Abstract:
The air damper includes a housing with cylindrical walls and a piston assembly reciprocating therein. The piston assembly includes an interior surface against which a seal abuts. The interior surface is textured in a grained pattern so that interstices are formed between the seal and the interior surface thereby forming an effective air passageway for damping. A cylindrical spacer spaces the interior surface from a retainer and the seal is engaged around the cylindrical spacer and between the retainer and the interior surface. An alternative embodiment inserts textile material through a damping orifice in order to vary the rate of damping.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention pertains to air dampers with adjustable air flow rates. The adjustable air flow rates are achieved by the degree of graining or texturing of a plate which contacts the seal or by inserting a mold or assembling a media, such as a filter into a shaft or housing of the damper. 
     2. Description of the Prior Art 
     In the prior art, air dampers are known. However, typical prior art air dampers do not allow for simple adjustment of the air flow rate which controls the damping. As the damping is typically controlled by an orifice through which the air flows, such adjustment is typically done by varying the size of the orifice which requires a re-design of the air damper. 
     The damping rate of prior art dampers can be limited due to tooling restrictions, and tooling variations can create damping variations. Similarly, slow damping rates are difficult to achieve with prior art designs. Likewise, small variations in damping rates are difficult to achieve with prior art designs. 
     Examples of prior art include U.S. Pat. No. 5,603,574 entitled “Fluid Dampened Support Having Variable Stiffness and Damping”, issued on Feb. 18, 1997 to Ide et al. which discloses a fluid dampened support having variable stiffness and damping. Electric discharge machining is used for the purpose of achieving fine tolerances. U.S. Pat. No. 5,697,477 entitled “Air Damper”, issued on Dec. 16, 1997 to Hiramoto et al. discloses an air damper with a tapered functional damper with a plunger and a piston, and further discloses a cylindrical tapered body and an O-ring resulting in two separate chambers. U.S. Pat. No. 5,647,578 entitled “Latch Mechanism”, issued on Jul. 15, 1997 to Bivens discloses a latch mechanism with an O-ring with a tapered surface. U.S. Pat. No. 4,877,155 entitled “Spill Protecting Apparatus”, issued on Oct. 31, 1989 to Tull discloses an apparatus which includes an air damper which includes a seal at an open end of the cylinder and compressed gas in two chambers so that both air and friction retard or damp movement of the piston. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an air damper in which the damping rate can be varied without the need for a substantial re-design of the air damper. 
     It is therefore a further object of this invention to provide an air damper in which slow damping rates can be achieved. 
     It is therefore a still further object of this invention to provide an air damper in which damping rates are repeatable from damper to damper. 
     It is therefore a still further object of this invention to provide an air damper in which small changes in damping rates can be achieved. 
     It is therefore a still further object of the present invention to provide an air damper in which the damping rate can be varied with a minimal additional cost. 
     These and other objects are attained by providing an air damper in which the damping is effected by air passing between a seal and a textured or grained plate within the plunger. By varying the depth and/or degree of texturing or graining, the effective air flow area can be varied thereby varying the degree of damping. Alternatively, a mold can be inserted or a media, such as a filter, can be assembled into a shaft or housing of a damper in order to vary the amount of air flow. 
     More particularly, the air damper includes a shaft, a seal, a housing, a retainer and a plunger, the plunger having the textured surface. In operation, when the damper is extended, the seal extends between the outer diameter of the seal and the inner diameter of the housing and between the top grained surface of the plunger and the bottom wall of the seal. The grained surface on the plunger allows a very accurately controlled amount of air to be metered from one side of the seal to the other, thereby causing a slow consist damped rate. This airflow rate can be varied by simply changing the grained finish. These variations in airflow rate can be small or large and are very repeatable from one damper to another. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein: 
     FIG. 1 is a partially exploded plan view of the housing and piston of the first embodiment of the air damper of the present invention. Additionally, FIG. 1 illustrates in phantom a filter media which can be inserted in the second embodiment of the air damper of the present invention. 
     FIG. 2 is a cross-sectional view of the housing of the air damper of the present invention. 
     FIG. 3 is a cross-sectional view of the piston of the first embodiment of the air damper of the present invention. 
     FIG. 4 is a perspective view of the plunger of the first embodiment of the air damper of the present invention. 
     FIG. 5 is a top view of the plunger of the first embodiment of the air damper of the present invention. 
     FIG. 6 is a cross-sectional view of the plunger of the first embodiment of the air damper of the present invention along plane  6 — 6  of FIG.  5 . 
     FIG. 7 is a side cross-sectional view of the seal of the first embodiment of the air damper of the present invention. 
     FIG. 8 is a perspective view of the retainer of the first embodiment of the air damper of the present invention. 
     FIG. 9 is a side plan view of the shaft of the first embodiment of the air damper of the present invention. 
     FIG. 10 is a cross-sectional view of the first alternative piston assembly of the present invention. 
     FIG. 11 is a cross-sectional view of the second alternative piston assembly of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings in detail, one sees that FIG. 1 is a partially exploded side plan view of air damper  10  of the first embodiment of the present invention, showing the housing  12  receiving the piston assembly  14  attached to shaft  16 , and further receiving cap  18 , through which shaft  16  reciprocates. Textile material  100  is illustrated in phantom, but is not envisioned as part of the first embodiment, but rather in the second embodiment as described hereinafter. 
     As shown in FIG. 2, housing  12  includes cylindrical walls  20  with closed end  22  and chamfered mouth  24 . Closed end  22  includes cylindrical flange  26  extending from area of reduced diameter  28  in order to provide an attachment element to a structural element such as a refrigerator or freezer (not shown). Those skilled in the art will realize that such an air damper is useful in many different applications. 
     As shown in FIG. 1, cap  18  includes lip  30  for engaging chamfered mouth  24  of housing  12  and further includes central aperture  32  through which shaft  16  reciprocates. Cap  18  prevents piston assembly  14  from being withdrawn from housing  10  during operation. 
     As shown in FIG. 3, piston assembly  14  includes plunger  36 , seal  38  and retainer  58 . As further shown in FIGS. 4,  5  and  6 , plunger  36  includes lower toroidal plate  40  and central cylindrical longitudinal spacer  42  with radially extending spacer ribs  44 . Parallel attachment tabs  46 ,  48  extend from central cylindrical longitudinal spacer  42  and include apertures  50 ,  52 , respectively, and form gap  54  therebetween. 
     Grained surface  41  of lower toroidal plate  40  is radially outward from central cylindrical longitudinal spacer  42  and includes a grained or textured surface wherein portions of the surface deviate from planar. As will be described hereinafter, these deviations form interstices between grained surface  41  and seal  76  thereby forming the effective air passageway for the damper  10  and variations of the degree of these deviations can vary the effective area of the air passageway thereby varying the damping strength, possibly over a very small gradation, in a very predictable and repeatable manner. 
     As shown in FIG. 8, retainer  58  is generally planar and includes four outwardly extending portions  59 ,  60 ,  61 ,  62  alternating with concave portions  63 ,  64 ,  65 ,  66 . Parallel guide slots  68 ,  70  are formed at a central location of retainer  58  with isthmus  60  formed therebetween. As shown in FIG. 3, during assembly, parallel attachment tabs  46 ,  48  of plunger  36  extend through parallel guide slots  68 ,  70  and isthmus  60  extends through gap  54 . As retainer  58  is longitudinally spaced from lower toroidal plate  40  by central cylindrical longitudinal spacer  42 , toroidal gap  72  is formed to engage seal  76 . Seal  76  is further internally radially engaged or positioned by radially extending spacer ribs  44 . 
     As shown in FIGS. 3 and 7, seal  76  is generally toroidal with radially inward wall  78  and radially outward wall  80  facing generally downward in the illustrated orientations, or toward chamfered mouth  24  of housing  12  after insertion of piston assembly  14  into housing  12 . Radial wall  82  extends between radially inward wall  78  and radially outward wall  80 . Radial wall  82  further urges against grained surface  41  of lower toroidal plate  40 . As grained surface  41  includes portions which deviate from planar, interstices are formed between grained surface  41  and radial wall  82  of seal  76  which form the effective air passageway for the damping function of damper  10 . This air passageway provides communication between the chamber within the housing  12  as bounded by the piston assembly  14  and closed end  22  and the chamber of essentially atmospheric pressure formed between piston assembly  14  and mouth  24  of housing  12 . Increases in these deviations resulting from increased graining or increased texturing increase the interstices and likewise increase the effective area of the air passageway thereby varying the damping of damper  10 . 
     As shown in FIG. 9, shaft  16  includes a generally cylindrical central portion  88  with first end  90  including radially outwardly extending cylindrical bosses  92 ,  94  which, as shown in FIG. 3, engage apertures  50 ,  52  of parallel attachment tabs  46 ,  48  of plunger  36 . Second end  96  of shaft  16  includes attachment element  98  which typically attaches to a door or similar structural element (not shown). 
     A second embodiment of air damper  10  is taught by the textile material  100  shown in phantom in FIG.  1 . Typically, this second embodiment does not require the piston assembly structure taught hereinabove but would typically involve a structure as disclosed in more detail in U.S. patent application Ser. No. 09/177,029, entitled “Silent Damper with Anti-Rattle Shaft”, filed on Oct. 22, 1998, the disclosure of which is hereby incorporated by reference. The textile material  100 , such as a filter or GORE® material, extends through the damping orifice of the piston thereby effectively increasing the air flow resistance thereby increasing the damping. This textile material  100  can be increased or decreased by fine increments to vary the strength of the damping and obviously does not add substantially to the costs of the damper. 
     First and second alternative embodiments of piston assembly  14  are disclosed in FIGS. 10 and 11. Piston assembly  14  includes parallel attachment tabs  46 ,  48  with apertures  50 ,  52  similar to those disclosed in FIG.  3 . However, piston assembly  14  is a relatively unitary piece with toroidal channel  72  formed therein to engage seal  76 . In FIG. 10, the upper and lower radially oriented toroidal surfaces  73 ,  75  are grained or textured to provide the interstices as described hereinabove and are urged against seal  76 . In FIG. 10, gap  77  is formed between inner cylindrical wall  79  to provide an air passageway. In FIG. 11, similarly, inner cylindrical wall  79  includes the grained or textured surface to provide the interstices described hereinabove and is urged against seal  76 . There is “play”, however, between upper and lower radially oriented surface  73 ,  75  and inner cylindrical wall  79 , illustrated as gaps  81 ,  83 , in order to provide an air passageway. 
     In order to use damper  10 , the installer may be supplied with an assembled damper  10 , or may have the choice of various seals  76  and various plungers  36  with different degrees of texturing or graining. The installer would assemble the damper  10  with the various desired elements as taught above and typically attach cylindrical flange  26  to a fixed structure, such as a refrigerator or freezer body, and would attach attachment element  98  of shaft  16  to a moveable structure, such as a door of a refrigerator or freezer body. 
     Thus the several aforementioned objects and advantages are most effectively attained. Although preferred embodiments of the invention have been disclosed and described in detail herein, it should be understood that this invention is in no sense limited thereby and its scope is to be determined by that of the appended claims.