GB2303194A

GB2303194A - Gas spring for hatchback

Info

Publication number: GB2303194A
Application number: GB9514329A
Authority: GB
Inventors: Etienne Perrin; Dominique Dony
Original assignee: Draftex Industries Ltd
Current assignee: Laird Holdings Ltd
Priority date: 1995-07-13
Filing date: 1995-07-13
Publication date: 1997-02-12
Anticipated expiration: 2015-07-13
Also published as: FR2736697B1; FR2736697A1; GB2303194B; GB9514329D0

Abstract

A gas spring for the hatchback or other closure of a motor vehicle automatically stops the closure at a position intermediate its fully open and fully closed positions. It comprises a cylinder (10) with a piston (26) dividing it into two chambers (32,34) connected by a restricted gas flow path through groove and bore (36,37) from the second chamber to the first as the piston moves from an inner position towards a second, outer position. The piston rod (18) also passes through a third chamber (57), which is further from the piston than the second chamber (34) and has sealing means e.g. ring (46) which, when in the third chamber, seals the third chamber e.g against wall portion (58A) to arrest movement of the piston rod in the intermediate position. Further opening movement is enabled by manual movement of control means e.g. rod (62) to lift valve (70) from head (38) of piston (26) to allow gas to flow from the third chamber (57) via bore (48) and passage (76) in piston rod (18), to by-pass the sealing means.

Description

GAS SPRING The invention relates to gas springs.

Gas springs embodying the invention and to be described below by way of example can be used in motor vehicles for easing the opening of closure members such as luggage and engine compartment lids and hatchbacks. However, they may be used for other purposes.

According to the invention, there is provided a gas compression spring for moving a member pivotted on a body from a first position corresponding to compression of the spring to a second position, comprising: an arrangement of a piston movable within cylinder means, the piston carrying a piston rod slidingly and sealingly extending outwardly of the cylinder means; one of the piston and the cylinder means being adapted for connection to the body and the other thereof being adapted for connection to the member; the interior of the cylinder means being filled with gas under pressure and the piston dividing the interior of the cylinder means into a first chamber defined at least in part by the head of the piston and a second chamber through which the piston rod extends; the first and second chambers being interconnected by first gas flow means providing a restricted gas flow path permitting limited flow of gas from the second chamber to the first chamber as the gas pressure exerted on the piston head moves the piston rod from an inner piston rod position towards an outer piston rod position more outwardly of the cylinder means, whereby to move the member towards the second position; the interior of the cylinder means also including means defining a third chamber through which the piston rod passes and which is further from the piston than the second chamber; the piston rod carrying sealing means which moves between the second chamber and the third chamber as the piston rod moves between the inner and outer piston rod positions; the piston rod sealing means being adapted when in the third chamber to seal off the third chamber so as to arrest movement of the piston rod at an intermediate position between the inner and outer piston rod positions; and control means operable from outside the cylinder means for by-passing the sealing means to permit resumption of movement of the piston rod.

Gas springs embodying the invention, and for use in controllably opening hatchbacks in motor vehicles, will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a longitudinal section through one of the gas springs; Figure 2 is a scrap section through a fixture for securing the gas spring of Figure 2 in position and for use in controlling its operation; Figure 3 is a longitudinal section corresponding to Figure 1 but through another one of the gas springs; Figures 4 and 5 are enlarged cross-sections through modified parts of the gas spring of Figure 3; Figure 6 is a longitudinal section through part of another of the gas springs; Figure 7 is an end view of the gas spring of Figure 6; Figure 8 is a longitudinal section through part of a further one of the gas springs;; Figure 9 corresponds to Figure 8 but shows a further modification; and Figure 10 corresponds to Figures 8 and 9 and shows yet another modification.

Referring to Figure 1, the gas spring comprises a cylindrical body 10 having a closed end 12 on which is mounted a fixture 14.

The opposite end of the cylinder is closed off by an integral cap 16 which is apertured to allow passage of a hollow piston rod 18.

The piston rod 18 slides in a guide 20 and through an airtight seal 22. The piston rod 18 is attached to a fixture 24 (see Figure 2).

In use, the gas spring is mounted on a vehicle body so as to control the pivotting movement of a horizontally pivotted closure member such as the hatchback, the lid of a luggage compartment, or the bonnet of the engine compartment. One of the fixtures 14,24 is attached to the body of the vehicle and the other is attached to the hatchback (or other movable member). The gas spring may, however, be used in many other applications.

Within the cylinder 10, the piston rod 18 is attached to a piston 26 which is provided with a circular groove 28 in which is loosely located a sealing ring 30, the groove 28 being wider than the sealing ring. The piston 26 and the sealing ring 30 separate first and second chambers 32 and 34 within the cylinder.

However, these chambers 32,34 are controllably interconnected (in a manner to be explained) by a radial bore 36 and several axially directed bores 37.

The piston has a head 40 and a hollow cylindrical extension 42 rigid with and sealed to the outside of one end of the piston rod 18. At its end opposite to the head of the piston, the cylindrical extension 42 is provided with a circular channel 44 in which is seated a sealing ring 46.

At its distal end, the hollow cylindrical extension 42 is provided with a radial bore 48 which interconnects the chamber 34 with the hollow interior of the piston rod 18.

The cylindrical body 10 is also provided with a cylindrical insert 56 defining a chamber 57 and is rigid with and sealed to the inside of the body 10. The insert 56 provides a cylindrical inside wall 58 having a portion 58A which is smooth and uninterrupted and a portion 58B in which is formed a longitudinal groove 60.

A control rod 62 extends within the hollow interior of the piston rod 18. The control rod 62 is generally of lesser external diameter than the internal diameter of the hollow interior of the piston rod 18. However, approximately mid-way along its length, the control rod 62 has an enlarged piston portion 64 having a groove 66 in which is seated a sealing ring 68 which provides a gas-type seal with the wall of the hollow interior of the piston rod 18.

At its innermost end, the control rod 62 carries a valve member 70 which protrudes through an aperture 72 in the head 38 of the piston 26 and is sealed to this aperture by a sealing ring 74.

As indicated in Figure 1, the bore 48 thus interconnects the chamber 34 with a passageway 76 which is defined between the outside of the control rod 62 and the interior wall of the piston rod 18 and the interior wall of the hollow cylindrical extension 42.

The whole of the interior of the body 10 is filled with gas, such as nitrogen, under pressure - except that this gas will not enter the space 78 between the outside of the control rod 62 and the interior wall of the right hand end (as viewed in Figure 1) of the piston rod 18.

As shown in Figure 2, the outside of the piston rod 18 is secured within the fixture 24, such as by being threadably engaged with a bore 80 in the body 82 of the fixture. The control rod 62 protrudes beyond the end of the piston rod 80 into a slot 84 formed in a rod 86 which is rigid with and rotatable by means of a knurled knob 88. The body 82 is also formed with an aperture 90 by means of which it can be secured to the body of the vehicle or the hatchback (or other movable member).

The operation of the gas spring of Figures 1 and 2 will now be described.

It will initially be assumed that the hatchback to which the gas spring is attached and whose movement is to be controlled is closed so that the piston 26 is at the left hand end of the cylindrical body 10, as viewed in Figure 1, and the piston rod 18 (and thus the control rod 62) are substantially retracted into the body 10.

When the hatchback is unlatched and raised slightly, the gas pressure within the body 10 causes the piston 26, and thus the piston and control rods 18 and 62, to move to the right, the gas pressure within the chamber 32 exerting a greater force on the face of the head 38 of the piston 26 than the gas pressure within the chamber 34 exerts on the underside of the piston 26, because of the greater surface area of the piston head 38. In addition, the gas pressure within the chamber 32 holds the valve member 70 of the control rod 62 in sealing contact with the sealing ring 74. The gas pressure exerted on the piston is sufficient to provide a force capable of lifting the hatchback.

As the piston 26 moves to the right, sealing ring 30 is held at the left hand side of the groove 28 by frictional force.

Chambers 32 and 34 are thus interconnected via the bore 36 and the bores 37, and also through the gap 39 between the piston 26 and the cylinder 10, the interconnection taking place under the sealing ring. The size of the bore 36 thus controls the transfer of gas and therefore the speed of the piston. As the piston rod 18 continues to move to the right, the hatchback will thus be raised towards its open position.

As movement of the piston 26 and the piston and control rods 18 and 62 to the right continues, the cylindrical extension 42 of the piston enters the chamber 57. Initially, the sealing ring 46 will make sealing contact with the smooth wall portion 58A of the interior of the insert 36. The resulting seal will cause pressure to build up within the chamber 57, and oppose the movement of the piston 26. The weight of the hatchback now balances the force exerted on the piston by the gas in the spring and the piston stops. In this way, therefore, the hatchback is automatically stopped at an intermediate point during the raising operation and is thus prevented from opening further, and from closing. The position of this intermediate point depends on the position of the smooth wall portion 58A in relation to the length of the cylindrical body 10.The intermediate point can thus be selected so that the hatchback is sufficiently opened to enable easy access but so that the hatchback does not come into damaging contact with a garage ceiling or similar obstacle.

In addition, because the hatchback is prevented from closing, the danger of unexpected closing of the hatchback, such as might otherwise occur in cold weather which reduces the pressure of the gas within the cylindrical body 10, is avoided.

If the hatchback is required to be moved from the intermediate position, the user partially rotates the knurled knob 88 (Figure 2), causing the rotary rod 86 to turn slightly and to move the control rod 62 slightly to the left (as viewed in Figures 1 and 2). This movement lifts the valve member 70 of the control rod 62 away from (to the left) the sealing ring 74 in the head 38 of the piston. The interior of chamber 57 is thus connected to chamber 32 via bore 48 and passageway 76. The gas pressure which has thus built up within chamber 58 is released. The resultant gas pressure on the piston is now sufficient to overcome the weight of the hatchback again and the piston consequently moves to the right as viewed in Figure 1 and the hatchback is lifted to its fully open position. The user can now return knob 88 to its original position.During the further piston movement, build-up of gas pressure within chamber 58 is prevented by the groove 58B which interconnects chamber 58 with chamber 34.

Chamber 34 is in turn connected to chamber 32 via the bores 37 and the bore 36.

If, instead, the user applies a slight lowering force to the hatchback after moving the knob 88 into its released position, the effective weight of the hatchback is increased and overcomes the gas pressure exerted on the piston, thus lowering the hatchback and moving the piston to the left (as viewed in Figure 1). During this movement of the piston, the frictional force acting on the sealing ring 30 moves it to the right hand side of the groove 28. Gas pressure can now transfer from chamber 34 to chamber 32 via bores 37, under the sealing ring 30, and into chamber 32 via the left hand side of the ring 30 and thence through the gap 40 between the piston and the cylinder.

After the movement of the piston 26 has caused the sealing ring 46 to clear the interior wall 58 of the chamber 57, the user can return the knob 58 to its locking position, while continuing to lower the hatchback. This facility enables the user to have full control over movement of the hatchback and over the extent of such movement. Thus, a short person can stop the hatchback from rising to its fully raised position, from which such person might have difficulty in reaching it to return it manually.

If the hatchback is to be returned to the closed position from the fully opened position, the user applies a manual lowering force to the hatchback. Again, therefore, the effective weight of the hatchback is increased, and overcomes the gas pressure exerted on the piston. The piston therefore moves to the left and the hatchback is lowered. During the initial lowering movement, gas transfer between chambers 57 and 34 takes place through groove 60. When the sealing ring 44 reaches the smooth wall portion 58A, gas transfer between chambers 57 and 34 can no longer take place and the piston stops, the resultant pressure on the piston now balancing the weight of the hatchback. The hatchback can be lowered from this stopped position in the manner explained above.

If the piston is stopped with the sealing ring 46 in contact with the smooth wall portion 58A of the cylindrical insert 56 and the user applies a lifting force to the hatchback without moving the knob 88 to the released position, the resultant movement of the piston to the right (as viewed in Figure 1) will cause a build-up of pressure in chamber 57. If this pressure becomes excessive, it will cause the valve member 70 to be moved away from the sealing ring 74 in the head 38 of the piston, thus preventing possible damage to the sealing ring 46 (which might be caused by this excess pressure).

The gas spring of Figure 3 will now be described. Parts in Figure 3 which correspond to parts in Figures 1 and 2 are correspondingly referenced.

In the gas spring of Figures 1 and 2, the user's control of the movement of the hatchback away from the intermediate arrest position was carried out by means of the control rod 62 passing through the hollow interior of the piston rod 18. In the gas spring of Figure 3, such control is exerted from the opposite end of the cylindrical body 10, and the piston rod 18 is solid.

As shown in Figure 3, the cylindrical body 10 incorporates a concentric cylinder 100 which is positioned within the cylindrical body 10 and spaced from it by a narrow concentric passageway 102. The piston 26 slides within the concentric cylinder 100, and is sealed thereto by the sealing ring 30.

The cylindrical insert 56 is secured within the concentric cylinder 100 and sealed thereto by a sealing ring 104.

The interior of the chamber 57 is connected to the narrow concentric passageway 102 by a through bore 106.

In the gas spring of Figure 3, the fixture 28, by means of which the corresponding end of the gas spring is secured to the vehicle body or to the hatchback or to the hatchback, as the case may be, is hollow. A control rod 108, for controlling the operation of the gas spring in a manner to be described, passes through the fixture 28 and operates a control mechanism indicated generally at 110.

The control rod 108 passes through an end fitting 112 to which it is sealed by a sealing ring 114. The fitting 112, together with a rigid ring 116, define a hollow chamber 118. At a chamber 119, the diameter of the rod is reduced to form a narrow diameter portion 120 which passes through chamber 118. The narrow concentric passageway 102 is connected to the interior of the chamber 118 via a radially directed passageway 122.

After passing through the chamber 118, the narrow portion 120 increases in diameter at a chamfer 123 to form an enlarged portion 124 which is sealed by a sealing ring 126 to the interior of a block 128. The block 128 is recessed to receive the rigid ring 116. In addition, it carries a further sealing ring 130 which makes sealing contact with the interior of the concentric cylinder 100.

The control rod 108 is terminated in a nut 132 which is located in a bore 134 in open communication with the chamber 32.

Initial operation of the gas spring of Figure 3 is the same as for the gas spring of Figures 1 and 2. Thus, to open the hatchback, the user unlatches it and manually lifts it slightly.

The gas pressure within chamber 32 thus moves the piston 26 to the right in the manner already explained. As previously explained, gas transfer between chambers 34 and 32 takes place through bores 37 and bore 36, the sealing ring 30 being held at the left hand side of the groove 28 by the frictional force acting on it.

When the piston 26 has moved sufficiently to the right (as viewed in Figure 3), the sealing ring 46 will make sealing contact with the smooth walled portion 58A of the wall 58 of the chamber 57.

Gas pressure will build up within chamber 57; although chamber 57 is connected via bore 106 and passageway 102 to chamber 118, the gas cannot escape from chamber 118 because of the sealing rings 114 and 126. This build-up of pressure within chamber 57 reduces the force exerted on the hatchback and the hatchback stops, its weight now balancing the lifting force of the spring.

The hatchback thus stops in the intermediate position corresponding to the intermediate position for the gas spring of Figures 1 and 2.

If the user wishes to raise or lower the hatchback from this intermediate position, it is necessary to move the control rod 108 slightly to the right, as viewed in Figure 3. The narrowed portion 120 of the control rod 108 thus becomes aligned with the sealing ring 126. Chamber 118 is thus connected to chamber 32.

Gas pressure is no longer trapped in chamber 57. If the user lifts the hatchback slightly, the gas pressure in chamber 32 will move the piston 26 to the right and lift the hatchback to its fully open position. Once the piston has moved sufficiently so that sealing ring 46 becomes aligned with the portion 58B of the chamber 57, the knob 108 can be released (so as to move back to the position illustrated); gas pressure build-up in chamber 57 is prevented by the groove 60.

If instead, the user wishes to lower the hatchback from the intermediate position, slight manual lowering force is applied to the hatchback. Gas transfer takes place from chamber 57 into chamber 32 through bore 106, passageway 102 and chamber 118. As soon as the piston 26 has moved sufficiently to the left so that the sealing ring 46 has cleared the cylindrical insert 56, the user can move the control rod 108 back to the locking position (as illustrated in Figure 3) and the weight of the hatchback lowers the piston 26 against the gas pressure in chamber 32.

During the resultant movement of the piston 26 to the left (as viewed in Figure 3), sealing ring 30 is moved to the right hand side of the slot 28 and gas can transfer between chambers 34 and 32 via bores 37 and thence under the sealing ring, through the gap between the sealing ring and the left hand side of the groove 28 and via gap 40.

If the raised hatchback is to be lowered from the full open position, the operation is similar: manual lowering force is applied by the user, and gas pressure transfer takes place between chambers 57 and 34 via groove 60. When the sealing ring 46 contacts the smooth wall 58A of the chamber 57, the user momentarily moves the control rod 108 to the right, to allow gas pressure transfer to take place between chamber 57 and chamber 32 via bore 106, passageway 102 and chamber 118. Thereafter, the control rod 108 can be moved back to the locked position illustrated.

Figure 4 shows a modified form of the mechanism 110 at the left hand end of the gas spring illustrated in Figure 3. Parts in Figure 4 corresponding to those in Figure 3 are similarly referenced.

In the mechanism 110 of Figure 4, the control rod 108 of Figure 3 is replaced by a control rod 108A and an operating rod 108B.

Control rod 108A has a narrowed portion 120 passing through chamber 118 and connecting with an enlarged portion 126. Sealing rings 114 and 126 corresponding to those in Figure 3 are similarly provided.

The opposite end of the control rod 108A in Figure 4 passes into a transverse bore 140 in which is mounted the radially directed operating rod 108B which is in contact with the distal end of the control rod 108A. Operating rod 108B is flexibly mounted enabling it to be moved in the direction of the arrow A so as to move the control rod 108A downward as viewed in Figure 4 (corresponding to movement to the right as viewed in Figure 3), thus placing chamber 118 in communication with chamber 32 in the manner explained with reference to Figure 3 and for the same purpose.

The fixture 28 for attaching the gas spring to the hatchback or vehicle body comprises, in this case, a socket 142.

An important feature of the mechanism 110 of Figure 4 is that the narrowed portion 120 of the rod 108A is the same diameter as the rod itself; thus there is no chamfer 119 corresponding to that shown in Figure 3. Therefore, the pressure in the chamber 118 (acting through passageway 102 from chamber 57) produces a force acting on chamfer 123 tending to move the enlarged portion 124 out of the chamber 118. This force thus reduces the force which the user has to exert on the rod 108A to connect chamber 118 to chamber 32. In addition, if the user should attempt to lift the hatchback without moving the rod 108A to the released position, the resultant increased pressure in chamber 57 is able itself to move the enlarged diameter portion 124 out of the chamber 118, thus connecting chamber 57 to chamber 32.This reduces the pressure in chamber 57 which might otherwise damage the sealing ring 46. In the mechanism 110 of Figure 3, the pressure within chamber 118 acts substantially equally in both directions (on chamfers 119 and 123) on rod 108 and these advantages are not obtained.

Figure 5 shows a further form which the control mechanism 110 can take. Again, parts in Figure 5 which correspond to those in Figure 3 are similarly referenced.

In Figure 5, the control member 108 extends radially through the wall of the cylindrical body 10. The member 108 is screwthreadedly attached to a rod 150 which extends through a chamber 152 and has an enlarged head 154. Rod 150 slides within a cylinder 156 to which it is sealed by a sealing ring 158.

Cylinder 156 is in turn sealed by a sealing ring 160 to a main body 162.

Main body 162 is sealed by a sealing ring 164 to the cylindrical body 10 and by a sealing ring 166 to the concentric cylinder 100.

The main body 162 has a radial bore 168 in communication with the concentric narrow passage 102 (Fig. 3). The radial bore 168 communicates with an axial bore 170 which is closed off at an end 172, its other end being in communication through a bore 173 with the interior of the chamber 152. On the opposite side to the enlarged head 154, the chamber 152 communicates with a bore 174 which extends parallel to the access of the gas spring into communication with the chamber 32.

The user can place chamber 57 (Figure 3) into communication with chamber 32 by pressing on a knob 176 carried by the rod 108 so as to move the rod in the direction of the arrow B (Figure 5).

The enlarged head 154 is displaced to the right, away from sealing ring 160. Chamber 57 is thus placed into communication with chamber 32 via bore 106 (Fig. 3), passageway 102, bore 168, bore 170, chamber 152 and bore 174.

In the gas spring illustrated in Figure 6, parts corresponding to parts in Figures 1 and 3 are correspondingly referenced. In the gas spring of Figure 6, the piston rod 18 is solid, like the gas spring of Figure 3. However, unlike the gas spring of Figure 3, there is no concentric cylinder 100 or passageway 102.

Instead, chamber 57 can be controllably connected to chamber 32 by a control mechanism 180 which is mounted on the side of the cylindrical body 10.

The control mechanism 180 comprises a main body 182 having an open end in which is inserted a closure member 184 defining a chamber 186. A control rod 188 passes into and through the chamber 186 and has an enlarged head 190. A sealing ring 192 seals around the rod 188 where it enters the chamber 186, and a sealing ring 194 seals against the enlarged head 190.

The chamber 57 is connected to the chamber 186 through a bore 196. The chamber 187 on the left hand end of the enlarged head 190 is connected to the chamber 34 through a radial bore 198.

The control mechanism 180 is clamped to the cylindrical body 10 by bolted clamps 199 and 200 (see Figure 7 also). Seals 202 and 204 seal the mechanism 182 to the cylindrical body 10 in a gastight manner.

The operation of the gas spring of Figure 6 is generally as previously described. In order to release the gas spring from the intermediate arrest position, the user presses the control rod 188 to the left, as viewed in Figure 6. This separates the enlarged head 190 from the sealing ring 194. Chamber 57 is thus connected, via bore 196 and bore 198, to chamber 34, so as to permit the release of the built-up gas pressure in chamber 57 in the manner already explained.

The control mechanism can be arranged to be electrically operated or can be replaced by an electro-valve.

Figure 8 illustrates part of a modified form of the gas spring of Figure 3, and parts corresponding to those in Figure 3 are similarly referenced.

In the control mechanisms of Figures 5 and 6, the control rod has only a single chamfer 123, like the mechanism of Figure 4, thus ensuring that the resultant pressure within chamber 152 or 186 tends to move the mechanism to the released position with the advantages stated above in relation to Figure 4.

In the gas spring of Figure 8, the narrow concentric passageway 102 is connected to the chamber 57 through the open end of the cylindrical insert 56 and a groove 204 in the end seal 22. This manner of connection replaces the radially directed bore 106 of Figure 3, but does not affect the operation.

A more significant difference between the gas spring of Figure 8 and the gas spring of Figure 3 is that, in the gas spring of Figure 8, the groove 44, in which the sealing ring 46 is located at the end of the cylindrical extension 42 of the piston 26, has a greater width so that the sealing ring 46 can move in a generally axial direction. In addition, a radially directed slot 206 in one face of the groove 44 connects with a slot 208 in the base of the groove 44.

When the gas spring operates to raise the hatchback and the cylindrical extension 42 enters the chamber 57, the frictional force between the sealing ring 46 and the smooth part 58A of the wall of the chamber 57 holds the sealing ring in the position illustrated in Figure 8, against wall 209 of groove 44. Sealing ring 46 blocks communication between chamber 37 and slot 208 There is thus no connection between chamber 57 and chamber 32.

The hatchback stops in the intermediate position. It can only be moved towards the fully open position by connecting chamber 57 to chamber 32 via passageway 102 in the manner explained in connection with the preceding Figures, such as by means of the control mechanism 110 (Figure 3). However, the hatchback can be lowered from the intermediate position without use of the mechanism 110. It is simply necessary for the user to apply a lowering force to increase the effective weight of the hatchback.

The resultant slight movement of the cylindrical extension 42 to the left (as viewed in Figure 8) causes the frictional force between the sealing ring 46 and the smooth part 58A of the wall of the chamber 57 to move the sealing ring to the opposite wall 210 of the groove 44. Chamber 57 is now connected to the chamber 34 via slots 206 and 208, under the sealing ring 30 and between the sealing ring 30 and the other wall of groove 44.

Figure 9 shows a modification of the arrangement shown in Figure 8. In Figure 9, the significant difference is that the slot 206 is provided in the wall 210 of the slot 44. When the gas pressure within the gas spring is raising the hatchback and moving the cylindrical extension 42 to the right as viewed in Figure 10, frictional force between the smooth part 58A of the wall of the chamber 57 and the sealing ring 46 holds the sealing ring 46 against wall 210 in groove 44. In this position of the sealing ring 46, chamber 57 is connected to chamber 34 via slots 206 and 208. Therefore, movement of the piston is not arrested when the sealing ring 46 contacts the smooth walled portion 58A.

The hatchback thus rises to its fully opened position.

During manual lowering of the hatchback, frictional force acting on the sealing ring 46 moves it into contact with the wall 209 of the groove 44 as viewed in Figure 9. The sealing ring now blocks transfer of gas pressure through slots 206 and 208.

However, during the initial lowering movement of the hatchback, gas pressure transfer can still take place via groove 60. When the sealing ring 46 comes into contact with the smooth walled portion 56A of the cylindrical insert 56, though, no gas pressure transfer between chambers 57 and 34 can take place. The hatchback movement thus stops. The user can thereafter lower the hatchback only by momentarily operating the control mechanism 110 (Figure 3), or a similar control mechanism in accordance with Figure 4 or 5 for example. This momentary operation of the control mechanism connects chamber 57 to chamber 32 via the concentric passageway 102, and the hatchback can now be lowered fully. The groove 58B can be made very short in length or can be absent completely.The arrangement of Figure 10 can thus provide a system in which the hatchback can be releasably locked in the fully open position.

Figure 10 shows a further modification. The arrangement of Figure 10 is similar to that of Figure 8, except that the internal wall of the cylindrical insert 56 is not provided with any groove 60. Therefore, when the gas spring is lifting the hatchback towards the open position, movement will stop as soon as the cylindrical extension 42 carried by the piston enters the cylindrical insert 56; the sealing ring 46, being moved into contact with wall 210 of groove 44 by the frictional force acting on it, will prevent gas pressure transfer out of chamber 57.

However, the operator can permit the hatchback to open by operation of the control mechanism 110 (Figure 3). By operating this control mechanism, the user is able to connect chamber 57 with chamber 32 via the passageway 102. Therefore, gas pressure transfer can take place and the hatchback can rise towards the open position. The user can arrest the upward movement of the hatchback at any desired position, simply by moving the control mechanism 110 to the locked position, which prevents further gas pressure transfer.

The user can lower the hatchback simply by applying a manual lowering force to it. When the cylindrical extension 42 begins to move outwardly of the cylindrical insert 56, during such lowering movement, the sealing ring 46 moves into contact with wall 209 of the groove 44 and connects chambers 57 and 34 via grooves 206 and 208. Gas pressure transfer can take place, thus permitting lowering movement of the hatchback.

Claims

1. A gas compression spring for moving a member pivotted on a body from a first position corresponding to compression of the spring to a second position, comprising: an arrangement of a piston movable within cylinder means, the piston carrying a piston rod slidingly and sealingly extending outwardly of the cylinder means; one of the piston and the cylinder means being adapted for connection to the body and the other thereof being adapted for connection to the member; the interior of the cylinder means being filled with gas under pressure and the piston dividing the interior of the cylinder means into a first chamber defined at least in part by the head of the piston and a second chamber through which the piston rod extends; the first and second chambers being interconnected by first gas flow means providing a restricted gas flow path permitting limited flow of gas from the second chamber to the first chamber as the gas pressure exerted on the piston head moves the piston rod from an inner piston rod position towards an outer piston rod position more outwardly of the cylinder means, whereby to move the member towards the second position; the interior of the cylinder means also including means defining a third chamber through which the piston rod passes and which is further from the piston than the second chamber; the piston rod carrying sealing means which moves between the second chamber and the third chamber as the piston rod moves between the inner and outer piston rod positions; the piston rod sealing means being adapted when in the third chamber to seal off the third chamber so as to arrest movement of the piston rod at an intermediate position between the inner and outer piston rod positions; and control means operable from outside the cylinder means for by-passing the sealing means to permit resumption of movement of the piston rod.

2. A gas spring according to claim 1, in which the control means controls a gas passage for connecting the third chamber to one of the other chambers.

3. A gas spring according to claim 2, in which the gas passage connects the third chamber to the first chamber.

4. A gas spring according to claim 3, in which the gas passage comprises a hollow interior part of the piston rod which connects with an opening through the piston rod at a position further from the head of the piston than the sealing means, the hollow interior of the piston rod being controllably connected to the first chamber via valve means operable by the control means.

5. A gas spring according to claim 4, in which the valve means comprises a valve member sealingly seated within an opening in the head of the piston which connects with the hollow interior of the piston rod, the valve member being held in sealing engagement with the opening via the gas pressure within the first chamber, the control means comprising manually operable means movable through the hollow interior of the piston rod for unsealing the valve.

6. A gas spring according to claim 5, in which the manually operable means comprises a control rod extending through the hollow interior of the piston rod and out of the cylinder means at the opposite end thereof to the head of the piston, and including a manually operable control member for moving the control rod longitudinally with respect to the piston rod.

7. A gas spring according to claim 3, in which the gas passage comprises a passageway connecting the interior of the third chamber to an intermediate chamber which is closed off from the first chamber by releasable valve means, the control means comprising a manually operable control member for releasing the valve means whereby to connect the intermediate chamber, and thus the third chamber, to the interior of the first chamber.

8. A gas spring according to claim 7, in which the intermediate chamber is positioned adjacent the end of the cylinder means closest to the head of the piston, and in which the control member comprises a member extending through that end of the cylinder means.

9. A gas spring according to claim 7, in which the intermediate chamber is positioned adjacent the end of the cylinder means closest to the head of the piston, and in which the control member comprises a member extending through the wall of the cylinder means adjacent that end thereof.

10. A gas spring according to any one of claims 7 to 9, in which the passageway comprises a passageway defined within the wall of the cylinder means.

11. A gas spring according to any one of claims 7 to 9, in which the cylinder means over at least part of its length comprises an outer cylindrical wall and an inner concentric sleeve within which the piston moves, the passageway being defined between the outer cylindrical wall and the concentric sleeve.

12. A gas spring according to claim 2, in which the gas passage comprises a passageway extending from the interior of the third chamber to an intermediate chamber positioned outside the cylinder, the intermediate chamber being connected through releasable valve means to the interior of one of the first and second chambers, the control means including a manually operable control member for releasing the valve means so as to connect the third chamber to the said one of the first and second chambers via the intermediate chamber.

12. A gas spring according to claim 11, in which the said one of the first and second chambers is the second chamber, and in which the intermediate chamber is positioned within a housing clamped to the outside of the cylinder intermediate its two ends.

13. A gas spring according to any preceding claim, in which the first gas flow means comprises means defining a groove in the wall of the cylinder which by-passes the piston and interconnects the first and second chambers over at least a portion of the movement of the piston.

14. A gas spring according to any one of claims 1 to 12, in which the first gas flow means comprises piston sealing means carried by the piston and forming a seal between the piston and the cylinder means and a passage carried by the piston and extending from the side of the piston sealing means within the first chamber to the opposite side thereof.

15. A gas spring according to any preceding claim, in which the piston rod sealing means seals the third chamber when the piston rod is moving in a predetermined direction between the inner and outer piston rod positions but does not seal the third chamber when the piston rod is moving in the opposite direction.

16. A gas spring according to claim 15, comprising a passage carried by the piston rod and extending from the side of the piston rod sealing means closer to the third chamber to the side thereof closer to the second chamber, the piston rod sealing means being movable between a first position in which it closes the passage and a second position in which it opens the passage, the piston rod sealing means being urged into its first position by frictional contact between the sealing means and the wall of the third chamber when the piston rod is moving in the predetermined direction and being urged into its second position by such frictional contact when the piston rod is moving in the opposite direction.

17. A gas spring according to claim 16, in which the third chamber extends longitudinally over part of the interior of the cylinder means and has an open end into and through which the piston rod extends, the third chamber having a first interior wall surface portion against which the piston rod sealing means makes gas-tight sealing contact, the third chamber having a second interior wall surface portion which is spaced further from the piston than the first wall surface portion, the second wall surface portion defining second gas flow means which provide a gas flow path by-passing the piston rod sealing means when the sealing means has moved beyond the first interior wall surface portion.

18. A gas spring according to any preceding claim, in which the third chamber extends longitudinally over part of the interior of the cylinder means and has an open end into and through which the piston rod extends.

19. A gas spring according to any preceding claim, in which the means defining the third chamber comprises a separate cylindrical insert in the cylinder.

20. A gas spring, substantially as described with reference to Figure 1 of the accompanying drawings.

21. A gas spring, substantially as described with reference to Figures 1 and 2 of the accompanying drawings.

22. A gas spring, substantially as described with reference to Figure 3 of the accompanying drawings.

23. A gas spring, substantially as described with reference to Figure 4 of the accompanying drawings.

24. A gas spring, substantially as described with reference to Figure 5 of the accompanying drawings.

25. A gas spring, substantially as described with reference to Figure 6 of the accompanying drawings.

26. A gas spring, substantially as described with reference to Figure 7 of the accompanying drawings.

27. A gas spring, substantially as described with reference to Figure 8 of the accompanying drawings.

28. A gas spring, substantially as described with reference to Figure 9 of the accompanying drawings.

29. A gas spring, substantially as described with reference to Figure 10 of the accompanying drawings.