FIELD OF THE INVENTION

The invention generally relates to saw blades and more particularly to a set of counter-moving and counter-cutting saw blades, preferably circular saw blades, with respective series of teeth having cut cleaning and smoothing capability.

BACKGROUND OF THE INVENTION

It is well known in the art to which this invention appertains that a set or pair of counter-cutting saw blades and in particular, oppositely rotating circular saw blades, has each of the blades thereof characterized by a series of unidirectional teeth. Hence, such feature leaves no choice to the user but to mount the respective saw blades on corresponding spindles of a sawing machine in a manner that it must be ascertained that the respective teeth are facing or pointing towards the forward stroke or thrust direction of cutting or directional rotation of the respective spindles, otherwise no cutting actions would be possible for the pair of saw blades.

Furthermore, such saw blades are of two categories, namely: rip cut or cross cut saw blades with smaller number of teeth that provide or effect quick/ fast but rough cuts characterized by a poor surface finish; and finish cut saw blades with relatively large number of teeth that provide or effect slow but smooth clean cuts, especially in wood. Thus, there is always a disadvantage or downside when opting or choosing a kind of cut when using both types of saw blades. Usually, the existing pair of counter-cutting circular saw blades with unidirectional cutting teeth falls under the rip cut or cross cut saw blade category, thus, the resulting cut is relatively a rough cut.

Certainly, with the foregoing drawback or shortcoming of the prior art, a kind of saw blade that can cut fast with a clean smooth cut by itself or when co-axially and counter-rotatively mounted in a set or pair is desirable for users as well as for manufacturers since one blade in lieu of or as substitute for the two conventional blades would practically and obviously incur and translate into significant raw material savings and reduced environmental pollution.

Quite a number of prior art documents or references would show that the trend of advancement is headed towards or confined with merely improving the unidirectional blades used singly or in combination including installation aspects like improving on blade spacers as shown in the following patents.

Ericsson US Patent Pub. No. US 2004/0182217 A1 or WO 2008/ 057027 relates to a pair of unidirectional saw blades of opposite directional rotations that are adjacently mounted face to face with a spacer means in a form of a circumferential ridge formed on one of the blade bodies provided therebetween. The forming of the ridge involves a complex machine turning or milling of the blade body which pose a manufacturing disadvantage. Further, with the relatively larger total frictional contact area of the built-in ridge in usage, there is a high potential and tendency for heat build-up in the cutter element zone, which is detrimental and affects the metallurgical properties of the blades, and in turn, the cutting operation. When operating under load, the saw blades would likely develop metal fatigue and cracks due to heat-induced material property alteration in the affected area or zone, resulting in a shorter or reduced useful life of the blades.

Clarke US Patent No. 4,641 ,562 relates to a circular saw blade that operates with two differently sized and toothed blades mounted coaxially adjacent to one another such that when used to cut through a workpiece, the larger first blade makes a fast rough cut and the second smaller blade follows partially within the path of the first blade and provides a smooth, finished cut. Using this type of blades in a pair or set of counter-cutting, oppositely rotating saw blades would result in four blades, which appears to be technically impractical and uneconomical.

Vollmer et. al. US Patent No. 4,133,240 pertains to unidirectional cutting teeth for circular saw blades, and discloses an improved raker and low teeth inserts whose inclinations or angularities of planar surface faces and/or facets defining cutting edges are improved, are alternatively positioned about the periphery of the circular saw blade purposely for a substantially improved blade performance, particularly in the area of wear. Bidirectional cutting teeth is not part of this invention's teaching.

SUMMARY OF THE INVENTION

The present invention seeks to overcome the shortcomings of the prior art by providing a set or pair of counter-moving, preferably rotational, and counter-cutting saw blades with respective series of teeth that is characterized by or provides oppositely directed dual cutting edges. Depending on the direction of the blades' forward thrust/motion or rotation, the cutting edges that point towards such direction are the active cutting edges effecting a fast rough cut into a workpiece, while the non-active cutting edges pointing to the opposite direction trailing or following right behind the active cutting edges effect a cut-smoothing or cleaning action, i.e. scraping or chipping off unwanted cut debris, remnants or imperfection, resulting in a quickly done clean and smooth cut along opposing directions or distal or outer sides of the blades. Thus, with the saw blades of the invention respectively functioning as rip or cross cut blade and at the same time finish cut saw blade, their combined counter-cutting capacities in opposite directions certainly result in a relatively faster and smoother cut, especially for medium to heavy duty cutting operation.

The invention is further characterized by a plurality of removable spacer inserts tightly fitted into corresponding holes circumferentially and spaced ly provided on the body of at least one of the saw blades such that a narrow clearance or space gap is provided in between the blades, and heat build-up tendency due to spacer frictional contact during operation is substantially reduced. Another important feature of the invention is that the saw blades are mountably flappable or reversible with respect to each other such that a reversal of the blade position consequently interchanges the cutting and cut-smoothing functionalities of said cutting edges. A sufficient extended useful life of the blades can therefore be attained. It is therefore the primary object of the invention to provide a set of counter-cutting and counter-moving or rotational saw blades with respective series of teeth that is characterized by or provides oppositely directed dual cutting edges that are capable of making a smooth cut at a relatively and favorably fast cutting rate or speed due mainly to a collective action of a pair of counter-cutting blades respectively performing combined cutting and trailing cut-smoothing actions.

Another object thereof is to provide a set of counter-cutting and counter-moving or rotational saw blades with respective series of teeth that can be installed or mounted on a sawing device or machine without any particular reference to forward thrust or rotational direction of cutting such as the respective spindle directions of a circular saw machine.

Still another object thereof is to provide a set of counter-cutting and counter-moving or rotational saw blades with respective series of teeth, whose blades can be mountably reversed or flipped over for another use just like a new saw blade in which the positive sharp angle or active cutting edges of the previous use now become the inverse angle or inactive cutting edges to do the cut-smoothing action and vice versa. Hence, the useful life of the blades is significantly increased or extended to at most about 300%.

Yet another object thereof is to provide a set of counter-cutting and counter-moving or rotational saw blades with respective series of teeth that incurs significant reduction of steel consumption and hard alloy used for manufacturing saw blades by about 50%, resulting in substantial reduction of environmental pollution.

A further object thereof is to provide a set of counter-cutting and counter-moving or rotational saw blades with respective series of teeth that adapts removably hole-fitted spacer inserts with minimal frictional heat buildup in usage, separating the blades apart through a narrow gap or clearance defined thereby. BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the invention are better understood and appreciated from the following detailed description made in conjunction with the appended drawings, in which:

FIG. 1 is a cut-away, perspective view of a preferred embodiment or illustrative example of the present invention;

FIG. 2 is a cross-sectional view thereof taken along line 2-2 of FIG. 1;

FIG. 3 is a plan view thereof as adopted or embodied in one of the circular saw blades without spacer inserts; and

FIG. 4 is a plan view thereof as adopted or embodied in one of the circular saw blades with spacer inserts.

DETAILED DESCRIPTION

Before describing the invention in detail, it is to be understood that the phraseologies and terminologies employed herein are for purposes of description only to support an enabling disclosure that describes the best mode or illustrative example/embodiment of the invention, thus should not be regarded as limiting.

Referring now to the drawings in detail wherein like reference numerals designate the same parts or elements all throughout the description, there is shown in FIG. 1 a set, preferably a pair, of oppositely moving or counter- moving (preferably rotational motion such as in a circular sawing machine), and counter-cutting co-axial saw blades generally designated by reference numeral 8. Each saw blade 9 has a series of teeth 11 with cut cleaning and smoothing capability due to a provision thereon of oppositely directed dual cutting edges 12,12'. Further, each saw blade 9 comprises of a co-axially mountable cutter head or blade body 10 that is capable of being mounted to or installed on a sawing device or machine (not shown), preferably a circular sawing machine, and the series of teeth 11 individually protrudes and is directionally disposed along the toothed edge portion of the body 10.

For purposes of an enabling disclosure, it is a preference herein to use and describe, as an illustrative example or preferred embodiment of the invention, a circular body 10' of a circular saw blade 9' in a set or pair of circular saw blades 8' being suited for a circular saw machine (not shown). The set or pair of saw blades 8,8' as embodied in the invention is characterized by the following:

(1) Each saw blade 9,9' whose series of teeth 11 comprising the oppositely directed dual or symmetrical cutting edges 12,12' (shown in bold lines) that complement each other in each of the teeth 11 wherein the cutting edge 12 is the one facing or pointing (shown by arrows "A1") towards the direction of cutting (shown by an arrow "A"), while the other cutting edge 12' is the one at the opposite side of the cutting edge 12, which faces or points (shown by arrows "A2") towards the opposite direction. In a cutting operation or process through the cutting direction "A", the cutting edge 12 is in an active sharp cutting angle or position pointing towards (shown by the arrow "A1") the direction of cutting "A" such that it effects a cutting action as shown by arrows "B1", preferably performing a fast rough cut, upon contact with a workpiece 13. On the other hand, also during such operation, the cutting edge 12', preferably performing a fast finish cut, is in a non-cutting inverse angle or position pointing away (shown by the arrow "A2") from the direction of cutting "A" with the blunt or unsharpened back portion 12a thereof being the one acting against the cut surface immediately after the cutting action "B1" as shown by arrows "B2", hence, the result would be one of scraping, surface cleaning and smoothing of the cut surface, producing a quality smooth and clean finish cut, most especially in wood or metal;

(2) The saw blades 9,9' are adjacently mounted co-axially face to face with and apart from each other by a plurality of removable spacer inserts 16 tightly fitted into corresponding holes 16a, preferably of about 2 millimeter in diameter, provided circumferentially and spacedly disposed on the body 10,10' of at least one of the saw blades 9,9'. Such set-up produces or defines a narrow clearance or space gap 17 in between the saw blades 9,9'. The number of spacer inserts 16 depends on the size or diameter of the blade body, which is preferably 9 in the illustrative example shown in FIG. 4. In usage or operation, the spacer inserts 16 reduce heat build up and at the same time keep the pair of blades together, ensuring a smooth and vibration- free cutting operation;

(3) The saw blades 9,9' are mountably flappable or reversible with respect to each other such that a reversal of the blade position consequently interchanges the cutting and cut-smoothing functionalities of the cutting edges 12,12', that is, from being in an active cutting position performing cutting action to a non-cutting inverse position effecting cut-smoothing action, and vice versa.

It is preferred that each of the series of teeth 11 is a unitary element having the oppositely directed symmetrical cutting edges 12,12' being made integral and unitary parts thereof, making the series of teeth 11 composed of double-edged teeth 11'. As shown in FIGs. 1 and 2, the double-edged teeth 11' have convergently and downwardly tapered top edge portion 11a defining a pair of oppositely directed pointed cutting corners 11b and forming a generally dovetail-like tooth profile. Thus, mounting or installing of the saw blade 9,9' into the sawing machine, e.g. circular saw machine, can be done without any particular reference to directional rotation (or forward thrust for a non-circular sawing device) of the machine's spindles 15,15', which is for the convenience of the user. Whether being preferably comprised of a unitary, double-edged and dovetail-like profiled teeth 11', or complementing oppositely directed and adjacently disposed separate elements/teeth (not shown), the series of teeth 11 has the cutting edges 12,12' thereof being made parts of respective cutting elements 14 that define the teeth's opposite sides. With such set-up and features, the cutting and cut-smoothing actions (shown by the arrows "B1","B2") take place or are effected along the top edge 14a and opposite side edges 14b of the cutting elements 14 or teeth 11,11' during the cutting operation. Further, the saw blade 9,9' can be flipped or turned over for another use just like a new saw blade in which the positive sharp angle or active cutting edges of the previous use now become the inverse angle or inactive cutting edges to do the cut-smoothing action and vice versa, especially when used as counter facing and oppositely rotating twin blades in a pair of circular saw blades for medium to heavy duty cutting operations.

Preferably, the cutting elements 14 are made of hard metal or any suitable cutting material, and the sawing device or machine is preferably a 5 circular saw as aforementioned, though other similar hand tools or devices/machines are also applicable such as jig saw, band saw and hack saw. As regards the spacer inserts 16, they can be made of a material such any one or combination of metal, plastic, ceramic, composite or any suitable material that has a minimal heat build-up tendency due to frictional contact. l o Before defining the scope of the following claims, it is to be understood that the invention is not limited in its applications to the details of the illustrative examples or variations set forth in the preceding description and drawings. It is to be noted that the invention is capable of other variations and limitless applications not disclosed herein. Further, this invention is likewise

15 capable of being practiced and carried out in various ways falling within the teaching and scope of the following claims.