GB2148541A - Machine for operating progressively along a marginal portion of a workpiece of sheet material - Google Patents

Abstract

A cementing and folding machine. e.g. for operating on leather or fabric, having an "automatic" operating mode is provided with a facility for varying the "density" of snip, or other marginal operation at the discretion of the operator. To this end, a plurality of sensors is provided for monitoring the marginal portion, the condition of each of which is monitored at regular intervals in an operating cycle and stored in binary form. The bit value of all these "stores" is aggregated and the aggregate value is compared to a comparator value in order to determine whether or not a snip is to be effected in any one operating cycle (main shaft rotation). The comparator value is controlled by the operator, using a potentiometer the output voltage of which is converted to a digital value through an analogue- to-digital converter. It is envisaged that in addition to controlling the density of snip, the density of peat may also be controlled using the same principle. Furthermore, it is envisaged that the invention is also applicable to other margin treatment machines, e.g. stitching machines.

Description

SPECIFICATION Machine for operating progressively along a marginal portion of a workpiece of sheet material This invention is concerned with a machine for operating progressively along a marginal portion of a workpiece of sheet material, said machine comprising operating instrumentalities arranged at an operating locality of the machine for feeding a workpiece through the operating locality and for performing thereat an operation upon a marginal portion of such workpiece, and sensing means arranged "upstream" of the operating locality for detecting the approach to the operating locality of a corner (as herein defined) in such marginal portion, said sensing means comprising a sensor which detects the presence or absence of a marginal portion of a workpiece and the status of which is determined accordingly.

The term "corner" where used herein with reference to a workpiece margin is intended to indicate a portion of the margin which is curved, when viewing the workpiece in plan.

Furthermore, the term "outside" where used herein in relation to a corner, is intended to indicate that the radius of curvature of the corner passes through the area of the workpiece, while the term "inside" where used herein in relation to a corner, is intended to indicate that the radius of curvature of the corner extends away from the workpiece.

The present invention is applicable to various types of machines, e.g. stitching machines and folding machines, and is particularly applicable where the workpiece is to be operated upon are made of e.g. leather or fabric.

One such machine, which is described in our co-pending UK Patent Application 8316900, is a so-called thermo-cementing and folding machine, wherein the operating instrumentalities comprise folding instrumentalities arranged at the operating locality of the machine and workpiece feeding means for feeding a workpiece through the operating locality in such a manner that a marginal portion thereof can be operated upon by the folding instrumentatities. In addition, the operating instrumentalities also comprises a snipper device, also arranged at the operating locality, for snipping the marginal portion of a workpiece as it is fed therethrough, operation of the snipper device, when actuated, being in timed relation with operation of the folding instrumentalities.

In said machine, furthermore, an array of sensors is provided, in the form of a plurality of the emitters, which are arranged "upstream" of the operating locality of the machine and over which the workpiece can be fed, said emitters co-operating with a receiver located thereabove. These emitters serve to control certain functions of the machine, namely the switching on and off of adhesive, the operation of the snipper device and the operation of the workpiece feeding means for purposes of forming pleats in the margin of a workpiece being folded over, these latter two functions being of course dependent upon the sensing of the approach of a corner to the operating locality of the machine. This type of "automatic" control is of course well-known in machines of this type.

In order to control the density of pleating or of snipping, it has been customary to provide, for each operation, one or more sensors, the arrangement being such that, where more than one sensor is so provided, one sensor is selected for use with a particular workpiece; in general, this selection will be made on the basis of the degree of curvature of the workpiece margin and the operator's assessment of the amount of pleat or snipping required in order to achieve the best result from a folding point of view.

In practice, because of general machine vibration and further because of the intermittent feed of a workpiece, conventional in machines of this type, the edge of the workpiece tends to "flutter" in the vicinity of the active sensor so that, assuming the emitter forming part of the sensor is pulsed a number of times during each feed step, different signals may be obtained from the sensor. Since these signals serve to control an actuator for the operating instrumentality, e.g. the snipping knife, the problem thus arises of frequently changing signals within each feed step, leading to "chattering" of said actuator.

In order to overcome this problem of chatter, therefore, the sensitivity of the sensor has effectively been deadened, with the result that the operation of the operating instrumentality is actuated only where the sensor is effectively fully covered (in the case of the snipper device control, or alternatively uncovered, in the case of the workpiece feeding means) during the whole of a feed step.

By rendering the sensors less sensitive, however, the distance between adjacent sensors becomes of significance, and, in certain cases it has been found that selection of one sensor for a particular workpiece will produce a margin which is e.g. snipped along the whole of its length, while the selection of the next adjacent sensor produces a workpiece the margin of which is snipped to a very small extent or not at all.

A similar problem may also arise in other machines for operating progressively along a marginal portion of a workpiece of sheet material, e. g. stitching machines, especially when such machines are provided with e.g.

automatic steering means also controlled by an array of sensors arranged "upstream" of the operating locality.

It is thus the object of the present invention to provide an improved machine for operating progressively along a marginal portion of a workpiece of sheet material, wherein the control of actuation of one or more of the operating instrumentalities can be more accurately controlled by the operator using existing sensors.

This object is resolved in accordance with the invention, in a machine as set out in the first paragraph above, in that the machine further comprises means for reading the status of the sensor, means operable at predetermined intervals for storing, in the form of a binary value, the status of the sensor as read by said reading means, means for aggregating the stored values, operator-controlled means for determining a comparator value, means for comparing the aggregate value with said comparator value, and means operable in response to an actuation signal generated as a result of the comparison of said values for controlling the operation of at least one of said operating instrumentalities.

It will thus be appreciated that the "fl6tter- ing" of the workpiece margin as it is fed, which previously was considered to present a problem, can now be utilised to afford a means by which the operator can exercise discretion in respect of the control of the operation of the operating instrumentality by the expedient of constantly updating a data byte according to the status or condition of the sensor and by storing the latest update a number of times within each operating cycle so that an aggregate or average of the number of times the sensor has been actuated in the preceding cycle can be computed and this aggregate value compared with a comparator value which is determined under the control of the operator. Thus, by increasing the comparator value the incidence of operation of the operating instrumentality can be reduced and vice versa.

Conveniently in the machine in accordance with the invention the operator-controlled means comprises a potentiometer the output voltage of which is variable under operator control, and this output voltage is converted, by an analogue-to-digital converter, to a digital value constituting the comparator value.

Furthermore, for timing the storing of the status of the sensor as aforesaid, a shaft encoder is provided, mounted on a main drive shaft of the machine which controls the operation of the operating instrumentalities, said encoder supplying pulses at predetermined intervals (according to its speed of rotation) which cause the status storing means to be actuated. In practice, it has been found that eight pulses per revolution of the main drive shaft are sufficient for this purpose.

Whereas the invention in its broadest aspects relates to the provision of a single sensor, it has been found in practice that an enhanced result can be obtained when the sensing means comprises a plurality of sensors arranged in an array extending generally transversely in the direction of workpiece feed, each sensor detecting the presence or absence of a marginal portion of a workpiece and the status thereof being determined accordingly. In such a case, furthermore, the sensor status reading means reads the status of each of the sensors, the sensor status storing means stores as aforesaid the status of each of the sensors, and the aggregating means aggregates the stored values for comparison with the comparator value.A special benefit of utilising more than one sensor arises where the amplitude of flutter of the workpiece margin extends beyond the distance between two adjacent sensors, and it has been found that, using the present invention, the line representing the boundary between an "actuation" and a "no actuation" signal can be made infinitely variable between the two adjacent sensors.

Whereas the combination of a plurality of sensors and the operator-controlled means for determining the comparator value represents an important advantage, it has been found also that, where a plurality of sensors is used, advantage can often-be achieved without any variation of the comparator value. For example, where the operating instrumentality is constituted by workpiece feeding means, and the control is for controlling the pleating of the workpiece margin, in certain circumstances it may be considered adequate to fix the comparator value in all cases; for example, this may prove adequate where a sharp corner is sensed at the end of a marginal portion being operated upon.Nevertheless, the provision of a plurality of sensors operating in the manner described above will be sufficient to enable the approaching shape of the workpiece margin to be defined in terms of binary values and appropriate control signals thus be fed to the operating instrumentality.

Consequently, the invention also provides, in another of its several aspects, a machine having the features set out in claim 10.

As previously mentioned, the invention is especially, but not exclusively, appropriate for use in edge folding machines both for the purpose of controlling the pleating of workpiece margins and also the snipping thereof.

In the former case, the operating instrumentalities comprises folding instrumentalities arranged at the operating locality of the machine, said instrumentalities comprising a creaser foot and a reciprocating element (e.g.

a lip turner) for folding the marginal portion of a workpiece over the creaser foot, together with workpiece feeding means for feeding a workpiece through the operating locality in such a manner that a marginal portion thereof can be operated upon by the folding instrumentalites. In such an arrangement, furthermore, conventionally the workpiece feeding means comprises an orbitally operating hammer-and-anvil arrangement by which a workpiece can be fed step-by-step through the operating locality, the rate at which said arrangement is caused to operate being variable under operator control (that is to say the speed of rotation of the aforementioned drive shaft, controlling the operation of the hammer-and-anvil arrangement, can be controlled by the operator), and furthermore the distance through which the workpiece is fed in each step by said arrangement is varied in response to an actuation signal generated as a result of the comparison of the aggregate and comparator values (that is to say the feed length in each step is variable under this "automatic" control). Where the invention, on the other hand, is applied to a snipping operation, the operating instrumentalities also comprise a snipper device, also arranged at the operating locality, for snipping the marginal portion of the workpiece as it is fed therethrough, operation of the snipper device, when actuated, being in timed relation with operation of the folding instrumentalities.As is conventional in such machines, furthermore, preferably means for actuating the snipper device comprises a latch arrangement which is caused to be engaged by means of an actuator, and in the machine in accordance with the invention the actuator is conveniently operated in response to the actuation signal. More especially, also as is conventional, and preferably in accordance with the present invention, the snipper device is cyclically driven and the latch arrangement can be engaged only at a predetermined time in each cycle, the arrangement being such that a "mains interrupt" signal is generated in accordance with the frequency of an electrical power supply to the machine, and the actuator is operated in response to such "mains interrupt" signal, when an actuation signal has been generated as aforesaid as a result of the comparison of the aggregate and comparator values.

Other aspects of the invention, generally along the lines as set out above, are to be found set out in claims 2 and 4.

There now follows a detailed description, to be read with reference to the accompanying drawings, of one machine in accordance with the invention, which machine has been selected for description merely by way exemplification of the invention and not by way of limitation thereof.

In the accompanying drawings: Figure 1 is a front view of the machine now to be described; Figure 2 is a blocked diagram of an electronic control circuit of said machine; Figures 3a and 3b represent part of computer software by which the machine operation is controlled; and Figure 4 is a diagram indicating an archive store in such computer software.

The machine now to be described is a socalled thermo-cementing and folding machine, which finds use in the shoe industry and allied trades, and is generally similar, except as hereinafter described, to the machine described in our co-pending UK Patent Application No. 8316900. The machine thus comprises a work table 10 on which a workpiece can be supported at an operating locality of the machine, at which conventional folding instrumentalities are located, comprising a fold-initiating block 1 2 having an upwardly curved work-guiding surface 14, a gauge finger 16, a creaser foot 22 and a lip turner 20, which completes the fold of the workpiece margin over the creaser foot.During folding, adhesive can be applied to the workpiece margin through an outlet in the creaser foot, to which adhesive is supplied via a delivery tube 24 from a melt chamber 28 under the action of a gear pump 26. The melt chamber 28, delivery tube 24 and creaser foot 22 are heated respectively by heaters H1, H2, H3.

Other features of the folding instrumentalities are , shown in Figure 1.

"Downstream" of the folding instrumentalties is located a conventional snipping device generally designated 30, comprising a fixed and a movable blade 32, 34, and conventional workpiece feeding means in the form of an orbitally moving hammer-and-anvil arrangement (not shown), which also serves to consolidate the fold. A work release clamp (not shown) is also provided for clamping the work against the under-side of the creaser foot during the return movement of the hammerand-anvil arrangement.

The hammer-and-anvil arrangement is driven through a main drive shaft (not shown) by means of an electric motor (not shown) through a clutch. The motor speed, and thus the workpiece feed speed, is controlled by a first treadle (not shown). In addition, a second treadle (also not shown) is provided, constituting a foot switch actuating two switches S6, S7 by selectively depresssing respectively the toeward and heelward portions of the foot switch. Switch S6 serves to reduce the feed length, i.e. the amount through which the hammer-and-anvil arrangement moves foreand-aft for each revolution of the main drive shaft, and thus serves to effect pleating of the folded over margin of the workpiece; switch S7 causes the snipping device 30 to operate.

For controlling the feed length, "maximum" and "minimum" stops 46, 48 are provided, projecting through a slot 50 in a control panel 36 of the machine to facilitate operator setting. A knee-operated switch S5 is also provided, which is a multi-functional switch the operation of which is described in detail in the aforementioned specification.

The control panel 36 of the machine also has a "mains on/off" switch S1 with associated pilot lamp PL1, a "motor on/off" switch S2 with associated pilot light PL2, a "work lamp on/off" switch S3, a control knob 42 by which the operator can set the operating speed of a motor M, driving the gear pump 26, in relation to the main motor speed, a further control knob 44 by which the operator can control the amount of so-called adhesive suck-back at the end of an operating cycle of the machine, and a control knob 52 by which the operator can control the heater H3, and thus the temperature of the creaser foot 22.

In addition, the control panel 36 has a further five switches, viz: switch S4, which is a three-position switch by which "adhesive off", "adhesive on" and "adhesive meter modify" may be selected.

When the last-mentioned position is selected, the rate of adhesive supply is reduced when short feeding (pleating) is selected; switch S8, by which the operator can select "snip and pleat", that is to say the feed length is reduced when the snipping device is actuated; switch S9, by which the operator can select a first, so-called "automatic", operating mode and a second, so-called "manual", operating mode; switch S10, which is a three-position switch by which the operator can selectively utilise the knee-switch S5 when the machine is operating in its "automatic" operating mode.

More specifically, switch S10 can be switched between "off", in which the knee-switch S5 is not effective, an "adhesive inhibit" position, in which, when the knee-switch S5 is held operated, the supply of adhesive to the creaser foot 22 is inhibited, and a "snip inhibit" position, in which the snipping device 30 is disabled, while the knee-switch S5 is held depressed; and switch S11, by which the operator can select which of two sensors, in the form of emitters El, E2 (constituting first sensing means of the machine), will be utilised to control switching off the adhesive supply at the end of an operating cycle.

Also mounted in the control panel 36 is a further control knob 54 by which the operator can control the "density" of snipping effected by the snipping device 30 when the machine is operating in automatic operating mode (as selected by switch S9); the function of this knob 52 and associated circuitry will be described hereinafter in detail.

The machine comprises, in addition to emitters El and E2 already mentioned, four emitters E3, E4, E5, E6, forming part of the control for the snipping device 30 when the machine is in automatic operating mode, and a further emitter E7 by which the operation of the workpiece feeding means is controlled, also in the automatic operating mode of the machine, to cause pleating take place. The emitters El to E7, which constitute sensing means of the machine, are arranged in an array just "upstream" of the operating locality. The general arrangement of the array can be seen in Figure 2. Co-operating with the emitters El to E7, furthermore, is a receiver E/R which senses whether an emitter is covered by a workpiece or not so that the presence or absence of a workpiece at the operating locality and the approach of "inside" and "outside" corner to the operating locality can be sensed.

In the machine in accordance with the invention, when switch S1 is switched on, mains power is supplied to two solenoids SOL1, SOL2, to heaters H1, H2, and also to a transformer (not shown) which steps down the voltage to 1 2 volts. The solenoid SOL1 is effective when actuated to switch the feed length between "maximum" and "minimum" as determined by the stops 46, 48; when the machine is in its automatic operating mode, this solenoid is energised in response to emitter E7 being uncovered by an "outside" corner approaching the operating locality, while, in the manual operating mode, this solenoid is energised by operation of switch S6.Solenoid SOL2 is effective when actuated to actuate the snipping device 30; this solenoid is energised, in an automatic operating mode, in a manner to be described hereinafter and, in a manual operating mode, when switch S7 is actuated, The 1 2V a. c. supply from the transformer is supplied to a work lamp circuit, which includes the switch S3, and to the heater H3.

In addition, from this circuit is derived an unsmoothed 1 2 volt a.c. circuit which supplies power to a mains-controlled control box Ml supplying a 'mains interrupt" signal to be referred to hereinafter. In addition, there is derived from the 1 2V a.c. circuit a smoothed 1 2V d. c. circuit which supplies power to the motor M (which is constituted by an n.c.

motor, e.g. a stepping motor). From the smoothed 1 2V d.c. circuit, furthermore, is derived a 5V circuit, which drives a central processor unit CPU and associated circuits, and supplies power to switches S4 to S11, thermisters TS1, TS2, TS3 and potentiometers VR4, VR5, VR6 and VR12, each of which will be referred to hereinafter.

The central processor unit CPU, which controls the machine, is constituted by a singlechip 8-bit micro-computer (in casu, a Zilog Z8681 which, in addition to a micro-processor, also incorporates a random access memory/ scratch pad RAM (shown separately in Fig. 2); this micro-computer is obtainable from Zilog Inc). For the internal timing of the CPU a system clock C, comprising a free-running 8 MHZ crystal, is provided. The CPU is connected via input-output bus l/OB with input and output ports IP, OP and via a memory address and data bus DB with a non-volatile memory in the form of an EPROM (erasable programmable read-only memory), which is accessed by the CPU via the data bus DB for instructions to execute. A conventional decoder D is also provided for controlling the functioning of the input and output ports IP, OP.In addition, an analogue-to-digital converter ADC is provided, to which signals are supplied by the potentiometers VR4, VR5, VR6, VR12, thermisters TS1, TS2, TS3, and switches S4 and SIO. The ADC is interrogated by the CPU, via the I/O bus, each time a mains interrupt signal is supplied to the CPU by the control box Ml. More particularly, the various channels of the ADC are interrogated in turn, one in response to each mains interrupt in a so-called "wrap around" sequence.

The ADC, in response to a signal from the decoder D, supplies information as to the state of the interrogated channel via the input port IP. Switches S5 to S9 and S11 supply information via the input port in response to an enabling signal from the decoder D. The control circuit also comprises a re-set subcircuit R which is directly connected into the CPU and by which, upon starting up of the machine, the CPU is enabled to set the controls to their correct state in a rapid manner. A shaft encoder E driven by the main drive shaft is also provided having a direct "interrupt" input to the CPU.

In response to the various signals thus supplied to the CPU, the CPU supplies outputs, via output port OP, to the sub-circuits controlling the heaters H1, H2, H3, the solenoids SOL1, SOL2, stepping motor drive SMD emitters El to E7, various LEDs and relay RLl. This relay serves as a "watch dog" over the whole of the control circuit. To this end, it is maintained in a "made" condition during normal operation of the machine by a control sub-circuit which is "refreshed" at regular intervals, failure to refresh the subcircuit causing the relay RL1 to drop out.

More particularly, the sub-circuit receives a signal at each mains interrupt, the signal serving to change the state of the circuit between "1" and "0", the arrangement being such that switching to the "1" state constituting the "refresh" signal. The subcircuit is arranged to become de-energised, in the absence of a refresh signal, after a time interval which is greater than the interval between two "1" signals. De-energisation of the sub-circuit of course switches off the relay, thereby terminating the power supply to the machine.

In the machine in accordance with the invention the emitters El to E7, constituting the various sensing sensors, are actuated in response to control pulses supplied by the CPU sequentially thereto at each system clock interrupt and emit pulses of infra-red radiation, which are separately received by the receiver E/R located in the machine head above the emitters. In other machines in accordance with the invention other types of sensing means may of course be utilised.

Thermisters TS1 to TS3, referred to above, serve to sense the temperature of respectively the melt chamber 28, delivery tube 24 and creaser foot 22 and thus, through the CPU, to control the output of the heaters H1, H2, H3 respectively. Potentiometers VR4, VR5, VR6 and VR 1 2 are controlled respectively by the control knobs 42, 44, 52, 54 and provide appropriate signals through the ADC in accordance with the settings of those control knobs.

The operation of the machine is generally similar to that of the machine as described in the aforementioned UK Patent Application, and consequently the following description will relate merely to the manner in which the operation of the snipping device 30 is controlled when the automatic operating mode of the machine is selected.

As already mentioned above, the emitters El to E7 are pulsed sequentially at each system clock interrupt, which takes place every 250 micro seconds, and the status or condition of each of the emitters E3, E4, E5, E6 are recorded in a data byte; this byte thus provides the latest scan data available in relation to the status of the sensors. Utilisation of the data thus recorded then takes place in response to the encoder E interrupt, also referred to above. In practice, the encoder supplies sixteen pulses for each rotation of the main drive shaft of the machine. For the purposes of controlling the operation of the snipping device, however, the programme set out in Figure 3a operates only at every alternate encoder pulse.

Referring to Figure 3a, in response to each encoder pulse the latest scan data is read (step 800) and thereafter the archive for each of the emitters E3, E4, ES, E6 is updated (steps 810, 820, 830, 840). As can be seen from Figure 4, each archive comprises one 8bit data byte and the updating is achieved by rotating the bits from right to left (viewing Figure 4), the bit read from the latest scan data being entered at the right hand end and the oldest data bit being released. Bearing in mind, that the updating takes place eight times for each rotation of the main drive shaft, it will be appreciated that, at any given time, the archive stores all the data for the preceding rotation.

After the four archives have been updated as aforesaid, the bit values stored in each archive are summed or aggregated (step 850).

In practice, the summing of the bits, which are in the form of "1" or "O", is effectively to count the number of times "1" is stored (as opposed to adding the binary numbers stored in each archive), and to this end each archive is rotated through a count flag which counts each ''1" supplied thereto. Thus, viewing Fig. 4, archive (E3) has a value of "8", archive (E4) "5", archive (E5) "3" and archive (E6) "4". The sum of these values, therefore, in the case of Fig. 4 is "20".

For comparison with a comparator value provided by potentiometer VR 12, this aggregate value (E3 to 6) is then multiplied by 7 (step 860).

Figure 3b represent a background routine of the control for the snipping device 30. This routine is of course rendered operational when switch S9 is switched to "automatic" and would of course be disabled by the kneeswitch S5, if switch S10 is switched to its "snip inhibit" position. The routine of Figure 3b is dependent upon the setting of the potentiometer VR1 2. This potentiometer is infinitely variable, under operator control, by means of control knob 54, and its output voltage is supplied to the ADC which converts it to a number between 0 and 255. In executing the background routine, the value (VR 1 2) is interrogated as to whether it is equal to or exceeds 225 (step 870); such a condition arises when the knob 54 is turned fully anticlockwise.In the event of the number equalling or exceeding 225, a signal de-energising solenoid SOL2 is generated (step 890). If the value (VR12) is less than 225, then it is compared with the value "7 x (E3 to 6)" (step 880); that is to say, the total value of the "1" bits in the archives (E3 to E6), multiplied by 7, is compared with the value (VR 12). If the value "7 X (E3 to 6)" is greater than or equals value (VR 1 2), then a signal is generated to energise solenoid SOL 2 (step 900), while if value "7 X (E3 to 6)" is less than value (VR 1 2), then a signal is generated to de-energise solenoid SOL2 (step 890).

It will thus be appreciated that, by varying the value (VR12), the incidence of energising and de-energising solenoid SOL2 can be controlled by the operator. Furthermore, it is not necessary for the operator to be provided with any particular settings, but rather the operator can use her discretion for selecting more or less "snip" according to the particular type of workpiece being operated upon.

The switching of the solenoid SOL2 is signalled when the CPU is supplied by a "mains interrupt" signal from control box Ml, as referred to above. Thus, upon receipt of such signal, the processor CPU looks at the background routine to ascertain whether SOL2 should be energised or de-energised.

As is conventional in machines of this type, the drive to the snipper device 30 is achieved through a linkage having a latching connection to a drive element driven from the main drive shaft. To achieve this connection, a latch arrangement (not shown) is provided, which is spring-urged into an inoperative condition from which it is urged, by means of the solenoid SOL2, into operative position when the solenoid is energised. Because the connection is mechanical, it will of course be appreciated that the latch arrangement can engage to form the latching connection only at a given point in the rotation of the main drive shaft. Furthermore, the latching connection can become disconnected also only once in each operating cycle of the main drive shaft. In practice, when the energising of SOL2 is flagged, the solenoid is energised at the next mains interrupt, overcoming the force of the spring and urging the latch arrangement into operative condition, into which it in fact moves at the appropriate time in the cycle. Similarly, flagging "de-energise SOL2" leads to the latch arrangement being disconnected at an appropriate time in the cycle.

It will of course be appreciated that, while the invention has been described in terms of the "snip" routine, the underlying principles of the invention are equally applicable to the control of the "pleating" operation, and indeed more broadly than in cementing and folding machines alone, mutatis mutandis.

Claims (11)

1. A machine for operating progressively along a marginal portion of a workpiece of sheet material, said machine comprising operating instrumentalities arranged at an operating locality of the machine for feeding a workpiece through the operating locality and for performing thereat an operation upon a marginal portion of such workpiece.

sensing means arranged "upstream" of the operating locality for detecting the approach to the operating locality of a corner (as herein defined) in such marginal portion, said sensing means comprising a sensor which detects the presence or absence of a marginal portion of a workpiece and the status of which is determined accordingly, means for reading the status of the sensor, means operable at predetermined intervals for storing, in the form of a binary value, the status of the sensor as read by said reading means, means for aggregating the stored values, operator-controlled means for determining a comparator value, means for comparing the aggregate value with said comparator value, and means operable in response to an actuation signal generated as a result of the comparison of said values for controlling the operation of at least one of said operating instrumentalities.

2. An edge folding machine for progressively folding over and securing a marginal portion of a workpiece of sheet material, said machine comprising folding instrumentalities arranged at an operating locality of the machine, comprising a creaser foot and a reciprocating element for folding the marginal portion of a workpiece over the creaser foot, workpiece feeding means for feeding a workpiece through the operating locality in such manner that a marginal portion thereof can be operated upon by the folding instrumentalities, sensing means arranged "upstream" of the operating locality for detecting the approach to the operating locality of a corner (as herein defined) in such marginal portion, said sensing means comprising a sensor which detects the presence or absence of a marginal portion of a workpiece and the status of which is determined accordingly, means for reading the status of the sensor, means operable at predetermined intervals for storing, in the form of a binary value, the status of the sensor as read by said reading means, means for aggregating the stored values, operator-controlled means for determining a comparator value, means for comparing the aggregate value with said comparator value, and means operable in response to an actuation signal generated as a result of the comparison of said values for varying, in relation to the rate of reciprocation of said element of the folding instrumentalities, the rate at which the workpiece is fed by the workpiece feeding means through the operating locality.

3. A machine according to claim 2 wherein the workpiece feeding means comprises an orbitally operating hammer-and-anvil arrangement by which a workpiece can be fed stepby-step through the operating locality, the rate at which said arrangement is caused to operate being variable under operator control, and further wherein the distance through which the workpiece is fed in each step by said arrangement is varied in response to an actuation signal generated as a result of the comparison of the aggregate and comparator values.

4. An edge folding machine for progressively folding over and securing a marginal portion of a workpiece of sheet material, said machine comprising folding instrumentalities arranged at an operating locality of the machine, workpiece feeding means for feeding a workpiece through the operating locality in such manner that a marginal portion thereof can be operated upon by the folding instrumentalities, a snipper device also arranged at the operating locality for snipping the marginal portion of the workpiece as it is fed therethrough, operation of the snipper device, when actuated, being in timed relation with operation of the folding instrumentalities, sensing means arranged "upstream" of the operating locality for detecting the approach to the operating locality of a corner (as herein defined) in such marginal portion, said sensing means comprising a sensor which detects the presence or absence of a marginal portion of a workpiece and the status of which is determined accordingly, means for reading the status of the sensor, means operable at predetermined intervals for storing, in the form of a binary value, the status of the sensor as read by said reading means, means for aggregating the stored values, operator-controlled means for determining a comparator value, means for comparing the aggregate value with said comparator value, means operable in response to an actuation signal generated as a result of the comparison of said values for actuating the snipper device.

5. A machine according to claim 4 wherein means for actuating the snipper device comprises a latch arrangement which is caused to be engaged by means of an actuator operated in response to said actuation signal.

6. A machine according to claim 5 wherein the snipper device is cyclically driven and the latch arrangement can be engaged only at a predetermined time in each cycle, and further wherein a "mains interrupt" signal is generated in accordance with the frequency of an electrical power supply to the machine, the actuator being operated in response to a "mains interrupt" signal, when an actuation signal has been generated as aforesaid as a result of the comparison of the aggregate and comparator values.

7. A machine according to any one of the preceding claims wherein the operator-controlled means comprises a potentiometer the output voltage of which is variable under operator control, and further wherein an analogue-to-digital convertor is provided for converting said voltage to a digital value, constituting the comparator value.

8. A machine according to any one of the preceding claims wherein the means for storing the status of the sensor as aforesaid is actuated each time a pulse is supplied thereto from an encoder which is mounted on a main drive shaft of the machine, said shaft control ling the operation of the operating instrumentalities.

9. A machine according to any one of the preceding claims wherein the sensing means comprises a plurality of sensors arranged in an array extending generally transversely of the direction of workpiece feed, each of which sensors detects the presence or absence of a marginal portion of a workpiece and the status of each of which is determined accordingly, and further wherein the sensor status reading means reads the status of each of the sensors, the sensor status storing means stores as aforesaid the status of each of the sensors, and the aggregating means aggregates the stored values for comparison with the comparator value.

10. A machine for operating progressively along a marginal portion of a workpiece of sheet material, said machine comprising operating instrumentalities arranged at an operating locality of the machine for feeding a workpiece through the operating locality and for performing thereat an operation upon a marginal portion of such workpiece, sensing means arranged "upstream" of the operating locality for detecting the approach to the operating locality of a corner (as herein defined) in such marginal portion, said sensing means comprising a plurality of sensors in an array extending generally transversely of the direction of workpiece feed, each of which sensors detects the presence or absence of a marginal portion of a workpiece and the status of each of which is determined accordingly, means for reading the status of each of the sensors, means operable at predetermined intervals for storing, in the form of a binary value, the status of each of the sensors as read by said reading means, means for aggregating the stored values, means for comparing the aggregate value with a pre-set comparator value, and means operable in response to an actuation signal generated as a result of the comparison of the aggregate and comparator values for controlling the operation of at least one of the operating instrumentalities.

11. A cementing and folding machine constructed arranged and adapted to operate substantially as hereinbefore described with reference to the accompanying drawings.