EP0083912A1

EP0083912A1 - System and method for subordinating a first electric motor to a second electric motor and a wrapping machine using the system

Info

Publication number: EP0083912A1
Application number: EP82830307A
Authority: EP
Inventors: Carlo Ludovico Bruno
Original assignee: ALISYNCRO Srl
Current assignee: ALISYNCRO Srl
Priority date: 1982-01-05
Filing date: 1982-12-27
Publication date: 1983-07-20
Also published as: IT8267004A0; DE83912T1; JPS58160224A; IT1154404B

Abstract

The invention relates to a system and method for subordinating a first electric motor (18) to a second electric motor (20). The system according to the invention provides for the use of a strip (2) which bears at least one series of marks spaced longitudinally thereof in a predetermined manner and is driven to move along its longitudinal direction by the second electric motor (20). A reading device (26) is fixed relative to the strip signals the passage of the said marks to control means (27) which supply the first motor (18) with a signal which is a function of the frequency of reading of the said marks, in order to vary the velocity of the first motor (18) with time according to a predetermined law linked to the speed of the second motor (20). The system is usable, for example, in a wrapping machine for confectionery products.

Description

The present invention relates to systems for subordinating a first electric motor to a second electric motor. The term "subordinating system" is used in the present specification, and in the claims which follow, to indicate a system whereby the speed of the first electric motor (the "subordinate" motor or "slave" motor) is varied in a predetermined manner dependent on the speed of a second electric motor (the "subordinating" motor or "master" motor).
The object of the present invention is to provide a subordinating system which is simple, reliable, and economic.
The main characteristic of the system according to the invention lies in the fact that it includes:

a strip which bears at least one series of marks spaced longitudinally thereon in a predetermined manner and is driven to move in its longitudinal direction by the second electric motor;
a reading device fixed relative to the strip and arranged to detect the passage of the said marks, and
control means for receiving the output signals from the reading device and supplying to the first motor a signal which is a function of the frequency of reading of the said marks to vary the speed of the first motor with time according to a predetermined law linked to the speed of the second motor.

The invention also provides a method for subordinating a first electric motor to a second electric motor the main characteristic of which lies in the fact that there is provided a strip which bears at least one series of marks spaced longitudinally thereon in a predetermined manner and is driven to move in its longitudinal direction by the second electric motor, a reading device fixed relative to the strip which is arranged to detect the passage of the said marks, and in that there is supplied to the first motor a signal which is a function of the frequency of reading of the said marks, to vary with time and the speed of the first motor according to a predetermined law linked to the speed of the second motor.
The system and the method according to the present invention can be used advantageously in any field whenever it is necessary to achieve subordination of a first electric motor to a second electric motor.
According to a further aspect, the invention also provides for a particular application of the said system to a wrapping machine of the "fin-seal" type for confectionery products.
In this branch of the art, the term "fin-seal" means wrapping machines for confectionery products, comprising:

means for folding a paper strip which unrolls from a feed roll so as to bring its longitudinal edges into contact with each other to form a tube having an external longitudinal fin constituted by the two said longitudinal edges in juxtaposition;
at least one pair of wheels which engage the two sides of the longitudinal fin to join the two said longitudinal juxtaposed edges and draw the paper tube in its longitudinal direction;
means for transferring a series of articles to be wrapped into the said paper tube in longitudinally spaced positions, and
a pair of transverse joining and cutting jaws between which the paper tube is passed at the output from the wrapping machine, the jaws cooperating to join the walls of the paper tube together so as to form a transverse fin in the zone between one article and the next and to separate each article from the next, these jaws including two contra-rotating arms having outer working ends with circular trajectories which are substantially tangential to the paper tube on opposite sides of its axis.

In known fin-seal wrapping machines, the rotation of the transverse cutting and joining jaws is driven by the same.motor as that which drives the drawing wheels for the paper tube. However, a relatively complicated mechanical transmission is connected between the motor and the jaws and is arranged so as to give rise to a non-uniform drive of the jaws during each rotation. The necessity of imparting a non-uniform motion to the jaws results from the fact that in general, on the one hand, the circumference through which the working end of the jaw travels in a rotation of 360° is different from tht length of the paper between one cut and the next (the wrapping machine is used for different articles having different lengths) and that, on the other hand, the peripheral velocity of the working end of the jaw during the joining and cutting operation must be substantially equal to the speed of the paper.
In the known fin-seal machines, it is necessary, when it passes from one article having a predetermined length to another article having a different length, to adjust the mechanical transmission interposed between the motor and the jaws so as to satisfy the aforementioned requirement.
A further object of the present invention is to provide a wrapping machine of the type specified above which avoids the use of the said mechanical transmission between the motor and the jaws and also the need for the related adjusting operations.
In order to achieve this further object, the invention provides a wrapping machine of the type specified above, characterised in that it further includes:

a first motor which drives the transverse cutting and joining jaws;
a second motor which drives the drawing wheels for the pater tube;
a series of marks located on the strip and spaced longitudinally from each other in a predetermined manner;
a fixed reading device arranged to detect the passage of the said marks, and
control means arranged to receive the output signals from the reading device and supply the first motor with a signal which is the function of the frequency of reading of the said marks to vary the speed of the first motor according to a predetermined law during each rotation of the jaws, whereby:
- - the working ends of the jaws are in the zone tangential to the axis of the paper tube each time a zone of the tube between two successive articles is in this tangential zone, and
- - the working ends of the jaws have a peripheral velocity in the tangential zone which is substantially equal to the speed of advance of the paper tube.

According to a further characteristic, the said marks are constituted by impressed marks.
Preferably, moreover, the said marks are disposed on the longitudinal fin of the paper tube.
In one particular embodiment, the detector device is constituted by photoelectric cell means.
Further characteristics and advantages of the present invention will emerge from the description which follows with reference to the appended drawings, provided purely by way of non-limiting example, in which:

Figures 1 and 2 are two perspective views of a wrapped article which can be obtained by means of a wrapping machine according to the invention;
Figure 3 is a schematic side view of a wrapping machine according to the invention;
Figure 4 is a section taken on the line IV-IV of Figure 3;
Figure 5 is a perspective view on an enlarged scale of a detail of Figure 3;
Figures 6a, 6b, 7a, 7b and 8 illustrate the principle of operation of the system according to the invention, and
Figure 9 is a schematic view of the system according to the invention.

Figures 1 to 8 refer to an application of the system according to the present invention to a wrapping machine for confectionery products.
With particular reference to Figures 3 to 5, the wrapping machine, which is generally indicated by reference numeral 1, uses a paper strip 2 which unrolls from a roll 3 and is intended to form wrappers for the articles fed to the wrapping machine.
As the strip 2 unwinds from the roll 3, it is folded so as to bring its two longitudinal edges 4 (see Figure 5) into contact with each other so as to form a tube 5 (see Figure 4) having underneath it a longitudinal fin 6 constituted by the two longitudinal edges 4 in juxtaposition.
The wrapping machine 1 is provided with two longitudinal supports 7 having opposing L-sections, which support the paper tube 5 and define together a slot 8 (see Figure 4) through which projects the longitudinal lower fin 6 of the paper tube 5.
The wrapping machine is further provided with a series of pairs of wheels 9 which engage the two sides of the longitudinal fin 6 to join the two juxtaposed longitudinal edges 4 of the strip 2 and draw the paper tube 5 along in its longitudinal direction, making it slide on the support 7.
Immediately upstream of the forming end of the paper tube 5 is disposed the discharge end of a conveyor device 10 which feeds a series of longitudinal-spaced articles 11 to be wrapped into the paper tube 5. The articles 11 are thrust into the paper tube 5 by blades 12 of the conveyor 10 at a speed substantially equal to that of the longitudinal translational movement of the paper tube 5. The articles are deposited on the lower inner surface of the paper tube and are entrained longitudinally thereby.
The wrapping machine is provided at its output end with a pair of transverse cutting and joining jaws 13 between which the paper tube is made to pass.
The jaws 13 cooperate with each other so as to join the walls of the paper tube together in a zone between one article and the next and to separate each article from the next.
The jaws 11 are constituted by. a .rotary member including one or more arms (in Figure 3 the jaws are illustrated with a single arm) each of which has an external working end. The circular trajectories of the working ends of the two jaws 13 are substantially tangential to the paper tube 5 on opposite sides of its axis. The joining effected by the jaws 13, as well as that effected by the wheels 9, may be heat sealing, for example.
In the case of the two longitudinal edges 4 which form the fin 6, the joining may also be achieved when cold by using wheels 9 having a scored surface so as to impress milling on the said longitudinal edges.
The joining operation effected by the two jaws 13 gives rise to the formation of a transverse fin at at each end of the wrapper of each article 11-The wrapped article obtained is illustrated in Figure 1. In this figure, the reference numeral 14 generally indicates the wrapper of the article (which is in the form of a tablet) and reference numeral 15 indicates each of the two transverse fins obtained as a result of the joining effected by the jaws 13. Finally, reference numeral 16 indicates the longitudinal lower fin of the wrapper 14 corresponding to that portion of the longitudinal fin 6 of the paper tube 5 which is separated as a result of the cutting operation described above.
Figure 2 illustrates the wrapped article with the fin 16 folded so as to be disposed parallel and adjacent the lower surface of the wrapping 14, a condition in which the product is then sold..
As illustrated in Figure 3, the wrapped products which are obtained after the cutting and joining operation performed by, the jaws 13 are conveyed by the conveyor device 17 to the output of the machine.
Wrapping machines of the type described above are known and are called "fin-seal" wrapping machines in this branch of the art.
In machines of this type which have been made up to now, the jaws 13 are controlled by an electric motor (which is the same as that which drives the conveyor device 10 and the wheels 9 for drawing the paper tube 5) with the interpositioning of an adjustable mechanical transmission arranged to impart non-uniform motion to the jaws 13 during each revolution.
The need to vary the velocity of the jaws 13 during each revolution results from two circumstances: on the one hand, the length of the circular trajectory of the working end of each jaw 13 does not, in general, coincide with the distance along which the transverse fins 15 of the wrapped article must be formed (they could coincide for a particular article but this coincidence will no longer occur upon passing to an article of a different length); on the other hand, the working ends of the jaws 13 must have a velocity substantially equal to the translational speed of the paper tube, when this is in the working zone, in order to perform the cutting and joining operation.
The mechanical transmission used in known machines to impart this non-uniform motion to the jaws 13 is relatively complex in that it must allow the motion of the jaws to be adjusted to the different lengths of articles, and hence requires intervention by the operator every time a type of product fed to the wrapping machine is changed.
According to the invention, the jaws 13 are driven by a first electric motor 18 (Figure 3), the wheels 9 for drawing the paper tube 5 are driven by a second electric motor 20, and the motor 18 is made subordinate to the motor 20 in the manner described in detail below.
The paper strip 2 is provided with a series of marks 19 of a different material from that constituting the strip or of a different colour from the strip, the marks being spaced longitudinally on at least one of the two longitudinal edges 4 of the strip. The marks 19 give rise to an equal number of marks 21 on the longitudinal fin 6 of the paper tube 5.
The wrapping machine is provided with a sensor device arranged to detect the passage of the marks 21.
In the particular example illustrated, this sensor device is constituted by a photoelectric cell 22 (see Figures 3 and 5) which receives a light signal from a device 23.
The sensor 22 is connected to an electronic control box 28 including a frequency/analogue converter arranged to supply to the motor 18 a control signal which is a function of the frequency of reading of the marks 21, so as to allow the speed of the motor 18 to be varied according to a predetermined law according to the disposition of the marks on the longitudinal fin 6.
In the example illustrated, the marks 21 on the longitudinal fin 6 are spaced from each other in a predetermined non-uniform manner. Moreover, the disposition of these marks is repeated identically on each section of the strip corresponding to a rotation of the jaws 13, whereby the speed of the motor is varied according to a predetermined law during each revolution of the jaws.
In the lower part of Figure 8 is illustrated an example of the said non-uniform distribution of the marks 21 on a section of the longitudinal fin 6, corresponding to the rotation of the jaws through one revolution. One jaw 13 is illustrated schematically in the left-hand part of Figure 8. The arrow F indicates the sense of rotation of the jaw and V indicates the peripheral velocity of the working end of the jaw, which follows a circular trajectory indicated by the broken line L.
By arranging the marks 21 in the manner illustrated in Figure 1, one obtains a variation of the peripheral velocity V of the working end of the jaw 13 with time, during each revolution of the jaw, of the type represented qualitatively by the curve A in the diagram of Figure 8. In this diagram, the time t indicates the instant at which the jaw 13 is in its working condition, that is, in the position in which the joining and cutting operation is performed; the time to indicates the instant at which the jaw 13 is in the diametrally opposed position to the working position, and the time t₂ indicates the instant at which the jaw-turns into this position. The interval t₂-t₀ thus corresponds to the time necessary for the jaw to carry out one revolution. Finally, in the diagram of Figure 8, V indicates the value corresponding to the translational speed of the paper tube 5.
Naturally, it is possible to provide different series of marks on the longitudinal fin 6 of the paper tube 5. For example, in addition to the series of marks 21 spaced from each other in the manner illustrated in Figure 8, a series of marks 24 (see Figure 8 also) which are uniformly spaced from each other may be provided on the fin 6. Clearly, in this case, it is necessary to provide a second sensor device for reading marks 2₄. This reader is used to generate a signal indicative of the speed of the paper tube 5, that is, of the speed of the motor 20. This allows not only the velocity of the jaw to be varied during each revolution in the manner described above, but also the motor 18 which drives the jaw to be made to follow any fluctuations in the speed of the motor 20 which drives the drawing of the paper tube.
In more detail, by providing the two series of marks 21, 24 illustrated in Figure 8, it is possible to achieve the following result:

If the angular velocity 0 ₂₀ of the motor 20 is kept constant with time, as indicated in the diagram of Figure 6a, that is, the translational speed of the paper tube 5 is kept constant with time, the velocity V of the working end of the jaw varies, for example, according to the curve illustrated in the diagram pf Figure 6b, on each revolution of the jaw.

If, however, the angular velocity ω₂₀ of the motor 20 undergoes fluctuations, for example, of the type indicated in the diagram of Figure 7a, the velocity V is made to vary according to the curve illustrated in the diagram of Figure 7b. This latter curve corresponds to the superposition of the variation in velocity determined by the said fluctuations of the velocity of the motor 20 on the law of variation illustrated in Figure 6b.
Therefore, each jaw is driven to carry out a predetermined non-uniform motion and, at the same time, any fluctuation in the speed of the paper tube 5 gives rise to a corresponding variation in the speed of the jaws.
As is clearly stated above, in wrapping machines according to the present invention, the law of -motion imparted to the jaws depends on the disposition of the marks 21 on the longitudinal fin 6 of the paper tube. Since for each particular length of articles to be wrapped a corresponding law of motion of the jaws must be realised, it follows that for each different length of article a strip with a different disposition of marks must be provided. This does not result in any complication in that it is always necessary to provide a particular strip for each particular type of article to be wrapped, the writing and any designs on this strip obviously being different for each type of article to be wrapped.
From the preceding description, it is clear that the wrapping machine according to the present invention is simpler and more functional than machines of known type, and allows the elimination of the complicated mechanical transmission between the jaws and the corresponding drive motor as well as the need to act on the mechanical transmission every time the length of article is varied in order to adjust the movement of the jaws to the new length.
Although the system according to the present invention has been described with reference to a fin-seal wrapping machine, the system is of general application, being usable any time it is desired to subordinate a first electric motor to a second electric motor, for example, when it is wished to vary the speed of the first electric motor in a manner identical to that which occurs with the second electric motor, or when the speed of the first motor varies according to a predetermined law with respect to the speed of the second motor.
In general, the scheme of the system according to the present invention is that illustrated in Figure 9.
With reference to this Figure, M1 indicates the "subordinate motor" or "slave motor" and M2 indicates the "subordinating motor" or "master motor".
The motor M2 drives the longitudinal movement of a strip 25 bearing a series of marks (not illustrated) spaced longitudinally from each other and constituted, for example, by marks similar to the marks 21 which have been described above.
The passage of the marks on the strip is detected by a reading device 26 connected to control means 27. These control means are arranged to receive the output signals from the reading device 26 and supply the electric motor Ml with a signal which is a function of the frequency of reading of the said marks, to vary the velocity of the motor Ml with time according to a predetermined law which depends on the disposition of the marks on the strip 25 and which is linked to speed of the motor M2.
From what has been stated above, it is seen that the more general inventive concept which is behind present invention is that of providing subordination between the two electric motors by feeding to the "slave motor" information formed by the reading of "marks" carried by a sliding strip driven by the "master motor".

Claims

1. System for subordinating a first electric motor (18;M1) to a second electric motor (20;M2), characterised in that it comprises:

a strip (6;25) which bears at least one series of marks (21) spaced longitudinally in predetermined manner and is driven to move in its longitudinal direction by the second electric motor (20;M2);

a reading device (22;26) fixed relative to the strip (6;25) and arranged to detect the passage of the said mark (21), and

control means (23;27) arranged to receive the output signals from the reading device (22;26) and supply to the first motor (18;M1) a signal which is a function of the frequency of reading of the said marks (21) to vary the speed of the first motor (18;M1) with time according to a predetermined law linked to the velocity of the second motor (20;M2).

2. System according to Claim 1, in which the said strip is a paper strip (2) used in a wrapping machine comprising:

means for folding the paper strip (2) which unrolls from a feed roll (3) so as to bring its two longitudinal edges (4) into contact with each other so as to form a tube (5) having an external longitudinal fin (6) constituted by the two said longitudinal edges (4) in juxtaposition;

at least one pair of wheels (9) which engage the two sides of the said longitudinal fin (6) to join the two said juxtaposed longitudinal edges (4) together and draw the paper tube (5) in its longitudinal direction;

means for transferring a series of articles (11) to be wrapped into the said paper tube (5) in longitudinally spaced positions;

a pair of transverse cutting and joining jaws (13) between which the paper tube (5) is made to pass at the output of the wrapping machine, the jaws cooperating with each other to join the walls of the paper tube (5) together so as to form a transverse fin (15) in the zone between one article and the next and to separate each wrapped article (14) from the next, these jaws (13) including two contra-rotating arms having outer working ends with circular trajectories which are substantially tangential to the paper tube (5) on opposite sides of its axis, _.

characterised in that the said first motor (18) drives the jaws (13);

the said second motor (20) drives the drawing wheels (9) for the paper tube;

and in that the said marks (21) on the strip are spaced from each other so as to determine a variation in the speed of the first motor (18) during each revolution thereof to allow:

- the working ends of the jaws (13) to be in the zone tangential to the axis of the paper tube (5) each time a zone of the tube (5) between two successive articles (11) is in this tangential zone, and

- the working ends of the jaws (13) have a peripheral velocity substantially equal to speed of advance of the paper tube in the said tangential zone.-3. System according to Claim 2, characterised in that the said marks are constituted by impressed marks (24).

4. System according to Claim 2, characterised in that the said marks are disposed on the longitudinal fin (6) of the paper tube (5).

5. System according to Claim 2, characterised in that the reading device (22) comprises photoelectric cell means.

6. Method of subordinating a first electric motor (18;M1) to a second electric motor (20;M2), characterised in that there is provided:

a strip (6;25) which bears at least one series of marks (21) spaced longitudinally in a predetermined manner and is driven for movement in its. longitudinal direction by the second electric motor (20;M2);

a reading device (22;26) fixed relative to the strip (6;25) and arranged to detect the passage of the said marks (21),

and in that there is supplied to the first motor (18;M1) a control signal which is a function of the frequency of reading of the said marks (21), to vary with time the speed of the first motor (18;M1) according to a predetermined law linked to the speed of the second motor (20;M2).

7. Wrapping machine including:

means for folding a paper strip (2) which unrolls from a feed roll (3) so as to bring its two longitudinal edges (4) into contact with each other so as to form a tube (5) having an external longitudinal fin (-6) constituted by the two said longitudinal edges (4) in juxtaposition;

at least one pair of wheels (9) which engage the two sides of the longitudinal fin (6) to join the two said juxtaposed longitudinal edges (4) together and draw the paper tube (5) along in its longitudinal direction;

means (10) for transferring a series of articles (11) to be wrapped into the said paper tube (5) in longitudinally spaced positions, and

a pair of transverse cutting and joining jaws (13) between which the paper tube (5) is made to pass at the output of the wrapping machine, the jaws cooperating with each other to join the walls of the paper tube (5) together so as to form a transverse fin. (15) in the zone between one article and another and to separate each wrapped article (14) from the next, these jaws (13) comprising two contra-rotating arms having outer working ends with circular trajectories which are substantially tangential to the paper tube on opposite sides of its axis,

characterised in that this machine further includes:

a first motor (18) which drives the jaws (13);

a second motor (20) which drives the drawing wheels (9) for the paper tube (5);

a series of marks (21, 24) located on the strip (2) and spaced longitudinally of each other in a predetermined manner;

a fixed reading device (22) arranged to detect the passage of the said marks (21, 24) and

control means (23) arranged to receive the output signals from reading device (22) and supply to the first motor (18) a signal which is a function of the frequency of reading of the said marks (21) to vary the velocity of the first motor (18) according to a predetermined law during each revolution of the latter, whereby:

- the working ends of the jaws (13) are in the zone tangential to the axis of the paper tube (5) each time a zone of the tube (5) between two successive articles (11) is in this tangential zone, _and

- the working ends of the jaws (13) have a peripheral velocity which is substantially equal to the speed of advance of the paper tube (5) in the said tangential zone. I

8. Wrapping machine according to Claim 7, characterised in that the said marks are constituted by impressed marks (21).

9. Wrapping machine according to Claim 7, characterised in that the said marks are disposed on the longitudinal fin (6) of the paper tube (5).

10. Wrapping machine according to Claim 7, characterised in that the reading device (22) comprises photoelectric cell means.

11. Wrapping machine according to Claim 7, characterised in that two series of marks are provided on the paper strip (2):

a first series of marks (21) spaced from each other in a non-uniform predetermined manner, the disposition of these marks (21) being repeated identically along each section of the strip corresponding to a rotation of a first motor (18) to allow the said variation of the speed of the first motor (18) to be achieved during each revolution, and

a second series of marks (24) uniformly spaced from each other, the reading of which is used to generate a signal indicative of the speed of the strip, that is, of the speed of the second motor (20), so as to allow the first motor (18) to follow the variations in speed of the second motor (20).