Patent Description:
Suspension systems are provided to filter or isolate the vehicle's body (sprung portion) from the vehicle's wheels and axles (unsprung portion) when the vehicle travels over vertical road surface irregularities as well as to control body and wheel motion. In addition, suspension systems are also used to maintain an average vehicle attitude to promote improved stability of the vehicle during maneuvering. The typical passive suspension system includes a spring and a damping device in parallel with the spring which are located between the sprung portion and the unsprung portion of the vehicle.

Due to an increase in the complexity of vehicle body and suspension, the length of a shock absorber or damper assembly becomes more and more critical because it has a direct impact in the installation, placement (space) and the cost of the vehicle body.

One such a damper assembly is disclosed in <CIT>. The damper assembly comprises a main tube extending along a center axis between a first end and a second end. The main tube defines a fluid chamber extending therebetween for containing a working fluid. A main piston is slidably disposed in the fluid chamber dividing the fluid chamber in to a compression chamber and a rebound chamber. A piston rod extends along the center axis and coupled to the main piston for moving the main piston between a compression stroke and a rebound stroke. An external tube, radially spaced apart from the main tube, extends about the main tube between a closed end and an opened end. The closed end is adjacent the first end. The opened end is adjacent to the second end. The external tube and the main tube define a compensation chamber extending therebetween.

The present invention provides a damper assembly. The damper assembly comprises a monotube damper and a twintube damper in a telescopic configuration. The monotube damper includes a first tube, a rod disposed at least partially within the first tube and coaxially therewith, and a first piston connected to the rod and slidably disposed within the first tube. The twintube damper includes a second tube and a third tube each disposed coaxially around the monotube damper, the second tube having an upper end and a closed lower end opposite from the upper end, and the third tube disposed within the second tube and defining an annular chamber therebetween. The twintube damper includes a second piston connected to an axial end of the first tube dividing an interior of the third tube into an upper twintube chamber and a lower twintube chamber, the second piston defining a twintube passage providing fluid communication between the upper twintube chamber and the lower twintube chamber. The twintube damper also includes a base valve having a base member disposed adjacent to the closed lower end of the second tube and defining at least one base passage therethrough and providing fluid communication between the lower twintube chamber and the annular chamber. The damper assembly also includes a seal configured to selectively block fluid flow through one of the twintube passage or the base passage and based on an axial position of the first tube relative to the second tube.

The present invention provides a damper assembly. The damper assembly comprises a monotube damper and a twintube damper in a telescopic configuration. The monotube damper includes a first tube, a rod disposed at least partially within the first tube and coaxially therewith, and a first piston connected to the rod and slidably disposed within the first tube. The twintube damper includes a second tube and a third tube each disposed coaxially around the monotube damper, the second tube having an upper end and a closed lower end opposite from the upper end, and the third tube disposed within the second tube and defining an annular chamber therebetween. The twintube damper includes a second piston connected to an axial end of the first tube dividing an interior of the third tube into an upper twintube chamber and a lower twintube chamber, the second piston defining a twintube passage providing fluid communication between the upper twintube chamber and the lower twintube chamber. The twintube damper also includes a base valve having a base member disposed adjacent to the closed lower end of the second tube and defining at least one base passage therethrough and providing fluid communication between the lower twintube chamber and the annular chamber. The damper assembly also includes a seal configured to selectively block fluid flow through the twintube passage of the second piston based on an axial position of the first tube relative to the second tube.

The present invention provides a damper assembly. The damper assembly comprises a monotube damper and a twintube damper in a telescopic configuration. The monotube damper includes a first tube, a rod disposed at least partially within the first tube and coaxially therewith, and a first piston connected to the rod and slidably disposed within the first tube. The twintube damper includes a second tube and a third tube each disposed coaxially around the monotube damper, the second tube having an upper end and a closed lower end opposite from the upper end, and the third tube disposed within the second tube and defining an annular chamber therebetween. The twintube damper includes a second piston connected to an axial end of the first tube dividing an interior of the third tube into an upper twintube chamber and a lower twintube chamber, the second piston defining a twintube passage providing fluid communication between the upper twintube chamber and the lower twintube chamber. The twintube damper also includes a base valve having a base member disposed adjacent to the closed lower end of the second tube and defining at least one base passage therethrough and providing fluid communication between the lower twintube chamber and the annular chamber. The damper assembly also includes a seal configured to selectively block fluid flow through the base passage of the base member based on an axial position of the first tube relative to the second tube.

Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a damper assembly <NUM>, <NUM> is provided. The damper assembly <NUM>, <NUM> may also be called a shock absorber, and may be used as part of a suspension system in a motor vehicle, such as a car or truck. The damper assembly <NUM>, <NUM> of the present disclosure may minimizes damper overall length while maintaining the same stroke length. The damper assembly <NUM>, <NUM> of the present disclosure also provides simplified design when compared with some conventional dampers, which lowers the cost of the vehicle body.

The damper assembly <NUM>, <NUM> is designed to have a relatively small body with a maximized stroke. When compared with conventional dampers, the damper assembly <NUM>, <NUM> may have considerably shorter compressed length while keeping a similar or equal stroke. The damper assembly <NUM>, <NUM> of the present disclosure may provide many benefits at the vehicle level. It may provide for a more compact rear suspension, allowing passenger and light commercial vehicles to have additional space for a trunk and/or for batteries (e.g. in electrified vehicles).

The damper assembly <NUM>, <NUM> of the present disclosure utilizes a two-piece (telescopic) rod including a first rod and a second rod in the form of a moving monotube. The damper assembly <NUM>, <NUM> of the present disclosure may incorporate existing parts and existing assembly designs, with some additional components and design aspects. The damper assembly <NUM>, <NUM> of the present disclosure may incorporate a concept of a damper with a divided scope of work. The first rod and the second rod may not move simultaneously, but in sequence. The monotube damper may provide damping and simultaneously function as the second rod for the twintube damper, which also provides a damping function.

Movement of the first rod and the second rod (monotube) is realized sequentially by the appropriate selection of valve characteristics: monotube piston valve, twin-tube piston valve, and base valve - by properly tuning of the valves. There are two separated oil chambers - a mono-tube oil chamber and a twin-tube oil chamber.

The damper assembly <NUM>, <NUM> of the present disclosure may provide several advantages over conventional dampers. It may provide a compressed length that is approximately <NUM>% shortened compared to conventional twin tube dampers having a similar extended length. The damper assembly <NUM>, <NUM> of the present disclosure includes design aspects and components based on proven solutions and technologies of monotube and twin tube dampers. The damper assembly <NUM>, <NUM> of the present disclosure provides for temperature compensation by incorporating two separated gas chambers. The damper assembly <NUM>, <NUM> of the present disclosure may exhibit no cavitation phenomena on both sides (caused by temperature influence oil volume), and no multiplication of force from gas. It does not exhibit any high-pressure build-up with rebound movement. The damper assembly <NUM>, <NUM> of the present disclosure provides is much simpler than other, competing designs, with less seals and guiding parts.

<FIG> is a cutaway view of a first damper assembly <NUM> in accordance with an embodiment of the present invention. The first damper assembly <NUM> includes a monotube damper <NUM> and a first twintube damper <NUM> in a telescopic configuration.

The monotube damper <NUM> includes a first rod <NUM> extending along an axis A and translatable along the axis A. The first rod <NUM> includes a proximal end <NUM> and a distal end <NUM> spaced apart from the proximal end <NUM> along the axis A. The first rod <NUM> includes a shoulder <NUM> spaced apart from the distal end <NUM> and configured for attachment to an external structure, such as a suspension component or a chassis-mounted bracket on a vehicle. In some embodiments, the first rod <NUM> may include an external threading (not shown) between the distal end <NUM> and the shoulder <NUM> for attachment to the external structure. The monotube damper <NUM> also includes a first tube <NUM> having a tubular shape coaxial with the axis A and having a first end <NUM> and a second end <NUM> opposite from the first end <NUM>. A first cap <NUM> is disposed within the first tube <NUM> adjacent the first end <NUM>, providing a fluid-tight seal. The first cap <NUM> defines a first bore <NUM>, and the first rod <NUM> passes through the first bore <NUM> in a fluid-tight seal, and configured to allow the first rod <NUM> to translate along the axis A relative to the first tube <NUM>.

A first piston <NUM> is slidably disposed within the first tube <NUM> and connected to the first rod <NUM> adjacent to the proximal end <NUM>. The first piston <NUM> divides the interior of the first tube <NUM> into a first chamber <NUM> and a second chamber <NUM>. The first chamber <NUM> extends between the first cap <NUM> and the first piston <NUM>. The second chamber <NUM> is on an opposite side of the first piston <NUM> from the first chamber <NUM>. The first piston <NUM> includes one or more monotube passages <NUM> extending therethrough, providing fluid communication between the first chamber <NUM> and the second chamber <NUM>. Fluid may be channeled through the monotube passages <NUM> as the first piston <NUM> is moved through the first tube <NUM> to provide a damping function of the monotube damper <NUM>.

In some embodiments, the first piston <NUM> may include one or more discs or other structures (not shown in the drawing) to selectively limit fluid flow through the monotube passages <NUM> in a compression direction and/or in a rebound direction.

A gas cup <NUM> is disposed within the first tube <NUM>, between the first piston <NUM> and the second end <NUM>. The gas cup <NUM> may define a third chamber <NUM> extending between the gas cup <NUM> and the second end <NUM> of the first tube <NUM>. The gas cup <NUM> may be fluid-tight to separate the second chamber <NUM>, from the third chamber <NUM>. The first chamber <NUM> and the second chamber <NUM> may contain a liquid, such as oil, and the third chamber <NUM> may contain a gas. In some embodiments, the gas cup <NUM> may be movable within the first tube <NUM> to compress the gas in the third chamber <NUM> in response to a compressive force on the first rod <NUM> to provide a spring function of the monotube damper <NUM> and compensation for oil volume change with temperature.

A first ring <NUM> is disposed around the first rod <NUM> adjacent to the first piston <NUM> and configured to engage the first cap <NUM> to smooth end of rebound movement by increasing a rebound damping force adjacent to an end of travel position of the first rod <NUM> in a rebound direction (i.e. outwardly from the first tube <NUM>). Additionally or alternatively, the first ring <NUM> may limit travel of the first rod <NUM> outwardly from the first tube <NUM>. The first cap <NUM> includes first slots <NUM> defining a smooth end-rebound chamber configured to receive the first ring <NUM> when the first rod <NUM> is in a fully extended position, with the first piston <NUM> adjacent to the first cap <NUM>. The first ring <NUM> and the first slots <NUM> may function together as a hydraulic rebound stop.

A second ring <NUM> is disposed around the proximal end <NUM> of the first rod <NUM> and configured to engage the gas cup <NUM> for smoothing end of compression movement by increasing a compression damping force adjacent to an end of travel position of the first rod <NUM> in a compression direction (i.e. into the first tube <NUM>). Additionally or alternatively, the second ring <NUM> may limit travel of the first rod <NUM> into the first tube <NUM>. The gas cup <NUM> includes second slots <NUM> defining a smooth end-compression chamber configured to receive the second ring <NUM> when the first rod <NUM> is in a fully inserted position, with the first piston <NUM> adjacent to the gas cup <NUM>. The second ring <NUM> and the second slots <NUM> may function together as a hydraulic compression stop. The rings <NUM>, <NUM> may help to provide a smooth transition from a low level of damping (low forces from monotube-only damping) to a high level of damping (high forces from twintube + monotube damping).

The first twintube damper <NUM> includes a second tube <NUM> having a tubular shape coaxial with the axis A and having an upper end <NUM> and a lower end <NUM> opposite from the upper end <NUM>. The second tube <NUM> is closed at the lower end <NUM>. A second cap <NUM> is disposed within the second tube <NUM> adjacent the upper end <NUM>, providing a fluid-tight seal. The second cap <NUM> defines a second bore <NUM>, and the first tube <NUM> passes through the second bore <NUM> in a fluid-tight seal, and configured to allow the first tube <NUM> to translate along the axis A relative to the second tube <NUM>. The first tube <NUM> of the monotube damper <NUM>, therefore, functions as a second rod in the twintube damper <NUM>. The first twintube damper <NUM> also includes a third tube <NUM> having a tubular shape coaxial with the axis A and located inside of the second tube <NUM>. The third tube <NUM> has an outside diameter that is smaller than an inside diameter of the second tube <NUM>, providing an annular chamber <NUM> between the second tube <NUM> and the third tube <NUM>.

The first twintube damper <NUM> also includes a second piston <NUM> connected to the second end <NUM> of the first tube <NUM>. The second piston <NUM> is disposed within the third tube <NUM> and in sealing engagement with an interior surface of the third tube <NUM>. The second piston <NUM> may enclose the third chamber <NUM> of the first tube <NUM>, preventing gas from escaping therefrom. The second piston <NUM> includes a top face <NUM> facing toward the second cap <NUM>, and a bottom face <NUM>, facing opposite the top face <NUM>. The second piston <NUM> divides the interior of the third tube <NUM> into an upper twintube chamber <NUM> and a lower twintube chamber <NUM>. The upper twintube chamber <NUM> extends between the second cap <NUM> and the second piston <NUM>. The second piston <NUM> includes one or more first selective twintube passages 93A, one or more second selective twintube passages 93B extending therethrough, with each of the selective twintube passages 93A, 93B selectively providing fluid communication between the upper twintube chamber <NUM> and the lower twintube chamber <NUM>. The second piston <NUM> includes one or more invariable twintube passages <NUM> extending therethrough, with each of the invariable twintube passages <NUM> providing fluid communication between the upper twintube chamber <NUM> and the lower twintube chamber <NUM>. Fluid may be channeled through either or both of the selective twintube passages 93A, 93B and/or the invariable twintube passages <NUM> as the second piston <NUM> is moved through the third tube <NUM> to provide a damping function of the twintube damper <NUM>. In some embodiments, the second piston <NUM> may include one or more discs or other structures to selectively limit fluid flow through the selective twintube passages 93A, 93B and/or the invariable twintube passages <NUM> as the second piston <NUM> moves through the third tube <NUM> in either or both of a compression direction or a rebound direction.

The first twintube damper <NUM> also includes a first base valve <NUM> disposed within the second tube <NUM> and adjacent to the lower end <NUM>. The first base valve <NUM> includes a first base member <NUM> that defines a plurality of first base compression passages <NUM> providing fluid communication between the lower twintube chamber <NUM> and the annular chamber <NUM> in compression movement. Fluid may be channeled through the first base passages <NUM> as the second piston <NUM> is moved through the third tube <NUM> (in compression movement) to provide a further damping function of the twintube damper <NUM>. The first base valve <NUM> includes also first base rebound passages <NUM> providing fluid communication between the annular chamber <NUM> and the lower twintube chamber <NUM> in rebound movement. In some embodiments, the first base valve <NUM> may include one or more discs or other structures to selectively limit fluid flow through the first base compression passages <NUM> and first base rebound passages <NUM>. The first base passages <NUM> may be called position-independent base passages, and the amount of fluid flow therethrough may be independent of the axial an axial position of the first tube <NUM> relative to the second tube <NUM>. These position-independent base passages are contrasted with second base passages <NUM>, discussed below with reference to <FIG>, and which have flow characteristics varies depending on an axial position of the first tube <NUM> relative to the second tube <NUM>.

The first damper assembly <NUM> includes a mounting ring <NUM> (or another element that allows the mounting of the shock absorber in the suspension) attached to the closed lower end <NUM> of the second tube <NUM>. The mounting ring <NUM> may be attached to a second external structure, such as a suspension component or a chassis-mounted bracket on a vehicle.

The first twintube damper <NUM> also includes a first compressive member <NUM> with a first seal <NUM> located in the upper twintube chamber <NUM> and extending from the second cap <NUM> to a top face <NUM> of second piston <NUM>. The first compressive member <NUM> with the first seal <NUM> may be fixed to the second cap <NUM>, and the first seal <NUM> may be free to selectively engage the second piston <NUM>, thereby strengthening damping forces in the rebound direction. The first compressive member <NUM> may include a coil spring. Additionally or alternatively, the first compressive member <NUM> may include a resilient material, such as rubber or foam. When the first twintube damper <NUM> is in a nominal position, as shown in <FIG>, (or any further extended position) the first seal <NUM> contacts the top face <NUM> of the second piston <NUM> and covers only the second selective twintube passages 93B, thereby restricting fluid flow therethrough. When the twin tube damper <NUM> is any further compressed position (starting from nominal position, as shown in <FIG>. ), the first seal <NUM> is no longer in contact with the top face <NUM> of the second piston <NUM>, and does not cover the second selective twintube passages 93B. Therefore, the first seal <NUM> ceases to restrict fluid flow through the second piston <NUM> as the twin tube damper <NUM> is compressed from the nominal position. The first seal <NUM> may have an annular or ring shape. In some embodiments, the first seal <NUM> may be disposed within and adjacent to an interior surface of the third tube <NUM>. However, the first seal <NUM> may have a different shape, size, and/or position.

The first twintube damper <NUM> also includes a second compressive member <NUM> with a second seal <NUM> located in the lower twintube chamber <NUM> and extending from the first base valve <NUM> to bottom surface <NUM> of the second piston <NUM>. The second compressive member <NUM> with the second seal <NUM> may be fixed to the first base valve <NUM>, and the second seal <NUM> may be free to selectively engage the second piston <NUM>, thereby strengthening damping forces in the compression direction. The second compressive member <NUM> may include a coil spring. Additionally or alternatively, the second compressive member <NUM> may include a resilient material, such as rubber or foam. When the first twintube damper <NUM> is in a nominal position, as shown in <FIG>, (or any further compressed position) the second seal <NUM> contacts the bottom face <NUM> of the second piston <NUM> and covers only the first selective twintube passages 93A, thereby restricting fluid flow therethrough, and simultaneously strengthening of damping forces of the second piston <NUM>. When the twin tube damper <NUM> is any further extended position (starting from nominal position, as shown in <FIG>. ), the second seal <NUM> is no longer in contact with the bottom face <NUM> of the second piston <NUM>, and does not cover the first selective twintube passages 93A. Therefore, the second seal <NUM> ceases to restrict fluid flow through the second piston <NUM> as the twin tube damper <NUM> is extended in a rebound direction from the nominal position. The second seal <NUM> may have an annular or ring shape. In some embodiments, the second seal <NUM> may be disposed within and adjacent to an interior surface of the third tube <NUM>. However, the second seal <NUM> may have a different shape, size, and/or position.

<FIG> shows the first damper assembly <NUM> in a compressed position. As the first damper assembly <NUM> is compressed from its nominal position, the monotube damper <NUM> may first be compressed. When the monotube damper <NUM> is compressed beyond a predetermined (maximum) amount, the first twintube damper <NUM> may then compress. When the second piston <NUM> of the first twintube damper <NUM> is moved from its nominal position and downwardly toward the mounting ring <NUM> (or other mounting section/part) , the second compressive member <NUM> with the second seal <NUM> is compressed, and the first compressive member <NUM> with the first seal <NUM> is spaced apart from the second piston <NUM>.

<FIG> shows the first damper assembly <NUM> in an extended position. As the first damper assembly <NUM> is extended from its nominal position, the monotube damper <NUM> may first be extended. When the monotube damper <NUM> is extended beyond a predetermined (maximum) amount, the first twintube damper <NUM> may then extend. When the second piston <NUM> of the first twintube damper <NUM> is moved from its nominal position and upwardly away from the mounting ring <NUM> (or other mounting section/part), the first compressive member <NUM> with the first seal <NUM> is compressed, and the second compressive member <NUM> with the second seal <NUM> is spaced apart from the second piston <NUM>.

The full stroke of the telescopic damper assembly "L" is provided by: the stroke of the monotube piston rod (i.e. first rod <NUM>) "L1" + the stroke of the "twintube piston rod" (i.e. first tube <NUM>) "L2".

As shown in <FIG>, the second seal <NUM> selectively blocks fluid flow through the first selective twintube passages 93A based on an axial position of the first tube <NUM> relative to the second tube <NUM>, with the twintube damper <NUM> compressed beyond a given position where the second seal <NUM> contacts the second piston <NUM>. Likewise, the first seal <NUM> selectively blocks fluid flow through the second selective twintube passages 93B based on an axial position of the first tube <NUM> relative to the second tube <NUM>, with the twintube damper <NUM> extended beyond a given position where the first seal <NUM> contacts the second piston <NUM>.

<FIG> show cutaway views of the first damper assembly <NUM> at various positions in a compression stroke. Specifically, <FIG> shows the first damper assembly <NUM> in a full-extended position; <FIG> shows the first damper assembly <NUM> in mid-extended position; <FIG> shows the first damper assembly <NUM> in nominal position, which may be midway between full extended and full-compressed positions; <FIG> shows the first damper assembly <NUM> in mid-compressed position; and <FIG> shows the first damper assembly <NUM> in a compressed position.

Compressing the first damper assembly <NUM> from the full-extended position to the mid-extended position may include a force due to a valve restriction of the second piston <NUM> (which is not supported by the second compressive member <NUM>) plus a force due to restriction of the first base valve <NUM> to be less than the force due to a valve restriction of the first piston <NUM> of the monotube damper <NUM>. Thus, the first twintube damper <NUM> may be compressed to its nominal position before the monotube damper <NUM> moves from its fully-extended position. After the first twintube damper <NUM> is compressed to its nominal position, the second piston <NUM> stops contacting the first seal <NUM> and starts contacting the second seal <NUM>. At this point, the first twintube damper <NUM> has increased damping force due to the second piston <NUM> being reinforced by force applied by the second seal <NUM> and by the second seal <NUM> restricting fluid flow therethrough. With the first twintube damper <NUM> having the increased damping force, compressive force applied to the first rod <NUM> causes the monotube damper <NUM> to move from its fully-extended position to its nominal position, and then to the full-compressed position, with the first piston <NUM> spaced away from the first cap <NUM>.

Compressing the first damper assembly <NUM> beyond the nominal position may include the force due to the valve restriction of the first piston <NUM> to be less than the force due to the valve restriction of the second piston <NUM>, supported by the second compressive member <NUM> with the second seal <NUM>, plus the force due to restriction of the first base valve <NUM>. Thus, the monotube damper <NUM> may continue to be compressed until the monotube damper <NUM> is in a full-compressed position with the proximal end <NUM> of the first rod <NUM> and the second ring <NUM> contacting the gas cup <NUM>. Only then may the first twintube damper <NUM> may be compressed beyond its nominal position.

<FIG> show cutaway views of the damper assembly of <FIG> at various positions in a rebound stroke. Specifically, <FIG> shows the first damper assembly <NUM> in a full-compressed position; <FIG> shows the first damper assembly <NUM> in mid-compressed position; <FIG> shows the first damper assembly <NUM> in nominal position, which may be midway between full extended and full-compressed positions; <FIG> shows the first damper assembly <NUM> in mid-extended position; and <FIG> shows the first damper assembly <NUM> in a full-extended position.

<FIG> is a cutaway view of a second damper assembly <NUM> in accordance with an embodiment of the present invention. The second damper assembly <NUM> includes a monotube damper <NUM> and a second twintube damper <NUM> in a telescopic configuration. The monotube damper <NUM> of the second damper assembly <NUM> may be similar or identical to the monotube damper <NUM> of the first damper assembly <NUM>. The second twintube damper <NUM> of the second damper assembly <NUM> may be similar or identical to the first twintube damper <NUM> of the first damper assembly <NUM>, with a few differences described herein. In place of the first base valve <NUM>, the second twintube damper <NUM> of the second damper assembly <NUM> includes a second base valve <NUM> disposed within the second tube <NUM> and adjacent to the lower end <NUM>. Like the first base member <NUM> of the first base valve <NUM>, the second base valve <NUM> includes a second base member <NUM> that defines a plurality of first base passages <NUM> providing fluid communication between the lower twintube chamber <NUM> and the annular chamber <NUM>. In some embodiments, the second base valve <NUM> may include one or more discs or other structures to selectively limit fluid flow through the first base passages <NUM>. The second base member <NUM> also defines a plurality of second base passages <NUM> providing fluid communication between the lower twintube chamber <NUM> and the annular chamber <NUM>. Fluid may be channeled through the first base passages <NUM> and/or the second base passages <NUM> as the second piston <NUM> is moved through the third tube <NUM> to provide a damping function of the second twintube damper <NUM>. One or more of the first base passages <NUM> and one or more of the second base passages <NUM> may share a common section, such as a common radial passage <NUM> shown on <FIG>.

In place of the second compressive member <NUM> and the second seal <NUM>, the second twintube damper <NUM> includes a third compressive member <NUM> and a third seal <NUM>. The compressive member <NUM> is located in the lower twintube chamber <NUM> and extends from the second piston <NUM> toward the second base valve <NUM>. The third seal <NUM> is attached to the third compressive member <NUM> and located between the third compressive member <NUM> and the second base valve <NUM>. The third compressive member <NUM> may be fixed to the second piston <NUM>, and the third seal <NUM> may be free to selectively engage the second base valve <NUM>, thereby strengthening damping forces in the compression direction. The third compressive member <NUM> may include a coil spring. Additionally or alternatively, the third compressive member <NUM> may include a resilient material, such as rubber or foam. When the second twintube damper <NUM> is in a nominal position, as shown in <FIG>, (or any further compressed position) the third seal <NUM> contacts the second base valve <NUM> and covers the one or more of the second base passages <NUM>, thereby restricting fluid flow therethrough. When the second twintube damper <NUM> is in any further extended position (from the nominal position), the third seal <NUM> is no longer contact with the second base valve <NUM> and does not cover the one or more of the second base passages <NUM>. Therefore, the third seal <NUM> ceases to restrict fluid flow through the second base valve <NUM> as the second twintube damper <NUM> is extended in the rebound direction from the nominal position. The third seal <NUM> may have an annular or ring shape. In some embodiments, the third seal <NUM> may be disposed within and adjacent to an interior surface of the third tube <NUM>. However, the third seal <NUM> may have a different shape, size, and/or position.

As shown in <FIG>, the third seal <NUM> selectively blocks fluid flow through the second base passages <NUM> based on an axial position of the first tube <NUM> relative to the second tube <NUM>, with the twintube damper <NUM> compressed beyond a given position.

<FIG> show cutaway views of the second damper assembly <NUM> at various positions in a compression stroke. Specifically, <FIG> shows the second damper assembly <NUM> in a full-extended position; <FIG> shows the second damper assembly <NUM> in mid-extended position; <FIG> shows the second damper assembly <NUM> in nominal position, which may be midway between full extended and full-compressed positions; <FIG> shows the second damper assembly <NUM> in mid-compressed position; and <FIG> shows the second damper assembly <NUM> in a full compressed position.

Compressing the second damper assembly <NUM> from the full-extended position to the mid-extended position may include a force due to restrictions of the second piston <NUM> and the second base valve <NUM> (which is not supported by the second compressive member <NUM> with the third seal <NUM>) to be less than the force due to a valve restriction of the first piston <NUM> of the monotube damper <NUM>. Thus, the second twintube damper <NUM> may be compressed to its nominal position before the monotube damper <NUM> moves from its fully-extended position. After the second twintube damper <NUM> is compressed to its nominal position, with the third seal <NUM> contacting the second base valve <NUM>, the monotube damper <NUM> may move from its fully-extended position to its nominal position, and then to the full-compressed position with the first piston <NUM> spaced away from the first cap <NUM>. In other words, when the second twintube damper <NUM> is compressed to its nominal position, the second compressive member <NUM> with the third seal <NUM> increases the damping force of the second twintube damper <NUM>. This increased damping force is caused by a combination of the second compressive member <NUM> being compressed and an increased damping force produced by the second base valve <NUM> (due to the third seal <NUM> restricting fluid flow therethrough). With the second twintube damper <NUM> in this configuration, compressive force applied to the first rod <NUM> may cause the monotube damper <NUM> to move from its fully-extended position to its nominal position and then to full-compressed position.

Compressing the second twintube damper <NUM> of the second damper assembly <NUM> beyond its nominal position may include the force due to the valve restriction of the first piston <NUM> to be less than the damping force of the second twintube damper <NUM> due to the valve restriction of the second piston <NUM>, and with second base valve <NUM> supported by the third compressive member <NUM> with the third seal <NUM>. Thus, the monotube damper <NUM> may continue to be compressed until the monotube damper <NUM> is in a full-compressed position with the proximal end <NUM> of the first rod <NUM> or the second ring <NUM> contacting the gas cup <NUM>. Only then may the second twintube damper <NUM> may be compressed beyond its nominal position.

<FIG> show cutaway views of the second damper assembly <NUM> at various positions in a rebound stroke. Specifically, <FIG> shows the second damper assembly <NUM> in a compressed position; <FIG> shows the second damper assembly <NUM> in mid-compressed position; <FIG> shows the second damper assembly <NUM> in nominal position, which may be midway between full extended and full-compressed positions; <FIG> shows the second damper assembly <NUM> in mid-extended position; and <FIG> shows the second damper assembly <NUM> in a full-extended position.

As shown in <FIG>, the second damper assembly <NUM> extends in a rebound stroke similar to its function in the compression stroke, but in the opposite direction. The twintube damper <NUM> first moves from its full-compressed position, shown in <FIG> to its nominal position shown in <FIG>, while the monotube damper <NUM> remains in its full-compressed position. Subsequently, and as shown in <FIG>, the monotube damper <NUM> extends from its full-compressed position, through a nominal position shown in <FIG>, and then to a full-extended position shown in <FIG>. After the monotube damper <NUM> has reached its full-extended position, as shown in <FIG>, the twintube damper <NUM> moves from its nominal position to its full-extended position, as shown in <FIG>.

When the first rod <NUM> in its fully extended position, and compression movement is starting: the characteristic of damping of the second piston <NUM> is weaker than the first piston <NUM>. With the compression movement, starting from the extended position (either from full-extended or from mid-extended) - till nominal position, the second piston <NUM> is not reinforced by the compression enhancement (i.e. by the second compressive member <NUM> with second seal <NUM> for the second piston <NUM> in first twintube damper <NUM>; or by the third compressive member <NUM> with third seal <NUM> for second base valve <NUM> in second twin tube damper <NUM>) - then the restriction of the second piston <NUM> is less than the valve restriction of the first piston <NUM>. Thus, a first damping level is realized by moving the first tube <NUM>. This valve characteristic continues until the first tube <NUM> reaches its nominal position. When the first tube <NUM> reaches its nominal position, the second piston <NUM> is supported by the compression enhancement (i.e. by the second compressive member <NUM> with second seal <NUM> for the second piston <NUM> in first twintube damper <NUM>; or by the third compressive member <NUM> with third seal <NUM> for second base valve <NUM> in second twin tube damper <NUM>), then the characteristic of the second piston <NUM> is changed. It is stronger than the valve characteristic of the first piston <NUM>. In this configuration, a second level of damping is engaged.

Compression hydraulic balance requirement (from damper full extended position to nominal position): valve restriction of the second piston <NUM> (unsupported by compression enhancement) + valve restriction of the base valve <NUM>, <NUM> < valve restriction of the first piston <NUM>.

Starting from the nominal position, during compression stroke - a second damping level is realized by moving of the first rod <NUM> relative to the first tube <NUM> of the monotube damper <NUM>. The first piston <NUM> is weaker than the second piston <NUM>. This enables the first piston <NUM> to reach the full-compressed position in the monotube. In the range of relatively small car body displacements from nominal position (low damping forces), damping is only provided by fluid flow through the first piston <NUM> in the monotube damper <NUM>. After the first rod <NUM> reaches a full-compressed position, a third level of damping by is engaged by the second piston <NUM>, supported by compression enhancement. There are two options (two concepts) for realizing second level of damping. Those two concepts correspond to the first twintube damper <NUM> and the second twintube damper <NUM>.

In the first twintube damper <NUM>, the third level of compression damping is realized through the first base valve <NUM> plus compression damping of second piston <NUM> with compression enhancement from the second compressive member <NUM> with second seal <NUM>. Thus the strengthened second piston <NUM> is engaged and performs together with first base valve <NUM> to provide damping for the remaining displacement of car body (high damping forces in compression).

In the second twintube damper <NUM>, the third level of damping is realized through the second piston <NUM> and the second base valve <NUM> with compression enhancement from the third compressive member <NUM> with the third seal <NUM>. Thus, the strengthened base valve <NUM> is engaged and performs together with the second piston <NUM> to provide damping for the remaining displacement of car body (high damping forces in compression).

Compression hydraulic balance requirement (from damper nominal position to full compressed position): valve restriction of the first piston <NUM> < valve restriction of the second piston <NUM> (supported by compression enhancement) + valve restriction of the base valve <NUM>, <NUM>.

After the first rod <NUM> reaches a fully compressed position, and rebound movement is starting: the valve restriction characteristic of the second piston <NUM> is weaker than the first piston <NUM>. For the first tube <NUM> rebound movement, starting from the compressed position, (either from full-compressed or from mid-compressed) to the nominal position, the second piston <NUM> is not reinforced by the first compressive member <NUM> with the first seal <NUM>. In this configuration, the restriction on the second piston <NUM> is less than the valve restriction of the first piston <NUM>. Thus, the first damping level is realized then by the second piston <NUM> (moving of the first tube <NUM>). This valve restriction characteristic of the second piston <NUM> continues until the first tube <NUM> reaches the nominal position. When the first tube <NUM> reaches its nominal position, the second piston <NUM> damping characteristic is changed due to reinforcement by the first compressive member <NUM> with the first seal <NUM>. At this time, the damping characteristic of the second piston <NUM> increases. It becomes stronger than the valve restriction of the first piston <NUM>. In this configuration, a second level of damping is engaged.

Rebound hydraulic balance requirement (from damper full compressed position to nominal position): the valve restriction of the second piston <NUM> (unsupported by the first compressive member <NUM>) < the valve restriction of the first piston <NUM>.

Starting from nominal position, during rebound stroke - second damping level is realized by moving the first rod <NUM>. In this configuration, the first piston <NUM> is weaker than the second piston <NUM>. This enables the first piston <NUM> to reach the full-extended position in the monotube. In the range of relatively small car body displacements from nominal position (low damping forces), damping is only provided by the valve restriction of the first piston <NUM> in the monotube damper <NUM>. After the first rod <NUM> reaches full-extended position, a third level of damping is engaged. The second piston <NUM>, supported by the first compressive member <NUM> with the first seal <NUM>, is engaged and performs damping for further displacement of the car body (with high rebound damping forces).

Rebound hydraulic balance requirement (from damper nominal position to full extended position): valve restriction of the first piston <NUM> < valve restriction of the second piston <NUM>, supported by the first compressive member <NUM> with the first seal <NUM>).

Starting from the nominal position, damping of the telescopic damper is realized: in a first level of damping by the first piston <NUM> (as shown <FIG>, <FIG>, <FIG> and <FIG>), and in a second level of damping by the second piston <NUM> and the base valve <NUM>, <NUM> (in compression). This may be similar to a conventional twin-tube damper, except that second piston <NUM> in the damper assembly <NUM>, <NUM> of the present disclosure has a variable characteristic - for half of the rebound stroke (starting from full-compressed) of the first tube <NUM>, the second piston <NUM> is weaker than the first piston <NUM>, until nominal position is reached. After that, and for the remainder of the rebound stroke, the second piston <NUM> is stronger than the valve restriction of the first piston <NUM>. For the first half of the compression stroke (starting from full-extended), the second piston <NUM> is weaker than the first piston <NUM> (until nominal position is reached), and for the remainder of the compression stroke, second piston <NUM> is stronger than the valve restriction of the first piston <NUM>. Strengthening of the second piston <NUM> is provided by the enhancements - in the rebound direction by the first compressive member <NUM> with the first seal <NUM> (starting from the nominal position of the first tube <NUM>), and in the compression direction by the compression enhancement (i.e. by the second compressive member <NUM> with the second seal <NUM> for the second piston <NUM> in first twintube damper <NUM>; or by the third compressive member <NUM> with third seal <NUM> for second base valve <NUM> in second twin tube damper <NUM>), also starting from the nominal position of the first tube <NUM>.

It is significant that the characteristic of the second piston <NUM> is variable depending on the position of the first tube <NUM> and the direction of movement of the car body.

In nominal position second piston <NUM> is supported by enhancements from both sides (the first compressive member <NUM> with the first seal <NUM> and one of the second compressive member <NUM> with the second seal <NUM> or the third compressive member <NUM> with the third seal <NUM> for second base valve <NUM>). The fixed position of the enhancement (i.e. the first seal <NUM> , the second seal <NUM> or the third seal <NUM> for second base valve <NUM>) in the nominal position is ensured by enhancement spring aids.

With the compression of the first tube <NUM> - starting from the damper nominal position, the second piston <NUM> is reinforced by the compression enhancement (i.e. the second compressive member <NUM> with the second seal <NUM> or the third compressive member <NUM> with the third seal <NUM> for second base valve <NUM>). With the rebound movement of the first tube <NUM> - starting from the nominal position, the second piston <NUM> will be reinforced by the first compressive member <NUM> with the first seal <NUM>.

One or more of the pistons <NUM>, <NUM> and/or the base valves <NUM>, <NUM> may be configured for double-sided operation, causing some restriction to fluid flow in one direction and a relatively higher restriction to fluid flow in an opposite direction. For example, one or more of the pistons <NUM>, <NUM> and/or the base valves <NUM>, <NUM> may consist of an orifice, one or more clamped deflective discs, and calibrated holes for tuning the amount of restriction to fluid flow over a wide range of damper velocities in the compression stroke and/or the rebound stroke. In some embodiments, each of the pistons <NUM>, <NUM> and the base valves <NUM>, <NUM> may be configured for double-sided operation, consisting of one or more orifices, one or more clamped deflective discs, and one or more calibrated holes.

Claim 1:
A damper assembly (<NUM>, <NUM>) comprising:
a monotube damper (<NUM>) and a twintube damper (<NUM>, <NUM>) in a telescopic configuration;
the monotube damper (<NUM>) including a first tube (<NUM>), a rod (<NUM>) disposed at least partially within the first tube (<NUM>) and coaxially therewith, and a first piston (<NUM>) connected to the rod (<NUM>) and slidably disposed within the first tube (<NUM>);
the twintube damper (<NUM>, <NUM>) including a second tube (<NUM>) and a third tube (<NUM>) each disposed coaxially around the monotube damper (<NUM>), the second tube (<NUM>) having an upper end (<NUM>) and a closed lower end (<NUM>) opposite from the upper end (<NUM>), and the third tube (<NUM>) disposed within the second tube (<NUM>) and defining an annular chamber (<NUM>) therebetween;
the twintube damper (<NUM>, <NUM>) including a second piston (<NUM>) connected to an axial end (<NUM>) of the first tube (<NUM>) dividing an interior of the third tube (<NUM>) into an upper twintube chamber (<NUM>) and a lower twintube chamber (<NUM>), the second piston (<NUM>) defining a twintube passage (<NUM>, <NUM>) providing fluid communication between the upper twintube chamber (<NUM>) and the lower twintube chamber (<NUM>);
the twintube damper (<NUM>, <NUM>) including a base valve (<NUM>, <NUM>) having a base member (<NUM>, <NUM>) disposed adjacent to the closed lower end (<NUM>) of the second tube (<NUM>) and defining at least one base passage (<NUM>, <NUM>) therethrough and providing fluid communication between the lower twintube chamber (<NUM>) and the annular chamber (<NUM>); and
a seal (<NUM>, <NUM>, <NUM>) configured to selectively block fluid flow through one of the twintube passage (<NUM>, <NUM>) or the base passage (<NUM>, <NUM>) based on an axial position of the first tube (<NUM>) relative to the second tube (<NUM>).