Viscous fluid damper

• US 3,907,079 A
• Filed: 10/31/1973
• Issued: 09/23/1975
• Est. Priority Date: 10/31/1973
• Status: Expired due to Term

• Current Assignee: Arthur S. Chapman
• Original Assignee: Arthur S. Chapman
• Inventors: Chapman, Arthur S.
• Primary Examiner(s): Halvosa, George E. A.
• Application Number:
  US05/411,508
• Time in Patent Office: 692 Days
• Field of Search: 188/290,296,268,316,288 192/58R,58B,58C,58A 73/134
• US Class Current: 188/290
• CPC Class Codes: F16F 15/0235 where a rotating member is in contact with fluid rotary viscous dampers per se F16F9/12; suppression of vibrations in rotating systems containing a fluid F16F15/16

Abstract

A fluid damper including a stator and rotor has a plurality of individual annular areas of different concurrent shear rates. The different annular areas of a disc are used in combination to control the characteristic of the damper to provide substantial nonlinearity in the damping coefficient of a high viscosity, silicone damping fluid, i.e., decreasing apparent viscosity with increasing shear rate. An annular area of large diameter provides high shear rates in the fluid in a small gap spacing to produce the nonlinearity in the damper characteristic. A small annular area is the location of small diameter seals for minimum break-away friction. A large gap spacing minimizes shear resistance in the small annular area of low angular velocity having approximately a linear damping characteristic. The resultant damping characteristic of the combination retains substantial nonlinearity for effectively limiting the torque requirements at high shear rates.

Claims

1. A fluid damper comprising:

damper surfaces arranged in opposing relationship and disposed to provide a gap for damping fluid wherein said gap comprises a plurality of different gap spacings between at least two opposing damper surfaces;

said damping fluid comprising a fluid of high viscosity having a linearly increasing shear resistance at lower shear stresses and substantial limiting of shear resistance at higher shear stresses and filling said gap; and

means for supporting the opposing damper surfaces for relative movement to produce different rates of non-turbulent shear concurrently in the damping fluid disposed in the gap over the operating range of said damper including a higher rate of shear in the fluid in the smaller gap spacing for increasing the shear stresses in the smaller gap in order to provide the desired limiting of shear resistance characteristics for the damper.

2. The fluid damper according to claim 1 in which the damper surfaces are annular and at least one of said opposing damper surfaces is supported for rotation to produce said relative movement and shear stresses in the damping fluid.

3. The fluid damper according to claim 2 in which the rates of relative movement of annular sections of said opposing surfaces is different to provide different shear stresses in the damping fluid.

4. The fluid damper according to claim 3 in which the annular section having a lower rate of relative movement for lower shear stresses has a larger gap spacing for further reducing shear stresses in the damping fluid in the larger gap.

5. A fluid damper comprising:

damper surfaces arranged in opposing relationship and disposed to provide a gap for damping fluid wherein said gap comprises a plurality of different gap spacings between at least two opposing damper surfaces;

said damping fluid comprising a fluid of high viscosity having a linearly increasing shear resistance at lower shear stresses and substantial limiting of shear resistance at higher shear stresses and filling said gap;

means for supporting the opposing damper surfaces for relative movement to produce different rates of shear concurrently in the damping fluid disposed in the gap over the operating range of said damper including a higher rate of shear in the fluid in the smaller gap spacing for increasing the shear stresses in the smAller gap in order to provide the desired limiting of shear resistance characteristics for the damper; and

said opposing damper surfaces include radially disposed inner and outer pairs of opposing annular sections of smaller and larger radii respectively, and larger and smaller gap spacings respectively, and said means for supporting the damper surfaces for relative movement provides support for rotational movement between the inner opposing annular sections and the outer annular sections are supported for rotational movement by respective inner sections.

6. The fluid damper according to claim 5 in which the support means includes an annular seal having opposing surfaces disposed along the inner peripheries of the pair of inner annular sections for maintaining the damping fluid in the gap between relatively movable opposing damper surfaces.

7. The fluid damper according to claim 5 in which the damping fluid comprises a non-Newtonian fluid having a linear increase in shear resistance of the damping fluid at lower shear rates, between opposing annular sections of the inner pair and within the range of rates of movement in the operation of the damper.

8. The fluid damper according to claim 5 in which the damping fluid comprises a non-Newtonian fluid responsive to upper range of rates of operational movement to produce shear stresses in the damping fluid between the outer pair of annular sections that is nonlinear, decreasing substantially the rate of increase in shear resistance in the upper range of rates.

9. The fluid damper according to claim 1 in which one of said damper surfaces comprises a disc supported for relative rotation by the support means and the support means further includes a seal for retaining the damping fluid and providing for rotational movement between the disc and opposing damper surface near the inner periphery of the disc to minimize opposing and engaging areas of relatively movable seals and break-away friction thereof.

10. The fluid damper according to claim 9 in which said damping fluid comprises silicone damping fluid having a high viscosity of at least approximately 30,000 centistokes.

11. The fluid damper according to claim 9 in which said damping fluid is dimethyl polysiloxane having a viscosity in the approximate range of fluid viscosities on the order of 3,000 to 5 million centistokes.

12. The method of damping comprising the following steps:

forming at least one pair of opposing annular damper surfaces to provide incremental gap spacing between the surfaces;

filling the gap spacing with a highly viscous fluid having a non-linear characteristic of decreasing apparent viscosity at higher shear stresses; and

disposing the damper surfaces for relative rotational movement to provide inner and outer annuli having relatively large and small gaps, respectively, for producing corresponding non-turbulent shear stresses in the damping fluid in the gap as a function of the gap spacing and rates of movement, respectively including said higher shear stresses in the small gap in the upper operating range of rotational movement to produce limiting of shear resistance in the upper operating range.

13. The method according to claim 12 in which the incremental gap spacings are formed by forming the opposing annular surfaces of a damper enclosure to produce annular sections and disposing a disc, relatively rotatable to the enclosure and between said opposing damper enclosure surfaces.

14. The method according to claim 13 including the additional step of dynamically sealing the enclosure for relative movement along the inner annulus and between surfaces of the disc and damper surfaces of the enclosure.