MXPA97004403A - Least return gas spring - Google Patents

Abstract

The present invention relates to a gas spring, characterized in that it comprises: an elongated tubular armature having a pair of separate ends, an axially oscillating shell received inside and protruding from one end of the armature and movable between positions extended and retracted, a first piston within the armature connected to the connecting rod for movement therewith, a second piston within the armature and placed between a first piston and the other end of the armature, the first piston being in cooperation with the armature defining a first fluid chamber between one end of the armature and a first piston, the fluid chamber receives therein a substantially incompressible liquid hydraulic fluid, the first and second pistons in cooperation with the armature define a second fluid chamber which receives in the same liquid hydraulic fluid, the second piston in cooperation with the armor defines a third chamber and Between the other end of the armature and the second piston, the third chamber receives therein a compressed gas under pressure by which it flexibly drives the first piston and the rod to an extended position of the rod, at least one check valve transported by the first piston and constructed and arranged to allow the flow of liquid hydraulic fluid from the second fluid chamber to the first fluid chamber when it is opened to prevent the flow of liquid hydraulic fluid from the first fluid chamber to the second chamber of fluid when closed, each of at least one check valve closes while the connecting rod and the first piston move towards its extended position, a delay valve carried by the first piston and constructed and arranged to allow the flow of liquid hydraulic fluid from the first fluid chamber to the second fluid chamber when it is opened, to avoid the flow of the hydraulic fluid liquid liquid from the second fluid chamber to the first fluid chamber when closed, and which remains closed to retard the flow of liquid hydraulic fluid from the first fluid chamber to the second fluid chamber while each of at least one The check valve is closed, and then the first piston completes movement towards the other end of the cover and is positioned and urged to move towards one end of the cover by the compressed gas in the first chamber and the liquid hydraulic fluid in the first chamber. Second chamber, the cover is constructed to retain a constant quantity of liquid hydraulic fluid, and the armature, the first piston and at least one check valve and a delay valve are constructed and arranged so that the entire hydraulic fluid that flows inside and between the first and second chambers is controlled and produced only through the check and check valves

Description

RETURN SPRING GAS SPRING Field of Invention This invention relates to gas springs, and more particularly to a gas spring having a piston with a slow return stroke.

Background of the Invention A typical gas spring was built for die stamping applications. steel with a control rod connected to a piston slidably received in a cylinder having a cavity which is pre-charged at a predetermined pressure with an inert gas such as nitrogen. When the rod and the piston are forced into the cavity, the gas is compressed at a maximum operating pressure which depends on the volume of the cavity and the effective area and the load of the piston. When the force applied to the connecting rod is removed, the compressed gas within the cavity immediately forces the piston and connecting rod into their fully extended position. In some applications, the drive mechanism of a stamping press includes a stork and meshing gears. When lowering or advancing the stroke of REF: 24469 the press, the force of a driving gear is applied through the teeth of the gear meshed to one face of the teeth of the driven gear. This closes the stamping dies and causes the rod and the piston to retract and compress the gas within the cavity. When the drive mechanism of the press advances towards the transition of the stroke down towards the return stroke, the gear mechanism momentarily passes through an unloaded or neutral position. Through the neutral position, when the force applied by the drive gear changes from advancing the die or die to the return of the die or die, a period occurs where the teeth of the drive gear do not apply a load to the teeth of the driven gear . A problem develops because a typical drive mechanism of this type has a free play or mismatch of approximately 0.060 inches. When the press advances from the load downward to the return stroke, a typical gas spring applies an intermediate force through the piston rod to the dies or dies in the press. This intermediate force is transmitted through the press drive mechanism by accelerating the driven gear through the neutral position causing the gear teeth driven to strike on the other side of the driving gear teeth.

This causes excessive wear and damage to the gear teeth and premature gear failure which is costly and time consuming to repair.

Brief Description of the Invention According to this invention, the gas spring momentarily stops in its compressed position enough for the drive mechanism to pass through the neutral zone and the teeth of the drive gear to re-engage with the teeth of the driven gear before the The gas spring load is transmitted through the dies or dies to the drive mechanism and the press gears. The gas spring has an armature, a first piston received within the armature, a piston rod projecting from one end of the armature and connected to the first piston, and a second piston received within the armature between the first piston and the piston. the other end of the armor. A compressible gas is received within the armature in a gas chamber between the second piston and the other end of the armature. An incompressible hydraulic fluid is received within the armature in a first fluid chamber between one end of the armature and the first piston and a second fluid chamber between the first and second pistons. A delay valve and a check valve are positioned within the first piston to transfer fluid between the fluid chambers. A force is applied to the piston rod, the first piston retracts towards the other end of the armature causing a greater fluid pressure in the second fluid chamber. Some fluid passes through the check valve into the first fluid chamber. To maintain constant total fluid chamber volume, the second piston retracts, compressing the gas in the gas chamber. When the force is removed from the connecting rod and the first piston, the compressed gas applies a force to the second piston which in turn produces a greater fluid pressure in the first fluid chamber. The delay valve momentarily blocks the flow of fluid from the first fluid chamber back to the second fluid chamber causing the first piston to stop in the retracted position. When the delay valve opens, fluid flows into the second fluid chamber, which in turn allows the first piston and connecting rod to move back to their extended positions. The objects, features and advantages of the invention, to provide a self-contained gas spring having slow return characteristics, do not require reservoirs and external fluid or hydraulic gas pipes, do not require external electric control or delay circuits, can be used in the Stamping equipment with existing steel matrix, does not require modifications of existing equipment for installation, has a long service life, and is self-contained, resistant, durable, reliable, relatively simple in design and economical to manufacture and assembly.

Brief Description of the Drawings These and other objects, features and advantages of this invention will be apparent from the following detailed description of the preferred embodiments and the best mode, the appended claims and the accompanying drawings in which: Figure 1 is a fragmented sectional view of a gas spring according to the invention shown with the first piston having started the downward stroke, Figure 2 is a fragmentary sectional view of the gas spring shown in Figure 1 with the first piston shown in the fully retracted position, Figure 3 is a fragmentary sectional view of the gas spring shown in Figure 1 with the first piston having started the return stroke; Figure 4 is a fragmentary sectional view of another preferred embodiment of the gas spring according to the invention; showing the connecting rod moving towards a retracted position with the delay valve in its closed position, Figure 5 is a Fig. 6 is a fragmentary section view of the gas spring of Fig. 4 with the connecting rod in its most extended position in the retard valve in its open position, Fig. 6 is a fragmented elongated sectional view of the retard valve as shown in Figs. Figure 4, and Figure 7 is a fragmentary sectional view of the delay valve taken along line 7-7 of Figure 6.

Detailed Description of the Preferred Modalities Referring in more detail to the drawings, Figures 1-3 illustrate a gas spring 10 with a piston rod 12 projecting from one end 14 of a frame 16 and connected to a first piston 18 slidably received within the armor A second piston 20 is positioned between the first piston and the other end 22 of the armature. A check valve assembly 24 and the delay valve assembly 26 are positioned within the first piston. A bearing and seal assembly 28 are positioned at one end 14 to seal an end and to provide a seal around the piston rod 12. As shown in Figure 1, the armature 16 comprises an elongated tube 30 having openings 32. and 34 at its ends. A cap at the end 36 is fixed to the opening 34 and welded to the tube to seal the end 22 of the armature. As shown in Figure 4, the end cap 36 can be integrally formed with the tube 30. The piston rod 12 is positioned axially within the armature 16 and projects from the armature through the aperture 32. The first piston 18 oscillates axially within the armature 16 and is connected to the rod 12 to move axially therewith. The bearing and seal assembly 28 is received within the opening 32 and has an annular housing 38 which defines a central connecting rod opening 40 through which the connecting rod of the piston 12 extends. The piston rod 12 is sealed to oscillate axially by means of a rod bearing 42 pressurized in the housing 38. The rod bearing 42 is preferably formed of sintered brass as a ring-shaped sleeve impregnated with lubricant. Also positioned within the opening of the rod 40 is a rod seal 44 supported by the housing 38 and which provides a seal against fluids therebetween. A fluid seal is provided between the armature 16 and the housing 38 by means of a 0-shaped ring 46 received in an annular ring groove 48 in the housing 38. To retain the bearing and seal assembly 28 within the opening 32, a slotted ring 50 is received in an annular groove 52 therebetween. A dust cap (not shown) is received in a slot 54 in the armature 16. The second piston 20 oscillates axially within the armature 16 between the first piston 18 and the other end 22.

A gas chamber 62 is defined by the space between the second piston 20 and the end layer 36 inside the armature 16. A compressible gas, such as nitrogen, is sealed within the gas chamber 62 usually at a pressure of approximately 2,000 psi and is further compressed when the second piston 20 moves toward the end 22 of the armature. An essential oil or incompressible hydraulic fluid is confined within a first fluid chamber 64 and a second fluid chamber 66. The first fluid chamber 64 is defined by the space between the bearing and seal assembly 28 and the first piston 18. Within the armature 16. The second fluid chamber 66 is defined by the space between the first piston 18 and the second piston 20 within the armature 16. The hydraulic fluid is preferably of relatively high viscosity and suitable for high applications. temperature of up to at least 200 ° F. To provide a seal against fluids between the armature and the first piston and to separate the first and second fluid chambers, a clean seal 68 is placed in an annular groove 70 in the cylindrical surface 72 of the first piston 18. The first piston 18 has a first surface 74 in the first fluid chamber 64 and a second surface 76 in the second fluid chamber. do 66, both essentially flat. The second piston 20 has a cup-shaped cylindrical body 80 with an essentially flat surface 82 in the second fluid chamber 66 and a cup-shaped compression surface 84 in the gas chamber 62. To provide a seal against fluids between the piston 20 and the armature 16 and consequently the chambers 62 and 66, the external cylindrical surface 86 of the body 80 has a pair of seals 80 received in two recessed annular grooves 90. The check valve 24 has a housing 116 placed under pressure in a bore 118 in the piston 18 and communicates through a passage 120 with the first fluid chamber 64. A movable valve member 122 passes over a complementary seat 124 when closed to prevent fluid flow from the first chamber 64 to the second chamber 66 and when it is not sitting open to allow the flow of the opposite fluid from the second to the first chamber. In a preferred embodiment of the present invention, the delay valve assembly 26, as shown in Figures 1 and 2, is located within a valve chamber '142 in the first piston 18 to allow controlled flow of fluid of the first fluid chamber 64 back to the second fluid chamber 66. A cylindrical bore 144 through the first piston 18 has a fluid inlet 146 communicating with the first fluid chamber 64. The bore 144 also has a fluid outlet 148 communicating with the valve chamber 142 which in turn communicates with the second fluid chamber 66 allowing fluid to pass from the first to the second fluid chamber when the delay valve 26 is opens. As shown in Figures 1 and 2, the valve chamber 142 comprises a cylindrical counter-drilling 150 which opens axially towards the surface 76 of the first piston 18 with an open end 152 communicating with the second fluid chamber 66 and another end 154 communicating with an axial blind bore 156. An annular groove 158 in counterbore 150 communicates with bore 144 through fluid outlet 148. Blind bore 156 communicates with first fluid chamber 64 through of the first passage 160 and the second passage 162 opposed to each other through the rod of the piston 12. A metering orifice 164 is pressed towards the first passage 160 to controllably regulate the flow velocity of the hydraulic fluid from the first fluid chamber 64 through the first passage and towards the blind perforation 156 and consequently the other end 154 of the counter-perforation 150. A miniválvula retention of a via 166 is pressed towards a counter-perforation in the second passage 162 to allow the fluid to be purged from the other end 154 while preventing the inverted flow of fluid through the second passage 162. The retention mini-valve 166 comprises a globe valve 168, a valve seat 170 and a compression spring 172. The spring 172 applies sufficient force to the balloon valve 168 so that it remains still in contact with the seat 170 until the fluid pressure within the blind bore 156 and the other end 154 exceeds enough fluid pressure in the first fluid chamber. The delay valve 26 has a cup-shaped cylindrical body 180 having an open end 182 that coincides with the open end 152 of the counter-drill 150 and a closed end 184 that coincides with the other end 154 of the counter-drill 150. The surface The external body 180 has an essentially uniform cylindrical section 136 adjacent the open end 182 and a perforated section 188 adjacent the closed end of the body 180. The perforated section 188 has a series of perforations 190 through and spaced around the body circumference 180. to allow fluid to pass from outside the body 180 through the perforations 190 towards the hollow cup-shaped portion of the body 180. As shown in Figure 3, three annular grooves 192, 194, 196 are spaced apart of the body 180; the slot 192 adjacent the closed end 184, the slot 194 positioned between the uniform section 186 and the perforated section 188, and the slot 196 adjacent the open end 182 of the body 180. Each of the slots 192, 194 and 196 retains a ring in the form of O 193, 195, 197 to provide a seal between the body of the valve 180 and the valve chamber 142 thereby sealing the perforated section of the uniform section. The body of the valve 180 is retained within the valve chamber 142 by a retaining ring 198 removably received in an annular groove 200 in the counter-drill 150 adjacent the open end 152. When the valve body is in contact with the other end 154, the uniform section 186 remains on the outlet 148 of the bore 144, thereby preventing the flow of fluid through the bore 144. When the valve body is in contact with the retainer ring 198. , the perforated section 188 and the perforations 190 align with the outlet 148 and the perforation 144, thereby allowing the flow of fluid through the perforation 144 and the perforations 190, thereby creating a flow path from the first chamber. of fluid 60 to the second fluid chamber 66. In operation, the gas spring 10 has an external force applied to the piston rod as shown in Figures 1-3. In the downward stroke as shown in Figure 1, the fluid pressure in the second fluid chamber 66 will be greater than the pressure in the first fluid chamber 64. The higher fluid pressure forces the body of the delay valve 180 towards the bottom at the other end 154 of the counter-puncture 150 of the valve chamber 142. This forces any hydraulic fluid into the other end 154 to be purged through the second gate 162. and a retention mini-valve 166 into the first fluid chamber 64. The uniform section 186 is then placed over the fluid outlet 148 of the bore 144 thereby closing fluid communication between the second fluid chamber 66 and the first fluid chamber 64 through the bore 144 The increased fluid pressure in the second fluid chamber also causes the check valve assembly 24 to open allowing the fluid to flow freely from the second fluid chamber 66 to the first fluid chamber 64 through the bore 120. Because the rate of change of the volumetric space within the first fluid chamber 64 is always less than the rate of change in the second fluid chamber 66, all the hydraulic fluid can not be transferred from the second chamber through the check valve 24 into the bore 118. The total volume of the chambers 64 and 66 remains constant while the relative volume changes as the hydraulic fluid is transferred. To maintain the total volume of the chambers 64 and 66 constant, the second piston 20 moves axially towards the other end 22 of the armature 16 which compresses the gas into the gas chamber 62. Figure 2 illustrates the gas spring in a state of equilibrium where the first piston has been stopped moving towards the other end 22 of the gas spring and has not yet stopped moving towards an end 14. This background of the stroke condition is achieved when the external force applied to the piston rod is equivalent to the force applied by the compressed gas within the gas chamber 62. When the external force is removed from the rod, the force applied to the second piston 20 by the gas within the chamber 62 creates a condition of higher pressure in the first fluid chamber 64 thereby closing the check valve 24.

This prevents the fluid from flowing back through the bore 118 from the first fluid chamber 64 back to the second fluid chamber 66. The increased pressure within the first fluid chamber 64 also forces the retention mini-valve 166 to close , thereby preventing the fluid from passing through the second passage 162 towards the other end 154 of the valve chamber 142. The body of the delay valve 180 remains at the bottom against the other end 154 inside the valve. the chamber 142, consequently the uniform section 186 of the valve body, aligned with the bore 144, prevents the fluid from passing from the first fluid chamber 64 through the bore back to the second fluid chamber 66. In this mode, the fluid within the first fluid chamber can only pass through the metering orifice 164 of the first passage 160 and into the blind bore 156 and consequently to the other end. 154. When the fluid gradually passes through the metering orifice towards the blind bore at the other end of the valve chamber, the body of the valve 180 is gradually forced to move towards the bottom against the retainer ring 198. Since the hydraulic fluid is essentially incompressible, the first piston 18 and the rod 12 stop at the bottom of the stroke position shown in Figure 2 until the perforations 190 and the body of the valve 180 are aligned with the fluid outlet 148 of the perforation 144. The stopping time is controlled by varying the flow characteristics of the dosing orifice 164 and the volume of fluid needed to move the body of the retard valve 180 from the other end of the valve chamber towards contact with the valve. the retaining ring. Once the perforations 190 are aligned with the annular groove 158, fluid from the first fluid chamber 64 can pass through the perforation 144 towards the groove 158, through the perforations 190, and the open end 152 of the valve chamber, the open end 182 of the delay valve, and to the second fluid chamber 66. The first piston 18 and the piston rod 12 will then move through the return stroke as shown in the Figure 3 to their fully extended positions. Heavy loads and high fluid pressures within the gas spring (in the range of 2000-6000 psi) produce high operating temperatures. Preferably, the temperature should remain at approximately 140-160 ° F. To prevent the degradation of the hydraulic fluid, the temperature inside the cylinder should not exceed approximately 200 ° F. To control the operating temperature, numerous techniques can be employed. cooling. Cooling water can be run through a coil wound around the cylinder, a cold water jacket can be wound around the cylinder, or the fluid can be blown continuously or intermittently on the cylinder. In another preferred embodiment of the invention as shown in Figures 4-6, a gas spring 240 embodying this invention has an additional feature that provides a return cushion for a first piston 242 and a connecting rod 244 and provides an initial force Desirable high necessary to start the compression stroke down the first piston and the connecting rod. The piston rod 244 has a larger diameter cylindrical flange 246 extending radially outwardly of the rod. The rim 246 is in contact with the first piston 242 at one end and has a radially outwardly extending ridge of larger diameter 248 at its opposite end. A bearing and seal assembly 250 has a corresponding recessed annular counter-perforation 252 having a radially outwardly beveled edge 254 for defining the rim 246 and the flange 248 when the piston 242 and the rod 244 are in their fully extended position. In operationWhen the piston 242 and the rod 244 move towards their fully extended position, the flange 248 enters the counter drilling 252 trapping hydraulic fluid within the counter drill. To control the rate at which hydraulic fluid can be spilled by the flange or flange 248, a radial clearance of approximately 0.010 inches is preferred between the flange and the counter-drill. The trapped hydraulic fluid provides a buffer between the flange 246 and the bearing and seal assembly 250 when the piston and rod move towards the extended position, and then spills between the flange or flange 248 and the counterdrill 252 which allows the flange 246 extends fully towards the counter-perforation. A higher initial load desired to start the first piston 242 in its downward stroke is also achieved by the structure of this mode. When the piston 242 begins to move towards its retracted position, the flange 246 and the flange 248 begin to creep from the counter-perforation 252. The free space adjusted between the flange and the counter-perforation prohibit the fluid from freely passing around. the flange or flange towards the evacuated space on the side of the flange or flange oriented towards the counter-perforation. When the first piston 242 moves towards the other end of the armature 16, the volume of the first fluid chamber 64 increases. The radial free space set between the flange and counter-perforation essentially prevents the fluid filling the evacuated space from momentarily reducing the rate of volume change of the first fluid chamber. In this way, the initial displacement of the connecting rod and the first piston produces less fluid transfer from the second fluid chamber towards the first fluid chamber and consequently the displacement of the second piston. This produces a greater initial compression of the gas in the gas chamber and in this way a greater initial resistance to the movement of the connecting rod and the first piston. The greater initial resistance is also achieved by the vacuum that exists momentarily in the evacuated space. Once the flange or flange 248 moves axially beyond the counter-drilling 252, the gas spring 240 functions like the gas spring 10 described in the previous embodiment. Another feature of the gas spring 240 is the removal of O-rings 193, 195 and 197 from the delay valve assembly. As shown in Figure 6, the delay valve assembly 280 has a valve chamber 282 on the first piston 242. The valve chamber 282 comprises a cylindrical counter drilling 284 that opens axially toward a surface 285 of the first piston 242 with an open end 286 in communication with the second fluid chamber 66 and another end 288 in communication with a blind perforation 292. An annular slot 290 in the counter-perforation 284 communicates with the perforation 144 through the fluid inlet 148. Blind bore 292 communicates with the first fluid chamber 64 through the first passage 160 and the second passage 162 opposite each other through the flange 246 and offset 90 ° from the bore 116 and the bore 144 as shown in Figs. 5 -7. As not shown in this embodiment, the metering orifice 164 is pressed towards the first passage 160 and the retention mini-valve 166 is pressed into the second passage 162 and both operate as described above. The delay valve assembly 280 has a cup-shaped cylindrical body 298 having an open end 300 that coincides with the open end 286 of the counter-drill 284 and a closed end 302 that engages with the other end 288 of the counter-drill. 284. The outer surface of the body 298 is an essentially cylindrical surface having a series of perforations 304 through and spaced around the circumference of the body 298 near the closed end 302. Removing the grooves 192, 194 and 196 and the O-rings 193, 195 and 197, the mode depends on an adjustment in the closed tolerance slip between the body of the delay valve 298 and the cylindrical counter-drilling 284 of the valve chamber for substantially prevent all fluid flow between them. Any negligible leakage of the hydraulic fluid can be taken into account in the design of the dosing orifice and the delay chamber. The hydraulic fluid can then only flow from the first chamber 64 to the second chamber 66 when the delay valve is positioned so that the perforations 304 are aligned with the perforation 144. To ensure that the delay valve remains in its closed position until the fluid pressure at the closed end of the valve chamber is forced to open, one end of a compression spring 306 is placed in a cavity 308 at the open end of the body 298. The other end of the spring compression is received on a flange 312 of an annular retaining ring 314 inserted in the open end of the bore 284 and retained at the open end by a split ring 316 received in a slot 318 in the counter-drill and on a rim 320 of the ring. Another feature of the gas spring 240, as shown in Figures 4 and 5, is an abutment and bearing assembly structure and alternative seal 250. The bearing and seal assembly 250 has external threads 330 for coupling adjacent complementary internal threads. to end 14 of the armature 16 to connect the bearing and seal assembly to the armature. The assembly 250 also includes a threaded purge screw 334 received within a bore 336 having complementary threads 338 for purging air within the armature 16. A cavity 340 formed between the bearing 42 and the seal housing 38 communicates with the perforation 336 allowing air passing between bearing 42 and housing 38 to be purged from the cylinder after opening the bleed screw. This allows air to be purged from the hydraulic fluid in chambers 64 and 66 and associated valves 22 and 26 and related passages. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates. Having described the invention as above, property is claimed as contained in the following:

Claims (16)

1. A gas spring, characterized in that it comprises, an elongated tubular armature having a pair of spaced ends, an axially oscillating rod received inside and projecting from one end of the armature and moving between the extended and retracted positions, a first piston within the armature and connected to the connecting rod to move with it, a second piston within the armature and placed between the first piston and the other end of the armature, the first piston in cooperation with the armature defining a first fluid chamber between an end of the framework and the first piston to receive therein an essentially incompressible hydraulic fluid, the first and second pistons in cooperation with the armature defining a second fluid chamber for receiving the hydraulic fluid therein, the second piston in cooperation with the armature defines a third chamber between the other end of the armature and the second piston to receive a gas in it pressure, at least one check valve supported by the first piston and constructed and arranged to allow the flow of hydraulic fluid from the second fluid chamber to the first fluid chamber when it is opened and to prevent the flow of hydraulic fluid from the first fluid chamber to the second fluid chamber when closed, and a retard valve carried or supported by the first piston and constructed and arranged to retard the flow of hydraulic fluid from the first fluid chamber to the second fluid chamber when the check valve is closed until the first piston completes the transit of moving towards the other end of the armature to move towards one end of the armature.

2. The gas spring according to claim 1, characterized in that it has at least two check valves.

3. The gas spring according to claim 1, characterized in that the delay valve retards the flow of the hydraulic fluid from the first fluid chamber to the second fluid chamber for a determinable time after the first piston completes the transit of moving. towards the other end of the armature to move towards one end of the armature.

4. The gas spring according to claim 1, characterized in that the delay valve comprises, a valve chamber and a valve body positioned within the chamber and that oscillates between the open and closed positions, preventing the flow of hydraulic fluid from the first fluid chamber to the second fluid chamber when closed and allowing hydraulic flow when open.

5. The gas spring according to claim 4, characterized in that the delay valve further comprises a first gate for controllably purging hydraulic fluid from the first fluid chamber towards the valve chamber forcing the valve body to move towards its open position.

6. The gas spring according to claim 5, characterized in that the first gate includes a metering orifice to controllably purge the hydraulic fluid to the valve chamber.

7. The gas spring according to claim 5, characterized in that the delay valve further comprises a second gate for purging the hydraulic fluid from the valve chamber when the valve body is moved to its closed position.

8. The gas spring according to claim 7, characterized in that the second gate includes a check valve that allows fluid to flow through the second gate from the valve chamber into the first fluid chamber and prevents fluid flow back through the second gate into the valve chamber.

9. The gas spring according to claim 4, characterized in that the valve chamber and the valve body communicate directly with the second fluid chamber so that the valve body when in its open position allows the Hydraulic fluid flows from the first fluid chamber through the body of the valve into the second fluid chamber.

10. The gas spring according to claim 9, characterized in that the valve body is a cup-shaped cylinder having a side wall, a closed end and an open opposite end and wherein the cylinder has at least one bore that passes through the side wall of the cylinder.

11. The gas spring according to claim 10, characterized in that the cylinder has two or more such perforations.

12. The gas spring according to claim 1, characterized in that the connecting rod includes a flange and an end of the armature and includes a complementary cavity for receiving the flange when the piston is in its extended position.

13. The gas spring according to claim 12, characterized in that the flange includes an outwardly extending annular flange or flange positioned at the end of the flange closest to the cavity to be received within said cavity.

14. The gas spring according to claim 13, characterized in that the flange and the cavity have a diametral clearance of between about 0.01C of an inch.

15. The gas spring according to claim 1, characterized in that one end of the armature includes a purge valve for releasing air from the first fluid chamber.

16. A gas spring, characterized in that it comprises, an elongated tubular armature having a pair of spaced ends, an axially oscillating rod received inside and projecting from one end of the armature and moving between the extended and retracted positions, a first piston within the armature and connected to the connecting rod to move with it, a second piston inside the armature and placed between the first piston and the other end of the armature, the first piston in cooperation with the armor defines a first chamber of fluid to receive therein an essentially incompressible hydraulic fluid, the first and second pistons in cooperation with the armature define a second fluid chamber for receiving the hydraulic fluid therein, the second piston in cooperation with the armature defines a third chamber for receiving a gas under pressure therein , at least one check valve carried or supported by the first piston constructed and arranged to allow the flow of hydraulic fluid from the second fluid chamber to the first fluid chamber when it is open and to prevent the flow of hydraulic fluid from the first fluid chamber to the second fluid chamber when closed, and a valve of delay carried or supported by the first piston and constructed and arranged to retard the flow-of hydraulic fluid from the first fluid chamber to the second fluid chamber when the check valve is closed for a determinable time after the first complete piston the transition of the movement towards the other end of the armature, the delay valve comprises a valve chamber and a valve body positioned within the chamber and oscillating between the open and closed positions.