Description

Chain for ornamental stone sawing machines, without locking pegs for the pivot pin

Technical Field

The present invention relates to an improved chain saw or cutting chain, as used in sawing machines for sawing marble, and generally, ornamental stones. These sawing machines have an arm that can be oriented and which has a flat shape, with guides for the chain, and drive and idle pinions respectively at the ends of the arm itself.

More particularly, the invention concerns a cutting chain which has no locking peg for locking the pivot pin allowing pivoting between an inner chain link and an outer chain link.

Background Art

The cutting chains of the background art include an endless series of chain links, wherein each "inner" chain link is pivotally connected with two "outer" chain links and these outer and inner chain links are arranged so as to alternate. Each outer chain link supports a cutting tool carrying small plates of hard material (e.g. hard metals, tungsten carbides, polycristalline diamond, etc.). Instead, each "traditional inner chain link" is formed by a constant-thickness plate, a first half of which is inserted into a first and adjacent outer chain link, while the other half is introduced into a second and adjacent outer chain link, located on the opposite side of the inner chain link.

A recent patent (whose assignee is the present applicant), application number RM 98 A 000751 and granted patent number No. 1,302,903, further discloses a chain whose inner chain links are not of constant thickness, but have central projections

on each side, in order to distribute the lateral load also on the inner chain links, thereby limiting the wear in particular during the execution of horizontal cuts. Moreover, a liquid lubricant can flow through channels formed on said central projections of an inner chain link, thereby facilitating a more uniform distribution of the same lubricant on the whole surface of the chain, to improve sliding performance of the chain within the guide of the orientable arm of the sawing machine.

Specifically, the lubricant flow channels may have a comb-like configuration as shown in the drawings of the above patent, corresponding to a preferred, though non-limitative embodiment of that invention.

The Italian patent No. 1,302,903 has been mentioned in order to show how the present invention may be applied preferably to a chain having inner chain links with central projections, and even more preferably having lubricant flow channels on this central projection. However, it will be appreciated that the present invention is indifferently applicable also to a chain having "traditional inner chain links", that is, inner chain links of constant thickness.

Additionally, the present invention may also be applied to chains having outer chain links that support more than one small plate on the cutting tool, for instance a pair of such small plates. Actually, the present invention generally relates to a specific new system used to pivotally connect an inner chain link to an outer chain link. Thus, in particular, the description of the Italian patent No. 1,302,903 can be considered integrally incorporated for reference in the present description for clarifying any technical detail whatsoever, relating the application of the present invention to a chain with inner chain links having a projection on each of its sides.

In general, known chain saws, used in sawing machines for sawing ornamental stones, have many drawbacks as concerns the pivot system between an outer chain link and an inner chain link.

A first of these drawbacks is that the peg - whose function is to prevent any rotation of the pivot pin relative to the outer chain link and to prevent the pivot pin from "sliding out" (coming out) of the chain - is subject to wear, and it could cause, once broken, the sliding out of the pivot pin, or it could cause a slight protrusion of the same peg on the opposite side, or a slight protrusion of the pivot pin with respect to the surface of the chain, and in this way it could give rise to problems at the guide entry when such a slightly protruding pin - or the peg - reach the guide entry (lead-in) of the chain guide, after passing beyond the free space between the drive pinion and the guide. Moreover, even assuming that the pivot pin does not come out of the chain, it could nevertheless start rotating within its seat, ovalising this seat, and giving rise to the ensuing problems which are well known to those skilled in the art. Furthermore, in the background art, the slot on the outer chain link, which receives the folded (bent) part of the peg to prevent rotation of the pivot pin relative to the outer chain link, forms a weakening point of the outer chain link, since it decreases the thickness of the material and could be the source of ensuing cracks or lead to other problems, as a consequence of the stresses that occur in operation. Therefore, an object of the present invention is to produce an improved chain saw (cutting chain), used in sawing machines for cutting marble or other ornamental kinds of stone, which minimises maintenance works and idle times for the sawing machine, that were due to wear or breakage of the background art pegs. Actually, the peg is omitted altogether in the pivot system of the present invention. A further object is to improve lubrication at the articulation point, to reduce the occurrence of failures.

Still another object is to eliminate protruding parts subject to wear - e.g. the pegs of the background art - from the surface of the outer chain link.

Still another object of the present invention is the elimination of the slots that were used in the background art to bend the pegs, and which could trigger the formation of cracks and weaken the outer chain link by reducing its resistant thickness. A further object is to provide a pivot system between inner and outer chain links which lends itself to automatisation of the chain assembling process, at the time the sawing machine is built and supplied to a customer, but additionally, an object is also to provide a pivot system that facilitates chain repair operations in a quarry, where such repair must necessarily be performed manually. Still a further object of the present invention is to reduce the number of components to be assembled. In fact, due to the absence/elimination of the pegs there will be less transport problems, problems of material to be stored, of loss of pieces, etc. Obviously, however, the main object of the present invention amounts to insuring a noticeably higher reliability of the chain as compared with conventional chains, considering the normally occurring troubles at the articulation points between inner and outer chain links (e.g. breakage of the pivot pins or of the pegs) which bring about machine idle times and require laborious/inconvenient repair works.

Disclosure of Invention

The present invention attains its objects by means of the features defined in claim 1.

In substance, instead of using a peg in order to lock the pivot pin with respect to the outer chain link, by bending (folding) the peg inside the corresponding slot conventionally provided on the outer chain link, with all ensuing problems resulting from this procedure (wear of the peg, its possible breakage, weakening of the resistant cross-section of the pivot pin, etc.), the pivot pin is directly locked, that is fixed, on the inner chain link. Therefore, there will be a relative rotation

between the pivot pin and the outer chain link, in contrast with the standard teachings of the background art, according to which the relative rotation takes place between the pivot pin and the inner chain link. There will be no protruding elements, since the pivot pin is flush with the lateral surface of the outer chain link.

In particular, the fixing of the pivot pin on the inner chain link is realised by the action of pressure, by introducing it in a hole of the inner chain link while appropriately selecting dimensional tolerances. Preferably, the pivot pin will include snap-lock insertion means for allowing the snap insertion in the respective hole of the inner chain link. Advantageously, the snap insertion of the pivot pin is obtained by providing an elastic element, or spring element, within the same pivot pin, acting with a predetermined preload on a small sphere that laterally projects from the pivot pin but remains confined - after upsetting - inside a transversal bore of the pivot pin, this transversal bore terminating inside a hollow space - within the pivot pin - used to receive the spring element.

The elastic, or spring element, is preferably not permanently deformable (high memory), to allow a long duration/use of the pivot pin. Anyway, when the pivot pin is in its locked condition in the hole of the inner chain link, said small sphere protrudes inside a (partial or complete) circular groove, obtained on the hole wall of the inner chain link. Preferably, the outer chain link holes which receive the pivot pin are perfectly circular in this case, since for instance the slot used to receive the peg of the background art after its bending is no more required. The inner chain link may have a constant thickness, or alternatively, it may present central projections for the distribution of the load. Advantageously, said central projections will have lubrication channels. In any case, the present invention is applicable to any kind of already existing chain, provided it is suited to allow a "conversion" from the old peg-based pivot system to a system according to the present invention.

Brief Description of Drawings

The present invention will now be disclosed in more detail with reference to preferred embodiments, which are illustrative but neither limitative nor binding with respect to the concept on which the present invention is based. In the drawings:

FIGURE 1 is a perspective and general exploded view showing the main components of the chain according to the present invention, in a first possible, non-binding embodiment;

FIGURE 2 is a view of a simple already assembled portion of the chain according to Fig. 1 , including three inner chain links and three outer chain links;

FIGURE 3 is a perspective view that specifically shows the innovative pivot system of the present invention, applied to a connection between an outer chain link and an inner chain link with central projection on each side, as in Figs. 1 and 2;

FIGURE 4 shows the components of Fig. 3 in the assembled condition;

FIGURE 5 respectively shows a cross section and a lateral view of the innovative pivot pin of the present invention;

FIGURE 6 is a vertical cross-sectional view (section A-A of Fig. 7) of an outer chain link connected to an inner chain link;

FIGURE 7 is a plan view from above (direction of arrow D of Fig. 6) of the object shown in Fig. 6;

FIGURE 8 is a view similar to Fig. 4, from a different angle of observation;

FIGURE 9 is a vertical, central, and longitudinal sectional view of the outer chain link according to the present invention, in the direction defined by C-C (vertical plane C-C) in Fig. 11;

FIGURE 10 is a front view (see direction of arrow B in Fig. 9) of the outer chain link of Fig. 9;

FIGURE 11 is a plan view from above of Fig. 10;

FIGURE 12 is a perspective view of the outer chain link of the present invention intentionally showing some details in transparency;

FIGURE 13 is a view similar to Fig. 8 with details intentionally shown in transparency;

FIGURE 14 is a view similar to Fig. 1, showing a second possible embodiment of chain according to the present invention, in which the inner chain links are "traditional inner chain links", that is, of constant tickness (without central projections);

FIGURE 15 is a perspective view, a lateral view, and a cross-sectional view of a further embodiment of the invention;

FIGURE 16 is a view fully analogous to Fig. 3, in which however there are provided nail-shaped recesses on the edge of the articulation holes (pivot holes) of the outer chain link (this solution with recesses 24 is nevertheless also applicable

to any other kind of chain employing the pivot system of the present invention, for instance to Fig. 14 and Fig. 15).

Description of some preferred embodiments of the present invention In the figures, to render the description less difficult to understand, identical reference numbers (or reference numbers with apexes) always denote the same components. Moreover, the present description omits all those details which are already known to the skilled person and which are irrelevant for understanding the present invention. For any explanation concerning the shape and function of inner chain links provided with projections, reference is made to the above mentioned Italian patent.

Fig. 1 shows a first embodiment of a chain according to the present invention that uses inner chain links 1 with central projections 2 presenting channels 3 for the passage of a lubricant. In the illustrated example, the channels 3 have a comb-like configuration, though they could all the same have another shape, or they could even be eliminated from the projection 2, since - as explained later in the description - the lubrication is in any case "external" and therefore easier to perform than in the background art. This concept of "external lubrication" will be made clear below.

Fig. 1 essentially shows first fixing means 4, 4', 4" used to fix a small plate 6 on a seat 5 obtained on a cutting tool 10, and second fixing means 7, 8, 9 for attaching the cutting tool 10 on the outer chain link 11 of the present invention. Said first and second fixing means are preferably of a removable kind, as shown in the figure.

Fig. 1 also shows a pivot pin 12 according to the present invention.

It may be seen in Fig.l that the outer chain link 11 has two flanks 13 a, 13b, apt to receive from one side and from the opposite side two respective inner chain links

(see for instance Fig. 8 which for illustrative purposes shows the insertion of only one inner chain link 1, the other being inserted symmetrically from the opposite side but being omitted from Fig. 1). The assembled state of three pairs of inner/outer chain links 1/11, is depicted in Fig.2, and the cutting chain is formed by a alternate and endless series of such pairs 1, 11 of chain links.

In the figures, it may be noted the complete absence of any traditional peg for locking the pivot pin 12. Moreover, it may be noted that holes 14 present on the outer chain link do not, as a consequence, have slots for allowing the bending of pegs. In other words, these holes 14 are round and serve exclusively for the insertion of the pivot pin 12.

Each pivot pin 12 is received inside two opposite pivot holes 14 of the outer chain link, which are respectively located on the flank 13a and the flank 13b, and it is also driven through a corresponding hole 15 of the inner chain link 1, which must be aligned beforehand to this pair of holes 14, 14. The respective diameters of the pivot pin 12 (external diameter), of the opposite pair of pivot holes 14, and of the hole 15 of the inner chain link, are selected in such a way that the pivot pin 12 can easily pass through the holes 14, 14, while a certain pressure needs to be exerted in order to guide the pivot pin through the hole 15 of the inner chain link . In other words, the pivot pin 12 will then remain fixed at its central portion inside the hole

15 of the inner chain link 1, and the pivot pin 12 will thereafter only be able to rotate with respect to the surface of the hole wall of the holes 14 of the outer chain link. Contrary to background art teachings, relative rotation according to the present invention occurs between the lateral surface 16, at both ends of the pivot pin 12, and the inner wall or surface of the holes 14. The portion of lateral surface 16, corresponding to the central portion of the pivot pin 12, will remain fixed (locked) inside the wall of the hole 15, thus preventing any possible relative rotation

between the pin 12 and the inner chain link 1.

The surfaces in relative motion being located externally, and no more internally as in the background art, the lubrication will be "external" and will therefore be performed more easily, on both sides of the outer chain link 11. Thus, it will suffice to "lubricate the holes 14". In particular, if desired, the lubrication channels 3 could also be omitted from the central projections 2 for load distribution.

Tolerances of the various diameters of the holes and of the pivot pin will be selected in such a manner that the pressure required to drive (press) the pivot pin 12 into the hole can also be applied manually by means of a hammer-stroke. In any case, the process for assembling the chain can be rendered automatic by adopting a suitable machine not included in the present invention. From Fig. 2, for instance, it can be seen that the circular surface 17 at both ends of the pin 12, is flush with the remaining external lateral surface 18 of the flanks 13a,b of the outer chain link 11. It follows that there will be no protruding parts

(compare the pegs of the background art), so that under this aspect, no parts exist that are subject to wear inside the guides of the sawing machine arm, nor protrusions that could give rise to problems at the entry (lead-in) of these guides, where a free section of the chain is guided into the guide itself. Moreover, since the holes 14 are circular and do not include any bending slot, there are no potential regions of formation of cracks or weakening zones of the material.

As shown in Fig. 5, the pivot pin 12 could have a circular bevelling (that is, chamfered) zone 19 at both ends, in order to facilitate its insertion into the holes 14.

Analogously, this bevelling could be provided in the holes 14, obviously on their external side.

According to the present invention, preferably the pivot pin 12 has a small

metallic sphere 20 urged by an elastic preload exerted by an elastic material or helical spring, 21. This elastic element 21 is lodged inside a respective hollow space within the pivot pin 12. In the rest position, in absence of external forces, the small sphere 20 projects a certain distance beyond the lateral wall 16 of the cylinder, being urged by the elastic element 21, the latter having a high elastic memory (for example a suitable non deformable material is Eladur™ ). The small sphere 20 is introduced in a transversal bore extending parallel to the pin basis surfaces 17, this transversal bore being provided on the central portion of the lateral wall 16 (equidistantly from the basis surfaces 17) of the pivot pin 12, that is, in that portion which engages and remains fixed within the hole 15 of the inner chain link 1. The transversal bore terminates in the hollow space inside which the elastic element 21 is received. The end of the transversal bore leading outside, has been upset (zone 22 in Fig. 5), in order to reduce the diameter of the outer end of the transversal bore, thereby preventing the small sphere 20 from coming out, which then can project out only by a small distance as shown in the upper part of Fig. 5 (cross section parallel to the basis surfaces 17 in a plane equidistant from these surfaces).

As best shown in Fig. 8, each inner chain link 1 has a circular groove 23 obtained in each of its two holes 15, on the cylindrical wall of a respective hole 15. When a pivot pin 12 is introduced in an aligned set of holes 14-15-14 of the outer chain link and of the inner chain link, for instance by means of a hammer-stroke, or by using another tool, or automatically with an appropriate machine (press) provided with a suitable tool, the small sphere 20 is first urged completely into the transversal bore of the pin 12, and subsequently it snap fits into the circular groove 23 of the hole 15. This is a totally reliable system that avoids the accidental detachment or "unthreading" of the pivot pin 12. It is conceivable that the circular groove 23 could extend only along part of a complete circle, e.g. a circle arc of 90°-120°. With reference to Fig. 6 it is

preferred that this partial circular groove 23 extends only along that side of the cylindrical wall of the hole 15, opposite to the side marked by an "R", since in this manner, on the side "R" which is subject to a traction during the operation of the chain, the load will distribute itself on a solid (continuous) surface - without grooves - of the hole wall.

The present invention has the further advantage that in contrast with a conventional pivot pin which is axially bored to receive the peg and which has seats (cavities) allowing to bend and receive the bent peg ends, the pivot pin of the present invention is surely more resistant, due to the greater resistant cross section formed by the material. If the small sphere is not used, the pivot pin could even form a solid (full) body, although the probability of its detachment ("unthreading") would clearly be greater.

The present invention can be applied to all kinds of already existing chain saws, on condition that it is possible to use this specific pivot system between the outer and inner chain links.

The material employed to produce the pin and the chain links is usually hardened steel, though the invention comprises the use of materials with similar properties. Fig. 15 shows a further embodiment of the invention. In this case the pivot pin 12 is conical and has cylindrical ends. The holes 14 have slightly different diameters on one flank, with respect to the opposite flank, of the outer chain link.

The pin 12 is press-fitted and thereby fixed in the hole 15 of the inner chain link as in the other embodiments. Preferably the arrangement of the pair of holes 14 on the outer chain link is inverted, that is, the two pins 12 are inserted in the outer chain link from opposite flanks of the outer chain link.

Actually, in Fig. 15, on the left lower side, it can be seen that one hole 14 has a diameter greater than that of the other hole 14.

Finally, Fig. 16 shows an embodiment which is identical to the embodiment of Fig. 3, except that nail-shaped recesses 24 are provided on the edge of the pivot holes 14 of the outer chain links. Preferably, the recesses 24 point in the direction parallel to the advancement movement of the chain, as indicated in Fig. 16, and serve to collect a certain amount of lubricant, in order to improve the lubrication of the surfaces which rotate relative to each other, that is, the lateral surface of the pin 16 and the surface of a hole 14.

The maximum extension (maximum diameter) of a recess 24 will preferably be equal to 0.3 to 0.5 times the diameter of the respective hole 14. The maximum depth (maximum "thickness") of a recess 24 will preferably be 0.4 to 0.7 times the thickness of a flank (wall) of the outer chain link (depth of a pivot hole 14 of an outer chain link).

Preferably, each hole 14 will be provided with such a recess 24, the latter being preferably "nail-shaped" as in Fig. 16. This small size of the recess 24 does not weaken the structure.

Industrial Application

The present invention allows to produce chain saws for sawing machines provided with such cutting chains which are employable in quarries of ornamental stones, like marble, travertine, etc. and have a more reliable operation, while insuring a higher productivity/yield and less maintenance. The assembling of the chain is also facilitated and lends itself to automation.

List of reference terms and signs 1, 101 inner chain link

2 central projection

3 lubrication channels

4, 4', 4" cutting plate fixing means

5 seat of cutting plate

6 cutting plate

7, 8, 9 cutting tool (10) fixing means

10 cutting tool 11 outer chain link

12 pivot pin 13a, 13b flanks of the outer chain link

14 pivot holes of the outer chain link

15 holes of the inner chain link 16 lateral surface of the pivot pin

17 bases of the pivot pin

18 outer lateral surface of the flanks 13a, 13b

19 chamfered zone at the ends of the pivot pin

20 small sphere 21 elastic element

22 upset zone on the pivot pin surface

23 (partial) groove in the holes 15 of the outer chain links

24 lubrication recess