FR2702988A1 - Saw chain for chain motor saws. - Google Patents

Abstract

The present invention relates to a saw chain for chain saws, equipped with drive links (2), assembly links (4) and cutting links (3) which are hingedly connected to each other by means of rivets (6) whose heads (7) bear outside the rivet holes (10) on the side flanks of the links. Known saw chains have long exhibited convex rivet heads and the invention aims to transform the known saw chain so that the rivet assembly in total exhibits increased mechanical strength for favorable friction conditions, without this. leads to technical drawbacks in terms of manufacture. This object is achieved by making the rivet heads (7), at least approximately in the region of the rivet hole (10), concave.

Description

i Saw chain for chain motor saws The present invention

concerns a saw chain

  for chain motor saws, fitted with chain links

  drag, assembly links as well as mail-

  cutting edges which are hingedly connected between

  them by rivets whose heads are supported, ex-

  inside of the rivet holes, against the lateral flanks

links.

  In known sawing chains of this kind the various links of the chain are connected in an articulated manner by rivets with convex head so that the

  convex surfaces of the rivet heads protrude laterally

  Lately on the two sides of the bars of the different links connected to each other by the rivets. Particularly in the case of wood with long fibers, the rivet heads risk, by circulating on the guide bar, of being constantly in contact with the lateral flanks of the saw cut since the wood fibers bounce in the saw cut The chain assembly rivets

  sawing are subject to extremely high stresses.

  They must have a high dynamic resistance to repeated efforts and be resistant to very high tensile and shear forces which, for high speeds of circulation, are exerted on them during the cutting work Consequently, the known assemblies,

  made with convex head rivets, require re-

  mechanical strength corresponding to these high constraints as well as an appropriate and sufficient dimensioning In addition, the usual rivets with convex laying head have the disadvantage that, from the edge of the rivet head to the middle of that here the gap between the

  surface of the rivet head and the saw cut shrinks

  cit wedge shaped, shavings can easily

  remain wedged, which can lead to loss of

  dement. The object of the present invention is to transform the method of construction, generally practiced for decades, of assembly rivets with convex head of such

  the way that the rivet connection presents in defi-

  nitive increased mechanical resistance that it is ob-

  hold without technical disadvantages in terms of fa-

  brication and which also presents conditions of

more favorable friction.

  This object is achieved, with regard to a saw chain for chain motor saws, equipped with drive links, connecting links as well as cutting links which are connected together in an articulated manner by rivets whose heads are supported, to

  the outside of the rivet holes, against the lateral flanks

  rals of the links, according to the invention by the fact that the

  rivet heads are made, at least approximately

  In the region of the rivet hole, in a concave form. Consequently, in the case of a chain-saw, the rivet heads have a shallow concave curvature which, oriented towards the rivet shank and arranged symmetrically. relative to the latter, in the radially outer region of the rivet head is transformed into an annular bead so that the latter forms a thickening in comparison with the

  slightly concave region located roughly centrally.

  In this respect the curvature in the concave region is uniform Advantageously, the ratio of the radius of

  curvature to the diameter of the rivet shank is included

  between 1.5 and 3 and is preferably equal to 2.

  To improve the tracing of the fibers and,

  te, in order to increase the mechanical resistance and

  duire the friction of the rivet head against the side walls of the saw cut the transition region from the concave part to the annular bead is, according to the invention

  tion carried out so as to progressively evolve

  avoid places of discontinuity or interruption

  tion in the curved line of the generators.

  Advantageously, the concave curvature that is to say

  say the concave recess of the rivet head is reali-

  sée, for an observer looking towards the axis of the rivet, in such a way that this recess covers at least approximately the section of the rivet hole and this perpendicularly to the axis of the latter. press-shaped, for example during the roller process, by delivery or the like, of the concave rivet head a favorable distribution of

  pressure, for a fiber tracing at the same time favorable

  maple in the radially outer region of the bead

  annular and, consequently, a high degree of resistance

  canic be assured It is also for this purpose that the concave rivet head with the annular bead is, for an observer looking towards the axis of the rivet, axially outside the lateral bearing surfaces of the elements of the chain arranged them

  facing each other and linked together by the ri-

  vets, i.e. the rivet head and the bead

  ring protrude beyond the lateral bearing surfaces

  rales Thus the concave embodiment provided for

  the rivet is limited to the part of the rivet head made

  protruding beyond the lateral flanks of the chain link bars Therefore, the rivet head

  may, during manufacture, either by means of

  roller formation, delivery or the like, be

  strongly compressed The rivet head has pro-

  properties of mechanical strength particularly favorable

  when when, according to another characteristic of the invention,

  tion, the annular bead present, observed directly

  the axis of the rivet, its greatest thickness approxi-

  matively in the region of the outer periphery of the

  Rivet hole Advantageously, for an observer

  keeping in the direction of the rivet axis, at least 50% of the mass of the annular bead is located radially

the outside of the rivet hole.

  In an advantageous embodiment the padding

  let annular and the evolution of the concave region of the

  rivet head are matched to each other and dimen-

  in such a way that in the finished rivet head

  the fibers of the constituent material of the ra-

  outer dialing of the annular bead extend at least approximately parallel to the surface of the link

  chain on which the bead is supported.

  Another characteristic of the invention consists in that the ratio of the maximum thickness of the annular bead to the minimum thickness of the rivet head is

  between 1.2 and 5 and is preferably equal to 2.

  The object of the invention is explained in more detail below with the aid of an exemplary embodiment illustrated in the accompanying drawings in which:

  Figure 1 shows, in side view, part of a

  do not chain saw; Figure 2 shows a section through a link

  assembly which is connected by a rivet to a link

  pant, the hitherto usual convex embodiment of the rivet head being indicated by dashed lines;

  Figure 3 shows the same section through an as-

  semblage corresponding to figure 2, the form of realization

  sation according to the invention of the rivet head being drawn

  born in the left half and the classic shape of the head

  rivet in the right half; the arrows on the outside of the rivet head indicate the direction of thrust of the riveting tool respectively for the concave shape and for the conventional convex shape of the rivet head; the arrows inside the rivet assembly indicate the direction of the resulting pressure inside the rivet; and Figure 4 shows a section similar to that of Figure 3, the left half also representing the rivet head according to the invention and the right half the conventional rivet head with the respective fiber pattern in the

rivet head.

  The sawing chain l has, as illustrated in FIG. 1, drive links 2, cutting links 3 as well as assembly links, also called fishplates 4 and rivets 6 by means of which these links are connected in a manner articulated to form a chain The cutting links 3 can be made in the form of planing or tearing teeth or in another way, the depth limiter 5 and the cutting links 3 being in the embodiment made in one single piece It is however also conceivable that the depth limiters constitute links separated from the chain or that additional safety members are still provided The assembly rivets 6 are constituted by a rod provided on both sides with rivet heads 7, 7 which, outside the rivet holes 10, bear against the lateral flanks of the chain links, namely against their

flat bar parts.

  As the figures show, the heads of the rivets

  are according to the invention carried out, at least approximate-

  lying in the region of the rivet holes 10, in a concave form, the concave curvature, as a recess, being situated in the central region of the rivet head and re-

  covering at least approximately the rivet hole 10.

  The concave recess 8 of the rivet head 7 is transformed

  me, in its radially outer marginal region, in a convexly curved bead 9 which forms a bead

  annular This annular bead 9 is advantageously

  surely, for an observer looking towards

  the 6 "axis of the rivet, with at least 50% of its share of

  face radially outside the rivet hole 10.

  The bottom line is that the generators of the curvature

  concave 8 join, without abrupt variations or inter-

  ruptures, in order to obtain a favorable pressure orientation and tracing of fibers and coefficients of

  advantageous friction, the greater curvature of the stuffing

  annular let Thus it is obtained for the rivet head a shape in which the annular bead 9, observed in the direction of the rivet axis 6 ", has its strongest

  thickness approximately in the region of the periphery

  external line 12 of the rivet hole 10, so that the o

  pressure orientation and fiber tracing favora-

  bles, shown in Figures 3 and 4, are favored for the rivet head according to the invention The mechanical strength in case of shearing of the rivet head is greater than that of a convex rivet head since for the same section of shear tracing the fibers

is more favorable.

  The saw chain shown by way of example in FIG. 1 is made in such a way that the wall of the rivet hole, that is to say the bearing surface of the rivet hole, is enlarged, by a conical part. 10 ′, in the direction of the bearing surfaces 11 In an embodiment of this kind, the greatest thickness d of the annular bead 9 is advantageously in the

  region of the outer periphery 12 of the conical part

than 10 'from rivet hole 10.

  It appears from FIG. 4 that the rivet head has obtained a shape for which the fibers of the material

  constitutive, designated by 13, extend, in the regi-

  radially outer of the annular bead 9, at

  less approximately parallel to the surface of ap-

  then the chain link, so that the mechanical resistance of the riveting is greater than for a convex rivet head In addition, the pressure exerted on the wall of the hole between the rivet rod 6 'and the corresponding rivet hole in the links to be connected is more

  strong This increased pressure is obtained thanks to the

  deformation stops modified during the ri-

  vetage (see figure 3) The arrows which on this figure

  on the outside of the rivet head 7

  show the strain pressure that the bank tool

  tage exerts and which results in a higher radial pressure in the rivet rod According to the number

  arrows the pressure exerted on the collar of the ri-

  vet is, as shown in figure 3, less since the pressure can only distribute itself one

  times Due to the convex shape of the edge tool

  tage pressure orientation during pre-riveting

  feels, over a large part of the concave surface of the rivet head, already a radial component which clearly improves the pronounced character of the radial pressure

  exerted in the rod of the rivet against the wall of the hole.

  Unlike the usual convex embodiment, also shown in Figures 3 and 4, of the head

  rivet and for which the fibers are strongly re-

  trodden and folded at the ends practically of 1800, in the embodiment according to the invention these fibers are pushed back, without intensive repression, out of the axis of the rivet rod 6 'towards the outside and thus folded

  maximum of 900 Thus the tracing of the fibers in the sec-

  decisive tion for the shear strength of the rivet head is hardly disturbed, which has a favorable effect on the shear strength Thanks to the increase in the mechanical strength of the riveting

  it is possible to make the rivet head in its

  appears in a smaller volume and in a flatter form, as shown in Figure 2, where the width Bl of a rivet with a convex laying head is greater than the width

  B 2 of a rivet with concave laying head.

  As already indicated, flatter rivet heads

  according to the invention have less lateral friction

  ral of the chain in the saw cut In addition, it is

  possible to make the elbow of the cutting teeth less ai-

  gu, which leads to a narrowing of the saw cut.

  The reduction in the width of the saw cut results in

  also a decrease in co-removal work

  skins necessary for sawing this allows faster sawing. Favorable material creep when riveting a concave rivet head also offers advantages

  on the technical level of manufacturing Due to the

  reduced formation of riveting material

  sions required for riveting are low The wear and tear

  tils and riveting machinery is reduced and the

  riveting rates can be increased It is

  be practically excluded that the axial pressure exerted on

  the rod of the rivet makes the collar of the latter jump.

  To obtain high pressures on the wall of the holes

  rivet with convex rivet heads it is necessary

  be sure to subject the rivet to a prior discharge before proceeding to riveting In the event of riveting with Q a concave rivet head this prior discharge can each time be reduced or entirely omitted depending on the requirements in terms of mechanical resistance This increases the safety of manufacturing because bursts of rivet collars can also occur by

  continuation of the prior refoulement In addition, for a

  vet with concave head the amount of material used is

  less, which at the same time reduces the manufacturing cost

  tion of the rivet and conduit, in particular in combination

  with cutting teeth with a less acute elbow, at a dimi-

  weight of the chain This also translates

  by a reduction in vibrations and noise produced.

  Another advantage is described below When repairing a saw chain and when lengthening an individual chain from a roller

  chain (goods by the meter), for example by a re-

  seller, the riveting must be undone by pushing or striking the rivet so as to

  expel it In the case of the convenient embodiment

  xe, known so far, of the rivet the differentiation tool spreads

  often pulls away from the middle of the rivet or even slides out of

  contact with the convex rivet head This is particularly

  so when strings are broken down by

  resellers, or even on site by drilled workers

  third parties, who often pull rivets out of the chains using an improper tool, for example a hammer or a punch. In these conditions, neighboring parts of

  the chain or the tool itself may be damaged.

  In the case of a concave rivet head the drift tool

  self-centered vetting, before or at the start of the pro-

  discontinuation of differentiation, so that damage to the components of the chain or the tool is excluded. It has been found that a preferred embodiment is obtained when, for a diameter of the rivet rod of between 2 mm and 5 mm, the radius R of the concave recess 8 of the rivet head 7 has a value which is between 3 mm and 15 mm In addition, it is advantageous

  gous than the ratio of the maximum thickness d of the stuffing

  let annular 9 to the minimum thickness dl of the rivet head 7 (see Figure 2) is between 1.2 and 5, and is preferably equal to 2, so that, despite the concave curvature 8, the head of rivet 7 still has sufficient material outside the actual rivet hole 10 in the region of the bearing surfaces

  planes 11 of the side walls of the chain links.

1 1

Claims (11)

  1 Saw chain for chain motor saws,   equipped with training links, connecting links   as well as cutting links, which are connected   be them articulated by rivets, the heads of which bear, outside the rivet holes, on the lateral flanks of the links, characterized in that   that the rivet heads (7) are made, at least ap-   approximately in the region of the rivet hole (10), in a concave form.   2 Saw chain according to claim 1, charac-   characterized in that the concave recess (8) of the head   rivet (7) is transformed, in the marginal region radia-   lement exterior (9) of the rivet head, in a stuffing convex let (9).   3 Saw chain according to claim l or 2, ca-   characterized in that the concave recess (8) and the bour-   annular reel (9) meet gradually.   4 Saw chain according to any one of the res-   previous indications, characterized in that the part   concave (8) of the rivet head (7) covers, for an ob-   servant looking in the direction of the rivet axis   (6 "), the section of the rivet hole (10) at least approxi- matively.   5 Saw chain according to any one of the res-   previous indications, characterized in that the padding   annular let (9) present, for a watching observer   towards the rivet axis (6 "), its thickest   approximately in the region of the periphery   outside (12) of the rivet hole (10).   6 Saw chain in which the wall of a rivet hole (10) widens conically outwards in the direction of the rivet head (7) according to any one   of the preceding claims, characterized in that the   greater thickness (d) of the annular bead (9) is in the region of the outer periphery of the   conical part (10 ') of the rivet hole (10).   7 Saw chain according to any one of the res-   above, characterized in that, for an observer looking towards the rivet axis (6 "), at least 50% of the constituent mass of the annular bead (9) is located radially outside the rivet hole (10).   8 Saw chain according to any one of the res-   dications preceding, characterized in that the fibers of the constituent material extend, in the radially outer region of the annular bead (9), at least approximately parallel to the bearing surface (11) links in the chain.   9 Saw chain according to any one of the res-   dications preceding, characterized in that, for a diameter of rivet rod between 2 mm and 5 mm, the radius (R) of the concave recess (8) of the rivet head   (7) has a value between 3 mm and 15 mm.   10 Saw chain according to any one of the res-   dications preceding, characterized in that the rivet head (7), including the annular bead (9) and the concave curvature (8), is located axially outside the lateral bearing surfaces (11) of the links ( 2; 3;   4; 5) of the saw chain connected by the rivet.   11 Saw chain according to any one of the preceding claims, characterized in that the ratio   from the maximum thickness (d) of the annular bead (9) to the minimum thickness (dl) of the rivet head (7) is between 1.2 and 5 and is preferably equal to 2.