This invention relates generally to a damper, and more particularly, to a noncavitating damper having a material separating a compressible fluid from another fluid.
As known, dampers dampen movements of components moveable relative to each other. In one example, a damper dampens movement of a component, such as a suspension component, on a zero turn radius lawn mower. Some dampers include a rod extending from a tube. One rod end is coupled to a first component, and an opposite rod end is coupled to a piston structure within the tube. The tube mounts to a second component. The rod is axially moveable relative to the tube between a fully extended position and a fully retracted position.
The piston structure moves against oil in the tube as the rod moves to a retracted position. A metering device controls movement of oil within the tube to control the damping rate of the damper. Some dampers include an air pocket, within the oil, that compresses to accommodate movement of the rod further within the tube. As known, such air pockets can undesireably cause irregular damping motions or cavitation, particularly when the air pocket moves through the metering device. Some noncavitating dampers have been developed that include a floating member axially separating the oil from the air pocket. As known, such noncavitating dampers are longer than other dampers because the noncavitating dampers must provide axial space for the floating member and the air pocket, in addition to the rod and the piston structure. These longer, noncavitating dampers are often difficult to package, especially within confined areas.
An example damper assembly includes a tube, a piston assembly axially moveable relative to the tube between an extended position and a retracted position, and a material encapsulating a first fluid. The piston assembly is configured to compress the first fluid using a second fluid.
A example method for controlling movement of a damper assembly includes encapsulating a first fluid within a material, moving a piston assembly to displace a second fluid, and compressing the first fluid using the displaced second fluid.
These and other features of the example disclosure can be best understood from the following specification and drawings, the following of which is a brief description:
Referring to
The damper tube 18 is pivotably coupled to a second component 34 at 36. In this example, the first component 30 and the second component 34 are vehicle components, such as steering components for a zero-turn radius lawn mower. As known, moving the rod 26 along an axis x between extended positions and retracted positions facilitates damped relative movements between the first component 30 and the second component 34.
In this example, the annular space 24 within the damper assembly 10 accommodates a material 38 encapsulating a first fluid 42, which is air in this example. The damper assembly 10 also includes a second fluid 50 that is moveable between the annular space 24 and the damper tube. The second fluid 50, which is oil in this example, is substantially noncompressible. Accordingly, the piston structure 14 displaces, rather than compresses, the second fluid 50 as the rod 26 moves to the retracted position.
The displaced second fluid 50 flows through a metering device 46 to the annular space 24 and exerts force on the material 38. These forces increase as the piston structure 14 forces more of the second fluid 50 into the annular space 24 against the material 38. Sufficient force on the material 38 compresses the first fluid 42 within the material 38 in a radial direction relative to the axis x. Compressing the first fluid 42 creates space within the annular space 24 for accommodating more of the second fluid 50 flowing through the metering device 46.
Moving the rod 26 in the opposite direction (from retracted positions to extended positions) relieves pressure on the material 38 as the second fluid 50 flows back through the metering device 46 to the damper tube 18. The first fluid 42 expands within the material 38 to fill the area within the annular space 24 vacated by the second fluid 50. As the material 38 encapsulates the first fluid 42 in this example, only the second fluid 50 flows through the metering device 46. In one example, the first fluid 42, expanding within the material 38, helps urge the second fluid 50 to the damper tube 18.
Referring to
In this example, the material 38 is a CPE-EPDM foam material having a density of about 30 lb/ft3 (480 kg/m3). In some examples, the material 38 helps control movement characteristics (e.g., speed, smoothness, etc.) of the damper assembly 10. For example, the denser the material 38, the faster the rod 26 moves to the extended position. Also, in some examples, the material 38 does not encapsulate the first fluid 42, but instead separates the first fluid 42 from the second fluid 50.
Although the material 38 is described as foam in this example, those skilled in the art and having the benefit of this disclosure will understand that other materials are suitable for separating the first fluid 42 from the second fluid 50, and further that arrangements (other than positioning the material 38 within the annular space 24) are possible and fall within the scope of the disclosed embodiment.
In this example, the material 38 has an “o”-shaped cross-section and holds the radial position of the damper tube 18 within the housing 22. That is, radial movements of the damper tube 18 within the housing 22 in direction Y are limited by the damper tube 18 contacting the material 38. A crimped portion 54 of the housing 22 also limits relative movements between the damper tube 18 and the housing 22. A seal 58 near the crimped portion 54 limits movement of the second fluid 50 from the annular space 24. Arranging the damper tube 18 in this manner facilitates accommodating misalignments between the housing 22, the damper tube 18, and other components of the damper assembly 10.
In this disclosure, like reference numerals designate like elements where appropriate, and reference numerals with the addition of one-hundred or multiples thereof designate modified elements. The modified elements incorporate the same features and benefits of the corresponding modified elements, expect where stated otherwise.
Referring now to
The feature 74, in this example, is a bump extending radially inward past a radially outer edge 76 of the flange 70 on the spacer 66. The feature 74 prevents further movement of the spacer 66 along axis X away from the spring 62. Crimping, knurling, and other manufacturing processes are used to form the feature 74 in this example.
Referring to
Features of these examples include a noncavitating damper having a shorter overall length than previous designs while incorporating two fluids separated by a material. Another feature includes limiting relative movement of the damper tube utilizing the material separating the fluids. A feature of the examples that move to a repeatable return position is returning a piston assembly to a repeatable position to return a throttle to a neutral position in a zero turn radius lawnmower.
Although a preferred embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.