US2988154A

US2988154A - Blade wheel propeller

Info

Publication number: US2988154A
Application number: US676345A
Authority: US
Inventors: Hub Wilhelm
Original assignee: JM Voith GmbH
Current assignee: JM Voith GmbH
Priority date: 1956-08-10
Filing date: 1957-08-05
Publication date: 1961-06-13
Anticipated expiration: 1978-06-13

Description

June 13, 1961 w. HUB

BLADE WHEEL PROPELLER ,2 Sheets-Sheet 1 Filed Aug. 5, 1957 INVENTOR. M/fe/m /,5

June 13, 1961 w HUB 2,988,154

7 BLADE WHEEL PROPELLER Filed Aug. 5, 1957 2 Sheets-Sheet 2 INVENTOR fi/z 7f 6 /m 14/06 United States Patent Ofiice Patented June 13, 1961 2,988,154 BLADE WHEEL PROPELLER Wilhelm Hub, Heidenheim, Germany, assignor to J. M.

Voith G.m.b.H. Maschinenfabrik, Heidenheim, Germany Filed Aug. 5, 1957, Ser. No. 676,345 Claims priority, application Germany Aug. 10, 1956 11 Claims. (Cl. 1'70-146) The present invention relates to ship propellers and, more particularly, to blade wheel propellers also called cycloidal propellers, in which a plurality of :blades arranged substantially parallel to the shaft of the propeller are rotatably journalled in a rotatable propeller body confining a chamber filled with oil. The blades of such blade wheel propellers all of which are immersed in the water are caused to carry out an oscillating movement. This oscillating movement is brought about by a control device arranged in the center of the propeller and is conveyed to the blades by a blade drive mechanism mostly called kinematics. A cycloidal propeller of this general type is described for instance in US. Patent No. 2,753,006.

With modern high speed cycloidal propellers, the said control device or control center is adjustable at random in two directions. In this way, the blade oscillations can be varied in such a way that depending on the position of the control center, the water flow produced by the blades during rotation of the propeller may be directed in any desired direction. The rotatable propeller body is connected with a hollow drive shaft and is supported by a stub shaft extending into the hollow drive shaft. Also the control of the oscillating movement of the blades is elfected through the hollow propeller drive shaft.

The rotatable propeller body which may also be called the propeller rotor is filled with oil for lubricating the blade drive mechanism and the bearings for the blades. If such a propeller is located relatively low, i.e. if the oil level in the propeller rotor also at a standstill of the propeller and with the ship unloaded is still located below the Water level, the water pressure at that point where the blade shanks pass through the bottom of the propeller rotor will sometimes be considerably higher than the hydrostatic counter pressure of the oil within the chamber of the propeller rotor. This is due to the fact that, when the propeller is at a standstill, the centrifugal force of the lubricating oil which rotates with the propeller rotor is not effective any longer. Therefore, there exists the danger that the water will penetrate through the hearing gap into the bearings for the blade shanks whereby the oil filling will be displaced and the bearing will start to rust. This, however, makes a premature replacement of the bearings necessary. While this replacement is being carried out, the ship can, of course, not be employed for its intended purpose. In order to avoid these drawbacks, it has been suggested to provide two sealings or packings one behind the other at the points where the blade shanks enter the propeller rotor. More specifically, one sealing or packing was provided to prevent water from entering the propeller rotor which scaling is called the front sealing sleeve, while the second sealing or packing was provided to prevent the oil from escaping from the propeller rotor; said last mentioned sealing is called the rear sealing sleeve. Both sealing sleeves are slightly pressed against the respective blade shank by means of annular springs.

The arrangement set forth in the preceding paragraph, however, has not been quite satisfactory due to the fact that it frequently occurred that the front sealing sleeve wore much faster than the rear sealing sleeve and therefore lost its sealing action much earlier than the rear sealing sleeve. This fact has its reason in that the front sealing sleeve is continuously exposed to the dirt and sandcontaining water and thereby is exposed to the abrasive effect of said dirt and sand-containing water. In contrast thereto, the rear sealing sleeve is surrounded by oil and, therefore, is worn to a considerably less extent. However, as soon as the front sealing sleeve or packing loses its sealing ability, the lip of the rear sealing sleeve or packing is already at a relatively low water pressure lifted oh? its seat by the entering water because the spring pressure by means of which the sleeve lips are pressed against the respective blade shank must be relatively low in order to keep the friction wear as low as possible. Thus, in such an instance the water is able already at a relatively low pressure to enter the bearings for the blade shank and from there can enter the chamber of the propeller rotor.

It is, therefore, an object of the present invention to provide a blade wheel propeller structure which will overcome the above mentioned drawback-s.

It is another object of this invention to provide a simplified and more effective sealing of the blade shanks of blade wheel propellers than was heretofore available.

It is a further object of this invention to provide an improved blade shaft sealing as set forth in the preceding paragraph, which will considerably facilitate the early recognition of any possible damage in the sealing system.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 represents a cross section through a blade wheel ship propeller according to the present invention.

FIG. 2. illustrates a partial section through a modified blade wheel ship propeller according to the invention.

FIG. 3 is a partial section through still another modification of the invention.

General arrangement In order to overcome the drawbacks outlined above, according to the present invention that stationary structural member which extends into the hollow driving shaft for the propeller is designed as central closing lid, i.e. concentrically arranged with regard to the propeller axis, for closing the oil chamber formed by the propeller rotor or by the propeller rotor together with the hollow propeller drive shaft. Furthermore, in conformity with the present invention, conduit means extend through said lid which establish communication between said oil chamber and a pressure source the pressure of which at least equals the static pressure head of the water at the depth of immersion of the propeller. In this way, according to the invention, a plurality of blade shanks in the rotatable housing of a blade wheel ship propeller is sealed by a single additional seal--oil pressure head seal-which is not arranged on the blade shanks but is remote therefrom and seals the propeller inner chamber toward the outside. In addition thereto, the said seal is effected by placing under pressure the chamber between the said seal and the seals on the blade shafts.

The required oil pressure in the propeller chamber is expediently obtained by correspondingly increasing the oil level in an oil gauge pipe communicating with the said propeller chamber, said gauge pipe having an overflow communicating with a small storage container. In this way, a possible loss in oil can at least for a certain time be compensated for without loss in the hydrostatic pressure head.

Structural arrangement Referring now tothe drawings in detail and FIG. 1 thereof in particular, the propeller housing 1 connected to the hull of the ship has journalled therein the propeller wheel or rotor 2 which is driven through the hollow shaft 3 3 and the bevel gear 4. The rotor 2 comprises anti-friction bearings 7 in which are journalled the shanks 6 of the propeller blades 5. At the opening 8 where the shank 6 passes through the bottom of the rotor toward the outside, there are arranged the rear sealing sleeve 9 for the oil sealing and the front sealing sleeve 10 for preventing the water from entering the interior of the chamber 200. The chamber 200 is filled with oil which by means of a pump 11 is withdrawn from a reservoir 12 in the stationary housing and is conveyed in a

circuit

13, 130* to the bevel gear drive 4 for lubricating the same from where said oil is again returned to the reservoir 12. Branching "off from this circuit is a branch circuit comprising a check -valve 14, a conduit 15 and a bore 16 in the control stick 17 from where the oil passes into the chamber 200 of the propeller rotor 2. From here the oil passes through a level to drop, according to a further development of the invention a check valve 14 is provided at the point where the branch circuit enters the propeller. The outside of the propeller shaft 3 is by means of a sealing 19 sealed against the housing portion 20 and the reservoir 12.

Arranged between the stationary stub shaft 21 carrying the propeller, and the hollow propeller shaft 3 is a seal '22 in form of an oil pressure head by means of which pressure oil is prevented from entering the chamber 23 for the bevel gear drive 4 and from passing therefrom into the reservoir 12. Therefore, the level of oil under pressure can rise in the propeller inner chamber and at a corresponding higher pressure can pass through conduit 24 into the oil gauge pipe 25 and into the elevated reservoir 18 and through the overflow 26 of the reservoir 18 as well as conduit 27 can return to the reservoir 12. The overflow 26 of the said elevated reservoir 18 is arranged at such a height above the water level CWL that the oil level 28 will still be above the water level when the propeller is immersed to its largest extent so that at the opening 8 there will still exist a sufliciently high oil pressure with regard to the water pressure prevailing at said opening so that water will safely be prevented from entering the bearing 7 for the blades even if a sealing sleev should be defective.

The arrangement of the above mentioned oil pressure head sealing and the higher oil pressure in the propeller chamber established thereby will thus prevent water from entering through other sealed portions of the housing if their sealings should have become defective in the course of time. Such damages could, for instance, occur at the covers covering the bearing bushings for the blades, or at other portions of the propeller.

According to the embodiment shown in FIG. 2 the oil circulation is effected through a cylinder with pressureloaded piston instead of the oil gauge pipe. More specifically, according to FIG. 2 the pressure oil is again circulated inasmuch as it is Withdrawn by a pump 11 from the reservoir 12 and passed through conduit 13, check valve 14 and conduit 15 into the propeller chamber 200 and from there through

conduits

24 and 27 back into the reservoir 12. In order to make it possible to maintain the required oil pressure in the propeller chamber 200 not only during the rotation of the propeller 'but also when the propeller is at a standstill, thereby maintaining the required oil pressure also during a standstill of the pressure oil pump 11 coupled to the propeller rotor, a check valve is interposed in the oil circuit between the pressure

oil return conduits

24, 27. This check valve consists of a cylinder 30 having movably mounted therein a piston 31 which is under the load of a spring 32. This piston controls or throttles the oil discharge opening 33 in conformity with the oil pressure in the return QQ l u 24 4 and thus in conformity with the oil pressure at the opening 3 where the propeller shanks pass from the inside of the propeller rotor to the outside thereof.

As will be seen from FIG. 2, a hollow stub shaft 21 engages the hollow drive shaft 3, said stub shaft 21 closing the propeller chamber 200 at the top portion thereof. The hollow shaft 3 serves more or less as guiding means for the stub shaft 21. To this end, slide bearings 2212 are provided between the inner Wall of the hollow shaft 3 and the outer wall of the stub shaft 21. The said slide bearings 22:; together with the sealing 2'2 interposed between the upper end faces of hollow shaft 3 and the flange 21a of the stub shaft act as oil pressure head seal. The sealing 22 serves as supporting hearing. The propeller chamber 200 communicates through a

conduit

15, 24 in the stub shaft with the pressure oil supply and discharge conduits. Furthermore, the said stub shaft also houses the bearing means for the control rod 17 passed centrally through said stub shaft. Pins 29 arranged in the propeller housing secure the said stub shaft against displacement.

The thrust of spring 32 is so selected and the effective surface of piston 31 acted upon by pressure oil is so dimensioned that the outlet 33 is completely closed by piston 31 when the propeller and thereby the oil pump are at a standstill, in other words when there is no oil pressure in the oil circuit, whereby the return of oil through conduit 27 into the reservoir 12 is blocked.

3 The arrangement according to FIG. 2 operates in the following manner:

When the propeller 2 rotates and thereby the propeller rotor driven pressure oil pump 11 likewise rotates which latter in this instance consists of a displacement pump such as a gear pump, the oil pressure in conduit 13 and thus in the propeller chamber 200 and likewise in the discharge conduit 24 and in cylinder 30 will increase in conformity with the pump speed. As a result thereof, the piston 31 is lifted up against the thrust of spring 32 up to .the release of the outlet 33. From this point on there is again established an oil circulation. More specifically, piston 31 releases the outlet 33 in conformity with the adjusted pressure'spring 32 only at a pressure head which at least equals the static pressure head of the water at the depth of immersion of the propeller. Expediently, however, piston 31 should just release the outlet 33 at a slightly higher oil pressure in the propeller chamber 200. This position of piston 31 is shown in FIG. 2. With a further increase in the pump speed, the outlet 33 is gradually released by the upward moving piston 31 which means that the throttling cross section at the outlet 33 is increased. This has a compensating effect upon the oil pressure within the circuit, however, only if no or practically no oil escapes at the blade exit openings or anywhere else. If, however, propeller oil escapes at any damaged sealing point of the rotor, it will be evident that for instance with the same pump speed, the oil pressure in the propeller chamber would drop somewhat and the piston 31 due to the counter pressure of spring 32 would be displaced downwardly against the thrust of the oil circuit whereby the throttling cross section at the outlet 33 would be decreased. In such circumstances, considerably less oil would return to conduit 27 which would bring about a new increase in pressure in the circuit or would at least maintain the oil pressure.

When the propeller 2 and thereby also the pressure oil pump 11 are at a standstill, the oil pressure in the oil circuit and similarly in the cylinder 30 will subside. Due to the effect of the pressure spring 32, the piston 31 presses ,upon the oil column in cylinder 30. As a result thereof, oil is displaced from the cylinder 30 into "the conduit 27 and this until the downwardly moving piston 31 has completely covered the outlet 33. At that time due to the effect of the spring-loaded piston 31, an oil pressure will still exist at the blade shank exit bore of the -'propeller chamber 200 which latter at its inlet side is according to FIG. 1.

. propeller.

closed by the check valves 14 and 14a and is furthermore closed by the oil pressure head sealing 22; The said oil pressure will at said exit openings approximately equal the static pressure head of the water at said exit openings provided that no or practically no oil can escape from any effective portions in the propeller.

If, however, oil should escape which can hardly be prevented in practice, the piston 31 follows, and oil from the cylinder chamber 30 is pressed into the conduit 24 and thereby into the propeller chamber 200. To this end, the cylinder 30 is somewhat higher than would actually be necessary. This makes it possible first to employ the cylinder 30 as oil storage chamber similar to the reservoir 18 of the broadened oil gauge pipe 25 However, care is taken that this stored oil will not be completely used up. To this end, an auxiliary pump 37 adapted to be driven by an electric motor 36 is provided. The suction conduit 38 of this auxiliary pump communicates with the reservoir 12, while the pressure conduit 39 of pump 37 communicates with the inlet opening 15. When the propeller is at a standstill, pump 37 will if necessary supplement the quantity of propeller oil. The control of this supplementary filling is effected electrically. To this end, piston 31 controls a switch 34 for the electric conduit 35 of the auxiliary pump motor 36. As soon as piston 31 after covering the outlet 33 has reached a certain position, it closes the switch 34, thereby starting motor 36. As a result thereof, the auxiliary pump 37 starts its delivery. Not only the oil pressure in the propeller chamber will thus be maintained but depending on the dimensions of the pump, also oil may additionally be pumped into the propeller. A possible return of the oil from the propeller chamber through conduit 13 is blocked by means of the check valve 14. The switch 34 is provided with correspondingly long sliding contacts so that the pump will deliver not only for a short instance but over a certain stroke of the piston 31.

In order to prevent the piston during its downward stroke from completely blocking the discharge conduit 24 whereby a renewed lifting or upward movement of the piston would be prevented, the cylinder bottom is provided with an elevation 40 limiting the lowermost position of the piston. This position may be reached when the loss in oil from the propeller exceeds the post filling by the auxiliary pump with this lowermost piston position. Therefore, it is expedient to cause the piston to actuate, for instance in an electric manner signalling lamps or other signals which would indicate the necessary repair of a defective portion.

If desired, instead of employing the auxiliary pump 37 and driving the same by the auxiliary motor 36, it

would, of course, also be possible to drive the main pump 11 by the auxiliary pump 36. In such an instance, however, it would be necessary to provide a detachable clutch connecting the main pump with the propeller rotor so that the main pump could be disconnected from the propeller, when the latter is at a standstill, and could be driven separately by the auxiliary motor 36.

Instead of providing a cylinder with pressure-loaded piston, it would also be possible to connect the oil discharge 24 with a pressure air chamber. In such an instance, the

pressure oil pump

11 or 37 would be controlled by a pressure gauge connected to said pressure air chamber.

FIG. 3 illustrates a partial section through a blade wheel ship propeller equipped with a pump oil circuit and an oil throttle provided at the oil exit from the The arrangement of FIG. 3 likewise comprises an oil pressure head sealing 22. Also in this instance no oil gauge pipe is provided. Instead, according to the present invention, a fixed oil throttle 41 is provided in the oil discharge conduit 24 from the propeller housing which conduit 24 'forms again part of a

partial circuit

13, 24, 27 through which oil is passed by the gear pump 11. The said fixed oil throttle 4l1 maintains the oil pressure in the propeller chamber by means of the oil pressure pump 11. However, in this instance it is necessary, in order to vary or maintain the oil pressure in the propeller chamber constant, to install an automatically driven controllable oil pump which is expediently controlled in conformity with the depth of immersion of the ship.

To this end, there is provided a float 50 floating on the constant water line CWL and linked through a bar 51 to a lever 55 pivotally supported by a pivot 52. The free end of lever 53 is designed as cam 54 for cooperation with a roller 55. Roller 55 is connected to a valve cone 58 through the intervention of a pressure spring 57, said spring and said valve cone being mounted in a housing 56 having a passage 59 communicating with pipe line 13. The passage 59 is controlled by the valve cone 58. The housing 56 has furthermore connected thereto a discharge pipe line 60.

When the ship is unloaded so that it rises and, therefore, a lower oil counter pressure will be required where the blade pivot extends outwardly, the lever 53 will, due to the rising float 50, be tilted in clockwise direction so that roller 55 rollingly engaging cam 54 will able due to the effect of pressure spring 57 to move upwardly. As a result thereof, the tension of pressure spring 57 will decrease, and from a certain predetermined oil pressure on, the valve cone 58 will be lifted by the oil pressure produced by pressure pump 11 and now exceeding the counter thrust of spring 57. Consequently, a portion of the oil flowing in line 13 will be able to pass through passage 59 into the discharge line 60 from where, if so desired, it may return to the reservoir 12. In this way, the pressure in line 13 drops to the extent necessary for the new immersion depth of the propeller.

It is obvious that the pressure spring will, of course, be so adjusted that when the ship has reached its maximum depth of immersion, the valve cone 58 will just engage its seat in a sealing manner so that no oil can pass from line 13 through passage 59 into line 60.

As will be evident from the above, the arrangement according to the present invention brings about a considerable simplification of the sealing problem of the blade shanks of blade wheel ship propellers. Any damage in the sealing system for the blade shanks can easily be spotted because as soon as one sleeve loses its sealing ability, pressure oil will escape through the defective portion on the blade pivot, and such unusual excessive consumption in lubricant can be made to indicate itself in the oil reservoir in any desired manner for instance by a float or by establishing electric contacts for closing the circuits of signalling devices. The arrangement is such that as long as such loss in oil can be replaced by the oil reserve carried by the ship, the latter can still make the next port Without risking that water will enter the blade shank bearings. As long as the loss in oil is within certain limits, the repair of the sealing system may be delayed up to the time the next overhauling of the ship will be due.

It is, of course, to be understood that the present invention is, by no means, limited to the particular constructions shown in the drawings, but also comprises any modifications within the scope of the appended claims.

What I claim is:

1. In a blade wheel propeller arrangement for a ship, which includes a rotatable propeller body having a hollow drive shaft connected thereto and having the shanks of a plurality of propeller blades journalled in said propeller body for an oscillating movement of said blades, said propeller body forming an oil chamber adapted to receive and store oil, the combination of: stationary including a tubular extension extending into said hollow shafit and provided with a closing member for said oil chamber, housing means surrounding said drive shatt, first sealing means interposed between said hollow shaft and said tubular extension to to said oil chamber, said system including a fluid pressure source and conduit means between said source and said oil chamber and extending through said closing member to establish communication between said source and said chamber to maintain pressure in the fluid in said chamber, the pressure exerted by said fluid pressure source being at least as great as the static pressure head at the respective depth of immersion of said blades in the water in which the ship equipped with said propeller arrangement floats.

2. In a blade wheel propeller arrangement for a ship, which includes a rotatable propeller body having a hollow drive shaft connected thereto and having the shanks ot a plurality of propeller blades journal-led in said propeller body for an oscillating movement of said blades, said propeller body forming an oil chamber adapted to receive and store oil, the combination of: a stationary stub shaft extending into said hollow drive shaft and forming a pivot bearing for said propeller body, first sealing means interposed between said hollow drive shaft and said stub shatt and arranged on the outside of the latter, said stub shaft being provided with a closing member for closing said oil chamber, housing means surrounding said drive shaft, second sealing means interposed between said housing means and said drive shatt, third sealing means interposed between said shanks and said rotatable propeller body for eilecting an oil seal therebetween, a fluid supply system connected to said oil chamber, said system including a fluid pressure source and conduit means between said source and said oil chamber and extending through said closing member to establish communication between said source and said chamber to maintain pressure in the fluid in said chamber, the pressure exerted by said fluid pressure source being at least as great as the static pressure head at the respective depth of immersion of said blades in the water in which the ship equipped with said propeller arrangement floats.

3. In a blade wheel propeller arrangement for a ship, which includes a rotatable propeller body having a hollow drive shaft connected thereto and having the shanks of a plurality of propeller blades journalled in said propeller body for an oscillating movement of said blades, said propeller body forming an oil chamber adapted to receive and store oil, the combination of: a stationary stub shaft extending into said hollow drive shaft, radial and thrust bearing means interposed between said stub shaft and said propeller body for supporting the latter, first sealing means interposed between said hollow drive shaft and said stub shaft and arranged on the outside of the latter, said stub shalt being provided with a closing member for closing said oil chamber, stationary housing means surrounding said drive shaft, second sealing means interposed between said housing means and said drive shaft outside said bearing means, third sealing means interposed between said shanks and said rotatable propeller body for effecting an oil seal therebetween, a fluid supply system connected to said oil chamber, said system including a fluid pressure source and conduit means between said source and said oi-l chamber and extending through said closing member to establish communication between said source and said chamber to maintain pressure in the fluid in said chamber, the pressure exerted by said fluid pressure source being at least as great as static pressure head at the respective depth of immersion of said blades in the water in which the through said conduit means.

4. In a blade wheel propeller arrangement for a ship,

8 which includes a rotatable propeller body having a hollow drive shaft connected thereto and having theshanks of a plurality of propeller blades journalled in said propeller body for an oscillating movement of said blades, said propeller body forming a chamber adapted toreceive oil, and an oil reservoir arranged for communication with said chamber, the combination of: stationary tubular means extending into said hollow shaft and provided with a closing member for said chamber, stationary housing means surrounding said drive shaft, first sealing means interposed between said housing means and said drive shaft, second sealing means interposed between said tubular means and drive shaft to effect a seal therebetween, third sealing means interposed between said shanks and said rotatable propeller body for eflecting an oil seal therebetween, pumping means, conduit means communicating with said chamber, said pumping means and said conduit means including said chamber forming a circulation circuit to allow said pump to withdraw oil firom said reservoir and to pump said withdrawn oil through said conduit means and said chamber back into said reservoir, and check valve means arranged in said conduit means and adapted at a standstill of said pump means to prevent oil under pressure from flowing in the reverse direction with regard to its normal flow, the pressure of said pump means at least equaling the static pressure head at the respective depth of immersion of said blades in the water in which the ship equipped with said propeller arrangement floats.

5. In a blade wheel propeller arrangement for a ship, which includes a rotatable propeller body having a hollow drive shaft connected thereto and having the shanks of a plurality of propeller blades journalled in said propeller body for an oscillating movement of said blades, said propeller body forming a chamber adapted to receive oil, and an oil reservoir arranged for communication with said chamber, the combination of: stationary tubular means extending into said hollow shaft for supporting said propeller body and provided with a closing member for said chamber, housing means surrounding said drive shaft, first sealing means interposed between said housing means and said drive shaft, second sealing means interposed between said tubular means and drive shaiit to etfect a seal therebetween, third sealing means interposed between said shanks and said rotatable propeller body for effecting an oil seal therebetween, pumping means, conduit means communicating with said chamber, said pumping means and said conduit means including said chamber forming a circulation circuit to allow said pump to withdraw oil from said reservoir and to pump said withdrawn oil through said conduit means and said chamber back into said reservoir, check valve means arranged in said conduit means and adapted at a standstill of said pump means to prevent oil under pressure from flowing in the reverse direction with regard to its normal flow, the pressure of said pump means at least equaling the static pressure head at the respective depth of immersion of said blades in the water in which the ship equipped with said propeller arrangement floats, and pressure relief valve means arranged in said conduit means between said rotatable propeller body and said oil reservoir.

6. A blade wheel propeller arrangement according to claim 5, in which said pressure relief valve comprises a cylinder having an inlet opening communicating with said chamber and an outlet opening communicating with said reservoir, a piston reciprocab-ly mounted in said cylinder for controlling said outlet opening, and resilient pressure exerting means acting upon said piston and urging the same in a direction to close said outlet opening, said piston being under a preload equalling at least the static pressure head at the respective depth of immersion ot the propeller in the Water in which the propeller equipped ship floats.

7. An arrangement according to claim 6, which. includes auxiliary means adapted to become efiective in response to a drop of the oil pressure below a certain pressure for automatically increasing the oil pressure in said conduit means.

8. A blade wheel propeller arrangement for a ship, which includes a rotatable body having a hollow drive shaft connected thereto and having the shanks of a plurality of blades journalled in said propeller body for an oscillating movement of said blades, said propeller body forming a chamber adapted to receive oil, and an oil reservoir communicating with said chamber, the combination of: circulating conduit means, pump means in terposed in said conduit means and arranged to circulate oil under pressure from said reservoir through said chamber and back to said reservoir, choke means arranged in said conduit means between said chamber and said reservoir, stationary tubular means extending into said hollow shaft for supporting said propeller body and forming a closing member for said chamber, housing means surrounding said drive shaft, first sealing means interposed between said housing means and said drive shaft, second sealing means interposed between said tubular means and drive shaft to effect a seal therebetween, and third sealing means interposed between said shanks and said rotatable body for effecting an oil seal therebetween, the pressure of said pump means while in operation at least equalling the static pressure head of the respective depth of immersion of said blades in the water in which the ship equipped with said propeller arrangement floats.

9. An arrangement according to claim 8, in which said pump means is a variable pressure pump.

10. An arrangement according to claim 8, in which the pressure of said pump means is variable in conformity with the depth of immersion of the ship equipped with said propeller arrangement.

11. In a blade wheel propelled arrangement for a ship, which includes a rotatable propeller body having the shanks of a plurality of propeller blades journalled there in for an oscillating movement of said blades, said propeller body forming an oil chamber adapted to receive and store oil, the combination of: a hollow drive shaft connected to said rotatable propeller body, stationary means including a tubular extension extending into said hollow shaft and provided with a closing member for said oil chamber, a tubular neck extending around said tubular extension in slightly spaced relationship thereto and having its lower end connected to said ship so as to be stationary with regard to said drive shatt, first sealing means interposed between said hollow drive shaft and said tubular extension to seal the latter relative to said hollow drive shaft, second sealing means between the upper end of said tubular neck and the adjacent peripheral portion of said hollow drive shaft, third sealing means interposed between said shanks and said rotatable propeller body for effecting an oil seal therebetween, a fluid supply system connected to said oil chamber, said system including a fluid pressure source and conduit means between said source and said oil chamber and extending through said closing member to establish communication between said source and said chamber to maintain pressure in the fluid in said chamher, the pressure exerted by said fluid pressure source being at least as great as the static pressure head at the respective depth of immersion of said blades in the water in which the ship equipped with said propeller arrangement floats.

References Cited in the file of this patent UNITED STATES PATENTS 2,028,448 'Harza Jan. 21, 1936 2,636,714 Willi Apr. 28, 1953 FOREIGN PATENTS 596,035 Great Britain Dec. 24, 1947 672,055 Great Britain May 14, 1952 692,403 Great Britain June 3, 1953