is necessary to adjust the spacing further in order to obtain a graphic- alle fully acceptable product. An example is shown by the word "Tractor" as illustrated in Fig. 8, from which it is noticeable that even negative spacing as between "_T" and the following "r" may be required. Thus, each pair of letters should be accorded a spacing correction, which is conveniently expressed by the distance - positive or negative - between the relevant spatial points, corresponding to Δd in Fig. 7. The correct indexing of the sign tape between the punching of the two letters of Fig. 7 will thus be d_n ^+.d _k ⁺ Δd_kn, while correspondingly the indexing between "T" and the following "r" in Fig. 8 will be d_r ⁺ d_T ⁺ Δd_Tr, where Δd_Tr is negative. It should be noted that Fig. 7 is an illustrative more than correct representation, since Δd_kn could in fact be rather close to-zero.
As previously explained, when all the possible spacing corrections have been found empirically and been read into the controlling computer the punching machine will thereafter be operative based on these constants. Control means may even be provided for increasing the general standard spacing between the letters for producing a more open text, and in such cases even the correction constants could need correction until they become unimportant when the general spacing is very large.
The sign production machine illustrated in Figs. 9-15 operates according to the principles already described, but comprises some important modifications. Thus, a major difference from the machine according to _Fig. 1 is that the sign sheet strip or tape is handled with its cross direction oriented upright.
The machine as shown in Figs. 9 and 10 comprises a housing 70 having an inclined front shelf portion 72 located underneath a sign tape conveyor 74, which consists of two edgewise superimposed conveyor belts 76 extending horizontally behind a glass cover 78 (see also Fig. 11), and a die plate magazine housing 84. On the top side of the latter housing a tape supply reel 86 is mounted on a shaft 88, which is actively rotatable by an associated motor (not shown) for unreeling the tape, designated 90, according to the requirements as determined by the operation of the indexing unit 82. The tape passes a guiding pin 92 mounted on a lever 94 which is horizontally pivotable about the axis of the driving shaft 88 and is biased in anticlockwise direction (Fig. 10), whereby the tape .90 will be kept under tension as it passes a stationary guiding pin 95 on its way to the indexing station 82. As the tape is pulled through the punching station 80 with the reel motor stopped the lever 94 will be drawn clockwise until, in well known manner, it actuates a starter switch for the reel motor, whereafter more tape is reeled off faster than it passes the punching station, thus enabling the lever 94 to return anticlockwise to a motor stop position, all such that the tape is steadily suitably tensioned.
As the punched tape 96 leaves the indexing station 80 it enters into engagement with the relevant conveyor belt or belts 76, in the example shown only the lower belt 76. Behind each of the belts 76 (see Fig. 11) is mounted a suction box 96 which is open towards the rear belt side and is connected with a vacuum source V through a pipe 98, which may be provided with a stop valve 100. The belts 76 pass around opposed end rollers 102, of which one is driven by a motor 104 in synchronism with the operation of the indexing motor of station 82. Each belt 76 is provided with two rows of holes 106, through which the respective suction box 96 communicates with the space in front of the belt.
As the punched tape end, designated 108, engages the front side of the relevant belt 76, therefore, it will be sucked against the front side of the belt and thus be moved along with the belt. Preferably the belts are moved, in said synchronism, a little faster than corresponding to the tape speed as defined by the indexing means of the station 82, whereby the belt will slide on the rear tape side at moderate relative forward speed and thus exert a certain pull in the tape.
In the example shown the tape 90,108 is of a small width corresponding to that of the lower belt 76, and for saving idle suction through the holes 106 of the upper belt 76 the valve 100 of the upper suction box 96 may here be closed.
When the punched tape end 108 has proceeded far enough to be ready as a desired sign member a cutter device (not shown) located immediately downstream of the indexing station 82 is actuated to cut off the tape end portion 108, and immediately thereafter the suction through the holes 106 is brought to cease by automatic closing of the connection to the vacuum source V or otherwise by a temporary relief of the effective vacuum inside the suction box 96, whereby the cut off tape end portion 108 will leave the belt and fall down onto the shelf member 72, from where the operator may remove it from the machine.
A preferred indexing arrangement of the station 82 is illustrated in Fig. 12. It comprises a pair of vertical rollers 110 and 112, of which the former is held by brackets 114 rigidly connected with the chassis of the machine, while the roller itself is drivingly connected with an indexing motor 116, the operation of which is controlled by a central control unit 118. The opposed roller 112 is held by brackets 120 which are individually connected with pressure cylinders 122 receiving their operative pressure from a pressure source 124 through a variable pressure control unit 126. The latter is connected with a system of sensors 128 arranged so as to sense the height position (presenee/ absence) of at least one of the longitudinal edges of the tape 90, and the unit 126 is of a type operable to change or adjust the pressure as applied to the associated cylinder 122 in response to the sensing of the relevant sensor 128. For making the prepared letters on the punched sign member appear along a straight common base line it is important that the tape 90 be guided through the punching station 80 with a constant relative height position, and this is achievable by means of the system shown in Fig. 12, because if a sensor 128 reacts to a deviation from the desired height position of the type, then the counter pressure roller 112 will be caused to exert an increased pressure on the tape edge which has been displaced towards the respective end of the roller, and by the resulting differentiated pressure on the opposed tape edges the tape will tend to get vertically displaced anyway from the edge area of relatively increased pressure between the rollers 110 and 112, i.e. the tape height position will be steadily adjusted to correspond to the fixed positions of the sensors 128.
The die plate magazine housing 84 contains a magazine unit 28 fully corresponding to the circular magazine shown in Figs. 1, 2 and 5, but oriented with a vertical axis of rotation, see Fig. 10, in which the indexing magazine rotating motor is designated 130. Thus, the single die plates 30 of the magazine will be displaceable into an operative position by being lifted upwardly from the rotary magazine structure, and the punching station 80 includes means for such vertical lifting of the die plates.
The interior of the punching station 80 is illustrated in Fig. 13, which also shows the indexing driving rollers 110,112 of the subsequent indexing station 82. The punching station comprises as main parts a front counter pressure plate member 132, a die plate lift device 134 and a pressing shoe 136. The plate member 132 is mounted just inside a removable cover portion 138 (Fig. 10) of the outer housing of the station 80, and the plate member 132 itself may be associated with the cover portion so as to be removable together therewith. In a preferred embodiment, however, the plate member 132 is raisable by means of a separate working cylinder for giving access, when required, to the space in front of the pressing shoe 13,6, and in its lowered position the plate member is then backed by fixed backing portions projecting along the vertical edge areas of the plate member.
The die plate lift device 134 comprises a stationary vertical working cylinder 140, the piston rod 142 of which carries a lift member 144 having a pair of lower T-shaped protrusions 146 corresponding to the elements 58,60 of Fig. 5. The lift member 144 is lowerable through a slot 148 in the top side of the magazine housing 84 (Fig. 10) to a lower position in which the protrusions 146 cooperate with the top portions of the die plates in the rotary magazine 28 (Fig. 10) corresponding to the described engagement between the elements 60 and 62 of Fig. 5, i.e. the lift member may be lowered for engaging any selected die plate 30 and then be lifted, with the magazine standing still, up to the position shown in Fig. 13, in which the raised die plate 30 is shown in dotted lines.
A pair of fixed stop members 150 is located adjacent the top position of the lift member, e.g. rigidly connected with the fixed cylinder 140 as shown. Each stop member has a lower shoulder portion 152 which acts as an abutment for the top side of the respective top corner portion of the die plate 30, whereby all the consecutive die plates will be lifted to exactly the same height position. Outside the shoulder portion 152 each stop member 150 has a downward projection 154, the inner side of which acts as a centering side support for the respective die plate corner.
The pressure shoe 136 is mounted on the piston rod of a cylinder 156, which is power supplied from a pressure source 158 through a pressure control unit 160, which is operatively connected with the main control unit C through a memory unit Mp.
According to the invention it is realized that the pressure as both sufficient and necessary for the die cutting or punching of the single letters or characters will not ideally be the same for all of them, e.g. because an "i" will require a pressure which is considerably smaller than required for an "M", while the latter pressure could cause damage if applied to an "i" or to a colon. The correct pressure will depend of the total operative area or length of the punching ridge or ridges 34 (Fig. 2) of each die plate, and though some different die plates may require the same pressure it has nevertheless been found that in practice it is relevant to distinguish between some 250 different punching pressures in a machine operable to handle various alphabet types with a maximum letter height of ca. 20 cm. For effectively distinguishing between different required pressures it would be possible to provide each die plate 30 with a code marking which could be read or sensed by a reader unit e.g. in the raised position of each selected die plate or during its lifting movement towards the raised operative position, whereby the reader unit could serve to control the pressure control unit 160 according to the sensed requirements, such that the pressure exerted on the pressing shoe 136 would be controlled by the selected die plate itself. Again, however, once a computer has been chosen as the main control unit C it will be readily understood that the pressure control unit 160 may be controlled by receiving the required differentiated signals from the computer C either directly or through a separate memory unit Mp (Fig. 13), this unit receiving from the control unit C an information as to the letter to be handled and transforming this information into an appropriate control signal to the pressure control unit 160. It should be mentioned that usable pressure control units 160 are already commercially available.
The pressing shoe 136 consists of a rear holding member 162, see also Fig. 14, which serves as a backing element for an outer pressing member designated 164 in Fig. 13 and 166 in Fig. 14. The holding member 162 as secured to the piston rod of the cylinder 156 is provided with a rear connector stub 168, which is connected to a vacuum source (not shown) through a pipe 170 (Fig. 13) and a bellow hose 172, the latter allowing for the pressing shoe 136 to reciprocate as required. As shown in Fig. 14 the front side of the holding member 162 is provided with a pair of slightly protruding sealing rings 174 each encircling a slightly retracted surface area 176 having a central opening 178 which, in a manner not shown, is in communication with the connector stub 168. Moreover the front side of the holding member 162 is provided with cornerwise arranged protrusions 180.
Considering first Fig. 14 the pressing member 166 has a rear side adapted to be received against the front side of the holding members 162, i.e. having holes to receive the protrusions 180 and surface portions to be sealingly engaged by the sealing rings 174. Within each of these circular surface portions is provided an opening (not shown) which communicates with a plurality of openings 182 in the front side of the pressing member 166, these openings 182 being located in rearwardly , oblique lateral front side portions 184, while the central front side portion 186 is unbroken and parallel with the holding member 162. Thus, when the pressing member 166 is placed against the holding member 162, guided on the protrusions 180, the vacuum as supplied through the connector stub 168 will appear in the front openings 182, and besides the same vacuum as confined within the sealing rings 174 will serve to firmly, yet releasably, holding the pressing member 166 in its mounted position on the holding member 162.
The pressing member 164 as shown in Fig. 13 is designed quite similar to the member 166 of Fig. 14, except that the front holes 182 are located solely in a lowermost portion of the oblique side portions 184, corresponding to the height portion of the pressing member as actually cooperating with the tape 90, this tape being of relatively small width.
As shown in Fig. 15, when the cylinder 156 is actuated to force the pressing shoe 136 forwardly against the tape 90 in order to force the tape against the selected raised die plate 30 as backed by the plate member 132, the tape 90 will be displaced out of its straight run between the stationary guiding pin 195 and the indexing rollers 110,112, such that it engages the outer oblique front side portions 184 of the pressing member 166. This involves that the tape is engaged by the suction through the front openings 182, whereby the tape is being held generally against the front side of the pressing shoe 136 during the active operation and initial retraction thereof, whereby any undesirable displacement of the tape is counteracted. In this connection it should be mentioned that initially it is desirable that the tape 90 is well shaped from the counter pressure plate member 132 for giving free space to the operation of the die plate lifting member 144.
It will be appreciated that the pressing member 164 of Fig. 13 will cause no idle suction through openings 182 located outside the tape engaging area of the pressing member, while on the other hand the pressing member 166 of Fig. 14 will be usable when the tape as used is as wide as corresponding to the full height of this pressing member. Especially with the use of the tape height positioning system of Fig. 12 it will be unimportant whether a tape of small width is wanted to cooperate with a higher or lower portion of the pressing shoe 136, and it will always be possible to mount on the holding member 162 a pressing member 164 or 166 adapted to the particular height position and width of the tape.
The vertical orientation of the cross direction of the tape 90 as described in connection with Figs. 9-15 and as compared with the horizontal orientation according to Fig. 1 and 2 is advantageous in that the die plates 30 will not be subjected to wear during their movements to and from their operative position and that the die plate magazines will be easier to handle when they are to be exchanged, already because the die plates as standing on the bottom of the magazine pockets or compartments will safely maintain their positions when the cylindrical magazines are moved generally in the lying position as indicated in Fig. 10. The necessary connection between the magazine 28 and the driving means of the indexing motor 130 may be designed in such a manner that the magazine is engageable with the driving means by a horizontal displacement of the magazine into its operative position. Correspondingly, when the magazine is to be removed it may be pushed or pulled away from the said engagement, carried on suitable support means inside the housing 84, and suitable transfer means may be provided for handling or conveying the magazines between a nearby magazine store and the admission opening of the housing 84 as shown closed by a door in Fig. 10.
It will be appreciated that the driving engagement betwen the magazine 28 and its indexing motor may be arranged and designed in any of a wide variety.of possible manners based on ordinary skill. It is of course important that the magazine should assume a well defined position relative the indexing driving system in order to ensure full operative coordination between the control means and the single selected letters or die plates.
It would be possible to provide the magazines themselves with a circular row of code markings indicative of the single letters, whereby a reader device could be used for causing the rotating magazine to stop in correct response to the selection of the.consecutive letters or die plates. However, a preferred arrangement is the use of a centrally controlled indexing mechanism, which for each selection causes the magazine to be moved through the path as required for correct positioning of the following letter underneath the punching station. In this connection it is advantageous to use a rotary type of magazine rather than a straight magazine operating by reciprocation, because temperature variations would cause the straight magazine to change its length and therewith change the necessary displacement of the magazine for bringing a new die plate into the correct position for operation in the punching station, while a thermal expansion of the cylindrical and rotary magazine will leave the angular positions of the die plates unchanged, such that the required angular indexing of the magazine will need no correction under varying thermal conditions, and adjustments may be carried out at ambient temperature despite the much higher operational temperature of the magazine inside the housing 84. In the housing 84 is provided means (not shown) for maintaining the magazine and the die plates heated generally to such a level that the die plates can be lifted in the punching station and complete their punching operation with the required temperature without being additionally heated while they are lifted.
With reference to Figs. 10 and 13 it should be mentioned that in practice the housing of the punching station 80 may include a common carrier structure for the front plate member 132 and the vertical cylinder 140 as well as the stop members 150, this carrier structure together with these parts being raisable as a whole inside the said housing by means of a suitable lifting arrangement such as a separate vertical working cylinder, whereby there will be fully free access to the pressing shoe 136 when the front cover 138 (Fig. 10) is removed.
When in Fig. 15 the tape 90 is forced out of its straight line between the indexing rollers 110,112 and a guiding member on the other side of the punching station, e.g. the roller 95, a first consequence is that in the situation shown in Fig. 13 there will be sufficient free space for the operation of the lift member 144 between the tape 90 and the counter pressure plate member 132, whereby the latter need not be operatively displaceable towards the tape. Another consequence or advantage is that by the end of the punching operation, when the pressing shoe 136. is retracted, the tape will seek to straighten itself by the pull exerted therein, whereby it will be actively drawn off the punching plate 30. Thus, any tendency of the tape to stick to the punching plate will be counteracted. also because of the suction holes 182.
It has already been mentioned that with letters of small height it will be possible to provide the punching plates with two or more letters belonging to different typographical systems when these letters are positioned on the punching plate so as to not overlap each other in the letter height direction, whereby the letters are selectable by placing the tape so as to cooperate with one of them only, of course with the tape being of the required width. As an example it is indicated in dotted lines in Fig. 13 that the punching plate 30 may show a lower small size letter "A" for cooperation with the tape 90 as shown and an upper larger size "A" for cooperation with a tape of increased width. With the tape position control system described in connection with Fig. 12 it will be perfectly possible to work with a tape which is located in a position just above that of the tape 90, whereby the series of uppermost letters on the punching plates will constitute a separate typographic system to be used with a tape somewhat broader than the tape 90 and located in a higher position.
In Fig. 16 is schematically shown a printing system according to the invention with a more detailed illustrated control system. The main parts of the printing apparatus are an indexable magazine 190 holding a row of printing or punching plate members 192, a drive unit 194 for indexing the magazine, a lift unit 196 for bringing a selected plate member 192 into an operative position in a printing or punching station at one side of a print receiving tape 198, a pressing member 200 arranged in the same station at the other side of the tape, and drive unit 202 for indexing the tape through the printing or punching station.
The magazine 190 is rectilinear and reciprocable forth and back by the indexing unit 194. The magazine has a row of partitions 204 forming pockets for the plate members 192, and the bottom of the magazine is open along a middle area thereof so as to enable the lower edge of the plate members 192 as standing on the remaining outer bottom portions to be engaged by the top end of a lift plate 206 as associated with the said lift unit 196, whereby any selected plate member 192 according to the position of. the magazine 190 is liftable into its operative position, principally fully corresponding to the system of Figs. 9-15.
The control equipment comprises a read in unit 208 for receiving the particular sign text order or orders and transferring the same to a control unit 210 functioning as the operative control unit of the printing system by sequentially feeding to the remaining control system the required signals as identifying the letters to be printed. In the example shown it is supposed that the letter "B" has just been printed and that the letter "E" is now going,to be printed.
Thus, the control unit 210 shows an output signal identifying the letter "E", and this signal is applied to four receiver units as follows:

1) A magazine indexing control unit 212 receives the "E"-signal and actuates the indexing unit 194 to displace the magazine 190 from the previous "B"-position to the new "E"-position, the control unit 212 having incorporated therein all necessary information and means for effecting such a displacement from any preceding letter to any new letter according to well known control principles. When the magazine has reached its new position the indexing control unit 212 (if not the central control unit 210) may actuate. the lift unit 196,206 through a lift control unit 214, such that the plate member 192 as shown lifted in the magazine 190 corresponds to the new letter "E".
2) The "E"-signal is applied to a letter register unit 216 which is in advance coded with information as to the necessary printing pressure of each single letter. The selective output of this unit is connected to a pressure control unit 218 serving to adjust the pressure as applied to the pressing member 200 from a pressure source 220 through a working cylinder 222. It is indicated by an arrow that the output of the unit 216 refers to the letter "E". Once the said adjustment has been effected the pressure connection to the cylinder 222 may be opened through valve means not shown and controlled e.g. by the central control unit in response to all other conditions being in order for the printing operation to be carried out.
3) Another letter register unit 224 receiving the said "E"-signal is connected with a tape indexing control unit 226 and is prepared so as to memorize for each single letter the graphical width of the letter such that the selective output signal of the unit 224, here referring to "E", will enable the tape indexing control unit 226 to cause the tape indexing means 202 to displace the tape 198. sufficiently to clear the printing area thereon for receiving the "E"-print with a basically necessary spacing from the "B" as printed in the preceding operation cycle.
4) The "E"-signal is also applied to a double letter register 228 having as many stages as corresponding to all possible or relevant combinations of two consecutive letters. The letter as actually processed ("E") is read into a section of the register 228 corresponding to a second column of letters following a first column of all letters such that all letter combinations are represented by the various stages of the register unit 228. A shift control circuit 230 is provided for causing the previously processed letter to be shifted from the second to the first column, whereby in the example shown all "B"-stages of the first column will be actuated, while all "E"-stages of the second column will be actuated. Thus there will be only one double stage, viz. "BE" which will be fully actuated, and the unit 228 is adapted so as to produce an output signal indicative solely to the particular actuated double stage thereof. Each of the double stages is accorded an information as to the necesary spacing between the two particular letters thereof, and conveniently this information refers to the required size of Δd as discussed in connection with Fig. 7.

The selective output signal of the register unit 228, as represented by an arrow outside the double stage "BE", is fed to a spacing correction unit 232 which transforms the signal into control terms readable by the tape indexing unit 202, and the output of the unit 228 is brought together with the output of the tape indexing control unit 226 in an adder unit 234, whereby the resulting tape indexing will be determined by the required width of the letter "E" as spaced "normally" from the preceding letter "B" and as corrected by any special spacing requirements between just these two letters.
In the example here described the already discussed reference line of the various letters will be the rear or left hand side line of the letters, because the tape 198 is caused to be displaced in accordance with the width of the following letter to be printed plus the possibly required spacing correction between the two particular letters. The required indexing of the tape, therefore, will be entirely independent of the width of the foregoing letter, i.e. of the position of the front side. line thereof, if the letters are printed according to the usual reading direction.
It will be readily understood, however, that the printing may be effected with a direction opposite to the normal reading direction and even with the letters oriented upside down, as long as the resulting product, the sign member itself, is mountable as a normally readable sign.
When the double register unit 288 is adapted so as to contain the described specific information referring to the individual pairs of letters it could as well include further information as to the letter widths. In that case it would be possible to use the letter middle line as reference line, because the unit 228 could then for each new printing cause the indexing unit 202 to index the tape according to the expression "half the width of the first letter plus half the width of the second letter plus the spacing correction therebetween" as previously discussed.

Claims

1. A method of manufacturing transfer sign members (52), whereby letter members of sheet material are placed on a carrier sheet (44) with a desired individual spacing between consecutive letters or characters, characterized in that the letter members of each individual sign member are provided integrally with the sign member by punching the contour of the consecutive letters in a sheet material surface layer (46) of a sandwich tape including a carrier layer (44) for said sheet layer (46), the punching being effected in a successive manner by means of individual punching tools (30) which are brought into operative engagement with the sheet layer (46) at such places thereof which correspond to the individual letter widthes and the desired individual spacing between the consecutive letters, the latter spacing preferably being based on automatic reading out of individual spacing corrections from a correction register constituting a memory unit for predetermined spacings or spacing corrections for all relevant pairs of letters or characters.

2. A method according to claim 1, whereby the sheet tape (24) is indexed past a punching station (10), to which the relevant punching tools (30) are consecutively supplied and actuated, the desired spacing between the letters being controlled by indexing the tape according to the individual requirements of each letter and letter combination.

3. An apparatus for manufacturing sign members according to the method claimed in claims 1 or.2, including a punching station (10), means (20,22) for advancing a sign carrier (24) through this station, means for successively supplying to said punching station a number of individual letter punching tool elements (30) as required for the desired sign text, a magazine structure (28) for said punching tool elements, means for actuating the punching tool elements successively in said punching station, and control means for operatively adjusting the spacing between the various pairs of letters according to predetermined individual requirements.

4. An apparatus according to claim 3, in which said control means include a memory register for correct spacing or spacing correction referring to the various letters in all relevant combinations thereof.

5. An apparatus according to claim 3, in which the tool magazine is made as a movable container (28) having a row of compartments or holding means (32) for individual letter punching tool plates (30) and being operatively connected with drive means for controlled indexing of the magazine in order to position any selected punching tool plate in register with the punching station, in which means (56,58) are provided for bringing the selected tool plate out of the magazine into an operative position in the punching station and then back to the magazine.

6. An apparatus according to claim 5, in which the tool magazine is a rotary cylindric container provided with flat radial pockets (32) for receiving the tool plates (30) .

7. An apparatus according to claim 6,in which the magazine is mounted with its cylinder axis oriented vertically, while the punching station (10) is adapted to receive the-consecutive tool plates (30) as these are lifted directly off their respective-magazine pockets (32) and to cause the respective tool plate to be forced against a receiver sign member tape which is correspondingly vertically oriented.

8. An apparatus according to claim 4 or 7', in which the means for actuating the punching tool elements are adapted so as to exert onto the respective elements an individual punching pressure according to the requirements of each single tool element or each letter on one tool element, a pressure control unit (Mp,218) being provided for effecting these individual pressures based on specific control signals from the main control equipment or from a sensing unit for identifying the tool element to be actuated.

9. An apparatus according to claim 5, in which the tool magazine is housed and indexed in a heated space inside a magazine cabinet.

10. An apparatus according to claim 4, wherein the control means for indexing the sign tape are adapted so as to operate according to the expression "half the width of the letter plus half the width of the following or preceding letter plus the required individual spacing or spacing correction between these particular letters", and wherein the letters on the punching tool plates are located thereon with the middle line of the letters coinciding with the middle line of the respective tool plates.