When diving from a boat, divers routinely deploy a weighted line attached to a surface marker float or buoy to provide a guide to the seabed. It is a physically exhausting and physiologically risky task for divers to manually retrieve the 20-25 kilogram weight and length of rope at the end of a dive.

Mechanical devices, for example electrically powered winches or manually operated windlass, are available to aid retrieval of weights from the seabed, but these devices are often bulky and expensive and therefore not practical onboard small craft.

Flotation hoists are an alternative to mechanical devices. An inflatable bladder is submerged and attached to the sunken weight. When the bladder is inflated the buoyancy raises the weight towards the surface. Although effective this form of retrieval is not suited to the task and requires a diver to set the flotation device.

Other techniques make use of the forward motion of the craft to lift the weight. This is achieved by. passing the anchor rope through a ring on a float or buoy and attaching the end of the rope to the craft. As'the craft moves away from the float the buoyancy of the float combined with the forward motion of the craft raises the weight.

Because the rope passes freely through the ring the weight can fall back to the seabed once the craft stops moving. To prevent this the operator must retrieve the rope while the craft is in motion, which may require as much effort as raising the weight while the craft is at rest.

Other refinements on this theme have included gripping devices to secure the weight once the craft is stopped. These can work well, but the mechanisms are often complex, difficult to use and can damage the rope.

This invention provides a compact and simple mechanism for retrieving a submerged weight attached to a rope and eliminates significant manual effort.

The invention accordingly provides a device for controlling the motion of rope comprising a cam block having a curved working surface and a pivot means at a rearward end; a rope guiding frame pivotally attached at the rearward end of the cam block to the pivot means on the cam block and engaging the curved working surface of the cam block at the forward end; a means for connecting the cam block to a holder, wherein the rope guide interacts with the cam block to allow rope to slide in one direction towards the forward end, and for selectively preventing the rope from moving backwards when the block and guide are so mutually orientated that the guide is forced against the block, but when the mutual orientation is such that the guide is not forced against the block, the rope may run freely in the guide.

Preferably, the camming block and the guide are substantially D shaped.

Advantageously, the rope guide comprises 2 side elements hingeably attached at one end and secured to the connecting means at the other. The means for securing the side elements may be an aperture in each side element through which the connecting means is located.

Advantageously, the connecting means of the device is a snap-shackle, which makes engaging a buoy in sea conditions that much easier.

Advantageously, the rope guide and connecting means can be co-pivoting around the pivot means on the cam block.

Preferably, the curved working surface is at least partially roughed. This will provide a better grip on the rope Preferably the cam block, the rope guide and the connecting means are made from stainless steel.

Additionally the invention provides a method of retrieving a weight from the waterbed comprising, attaching the device as referred to above to a buoy position above the weight, passing a rope attached to the weight through rope guide frame, attaching the rope to the water craft, moving the water craft in a direction away from the weight

to raise the weight off the bed, and causing the guide to engage the camming block, and thereby stopping the rope sliding back moving the watercraft back to the buoy securing the weight and/or buoy onboard the craft.

It uses the buoyancy of the marker float or buoy and the forward motion of the boat to raise the weight from the seabed.

The device will secure the weight in the raised position allowing the free rope to be gathered in before the weight itself is retrieved onboard the craft.

The device is simple to manufacture, robust, compact and lightweight in construction, easy to use and does not damage the rope. It is ideally suited for use by divers or anybody onboard small craft requiring to retrieve weights from the seabed.

An embodiment of the invention will now be described by way of example only and with reference to the attached drawings Fig 1 15t embodiment device components Fig 2 15t embodiment components assembled-plan view Fig 3 15t embodiment components assembled-side view Fig 4 Operational use for raising a weight Fig 5 Detail of device in operation Fig 6 2nd embodiment device components Fig 7 2nd embodiment components assembled-plan view Fig 8 2nd embodiment components assembled-side view Fig 1 shows the three separate components of a first embodiment of the invention.

These are a snap-shackle connector 1 ; a rope guide 2, and the cam, 3. The rope guide 2 is a D-shaped shackle having a pin 6 providing a link between an aperture in each arm of the guide. When assembled the components resemble the device shown in Figs 2-3. The pin 6 of the D-shackle provides a pivot for the cam and secures the snap-shackle 1. The snap-shackle provides a quick method of securing the device to the buoy 8. The cam is sufficiently heavy so that when the rope 7 is not moving it is

locked against the rope guide 2. Shallow grooves 9 are machined into the curved face 10 of the cam 3 to provide a secure grip against the rope.

All components are manufactured from stainless steel so that they are resistant to corrosion.

Fig 6 shows the separate components of a second embodiment of the invention.

These are a snap-shackle connector 1, a two-part rope guide 2, and the cam 3. The cam 3 is attached to one half of the rope guide 2 by a fastener4 which allows it to rotate. The cam is sufficiently heavy so that in operation, when the rope 7 is not moving it is locked against the guide 2.

The rope guide 2 may be opened, as shown in fig 6, to allow capture of the rope 7.

With the rope 7 in place, the guide is closed and then locked by the attachment of the snap-shackle 1, as shown in figs 7-8. The snap-shackle 1 also provides means of securing the device to the buoy 8.

To retrieve the submerged weight 11 from the seabed 12 the following operation applies. This operation is described with reference to Fig 4. The weight 11 isshown as an anchor but can be any other form of weighted object.

The camming device is secured to the float or buoy 8 using the snap-shackle 1. The surface end of the rope 7 is detached from the buoy and passed through the rope guide 2 so that the cam 3 rests on top of the rope. Fig 5 shows this in detail. The free end of the rope 7 is secured to the stern of the craft 13.

As the craft 13 motors slowly away from the buoy, the rope 7 passes freely between the rope guide and the cam. The forward motion of the craft raises the weight 11 from the seabed 12 and the buoyancy of the float or buoy supports the weight. When the weight reached the surface the boat stops. The cam 3 prevents the weight 11 from falling back to the seabed allowing the craft 13 to motor back towards the buoy 8, retrieving the rope 7 from the surface as it goes. The weight and buoy can be secured alongside and lifted onboard.

The device is ideally suited to aid the retrieval of a weighted or anchor line onboard a small craft.

The present invention affords a simple yet very effective device that facilitates belaying of rope in many situations and in particular to facilitating the raising of a submerged weight by the action of the associated water craft. There is no need for additional motors or drive mechanisms, nor is there a need for the operator to labour at lifting the weight from the seabed up to the craft.

Although reference is made throughout to a rope, this word is used to cover all equivalents such as cables, cords, wires, and lines.

The invention has been disclosed in relation to specific embodiments. However, it should be understood that the invention is not limited to the specific features shown, since these comprise only a preferred form of putting the invention into effect. All equivalents to those claimed are intended to be embraced herein.

The camming device provides alternatively a one way rope passage controller or a free passage rope guide depending on the angle of the rope to the orientation of the cam block.