Cutting – Tool or tool with support – Endless band or belt type
Patent
1985-04-22
1987-08-25
Yost, Frank T.
Cutting
Tool or tool with support
Endless band or belt type
83835, B27B 3306
Patent
active
046884580
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to bandsaw blades for milling timber and, more particularly, to tooth forms for use in such blades. Its objective is to allow the production of bandsaw blades which have a longer effective cutting time, improved production rates, lower power consumption and reduced kerf loss.
BACKGROUND ART
Though diminishing timber resources and increasing energy costs have created a strong demand for more efficient timber milling techniques, little attention has been paid to the improvement of tooth design. This is because saw tooth design is a well-worked art with a sound theoretical and empirical base which has determined the tooth shapes used on large bandsaws for many years. A steady increase in bandsaw performance has been achieved over the past thirty years by the use of improved alloy steel for blades, particularly through the introduction of steels and equipment which allows saw teeth to be sharpened and locally hardened at the mill. The tough alloys used reduce tip breakage and, when hardened, are resistant to abrasive wear, which is particularly important when sawing highly siliceous timber. Basic saw tooth shape, however, has remained essentially unchanged during this period.
DISCLOSURE OF INVENTION
In such a well-worked art and in such an economic climate, it would be most surprising to find that productivity improvements of up to 30% could be obtained using existing saw blade alloys and hardening techniques by changing tooth profile and by carefully controlling tip hardness, yet the present invention demonstrates such improvements are realistic. Instead of the conventional trapezoidal, or flat-top, tooth shape employed for in-line and swaged bandsaws, the teeth formed in accordance with the present invention each have a cutting tip which, in front profile, is triangular in shape, with, for instance, an elongate pentagonal or pointed-top, tooth shape, with a central apical point and two side points. Preferably, the apical angle (.theta.), namely, the included angle of the central point is, from 60.degree. to 140.degree., while the side or base angles (.gamma.) of the triangular tip are from 20.degree. to 60.degree..
It is also preferable, but not essential, for the tooth hook angle, in side profile, to be significantly increased over that which is conventional. Thus, hook angles as large as 35.degree. are now employed cutting very dense and silicious timbers, in which the conventional angles of up to 25.degree. only were traditionally used. Similarly, the sharpness angle is preferably reduced to improve penetration; angles of as little as 35.degree. may be used with softwoods, though angles from 40.degree. to 45.degree. will be more usual. Clearance angles of from 15.degree. to 20.degree. are thus contemplated.
The pointed-top tooth form allows the overall width of the tooth to be significantly reduced without increasing lateral vibration when in use, so that valuable reductions in kerf loss can be obtained. For optimum performance, it is recommended that teeth formed in accordance with the present invention should be high-frequency induction hardened to give a tip hardness of between 900 and 920 Diamond Pyramid hardness number (DPN). A convenient way, according to the present invention, of obtaining this hardness at the mill without using elaborate and destructive hardness measurements, is to employ standard hardening grade blade steels and to adjust the high-frequency coil inductor until a dark blue temper band is produced on the face of the tooth such that its top lies between 0.5 and 1.3 times the blade thickness below the tooth apex. Forced cooling by way of an air flow is preferably used to ensure that all teeth are treated uniformly.
To further portray the nature of the present invention, a detailed comparison between the performance of a bandsaw with conventional tooth form and one with the tooth form of the present invention will be described with reference to the accompanying drawings. First, however, a brief review of the theoretical considerations unde
REFERENCES:
patent: 604603 (1898-05-01), Caruthers
patent: 1130650 (1915-03-01), Whitaker
patent: 1352140 (1920-09-01), Napier
patent: 2644494 (1953-07-01), Lundberg
patent: 2734533 (1956-02-01), Roberts
patent: 2787299 (1957-04-01), Anderson
patent: 3651841 (1972-03-01), Ohlsson
patent: 4031793 (1977-06-01), Miaskoff
patent: 4232578 (1980-11-01), Stellinger et al.
The Minister for Industry and Decentralisation of the State of N
Yost Frank T.
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