CA1209550A - Turntable mounted elevatable member - Google Patents
Turntable mounted elevatable memberInfo
- Publication number
- CA1209550A CA1209550A CA000410910A CA410910A CA1209550A CA 1209550 A CA1209550 A CA 1209550A CA 000410910 A CA000410910 A CA 000410910A CA 410910 A CA410910 A CA 410910A CA 1209550 A CA1209550 A CA 1209550A
- Authority
- CA
- Canada
- Prior art keywords
- ladder
- ram
- turntable
- dual
- axis
- 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
- 230000009977 dual effect Effects 0.000 claims abstract description 15
- 230000003028 elevating effect Effects 0.000 claims description 3
- 238000009428 plumbing Methods 0.000 abstract description 13
- 239000012530 fluid Substances 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000010276 construction Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- ZPEZUAAEBBHXBT-WCCKRBBISA-N (2s)-2-amino-3-methylbutanoic acid;2-amino-3-methylbutanoic acid Chemical compound CC(C)C(N)C(O)=O.CC(C)[C@H](N)C(O)=O ZPEZUAAEBBHXBT-WCCKRBBISA-N 0.000 description 1
- 229920002892 amber Polymers 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 210000002445 nipple Anatomy 0.000 description 1
- 230000003019 stabilising effect Effects 0.000 description 1
Classifications
-
- 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
- B66F11/00—Lifting devices specially adapted for particular uses not otherwise provided for
- B66F11/04—Lifting devices specially adapted for particular uses not otherwise provided for for movable platforms or cabins, e.g. on vehicles, permitting workmen to place themselves in any desired position for carrying out required operations
- B66F11/044—Working platforms suspended from booms
-
- E—FIXED CONSTRUCTIONS
- E06—DOORS, WINDOWS, SHUTTERS, OR ROLLER BLINDS IN GENERAL; LADDERS
- E06C—LADDERS
- E06C5/00—Ladders characterised by being mounted on undercarriages or vehicles Securing ladders on vehicles
- E06C5/02—Ladders characterised by being mounted on undercarriages or vehicles Securing ladders on vehicles with rigid longitudinal members
- E06C5/04—Ladders characterised by being mounted on undercarriages or vehicles Securing ladders on vehicles with rigid longitudinal members capable of being elevated or extended ; Fastening means during transport, e.g. mechanical, hydraulic
- E06C5/06—Ladders characterised by being mounted on undercarriages or vehicles Securing ladders on vehicles with rigid longitudinal members capable of being elevated or extended ; Fastening means during transport, e.g. mechanical, hydraulic by piston and cylinder, or equivalent means, operated by a pressure medium
-
- E—FIXED CONSTRUCTIONS
- E06—DOORS, WINDOWS, SHUTTERS, OR ROLLER BLINDS IN GENERAL; LADDERS
- E06C—LADDERS
- E06C5/00—Ladders characterised by being mounted on undercarriages or vehicles Securing ladders on vehicles
- E06C5/32—Accessories, e.g. brakes on ladders
- E06C5/36—Safety devices against slipping or falling of ladders; Safety devices against overloading ladders
-
- E—FIXED CONSTRUCTIONS
- E06—DOORS, WINDOWS, SHUTTERS, OR ROLLER BLINDS IN GENERAL; LADDERS
- E06C—LADDERS
- E06C5/00—Ladders characterised by being mounted on undercarriages or vehicles Securing ladders on vehicles
- E06C5/32—Accessories, e.g. brakes on ladders
- E06C5/40—Devices for canting ladders laterally
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Structural Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Ladders (AREA)
Abstract
A B S T R A C T
TURNTABLE MOUNTED ELEVATABLE MEMBER
A turntable mounted elevatable member such as a ladder uses a dual concentric ram for elevation thereby providing two independent hydraulic circuits for safety and avoiding the need for mechanical locks. The single point mounting at each end of the ram permits the movement required for plumbing the ladder without the need for the complexity required to control two separate elevation rams during plumbing. The dual ram has a retraction chamber to enable the ladder to be held against lifting due to external influences. Lock valves for the separate volumes of the ram are built into the base. The invention can also be embodied in a turntable mounted elevatable man-carrying platform.
TURNTABLE MOUNTED ELEVATABLE MEMBER
A turntable mounted elevatable member such as a ladder uses a dual concentric ram for elevation thereby providing two independent hydraulic circuits for safety and avoiding the need for mechanical locks. The single point mounting at each end of the ram permits the movement required for plumbing the ladder without the need for the complexity required to control two separate elevation rams during plumbing. The dual ram has a retraction chamber to enable the ladder to be held against lifting due to external influences. Lock valves for the separate volumes of the ram are built into the base. The invention can also be embodied in a turntable mounted elevatable man-carrying platform.
Description
~LZ~9S5a9 This invention relates to a turntable mounted elevatable member having personnel support means such as a turntable ladder suitable for use on a fire figh~ing and rescue vehicle or a man carrying platform.
Fire fighting and rescue vehicles are usually provided with a ladder mounted on a turntable which-can be extended to bring the head of the ladder to a desired position either to enable a fireman to direct a jet of water on to the fire or to provide an escape route for 10 persons trapped by the fire. It is a safety requirement of turntable ladders that where the elevation of the ladder is performed by hydraulic-rams a~ hydraulic lock must be provided at the base of each ram to prevent uncontrolled depression of the ladder. ~In addition, a mechanical 15 lock should also preferably be provided in the case o~
two or more rams and must be provided where a single r~m only is used. These requirements are clearly sensible, but they give rise to difficulties in enabling the ladder to be trained in all required directions. I* the vehicle 20 is standing on a level site, such as a road; orlthe turn-table axis is movable~so that the plane of the turntable is horizontal, there is no problem, but if it is necess~ry to provide for plumbing of the ladder so that the rungs of tha ladder are horizontal even though the vehicle and the 25 plane of the turntable are not horizontal, then the rotation .. . .
of the ladder axis to permit the plumbing of the ladder is complicated by the safety requirements described above.
If the ladder is elevated by means of two hydraulic rams, then all that is required by the safety legislation is that 30 these rams have hydraulic locks, but the plumbing of the~
, s~ l - 3 - i , ladder wilI mean that the two rams must have different lengths and also must be provided with universal joints for connecting them to the ladder and the mounting. As a result the control of the rams and the construction of the ladder is complicated. Other and similarly complicated methods involve the use of an additional turntable or a multiple slew ring having two opposed wedges to effect the plumbing. On the other hand, if a single elevation ram is provided, 10 with self-aligning bearings at both ends, then the plumbing movement of the ladder would be allowed i for and the overall system would be relatively straightforward. However, the safety legislation requires that a single elevation ram must be fitted 15 with a mechanical lock which is not only expensive and introduces complication but also prevents the ram from being simply constructed as double acting, which feature would be useful for stabilising the ladder against wind pressure and water jet reaction.
Although the safety requirements for man carrying platforms are not as stringent as those for fire escape ladders, it would be clearly desirable to -~
make such plat~orms as safe as reasonably possible.
It is an object of the present invention to provide a turntable mounted elevatable member in which the difficulties described above are substantially overcome.
~ccordi.ng to the present invention there is provided a turntable mounted elevatable ladder suitable for mounting on a vehicle, in which the ladder is mounted on an elevation axis parallel to rungs of the ladder, which axis is pivoted at its centre on the turntable and hydraulic ram means are provided to tilt the axis about its centre relative to the turntable thereby to raise and lower the ends of the axis about its centre so as to permit the axis and therefore also the rungs to be made horizontal when the turntable is inclined to the horizontal, wherein there is provided a single dual concentric hydraulic ram extending between self-aligning bearings on the turntable and on the ladder for elevating the ladder by rotating it about the elevation axis.
The dual concentric ram may have cylinder diameters close to the ratio 1 : v~2 so that the effective piston areas of the two expansion cylinders of the ram are substa~tially equal. The cylinder diameters may be of i~
suitably related standard sizes, such as 6" and ~
160 mm and 110 mm or 1~0 mm and 100 mm, so that manufac~uring and s~rvicing costs can be kept down. The ram may also include a retracting chamber to enable hydraulic pre~sure ¦~
therein to oppose lifting of the member by wind pressure 10 or water jet reaction~
For ~afety reasons, the -two expan~ion-cylinders of the dual ram may have individual hydraulic lock vlaves which may be load control valves instead of pilot-operated check valves to giv~ smoother operation of the ram and 15 therefore also smoother elevation of the member. In order to prevent the ram extending due to external influences such as wind pressure or water jet reaction, a further load control val~e m~y-be ~onnected to the inlet to the retracting ch~m~er~.- T~e-t~ree valves may ~e built int~
20 ~he~base of the ram.
III order that the invention may be fully understood and carried out into effect it will now be described with reference to an exa~ple shown in the accompanying drawings, of which:-FIGURE 1 is a diagram illustrating the di~ferent movements required of a turntable ladder, FIGURE 2 shows in detail the mounting of a turntable ladder in accordance with one example of the invention' lZ(~9S50 FIGURE 3 shows the cross-section of a dual concentric ram suitable for use in the present invention, and FIGURE ~ is an hydraulic circuit diagram showing how the dual concentric ram might be controlled.
Referring now to Figure 1, a turntable ladder A has four degrees of freedom. It is rotatable about a vertical axis B by rotation of the turntable, it is extendible along its length by means which will not be described in this specification since they form no part of the present invention, it can be raised to a required elevation, and it can be plumbed by rotation about an axis which may be either horizontal or extend alongthe length of the ladder . .
or about some line lying between them or approximating either of them. As explained above, the purpose of the plumbing 15 movements is to keep the rungs of the ladder horizontal despite departure of the rotation axis B from the ve~tical.
Similar~ considerations apply to the plumbing of a turntable mounted man-carrying platform on an articulated arm.
Figure 2 shows a part of a ladder 1 mounted on a turn-20 table 2. The turntable 2 has a built-up bracket (3) supporting a substantially horizontal bearing ~ on which the ladder 1 is mounted on an elevation bearing 5. Two plumbing rams 6A and 6B are provided mounted on the bracket 3 and attached to the ends of the elevation bearing 5 to adjust 25 the attitude of the bearing 5 about the generally horizontal axis defined by the bearing 4 so as to effect the plumbing of the ladder. The elevation of the ladder r ~D 2(~9~550 is effected by a dual concentric ram 7 extending from a self-aligning bearing 8 on the bracket 3 to a self-aligning bearing 9 on the ladder 1. It will be apparent ~hat extension of the ram 7 will result in elevation of the ladder 1 about the bearing 5. ~he ladder 1 is shown in the fully lowered position. The bearing a may be arranged to ke substantially horizontal. ' I
Figure 3 shows in cxoss-section one form of construction of the dual concentric hydraulic ram 7 shown in Figure 2.
10 In Figure 3, the ram which,extends from the self-aligning bearing 8 to the self-aligning bearing 9 has an external cylinder 11 in which moves a.piston 12 mounted on an internal cylinder 13 which is attachPd to the bearing 9.
Within the internal cylinder 13 there is provided a piston lS la which is fixed within the external cylinder 11, so that as the piston 12 moves within the cylinder 11, so the piston la moves within the cylinder 13. The piston la is mounted on a tubular support 150 A seal 16 is provid~d between the cylinders 11 and 13, is fixed to the cylinder' 11 and allows sliding movement of the cylinder 13. The ram 7 has 'three volumes. A first volume 17 is between the external cylinder 11 and the tubular support 15 and bounded by the pistons 12 and 1~. A second volume 18 is contained within the internal cylinder 13 and is bounded by the piston 1~.
25 A third vo~lume 19 is fonmed between the external cylinder 11, the internal cylinder 13 and-is bounded by the piston 12 and thei`,seal 16. On extension of the ram koth volumes 17 and 18 increase and the volume 19 decreases, ana on retraction of the ram the volumes 17 and 18 decrease and volume 19 ~increases. Built into the base of the ram are valves~2~ 22 and 3~3 which are used to sontrol the ingress and egress of hydraulic ~luid in the three volumes of the ram. The operation of the valves 20, 21, 22 5 and 33 will be described later with reference to Figure a. 1.
The use of a single concentric ram satisfies the safety requirements in that it provides two hydraulically separate pressure c~ambers, and since these are placed concentrically one about the other, they not only avoid 10 the problems of offset constructional loading in the event of failure of one of the hydraulic systems, but also they permit the freedom of movement required by the plumbing movement of the ladder without ~he need to alter the volumes of the two pressure chambers differentially as would 15 be required if two separate rams were employed. Preferably, the effec~ive areas of the pistons 12 and 1~ should be the same so that the load is shared equally between the hydraulic systems feeding the volume 17 and the volume 18, and in the event of failure of either system the working 20 system is then subjected to just double its normal load. If any other relationship between the areas of the rams is employed, then the failure of the larger system would give rise to more than double the pressure in the smaller system. Since the piston 12 is annular and the piston la is circular, it 25 follows that to achieve the equal piston areas the internal diameter P of the external cylinder 11 should be ~2 x the internal diameter Q of the internal cyllnder 13. In order ~9~iS~
g 1:
to simplify servicing and reduce costs, it is preferable 1, that standard sizes of cylinder material and seals be employed and suitable combinations for the values of P and Q are:
P 6" 160 mm 1~0 mm Q ~" 110 mm 100 mm Figure ~, which is a hydraulic circuit diagram for controlling the dual concentric ram, shows the three volumes 17, 18 and 19 referred to in Figure 3, and the valves 20, 10 21, 22. and 33 shown in the base of the ram 7 in Figure 3., The valves 20 and 21 are load control valves and are connected to permit the flow of oil from the volumes 17 and 18 respectively when opened by a pilot signal supplied along a line 23. The valves 20 and 21 are by-passed by 15 one-way valves 2~ and 25 respectively which are arranged to allow fluid to enter the volumes 17 and 1~3. The fluid under pressure for extending ~he ram 7 is produced by an hydraulic pump 26 and applied to the valves 2~ and 25 through a three-position control valve 27 and a line 28. The line 28 20 is also connected to the load'co~trol valve 22 to open this valve and permit oil to escape from the volume 19 whilst the ram 7 is being exte~d.ed~.:~h'e~'return oil from the volume 19 passing through the load.co~l~.valv~'22'flows along-a line 29 and through the control valve 27 to a reservoir 30.
25 A fluid pressure control valve 31 is provided to limit the output pressure of the pump 26. The valve 33 is connected I
S5~ `
.~ .
between the volume 19 and the reservoir 30 to relieve excess pressure due to thermal expansion or certain combinations of seal and cylinder failure. The valves 22 and 33 are combined in a single cartridge (Fig.3).
In order to extend the ram 7 thé control valve 27 is moved to the left permitting oil to flow from the pump 26 ~.
through the line 28 and the valves 2~ and 25 into the volumes 17 and 18~ Oil ejected from the volume 19 is returned through the load control valve 22 held open by the 10 pressure in the line 28, which oil flows through the line 29 back through the control valve 27 to the reservoir 30.
Retraction of the ram 7 is effected by m~ving the control valve 27 to the right so that fluid pressure from the pump 26 flows along the line 29 through the valve 22 into the 15 volume 19. This fluid pressure is also applied via the line 23 to open the lo~d control valves 20 and 21 and permit the oil to be released from the volumes 17 and 18. Fluid pressure connections are also provided from the volumes 17 and 18 to control the load control valves 20 and 21 so that 20 any *endency for the ladder to depress too rapidly w.ill result in closure of the valves 20 and 21 as a result of the reduction in pressure. It has been found in practice that the valves 20 and 21 operate smoothly to contxol the pressure in the volumes 17 and 18.
Fire fighting and rescue vehicles are usually provided with a ladder mounted on a turntable which-can be extended to bring the head of the ladder to a desired position either to enable a fireman to direct a jet of water on to the fire or to provide an escape route for 10 persons trapped by the fire. It is a safety requirement of turntable ladders that where the elevation of the ladder is performed by hydraulic-rams a~ hydraulic lock must be provided at the base of each ram to prevent uncontrolled depression of the ladder. ~In addition, a mechanical 15 lock should also preferably be provided in the case o~
two or more rams and must be provided where a single r~m only is used. These requirements are clearly sensible, but they give rise to difficulties in enabling the ladder to be trained in all required directions. I* the vehicle 20 is standing on a level site, such as a road; orlthe turn-table axis is movable~so that the plane of the turntable is horizontal, there is no problem, but if it is necess~ry to provide for plumbing of the ladder so that the rungs of tha ladder are horizontal even though the vehicle and the 25 plane of the turntable are not horizontal, then the rotation .. . .
of the ladder axis to permit the plumbing of the ladder is complicated by the safety requirements described above.
If the ladder is elevated by means of two hydraulic rams, then all that is required by the safety legislation is that 30 these rams have hydraulic locks, but the plumbing of the~
, s~ l - 3 - i , ladder wilI mean that the two rams must have different lengths and also must be provided with universal joints for connecting them to the ladder and the mounting. As a result the control of the rams and the construction of the ladder is complicated. Other and similarly complicated methods involve the use of an additional turntable or a multiple slew ring having two opposed wedges to effect the plumbing. On the other hand, if a single elevation ram is provided, 10 with self-aligning bearings at both ends, then the plumbing movement of the ladder would be allowed i for and the overall system would be relatively straightforward. However, the safety legislation requires that a single elevation ram must be fitted 15 with a mechanical lock which is not only expensive and introduces complication but also prevents the ram from being simply constructed as double acting, which feature would be useful for stabilising the ladder against wind pressure and water jet reaction.
Although the safety requirements for man carrying platforms are not as stringent as those for fire escape ladders, it would be clearly desirable to -~
make such plat~orms as safe as reasonably possible.
It is an object of the present invention to provide a turntable mounted elevatable member in which the difficulties described above are substantially overcome.
~ccordi.ng to the present invention there is provided a turntable mounted elevatable ladder suitable for mounting on a vehicle, in which the ladder is mounted on an elevation axis parallel to rungs of the ladder, which axis is pivoted at its centre on the turntable and hydraulic ram means are provided to tilt the axis about its centre relative to the turntable thereby to raise and lower the ends of the axis about its centre so as to permit the axis and therefore also the rungs to be made horizontal when the turntable is inclined to the horizontal, wherein there is provided a single dual concentric hydraulic ram extending between self-aligning bearings on the turntable and on the ladder for elevating the ladder by rotating it about the elevation axis.
The dual concentric ram may have cylinder diameters close to the ratio 1 : v~2 so that the effective piston areas of the two expansion cylinders of the ram are substa~tially equal. The cylinder diameters may be of i~
suitably related standard sizes, such as 6" and ~
160 mm and 110 mm or 1~0 mm and 100 mm, so that manufac~uring and s~rvicing costs can be kept down. The ram may also include a retracting chamber to enable hydraulic pre~sure ¦~
therein to oppose lifting of the member by wind pressure 10 or water jet reaction~
For ~afety reasons, the -two expan~ion-cylinders of the dual ram may have individual hydraulic lock vlaves which may be load control valves instead of pilot-operated check valves to giv~ smoother operation of the ram and 15 therefore also smoother elevation of the member. In order to prevent the ram extending due to external influences such as wind pressure or water jet reaction, a further load control val~e m~y-be ~onnected to the inlet to the retracting ch~m~er~.- T~e-t~ree valves may ~e built int~
20 ~he~base of the ram.
III order that the invention may be fully understood and carried out into effect it will now be described with reference to an exa~ple shown in the accompanying drawings, of which:-FIGURE 1 is a diagram illustrating the di~ferent movements required of a turntable ladder, FIGURE 2 shows in detail the mounting of a turntable ladder in accordance with one example of the invention' lZ(~9S50 FIGURE 3 shows the cross-section of a dual concentric ram suitable for use in the present invention, and FIGURE ~ is an hydraulic circuit diagram showing how the dual concentric ram might be controlled.
Referring now to Figure 1, a turntable ladder A has four degrees of freedom. It is rotatable about a vertical axis B by rotation of the turntable, it is extendible along its length by means which will not be described in this specification since they form no part of the present invention, it can be raised to a required elevation, and it can be plumbed by rotation about an axis which may be either horizontal or extend alongthe length of the ladder . .
or about some line lying between them or approximating either of them. As explained above, the purpose of the plumbing 15 movements is to keep the rungs of the ladder horizontal despite departure of the rotation axis B from the ve~tical.
Similar~ considerations apply to the plumbing of a turntable mounted man-carrying platform on an articulated arm.
Figure 2 shows a part of a ladder 1 mounted on a turn-20 table 2. The turntable 2 has a built-up bracket (3) supporting a substantially horizontal bearing ~ on which the ladder 1 is mounted on an elevation bearing 5. Two plumbing rams 6A and 6B are provided mounted on the bracket 3 and attached to the ends of the elevation bearing 5 to adjust 25 the attitude of the bearing 5 about the generally horizontal axis defined by the bearing 4 so as to effect the plumbing of the ladder. The elevation of the ladder r ~D 2(~9~550 is effected by a dual concentric ram 7 extending from a self-aligning bearing 8 on the bracket 3 to a self-aligning bearing 9 on the ladder 1. It will be apparent ~hat extension of the ram 7 will result in elevation of the ladder 1 about the bearing 5. ~he ladder 1 is shown in the fully lowered position. The bearing a may be arranged to ke substantially horizontal. ' I
Figure 3 shows in cxoss-section one form of construction of the dual concentric hydraulic ram 7 shown in Figure 2.
10 In Figure 3, the ram which,extends from the self-aligning bearing 8 to the self-aligning bearing 9 has an external cylinder 11 in which moves a.piston 12 mounted on an internal cylinder 13 which is attachPd to the bearing 9.
Within the internal cylinder 13 there is provided a piston lS la which is fixed within the external cylinder 11, so that as the piston 12 moves within the cylinder 11, so the piston la moves within the cylinder 13. The piston la is mounted on a tubular support 150 A seal 16 is provid~d between the cylinders 11 and 13, is fixed to the cylinder' 11 and allows sliding movement of the cylinder 13. The ram 7 has 'three volumes. A first volume 17 is between the external cylinder 11 and the tubular support 15 and bounded by the pistons 12 and 1~. A second volume 18 is contained within the internal cylinder 13 and is bounded by the piston 1~.
25 A third vo~lume 19 is fonmed between the external cylinder 11, the internal cylinder 13 and-is bounded by the piston 12 and thei`,seal 16. On extension of the ram koth volumes 17 and 18 increase and the volume 19 decreases, ana on retraction of the ram the volumes 17 and 18 decrease and volume 19 ~increases. Built into the base of the ram are valves~2~ 22 and 3~3 which are used to sontrol the ingress and egress of hydraulic ~luid in the three volumes of the ram. The operation of the valves 20, 21, 22 5 and 33 will be described later with reference to Figure a. 1.
The use of a single concentric ram satisfies the safety requirements in that it provides two hydraulically separate pressure c~ambers, and since these are placed concentrically one about the other, they not only avoid 10 the problems of offset constructional loading in the event of failure of one of the hydraulic systems, but also they permit the freedom of movement required by the plumbing movement of the ladder without ~he need to alter the volumes of the two pressure chambers differentially as would 15 be required if two separate rams were employed. Preferably, the effec~ive areas of the pistons 12 and 1~ should be the same so that the load is shared equally between the hydraulic systems feeding the volume 17 and the volume 18, and in the event of failure of either system the working 20 system is then subjected to just double its normal load. If any other relationship between the areas of the rams is employed, then the failure of the larger system would give rise to more than double the pressure in the smaller system. Since the piston 12 is annular and the piston la is circular, it 25 follows that to achieve the equal piston areas the internal diameter P of the external cylinder 11 should be ~2 x the internal diameter Q of the internal cyllnder 13. In order ~9~iS~
g 1:
to simplify servicing and reduce costs, it is preferable 1, that standard sizes of cylinder material and seals be employed and suitable combinations for the values of P and Q are:
P 6" 160 mm 1~0 mm Q ~" 110 mm 100 mm Figure ~, which is a hydraulic circuit diagram for controlling the dual concentric ram, shows the three volumes 17, 18 and 19 referred to in Figure 3, and the valves 20, 10 21, 22. and 33 shown in the base of the ram 7 in Figure 3., The valves 20 and 21 are load control valves and are connected to permit the flow of oil from the volumes 17 and 18 respectively when opened by a pilot signal supplied along a line 23. The valves 20 and 21 are by-passed by 15 one-way valves 2~ and 25 respectively which are arranged to allow fluid to enter the volumes 17 and 1~3. The fluid under pressure for extending ~he ram 7 is produced by an hydraulic pump 26 and applied to the valves 2~ and 25 through a three-position control valve 27 and a line 28. The line 28 20 is also connected to the load'co~trol valve 22 to open this valve and permit oil to escape from the volume 19 whilst the ram 7 is being exte~d.ed~.:~h'e~'return oil from the volume 19 passing through the load.co~l~.valv~'22'flows along-a line 29 and through the control valve 27 to a reservoir 30.
25 A fluid pressure control valve 31 is provided to limit the output pressure of the pump 26. The valve 33 is connected I
S5~ `
.~ .
between the volume 19 and the reservoir 30 to relieve excess pressure due to thermal expansion or certain combinations of seal and cylinder failure. The valves 22 and 33 are combined in a single cartridge (Fig.3).
In order to extend the ram 7 thé control valve 27 is moved to the left permitting oil to flow from the pump 26 ~.
through the line 28 and the valves 2~ and 25 into the volumes 17 and 18~ Oil ejected from the volume 19 is returned through the load control valve 22 held open by the 10 pressure in the line 28, which oil flows through the line 29 back through the control valve 27 to the reservoir 30.
Retraction of the ram 7 is effected by m~ving the control valve 27 to the right so that fluid pressure from the pump 26 flows along the line 29 through the valve 22 into the 15 volume 19. This fluid pressure is also applied via the line 23 to open the lo~d control valves 20 and 21 and permit the oil to be released from the volumes 17 and 18. Fluid pressure connections are also provided from the volumes 17 and 18 to control the load control valves 20 and 21 so that 20 any *endency for the ladder to depress too rapidly w.ill result in closure of the valves 20 and 21 as a result of the reduction in pressure. It has been found in practice that the valves 20 and 21 operate smoothly to contxol the pressure in the volumes 17 and 18.
2~ In order to prevent the ram 7 from being extended due to an external influence, such as wind pressure or water jet reaction, the valve 22 is provided to prevent oil from ~ ` ~L2~SS6~
leaving the volume 19 except when required to do soO Relief valve 33 is provided to limit induced pressure to a safe level.
For convenience and safety, by avoiding external connections the valves 20, 21, 22, 2~, 25 and 33 are all built into the base of the ram 7, as indicated by the ¦~
broken rectangle 32 in Figure ~. Conventional bleed nipples should be provided where necessary-in the hydraulic system to permit air to be forced out of the system which otherwise 10 would interfere with the effectiveness of the hydraulic control. This also provides a safe means of checking the correct individual operation of valves 20 and 21.
The invention can also be applied to an elevatable man~carrying platform to keep the platform level despite 15 inclination of the turntable carrying the platform. The use of a dual-concentric ram for elevating the arm carrying the platform would permit the plumbing of the platform to be carried out in a straightforward way whilst enabling the provision of the additional safety resulting from the use of independent hydraulic circuits to elevate the platform.
leaving the volume 19 except when required to do soO Relief valve 33 is provided to limit induced pressure to a safe level.
For convenience and safety, by avoiding external connections the valves 20, 21, 22, 2~, 25 and 33 are all built into the base of the ram 7, as indicated by the ¦~
broken rectangle 32 in Figure ~. Conventional bleed nipples should be provided where necessary-in the hydraulic system to permit air to be forced out of the system which otherwise 10 would interfere with the effectiveness of the hydraulic control. This also provides a safe means of checking the correct individual operation of valves 20 and 21.
The invention can also be applied to an elevatable man~carrying platform to keep the platform level despite 15 inclination of the turntable carrying the platform. The use of a dual-concentric ram for elevating the arm carrying the platform would permit the plumbing of the platform to be carried out in a straightforward way whilst enabling the provision of the additional safety resulting from the use of independent hydraulic circuits to elevate the platform.
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A turntable mounted elevatable ladder suitable for mounting on a vehicle, in which the ladder is mounted on an elevation axis parallel to rungs of the ladder, which axis is pivoted at its centre on the turntable and hydraulic ram means are provided to tilt the axis about its centre relative to the turntable thereby to raise and lower the ends of the axis about its centre so as to permit the axis and therefore also the rungs to be made horizontal when the turntable is inclined to the horizontal, wherein there is provided a single dual concentric hydraulic ram extending between self-aligning bearings on the turntable and on the ladder for elevating the ladder by rotating it about the elevation axis.
2. A ladder according to claim 1 wherein the dual concentric ram has two expansion cylinders, one outside the other, with diameters close to the ratio 1:?2 so that the piston areas of the two cylinders are substantially equal.
3. A ladder according to claim 2 wherein the two expansion cylinders of the dual concentric ram have individual lock valve for preventing undesired egress of oil from the expansion cylinders.
4. A ladder according to claim 2 wherein the dual concentric ram also includes a retraction volume.
5. A ladder according to claim 3 wherein the dual concentric ram also includes a retraction volume and a load control valve for preventing undesired egress of oil from the retraction volume due to external influences.
6. A ladder according to claim 3 or 5 wherein the lock valves are load control valves, controlled by a control pressure balanced against the pressure in the respective expansion cylinder.
7. A ladder according to claim 5 further including a relief valve to limit the pressure induced within the volumes of the dual-concentric ram.
8. A ladder according to claim 3 or 5 wherein the valves are built into the base of the dual-concentric ram.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08127094A GB2105298B (en) | 1981-09-08 | 1981-09-08 | Turntable mounted elevatable member |
| GB8127094 | 1981-09-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1209550A true CA1209550A (en) | 1986-08-12 |
Family
ID=10524365
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000410910A Expired CA1209550A (en) | 1981-09-08 | 1982-09-07 | Turntable mounted elevatable member |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1209550A (en) |
| DE (1) | DE3232597A1 (en) |
| GB (1) | GB2105298B (en) |
| IT (1) | IT1155232B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2924703B1 (en) * | 2007-12-11 | 2010-01-15 | Gimaex Internat | AERIAL LIFTING DEVICE AND VEHICLE EQUIPPED WITH SUCH A DEVICE |
-
1981
- 1981-09-08 GB GB08127094A patent/GB2105298B/en not_active Expired
-
1982
- 1982-09-02 DE DE19823232597 patent/DE3232597A1/en not_active Withdrawn
- 1982-09-07 IT IT49084/82A patent/IT1155232B/en active
- 1982-09-07 CA CA000410910A patent/CA1209550A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| IT1155232B (en) | 1987-01-21 |
| DE3232597A1 (en) | 1983-04-28 |
| GB2105298A (en) | 1983-03-23 |
| IT8249084A0 (en) | 1982-09-07 |
| GB2105298B (en) | 1985-05-30 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |