Feed advance drive mechanism especially for a packaging machine

Abstract

The present drive mechanism provides especially for a packaging machine a non-uniform drive speed for producing packings from a pair of webs of packing material drawn respectively from a pair of supply rolls. The drive motor for the feed advance of said webs of packing material is switched off, preferably when the gear means of the drive mechanism reach the greatest speed ratio. The packing tools are switched on when the drive motor is switched off and vice versa.

Description

BACKGROUND OF THE INVENTION

In packing machines which produce packages from two webs of packing material one of the webs of packing material is securely held between a pair of parallel, periodically driven roller chains having holding clamps for said web. In such packing machines the intermittent feed advance of the roller chains is conventionally provided by means of drive gears having an intermittent or interrupted turning movement.

A packing machine of this type is described, for example, in U.S. Pat. No. 3,061,984. A further example of such a packing machine is described in French Patent application No. 7,240,076. These references disclose the details of packing machines of the type in which the feed advance drive mechanism of the present invention may be employed.

In the known feed advance drive arrangements the feed advance is accomplished with a comparatively high acceleration at the start and with a relatively high deceleration at the end of the feed advance cycle. This can cause spilling where liquids or granular materials are packaged and the containers are still open.

OBJECTS OF THE INVENTION

In view of the foregoing, it is an object of this invention to provide a feed advance drive mechanism for a packing machine which will avoid the disadvantages of the prior art. More specifically the invention aims at providing a gently operating feed advance mechanism for a packing machine so that the spilling of liquid or granular materials in open containers will be avoided. In other words, the transport of filled, but still open containers must be assured without spilling.

SUMMARY OF THE INVENTION

In accordance with the invention the above objects are achieved by providing a feed advance drive mechanism for a packing machine with a non-uniform turning movement. First switching means are provided which in response to the drive means switch the motor off. A control arrangement is provided for controlling the packing tools of the packing machine. The control arrangement includes second switching means for re-energizing the drive motor after the functions of the packing tools have been completed. Incidentally, said tools include, for example, tools for forming and sealing a package.

In a particularly advantageous embodiment of the invention, the first switching means for switching the drive motor off is arranged in such a manner that the drive motor is switched off at the instant of the greatest rotational speed ratio of the gear drive. In other words, the drive motor is switched off at the instant when the ratio of the speed of an output drive shaft to the speed of the motor is the greatest.

The feed advance drive mechanism according to the invention is further arranged so that the control arrangement initiates the operation of the package forming or sealing tool means at the instance when the drive motor is switched off. Preferably, the contol arrangement switches the drive motor on again when the functions of the forming and/or sealing tools have been completed. The drive motor is preferably a braking motor.

The wheel drive means of the feed advance drive mechanism in accordance with the invention may be gears. In order to provide a non-uniform turning movement, two elliptical spur gears may be employed whereby the rotational axes of the elliptical gears are located at the focus points of the respective ellipses.

In a further embodiment of the invention, the gear drive may provide a non-uniform turning movement by employing two oval gears having central turning axes. In this arrangement, as in the arrangement employing elliptical spur gears, the rotational speed ratio is w=1.

In a modified arrangement in accordance with the invention a non-uniform turning movement may be accomplished by employing a normal circular gear having an eccentric rotational axis and meshing with an oval gear having a central rotational axis. In this arrangement a rotational speed ratio of w=2 is provided.

BRIEF FIGURE DESCRIPTION

In order that the invention may be clearly understood, it will now be described with reference to the accompanying drawings, wherein:

FIG. 1 illustrates a feed advance drive mechanism in accordance with one embodiment of the invention employing two elliptical gears, whereby the rotational axes of the gears are located at a respective focus point of the corresponding ellipses;

FIG. 2 is a plan view of the mechanism of FIG. 1 as viewed in the direction of the arrow A in FIG. 1;

FIG. 3 illustrates a modification of the mechanism of FIG. 1 employing a pair of oval gears each having a central rotational axis;

FIG. 4 is a view of a further modification of the feed advance drive mechanism of FIG. 1, employing a circular gear having an off center turning axis, and an oval gear having a central turning axis; and

FIG. 5 is a simplified circuit diagram of a control apparatus that may be employed in the arrangements of FIGS. 1 to 4.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIGS. 1 and 2 illustrate a feed advance drive mechanism in accordance with one embodiment of the invention. In this arrangement a drive motor 1, preferably a braking motor, is mounted on a suitable support 20a as shown in FIG. 1. The support 20a is part of the frame structure not shown. A sprocket wheel 4 is rigidly mounted on a shaft 5, the shaft 5 being journaled for rotation in a frame plate 20, as shown in FIG. 2. The support member 20a may be secured to the base plate 20 by any suitable means. The drive motor 1 is provided with a drive sprocket wheel 2. A roller chain 3 connects the sprocket 4 by means of the sprocket 2.

An elliptical gear wheel 6 is also secured to the shaft 5. The turning or rotational axis of the elliptical gear 6 is located at one of the focus points of the respective ellipses. A second elliptical gear 7 is affixed to a shaft 8, the shaft 8 being journaled for rotation in the base plate 20. The elliptical gear 7 meshes with the elliptical gear 6. The rotational axis of the gear 7 is also located at one of the focus points of the ellipses of this gear 7. An exchangeable circular gear 9 is removably affixed to the shaft 8. For example, a nut 8a may be provided on the end of the shaft 8 in order to exchange gear 9 for another gear of a different size. By exchanging the gear 9 different feed advance movements may be obtained depending on the size of the package to be produced.

A spur gear 13 is affixed to a shaft 15 which is journaled for rotation in the base plate 20. A support member 14a is pivotally mounted on the shaft 15 between the spur gear 13 and the base plate 20, please see FIG. 2. A spur gear 10, meshing with the exchangeable gear 9 is rotatably supported on a journal 12 carried by the support member 14a. A spur gear 11 mounted to rotate with the spur gear 10 on the journal 12 meshes with the spur gear 13.

The support member 14a is provided with an arcuate slot 14b. A clamping screw 14c extends through the slot 14b and is threaded in the base plate 20. Upon loosening of the clamping screw 14c, the support 14a may be shifted whereby the axis of the gears 10 and 11 is rotated about the axis of the spur gear 13 in order to accommodate gears 9 of different sizes. The support 14a is secured in the new position by tightening the clamping screw 14c again.

Sprocket wheels 16 are affixed to the shaft 15 on the side of the base plate 20 opposite the spur gear 13 and endless roller chains 17 are provided on the sprockets 16, whereby the sprockets 16 drive the chains 17. The endless chains 17 carry suitable clamping devices (not shown) for moving the lower web of packing material through the packing machine.

The shaft 15 is also journaled in a further base plate 20b as appears in FIG. 2. The base plates 20 and 20b are fixedly mounted as part of the housing (not shown) of the packing machine.

A lower packing web 50 from a supply roll 51 is directed, for example, by means of roller 52 to the upper side of the drive chain 17, as indicated by the arrow 53, to pass a first working station 54. The working station 54 may, for example, be comprised of suitable working tools for forming a package from the lower packing web. In addition, an upper packing web 55 is directed to the chains 17 from a supply roll 56, for example, by means of rollers 57, in the direction indicated by arrow 58. The web 55, and the web 50 after having passed the station 54, are then directed on the chain 17, with the upper web overlying the lower web 50 to a further work station 59, for example, a sealing station. The means for feeding the webs to the conveyor and the processing of the webs to form packages is conventional.

In order to obtain the necessary intermittent feed advance for the lower web of packing material, a switching cam 18 is affixed to the sprocket 4 for engaging a tripping switch in a control apparatus 19 mounted, for example, to the support member 20a. The cam 18 is so positioned that it will engage the switch in the control apparatus 19 at the instant of the greatest rotational speed ratio between the gears 6 and 7 in order to switch off the braking motor 1 at said instant time. At the same time, the control apparatus causes the operation of the tools 54 and 59 of the packing machine, for the forming of containers from the lower web of the packing material and for the sealing of the filled containers with the upper web of the packing material, if desired, after an evacuation of the containers. The control apparatus 19 comprises further switching means for switching on the brake motor 1 following the termination of the tool operation.

FIG. 3 shows a modification of the arrangement of FIGS. 1 and 2, wherein the elliptical gears 6 and 7 have been replaced by oval gears 6b and 7b. The oval gears 6b, 7b are affixed to the shafts 5, 8 at the respective central rotational axes of the oval gears.

In a still further embodiment of the invention, as illustrated in FIG. 4, the elliptical gears 6, 7 have been replaced by a normal circular gear 6c and an oval gear 7c meshing with the circular gear 6c. The circular gear 6c is affixed to the shaft 5 at an eccentric rotational axis, and the oval gear 7c is affixed to the shaft 8 at a central rotational axis.

Otherwise, the embodiments of the invention illustrated in FIGS. 3 and 4 correspond to the embodiments illustrated in FIGS. 1 and 2.

The switching circuit of FIG. 5 embodies an example of the control means 19. An ON-OFF switch 30 initially starts the motor 1, whereby the cam 18 rotates with the gear 4 until it actuates a switch 18' to open contact 31 and to close contacts 32 and 33. Opening of the contact 31 stops the motor 1. Closing of contact 32 prepares a bypass circuit 34 for restarting the motor 1 at the end of an operational cycle of the tool drive. Closing of contact 33 starts the tool drive. At the end of any tool drive cycle a cam 38 temporarily operates a switch 37 to close contact 35 and to open contact 36 whereby the motor 1 is restarted and the tool drive is stopped. The restarting of the motor 1 moves the cam 18 off the switch 18' and the motor 1 will run again until cam 18 again actuates the switch 18'. Thus, the motor 1 will run when the tool drive is stopped and vice versa.

Although the invention has been described with reference to specific example embodiments, it is to be understood, that it is intended to cover all modifications and equivalents within the scope of the appended claims.

Claims

What is claimed is:

1. In a web feed advance drive mechanism for a packing machine for forming packages from a pair of webs of packing material drawn from respective supply rolls, said packing machine being of the type having working tools for forming and sealing said webs, wherein the feed advance drive includes a drive motor, an output shaft, and means driving said output shaft by said motor; the improvement comprising wheeled drive means coupled to said drive motor and to said output shaft for operating said output shaft with a non-uniform rotational speed, first control means operatively responsive to said wheeled drive means for switching said drive motor off, and further control means responsive to a working tool in said packing machine for re-energizing said drive motor, said first control means for switching said motor off comprising means responsive to said wheeled drive means for switching said motor off at the instant of the greatest rotational speed ratio of said wheeled drive means.

2. The drive mechanism of claim 1, wherein said further control means for said working tools comprises means for energizing said working tools substantially with the switching off of said drive motor.

3. The drive mechanism of claim 2, wherein said further switching means of the control means for re-energizing said drive motor are responsive to the termination of the operation of said working tools for re-energizing said drive motor substantially when the working tools stop.

4. The drive mechanism of claim 1, wherein said drive motor is a brake motor.

5. The drive mechanism of claim 1, wherein said wheeled drive means comprises drive gear wheels.

6. The drive mechanism of claim 5, wherein said drive gear wheels comprises a pair of intermeshing elliptical spur gears each having its respective rotational axis at one of its focus points of the ellipses for providing said non-uniform rotational speed.

7. The drive mechanism of claim 5, wherein said drive gear wheels comprise a pair of intermeshing oval gears having central turning axes for providing said non-uniform rotational speed.

8. The drive mechanism of claim 5, wherein said drive gear wheels comprise a circular gear wheel having an eccentric rotational axis and an oval gear wheel having a central rotational axis, said gear wheels meshing with each other for providing said non-uniform rotational speed.

9. In a packing machine of the type comprising conveyor means, means for feeding an upper and a lower web of packing material to said conveyor, working tool means for processing said webs as they are driven by said conveyor, a drive motor, and means coupling said drive motor to drive said conveyor; the improvement wherein said coupling means comprises a pair of gears with intermeshed teeth coupled to non-uniformly drive said conveyor means, whereby the speed ratio between the rotational speed of said motor and the speed of said conveyor varies periodically, said coupling means further comprising switching means for switching said drive motor off when said ratio reaches its maximum value and wherein said packing machine further comprises means responsive to said working tool means for reenergizing said drive motor.