GB2141968A - Cementing and folding machine - Google Patents

Abstract

A cementing and folding machine has a facility (switch S9) for selecting between a "manual" and an "automatic" operating mode. The machine has the conventional facilities for pleating (reduced feed length) along "outside" corners and for snipping along "inside" corners, as well as controls for switching the adhesive supply on and off. In addition, the machine has a facility (switch S8) for causing pleating to take place when snipping is selected, and further has a facility (switch S4) for selecting between "no adhesive", "adhesive on", and "reduced adhesive supply when pleating selected." The machine has the further facility (switch S10) whereby, in automatic operating mode, the knee-switch (S5) may selectively be used to override either the adhesive supply or the operation of the edge snipping means. <IMAGE>

Description

SPECIFICATION Cementing and folding machine This invention is concerned with a cementing and folding machine comprising folding instrumentalities arranged at an operating locality, for folding the edge of a workpiece fed therepast, adhesive-applying means also arranged at said operating locality, for applying adhesive to the portion of the workpiece edge being folded by the folding instrumentalities, workpiece feeding means by which the workpiece can be fed through the operating locality, said means serving also to press the folded edge portion to cause it be bonded by the adhesive applied thereto, edge snipping means arranged at the operating locality for snipping the workpiece edge, and control means comprising first control means for controlling the supply of adhesive to the adhesive-applying means, second control means for controlling the rate at which the workpiece is fed through the operating locality by the workpiece feeding means, and third control means for controlling the operation of the edge snipping means, Cementing and folding machines of the above type are well-known and are available in a variety of versions. In one version (hereinafter called a "manual" machine), for example, as described in EP-A No. 83306752.3, an operator-actuatable switch (knee switch) is provided for operating the first control means.In addition, in said machine the workpiece is fed intermittently through the operating locality and both the frequency of the feed steps ("feed speed") and the length of each step ("feed length") are separately variable, the feed length variation being controlled by the second control means, whereby a pleating operation can be performed on the workpiece edge (as is conventional in machines of this type). For operating the second control means and also the third control means, a "heel-and-toe" treadle is provided, depression of the toeward end operating the second control means and depression of the heelward end operating the third control means. A further treadle-operated switch is provided for controlling the feed speed.

In a different version of the machine, usually referred to as an "automatic" machine, control of the various control means conventionally is respectively by first, second and third sensing means, these sensing means being arranged in an array "upstream" of the operating locality of the machine, and each sensing means being actuated by sensing the position of a workpiece edge in relation thereto. In general, the feed speed control remains under the control of the operator.

In certain instances, it has been found desirable that, using a so-called automatic machine, one or more of its automatic functions is able to be overridden or replaced by direct operator control, and to this end additional controls have from time to time been provided on the automatic version. However, the complexity of the controls of the commercially available machines of this type have rendered it difficult to provide all the combinations of functions and controls which may be desirable in a shoe factory environment.

It is the object of the present invention to provide an improved cementing and folding machine which is more versatile in its operating modes than has previously been the case.

This object is resolved in accordance with the invention, in a machine as set out in the first paragraph above, in that the supply of adhesive to the adhesive-applying means and the operation of the edge snipping means during the operation of the machine can be inhibited respectively by operation of the first and third control means in response to the actuation of operator-actuatable switch means, which means comprises a switch which is actuatable by the operator during the machine operation, and pre-selector means whereby the switch can be rendered operable either to cause the supply of adhesive to be inhibited or to cause the operation of the edge snipping means to be inhibited.

In this way, a single switch may be utilised selectively for inhibiting certain of the functions of an automatically controlled machine, thereby rendering the machine significantly more versatile then has previously been the case. It will of course be appreciated that the need to inhibit the supply of adhesive at the same as inhibiting snipping is rare, and any disadvantage arising from not being able to inhibit both at once is outweighed by the advantage of the operator being able to use the same switch during the machine operation for inhibiting a pre-selected one of the two functions.In certain circumstances it may be desirable for neither "inhibit" functions to be performed during the machine operation, and therefore, in order to avoid any risk of the switch being accidentally operated, the pre-selector means can be switched to render actuation of the switch ineffective to inhibit either function.

It will be appreciated that the machine in accordance with the invention can thus operate in an automatic mode, and to this end conveniently first sensing means is provided for sensing the presence of a workpiece at the operating locality, in response to which sensing adhesive is caused to be supplied to the adhesive-applying means. Furthermore, in accordance with the present invention preferably said switch is actuatable to override the signal from the first sensing means.

More particularly, the present invention is applicable to machines having a first operating mode, in which the first control means is actuated in response to a signal from the first sensing means ("automatic" mode), and a second operating mode, in which the first sensing means is disabled and the operation of the first control means is under operator control ("manual" mode).In such a machine, conveniently in the second operating mode the switch is disabled from performing an "inhibit" function, but actuation thereof by the operator is effective directly to control the operation of the first control means, More particularly, when operating in the second operating mode, preferably the switch can, after having been actuated, be again actuated only having first being released (thereby alternatively switching the supply of adhesive on and off) while, when operating in the first operating mode, the switch performs its "inhibit" function only while held actuated.

In addition to the first sensing means, conveniently second and third sensing means are also provided for sensing respectively "outside" and "inside" corners in the workpiece edge approaching the operating locality, said second sensing means signalling the second control means and said third sensing means signalling the third control means.

The term ""outside" corner" where used herein with reference to a workpiece edge is intended to indicate a portion of the edge which is curved, wherein the radius passes through the area of the workpiece, while the term ""inside" corner", where used herein in relation to a workpiece edge, is intended to indicate a portion of the edge which is curved, the radius of curvature extending away from the workpiece. As is well-known, in folding an "outside" corner, because the area of the material to be folded over exceeds the area of material onto which it is folded, customarily pleating of the folded over portion takes place, while, in the case of an "inside" corner, because the area of the material to be folded over is less than that of the material onto which it is folded, the material to be folded over is snipped.

As in the case of first control means, furthermore, the switch is preferably actuatable to override the signal from the third sensing means to enable the operation of the edge snipping means to be inhibited. Furthermore, where the machine has a first and a second operating mode as set out above, preferably, when operating in the second operating mode, the second and third sensing means are disabled and the second and third control means are actuated under the control of the operator. In this way, it will be appreciated, the machine in accordance with the invention may be operated as a conventional "manual" machine or as a conventional "automatic" machine.

Still further to enhance the versatility of the machine, preferably further operator-actuatable selector means is provided by which, upon actuation of the third sensing means, in the first operating mode, selectively either the third control means only is operated or the second and third control means are operated together. In the latter case, the shortened feed length for each step reduces the speed at which the workpiece is fed through the operating locality while snipping the workpiece edge, so that relatively sharply curved "outside" corners can be accommodated. (It will of course be appreciated that conventionally, when the edge snipping means is actuated, the maximum feed length setting is at the same time selected, while for pleating the minimum setting is selected; the maximum and minimum feed length settings are of course made by the operator).In the machine in accordance with the invention, furthermore, where such further selector means is provided, preferably the switch is actuatable to override either the signal from the third sensing means only or the signals from the second and the third sensing means, according to the setting of the further selector means.

It will thus be appreciated that the machine in accordance with the invention has enhanced versatility over currently commercially available machines. To achieve this versatility, furthermore, without excessive cost penalties, preferably the machine is computer-controlled, e.g.

microprocessor-controlled.

There now follows a detailed description, to be read with reference to the accompanying drawings, of one machine in accordance with the invention. It will be appreciated that this machine has been selected for description merely by way of exempiification 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 block diagram of an electronic control circuit of said machine; and Figure 3a to 3d represent part of the computer software by which the machine operation is controlled.

The machine now to be described is a so-called 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 the aforementioned Patent Application. The machine thus comprises a work table 10 on which a workpiece can be supported at an operating locality ofthe 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 (not shown), which completes the fold of the workpiece edge over the creaser foot.During folding, adhesive can be applied to the workpiece edge 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 Fig. 1.

"Downstream" of the folding instrumentalities are located conventional edge snipping means generally designated 30, comprising a fixed and 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 hammer-and-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 depressing respectively the toeward and heelward portions of the foot switch. Switch S6 operates a solenoid SOL1 which serves to reduce the feed length, i.e. the amount through which the hammer-and-anvil arrangement moves fore-and-aft for each revolution of the main drive shaft, and thus serves to effect pleating of the folded over margin of the workpiece, as described more fully below. Switch S7 operates a solenoid SOL2 which causes the edge snipping means 30 to operate.For determining 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, also as described more fully below. A knee-operated switch S5 is also provided, which is a multi-functional switch the operation of which will be described later.

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 six 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 edge snipping means 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 pre-selector 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 edge snipping means is disabled, while the knee-switch S5 is held operated; 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 of the adhesive supply at the end of an operating cycle;; switch S12, which is a five-position switch, by which the operator can select one of four sensors, in the form of emitters E3, E4, E5, E6 (constituting third sensing means of the machine), or disable the third sensing means, by which solenoid SOL2 (operating the edge snipping means) is operated in the "automatic" operating mode.

The emitters El to E6 referred to above, together with a further emitter E7 (constituting second sensing means of the machine), by which the solenoid SOL1 (controlling pleating) is operated in the "automatic" operating mode of the machine, are arranged in an array just "upstream" of the operating locality. 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" corners 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 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, which constitutes second control means of the machine, 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 operating of switch S6.Solenoid SOL2, which constitutes third control means of the machine, is effective when actuated to actuate the edge snipping arrangement; this solenoid is energised, in an automatic operating mode, when a selected one of the emitters El to E4 becomes covered by an "inside" corner of a workpiece approaching the operating locality, 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 volts d.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 via a drive SMD (constituting first control means of the machine) 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 S12, thermisters TS1, TS2, TS3 and potentiometers VR4, VR5 and VR6, each of which will be referred to hereinafter.

The central processor unit CPU, which controls the machine, is constituted by a single-chip 8bit micro-computer (in casu, a Zilog Z8681 which, in addition to a microprocessor, also incorporates a random access memory/scratch pad RAM (shown separately in Fig. 2); this microprocessor 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, thermisters T81, TS2, TS3, and switches S4, S10, and S12. 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 sub-circuit 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 sub-circuits controlling the heaters H1, H2, H3, the solenoids SOL1, SOL2, drive SMD, emitters El to E7, various LEDs and relay RL1. 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 sub-circuit 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 sub-circuit 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, constituting the various sensing means, 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 H 1, H2, H3 respectively. Potentiometers VR4 to VR6 are controlled respectively by the control knobs 42,44,52 and provide appropriate signals through the ADC in accordance with the setting of those control knobs.

Figs.- 3a to 3d are flow chart of the software by which the machine is controlled. The script within each box is a shorthand reference to the command or enquiry being made; a full description of each step is appended to this specification.

In general, furthermore, step 210 enables the selected emitters while step 220 disables the various machine functions in readiness for the next operating cycle. Steps 230 to 390 control the "adhesive on" programme, provided an automatic operating mode has been selected at step 240. Similarly, steps 330 to 340 control the "adhesive off" procedure. It should be noted that, if no adhesive is required in the automatic operating mode, step 250 enables the "adhesive on" and "adhesive off" procedures to be avoided. Steps 350 to 410 relate to the "pleating" procedure, together with the "adhesive metering modify" procedure associated with pleating.

Steps 420 to 480 then relate to the "snipping" procedure. It should be noted that there is a sub-routine (steps 260 to 290) for enabling the adhesive supply to be inhibited and a similar sub-routine (steps 390 to 410) for inhibiting the operation of the snipping means 30. Steps 490 to 730 set out the programme for the manual operating mode, which may be selected at step 240.

Thus, in using the machine in accordance with the invention, the operator selects either a "manual" or "automatic" operating mode using switch S9, and also selects whether, when a snipping operation is to be performed, she also requires pleating to take place, using switch S8.

In addition, she sets switch S4 according to whether she requires no adhesive to be applied (e.g. when an initial operation is being performed on a new workpiece), or whether, with adhesive selected, the amount supplied is to be modified during pleating. In addition, if an automatic operating mode is selected, the operator, by switch S11, selects which of the emitters El, E2 is to be operational in switching off the adhesive supply at the end of the operating cycle, and also, by switch S12, which, if any, of emitters E3 to E6 is to be used for controlling the operation of the edge snipping means. Also, using switch S10 she selects whether she wishes to be able to inhibit either the supply of adhesive or the operation of the edge snipping means during the operating cycle.

It will be noted that, when knee-switch S5 is utilised in the manual operating mode, the gear pump 26 is actuated by operating the switch and cannot be de-actuated until the switch has been released and re-actuated, whereas when the switch S5 is utilised for inhibiting the adhesive supply or the operation of the edge snipping means, the inhibit function is operable only while the switch is held actuated.

Appendix 210 Enable emitters 220 Switch "off" solenoids SOL1, SOL2 and the drive SMD to motor M 230 Is bilevel input signal E2 "low" - indicating workpiece present? 240 Is bilevel signal input S9 "low" - indicating "manual" selected? 250 Is 3-position switch S4 switched "off" - motor M rendered inoperative? 260 Is 3-position switch Sl0 switched to select adhesive control override? 270 Is bilevel input signal S5 "low" - indicating knee-switch held actuated? 280 Signal "de-actuate SMD" 290 Signal "actuate SMD" 300 Is switch Sli switched to "energise Eel"? 310 Is bilevel input signal El "low" - sensing workpiece presence? 320 Is bilevel input signal E2 low - sensing workpiece presence? 330 Signal "de-actuate SMD" 340 Signal "de-actuate SMD" 350 Is bilevel input signal E7 "low" - indicating "pleat"required? 360 Is 3-position switch S4 switched to "reduced rate for motor M" setting? 370 Signal "reduced rate" for motor M 380 Signal "energise SOLl" - reduced feed length 390 Is bilevel input signal E(s) "low" - indicating.snip required? 400 Is bilevel signal input S8 "low" - indicating "snip and pleat" selected? 410 Signal "de-energise SOLl" - feed length restored 420 Is switch S10 "on" - indicating one of emitters E3 to E6 selected? 430 Is bilevel input signal E(s) "low" - indicating snip required? 440 Signal "de-energise SOL2" snipping knife de-actuated 450 Is 3-position switch Sl0 switched to select snip control override? 460 Is bilevel input signal 55 "low" - indicating knee-switch held actuated? 470 Signal "de-energise SOL2" snipping knife de-actuated 480 Signal Henergise SOL2" - snipping knife actuated 490 Set Flag A = 1 500 Is 3-position switch 84 switched "off" - motor M rendered inoperative? 510 Is bilevel signal input S5 "low" - indicating knee-switch operated? 520 Set Flag A = 1 530 Does Flag A = 1? 540 Set Flag A = 0 550 Is SMD actuated (gear pump being driven)? 560 Signal "de-actuate SMD" 580 Is 3-position switch S4 switched to "reduced rate for motor M" setting? 590 Is bilevel signal input 56 "low" - indicating "pleat" required? 600 Signal "reduced rate" for motor M 610 Is bilevel signal input S8 "low" - indicating "snip and pleat" selected? 620 Is bilevel input signal S7 "low" - indicating "snip" required? 630 Signal "full rate" for motor M 640 Signal "actuate SMD" 660 Is bilevel signal input S6 "low" - indicating "pleat" required? 670 Signal "energise SOL1" - reduced feed length 680 Is bilevel signal input S8 "low" - indicating "snip and pleat" selected? 690 Is bilevel signal input S7 "low" - indicating "snip" required? 700 Signal "de-energise SOL10 - feed length restored 710 Is bilevel signal input S7 1low" - indicating snip" required? 720 Signal "energize SOL2" - snipping knife actuated 730 Signal "de-energise SOL2" - snipping knife de-actuated

Claims (8)

1. Cementing and folding machine comprising folding instrumentalities arranged at an operating locality, for folding the edge of a workpiece fed therepast, adhesive-applying means also arranged at said operating locality, for applying adhesive to the portion of the workpiece edge being folded by the folding instrumentalities, workpiece feeding means by which the workpiece can be fed through the operating locality, said means serving also to press the folded edge portion to cause it be bonded by the adhesive applied thereto, edge snipping means arranged at the operating locality for snipping the workpiece edge, and control means comprising first control means for controlling the supply of adhesive to the adhesive-applying means, second control means for controlling the rate at which the workpiece is fed through the operating locality by the workpiece feeding means, and third control means for controlling the operation of the edge snipping means, characterised in that the supply of adhesive to the adhesive-applying means and the operation of the edge snipping means during the operation of the machine can be inhibited respectively by operation of the first and third control means in response to the actuation of operatoractuatable switch means, which means comprises a switch which is actuatable by the operator during the machine operation, and pre-selector means whereby the swiTch can be rendered operable either to cause the supply of adhesive to be inhibited or to cause the operation of the edge snipping means to be inhibited.

2. Machine according to claim 1 characterised in that the pre-selector means can be switched to render actuation of the switch ineffective to inhibit either the supply of adhesive or the operation of the edge snipping means.

3. Machine according to either one of claims 1 and 2 wherein first sensing means is provided for sensing the presence of a workpiece at the operating locality, in response to which sensing adhesive is caused to be supplied to the adhesive-applying means, characterised in that the switch is actuatable to override the signal from the first sensing means.

4. Machine according to claim 3 having a first operating mode, in which the first control means is actuated in response to a signal from the first sensing means, and a second operating mode, in which the first sensing means is disabled and the operation of the first control means is under operator control, characterised in that, in the second operating mode, the switch is disabled from performing an "inhibit" function, but actuation thereof by the operator is effective directly to control the operation of the first control means.

5. Machine according to claim 4 characterised in that, when operating in the second operating mode, the switch can, after having been actuated, be again actuated only having first been released (thereby alternately switching the supply of adhesive on and off), while, when operating in the first operating mode, the switch performs its "inhibit" function only while held actuated.

6. Machine according to any one of claims 1 to 3 wherein second and third sensing means are provided for sensing respectively an "outside" and an "inside" corner in the workpiece edge approaching the operating locality, said second sensing means signalling the second control means and said third sensing means signalling the third control means, characterised in that the switch is actuatable to override the signal from the third sensing means.

7. Machine according to either one of claims 4 and 5 wherein second and third sensing means are provided for sensing respectively an "outside" and an "inside" corner in the workpiece edge approaching the operating locality, said second sensing means signalling the second control means and said third sensing means signalling the third control means, characterised in that, when operating in the second operating mode, the second and third sensing means are disabled and the second and third control means are actuated under the control of the operator, and further characterised in that, when in the first operating mode, the switch is actuatable to override the signal from the third sensing means.

8. Machine according to either one of claims 6 and 7 wherein further operator-actuatable selector means is provided by which, upon actuation of the third sensing means, in the first operating mode, selectively either the third control means only is operated or the second and third control means are operated, characterised in that the switch is actuatable to override either the signal from the third sensing means only or the signals from the second and third sensing means, according to the setting of the further selector means.