Patent Grant
9914142
This application is a 371 of International PCT Application PCT/FR2010/051291, filed Jun. 24, 2010, which claims priority to French Application 0955058, filed Jul. 21, 2009, the entire contents of which are incorporated herein by reference.
The invention relates to a device and to a method for working with jets of cryogenic fluid, in particular liquid nitrogen, at high pressure, particularly for the surface treatment, stripping or scalping of coated or uncoated materials such as metals, concrete, wood, polymers, ceramics and plastics or any other type of material.
At the present time, the surface treatment of coated or uncoated materials, particularly the stripping, scalping or the like, is essentially done by sandblasting, by ultra high pressure (UHP) water spray, using a scourer, a pick hammer, a scabbier or alternatively via a chemical route.
However, when there must not be any water, for example in a nuclear environment, or any chemical product, for example because of severe environmental constraints, only so-called “dry” working processes can be used.
However, in certain instances, these “dry” processes are difficult to implement, are very laborious or are awkward to use or even generate additional pollution, for example because of the addition of shot or sand that has then to be reprocessed.
One alternative to these technologies relies on the use of cryogenic jets at very high pressure, as proposed by documents U.S. Pat. No. 7,310,955 and U.S. Pat. No. 7,316,363. In this case, use is made of one or more jets of liquid nitrogen at a pressure of 1000 to 4000 bar and at a cryogenic temperature of between, for example, −100 and −200° C., typically around −140 and −160° C., which are dispensed by a nozzle-holding tool driven in a rotary movement.
More specifically, this nozzle-holding tool is fixed to the end of a cryogenic fluid conveying pipeline which supplies the tool with cryogenic fluid. The pipeline and the tool are then given a rotary movement about the axis of the pipeline by a drive system involving pinions or belts powered by a motor.
The dynamic sealing of the rotary system is usually afforded by a rotary cylindrical sealing joint, typically made of Tivar®, arranged around the pipeline. Typically, this sealing joint of cylindrical shape has a bronze component passing longitudinally through it and is surrounded with a solid stainless steel component.
Because of the cryogenic temperature involved, it has been found in practice that the effectiveness of this sealing joint decreases as time goes on, and this in the fairly short term leads to leaks and therefore loss of process efficiency, particularly during operations of scalping concrete or stripping paint for example.
Specifically, under the effect of the cryogenic temperatures involved, the materials deform in different ways from one another, according to their respective thermal expansion coefficient, as illustrated in table I.
As may be seen, these materials react very differently to the cryogenic temperatures and as a result, during the alternating cooling and heating cycles, deformations or even damage to the sealing joint occur, and this happens all the more rapidly when the sealing joint is subjected to very high pressures, namely typically of up to 4000 bar.
Specifically, it has been found in practice that a clearance progressively appears between the sealing joint and the metal components and gives rise to leakages which prevent normal operation of the system. As a result of this, it is necessary regularly to change the sealing joint, leading to material and maintenance costs. Now, this is of critical importance in hazardous environments, notably in the nuclear or chemical sectors for example, where human intervention is to kept as infrequent as possible.
Document U.S. Pat. No. 4,369,850 describes a device fitted with a nozzle for dispensing water under pressure which nozzle is arranged at the downstream end of a water pipeline, itself arranged in a rotary cylindrical housing rotationally driven by a motor via a belt and pulley transmission mechanism, in which device the water pipeline is flexible and elbowed so as to be able to dispense a jet of water in a circular path so that holes can be made in the ground, that is to say in earth or the like.
However, that device is not entirely satisfactory because it does not allow the surface area impacted by the jet, at a given distance from the nozzle, to be varied, and this proves to be an appreciable disadvantage in certain applications, notably when stripping or scalping the surface, notably concrete.
A similar device is described elsewhere in DE-A-10236266.
In the light of that, the problem addressed is that of proposing a device for dispensing cryogenic fluid, particularly liquid nitrogen, which is reliable, which means to say with which not only do the problems associated with the wearing of the sealing joint and with leakage not exist, so as to remedy the aforementioned disadvantages but which also allows the area treated by the jet or jets of nitrogen at a given distance from the nozzle to be varied, notably when it is being used for stripping or scalping concrete.
The solution of the invention is therefore a device for dispensing one or more jets of cryogenic fluid, particularly liquid nitrogen, comprising a fluid conveying pipeline feeding one or more fluid dispensing nozzles arranged at the downstream end of said pipeline, and a motor collaborating with the fluid conveying pipeline via a rotary transmission shaft and a transmission mechanism, in which device:
Depending on circumstance, the device of the invention may comprise one or more of the following features:
The invention also relates to the use of a device according to the invention for dispensing, by means of one or more nozzles, a fluid in the form of one or more jets of fluid at a temperature of below −140° C. and at a pressure of at least 1500 bar, preferably between 2000 and 5000 bar, in order, by means of at least one jet of pressurized fluid, to carry out a surface treatment, i.e. a stripping or a scalping treatment on a material, particularly concrete.
Moreover, the invention also relates to a method for stripping or scalping concrete using a jet of liquid nitrogen implementing a device for dispensing one or more jets of liquid nitrogen at a pressure of at least 1500 bar and at a temperature of below −140° C., particularly a device according to the invention, comprising a liquid nitrogen conveying pipeline feeding one or more liquid nitrogen dispensing nozzles arranged at the downstream end of said pipeline, and a motor collaborating with the liquid nitrogen conveying pipeline via a rotary transmission shaft and a transmission mechanism, in which device the liquid nitrogen conveying pipeline comprises an upstream portion of first axis XX and a downstream portion of second axis YY, the first and second axes XX, YY between them making an angle α of between 5 and 50°, the downstream portion of second axis YY carrying the downstream end of the pipeline with said liquid nitrogen dispensing nozzle or nozzles, and the transmission mechanism comprises motion-inducing means acting on said downstream portion of pipeline to impart a determined movement to it, said transmission mechanism comprising a support pinion capable of rotational movement about a rotation axis situated at the center of said support pinion, the liquid nitrogen conveying pipeline being positioned eccentrically and running freely through said support pinion, and also a pinion drive means collaborating with the support pinion.
Depending on circumstance, the method of the invention may comprise one or more of the following features:
The method of the invention can be implemented by hand, that is to say by an operator, or alternatively can be implemented automatically or in an automated way, that is to say by a machine or by a robot.
For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:
According to one embodiment, the fluid that is to be dispensed is a fluid at cryogenic temperature and at high pressure, particularly liquid nitrogen at a pressure of between 1000 and 4000 bar and at a temperature of between −140 and −200° C. The fluid being taken from a fluid source (not shown) such as a compressor, a tank, a heat exchanger, a supply line, one or more gas cylinders or the like, supplying the upstream end of the fluid pipeline 7.
As illustrated in
The fluid conveying pipeline 7 for its part comprises an upstream portion 7a of first axis XX and a downstream portion 7b of second axis YY between them making an angle α of between 5 and 50°, typically of between 10 and 40° and preferably of the order of 20 to 30°.
The downstream portion 7b carries the downstream end of the pipeline 7 where the fluid dispensing nozzle or nozzles is or are arranged, for example on a nozzle-holding tool.
Moreover, the transmission mechanism 4a, 4b comprises motion-inducing means acting on the downstream portion 7b of pipeline so as to impart to it a determined movement, of whatever kind it might be, particularly a rotational or oscillatory movement. What should be understood by rotational movement is a movement which describes a circle or an ellipse, for example. The choice of the design of the component 4b will determine the type of movement chosen.
The motor 1 collaborating with the fluid conveying pipeline 7 via its rotary transmission shaft 2 and the transmission mechanism 4a, 4b to which the transmission shaft 2 transmits its rotational movement. The motor is a pneumatic motor, an electric motor, a gasoline engine or any other type of motor.
According to the invention, as visible in
The pipeline 7 is therefore arranged in a passage or orifice 10 formed through the body of the support pinion 4b, which passage is situated within the disk that the support pinion 4b forms, but not at the center of said disk.
For preference, the passage for the pipeline 7 is situated at least 1 mm away from the center of the pinion, which means to say from the axis of said support pinion 4b.
Moreover, a pinion drive means 4a, such as a drive pinion or a belt, collaborates with the support pinion 4b to drive the rotational movement of said support pinion 4b. More specifically, the transmission shaft 2, driven by the motor 1, collaborates with the pinion drive means 4a and the pinion drive means 4a itself collaborates with said support pinion 4b in order, via the pinion drive means 4a, to transmit the rotational movement of the transmission shaft 2 to the support pinion 4b and thus obtain a movement, preferably a circular movement, of the fluid dispensing nozzle or nozzles arranged at the downstream end of said pipeline 7, that is to say arranged on the nozzle-holding tool 5 used for dispensing the jets 6 of high-pressure fluid.
As illustrated in
The support pinion 4b is held by pinion-holding means 9 comprising one or more slippers or rolling bearings, notably a ball bearing as schematically illustrated in
It should be noted that elements 9, such as slippers, radial rolling bearings or spigots, are provided to maintain good rotation of the support pinion 4b. In fact, the support pinion 4b is grooved to accept the elements 9. The support pinion 4b is not held on its shaft. The pinion 4b is held by devices 9 which are positioned on the pinion 4b at a distance R from the axis of rotation of the pinion 4b which distance is greater than the distance r between the axis of rotation and the orifice 10, as illustrated in
Moreover, the fluid conveying pipeline 7 collaborates with anchor means 8, such as a gland, a clamp, a split nut, an elastic taper, a rack-pinion system or any other suitable mechanical device allowing the pipeline 7 to be held in position with respect to the rest of the jet dispensing device, said anchor means 8 being arranged on the pipeline 7 upstream of the support pinion 4b, i.e. the support pinion 4b is situated between the anchor means 8 and the end of the pipeline 7 bearing the nozzle or nozzles. In other words, the pipeline 7 is, on the one hand, kept stationary or approximately stationary in the region and because of the anchor means 8 and, on the other hand, comprises a downstream end 7b fitted with the nozzle or nozzles which is able to move and describes a given movement, preferably a circular movement, when the motor 1 drives the transmission shaft 2, the drive pinion 4a connected to the shaft 2, and the support pinion 4b which itself drives the tube 7 in a determined path, for example a circular path or the like.
The anchor point 8 is a mechanical element that allows the sliding of the pipeline 7 though the device and ultimately through the passage 10 to be blocked or unblocked.
The anchor point therefore makes it possible, for the time that the method is being implemented, to fix the length Lo, and therefore the diameter or the like of the circular path or the like described by the nozzle, in the knowledge that the distance between the anchor point 8 and the pinion 4b is fixed. Stated differently, modifying the length Lo is particularly advantageous for varying the radius of the circular path Ro described by the nozzle or nozzles for dispensing jets of high-pressure fluid as illustrated in
The mechanical element of the anchor point can be slackened off easily by the user, for example using an appropriate tool, if the user wishes to set or adjust the length Lo.
If the pipeline 7 is positioned on a movement machine or on a robot, it may prove difficult or impractical to slide the tube 7 through the device. It is therefore beneficial for the pipeline 7 to be split into two parts connected by a very-high-pressure static coupling 7c positioned upstream of the anchor point 8. This allows this part of the tube between 7c and the nozzle-holding tool 5 to be changed easily for a tube of suitable length allowing Lo to be adjusted to the desired length without the entirety of the tube 7 having to be moved or modified.
Furthermore, because this part of the pipeline is subject to deformation, it is preferable for it to be readily interchangeable for maintenance purposes.
In order to obtain sufficient pipeline 7 elastic deformation (flexibility), the properties of said pipeline 7, or at least of the part 7b of pipeline 7 situated between the anchor means 8 and the end carrying the nozzle-holding tool 5, are chosen with care, particularly the nature of the material of which the tube 7 is made, and its sizing, i.e. the inside and outside diameters of said tube.
For example, if it is a cryogenic fluid such as liquid nitrogen under high pressure that is being conveyed, use is preferably made of a stainless steel tube by way of pipeline 7, with inside and outside diameters as given in table II below.
As can be seen from table II, the 14.8 mm diameter tube is too rigid to be used to effect. Hence, typically, use is made of a tube in 316 grade stainless steel able to withstand high pressures (up to around 4000 bar) with an outside diameter of around 6.4 mm.
In order to make the tube still more flexible, it is possible to give said tube the form of a loop or pigtail, as shown in
Likewise, in order to ensure freedom of movement between the pinion 4b and the tube 7 at the orifice 10, a ball bearing or similar system may advantageously be positioned at 10 around the flexible tube 7.
A device according to the invention comprising a stainless steel tube with an external radius of 6.4 mm, supplied with liquid nitrogen at a temperature of −155° C. and at a pressure of 3500 bar, was tested without fatigue rupture over 2 000 000 cycles at a very high rotational speed of around 1100 rpm. Thus, according to the person skilled in the art of fatigue mechanics, the tube will not rupture through fatigue, whatever the number of cycles performed, particularly in excess of 2 000 000 cycles. The results obtained are therefore entirely satisfactory and the device works perfectly.
It is to be noted that a device according to the invention will not exactly reproduce the path of the jets followed by the systems used previously. A nozzle holder equipped with two nozzles used with the system described in U.S. Pat. No. 7,316,363 gives the two nozzles concentric circular paths with different radii, as illustrated in
The circles (
The device of the invention can be used for a manual application, as shown in
More specifically,
The device of the present invention can be applied to any heat treatment operation or process that involves rotating jets of fluid, particularly cryogenic fluids, such as surface treatment, stripping or scalping of a material, such as metals, concrete, stone, plastics, wood, ceramic, etc.
| Number | Date | Country | Kind |
|---|---|---|---|
| 09 55058 | Jul 2009 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR2010/051291 | 6/24/2010 | WO | 00 | 1/20/2012 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2011/010030 | 1/27/2011 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4369850 | Barker | Jan 1983 | A |
| 4736808 | James et al. | Apr 1988 | A |
| 5203842 | Mark et al. | Apr 1993 | A |
| 5533673 | Wilson et al. | Jul 1996 | A |
| 5794854 | Yie | Aug 1998 | A |
| 6758418 | Romanin et al. | Jul 2004 | B2 |
| 7310955 | Hume et al. | Dec 2007 | B2 |
| 7316363 | Hume et al. | Jan 2008 | B2 |
| 20010038039 | Schultz et al. | Nov 2001 | A1 |
| 20020109017 | Rogers et al. | Aug 2002 | A1 |
| 20060053165 | Hume et al. | Mar 2006 | A1 |
| Number | Date | Country |
|---|---|---|
| 4142740 | Jun 1993 | DE |
| 10236266 | Feb 2003 | DE |
| 102005001169 | Jun 2006 | DE |
| WO 9011134 | Oct 1990 | WO |
| Entry |
|---|
| French Search Report, FR 0955058, dated Jan. 6, 2010. |
| International Search Report, PCT/FR2010/051291, dated Oct. 12, 2010. |
| International Written Opinion, PCT/FR2010/051291, dated Feb. 7, 2012. |
| Number | Date | Country | |
|---|---|---|---|
| 20120222708 A1 | Sep 2012 | US |
