Line-handling block

Abstract: A block (1) for line-handling comprises two cheeks (3) and a rotatable sheave (6) sandwiched between the two cheeks. The two cheeks mate together through a central aperture of the sheave by a relative rotation of the cheeks via a bayonet fitting (5). The mated cheeks are secured to each other by fixing pins (9), which also secure a swivel attachment member (7) to the block. Bearing elements (15) are used for rotatably supporting the sheave to prevent its translational movement relative to the cheeks.

Description: This invention relates to a block for line-handling, more particularly, to a block for handling, guiding, turning or deflecting a line or a cable, such as a pulley block, a foot block or a turning block. In the past, line-handling blocks have included a rotatable sheave sandwiched between two cheeks, which were held together by means of nuts and bolts, rivets or the like. Therefore, it is a relatively time-consuming job to assemble such blocks. One such block is disclosed in US-A-1 406 560. The block includes two cheek members, the first cheek member having a post which serves as a spindle for a sheave, said post being threaded. It is stated that the second cheek member may be screwed down onto the post sandwiching the sheath between them. It is an object of this invention to provide a line-handling block which is easier to assemble than previous blocks. A feature of the present invention is a mating of flanges of the cheeks through the middle of the sheave and in such a way as to interengage the cheeks against being forced apart. This mating involves relative rotation of the cheeks by a bayonet coupling. This mating construction allows the use of fewer parts than previous ones, and is quick and simple to assemble. Having been mated, the two cheeks only require one or more further securing means to prevent any relative movement which might release their engagement. Because these need resist only relative rotation of the cheeks they may be smaller and less numerous than the fasteners used in previous blocks. To provide a thrust bearing for the sheave there may be an annular groove cut into each end wall of the sheave which has a mouth of restricted width. Ball bearing elements of a plastics material such as acetal are deformed somewhat and introduced into the groove through the restricted mouth. Once inside the groove, the elements return to a spherical shape, the diameter of which is larger than the width of the groove mouth and hence the elements are retained within the groove. The advantage of this arrangement is that the axial thrust bearings may be assembled with the sheave before the final assembly with the cheeks. Windows may be provided in the flanges of the mated body of the cheeks which give access to bearing elements, and allow flushing of those elements without the need to disassemble the pulley block. The windows also reduce the weight of the block. The block will also usually have a rotatable swivel pin which allows attachment of the block to some external body. This swivel pin is preferably retained in the block by constraint between a groove in the swivel pin and the securing means. The dual utility of the securing means again minimises the number of parts in the complete block and makes assembly of the block quicker and easier. It should be understood that the term line-handling block in this application includes all devices having similar functions, such as a pulley block, a foot block or a turning block, which can be fixed to the deck of a boat and used to deflect a line to a winch or some other part of the boat. In the drawings: Figure 1 is a face view of the pulley block; Figure 2 is a sectional elevation on the plane A-A of Figure 1; Figure 3 is a detail of Figure 1; Figure 4 is a section B-B of Figure 3; Figure 5 is a detail of a variant of Figure 1; Figure 6 is a section C-C of Figure 5; and Figure 7 is a detail of Figure 2. Figure 1 shows a line-handling block 1 including two metal cheeks 3 and a rotatable sheave 6. Bosses 4 are integral parts of the cheeks 3 and are mated by relative rotation of the cheeks, via a bayonet coupling 5 through an aperture in the centre of the sheave 6 in which its axis of rotation AR is positioned. Part of the cheeks 3 extend beyond the outer radius of the sheave 6 to form a head 2. In the head 2 there are securing means in the form of two fixing pins 9 each running through both cheeks 3 outside the diameter of the sheave 6; these fixing pins prevent relative rotation of the cheeks 3. Each fixing pin 9 is fixed in the block head 2 by either a screw 11 in either end (Figures 3 and 4) or by having the pin ends formed into rivets 12 (Figures 5 and 6). There is a swivel pin 7 in a hole 20 in the block head 2 formed equally by a semi-cylindrical recess in each of the two cheeks. Its axis is perpendicular to the axis of rotation of the sheave. The swivel pin 7 has a circumferential groove 8 of semi-circular cross-section in which the securing means, here two fixing pins 9 are seated. The fixing pins 9 are positioned at diametrically opposite sides of the groove 8 so that the swivel pin 7 is constrained to only move rotationally about its own axis. Part of the swivel pin 7 projects beyond the head stock 2 and has there a hole 10 to allow attachment of the block to an external body. There are two coaxial grub screws 19, one in a hole 22 in each cheek 3, which have an axis perpendicular to and coincident with the axis of the swivel pin 7. There are four blind bores 21 in the swivel pin 7 any of which may be aligned with grub screws 19 such that when the grub screws 19 are screwed into the bore 21, the swivel pin 7 is prevented from rotating about its axis. The pin 7 is hollowed by a hole to lighten it, as indicated by dotted lines 24, Figure 2, the hole having a diameter established by considering the loads the pin has to accommodate. The sheave 6 is borne radially in relation to the cheeks 3 by a roller bearing 14, made up of a plurality of roller bearing elements 13, each of which is in contact with the inner circular wall of the sheave 6 and the outer wall of the cheek bosses 4. Access to the roller bearing elements 13 is provided by windows 34 in the mated assembly of the cheek flanges 4. The sheave 6 is fixed axially by thrust bearings. These bearings are made up of slightly compressible plastics material ball elements 16 e.g. of an acetal resin, captured in circular grooves 17 in the end walls of the sheave 6. The thrust elements 16 have an undeformed diameter greater than the width of the mouth of the groove 17 which allows the thrust bearings 15 to be assembled with the sheave 6 before final assembly with the cheeks 3. There are two cutaways 23 in the block head 2 of each cheek 3. These serve to reduce the weight of the block 1. The block is assembled by fitting the axial thrust bearing elements 16 into the grooves 17 in the sheave 6. This assembly and the roller bearings 14 are fitted onto the boss 4 of one of the cheeks 3. The other cheek 3 is then offered up to the first and rotated so as to mate the cheeks 3 by the bayonet fixing 5. The swivel pin 7 is then introduced into the hole 20 in the block head 2. The two fixing pins 9 are then slid into the holes 18 in the head stock 2, to fix the cheeks 3 and the swivel pin 7, and are fixed by screws 11 or formation of the pin ends into rivets 12. Finally the grub screws 19 are screwed into the holes 22 in the cheeks 3, if desired.

Claims: A block (1) for line-handling comprising: first and second cheeks (3) having means (4) for mating with each other; a sheave (6) with a central aperture therein; said cheeks rotatably bearing the sheave for rotation about an axis (AR) in the central aperture thereof; the mating means (4) comprise interengagement means (5) for holding said cheeks together in the direction of said axis; the first and second cheeks (3) interengage with each other via the mating means (4) by a relative rotation therebetween; said first and second cheeks (3) are arranged to sandwich the sheave (6) rotatably therebetween and to mate with each other by interengagement of the mating means (4) through the central aperture of the sheave (6), characterized by the mating means (4) being a bayonet fitting (5). A block according to claim 1, wherein each of the first and second cheeks (3) comprises an outer portion (2) extending beyond an outer radius of the sheave (6), and further comprises at least one securing means (9) for fixing the first and second cheeks (3) to each other via said outer portion (2) so as to prevent relative rotational movement of interengaged first and second cheeks (3). A block according to claim 2, further comprising swivel attachment means (7), wherein said swivel attachment means is rotatably secured to said pulley block. A block according to claim 3 wherein said swivel attachment means comprises a shaft (7) directed away from the sheave, said shaft comprising an axially directed relief bore (24). A block according to claim 3 or claim 4 wherein the swivel attachment means is rotatably secured to the pulley block by a constraint (8) between itself and at least one of said securing means (9). A block according to any one of the preceding claims, further comprising second bearing means (15) between the sheave (6) and the cheeks (3) for preventing translational movement of said sheave (6) with respect to the cheeks (3). A block according to claim 6, wherein said sheave has at least one axial side face with a groove (17) formed thereon and said second bearing means comprise at least axial thrust bearing elements (16) captive within said groove. A block according to claim 7, wherein said groove (17) is formed with a restricted mouth, and said axial thrust bearing elements are balls (16) each having a natural diameter larger than said restricted mouth. A block according to any one of the preceding claims, wherein the mating means (4) comprise mating flanges with at least one window (34) formed therein to provide access to said first bearing means, said mating of the flange being by said bayonet fitting.

Inventors: COE PETER J, POWELL MELVYN, COE, PETER J., POWELL, MELVYN
Applicants: LEWMAR MARINE LTD, LEWMAR MARINE LIMITED
Application year: 1993
Main classification: B66D3
IPC codes: B66D3