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EP-3381578-B1 - NOZZLE-FLAPPER TYPE SERVO VALVE COMPRISING A TORSION SPRING

EP3381578B1EP 3381578 B1EP3381578 B1EP 3381578B1EP-3381578-B1

Inventors

  • Cis, Marcin
  • SAWICKI, Piotr

Dates

Publication Date
20260506
Application Date
20170327

Claims (14)

  1. A method of manufacturing a nozzle-flapper type servo valve (300) comprising a torsion spring (100;200), an armature (50;500) and flapper (60;600), the torsion spring (100;200) configured to bias the armature (50; 500) and flapper (60; 600) towards a rest position, the method comprising: providing a section of sheet metal (400); and the method characterised by : forming the torsion spring (100;200) from the section of sheet metal (400), wherein the torsion spring (100;200) is a substantially flat, single-piece of material.
  2. A method as claimed in claim 1, wherein the section of sheet metal (400) has a uniform thickness.
  3. A method as claimed in claim 1 or 2, wherein the step of forming comprises cutting out and/or stamping the torsion spring (100;200) from the section of sheet metal (400).
  4. A method as claimed in claim 1, 2 or 3, wherein the step of forming comprises one or more of: using a machine press or stamping press, laser cutting, wire-cut electrical discharge machining (EDM), blanking, embossing, bending, flanging, and coining.
  5. A method as claimed in any preceding claim, further comprising: determining a set of dimensions of the torsion spring (100;200) required to achieve a specific stiffness of said torsion spring (100;200); and forming the torsion spring (100;200) with the determined set of dimensions.
  6. A method as claimed in claim 5, wherein the torsion spring (100;200) comprises: a first portion (102;202) configured for attachment to a fixed housing; a second portion (110;210) configured for attachment to a moving component (50,60;500,600); and one or more torsion members (120;220) connecting the first portion (102;202) with the second portion (110;210); wherein the set of dimensions comprises one or more dimensions of the one or more torsion members (120;220).
  7. A method as claimed in claim 6, wherein the set of dimensions comprises a width (122) of the one or more torsion members (110,210).
  8. A method as claimed in claim 5, 6 or 7 wherein the set of dimensions comprises a thickness of the torsion spring (100;200).
  9. A nozzle-flapper type servo valve (300) comprising a torsion spring (100;200), an armature (50;500) and flapper (60;600), the torsion spring (100;200) configured to bias the armature (50; 500) and flapper (60; 600) towards a rest position, wherein the torsion spring (100;200) is formed from sheet metal, characterised in that the torsion spring (100;200) is a substantially flat, single-piece of material.
  10. A nozzle-flapper type servo valve (300) as claimed in claim 9, further comprising: a first portion (102;202) configured for attachment to a fixed housing; a second portion (110;210) configured for attachment to a moving component (50,60;500,600); and one or more torsion members (120;220) connecting the first portion (102;202) with the second portion (110;210).
  11. A nozzle-flapper type servo valve (300) as claimed in claim 9 or 10, wherein the torsion spring (100;200) has a uniform thickness.
  12. A nozzle-flapper type servo valve (300) as claimed in claim 9, 10 or 11, wherein the torsion spring (100;200) has a length defined along its longitudinal axis, and the thickness of the torsion spring is at least 20 times smaller than its length.
  13. A nozzle-flapper type servo valve (300) as claimed in claim 9, 10 or 11, wherein the torsion spring (100;200) has a length defined along its longitudinal axis, and the thickness of the torsion spring is at least 50 times smaller than its length.
  14. A nozzle-flapper type servo valve (300) as claimed in any of claims 9 to 13, wherein the plane formed by a major surface of the torsion spring (200) is perpendicular to the plane formed by a major surface of the armature (500).

Description

FIELD The present invention relates to nozzle-flapper type servo valves comprising torsion springs, as well as methods for manufacturing nozzle-flapper type servo valves comprising torsion springs. BACKGROUND A torsion spring is typically provided in a servo valve, for example an electrohydraulic servo valve incorporating a flapper nozzle assembly. The torsion spring may be connected to the armature of the servo valve to bias the armature and the component connected thereto (e.g., the flapper) towards a rest position. The torsion spring may, therefore, be seen as a negative feedback mechanism to the movement of the magnetic armature. Due to the tolerances and small movements in a servo valve, the stiffness of a torsion spring has to be determined and manufactured precisely. Furthermore, a torsion spring will typically be subject to a high number of use cycles (e.g., 10 per minute), and resistance to fatigue is also an important factor when designing and/or manufacturing this component. It is desired to provide a nozzle-flapper type servo valve with an improved torsion spring, and improved methods for manufacturing nozzle-flapper type servo valves with torsion springs. EP2202010A2 discloses a prior art method for forming a stamped metal part. US2005/012060A1, JPS6283571A, US5184645A, US 4285363 A on which the preamble of independent claims 1 and 9 is based, and GB1264859A disclose other prior art arrangements. SUMMARY In accordance with an aspect of the present invention, there is provided a method of manufacturing a nozzle-flapper type servo valve as set forth in claim 1. It has been found that manufacturing the torsion spring from sheet metal leads to improvements in the resistance to fatigue of the torsion spring over time, and also enables more precise manufacturing of the torsion spring. For example, the dimensions of the torsion spring can be more precisely tuned in order to provide a specific stiffness for a particular torsion spring, as well as more consistency when manufacturing a large volume of torsion springs. The section of sheet metal may have a uniform thickness, e.g., less than 1 mm, 0.8 mm, 0.6 mm, 0.5 mm, 0.4 mm or 0.3 mm. The step of forming may comprise cutting out and/or stamping the torsion spring from the section of sheet metal. The step of forming may comprise or further comprise one or more of: using a machine press or stamping press, laser cutting, wire-cut electrical discharge machining (EDM), blanking, embossing, bending, flanging, and coining. The method may further comprise determining a set of dimensions of the torsion spring required to achieve a specific stiffness of said torsion spring, and forming the torsion spring with the determined set of dimensions. The torsion spring may comprise a first portion configured for attachment to a fixed housing, a second portion configured for attachment to a moving component, and one or more torsion members connecting the first portion with the second portion. The set of dimensions may comprise one or more dimensions of the one or more torsion members, for example a width of the one or more torsion members. The set of dimensions may comprise a thickness of the torsion spring. The width of the torsion members may be increased, and/or the thickness of the torsion spring may be increased, to provide a stiffer torsion spring, or a greater resistance to movement (e.g., twisting) in use. The width of the torsion members may be reduced, and/or the thickness of the torsion spring may be decreased, to provide a less stiff torsion spring, or a lower resistance to movement (e.g., twisting) in use. The method may comprise forming a plurality of torsion springs from the section of sheet metal, wherein each torsion spring may be produced using any of the methods described above and herein. The method may comprise determining a set of dimensions of each torsion spring required to achieve a specific stiffness of each of said torsion springs, and forming each torsion springs with the determined set of dimensions. The specific stiffness and/or the set of dimensions may be the same, such that each torsion spring of the plurality of torsion springs has a consistent stiffness. In accordance with another aspect of the present invention, there is provided a nozzle-flapper type servo valve as set forth in claim 9. The torsion spring may further comprise a first portion configured for attachment to a fixed housing, a second portion configured for attachment to a moving component, and one or more torsion members connecting the first portion with the second portion. The torsion spring may have a uniform thickness, e.g., less than 1 mm, 0.8 mm, 0.6 mm, 0.5 mm, 0.4 mm or 0.3 mm. The torsion spring may have a length defined along its longitudinal axis, and the thickness of the torsion spring (e.g., perpendicular to its length) may be at least 20, 30, 40, 50, 60, 70, 80, 90 or 100 times smaller than its length. The fixed housing may be the housing of the servo valve, a