US1815096A - Stuffing box for ships' propeller shafts - Google Patents

Description

July 21, 1931. 7 c, w, CEDERVALL 1,815,096

STUFFING BOX FOR SHIPS PROPELLER SHAFTS Filed May 16, 1928 f c A INVENTOR; C. W fcJem afl A TTORNEYS.

Patented July 21, 1931 UNETED STATES CARL WILHELM CEDERVALL, OF GOT'IENBORG, SWEDEN STUFFING BOX FOR SHIPS PROPELLER SHAIETS Application filed May 16, 1928, Serial No 278,103, and in Great Britain February 18, 1928.

This invention relates to stuffing boxes for the rear end of screw propeller ships tail shafts of the class described in for instance the Swedish Patent No. 839 and British Patents No. 20741 of the year 1914 and No. 108307. The object of such stuffing boxes is to protect the tail shaft from the destructive corroding effect of the salt sea water. Though stuffing boxes in accordance with the said patents have proved themselves to be of a considerable value and have protected thousands of such propeller shafts from corrosion they do not in all circumstances entirely comply with the requirements of the present time. That depends mainly upon the fact that the sizes of the propelling machinery of seagoing ships and the turning velocity of their shafts have increased considerably in the course of time, especially the present. The increased length of the shafting makes it necessary to allow for considerable axial movements so as to compensate for the expansion and contraction of the material due to variation in temperature when running between the tropics and the colder waters, andthe increased revolving speed, which for instance is the result of the introduction of internal combustion engines for marine propulsion, demands good lubrication. The type of stuffing boxes for propeller shafts described in the specification of the aforesaid Swedish Patent No. 839 has solved the lubrication problem but does not meet the requirement of allowing for large expansion. This type worked quite well when it originally appeared, because ships were then of rather moderate sizes and is still the best type for such ships. The types according to my said two British specifications on the contrary have proved themselves very well suited to the expansion and, contraction of long shaftings, but they are not so perfect with regard to lubrication. I presume that the last-mentioned deficiency is due to the fact that the lubricant must pass the co-operating rotating surfaces from the periphery towards the centre, that is to say, contrary to the direction of centrifugal force and that, at higher speeds, the design of the device induces the rotary tightening part to operate in a similar way as a suction rotary pump and thus draw in the salt water into the spaces encircled by the stuffing box and prevents the lubricant from coming in contact with the tightening and wearing surfaces.

The present invention has for its object a device which combines the allowance for large variations in the length of shafting of the later patents, with the extraordinary 0 good lubricating properties of the first-mentioned Swedish patent.

In the accompanying drawings an embodiment of the improved device is illustrated, in which 65 Figure 1 is a sectional elevation of the stuffing box applied to a ships tail shaft,.and

Figure 2 is a partial cross section view of the same box on two difierent lines in Figure 1, viz., the upper part on line II 7G and the lower part on line IIII, the babbitt lining 22 being removed from the flange 20 to expose the oil grooves 28 therein.

In the drawing the fore end of the hub of the screw propeller "is designated 1, the tail 7 shaft 2, and the rear end of the stem tube 3.

On the hub 1 a flanged sleeve 4 is secured by studs 5, so that it encircles the tail shaft 2. To the stern tube 3 there is, by means of Sc studs 9, bolted a ring 6 formed with a flange 7 directed inwardly so as to partially cover the space 8 between the hub 1 and the stern tube 3. lVithin said space there is mounted another ring 10 on the tail shaft 2 5 encircling the sleeve 4 and provided with radially projecting lugs .11 which fit into axial slots 12 in the sleeve 4. Said lugs and slots cause the ring 10 to follow the rotation of the shaft 2 at the same time allowing a sliding motion along the shaft within practical limits.

Both side surfaces of the flange 7 are smooth and plane and at a right angle with the axis of the tail shaft. Towards the fore side surface 13 shoes 14 are pressed by means of spiral springs 15 disposed in pockets 16 and 17 in the ring and the shoes 14 respectively. Said springs tend to force the ring 10 in a direction towards the stern tube 3. In order to obtain a uniform pressure on the ring 10 a number of springs are dis posed at equal distances around the ring 10.

A flanged ring 18 is bolted by screws 19 to the rear end ofring 10 so that the flanged ring 18 will follow the axial movements of ring 10 as well as the rotation of the shaft '2. The flange 20 of ring 18 is made outwards and makes contact with the rear side surface 21 of the flange 7. To reduce the friction between flange 20 and flange surface 21 the operative surface of flange 20 may be lined with anti-friction metal 22 such as babbitt or the like. Alongthe inner cylindrical sur face of the ring 18 apacking 23 of suitable material is pressed against the outer cylindrical surface of the flanged ring 4 by means of a gland 24 and screws 25 so that thus a tightening joint is provided between the rings 4 and 18, and in such a manner that the axial movement in relation to each other is insured. As the shoes 14 are carried with the ring 10 when said ring revolves with the shaft 2, the springs 15 would be subjected to shearing stresses, if they were the sole carriers of the shoes 14. In order to preventsuch stresses upon the springs 15, connecting members 150 or pins may .be provided which do not prevent the axial motion between ring 10 and shoes 14 caused by the springs 15. It may be preferred that the plurality of shoes 14 is substituted by a continuous ring encircling the shaft 2 and provided with all the pockets 17 for the springs 15. j V

The lubricating oil flows from the interior of the stern tube 3 into the space 8 and through radial channels 26 on to the flange surface 13 so as to reduce the friction caused by the shoes 14 under pressure from the springs 15. Axial oil holes 27 convey the lubricant to the rear end of flange 7,

and obliquely cut oil grooves 28 in the op-' erative surface of the flange 20 allow the lubricant to enter between the two tightening and wearing surfaces at 21. The outwardly directed position of the rotary flange 20 with grooves 28 make these act as a centrifugal pump which flings the lubricant outwards over the wearing surfaces and insures thorough lubrication of the said surfaces as well as an effective means of preventing the salt water entering between same.

The pressure betweensurface 13 of flange 7 and shoes 14 depends entirely on the action of the springs 15 and as said springs have for their object to press the ring 10 in a di rection towards the stern tube 3 to such an extent that the screws 19 in rings 10 will effect co-operation between flange 20 and surface 21, there is no need for oilor watertight co-operation between the shoes 14 and surface 13. In consequence the lubrication of the last-mentioned parts is a secondary question and is provided for by the oil chan-- nels 26 which allow a free flow of the oil between the same.

Should the shafting be subjected to a variation in temperature so that its length becomes affected, for instance expanded, the tail shaft 2 with sleeve 4 will change its position axially in relation to the rings 18, 10 which is allowed for by means of the slots 12 while an oiltight joint is maintained by means of the packing 23. As the rings 18, 10 are kept tight against the flange 7 by means of springs 15 and shoes 14, the axial movement of the tail shaft 2 has no influence on the oil-tight co-operation between flanges 7 and 20, and thus no salt water can enter between same.

lVhen using the device described there is no need of any excessive oil pressure inside the box as is the case with existing stuffing boxes for similar purposes, because the centrifugal force acting on the lubricant within the grooves 28 spreads the lubricantover the proper surfaces as herebefore described, and the principal co-operative surfaces of flange 20 and flange 7 are held in contact by the springs 15. Moreover, the said contact can be increased automatically, if the rear end of surface of flange 21 is designed larger than the fore end surface of ring 10, as the pres sure of the water column on the first-mentioned surface will then always be in excess of the pressure on the fore end side, even if for instance the water would enter the box due to leakage therein. As long as the surfaces at 21 are in closecontact and the packing 23 also is tight no leakage can occur, and the water pressure outside the flange 20 will suffice, even if the surface of said flange is not larger than the fore end surface of ring 10, and if under the circumstances the springs 15 do not develop their original pressure on the shoes 14 respectively on the surface 13.

Having now particularly described and ascertained the nature of my said invention and in what manner the sameis to be performed, Ideclare that what I claim is In combination, a stern tube, a shaft passing through said tube and a hub thereon, a stufling box to prevent the admission of sea water to said tube, said stuffing box including a relatively stationary flanged ring attached to the stern tube having a sealing surface, a tighting flange mountedcto revolve with said shaft andto slide axially thereof and having a sealing surface coacting with the first mentioned sealing surface and di-

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