CA1227463A - Hydraulically operated cranes - Google Patents
Hydraulically operated cranesInfo
- Publication number
- CA1227463A CA1227463A CA000416599A CA416599A CA1227463A CA 1227463 A CA1227463 A CA 1227463A CA 000416599 A CA000416599 A CA 000416599A CA 416599 A CA416599 A CA 416599A CA 1227463 A CA1227463 A CA 1227463A
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- CA
- Canada
- Prior art keywords
- trolley
- hollow cylindrical
- crane
- sheave
- rope
- 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
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Abstract
ABSTRACT
A hydraulically operated crane of either the jib or bridge type it the hoist block supported from a trolley movable along the sup-port structure provided by the jib or bridge. The rope and sheave system to control the lifting and lowering of the hoist block provides a balanced fleet through system and the actuating power for the system is provided by a special hydraulic multiplying linear motor mounted in the jib or bridge. The arrangement of the sheaves is such that move-ment of the multiplying linear motor causes travel of the hoist rope to be balanced about the hoist block with the rope taken in or let out evenly over the trolley sheaves.
A hydraulically operated crane of either the jib or bridge type it the hoist block supported from a trolley movable along the sup-port structure provided by the jib or bridge. The rope and sheave system to control the lifting and lowering of the hoist block provides a balanced fleet through system and the actuating power for the system is provided by a special hydraulic multiplying linear motor mounted in the jib or bridge. The arrangement of the sheaves is such that move-ment of the multiplying linear motor causes travel of the hoist rope to be balanced about the hoist block with the rope taken in or let out evenly over the trolley sheaves.
Description
ABSTRACT
-A hydraulically opera-ted crane of either the jib or bridge type with the hoist block supported from a trolley movable along the sup-port structure provided by the jib or bridge. The rope and sheave system to control the lifting and lowering of the hoist block provides a balanced fleet through system and the actuating power for -the system is provided by a special hydraulic multiplying linear motor mounted in the jib or bridge. The arrangement of the sheaves is such that move-mint of the multiplying linear motor causes travel of the hoist rope to be balanced about the hoist block with the rope taken in or let out evenly over the trolley sheaves.
TITLE
"Improvements in or relating to hydraulically operated cranes".
This invention relates to hydraulically operated cranes.
BACKGROUND
_ The use of hydraulic power to operate cranes has been known and examples appear in the patent literature from an early time. Some of the more recent and more sophisticated examples can be found in United States Patent Specification Nazi, 2984191, 3872671, 3872674 and 3907120. Examples are also found in British patent literature and reference is made to British Patent Specification Noah and Noah.
Despite recognizing the possibility of adopting hydraulic prime movers the hydraulic crane has not met with any significant commercial 25 success. There are many reasons which contribute to this but print supply among the statewide or acknowledged disadvantages is -the tendency for hydraulic motors to leak or discharge oil. This is viewed as very undesirable in most situations where cranes will operate.
I believe the advantages which can be secured from the successful operation of a hydraulic crane considerably outweighs the disadvan-taxes particularly in view of the very high component cost necessary in an electrically powered crane and the high maintenance costs required to ensure satisfactory long term operation of such a crane.
By way of an example of such a disadvantage reference is specifically made to the energy dissipation means which must be incorporated in an electrically powered crane and these overheat and can lead to high maintenance costs or failure. I believe all these disadvantages can lo be overcome by the adoption of a hydraulically operated crane.
THE Present INvENTIorl Accordingly it is an object of the present invention to provide a hydraulically operated crane which will allow the advantages of a hydraulic system as opposed to an electrically operated crane system to be fully realized while also minimizing what has traditionally been accepted as the disadvantages of the hydraulic system.
It is another objective to introduce a means whereby forces in the hydraulic operating system are balanced tending to minimize wear or stress on some components and allowing for balanced and controlled movement of the load.
Accordingly in one aspect the invention consists in a hydraulic gaily operated crane comprising a support structure incorporating -trolley tracks, a -trolley traversable across said support structure, a hoist block supported from said trolley, rope and sheave system in said support structure to control the lifting or lowering of the hoist block and a separate sheave system in said support structure to control the traversing o-f the trolley across the support structure, with the rope and sheave system for the hoist providing a balanced fleet through system and with the actuating power for this system pro-voided by a hydraulic multiplying linear motor mounted in said support structure.
The support structure will usually comprise the jib of a power crane or the bridge of a traveling or fixed bridge crane.
A balanced fleet through system is easily achieved in the ire-versing mechanism by inserting a hydraulic multiplying linear motor in the support structure attached to the rope system controlling the movement or position of the trolley along that structure.
Lo In the case of the hoist block the balanced fleet through system comprises two revved sheaves movable by the hydraulic multiplying linear motor, a diverter sheave fixed in the structure and having the rope from one of the revved sheaves attached to the hydraulic multiplying motor passed thereabout, end return sheaves in the struck lure, trolley sheaves and a hoist block the construe lion and arrangement being such that with the introduction of the diverter sheave movement of the linear motor causes travel of the hoist rope to be balanced about the hoist block with the rope taken in or let out evenly over the trolley sheaves.
The hydraulic multiplying linear motor used can assume any known configuration which will move the revved sheaves to achieve the motions previously set forth. However, I have devised a hydraulic multiplying linear motor of particular configurations which I believe overcomes a number of the difficulties previously accounted with hydraulic systems and which would have an application outside -that specifically described with reference to the balanced fleet through system or indeed the crane itself.
Accordingly the hydraulic multiplying linear motor comprises twin opposed hydraulic cylinders, pistons operably arranged in said Solon-dons with each piston connected to the power takeoff point, tie rods connecting the operating cylinders over the operating length of the motion possible with the pistons, said motor being supported at least by fixing the end of one cylinder in the support structure and appropriately supporting the other cylinder.
In the present invention the hydraulic multiplying linear motor is connected so that -the revved sheave carrier is mounted at the power take-of point.
The opposed pistons connected to the power take-off are hollow with stopped ends adjacent the power take-off point so that in use the interior of the piston is filled with oil under pressure. This has two advantages. It means the weight of the assembly tending to create any bowing or bending moment in the structure has a counter-balancing effect as a consequence of the bourbon effect. Also the piston having oil under pressure is a better load carrier in the operating con-dictions experienced by the hydraulic multiplying linear motor.
Preferably the cylinder head assembly carries the sealing rings and guide bush in a manner which ensures easy maintenance and replace-mint.
Preferably the ropes are anchored relative to the reeve sheaves so that the forces generated upon load being applied through -the ropes -tends to balance, preventing or minimizing bending or eccentric load being placed on the pistons of the hydraulic multiplying linear motor.
US The opposed cylinder linear motor also operates in conjunction with the control mechanism adopted to take advantage of the metering out principle for speed control.
The cylinders in the linear motor are balanced with the input to lo 3 one cylinder balancing the output from the other cylinder in a manner such that the reserve supply of oil required in the system does not vary substantially. This allows a system to be operated either under a closed and controlled atmosphere or where there is little movement of air into and out of the reservoir tank thereby minimizing the dirt and other extraneous material what might otherwise be introduced into the system.
The support structure member for a traveling bridge crane pro-fireball comprises a hollow cylindrical structural member, a trolley Lo engaged about part of the circumference of the cylindrical structural member and running on rails substantially diametrically opposed through the cylindrical structural member and with the linear motor and associated sheaves and rope reeving used in the crane mounted within the cylindrical structural member.
The trolley is designed to support a torsional load relative to the cylindrical structural member.
The hydraulic control circuit for the crane includes including a hydraulic pump, a directional control valve to actuate a hydraulic motor in a forward or reverse direction and to connect the exhaust circuit through a control valve and metering valve with the control and metering valve used to regulate the speed and acceleration of the hydraulic motor.
Preferably the control valve delivers a flow of oil to the metering valve which compresses a biassing spring and opens a needle I valve.
Preferably the rate at which the oil is delivered -to the metering valve and the rate from the which the oil is discharged from -the valve in the control mode is the same and is independent of operator ~22'7~,~3 control.
DRYING DESCRIPTION
One preferred form of the invention and modifications thereof will now be described with reference to tune accompanying drawings in which Figure 1 is a part side elevation of a hydraulic crane according to the present invention, Figure 2 is d plan view of a crane in the mode of a traveling bridge crane again embodying the present invention, Figure 3 is a section -through A-A on figure 1, Figure 4 is an elevation of a hydraulic multiplying motor according to the present invention, Figure 5 is a plan view of the motor as shown in figure 4, Figure 6 is a detail of the cylinder head and sealing mechanism adopted therein, Figure 7 is a section through B-B on figure 5, Figure 8 is a section through C-C on figure 5, Figure 9 is a section through D-D on figure 5, Figure 10 is a schematic arrangement sorbing the rope reeving used for the hoist, Figure 11 is a schematic view showing -the rope reeving for the cross travel, Figure 12 is the control circuit for the cross travel across the bridge, Figure 13 is the hydraulic control circuit for the lifting and 25 lowering, and Figure 14 is the hydraulic control circuit For the long travel along the rails 4. PREFERRED EMBODIMENT
The preferred form of the invention will be described with reference to a traveling bridge crane although it will be appreciated that the invention in its various aspects may in the main be applied to any structure where the load is to be lifted and traversed relative to the structure. This of course includes tower cranes and other installations of the like type and also includes Goliath cranes. The predominant application for the invention will however be in the ire-violin bridge crane normally found in workshops warehouses or other areas requiring a lifting capacity.
The hydraulically operated crane 1 has as the main structural member 2 a cylindrical member formed by rolling or otherwise suitably forming from steel plates a member having a diameter consistent with the load to be lifted and the span. For example with a 10 tone crane of 20 moire span would involve a cylindrical member 2 having a diameter of approximately 1 Metro. This cylindrical member is carried on end carriers 3 which in turn are supported on rails carried in the usual manner on a suitable support structure such as -the top of a reinforced wall. It will be appreciated in the normal operation the rails will be parallel rails and the bridge 2 will move backwards and forwards along those rails.
Attached to one side of the cylinder 2 is a substantially horizon-tat rail 5 and approximately diametrically opposed thereto is a Further horizontal rail 6. A trolley 7 shown in figllre 2 comprises a framework 8 hooked about the member 2 is that wheels 9 supported in the frame will engage with the rail 5 and wheels 10 will engage with I the rail 6. In this way the trolley is supported hooked about the cylindrical structural member 2 with -the load being carried as a tangential load to the structural member. In this way a torsional load is applied to the bridge or main structural member 2 which maxim muses the efficiency of the tubular member. Strengthening ribs 11 are welded internally in the cylindrical member 2 at intervals at approxi-mutely 1l/2 metros to minims the likelihood of any localized buckling or failure as a consecluence of the horizontal loads being applied to the member.
It will be appreciated that the configuration adopted For the bridge of the crane could have an application without necessarily involving the remaining components of the invention. Louvre, it is highly desirable for this particular mode of bridge -to be used in con-junction with the remainder of the invention as will be explained horribly.
A lifting hook 12 is supported from a revved block 13 by a rope 14 which passes about sheaves 15 and 16 fixed to the trolley 7. It is desirable for maximizing maneuverability of the hook for the diameter of the sheaves 13, 15 and 16 and 17 and 18 to be kept as small as practicable. It will also be understood that in -the drawing a single rope system has been illustrated for simplicity but the invention could readily be applied to a multiple and particularly a two rope lifting system. The rope 14 after passing about the trolley sheaves 15 and 16 extends to the end of the bridge to pass about end return sheaves 17 and 18. The rope 14 after passing about the end return sheaves 17 then passes about a diverter sheave 19 which is fixed to the structural bridge before being connected to the sheave carrier at sheave 20. The rope 14 after passing about the end return sheaves 18 runs directly to the sheave carrier at sheave 21.
The sheave carrier sheaves 20 and 21 are supported on a hydraulic multiplying linear motor 22 which is illustrated in more detail in -figures 5 to 9.
The linear hydraulic motor is of a particular design and while i-t has special application in the present invention would also be apply-cable in other areas. There are a number of important and novel features in the design adopted for the linear hydraulic rotor.
The motor comprises two opposed cylinders 23 and 24 preferably being cylinders of the same diameter having operatively fitted therein piston rods 25 and 26 which are connected -to the sheave carrier 27.
The cylinders 23 and 24 are spaced apart by tie bars 28 with the operating distance of the linear motor controlled by the length of the tie bars.
A detail of the cylinder head as shown in figure 6, the piston 26 passes through a seal 29 and a guide bush 30 which is held in place by a retainer 31 bolted to the head by bolts 32. This particular construction allows for ease of maintenance in that split bushes can be removed when the bolts release the retainer and split seals are also designed to facilitate on-site maintenance.
Each of the pistons 25 and 26 is hollow with the stopped end adja-cent the sheave carrier. The volume in each of the cylinders and pistons is the same so that upon the sheave carrier being reciprocated through the operating distance the oil displaced from one equates with the oil introduced to the other. In this way there is no change of oil in the reserve tank enabling a sealed system to be use or at least minimizing the air movement into or out of the -tank which as explained previously has deleterious effects in the operation o-f the system.
The reeving system just described is schematically illustrated in Figure 10 end provides a balanced fleet -through system. The return sheaves 17 and 18 are fixed to the support structure as is also the diverter sheave 19.
~22'7~
The rope 14 is anchored at two points 32 and 33 in a plate 34 which is fixed at an angle to the end of the cylinder 24. This con-figuration is shown most clearly in figure 10 and it is designed so that the friction forces which operate on the piston are balanced.
The end 25 of the cylinder 23 is designed to be pinned to the support structure and the structure is also supported on a stand from under-neat on flexible brackets at each of the cylinder heads. It thisbway a stable structure is provided which will ensure that the linear hydraulic motor operates in a manner which will place the minimum stress and hence cause minimum wear to the seals. The possibility of any sag caused through the weight of the revved sheaves, sheave' carrier and pistons is to some extent off-set by the hollow pistons which are filled with oil under pressure and therefore tend to straighten under the bourbon effect. Sag is further reduced by the straightening effect of the hydraulic forces set up in the tie rods combined with the vertical flexibility of the supports so that as the bridge sags under load the reverse effect occurs on the engine.
The hydraulic control system will be described in detail hereafter but the pressure in the cylinders 23 and 24 are arranged such that the tie rods are always in tension. The cylinder 24 is the main operating cylinder and the cylinder 23 is a control cylinder which although playing a more minor role is still very significant from the point of view of operating of the linear motor and control.
With reference to figure 10 it will be apparent that operation of the linear motor reciprocates the revved sheaves 20 and 21. As these sheaves are moved to the left, the hook will be raised and as the sheaves are moved to the right the hook will be lowered. In either mode the rope 14 is either taken up or let down about the trolley ~2~7~163 sheaves 15 and 16 equally and this is caused because the rope 14 from the anchor point 32 passes about the sheave I and the deflector sheave 19 prior to returning to the end return sheave 17, in this way as the sheaves 20 and 21 move to the left the rope 14 will shorten the 5 length of the rope dependent from the sheave 15. Similarly taking the rope from the anchor point 33 it passes about the sheave 21 and then the end return sheaves 18 to the sheave 16. Movement in the same direction will also cause the rope to be raised about the sheave 16.
This balanced fleet through system has d number of control ad van-ala taxes in that -there is the minimum need to introduce braking or other controls to otherwise off-set eccentric or out of balance loads which can develop in the system The movement is more controlled and there is less likelihood of any jerking or rapid movement because of slack or rope stretch in the system when there is a change in the direct tonal movement In the illustrated example the linear motor has multiplying effect of 4 but this could be increased by introducing more sheaves in the system if -this was desired. With the illustrated example 1 moire of travel in the sheave carrier attached to the linear motor results in 2 meters ox movement of the hook Thus the operating pa stroke of the linear motor needs to be half of the required hook lift because of -the peculiar and special -features described such a distance of linear movement is feasible and normally the more complex reeving pattern which would be involved with more sheaves attached to the linear motor can be avoided.
Another peculiar advantage which can be achieved in the combined application o-f aspects according to the present invention is illustrated in figures 1 to 3 of the drawings where the linear motor and associated sheaves and rope reeving can be mounted inside -the Lo 3 cylindrical bridge 2 and below the neutral axis of the girder. This has a number of significant advantages. First, the lines of the completed crane are clean without any significant rope visibility in excess of that which would be visible in a conventional crane. The linear motor described is intended to minimize wear on components and hence should no-t be prone to leakage. However, in the event of any leakage occurring the oil would be discharged into the cylinder 2 and would not therefore fall into the area being serviced by the crane.
Secondly, the position of the linear motors below the neutral axis of La the girder not only reduces the deflection under load but also reduces the tensile stress in the girder. The effect is accentuated by the 'large forces created by the multiplying of the hoist ropes. Finally, by confining the motor and associated reeving system in the bridge i-t is confined and will not accumulate as much dirt as might otherwise be the case.
It is also necessary to ensure that the trolley 7 can be traversed across the bridge 2. Lucy traversing motion is achieved using a secondary 'linear motor 36 which is also located in the preferred embo-dominate within the bridge member 2. The linear motor has not been spew civically detailed in -the drawings but a schematic showing the opera-lion is illustrated in figure 11. The rope 37 is attached to the trolley 7 at points 38 and 39. The rope 37 passes about end return reeves 40 and 41 before returning to the sheave carrier 42 and the anchor sheaves 43 and 44. The operation of -this system is similar but simpler to that previously described. Movement of the linear motor 36 in one direction causes the trolley 7 to move across the bridge in one direction and movement in the opposite direction causes the return of the trolley. In -this case do is illustrated there is a multiplying ~L227~L~3 factor of 6 to 1 which means that the length of stroke required in the linear motor 36 can be less than that required in the main lifting linear motor.
For light duty work the convention winch drum with an endless rope driven by a single hydraulic motor would be suitable.
The hydraulic circuitry and control required is also designed to achieve specific advantages. In the drawings an electric motor 45 is mounted on a frame 46 associated with one end carriage. The electric motor drives a hydraulic pump which together with the hydraulic riser-lo void tank is housed in the chamber 47. The electrical control equip-mint necessary is also housed in this chamber.
The hydraulic control circuit necessary to operate the crane will be described horribly. The hydraulic circuits have been designed to achieve the following unique operating features. First, an operator may select any desired operating speed from almost zero to the maximum achievable by the system using a simple standard double depression type of pendant push button control station. Secondly, both positive and negative acceleration can be maintained constant irrespective of the load and are outside the control of the operator. The circuit adopted has a basic common factor which is applied to the lifting and the lowering of the load, the traversing of the trolley across the crane and the traversing of the bridge along the rails 4 where a bridge crane control is applied.
This common factor is based on the meter out principle of speed control which is to control the oil flow through the driving means by throttling the motion exhausts while the pump itself continues to run at full speed and full flow. There are many advantages which are 7~3 gained from this system but the main ones are stability as the driving means is always to some extent driven even when braking over-running loads as it occurs on the long travel and lowering and the fact that it facilitates pump pressure unloading at light loads on the crane hook and also facilitates the use of the desirable simple and inexpensive fixed displacement pump. However this does not preclude the use of a single variable displacement pressure compensated fro certain applications.
The control circuit will first be described with reference to lo figure 12 which is -the circuit for the cross travel of the trolley on the bridge. In the circuits like components will be given like numb biers and the positive displacement pump 50 driven by the electric motor 45 shown on the preceding drawings causes the oil to flow to the directional control valve 51 to the linear motor 36. The valve 51 is energized by the operator control and the directional arrows indicate the circuit connections possible. It is therefore apparent that in one position the pump will deliver oil under pressure to the side aye and in the other position the high pressure will be delivered to the side 36b. A relief valve 52 allows for oil to be exhausted in the event of excessive pressure build up. A spill-off valve 53 operates to control the pressure on the exhaust side of the circuit. This pressure has been set approximately 50 psi and if this pressure is exceeded the spill-off valve 9 operates allowing a bypass of oil back to the tank 54.
An interface valve 55 connects the exhaust circuit to the metering valve 56 and -thence back to the tank I The interface valve is capable of assuming three positions. In the Sinatra position illustrated the valve is closed preventing any passage of oil. If the interface valve is moved to the left oil can flow through to the metering valve 56. If the valve is moved to the right oil from the metering valve can flow through to exhaust to the tank 54.
The interface valve is important and must be able to assume any one of the three stated positions. To achieve this it is necessary for the control mechanism to be able to assume any one of the three stated positions. This can be achieved using a valve with two sole-nods. One solenoid operating as a push solenoid to move the valve to -the central position and -the second solenoid operating to take over to RIO move the valve to the accelerating mode if the control circuit is so actuated.
The flow of oil in the control circuit from the interface valve 55 into the metering valve 56 must be regulated so that there is -the same pressure drop irrespective of operating mode. As indicated above the pressure on the exhaust side through the spill-off valve is controlled at 50 psi. A control aperture 57 in the line between the interface valve and the metering valve results in a drop of pressure of half so that pressure at 50 psi is delivered to the metering valve at a pressure of 25 psi. When the interface valve is changed over to the decelerating mode the oil in the control chamber of the metering valve 56 is allowed to exhaust back to tank again -through the orifice 57 resulting in a further drop in pressure of 25 pounds, that is from the 25 pounds in the chamber to 0. This means that the flow in either direction is the same resulting in both acceleration and braking or deceleration Functioning at the same rate. The metering valve 56 is designed to control the rate at which oil in the exhaust circuit can pass back to the tank 54 through the filter 58. If the operator at the control mechanism pushes the controls necessary for acceleration ~2~3 the interface valve moves in the drawing to the left so that the 50 pound psi pressure can pass through the valve and through the orifice 57 to the metering chamber. This oil causes the piston 59 to be moved against the spring 60 opening the aperture 61 and thereby regulating the rate of oil which can be discharged through to the tank. As soon as the control circuit is set back to the central position the piston 59 is retained in the same position and hence the rate of movement of the notion remains constant. As soon as the interface valve is moved to the braking or the deceleration mode oil is displaced by the spring 60 to pass through the orifice 57 and valve 55 back to the tank I
The rate at which this oil is discharged and hence the rate at which the orifice 61 is closed is again the same as that for acceleration.
It will be apparent that this mode of operation is quite independent of the operator who can select a speed by actuating the controls but cannot control the rate at which that speed is increased or decreased and this is an important control function in the present invention.
Instead of using a biassing spring the piston 59 can also be post-toned using a convention single three position closed center direct tonal control valve operated by solenoids as described above.
If we now consider figure 14 the circuit for controlling the hoisting and lowering is illustrated. In this instance the hydraulic linear motor having the cylinders 23 and I is shown connected -to -the sheave carrier 27. In this case because of special protective requirelnents additional valves are introduced. It is necessary For 25 the circuit to include protection in the event of failure so that the load will not be dropped. This is achieved by including a drop check valve 62. Any failure in pressure will cause this valve to close and hold the load at the position adopted when the failure occurred. To i; I
enable the lowering circuit to operate it is necessary for a pilot control to maintain the drop check valve during the lowering mode.
This increases the pressure in the exhaust side and to prevent the spill-off valve aye operating at that lime a solenoid valve 63 is used which can isolate the spill-off valve aye. It is still necessary to have some pressure relief in the circuit and a pressure relief valve 64 is incorporated -to allow the exhaust oil to be spilled to tank a-t loll pressure and to provide the low pressure protection necessary for the cylinder 24. With these modifications the circuit is essentially Lo the same as that previously described. The constant displacement pump passes oil through the directional control valve and when the valve is arranged for lifting it is displaced to the left. Pressure is exerted in the cylinder 24 and the pressure in the exhaust circuit is retained at the 50 pounds per square inch pro-piously referred to which operates through the interface valve and metering valve to effect the speed and acceleration control as pro-piously described. In the lowering mode the solenoid valve 63 it energized thereby cutting out the valve aye. The oil is exhausted through valve 64 to tank 54 and at the same time sufficient pressure is caused to open the drop check valve 62. The speed and acceleration control is maintained in the same mode as that previously described.
As the valve aye is not Functioning in this mode it is also necessary to introduce a pressure reducing valve 65 so that the pressure applied to the speed and acceleration control through the interface and metering valve is maintained at 50 psi. The long travel circuit follows again a similar operating criteria and is illustrated in figure 14. In this case two separate hydraulic motors 67 and 68 are located on each side of the traveling bridge and are connected to the _ 18 -wheels of the bridge so that -they will provide motive power to cause one side or the other side of the bridge to be moved A sensor 69 is connected to the bridge on one side and operates from one of the horn-zontal rails or any other datum reference point selected to control the speeds of the motors and hence maintain the bridge in the correct configuration. The operator mode through the directional control valve is similar to that previously described as is also the interface and speed and acceleration control. The control circuit when in the braking mode has the motors 67 and 68 operating effectively as pumps.
lo It is therefore desirable to ensure that the oil displaced by the pump 50b does not further contribute to the pressures which will build up.
To this end a pressure relief valve 66 has been incorporated which will unload the main relief valve 52b in the standstill or braking conditions.
The directional control valves 51 and 51b are closed center valves so that when the controls are in the neutral position the valve is set to block the flow of oil to or from the motors controlling either the linear movement across the bridge or the motors controlling the long travel motion along the rail. This effectively operates as parking brakes for the crane.
-A hydraulically opera-ted crane of either the jib or bridge type with the hoist block supported from a trolley movable along the sup-port structure provided by the jib or bridge. The rope and sheave system to control the lifting and lowering of the hoist block provides a balanced fleet through system and the actuating power for -the system is provided by a special hydraulic multiplying linear motor mounted in the jib or bridge. The arrangement of the sheaves is such that move-mint of the multiplying linear motor causes travel of the hoist rope to be balanced about the hoist block with the rope taken in or let out evenly over the trolley sheaves.
TITLE
"Improvements in or relating to hydraulically operated cranes".
This invention relates to hydraulically operated cranes.
BACKGROUND
_ The use of hydraulic power to operate cranes has been known and examples appear in the patent literature from an early time. Some of the more recent and more sophisticated examples can be found in United States Patent Specification Nazi, 2984191, 3872671, 3872674 and 3907120. Examples are also found in British patent literature and reference is made to British Patent Specification Noah and Noah.
Despite recognizing the possibility of adopting hydraulic prime movers the hydraulic crane has not met with any significant commercial 25 success. There are many reasons which contribute to this but print supply among the statewide or acknowledged disadvantages is -the tendency for hydraulic motors to leak or discharge oil. This is viewed as very undesirable in most situations where cranes will operate.
I believe the advantages which can be secured from the successful operation of a hydraulic crane considerably outweighs the disadvan-taxes particularly in view of the very high component cost necessary in an electrically powered crane and the high maintenance costs required to ensure satisfactory long term operation of such a crane.
By way of an example of such a disadvantage reference is specifically made to the energy dissipation means which must be incorporated in an electrically powered crane and these overheat and can lead to high maintenance costs or failure. I believe all these disadvantages can lo be overcome by the adoption of a hydraulically operated crane.
THE Present INvENTIorl Accordingly it is an object of the present invention to provide a hydraulically operated crane which will allow the advantages of a hydraulic system as opposed to an electrically operated crane system to be fully realized while also minimizing what has traditionally been accepted as the disadvantages of the hydraulic system.
It is another objective to introduce a means whereby forces in the hydraulic operating system are balanced tending to minimize wear or stress on some components and allowing for balanced and controlled movement of the load.
Accordingly in one aspect the invention consists in a hydraulic gaily operated crane comprising a support structure incorporating -trolley tracks, a -trolley traversable across said support structure, a hoist block supported from said trolley, rope and sheave system in said support structure to control the lifting or lowering of the hoist block and a separate sheave system in said support structure to control the traversing o-f the trolley across the support structure, with the rope and sheave system for the hoist providing a balanced fleet through system and with the actuating power for this system pro-voided by a hydraulic multiplying linear motor mounted in said support structure.
The support structure will usually comprise the jib of a power crane or the bridge of a traveling or fixed bridge crane.
A balanced fleet through system is easily achieved in the ire-versing mechanism by inserting a hydraulic multiplying linear motor in the support structure attached to the rope system controlling the movement or position of the trolley along that structure.
Lo In the case of the hoist block the balanced fleet through system comprises two revved sheaves movable by the hydraulic multiplying linear motor, a diverter sheave fixed in the structure and having the rope from one of the revved sheaves attached to the hydraulic multiplying motor passed thereabout, end return sheaves in the struck lure, trolley sheaves and a hoist block the construe lion and arrangement being such that with the introduction of the diverter sheave movement of the linear motor causes travel of the hoist rope to be balanced about the hoist block with the rope taken in or let out evenly over the trolley sheaves.
The hydraulic multiplying linear motor used can assume any known configuration which will move the revved sheaves to achieve the motions previously set forth. However, I have devised a hydraulic multiplying linear motor of particular configurations which I believe overcomes a number of the difficulties previously accounted with hydraulic systems and which would have an application outside -that specifically described with reference to the balanced fleet through system or indeed the crane itself.
Accordingly the hydraulic multiplying linear motor comprises twin opposed hydraulic cylinders, pistons operably arranged in said Solon-dons with each piston connected to the power takeoff point, tie rods connecting the operating cylinders over the operating length of the motion possible with the pistons, said motor being supported at least by fixing the end of one cylinder in the support structure and appropriately supporting the other cylinder.
In the present invention the hydraulic multiplying linear motor is connected so that -the revved sheave carrier is mounted at the power take-of point.
The opposed pistons connected to the power take-off are hollow with stopped ends adjacent the power take-off point so that in use the interior of the piston is filled with oil under pressure. This has two advantages. It means the weight of the assembly tending to create any bowing or bending moment in the structure has a counter-balancing effect as a consequence of the bourbon effect. Also the piston having oil under pressure is a better load carrier in the operating con-dictions experienced by the hydraulic multiplying linear motor.
Preferably the cylinder head assembly carries the sealing rings and guide bush in a manner which ensures easy maintenance and replace-mint.
Preferably the ropes are anchored relative to the reeve sheaves so that the forces generated upon load being applied through -the ropes -tends to balance, preventing or minimizing bending or eccentric load being placed on the pistons of the hydraulic multiplying linear motor.
US The opposed cylinder linear motor also operates in conjunction with the control mechanism adopted to take advantage of the metering out principle for speed control.
The cylinders in the linear motor are balanced with the input to lo 3 one cylinder balancing the output from the other cylinder in a manner such that the reserve supply of oil required in the system does not vary substantially. This allows a system to be operated either under a closed and controlled atmosphere or where there is little movement of air into and out of the reservoir tank thereby minimizing the dirt and other extraneous material what might otherwise be introduced into the system.
The support structure member for a traveling bridge crane pro-fireball comprises a hollow cylindrical structural member, a trolley Lo engaged about part of the circumference of the cylindrical structural member and running on rails substantially diametrically opposed through the cylindrical structural member and with the linear motor and associated sheaves and rope reeving used in the crane mounted within the cylindrical structural member.
The trolley is designed to support a torsional load relative to the cylindrical structural member.
The hydraulic control circuit for the crane includes including a hydraulic pump, a directional control valve to actuate a hydraulic motor in a forward or reverse direction and to connect the exhaust circuit through a control valve and metering valve with the control and metering valve used to regulate the speed and acceleration of the hydraulic motor.
Preferably the control valve delivers a flow of oil to the metering valve which compresses a biassing spring and opens a needle I valve.
Preferably the rate at which the oil is delivered -to the metering valve and the rate from the which the oil is discharged from -the valve in the control mode is the same and is independent of operator ~22'7~,~3 control.
DRYING DESCRIPTION
One preferred form of the invention and modifications thereof will now be described with reference to tune accompanying drawings in which Figure 1 is a part side elevation of a hydraulic crane according to the present invention, Figure 2 is d plan view of a crane in the mode of a traveling bridge crane again embodying the present invention, Figure 3 is a section -through A-A on figure 1, Figure 4 is an elevation of a hydraulic multiplying motor according to the present invention, Figure 5 is a plan view of the motor as shown in figure 4, Figure 6 is a detail of the cylinder head and sealing mechanism adopted therein, Figure 7 is a section through B-B on figure 5, Figure 8 is a section through C-C on figure 5, Figure 9 is a section through D-D on figure 5, Figure 10 is a schematic arrangement sorbing the rope reeving used for the hoist, Figure 11 is a schematic view showing -the rope reeving for the cross travel, Figure 12 is the control circuit for the cross travel across the bridge, Figure 13 is the hydraulic control circuit for the lifting and 25 lowering, and Figure 14 is the hydraulic control circuit For the long travel along the rails 4. PREFERRED EMBODIMENT
The preferred form of the invention will be described with reference to a traveling bridge crane although it will be appreciated that the invention in its various aspects may in the main be applied to any structure where the load is to be lifted and traversed relative to the structure. This of course includes tower cranes and other installations of the like type and also includes Goliath cranes. The predominant application for the invention will however be in the ire-violin bridge crane normally found in workshops warehouses or other areas requiring a lifting capacity.
The hydraulically operated crane 1 has as the main structural member 2 a cylindrical member formed by rolling or otherwise suitably forming from steel plates a member having a diameter consistent with the load to be lifted and the span. For example with a 10 tone crane of 20 moire span would involve a cylindrical member 2 having a diameter of approximately 1 Metro. This cylindrical member is carried on end carriers 3 which in turn are supported on rails carried in the usual manner on a suitable support structure such as -the top of a reinforced wall. It will be appreciated in the normal operation the rails will be parallel rails and the bridge 2 will move backwards and forwards along those rails.
Attached to one side of the cylinder 2 is a substantially horizon-tat rail 5 and approximately diametrically opposed thereto is a Further horizontal rail 6. A trolley 7 shown in figllre 2 comprises a framework 8 hooked about the member 2 is that wheels 9 supported in the frame will engage with the rail 5 and wheels 10 will engage with I the rail 6. In this way the trolley is supported hooked about the cylindrical structural member 2 with -the load being carried as a tangential load to the structural member. In this way a torsional load is applied to the bridge or main structural member 2 which maxim muses the efficiency of the tubular member. Strengthening ribs 11 are welded internally in the cylindrical member 2 at intervals at approxi-mutely 1l/2 metros to minims the likelihood of any localized buckling or failure as a consecluence of the horizontal loads being applied to the member.
It will be appreciated that the configuration adopted For the bridge of the crane could have an application without necessarily involving the remaining components of the invention. Louvre, it is highly desirable for this particular mode of bridge -to be used in con-junction with the remainder of the invention as will be explained horribly.
A lifting hook 12 is supported from a revved block 13 by a rope 14 which passes about sheaves 15 and 16 fixed to the trolley 7. It is desirable for maximizing maneuverability of the hook for the diameter of the sheaves 13, 15 and 16 and 17 and 18 to be kept as small as practicable. It will also be understood that in -the drawing a single rope system has been illustrated for simplicity but the invention could readily be applied to a multiple and particularly a two rope lifting system. The rope 14 after passing about the trolley sheaves 15 and 16 extends to the end of the bridge to pass about end return sheaves 17 and 18. The rope 14 after passing about the end return sheaves 17 then passes about a diverter sheave 19 which is fixed to the structural bridge before being connected to the sheave carrier at sheave 20. The rope 14 after passing about the end return sheaves 18 runs directly to the sheave carrier at sheave 21.
The sheave carrier sheaves 20 and 21 are supported on a hydraulic multiplying linear motor 22 which is illustrated in more detail in -figures 5 to 9.
The linear hydraulic motor is of a particular design and while i-t has special application in the present invention would also be apply-cable in other areas. There are a number of important and novel features in the design adopted for the linear hydraulic rotor.
The motor comprises two opposed cylinders 23 and 24 preferably being cylinders of the same diameter having operatively fitted therein piston rods 25 and 26 which are connected -to the sheave carrier 27.
The cylinders 23 and 24 are spaced apart by tie bars 28 with the operating distance of the linear motor controlled by the length of the tie bars.
A detail of the cylinder head as shown in figure 6, the piston 26 passes through a seal 29 and a guide bush 30 which is held in place by a retainer 31 bolted to the head by bolts 32. This particular construction allows for ease of maintenance in that split bushes can be removed when the bolts release the retainer and split seals are also designed to facilitate on-site maintenance.
Each of the pistons 25 and 26 is hollow with the stopped end adja-cent the sheave carrier. The volume in each of the cylinders and pistons is the same so that upon the sheave carrier being reciprocated through the operating distance the oil displaced from one equates with the oil introduced to the other. In this way there is no change of oil in the reserve tank enabling a sealed system to be use or at least minimizing the air movement into or out of the -tank which as explained previously has deleterious effects in the operation o-f the system.
The reeving system just described is schematically illustrated in Figure 10 end provides a balanced fleet -through system. The return sheaves 17 and 18 are fixed to the support structure as is also the diverter sheave 19.
~22'7~
The rope 14 is anchored at two points 32 and 33 in a plate 34 which is fixed at an angle to the end of the cylinder 24. This con-figuration is shown most clearly in figure 10 and it is designed so that the friction forces which operate on the piston are balanced.
The end 25 of the cylinder 23 is designed to be pinned to the support structure and the structure is also supported on a stand from under-neat on flexible brackets at each of the cylinder heads. It thisbway a stable structure is provided which will ensure that the linear hydraulic motor operates in a manner which will place the minimum stress and hence cause minimum wear to the seals. The possibility of any sag caused through the weight of the revved sheaves, sheave' carrier and pistons is to some extent off-set by the hollow pistons which are filled with oil under pressure and therefore tend to straighten under the bourbon effect. Sag is further reduced by the straightening effect of the hydraulic forces set up in the tie rods combined with the vertical flexibility of the supports so that as the bridge sags under load the reverse effect occurs on the engine.
The hydraulic control system will be described in detail hereafter but the pressure in the cylinders 23 and 24 are arranged such that the tie rods are always in tension. The cylinder 24 is the main operating cylinder and the cylinder 23 is a control cylinder which although playing a more minor role is still very significant from the point of view of operating of the linear motor and control.
With reference to figure 10 it will be apparent that operation of the linear motor reciprocates the revved sheaves 20 and 21. As these sheaves are moved to the left, the hook will be raised and as the sheaves are moved to the right the hook will be lowered. In either mode the rope 14 is either taken up or let down about the trolley ~2~7~163 sheaves 15 and 16 equally and this is caused because the rope 14 from the anchor point 32 passes about the sheave I and the deflector sheave 19 prior to returning to the end return sheave 17, in this way as the sheaves 20 and 21 move to the left the rope 14 will shorten the 5 length of the rope dependent from the sheave 15. Similarly taking the rope from the anchor point 33 it passes about the sheave 21 and then the end return sheaves 18 to the sheave 16. Movement in the same direction will also cause the rope to be raised about the sheave 16.
This balanced fleet through system has d number of control ad van-ala taxes in that -there is the minimum need to introduce braking or other controls to otherwise off-set eccentric or out of balance loads which can develop in the system The movement is more controlled and there is less likelihood of any jerking or rapid movement because of slack or rope stretch in the system when there is a change in the direct tonal movement In the illustrated example the linear motor has multiplying effect of 4 but this could be increased by introducing more sheaves in the system if -this was desired. With the illustrated example 1 moire of travel in the sheave carrier attached to the linear motor results in 2 meters ox movement of the hook Thus the operating pa stroke of the linear motor needs to be half of the required hook lift because of -the peculiar and special -features described such a distance of linear movement is feasible and normally the more complex reeving pattern which would be involved with more sheaves attached to the linear motor can be avoided.
Another peculiar advantage which can be achieved in the combined application o-f aspects according to the present invention is illustrated in figures 1 to 3 of the drawings where the linear motor and associated sheaves and rope reeving can be mounted inside -the Lo 3 cylindrical bridge 2 and below the neutral axis of the girder. This has a number of significant advantages. First, the lines of the completed crane are clean without any significant rope visibility in excess of that which would be visible in a conventional crane. The linear motor described is intended to minimize wear on components and hence should no-t be prone to leakage. However, in the event of any leakage occurring the oil would be discharged into the cylinder 2 and would not therefore fall into the area being serviced by the crane.
Secondly, the position of the linear motors below the neutral axis of La the girder not only reduces the deflection under load but also reduces the tensile stress in the girder. The effect is accentuated by the 'large forces created by the multiplying of the hoist ropes. Finally, by confining the motor and associated reeving system in the bridge i-t is confined and will not accumulate as much dirt as might otherwise be the case.
It is also necessary to ensure that the trolley 7 can be traversed across the bridge 2. Lucy traversing motion is achieved using a secondary 'linear motor 36 which is also located in the preferred embo-dominate within the bridge member 2. The linear motor has not been spew civically detailed in -the drawings but a schematic showing the opera-lion is illustrated in figure 11. The rope 37 is attached to the trolley 7 at points 38 and 39. The rope 37 passes about end return reeves 40 and 41 before returning to the sheave carrier 42 and the anchor sheaves 43 and 44. The operation of -this system is similar but simpler to that previously described. Movement of the linear motor 36 in one direction causes the trolley 7 to move across the bridge in one direction and movement in the opposite direction causes the return of the trolley. In -this case do is illustrated there is a multiplying ~L227~L~3 factor of 6 to 1 which means that the length of stroke required in the linear motor 36 can be less than that required in the main lifting linear motor.
For light duty work the convention winch drum with an endless rope driven by a single hydraulic motor would be suitable.
The hydraulic circuitry and control required is also designed to achieve specific advantages. In the drawings an electric motor 45 is mounted on a frame 46 associated with one end carriage. The electric motor drives a hydraulic pump which together with the hydraulic riser-lo void tank is housed in the chamber 47. The electrical control equip-mint necessary is also housed in this chamber.
The hydraulic control circuit necessary to operate the crane will be described horribly. The hydraulic circuits have been designed to achieve the following unique operating features. First, an operator may select any desired operating speed from almost zero to the maximum achievable by the system using a simple standard double depression type of pendant push button control station. Secondly, both positive and negative acceleration can be maintained constant irrespective of the load and are outside the control of the operator. The circuit adopted has a basic common factor which is applied to the lifting and the lowering of the load, the traversing of the trolley across the crane and the traversing of the bridge along the rails 4 where a bridge crane control is applied.
This common factor is based on the meter out principle of speed control which is to control the oil flow through the driving means by throttling the motion exhausts while the pump itself continues to run at full speed and full flow. There are many advantages which are 7~3 gained from this system but the main ones are stability as the driving means is always to some extent driven even when braking over-running loads as it occurs on the long travel and lowering and the fact that it facilitates pump pressure unloading at light loads on the crane hook and also facilitates the use of the desirable simple and inexpensive fixed displacement pump. However this does not preclude the use of a single variable displacement pressure compensated fro certain applications.
The control circuit will first be described with reference to lo figure 12 which is -the circuit for the cross travel of the trolley on the bridge. In the circuits like components will be given like numb biers and the positive displacement pump 50 driven by the electric motor 45 shown on the preceding drawings causes the oil to flow to the directional control valve 51 to the linear motor 36. The valve 51 is energized by the operator control and the directional arrows indicate the circuit connections possible. It is therefore apparent that in one position the pump will deliver oil under pressure to the side aye and in the other position the high pressure will be delivered to the side 36b. A relief valve 52 allows for oil to be exhausted in the event of excessive pressure build up. A spill-off valve 53 operates to control the pressure on the exhaust side of the circuit. This pressure has been set approximately 50 psi and if this pressure is exceeded the spill-off valve 9 operates allowing a bypass of oil back to the tank 54.
An interface valve 55 connects the exhaust circuit to the metering valve 56 and -thence back to the tank I The interface valve is capable of assuming three positions. In the Sinatra position illustrated the valve is closed preventing any passage of oil. If the interface valve is moved to the left oil can flow through to the metering valve 56. If the valve is moved to the right oil from the metering valve can flow through to exhaust to the tank 54.
The interface valve is important and must be able to assume any one of the three stated positions. To achieve this it is necessary for the control mechanism to be able to assume any one of the three stated positions. This can be achieved using a valve with two sole-nods. One solenoid operating as a push solenoid to move the valve to -the central position and -the second solenoid operating to take over to RIO move the valve to the accelerating mode if the control circuit is so actuated.
The flow of oil in the control circuit from the interface valve 55 into the metering valve 56 must be regulated so that there is -the same pressure drop irrespective of operating mode. As indicated above the pressure on the exhaust side through the spill-off valve is controlled at 50 psi. A control aperture 57 in the line between the interface valve and the metering valve results in a drop of pressure of half so that pressure at 50 psi is delivered to the metering valve at a pressure of 25 psi. When the interface valve is changed over to the decelerating mode the oil in the control chamber of the metering valve 56 is allowed to exhaust back to tank again -through the orifice 57 resulting in a further drop in pressure of 25 pounds, that is from the 25 pounds in the chamber to 0. This means that the flow in either direction is the same resulting in both acceleration and braking or deceleration Functioning at the same rate. The metering valve 56 is designed to control the rate at which oil in the exhaust circuit can pass back to the tank 54 through the filter 58. If the operator at the control mechanism pushes the controls necessary for acceleration ~2~3 the interface valve moves in the drawing to the left so that the 50 pound psi pressure can pass through the valve and through the orifice 57 to the metering chamber. This oil causes the piston 59 to be moved against the spring 60 opening the aperture 61 and thereby regulating the rate of oil which can be discharged through to the tank. As soon as the control circuit is set back to the central position the piston 59 is retained in the same position and hence the rate of movement of the notion remains constant. As soon as the interface valve is moved to the braking or the deceleration mode oil is displaced by the spring 60 to pass through the orifice 57 and valve 55 back to the tank I
The rate at which this oil is discharged and hence the rate at which the orifice 61 is closed is again the same as that for acceleration.
It will be apparent that this mode of operation is quite independent of the operator who can select a speed by actuating the controls but cannot control the rate at which that speed is increased or decreased and this is an important control function in the present invention.
Instead of using a biassing spring the piston 59 can also be post-toned using a convention single three position closed center direct tonal control valve operated by solenoids as described above.
If we now consider figure 14 the circuit for controlling the hoisting and lowering is illustrated. In this instance the hydraulic linear motor having the cylinders 23 and I is shown connected -to -the sheave carrier 27. In this case because of special protective requirelnents additional valves are introduced. It is necessary For 25 the circuit to include protection in the event of failure so that the load will not be dropped. This is achieved by including a drop check valve 62. Any failure in pressure will cause this valve to close and hold the load at the position adopted when the failure occurred. To i; I
enable the lowering circuit to operate it is necessary for a pilot control to maintain the drop check valve during the lowering mode.
This increases the pressure in the exhaust side and to prevent the spill-off valve aye operating at that lime a solenoid valve 63 is used which can isolate the spill-off valve aye. It is still necessary to have some pressure relief in the circuit and a pressure relief valve 64 is incorporated -to allow the exhaust oil to be spilled to tank a-t loll pressure and to provide the low pressure protection necessary for the cylinder 24. With these modifications the circuit is essentially Lo the same as that previously described. The constant displacement pump passes oil through the directional control valve and when the valve is arranged for lifting it is displaced to the left. Pressure is exerted in the cylinder 24 and the pressure in the exhaust circuit is retained at the 50 pounds per square inch pro-piously referred to which operates through the interface valve and metering valve to effect the speed and acceleration control as pro-piously described. In the lowering mode the solenoid valve 63 it energized thereby cutting out the valve aye. The oil is exhausted through valve 64 to tank 54 and at the same time sufficient pressure is caused to open the drop check valve 62. The speed and acceleration control is maintained in the same mode as that previously described.
As the valve aye is not Functioning in this mode it is also necessary to introduce a pressure reducing valve 65 so that the pressure applied to the speed and acceleration control through the interface and metering valve is maintained at 50 psi. The long travel circuit follows again a similar operating criteria and is illustrated in figure 14. In this case two separate hydraulic motors 67 and 68 are located on each side of the traveling bridge and are connected to the _ 18 -wheels of the bridge so that -they will provide motive power to cause one side or the other side of the bridge to be moved A sensor 69 is connected to the bridge on one side and operates from one of the horn-zontal rails or any other datum reference point selected to control the speeds of the motors and hence maintain the bridge in the correct configuration. The operator mode through the directional control valve is similar to that previously described as is also the interface and speed and acceleration control. The control circuit when in the braking mode has the motors 67 and 68 operating effectively as pumps.
lo It is therefore desirable to ensure that the oil displaced by the pump 50b does not further contribute to the pressures which will build up.
To this end a pressure relief valve 66 has been incorporated which will unload the main relief valve 52b in the standstill or braking conditions.
The directional control valves 51 and 51b are closed center valves so that when the controls are in the neutral position the valve is set to block the flow of oil to or from the motors controlling either the linear movement across the bridge or the motors controlling the long travel motion along the rail. This effectively operates as parking brakes for the crane.
Claims (22)
1. A hydraulically operated crane comprising a support structure including a hollow cylindrical traveling bridge having a cylindrical wall and trolley tracks on the outside of said wall, a trolley traversible across said cylindrical bridge on said tracks, said tracks being so located for the trolley to produce a tangential load through the cylindrical wall with no local bending of said wall, a hoist block supported from said trolley, a rope and sheave system of the balanced fleet through type to control the lifting or lowering of the hoist block, said rope and sheave system comprising a rope, a multiplying system, trolley sheaves on said trolley, end sheaves mounted on the support structure at each end of the cylinder and a diverter sheave mounted on the support structure, the rope being reeved through the hoist block and trolley sheaves and about the end sheaves, with one end of the rope then returning directly to the multiplying system and the other end of the rope passing about the diverter sheave prior to returning to the multiplying system, and a separate rope and sheave system to control the traversing of the trolley across the bridge.
2. A hydraulically operated crane comprising a support structure, trolley tracks on said support structure, a trolley supported on said tracks, a hoist block supported from said trolley, a balanced fleet through rope and reeve system supported by said structure to control the lifting and lowering of the hoist block, a hydraulic multiplying linear motor having one end anchored in the support structure to provide operating power for the hoist block, said linear motor having twin opposed hydraulic cylinders, tie rods connecting the cylinders in line with the length of tie rods between adjacent ends of the cylinders determining the operating stroke of the linear motor, a reeve sheave carrier connected in the space between the cylinders to each operating piston extending from the cylinders, two reeve sheaves mounted on said reeve sheave carrier, end return sheaves at each end of said support structure, two trolley sheaves mounted on said trolley and a diverter sheave supported in said support structure with the operating rope for the hoist block having the ends anchored to a support base associated with the linear motor with the rope from one anchor point passing about one reeve sheave mounted on the reeve carrier supported by the pistons of the linear motor, and the end return sheaves at the end of the structure before being returned to the trolley sheave and about the hoist block and the rope from the other anchor point passing about the second reeve sheave on the reeve carrier supported by the pistons of the linear motor and about the diverter sheave before returning to pass about the end return sheaves at the opposite end of the structure and then to the second trolley sheave about the hoist block.
3. A crane as claimed in claim 2 wherein the pistons in the linear motor are hollow with stopped ends adjacent the reeve carrier so that in use the interior of the piston is filled with oil under pressure.
4. A crane as claimed in claim 2 wherein the ends of the rope for the hoist block are mounted on a mounting plate fixed to the end of one cylinder and at an angle designed so that the frictional forces which operate on the piston are balanced.
5. A crane as claimed in claim 2 wherein the support structure comprises a hollow cylindrical travelling bridge with trolley tracks on said cylindrical travelling bridge to support the trolley to the side of said cylindrical travelling bridge.
6. A crane as claimed in claim 5 wherein the linear motor and associated sheaves and rope reeving used in the crane are mounted within the cylindrical travelling bridge.
7. A crane as claimed in claim 2 wherein the travers-ing mechanism for the trolley comprises a rope and sheave system with the actuating power for this system being provided by a hydraulic multiplying linear motor.
8. A crane as claimed in claim 2 wherein a greater number of reeve blocks may be supported by the reeve carrier to provide a greater mechanical advantage between the operating stroke of linear motor and the distance moved by the hoist blocks.
9. A crane as claimed in claim 2 wherein the hydraulic control circuit or the crane includes a hydraulic pump, a directional control valve to actuate the hydraulic motor in a forward or reverse direction and to connect the exhaust circuits to a control valve and metering valve with the control and metering valve used to regulate the speed and acceleration of the hydraulic motor.
10. A crane as claimed in claim 9 wherein the control valve comprises a three positional hydraulic valve in one position delivering oil to one side of the hydraulic motor, in another position delivering oil to the other side of the hydraulic motor and in the third position closing off the flow of oil with the exhaust flow of oil from the control valve passing through the metering valve that can be opened or closed or maintained in a particular position using an operator controlled interface valve which inter-face valve in a first position allows a flow of oil to pass to open at a regulated rate the metering valve and in a second position allows a flow of oil to close at a regulated rate the metering valve and in the third position allows no oil to pass through the metering valve thereby effecting no alteration to the positioning of the metering valve.
11. A hydraulically operated crane comprising a support structure having a hollow cylindrical travelling bridge, trolley tracks on said cylindrical travelling bridge to support the trolley to a side of said travelling bridge, a hoist block supported from said trolley, a balanced fleet through rope and reeve system supported by said structure to control the lifting and lowering of the hoist block, a hydraulic multiplying linear motor having one end anchored in the support structure to provide operating power for the hoist block, said linear motor having twin opposed hydraulic cylinders, tie rods con-necting the cylinders in line with the length of tie rods between adjacent ends of the cylinders determining the operating stroke of the linear motor, a reeve sheave carrier connected in the space between the cylinders to each operating piston extending from the cylinders, two reeve sheaves mounted on said reeve sheave carrier, and return sheaves at each end of said support structure, two trolley sheaves mounted on said trolley and a diverter sheave supporter in said support structure with the operating rope for the hoist block having the ends anchored to a support base associated with the linear motor with the rope from one anchor point passing about one reeve sheave mounted on the reeve carrier supported by the pistons of the linear motor, and the end return sheaves at the end of the structure before being returned to the trolley sheave and about the hoist block and the rope from the other anchor point passing about the second reeve sheave on the reeve carrier supported by the pistons of the linear motor and about the diverter sheave before returning to pass about the end return sheaves at the opposite end of the structure and then to the second trolley sheave about the hoist block.
12. A crane comprising hollow cylindrical load trolley supporting girder means, support means for said hollow cylindrical girder means, trolley track means on the outside of the hollow cylindrical girder means for traversing a load along the hollow cylindrical girder, and a load trolley supported upon said trolley track means with the trolley track means arranged so that the line of action of the load forces is applied tangentially to said hollow cylindrical girder means.
13. A crane as claimed in claim 12 wherein the hollow cylindrical girder means comprises a single hollow cylindrical girder with the trolley track means comprising in turn an action rail attached to the outside of the single hollow cylindrical girder with the line of action of the load forces supported by the action rail applied tangentially substantially through the center line of the wall of the single hollow cylindrical girder and with a reaction rail attached to the opposite outside of the hollow cylindrical girder.
14. A crane as claimed in claim 13 wherein the action rail is supported by a support plate located so that the line of action of the load passes substantially centrally through the support plate and the wall of the single hollow cylindrical girder substantially at the horizontal axis of the girder.
15. A crane as claimed in claim 14 wherein the reaction rail is supported in a manner similar to the action rail with the reaction force passing substantially through the centre of the wall of the hollow cylindrical girder.
16. A crane comprising twin parallel hollow cylindrical girders, support means for said twin parallel hollow cylindrical girders, action trolley tracks on the outside of adjacent surfaces of each of the said twin parallel hollow cylindrical girders for traversing a load along said twin parallel hollow cylindrical girders, and a load trolley supported upon the action trolley tracks between the twin parallel hollow cylindrical girders so that the load is divided and the line of action of each component is applied tangentially to the associated hollow cylindrical girder.
17. A crane as claimed in claim 16 wherein each action rail is supported by a support plate located so that the line of action of the load passes substantially centrally through the support plate and the wall of the associated hollow cylindrical girder substantially at the horizontal axis of the girder.
18. A crane comprising hollow cylindrical load trolley supporting girder means, support means for said hollow cylindrical girder means, trolley track means on the outside of the hollow cylindrical girder means for traversing a load along the hollow cylindrical girder, a load trolley supported upon said trolley track means with the trolley track means arranged so that the line of action of the load forces is applied tangentially to said hollow cylindrical girder means, and reinforcing means associated with said hollow cylindrical girder means.
19. A crane as claimed in claim 18 wherein said reinforcing means comprises a reinforcing member welded to the top of each hollow cylindrical girder making up the hollow cylindrical girder means at the centre top to strengthen and raise the neutral axis of said hollow cylindrical girder.
20. A crane comprising hollow cylindrical load trolley supporting girder means, support means for said hollow cylindrical girder means, trolley track means on the outside of the hollow cylindrical girder means for traversing a load along the hollow cylindrical girder, a load trolley supported upon said trolley track means with the trolley track means arranged so that the line of action of the load force is applied tangentially to the said hollow cylindrical girder means, and hogging means mounted towards the base of said hollow cylindrical girder, said hogging means comprising a tensioning member extending the length of said hollow cylindrical girder means and anchored substantially to the ends thereof and tensioning means acting to induce a tension in said tension member.
21. A crane as claimed in claim 20 wherein a hydraulic hoist ram and associated rope and sheave system is mounted in the interior of the hollow cylindrical crane towards the base thereof with the anchor point of the hoisting cylinder attached to a lever pivotally supported on an anchor point and providing on the opposite side of the pivotal anchor point a mounting for said tensioning member with the tensioning member extending the length of the girder on the under side thereof so that the reaction force generated by the lifting cylinder is transmitted through the lever to tension the tensioning member.
22. A crane as claimed in claim 20 wherein a hydraulic cylinder is incorporated in a tensioning rod running towards the bottom of said hollow cylinder with said hydraulic cylinder generating the required tensioning force in the tensioning rod.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000416599A CA1227463A (en) | 1982-11-29 | 1982-11-29 | Hydraulically operated cranes |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000416599A CA1227463A (en) | 1982-11-29 | 1982-11-29 | Hydraulically operated cranes |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1227463A true CA1227463A (en) | 1987-09-29 |
Family
ID=4124043
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000416599A Expired CA1227463A (en) | 1982-11-29 | 1982-11-29 | Hydraulically operated cranes |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1227463A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101920907A (en) * | 2010-09-11 | 2010-12-22 | 大连华锐股份有限公司 | Main trolley of large shipbuilding portal crane |
-
1982
- 1982-11-29 CA CA000416599A patent/CA1227463A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101920907A (en) * | 2010-09-11 | 2010-12-22 | 大连华锐股份有限公司 | Main trolley of large shipbuilding portal crane |
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