WO1988002994A1

WO1988002994A1 - Cigarette making machine weight control

Info

Publication number: WO1988002994A1
Application number: PCT/GB1987/000762
Authority: WO
Inventors: Stanley Henry Dutton; Peter James Fryett; Robert Graham Waugh
Original assignee: Molins Ltd
Current assignee: Mpac Group PLC
Priority date: 1986-10-29
Filing date: 1987-10-28
Publication date: 1988-05-05
Anticipated expiration: 1989-04-29
Also published as: GB2196524A; EP0290500A1; GB8725202D0; GB8625900D0; CN87107209A; GB2196524B; BR8707519A; JPH01501039A

Abstract

A trimmer position control device for a cigarette making machine comprises a hydraulic amplifying unit (34) having an input member (32) movable through a predetermined relatively small distance and capable of applying a relatively small force; an output member (36, 38, 40) which moves in response to movement of the input member but, as a result of hydraulic pressure, with a more pronounced movement and a greater force; an air chamber (14) adjacent to the tobacco stream and having in it a suction pressure dependent upon the pressure drop through the tobacco stream; an electrical transducer (20) arranged to be exposed to the suction pressure in the chamber and to emit an electrical signal in response thereto; an amplifier for amplifying the electrical signal; and a positive displacement solenoid device (26) to which the amplified signal is applied and which is arranged to drive the input member (32) in response thereto.

Description

Cigarette Making Machine Weight Control

Cigarette making machines commonly include a trimmer which removes part of the tobacco stream formed by showering tobacco through a chimney onto a suction band. After trimming, the tobacco stream is enclosed in a continuous wrapper web to form a continuous cigarette rod which is then cut into separate rod portions.

The distance of the trimmer from the suction band is normally controlled continuously in order to control the amount of tobacco going into the cigarette rod. In the Molins Mark 8 and Mark 9 cigarette making machines, the trimmer control has two position control inputs, namely a relatively fast-responing control input derived from a pneumatic signal upstream of the trimmer, and a slower- responding input derived from a nucleonic device which monitors the weight per unit length of the completed continuous rod. A nucleonic device has a fast response, enabling it to detect voids in the cigarette rod and, if desired, to activate an ejection mechanism for ejecting defective cigarettes; however, the signal from the nucleonic device is normally transmitted to the trimmer via a motor with a control circuit which provides a relatively slow averaging effect.

The present invention is concerned with an improvement in the control to the trimmer derived from the pneumatic signal upstream of the trimmer. In the Mark 8 and Mark 9 machines the pneumatic signal has until now been derived from a chamber (commonly referred to as an "air cell") adjacent to the suction band in a region between the chimney and the trimmer; however, the air cell could in principle be located further upstream, above the chimney, in a region where the tobacco stream is nearly but not completely formed.

Our US patent number 3089497 describes the air cell concept and an early specific form of it. Reference is directed to that specification in its entirety. In particular reference is directed to the fact that the pneumatic signal is transmitted to a bellows (illustrated in the patent as a series of capsules 75) which expands and contracts in response to the varying suction pressure transmitted to it, and accordingly moves a rod 77 which in turn moves a rod 80 forming an input to an hydraulic amplifying unit. This unit causes a larger movement with a greater force to be transmitted to a rod 51 serving as the pneumatically-based position control Input for the trimmer. The present invention is concerned with an improved arrangement for providing that input.

According to the present invention, a trimmer position control device in a cigarette making machine comprises an hydraulic amplifying unit having an input member movable through a predetermined relatively small distance and capable of applying a relatively small force, an output member which moves in response to movement of the input member but, as a result of hydraulic pressure, with a more pronounced movement and a greater force, an air chamber adjacent to the tobacco stream and having in it a suction pressure dependent upon the pressure drop through the tobacco stream, an electrical transducer arranged to be exposed to the suction pressure in the chamber and to emit an electrical signal in response thereto, an amplifier for amplifying the electrical signal, and a positive displacement solenoid device to which the amplified signal is applied and which is arranged to drive the input member in response thereto.

The main difference between this invention and the form of pneumatically based trimmer control used for many years in the above- mentioned Molins machines lies in the replacement of the bellows with a positive displacement solenoid device driven in response to a transducer. In this context the term "positive displacement solenoid device" is intended to refer particularly to a self-centering solenoid device producing movement of its output member (the input to the hydraulic unit) with an ampl tude precisely related to the amplitude of the elctrical signal applied to the solenoid device. For this purpose, the solenoid device should preferably have an armature mounted on two axially spaced resilient diaphragms whereby the armature (which comprises or is coupled to the output member of the solenoid device) returns to a predetermined position when no electrical signal is applied to the solenoid. A suitable device for that purpose, we have found, is one designed to serve normally as a vibrator, an example being Vibrator type GWV4/2 made by Gearing & Watson (Electronics) Limited, England. An important advantage of this invention is that it provides a significantly faster response than the arrangement we have used until now. In particular, it avoids the response delay resulting from the unavoidable length of the pipe connecting the air cell to the bellows in the previous arrangement, and the disadvantageous consequences of tobacco dust contamination in the pipe and bellows.

In a preferred arrangement according to this invention, the electrical transducer is mounted in a casing close to the air cell, either within the suction chamber to which suction is applied to the suction band, or behind the suction chamber.

A trimmer control device according to this invention may, in principle, be the sole position control for the trimmer. However, it is preferably used in combination with an averaging control device responsive to the weight of the completed cigarette rod (e.g. a nucleonic device) as described above and in the above-mentioned patent.

An example of a trimmer control device according to this invention is shown diagrammatically in the accompanying drawings in w ich:

Figure 1 is a diagrammatic overall view of the device; and

Figure 2 is a diagrammatic sectional view of the solenoid device. As shown in Figure 1, a tobacco stream 10 is formed on a suction band 12 which moves past an air cell 14 mounted within a suction c amber through which suction is applied to the band 12 to hold the tobacco on the band. The air cell itself has a pipe 16 through which suction is transmitted to the cell from a separate suction source. As a result of the varying airflow resistance of the tobacco, the suction pressure in the cell 14 varies, and this variable suction pressure is transmitted by a pipe 18 to a transducer casing 20.

The casing 20 includes a solid-state differential pressure transducer, for example the transducer SCX01D made by Sensortec GmbH, Germany. One side of the diaphragm of this transducer is exposed to suction pressure from the pipe 18 while the other side is exposed to atmospheric pressure via pipe 22. The transducer emits an electrical signal which is transmitted via leads 24 to a positive displacement solenoid device 26 which is shown diagrammatically in Figure 2. As shown in Figure 2, the solenoid device comprises a solenoid

100 wound around an armature 102, a strong cylindrical magnet 104 having North and South poles at its ends, and two phosphor bronze diaphragms 106 which support opposite ends of the armature. The peripheries of the diaphragms are fixed in position so that the diaphragms return the armature to a 'pre determined centre position when no voltage is applied to the solenoid. A rod 32 is fixed to the armature and thus moves vertically upwards and downwards in response to the electrical signal from the transducer.

The device 26 is mounted at one end on a frame 28 via a screw threaded member 30 whereby the vertical position of the device 26 can be manually adjusted for zero setting. It should be added that this signal is subject to pre-a pl ification by a pre-ampl if ier incorporated in the case 20, and to further amplification by a main amplifier which may be incorporated into a case enclosing the solenoid device.

The rod 32 serves as the input member for an hydraulic amplifier 34 having an output shaft 36. The shaft 36 is rotated in response to movement of the rod 32, and in turn moves a trimmer control rod 38 via a crank 40 on the shaft 36. The hydraulic amplifier is powered by an hydraulic pump 42. The hydraulic amplifier and pump are of a construction previously used in Molins Mark 8 and Mark 9 machines.

The main amplifier may incorporate means for time shifting the signal, for example by means of a conventional "bucket brigade" type of circuit. By this means, movement of the trimmer by the rod 38 may be timed to coincide with the arrival at the trimmer of the portion of tobacco whose flow resistance was detected by the the transducer.

The pre-ampl if ier in the case 20 may, for example, be arranged to produce a zero output when the suction pressure in the air cell 14 is equal to 12 inches of water guage (305mm). Changes in the suction pressure above or below that average level, for example plus or minus 1.5 inches (38mm), result in positive or negative signals being applied to the solenoid, which consequently moves the rod 32 upwards or downwards to provide the appropriate adjustment to the trimmer position. The movement of the rod 32 may be plus or minus 1.6mm from the central datum position, and such movements may result in trimmer movements of up to plus or minus 8mm.

Claims

Claims:

1. A trimmer position control device for a cigarette making machine comprising an hydraulic amplifying unit (34) having an input member (32) movable through a predeter ined relatively small distance and capable of applying a relatively small force; an output member (36,38,40) which moves in response to movement of the input member but, as a result of hydraulic pressure, with a more pronounced movement and a greater force; an air chamber (14) adjacent to the tobacco stream and having in it a suction pressure dependent upon the pressure drop through the tobacco stream; an electrical transducer (20) arranged to be exposed to the suction pressure in the chamber and to emit an electrical signal in response thereto; an amplifier for amplifying the electrical signal; and a positive displacement solenoid device (26) to which the amplified signal is applied and which is arranged to drive the input member (32) in response thereto.

2. A device according to claim 1 in which the solenoid device (26) includes an armature (102) movabl mounted by a number of resil ient members (106) arranged to restore the armature to a datum position when no voltage is applied to the solenoid (100).

3. A device according to claim 2 in which the datum position of the armature (102) is a central position from which the armature is movable in opposite directions by oppositely flowing currents in the solenoid (100).

4. A device according to claim 3 in which the electrical transducer (20) and amplifier transmit opposite voltages to the solenoid (100) when the suction pressure in the air chamber (14) is respectively above or below a datum level, thus causing the trimmer to move in one direction or the other from an average or datum position.

5. A device according to claim 5 in which a solenoid (100) mounted around the armature (102) is in turn surrounded by a fixed magnet (104), the armature being movably mounted by two diaphragms (106) at the respective ends of the armature.

6. A device according to any one of claims 1 to 5 including means for time shifting the signal from the transducer so that each adjustment in the position of the trimmer coincides substantially with the arrival at the trimmer of the portion of tobacco whose flow resistance was detected by the transducer.

7. A device according to any one of claims 1 to 6 in which the electrical transducer (20) is mounted in a casing which is close to the air chamber (14) and is in communication therewith.

8. A device according to any one of claims 1 to 7 in which the solenoid device (26) is manually adjustable (part 30) in position for the purpose of zero setting.

9. A device according to any one of claims 1 to 8 arranged to control the trimmer in combination with a nucleonic device responsive to the weight per unit length of the completed cigarette rod.