AU764004B1 - Coupling device of free-cutting saw - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant: JENN FENG INDUSTRIAL CO., LTD Invention Title: COUPLING DEVICE OF FREE-CUTTING SAW The following statement is a full description of this invention, including the best method of performing it known to us: COUPLING DEVICE OF FREE-CUTTING SAW FIELD OF THE INVENTION [00011 The present invention relates generally to a free-cutting saw for cutting and removing under-wood and weeds, that includes an elongate bar having a front segment forming a rotary saw blade and a rear segment to which a power unit is mounted for driving the saw blade, and in particular to a coupling device for connecting the front and rear segments of the bar together.

BACKGROUND OF THE INVENTION [0002] A free-cutting saw including an elongate bar having opposite ends to which a rotary saw blade and a power unit are respectively mounted is widely used to cut and remove weeds and/or under-wood. An operator holds the bar with one or two hands to swing the saw blade at the front end of the bar across weeds or bushes to be removed for cutting off the weeds and the bushes. Conventionally, the hand-holding bar of the free-cutting saw is made as a single piece and the power unit is integrally mounted to the bar. Thus, exchange between parts of free-cutting saws made by different manufacturers is in general impossible.

[0003] Although bars having two or more pieces removably fixed together by a coupling device have been developed for the free-cutting saw, the conventional coupling device is of a sophisticated structure thereby complicating the operation thereof. In addition, the sophisticated structure reduces the mechanical reliability of the conventional coupling device, increasing maintenance expense and may even cause physical and property damages.

SUMMARY OFTHE INVENTION 100041 Thus, a primary object of the present invention is to provide a coupling device for a free-cutting saw which has a simple structure and good reliability.

[00051 Another object of the present invention is to provide a coupling device for a free-cutting saw which exchangeably couples cutting blades of different designs to the same power unit for performing different jobs.

[0006] A further object of the present invention is to provide a coupling device for readily and reliably coupling parts of a free-cutting saw together.

[0007] To achieve the above object, in accordance with the present invention, there is provided a free-cutting saw for removing weeds comprising an elongate bar comprised of front and rear bar segments to which a cutting blade assembly and a power unit are respectively mounted. A coupling device couples the front and rear bar segments together. The power unit has a driving axle having a polygonal end section. The cutting blade assembly has an axle having a polygonal end. The coupling device comprises a tubular body defining a central bore. A connector is fixed in the central bore and has a rotatable cylinder having opposite ends defining receiving bores having polygonal configuration for receiving and drivingly engaging the polygonal end sections of the axles thereby drivingly coupling the cutting blade assembly to the power unit. A retainer is pivoted to the tubular body and forms a pawl movable between a secured position where the pawl extends through a slot defined in the tubular body and engages a second slot defined in the front bar segment to secure the cutting blade assembly to the coupling device and a released position where the pawl disengages from the front bar segment to allow separation of the front bar segment from the coupling device. Two lugs are formed on the tubular body proximate each end of the tubular body and a slit is defined in the tubular body between the lugs. A bolt-nut pair extends through holes defined in the lug to secure the bar segment inside the tubular body.

BRIEF DESCRIPTION OF THE DRAWINGS 100081 The present invention will be apparent to those skilled in the art by reading the following description of a preferred embodiment thereof, with reference to the attached drawings, in which: Figure 1 is a perspective view of a coupling device constructed in accordance with the present invention; Figure 2 is an exploded view of the coupling device of the present invention; Figure 3 is a cross-sectional view showing that a blade-side segment of a bar of a free-cutting saw is to be fixed to a power-side segment of the bar by the coupling device of the present invention; Figure 4 is a cross-sectional view similar to Figure 3 but showing that the blade-side segment is secured by the coupling device of the present invention; Figure 5 is an exploded view of a free-cutting saw incorporating the coupling device of the present invention; and Figure 6 is an enlarged view of encircled portion VI of Figure DETAILED DESCRIPTION OF THE INVENTION [00091 With reference to the drawings and in particular to Figure 5, a free-cutting saw (not labeled) in which a coupling device constructed in accordance with the present invention, generally designated with reference numeral 1, is incorporated comprises a power.unit 2 mounted to a power-side segment 21 of an elongate bar and a cutting blade assembly 3 mounted to a blade-side segment 31 of the bar. The coupling device 1 of the present invention couples the segments 21, 31 of the bar together and forms a driving engagement between the power unit 2 and the cutting blade assembly 3.

100101 Also referring to Figures 1, 2 and 6, the coupling device 1 comprises a tubular body 11 defining a bore (not labeled) in which a connector 12 is fixed. The bore is sized to snugly receive the bar segments 21, 31 of the free-cutting saw therein. A rotary cylinder 121 is rotatably supported in the connector 12 and has two ends (not labeled) extending beyond opposite end faces of the connector 12. A polygonal bore 1211 is defined in each end of the rotary cylinder 121. The polygonal bore 1211 is a square hole in the embodiment illustrated. However, it can be of any polygonal shape.

[0011] The power unit 2 has a driving axle having a polygonal end section 211 extending beyond the power-side bar segment 21. The end section 211 of the driving axle of the power unit 2 has a cross section corresponding to the polygonal bore 1211 of the rotary cylinder 121 of the connector 12 whereby the end section 211 of the driving axle of the power unit 2 is snugly fit into the polygonal bore 1211 of the connector 12 and thus drivingly engages the rotary cylinder 121 of the connector 12. Similarly, the cutting blade assembly 3 has an axle having a polygonal end section 311 extending beyond an end face 32 of the bar segment 31.

The end section 311 is drivingly engageable with the corresponding polygonal bore 1211 of the rotary cylinder 121. Thus, the cutting blade assembly 3 is drivingly coupled to the power unit 2.

[00121 A retainer 13 is pivoted to the tubular body I1I by a pivot 14. In the embodiment illustrated, the retainer 13 comprises a flat member forming two spaced lug 131 in an underside thereof. A lug 111 is formed on the tubular body 11 and snugly received between the lugs 131 of the retainer 13. Aligned holes (not labeled) are defined in the lugs 111, 131 for receiving the pivot 14 to pivot the flat member of the retainer 13 to the tubular body 11. .The flat member of the retainer 13 forms a 4 pawl 133 on a first end thereof. In the embodiment illustrated, the pawls133 comprises a serrated edge of a perpendicular flange (not shown) formed on the first end of the retainer 13. A slot 113 is defined in the tubular body 11 and in communication with the bore of the tubular body 11. The retainer 13 is angularly movable between a secured position where the pawl 133 extends through the slot 113 and into the bore of the tubular body 11 and a released position where the pawl 133 is withdrawn out of the bore of the tubular body 11.

[0013] A biasing element 15, such as a helical spring, is mounted between the tubular body 11 and a second end of the retainer 13 for biasing the pawl 133 toward the secured position. Retaining holes 112, 132 are defined in the tubular body 11 and the retainer 13 for retaining ends of the helical spring 15. In the embodiment illustrated, the holes 112, 132 are defined in projections formed on the tubular body 11 and the retainer 13. In this respect, one of the retaining holes, such as the retaining hole 132, is made elongated/expanded for accommodating the projection of the other retaining hole, which is the retaining hole 112 in the embodiment illustrated, during the operation of the retainer 13.

[0014] Two opposite and spaced lugs 114 are formed on each lengthwise end of the tubular body 11 with a lengthwise slit (not labeled) defined in the tubular body therebetween. The bar segment 21, 3 1, once fit into the bore of the tubular body 11, is selectively secured by a bolt-nut pair 16 that extends through holes (not labeled) defined in the lugs 114. A manual knob 17 is provided for manually tightening the bolt-nut pair 16. Thus, no hand tool is required in securing the bar segments 21, 31 to the tubular body 1 I.

100151 Also referring to Figures 3 and 4, by manually moving the retainer 13 to the released position as shown in Figure 3, the end 32.of the blade-side bar segment 31 is allowed to completely insert into the bore of the tubular body 11. When the end 32 of the blade-side bar segment 31 is completely fit into the bore with the end section 311 of the axle of the cutting blade assembly 3 engaging the polygonal bore 1211 of the connector 12, the pawl 133 is automatically biased toward the secured position and engages slots 321 defined in the blade-side bar segment 31 to reliably secure the blade-side bar segment 31.

[0016] The pawl 133 is provided with an inclined camming surface as can be clearly identified in Figures 3 and 4 but not labeled for simplicity. When the blade-side bar segment 31 is fit into the tubular body 11, the camming surface is acted upon by the end 32 of the blade-side bar segment 31 and forced toward the released position to clear the bore of the tubular body 11 for the entry of the bar segment 31. When the bar segment 31 is completely fit into the tubular body 11, the biasing spring 15 automatically returns the pawl 133 to the secured position where the pawl 133 engages the slots 321 of the bar segment 31 and thus securing the bar segment 31.

[0017] Although the present invention has been described with reference to the preferred embodiment thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.

6a The words "comprising, having, including" should be interpreted in an inclusive sense, meaning that additional features may also be added.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or in any other country.

H -;II .E''11 1-1) P4 14

Claims (3)

16. The saw device as claimed in claim 9, wherein the tubular body has lengthwise ends, two opposite and spaced lugs being formed on the tubular body proximate to each lengthwise end of the tubular body, a lengthwise slit being defined in the tubular body between the two lugs, the lugs defined holes through which a bolt extends to secure the bar segment received in the central bore of the tubular body.

17. A coupling device substantially as hereinbefore described with reference to the accompanying drawings.

18. A saw device substantially as hereinbefore described with reference to the accompanying drawings. Dated this 19th day of June 2002 JENN FENG INDUSTRIAL CO., LTD By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia