GB2120364A - Hydrodynamic coupling - Google Patents

Abstract

A hydrodynamic coupling using as working fluid an incombustible water-based liquid, oil or synthetic liquid is equipped with a pressure relief device in the form of a pin (8) with a frangible disc (15) arranged in a casing space which communicates with the external atmosphere and with a space in the vicinity of the rotation axis of the two rotors (1, 2). Working fluid leaking past seal (10) is discharged via a passage (7) to protect bearing (6). <IMAGE>

Description

SPECIFICATION Hydrodynamic power transmitting construction with power transmitting medium of incombustible water-based liquid, oil or synthetic liquid This invention relates to an hydrodynamic power transmitting construction, preferably an hydrodynamic clutch, the liquid state power transmitting medium of which can be a water-based filling liquid, e.g. water itself, an oil or a synthetic liquid.

By "hydrodynamic clutch" it meant a structure, of which the essential components are a pump rotor fixed to a driving shaft a turbine rotor fixed to the shaft of the machine, and a half-casing which at least partiaily surrounds the turbine rotor and is connected mostly rigidly with the pump rotor; in special cases it is fixed to the turbine-rotor.

Hereinafter the invention will be described by the example of a hydrodynamic clutch. It will however, from the description, be apparent to experts that the above also applies to power transmitting systems operative with the above mentioned liquid mediums which are not intended to be clutch-like power transmitting systems but which transfer energy to the machine by means of a power transmission in working circumstances similar to those in the description.

The hydrodynamic clutch can have a ram space, a reservoir or something else.

In the case of hydrodynamic clutches operating with oil (hydrocarbon-based or synthetic liquid) as a filling liquid, the working liquid ensures iubricating of bearings. Thus these types have a common working space and bearing space. To avoid overloading-especially in the case of constantly filled hydrodynamic clutches screw with a fuse link is built in. The essential feature of this protection is a screw which is filled-in fact in a bore-with a metal which melts at a certain temperature and which is placed onto the casing of the clutch.

At the nominal temperatureor rather within a temperature range-the fuse link melts and allows the filling liquid to leave the working space. The departure of the liquid influences the extent of the transmissible torque and results in disconnection of the driving machine from the working machine.

Hydrodynamic clutches filled with incombustible liquids, e.g. emulsion of water as well as oil-filled hydrodynamic clutches have recently become widespread.

The specific increase of power characteristics, the saving of energy and especially the relatively low price of the filling liquid account for the use of water. With a water-filled clutch there has to be considered the essential difference in the change of the liquid's physical characteristics in comparison with that of hydrocarbon-based or synthetic working liquids. The protecting temperature of clutches exceeds 3730K (1000C). Also pressure protection is needed because of the low boiling point of the filling liquid. An efficient corrosion protection is required at the same time especially at the bearings.It has represented a difficult problem with water-filled hydrodynamic clutches to insulate the bearing satisfactorily in view of the fact that up to the security level any working circumstances can occur with all their results (e.g. saturation pressure). There were suggestions to run the bearing in emulsion or water but it could not be applied in working conditions owing to the resultant high corrosion.

The most common way of protecting the bearing is to build in special or normal packings between the working space and the bearing, which packings insulate the bearing from water or emulsion. Should the decrease of pressure iead from the inner working space through the bearing, leakage will happen due to the normal (or from normal different but still allowed) working of the clutch and wear of the packing components. Thus the bearing cannot be protected from the corrosive effect of the working liquid and this results in early damage of the bearing. Corrosion protection of the bearing is generally based on the consideration that the decrease of pressure coming from the inner working space does not penetrate through the bearing but evades it.

Another essential problem with water-fiiled hydrodynamic clutches is how to create adequate pressure protection. A well known way of creating adequate pressure protection is to weaken the clutch-casing so that it breaks when the highest permitted inner pressure is reached. It is obvious that this solution is rather expensive and that the next operation of the device is thereby complicated. It is also a solution to place a protective fangible protection onto the outer periphery of the casing in the same manner as the fuse link. This has the disadvantage that the exact determination and adjustment of pressure is difficult due to pressure caused by centrifugal force.

To overcome this insufficiency the applicant has devised the hereafter described mode of protection by means of a frangible disc which is the subject of Hungarian Patent No. 177894. This solution can be relied upon even under extreme working conditions and gives cheap protection against corrosion for the bearing and has an easily replaceable means of excess pressure protection. The pressure protection is achieved by a frangible disc head placed onto the end of a tube running from the outer casing of an hydrodynamic clutch to the lower part of the working space. The frangible disc head senses-through a working annular liquid layer-- the existing saturation pressure supposing that the function connection between the saturation pressure and temperature determines an exact working range in the case of water.In use it emerges that, besides its advantages, it has the disadvantage that the tube, reaching through the liquid layer and being in connection with the atmosphere, can cause additional losses in the hydrodynamic clutch. That is why the applicant has sought other ways of application of this correct principle, which enabled the applicant to save energy and material besides further improving working security.

The basis of the invention is the recognition that the security attained with the help of the frangible disc head situated on the penetrating tube can be achieved in an easier way during the nominal filling condition of the clutch. This happens in a way which is more comprehensive as it makes it possible to make use of all the mentioned advantages with a similar construction in the case of water-filled clutches thus synthesising different simple solutions, so that simple tasks can be performed more easily according to the common function and existing concrete requirements and needs.

According to the invention, which has characteristics common to those of our previous invention a protective device is a pin which penetrates into the area of the rotation axis of the hydrodynamic clutch and is situated in a space communicating with the outer atmosphere. The protective fitting is preferably a threaded pin, conveniently formed as a headed screw but hereinafter referred to as a pin in which a disc head is situated-in the well known way. One or several screws with a fuse link can also be applied in an advantageous form of the invention and the construction developed this way can be used favourably in hydraulic power transmissions using oil.

Our new solution differs from the previous one-while maintaining its several advantageous characteristics-in that a disc-headed protective device is situated in a completely different way and does not penetrate the working space, being connected to it only by a communicating channel; thus it does not directly modify the rotation conditions; the law of motion is the disc space; its structure is more simple and the technology of its mounting is more favourable. This protecting unit is adequate in the case of power transmissions with a water-based working medium, but the special advantage of the solution in accordance with the invention is that it can be applied in general: it only needs an additional known screw with a fuse-link in the case of oil hydraulic systems.

The invention is hereinafter described in detail by way of example with reference to the accompanying drawing in which: Fig. 1 shows a longitudinal section a preferred form of the hydrodynamic clutch for incombustible water-based working, which is suitable for working with oil or synthetic liquid without structural change or with a possible completion (by adding a fuse-linked screw).

Fig. 2 shows, on an enlarged scale, the disc-headed pin or screw.

As can be seen in Fig. 1 the hydrodynamic clutch comprises a pump rotor 1 driven by a motor through a flexible clutch, and a turbine rotor 2 fixed rigidly to the pump rotor 1. In the thus formed closed working space 4, the torque of the driving motor will be transmitted by a incombustible working liquid, preferably by water to the working machine of which the shaft is connected by a sleeve 14 supported by a bearing and fixed to the turbine rotor 2. A bore 12 is formed in the shaft sleeve 14 on the side of the machine and the end of the shaft of the driving motor can enter this bore 12 in given circumstances.On the driven side of the shaft sleeve 14 there is a bore 13, into which there enters the shaft of the working machine and which is fixed to the shaft sleeve 14 by a screw leading through the bore which connects the bores 12, 13 and which is driven into the shaft of the working machine. The shaft sleeve 14 is supported by bearings 6 which are protected by packing 5, e.g. sealing rings, against the working liquid. At the same time, the working space 4 is closed by packings 10 similar to the packings 5, as shown in Fig. 1, but the latter can be omitted in certain circumstances.The space between the packings 5 (when there are no packings 10 closing the working space between the packings 5 protecting the bearing and the working space 4) is connected through a channel 7 leading into the air or into a neutral buffer space to a space of which the pressure is the same or lower than that which causes a decrease of pressure through the bearings 6. Accordingly, the path of pressure decrease does not iead from the working space 4 through the bearings 6 but through the channels 7, that is the stream of the medium which is subject to the changing pressure conditions of the working space 4 and to the condition of the packings does not affect the bearings 6.Actually only the packing 10, if there is one in the construction closing the working space 4, is exposed to high pressure, while the loading of the other packing 5 protecting the bearing 6 indirectly is generally not considerable but it can also be high, yet leakage or corrosion, accordingly do not occur in practice. The mode of packing according to the invention considers the change of the physical characteristics of the water as the filling liquid due to the temperature. That is why it is suitable even for packing of the working liquid which is moving through the packing 10 closing the working space 4 and which changes partially or totally into steam.

A very important part of the hydrodynamic clutch according to the invention is a newly developed and arranged pressure security device. The saturation pressure in the clutch depends also on the temperature, and the saturation temperature with regard to the water-filling are closely related.

Therefore the pressure value can be indicated with enough security which is determinative regarding the machnical strength of the hydrodynamic clutch and other heat engineering circumstances. By contrast with earlier solutions, when the frangible disc pressure security device was to be found on the periphery of the hydrodynamic clutch where the determination and adjustment of the real value of the saturation pressure proved to be rather difficult due to the pressure caused by the centrifugal force, according to the invention the frangible disc pin 8 rotating together with the casing 3 penetrates into the practically liquid less revolving space 9 of the working space 4 due to the annular operative path of the working liquid, and which pin 8 is in the present instance a headed screw with frangible disc 1 5. The material of the frangible disc 15 is preferably lead-foil built into the screw. Materials other than lead-foil can be used under certain conditions.

When a dangerous pressure is reached disc 1 5 cracks thus causing a decrease of pressure through this crack as the screw is in an area of atmospheric pressure. After this decrease of pressure the working liquid leaves the working space 4 as steam or in a liquified state. Thus the driving and driven sides of the clutch are uncoupled.

The application of the frangible disc pin 8 (in the present case a headed screw) according to the invention is based on the recognition that the working medium of the hydrodynamic clutches never equals the total capacity of the clutch, but is always less, so a cylindrical liquid-free space forms around the shaft in the working space in normal working circumstances. The pressure protection unit situated in this space or in its vicinity senses the existing saturation pressure or that which is increased by the pressure of the several centimetres thick rotating liquid annulus, but the latter pressure causes a negligible change compared to the change in saturation pressure in the temperature area of 413-423 K (140-1 500 C). The change has an effect towards the increase of security.

After operation of this pressure protection device, re-starting is very simple. The frangible disc head just has to be replaced, in a manner analagous to the replacing of a screw with a fuse link.

It should be noted that several frangible disc pins 8 can be built into the hydrodynamic transmission mechanism to provide pressure protection and can be arranged so that the mechanism does not rotate together with the casing (e.g. on the switch of torque).

The well known fuse linked screw can be used in parallel as a protection against overloading besides the pressure protection device.

Although there has only been described an application of the invention to hydrodynamic clutches, the solution according to the invention refers also to other hydrodynamic power transmission constructions, e.g. to switch of torque mechanisms. The hydrodynamic clutch according to the invention is suitable for working with an incombustible filling liquid, preferably with water, and with hydrocarbonbased and synthetic liquids according to the following: The working conditions for different filling liquids can be attained by using the required group of the following structural unit varieties: A) Protection A.a. fuse linked screw (11) A.b. frangible disc pin (8) B) Packing B.b. between the bearing and the space at ambient pressure towards the working space (5); B.c. between the working space and the space (10) which is at atmospheric pressure.

C) Outgoing bore from between two sealing rings arranged between the bearing and the working space into the surrounding space.

Type of working Incombustible Hydrocarbon-based liquid: water filling oil Synthetic oil Protection (A) A.b. (A.a.) A.a. A.b. (A.a.) Packing (B) B.b., B.c. none as required Outgoing boring (C) Yes closed by stopper as required

Claims (3)

1. An hydrodynamic power transmitting construction having a pump rotor connected with the shaft of a driving machine, a turbine rotor connected with the shaft of a driven machine and a closed working space for rotors and the working liquid, wherein a shaft sleeve fixed to the turbine rotor is nested in bearings provided with protecting packing, the space between the working space and the packing being connected to an atmospheric or other buffer space, of which the pressure in any working conditions is less than or equal to the pressure causing a pressure decrease through the bearing, also considering the changes in the physical characteristics due to possible irregular temperatures during working and the construction having at least one excess pressure protection device, charcterized in that the protection device is a pin, preferably a threaded pin arranged in a space communicating with the outer atmospheric space and projecting into the vicinity of the rotation axis of the power transmission construction, the said pin containing a frangible disc.

2 A hydrodynamic power transmitting construction as claimed in claim 1, charcterized further by the provision of at least one fuse linked screw.

3. An hydrodynamic power transmitting construction including an excess pressure protection device positioned substantially as hereinbefore described with reference to, and and shown in, the accompanying drawing.