FR2576994A1 - DEVICE FOR CONTROLLING UNDESIRABLE MOVEMENTS, MOVEMENTS OR VIBRATIONS IN MECHANICAL OR HYDRAULIC SYSTEMS - Google Patents

Abstract

A. DEVICE FOR CONTROLLING UNDESIRABLE MOVEMENTS OR DISPLACEMENTS. B. IT INCLUDES A PAIR OF WATERPROOF BEDROOMS 8, 9, EACH OF WHICH HAS END WALLS 2, 4 AND SIDE WALLS 6, 7 FLEXIBLE IN ONE DIRECTION TO ALLOW RELATIVE MOVEMENT BETWEEN END WALLS 2, 4 AND CAUSE A CHANGE IN THE VOLUME OF EACH BEDROOM 8, 9; A COMMUNICATION 10, 11 BETWEEN THE SAID CHAMBERS 8, 9 ALLOWS THE TRANSFER OF THE FLUID FROM ONE CHAMBER TO ANOTHER AND SYSTEM 3 ALLOWS THE APPLICATION OF A FORCE OR A MOVEMENT IMPOSED ON AT LEAST ONE OF THE ENDED WALLS 2, 4, IN ORDER TO CAUSE A CHANGE IN THE VOLUME OF ONE OF BEDROOMS 8, 9 AND A MOVE OF THE FLUID FROM THE BEDROOM IN QUESTION TO THE OTHER BEDROOM. C. MANUFACTURING OF VALVES.

Description

- 1 * -

  The present invention relates to devices for controlling the displacements, movements or undesirable vibrations within

  mechanical or hydraulic systems.

  The invention applies in particular to dampers or damping devices making it possible to control the unstable oscillation behavior or "chatter" 1 within safety or control valves, although the invention is applicable, general control or control of vibrations and other undesirable movements, acceleration and imposed displacements

  included, within mechanical or hydraulic equipment.

  The phenomenon of valve beating or chatter can be caused by any of a number of factors (see "Valve Selection Handbook" RW Zappe, page 177 - Valve Selection Manual) and remains a problem today. permanent. The current technique is to try to reduce the possibility of chatter by modifying the characteristics of the system, rather than using a valve designed to alleviate the problem. The inventor is aware of only two proposals for so-called "anti-chatter!" Valves, both of which are based on the theory that friction on the valve stem should in principle reduce the likelihood of undesirable movement of the valve. In one case, the friction on the valve stem is ensured by means of an elastomer seal seated at the pressure of the liquid in the valve body, in the other case the friction on the valve stem is ensured. by means of a friction ring, which is subjected to the pressure of a prestressed spring In both cases, the main disadvantage of these arrangements is wear, which causes changes in the resistance characteristics, and therefore requires maintenance, and causes contamination of the valve stem or friction element, by foreign bodies, so that these arrangements can not be considered reliable as

  devices to prevent chatter.

  The inventor doubts that the theory can be put into practice and is not aware of any commercial application of the first mentioned valve. The second valve has been sold commercially, but has not proved satisfactory as a device to prevent the

grazing.

  The object of the present invention is to provide a device for reliably reducing unwanted movements within mechanical or hydraulic systems, and not having the

disadvantages outlined above.

  The invention provides a device for controlling undesirable movements or displacements, comprising a pair of sealed chambers containing a fluid; each of said chambers having end walls and side walls, said side walls being flexible in one direction to allow relative movement between the respective end walls of said chambers and to cause a corresponding change in the volume of each of the chambers; between said chambers so as to allow the passage of fluid from one chamber to another; and a system for applying a force or motion imposed on at least one of the end walls, so as to cause a change in the volume of one of the chambers and a displacement of the fluid in the chamber.

question to the other room.

  As the imposed force or movement causes the fluid to move from one chamber to the other, the difference in

  pressure between the rooms opposes the force or movement imposed.

  The characteristic resistance of the device can be modified by changing the dimensions of the chambers or the dimensions of the passage allowing the displacement of the fluid from one chamber to another. It is also possible to modify the characteristic resistance of the device by changing the characteristics of the fluid. For example, changing the density, the viscosity and the compressibility of the fluid makes it possible to modify the characteristic resistance with respect to accelerations, velocities and imposed displacements. The chambers are preferably essentially cylindrical

  and the side walls are axially and substantially flexible

  inflexible in the circumferential direction. Given the essentially circumferential inflexibility of the side walls, an axial extension or compression of the chambers causes a change in the internal volume, which in turn causes the displacement of an equivalent volume of fluid

from one bedroom to the other bedroom.

  The side walls of the chambers may be in the form of convoluted bellows made of stainless steel or other non-corrosive material having the required strength properties. The characteristics of the bellows are mainly determined by the imposed force to be applied to the device, by the maximum and minimum axial deformation expected from the wall, by the maximum and minimum pressure desired within the chambers, by the number of pressure and displacement cycles.

  contemplated and by the nature of the fluid to be used.

  Presently preferred structures of the invention are hereinafter described with reference to the diagrams. It is shown: FIGS. 1 to 3: various schematized configurations of the damper -3- or damping device according to the invention, FIG. 4 a preferred configuration of the device attached to the valve stem of a typical relief valve, and Figure 5: another preferred embodiment of a damper or damping device. Referring firstly to the configuration of the choke or damping device shown schematically in Figure 1 of the diagrams, the choke comprises a bobbin or bobbin-shaped portion 1

  defining an end wall 2, a central axis 3 and an end wall 4.

  A common central end wall 5 is slidably positioned on the axis 3. The end walls 2 and 4 and the central end wall 5 are respectively connected by side walls 6 and 7 so as to define closed chambers. 8 and 9. In the illustrated structure, the sidewalls 6 and 7 each have the shape of a convoluted stainless steel bellows or other suitable device which is axially flexible but substantially rigid in the circumferential direction. The common central end wall 5 has two passages 10 and 11 so that the fluid (eg mineral oil) contained in the chambers 8 and 9 can flow between the chambers. A force or imposed movement, represented by the arrows, exerted on the central end wall 5 causes the displacement of this wall 5 in one direction or the other, and the fluid within one of the chambers 8 and 9 is moved to the opposite chamber, so that the pressure difference obtained between chambers 8 and 9

  opposes force or imposed movement.

  In the choke illustrated in Figure 2 of the drawings, a common end wall 12 supports a vertical rod 13, which in turn supports, via a trunnion, a lever 21 to which end walls 14 and 15 are fixed so as to pivot. Side walls 16 and 17 connect the end walls 14 and 15 and the common end wall 12 so as to form chambers 18 and 19. The common end wall 12 has a passage 20 for the fluid, said passage 20 opening into each of the chambers 18 and 19. A force or a movement imposes., represented by the arrows, exerted on the articulated lever 21 forces the fluid contained within one of the chambers 18 or 19 to move towards the other chamber, so that that the pressure difference obtained between the rooms

  18 and 19 opposes the force or the imposing imposes.

  In the sketcher illustrated in FIG. 3 of the diagrams, the ends 22 and 23 are connected by a duct 24 to the ends 25 and, respectively, to the end 22 and 23. 23 by means of walls 27 and 29, and to form chambers 29 and 30. An eye-piece poses: presented by the arrows, exerted on one of the end walls 25 or 26 constrained by fluid contained within one of chambers 29 or 30 to move towards

  the other room, as in the preceding structures.

  Because of its simplicity of construction and its propensity to achieve valve damping, the choke shown in Figure 1 is preferred for this function, and a typical assembly for connecting the choke to a safety valve of the known type is shown in Figure 4 diagrams. In this arrangement, the structure of the choke is housed in an enclosure 31 to which the common end wall 5 is fixed rigidly by means of a weld or the like. The enclosure or housing 31 is attached to the top of the safety valve 32 of known structure, only part of which is shown in the figure, and the lower part of the axis 3 is bifurcated (divided in two) to allow fixing the pin 3 to the upper part of the rod 33 of a safety valve 32, for example by means of a cotter pin as illustrated. The end walls 2 and 4 are welded to the axis 3 and the passage 11 in the common end wall 5, which is intended for the fluid, is formed by a tube whose ends are flared. The convoluted bellows 6 and 7 of stainless steel are sealingly connected to the end walls 2 and 4 and to the common end wall 5 by means of a weld or other means conforming to the uses or standards of the manufacturer of the bellows. By this arrangement, the slightest movement of the valve stem 33, caused by the operation of the relief valve 32, causes the end walls 2 and 4 to move relative to the common end wall 5. As a result, the fluid is moved from one of the chambers 8 or 9 to the other chamber, so that

  the movement of the valve stem 33 is damped.

  In the illustrated structure of the choke, the bellows 6 and 7 are preferably designed in accordance with the standards of the US Expansion Joint Manufacturers Association (Association of Manufacturers of Expansion Joints), so as to match the pressures and deformations. required. A damping of the order of 10 N.m. s, for example, necessary to prevent the chatter of a valve having a type "3" orifice, with a defined pressure of 1.0 MPa and a "flush" of 10 X, located on a vase

  10 m 'containing air at 20 C. Such an arrangement would have a displacement

  5 mm, a pressure of the order of 100 kPa; the walls being designed

  for combined displacement and pressure cycles of 106.

  The diameter of the orifice II within the common end wall 5 should not exceed by more than 0.10 mm the diameter of the rod C. In this structure or configuration, the passage between the chambers is formed 4 by a inner diameter tube of about 3.5 mm, 50 mm in length and flared ends, as shown. The fluid used is preferably a mineral oil whose dynamic viscosity is 0.16 Ns m 2. For a valve having the characteristics stated above, the end walls 2 and 4 must have a diameter of about 80 mm and the bellows 6 and 7 must have a length of approximately 93.5 mm. All the subjects-

  used are preferably 316 stainless steel.

  Referring now to Figure 5 of the drawings, a preferred choke structure of the type illustrated in Figure 3 of the drawings will now be described. In this arrangement, an external passageway for the fluid is formed by a tube 40 attached to end-through-end connections 41 and 42. As in the preceding choppers, convoluted bellows or diaphragms 43 and 44 connect the end walls. 41 and 42 and the common end wall 45. A bracket 46 is attached to the end wall 41 and an open type bracket is attached to the common end wall 45. A spacer plate 49 maintains the end walls 41 and 42 spaced apart from each other by a predefined spacing, so that the common end wall 45 can move through the bracket 47 to stifle the movements of the element integral with said fixing lug 47. A removable fluid resistor 48 is positioned in the tube 40 and makes it possible to vary the properties

damping the device.

  The choke or damping device made according to the present invention offers the following advantages:

  (a) There are no mechanical seals.

  (b) There is no passage likely to leak the fluid contained in the damping device; therefore, the

  risk of fluid loss is eliminated and any contamination of the environment

  is impossible. Conversely, the environment can not contaminate the fluid. The device can therefore operate in environments

  sensitive or in degrading environments.

  (c) Contact between moving parts is not required.

  As a result, wear is minimal and maintenance is zero.

  (d) The minimal wear ensures the longevity of the device and

  the precise maintenance of the resistance characteristics.

  (e) No external fluid reservoir is needed.

  It should also be noted, although the structure of the choke illustrated in Figure 2 of the diagrams is currently the preferred one for the illustrated relief valve, that other configurations may be used for similar results . Also, the chambers can be arranged in many configurations other than those illustrated by the diagrams, so that the invention can not be considered as limited to the illustrated configurations.

in the present.

Claims (9)

  Device for controlling undesirable movements or displacements, characterized in that it comprises a pair of sealed chambers (8,9; 18,19; 28,29) containing a fluid; each of said chambers having end walls (2,4,5; 12,14,15; 22,23,25,26) and side walls (6,7; 16,17; 27,28), said side walls (6,7; 16,17; 27,28) being flexible in one direction to allow relative movement between the walls   end portions (2,4,5; 12,14,15; 22,23,25,26) of said chambers   (8,9; 18,19; 28,29) and to bring about a correspon-   the volume of each of the chambers (8,9; 18,19; 28,29); a communication (10,11; 20,24) between the chambers (8,9; 18,19; 28,29) so as to allow the passage of fluid from one chamber to another; and a system (3,13,21; 46,47) for applying a force or motion imposed on at least one of the end walls   (2,4,5; 12,14,15; 22,23,25,26), so as to cause a change in   the volume of one of the chambers (8,9; 18,19; 28,29) and one   fluid of the chamber (8,9; 18,19; 28,29) in question to the other chamber (8,9; 18,19; 28,29) o 2. Device according to claim 1, characterized in that said side walls (6,7; 16,17; 27,28) are substantially cylindrical and axially flexible, and substantially   inflexible or rigid in the circumferential direction.   3. Device according to claim 2, characterized in that said side walls are convoluted bellows (6,7; 16,17; 27,28) made of a non-corrosive material, such as for example   stainless steel, having the required strength.   Device for controlling undesirable movements or displacements, characterized in that it comprises separate end walls (2, 14, 14, 15) and an end wall (5, 12).   convoluted bellows (6,7, 16,17, 27,28) attached to each   one of the end walls (2,24914,25) and said common end wall (5; 12) so as to define a pair of chambers (8,9; 1,819) containing fluid; iesdita scuff.te tz   .. ç. In this case, it is possible to use one of the following methods: eg CLMF: flexible or rigid in the other direction to allow movement   relative relationship between said end walls (2.24; 14.25) and said common end wall (5; 12); a passage (10,11; 20) in said common end wall (5; 12) opening into each of said chambers (8,9; 18,19) so as to allow the fluid to pass   from one room to another; as well as a system for applying   forcing a force or a movement imposed on at least one of said end walls (2, 24, 14, 25) or said common wall (5; 12) so as to lengthen or compress axially said chambers (8, 9; , 19), for modifying the volume of said chambers (8,9; 18,19) and causing displacement, from a chamber to   the other, with an equivalent volume of fluid.   5. Device according to claim 4, characterized in that said end walls (2,4) are rigidly connected, being at a distance from one another, to a central axis or rod (3). ; said common wall (5) being located between said   end walls (2,4) and having a central opening through   towards which the axis or the central rod (3) passes.   6. Apparatus according to claim 4, characterized in that said end wall (12) common forms a seat on which said bellows (16,17) are installed side by side; said end walls (14, 15) being connected by an articulated lever (21)   on which the imposed force or movement is exercised.   7. Device according to claim 5, characterized in that said common end wall (5) is fixed rigidly to a chamber or a housing (31) containing said device; said force or imposed movement being exerted on said axis or said central rod (3).   8. Device according to claim 7, characterized in that the passage for the fluid is formed by a tube (11) having flared ends.   9. Device according to claim 1, 2 or 3, characterized in that said passage for the fluid is constituted by an external pipe (40) connected to orifices in the corresponding end walls (41, 42) of said chambers; said pipe comprising a fluid resistance (48) performing the control imposed by said device.