Patent Application
20060243097
The present invention relates to saw chains used on chain saws having hardened cutting elements and related methods, such as methods for producing such saw chains and components thereof.
Chain saws are commonly used for cutting wood. Although chain a saws are frequently used for the cutting of wood, they are also used to perform many other cutting tasks. For example, chain saws can be used for cutting other materials. In some applications, such as firefighting, it is common for chain saws to be used for cutting wood, nails, metals, concrete, tile, and other relatively hard materials in an emergency situation. These hard materials are encountered when a chain saw is used to cut through floors, walls or other structural components in responding to a fire.
As a chain saw is used, the cutting members of the saw chain will typically wear down quickly and require frequent sharpening. This is true even with relatively soft materials, such as soft woods. It is a much greater problem when cutting harder materials. Even the mere striking of nails or screws while cutting through wooden wall or floor structures is very derogatory and can immediately dull a saw chain. When the saw chain cutting members become dull, the chain saw is temporarily taken out of service so that the cutting members can be resharpened.
The amount of wear exhibited by the saw chain, and the frequency at which such resharpening is required will vary depending on the demands placed on the saw chain. The required frequency of resharpening also depends on the construction and quality of the saw chain. Unfortunately, the cutting members of conventional saw chains tend to become dull quickly under easy conditions in wood, and they dull extremely fast when materials other than wood are encountered.
There has long been a need for a saw chain which is more resistant to wear and dulling, which is convenient and cost effective to manufacture, and which reduces the expenses associated with saw chain sharpening and other maintenance. This need has been especially acute for those who use saw chains for the cutting of materials other than wood or those who encounter rocks, soil or other material while cutting wood.
In an effort to meet this need, some saw chains having carbide cutting teeth have been produced. These saw chains have satisfied some of the aforementioned needs, but unfortunately the production of such saw chains requires expensive production techniques, such as manually affixing of each cutting element. Such saw chains are also expensive to maintain due to frequent breakage of the hardened cutting elements. Breakage and dislodgement of the hardened cutting elements has severely impeded their acceptance in the market for saw chains.
A need thus remains for a saw chain with increased resistance to breakage, general wear and extreme dulling and which is economical to produce and maintain. These and other benefits may be provided by the novel features and aspects of the inventions described herein.
Preferred forms or embodiments of the inventions are explained and characterized herein, often with reference to the accompanying drawings. The drawings also serve as part of the disclosure of the inventions made in the current application. Such drawings are briefly described below.
Introductory Note
The readers of this document should understand that the embodiments described herein may rely on terminology used in any section of this document and other terms readily apparent from the drawings and language common therefor. This document is premised upon using one or more terms with one embodiment that may also apply to other embodiments for similar structures, functions, features and aspects of the invention. Wording used in the claims is also descriptive of the invention and the text of the claims is incorporated by reference into the description entirely in the form of the claims as originally filed. Terminology used with one, some or all embodiments may be used for describing and defining the technology and exclusive rights associated herewith.
Chain Saw
Referring to
In operation, the engine and drive mechanism of the chain saw cause the saw chain 20a to move in a circuitous manner. The saw chain travels along the periphery of the cutting bar 15 so that the cutting members of the flexible saw chain 20a are supported and can be used to cut through various materials. In this document, the numeral 20 will be used to refer to conventional saw chains (
Saw Chain
Turning now to
Tie links commonly called tie straps 25a are used along both sides of the saw chain except where a cutter is placed. The tie straps are typically made using two different types of links. Preset tie straps 25f have projecting pivot studs 25d which extend through holes in the adjoining drive links 25b. Studs 25d also extend where appropriate through holes 50, 51 in the cutters. Where there are not cutters, the preset tie strap studs also are received through holes in opposing common tie links or tie straps 25e. The pivot studs are thus installed through the drive links and opposite tie straps 25e and then upset to form rivets.
The drive links are connected by the preset tie straps and mating common tie straps while allowing relative pivotal action so that the chain can conform to the curved guide bar periphery. The saw chain also is curved and trained about a drive gear (not illustrated) within the chain saw housing 16. Depending tangs 25c of the drive links 25b are typically received in a guide bar groove (not illustrated) that extends about the periphery of the guide bar adjacent to contacting areas against which the saw chain bears and is guided. The guide bar may include a distal end or tip which includes a guide bar sprocket (not shown) or the guide bar tip may merely be provided with a guide bar groove or channel.
Both the regular drive links 25l and bumper drive links 25k have first and second apertures 25m and 25n. The pivot studs 25d of the preset tie links 25f extend through the apertures 25m and 25n of the drive links.
Conventional Cutting Member
Referring to
Cutter 22a includes a cutter body 34. Cutter body 34 preferably includes a side plate portion 37 and top plate portion 57. The side plate portion of the cutter body is preferably integrally formed with the top plate portion to provide toughness to handle the impactive forces experienced by the cutter during operation. Together the side plate and top plate make up the cutter body. The cutter body 34 includes a front portion 35 and a rear portion 36. The cutter body 34 is defined in part by a leading edge 40, a lower edge 41, and a trailing edge 42. The side plate portion of cutter body 34 is also defined in part by an inner face 46 and an outer face 47.
A front or first aperture 50 and a rear or second aperture 51 which extend through the cutter body 34, and are configured to receive studs 25d, pins or rivets 30 which serve to connect the cutter 22a to the saw chain 20 drive links 25b and opposing tie straps. The opposing tie straps are typically preset tie straps that extend through holes in two adjacent drive links, such as through holes 50 and 51. The pivot studs 25d are then upset to form rivets 30.
Referring still to
The front portion 35 of the cutter body 34 preferably extends upwardly to form a depth limiter or depth gauge 77 which in operation controls or limits the depth of the cut which is made by the cutting member 22. The depth limiter is preferably a ramped depth gauge which slopes from the front 40 toward gullet 72. The space between the front part of the cutter, such as depth gauge 70, and the vertical cutting tooth 66 forms a recessed gullet 72. The gullet serves to facilitate chip removal during cutting with the saw chain.
Cutter Inset
Referring to
Examples of hardened wear part materials which may be useful alone or in combinations include tungsten carbide, titanium carbide, tantalum carbide, chromium carbide and silicon carbide. Other hard facing materials may be suitable, including currently available materials or materials developed hereafter. Typically tungsten carbide is now most available, economical and provides desirable mechanical properties and wear resistance, thus it is currently preferred. Mixtures of such carbides in various proportions may also be suitable depending on the mixture being selected.
A preferred formulation found useful in this invention is a grade C-11 tungsten carbide (87%) with cobalt binder (13%). This formulation provides a hardness on the Rockwell A scale of approximately 88.5±0.5. The approximate density is 14.20±0.1 grams/cubic centimeter. Transverse rupture strength of approximately 460,000 pounds per square inch is provided with this formulation. Other formulations which provide good wear resistance and toughness to resist breakage of the cutting element may also be suitable in constructions according to this invention.
Various binder materials may be used to produce the cemented carbides or other hardened cutting element materials. Other suitable materials may include cobalt, nickel, titanium carbide, tantalum carbide, tungsten carbide, and other materials which are now known or hereafter developed to aid or act as binder materials.
The carbide cutter element 70 is advantageously configured so that it can be attached to a conventional saw chain 20 as described in detail below. The cutter element or insert 70 of the present invention offers several advantages. For example, there is no need to grind, machine, or otherwise modify the conventional saw chain 20 (
Rear Portion—Cutter Inset
The rear portion 71 of the carbide cutter inset 70 includes a convex semi-cylindrical surface 77 which is sized and configured for attachment to the semi-cylindrical concave portion of tooth face 64 (see
The cutter inset 70 can be attached to the tooth face 64 of the cutting member 22 by a variety of suitable means. By way of example, and not by way of limitation, the cutter inset 70 can be attached using heating, such as by baking, flame heating, induction brazing or other suitable heating methods. The configuration described above leaves a space of about 1/32 of an inch between the semi-cylindrical attachment surface 77 and the curved tooth face 64 when the tooth face 64 and the cutter inset 70 are in complimentary apposition. This space is provided for being filled when the attachment or connection is formed between these two parts using a connection material or materials.
A variety of materials can be used during the brazing or other method of connecting to form the connection or attachment, and the use of various suitable materials now known or hereafter developed is contemplated by the present invention. In one implementation, silver solder (not shown) is used during the connection process to form the attachment. In another implementation, a tri-metal shim 80 (shown in
The complementary relationship between the concave cutter face and convex surface 77 provides improved distribution of forces generated against the inset and supporting cutter. This mating semi-cylindrical connect has been discovered to be superior by the inventor for minimizing break-out of the inset.
Front Portion—Cutter Inset
Referring once again to
The corners 104 of the cutting face 90 are beveled at a suitable angle. As shown, the beveled corners are angled at 45 degrees relative to the adjacent side edges. For example, the edges 93 and 94 of the inset cutting face have a beveled corner 104. These beveled corners 104 are discussed in more detail below. Alternative forms of providing a smooth non-perpendicular edge may also be workable in some situations, such as rounded or otherwise smoothed where the junction occurs.
Body Portion—Cutter Inset
Referring once again to
As shown best in
The cutter inset 70 thus shaped is advantageous in that it can be alternatively attached to either a left-hand saw chain cutting member 22a or to a right-hand saw chain cutting member 22b (as shown in
Cutter Inset Adjustable Rake
In general, the convex inset surface 77 is capable of being adjusted to different angular orientations within the concave receptacle formed by the original filing of the cutter face. The inset can be adjusted from a positive rake to a negative rake. A positive rake positions the inset to lean forward, thus cutting more aggressively. A negative rake positions the inset to lean rearwardly and produces a less aggressive cutting action. The ranges of positive and negative rake angles that are acceptable vary on the material being cut. For example, metal is preferably cut using a negative rake to reduce cutting forces generated at the inset. Softer materials may best be cut using a positive rake. Generally rake angles of ±10° of arc will cover a wide variety of materials. Larger rake angles may be possible with some materials.
The variable rake angle allows a common saw chain to be fitted with the hard insets to meet the user's desires or the needs of the material being cut. For common materials rake angles of ±5° of arc are preferred.
The Modified Saw Chain
Referring now to
The segment of saw chain 20a shown in
If one or more of the carbide cutter insets 70 become detached from the saw chain 20a, the loss of a cutter inset 70 will not in general render the saw chain 20a unusable. If a cutter inset 70 is dislodged from a cutting member 22, the original tooth face 64 will be revealed and made available for cutting. The tooth face 64 which is revealed by the loss of a cutting inset 70 is able to perform cutting functions, even though it may become dulled with continued use.
Methods
Other embodiments of the present invention contemplate methods for attaching the carbide cutter inset 70 to the tooth face 64 of a conventional saw chain 20 cutting member 22. Some of these methods which were briefly discussed above are now described in detail.
In one embodiment, the method includes selecting or otherwise providing a cutter inset 70 of complementary shape along the rear surface thereof to the cutting face 64 of the saw chain. The complementary shapes are preferably semi-cylindrical. The rear surface forms an attachment surface 77.
The selecting also preferably includes using an inset having a front portion 73 including a cutting face 90 which has beveled or smoothed cutting face corners thereon and most preferably beveled or chamfered corner edges, or even more preferably both beveled corners and chamfered corner edges or curved equivalents.
The selecting or providing steps for the insets also may include other preferred configurations, shapes, and sizes as needed for the cutters being fitted with the insets and the desired saw chain sizes and configurations desired.
After providing the carbide cutter inset 70, preferred methods include attaching the cutter inset 70 to the tooth face 64. This is preferably done by brazing, soldering or other forms of welding suitable for the materials being used.
The attaching of inset 70 to cutter face 66 is advantageously done using a shim or layer of connecting material which is capable of bonding or adhering to both the cutter face and the hard material used for the cutter inset 70. In one form of the methods, the shim or layer of connecting material is attached first to the inset. In still other methods according hereto, the cutter, connecting material, and inset are brought into juxtaposition and then joined simultaneously. A further possible approach involves connecting the layer of connecting material to the cutting face semi-cylindrical surface of the cutter.
The attaching may further include heating the parts being attached to a suitable temperature such that the connecting material or material become capable of bonding to the cutter and to the hard inset.
In a further method or methods according to this invention, the connecting material may be applied to the inset attachment surface first. This may be accomplished using suitable connecting materials, such as silver solder, which is heated and applied to the attachment surface. In another form the connecting material may be in the form of a pre-formed shim. The pre-formed shim may be placed upon the attachment surface of the inset and then heated. One preferred manner of connecting the shim or other connecting materials to the attachment surface of the inset is to bake the inset and shim or other connecting material to a suitable temperature to cause the shim, silver solder, or other connecting material to perform by bonding the connecting material to the inset attachment surface prior to connection with the saw chain.
In the methods indicated in the prior paragraph, the heating of the connecting material and inset is performed first. The resulting inset and connection material results in a prepared inset with connection material bonded thereto. The prepared insets may then experience cooling and stockpiling awaiting attachment to the saw chain cutters.
In some of the preferred methods, the heating step may be accomplished using magnetic induction heating. The heating may also be performed by flame heating, baking or other suitable heating techniques.
The present invention contemplates selecting a suitable solder or other connecting material for the connecting or attaching on the insert to the cutter face. In one implementation, silver solder is used in a brazing process to attach the carbide cutter inset 70 to the tooth face 64 of the conventional saw chain 20 cutting member 22. In another implementation, the method includes the use of a shim made of a three layer material, such as tri-metal shim 80 (shown in
In some methods according to the invention, after the inset 70 or prepared inset has been attached to the cutter face 64, the process is further performed by repeating the attaching of the insets to all or a plurality of the cutters on the saw chain. In general, no grinding or further processing is needed to the saw chain or insets attached to the cutters. This is a clear advantage over methods which require grinding and/or machining after such an attachment has been made.
The connecting between the inset and cutter may be performed in a manner wherein the insets are provided with the connecting material prior to joinder of the resulting prepared inset to the cutter face. This can be done by baking the silver solder or shim, such as shim 80, onto the attachment surface of the inset. The prepared insets can then be attached to the cutters of the saw chains with the saw chains intact. Alternatively, the insets may be affixed to the cutters and then the saw chain assembled.
The tri-metal shim consists of silver solder copper and then another layer of silver solder. The shim is formed in a die to the outer shape of the cylindrical portion of the carbide insert. It is then attached to the carbide insert by induction welding or baked to a temperature that allows the silver solder to flow only on one side, then cooled. The carbide is then set in a jig manually that holds the carbide in place next to the chassis where it is reheated and welded in place by flame welding (gas).
The tri-metal shim consists of silver solder, copper, and then another layer of silver solder. The shim is formed in a die to the outer shape of the cylindrical portion of the carbide insert. It is then attached to the carbide insert by induction welding or baked to a temperature that allows the silver solder to flow only on one side, then cooled. The carbide pieces are put in a vibratory shaker and sorted where they then slide down into a fixture that holds the carbide in place next to the chain chassis and heated by means of induction welding or flame welding (gas). The chain automatically advances to the next position and the next piece of carbide is indexed into place and welded.
The carbide inserts are set in place by a mechanical means in which it is automated and does not require any application of manual labor.
Interpretation Note
The invention has been described in language directed to the current embodiments shown and described with regard to various structural and methodological features. The scope of protection as defined by the claims is not intended to be necessarily limited to the specific features shown and described. Other forms and equivalents for implementing the inventions can be made without departing from the scope of concepts properly protected hereby.
