Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
  • F15B11/06—Servomotor systems without provision for follow-up action; Circuits therefor involving features specific to the use of a compressible medium, e.g. air, steam
  • F15B11/072—Combined pneumatic-hydraulic systems
  • F15B11/076—Combined pneumatic-hydraulic systems with pneumatic drive or displacement and speed control or stopping by hydraulic braking
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/40—Flow control
  • F15B2211/405—Flow control characterised by the type of flow control means or valve
  • F15B2211/40515—Flow control characterised by the type of flow control means or valve with variable throttles or orifices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/40—Flow control
  • F15B2211/415—Flow control characterised by the connections of the flow control means in the circuit
  • F15B2211/41527—Flow control characterised by the connections of the flow control means in the circuit being connected to an output member and a directional control valve
  • F15B2211/41536—Flow control characterised by the connections of the flow control means in the circuit being connected to an output member and a directional control valve being connected to multiple ports of an output member
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/40—Flow control
  • F15B2211/47—Flow control in one direction only
  • F15B2211/473—Flow control in one direction only without restriction in the reverse direction
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
  • F15B2211/755—Control of acceleration or deceleration of the output member
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/80—Other types of control related to particular problems or conditions
  • F15B2211/885—Control specific to the type of fluid, e.g. specific to magnetorheological fluid
  • F15B2211/8855—Compressible fluids, e.g. specific to pneumatics

Definitions

• Fluid-power cylinder provided with a cushioning device
• This invention relates to a fluid-power cylinder provide with a cushioning device for cushioning the movements of the piston in the cylinder.
• a cushioning device for cushioning the movements of the piston in the cylinder.
• Fluid-power cylinders often require a cushioning device which retards the piston at one or both ends of its stroke within the cylinder.
• a residual volume of fluid trapped in a cushioning compartment is allow to escape from the cushioning compartment only through a 10 restricted discharge passage in order to retard the movement of the piston during the final portion of its stroke.
• a problem which is present in many prior art cushioning devices is that the cushioning effect is dependent on the dimensional accuracy of components which move relative to on 15 another and define the restricted discharge passage between them. Wear of these components also affects the cushioning effect which may therefore be gradually reduced in the cours of time.
• An object of this invention is to provide a fluid-power cylinder provided with a cushioning device which is improved 25 in respect of the above-mentioned problems.
• a fluid- power cylinder comprising a power cylinder member, a power piston member, which includes a power piston body reciprocabl in the power cylinder member between opposed end positions an 30 a piston rod secured to the power piston body and projecting from one end of the power cylinder member, and a device for * cushioning the relative movements of the power cylinder membe ⁇ and the power piston member at the end positions, which devic comprises for each end position a cushioning piston on one of 35 the power cylinder and power piston members and a cushioning cylinder on the other member, the cushioning cylinder definin a cushioning compartment having a closed inner end and an ope outer end in which the cushioning piston is receivable when i approaches the end position, and a cushioning fluid reservoir in constant fluid flow communication with both cushioning compartments, a restricted discharge passage providing the sole path for escape of cushioning fluid from the associated cushioning compartment to the cushioning fluid reservoir when the cushioning piston is received in the cushioning cylinder.
• the piston rod of the power piston member is hollow, it interior being in constant unrestricted communication with th cushioning fluid reservoir,
• the cushioning cylinders are located within the piston rod of the power piston member and axially spaced apart, adja cent cylinder ends being open to define the open outer ends o the cushioning compartments,
• each cushioning piston is provided exteriorly with a fluid seal adapted to sealingly engage the interior wall of the associated cushioning cylinder when the cushioning piston is moving in the cushioning cylinder towards the inner end of the cushioning compartment and to permit substantially un ⁇ restricted fluid flow between the cushioning piston and the interior wall of the cushioning cylinder when the cushioning piston is moving in the cushioning cylinder towards the outer end of the cushioning compartment, and
• the discharge passage is a passage which is provided in the cushioning piston and bypasses the fluid seal.
• Fig. 1 is a longitudinal sectional view of a fluid-power cylinder embodying the invention
• Fig. 2 is an enlarged longitudinal sectional view of a portion of the fluid-power cylinder of Fig. 1.
• the invention is embodied in a double-acting pneumatic cylinder provided with a hydraulic device for cushioning the stroke of the power piston member o the cylinder at both end positions or stroke ends.
• Two sepa- rate cushioning cylinders are provided within a tubular pisto rod of the power piston member and reciprocate therewith, and a dual cushioning piston is stationary with respect to the power cylinder member in which the power piston member is reciprocable.
• the inven tion may be embodied in other types of fluid-power cylinders, e.g. single-acting cylinders, cylinders in which cushioning i effected only at one end position or stroke end, and cylinder in which the same kind of fluid is used both as working fluid and cushioning fluid.
• the illustrated fluid-power cylinder comprises a power cylinder member generally designated by 11 and a power piston member 12 which is reciprocable in the power cylinder member. It also comprises a hydraulic cushioning device including a pair of cushioning cylinders 13, a dual cushioning piston 14 with an associated support tube 15 and a cushioning liquid reservoir 16.
• Main components of the power cylinder member 11 are a cylindrical tube 20 of circular cross-section and front and rear end walls 21 and 22, respectively, which sealingly close the ends of the tube and are provided with connectors 23 and 24, respectively, through which the working fluid, namely compressed air, is supplied and discharged.
• the rear end wall 22 is made integral with the cushioning liquid reservoir 16.
• Mounted on the reservoir 16 are a pair of aligned pivot pins
• the power piston member 12 comprises a power piston body
• the cushioning cylinders 13 of the cushioning device are formed by front and rear cylindrical sleeves which are secure in the hollow piston rod 29 adjacent respectively the front and the rear end thereof.
• the adjacent ends of the two sleeve are internally bevelled or widened.
• the sleeves 13 define a pair of cushioning compartments 31A, 3IB, which are open towards the interior 32 of the piston rod at their outer, adjacent ends but are otherwise closed.
• the dual cushioning piston 14 is secured to the front end of the support tube 15 which in turn has its rear end secured to the cylinder end wall 22 and is in constant open communica tion with a cushioning liquid compartment 33 in the cushionin liquid reservoir 16.
• the support tube 15 extends through a sliding seal 34 in the power piston body 26 and through the rear cushioning cylinder sleeve 13.
• the cushioning piston 14 comprises a front piston section 14A and a rear piston section 14B.
• the front cushioning piston section 14A is moved inwardly in the front cushioning cylinder compartment 31A to the vicinity of the inner end or bottom of the compartment.
• the rear cushioning piston section 14B is moved inwardly in the rear cushioning cylinder compartment 3IB to the vicinity of the inner end or bottom thereof.
• the dual cushioning piston 14 comprises a dumbbell-shaped metal body, the enlarged end portions of which form the front and rear cushioning piston sections 14A, 14B and have a dia ⁇ meter slightly smaller than the inner diameter of the cushion ing cylinder sleeves 13. The difference in diameters is suffi cient to permit a substantially unrestricted liquid flow through the gap between each cushioning cylinder sleeve 13 an the associated cushioning piston section 14A, 14B received therein.
• Each cushioning piston section 14A, 14B is provided with an external circumferential groove 35A, 35B, which accommo- dates a frusto-conical sealing ring 36A, 36B of relatively soft material.
• the sealing rings are opposed such that their larger ends, which are adapted to engage sealingly the inte ⁇ rior wall of the cushioning cylinder sleeves 13, are directed away from one another, i.e. towards the inner ends of the cushioning compartments.
• a centra axial passage 37 which is in constant open communication with the interior of the support tube 15 and thus with the cushion ing liquid compartment 33. Inserted in the front end of this passage is a calibrated restrictor 38. By way of a transverse passage 39 the central portion of the passage 37 is in con ⁇ stant unrestricted communication with the space around the cushioning piston.
• an axial passage 40 which is in constant unrestricte communication with the piston rod space 32 and is in constant but restricted communication with the space around the cushioning piston, the last-mentioned communication being by way of a calibrated restriction 41 located between the two sealing rings a small distance from the sealing ring 36B.
• the piston rod space 32 and the spaces communicating with it are always filled with the cushioning liquid.
• the front cushioning cylinder compartment 31A define in front of the front cushioning piston section 14A expands.
• the cushioning compartment 31A is successively filled with cushioning liquid which flows against very little resistance into the compartment past the sealing ring 36A because this sealing ring is pressed into its groove 35A.
• the sealing ring 36A acts as a valve (one-way valve) which opens automatically to permit liquid flow into the front cushioning cylinder compartment 31A.
• the rear cushioning piston section 14B When the power piston member 12 approaches its outer end position, the rear cushioning piston section 14B is received in the rear cushioning cylinder sleeve 13.
• the rear sealing ring 36B because of its frusto-conical shape, is caused to engage sealingly the inner wall of the sleeve (one-way valve action) .
• the only path through which the cushioning liquid trapped in the rear cushioning cylinder compartment 3IB can escape is therefore formed by the passage 40 containing the calibrated restriction 41. By virtue of its cross-sectional area, this restriction determines the rate at which the power piston member 12 continues its movement to the outer end position.
• the calibrated restricto 38 in the front cushioning piston section 14A determines the rate at which the final portion of this retraction takes place.
• the cushioning device In use, there is no wear of those elements, namely the restrictors 38 and 41, of the cushioning device which deter- mine the speed at which the power piston member 12 moves near the end positions, assuming that the forces acting on the power piston member 12 are given. These elements therefore do not undergo any change in respect of their predetermined cross-sectional flow area during the useful life of the cushioning device. Moreover, because it is also easy to desig the restrictors with the desired cross-sectional flow area an to ensure that the cushioning liquid trapped in the cushionin cylinder compartments cannot escape except through the re ⁇ strictors, the cushioning device can be designed to provide the desired cushioning effect.
• the calibrated restrictors are fixed, but it is of course within the scope of the inven ⁇ tion to make them adjustable.
• the cushioning liquid reservoir 16, the main body of whic is made integral with the rear cylinder end wall 22, has a substantially circular cylindrical exterior shape and is sealingly closed at its rear end by means of a screw-threaded cover 42.
• the two aligned pivot pins 25 are secured to a circular clamp 43 which is held in position about the cushioning liqui reservoir 16 by means of a bolt 44 which is passed through a pair of outwardly bent flanges 45 of the clamp.
• the clamp 43 is secured axially in its position, and possibly also against rotation, on the cushioning liquid reservoir by a ridge 46 on the inner side of the clamp or by any other suitable projec ⁇ tion which engages a corresponding groove or recess 47 on the outer side of the cushioning liquid reservoir 16.

Landscapes

• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Actuator (AREA)
• Fluid-Damping Devices (AREA)
• Braking Arrangements (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20373885

Family Applications (1)

Country Status (5)

Cited By (1)

Citations (1)

• 1988
  • 1988-11-08 SE SE8804035A patent/SE465529B/sv not_active IP Right Cessation
• 1989
  • 1989-11-02 WO PCT/SE1989/000624 patent/WO1990005245A1/en active IP Right Grant
  • 1989-11-02 EP EP89912017A patent/EP0442908B1/en not_active Expired - Lifetime
  • 1989-11-02 DE DE68914848T patent/DE68914848T2/de not_active Expired - Fee Related
  • 1989-11-06 CA CA 2002278 patent/CA2002278A1/en not_active Abandoned

Patent Citations (1)

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