US2873587A - Combination spare and service tail shaft assembly - Google Patents

Description

N. LYRlTZlS Feb. 17, 1959 COMBINATION SPARE AND SERVICE TAIL SHAFT ASSEMBLY Filed Dec. 27, 1957 INVENTOR. MAW/10f [He/72m AIME/VH4! nited States V COMBINATION SPARE AND SERVICE TAIL SHAFT ASSEMBLY t Nikolaos Lyritzis, New York, N. Y.

Application December 27, 1957, Serial No. 785,556 7 Claims. (Cl. 64-1) intermediate shaft. The power source of the ship is connected to the intermediate shaft which transmits rotary power to the propeller. It has been found that after varying periods of service tirne'the conical portion of the, tall or propeller shaft exterior of the stern tube or frame of the ship, and to which the propeller is keyed, will begin to shear or fracture. This fracture generally occurs at the forward end of the conical section of the tail shaft adjacent the propeller, which is a high stress area and subject to corrosion.

When a fracture of this type occurs while the ship is in a foreign port the ship must remain in that'port until a replacement tail shaft can be fabricated and sent to theship for installation. This disrupts the ships schedule which is costly, often necessitating that the ship remain out of service for weeks. In order to decrease the period of time that a ship is out of service when a fracture develops in the tail shaft, it has heretofore been the practice for ships to carry a spare tail shaft. This enables a ship which has been disabled while distant from its home port due to a fracturein the tail shaft, to proceed to the nearest drydock and replace the fractured tail shaft with the spare. This has the advantage of enabling the ship to be put quickly back in service. The disadvantage, however, is thatthis practice necessitates thateach ship carry a spare tail shaft which is expensive. These tail. shafts r costapproximately $35,000 fora 70,000 tonship and represents a considerable standby investment.

In view of the foregoing it is the primary object of this invention to provide a combination spare and service tail shaft assembly in which the conical end portion can be cut off; after a fracture occurs, a new conical end machined and the tail, shaft extended so that its length is equivalent to the lengthof the originaltailshaft assembly.

Another object ofthe present invention is to provide an insert for tail shaftassemblies which is inexpensive to fabricate as compared to the tail shaft, and which may be carried by ships in lieu of a spare tail shaft.

For a better understanding of the present invention as well as further objects and features thereof, reference is made tothe fcllowing detailed description to be read in conjunction with the accompanying drawings wherein like components in the several views are identified by like reference numerals,

, Figure 1 is'a s de elevation of a tail shaft assembly presatent 7 ently used, portions of the assembly being shown in cross section in order to illustrate structural details.

Figure 2 is. a side elevation of the tail shaft assembly inaccordance with the present invention. i

Figure 3 is a side .elevationof the tail shaft illustrated in Figure 2 after a fracture has occurred in the conical end section. n

Figure 4 is a side elevation of the tail shaft illustrated in Figure 3 after a new conical end section has been machined and the tail shaft moved rearward such that the new conical section lies in the same vertical plane as the old conical section which has been removed.

FigureSis a side elevation of a tail shaft assembly embodying the principles. of the present invention, an insert having been provided between the tail and intermediate shafts, and n i t Figure 6 is ,a perspective view of the insert.

Referring now to the figures, and particularly to Figure 1, there is illustrated a tail of propeller shaft it and an intermediate ,Shaftill, as installed and used in present day steamships. The intermediate shaft 11 is connected at its forward end tothe ships source of power (not shown) and is rotatively" supported in bearing 12.

The tail or propeller shaft which is designated generally by the numeral 10, is coupled to the intermediate shaft 11 by bolts 13, andforms an axial extension thereof. A bronze sleeve 14 annularly surrounds the tail shaft 10 andiprotects the tail shaft from corrosion. The tail shaft 10 is. rotatively supported by the stern tube 15 which has a lining 16 with a low coefficient of friction, such for example aslignum vitae. 'This'lining is held in position by a bronze sleeve .17. The, bulkhead of the ship .is designated generallyJat 18 and the annular gland at 19; the purpose ofthe latter beingtoprevent water from enters ing the ship. n

The rear end of the tail shaft 10 is formed with a conical sectionltl'to which the propeller 21 is secured and.

held in positionby the bolt 22. A cap 23 protects the bolt 22 from corrosion. The foregoing are details of propeller shaft assemblies which are well known to those skilled in the art.

After varyingperiods, ofservice time the tail shaft 10 will frequently crack or develop fractures in the conical end section 20 due to corrosion and. concentration of stresses. These cracks or fractures generally develop in the area of theconicalendsectionlti representing the clearance between the fo-rwar d face of the propeller fzl and the stern tube 15, as illustrated in Figure 3. When a crack or fracture of this type occurs it has heretofore been the practice to remove the tail shaft 10 and replace it with a new one. In order to avoid excessive delays virtually every ship today carries a spare tail shaft, which represents a considerable'stand-by investment;

Previous efforts to repair and utilize a tail shaft after a crack or fracture develops in the conical end section have proven' impractical and been thought impossible. This is due to therelative spacing between thebulkhead i8 and the flange 24 on the forward end of the tail shaft it? which hasheretofore prevented the tail shaft from being moved. rearward." This spacing is generally small since tail shafts are made as short as-possible due totheir cost as compared to intermediate shafts. This is due to their greaterdiameteriand the cost of theliners.

The present inventionenables a tail shaftto continue in. service after a crack or fracture occurs: in the conical end section. This is accomplished by initially installing a tail shaft 10 which. is longer thantail shafts. presently used. The length of. theintermediate shaft 11' is decreased proportionately such thattthe overall length of the tailcand inte mediateshaft combination in accordance With the present invention is identical to that of existing assess"? tail and intermediate shaft combinations. In this manner the improved tail and intermediate shaft combination of the present invention may be installed on new or existing ships without necessitating any structural changes in the bearings or mountings.

An extensible tail shaft in accordance with the present invention is illustrated in Figures 2.through 5. As illustrated in' these'figures, and particularly in Figure 2, the tail shaft of the present invention is made longer than present day tail shafts, and greater in length than that required upon installation. The extension in length is designated by the numeral 25 and is equivalent to, or slightly greater than, the length of the conical end sec tion 20 and its threaded portion for engagement of the bolt 22, this length being designated generally by the numeral 26. The intermediate shaft 11' of the present invention is made shorter by the amount of the extension 25. In this manner the combined length of the tail and intermediate shaft of the present invention is equivalent to the combined length of presently used tail and intermediate shafts. This is illustrated from a comparison of Figures 1 and 2;. The tail and inter-,

mediate shafts of the present invention may be installed in the same manner as present shafts.

When the tail shaft of the present invention fracturcs or shears at the conical end section 20, such for example as at 27 illustrated in Figure 3, the tail shaft 10' is uncoupled from the intermediate shaft 11' and removed from the ship. The damaged conical end section is cut off at shoulder 28 and a new conical end 20' machined. As illustrated in Figure 4 the tail shaft 10, after the removal of the conical end section 20' is the same length as the presently used tail shafts 10.

After the new conical end 20' has been machined the tail shaft 10 is reinserted in the ship. Due to the removal of the conical end section 20', however, the tail shaft 10' does not occupy its original position but is displaced rearward such that the propeller 21, when secured to the conical end 20', will be in the same vertical plane as originally. When the tail shaft 10 is positioned in this manner the flange 24 of the tail shaft will be spaced from'the flange 29 of the intermediate shaft by the axial distance represented by the removal of the conical section 20. This is best illustrated by Figure 4.

In order to couple the tail shaft 10' and the intermediate shaft 11 together an insert shaft, generally designated by the numeral 30, is interposed between the two. As illustrated in Figure 5 the axial length of this insert 30 is equal to, or slightly greater than the length of the conical end section 20 that was removed. This in sert 30, when placed in position, forms an axial extension of the tail and intermediate shafts and effectively couples these shafts together.

As can be seen from the foregoing, through the utilization of the present invention it is no longer necessary for a ship to carry an expensive spare tail shaft. In lieu of a spare tail shaft all that the ship must carry as a spare is the insert 30. This insert 30 requires no lining and cost approximately $2,000 as contrasted to $35,000 for a tail shaft fora 70,000 ton ship.

I claim:

1. A repairable shaft assembly comprising a tail shaft having a tail portion at one end thereof for mounting a propeller and a coupling portion at the other end thereof, an intermediate shaft engageablc, with said coupling portion to transmit rotary motion to said propeller, and an insert having an axial length corresponding substantiallyto that of said tail portion and adapted to intercouple said coupling portion with said intermediate shaft to restore the length of said assembly to its initial value in the event it is necessary to sever the existing tail 7 portion and to reform said tail portion on said tail shaft.

2 A repairable shaft assembly comprising a tail shaft having a tail portion at one end thereof for mounting a tail shaft having a conical tail portion of predetermined,

propeller and a coupling flange at the other end thereof, an intermediate shaft engageable with the coupling flange of said tail shaft to form an axial extension thereof and transmit rotary motion to said propeller, and an insert shaft having an axial length corresponding substantially to that of said tail portion and adapted to intercouplc said coupling flange with said intermediate shaft to restore the length of said assembly to its initial'value in the event it is necessary to sever the existing tail portion and to reform said tail portion on said tail shaft.

3. A repairable shaft assembly for transmitting rotary motion from a power source to a propeller comprising a tail shaft having a tail portion at one end thereof for mounting a propeller and a first coupling flange at the other end thereof, an intermediate shaft having a second coupling flange at one end thereof engageable with the first coupling flange of said tail shaft to form an axial extension thereof, the other end of said intermediate shaft being linked to a power source to transmit rotary motion to said propeller, and an insert shaft having an axial length corresponding substantially to that of said tail portion of the tail shaft, said insert having coupling flanges at each end, one of said coupling flanges of 'said insert adapted to intercouple with the first coupling flange of said tail shaft and the other coupling flange of said insert adapted to intercouple with the second coupling flange of said intermediate shaft to restore the length of said assembly to its initial value in the event it is necessary to sever the existing tail portion and to reform said tail portion on said tail shaft. 7

4. A repairable shaft assembly for transmitting rotary motion from a power source to a propeller comprising a length at one end thereof for mounting a propeller and a first coupling flange at the other end thereof, an intermediate shaft having a second coupling flange at one end thereof engageable with the first couplingflange of said tail shaft to form an axial extension thereof, the other end of said intermediate shaft being linked to a power source to transmit rotary motion to said propeller, and an insert shaft having an axial length corresponding substantially to that of said tail portion of the tail shaft, said insert having coupling flanges at each end, one of said coupling flanges of said insert adapted to interc'ouple with the first coupling flange of said tail shaft and the other coupling flange of said insert adapted to intercouple with the second coupling flange of .said intermediate shaft to restore the length of said assembly to its initial value in the event it is necessary to sever the existing tail portion and to reform said tail portion on said tail shaft.

5. A repairable shaft assembly for transmitting rotary motion from a power source to a propeller, said assembly comprising a tail shaft for supporting said propeller and including a tail. portion at one end on which said pro-' peller is mountable anda coupling portion at the other end thereof, an intermediate shaft engageable with the coupling portion of the tail shaft to link said propeller to a power source, said tail shaft having an axial dimension exceeding'the axial dimension of a given standard tail shaft by a predetermined length, and an insert having an axial length corresponding to said predetermined dimension which saidtail shaft is lengthened to intercouple said tail shaft with said intermediate shaft in the event said tail portion is severed from said tail shaft and a new tail portion formed thereon whereby the length ofjthe resultant assembly including said insert is, substantially the same as the length of the original assembly before re moval of said tail portion. H g:

6. A repairable shaft assembly for transmitting rotary motion from a power source to a propeller, said assembly comprising a tail shaft for supporting said propeller and including a tail portion at one end o'n which said-pro 'peller is mountable and a coupling" flange 'at theother end thereof, an intermediate shaft engageable with the 5 coupling flange of the tail shaft to form an axial extension thereof linking said propeller to a power source, said tail shaft having an axial dimension exceeding the axial dimension of a given standard tail shaft by a predetermined length and said intermediate shaft having an axial dimension less than the axial dimension of a given standard intermediate shaft by said predetermined length, and an insert having an axial length corresponding to said predetermined dimension by which said tail shaft is lengthened and said intermediate shaft is shortened to intercouple said tail shaft with said intermediate shaft in the event said tail portion is severed from said tail shaft and a new tail portion formed thereon whereby the length of the resultant assembly including said insert is substantially the same as the length of the original assembly before removal of said tail portion.

7. A repairable shaft assembly for transmitting rotary motion from a power source to a propeller, said assembly comprising a tail shaft for supporting said propeller and including a conical tail portion at one end of predetermined length on which said propeller is mountable and a coupling flange at the other end thereof an intermediate shaft engageable with the coupling flange of the tail shaft to form an axial extension thereof linking said propeller to a power source, said tail shaft having an axial dimension exceeding the axial dimension of a given standard tail shaft by the axial length of said conical portion and said intermediate shaft having an axial dimension less than the axial dimension of a. given standard intermediate shaft by the axial length of said conical tail portion, and an insert having an axial length corresponding to the axial length of said conical tail portion to intercouple said tail shaft with said intermediate shaft in the event said tail portion is severed from said tail shaft and a new tail portion formed thereon whereby the length of the resultant assembly including said insert is substantially the same as the length of the original assembly before removal of said tail portion.

References Cited in the file of this patent UNITED STATES PATENTS 699,356 Verity May 6, 1902 1,139,182 Henthorn et a1 May 11, 1915 1,379,558 Hatfner May 24, 1921

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