The invention relates to a chain, in particular case-hardened hoist chain, having chain links which are produced from D-profile steel sections by bending and welding and which are rounded in the region of the transition between their flanks and their outer, essentially flat circumferential surface.
Chains with D-profile sections have a flat surface running around the outside of the link. Compared to round chain, this surface reduces the surface pressure on the supporting surface of the chain wheels driving and/or deflecting the chain. Less surface pressure translates into less chain wheel and chain link wear.
A prior patent, EP 0816717 A2, discloses a chain of D-profile sections in which the outer circumferential surface merges via sharp edges into the rectilinear flanks of the particular section. These edges are slightly rounded, and the radius of the rounding is very small in order to avoid a cross-sectional reduction in the link profile. This is also the case in other relevant chains used in practice.
In our patent, the rounding radius in the region of the transition between the flanks and the outer, essentially flat circumferential surface of the chain links is equal to 0.2 to 0.4 times the value of the distance between the lateral flanks of the chain links. The design noticeably increases its dynamic strength and the service life of the chain, without a corresponding deterioration in the wear ratios. By making the edges rounder, the inner width of the chain links can be made smaller, which further increases the chain life.
The longitudinal limbs of the chain also have flattened zones. The partial change in the links’ cross-section, and the structural compression caused during the flattening process further increase the dynamic strength of the links.
It can be seen that the inner width bi of chain links belonging to the prior art (Fig. 1) has to be larger than the inner width bi of the chain links that are illustrated in Figs. 2 and 3. The edges of these latter links are rounded, with rounding radii of 0.2 times (Fig. 2) and 0.4 times (Fig. 3) the value of the distance A between the flanks 2, 3 of the links. The value A here is equal to the height H of the D-profile cross section in the region of the plane running through the centres of the two longitudinal limbs of the particular link. At the rounded ends, the distance A may be less than the maximum height H.
The short chain piece which is illustrated in Fig. 4 and consists of four chain links has different alternating chain links. In the case of the first and third chain links from the left, numbered 6 and illustrated in Figs. 5 to 7, the longitudinal limbs 8 and 9, which are connected to each other by rounded ends 10 and 11, are provided on opposite sides with flattened zones 12 and 13 which are produced by plastic deformation and, on opposite sides of the longitudinal limbs 8, 9, are oriented essentially perpendicular with respect to a plane running through the centres of the two longitudinal limbs 8, 9. The plastic deformation results in a compression of the material and displacement of the material in the region of the cross section of the longitudinal limbs 8 and 9, as can be seen with reference to the bulges 14 and 15 in Fig. 7.
In the case of the second and fourth links in the chain section in Fig. 4, numbered 7 and illustrated in Figs. 8 to 10, the longitudinal limbs 8 and 9 are provided on their respective opposite sides with flattened zones 16 and 17 which are oriented parallel to a plane running through the centers of the two longitudinal limbs 8 and 9. Also in the case of the links according to the Figs. 8 to 10, there is a structural compression and displacement of material in the region of the longitudinal limbs 8 and 9 leading in this case to bulges 18 and 19.
If a chain strand of the type illustrated in Fig. 4 is used, the first and third links (6) would be arranged so that they pass through the particular pocket chain wheel as horizontal links while the second and fourth links (7) would form vertical links.
