This invention relates to identification printing apparatus and in particular, but not exclusively, to apparatus for printing identification on a cable or the like. It is known to print identification on cables or on tubing for attachment to cables by a variety of means. One group of machines uses a print head comprising a number of wheels which are heated so as to print characters on the periphery of the wheel when pressed against foil overlying the cable or tubing. At present, these wheels are indexed by means of a toothed wheel which is manually aligned with the selected print wheel in the print head and then manually rotated to rotate the print wheel. The present invention consists in apparatus for printing an identification on a cable or the like, including a print head having a plurality of side-by-side individually rotatable wheels with notches around their peripheries and print characters formed on the interposed lands, the wheels being mounted in the head with their notches axially aligned and an automatic indexing mechanism, including a carriage axially movable relative to the print head, a shaft rotatably mounted on the carriage, an indexing element mounted on the shaft for rotation therewith and engagable in a notch of a

print wheel according to the axial position- of the carriage, a first motor for moving the carriage, and hence the indexing element, axially to select the print wheel to be engaged by the indexing element and a second motor for rotating the shaft, and hence the indexing element, such that the indexing element indexes the selected print wheel to move a selected character to a print position.

In a preferred embodiment the indexing element is a sprocket wheel, at least one of the motors is a stepper motor and the carriage is mounted on a lead screw driven by the first motor. The second motor may be mounted on the carriage.

The above apparatus may be in the form of original equipment or in the form of a retrofittable unit for converting existing manual machines.

The invention may also include apparatus as defined above, having a plurality of print heads and a respective indexing element/shaft assembly and second motor for each print head. In a preferred arrangement there are a pair of heads and the indexing elements are on opposite sides of the carriage and hence of the heads. Such apparatus may further comprise control means for the indexing mechanism for operating

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the first and second motors such that the upstream head in the direction of movement of cable through the apparatus prints the same identification as that printed immediately previously by the downstream head. The control means may further operate the first motor such that the carriage moves a minimum distance in any given indexing cycle.

In any of the above forms of apparatus the print wheels may be moveable towards the cable but it is preferred that the apparatus includes a moveable anvil for engaging the cable with the print head either directly or through the medium of a coloured foil. The anvil may have a groove or channel for receiving the cable and may be provided with clips or the like for retaining the cable in the channel during movement to and from the print head.

The apparatus may include means for varying the pressure applied by the anvil in accordance with the number and/or size of the characters to be printed. For example,the anvil may be solenoid activated and the pressure varying means may include means for varying the voltage supplied to the solenoid. Thus, the voltage may be chopped and means may be provided for varying the period for which the chopped voltage is o££ or on, so as to vary the average voltage suppli to the solenoid.

The apparatus may further include means for feeding the cable past the print heads in a timed sequence with the operation of the apparatus.

From a further aspect, the invention consists in apparatus for printing an identification on a cable o "the like,including a print head, an anvil for pressing the cable against the print head (either directly or indirectly) and means for varying the pressureapplied by the anvil in accordance with the physical characteristics of the identification to be printed.

From another aspect, the invention, consists in apparatus ^" for printing .identification ^" on a cable αr. the like, including a pair of side-by-side print heads past which a cable can be moved and means for altering the identifications printed by the heads such that the upstream head, in the direction of cable movement, prints the same identification as that printed immediately previously by the downstream head.

The result of this arrangement is that thereare lengths αf cable having the same identification printed at either end with a small space before the next identification. The cable can then be chopped between unlike pairs of identifications to provide lengths of cable correctly identified at each end.

From a still further aspect the invention consists in apparatus for printing an identification on a cable or the like, including a print head and means for moving the cable into direct or indirect contact with the print head.

Although the invention has been defined above, it is to be understood that it includes any inventive combination of the features set out above or in the following description. The invention may be performed in various ways and a specific embodiment will now be described, with, reference to the following drawings, in which;

Figure 1 is a schematic view of printing apparatus; Figure 2 is a plan view from above of a printing machine of the apparatus of Figure 1;

Figure 3 is a side view of the machine of Figure 2;

Figure 4 is a partial end view on the arrow A of the machine of Figure 2;

Figure 5 illustrates a 'manual' print unit fitted automatic indexing apparatus; and

Figure 6 illustrates the engagement between a print wheel and sprocket wheel.

Referring to Figure 1 cable printing apparatus comprises a printing machine 10 through which a cable 11 is intermittently drawn by a driven reel 12 from a supply reel 13. The operation of the machine 10 and 5 reel 12 is controlled by a computer 14 having a key¬ board 15. In order to keep the cable taut, the supply reel 13 may also be driven and under computer control.

Turning to Figures 2 to 4, the printing machine 10 has a pair of print heads 16, 17 spaced 10 along the path of travel of the cable 11 and a movable anvil 18, which receives the cable in a channel 19. Foil reels are provided at 20 and 21 so that coloured foil can be drawn between the print heads and the anvils and over tensioning rollers 22, 23. ,15 Thus, in use the anvil 18 is moved upwardly to press the cable against the print heads 16, 17 through the coloured foil to print the identification set on the print heads.

Each print head comprises a series of side- 20. by-side print wheels 24, each of which is notched about its periphery to provide interposed lands on which print characters are formed. The wheels are heated (by means not shown) to assist the transfer of colour onto the cable. They are each individually rotatable to allow

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the identification at the lower print position to be altered.

This adjustment is achieved by engaging a toothed or sprocket wheel 25 in the notches or recesses in the periphery of any given print wheel and rotating the sprocket wheel 25 to cause rotation of that print wheel. This is illustrated in Figure 6. In the printing machine 10, an individual sprocket wheel 25 is provided for each print head 16, 17 and it will be seen that they are located on opposite sides of the print heads with respect to each other. The sprocket wheels 25 are carried on respective shafts 26, for rotation therewith, which extend between walls 27 and 28 of a carriage 29. This carriage is mounted for axial movement with respect to the print head 16, 17 by means o ^' f a lead screw 30 to which it is threadingly engaged. A stepper motor 31 is provided for rotating the lead screw 30 to achieve axial movement of the carriage 29 and the carriage in turn supports a pair of further stepper motors 32, 33 which are arranged to rotate respective shafts 26 by means of belt drives 34.

Thus, it can be seen that by appropriate rotation of the lead screw 30, the sprocket wheels 25 can be located adjacent any respective print wheel 24 in the head 16 or 17 and can index that wheel by appropriate rotation caused by its respective motor

32, 33. As the sprocket wheels have individual rotational motors, the indexing in any particular operation can be varied between heads. Indeed, if for example, one head is changing both tens and units

5 in an identification whilst the other is only changing units, then one of the sprocket wheels will not rotate when they are opposite 'the tens' print wheel.

The computer 15 is arranged to select the

10. identification to be located in the print positions on the print head 16, 17 and then to compute the shortest carriage travel which can achieve the requisite identifications. As has been explained above, by having the identification of print head 17 lagging that

15 on the downstream head 16 it is possible to print either end of a cable length so that it may be sub¬ sequently cut. The operation of the drive reel 12 determines the length of cables achieved.

The construction and the operation of the

20 anvil 18 will now be described in more detail,- with reference to Figure 4. As can be seen in that Figure, the anvil 18 is mounted on a chassis 35 which is pivoted about a horizontal axis at 36. The generally triangular chassis 35 is engaged at its lowest corner

25 37 by a link 38a of a solenoid, generally indicated at 38, such that contraction of the solenoid causes

upward (printing) movement of the anvil 18 into the position shown in Figure 4. Switching off of the solenoid 38 returns the chassis 35 to its ghost line position where it engages adjustable stop 39. The tensioning rollers 22, 23 are operatively connected to the chassis 35 and anvil 18.

Surprisingly, it has been deteremined that the pressure applied by the anvil is desirably adjusted in accordance with the number or size of characters which are to be printed in any cycle. This pressure is a function of the extent of movement of the chassis 35 and hence the solenoid 38. Accordingly, the computer controls the average voltage supplied during the 'on' period of the solenoid as a function of the identificaitons to be printed and it can efficiently alter this by controlling the 'on' or 'off period of a chopped voltage supply to the solenoid.

Thus, the applicants' apparatus not only allows ready automatic indexing of the print head, but the provision of two controlled print heads enables the printing of the same identification at either end of the cable with considerable flexibility and speed. To assist easy reading the printed characters in the 'same' identifications may be in the opposite order that the identification is always read from the nearest end.

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Further, the use of a moving anvil, as opposed to a moving print head, not only simplifies the mechanism but also allows for very precise pressure control. Figure 6 illustrates a retrofittable automatic drive unit 40 for automating existing manually operated printing apparatus. The unit 40 is coupled to and hence incorporates the existing sprocket wheel shaft 41 by a coupling 42. The unit 40 has a frame 43 mountable on the existing apparatus and comprising support shafts 44, 45 and end plate 47. The shaft 45 supports a carriage 48 which is drivingly engaged at 49 to the output shaft 50 of a first motor 51 mounted on plate 47 to move the carriage 48 along shaft 45. Carriage 48 carries a second motor 52 which is engaged to shaft 41 by coupling 42 to rotate the sprocket wheel 25. By suitable operation of the motors 51, 52 the sprocket wheel 25 can index any of the print wheels 24 in the manner described above. Control apparatus of the type shown in Figure 1 is again used.

In either case the apparatus may be arranged to produce a synchronising signal so that printed lengths of cable can be cut whilst the cable drive is halted for printing to occur. It will be appreciated that the apparatus is designed to operate on a continuous cyclic basis to produce batches of individually identified cable lengths or it can be programmed to produce 'one-off cable lengths.