Pneumatic device for controlling the filling of a container

Abstract

Filling head for containers with a liquid is provided with separate air-supplied duct having lower end terminating at desired level of liquid in container. When liquid level rises above that end, flow of air is cut off and this causes actuation of valve cutting off in flow of liquid.

Description

In order to stop the filling of containers such as bottles, for example, when these are being filled by a machine, it has already been suggested that devices be used which comprise, either separately or in combination, members resting on the necks of the bottles and means for creating a pressure or partial vacuum inside the bottle during filling. Such means cannot be used when the bottles to be filled have relatively flexible walls, as is the case with bottles made of a plastic material.

It has also been suggested that a tube be used which permits only a small amount of air to flow therethrough. This tube is positioned substantially parallel to the filling tube. When the level of the liquid in the bottle reaches a predetermined level, the tube through which the compressed air escapes has its orifice obstructed by the liquid filling the bottle and this produces a signal which actuates control means to stop the flow of liquid. In such devices, difficulty usually results from the fact that the control means utilizing the level-indicating signal to stop the flow of fluid ordinarily utilize fluidic techniques in which, for example, the variation of a small flow of air which acts as a pilot flow produces a variation in a large flow of air or a modification in a circuit supplied by the large flow of air. However, in fluidic techniques it is necessary to use air which has been extremely well filtered so that the dimensions of the dust particles therein are less than about 0.3 microns. This limitation leads to substantial expense, which considerably increases the cost of the control devices in question.

It is the object of the present invention to provide a device utilizing an air supply tube positioned substantially parallel to the liquid-admitting tube through which the container is filled. The air supply tube, called a level detecting probe, is supplied with relatively unpurified air, which may contain dust particles as large as 15 to 20 microns in diameter. This probe makes it possible to control the inlet valve of the liquid supply means with a simple pneumatic device which is relatively inexpensive.

The present invention accordingly relates to a new article of manufacture which comprises a pneumatic device for controlling the filling of a container, said device having at least one filling head comprising a tube through which the filling liquid is introduced into the container, and a level detecting probe through which a small flow of air is introduced into the container, the orifice of the probe being situated at a predetermined level at which filling of the container is to be stopped, the liquid supply tube being equipped with a valve controlling the liquid supply, and control means being provided between said valve and the level detecting probe. This device is characterized by the fact that the control means comprises a first valve supplied with compressed air, said first valve supplying in parallel a detector for the presence of the container which is open when there is no container and closed in the contrary case, and the first end of the movable rod of a pneumatic distributor supplied with compressed gas. In parallel at the outlet of the pneumatic distributor is a pneumatically controlled flap valve for controlling the supply of liquid from the distributing head and a pneumatic amplifier the output of which is connected to the second end of the pneumatic distributor rod. Finally, there is a flow-limiting device the output of which supplies the control for the said pneumatic amplifier. Preferably there is also a second valve comprising a first supply connected to the flow limiter and a second supply connected to a source of compressed gas, the output of this second valve supplying the level detecting probe from one or the other of its two sources.

In a preferred embodiment of the invention the device according to the invention is supplied with compressed air from the output of an air purifying station. This station comprises at least one expansion valve and one filter. The second valve of the device comprises in addition to the supply connected to the flow limiter means a pneumatic supply identical to that of the distributor and the first valve. The flow limiting device consists of an adjustable needle and a stationary diaphragm. The pneumatic distributor is a three-way slide valve or a five-way valve in which one outlet is permanently closed when a five-way distributor is used together with a single acting hydraulic jack. The first and second valves of the device are mechanically controlled.

It is a further object of the present invention to provide as a new article of manufacture a machine for filling containers such as plastic bottles, which machine comprises means for displacing the containers to be filled characterized by the fact that said machine comprises at at least one point a distributing head inserted in a device such as the one which has just been described.

In a preferred method of operation the machine comprises mobile means for continuously advancing the containers to be filled, the first and second valves of the device being fixed to the movable member so as to move with it and being mechanically actuated by stationary cams fixed to the frame of the machine. The first valve is open for a short time before the step of filling the container filled by the distributing head associated with said valve. The second valve is operated by a cam fixed to the frame of the machine so as to connect the detecting probe and the direct supply of compressed gas after the end of the filling step.

It will be seen that the device according to the invention utilizes only conventional pneumatic controls and consequently makes it possible to use relatively impure compressed air. Moreover, this device may be used for all sorts of liquids, even when said liquids have a tendency to stop up the tube constituting the level detecting probe. In effect, after each filling of the container, action on the second valve makes it possible to blow a substantial amount of air through the tube constituting the level detecting probe so as to assure its cleaning and eventual unstopping. Finally, when the container to be filled is defective, for example, if it has a hole in it, the second valve of the device may be manually actuated so as to immediately stop the filling of liquid by closing the flap valve of the device.

In order that the object of the invention may be better understood and to more explicitly explain the operation thereof, a preferred embodiment will now be described, purely by way of illustration and example, with reference to the accompanying drawings in which:

FIG. 1 is a circuit diagram of the control means according to the invention;

FIG. 2 schematically illustrates a device according to the invention with the different components in the position which they occupy when there is no bottle in a position to be filled;

FIG. 3 represents the device of FIG. 2 when, after location of the bottle, the first valve has been actuated to begin filling;

FIG. 4 represents the device of FIG. 2 when the bottle is full;

FIG. 5 represents the device of FIG. 2 after filling has been completed when a glob blocks the level detecting probe, the position shown in broken lines being that taken by the components of the device when the second valve is actuated to clean the level detecting probe; and

FIG. 6 is a schematic plan view showing a machine for filling bottles utilizing the control device illustrated on FIGS. 2 to 5.

In the drawings, reference numeral 1 indicates a conveyor chain for carrying bottles 2 made of a flexible plastic material. The bottles 2, which are to be filled with a liquid to a predetermined level, arrive at 3 at a level beneath the level to which they are to be filled. The machine according to the invention is a circular machine of a conventional type, the rotatable cylinder 4 of which carries on its periphery a series of distributing heads. The direction of rotation of the cylinder, the details of which have not been illustrated in the drawing, is indicated on FIG. 6 by the arrow F. When the bottles 2 are brought by the machine from point 3 to point 5, each bottle which has come into alignment with a distributing head, moves parallel to the axis of the machine so that the liquid supply tube of the distributing head adjacent to the bottle 2 in question comes into position inside the neck of the bottle 2.

Each distributing head comprises a supply tube 6 through which the liquid for filling the bottles 2 is introduced into the bottles. The tube 6 of each distributing head is connected to a ball valve 7 through a duct 6a. The ball valve 7 is supplied with liquid through a duct 8. The ball valve 7 consists of a body 9 enclosing a ball 10 which seals against an annular seat 11, the ball being biased against the seat 11 by a spring 12. A contact member 13 acts on the ball 10 and urges it in a direction opposite to that in which it is biased by the spring 12. The contact member is controlled by a piston 14 subjected to air pressure which reaches the valve 7 through a duct 15.

Each distributing head positioned around the cylinder 4 also comprises, in the central part of tube 6, a tube 16 which opens at a level slightly higher than that of the end of the tube 6. The tube 16 constitutes the level detecting probe associated with the tube 6. When the bottle is completely full its position with respect to the tube 6 is such that the level of liquid is above the end of the tube 16 and blocks the latter tube. A bottle centering device 17 is associated with the tubes 6 and 16. The centering device 17 is slidable with respect to the frame which supports the tubes 6 and 16 and comprises a centering ring 18 the central orifice of which is shaped to come into position around the neck of the bottle 2 when the bottle rises toward the tubes 6 and 16 between the points 3 and 5 of the machine. When the bottle 2 is in position near the end of its vertical course, it pushes up the centering ring 18 which, through the rod 19, closes an orifice 21 leading to a duct 22. The closing of the orifice 21 results from the pushing of an elastic circular valve member 20 fixed to the rod 19 against a block 23 on the frame of the distributing head. The rod 19 is mounted to slide vertically in the block 23.

A control device is associated with each distributing head mounted on the rotating cylinder 4 and a diagram of this control device is shown on FIG. 1. This device comprises a first valve 24, the inlet 25 of which is supplied with compressed air. The compressed air is furnished from a purification station comprising an expansion valve 26 and two filters 27a, 27b. (See FIG. 2.) The filter 27a is supplied through a duct 28 from a source of compressed air and the outlet of the purification station is through the duct 29 at a pressure between 2.8 and 4 bars. The purification is sufficient to limit the average diameter of the dust in the air to less than 30 microns. The first valve 24 is connected to supply in parallel the duct 22 and a pneumatic distributor 30 comprising a slidable spool. The inlet 31 of the distributor 30 is connected to the duct 29. The outlet of the distributor 30 is a duct 32. The spool of the distributor 30 may be pushed in one direction by the application of compressed air to its first end through the duct 33 and, in the opposite direction, by the application of compressed air to its second end through a duct 34. The duct 32 supplies in parallel the inlet 15 of the valve 7 and the inlet 35 of a pneumatic amplifier 36, as well as a flow-limiting device 37. As shown in FIG. 2, the flow-limiting device 37 comprises in series an adjustable needle-type flow limiter 44 and a stationary diaphragm 45. The pilot duct 38 of the amplifier 36 is connected to the output of the flow-limiting device 37 and the output 39 of the amplifier 36 is connected to the duct 34. The output of the flow-limiting device 37 is also connected to the first input 40 of the second valve 41, the second input 42 of which is connected to the duct 29 through a flow limiter 63. The output 43 of the second valve 41 is connected to the level detecting probe 16.

The pneumatic amplifier 36, of a conventional type, comprises a first elastic membrane 46 which is adapted to close an orifice 47. The chamber 48 defined between the membrane 46 and the orifice 47 is connected to the open air by vents 49. In the body of the amplifier 36 is a movable piston 50 connected to a second membrane 51. The movable piston 50 is pierced by an axial duct 52 and carries at its lower end a valve member 53 cooperating with a valve seat 54 fixed to the housing. Beneath the valve member 53 is the input duct 35. Midway of the piston 50 the housing of the amplifier 36 carries the output duct 39. The pilot duct 38 is connected to a chamber 55 formed on the side of the membrane 46 remote from the chamber 48.

The operation of the control device according to the invention will be easily understood. When a bottle 2 is brought by the chain 1 into alignment with a distributing head carried by the cylinder 4 it is subjected between the points 3 and 5 of the machine to a vertical translational movement which brings it into contact with centering ring 18, which closes the duct 22 by closing the valve 20. When the machine continues to rotate the control arm 24a of the first valve 24 comes into alignment with the point 56 of the machine and into contact with a cocking cam. The initial position of the valve 24 corresponds to the absence of any connection between the input 25 and the output of the valve. The action of the cocking cam establishes this connection. If no bottle is in alignment with the corresponding distributing head the compressed air from the duct 25 is divided evenly between the ducts 33 and 22 and the pressure of air in the duct 33 is then insufficient to actuate the distributor 30. On the contrary, if the duct 22 has been closed as a consequence of the presence of a bottle 2 in alignment with the distribution head, the spool of the distributor 30 moves to establish a connection between the duct 31 and the duct 32 where this did not previously exist. The supply of compressed air from the duct 32 results in bringing compressed air to bear on the piston 14 and opening the valve 7 by exerting pressure against the ball 10. The duct 6 is thus supplied and filling of the bottle 2 begins. The bottle is filled until it reaches point 57 of the machine, that is to say, up to the moment at which the level of the liquid in the bottle becomes sufficiently high to close the orifice in the level detecting probe 16. When the duct 32 is supplied, the flow-limiting device 37 makes it possible to simultaneously fill the ducts 38 and 40. The second valve 41 then connects the duct 40 to the duct 43 so that a certain amount of air flows through the detecting probe 16 and escapes through the neck of the bottle. Under these conditions, the pressure of compressed air exerted on the membrane 46 of the amplifier 36 is insufficient to bring this membrane against the orifice 47 so as to close it. In this case the compressed air supplied to the amplifier 36 through the duct 35 compresses the valve member 53 against its seat 54 so that the output duct 39 is not supplied with compressed air. Some air therefore escapes through the axial duct 52 and the vents 49. On the contrary, when the escape of air through the detecting probe 16 is prevented after complete filling of the bottle, the pressure of compressed air in the duct 38 increases so that the membrane 46 closes the orifice 47. This produces on one side of the membrane 51 a counter-pressure which balances the pressure of the compressed air supplied through the duct 35. This opens the valve 53, 54 so that the duct 39 is supplied. The duct 34 is then supplied with compressed air which actuates the distributor valve 30 so that the connection 31-32 is closed. It follows that the duct 15 is no longer supplied so that the ball 10 biassed by its spring 12 closes the valve 7 which stops the flow of liquid into the bottle 2. Simultaneously the blowing of air through the probe 16 is stopped which prevents the formation of bubbles in the liquid within the bottle.

When the cylinder 4 continues its rotation in the direction of the arrow F the distribution head comes into alignment with the point 58 of the machine, and an uncocking device may be provided at this point which is not shown in the drawings of FIGS. 2 to 5. This device makes it possible, through a complementary pneumatic distributor, to temporarily supply the duct 38 to actuate distributor 30. The function of this uncocking distributor is to assure that the last step in the operation takes place even if the liquid has not reached a level desired in the bottle, or even if the level detector has not operated, in which case the bottle would have overflowed.

Between the point 58 and the point 59 of the machine the filled bottle is translated in a vertical downward direction so as to disengage it from the tubes 6 and 16 and remove it by means of the conveyor chain 1 around the driving drum 60. At the point 61 on the path of travel of the distributing head, the mechanical control 41a of the second valve 41 comes into contact with a blowing cam which establishes a connection between the ducts 42 and 43 during the entire time the distributing head is moving between the point 61 and 62 of the machine. A substantial amount of air is thus blown into the detecting probe 16, the amount of which may be regulated by means of a pressure regulator 63 positioned on the duct 42. This energetic blowing serves the purpose of cleaning the end of the detecting probe so as to avoid its blockage even when filled with thick liquids or to dry it rapidly so as to ensure its proper operation as a detector. The distribution head then arrives again at point 3 of the machine and comes into position above an empty bottle 2.

It should be noted that the control device which has just been described and the corresponding filling machine are relatively inexpensive. The different components utilized make it possible to work with air which has not been highly purified. The level detection is carried out at a very low pressure since the air which passes through the probe is delivered by the flow limiting device 37. It follows that this detection takes place under very good conditions and, in particular, that it is not influenced by the speed of movement of the distributing head, by the inside wall of the neck, or by the flow of air leaving the bottle because of the injection of liquid. Moreover, all the apparatus of the control device according to the invention associated with each of the distributor heads of the machine according to the invention may be grouped within a small casing which is rapidly interchangable in case of trouble. Finally the level control device does not require any sealing contact with the neck of the bottle and does not produce any partial vacuum in the bottle so that it may be utilized for filling bottles having flexible walls such as those made of a plastic material.

It will of course be appreciated that the embodiment which has just been described has been given purely by way of illustration and example and may be modified as to detail without thereby departing from the basic principles of the invention.

Claims

What is claimed is:

1. In a pneumatic device for controlling the filling of containers, said device comprising at least one filling head including a liquid supply tube for introducing liquid into a container and a level detecting probe through which a flow of air is simultaneously introduced into said container, said probe having an opening positioned near a predetermined level to which a container in filling position relative to said head is to be filled, said liquid supply tube being provided with a liquid control valve controlling the flow of liquid therethrough, and control means connected between said liquid control valve and said level detecting probe, the improvement according to which said control means comprises:

a detector valve responsive to the presence of a container in said filling position and a first gas control valve connected to supply gas to said detector valve,

a pneumatic distributor having a control member therein which controls the flow of gas through said distributor, the output of said distributor being connected to actuate said liquid control valve and the output of said first gas valve being connected to said distributor at one side of said control member, the pressure supplied to said distributor from said first gas valve being insufficient to operate said control member to open said liquid control valve when said detector valve is open, but sufficient to do so when said detector valve is closed,

a pneumatic pressure regulator having a main inlet, a main outlet and a control inlet the application of pressure to which increases the flow between said main inlet and main outlet, and said main inlet connected to the output of said pneumatic distributor and its main outlet connected to the other side of said control member,

a flow-limiting device connected between the output of said pneumatic distributor and the control inlet of said pneumatic pressure regulator,

a second gas control valve having a first input connected to said flow-limiting device and a second input connected to a source of compressed gas, the output of said second gas-control valve being connected to supply said level-detecting probe only with gas from said flow limiting device when said second gas valve is in a first position and only with gas from the second input of said second gas control valve when said second gas control valve is in a second position,

whereby whenever flow from said second gas control valve input through said second gas valve is blocked by closure of the opening in said probe or by location of said second gas valve in its second position, the resulting pressure in the second input of said second gas control valve is applied to the control inlet of said pneumatic pressure regulator to increase the output pressure applied through said regulator to said other side of said control member, thereby reversing the position of said distributor to close said liquid supply valve.

2. Device as claimed in claim 1 connected to be supplied with compressed air from the output of air purifying means comprising at least one expansion valve and at least one filter.

3. Device as claimed in claim 1 in which the second input of the second gas control valve is derived from the same source of supply as that of the distributor and first gas control valve.

4. Device as claimed in claim 1 in which the flow-limiting device consists of an adjustable needle and a stationary diaphragm.

5. Device as claimed in claim 1 in which the first and second gas-control valves are mechanically actuated.

6. Machine for filling containers made of plastic material which comprises means for displacing containers to be filled and at least one device as claimed in claim 1.

7. Machine as claimed in claim 6 which comprises a movable member for continuously displacing the containers to be filled, the first and second gas-control valves of the device being mounted on the movable member to travel therewith and being mechanically actuated by stationary cams mounted on the frame of the machine.

8. Machine as claimed in claim 6 in which the first gas-control valve is open for a short time before said filling position is reached.

9. Machine as claimed in claim 6 in which the second gas-control valve is actuated by a stationary cam mounted on the frame of the machine to connect the detecting probe directly to a supply of compressed gas after a container has left said filling position.

10. Device as claimed in claim 1 in which the pneumatic distributor is a slide valve having three ports or one having five ports in which one outlet is closed, and one port is connected to a single-acting hydraulic jack.