Metal working – Means to assemble or disassemble – Puller or pusher means – contained force multiplying operator
Reexamination Certificate
1999-03-05
2001-02-20
Watson, Robert C. (Department: 3723)
Metal working
Means to assemble or disassemble
Puller or pusher means, contained force multiplying operator
Reexamination Certificate
active
06189191
ABSTRACT:
The invention relates to a method for attaching a tooth bit to a blade used in sawing, in which method a shapelocked tooth bit is arranged in a bit seat which is formed in a blade body and which is curved with respect to a center of rotation.
The invention further relates to a tool for attaching the tooth bit, the tool being intended for inserting the shapelocked tooth bit used in sawing into the bit seat which is formed in the blade body and which is curved with respect to the center of rotation.
Shapelocked, replaceable tooth bits are used, for instance, in circular saw blades employed in woodworking, as well as in band saw blades, handsaw blades, gang or bow saw blades and the like. Thanks to the shapelocked arrangement, tooth bits need not be brazed, riveted or installed in any other fixed manner to a blade body, but the tooth bits are firmly locked to place thanks to the tooth bit and the matching bit seat provided in the blade body. In principle, one advantage of the shapelocked arrangement over attachment by brazing, for instance, is that it is quick to carry out and tooth bits can be changed easily. Tooth bit attachment may take place on site, and it is not even necessary to detach the blade for replacing tooth bits. In practice, there is currently no suitable tool wherewith the shapelocked tooth bits could be inserted into their seats quickly, yet without damaging the tooth bit in any way. At present, tooth bits are attached in a fairly clumsy manner, for instance, by forcing them into their seats by means of various pliers or by tapping them to position with a hammer. It is obvious that this kind of insertion cannot be effective nor advantageous as regards the tooth bit. Since the tooth bit is generally made of the hardest possible material in view of its wear resistance, such as high-speed steel, hard metal, ceramic or some other suitable tooth bit material, the tooth bit does not stand such rough handling as described above, but due to its brittleness it breaks relatively easily. In addition, the pre-sharpened cutting edges of the tooth bit may be damaged when current insertion methods are employed.
The object of the present invention is to provide a method and a tool which avoid the drawbacks of the prior art and which enable efficient, and yet gentle, handling of the tooth bits.
The method of the invention is characterized in that the tooth bit is inserted into its seat by rotating it with respect to the seat with a tool which comprises at least two insertion heads arranged on the opposite sides of the tooth bit.
The tool in accordance with the invention is further characterized by comprising at least two insertion heads to be arranged against the tooth bit, the insertion heads being arranged on the opposite sides of the tooth bit, and means for exerting a turning force on the tooth bit by means of the insertion head, whereby the tooth bit is arranged to rotate into its seat.
The basic idea of the invention is that the tooth bit to be attached is mainly subjected to a rotational motion only, by which the tooth bit can be turned to a correct position in its seat where it is firmly held in place by means of the shapelocked arrangement. A further substantial point is that the tool has at least two insertion heads arranged on different sides of the tooth bit, which enable the tooth bit to be turned when the turning force is exerted thereon by means of the insertion heads. Further, the basic idea of one preferred embodiment of the invention is that the tooth bit is turned such that the center of rotation is substantially identical to the center of the circular bit seat formed in the blade body. The basic idea of a second preferred embodiment of the invention is that the tool, by means of its supporting means, bears against the blade body in such a way that a turning means mounted rotatably with bearings on the supporting means and acting on the tooth bit can thus be turned substantially with respect to the bit seat's center of rotation. Further, the basic idea of a third preferred embodiment of the invention is that the turning means, which turns the tooth bit, is arranged to turn with respect to the bit seat's center of rotation by means of an appropriate link mechanism. The basic idea of yet a fourth preferred embodiment is that the tool comprises a link mechanism or the like for increasing the force by which the tooth bit is turned when inserting.
The invention has an advantage that the tooth bit is almost only subjected to the rotational motion which is substantial to mounting, but not to considerable upward or downward forces, which could damage the tooth bit or the bit seat. When the forces used for mounting are exerted correctly, less force is needed than in previous solutions. On the other hand, the fit between the tooth bit and the bit seat formed in the blade body can be made tighter than before, and so the tooth bit can be attached more firmly than before, whereby it is prevented from vibrating or otherwise moving with respect to the blade body, which would have an adverse effect on the durability and sawing properties of the tooth bit. Additionally, firmer attachment enables in principle increased sawing efficiency. Furthermore, another advantage is that by means of the purpose-made tool the tooth bits can be inserted considerably quicker than before. The fact that bits will no longer get broken during insertion also contributes to the quickness. Thanks to quicker insertion, the blade can be quickly put back to productive use when necessary. Moreover, it is more convenient and easier than before to perform the insertion, and thus it is more likely that the tooth bits will be replaced as soon as a fault is noticed, and there will no longer be any temptation to saw with inefficient, dull or broken tooth bits which involve a risk of even greater damage. One more advantage is that the insertion tool in accordance with the invention has a surprisingly simple structure and operating principle, and consequently it is durable and inexpensive to manufacture. Moreover, it can be used under all conditions and irrespective of external driving force. In addition, it is so simple to use that it is practically impossible to use it incorrectly, and thus even a less experienced person can always insert the bits correctly.
REFERENCES:
patent: 2049489 (1936-08-01), Christen
patent: 3097547 (1963-07-01), Krekeler
patent: 3769683 (1973-11-01), Krekeler
patent: 4999898 (1991-03-01), Schmeling
Alston & Bird LLP
Hackman TTT OY AB
Watson Robert C.
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