A number of different solutions are known for axially fixing a propeller hub of a pushing propeller on a propeller shaft. Commonly, the shaft is made with an abut- ment in front of the propeller, against which a forward facing surface of the hub abuts. The aft facing end portion of the shaft is threaded. A nut screwed onto the threaded portion presses the hub against the abutment on the shaft. When driving forward, the axial force of the propeller presses the propeller hub against the abut- ment on the propeller shaft, which means that the nut behind the propeller will only be loaded by its own pre-tension. In reverse, however, the situation is the opposite since the axial force of the propeller on the hub will place a load on the nut. In order to assure that the nut will not screw off when reversing, some form of nut lock is re- quired to prevent or in any case limit the possibility for the nut to rotate. A number of methods of locking a nut on a rotating shaft are known. A common solution uses a lock screw, which is screwed into a threaded bore in the end of the shaft and presses against the nut. Another solution uses a washer held tightly by the nut and having an inner profile, e. g. a projection, which extends into an axial groove in the threaded portion of the shaft. One or more portions of the radially outer portion of the washer are folded over the nut, providing a fixed engagement between the com- ponents.

These previously known solutions for fixing a propeller hub axially on a propeller shaft usually work quite satisfactorily for pushing propellers, since the nut is only loaded when reversing, which normally occurs at low speed and consequently with

relatively low load on the nut as compared with the load on the shaft abutment when driving at high speed forward. Furthermore, the combined operating time during which a boat is driven in reverse is normally only a fraction of the time for driving forward.

If a pulling propeller were to be fixed in a corresponding manner by locking the propeller hub axially between a shaft abutment lying behind the hub and a nut screwed onto a forwardly facing end of the shaft, the situation would be just the opposite, i. e. the nut, during most of its operation, would be loaded with very large forces, which would place exceptional requirements on the threaded engagement and the means for locking the nut.

The purpose of the present invention is to achieve a propeller device of the type de- scribed by way of introduction, which is particularly, but not exclusively, intended to establish secure axial locking of the propeller hub of a pulling propeller on a pro- peller shaft.

This is achieved according to the invention by virtue of the fact that the propeller shaft is provided with a peripheral groove in the area of the propeller hub, and that the lock means comprise, firstly, a divided lock ring which is mounted in the groove and abuts with a radial surface against a radial surface on the hub, and, secondly, a sleeve element which abuts with a radial surface against the opposite radial surface of the lock ring and is fixed by means of fasteners to the propeller hub.

The lock ring functions in the same way as the above described abutment on the propeller shaft, i. e. it absorbs the reactive forces on the propeller hub in one axial direction, while the sleeve element has primarily the function of holding the annular parts and keeping them in place in the groove and possibly absorbing reactive forces on the propeller hub in the other direction. By virtue of the fact that the lock ring

functions as a removable abutment on the propeller shaft, it is particularly suited for use, together with the sleeve element, as a forward axial stop for a pulling propeller, which must be slipped onto the shaft from the forward portion in the aft direction and where an abutment machine onto the shaft consequently cannot be used as a forward stop. The fasteners are preferably screws passing through bores in the sleeve element and screwed into threaded bores in the hub. The screws hold together the sleeve and the hub. The lock ring, together with the sleeve element, can also be used as a secure rear abutment for a pushing propeller, which has a propeller shaft with an abutment on the shaft as a forward stop.

The invention will be described in more detail with reference to the examples shown in the accompanying drawings, where Fig. 1 shows a longitudinal section through one embodiment of a pulling propeller device with two propeller hubs fixed with lock devices on individual propeller shafts, Fig. 2 shows an end view of one embo- diment of a lock ring in Fig. 3, and Fig. 3 shows an end view of a sleeve element.

In Fig. 1,1 designates a bearing sleeve which is a portion of a propeller drive of the type shown and described in SE-A-9704786. In the sleeve 1, a first propeller shaft 2 is mounted in a needle bearing 3. The shaft 2 is a hollow shaft through which a sec- ond propeller shaft 4 extends and is mounted in a needle bearing 5 in the hollow shaft 2. The end portions of the shafts 2 and 4, respectively, are provided with splines 6 and 7, respectively. The hollow shaft 2 supports a first propeller hub 8, which has internal splines 9 in engagement with the splines 6 of the shaft to rota- tionally fix the hub to the shaft. The second propeller shaft 4 supports a second pro- peller hub 10 with internal splines 11 in engagement with the splines 7 of the shaft to rotationally fix the hub to the shaft.

The propeller shafts 2 and 4 are driven in counter-rotation by means of a known transmission (not shown in more detail here). In Fig. 1, one propeller blade 12 is shown on the after-hub 8. In practice, a known propeller combination, which is

known per se, with a three-bladed fore-propeller and a four-bladed after-propeller of somewhat smaller diameter than the fore-propeller can be used. In front of the fore- propeller hub 10, there is a nose cone 13 screwed fast by means of a screw 15 screwed into a threaded bore 14 in the shaft 4.

The axial positions of the hubs 8 and 10 on the shafts are determined by the position of a peripheral groove 16 and 17, respectively, in each shaft. A lock ring 18 and 19, respectively, in each groove 16 and 17, respectively, fixes, together with sleeve ele- ments 20 and 21, respectively, the hubs 8 and 10, respectively, without play on their shafts 2 and 4, respectively.

The lock rings 18 and 19 each consist of two ring halves, of which the ring 18, with its two ring halves 18a and 18b, is shown separately in Fig. 2. The respective lock ring 18 and 19 is held together and is joined to the associated hub 8 and 10, respec- tively, with the aid of the sleeve elements 20 and 21, respectively. The sleeve ele- ments 20 and 21 have through-bores 20c and 21c, respectively, holding screws 24 which are screwed into threaded bores 25 in each hub 8 and 10, respectively.

As can be seen in Fig. 1, the lock rings 18,19 have a rectangular cross-sectional shape and the grooves 16,17 have a corresponding cross-sectional shape. The sleeve elements 20 and 21, respectively, are provided with individual depressions with a cross-section adapted to the cross-sections of the rings 18,19. This means that the respective lock ring 18,19 will abut with a flat lateral surface against a flat end surface 27 on the associated hub and with an opposite flat lateral surface against a flat surface 28 in the depression 26 at the same time as the surfaces of the respec- tive sleeve elements 20,21 abut against the surfaces 27 on the hubs. When driving forward, the lock rings 18,19 transmit the entire axial reactive force from the pro- pellers to the shafts.

The invention has been described above with reference to lock rings 18, 19, which consist of two separate ring halves 18a, 18b and 19a, 19b, respectively, but within the scope of the invention it is also possible, depending on the stresses on the rings, to use spring lock rings which are only cut at one location.