Passive Resettable Stiffness Damper

Abstract

A passive resettable stiffness damper is described and shown. The passive resettable stiffness damper is of a compact and simplified design and is configured to produce a damping force that optimally varies with the vibration-causing load. The passive resettable stiffness damper includes a cylinder, such as, but not limited to, a pneumatic or hydraulic cylinder, having a reciprocating piston and one or a pair of associated protruding piston rods. A reset mechanism is mounted on or otherwise associated with the cylinder. The reset mechanism includes a mechanically operated toggle valve with a spring return and a series of disks coupled to corresponding shafts to form a gear train. The gear train disk and shaft assembly is capable of rotation but is limited in translation.

Description

[Technical Field]

[0001]

[0001] Exemplary embodiments of the present general concept are directed to passive resettable stiffness devices that may be used, for example, to enable effective vibration damping of an object. [Background technology]

[0002]

[0002] Vibration control techniques are used to protect structures from dynamic loads by dissipating energy that would otherwise be absorbed by the structure. The characteristics of the vibration control technique are dictated by the type of structure and dynamic load.

[0003]

[0003] In the field of structural engineering, vibration control techniques are utilized to protect buildings and bridge structures from ground movements caused by earthquakes. These vibration control techniques, often referred to as dampers, come in many different forms depending on their energy dissipation mechanisms and power requirements. The most reliable type of damper is the passive damper, which does not require external power and generates forces in direct response to the structure's movements. Passive dampers include, but are not limited to, viscous dampers, viscoelastic dampers, friction dampers, and metallic yield dampers. Summary of the Invention [Problem to be solved by the invention]

[0004]

[0004] An exemplary embodiment of the present general concept presents a passive resettable stiffness damper (PRSD) device that incorporates the aforementioned desirable characteristics. [Means for solving the problem]

[0005] An exemplary PRSD device embodiment includes, but is not limited to, a cylinder, such as a pneumatic or hydraulic cylinder, having a reciprocating piston and one or a pair of associated protruding piston rods. A reset mechanism is mounted on or otherwise associated with the cylinder. The reset mechanism includes a mechanically operated toggle valve with a spring return and a series of disks coupled to corresponding shafts to form a gear train. The gear train disk and shaft assembly is capable of rotation but is limited in translation.

[0006] The toggle valve of the reset mechanism is disposed in a bypass loop connecting the cylinder volumes on either side of the piston and operates to regulate the flow of fluid therebetween, opening and closing depending on the position of a toggle coupled to the valve.

[0007]

[0007] The reset mechanism is positioned relative to the cylinder so that a first disk of the gear train contacts the piston rod of the cylinder and another disk of the gear train contacts the toggle of the toggle valve. Thus, extension or contraction of the piston rod of the cylinder in response to vibration forces causes rotation of the first disk, which in turn causes rotation of the disk contacting the toggle of the toggle valve. Rotation of the disk contacting the toggle of the toggle valve results in displacement of the toggle, which moves the toggle valve. By this process, the valve opens and closes each time the piston changes direction, thereby resetting the damper force generated by the PRSD.

[0008] Other aspects and features of the inventive concepts will become apparent to those skilled in the art upon review of the following detailed description of illustrative embodiments in conjunction with the accompanying drawings.

[0009] In the drawings and the following description of exemplary embodiments, like reference numerals throughout the figures refer to the same or equivalent features. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an isometric view of an exemplary embodiment of a single-sided passive resettable stiffness damper (PRSD) in accordance with the concepts of the present invention. FIG. [Figure 2]

[0011] FIG. 2 is a top view of the exemplary one-sided PRSD of FIG. 1. [Figure 3]

[0012] FIG. 2 is a side view of the exemplary unilateral PRSD of FIG. 1. [Figure 4]

[0013] FIG. 2 is an end view of the exemplary one-sided PRSD of FIG. 1. [Figure 5]

[0014] FIG. 2 is an opposite end view of the exemplary one-sided PRSD of FIG. 1. [Figure 6]

[0015] FIG. 2 is an isometric cross-sectional view of the exemplary one-sided PRSD of FIG. 1. [Figure 7]

[0016] FIG. 2 is an exploded view of the exemplary one-sided PRSD of FIG. 1. [Figure 8]

[0017] FIG. 2 is an enlarged view of a portion of the exemplary unilateral PRSD of FIG. 1. [Figure 9A]

[0018] 2A-2C illustrate toggle positions of the reset mechanism of the exemplary single-sided PRSD of FIG. 1. [Figure 9B] 2A-2C illustrate toggle positions of the reset mechanism of the exemplary single-sided PRSD of FIG. 1. [Figure 9C] 2A-2C illustrate toggle positions of the reset mechanism of the exemplary single-sided PRSD of FIG. 1. [Figure 10A]

[0019] FIG. 9D is an enlarged view of a toggle of the reset mechanism shown in FIGS. 9A to 9C. [Figure 10B] FIG. 9D is an enlarged view of a toggle of the reset mechanism shown in FIGS. 9A to 9C. [Figure 11]

[0020] FIG. 1 is an isometric view of an exemplary embodiment of a bilateral passive resettable stiffness damper (PRSD) in accordance with the concepts of the present invention; [Figure 12]

[0021] FIG. 12 is a top view of the exemplary bilateral PRSD of FIG. 11. [Figure 13]

[0022] FIG. 12 is a side view of the exemplary bilateral PRSD of FIG. 11. [Figure 14]

[0023] FIG. 12 is an enlarged end view of the exemplary bilateral PRSD of FIG. 11. [Figure 15]

[0024] FIG. 12 is an enlarged end view of the opposite side of the exemplary bilateral PRSD of FIG. 11. [Figure 16]

[0025] FIG. 12 is an isometric cross-sectional view of the exemplary bilateral PRSD of FIG. [Figure 17]

[0026] FIG. 12 is an exploded view of the exemplary bilateral PRSD of FIG. 11. [Figure 18]

[0027] 10 is a graph of damper force and piston displacement for an exemplary embodiment of a one-sided closed-loop PRSD in accordance with concepts of the present invention. [Figure 19]

[0028] 10 is a graph of damper force and piston displacement for an exemplary embodiment of a single-sided open-loop PRSD in accordance with concepts of the present invention. [Figure 20]

[0029] 10 is a graph of damper force and piston displacement for an exemplary embodiment of a two-sided closed-loop PRSD in accordance with concepts of the present invention. [Figure 21]

[0030] 10 is a graph of damper force and piston displacement for an exemplary embodiment of a double-sided open-loop PRSD in accordance with concepts of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011]

[0031] One exemplary embodiment of a single-sided passive resettable stiffness damper (PRSD) 5 is shown in Figures 1-7. As used herein, the term "single-sided" refers to the fact that the cylinder component of the PRSD has a single piston rod that only extends or retracts from one end of the cylinder.

[0012]

[0032] As shown, the exemplary PRSD 5 includes a cylinder 10 containing a piston, such as, but not limited to, a pneumatic or hydraulic cylinder. A reset mechanism 15 is mounted on or otherwise associated with the cylinder so as to overhang the cylinder's protruding piston rod 20. The reset mechanism includes a mechanically operated toggle valve 25 with a spring return and a plurality of discs 30. Each "disk," which may be a toothed gear or another form of disc, is connected to a shaft 35 and configured to contact (e.g., via tooth engagement, friction, etc.) and impart rotational movement relative to one another upon application of a rotational driving force to at least one disc. The shaft 35 is preferably supported by a rigid frame 40, such that the discs and shaft are rotatable but limited in translation.

[0013]

[0033] Referring now also to FIG. 8, further details regarding the structure and operation of the reset mechanism 15 can be seen. As shown, a first disk (Disk 1) is fixed to a preferably rigid first shaft (Shaft 1) between a pair of similar second disks (Disk 2), each of which has a diameter larger than that of the first disk (Disk 1). The first disk (Disk 1), second disk (Disk 2), and first shaft (Shaft 1) rotate together and therefore have the same angular displacement, rotational speed, and acceleration. The reset mechanism 15 is positioned relative to the cylinder 10 so that the first disk (Disk 1) contacts the cylinder's piston rod 20, which causes the first disk (Disk 1), second disk (Disk 2), and first shaft (Shaft 1) to rotate as a unit when the piston rod is extended or retracted.

[0014]

[0034] A fourth disk (Disk 4) is fixed to a preferably rigid second shaft (Shaft 2) between a pair of similar third disks (Disk 3), each of which has a diameter smaller than that of the fourth disk (Disk 4). The fourth disk (Disk 4), third disk (Disk 3), and second shaft (Shaft 2) rotate together and therefore have the same angular displacement, rotational speed, and acceleration. Engagement of the second disk (Disk 2) on the first shaft (Shaft 1) with the third disk (Disk 3) on the second shaft (Shaft 2) causes the fourth disk (Disk 4), third disk (Disk 3), and second shaft (Shaft 2) to rotate together as the first disk (Disk 1), second disk (Disk 2), and first shaft (Shaft 1) rotate together.

[0015]

[0035] 1-8, the mechanically operated toggle valve 25 is mounted higher than the disk 30 and shaft 35 of the reset mechanism 15. As best seen in FIG. 8, the periphery of a larger fourth disk (Disk 4) on the second shaft (Shaft 2) contacts the free end of the toggle 45 of the mechanically operated toggle valve 25 but does not contact the piston rod 20 of the cylinder 10. Rotation of the fourth disk (Disk 4) causes displacement of the toggle 45 which moves the toggle valve 25.

[0016]

[0036] It should be noted that each of the toggles 45 seen in Figures 2, 6, and 7, the toggle seen in Figure 8, and the toggle 75 seen in Figures 12, 16, and 17 are depicted diagrammatically and generally only. An actual PRSD embodiment according to the concepts of the present invention is preferably utilized and operated with a toggle having a reciprocating tip, as shown in Figures 9A-9C and 10A-10B and described in connection therewith herein.

[0017]

[0037] In this exemplary embodiment of PRSD5, the gear train disk 30 configuration amplifies the toggle displacement of the toggle valve 25 relative to the displacement of the cylinder piston rod 20 (and piston), so that the toggle displacement is greater than the piston rod displacement. If more amplification (e.g., larger movements) is required, additional disks and shafts may be added between the first shaft (shaft 1) and the second shaft (shaft 2) to increase the movement amplification while still utilizing relatively small diameter disks.

[0018]

[0038] The toggle valve 25 of the reset mechanism is located in a bypass loop (not shown) that connects the cylinder volumes on either side of the piston of the cylinder 10 and regulates the flow of fluid therebetween. Referring now to Figures 9A-9C, it can be better understood that the toggle valve 25 is closed when the toggle 45 is in the right position (Figure 9A) or the left position (Figure 9C), and that the valve is open when the toggle is in the center position (Figure 9B). Note that all of the above positions refer to the reset mechanism diagram shown in Figure 8.

[0019]

[0039] For the exemplary PRSD 5 shown in Figures 1-7, the initial position of the toggle is the right position shown in Figure 9A. If displacement of the cylinder piston rod 20 causes counterclockwise rotation (with respect to the view of the reset mechanism 15 shown in Figure 8) of the first disc (Disc 1) and, through gear train interaction, clockwise rotation of the fourth disc (Disc 4), the toggle will remain in the right position, the toggle valve 25 will remain closed, and the damper force will increase.

[0020]

[0040] As the piston rod 20 of the cylinder 10 changes direction, the first disc (Disc 1) rotates in a clockwise direction, which, through gear train interaction, rotates the fourth disc (Disc 4) in a counterclockwise direction. The counterclockwise rotation of the fourth disc (Disc 4) first moves the toggle from the right position in FIG. 9A to the center position shown in FIG. 9B. During this time, the toggle valve opens and the damper force decreases to zero. As the piston rod 20 continues to move in the same direction, further counterclockwise rotation of the fourth disc (Disc 4) moves the toggle from the center position in FIG. 9B to the left position shown in FIG. 9C, at which point the toggle valve 25 closes and the damper force increases again.

[0021]

[0041] With the end of the toggle in contact with the fourth disc (Disc 4) oriented in the left position shown in Figure 9C, the piston and piston rod 20 change direction and the toggle is moved towards the right position shown in Figure 9A, repeatedly opening and closing the toggle valve 25. Through this process, a reset of the damping force occurs each time the piston changes direction.

[0022]

[0042] As previously described and shown in FIGS. 9A-9C, resetting the damping force of the exemplary PRSD 5 requires the toggle 45 on the mechanically operated toggle valve 25 to change its position relative to the fourth disc (disk 4). More specifically, the point of contact P between the toggle 45 and the fourth disc (disk 4) moves along the periphery of the fourth disc (disk 4) as shown. Because this requires a change in length ΔL of the toggle 45, the toggle is preferably configured to include a reciprocating tip or to allow compression of the toggle length as shown in FIGS. 9A-9C and 10A-10B. In the case of the toggle 45 shown in FIGS. 9A-9C and 10A-10B, the toggle tip comprises a hollow shaft having an inner diameter slightly larger than the outer diameter of the toggle shaft and is held in sliding (reciprocating) relationship on the toggle shaft. A pre-compressed spring is mounted on the toggle shaft between the tip of the toggle and the end of the toggle that is pinned or otherwise pivotally attached to the toggle valve 25. Thus, as the toggle 45 moves from one side of the fourth disc (Disc 4) to the other, the tip of the toggle undergoes a linear displacement relative to the length of the toggle shaft corresponding to the required change in toggle length ΔL.

[0023]

[0043] It should be noted that the use of a toggle valve having a toggle with a reciprocating tip (or similar configuration) has several advantages, including, but not limited to: (1) the energy dissipation capability of the PRSD is enhanced because the toggle action only opens the toggle valve for a short time during reset, (2) the energy dissipation capability of the PRSD is enhanced by the toggle valve, which allows for a high flow rate with a low spring return force, (3) the reset mechanism is simplified compared to certain resettable semi-passive stiffness dampers (RSPSDs) and resettable passive stiffness dampers (RPSDs) of known designs, and (4) the PRSD is more compact due to the simplified reset mechanism.

[0024]

[0044] An exemplary embodiment of a bilateral passive resettable stiffness damper (PRSD) 50 is shown in Figures 11-17. As used herein, the term "bilateral" refers only to the fact that the cylinder component of the PRSD has two piston rods that extend and retract from opposite ends of the cylinder.

[0025]

[0045] As shown, the exemplary double-sided PRSD 50 includes a cylinder 55 containing a piston, such as, but not limited to, a pneumatic or hydraulic cylinder. A reset mechanism 60 is mounted on or otherwise associated with each end of the cylinder such that each reset mechanism 60 overhangs a corresponding piston rod 65, 70 of the cylinder 55.

[0026]

[0046] In this exemplary double-sided PRSD embodiment 50, each reset mechanism 60 is of the same design, construction, and operation as the reset mechanism 15 used in the exemplary single-sided PRSD 5. Accordingly, the toggle 75 of each reset mechanism 60 is also coupled to an associated toggle valve and has a free end that contacts the periphery of the fourth disk (Disk 4) on the second shaft (Shaft 2) of the gear train, as generally shown in FIG. 8 . A more detailed listing of the components of the reset mechanism 60 need not be repeated here. Similarly, the descriptions provided above regarding the interaction of the reset mechanism components (and FIG. 8 ), the movement of the toggle and the reset of the damper (and FIGS. 9A-9C ), and the change in the toggle length of the toggle valve (and FIGS. 10A-10B ) also apply equally to the reset mechanism 60 of the exemplary double-sided PRSD 50. Of course, one difference is that the opening and closing of the valve and the reset of the damper occur as a result of the operation of two reset mechanisms 60 in the exemplary double-sided PRSD 50, as opposed to the single reset mechanism 15 for the exemplary single-sided PRSD 50.

[0027]

[0047] One advantage of a double-sided PRSD over a single-sided PRSD is that the use of two toggle valves in a double-sided PRSD allows for twice the effective fluid flow rate of a single toggle valve in a single-sided PRSD. This higher fluid flow rate increases the rate at which the damper force drops to zero when the valves open during reset, thereby improving the energy dissipation capability of the PRSD.

[0028]

[0048] In both the exemplary single-sided and double-sided PRSD embodiments shown and described herein, a toggle valve is in a bypass loop connecting the cylinder volumes on either side of the cylinder piston. Movement of the cylinder piston creates pressure on one side of the cylinder and a vacuum on the other side. During reset, the toggle valve opens, the pressure equalizes, and the damper force drops to zero. Because the volume of gas inside the cylinder remains constant, such PRSD embodiments may be described as closed-loop systems.

[0029]

[0049] One advantage of a closed-loop system over an open-loop system is that the gas inside the damper cylinder can be compressed, increasing the damping force. Another advantage of a closed-loop system over an open-loop system is that because the damping force is generated by both the pressure on one side of the cylinder piston and the vacuum on the other side of the cylinder piston, the closed-loop design can produce approximately twice the damping force of an open-loop design. In PRSD embodiments in which pressurized cylinders are used, the pressure in the cylinder is preferably monitored to detect leaks that could cause a pressure drop on one or both sides of the cylinder and a resulting change in damping characteristics.

[0030]

[0050] In an alternative embodiment of the PRSD, one port of the toggle valve remains open to atmosphere, resulting in an open-loop PRSD. In an open-loop PRSD, the movement of the cylinder piston pressurizes the cylinder volume on one side of the piston while leaving the cylinder volume on the other side of the piston open to atmospheric pressure. When the piston changes direction, a reset occurs, venting the previously pressurized cylinder volume to atmosphere and pressurizing the cylinder volume previously open to atmospheric pressure.

[0031]

[0051] The advantage of an open-loop system is that a new volume of air is pressurized each time the cylinder piston changes direction. As a result, the PRSD does not overheat during use and the damping characteristics remain constant.

[0032]

[0052] To verify the concept of the present invention, prototype PRSDs using atmospheric air were constructed and tested. A total of four PRSDs were tested: (1) a single-sided closed-loop PRSD, (2) a single-sided open-loop PRSD, (3) a double-sided closed-loop PRSD, and (4) a double-sided open-loop PRSD.

[0033]

[0053] During testing, each prototype PRSD was subjected to 40 cycles of sinusoidal cylinder piston displacement with an amplitude of 30 mm and a frequency of 0.25 Hz. The output force for each prototype PRSD was plotted against piston displacement.

[0034]

[0054] The results of the aforementioned tests are shown in Figures 18-21. As can be seen, the force-displacement loops show that all of the prototype PRSDs behaved as intended, with the damping force increasing with increasing piston displacement and decreasing to zero with each change in piston direction. Figures 18-21 further show that the force-displacement loops for all four prototype PRSDs were stable, with little variation in the force-displacement characteristics over 40 cycles of motion.

[0035]

[0055] A comparison of Figures 18 and 19 and Figures 20 and 21 shows that the closed-loop PRSD embodiment has a higher effective stiffness than the open-loop PRSD embodiment, which may be due to the fact that the closed-loop embodiment utilizes the cylinder volume on both sides of the piston-cylinder during operation (one volume pressurized, the other volume vacuum), while the open-loop embodiment utilizes only the cylinder volume on one side of the cylinder piston (pressurized).

[0036]

[0056] Similarly, a comparison of Figures 18 and 20, and Figures 19 and 21, shows that the double-sided PRSD has a higher peak damping force than the single-sided PRSD. This may be due to the fact that the double-sided PRSD has a cylinder piston that extends from both sides of the cylinder, which approximately doubles the amount of friction between the piston rod and the seal.

[0037]

[0057] While certain exemplary embodiments of the inventive concepts are described in detail above, the scope of the general inventive concepts is not to be deemed limited by such disclosure, and modifications may be made without departing from the spirit of the general inventive concepts as defined by the following claims.

Claims

1. 1. A single-sided passive resettable stiffness damper (PRSD), comprising: a cylinder having a reciprocating piston with an associated piston rod, said piston rod extending from a first end of said cylinder; a reset mechanism associated with the cylinder and positioned near the first end thereof, a mechanically operated toggle valve having a spring return and disposed in a fluid flow path with said cylinder; a gear train having a plurality of rotatable discs configured and arranged such that linear displacement of the piston rod can cause rotation of the discs of the gear train; and a toggle having one end pivotally coupled to said toggle valve and an opposite free end in contact with a disc of said gear train; a reset mechanism including: Equipped with A PRSD, wherein changes in the direction of rotation of the gear train disc caused by the reciprocating motion of the piston rod each cause the toggle to vary the fluid flow path through the toggle valve, thereby resetting the PRSD.

2. There is a bilateral passive resettable stiffness damper (PRSD), a cylinder having a reciprocating piston with a pair of piston rods extending from opposite ends of the cylinder; a respective reset mechanism disposed near each end of the cylinder and associated with a corresponding one of the piston rods, each reset mechanism comprising: a mechanically operated toggle valve having a spring return and disposed in a fluid flow path with said cylinder; a gear train having a plurality of rotatable discs configured and arranged such that linear displacement of the associated piston rod can cause rotation of the discs of the gear train; and a toggle having one end pivotally coupled to said toggle valve and an opposite free end in contact with a disc of said gear train; a reset mechanism including: Equipped with A PRSD, wherein changes in the direction of rotation of the gear train disc of the reset mechanism caused by the reciprocating motion of the piston rod can each cause the toggle to vary the fluid flow path through the toggle valve, thereby resetting the PRSD.

Images