CA1302206C - Hydraulic cylinder-piston unit with a safety device - Google Patents
Hydraulic cylinder-piston unit with a safety deviceInfo
- Publication number
- CA1302206C CA1302206C CA000524460A CA524460A CA1302206C CA 1302206 C CA1302206 C CA 1302206C CA 000524460 A CA000524460 A CA 000524460A CA 524460 A CA524460 A CA 524460A CA 1302206 C CA1302206 C CA 1302206C
- Authority
- CA
- Canada
- Prior art keywords
- cylinder
- piston
- stop member
- rod
- piston unit
- 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 - Lifetime
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
- F15B15/20—Other details, e.g. assembly with regulating devices
- F15B15/26—Locking mechanisms
- F15B15/261—Locking mechanisms using positive interengagement, e.g. balls and grooves, for locking in the end positions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B66—HOISTING; LIFTING; HAULING
- B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
- B66F3/00—Devices, e.g. jacks, adapted for uninterrupted lifting of loads
- B66F3/24—Devices, e.g. jacks, adapted for uninterrupted lifting of loads fluid-pressure operated
- B66F3/25—Constructional features
- B66F3/30—Constructional features with positive brakes or locks
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B66—HOISTING; LIFTING; HAULING
- B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
- B66F7/00—Lifting frames, e.g. for lifting vehicles; Platform lifts
- B66F7/06—Lifting frames, e.g. for lifting vehicles; Platform lifts with platforms supported by levers for vertical movement
- B66F7/0641—Single levers, e.g. parallel links
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B66—HOISTING; LIFTING; HAULING
- B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
- B66F7/00—Lifting frames, e.g. for lifting vehicles; Platform lifts
- B66F7/06—Lifting frames, e.g. for lifting vehicles; Platform lifts with platforms supported by levers for vertical movement
- B66F7/08—Lifting frames, e.g. for lifting vehicles; Platform lifts with platforms supported by levers for vertical movement hydraulically or pneumatically operated
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Geology (AREA)
- Structural Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- General Engineering & Computer Science (AREA)
- Actuator (AREA)
- Fluid-Pressure Circuits (AREA)
- Braking Systems And Boosters (AREA)
- Current-Collector Devices For Electrically Propelled Vehicles (AREA)
- Forklifts And Lifting Vehicles (AREA)
- Hydraulic Motors (AREA)
- Types And Forms Of Lifts (AREA)
- Vehicle Cleaning, Maintenance, Repair, Refitting, And Outriggers (AREA)
Abstract
A B S T R A C T
A hydraulic cylinder-piston unit provided with a mechanical safety device, particularly for motor vehicle lifts of pantograph type and comprising a cylinder in which there slides a piston provided with a rod emerging from an endpiece of said cylinder, and comprising inside the cylinder a portion provided with toothing extending along the axis of said cylinder and cooperating with at least one deactivatable stop member which during the elongation stage of said cylinder-piston unit moves relative to said toothed portion by yielding elastically in its passage from one tooth to the next, whereas during the retraction stage it engages in the facing notch defined by two successive teeth, to thus form the mechanical safety stop.
A hydraulic cylinder-piston unit provided with a mechanical safety device, particularly for motor vehicle lifts of pantograph type and comprising a cylinder in which there slides a piston provided with a rod emerging from an endpiece of said cylinder, and comprising inside the cylinder a portion provided with toothing extending along the axis of said cylinder and cooperating with at least one deactivatable stop member which during the elongation stage of said cylinder-piston unit moves relative to said toothed portion by yielding elastically in its passage from one tooth to the next, whereas during the retraction stage it engages in the facing notch defined by two successive teeth, to thus form the mechanical safety stop.
Description
220~
Ihis invention rela~es ~o a hydrdulic cylinder-piston unit provided wi-th a mechanical safety device, particularly for motor vehicle lifts of the pantograph type.
Mo-tor vehicle lifts of the pantograph type are known.
5 They generally comprises a pair of runways and cylinder-piston unlts which raise said runways, on which the vehicle to be lifted has been previously positioned.
Current accident-prevention regulations require the provision of mechanical safety systerns to ensure that the 10 level attained by the runways is mainteined, even if the pressure of the hydraulic circuit feeding the cylinder-pistons units accidentally falls.
Known safety systems generally consist of racks engaged by pawl assernblies which allow the racks to move Preely 15 relative to them during the raising of the lift, but prevent their opposite movement, thus ensuring stability of the attained configuration.
To lower the lift it is necessary firstly to disengage ~ he pawl assemblies frorn the corresponding rack, and then 20 discharge the opera~.ing fluid ~rom the cylinder-piston units.
Known rllechanical safety systems for application to hydraulic cylinder-piston units, in particular for operating lifts of the pantograph type, have cer-tain drawbacks, and in ~k parti.cular:
- their installation is somewhat complicated because it involves additional work beyond that required for installing the cylinder-piston units, 5 - they are somewhat bulky, this being o~ten difficult tO
reconcile with the limited space available, - they require a self-contained system or circuit for deactivating them during the lowering of the lift.
An object of the invention is to obviate these drawbacks 10 by providing a hydrauli.c cylinder-piston unit with an associated mechanical safety device which is without bulk and requi~es no special additional installation work.
A further object of the invention is to provide a hydraulic cylinder-piston unit with an associated mechanical 15 safety device which for disengaging this latter uses the actual hydraulic feed circuit of the cylinder-piston unit.
These and further objects which will be apparent from the description given hereina~ter are attai,ned according to the invention by a hydraullc cylinder-piston unit provided 20 with a mechanical safety device, comprising a cylinder in which there slides a piston provided with a rod emerging from an endpiece of said cylinder, characterised by comprising inside the cylinder a portion provided wi-th toothing ~3~
extending along the axis of said cylinder and cooperating with at least one deactivatable stop member which during the elongation stage of said cylinder-piston unit moves relative to said toothed portion by yielding elastically in its 5 passage from one tooth to the next, whereas during the re~raction staye it engages in the facing notch defined by two successlve teeth, to thus form the mechanical safety stop.
Preferably, . the cylinder of the hydraulic cylinder-10 piston unit according to the invention can be formed with one endpiece closed and the other endpiece comprising a hole for the oil-tight passage of the piston rod, this rod being hollow and housing in its interior a second rod which is fixed at one end to the closed endpiece of said cylind.er, is 15 mobile axially relative to said hollow rod by means of said piston, and is provided with a toothed portion cooperating with a pawl assembly rigid with said hollow rod.
Preferabl.y, acco:cding to the invention, the piston can comprise radial recesses opening into the passage bore.~for ~Osaid second rod, in order to guide stop blocks which are kept elastically adhering to t:he lateral surface of said second rod and are provided with rneans for causing them to retract into the body of the piston.
~..~,., Also according to the present invention, there is provided a hydraulic cylinder-piston unit provided with a mechanical safety device, comprising a cylinder having a closed endpiece and in which there slides a piston provided wl-th a hollow rod emerging from an opposite enpiece of said cylinder, said rod housing in its interior a second toothed rod which is fixed at one end to the closed endpiece of said cylinder,is movable axially relative to said hollow rod by means of said piston, and cooperates with a pawl assembly housed in the piston and comprising at least one stop member, which during an elongation state of the cylinder piston unit, moves relative to the toothed rod by yielding elastically in its passage from one tooth to the next tooth, whereas during a retraction state said at least are stop member engages in a facing noth defined by two successive teeth, to thus form the mechanical safety device, the pawl assembly comprising for each stop member a plunger communicating with a rod end chamber of the cylinder and acting, when in presence of slight pressure in said chamber, in a sense of withdrawing the respective stop member into the /
.~ -. .~
~2;~
Preferably, according to the invention, the stop pawl assembly for the toothed rod can be provided with a sensor which detects its deactivated state.
A preferred embodiment of the present invention is 5 described hereinafter by way of non-limiting example with reference to the accompanying drawings in which:
Figure 1 is a perspective diagrammatic view of a lift of the pantograph type provided with hydraulic cylinder-piston units according to the invention;
0 Figure 2 is an axial section through a cylinder-piston unit to an enlarged scale;
Figure 3 is a partial longitudinal section through the piston of the cylinder-piston unit to an enlarged scale;
Figure 4 is a section ,therethrough on the line IV-IV of Figure 3, As can be seen from the figures, the hydraulic cylinder-piston unit according to the invention comprises a cylinder 1 closed lowerly by a sol:id endpiece 2, and closed upperly by an endpiece 3 comprising a central circular hole for~-the oil-20 tight passage of a rod ~.
When used in a lift (see Figure 1), the endpiece 2 is provided with a lug for its connection and hinging to a lower longitudinal member 6 of the lift, and the outer end of the ~3~22~6 rod 4 is provided Witll a head 5 for its connection and hinging to an upright 8.
*he rod 4, which is hollow, is connected to a piston 9 slidable in an oil-tight manner inside the cylinder 1. In the 5 interior of the rod 4 there is housed a further rod 10, which comprises a plurality of equidistant circumferential notches 11 having a profile such as to form a sawtooth pattern, as can be seen from Figure 2. The rod 10 is mobile axially relative -to the rod 4, and is fixed at one end to the 10 endpiece 2 of the cylinder 1. The rod 10 also traverses the piston 9, without any need for sealing.
In the endpiece 2 there is provided an aperture 12 for the passage of oil into and from the cylinder 1, and an aperture 13 is provided in the lateral surface of the 15 cylinder 1 in proximity to the endpiece 3.
The piston 9 cons:ists substantially of a pair of annular ~langes indicated overall by 14 and 14', and joined together by screws.
These flanges have an outer profile whic~ is 20complementary to the profile of a rubber gasket 15 which seals the piston 9 against the inner lateral surface of the cylinder 1.
The upper flange 14, which is screwed to the rod 4, ~IL3~22~6 comprises three radial recesses 16 disposed at 120x apart, in which stop blocks 17 can slide.
~ lore specifically, each stop block 17 has its front profile curved to correspond to the facing surface of the S toothed rod 10, and coMprises two cylindrical cavitles 18 for housing small helical springs 19 interposed between said block 17 a,nd the shoulder 20 which delimits the rear of the corresponding recess 16. It also comprises an inner cavity having an inclined surface 21 facing upwards in Figure 3. On said lnclined surface there rests the eccentric stem 22 of a plunger 23 mobile axially in a sealed manner within a corresponding cylindrical cavity 24 formed in the upper flange 14 and communicating with the interior of the cylinder 1.
As there exists a cylindrical cavity 24 for each o~ the three blocks 17 and as the guide recesses 16 Por these latter are disposed at 120, apart, the three cylindrical cavities 24 ., are also disposed at 120 apar-t.
The operation of the hydraulic cylinder-piGton~ unit ~0 according to the invention is as follows:
when in the rest state (minimum elongation) the piston 9 is in its lower end-of-stroke position, that cylindrical portion o~ the rod 10 not provided with toothing faces the three -` ~3~22~6 blocks 17, the three blocks 17 are urged by the respective springs 19 to adhere to the cylindrical surface of the rod 10, and the plungers 23 are raised. The piston 9, which is in its lowered position, divides the inner bore of the cylinder 5 1 into two regions: narnely the lower region connected to the inlet aperture 12, and comprising the annular cavity defined by the pis.ton 9,and lower endpiece 2 and also extending into the space defined by the rods 4 and 10; and the upper region connected to the outlet aperture 13, and comprising the 10 annular cavity defined vertically by -the piston 9 and the upper endpiece 3. Under these conditions the two regions are at the same pressure.
In order to raise the lift, oil is fed under pressure into the cylinder 1 through the aperture 12. This feed causes 15 the piston 9 to rise, and the cylinder-piston unit to undergo corresponding elongation.
As the piston 9 wlthdraws Prom the lower endpiece 3, the rod 10, which is ,Pi~ed to this latter, withdraws from the rod ~ and thus its la~,eral surface slides in front of the'end of 20 the three stop blocks 17, which are urged to adhere elastically thereto.
As oil feed into the cylinder 1 continues, there is a progressive withdrawal of the rod 10 from the .rod 4, with . ~-~3~2~
successive intervention of the stop blocks 17, which because of the sawtooth profile of ~he circulnferential notches 11 retract into the body of the flange 14 as they pass between one notch and the next, and elastically emer.ge in a snapwise 5 manner each time a notch appears in front of -them.
It is apparerl-t ~hat when they are in their elnerged state they constitute a mechanical safety stop which prevents the rod q from retract:ing i.n~o the cylinder 1, ever if the pressure o~ the feed circuit should accidentally f~ll.
~ihen this elongaciorl of the cylinder-piston unil is complete, the feed of oil is suspended and a small arnount o~
this latter is allowed to escape through the aperture 12, in order to ensure the mechanical engage~nent o~ the blocks 17 in the corresponding notch 11.
Ln order to lower the lift and thus cause each rod ~ to retract into the respective cylinder 1, the cylinder-piston units are firstly rnade to elongate sllghtly by normal methods in order to disengage the st;op bloclcs 17 frorn the relat:ive notch 11. Oil ls ~hen fed through the aperture 13. Its 20 pressure acts init:ially on t.he plungers 23, which descend and press by way of their stern 22 against the inclined surface 21 of the corresponding stop block 17. By virtue of this, the bloclcs 17 are withdrawn into the piston 9 aloncJ the ``:
~31D2;~
respective recesses 16, so that they no longer interfere with the toothed rod 10. By continuously ~eeding oil through the aperture 13 with simultaneouse discharge of other oil through the aperture 12, the piston 9 is made to descend, with the 5 toothed rod 10, which is no longer hindered by the stop blocks 17, simultaneously retracting into the rod 4.
The retraction of the stop blocks 17 in-to the piston 9 is opposed by the elastic reaction of the springs 19, and consequently, when the overpressure in the upper chamber of 10 the cylinder 1 ceases, this reaction prevails and urges the blocks 17 into their engaged state and, by virtue of the interaction between each stem 22 and the inclined surface 21 of the relative block 17, causes the release plungers 23 to rise and to return to their rest configuration.
From the aforegoing it is apparent that the hydraulic cylinder-piston unit according to the invention has numerous advan-tages over conventional cylinder-piston units provided with an external mechanical safety device, in that:
- it involves prac~ically no substantial size increase deriving frorn the mechanical safety device, - lt enables the mechanical safety device to be installed without requiring any work additional to that re~uired for installing the cylinder-piston uni-t, ~31)~2~
- it requires no independent device or circuit for releasing the mechanical safety device before the retraction of the rod into the cylinder is commenced, - it provides a high guarantee of correct operation and long life, in that all the moving parts operate immersed in oil.
The cylinder-piston unit according to the invention is used advan~ageously in pantograph lifts of the type shown diagrammatically in Figure 1. In this application, if the lift has no direct transverse connections between the 10 runways, it is preferable tO be able to check that the stop blocks are effectively in their disengaged state before lowering the lift, so as to prevent any possible dangerous consequences deriving from unbalanced loads. For this purpose, between the rear shoulder 20 of at least one radial 15 recess 16 and ~he corresponding stop block 17 of each cylinder-piston unit there is provided a member, such as a microswitch 25, which enables the lift to be lowered onl~ if activated by the bloclc when in its rear end~of-travel position.
Ihis invention rela~es ~o a hydrdulic cylinder-piston unit provided wi-th a mechanical safety device, particularly for motor vehicle lifts of the pantograph type.
Mo-tor vehicle lifts of the pantograph type are known.
5 They generally comprises a pair of runways and cylinder-piston unlts which raise said runways, on which the vehicle to be lifted has been previously positioned.
Current accident-prevention regulations require the provision of mechanical safety systerns to ensure that the 10 level attained by the runways is mainteined, even if the pressure of the hydraulic circuit feeding the cylinder-pistons units accidentally falls.
Known safety systems generally consist of racks engaged by pawl assernblies which allow the racks to move Preely 15 relative to them during the raising of the lift, but prevent their opposite movement, thus ensuring stability of the attained configuration.
To lower the lift it is necessary firstly to disengage ~ he pawl assemblies frorn the corresponding rack, and then 20 discharge the opera~.ing fluid ~rom the cylinder-piston units.
Known rllechanical safety systems for application to hydraulic cylinder-piston units, in particular for operating lifts of the pantograph type, have cer-tain drawbacks, and in ~k parti.cular:
- their installation is somewhat complicated because it involves additional work beyond that required for installing the cylinder-piston units, 5 - they are somewhat bulky, this being o~ten difficult tO
reconcile with the limited space available, - they require a self-contained system or circuit for deactivating them during the lowering of the lift.
An object of the invention is to obviate these drawbacks 10 by providing a hydrauli.c cylinder-piston unit with an associated mechanical safety device which is without bulk and requi~es no special additional installation work.
A further object of the invention is to provide a hydraulic cylinder-piston unit with an associated mechanical 15 safety device which for disengaging this latter uses the actual hydraulic feed circuit of the cylinder-piston unit.
These and further objects which will be apparent from the description given hereina~ter are attai,ned according to the invention by a hydraullc cylinder-piston unit provided 20 with a mechanical safety device, comprising a cylinder in which there slides a piston provided with a rod emerging from an endpiece of said cylinder, characterised by comprising inside the cylinder a portion provided wi-th toothing ~3~
extending along the axis of said cylinder and cooperating with at least one deactivatable stop member which during the elongation stage of said cylinder-piston unit moves relative to said toothed portion by yielding elastically in its 5 passage from one tooth to the next, whereas during the re~raction staye it engages in the facing notch defined by two successlve teeth, to thus form the mechanical safety stop.
Preferably, . the cylinder of the hydraulic cylinder-10 piston unit according to the invention can be formed with one endpiece closed and the other endpiece comprising a hole for the oil-tight passage of the piston rod, this rod being hollow and housing in its interior a second rod which is fixed at one end to the closed endpiece of said cylind.er, is 15 mobile axially relative to said hollow rod by means of said piston, and is provided with a toothed portion cooperating with a pawl assembly rigid with said hollow rod.
Preferabl.y, acco:cding to the invention, the piston can comprise radial recesses opening into the passage bore.~for ~Osaid second rod, in order to guide stop blocks which are kept elastically adhering to t:he lateral surface of said second rod and are provided with rneans for causing them to retract into the body of the piston.
~..~,., Also according to the present invention, there is provided a hydraulic cylinder-piston unit provided with a mechanical safety device, comprising a cylinder having a closed endpiece and in which there slides a piston provided wl-th a hollow rod emerging from an opposite enpiece of said cylinder, said rod housing in its interior a second toothed rod which is fixed at one end to the closed endpiece of said cylinder,is movable axially relative to said hollow rod by means of said piston, and cooperates with a pawl assembly housed in the piston and comprising at least one stop member, which during an elongation state of the cylinder piston unit, moves relative to the toothed rod by yielding elastically in its passage from one tooth to the next tooth, whereas during a retraction state said at least are stop member engages in a facing noth defined by two successive teeth, to thus form the mechanical safety device, the pawl assembly comprising for each stop member a plunger communicating with a rod end chamber of the cylinder and acting, when in presence of slight pressure in said chamber, in a sense of withdrawing the respective stop member into the /
.~ -. .~
~2;~
Preferably, according to the invention, the stop pawl assembly for the toothed rod can be provided with a sensor which detects its deactivated state.
A preferred embodiment of the present invention is 5 described hereinafter by way of non-limiting example with reference to the accompanying drawings in which:
Figure 1 is a perspective diagrammatic view of a lift of the pantograph type provided with hydraulic cylinder-piston units according to the invention;
0 Figure 2 is an axial section through a cylinder-piston unit to an enlarged scale;
Figure 3 is a partial longitudinal section through the piston of the cylinder-piston unit to an enlarged scale;
Figure 4 is a section ,therethrough on the line IV-IV of Figure 3, As can be seen from the figures, the hydraulic cylinder-piston unit according to the invention comprises a cylinder 1 closed lowerly by a sol:id endpiece 2, and closed upperly by an endpiece 3 comprising a central circular hole for~-the oil-20 tight passage of a rod ~.
When used in a lift (see Figure 1), the endpiece 2 is provided with a lug for its connection and hinging to a lower longitudinal member 6 of the lift, and the outer end of the ~3~22~6 rod 4 is provided Witll a head 5 for its connection and hinging to an upright 8.
*he rod 4, which is hollow, is connected to a piston 9 slidable in an oil-tight manner inside the cylinder 1. In the 5 interior of the rod 4 there is housed a further rod 10, which comprises a plurality of equidistant circumferential notches 11 having a profile such as to form a sawtooth pattern, as can be seen from Figure 2. The rod 10 is mobile axially relative -to the rod 4, and is fixed at one end to the 10 endpiece 2 of the cylinder 1. The rod 10 also traverses the piston 9, without any need for sealing.
In the endpiece 2 there is provided an aperture 12 for the passage of oil into and from the cylinder 1, and an aperture 13 is provided in the lateral surface of the 15 cylinder 1 in proximity to the endpiece 3.
The piston 9 cons:ists substantially of a pair of annular ~langes indicated overall by 14 and 14', and joined together by screws.
These flanges have an outer profile whic~ is 20complementary to the profile of a rubber gasket 15 which seals the piston 9 against the inner lateral surface of the cylinder 1.
The upper flange 14, which is screwed to the rod 4, ~IL3~22~6 comprises three radial recesses 16 disposed at 120x apart, in which stop blocks 17 can slide.
~ lore specifically, each stop block 17 has its front profile curved to correspond to the facing surface of the S toothed rod 10, and coMprises two cylindrical cavitles 18 for housing small helical springs 19 interposed between said block 17 a,nd the shoulder 20 which delimits the rear of the corresponding recess 16. It also comprises an inner cavity having an inclined surface 21 facing upwards in Figure 3. On said lnclined surface there rests the eccentric stem 22 of a plunger 23 mobile axially in a sealed manner within a corresponding cylindrical cavity 24 formed in the upper flange 14 and communicating with the interior of the cylinder 1.
As there exists a cylindrical cavity 24 for each o~ the three blocks 17 and as the guide recesses 16 Por these latter are disposed at 120, apart, the three cylindrical cavities 24 ., are also disposed at 120 apar-t.
The operation of the hydraulic cylinder-piGton~ unit ~0 according to the invention is as follows:
when in the rest state (minimum elongation) the piston 9 is in its lower end-of-stroke position, that cylindrical portion o~ the rod 10 not provided with toothing faces the three -` ~3~22~6 blocks 17, the three blocks 17 are urged by the respective springs 19 to adhere to the cylindrical surface of the rod 10, and the plungers 23 are raised. The piston 9, which is in its lowered position, divides the inner bore of the cylinder 5 1 into two regions: narnely the lower region connected to the inlet aperture 12, and comprising the annular cavity defined by the pis.ton 9,and lower endpiece 2 and also extending into the space defined by the rods 4 and 10; and the upper region connected to the outlet aperture 13, and comprising the 10 annular cavity defined vertically by -the piston 9 and the upper endpiece 3. Under these conditions the two regions are at the same pressure.
In order to raise the lift, oil is fed under pressure into the cylinder 1 through the aperture 12. This feed causes 15 the piston 9 to rise, and the cylinder-piston unit to undergo corresponding elongation.
As the piston 9 wlthdraws Prom the lower endpiece 3, the rod 10, which is ,Pi~ed to this latter, withdraws from the rod ~ and thus its la~,eral surface slides in front of the'end of 20 the three stop blocks 17, which are urged to adhere elastically thereto.
As oil feed into the cylinder 1 continues, there is a progressive withdrawal of the rod 10 from the .rod 4, with . ~-~3~2~
successive intervention of the stop blocks 17, which because of the sawtooth profile of ~he circulnferential notches 11 retract into the body of the flange 14 as they pass between one notch and the next, and elastically emer.ge in a snapwise 5 manner each time a notch appears in front of -them.
It is apparerl-t ~hat when they are in their elnerged state they constitute a mechanical safety stop which prevents the rod q from retract:ing i.n~o the cylinder 1, ever if the pressure o~ the feed circuit should accidentally f~ll.
~ihen this elongaciorl of the cylinder-piston unil is complete, the feed of oil is suspended and a small arnount o~
this latter is allowed to escape through the aperture 12, in order to ensure the mechanical engage~nent o~ the blocks 17 in the corresponding notch 11.
Ln order to lower the lift and thus cause each rod ~ to retract into the respective cylinder 1, the cylinder-piston units are firstly rnade to elongate sllghtly by normal methods in order to disengage the st;op bloclcs 17 frorn the relat:ive notch 11. Oil ls ~hen fed through the aperture 13. Its 20 pressure acts init:ially on t.he plungers 23, which descend and press by way of their stern 22 against the inclined surface 21 of the corresponding stop block 17. By virtue of this, the bloclcs 17 are withdrawn into the piston 9 aloncJ the ``:
~31D2;~
respective recesses 16, so that they no longer interfere with the toothed rod 10. By continuously ~eeding oil through the aperture 13 with simultaneouse discharge of other oil through the aperture 12, the piston 9 is made to descend, with the 5 toothed rod 10, which is no longer hindered by the stop blocks 17, simultaneously retracting into the rod 4.
The retraction of the stop blocks 17 in-to the piston 9 is opposed by the elastic reaction of the springs 19, and consequently, when the overpressure in the upper chamber of 10 the cylinder 1 ceases, this reaction prevails and urges the blocks 17 into their engaged state and, by virtue of the interaction between each stem 22 and the inclined surface 21 of the relative block 17, causes the release plungers 23 to rise and to return to their rest configuration.
From the aforegoing it is apparent that the hydraulic cylinder-piston unit according to the invention has numerous advan-tages over conventional cylinder-piston units provided with an external mechanical safety device, in that:
- it involves prac~ically no substantial size increase deriving frorn the mechanical safety device, - lt enables the mechanical safety device to be installed without requiring any work additional to that re~uired for installing the cylinder-piston uni-t, ~31)~2~
- it requires no independent device or circuit for releasing the mechanical safety device before the retraction of the rod into the cylinder is commenced, - it provides a high guarantee of correct operation and long life, in that all the moving parts operate immersed in oil.
The cylinder-piston unit according to the invention is used advan~ageously in pantograph lifts of the type shown diagrammatically in Figure 1. In this application, if the lift has no direct transverse connections between the 10 runways, it is preferable tO be able to check that the stop blocks are effectively in their disengaged state before lowering the lift, so as to prevent any possible dangerous consequences deriving from unbalanced loads. For this purpose, between the rear shoulder 20 of at least one radial 15 recess 16 and ~he corresponding stop block 17 of each cylinder-piston unit there is provided a member, such as a microswitch 25, which enables the lift to be lowered onl~ if activated by the bloclc when in its rear end~of-travel position.
Claims (5)
1. A hydraulic cylinder-piston unit provided with a mechanical safety device, comprising a cylinder having a closed endpiece and in which there slides a piston provided with a hollow rod emerging from an opposite endpiece of said cylinder, said rod housing in its interior a second toothed rod which is fixed at one end to the closed endpiece of said cylinder, is movable axially relative to said hollow rod by means of said piston, and cooperates with a pawl asssembly housed in the piston and comprising at least one stop member, which during an elongation state of the cylinder-piston unit, moves relative to the toothed rod by yielding elastically in its passage from one tooth to the next tooth, whereas during a retraction state said at least one stop member engages in a facing notch defined by two successive teeth, to thus form the mechanical safety device, the pawl assembly comprising for each stop member a plunger communicating with a rod end chamber of the cylinder and acting, when in presence of slight pressure in said chamber, in a sense of withdrawing the respective stop member into the piston.
2. A hydraulic cylinder-piston unit as claimed in claim 1, wherein the plunger is provided with a stem cooperating with an inclined surface provided in the corresponding stop member in order, as a result of its axial movement, to cause the corresponding stop member to withdraw into the piston.
3. A hydraulic cylinder-piston unit as claimed in claim 1, wherein each stop member is provided with a sensor which detects its deactivated state.
4. A hydraulic cylinder-piston unit as claimed in claim 3, wherein said sensor detects when each stop member has reached its end-of-travel position in a corresponding guide recess foreseen in the piston.
5. A hydraulic cylinder-piston unit as claimed in claim 4, wherein the sensor consists of a microswitch, which is activated by the corresponding stop member when said corresponding stop member reaches its rear end-of-travel position.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT84159A/85 | 1985-12-05 | ||
| IT8584159A IT1214977B (en) | 1985-12-05 | 1985-12-05 | FLUODYNAMIC JACK PROVIDED WITH MECHANICAL SAFETY DEVICE, IN PARTICULAR FOR PANTOGRAPH LIFTING BRIDGES FOR VEHICLES. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1302206C true CA1302206C (en) | 1992-06-02 |
Family
ID=11324937
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000524460A Expired - Lifetime CA1302206C (en) | 1985-12-05 | 1986-12-03 | Hydraulic cylinder-piston unit with a safety device |
Country Status (10)
| Country | Link |
|---|---|
| EP (2) | EP0224914B1 (en) |
| AT (1) | ATE53896T1 (en) |
| AU (1) | AU604673B2 (en) |
| CA (1) | CA1302206C (en) |
| DE (1) | DE3670888D1 (en) |
| ES (1) | ES2013593B3 (en) |
| GR (1) | GR3000525T3 (en) |
| IL (1) | IL80838A (en) |
| IT (1) | IT1214977B (en) |
| WO (1) | WO1987003655A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT1237417B (en) * | 1989-01-18 | 1993-06-01 | Eride Rossato | MOTOR VEHICLE LIFTING DEVICE, PARTICULARLY FOR BODYWORKS. |
| IT1282522B1 (en) * | 1995-05-19 | 1998-03-23 | Eride Rossato | PANTOGRAPH LIFT BRIDGE FOR VEHICLES |
| AU701019B2 (en) * | 1995-11-14 | 1999-01-21 | Hilland Pty Ltd Trading As Edmo Equipment | Vehicle jack and stand |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE211847C (en) * | ||||
| USRE25334E (en) * | 1963-02-19 | Piston cylinder apparatus | ||
| GB211412A (en) * | 1923-07-23 | 1924-02-21 | Charles Frederick Webb | Improvements relating to pneumatic lifting jacks |
| GB490886A (en) * | 1936-11-27 | 1938-08-23 | Servo Frein Dewandre Sa | Control device with pre-determined successive positions |
| US2540578A (en) * | 1945-09-27 | 1951-02-06 | Lockheed Aircraft Corp | Hydraulic internal locking jack |
| FR952142A (en) * | 1946-08-15 | 1949-11-09 | C V Fabriek Voor Auto En Machb | Locking and braking system |
| US3020888A (en) * | 1959-07-02 | 1962-02-13 | Gen Electric | Linear motion-producing device with lock |
| US3104593A (en) * | 1960-12-28 | 1963-09-24 | Regent Jack Mfg Co Inc | Fluid actuators |
| US3180234A (en) * | 1963-07-25 | 1965-04-27 | Jarry Hydraulics Ltd | Dual-position lockable actuator |
| AU557669B2 (en) * | 1981-08-04 | 1987-01-08 | Alfarm Australia Limited | Hydraulic cylinder with locking mechanism |
| IL67722A0 (en) * | 1982-02-05 | 1983-05-15 | Plessey Overseas | Container with memory |
| AU548927B2 (en) * | 1982-06-11 | 1986-01-09 | Terrance Arthur Baroody | Tubing tee joint |
-
1985
- 1985-12-05 IT IT8584159A patent/IT1214977B/en active
-
1986
- 1986-12-02 ES ES86116771T patent/ES2013593B3/en not_active Expired - Lifetime
- 1986-12-02 IL IL80838A patent/IL80838A/en not_active IP Right Cessation
- 1986-12-02 EP EP86116771A patent/EP0224914B1/en not_active Expired - Lifetime
- 1986-12-02 AT AT87900094T patent/ATE53896T1/en not_active IP Right Cessation
- 1986-12-02 WO PCT/EP1986/000696 patent/WO1987003655A1/en active IP Right Grant
- 1986-12-02 AU AU68313/87A patent/AU604673B2/en not_active Ceased
- 1986-12-02 EP EP87900094A patent/EP0293368B1/en not_active Expired - Lifetime
- 1986-12-02 DE DE8787900094T patent/DE3670888D1/en not_active Expired - Lifetime
- 1986-12-03 CA CA000524460A patent/CA1302206C/en not_active Expired - Lifetime
-
1990
- 1990-05-31 GR GR90400341T patent/GR3000525T3/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| IL80838A0 (en) | 1987-03-31 |
| GR3000525T3 (en) | 1991-07-31 |
| EP0293368A1 (en) | 1988-12-07 |
| EP0293368B1 (en) | 1990-05-02 |
| EP0224914A1 (en) | 1987-06-10 |
| AU6831387A (en) | 1987-06-30 |
| ATE53896T1 (en) | 1990-06-15 |
| AU604673B2 (en) | 1991-01-03 |
| IT1214977B (en) | 1990-01-31 |
| IL80838A (en) | 1991-01-31 |
| EP0224914B1 (en) | 1990-03-07 |
| WO1987003655A1 (en) | 1987-06-18 |
| IT8584159A0 (en) | 1985-12-05 |
| ES2013593B3 (en) | 1990-05-16 |
| DE3670888D1 (en) | 1990-06-07 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |