This invention relates to an improved swivel.

Swivels for rowing boats can be mounted for pivotal movement about an axis which extends preferably vertically. Swivels have a thrust face against which a flat surface of an oar acts for transmitting the force generated by the stroke of the blade in the water from the oar to the boat. The swivel may be mounted on a rigger.

The plane of the blade of an oar is generally pitched relative to the plane of the flat force-transmitting surface of the oar, normally by an angle of 2°. The swivel too generally has its thrust face pitched, normally by an angle of 2°, so that in combination, the two pitch angles give the blade of the oar a rake or effective operating angle of 4° in the water.

It is advantageous to be able to make adjustments to the blade rake angle, for example, in response to different conditions of the water or to suit or compensate for different oarsmen. Other adjustments are also advantageously possible, for example, altering the vertical height of the swivel on the boat or altering the angle of its pivot axis relative to the boat.

Conventionally, swivels have been designed so that to make adjustments to the blade rake angle has meant having to dismount the swivel from the rigger, adjust it and then remount it. This is relatively

time-consuming and necessitates the use of tools as well as, in some cases, a range of different replacement parts.

The present invention provides a swivel which can be adjusted for a range of different blade rake angles, but without the attendant disadvantages of conventionally adjustable swivels.

According to the invention there is provided a swivel of the kind in which there is means for mounting the swivel in relation to a boat for rotation about a preferably vertically extending axis, and means for mounting an oar including a thrust face for transmitting the force generated by the stroke of the oar to the boat, in which the swivel incorporates means for adjusting the pitch angle of the thrust face relative to said swivel axis whereby to enable adjustment of the effective operating angle of the blade in the water.

By way of example, embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a part sectional view of a swivel according to the invention, and

Figures 2a and 2b show details of the adjustment mechanism of the swivel of Figure 1.

Figure 3 is a part sectional view of a second embodiment of a swivel according to the invention.

Figure 4 is an elevational view of part of the second embodiment of the swivel shown in Figure 3.

Figure 5 is a partial plan view of the second embodiment of the swivel shown in Figure 3.

Figure 6 is a partial sectional view of a third embodiment of a swivel according to the invention.

Figure 7 is an elevational view of part of the third embodiment of the swivel shown in Figure 6.

Figures 8 and 9 show respectively modifications of the second and third embodiments of swivels according to the invention by elevational views of a part of each swivel.

There is seen in Figure l a swivel 10. The swivel 10 is of the kind which is pivotally mounted on a rigger 11 (shown partly) of a rowing boat (not shown) by means of a spindle 12. The spindle 12 defines an axis of rotation 13 for the swivel 10, which axis is preferably arranged to extend vertically.

The spindle 12 is retained on the rigger 11 by means of nuts 14. Cam washers 15 may be provided which enable the angle of the spindle axis 13 to be varied relative to the rigger 11 and plain washers 16 may be provided which enable the vertical position of the swivel 10 to be adjusted relative to the rigger 11.

The swivel 10 comprises a main body portion 17 which has a bore 18 in which the spindle 12 is journalled. Extending from the main body portion 17 is an arm having a bottom portion 19 and an outer portion 20. The bottom and outer arm portions 19 and 20 of the swivel 10 are to support and hold an oar 21 and a locking bolt 22 is to retain the oar in

position in the swivel, as shown.

The swivel 10 is advantageously made of moulded plastics material for lightness and strength.

Incorporated in the swivel 10 here is an element 23 which has a thrust face 24. The thrust face 24 is engaged by a flat surface 25 of the oar 21 and this transmits the force which is generated by the stroke of the blade 21a in the water from the oar to the boat via the rigger.

The element 23 sits in an arcuate channel 25 in which it can articluate and a tongue 26 and groove 27 arrangement guides articulating movement of the element. Articulating movement of the element 23 alters the pitch angle of the thrust face 24 relative to the swivel axis 13 and this is achieved by rotating a cam 28. Cam 28 is conveniently journalled on to the spindle 12 and, as can be seen in Figures 2a and 2b, the cam 28 is in the general form of an eccentric cylinder. A spring-loaded detent 29 is provided which is engagable in a series of depressions 30 to enable indexing of the cam 28 for a range of different adjustments between end positions shown in Figures 2a and 2b. The cam 28 may be knurled or have a knob or the like to enable it to be rotated quite simply by hand. Here, the cam 28 is rotatable to give seven different thrust face positions, each position giving an adjustment of about 1°.

In an alternative form, the cam may be polygonally shaped, that is, having a plurality of discrete faces which are set at different radial distances from the cam pivot axis and which could selectively engage the element 23. This would avoid

the need for the spring indexing mechanism of the cam.

A resilient ring 31 is used here for retaining the element 23.

There is seen in Figure 1 the oar 21 with its blade 21a. It can be seen that the plane of the blade 21a of the oar 21 is pitched with respect to the plane of the flat force-transmitting surface 25 of the oar, this being indicated by angle a. Oars are conventionally made in this way, as handed pairs, though it would be possible to use oars with a zero pitch.

The pitch of the thrust face 24 is adjustable here, and is shown in Figure 1 as angle b. This, combined with the pitch angle a of the oar 21, means that the blade 21a has a rake or effective operating angle of a+b in the water.

A second embodiment for the swivel according to the invention can be seen in Figures 3, 4 and 5. The embodiment is very similar to the first embodiment hereinbefore described and equivalent components have been assigned equivalent reference numerals.

The swivel of the second embodiment has a cam 40 which is reduced in size in its axial dimension with respect to the cam 28 of the first embodiment. The cam 40 is positioned at the top half of the recess defined in the swivel. The cam 40 is retained in this position by resilient means such as a helical spring 41. The cam 40 is rotatable about the swivel axis 13.

A protrusion 42 of the cam 40 engages with recesses 43, as can be seen in Figure 4. . The

engagement between the protrusion 42 and the recesses 43 prevents the cam 40 from rotating unless the oarsman urges the cam to do so.

The cam has a profiled shape as can be seen in the plan view of Figure 5. The thrust face 44 is pivotted about a point 45. The thrust face 44 is held against the cam 40 by resilient means such as a band of an elastic material 46. Rotation of the cam about the axis 13 causes the thrust face 44 to rotate about the pivotal axis 45. In this way, the second embodiment achieves adjustment of the pitch angle b.

The positions of the indentation 43 can be chosen to correspond with a particular pitch angle a + b. Therefore, the oarsman can see at a glance the pitch angle he has chosen.

The third embodiment of a swivel according to the invention that shall be described corresponds largely to the second embodiment hereinbefore described. The third embodiment can be seen with reference to Figures 6 and 7. Once again, a cam 50 is biased against the top end of the recess defined by the swivel. However, in the third embodiment the biasing force is applied to the cam member 50 by a resilient washer 51 which is positioned upon a positioning member 52.

The cam 50 has a protrusion 53 extending therefrom. The protrustion 53 engages with recesses 54 to prevent the cam 50 from rotating about the swivel axis 13 unless the oarsman forces the cam to rotate.

Resilient means 54 in the form of a band of

elastic material, bias the thrust plate 55 against the cam 50. The cam 50 is profiled in a similar fashion to the cam 40 and rotation of the cam about the swivel axis 13 causes the thrust face 55 to rotate about its pivot 56. In this way, the third embodiment allows adjustment of pitch angle of an oar.

The second and third embodiment of the invention can be modified by providing ratchet means disposed upon the cam, which ratchet means prevent rotation of the cam about the pivotal axis of the swivel unless the oarsman urges the cam to rotate. The modification of the second embodiment can be seen in Figure 8 and the modification of the third embodiment can be seen in Figure 9.

In both modifications shown in Figures 8 and 9, the ratchet means are provided by machining the upper surface 61 of the recess 60 defined in the swivel to provide a series of grooves 62 extending radially from the pivotal axis 13 of the swivel. Each of the cams of the embodiment shown in Figures 8 and 9 are similarly provided with a series of grooves machined in the upper surface thereof. The grooves extend radially from the pivotal axis of the cam.

The grooves on the cam 63 engage with protrusions between the grooves 62 and therefore the cam 63 is prevented from free rotation about the pivotal axis 13, unless the oarsman urges rotation.

Any of the embodiments previously hereinbefore described can be further modified as is shown in Figure 10. In Figure 10 an adjustment mechanism 70 is shown which can comprise any of the adjustment mechanisms previously described. In Figure 10, the

second embodiment hereinbefore described is actually shown in its further modified form.

In the embodiment of Fig 10 the cam 42 instead of just acting upon a separate thrust plate of the swivel acts to rotate the U-shaped portion 71 of the swivel. The thrust plate 73 shown in Figure 10 is integral with the U-shaped section 71. The hold U-shaped section 71 is pivotal about an axis 72. The cam 42 acts to rotate the U-shaped section 71 about the pivotal axis 72. This modification has the advantage of maintaining the internal shape of the U-shape section 71.

It is advantageous to be able to adjust the effective operating angle of the blade of an oar, for example, in response to different conditions of the water or perhaps to suit or accommodate different oarsmen. This can be achieved in situ and without tools using the swivel described herein by a simple hand adjustment.

It will be appreciated that many different constructions are possible which provide a ready means of adjustment of the swivel for the purpose of adjusting the oar blade rake angle. For example, instead of the rotating cam adjustor described, a sliding wedge arrangement could be provided. Alternatively, if the thrust face was provided as an integral part of the swivel body itself, it would be possible to provide some means for adjusting the angle of the entire swivel body relative to the spindle, eg by means of an eccentric conical sleeve between the spindle and swivel body.