CA1189883A - Cushioning devices - Google Patents
Cushioning devicesInfo
- Publication number
- CA1189883A CA1189883A CA000409571A CA409571A CA1189883A CA 1189883 A CA1189883 A CA 1189883A CA 000409571 A CA000409571 A CA 000409571A CA 409571 A CA409571 A CA 409571A CA 1189883 A CA1189883 A CA 1189883A
- Authority
- CA
- Canada
- Prior art keywords
- tube
- base
- rod
- chamber
- plunger
- 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
Links
- 239000000872 buffer Substances 0.000 claims abstract description 54
- 239000007788 liquid Substances 0.000 claims abstract description 7
- 239000012530 fluid Substances 0.000 claims description 24
- 238000007789 sealing Methods 0.000 claims description 9
- 230000000452 restraining effect Effects 0.000 claims description 5
- 238000000926 separation method Methods 0.000 claims description 4
- 238000004891 communication Methods 0.000 claims description 3
- 238000013016 damping Methods 0.000 claims description 3
- 238000013022 venting Methods 0.000 claims description 3
- 239000007853 buffer solution Substances 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 16
- 150000001875 compounds Chemical class 0.000 description 3
- 239000000945 filler Substances 0.000 description 3
- 125000006850 spacer group Chemical group 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000033228 biological regulation Effects 0.000 description 2
- 239000000565 sealant Substances 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 1
- CEJLBZWIKQJOAT-UHFFFAOYSA-N dichloroisocyanuric acid Chemical compound ClN1C(=O)NC(=O)N(Cl)C1=O CEJLBZWIKQJOAT-UHFFFAOYSA-N 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000013011 mating Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Landscapes
- Fluid-Damping Devices (AREA)
Abstract
"Cushioning Devices"
ABSTRACT OF THE DISCLOSURE
A lift buffer has a gas spring acting to provide the recoil force on the buffer plunger which slides within a ported tube. The gas spring chamber is within the buffer plunger. The gas spring rod is urged against the buffer base by the gas pressure and carries a disc at its lower end. A vent hole in the base vents from between the disc and the base to the annular low pressure liquid reservoir that surrounds the ported tube.
ABSTRACT OF THE DISCLOSURE
A lift buffer has a gas spring acting to provide the recoil force on the buffer plunger which slides within a ported tube. The gas spring chamber is within the buffer plunger. The gas spring rod is urged against the buffer base by the gas pressure and carries a disc at its lower end. A vent hole in the base vents from between the disc and the base to the annular low pressure liquid reservoir that surrounds the ported tube.
Description
E
t DESCRIPTION
This invention relates to cushioning devices of the kind which comprise a base; a t cylindrical tube which projects from the base, the tube having a series of holes formed in it at 5 axially spaced locations, the holes extending through the wall of the tube and serving as communication ports for the passage of hydraulic fluid between the cylinder space within the tube and an annular hydraulic fluid reservoir which surrounds 10 the tube; a hollow buffer plunger which is a sliding fit in the bore of the tube; and resilient means which urge the plunger relative to the tube and away from the base. Such cushioning devices are referred to as "cushioning de~ices o~ the kind re~erred tol' 15 in the remainder of this Specificatlon.
A particular use o~ a cushioning device of the klnd referred to is as a lift buffer. E
m e resilient means of one form of such a lift buffer which is used widely comprise one or 20 more helical springs which act between the base and a flange at the top of the buffer plunger and which surround the tube, the lower part of the hellcal spring or grcup of helical springs being immersed in hydraulic fluid in the reservoir. Various alternative 3 -- t arrangements of coil springs inside or outside the t tube (such as a tension spring acting within the tube between a closure at the top of the tubè and the buf~er plunger as shown in German Auslegeschr~ft c~
No. 1 218 678~ have been proposed for a variety of t reasons but the resultant lift buffers have usually ~t had disadvantages of one form or another. c An object of this invention is to provide r a cushioning de~ice of the klnd referred to in which the resilient me~ns exert a force on the bu~fer plunger which is sufficient to satisfy certain regulations and yet which is ~lmple to construct.
Official regulations concerning lift buffers also direct that it be possible to check the level of hydraulic fluid in the buffer by removing a filler plug or similar device~ Hence the resilient means of a lift buffer must be arranged to urge the buffer plunger upwards without pressurising -the hydraulic fluid reservoir.
Compre~ion of a cushionlng devlce of the kind referred to is cushioned by displacement o~ , hydraulic fluid from within the tube in front of the buffer plunger laterally through the holes in the tube that are not blocked by the plunger. ~ery high hydraulic fluid pressures can be established inside the tube during compressio~.
__ _ _ _ _ _ _ , - 4 - ~
.
-According to this inventio~ there is ~r provided a cushioning device comprising a base; a cylindrical tube which pro~ects from the base 9 the tube having a series of holes formed in it at ~xially 5 spaced locations 9 the holes extending through the wall o~ the tube and serving as communication ports for the passage of hydraulic fluid between the cylinder space within the tube and an annular hydraulic fluid reservoir which surrounds the tube; a hollow 10 buffer plunger ~hich is a sliding fit in the bore of t the tube; and resilient ~eans which urge the plunger relative to the ~ube and away from the base;
wherein the resilient means comprise a gas spring which essentially comprises a variable volume .-15 chamber ~illed with compressed gas which is formed by the hollow interior oi the hollow buffer plunger, and a rod w~ich is a sliding fit within an aperture t in the end wall of the chamber that is nearer to the base, which projects into the cylinder space and 20 which is urged into contact with the base by gas pressure within the chamber whereby the volume of the gas ~illed chamber is reduced by the rod as the buffer plunger moves towards the base, there being ~Y~3 I
sealing means which co-operate with the rod and seal against fluid ~low through the aperture.
Means are preferably provided which oppose separation of the rod from the base. Such separation opposing means may comprise a disc which ls fitted to the rod and which slides within the tube and means for venting the space between the disc and the base.
Where the tube projects upwards from -the base, the sealing means may include a volume of liquid which lies on the lower end wall of the chamber within the chamber and surrcunds the rod so ! as to form a liquid seal against escape of gas ~rom within the chamber around the rod.
Conveniently, the cylindrical tube is spigotte-1 into a ring which is fixed to the base.
The cylindrical tube may be clamped against the base by clamping means which form part of an outer casing of the cushioning devise. Conveniently the clamping means comprise a clamping ring within which the buffer plunger slides and which is screwed into a plate which forms the top of the outer casing.
~ en ~ransporting hydraulic buffers~ in which the plunger has an appreciable stroke 9 it is desirable that the plunger is held in the retracted position during transport~ This not only reduces the overall length of the unit for handling or enclosing within a packing case but it also protects the surface of the plunger from damage during transport.
~hen the resilient means of the buffer comprise a spring it may not be practical to hold the buffer in the closed position due to the strength of the spring but even if the load o~ the spring is comparatively low, it could be dangerous because as soon as the restraining means is removed ~rom the plunger it could extend very rapidly under the influence of the spring.
When the resilient means comprise a gas spring as described, it is possible to provide sufficiently restricted damping across the piston head that, when the restraining means on the plunger are xeleased, -the plunger would not extend rapidly and not present any dangerO
One form of lift bu~fer in which this invention is embodied is described now by way o~
exampIe with reference to the accompanying drawings 9 of which:
Figure 1 is a sectioned view of the li~t buffer with the bu~fer plunger shown in elevation, the section being on the line I-I shown in Figure 2;
Figure 2 is a section on the line II-II
shown in Figure 1; and Figure 3 is a fragmentary section on the line III-III in Figure 1.
The lift buffer has a base plate 100 A
5 ring 11 is welded to the upper surface of the base t plate 10 at circumferentially spaced locations 12 as shown in Figure 2. The ring 11 is chamfered at the upper end of its cen-tral aperture.
A tube 13 is spigotted into the ring 11 10 and projects upwards from the base plate 10. A
series of holes 14 are formed through the wall of -the tube 13 at vertically-spaced locations.
An outer tube 15 surrounds the tube 13 substantially coaxially and is welded to the base 15 plate 10 at its lower end and to an annular cover plate 16 at its upper end. The central aperture o~
the annular cover plate 16 is tapped. A clamp ring 17 is screwed into the tapped central aperture of the annular cover plate 16 and has a depending 20 a~nular projection 18 which is spigotted intc the bore of the ported tube 13~ Hence the tuhe 13 is both located radially at its upper end and held with its lower end in contact with the base plate 10 by the clamp ring 17. The base plate 10, the outer tube 15, the cover plate 16 and the clamp ring 17 together form a hydraulic fluid container which is an outer E
casing of the buffer. A hole ~9 is formed in the upper surface of the base plate 10 between an ad~acent pair of the welds 12 with its centre substantially directly below the outer surface of 5 the ported tube 13. The diameter of the hole 19 is r greater than the combined radial thickness of the ring 11 and the tube 13. F
The central aperture of the clamp ring 17 is formed as a cylindrical bore. The inside 10 diameter of the ring 17 is less than the diameter o~
the bore of the ported ~ube 13. A plastic sleeve bearing is accommodated in an annular groove 2, which r:
is formed in the bore of the ring 17. A scraper ring seal 22 is housed in a recess at the top of the bore 15 of the ring 17.
A buffer plunger 23 comprises a tube 24 which is a sliding fit wi-thin the bore of the clamp ring 17. The top of the tube 24 is closed by an end cap 25 which con~eniently i~ welded to the tube 24. ~
20 m e lo~wer end of the tube 24 is clo~ed by a bearing ~.
sleeve 26. A cup-shaped piston head 27 ls ~itted onto the lower end of the tube 24 and is a sliding fit in the bore of the ported tube 13. A hole is formed at the centre of the base of the piston head 25 27.
me bearing sleeve 26 has an upper smaller r r~
~ 3 diameter portion which projects into the lower end of the tube 24 and which has a circumferential groove formed in its outer cylindrical surface, there being a sealing ring 28 housed in that groove so that it engages the tube 24 to form a fluid-tight seal between the sleeve 26 and the tube 24. The remainder of the sleeve 26 is spigotted into the cavity of the ~.
cup-shaped piston head 27 which is held against -removal from the tube 24, by the engagement of a swaged portion 29 ad~acent its brim within a circumferential groove which is formed in the outer surface of the tube 24. T~o circumferential grooves ~0 and 31 are formed in the bore of the bearing sleeve 26 at axially-spaced locations. A compound sealing ring which comprises an 109 ring with an annular lip seal ~itted snugly within its central aperture is fit-ted within each groove 30 7 31 . me two lip seals f'ace in opposl-te directions so that each one is arranged to seal against flow of liquid ~o towards the centre of the bearing sleeve 26 ~rom the adjacent end of it~ bore. m e inslde diameter-of each of the compound sealing rings when it is in its natural relaxed condition is less than the diameter of the bore of the bearing sleeve 26.
A rod 32 extends through the bore of the bearing sleeve 26 with a sliding clearance and is i ~ 10 engaged by the two compound sealing rings. It also extends through the central hole in the base of the cup-shaped piston head 27. A piston head 33 is carried by the upper end of the rod 32. An outwardly-sprung ring 34 9 which engages the surface of the bore o~ the buffer plunger tube 24 so as to make a substantial gas-tlght seal with the bore of the tube 24, is located in a circumferential groove 35 formed in the piston head 33. There is an annular clearance between the inner periphery of the ring 34 a~d the base of the groove 35. Passages 36 and ~7 are formed by holes or grooves in the annular flange portions of the piston head 33 that ~orm the side walls of the circumferential groove 35. The passages 36 and 37 form a path for gas flow across the plston head 33. m e dimensions of the pas~age 36 through the upper annular flange portion of the piston head 33 are suoh that gas ~low through lt is restricted so that movement o~ the piston rod ~ is damped~ A cylindrical disc 38 9 ~hich ~s a neat ~lidi~g fit in the ported tube 13~ is fitted onto the lower end portion of the plston rod 32 and tends to be seated on the base plate 100 A small quantity of hydraulic ~luid 39 is contained within the tube 24 or. top of the bearing sleeve 26.
Two holes are provided in the annular cover ~, plate 150 One is ~or a dipstick 41. The other is a filler hole which is normally closed by a removable cap 42.
The cylinder spaces ~ormed wi-thin the hollow bu~fer plunger 23 on either side of the ring ~4 that is carried by the piston head 3~ are filled with a compressed gas, such as nitrogen or air.
Hence the plunger tube 24 forms a cylinder ~or a gas spring. The hydraulic fluid on top of the bearing sleeve 26 forms a liquid seal around the rod 3~
which prevents escape of gas from within the tube 24 arolmd the piston rod 32.
The interior of the ported tube 13 below the buffer plunger 23 is filled with hydraulic fluid, The annular space around the tube 13 within the tube 15 is a low pressure hydraulic fluid reservoir, there being an air space above the level of fluid in the reservolr.
The volume of hydraulic fluid in the buffer should be such as to maintai~ the reservoir level a little above the lower end of the piston head 33 when the buffer plunger 23 is at the upper end o~ its travel. The reservoir is filled or topped up by pouring hydraulic fluid through the hole which is opened when the filler cap 42 is removed.
If the buffer plunger 23 is forced downp ,, , o - 12 - .
when the bui~fer is installed at the foot of a lift shaft, it moves relative to the rod 32 and the -piston head 33 so that the distance between the piston head 33 and the end cap 25 is reduced.
5 Downwards movement of the cup-shaped piston head 27 progressively cuts o~f escape of hydraulic fluid from within the ported tube 13 through the holes 14 so that the speed of downwards movement of the buffer plunger 23 is reduced progressively u~til it is 10 substantially zero when the lower-most hole 14 has been covered. The disc 38 is seated on the base plate 10 as the buffer plunger 23 is forced downwards. Very high fluid pressures can be established inside the tube 13. m e hole 19 ln the 15 base plate 10 ensures that any fluid which leaks between the tube 13 and the disc 38 does not create a pressure build up below the disc 38 or across ^~he end face of the tube 13 because it more than spans the tube 13 and the ring 11 so that any ~luid which 20 passes the disc ~8 can e~cape ~reely to the reservoir. me reactlon to the compressed gas loading on the piston head 33 and the portion of the rod 32 within the hollow buffer plunger 23 causes the buffer plunger 23 to move upwards back to the 25 upper end of its travel when -the downwards force is t removed from the buffer plunger 23~ The speed of such upwards movement of the buffer plunger 23 is controlled by the damping effect a~forded by the passage 36 through which must pass all gas that ls displaced ~rom the cylinder space below the piston head 33 to the cylinder space above the piston head ~3.
The base plate 10 may have a recess formed at the centre of its upper surface. That central recess can be used during assembly of the buffer 9 firstly as a register to locate the ring 11 whilst it is welded to the base plate 10, and then to locate a fixture which accurately locates the end cover 16 concentric with and square to the base plate 10 whilst the tube 15 is welded to the base plate 10 and the end cover 16 is welded to the tube 15.
There may be an annular clearance between the disc 38 and the ported tube 13 instead of the disc 38 being a sliding fit in that tube 13, in which case the disc 38 would be provided with a piston ring located in a circumferential groove, the piston ring serving to obstruct leakage of hydraulic fluid between the disc 38 and the tube 13.
An oil re-taining seal may be accommodated in a recess which is formed at the bottom of the bore f the clamp ring 17, a gasket may be provided to seal the dipstick hole when the dipstick 41 is inserted and setting sealant may be applied.to the upper end o~
the joint between the clamp ring 17 and the cover plate 160 However the prov~sion of such a seal 9 ~, gasket and sealant is optional because the buffer always stands vertically with the plunger 23 extending upwards. I
The bore of the ported tube 13 may be rebated at the upper end and the depending annular projection 18 o~ the clamp ring 17 stepped externally, the lower portion of the projection 18 which has the smaller diameter external surface portion being spigotted into the bore of the tube 1~ and the remainder of the projection 18 being spigo-tted into the rebated bore portion of the tube 13.
Means other than the interengaging spigots and rebated bore ~ust described may be used to ensure that the lift bu~fer can only be assembled with the ported tube 13 the right way up which is of practical significancé because the operation of the buffer is ~0 dependent upon the arrangement of the holes 14 in the tube 13. Such other means may comprise mating frusto-conical surfaces on the ported tube and the clamp ring.
The cup-shaped piston head 27 may be screwed onto the tube 24 and held against removal 9 the length of the thread engagement between that piston head 27 91~3 and the tube 24 being sufficient to ensure that, if that piston head 27 is unscrewed whilst the buffer plunger 23 is inflated9 the sealing ring 28 would be ~orced out of the tube 24 and the gas pressure 5 released before the piston head 27 is separated from the tube 24.
The top of the plunger tube 24 may be formed as a closed ended forging rather than by welding the end cap 25 to the tube as described 10 above. Such a forged plunger tube is preferred to the welded structure where it is economically viable as would be the case with short stroke buffers 9 because of its superior gas retention characteristics.
A short thin walled tubular spacer may be provided 15 between the cup-shaped piston head 27 and the depending annular projection 18 of the clamp ring 17 in order to locate the buffer plunger 23 relative to the clamp ring 17 at the upper end of its travel. The spacer may be an outwardly-sprung slotted tube spring spacer 20 located between the buf~er plunger tube 24 and the ported tube 13. r me buffer may be provided with restraini~g means for holding the buffer plunger 23 in the retracted location for transport prior to installation 25 of the buffer for use. Such restraining me~ns may t comprise ~ pair of hairpin type springs which are L
r located at their ends in suitable holes which are formed in a plate which is carried by the outer end of the buffer plunger 23. The middle portions of the ~prings would be retained engaged in locating grooves when the buffer plunger 23 is retracted, each such locating groove being formed in the underside of a respective one of a pair of brackets which are welded to the outer surface of the outer casing tube 15 on opposite sides of that tube 15.
The form of each locating groove would be such that the middle portion of the respective hairpin spring is deflected from the location to which it is urged by the resilience of that spring as it passes over the respective bracket with movement of the buffer plunger 23 to its retracted location. Hence, the middle portion of each hairpin spring is urged into engagement within the respectiYe locating groove by the natural resilience of the material from which it is construc*ed-In order to release the restraining means and allow the buffer to extend due to the action of the gas spring incorporated in it~ such as would be desirable when the buffer has been installed for use~
the middle portions of the hairpin springs would be pulled out of engagement from their respective locating grooves.
,,,,,,,,, ., . , .. ,,, ., . , ___ _ __ ~, .~ . , .. _~_ , ........ .
- ~7 -The brackets may be provided with holes to provide slinging points when the buffer is being handled or installed in the bottom of an elevator shaft pin. In the case o~ very long stroke buffers9 where some support at the upper end of the casing is desirable, the brackets may be used for the attachment of suitable support members which are fixed to the normal elevator shaft framework at their other ends.
1~ There may be more than one hole 19 for venting from between the disc 38 and the base 10 to the reser~oir. For example, there may be four such vent holes arranged with their centres lying at spaced locations about a common pitch circle which is substantially directly below and similarly sized to the outer surface of the ported tube 13. Each such vent hole may lie between an adjacent pair of the welds 12.
t DESCRIPTION
This invention relates to cushioning devices of the kind which comprise a base; a t cylindrical tube which projects from the base, the tube having a series of holes formed in it at 5 axially spaced locations, the holes extending through the wall of the tube and serving as communication ports for the passage of hydraulic fluid between the cylinder space within the tube and an annular hydraulic fluid reservoir which surrounds 10 the tube; a hollow buffer plunger which is a sliding fit in the bore of the tube; and resilient means which urge the plunger relative to the tube and away from the base. Such cushioning devices are referred to as "cushioning de~ices o~ the kind re~erred tol' 15 in the remainder of this Specificatlon.
A particular use o~ a cushioning device of the klnd referred to is as a lift buffer. E
m e resilient means of one form of such a lift buffer which is used widely comprise one or 20 more helical springs which act between the base and a flange at the top of the buffer plunger and which surround the tube, the lower part of the hellcal spring or grcup of helical springs being immersed in hydraulic fluid in the reservoir. Various alternative 3 -- t arrangements of coil springs inside or outside the t tube (such as a tension spring acting within the tube between a closure at the top of the tubè and the buf~er plunger as shown in German Auslegeschr~ft c~
No. 1 218 678~ have been proposed for a variety of t reasons but the resultant lift buffers have usually ~t had disadvantages of one form or another. c An object of this invention is to provide r a cushioning de~ice of the klnd referred to in which the resilient me~ns exert a force on the bu~fer plunger which is sufficient to satisfy certain regulations and yet which is ~lmple to construct.
Official regulations concerning lift buffers also direct that it be possible to check the level of hydraulic fluid in the buffer by removing a filler plug or similar device~ Hence the resilient means of a lift buffer must be arranged to urge the buffer plunger upwards without pressurising -the hydraulic fluid reservoir.
Compre~ion of a cushionlng devlce of the kind referred to is cushioned by displacement o~ , hydraulic fluid from within the tube in front of the buffer plunger laterally through the holes in the tube that are not blocked by the plunger. ~ery high hydraulic fluid pressures can be established inside the tube during compressio~.
__ _ _ _ _ _ _ , - 4 - ~
.
-According to this inventio~ there is ~r provided a cushioning device comprising a base; a cylindrical tube which pro~ects from the base 9 the tube having a series of holes formed in it at ~xially 5 spaced locations 9 the holes extending through the wall o~ the tube and serving as communication ports for the passage of hydraulic fluid between the cylinder space within the tube and an annular hydraulic fluid reservoir which surrounds the tube; a hollow 10 buffer plunger ~hich is a sliding fit in the bore of t the tube; and resilient ~eans which urge the plunger relative to the ~ube and away from the base;
wherein the resilient means comprise a gas spring which essentially comprises a variable volume .-15 chamber ~illed with compressed gas which is formed by the hollow interior oi the hollow buffer plunger, and a rod w~ich is a sliding fit within an aperture t in the end wall of the chamber that is nearer to the base, which projects into the cylinder space and 20 which is urged into contact with the base by gas pressure within the chamber whereby the volume of the gas ~illed chamber is reduced by the rod as the buffer plunger moves towards the base, there being ~Y~3 I
sealing means which co-operate with the rod and seal against fluid ~low through the aperture.
Means are preferably provided which oppose separation of the rod from the base. Such separation opposing means may comprise a disc which ls fitted to the rod and which slides within the tube and means for venting the space between the disc and the base.
Where the tube projects upwards from -the base, the sealing means may include a volume of liquid which lies on the lower end wall of the chamber within the chamber and surrcunds the rod so ! as to form a liquid seal against escape of gas ~rom within the chamber around the rod.
Conveniently, the cylindrical tube is spigotte-1 into a ring which is fixed to the base.
The cylindrical tube may be clamped against the base by clamping means which form part of an outer casing of the cushioning devise. Conveniently the clamping means comprise a clamping ring within which the buffer plunger slides and which is screwed into a plate which forms the top of the outer casing.
~ en ~ransporting hydraulic buffers~ in which the plunger has an appreciable stroke 9 it is desirable that the plunger is held in the retracted position during transport~ This not only reduces the overall length of the unit for handling or enclosing within a packing case but it also protects the surface of the plunger from damage during transport.
~hen the resilient means of the buffer comprise a spring it may not be practical to hold the buffer in the closed position due to the strength of the spring but even if the load o~ the spring is comparatively low, it could be dangerous because as soon as the restraining means is removed ~rom the plunger it could extend very rapidly under the influence of the spring.
When the resilient means comprise a gas spring as described, it is possible to provide sufficiently restricted damping across the piston head that, when the restraining means on the plunger are xeleased, -the plunger would not extend rapidly and not present any dangerO
One form of lift bu~fer in which this invention is embodied is described now by way o~
exampIe with reference to the accompanying drawings 9 of which:
Figure 1 is a sectioned view of the li~t buffer with the bu~fer plunger shown in elevation, the section being on the line I-I shown in Figure 2;
Figure 2 is a section on the line II-II
shown in Figure 1; and Figure 3 is a fragmentary section on the line III-III in Figure 1.
The lift buffer has a base plate 100 A
5 ring 11 is welded to the upper surface of the base t plate 10 at circumferentially spaced locations 12 as shown in Figure 2. The ring 11 is chamfered at the upper end of its cen-tral aperture.
A tube 13 is spigotted into the ring 11 10 and projects upwards from the base plate 10. A
series of holes 14 are formed through the wall of -the tube 13 at vertically-spaced locations.
An outer tube 15 surrounds the tube 13 substantially coaxially and is welded to the base 15 plate 10 at its lower end and to an annular cover plate 16 at its upper end. The central aperture o~
the annular cover plate 16 is tapped. A clamp ring 17 is screwed into the tapped central aperture of the annular cover plate 16 and has a depending 20 a~nular projection 18 which is spigotted intc the bore of the ported tube 13~ Hence the tuhe 13 is both located radially at its upper end and held with its lower end in contact with the base plate 10 by the clamp ring 17. The base plate 10, the outer tube 15, the cover plate 16 and the clamp ring 17 together form a hydraulic fluid container which is an outer E
casing of the buffer. A hole ~9 is formed in the upper surface of the base plate 10 between an ad~acent pair of the welds 12 with its centre substantially directly below the outer surface of 5 the ported tube 13. The diameter of the hole 19 is r greater than the combined radial thickness of the ring 11 and the tube 13. F
The central aperture of the clamp ring 17 is formed as a cylindrical bore. The inside 10 diameter of the ring 17 is less than the diameter o~
the bore of the ported ~ube 13. A plastic sleeve bearing is accommodated in an annular groove 2, which r:
is formed in the bore of the ring 17. A scraper ring seal 22 is housed in a recess at the top of the bore 15 of the ring 17.
A buffer plunger 23 comprises a tube 24 which is a sliding fit wi-thin the bore of the clamp ring 17. The top of the tube 24 is closed by an end cap 25 which con~eniently i~ welded to the tube 24. ~
20 m e lo~wer end of the tube 24 is clo~ed by a bearing ~.
sleeve 26. A cup-shaped piston head 27 ls ~itted onto the lower end of the tube 24 and is a sliding fit in the bore of the ported tube 13. A hole is formed at the centre of the base of the piston head 25 27.
me bearing sleeve 26 has an upper smaller r r~
~ 3 diameter portion which projects into the lower end of the tube 24 and which has a circumferential groove formed in its outer cylindrical surface, there being a sealing ring 28 housed in that groove so that it engages the tube 24 to form a fluid-tight seal between the sleeve 26 and the tube 24. The remainder of the sleeve 26 is spigotted into the cavity of the ~.
cup-shaped piston head 27 which is held against -removal from the tube 24, by the engagement of a swaged portion 29 ad~acent its brim within a circumferential groove which is formed in the outer surface of the tube 24. T~o circumferential grooves ~0 and 31 are formed in the bore of the bearing sleeve 26 at axially-spaced locations. A compound sealing ring which comprises an 109 ring with an annular lip seal ~itted snugly within its central aperture is fit-ted within each groove 30 7 31 . me two lip seals f'ace in opposl-te directions so that each one is arranged to seal against flow of liquid ~o towards the centre of the bearing sleeve 26 ~rom the adjacent end of it~ bore. m e inslde diameter-of each of the compound sealing rings when it is in its natural relaxed condition is less than the diameter of the bore of the bearing sleeve 26.
A rod 32 extends through the bore of the bearing sleeve 26 with a sliding clearance and is i ~ 10 engaged by the two compound sealing rings. It also extends through the central hole in the base of the cup-shaped piston head 27. A piston head 33 is carried by the upper end of the rod 32. An outwardly-sprung ring 34 9 which engages the surface of the bore o~ the buffer plunger tube 24 so as to make a substantial gas-tlght seal with the bore of the tube 24, is located in a circumferential groove 35 formed in the piston head 33. There is an annular clearance between the inner periphery of the ring 34 a~d the base of the groove 35. Passages 36 and ~7 are formed by holes or grooves in the annular flange portions of the piston head 33 that ~orm the side walls of the circumferential groove 35. The passages 36 and 37 form a path for gas flow across the plston head 33. m e dimensions of the pas~age 36 through the upper annular flange portion of the piston head 33 are suoh that gas ~low through lt is restricted so that movement o~ the piston rod ~ is damped~ A cylindrical disc 38 9 ~hich ~s a neat ~lidi~g fit in the ported tube 13~ is fitted onto the lower end portion of the plston rod 32 and tends to be seated on the base plate 100 A small quantity of hydraulic ~luid 39 is contained within the tube 24 or. top of the bearing sleeve 26.
Two holes are provided in the annular cover ~, plate 150 One is ~or a dipstick 41. The other is a filler hole which is normally closed by a removable cap 42.
The cylinder spaces ~ormed wi-thin the hollow bu~fer plunger 23 on either side of the ring ~4 that is carried by the piston head 3~ are filled with a compressed gas, such as nitrogen or air.
Hence the plunger tube 24 forms a cylinder ~or a gas spring. The hydraulic fluid on top of the bearing sleeve 26 forms a liquid seal around the rod 3~
which prevents escape of gas from within the tube 24 arolmd the piston rod 32.
The interior of the ported tube 13 below the buffer plunger 23 is filled with hydraulic fluid, The annular space around the tube 13 within the tube 15 is a low pressure hydraulic fluid reservoir, there being an air space above the level of fluid in the reservolr.
The volume of hydraulic fluid in the buffer should be such as to maintai~ the reservoir level a little above the lower end of the piston head 33 when the buffer plunger 23 is at the upper end o~ its travel. The reservoir is filled or topped up by pouring hydraulic fluid through the hole which is opened when the filler cap 42 is removed.
If the buffer plunger 23 is forced downp ,, , o - 12 - .
when the bui~fer is installed at the foot of a lift shaft, it moves relative to the rod 32 and the -piston head 33 so that the distance between the piston head 33 and the end cap 25 is reduced.
5 Downwards movement of the cup-shaped piston head 27 progressively cuts o~f escape of hydraulic fluid from within the ported tube 13 through the holes 14 so that the speed of downwards movement of the buffer plunger 23 is reduced progressively u~til it is 10 substantially zero when the lower-most hole 14 has been covered. The disc 38 is seated on the base plate 10 as the buffer plunger 23 is forced downwards. Very high fluid pressures can be established inside the tube 13. m e hole 19 ln the 15 base plate 10 ensures that any fluid which leaks between the tube 13 and the disc 38 does not create a pressure build up below the disc 38 or across ^~he end face of the tube 13 because it more than spans the tube 13 and the ring 11 so that any ~luid which 20 passes the disc ~8 can e~cape ~reely to the reservoir. me reactlon to the compressed gas loading on the piston head 33 and the portion of the rod 32 within the hollow buffer plunger 23 causes the buffer plunger 23 to move upwards back to the 25 upper end of its travel when -the downwards force is t removed from the buffer plunger 23~ The speed of such upwards movement of the buffer plunger 23 is controlled by the damping effect a~forded by the passage 36 through which must pass all gas that ls displaced ~rom the cylinder space below the piston head 33 to the cylinder space above the piston head ~3.
The base plate 10 may have a recess formed at the centre of its upper surface. That central recess can be used during assembly of the buffer 9 firstly as a register to locate the ring 11 whilst it is welded to the base plate 10, and then to locate a fixture which accurately locates the end cover 16 concentric with and square to the base plate 10 whilst the tube 15 is welded to the base plate 10 and the end cover 16 is welded to the tube 15.
There may be an annular clearance between the disc 38 and the ported tube 13 instead of the disc 38 being a sliding fit in that tube 13, in which case the disc 38 would be provided with a piston ring located in a circumferential groove, the piston ring serving to obstruct leakage of hydraulic fluid between the disc 38 and the tube 13.
An oil re-taining seal may be accommodated in a recess which is formed at the bottom of the bore f the clamp ring 17, a gasket may be provided to seal the dipstick hole when the dipstick 41 is inserted and setting sealant may be applied.to the upper end o~
the joint between the clamp ring 17 and the cover plate 160 However the prov~sion of such a seal 9 ~, gasket and sealant is optional because the buffer always stands vertically with the plunger 23 extending upwards. I
The bore of the ported tube 13 may be rebated at the upper end and the depending annular projection 18 o~ the clamp ring 17 stepped externally, the lower portion of the projection 18 which has the smaller diameter external surface portion being spigotted into the bore of the tube 1~ and the remainder of the projection 18 being spigo-tted into the rebated bore portion of the tube 13.
Means other than the interengaging spigots and rebated bore ~ust described may be used to ensure that the lift bu~fer can only be assembled with the ported tube 13 the right way up which is of practical significancé because the operation of the buffer is ~0 dependent upon the arrangement of the holes 14 in the tube 13. Such other means may comprise mating frusto-conical surfaces on the ported tube and the clamp ring.
The cup-shaped piston head 27 may be screwed onto the tube 24 and held against removal 9 the length of the thread engagement between that piston head 27 91~3 and the tube 24 being sufficient to ensure that, if that piston head 27 is unscrewed whilst the buffer plunger 23 is inflated9 the sealing ring 28 would be ~orced out of the tube 24 and the gas pressure 5 released before the piston head 27 is separated from the tube 24.
The top of the plunger tube 24 may be formed as a closed ended forging rather than by welding the end cap 25 to the tube as described 10 above. Such a forged plunger tube is preferred to the welded structure where it is economically viable as would be the case with short stroke buffers 9 because of its superior gas retention characteristics.
A short thin walled tubular spacer may be provided 15 between the cup-shaped piston head 27 and the depending annular projection 18 of the clamp ring 17 in order to locate the buffer plunger 23 relative to the clamp ring 17 at the upper end of its travel. The spacer may be an outwardly-sprung slotted tube spring spacer 20 located between the buf~er plunger tube 24 and the ported tube 13. r me buffer may be provided with restraini~g means for holding the buffer plunger 23 in the retracted location for transport prior to installation 25 of the buffer for use. Such restraining me~ns may t comprise ~ pair of hairpin type springs which are L
r located at their ends in suitable holes which are formed in a plate which is carried by the outer end of the buffer plunger 23. The middle portions of the ~prings would be retained engaged in locating grooves when the buffer plunger 23 is retracted, each such locating groove being formed in the underside of a respective one of a pair of brackets which are welded to the outer surface of the outer casing tube 15 on opposite sides of that tube 15.
The form of each locating groove would be such that the middle portion of the respective hairpin spring is deflected from the location to which it is urged by the resilience of that spring as it passes over the respective bracket with movement of the buffer plunger 23 to its retracted location. Hence, the middle portion of each hairpin spring is urged into engagement within the respectiYe locating groove by the natural resilience of the material from which it is construc*ed-In order to release the restraining means and allow the buffer to extend due to the action of the gas spring incorporated in it~ such as would be desirable when the buffer has been installed for use~
the middle portions of the hairpin springs would be pulled out of engagement from their respective locating grooves.
,,,,,,,,, ., . , .. ,,, ., . , ___ _ __ ~, .~ . , .. _~_ , ........ .
- ~7 -The brackets may be provided with holes to provide slinging points when the buffer is being handled or installed in the bottom of an elevator shaft pin. In the case o~ very long stroke buffers9 where some support at the upper end of the casing is desirable, the brackets may be used for the attachment of suitable support members which are fixed to the normal elevator shaft framework at their other ends.
1~ There may be more than one hole 19 for venting from between the disc 38 and the base 10 to the reser~oir. For example, there may be four such vent holes arranged with their centres lying at spaced locations about a common pitch circle which is substantially directly below and similarly sized to the outer surface of the ported tube 13. Each such vent hole may lie between an adjacent pair of the welds 12.
Claims (7)
1. A cushioning device comprising a base; a cylindrical tube which projects from the base, the tube having a series of holes formed in it at axially spaced locations, the holes extending through the wall of the tube and serving as communication ports for the passage of hydraulic fluid between the cylinder space within the tube and an annular hydraulic fluid reservoir which surrounds the tube; a hollow buffer plunger which is a sliding fit in the bore of the tube; and resilient means which urge the plunger relative to the tube and away from the base; wherein said resilient means comprise a gas spring which essentially comprises a variable volume chamber filled with compressed gas which is formed by the interior of the hollow buffer plunger, and a rod which is a sliding fit within an aperture in the end wall of the chamber that is nearer to the base, which projects into the cylinder space and which is urged into contact with said base by gas pressure within said chamber whereby the volume of the gas filled chamber is reduced by the rod as the buffer plunger moves towards the base, there being sealing means which co-operate with the rod and seal against fluid flow through said aperture.
2. A cushioning device according to Claim 1, including means which oppose separation of the rod and the base.
3. A cushioning device according to Claim 2, wherein said separation opposing means comprise a disc which is fitted to the rod and which slides within the tube and means for venting the space between the disc and the base.
4. A cushioning device according to any one of Claims 1 to 3, in which the tube projects upwards from the base, wherein said sealing means include a volume of liquid which lies on the lower end wall of the chamber within the chamber and surrounds the rod so as to form a liquid seal against escape of gas from within the chamber around the rod.
5. A cushioning device according to Claim 1, wherein the cylindrical tube is spigotted into a ring which is fixed to the base.
6. A cushioning device according to Claim 5, wherein the cylindrical tube is clamped against the base by clamping means which form part of an outer casing of the device.
7. A cushioning device according to any one of Claims 1 to 3 in which damping means are provided for controlling the rate of increase in volume of the gas-filled chamber, wherein restraining means are provided for holding the buffer plunger in its retracted location within the tube.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000409571A CA1189883A (en) | 1982-08-17 | 1982-08-17 | Cushioning devices |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000409571A CA1189883A (en) | 1982-08-17 | 1982-08-17 | Cushioning devices |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1189883A true CA1189883A (en) | 1985-07-02 |
Family
ID=4123422
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000409571A Expired CA1189883A (en) | 1982-08-17 | 1982-08-17 | Cushioning devices |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1189883A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114480821A (en) * | 2021-12-31 | 2022-05-13 | 太原重工股份有限公司 | Batch heat treatment method for high aspect ratio shaft forgings |
-
1982
- 1982-08-17 CA CA000409571A patent/CA1189883A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114480821A (en) * | 2021-12-31 | 2022-05-13 | 太原重工股份有限公司 | Batch heat treatment method for high aspect ratio shaft forgings |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US3970292A (en) | Oil and air suspension devices | |
| EP0021698B1 (en) | Cushioning devices | |
| US5593007A (en) | Shock absorber with third fluid chamber | |
| US4189033A (en) | Shock absorber | |
| US4005769A (en) | Sealing arrangement for a shock absorber having an annular reservoir | |
| US4795009A (en) | Twin-tube type shock absorber | |
| US4360192A (en) | Gas spring, filling and sealing structure | |
| US4145067A (en) | Suspension system for a motor vehicle | |
| US3752498A (en) | Oleo-pneumatic suspension assembly | |
| JPH026367B2 (en) | ||
| US4392664A (en) | Front fork of motorcycle | |
| US10843671B2 (en) | Housing block, in particular for a hydraulic unit of an electronically slip-controllable vehicle brake system | |
| US4274517A (en) | Hydraulic shock absorber | |
| US5011121A (en) | Seal for gas spring | |
| US4786037A (en) | Arrangement for a spring suspension system | |
| US3021926A (en) | Shock absorbers or vibration dampers | |
| KR100880820B1 (en) | 유체 Method and device for filling fluid in absorber | |
| CA1189883A (en) | Cushioning devices | |
| US5682966A (en) | Rear shock absorber for bicycles | |
| US4049251A (en) | Shock absorbing strut assembly | |
| US4085925A (en) | Hydro-pneumatic shock absorber | |
| EP2413001A1 (en) | Motorcycle fork assembly with improved oil drainage system. | |
| US3513947A (en) | Hydraulic vibration damper | |
| JPS5927461B2 (en) | cylinder device | |
| US4050684A (en) | Velocity sensitive dual rate shock strut |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |