DE1133577B - Machine for testing containers, e.g. B. tin cans, for leaks - Google Patents

Description

The invention is directed to machines for testing containers, e.g. B. tin cans, for leaks with a can conveyor wheel to which the cans open on one side are fed and by means of automatically controlled clamping devices arranged on its circumference a compressed air passage opening provided closing plate can be tensioned gas-tight, and with each of the Passage openings leading lines on a valve body rotatable together with the conveyor wheel a valve controlling the compressed air inlet, and with in each of these lines arranged pressure-sensitive transmission devices that respond to the drop in air pressure respond to existing leaks in a container and in which the pressure-sensitive Transmission device controls an electrical circuit based on an existing Leak responds and actuates a device to eject leaky cans.

In a can testing machine which has been known for many years and in which the Can body clamped on a conveyor wheel provided with receptacles and fed by means of Compressed air are tested one after the other, the compressed air is in two chambers of a pressure sensitive Transmission device initiated, which are separated from each other airtight by a membrane and the pressure drop that occurs on the test side is used to control an ejector device used, which is operated mechanically in this machine by an advanced ram whose movement is controlled by a valve, which in turn is set by the membrane will.

Later attempts were made to improve this test, which was inadequate in practice, by using a transmission device containing a spring-loaded piston via an electrical contact, which switches on or off has controlled an electrical circuit for the ejector device. However, in order to close the normally open contact pair, a considerable pressure drop is required in the can. This test device therefore only responds reliably to major leaks. Ever But the smaller the leaks and the lower the loss of compressed air in the airtight clamped Box body is during the test path, the more uncertain the result of the test becomes.

The known testing machines work relatively slowly, so that in the presence of minor leaks, one for triggering the AusMaschine for testing containers,
e.g. tin cans, for leaks

Applicant:
The Metal Box Company Limited, London

Representative: Dipl.-Ing. H. Albrecht, patent attorney,
Berlin-Frohnau, Edelhofdamm 26

Claimed priority:
Great Britain May 8, 1958 (No. 14 820)

Arthur Leslie Stuchbery, Enfield, Middlesex,
Stanley LLewellyn Harris, High Wycombe,

Buckinghamshire (UK),
and John Alfred Drake, N. Adelaide,

South Australia (Australia),
have been named as inventors

launcher device sufficient pressure drop in the transmission device during the test path can be evoked. Nevertheless, the uncertainty of the test result remains.

The object of the invention is to improve the sensitivity of a can testing machine and to increase the test speed to even the smallest leaks in a fraction of a Second to be able to check.

Based on a testing machine in which the Pressure sensitive transmission device controls an electrical circuit, this task becomes solved in that the electrical circuit consists of an electronic detector circuit, which for influencing a pressure drop in the transmission device with a built-in there electrical measuring element is coupled, which is advantageously a pressure-sensitive capacitor.

With the machine according to the invention, about 950 containers per minute can be perfectly checked, with the machine still on the smallest leaks that are on the order of hundredths of a millimeter can be located, responds reliably, although about 15 containers are checked per second will.

209 620/145

3 4

Capacitor load cells for pressure measurements are The number of transmission devices and

known per se. They are mostly used to accommodate isolation valves corresponding to the number of cans outside Pressures set up and can lead to cuts on the feed wheel. To their power connection Pressure measurements, to name an example, are referenced by the ported carrier of the can If they are arranged in a measuring circle, a conveyor wheel rotatable with it is coaxially arranged are. For the purposes of the invention, however, they are unordered two-row electric commutators usable. of electrically conductive segments, which locally

An advantageous embodiment of the invention is assigned to fixed electrical current collectors, consists in that each transmission device in wherein the segments of a row each with the in a manner known per se, a first chamber and a flat electrode of the associated second transmission Chamber separated by a membrane and the segments of the other row are, has, wherein the membrane is electrically conductive in each case with the associated coarse display device, and a part of the capacitor is the opposite of which the pressure-sensitive electrical switch is de-electrode a flat sta- holds that can be adjusted at a distance and is in an electrically conductive connection, tionary electrode, which is in one of the chambers 15 so that the invention can be more clearly understood is arranged and connected to a supply line. based on an exemplary embodiment

Here, the first chamber is advantageously described standing with reference to the drawings, Transmission device with the passage opening in which means

in the can conveyor wheel through a line in connection- Fig. 1 is a view of part of the testing machine

dung, while the flat counter electrode is arranged in the second chamber for testing containers for leaks. FIG. 2 shows a section in the direction AA of FIG. 1,

The electronic detector - FIG. 3 expediently contains a partial view in the direction of arrow D

circle an oscillator, which is controlled by a tuned in Fig. 1,

Circle is controllable, and a frequency modulation Fig. 4 is an enlarged view of a coarse detector, the indicator for leaks with an output of the oscillator, as shown in FIG where each of the capacitors is the over- showing,

support devices with the input of the Fig. 5 is a partial view of part of a rotary

A correct circle can be connected to the generating electrical commutator, and if there is a pressure drop, the frequency of the oscillator- Fig. 6 shows a section in the direction BB of Fig. 1

gate output changes and the frequency change 30 and

by the frequency modulation detector a display Fig. 7 a current flow of electrical display means,

Indicator signal for the presence of a leaky which, when responding, indicates the presence of a leakage container causes. place in the container.

A variable capacitor with which according to FIGS. 1 and 2 of the drawings has an advantage is advantageous

Matched input circuit connected in parallel, the 35 the testing machine for containers, preferably sheet metal is set so that there are differences between the bushings, for the detection of leaks a ring thermoplastic Capacity of the first chamber and shaped support 1 with openings 2. The ringdes The container and the second chamber of the over-shaped carrier is on the edge 3 (Fig. 2) one Compensated for carrying device. The electronic wheel is attached, which has a number of spokes 4 Detector circuit can have an electromechanical 40, which with the hub 5 (Fig. 2) in one piece Device, for example an electromagnetic exist. The hub 5 is on a shaft 6 by means Relay which attaches the container ejection device to a wedge 7, and the shaft 6 runs in Latted, included, this device with the like 8 of bearing blocks 9 (Fig. 1). Output of the frequency modulation detector and with on the outer periphery of the wheel 3 is a

one of the rough indication of leaks are used- 45 ring 10 with outwardly directed teeth 11 serve pressure-sensitive device effectively strengthens that with a drive wheel that is not darverbunden is. is set, are engaged. Due to the drive it is also useful to have the compressed air inlet, the wheel rotates counter-clockwise, controlling valve a controllable separation as indicated by the arrow C in Fig. 1 is. Of the valve in which 50 support 1 leads to the transmission device consists of deformable material, Renden line arranged by one on top of the other, for example rubber, and there are means preceding Control cams can be operated and the two who work together with support 1 are in hand, Supply lines to the two chambers opens or gas closes around the opening of a container 12 (Fig. 2), and the rough indication of leaking connection with the support 1 above each in The pressure-sensitive device used for this purpose is to be brought to the opening 2 contained in it. This one in the line between the inlet valve and the purpose there is a separating valve on a screw spindle 14 arranged, which a pressure drop solidified press plate 13 (Fig. 2). The spindle 14 is in between the container and the inlet valve attached to the eye 15 of an arm 16 which is attached to a shows. The isolation valve can be a shut-off valve clamp 17, which is adjustable on the bolt 18 and in its closed position if it is the chambers 60. The bolt 18 is slidably in a bush 19 geder Transmission device separates from one another, leads which can be actuated through the edge 3 of the wheel be. goes. The other end of the bolt 18 is connected to a pressure-sensitive device for the coarse toggle, which in turn is attached to a lever 20 The display expediently contains a pressure-sensitive device, which is attached to a roller 21 at its free end electrical switch which carries 65 in the course of the feed.

the compressed air to the transmission device and this roller 21 acts with the cam surface 22

the subsequent closing of the supply valve (Fig. 1) on the machine together to release the pressure any pressure drop is addressable. plate 13 against the edge 3 of the wheel or from him

5 6

to move away to correspondingly the opening of the means of a rubber sealing ring, which is not dar-vessel to clamp on the support 1 and which is set and is located in a groove, causes.

The container can also be released from the support again. A capacitor made up of parallel plates

A socket 23 (Fig. 2) is attached to each opening 2 through the membrane 29 and the flat elec-

ordered, which sits in another socket 24, formed 5 trode 45, and the connection point 47 is with

which passes through a hole in the rim 3 of the wheel to the central conductor of a coaxial cable. One end of the gas line 25 is connected to it, which is connected by a grounded jacket tube 49

of the socket 24, and the other end of which goes through.

Gas line is related to the electrical The sensitivity of the transducer

pressure-sensitive transmission member 26, the later a change in capacity, which is caused by a

ter is only referred to as a transmitter and the change in a pressure is caused,

a first chamber 27 and a second chamber depend on the distance between the membrane 29

mer 28 is made, both by a resilient steel and the surface of the electrode 45 from.

membrane are separated from each other. The distance can be adjusted by adjusting nut 50

Mern 27 and 28 are in turn set by channels 30 15 (Fig. 2), which are threaded on the

and 31 connected to a separating valve 32, which bolt 46 is seated. If the adjustment

belongs to the class of shut-off valves and the required sensitivity is set, the

is activated when it is closed, the Kam transformer is closed.

mern 27 and 28 from each other and from a gas The arrangement of a transmitter 26 and one

line 33 to separate the valve 32 through 20 isolation valve 32, as described previously,

a channel 34 communicates. is provided for each opening 2 in the support 1. the

The isolating valve 32 has a closure 35, the gas line 33 for each opening runs radially to the wheel pressed against the openings of the channels 30 and 31 and is provided with a rotating gas supply which is movable with the wheel when the valve is in its closed position, tied together,
is as shown in FIG. This 25 The rotary part of the rotating inlet valve is a closed position is effected by means of springs 36 which are connected between ring 51, which is connected to the wheel by headless bolts 52, the closure 35 and a plate 37, one of which is shown in FIG . The shutter 35 and the plate 37 is. Each of the gas lines 33 is connected to a barrel on a pin 38, the square transverse channel 53, which is correspondingly arranged in the section, and the pin 38 is provided with a ring 51. The channels 53 are in one piece with the pivot pin 39, which is open through the inner surface 54, this inner surface going through the wall of the valve and on which one is inclined with respect to the shaft 6, that is to say is conical. Valve operating lever 40 (Fig. 1) is attached. Two The counter conical surface on a fixed ring part 55 rollers 41 and 42 are at the ends of the lever 40 has an inlet and an outlet channel, both of which are arranged as shown in FIG work with their associated curve inlet and outlet lines 56 and 57 (Fig. 1) flatten 43 and 44, which are tied to the frame. When the wheel is in the direction of arrow C on the machine. The shape of the control cam 43 (FIG. 1) rotates, so the gas lines 33 are shown in FIG. 3. each other via the channels 53 with the inlet channel

When the lever 40 is vertical, as shown in 40 each transmitter is connected. Compressed gas

Fig. 3 is shown in full lines, then that is successively fed to each transmitter and

Isolation valve 32 open. The rotation of each container is time dependent on the rotation of the

of the wheel, the roller 41 slides along the control wheel checked.

surface 43 and causes the lever 40 to rotate. When each container has been checked, it opens counterclockwise up to the horizontal 45 its isolating valve 32 under the action of the control cam 44, Position shown in dashed lines in Fig. 3 and the compressed gas in the container is turned off is, in which the isolation valve 32 is left closed when the container from the support 1 ghost. In this closed position the cam is released.

mern 27 and 28 from each other and from the gas A coarse indicator for possible leakage 33 separated. 50 digits is a pressure-sensitive electrical switch

The roller 32 of the ¹ meter 58 shown in FIG

bels 40 with the cam 44 together to and connected to the gas line 33 associated with it

Lever 40 back to the vertical position as in FIG. The coarse indicator 58 is shown in the example in FIG.

Fig. 3 shown to turn back, in which the separation is made. It consists of a gas-tight housing 59,

valve 32 is open again and the chambers 27 55 to which the gas line 33 is connected airtight

and 28 is connected to one another and to the gas line 33. The gas line 33 is divided into two parts

binds. and the housing 59 divided into three chambers,

In the second chamber 28 of the transmitter 26 is namely a chamber 60 in which the two a flat electrode 45 (Fig. 2) is arranged. You open ends of the gas line 33 and with the is for example welded or soldered by a bolt 46 made of an electrically conductive 6 ° housing Material carried, which are in a connection point 47, further a chamber 61, which is connected to the chamber 60 ends. The bolt46 goes through an insulating bushing 48 through a channel 62 and communicates with the through. A resilient steel plate 142 is between a central stop surface 63 on the wall, which the electrode 45 and the housing of the transmitter separating the chamber 61 from the chamber 60, arranged on and electrically isolated from it. The 65 has, and also a chamber 64, which of the Spring 142 creates a resilient, electrically isolated chamber 61 through a membrane 65 made of electrically Attachment of the electrode 45. A gas-tight insulating material is separated. The Chamber 64 The end around the electrode holder 46 is under atmospheric pressure. A contact

7 8

bolt 66 is in a central hole that can be put in each opening 2 of the wheel as soon as it is the membrane 65 is, the end of the container feed path 89 passes by means of a nut 67, fastened, with washers 68 the gas-tight connec- As already mentioned, the opening of each container Secure the connection to the bolt 66. The discs 68 are gas-tight with the deformable support 1 through the electrically conductive, and the electrical connection 5 associated pressure plate 13 is connected, to the bolt 66 is by a spring 69 to a For testing a container 12, which is just about

Connection 70 made, which is located through a socket 71 of an opening 2 of the wheel, must immediately is isolated from the housing 59 of the gross leak detector. the roller 21 of the relevant opening with the A wire connected to terminal 70 leads control surface 22 to come into action and cause through the grounded tube 49, which with the Ge io the pressure plate 13 houses against the support 59 is connected through. The force that moves the container 12 into gas-tight contact exerted by the spring 69 on the membrane 65 is brought with the support 1. After the wheel is such that when the chambers 64 and 61 has rotated a predetermined angle, that is Both are under atmospheric pressure, the channel 53 for the gas line 33 of this opening, over Nut 67 touches the stop 63 and thereby the 15 in which the container is located is connected brought to earth with the connection 70 with the inlet channel which is connected to the supply, but that when pressurized gas is connected in the chimney line 56, so that compressed gas mer61 is present, the membrane against which the line 33 is fed. The isolation valve 32 Spring 69 is moved and the contact of nut 67 is open at this time and the pressurized gas is is interrupted with the stop 63. 20 the chambers 27 and 28 of the transformer 26 and

The wires from the transmitters and through the gas line 25 are fed to the container 12. Gross leak detectors 58 come with a once the channel 53 has passed the inlet channel electrical commutator 72 (Fig. 2), which is connected to the gas pipes and those to the opening the ring 51 is connected by bolts 73, so voltage 2 connected devices abdaß from the gas supply it is arranged coaxially to the wheel. In Fig. 5, 25 is cut and contain that under the pressure the commutator shown in a partial view. He's standing gas.

Has two commutator rings with electrical conduction If there is no gross leak in the container

tend segments 74 and 75 and a ring 76, which is a rapid pressure drop which establishes the connection to the earth. The seg- ment would effect the diaphragm 65 (Figs. 2 and 4) Elements 74 and 75 and the commutator ring 76 can 30 the coarse display device 58 against the wire for example from the rhodium-plated coupling of the spring 69, so that the fer exist. Each of the segments 74 is with the zen contact between the stop surface 63 and the central line of the coaxial cable connected, the nut 67 is interrupted. However, if a with the connection 47 of the transmitter for one of the larger leaks in the container Openings is in communication. Each of the Seg- 35 is, for example due to a poorly executed mente 75, which is on the same radius of the commu seam or in that the container happens to be tators as a corresponding segment 74 is located, should not have a bottom, so the pressure in the connected to the wire which suddenly dropped from the coarse display line 33. While the feeding device 58 of the corresponding opening valve 51 to 55 is closed, the is bound. The commutator ring 76 is with the 40 nut 67 the stop 63 touch so that the Housing 77 of the commutator connected. Terminal 70 is grounded.

On a bracket 78, which is pre-fastened to the fixed part 55 after turning the wheel around another there is a support 79 (Fig. 6) for three fixed angles, the roller 41 runs (Fig. 1 and 3) tionary electrical current collector, which consists of one against the stationary control surface 43, and the suitable separation Material, e.g. B. a gold alloy, valve 32 will be created by the movement of the roller and each run on a commutator ring. long the control surface closed. During the period The current collectors are shown in detail in FIG. 6 between the closing of the supply valve and and consist of current collector parts 80, when the isolating valve is closed, the pressure in 81 and 82, which are located in insulating sockets 83 in the chambers 27 and 28 of the transformer 26 Support 79 lead. The parts 80, 81 and 82 stand 50 have balanced, and if so then the isolation valve under the pressure of the springs 84 and being closed by the pressure in the this in contact with the commutator rings 74, 75 chamber 28 similar to that in the container 12 and 76 held, the electrical connections being. The wheel continues to turn, and if there is one gen between the pantographs to the leakage in the container, so the Keys 85, 86 and 87, by means of springs 84, create pressure in chamber 27 while the wheel is advanced will. The electrical lines that rotate from fall, so that the diaphragm 29 is adjusted the connections 85 and 86 come, and so are the capacitance between the membrane 29 and in a tube 88. They lead to electrically operated the flat electrode 45 being changed. In the meantime Display means which indicate the presence of an un- the wheel reaches the position in which the segments 74 tightness in a container, which is located in the test 60 and 75 of the commutator, which accordingly with position is displayed. The details of the connection 70 of the pressure sensitive switch are described with reference to FIG. The connection and the connection 47 of the transformer are connected Final 87 is due to earth. which is the opening over which the container

The wheel rotates in the direction of arrow C of the ter 12 is in the test position, is associated with the Fig. 1, and feed devices for the 65 current collectors 80 and 81 come into contact, Holders, which are known per se, contain an In this moment there is a measurable change in the container feed track 89. A star wheel 90 is pre-electrical capacity of the transformer available, seen to put one container in position at a time. If there is a leak in the container,

9 10

is available as soon as a connection of the Stromabneh- anode of the tube Vl is the primary coil 95 one

mer80und81 connected to the corresponding segments of transformer Tl. Parallel to this

of the commutator is established, the electrical primary coil is connected to a capacitor 96. Both together

address actuatable means, as men below form a resonance circuit. The anode of the

described, indicate or cause that the loading 5 tube Vl is also via a capacitor 97

holder must be ejected. with the end of a coil 98 of a coupling transmission

If the wheel continues to rotate, the isolating former T 2 is connected. The other coil 99 this one

valve 32 by running up the roller 42 on the transformer is through a CR coupling circuit

Control surface 44 open, and the container can be connected to the control grid of the tube Vl , and

by a container removal device 91 (Fig. 1), io also parallel to the coil 99 a fixed condenser

which is known per se, from the support removed sator 100 and a variable capacitor 101

will. This unloading device 91 includes an arranged. The parallel capacitor plates,

container ejection opening, not shown. through the membrane 29 and the flat elec-

If a container does not have any leaks, the coarse display device remains open, 15 and there is no pressure drop as a result of an uncoil 99 through the commutator when the test wheel is leak-proof the membrane 29 of the transmitter 26 rotates. The effective initial capacity in which the grid circle would be adjusted during the rotation of the wheel is therefore the sum of the capacity of the parallel transfer plates so that the container through the device 91 has not been adjusted when the membrane 29 of the dispensing station for non-leaky containers has not been adjusted is, and the deal is taken. capacitance of the capacitors 100 and 101.

As soon as compressed gas enters the container by setting the variable condenser 101, the supply valve and the isolating valve at the beginning of the grid circuit can be tuned so that it comes with a test operation, so a work of the same frequency as that of the tuned by the supplied compressed gas is done, 25 anode circuit is in resonance. The variable because it is already in the container, in the gas condenser 101 is preset to a value, lines and gas in the transmitter that compresses the differences between the thermal capacities, and thereby a certain capacity of the first chamber 27, the transmitter 26 Develops warmth. The work done in compressing the and the container 12 and the thermal capacity of gas in the container 12, in the gas lines 25, 30 of the second chamber 28, and in the chamber 27 will be greater as a result of this difference in thermal capacities than that which when the gas contained in the chamber 28 is compressed, a movement of the membrane 29 is effected, so that a drop in the capacity of the parallel more heat in the container 12 and in the chamber 27 causes the capacitor plate in the transmitter 26, and than in the chamber 28 is generated. Furthermore, this drop in capacitance is compensated for by the thermal capacitance of the device connected to one side of the membrane 29 by releasing a predetermined amount of capacitance in the lattice circle of the tube VI membrane. To be different from the one that communicates with the other for this purpose it is expedient to use a variable side of the membrane, and the air condenser with a trimmer condenser to use surface area for cooling the container 12 40, which is in parallel as the variable and the Pipeline 25 is much larger than that condenser 101. The secondary winding 102 of the for cooling the chamber 28. For this reason transformer Tl is by means of a condenser 103, temperature differences, although the pressure in and is matched to the control grid of a Pentden chambers 27 and 103 28, after the separating ode V 2 , which is connected to the adjacent valve 32, will be the same, after that 45 circle a phase change frequency modulation tending to create pressure differences between detectors of a known type. The brake or the chambers 27 and 28 cause, even if the safety gate of the tube V 2 is by means of a CR- there is no leakage in the container. Coupling circuit Lest connected to the anode of the oscillator tube Vl by these differences an initial, and an anode charging resistor 104 take a container located in order loading 50 high value is is forfeited to the anode of tube F 2, they are compensated for by an elec - bound. A change in the frequency of the oscillator trically actuated device, which appears as a drop in the direct current output carrier26 through the commutator 72 in connection with voltage at the anode of the tube V 2. A filter is composed of a resistor 105 and circuit

The aforementioned electrically operated device 55, a capacitor 106, connects the anode of the

is shown in Figure 7 of the drawings. It contains tube V 2 with the grid of a cathode amplifier

an electromagnetic relay 92, which connects the tube V 3, and the output from the cathode

container ejection device actuated. amplifier tube V 3 is through a grid resistance

The relay 92 is on the one hand with a raised stand 107 with a grid Gl of a double voltage source HT, on the other hand connected via a 60 triode V4 , which with its adjacent circuit, the tubes Vl, V 2, V 3 and V 4 contains a Schmidt circuit Trigger circuit known with a line 94 in connection, which in turn forms the type.

with the current collector 80 and accordingly the triode, which the grid Gl and the assigned

with each of the transducers 26 successively contained in the hearing anode A1 is normally conductive

Connection. 65 and is equipped with a neon indicator lamp 108

The tube Vl forms with the one connected to it, which indicates the state of the trigger circuit.

This circuit has a matched anode and shows. The other anode A 2 of tube V 4 is over

tuned grid working oscillator. With one resistor 109 with the coil of the relay 92

tied together. The cathode of the cathode amplifier V3 is connected to the current collector 81 of the commutator (FIG. 6) via a resistor 110. In this way, the coarse display devices 58, which are indicated schematically in Fig. 7, are in turn connected to the grid Gl when the test wheel rotates.

The values of the components that form the trigger circuit are chosen so that when the voltage of the Grid Gl falls below a predetermined value, the circuit responds and the relay 92 is energized. The breakover threshold of Schmidt's trigger circuit is arranged in such a way that the circuit only operates when a drop in potential is responsive to either a change in the frequency of the oscillator as a result of the displacement of a membrane 29 due to the presence of a leak in a container or from the connection of a closed coarse detector 58 to the grid Gl. on in this way there are other, as it were, spurious changes in the frequency of the oscillator that arise can, if the transmitters are successively connected to the line 94, with respect to the triggering of the Schmidt trigger circuit is ineffective. The relay 92 shows when it responds, the presence of a leak in a container and in turn controls the container ejection device, when the presence of a leak is indicated.

In order to also be able to test containers of different sizes, the variable capacitor 101 can be set to a predetermined value for each container size. This setting is the only one that is necessary in the circuit when changing from one container size to another when testing. It should be readily understood that when testing small containers, either the speed of testing or the testing accuracy can be increased over that of testing large containers.

The relative lengths of time for gas admission and equilibration, testing and removal and feeding a vessel behave roughly like 4:10: 3, and the testing machine according to the invention is capable of handling approximately 950 containers with leaks on the order of 0.05 mm Check diameter per minute.

Compressed air is usually used to test the containers, but it is also possible when there are special requests to use any suitable gas.

The rollers 41 and 42 (Figures 1 and 2) for each opening can also be replaced by a single roller which is arranged on a lever 40. These only role would then with both control surfaces 43 and 44 for opening and closing the Separating valve 32 work together.

In the preceding description, the feed valve is intended to be common to all transmitters 26 be. It is, however, possible, if desired, to connect to the pressure generator through a Stuffing box and a hole drilled in the wheel shaft 6, and so to an annular part of the Establish main gas supply to each transmitter, each of which has a transmitter cam controlled feed valve is provided. With this arrangement, the coarse display devices for Leaks with a tap between the isolating and supply valves of the corresponding Transformer connected. This maintains the gas pressure uninterruptedly up to each supply valve.

Claims (11)

PATENT CLAIMS: 1. Machine for testing containers, e.g. B. tin cans, for leaks with a can conveyor wheel, to which the cans open on one side are fed and can be tensioned gas-tight by arranged on its circumference and automatically controlled clamping devices against the end plate provided with a compressed air passage opening, and with lines leading to each of the passage openings a valve body, rotatable together with the feed wheel, of a valve controlling the compressed air inlet are connected, and with pressure-sensitive transmission devices arranged in each of these lines, which respond to the drop in air pressure in the event of leaks in one of the containers and in which the pressure-sensitive transmission device controls an electrical circuit, responsive to an existing leakage and operates a device for the extraction of leaking cans, characterized in that the electrical circuit of an electronic detector circuit (92-110) which which is coupled to an electrical measuring element (29, 45) installed there for influencing by a pressure drop in the transmission device (26). 2. Machine according to claim 1, characterized in that the electrical measuring element (29, 45) is a pressure sensitive capacitor. 3. Machine according to claims 1 and 2, characterized in that each transmission device (26) in a manner known per se, a first chamber (27) and a second chamber (28) which are separated by a membrane (29), and that the membrane (29) is electrically conductive and is a part of the capacitor, the counter electrode of which is a flat, adjustable distance, stationary Electrode (45) is arranged in one of the chambers and connected to a supply line is. 4. Machine according to claim 3, characterized in that the first chamber (27) of the transmitter with the passage opening (2) in the can conveyor wheel through a line (25) in connection stands and that the flat counter electrode (45) is arranged in the second chamber (28). 5. Machine according to one of claims 1 to 4, characterized in that the electronic detector circuit contains an oscillator (F1) which can be controlled by a tuned circuit, and a frequency modulation detector (V 2) which is connected to an output of the oscillator and that each of the capacitors (45, 29) of the transmission devices (26) can be brought into connection with the input (94) of the tuned circuit and changes the frequency of the oscillator output when the pressure drops, the frequency change being an indication signal for the presence of one by the frequency modulation detector causes leaky container. 6. Machine according to claim 5, characterized in that a variable capacitor (101) is connected in parallel with the tuned input circuit, which is set to have differences between the thermal capacity of the first chamber (27) and the container (12) and the second chamber (28) of the transmitter (26) compensated. 7. Machine according to claim 5 or 6, characterized in that the electrical detector circuit an electromechanical device (92), for example an electromagnetic relay, which actuates the container ejection device, this device (92) with the output of the frequency modulation detector and with one of the rough indicators of leaks serving pressure sensitive device (58) is operatively connected. 8. Machine according to one of claims 1 to 7, characterized in that in addition to the the valve (51 to 55) controlling the compressed air inlet, a separately controllable isolating valve (32) in the line leading to the transmission device (33), which is passed through successive Control cams (43 and 44) can be actuated, is arranged and the two supply lines (30, 31) close the two chambers (27, 28) opens and closes and that the pressure-sensitive device (58) is arranged in the line (33) between the inlet valve and the isolation valve, the one Indicates pressure drop between the container (12) and the inlet valve. 9. Machine according to claim 8, characterized in that the isolating valve is a shutoff valve is and in its closed position when it the chambers (27 and 28) separates from one another, can be actuated. 10. Machine according to claim 8 or 9, characterized in that the pressure-sensitive Device contains a pressure-sensitive electrical switch, which in the course of the feed the compressed air to the transfer device (26) and the subsequent closing of the supply valve (51 to 55) is responsive to any pressure drop. 11. Machine according to claims 1, 3 and 10, characterized in that the one with openings provided carrier (1) of the can conveyor wheel a rotatable with it, arranged coaxially electric commutator (72) with two rows of electrically conductive segments (74, 75), which fixed electrical current collectors (80, 81) are assigned, and that the Segments (74) of the one row each with the flat electrodes (45) of the associated transmission devices and the segments (75) of the other row each with the associated coarse display device (58), which contains the pressure-sensitive electrical switch, are in electrically conductive connection. Considered publications: German Patent No. 584,400; British Patent No. 3788 of 1905; "Archives for Technical Measurement", 1932, November, sheet V 132-5. For this purpose 2 sheets of drawings