BACKGROUND OF THE INVENTION

[0001] The present invention relates to a damper, particularly one which includes ventilation apertures in the piston and housing to improve the damping action and lifetime of the damper.

[0002] Dampers of the type disclosed in U.S. Publication No. 2003/0183994 and in U.S.

Patent No. 7,549,519 are employed in connection with a variety of appliances, such as suspending the tub of a washing machine during washing and spin drying cycles to stabilize the drum, particularly in the event unbalanced loads a re encountered. Such dampers typically include grease or other lubricant to lubricate a friction element associated with the piston of the damper. As the damping piston moves up and down during heavy use, the air in the damper is compressed and grease within the damper moves. This generates significant heat and tends to shorten the lifetime of existing dampers.

SUMMARY OF THE INVENTION

[0003] In order to alleviate the overheating problem due to the movement of grease within the damper cylinder as well as the compression of air, the system of the present invention provides ventilation apertures through the piston allowing the friction element to engage the inner side walls of the cylindrical damper while at the same time allowing air and/or grease to escape from one side of the piston to the other without seriously affecting the damping action. Also, the present invention contemplates the position of vent apertures in the upper or lower caps of the damper to allow air to escape outside the damper as necessary during operation.

[0004] Dampers embodying the present invention include a piston housing comprising a cylindrical tube with a polymeric spool-shaped piston mounted therein for supporting a friction element. The piston is coupled to a friction rod extending through a cap at one end of the housing. A spring extends between the piston and the capped end. The spool-shaped piston includes one or more relatively large venting apertures extending axially therethrough, such that, as the piston moves within the housing, air and/or grease may move through the piston. I n some embodiments of the invention, a pertures may be formed in end ca ps in the housing to allow air to enter and exit the housing during use.

[0005] With such structure, a ventilated damper is provided which may include both venting features to reduce the heat generated by the da mper during heavy use, thereby improving the functioning of the damper and extending its life. These and other features, objects a nd advantages of the present invention wi ll become a pparent upon reading the following description thereof together with reference to the accompanying drawings.

BRI EF DESCRI PTION OF TH E DRAWINGS

[0006] Fig. 1 is a perspective pictorial view of a washing machine, shown pa rtly broken away, illustrating the mounting of two dam pers embodying the present invention;

[0007] Fig. 2 is an enlarged vertical cross-sectiona l view of a dam per em bodying the present invention;

[0008] Fig. 3 is a perspective view of one embodiment of a spool-shaped piston embodying the present invention;

[0009] Fig. 4 is a cross-sectional view of the piston shown in Fig. 3, taken along section lines IV-IV of Fig. 3;

[0010] Fig. 5 is a cross-sectional view of the piston shown in Fig. 3, taken along section lines V-V of Fig. 3;

[0011] Fig. 6 is a perspective view of an a lternative embodiment of a spool-shaped piston embodying the present invention;

[0012] Fig. 7 is a cross-sectional view of the piston shown in Fig. 6, taken along section lines VII-VI I of Fig. 6;

[0013] Fig. 8 is a cross-sectional view of the piston shown in Fig. 6, taken along section lines VI M-VI M of Fig. 6;

[0014] Fig. 9 is a perspective view of yet another alternative embodiment of a spool- shaped piston em bodying the present invention;

[0015] Fig. 10 is a cross-sectional view of the piston shown in Fig. 9, taken along section lines X-X of Fig. 9; [0016] Fig. 11 is a cross-sectional view of the piston shown in Fig. 9, taken along section lines XI-XI of Fig. 9;

[0017] Fig. 12 is an enlarged fragmentary cross-sectional view showing the details of the piston shown in Figs. 9-11 installed in the dam per;

[0018] Fig. 13 is an enlarged fragmentary cross-sectional view of a vent aperture formed in the side of the upper ca p;

[0019] Fig. 14 is an enlarged fragmentary cross-sectional view of a vent aperture formed through the upper surface of the upper cap;

[0020] Fig. 15 is an enlarged fragmentary cross-sectional view of a vent a pertu re extending lateral ly through the chimney of the upper ca p;

[0021] Fig. 16 is an enlarged fragmentary cross-sectional view of a vent aperture formed in the bottom ca p of the damper; and

[0022] Fig. 17 is an enlarged fragmentary cross-sectional view of a vent aperture formed in the lower side of the bottom cap of the damper.

DETAI LED DESCRI PTION OF TH E PREFERRED EMBODI MENT

[0023] Referring initial ly to Fig. 1, there is shown a washing machine 10, which includes a cabinet and frame 12 housing a drum 14 for receiving clothes to be laundered through a hinged cover 16. Drum 14 is conventionally coupled to a drive mechanism which rotates and agitates clothes within the drum during wash and spin dry cycles. The drum 14 is subject to vibrations during normal operation of the machine and severe vibrations when there are unba lanced loads. I n order to accommodate such motion, the drum 14 is supported by a plura lity of dampers 20 (two shown in the pictoria l diagram of Fig. 1) at va rious locations. The dam pers are each mounted in a tension mode with a bracket 22 secured to the drum 14 and including a hemispherica l su rface engaging the rounded upper surface 54 of an end cap 50 (Fig. 2) of a damper 20. Each damper 20 includes a friction rod 40 extending therefrom which is secured to the fra me 12 of the machine by a bracket 15. Typica lly, four such dampers a re em ployed for suspending the drum 14 within ca binet 12 and provides the desired improved dam ping fu nction of this invention. The construction of various dampers 20 is described in detail in connection with Figs. 2- 17. [0024] In Fig. 2, there is shown a damper 20 embodying the present invention which includes a tubular housing 26, which receives a spool-shaped piston 28 which can be of different configurations, as shown in Figs. 3-11. Basically, the spool-shaped piston 28 includes friction pads 30 within an annular recess 29 of the piston, which engage the inner cylindrical surface 25 of tube 26. The friction rod 40 is held to the bottom of the spool-shaped piston 28 by a washer 36 and held in place by coined end 38 holding the lower end of the rod 40 against the lower surface of piston 28 when the rod is moving in an upward direction, as indicated by arrow A in Fig. 2. The rod extends through an aperture 53 in upper cap 50. Cap 50 is secured to tubular housing 26 and crimped in position at 52. Cap 50 includes a cylindrical, downwardly extending extension 56 surrounding friction rod 40 to stabilize its motion. Cap 50 includes a convexly curved upper surface 54, which is engaged by a concave surface of the mounting bracket 22 for the washer 10 shown in Fig. 1. This allows the damper to move to follow the motion of the washer drum 14 during its operation.

[0025] Rod 40 extends outwardly to a mounting end (not shown), which attaches to bracket 15 of machine 10, as illustrated in Fig. 1. Surrounding friction rod 40 and extending between the lower surface of cap 50 and the upper surface of piston 28 is a compression spring 60, which, unless under a load, tends to hold the piston in the lowered position as illustrated in Fig. 2. The bottom of tubula r housing 26 is enclosed by a lower end cap 62, which is held in position by an annular crimp at 64. An annular foam polymeric pad 30 is positioned in the annular recess 29 of piston 28. Pad 30 is injected with from 5 to 6 cubic centimeters (cc) of grease during assembly to provide a lubricious and yet somewhat frictional interface between the piston 28 (i.e., pad 30) and the inner surface 25 of tube 26.

[0026] The piston design is a significant departure from prior piston designs in that it includes significantly larger bypass apertures extending therethrough, typically having from at least three to five times greater cross-sectional area than that of existing damper cylinders. Piston 28 shown in Fig. 2 corresponds to the piston of Figs. 9-11 of the preferred embodiment of the invention.

[0027] Figs. 3-5 disclose one spool-shaped piston 70 which can be employed in the damper 20. Piston 70 is generally spool-shaped with a polymeric body, as are all of the pistons in this application, which are made of acetal, ABS, or polypropylene. Piston 70 includes an annular groove 74 for receiving an annular foam pad material, such as pad 30 disclosed in Fig. 2. It includes eight axially extending apertures 76 extending therethrough concentrically around the center aperture 73 for receiving friction rod 40, such as shown in Figs. 1 and 2. Fig. 5 illustrates the axial flow path of air through the spool-shaped piston, as shown by arrow B. The apertures 76 have curved entryways through opposite sides of the body of the piston to facilitate the flow of fluid (air or grease) therethrough. The piston 70 also includes a plurality of arcuate spaced-apart recesses 78, shown in Figs. 3 and 4, which reduce the amount of material, the weight, and, therefore, the cost of the piston 70. The axially extending apertures 76 of piston 70 collectively provide an air and/or grease passageway through the piston 70 having a cross-sectional area of at least 50 mm ² (square millimeters) and preferably about 66.5 mm ² .

[0028] An alternative, somewhat thinner, piston design 80 is shown in Figs. 6-8. Piston

80 likewise includes a center aperture 83 through which the friction rod 40 extends, as well as an annular recess 84 for receiving a lubricated foam friction pad, such as pad 30, therein. The piston includes a plurality of about eight apertures 86 extending axially therethrough, providing an air/grease flow path (one indicated by arrow C in Fig. 8) through the piston as it moves within the body 26 of damper 20. Piston 80, like piston 70, provides a passageway having a cross-sectional area of about 66.5 mm ² for the movement of air and/or grease therethrough. The exact geometry of apertures 86, like apertures 76 in the previous embodiment, can be varied somewhat to provide a larger passageway for the air and/or grease. Passageways 86 also have curved entryways through opposite sides of the body of the piston to facilitate the flow of fluid (air or grease) therethrough.

[0029] The preferred embodiment of the piston is shown in Figs. 9-11. Piston 28 comprises a generally spool-shaped member having an axially centered outer annular recess 29 for receiving the foam friction element or pad 30, as seen in Fig. 2. Piston 28 includes a center aperture 23 for receiving the friction rod 40 therethrough. The body of piston 28 includes four substantially arcuate and enlarged axially extending apertures 24, allowing the passage of air and/or grease therethrough. One of the apertures 24 is shown in Fig. 11 showing fluid flow in the direction indicated by a rrow D. Further, the piston 28 includes curved entryways 27 (Fig. 11) to facilitate the flow of fluid therethrough. This embodiment of piston 28, thus, employs four equal arcuately spaced apertures 24 of substantial dimension in circumscribing an arc of approximately 70° each and collectively provides a substantial passageway having a cross-sectional area in excess of 100 mm ² through the piston and, in one preferred embodiment, a passageway of 103 mm ² . The piston provides sufficient frictional contact between friction rod 40 and the inner surface 25 of cylinder 26 to achieve the desired damping control for the damper 20. The relatively la rge passageway defined by apertures 24 in the piston 28 is illustrated in the cross-sectional view of Fig. 12, which also shows the lower cap 62, including a depression 66 in its floor to provide clearance for the end 38 of friction rod 40 as it moves within tube 26 of the damper 20.

[0030] In addition to the enlarged passageways through the pistons 28, 70, and 80, as described above, the damper 20 may include apertures ventilating the interior volume (21 in Fig. 2) of the damper to the surrounding environment. Fig. 13 illustrates one manner by which the venting to the outside atmosphere can be accomplished by providing a venting aperture 57 in the upper cap 50. Aperture 57 extends radially outwardly from friction rod 40 under the lip 51 of cap 50 and above the crimp connection 52. This prevents water or other foreign material from the environment of washer drum 14 from entering the damper 20 inasmuch as the vent aperture 57 is protected by the overhanging lip 51 of cap 50.

[0031] In another embodiment, as seen in Fig. 14 and illustrated in Fig. 2, the vent aperture 55 is provided through the domed surface 54 of the ca p 50 in an axia l direction with aperture 55 communicating directly with the interior 21 of the damper 20. Although this is a somewhat more efficient manner in which air can be exhausted from or introduced into the damper, it is somewhat more susceptible to the introduction of unwanted fluids from the ambient surroundings.

[0032] Fig. 15 illustrates another embodiment of the venting of the interior 21 of damper

20 by means of a vent aperture 58 formed in the upper stem 59 of cap 50, also referred to as the chimney. In this embodiment, the inner diameter 53 of stem 59 in cap 50 is slightly greater than the outer diameter of friction rod 40, such that air can travel in the coaxial space between rod 40 and the inner cylindrical diameter 53 of cap 50, escape through the radially extending aperture 58, which communicates directly with the interior 21 of damper 20. [0033] In addition to the venting of material from the interior 21 of damper 20 through the upper cap 50, air can be vented through the damper 20 through the vent apertures in the base or lower cap 62, as illustrated in Figs. 16 and 17. In Fig. 16, the cap 62 includes an aperture 65 through the cap, such that, when piston 28 either moves in a downwardly or upwardly direction, air can be exhausted from or drawn into vent aperture 65. Similarly, in the embodiment shown in Fig. 17, the lower cap 62 includes a laterally extending vent aperture 67 to provide the same function. Aperture 67 is located below the crimp 64.

[0034] Thus, with a venting structure as shown in Figs. 3-17 of the piston designs, which can include a combination of cap venting and lower base venting, the movement of the pistons 28, 70, or 80 is not impeded by the compression of air within the cylinder nor is air compressed significantly to increase the temperature within the damper. This structure allows the damper to move relatively vigorously to provide damping action without overheating or excessive wearing of the friction pads employed.

[0035] It will become a pparent to those skilled in the art that various modifications to the preferred embodiment of the invention as described herein can be made without departing from the spirit or scope of the invention as defined by the appended claims.