WO1996001186A1

WO1996001186A1 - Printer tapes and cassettes

Info

Publication number: WO1996001186A1
Application number: PCT/NZ1995/000056
Authority: WO
Inventors: Robert Atkins; Colin Francis Johnson; Peter Royce Trotter
Original assignee: Robert Atkins; Colin Francis Johnson; Peter Royce Trotter
Priority date: 1994-07-01
Filing date: 1995-06-20
Publication date: 1996-01-18
Also published as: AU2685295A

Abstract

Portable apparatus (700) for replacement of a used ribbon with an inked thermoplastic (such as nylon) ribbon within an existing ribbon cartridge for an impact printer comprises: dispensing means (730) for one or more widths of ribbon, metering means (721) to measure the length dispensed, a motor drive (704) to move the ribbon through the cartridge, a heat-sealing device (720) for joining thermoplastic ribbons end-to-end, and trimming means to remove surplus material at the join. The heat-sealing device (720) is electrically heated under control, and the gap between its heatable jaws is controlled in order to limit any tendency to thicken. A method for use of the portable apparatus (700) includes cutting the old ribbon at an exposed position, joining new ribbon to the old, pulling the new ribbon through the cartridge, and when it emerges, joining new ribbon to new ribbon so that an endless loop is formed.

Description

PRINTER TAPES & CASSETTES

FIELD OF THE INVENTION

This invention relates to the field of office stationery and more particularly to the repair and replenishment of ribbon cartridges for impact printers such as typewriters and computer printers.

BACKGROUND

Typewriter, teleprinter, and the like ribbons used to be sold on open reels. When a ribbon was to be replaced it was wound onto one reel which was discarded, then a new full reel was inserted and the ribbon as threaded across to the old empty reel. The inconvenience of this (dirty fingers, time, etc) was overcome recently for typewriters and was adopted for printers for computers by providing the ribbon inside a cartridge or ready-to-use box, so that a replacement ribbon could be installed simply by locating the cartridge (with internal ribbon feed mechanism) inside the printer or typewriter so that the ribbon fed between the paper and the impact printing head.

Although the older typewriter ribbons fed in a to-and-fro pattern until depleted of ink, most cartridges provide an endless loop of ribbon which is fed in one direction only, stored usually as a bunched-up mass of several metres length and may be installed with a half-twist to extend the area that is used. (Some cartridges use carbon ribbons which can be used only once. We are more concerned with ribbons made from a fine woven nylon material impregnated with ink - these can be used repeatedly).

Endless nylon ribbons are widely used in home and business applications as only impact printers can cope with multi-part forms and in this respect at least have an advantage over those printers that use an xerographic process- such as laser printers. Dot-matrix printers are inherently cheap. The printing costs associated with a particular printer relate in part to the frequency of replacement of the ribbon. If a new cartridge assembly is bought, it tends to be expensive and as there are over 415 kinds of cartridge in use in New Zealand, stocks may be difficult to come by from time to time. There is therefore a new industry which takes old cartridges on a return or replacement basis and either re-inks the ribbon, leaving the old textile in place, or replaces the ribbon with a new, inked ribbon. This industry generally makes use of ultrasonic welding of ribbons where ribbon joining is carried out.

Ribbon joining has been relatively difficult to perform with previously available equipment. Inconsistent joins result in inconvenient downtime for printers, repeating print runs (which can be highly frustrating), and the like. Getting the right combination of time, heat, and applied pressure to provide a suitable combination of strength, thickness, flexibility and ink holding power has hitherto been difficult. As the previous equipment was large and not portable, there is a need to make a smaller, portable ribbon joining device which provides consistent reliable effective joints.

The present invention seeks to provide a better service in this area.

OBJECT

It is an object of the present invention to provide an improved apparatus and procedure for replacing inked ribbons in cartridges or one which will at least provide the public with a useful choice.

STATEMENT OF THE INVENTION

In a broad aspect the invention provides a portable workstation for use in replacing inked ribbons made of plastics materials in impact printer cartridges and the like, including (a) means to dispense ribbons, (b) means to measure the new ribbon supplied, (c) means to trim off any surplus ribbon at newly made joints, and (d) make effective joints in ribbons.

Preferably a motor drive is provided for turning at least one drive wheel of a cartridge.

Preferably the ribbon joining device is a compact heat-sealing device. Optionally it may be a device using an adhesive to form the joint.

More preferably the ribbon joining device uses a combination of pressure and conducted heat from an electrically heated wire to fuse a narrow zone of the ribbon.

Preferably the applied heating current and the duration of the current can be controlled closely in order to make a suitable joint. Preferably also the space within which the ribbons are heated together has closely controlled dimensions.

In a related aspect the invention provides a cutting plate for use in trimming off cut edges from a joined ribbon.

In a second main aspect the invention provides a method for replacing a ribbon in a cartridge comprising the steps of:-

(a) taking the workstation to the site where the cartridge is used,

(b) selecting a suitable width of ribbon,

(c) cutting across the old ribbon,

(d) joining one end of the new ribbon to the old ribbon, (e) winding the old ribbon out into a waste container and thereby drawing a similar length of new ribbon into the cartridge,

(f) once the join has emerged, cutting the new ribbon adjacent to the join, and

(g) closing the loop of new ribbon with another joint.

In a related aspect the invention provides a method for joining thermoplastic ribbons comprising the steps of:

(a) laying the two ribbons in overlapped fashion across a heat-sealing station under an upper jaw 201 and over a parallel lower jaw 202,

(b) closing the upper jaw of the heat-sealing station down onto the lower jaw, (c) applying a predetermined temperature to the ribbons for a predetermined time by causing a current to flow through a resistive heating wire in each jaw,

(d) waiting briefly, and

(e) taking the fused ribbons to a cutting station where the joint is clamped and the free ends can be shaved off from the joint with a sharp knife.

In another aspect the invention provides a method for monitoring the usage of new ribbons by periodically reading the counters on the metered dispensers.

Alternatively usage can be monitored by measuring the length of dispensed ribbon material.

DRAWINGS

The following is a description of a preferred form of the invention, given by way of example only, with reference to the accompanying diagrams.

Fig 1: is an illustration of a portable workstation for use in replacing ribbons.

Fig 2: is a cross section of a heat sealing device of the present invention.

Fig 3: is an illustration of a joined ribbon and of a holder for tripping free ends away from a join.

Fig 4: is a diagrammatic illustration of a joined ribbon in microscopic cross-section.

Fig 5: is an illustration of an AC control circuit for the present invention.

Fig 6: is an illustration of a DC control circuit for the present invention.

Fig 7: is a plan view of a preferred portable workstation for the present invention.

Fig 8: shows details of the metering rollers for the preferred workstation of the present invention.

Fig 9: shows details of one preferred resistance wire mounting of the present invention.

Fig 10: shows details of the preferred control circuit of the present invention.

PREFERRED EMBODIMENT

We plan to take advantage of the need for a speedy ribbon replacement service for replacing inked ribbons made of plastics materials in impact printer cartridges (as opposed to the usual mail or courier service to a remote depot) by equipping a number of individuals each with a portable workstation, conveniently within a suitcase. With this device, a cartridge containing a used ribbon can have its contents replaced at the customer's premises. This has a preferred end-result that a user of ribbons no longer has to hold large stocks of cartridges, because they can deteriorate in storage and dry out.

We have described two examples of the preferred embodiment. The first is a smaller, single suitcase holding a variety of ribbons, and is more suited to small-scale work with domestic printers having small cartridges. The second example is adapted for use with printer cartridges up to nearly 800 mm long, as found in some line printers, and is carried about within two cases; one being lined to protect the ribbons within from environmental and particularly thermal effects; the other containing the electrical motor controller and the ribbon joining equipment. Both embodiments and indeed any other which embodies the principles of this invention would preferably use a good quality pre-inked ribbon. One supply of such ribbon material is known as "Type 818".

EXAMPLE 1:

A portable workstation for use in replacing ribbons is shown in Figure 1. The suitcase 100 contains two major components, namely:

(a) a bank of optionally metered ribbon dispensers 106, and (b) means (101-105) to join up lengths of ribbon with a joint that can pass through an impact printer without disrupting either the ribbon feed mechanism or the quality of printing.

Optionally the suitcase can also hold a motor drive 107 to facilitate feeding of ribbons, and optionally it may also hold various tools and a repository for waste ribbon.

The motor drive 107 is shown here as a hand-held device rather like a cordless screwdriver, containing a battery and a motor and a driving spindle equipped with a general-purpose coupling tip that can be engaged with the take up spools or other ribbon advance devices of most if not all types of printer cartridge. A preferred drive may include rechargeable batteries and its housing may include connectors (not shown) to resupply energy whenever it is not in use.

The ribbon dispensers are shown as a row of slots, from each of which a length of ribbon extends and may be seized for consumption when the workstation is in use. There are at the moment 14 different sized ribbons in use. The number of dispensers illustrated at 106 may suffice for installations using small printers. The widest ribbons are generally limited to high-speed computer printers - where Example 2 is more appropriate. Under one mode of use, the meter dials beside each slot may be used to indicate actual consumption and hence the charge to the customer.

We have a method using this workstation for replacing a ribbon in a cartridge comprising the steps of:

(a) taking the workstation to the site where the cartridge is used,

(b) selecting a suitable width of ribbon,

(c) cutting across the old ribbon,

(d) joining one end of the new ribbon to the old ribbon,

(e) winding the old ribbon out into a waste container and thereby drawing a similar length of new ribbon into the cartridge,

(f) once the join has emerged, cutting the new ribbon adjacent to the join, and

(g) closing the loop of new ribbon with another joint.

This method should ensure that the new ribbon is stored within the cartridge in the same way that the old ribbon was stored, which is commonly in zigzag form between the upper and lower walls of the cartridge which are conveniently about the same distance apart as the ribbon is wide. If the original ribbon was configured as a Mδbius strip with a half-turn before joining, the new ribbon should follow the course of the old ribbon and emerge with any such twists already in place.

One of the problems we faced was to provide a suitable method for providing a join. Apart from the obvious requirements, namely to provide a joint that can pass through an impact printer without disrupting either the ribbon feed mechanism or the quality of printing, it is preferable to use a joining process that is quick and safe and cheap, does not require much ancillary equipment, and does not cause radiation of electrical or chemical pollution. Other methods such as ultrasonic heating have been found to be unsuitable for use in a portable workstation; size and price being major objections.

We have provided a precision heat-sealing process, akin to that used to seal polythene bags, which provides highly satisfactory joins yet does not unduly consume resources such as space nor emits interference.

This is conveniently located towards the front of the workstation as shown at 101 and 102, where 101 represents a flat base provided with horizontal guidelines against which the ribbons to be joined together can be placed. Once they are located, a handle 102 including a heatable face is pressed against a similar heatable face below and a controlled transient of heat is generated and made to melt and fuse the ribbon segments together.

The apparatus 200 is shown in section as Fig 2. The bulk of the upper and lower jaws are preferably made from a heat-resistant electrically insulating material such as "Paxolin" a type of urea-formaldehyde resin. If an aluminium bar or the like is used construction is more complex as extra insulation is required for the mounting of the electrically heated wires. The jaws 202, 203 are provided with insets which are lengthwise oriented thermal insulation strips 204 which can withstand heat and against which the heated wires are laid. Ceramic or composite materials are examples of suitable inserts. A heatable wire 206 is aligned along the length and on the inner surface of each jaw. The wire is covered by a layer 207 of (preferably) a PTFE-glass fibre tape (e.g. "Taconic" (TM)) which serves to carry heat yet prevent the melted plastic of the ribbons 208, 209 from sticking to the jaws. Note that in the drawing we have lifted the PTFE/glass tape upwards for clarity. As the thickness of each ribbon is about 120 microns, we have provided a controlled geometry to the heated space so that the melted ribbon is forced to assume a thickness of about 140 microns by including raised metal stops at each end of the jaws. These stops are of a height sufficient to provide the desired clearance of about 140 microns for the ribbons to be fused together. A reasonably precise clearance gives the heat-sealing process enough precision to form reliable joints which do not jam in the cartridge or in the printer during use.

Although the heated wire 206 is shown as a flat tape preferably about 1 to 1.5 mm wide, it may be preferable to provide it with a round cross-section to better use the heat radiated sideways to create a more gradual transition between melted and unmelted material. A preferred material for any heated wire is Nichrome. Preferably the wires are mounted under a slight tension by means of spring holders at both ends of each wire so that they remain in place even when heated and the wire lengthens slightly by thermal expansion.

It should be noted that variations in the above construction can be usefully implemented. For example we prefer to place a layer or strip of "Teflon" (R) on the side of the heated wire away from the ribbon to be joined, as well. This reduces the amount of heat conducted from the wire. We prefer to energise the two heated wires (one in each jaw) in series. If one fails, the assembly remains cold, while if they had been operated in parallel, failure of one wire would result in a warm, but ineffective heater which may confuse an operator, and unequal division of current may result in the case of parallel use of two intact wires.

Methods for mounting the wires and for coupling the heating current to wires which are held under tension in order to allow for expansion during heating are also subject to variation.

Our method for joining thermoplastic ribbons comprising the steps of:

(a) laying the two ribbons overlapped across a heat-sealing station and over a lower jaw,

(b) closing the upper jaw of the heat-sealing station down onto the lower jaw, (c) applying a predetermined temperature and pressure to the ribbons for a predetermined time by causing a current to flow through a resistive heating wire in each jaw,

(d) waiting briefly, and

(e) taking the fused ribbons to a cutting station where the joint is clamped and the free ends can be shaved off from the joint (preferably when bent to best expose the free ends) with a sharp knife such as a razor blade in a suitable holder.

EXAMPLE 2:

A second portable workstation for use in replacing ribbons is shown from above (plan view) in Figure 7. The suitcase 700, which is about 800 x 300 mm in internal capacity when opened out, opens into two working halves and in contrast to Example 1, a second case 730 is used to carry bulk pre-inked ribbon material.

The suitcase 700 contains on its left side the electronic controls 702 and the motor drive 704 (carried from place to place lying in the recess 703, and on the right side it holds the precision heat sealer 720 and a metering roller assembly 721 which can be carried about when placed in its recess 722. A jig for cutting free ends of joined ribbons (see Fig 3) can also be carried about in the recess.

Considering the left side in detail first, the control surface, populated with controls and indicators, is about 400 mm wide and 300 mm from front to back and the rear portion, which is regarded as a work surface is clear. (The device is generally used with the suitcase opened out flat and placed upon a table. Note that a number of preferred rubber feet (not shown) are provided so that the device or case will not scratch furniture.) When it is unpacked a power lead may be connected to either a mains supply or a DC supply depending on availability. The motor 704, which is mounted upon a support rod so that it is raised above the work surface and which may be mounted in any one of several different orientations) is powered by a flying lead from the socket 705.

We prefer a stepping motor at 704 because its speed can be closely controlled and because it offers the option of metering the consumption of new ribbon by counting step pulses but any kind of low-power controllable motor will do. The control knobs and displays include 706 (Heat timer)

707 (Motor direction)

708 (Waste ribbon length counter)

709 (Motor speed)

710 (New ribbon length counter - which is presettable) 711 (Heater voltage display)

712 (Heater voltage adjustment (used with 711))

713 (manual start motor)

714 (manual stop motor)

715 (auto run motor) 716 (Start heat cycle), adjacent to the ribbon joiner. Controls and displays relating to the duration and intensity of the applied heat, in conjunction with the configuration of the heating bars and given a reasonably consistent material to be joined, assure a consistent ribbon join. In use, the motor is coupled by a universal adaptor to the cartridge being replenished. It should be noted that some of the larger cartridges will span almost the full distance from 704 to the rollers 721.

Displays 708 and 710 are provided with count pulses by the roller assembly 721. Fig 8 shows in elevation view more details of the metering roller assembly. Each metering roller has a circumference of 100 mm and is provided with a revolution sensor preferably in the form of an aperture 809 made through a flange 810 together with a slotted optical switch device which can sense the presence of an aperture through the flange once in every revolution. Of course, other revolution sensors such as combinations of magnets and flux sensors such as magnetostrictive or Hall effect sensors, or even a bump and a nearby microswitch can be used as a revolution counter. As the roller 801 is made with a circumference of 100 mm, each count increment shown on the display 710 (or the display 708) corresponds to 100 mm of ribbon.

Considering the right side in detail, the control surface is about 400 mm wide and 300 mm from front to back. Again the rear portion is regarded as a work surface for ribbons traversing from the rollers to the cartridge, and the front surface carries the ribbon sealing mechanism. The roller assembly of Fig 8 is carried on a support 721 which may be placed in the recess 722 when not in use. The roller assembly is supported on a plate 806 and comprises a main metering roller 801, having a known circumference, and a flange including a revolution transducing device, (the aperture 809). Pinch rollers

802 and 803, generally of a resilient composition, are used to hold the ribbons against the metering roller to minimise slippage. The dotted line 804 represents a new ribbon being pulled from the supply box 730 into a cassette by the motor 704, and the doted line 805 represents a discarded ribbon being pulled from the cartridge and into a waste container (not shown). A second metering roller 808, with a pinch roller 807, may also be provided.

The ribbon dispenser of this example simply comprises a thermally insulated but openable box 730, lined with a suitable insulating material and preferably sealed with a smooth inner surface to facilitate cleaning, for it is to carry inked ribbons, and within it is preferably placed a bank of reels 731 on which are supported a number of spools of various sizes of pre-inked ribbon. One ribbon 732 is shown extended towards the roller assembly. The thermal insulation is provided because of the high temperatures that the inside of a car, or its luggage boot, may reach in summer weather, which would cause deterioration of the ribbons.

Our method using this workstation for replacing a ribbon in a cartridge comprising the steps of:

(a) taking the workstation to the site where the cartridge is used, (b) powering up,

(c) selecting a suitable length and width of ribbon from a manual holding a table of cartridge parameters for the 415 (approximately) cartridges available, and entering the length into the counter 710

(d) mounting the cartridge on the motor drive 704, (e)cutting across the old ribbon,

(f) threading the old and the new ribbons through the rollers.

(g) joining one end of the new ribbon to the old ribbon,

(h) winding the old ribbon out into a waste container and thereby drawing a similar length of new ribbon into the cartridge, (i) either when the metered amount of ribbon has been drawn in or when the join has emerged, cutting the new ribbon adjacent to the join, and (j) closing the loop of new ribbon with another joint.

The cartridge, which has not been opened up, is now equipped with a new inked ribbon and is ready for use.

As for the previous example, this method should ensure that the new ribbon is stored within the cartridge with the same mode of packing used for the old ribbon.

In this second Example the precision heat sealing device 720 is preferably placed at an angle of 45 degrees to the side of the box and will seal the ribbon at a preferred 45 degree slant. We provide a series of alignment guides like 723 on the surface on each side of the heat sealer against which guides ribbons can be aligned before joining The construction of the heat sealing device is similar to that of the first example, except that we have amended the mounting of the wires as shown in Fig 9. Fig 9 is a side view of one end of one jaw 900 of the heat joiner. 907 is an electrical lead to the connecting post 905 which is mounted within the material of the jaw 907. As our preferred jaw material is itself electrically insulating the mounting for the post may be either a hole or a threaded hole (if a brass bolt is used as the post. The resistance wire 903, again beneath a layer of PTFE (polytetrafluorethane or "Teflon" (R)) protection 904 and over a layer of ceramics and optionally further PTFE - the insert 910, is physically terminated in a swaged-on lug 906 or the like, which is hooked over a spring-loaded tensioning member 902. This may itself be made of spring steel or the like. It is preferably mounted on a base 909. A corresponding mount is also used at the other end of the wire 903. The resistance wire is held in close contact with the end of the post 905 at which point the electric power passes from the post to the wire. As the post (preferably made of brass) has a high heat capacity the wire tends not to heat up and oxidise over the post. We have found that this connection method avoids hot spots due to inadvertent local heavy current densities developing at the termination of the wire and so causing premature failure.

This heat sealing or ribbon joining device is again constructed to leave a gap of about 140 microns when firmly closed by including metal stops at each end of the jaws. These stops are of a height sufficient to provide the desired clearance of about 140 microns for the ribbons to be fused together.

Fig 10 illustrates a circuit diagram 1000 for the preferred control electronics of the invention. Here, 1023 is the positive supply voltage bus, 1025 is. an internal 12-volt regulated bus (regulated by three-terminal regulator 1016) and 1024 is a ground, or reference bus. Switches 1002 and 1003 (forward, and reverse motor drive, respectively, are coupled to switch 1001 joined to the stepping motor board 1005. The commercial board also includes a speed control 1004 and four outputs to a stepping motor at 1006. This stepping motor is the one used to advance ribbon into and through the cartridge.

The other commercial board, 1007, is a metering board used for counting the amount of ribbon dispensed (in terms of revolutions of a pulley gripping the ribbon). Counter 1008 is a rewind ribbon counter. Counter 1009 is a total in/out counter. Item 1010 is the amplifier for the metering transducer. It is also joined to a preset in/out counter 1011, which may be used to predetermine the amount of ribbon to be dispensed. Counter 1012 counts the total number of cartridges processed; it is made to increment by the adjacent press-button switch. Relay 1013 is an auto-stop relay (acting on contacts at top left of the motor board 1005). R2 is a manual stop relay (its contacts also acting on contacts at top left of the motor board 1005). Switches 1019 set the board in "auto" mode, and switches 1020 set the board in its manual mode of operation.

The actual welding control is shown at 1017; a timer, and a "start" button 1018. These close the relay 1026 which causes a suitably high current to pass through the resistance wire of the heater for a predetermined interval. The voltmeter 1022 is linked to the 12V bus through a resistor network. Although this circuit provides no control via the voltmeter and an analogue setting of heater current, other embodiments may do so. In this case we prefer to establish a "hotness" by judicious choice of resistance wire and applied voltage, and closely control the duration of the application of current. Other versions may control both duration and temperature. The circuit of Fig 10 does not show conventional power supplies used to activate these components and the heater itself from an input mains or battery supply.

RIBBON JOINTS

A joined ribbon has an appearance similar to that of Figs 3 and 4. We prefer to make a single slanted join as shown at 303, here joining ribbons 301 and 302. In microscopic cross-section, a joint may resemble the section in Fig 4, where 402 represents a single weft fibre, the join 401 has been heated thereby compressing and fusing the fibres therein, and 403 is a trimmed edge which has been cut off the joint using a cutting device 405 to trim or plane the ribbon against a flat holder incorporating a narrow slit 406 through which the ribbon is passed until the holder holds the ribbon at the joint. For simplicity, Fig 4 does not show any weft fibres of the ribbon which would for example occupy the space between the two separated lines of fused fibres at 401. Fig 4 is not to scale in that the length axis is foreshortened for simplicity.

We provide a cutting device (see Fig 3) for use in trimming off cut edges from a joined ribbon as a part of the tools supplied with each workstation. This comprises a (preferably metal) rectangular block 304, 313 which has a smooth upper surface formed from two knife blades 307, 309 lying with their (slightly dulled) sharp edges, which are preferably about 100 mm long) placed parallel to each other and separated by about 140 microns to form a slit 308. The upper surfaces are flat as indicated in the section at 311 (taken along 310-310) to facilitate the cutting operation. There is an aperture 306 of about 25 mm diameter at one end of the slit, The freshly joined ribbon having free ends depending from the joint is folded over at the joint and a free end is grasped, pulled up through the 25 mm aperture, and slid sideways along the slit 308. At this time the ribbon is preferably at an angle, so that the joint itself is parallel to the surface of the block and the remainder of the ribbon lies in the space underneath, 312. The free end is not cut away from the joint by cutting, using the surface of the slit as a guide. The edges of the slit are preferably not themselves used as cutters. Posts 305 are used to hold the block over the edge of the suitcase.

A resulting joint made by our precision heat joining device appears to be almost as strong as intact ribbon and in our experience is far superior to joints made by other methods, such as ultrasonic welding. The joint offers no substantial projections to engage with parts of the cartridge or the printer.

In Figs 5 and 6 we provide two simplified circuits for providing bursts of current to the joining device. Fig 5 is an illustration of an AC control circuit for the present invention, suitable for use when a mains supply is available, and Fig 6 is a DC control circuit for the present invention, which may be used with an AC input and a rectifier, or with a battery supply such as a motor cycle battery or a nickel-cadmium battery stack.

Plug 501 of Fig 5 is a conventional mains plug. Typically the phase wire (alternatively the neutral wire) from it includes (a) a timer device 502 and a current control 503. The modulated supply is fed through a transformer 504 to step the voltage down to a few volts as is required for appropriate heating of the length of resistance wire 505 and 506 involved. A preferred mode of use is to vary the voltage using the control 712 so that the rectified voltage as detected at the meter 711 is within narrow limits.

In the workstation of Example 1, 105 is a power on-off switch, 104 is a control rheostat (which may actually control a TRIAC or silicon controlled rectifier), and 103 is a meter to indicate the actual power level as a result of operation of the control 104. In use one would normally adjust the control so that the meter needle rests against a datum point, so assuring a controlled supply to a precision of perhaps 3 to 5%. The timer 502 is preferably a preset timer and is preferably activated to close its internal connection by pressure on a momentary switch adjacent to the handle of the upper jaw 102. The circuit of Fig 6 assumes a DC input at 601, which may be obtained from the mains by a stepdown transformer and a rectifier, or a switched-mode power supply for greater lightness, or may be obtained from a storage battery. This circuit provides a current regulation function using the sense resistor Rl (603) to convert the heating current into a control voltage carried in the line 607, which is passed through the timer 602 when it is timing an interval Δt, to control the amount of current passed by the constant-current supply 604. This circuit has inherent temperature regulation thanks to the thermal coefficient of resistance of a metal when heated, so that the wires 605 and 606 can act as their own temperature sensors and so provide some temperature regulation.

ADVANTAGES

Advantages of this device include:

Portability; it is light, small and self-contained, can be powered by the mains or a battery and so can be taken to any site for ribbon replacement beside the printing device. This allows it to be used in a service where the ribbon replenisher is taken to the point of use, rather than mailing cartridges to a replenishing location.

Effectiveness; its improved ribbon joining device (the precision heat sealer) provides a consistent, lasting joint which does not interfere with use of the ribbon. In our experience, the joint is superior to joints made with other kinds of ribbon joining apparatus such as ultrasonic welding. Also, the use of new ribbon rather than re-inked ribbons provides a better result. (Re-inking is messy. The used ribbon may be worn away and so holds less ink, particularly in the region of the ribbon from where the ink is applied to the paper.)

Environmental benefits follow from the re-use of the cartridges rather than their disposal.

Finally, it will be appreciated that various alterations and modifications may be made to the foregoing without departing from the scope of this invention as set forth.

Claims

1. A portable workstation for use in replacing inked ribbons of the type used in impact printer cartridges and the like, wherein the workstation includes

(a) means to dispose of an old ribbon from within the cartridge,

(b) means to measure and dispense a new ribbon,

(c) means to pack the new ribbon into the cartridge,

(d) means to make functionally inapparent joints in ribbons, and (e) means to trim off any surplus ribbon at newly made joints.

2. A workstation as claimed in claim 1, wherein motor drive means is provided for engaging with and turning at least one drive wheel of a cartridge.

3. A workstation as claimed in claim 2, wherein measuring means is provided for determining the length of the new ribbon to be engaging with and turning at least one drive wheel of a cartridge.

4. A workstation as claimed in claim 1 including means to make functionally inapparent end-to-end joints between one segment of a ribbon and another segment, wherein the means comprises a contact heat-sealing device having two heatable press members capable of being pressed against each other; each limb having one facing and substantially non-resilient surface comprised of a non-adherent, heat-transmitting, material covering an elongated, heatable member, one limb capable of being placed above, and one limb capable of being placed below the ribbons to be joined; the device having means for establishing a precise separation between the limbs when in a closed, sealing position, and means for applying a controlled temperature to the ribbons for a controlled period of time.

5. A workstation as claimed in claim 4, wherein the contact heat-sealing device is adapted to apply a combination of pressure and conducted heat from an electrically heated wire across a narrow zone so that in use it can fuse a narrow zone of the ribbons together.

6. A workstation as claimed in claim 5, including means to trim off any surplus ribbon at newly made joints.

7. A method for joining thermoplastic ribbons comprising the steps of:

(a) laying the two ribbons in overlapped fashion across a heat-sealing station between a pair of jaws (b) closing the pair jaws,

(c) applying a predetermined temperature to the ribbons for a predetermined time by heating the pair of jaws until the ribbons have fused,

(d) waiting briefly, and

8. A method as claimed in claim 7, wherein the ribbons are fused together about a narrow zone.