GB2222654A

GB2222654A - Chain block assembly

Info

Publication number: GB2222654A
Application number: GB8816118A
Authority: GB
Inventors: Stephen Reginald Potts
Original assignee: WHEWAY BECKER Ltd
Current assignee: WHEWAY BECKER Ltd
Priority date: 1988-07-06
Filing date: 1988-07-06
Publication date: 1990-03-14
Also published as: GB8816118D0

Abstract

A chain block assembly 10 comprising a housing 11 having a lift wheel 12 rotatably mounted thereon and around which a chain C is entrained, the chain being adapted to support a load, and the chain comprising a plurality of interengaged links, each link comprising a closed loop made of material of non-circular cross-section, the cross-section having a maximum longitudinal dimension L which is greater than a maximum transverse dimension T and said transverse dimension lying in, or parallel to, a central plane P-P of the link. The non-circular cross section, as shown, comprises semi-circular end parts 31 interconnected by spaced parallel rectilinear parts 32. <IMAGE>

Description

Title: "Chain Block Assembly" Description of Invention This invention relates to a chain block assembly comprising a housing having a lift wheel rotatably mounted thereon and around which a chain is entrained, the chain being adapted to support a load.

The lift wheel is typically rotatably driven by an electric motor or by hand, for example, by means of a drive sprocket engaged with an endless loop of a drive chain and rotatable by manual pulling on the drive chain, the drive sprocket being connected, typically through gears, to the lift wheel to rotate the lift wheel.

The chain may provide a single purchase or a multi-purchese tackle to support the load.

The design of a chain block assembly is essentially governed by the load it is desired to support on the chain, and this controls the size of chain needed. Having thus determined the necessary size of chain, the size of the lift wheel is correspondingly determined as it has to have pockets of correct size to receive the chain. The size of the lift wheel determines the size of the block housing. Thus the block assembly dimensions, weight and manufacturing costs are directly related to the lift wheel size.

An object of the invention is to provide a new and improved chain block assembly, and more particularly a chain block assembly which has a better cost and/or size and/or weight to load carrying capacity ratio than chain block assemblies known hitherto.

According to the present invention we provide a chain block assembly comprising a housing having a lift wheel rotatably mounted thereon and around which a chain is entrained, the chain being adapted to support a load, and the chain comprising a plurality of interengaged links, each link comprising a closed loop made of material of non-circular cross-section, the cross-section having a maximum longitudinal dimension which is greater than a maximum transverse direction and said transverse direction lying in, or parallel to, a central plane of the link.

The non-circular cross-section may comprise semi-circular end parts interconnected by spaced parallel rectilinear parts.

The maximum transverse dimension may be the same or substantially the same as the diameter of a chain of circular cross-section which would be conventionally used with said lift wheel.

The lift wheel may have the same pitch as a conventional lift wheel for us with a conventional chain of circular cross-section links having a diameter the same or substantially the same as said maximum transverse dimension.

The area of the cross-section may be in a predetermined relationship to the cross-sectional area of a chain the links of which are comprised of material of circular cross-section and which is of a maximum dimension which would be conventionally used with said lift wheel.

Said predetermined relationship may be such that the area of the crosssection of a chain according to the present invention is greater than the area of the cross-section of said maximum size of chain conventionally used.

The cross-sectional area of the chain may be greater than pi multiplied by the square of half said maximum transverse dimension.

The area may be not less than 30% greater, may be 30-50% greater and preferably is about 40% greater.

Each link may have been made by bending the link to said closed loop shape from stock of said non-circular cross-section.

Preferably, the non circular section is constant throughout each link.

An example of the invention will now be described with reference to the accompanying drawings wherein FIGURE I is a diagrammatic cross-sectional view through part of a chain block assembly embodying the invention, FIGURE 2 is a side elevation of part of the chain used in the chain block assembly of Figure I and FIGURE 3 is a section on the line 3-3 of Figure 2.

Referring to Figure I, there is shown a chain block assembly 10 comprising a housing I I within which a lift wheel 12 is rotatably mounted by bearings 13 provided in seats within the housing I I. The lift wheel 12 is fixed to rotate with a shaft 14 supported by the bearings 12 and which has fixed thereto a pinion 15 which meshes with a further pinion 16 fixed to rotate with a shaft 18 mounted in bearings 19 within the housing I 1 and carrying a pinion 20 which meshes with the further pinion 21 carried on the output shaft 23 of an electric motor 24 having a brake 25 for the shaft 23.If desired, the pinion 20 may be part of a slipping clutch arrangement so as to prevent overloading of the motor if the load to be lifted exceeds a predetermined weight or if the motor 24 is continued to be operated after a hook 26 has been raised into engagement with the housing I I. The housing 11 is provided with a suspension hook 27 so that the housing can be suspended from a suitable support.

A chain C is entrained around the lift wheel 12 and is anchored at one end, not shown, to the housing II of the block, whilst it is connected at its other end by a transverse pin, not shown, passing through the end loop of the chain, to the hook 26.

As best shown in Figures 2 to 3 the chain C comprises a plurality of inter-engaged links 30 each link comprising a closed loop made of material of non-circular cross-section.

As best shown in Figure 3 the non-circular cross-section has a maximum longitudinal dimension L which is greater than the maximum transverse dimension T. The maximum transverse dimension T lies in the central plane P-P of the link. By central plane of the link is meant the plane which contains the centre of the cross-sectional area at any position around the closed loop of the link.

In the present example the cross-sectional area comprises two spaced semi-circular parts 31 inter-connected by spaced parallel rectilinear parts 32 so that the cross-section is of generally oval shape.

In the present example the dimension L is 7.3mm and dimension T 5mm.

This provides a cross-sectional area which is substantially the same as that of a conventional chain made of material of circular cross-section and having a 2 diameter of 6.3 mum, i.e. 31mm . Thus, in the present example the chain has a breaking strength approximately equal to that of a chain of material 6.3mm diameter but since the dimension T is 5mm the chain can be accommodated by a lift wheel which is too small to receive a 6.3mm diameter chain.

Further, a conventional chain of circular cross-section of 5mm diameter has a pitch P, i.e. an internal loop dimension in the longitudinal direction of the loop, of 50mm, whilst a conventional chain with a crosssectional diamater of 6.3mm has a pitch P of 19mm. The non-circular chain of the present invention has a pitch P of 15mm.

Therefore, the present invention permits of the use of a smaller lift wheel than would conventionally be required for a conventional chain of the same strength to lift the same load than would be possible if the chain were made of material of circular cross-section. Moreover, the number of chain pockets in the wheel may be reduced which permits reduction in the pitch diameter of the wheel and hence the smaller the gear reduction for a desired chain hoisting velocity, thus permitting reduction in the size of the housing dimension, weight and manufacturing cost.

In the present example the width W of a loop, i.e. an internal loop dimension in the transverse direction of the loop is 1.25 x the dimension T described hereinbefore. Thus, the external width of a loop of the chain of the present embodiment is (5mm x 2) + 1.25 x 5 = 16.25mum. This is to be compared with the external width Wex of a conventional chain of circular cross-section of 6.3mm diameter, the external width of which would be (6.3 x 2) + 1.25 x 6.3 = 20.475mm. Thus the width of the sprockets in the lift wheel are reduced compared with those which would be necessary for a chain of conventional shape of the same load carrying capacity, further permitting reduction in the size of the lift wheel.

In determining the size of the chain, other considerations such as the manner in which the chain is connected to a hook, or other means for supporting a load, must be considered. For example, if the chain is connected to a hook solely by means of a transverse pin received within the end loop, the size of the chain must be such that that pin is adequately strong. If desired, however, the pin itself may be made of non-circular configuration so as to have a greater dimension in the longitudinal extent of the loop, thereby providing adequate strength, or by providing other means for connecting the hook or other supporting means for a load to the chain.

Although in the above example a chain block assembly having a single purchase is described, if desired a block assembly may be provided with a multi-purchase with appropriate numbers of lift wheels on upper and lower block assemblies.

If desired, instead of rotating the lift wheel by an electric motor as described hereinbefore, the lift wheel may be driven by a chain drive sprocket with which an endless loop of a drive chain is engaged so that the drive sprocket can be rotated by manual pulling on the drive chain and rotation of the drive sprocket being communicated, typically through appropriate gears, to the lift wheel to rotate the lift wheel. It should be appreciated that the dimensions given hereinbefore are solely by way of example and the invention may be applied to chains of other dimensions, also chains where the ratio of the transverse dimension to the longitudinal dimension differs from that described hereinbefore.

Preferably the cross-sectional area of the chain is greater than pi multiplied by the square of half the dimension T., and the area may be not less than 30% greater, or may be 30 - 50% greater and preferably is about 40% greater.

The chain is manufactured in conventional manner but using the above described non-circular stock, low alloy steel stock instead of circular stock.

That is, blanks are separated from a length of the non-circular stock, bent around a mandrel to provide a plurality of inter-linked closed loops and the adjacent ends of each blank of a loop are joined together, for example, by resistance butt welding.

Using non-circular stock particularly facilitates the chain making operation since it permits of the apparatus being provided with means to orientate the chain in a desired orientation so that the conventional weld preparation i.e. opposed bevels formed during cropping is correctly aligned in the apparatus.

If desired, the links may be manufactured in any other desired way. For example, the links may be manufactured from initially circular cross-section stock which is formed to provide said links made of non-circular material.

Although in the above example the case of a cross-section as illustrated in Figure 3 is described if desired the cross-section may be of other noncircular shape. For example, of elliptical shape or of other non-circular shape where the maximum longitudinal and transverse dimensions are as described above. For example, the chain cross-section may include two portions of equal longitudinal and/or transverse cross-section separated by portions of shorter length. In such a case whilst the two portions of maximum transverse, and/or longitudinal, dimension would not be coincident with or perpendicular to, said central plane they would be parallel, to or parallel to a perpendicular to, said plane and as a result when the chain is between the guide surfaces of the guide means then the maximum transverse dimension would be disposed so as to extend between the associated guide surfaces.

The features disclosed in the foregoing description, or the accompanying drawing, expressed in their specific forms or in terms of a means for performing the disclosed function, or a metal or process for attaining the disclosed result, or a class or group of substances or compositions, as appropriate, may, separately or any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS:

I. A chain block assembly comprising a housing having a lift wheel rotatably mounted thereon and around which a chain is entrained, the chain being adapted to support a load, and the chain comprising a plurality of interengaged links, each link comprising a closed loop made of material of non-circular cross-section, the cross-section having a maximum longitudinal dimension which is greater than a maximum transverse direction and said transverse direction lying in, or parallel to, a central plane of the link.
2. An assembly according to Claim I wherein the non-circular crosssection comprises semi-circular end parts interconnected by spaced parallel rectilinear parts.
3. An assembly according to Claim I or Claim 2 wherein the maximum transverse dimension is the same or substantially the same as the diameter of a chain of circular cross-section which would be conventionally used with said lift wheel.
4. An assembly according to any one of the preceding claims wherein the lift wheel has the same pitch as a conventional lift wheel for us with a conventional chain of circular cross-section links having a diameter the same or substantially the same as said maximum transverse dimension.
5. An assembly according to any one of the preceding claims wherein the area of the cross-section is in a predetermined relationship to the crosssectional area of a chain the links of which are comprised of material of circular cross-section and which is of a maximum dimension which would be conventionally used with said lift wheel.
6. An assembly according to Claim 5 wherein said predetermined relationship is such that the area of the cross-section of a chain according to the present invention is greater than the area of the cross-section of said maximum size of chain conventionally used.
7. An assembly according to any one of the preceding claims wherein the cross-sectional area of the chain is greater than pi multiplied by the square of half said maximum transverse dimension.
8. An assembly according to Claim 7 wherein the area is not less than 3096 greater than said multiple of pi.
9. An assembly according to Claim 7 wherein the area is 30-50% greater than said multiple of pi.
10. An assembly according to Claim 7 wherein said area is about 40% greater than said multiple of pi.
II. An assembly according to any one of the preceding claims wherein each link has been made by bending the link to said closed loop shape from stock of said non-circular cross-section.
12. An assembly according to any one of the preceding claims wherein the non circular section is constant throughout each link.
13. An assembly substantially as hereinbefore described with reference to the accompanying drawings.
14. Any novel feature or novel combination of feotures disclosed herein and/or shown in the accompanying drawings.