ANCHORING MECHANISM FOR A GUIDE POST

Anchoring mechanism for a guide post The present invention relates to an anchoring mechanism for a guide post as stated in the preamble of claim 1. Guide posts are often used on seabed frames. Normally four 203mm (8") posts are inserted in the frame at certain intervals. From the top of the posts a wire is run to the surface. These are kept tensioned. By means of the wires equipment can be lowered to the seabed frames and guide the equipment in position within the given tolerances . The posts can be permanent or replaceable ( retreat to the surface ) . There are two reasons for choosing the latter solution, one are the costs in connection with making all the posts which are needed permanently down on the frame, or that they may block the access for other equipment. The posts can be several meters long, often 3 to 4 meters. By making them replaceable a much smaller number would be needed.

Prior art replaceable guide posts have relatively complicated and costly mechanisms. A standard retrievable guide post has lockpins that are activated via a permanently installed wire within the post.

The patent GB A 2.225.798 discloses a replaceable guide post 17 which is lowered into the funnel 10 and temporarily locked by the lockpin 34. By lifting the guide post 17 upwards the sleeve 37 and the member 18 are slided upwards and the lock- ing ring 40 and the lockpin 43 are moved upwards and lock the guide post 17 to the funnel 10.

The patent US 4.828.035 discloses replaceable guide post A which is locked into the funnel 400 by means of a snap ring 120. The object of this invention is to provide an anchoring mechanism of a much more simpler construction and thus at considerably lower manufacturing costs.

According to the invention this object is achieved by the characteristic features stated in claim 1. Preferred embodi- ments are stated in the dependent claims.

The invention will now be described with reference to a preferred embodiment and to the drawings, wherein Fig. 1 is a sectional view in the longitudinal direction of a guide post anchored with the guide post lock to a funnel fastened to the seabed frame, Fig. 2 is a sectional view like Fig. 1 showing a situation when the guide post and the guide post lock are retrieved from the funnel, and Fig. 3 is a sectional view in the longitudinal direction of the guide post lock in a larger scale. Fig. 1 shows a guide post 1 in normal operational position, anchored in a seabed frame via a few lower lockpins 7 which extend radially out underneath the funnel 2 fastened in the seabed frame. The pins 7 are equipped with flanges on the inside of the guide post 1. It is appreciated that the post 1 is locked at the bottom against upward movement in the funnel 2 by means of guide post lock 5 and the lockpins 7. The guide post 1 is prevented from sliding downwards in the funnel 2 by an annular ridge 14 fastened to the guide post 1.

During the preparation at the surface for the installation in the funnel 2, the guide post lock 5 is mounted by raising the guide post lock somewhat within the guide post 1 and then pushing the upper lockpins 6 radially outwards so that they with the inwardly flanges are engaged in an inside annular groove 13 in the guide post lock 5. The guide post lock 5 will thus be prevented from sliding downwards. The upper lockpins 6 are further prevented from sliding radially inwards by means of an O-ring 9 abutting the sides of the axial slots 8 for the lockpins 6 in the guide post lock 5.

When the guide post 1 together with the guide post lock 5 by means of the wire 3 and the anchor lock 4 are let down into the funnel 2 which is locked to the frame, the funnel 2 will cause the upper lockpins 6 to move radially inwards (due to gravitation) until they are not locked in the annular groove 13. This means that the guide post lock 5 can slide further down in the guide post 1 and then press the lower lockpins 7 radially outwards. Initially the upper lockpins 6 will slide inwards, then the guide post lock 5 will slide downwards in the guide post 1 a distance, so that the upper lockpins 6 are unable to move outwards again. The lower lockpins 7 will then be subjected to a radial load due to the specific gravity of the guide post lock. However, the lower lockpins 7 will only slide to the outer position after they have arrived below the lower edge of the funnel 2. Then the guide post lock 5 will slide down to such an extent that the lower lockpins 7 will lock against the part of the guide post lock 5 having the larger diameter. The lower lockpins 7 are now able to take the load with which the wire is pulled.

When it is desired to retrieve the guide post 1, a weight 10 is dropped down the wire 3 (Fig. 2). The weight 10 is beating the anchor lock 4 downwards, in that the upper dogs 11 on the top of the anchor lock 4 having bevelled edges and can move resiliently inwards and the anchor lock is guided downwards and into the guide post lock 5. At the lower end of the anchor lock 4 there are several dogs 12 which can move resiliently in- wards because of their bevelled lower edges and allow that the anchor lock 4 is guided down to its appropriate position with the lower dogs 12 underneath the guide post lock 5. The lower dogs 12 will then move rapidly outwards and lock with their upper, radially extending edges the anchor lock 4 to the guide post lock 5. By pulling the guide post lock 5 via the anchor lock 4 and the wire 3 the lower lockpins 7 can move radially inwards. The guide post 1 is now released and can be retrieved to the surface.