Patent Application
20130168186
The invention relates to a hoisting device. The invention also relates to a component module for a hoisting or transferring device. Furthermore, the invention relates to a method in a hoisting device.
In various works, such as construction, repairing and maintenance works, various movable hoisting devices are used for lifting a person to a desired height level to perform the work.
In said hoisting devices, for example compressed air is applied as a pressurized medium effective on telescopic pneumatic cylinders for lifting loads, such as persons and tools. The compressed air has a given pressure level, for example 6 bar, and when the compressed air is fed into the cylinder, the pressure is effective on the inner surfaces of the cylinder in such a way that forces are generated which tend to extend the cylinder in its longitudinal direction. Said forces effective in the longitudinal direction of the cylinder are also transferred by the cylinder to the load connected to the cylinder, which load can thus be moved, for example elevated. The total force effective on the load depends in a known way on the product of the pressure level and the surface area. The effective surface area on which the pressure acts to extend the cylinder, depends on the structure of the cylinder and is typically equal to the surface area of the moving piston of the cylinder or the largest cross-sectional area of the inner part of the cylinder. The total force has to be sufficiently high to overcome an opposite force caused by the load and further to transfer the load by extending the cylinder. Opposite forces are also generated by friction caused by the cylinder and the load. The required total force can be determined in a way known as such, for example by applying the power balance equation of the cylinder.
For example, if the pressure level is 6 bar (600 kPa, 600 kN/m2) and the effective surface area of one cylinder is 0.002 m2, the power to be generated is 1.2 kN, which is sufficient for supporting a load of about 120 kg. In a corresponding manner, with two corresponding cylinders, said force can be carried by a pressure of only 3 bar.
Document DE-3909370-A1 discloses an example of a telescopic cylinder which is single acting in such a way that compressed air is used to extend the cylinder. The cylinder is contracted mechanically by using, for example, a winch and a cable. The cylinder can also be locked in a desired length by the winch. Document EP-0016921-A1 also discloses a telescopic cylinder which is coupled by a hose to a pressure tank. The cylinder is contracted mechanically by using, for example, a winch and a cable. Document US-2009/0057636-A1 discloses a lift device with a telescopic cylinder which is subject to constant pressure by a medium. The cylinder is allowed to extend by the effect of pressure, or the cylinder is retracted by means of a winch and a cable, by which the cylinder can also be locked in a desired length. The cylinder is connected by a hose to a pressure reservoir which is thus used as a storage for the medium during the use of the lift device. By means of cylinders, a lifted platform and a frame, a portable lift device is formed. The cylinders and pressure reservoirs are connected to the frame equipped with wheels.
The aim of the invention is to eliminate problems and drawbacks of the above-mentioned cylinders and particularly hoisting devices constructed by applying them, for example aerial work platforms.
The hoisting device according to the invention is presented in claim 1. The component module according to the invention is presented in claim 15. The method according to the invention is presented in claim 19.
In the hoisting device, hoisting is effected by means of a pressurized medium, and lowering by means of a mechanical retractor. The pressure of the medium is maintained constantly, and the lowering is performed by applying the retractor to generate a force to compress the medium.
An example of the solution has the significant advantage of a simple hoisting structure, in which the closed cylinder space is utilized for storing the pressurized medium. The pressure and the compressibility of the medium are utilized in elevating and lowering the work platform of the hoisting device. With the presented arrangement, the use and transportation of separate pressure tanks and connecting them to the cylinder are avoided.
In another example of the solution, a significant advantage is the simple integrated structure of the hoisting device, where the cavities, chambers or corresponding closed inner spaces are utilized for storing the pressurized medium. The pressurized medium in these spaces is in connection with the chamber of the medium in the cylinder. The connection is preferably free in such a way that the medium can move freely from the space into the cylinder when the cylinder is expanding, and from the cylinder into the space when the cylinder is retracting. The presented arrangement avoids the use and transportation of separate pressure tanks and connecting them to the hoisting device.
In the solution according to a third example, the chamber is an auxiliary chamber connected to or integrated in the cylinder structure and in connection with the chamber of the medium in the cylinder. The auxiliary chamber is in use either alone or together with the other chambers, operating according to their principles.
In the presented solutions, also a retractor, for example a winch, that can be controlled by e.g. a motor, is utilized for controlling the length of the cylinder. By means of the retractor, the cylinder can also be locked in a desired length, which also stabilizes the cylinder.
In particular, the presented solution utilizes hollow tubular structures which provide spaces for storing the pressurized medium. By utilizing various spaces, a large total volume of the medium is achieved, particularly compared with the volume of a conventional cylinder, wherein the pressure variations of the medium are smaller. The pressure variations result from changes in the volume of the cylinder. The dependence of the pressure variations on the change in the volume is known as such from the dependence presented, for example, in Boyle's law. The large total volume of the medium can also be achieved by a separate pressure reservoir according to the prior art, involving large pressure reservoirs which are difficult to use.
The presented solution provides a discrete hoisting device which is independent of medium distribution networks and which can also be transferred to a site without a medium distribution network available. The use of separate pressure reservoirs is also avoided with the solution.
With the presented solution, it is possible to construct a safe, low-pressure system that is well suited for construction, repair and maintenance works. The system is particularly a passenger hoist. The hoisting force required of the hoisting device can be easily determined by selecting one or more cylinders with a sufficient effective surface area for use. The applied pressure is typically lower than 6 bar, which is easily available. Preferably, the pressure is 2 to 3 bar, at the lowest even 0.5 bar or lower.
By the presented solution, it is also easy to lower the hoisting device quickly, for example in an emergency situation. The necessary element is, for example, a simple mechanical shut-off valve which normally remains shut off, for example by means of a preloaded spring, and which opens up a channel from said space to fresh air when pressed down. Now, said valve is also easy to place in the top of the hoisting device, within the reach of the person to be supported, because said space for the medium is provided, for example, within guards or railings supporting the person. In the prior art, such a valve is provided, for example, in the lower part of the hoisting device, where the supply of medium to the cylinder is provided and which is normally not within the reach of the person to be supported.
In an example of the solution, the retractor is shielded inside the cylinder, wherein the retractor is also safe for the user. In an example of the solution, a compressor or a blower for producing the compressed medium is also placed in the structure of the hoisting device.
In an embodiment of the solution, modularity is utilized in the structure of the frame, the cylinders and the work platform of the hoisting device, for example in such a way that a desired number of cylinder modules or base structure modules can be combined to various work platform modules. In this way, it is possible to construct various hoisting devices for different uses, particularly to vary their hoisting capacity.
In an embodiment, the cylinder and the base structure formed by the frame constitute a universal module which can also be applied to various uses, in which the load is to be moved for example horizontally and/or vertically, depending on the application. For example, various work platforms or tables for manipulating loads, particularly for lifting and lowering, can be connected to the module. The load consists of discrete loads as well as the structures connected to the module. The space for the pressurized medium is provided inside the cylinder, in its working chamber and, if necessary, also elsewhere in the structure of the cylinder or inside the base. Preferably, the retractor is also shielded inside the base and the cylinder, forming a compact structure. The module also comprises the necessary equipment and control devices and connections.
In an example, the cylinder can also be coupled to a portable structure in such a way that a closed space inside said structure can also be utilized as a storage of pressurized medium.
In the following, the invention will be described by means of some examples and with reference to the appended drawings, in which
In an example, the structure of the base 2, for example its frame 5 and/or its one or more supporting legs 3, delimit a closed chamber to which pressurized medium has access. Preferably, the frame 5 and/or the supporting leg 3 are made of a tube whose hollow interior constitutes said chamber. It is also possible to utilize various beams or housings which constitute the structure of the hoisting device and have a hollow interior.
The hoisting device 1 of
The chamber of the cylinder 4 is in direct contact with, for example, the chambers of the medium in the structure of the base 2. A channel or duct at the end of the cylinder 4 connects the chamber of the cylinder 4 to the chamber of the base 2, when the cylinder 4 is connected to the base 2, or said connection is formed by a separate tube or hose.
In an example, the work platform 6 can be lifted by the cylinder 4 to a height of 2.7 to 3.3 m. The sought load capacity to be lifted is about 120 kg. The work platform 6 is connected to the end or upper part of one or more cylinders 4, either directly or via another structure belonging to the work platform 6.
In an example, the structures of the work platform 6, for example its frame 7 and/or its one or more horizontal or vertical rails 8, delimit a closed chamber to which pressurized medium has access. Preferably, the frame 7 and/or the rail 8 are made of a tube whose hollow interior constitutes said chamber.
The chamber of the cylinder 4 is in direct contact with, for example, the chambers of the medium in the structure of the work platform 6. A channel or duct at the end of the cylinder 4 connects the chamber of the cylinder 4 to the chamber of the work platform 6, when the cylinder 4 is connected to the work platform 6, or said connection is formed by a separate tube or hose.
In the example shown in the figure, the upper end of the cylinder 4 forms a part of the structure of the work platform 6, and the rails 8 are connected directly to the vertical cylinder 4. The rails 8 are used to support a person standing on the frame 7. In addition to the rails 8, it is possible to use a gate that can be closed and opened, to increase safety.
Control means are also placed within the reach of the person standing on the frame 7, for controlling the operation of the hoisting device 1. They are, for example, electrically functioning switching means for controlling the hoisting device 1 to descend or ascend. The electrical power needed by the hoisting device 1 is preferably stored in at least one battery 20 that is placed in either the work platform 6 or the base 2. In particular, the switching means are used for controlling one or more electric retractors. In one example, a battery loading device that can be connected to an external electrical network is also provided in connection with the battery. The retractor is effective between the base 2 and the work platform 6, forcing the cylinder 4 to retract by the effect of the pulling force of the retractor, or enabling the extension of the cylinder 4 by the effect of the pressure of the medium. The retractor generates a counter force to the force generated by the medium. The pressure of the medium and the force generated by it are constantly effective in the hoisting device. The pressure may vary according to the total volume subject to the pressure. When the counter force is greater than the force generated by the medium, the work platform 6 can be moved lower, closer to the base 2 and the floor.
In an example, the control means are mechanical, wherein the retractor operates mechanically. Thus, an actuator, such as a crank handle, is provided within the reach of and available to the person standing on the work platform 6, for operating the retractor. In an example, the actuator can be coupled to a drilling machine or a screwdriver equipped with a battery to provide the driving force for operating the retractor. Thus, for example a winch is placed in the work platform 6, and the end of a cable or a cord used as a flexible pulling member of the winch is connected to the base 2, or the pulling member is connected to the work platform 6 but it is also coupled to the base 2, for example by means of one or more idler wheels. The hoisting device according to this example is independent of electric energy.
Several pulling devices can be used, wherein their operation is preferably synchronized. The pulling device can also be connected to the base 2. Thus, for example the winch can be placed in the base 2, and the end of the pulling member is connected to the work platform 6, or it is connected to the base 2 but the pulling member is also connected to the work platform 6, for example by means of one or more idler wheels.
In
The component shown in
Further,
The pressure in the chambers generates a force F hoisting the work platform 6 and sufficient to carry the weight of the work platform 6 as well as the equipment connected to it, the person to be hoisted, and the necessary tools, which together and separately make up the load to be transferred by the hoisting device. The force F is generated by the pressure p of the medium, acting on the effective surface area A of the cylinders 4. The pressurized medium is in a volume V which is at its maximum when the work platform 6 is in its uppermost position and at its minimum when the work platform 6 is in its lowermost position.
A valve 18 for discharging the medium from one or more chambers is also illustrated in
The structure of the hoisting device 1 is made of, for example, aluminium, to reduce the weight. A required number of ducts or corresponding connections are provided in connection with each chamber 14, 15 and 16, through which ducts it is possible to supply pressurized medium into the chamber or discharge it from the chamber. During the use of the hoisting device 1, no separate pressure source or pressure reservoir is applied, but pressurized medium stored in the chambers 14, 15 and 16 and its potential energy in the form of pressure is utilized.
The chamber 15 is for example the working chamber of the cylinder where the piston of the cylinder moves. If an auxiliary chamber is connected to or integrated in the structure of the cylinder 4, it is applied, with respect to the operation as well as the structure, in the same way as the above-presented chamber 14 or 16. The auxiliary chamber is typically connected to the chamber 15. Said auxiliary chamber can be used either alone or together with the chamber 14 or 16 in the hoisting device 1. Alternatively, either the chamber 14 or 16, or both of them, can be used in the hoisting device 1.
The pressure of the medium varies with the length of the cylinder 4, and with the volume of the chamber 15. When the work platform is in the elevated position, the pressure level is at the above-presented level in order to achieve a sufficient hoisting force, and when it is in the lowered position, the pressure of the compressed medium substantially rises as the chamber 15 becomes smaller. Preferably, the pressure of 6 to 8 bar is achieved, or the pressure is higher. The cylinder 4 and its chamber 15 are not connected to a separate pressure source or pressure container whose function would also be to level out pressure variations. If the other chambers, for example the chamber 14 or 16, or the auxiliary chamber, are in use, they are not connected to said pressure source or pressure reservoir either. Typically, the volume of the chambers 14 and 16 and the auxiliary chamber does not change during the operation as the volume of the chamber 15 does. The hoisting force is constantly effective, thanks to the pressure of the medium enclosed in the chamber 15. The volume of the medium enclosed in the chamber 15 can be increased by means of the other chambers or the auxiliary chamber, so that there is less variation in the pressure.
In an example, a compressor or a blower 19 is also placed in the structure, or module, of the hoisting device, for generating pressurized medium in one or more chambers. The compressor or blower 19 is selected according to the desired pressure level and the quantity of air needed. The compressor or blower is used to compensate for leaks and/or for loading an unpressurized chamber to a desired pressure. In an example, the compressor or blower 19 is powered by a battery 20 of the hoisting device, or it can be connected to an external electrical power network. In an example, the compressor is placed at least partly inside a chamber of pressurized medium or the cylinder.
In an example, the chamber is loaded to the desired pressure when the cylinder is in its extended position, or when the work platform is elevated, wherein the loading pressure level can be kept low. For loading, it is also possible to utilize said blower or compressor, after which the cylinder or chamber can also be closed or plugged. In an example, it is sufficient that air has access to the cylinder or chamber, when the cylinder is in its extended position, preferably in its maximum length, after which the cylinder or chamber is closed or plugged. The cylinder is selected in such a way that in a position that is shorter than the extended position but is still sufficient for the sought hoisting height, the pressure of the chamber is sufficient for the sought hoisting force. The pressure of the chamber has increased sufficiently during the retraction of the cylinder.
In different applications, the number and volume of the chambers, the number of cylinders, the size of the cylinder, and the pressure level used, as well as the allowed change in the pressure level will vary, and at the same time, they are interdependent. The dimensions are influenced by the sought capacity and the mode of operation of the hoisting device.
The invention is not limited solely to the above-presented examples or alternatives, but it can also be applied within the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20105944 | Sep 2010 | FI | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FI11/50785 | 9/13/2011 | WO | 00 | 3/8/2013 |
