GB2259507A

GB2259507A - The tightening of closures

Info

Publication number: GB2259507A
Application number: GB9119278A
Authority: GB
Inventors: Steven Midgley
Original assignee: C M MICRODAT Ltd
Current assignee: C M MICRODAT Ltd
Priority date: 1991-09-10
Filing date: 1991-09-10
Publication date: 1993-03-17
Anticipated expiration: 2011-09-10
Also published as: GB2259507B; GB9119278D0

Abstract

An apparatus for tightening closures 24 eg pressure valves or spears, to a predetermined torque in containers 11. The apparatus comprises a motor 2 with a variable speed controller 1, a driving head 3 driven by the motor 2 and shaped to engage lugs 25 in the closure 24 and torque sensing means 6, eg a strain gauge, for sensing the reaction torque of the motor 2. When the sensed torque reaches a predetermined level the motor 2 is stopped. In use a container 11, eg a beer keg, is delivered by conveyor to apparatus which detects its presence, by a position switch. The conveyor is then lowered and the container is held by support bars 10 and gripped firmly by retaining arms 9 which approximately centres the container below driving head 3. Driving head 3 is then lowered, by positioning means 4, and gently engages the closure due to collar (22. fig 2), springs (27, fig 2) and lever (30, fig 2). At this stage the motor may turn slowly or be stopped however the motor may be stated or its speed increased after contact has been made with a proximity switch. The speed is set to a pre-set maximum so that the predetermined torque is reached before maximum speed. <IMAGE>

Description

Improvements in or Relating to the Tightening of Closures The present invention relates to a device for tightening the closures of vessels of fluid, and more particularly to the tightening of closures including valves and pressure valves.

The present invention is particularly applicable to the tightening of the pressure valve of kegs for pressurised beer. A beer keg is a pressure-vessel including, usually on an end thereof, an orifice through which the beer is emptied. The orifice comprises an external neck, known as the barnes neck, including an internal thread. A pressure valve or spear is inserted into the barnes neck to control the emptying of the beer. The spear includes an external thread which engages with the internal thread of the barnes neck. It is important that the spear is sufficiently tightened to prevent leakage of the beer and to prevent the pressure from forcing the spear out of the neck. The head of the spear is conventionally in the form of an open-ended cylinder, the internal walls of which include diametrically opposed lugs by means of which a tightening means can be engaged with the spear.

Conventional methods of tightening the spear have relied on manual tightening, for example with a torque wrench. Some automated and semi-automated methods are known, in which pneumatically powered devices are used.

However, problems arise with the correct engagement of the tightening means with the lugs of the spear and with the accurate tightening of spear to a predetermined torque. In some pneumatic devices, an electronic torque sensing device has been located between the pneumatic torque generation source (air motor) and the head which engages the spear. The output of the torque sensing device is used to control the air supply to the pneumatic torque generation source. However, pneumatic systems in general are difficult to maintain and require close control of the air pressure.

Accordingly, the present invention seeks to provide an automated method and apparatus of tightening such closures accurately and reliably to a predetermined torque.

According to a first aspect of the present invention there is provided an apparatus for tightening a closure of a container to a predetermined torque, the apparatus comprising driving means controllable to allow gradual changes in rotational speed, a driving head driven by the driving means and adapted to engage the closure and torque sensing means for sensing the reaction torque of the driving means, the torque sensing means being operative to stop the driving means when a predetermined torque is reached.

According to a second aspect of the present invention there is provided a method of tightening a closure of a container to a predetermined torque comprising, engaging the closure with a driving head driven by a driving means, increasing the rotational speed of the driving head whilst sensing the reaction torque of the driving means and stopping the driving means when a predetermined torque is reached.

In an embodiment of the invention, the driving means is an electric motor. Desirably, the driving head is rotated slowly as it is brought into engagement with the closure, and the speed is subsequently increased.

In another embodiment of the invention, the torque is sensed by a load cell.

In a further embodiment of the invention, the torque sensing means senses the torque between the driving means and a fixed member.

In a still further embodiment, an error state is indicated if a predetermined speed of the head is reached before the predetermined torque.

For greater understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example only to the accompanying drawings in which Figure 1 is a schematic diagram of a valve tightener according to the invention; Figure 2 is a diagram showing several of the elements of Figure 1; Figure 3 is a diagram of the power switching circuit of the motor controller; Figure 4 illustrates the mounting of the drive head and motor; and Figure 5 shows the head of a valve to be tightened by the valve tightener of Figure 1.

Referring in particular to Figures 2 and 3, the drive means 2, comprising an electric motor, drives a drive head 3. The drive head can be raised and lowered by a drive head positioning means 4.

The drive motor 2 is mounted on a generally horizonal member 20 via a strain gauge 6. The member 20 is suspended so that it can more freely, for example by wires 13. Rotational movement of the member 20 is limited by the generally vertical member 21. The member 21 is fixedly attached to the apparatus frame 8, which is shown only in part. The drive head 3 is surrounded by a collar 22 which collar has a contour 23 such that, in conjunction with the ability of the drive head to more freely, when the drive head is lowered, it is automatically centred on the barnes neck 12.

A beer keg 11 is positioned approximately under the drive head by keg positioning means and its presence is sensed by a position switch (not shown).

The reaction torque between the drive head 3 and the keg may be measured by strain gauge 6 such as a load cell, which is connected to a motor speed controller 1 which governs the speed of electric motor 2.

The keg positioning means comprises a conveyor, a series of keg support bars 10 and keg retaining arms 9.

The keg retaining arms 9 are mounted on the frame 8 of the apparatus and are movable to extend inwards towards the centre of the apparatus until the ends thereof are brought into firm contact with the keg 11. Thus it will be seen that the keg positioning means is operable to position and hold barrels of a plurality of sizes.

The drive head 3 contains a plurality of diametrically opposed protrusions or dogs 26 which engage the lugs 25 of the top of the spear. The drive head positioning means preferably consists of an electric motor which raises and lowers the drive head.

The motor speed controller 1 is a variable frequency transistor inverter, and a circuit diagram of the power switching circuit thereof is shown in Figure 3. A desired speed may be set on the controller 1 and an output signal is delivered by the controller 1 upon the maximum speed being reached.

In use, a keg 11 is conveyed to the apparatus of the invention by a conveyor. When the arrival of the keg 11 is detected, the conveyor is lowered and the keg 11 is retained on support bars 10. The retaining arms 9 then extend inwards to retain the keg 11 firmly.

Preferably, four retaining arms 9 are provided. By means of the retaining arms 9, the keg 11 is approximately centred below the drive head 3. When the keg has been clamped by the retaining arms 9 and its presence detected, for example by a position switch, the motor controller is activated to cause the motor to rotate slowly. The drive head 3 is then lowered by the drive head positioning means 4, towards the spear of the keg 11, onto which it is automatically centred as described above. When the collar 22 is located on the barnes neck 12, the drive head positioning means continues to urge the drive head 3 towards the keg 11, compressing springs 27. The collar 22 includes an upper portion 28 having a waist 29. A lever 30 has a first end 31 mounted in the waist 29, a fulcrum 32 and a second end 33. The fulcrum 32 is dependent on the member 20.Thus, as the springs 27 are compressed by the downward movement of the drive head 3, the first end 31 of the lever 30 is retained by the waist 29 whilst the fulcrum is lowered with the driving means.

Thus the second end 33 is caused to move and engages with a shock absorbing means. This ensures a gentle vertical engagement of the drive head 3 with the spear 24.

At this stage, the motor 2 and the drive head 3 are still turning only slowly. Thus, the dogs of drive head 3 engage the lugs 25 of the spear 24 gently, damage to the lugs and to the spear 24 is avoided and correct engagement of the drive head with the spear 24 is ensured. Thereafter, the movement of the second end Causes 33 theAswitching of a proximity switch which causes the motor controller 1 to increase the speed of the motor. Alternatively, the drive head 3 may be lowered onto the spear 24 whilst the motor is not turning, the rotation being started after the drive head 3 is located on the spear 24.

When the drive head 3 is in place, the motor speed increases (or continues to increase) under the control of the motor speed controller. The controller is able to increase the speed of the motor until a pre-set maximum speed is reached. Thus the spear 24 is tightened into the barnes neck 12.

As the spear 24 is tightened, the reaction torque of the motor 2 urges the member 20 to rotate. This rotation is prevented by the member 21. The strain gauge (load cell) 6 senses the torque between the motor casing the member 20 and when a predetermined torque is reached, the motor 2 is stopped. The strain gauge 6 outputs an electric signal which is amplified and compared to a predetermined threshold value by a microprocessor unit. When this threshold value is exceeded (corresponding to the predetermined torque), a "stop" signal is output by the microprocessor unit to the deactivating input of the motor controller 1, causing the motor controller 1 to stop the motor 2.

Thus the spear 24 is tightened to the desired predetermined torque.

The drive head 3 is then raised, the retaining arms 9 are retracted, the conveyor is raised and the keg 11 is transported away. The apparatus is then ready for the next keg 11 and spear 24.

The settings of the controller 1 are chosen such that the preset maximum speed of the motor is not ordinarily reached before the spear 24 is tightened to its predetermined torque. If, therefore, the pre-set maximum speed is reached, an error condition is indicated, suggested that the drive head 3 has not correctly engaged the spear, that no spear is present, or that the spear has not engaged the barnes neck.

Claims

Claims:

1. An apparatus for tightening a closure of a container to a predetermined torque, the apparatus comprising: driving means controllable to allow gradual changes in rotational speed, a driving head driven by the driving means and adapted to engage the closure, and torque sensing means for sensing the reaction torque of the driving means, the torque sensing means being operative to stop the driving means when a predetermined torque is reached.

2. Apparatus according to claim 1 wherein the driving means is an electric motor.

3. Apparatus according to claim 1 or 2 wherein the driving means is operative to rotate the driving head slowly as the driving head is brought into engagement with the closure.

4. Apparatus according to claim 3 wherein the driving means is operative to rotate the driving head with increasing rotational velocity of the driving head until the closure is tightened.

5. Apparatus according to any preceding claim wherein the torque sensing means comprises a load cell.

6. Apparatus according to any preceding claim wherein the torque sensing means senses the torque between the driving means and a fixed member.

7. Apparatus according to any preceding claim including drive head positioning means operable to raise and lower the driving head.

8. Apparatus according to any preceding claim wherein the driving means is suspended from the drive head positioning means in rotatable manner.

9. Apparatus according to any preceding claim wherein the driving means is attached by the torque sensing means to a member suspended in rotatable manner but whose freedom to rotate is restricted such that a torque may be measured between the driving means and the suspended member when rotation of the driving means is restricted by the closure to be tightened.

10. Apparatus as claimed in any preceding claim in combination with the container having the closure.

11. The combination as claimed in claim 10 wherein the container is a pressure vessel having an orifice.

12. The combination as claimed in claim 11 wherein the orifice has an internally threaded neck.

13. The combination as claimed in claim 12 wherein the closure is a pressure valve, which is externally threaded to be inserted into the orifice, and wherein the head of the closure is an open-ended cylinder, the internal walls of which include diametrically opposed lugs.

14. Apparatus of the combination of any one of claims 10 to 13 wherein the driving head comprises a collar with a contour such that, upon being lowered onto the neck, it is automatically centered thereon.

15. Apparatus according to any one of claims 1 to 9, wherein the drive head contains a plurality of diametrically opposed protrusions for engaging lugs of the closure.

16. Apparatus according to any one of claims 1 to 9 or 15 having container positioning means comprising a conveyor, support bars, retaining arms and a proximity detector for positioning the container so that the closure is approximately aligned with the drive head.

17. Apparatus according to claim 16 wherein the proximity detector is operable to activate the driving means to begin rotating.

18. Apparatus according to claim 2 wherein the driving means is controlled by a motor speed controller.

19. Apparatus according to claim 18 wherein the motor speed controller is a variable frequency inverter.

20. Apparatus according to claim 18 or 19 wherein the speed controller gradually increases the speed of rotation of the driving means until a pre-set maximum speed is reached, and upon reaching the pre-set maximum speed the speed controller issues a speed indication signal irrespective of whether the said maximum torque has been reached.

21. Apparatus according to claim 20 wherein the driving means is operable to stop rotating upon the speed indication signal being issued.

22. A method of tightening a closure of a container to a predetermined torque comprising the steps of engaging the closure with a driving head driven by a driving means, increasing the rotational speed of the driving head whilst sensing the reaction torque of the driving means, and stopping the driving means when a pre-determined torque is reached.

23. A method as claimed in claim 22 preceded by the steps of bringing the container to the apparatus on a conveyor, and sensing the presence of the container when it reaches the apparatus and stopping the container by the apparatus.

24. A method as claimed in claim 23 wherein the container is stopped by lowering the conveyor and supporting the container on support bars.

25. A method as claimed in claim 22, 23 or 24 comprising the step of using position information of the container to start the driving means.

26. A method according to any of claims 22 to 25 comprising the additional steps of setting a predetermined maximum speed for the driving means, and stopping the driving means when that predetermined speed is reached irrespective of whether the said predetermined torque has been reached.

27. A container having a closure tightened by the method of any one of claims 22 to 26.

28. A container as claimed in claim 27 being a pressure vessel having an orifice with an internally threaded neck and wherein the closure is an externally threaded pressure valve.

29. Apparatus according to any one of claims 1 to 9 or 14 to 21, or combination of any one of claims 10 to 13,or method according to any one of claims 22 to 26, substantially as hereinbefore described with reference to the accompanying drawings