CA2049570C - Self-blocking gas spring with temperature-responsive bypass valve - Google Patents
Self-blocking gas spring with temperature-responsive bypass valveInfo
- Publication number
- CA2049570C CA2049570C CA 2049570 CA2049570A CA2049570C CA 2049570 C CA2049570 C CA 2049570C CA 2049570 CA2049570 CA 2049570 CA 2049570 A CA2049570 A CA 2049570A CA 2049570 C CA2049570 C CA 2049570C
- Authority
- CA
- Canada
- Prior art keywords
- bypass
- compartment
- valve body
- piston
- gas
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Landscapes
- Temperature-Responsive Valves (AREA)
- Safety Valves (AREA)
Abstract
A gas spring comprises a first bypass with a one-way valve that allows fluid to bypass the piston when the piston moves outward, a second bypass with a spring-biased valve that allows fluid to bypass the piston when the piston is pushed inward with a force exceeding the combined gas-spring and spring-biased valve forces, and a third bypass having a temperature-responsive valve that allows fluid to bypass the piston when the rod is pushed in but only when the temperature of the gas exceeds a selected level. The second and third bypasses and the spring-biased and temperature-responsive valves are incorporated into in a valve body that is affixed to the side of the piston that faces the closed end of the cylinder.
Description
s ~ S 7 13 `~ -Description Self-blocking Gas Spring With Temperature-responsive Bypass Valve Background of the Invention Gas springs are widely used to counterbalance the engine compartment hoods, trunk lids, rear windows, and tailgates of passenger cars, station wagons, and vans to facilitate opening them and to hold them open at or near a fully open position. It is well known that the force outputs of gas springs vary with the temperature of the gas (Boyle's law); at low temperatures the gas spring produces a force that is significantly less than the force produced at high temperatures. It is neces-sary, therefore, to design the gas spring so that itproduces a sufficient force to hold the hood, trunk lid or the like (hereinafter referred to as the "load") open at a suitably selected low temperature, for exam-ple, -30 degrees C. (Conventionally, the gas spring is designed to produce a force of about one to five pounds over the load at the hold-open position of the load at, say, -30 degrees C.) At high temperatures, the in-crease in the force output at the hold-open position may be as much as, say, 50 pounds, which means that the force required to move the load from the hold-open position toward closed ("handle load") is 50 pounds. A
handle load of that magnitude is obviously undesirable.
The inventors of the present invention have here-tofore invented a gas spring in which the difference between the handle loads at low and high ambient tem-peratures is significantly reduced, as compared to previously known gas springs. That invention was an improvement in a gas spring of the type having a spring-biased check valve that closes a bypass across the gas spring piston against fluid flow from the closed end compartment to the rod end compartment. In~
~,~
handle load of that magnitude is obviously undesirable.
The inventors of the present invention have here-tofore invented a gas spring in which the difference between the handle loads at low and high ambient tem-peratures is significantly reduced, as compared to previously known gas springs. That invention was an improvement in a gas spring of the type having a spring-biased check valve that closes a bypass across the gas spring piston against fluid flow from the closed end compartment to the rod end compartment. In~
~,~
2 ~ 7 ~
a gas spring of this type, the force of the gas spring opposing closing of the load is the total of the force due to gas pressure acting on the piston rod (the nor-mal gas spring force) and a force required to cause the spring-biased valve to open.
In particular, the prior invention, which is described and shown in PCT published application No.
W0 91/03664 (March 21, 1991), is a gas spring having a cylinder member defining a chamber, a closure at one end of the cylinder, a piston rod received in sealed relation to the cylinder member at the other end of the cylinder member and movable toward and away from the closure, and a piston affixed to the piston rod within the chamber and separating the chamber into an inward compartment adjacent said one end of the cylinder and an outward compartment adjacent said other end of the cylinder. The volumes of the compartments vary in accordance with the position of the piston. The cham-ber contains a liquid and a gas under a pressure higher than atmospheric pressure. A first bypass allows the liquid and gas to flow from the outward compartment to the inward compartment when the piston and rod move in the direction of the outward compartment in response to forces imposed on the rod in the outward direction. A
one-way valve closes the first bypass to prevent flow of gas and liquid therethrough from the inward compart-ment to the outward compartment at all temperatures. A
second bypass permits the gas and liquid to flow from the inward compartment to the outward compartment upon movement of the rod member toward the inward compart-ment, and a spring-biased one-way valve associated with the second bypass prevents flow therethrough in the absence of a predetermined pressure difference between the fluids in the inward and outward compartments. A
third bypass permits liquid and gas to flow from the inward compartment to the outward compartment and has a temperature-responsive valve associated with it for -closing it when the temperature of the gas spring is less than a predetermined temperature and opening it when the temperature of the gas spring is greater than a predetermined temperature.
The above-described prior invention is generally satisfactory as far as its function is concerned, but various aspects of its construction make it relatively difficult and expensive to manufacture. For example, it includes an axial bore and a radial bore in the piston rod, and those bores are costly to make. Simi-larly, relatively large amounts of metal have to be machined at the piston end of the piston rod for the valve disc and the piston, another costly operation.
Also, the bimetallic disc of the temperature-responsive valve requires particular attention to quality control to ensure that it is accurate and will cycle between open and closed at the desired temperatures. The O-ring seal, furthermore, has a relatively large diameter, compared to the diameter of the bimetallic disc, which is not an optimal arrangement for forming a good seal when the temperature-responsive valve is closed.
Summary of the Invention An object of the present invention is to provide a gas spring of the type described above that is easier and less expensive to make, that functions reliably and provides the advantage of the prior invention referred to above of greatly reducing the increase in handle load due to increase in temperature as compared to previously known gas springs.
The foregoing object is attained, according to the present invention, by a gas spring comprising a cylinder member defining a chamber, a closure at one end of the cylinder member, a piston rod received in sealed relation to the cylinder member at the other end of the cylinder member and movable toward and away from _4_ 2Q~Y~-7D
the closure, and a piston affixed to the piston rod within the chamber and separating the chamber into an inward compartment adjacent said one end of the cylinder and an outward compartment adjacent said other end of the cylinder, the volumes of the compartments varying in accordance with the position of the piston.
A valve body is joined to the face of the piston facing the inward compartment. A mass of a liquid is contained in part of the chamber, and a mass of gas under a pressure higher than atmospheric pressure is contained in the remaining part of the chamber. A
first bypass allows the liquid and gas to flow from the outward compartment to the inward compartment when the piston and rod move in the direction of the outward compartment in response to forces imposed on the rod in the outward direction. A valve closes the first bypass to prevent flow of gas and liquid therethrough from the inward compartment to the outward compartment, at least when the temperature of the gas spring is below a predetermined value. A second bypass permits the gas and liquid to flow from the inward compartment to the outward compartment upon movement of the rod toward the inward compartment, the second bypass including a passage through the piston and the valve body opening at a port in a wall of the valve body in the inward compartment and a port in a wall of the piston in the outward compartment. A spring-biased one-way valve received in a portion of the passage of the second bypass within the valve body prevents flow therethrough in the absence of a predetermined pressure difference between the liquid and gas in the inward and outward compartments. A third bypass including a passage through the piston and the valve body that opens at a port in a face of the valve body permits liquid and gas to flow from the inward compartment to the outward compartment, and a temperature-responsive valve associated with the third bypass closes it when the 2~57J
temperature of the gas spring is less than a pre-determined temperature and opens it when the tempera-ture of the gas spring is greater than a predetermined temperature. The temperature-responsive valve includes a bimetallic element secured to the valve body and having a seal element to seat in a sealing relation against a surface of the valve body over the port in the third bypass.
In one embodiment, the surface of the valve body against which the seal element seats is oriented obliquely to the axis of the cylinder member and is located proximate to one side of the cylinder member and the bimetallic element extends substantially dia-metrically of the cylinder member obliquely to the axis of the cylinder member. In another embodiment, the surface of the valve body against which the seal ele-ment seats is oriented substantially parallel to the axis of the cylinder member and the bimetallic element extends substantially parallel to the axis of the cylinder member. The gas spring may include a cap member mounted on the valve body so as to cover the bimetallic element while permitting it to move between a position at which the port is covered and a position at which the port is uncovered.
In an advantageous arrangement, the second bypass comprises a passage extending in the axial direction through the piston and the valve body opening to the inward compartment through a wall of the valve body.
The spring-biased one way valve is received within a portion of the passage within the valve body, and the third bypass includes a transverse passage in the valve body leading from the second bypass passage to the surface of the valve body against which the seal ele-ment of the bimetallic element seats.
The first bypass and third bypass may share a common passage through the piston and valve body. The temperature-responsive valve permits flow of gas and 2~.g~ u -liquid from the outward compartment to the inward com-partment at all times and prevents flow of gas and liquid from the inward compartment to the outward com-partment when the temperature of the gas spring is less than the predetermined temperature when the valve closes, which is required so that the spring-loaded valve of the second bypass is not circumvented at low temperatures. Alternatively, a one-way valve is provided in the first bypass passage for preventing fluid flow through it from the outward compartment to the inward compartment to prevent the second bypass from being circumvented at low temperatures.
For a better understanding of the invention, reference may be made to the following description of exemplary embodiments of the present invention, taken in conjunction with the accompanying drawings.
Description of the Drawings Fig. 1 is an axial cross-sectional view of a gas spring to which the present invention is applicable;
Figs. 2 and 3 are axial cross-sectional views of one embodiment of a piston and bypass valve unit, which is shown in the check-valve bypass mode and the temperature-responsive bypass mode, respectively;
Figs. 4 and 5 are axial cross-sectional views of a second embodiment of a piston and bypass valve unit, which is shown in the check-valve bypass mode and the temperature-responsive bypass mode, respectively; and Fig. 6 is an axial cross-sectional view of the unit of Fig. 4, modified so that the seal ring of the piston unit is fixed axially.
Description of the Embodiments The gas spring 10 of Fig. 1 comprises a cylinder 12 that is closed at one end by a cap 16. A piston rod 18 extends into the cylinder 12 through a seal assembly 20 in the rod end 21 of the cylinder.
7 ~
.
Fittings 22 and 24 are fastened to the cap 16 and piston rod 18, respectively, for connecting the gas spring to the vehicle body and the load (hood, trunk lid and the like).
A piston and bypass valve unit 26 is fastened to the end of the piston rod within the cylinder 12 and includes a piston seal ring 28 that divides the chamber within the cylinder into two compartments, the volumes of which vary according to the position of the piston.
There is an inward compartment IC between the piston seal ring and the cap 16 and an outward compartment OC
between the piston seal ring and the seal assembly 20.
Most of the free volume of the cylinder chamber con-tains air or nitrogen at a pressure of from about 300 to 4500 psi. The remainder contains a liquid, such as mineral oil.
An embodiment of a piston and bypass valve unit 26, according to the invention, suitable for a gas spring such as the one shown in Fig. 1 is illustrated 20 in Figs. 2 and 3. A piston assembly 100, which con-sists of a piston member 102 and a washer member 104, is secured to the end of a piston rod 106 and receives a sealing ring 108 in a ring groove 110. A first bypass, which allows fluid to flow from the outward compartment OC to the inward compartment IC when the piston rod is moving out of the cylinder member but is closed to flow in the other direction by the sealing ring, is a labyrinthine groove 112 formed in the face of the piston member 102 that opens into the base of the ring groove 110. When the piston rod is moving out of the cylinder, the sealing ring shifts upwardly in the ring groove due to friction with the cylinder wall and allows fluid to enter the inlet end 114 of the groove 112. The outlet end of the groove opens to a hole in the washer member that leads to the inward compartment. When the rod is moving into the cylinder, as shown in Figs. 2 and 3, the sealing ring seats in -8- ~ 7~
. .
the lower shoulder of the ring groove and prevents fluid from flowing through the first bypass. Bypasses based on labyrinthine grooves are well-known per se and are provided to control the velocity of the piston/rod when it moves in the rod-out direction.
A second bypass, which incorporates a spring-biased one-way valve, is a passage 116 that extends through the piston assembly 100 and through a valve body 118 that is attached to the piston assembly on the inward compartment side. The valve is a spring-loaded ball check valve, consisting of a check 120 and a spring 122, and is installed in the valve body 118. A
tubular port member 124 secured in the passage 116 provides a seat for the spring and mechanically secures the valve body to the piston assembly.
A temperature-responsive bypass comprises a passage 126 through the piston assembly and the valve body that opens at a port 128 in a surface 130 of the valve body oriented obliquely to the axis of the cylinder. A bimetallic element 132 is fastened, such as by screws 134, at one end to the valve body and receives at its other end a seal element 136, which is secured to the bimetallic element. The bimetallic element 132 extends substantially diametrically and obliquely across the cylinder, this arrangement allowing the element to be relatively long and, therefore, to be designed to be highly accurate in its temperature response. A tubular port member 138 received in the passage 126 retains a check 140 of a one-way check valve that prevents fluid from flowing through the third bypass when the piston rod is moving out of the cylinder. The port member is secured in holes in the piston and the valve body and mechanically joins the valve body to the piston.
When the piston rod is moving out of the cylinder against the force of a load, the check valves 120 and 140 close the second and third bypasses, and fluid 5 ~ ~
g .
flows past the piston from the outward to the inward compartment only through the labyrinthine first bypass 112, which is designed to throttle the fluid flow and limit the speed of rod-out movement of the rod. When the temperature of the bimetallic element 132 falls to a predetermined value built into it by design, the seal element 136 is held against the surface 130 of the valve body, as shown in Fig. 2, thereby forming a face seal that prevents the fluids in the gas spring from flowing through the third bypass from the inward to the outward compartment when the piston rod is moved into the cylinder. In this state the force resisting the movement of the rod into the cylinder is the total of the force generated by the gas and the force required to open the valve 120, 122, the latter force supple-menting the former at low temperatures to provide a hold-open force.
After the user lifts the load, assisted by the gas spring force, and releases the load, the load will fall a short distance, and the rod will move into the cylin-der far enough to move the piston 102,104 relative to the piston seal ring 108 (which remains stationary due to friction with the cylinder wall) and seat the seal ring 108 on the lower land 110 of the ring groove, thereby closing the first bypass; the piston seal ring constitutes, in this respect, a one-way valve for the first bypass. At this point, the second bypass across the piston is closed by the spring-biased check valve 120. The load will continue to fall until the rod and piston move far enough into the cylinder to produce a pressure increase in the inward compartment IC and a pressure drop in the outward compartment OC such that the pressure differential across the piston applies an outward force on the piston and rod equal to the difference between the load and the gas spring force, at which point the load is fully counter-balanced by the gas spring.
2~49S7~
j, . .
\
The spring-biased check valve 120 is designed to remain closed until the force applied to the rod, when the gas temperature is at the selected low value (e.g., minus 30 degrees C), slightly (e.g., 1 to 5 pounds) exceeds the load. At the low design temperature, the excess is the handle load required to move the load from the checked position. At higher temperatures, the handle load becomes greater, because the normal gas spring force increases with increasing temperature.
The force increment added by the spring-biased bypass valve (hereinafter called "valve force") is essentially constant at all temperatures.
When a sufficient handle load is applied to the load to overcome the total force output of the gas spring (normal gas spring force plus valve force), the spring-biased check valve opens and allows the liquid and gas to flow through the passage 116, as shown in Fig. 2. To prevent the handle load from becoming undesirably large when the gas spring is hot (which can result from a high ambient temperature, heating by the sun or engine heat), the invention provides for circum-venting the valve force when the gas spring is heated to a temperature above a selected value, hereinafter referred to as the "reset temperature." At temperatures above the reset temperature of the bimetallic element, the seal 136 is unseated from the surface 130, as shown in Fig. 3, the element 132 inverting from its low temperature state and thereby opening the third bypass (the passage 126) to permit fluid to flow through it from the inward to the outward compartment. Because the flow through the third bypass is essentially unrestricted, the second bypass becomes inoperative, and the force of the spring-loaded valve 120, 122 does not impede inward movement of the piston rod. In the open condition of the temperature-responsive valve, only the gas spring force resists movement of the piston rod in the inward direction.
7 ~
:` --11---Accordingly, the bimetallic element 132 is designed to reset and open the port when the temperature of the gas spring is sufficiently high so that the gas spring force exceeds the load, thus retaining the blocking function at a moderate temperature at and near the temperature when the valve pops open. Elimination of the valve force, however, reduces the handle load that the user has to exert to move the load toward closed when the gas spring is hot. Typically, the temperature-responsive valve will be designed to open at roughly 0 degrees C.
As is known per se, a portion 14 (Fig. 1) of the cylinder adjacent the cap may be of a larger diameter than the O.D. of the piston seal ring 108 to allow bypass of liquid and gas by circumventing the second bypass at low temperatures, thereby eliminating the valve force near closing of the load. At higher temperatures, the temperature-responsive valve circumvents the second bypass and eliminates the valve force over the entire stroke of the piston, so an enlarged section of the cylinder is unnecessary.
Indeed, the present invention eliminates the need for force release near closure in many cases when it might otherwise be called for.
A further embodiment of the invention is shown in Figs. 4 and 5. It is functionally substantially iden-tical to the embodiment of Figs. 2 and 3 but differs in structural detail. In the embodiment of Figs. 4 and 5, the piston assembly 200, including the piston member 202, the washer member 204, and the seal ring 208, and its manner of attachment to the piston rod 206, are the same as in the embodiment of Figs. 2 and 3. The first bypass, including the ring groove 210, the labyrinthine groove 212 and the inlet end 214, is likewise identi-cal, both structurally and functionally, to that of Figs. 2 and 3.
7 ~
-The second bypass in Figs. 4 and 5 comprises an axially extending passage 216 in an integrally formed valve body 218 that is attached to the piston assembly 200 on the inward compartment side. To that end, cylindrical studs 224 and 238 formed on the valve body 218 are secured to the piston assembly to fix the valve body in place. The passage 216 is enlarged over an inner portion 216a of its length for receipt of a spring-biased one way valve, consisting of a check valve body 220 and a coil spring 222. At the inner end, the passage 216a is further enlarged for receipt of an annular valve seat 223. With this arrangement, the spring 222, one-way valve body 220, and valve seat 223 may be top loaded into the valve body 218, thereby simplifying assembly. The seat 223 has a central bore which defines a port through which the passage 216 opens to the inner compartment.
The temperature-responsive bypass comprises a transverse passage 226 in the valve body 218 that opens through an axially extending surface 230 of the valve body. Preferably, the surface 230 is substantially parallel to and aligned with the axis of the cylinder member. A bimetallic element 232 is fastened at one end, e.g., by screws or rivets 234, to the valve body 218 adjacent its inner end. At the other end, the bimetallic element carries a seal element 236, which is secured to the bimetallic element. In this arrangement, the configuration of the bimetallic element 232 is simplified relative to that of Figs. 2 and 3 by eliminating the bend along the oblique valve body surface 130. To provide greater structural rigidity and accuracy in its temperature response, the bimetallic element 232 preferably has a shallow U-shaped cross section over an axially outer portion 231 of its length and a spherically indented portion 233 adjacent its axially inner end. The two axial end portions 235a and 235b are preferably flat. As will be ` -13- ~ 9ï7~
understood, the bimetallic element 232 presses the seal element 236 against the opening of passage 226 to prevent fluid flow therethrough (in the outward direction) so long as the ambient temperature is below the predetermined trip temperature of the bimetallic element 232.
Preferably, a protective cap 240 is attached to the valve body 218 to cover the bimetallic element 232.
The cap 240 preferably is U-shaped in transverse cross section and includes an end wall 244 so as completely to surround the element 232. An axial opening 246 in the end wall 244 permits fluid flow between the compartment IC and the passage 236.
When the piston is moving out of the cylinder against the force of a load, the check valve 220 closes the second bypass 216, and fluid flows past the piston from the outward to the inward compartment through the passage 226, causing the seal element 236 to lift away from the surface 230.
So long as the ambient temperature is below the trip temperature of the bimetallic element 232, the seal element 236 will remain seated against the surface 230, as shown in Fig. 4, in the absence of a pressure differential acting inwardly across the seal element 236. Thus at temperatures below the trip temperature of the bimetallic band 232 the seal element 236 functions as a one-way valve to permit inward fluid flow but not outward fluid flow through the passage 226. In this case, outward fluid flow (inward movement of the piston rod) can occur only if sufficient handle force is applied to overcome the spring-biased valve 220, as shown in Fig. 4. When the ambient temperature is above the reset temperature of the bimetallic element 232, the seal element 236 is unseated by the action of the bimetallic element 232, as shown in Fig.
5, and substantially unimpeded outward fluid flow through passages 226 and 216 is possible. In this 2 ~ ~ 9 ~ 7 ~
case, the spring-biased valve of the second bypass is circumvented and does not impede inward movement of the piston rod.
This dual function of the passage 226 and the bimetallic element 232 (i.e., as both (1) the first bypass and its associated valve for permitting fluid flow from the outer compartment to the inner compart-ment but preventing fluid flow from the inward compart-ment to the outward compartment except when the temper-ature is above the predetermined response temperatureand (2) as the third bypass and its associated temperature-responsive valve for permitting fluid flow from the inner compartment to the outer compartment when the temperature is above such predetermined response temperature) has the advantage of permitting a further simplification of the embodiment of Figs. 4 and 5. Thus as shown in Fig. 6, the seal ring 208 need not be axially movable to function as a one-way check valve and the labyrinthine groove 212 may be eliminated. In Fig. 6, the piston member 202' is axially enlarged relative to the thickness of the piston member 202 in Figs. 4 and 5 so as to capture the ring seal 208 against the disk 204.
a gas spring of this type, the force of the gas spring opposing closing of the load is the total of the force due to gas pressure acting on the piston rod (the nor-mal gas spring force) and a force required to cause the spring-biased valve to open.
In particular, the prior invention, which is described and shown in PCT published application No.
W0 91/03664 (March 21, 1991), is a gas spring having a cylinder member defining a chamber, a closure at one end of the cylinder, a piston rod received in sealed relation to the cylinder member at the other end of the cylinder member and movable toward and away from the closure, and a piston affixed to the piston rod within the chamber and separating the chamber into an inward compartment adjacent said one end of the cylinder and an outward compartment adjacent said other end of the cylinder. The volumes of the compartments vary in accordance with the position of the piston. The cham-ber contains a liquid and a gas under a pressure higher than atmospheric pressure. A first bypass allows the liquid and gas to flow from the outward compartment to the inward compartment when the piston and rod move in the direction of the outward compartment in response to forces imposed on the rod in the outward direction. A
one-way valve closes the first bypass to prevent flow of gas and liquid therethrough from the inward compart-ment to the outward compartment at all temperatures. A
second bypass permits the gas and liquid to flow from the inward compartment to the outward compartment upon movement of the rod member toward the inward compart-ment, and a spring-biased one-way valve associated with the second bypass prevents flow therethrough in the absence of a predetermined pressure difference between the fluids in the inward and outward compartments. A
third bypass permits liquid and gas to flow from the inward compartment to the outward compartment and has a temperature-responsive valve associated with it for -closing it when the temperature of the gas spring is less than a predetermined temperature and opening it when the temperature of the gas spring is greater than a predetermined temperature.
The above-described prior invention is generally satisfactory as far as its function is concerned, but various aspects of its construction make it relatively difficult and expensive to manufacture. For example, it includes an axial bore and a radial bore in the piston rod, and those bores are costly to make. Simi-larly, relatively large amounts of metal have to be machined at the piston end of the piston rod for the valve disc and the piston, another costly operation.
Also, the bimetallic disc of the temperature-responsive valve requires particular attention to quality control to ensure that it is accurate and will cycle between open and closed at the desired temperatures. The O-ring seal, furthermore, has a relatively large diameter, compared to the diameter of the bimetallic disc, which is not an optimal arrangement for forming a good seal when the temperature-responsive valve is closed.
Summary of the Invention An object of the present invention is to provide a gas spring of the type described above that is easier and less expensive to make, that functions reliably and provides the advantage of the prior invention referred to above of greatly reducing the increase in handle load due to increase in temperature as compared to previously known gas springs.
The foregoing object is attained, according to the present invention, by a gas spring comprising a cylinder member defining a chamber, a closure at one end of the cylinder member, a piston rod received in sealed relation to the cylinder member at the other end of the cylinder member and movable toward and away from _4_ 2Q~Y~-7D
the closure, and a piston affixed to the piston rod within the chamber and separating the chamber into an inward compartment adjacent said one end of the cylinder and an outward compartment adjacent said other end of the cylinder, the volumes of the compartments varying in accordance with the position of the piston.
A valve body is joined to the face of the piston facing the inward compartment. A mass of a liquid is contained in part of the chamber, and a mass of gas under a pressure higher than atmospheric pressure is contained in the remaining part of the chamber. A
first bypass allows the liquid and gas to flow from the outward compartment to the inward compartment when the piston and rod move in the direction of the outward compartment in response to forces imposed on the rod in the outward direction. A valve closes the first bypass to prevent flow of gas and liquid therethrough from the inward compartment to the outward compartment, at least when the temperature of the gas spring is below a predetermined value. A second bypass permits the gas and liquid to flow from the inward compartment to the outward compartment upon movement of the rod toward the inward compartment, the second bypass including a passage through the piston and the valve body opening at a port in a wall of the valve body in the inward compartment and a port in a wall of the piston in the outward compartment. A spring-biased one-way valve received in a portion of the passage of the second bypass within the valve body prevents flow therethrough in the absence of a predetermined pressure difference between the liquid and gas in the inward and outward compartments. A third bypass including a passage through the piston and the valve body that opens at a port in a face of the valve body permits liquid and gas to flow from the inward compartment to the outward compartment, and a temperature-responsive valve associated with the third bypass closes it when the 2~57J
temperature of the gas spring is less than a pre-determined temperature and opens it when the tempera-ture of the gas spring is greater than a predetermined temperature. The temperature-responsive valve includes a bimetallic element secured to the valve body and having a seal element to seat in a sealing relation against a surface of the valve body over the port in the third bypass.
In one embodiment, the surface of the valve body against which the seal element seats is oriented obliquely to the axis of the cylinder member and is located proximate to one side of the cylinder member and the bimetallic element extends substantially dia-metrically of the cylinder member obliquely to the axis of the cylinder member. In another embodiment, the surface of the valve body against which the seal ele-ment seats is oriented substantially parallel to the axis of the cylinder member and the bimetallic element extends substantially parallel to the axis of the cylinder member. The gas spring may include a cap member mounted on the valve body so as to cover the bimetallic element while permitting it to move between a position at which the port is covered and a position at which the port is uncovered.
In an advantageous arrangement, the second bypass comprises a passage extending in the axial direction through the piston and the valve body opening to the inward compartment through a wall of the valve body.
The spring-biased one way valve is received within a portion of the passage within the valve body, and the third bypass includes a transverse passage in the valve body leading from the second bypass passage to the surface of the valve body against which the seal ele-ment of the bimetallic element seats.
The first bypass and third bypass may share a common passage through the piston and valve body. The temperature-responsive valve permits flow of gas and 2~.g~ u -liquid from the outward compartment to the inward com-partment at all times and prevents flow of gas and liquid from the inward compartment to the outward com-partment when the temperature of the gas spring is less than the predetermined temperature when the valve closes, which is required so that the spring-loaded valve of the second bypass is not circumvented at low temperatures. Alternatively, a one-way valve is provided in the first bypass passage for preventing fluid flow through it from the outward compartment to the inward compartment to prevent the second bypass from being circumvented at low temperatures.
For a better understanding of the invention, reference may be made to the following description of exemplary embodiments of the present invention, taken in conjunction with the accompanying drawings.
Description of the Drawings Fig. 1 is an axial cross-sectional view of a gas spring to which the present invention is applicable;
Figs. 2 and 3 are axial cross-sectional views of one embodiment of a piston and bypass valve unit, which is shown in the check-valve bypass mode and the temperature-responsive bypass mode, respectively;
Figs. 4 and 5 are axial cross-sectional views of a second embodiment of a piston and bypass valve unit, which is shown in the check-valve bypass mode and the temperature-responsive bypass mode, respectively; and Fig. 6 is an axial cross-sectional view of the unit of Fig. 4, modified so that the seal ring of the piston unit is fixed axially.
Description of the Embodiments The gas spring 10 of Fig. 1 comprises a cylinder 12 that is closed at one end by a cap 16. A piston rod 18 extends into the cylinder 12 through a seal assembly 20 in the rod end 21 of the cylinder.
7 ~
.
Fittings 22 and 24 are fastened to the cap 16 and piston rod 18, respectively, for connecting the gas spring to the vehicle body and the load (hood, trunk lid and the like).
A piston and bypass valve unit 26 is fastened to the end of the piston rod within the cylinder 12 and includes a piston seal ring 28 that divides the chamber within the cylinder into two compartments, the volumes of which vary according to the position of the piston.
There is an inward compartment IC between the piston seal ring and the cap 16 and an outward compartment OC
between the piston seal ring and the seal assembly 20.
Most of the free volume of the cylinder chamber con-tains air or nitrogen at a pressure of from about 300 to 4500 psi. The remainder contains a liquid, such as mineral oil.
An embodiment of a piston and bypass valve unit 26, according to the invention, suitable for a gas spring such as the one shown in Fig. 1 is illustrated 20 in Figs. 2 and 3. A piston assembly 100, which con-sists of a piston member 102 and a washer member 104, is secured to the end of a piston rod 106 and receives a sealing ring 108 in a ring groove 110. A first bypass, which allows fluid to flow from the outward compartment OC to the inward compartment IC when the piston rod is moving out of the cylinder member but is closed to flow in the other direction by the sealing ring, is a labyrinthine groove 112 formed in the face of the piston member 102 that opens into the base of the ring groove 110. When the piston rod is moving out of the cylinder, the sealing ring shifts upwardly in the ring groove due to friction with the cylinder wall and allows fluid to enter the inlet end 114 of the groove 112. The outlet end of the groove opens to a hole in the washer member that leads to the inward compartment. When the rod is moving into the cylinder, as shown in Figs. 2 and 3, the sealing ring seats in -8- ~ 7~
. .
the lower shoulder of the ring groove and prevents fluid from flowing through the first bypass. Bypasses based on labyrinthine grooves are well-known per se and are provided to control the velocity of the piston/rod when it moves in the rod-out direction.
A second bypass, which incorporates a spring-biased one-way valve, is a passage 116 that extends through the piston assembly 100 and through a valve body 118 that is attached to the piston assembly on the inward compartment side. The valve is a spring-loaded ball check valve, consisting of a check 120 and a spring 122, and is installed in the valve body 118. A
tubular port member 124 secured in the passage 116 provides a seat for the spring and mechanically secures the valve body to the piston assembly.
A temperature-responsive bypass comprises a passage 126 through the piston assembly and the valve body that opens at a port 128 in a surface 130 of the valve body oriented obliquely to the axis of the cylinder. A bimetallic element 132 is fastened, such as by screws 134, at one end to the valve body and receives at its other end a seal element 136, which is secured to the bimetallic element. The bimetallic element 132 extends substantially diametrically and obliquely across the cylinder, this arrangement allowing the element to be relatively long and, therefore, to be designed to be highly accurate in its temperature response. A tubular port member 138 received in the passage 126 retains a check 140 of a one-way check valve that prevents fluid from flowing through the third bypass when the piston rod is moving out of the cylinder. The port member is secured in holes in the piston and the valve body and mechanically joins the valve body to the piston.
When the piston rod is moving out of the cylinder against the force of a load, the check valves 120 and 140 close the second and third bypasses, and fluid 5 ~ ~
g .
flows past the piston from the outward to the inward compartment only through the labyrinthine first bypass 112, which is designed to throttle the fluid flow and limit the speed of rod-out movement of the rod. When the temperature of the bimetallic element 132 falls to a predetermined value built into it by design, the seal element 136 is held against the surface 130 of the valve body, as shown in Fig. 2, thereby forming a face seal that prevents the fluids in the gas spring from flowing through the third bypass from the inward to the outward compartment when the piston rod is moved into the cylinder. In this state the force resisting the movement of the rod into the cylinder is the total of the force generated by the gas and the force required to open the valve 120, 122, the latter force supple-menting the former at low temperatures to provide a hold-open force.
After the user lifts the load, assisted by the gas spring force, and releases the load, the load will fall a short distance, and the rod will move into the cylin-der far enough to move the piston 102,104 relative to the piston seal ring 108 (which remains stationary due to friction with the cylinder wall) and seat the seal ring 108 on the lower land 110 of the ring groove, thereby closing the first bypass; the piston seal ring constitutes, in this respect, a one-way valve for the first bypass. At this point, the second bypass across the piston is closed by the spring-biased check valve 120. The load will continue to fall until the rod and piston move far enough into the cylinder to produce a pressure increase in the inward compartment IC and a pressure drop in the outward compartment OC such that the pressure differential across the piston applies an outward force on the piston and rod equal to the difference between the load and the gas spring force, at which point the load is fully counter-balanced by the gas spring.
2~49S7~
j, . .
\
The spring-biased check valve 120 is designed to remain closed until the force applied to the rod, when the gas temperature is at the selected low value (e.g., minus 30 degrees C), slightly (e.g., 1 to 5 pounds) exceeds the load. At the low design temperature, the excess is the handle load required to move the load from the checked position. At higher temperatures, the handle load becomes greater, because the normal gas spring force increases with increasing temperature.
The force increment added by the spring-biased bypass valve (hereinafter called "valve force") is essentially constant at all temperatures.
When a sufficient handle load is applied to the load to overcome the total force output of the gas spring (normal gas spring force plus valve force), the spring-biased check valve opens and allows the liquid and gas to flow through the passage 116, as shown in Fig. 2. To prevent the handle load from becoming undesirably large when the gas spring is hot (which can result from a high ambient temperature, heating by the sun or engine heat), the invention provides for circum-venting the valve force when the gas spring is heated to a temperature above a selected value, hereinafter referred to as the "reset temperature." At temperatures above the reset temperature of the bimetallic element, the seal 136 is unseated from the surface 130, as shown in Fig. 3, the element 132 inverting from its low temperature state and thereby opening the third bypass (the passage 126) to permit fluid to flow through it from the inward to the outward compartment. Because the flow through the third bypass is essentially unrestricted, the second bypass becomes inoperative, and the force of the spring-loaded valve 120, 122 does not impede inward movement of the piston rod. In the open condition of the temperature-responsive valve, only the gas spring force resists movement of the piston rod in the inward direction.
7 ~
:` --11---Accordingly, the bimetallic element 132 is designed to reset and open the port when the temperature of the gas spring is sufficiently high so that the gas spring force exceeds the load, thus retaining the blocking function at a moderate temperature at and near the temperature when the valve pops open. Elimination of the valve force, however, reduces the handle load that the user has to exert to move the load toward closed when the gas spring is hot. Typically, the temperature-responsive valve will be designed to open at roughly 0 degrees C.
As is known per se, a portion 14 (Fig. 1) of the cylinder adjacent the cap may be of a larger diameter than the O.D. of the piston seal ring 108 to allow bypass of liquid and gas by circumventing the second bypass at low temperatures, thereby eliminating the valve force near closing of the load. At higher temperatures, the temperature-responsive valve circumvents the second bypass and eliminates the valve force over the entire stroke of the piston, so an enlarged section of the cylinder is unnecessary.
Indeed, the present invention eliminates the need for force release near closure in many cases when it might otherwise be called for.
A further embodiment of the invention is shown in Figs. 4 and 5. It is functionally substantially iden-tical to the embodiment of Figs. 2 and 3 but differs in structural detail. In the embodiment of Figs. 4 and 5, the piston assembly 200, including the piston member 202, the washer member 204, and the seal ring 208, and its manner of attachment to the piston rod 206, are the same as in the embodiment of Figs. 2 and 3. The first bypass, including the ring groove 210, the labyrinthine groove 212 and the inlet end 214, is likewise identi-cal, both structurally and functionally, to that of Figs. 2 and 3.
7 ~
-The second bypass in Figs. 4 and 5 comprises an axially extending passage 216 in an integrally formed valve body 218 that is attached to the piston assembly 200 on the inward compartment side. To that end, cylindrical studs 224 and 238 formed on the valve body 218 are secured to the piston assembly to fix the valve body in place. The passage 216 is enlarged over an inner portion 216a of its length for receipt of a spring-biased one way valve, consisting of a check valve body 220 and a coil spring 222. At the inner end, the passage 216a is further enlarged for receipt of an annular valve seat 223. With this arrangement, the spring 222, one-way valve body 220, and valve seat 223 may be top loaded into the valve body 218, thereby simplifying assembly. The seat 223 has a central bore which defines a port through which the passage 216 opens to the inner compartment.
The temperature-responsive bypass comprises a transverse passage 226 in the valve body 218 that opens through an axially extending surface 230 of the valve body. Preferably, the surface 230 is substantially parallel to and aligned with the axis of the cylinder member. A bimetallic element 232 is fastened at one end, e.g., by screws or rivets 234, to the valve body 218 adjacent its inner end. At the other end, the bimetallic element carries a seal element 236, which is secured to the bimetallic element. In this arrangement, the configuration of the bimetallic element 232 is simplified relative to that of Figs. 2 and 3 by eliminating the bend along the oblique valve body surface 130. To provide greater structural rigidity and accuracy in its temperature response, the bimetallic element 232 preferably has a shallow U-shaped cross section over an axially outer portion 231 of its length and a spherically indented portion 233 adjacent its axially inner end. The two axial end portions 235a and 235b are preferably flat. As will be ` -13- ~ 9ï7~
understood, the bimetallic element 232 presses the seal element 236 against the opening of passage 226 to prevent fluid flow therethrough (in the outward direction) so long as the ambient temperature is below the predetermined trip temperature of the bimetallic element 232.
Preferably, a protective cap 240 is attached to the valve body 218 to cover the bimetallic element 232.
The cap 240 preferably is U-shaped in transverse cross section and includes an end wall 244 so as completely to surround the element 232. An axial opening 246 in the end wall 244 permits fluid flow between the compartment IC and the passage 236.
When the piston is moving out of the cylinder against the force of a load, the check valve 220 closes the second bypass 216, and fluid flows past the piston from the outward to the inward compartment through the passage 226, causing the seal element 236 to lift away from the surface 230.
So long as the ambient temperature is below the trip temperature of the bimetallic element 232, the seal element 236 will remain seated against the surface 230, as shown in Fig. 4, in the absence of a pressure differential acting inwardly across the seal element 236. Thus at temperatures below the trip temperature of the bimetallic band 232 the seal element 236 functions as a one-way valve to permit inward fluid flow but not outward fluid flow through the passage 226. In this case, outward fluid flow (inward movement of the piston rod) can occur only if sufficient handle force is applied to overcome the spring-biased valve 220, as shown in Fig. 4. When the ambient temperature is above the reset temperature of the bimetallic element 232, the seal element 236 is unseated by the action of the bimetallic element 232, as shown in Fig.
5, and substantially unimpeded outward fluid flow through passages 226 and 216 is possible. In this 2 ~ ~ 9 ~ 7 ~
case, the spring-biased valve of the second bypass is circumvented and does not impede inward movement of the piston rod.
This dual function of the passage 226 and the bimetallic element 232 (i.e., as both (1) the first bypass and its associated valve for permitting fluid flow from the outer compartment to the inner compart-ment but preventing fluid flow from the inward compart-ment to the outward compartment except when the temper-ature is above the predetermined response temperatureand (2) as the third bypass and its associated temperature-responsive valve for permitting fluid flow from the inner compartment to the outer compartment when the temperature is above such predetermined response temperature) has the advantage of permitting a further simplification of the embodiment of Figs. 4 and 5. Thus as shown in Fig. 6, the seal ring 208 need not be axially movable to function as a one-way check valve and the labyrinthine groove 212 may be eliminated. In Fig. 6, the piston member 202' is axially enlarged relative to the thickness of the piston member 202 in Figs. 4 and 5 so as to capture the ring seal 208 against the disk 204.
Claims (8)
1. A gas spring comprising a cylinder member defining a chamber and having a central longitudinal axis and a first end and a second end, a closure at the first end of the cylinder member, a piston rod received in sealed relation to the cylinder member at the second end of the cylinder member and movable toward and away from the closure, a piston affixed to the piston rod within the chamber and separating the chamber into an inward compartment adjacent the first end of the cylinder member and an outward compartment adjacent the second end of the cylinder member, the volumes of the compartments varying in accordance with the position of the piston, a valve body joined to the face of the piston facing the inward compartment, a mass of a liquid and a mass of gas under a pressure higher than atmospheric pressure contained in the chamber, means defining a first bypass for allowing the liquid and gas to flow from the outward compartment to the inward compartment when the piston and rod move toward the outward compartment in response to forces imposed on the rod, valve means for closing the first bypass to prevent flow of gas and liquid therethrough from the inward compartment to the outward compartment at least when the temperature of the gas spring is below a predetermined value, means defining a second bypass for permitting the gas and liquid to flow from the inward compartment to the outward compartment upon movement of the rod toward the inward compartment and including a passage through the piston and the valve body opening at a port in a wall of the valve body in the inward compartment and a port in a wall of the piston in the outward compartment, a spring-biased one-way valve received in a portion of the passage of the second bypass within the valve body for preventing flow therethrough when the difference between the pressure of the liquid and gas in the inward compartment and the pressure of the liquid and gas in the outward compartment is less than a predetermined amount, characterized in that there is a third bypass including a passage through the piston and the valve body that opens at a port in a face of the valve body for permitting liquid and gas to flow from the inward compartment to the outward compartment, and temperature-responsive valve means associated with the third bypass for closing the third bypass when the temperature of the gas spring is less than a predetermined temperature and opening the third bypass when the temperature of the gas spring is greater than a predetermined temperature including an elongated bimetallic element secured to the valve body at a location remote from the port of the third bypass and having a seal element attached thereto and positioned to seat in sealing relation against a surface of the valve body.
2. A gas spring according to claim 1 wherein the surface of the valve body against which the seal element seats is oriented obliquely to the axis of the cylinder member and is located proximate to one side of the cylinder member and the bimetallic element extends substantially diametrically of the cylinder member obliquely to the axis of the cylinder member.
3. A gas spring according to claim 1 and further comprising one-way valve means in the third bypass for preventing fluid flow from the outward compartment to the inward compartment.
4. A gas spring according to claim 1 wherein the surface of the valve body against which the seal element seats is oriented substantially parallel to the axis of the cylinder member and the bimetallic element extends substantially parallel to the axis of the cylinder member.
5. A gas spring according to claim 4 and further comprising a cap member mounted on the valve body so as to cover the bimetallic element while permitting movement thereof between a position at which the port is covered and a position at which the port is uncovered.
6. A gas spring according to claim 4 wherein the surface of the valve body against which the seal element seats is substantially aligned with the axis of the cylinder member.
7. A gas spring according to claim 4 wherein the second bypass comprises a passage extending in the axial direction through the piston and the valve body opening to the inward compartment through a wall of the valve body, the spring-biased one way valve is received within a portion of the passage within the valve body, and the third bypass includes a transverse passage in the valve body leading from the second bypass to the surface of the valve body against which the seal element of the bimetallic element seats.
8. A gas spring according to claim 1 wherein the first bypass means and third bypass means include a common passage through the piston and valve body and wherein the temperature-responsive valve means permits flow of gas and liquid from the outward compartment to the inward compartment at all times and prevents flow of gas and liquid from the inward compartment to the outward compartment only when the temperature of the gas spring is less than said predetermined temperature.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US57041690A | 1990-08-21 | 1990-08-21 | |
| US570,416 | 1990-08-21 | ||
| US07/671,016 US5106065A (en) | 1989-09-11 | 1991-03-18 | Self-blocking gas spring with temperature-responsive bypass valve |
| US671,016 | 1991-03-18 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2049570A1 CA2049570A1 (en) | 1992-02-22 |
| CA2049570C true CA2049570C (en) | 1994-11-01 |
Family
ID=27075324
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2049570 Expired - Fee Related CA2049570C (en) | 1990-08-21 | 1991-08-20 | Self-blocking gas spring with temperature-responsive bypass valve |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2049570C (en) |
-
1991
- 1991-08-20 CA CA 2049570 patent/CA2049570C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2049570A1 (en) | 1992-02-22 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5106065A (en) | Self-blocking gas spring with temperature-responsive bypass valve | |
| US5404972A (en) | Self-blocking gas spring with temperature-responsive bypass valve | |
| JPH04503560A (en) | Self-locking gas spring with temperature-sensitive bypass valve | |
| US4485899A (en) | Shock absorber unit for vehicles | |
| US6179099B1 (en) | Gas spring having an intermediate stop function and temperature compensation | |
| US4066279A (en) | Pneumatic spring of adjustable length | |
| US3621950A (en) | Shock absorber including valved bypass | |
| US4433759A (en) | Gas spring | |
| CA1175866A (en) | Multi-chamber temperature compensated pneumatic counterbalance | |
| US5722643A (en) | Temperature compensated safety gas spring | |
| US5738276A (en) | Valve | |
| US6007057A (en) | Gas spring with braking means | |
| US7484720B2 (en) | Temperature compensating valve assembly | |
| CA1314450C (en) | Valve operating system for internal combustion engine | |
| US4022377A (en) | Thermostatically operated sleeve valve construction | |
| US3674120A (en) | Auxiliary shock absorber damping valves | |
| CA2049570C (en) | Self-blocking gas spring with temperature-responsive bypass valve | |
| KR0157617B1 (en) | Self-blocking gas spring with temperature-responsive bypass valve | |
| US6092632A (en) | Gas spring with temperature compensation | |
| JPS5814939B2 (en) | Shock absorber | |
| US6357734B1 (en) | Suspension damper with vehicle spring preload | |
| US4560041A (en) | Shock absorber unit with temperature compensation | |
| JPS5831496B2 (en) | Shock absorber | |
| JPS6260570B2 (en) | ||
| JPS6227295B2 (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |