Cutting – By tool reciprocable along elongated edge – With means to support tool at opposite ends
Reexamination Certificate
2000-07-20
2003-04-22
Ashley, Boyer (Department: 3724)
Cutting
By tool reciprocable along elongated edge
With means to support tool at opposite ends
C083S747000, C083S427000
Reexamination Certificate
active
06550365
ABSTRACT:
Coping saws have been widely used all over the world. In the past, although many improvements have been made, there continue to be shortcomings such as low sawing efficiency, poor sawing quality, high waste of saw blades, large no-load power, serious vibration and noises, limited range of sawing thickness, limitation of shape change, and so on. Moreover, all of coping saw blades can not be rotated, which the sawteeth lie in one direction. The workpiece must be rotated in order to fulfill curvilinear sawing. This causes two serious problems. One problem is complexity of rotating the workpiece. In particular, when the workpiece is bulky, the sawing efficiency is very low. Another problem is the limited dimensions of the workpiece. That is, the length of the workpiece is not larger than the blade depth of the sweep saw, otherwise, the workpiece can not be rotated. Therefore, the coping saw has become larger and larger, and the sawed workpiece must be as small as possible. The above mentioned defects have badly limited the use of the coping saw. At present, a kind of coping saw with high quality is desired urgently in the market.
The object of the invention is to provide a coping saw, which has essentially overcome the above defects, and really met the requirements of high sawing efficiency and quality, low waste of saw blades and energy, slight vibration and noises. It also enlarges the sawing thickness range and is capable of being designed in any shape at will. It can optionally adjust the angle of the saw blades in a 360-degree range. The saw can saw any length workpiece. Furthermore, the saw has improved working efficiency. It is an invention totally different from the existing coping saws, not only in theory, but also in the actual shape and structure.
There are two important factors for good curvilinear sawing:
There are two most important factors for good curvilinear sawing:
(1) The saw blade must move vertically. Otherwise, the workpiece can not be cut or the saw blades will be broken when we swerve the workpiece.
(2) The saw blade must be strained tightly and the tension must be constant. Otherwise, the bend of the blade caused by the push of the workpiece may make the sawing fail or break the blade. In order to achieve high-quality curvilinear sawing, the coping saw must be designed to satisfy the above two conditions. However, such a coping saw has not existed until present invention.
According to prior art, there are three kinds of coping saws as follows:
(1) A coping saw with C-type rod.
The movement of the saw blades is not vertical yet the tension is constant.
(2) A coping saw with parallelogram-type rod.
It is evident that the saw blade has a fore-and-back movement along with its vertical movement while the saw rod is swinging up and down. Thus, the resultant movement of the saw blade is not really vertical, however, the tension is constant.
(3) A coping saw strained by spring.
The movement of the saw blade is vertical yet its tension is not constant. The tensile force of the spring varies according to the movement of the saw blade. The larger the amplitude of the saw blade, the larger the variation of the tensile force. Furthermore, the motor will stop running if the saw blade pulled by the spring is strained too tightly.
The expanding usage of these coping saws is rather limited due to the above-mentioned problems.
The other existing problems of these coping saws will be further described as follows:
(1) The amplitude of the saw blade moving up and down cannot be too large because large amplitude causes variations in the tension. Generally, the range of the saw blade's movement is limited between 7 mm and 15 mm, which leads to low sawing efficiency and poor sawing quality. Furthermore, such small amplitude, is only {fraction (1/16)}-⅙ of the total length of the saw blade such that most saw-teeth of the saw blade do not participate in sawing operation, which is a big waste.
(2) Most power from the motor is used to swing the saw rod or to pull the spring, which causes a large amount of no-load power consumption. The efficient power only accounts for one fifth of the total power.
(3) The swinging saw rod (sometimes it weighs 2 kg) and the tensile spring cause serious vibration and noises when a coping saw is running.
(4) The thicker the cut article is, the larger the resistance the saw blade will encounter if the blade does not move vertically, or has inconstant tension, and the saw blade is further apt to be broken. As a result, the thickness of the cut article is much limited.
(5) The rigid saw rod limits the variety of outline of the coping saw.
The above problems which exist in a coping saw are due to the saw blade's incapability of moving vertically, or its inconstant tension or the existance rigid saw rod.
Among all the coping saws that have been publicly disclosed, none of them can simultaneously realize constant tension and vertical movement of the saw blade.
Next, the applicant would like to compare present invention with related arts provided by the search.
(1) The saws disclosed in U.S. Pat. No. 2,753,898 are saws with C-type rod.
(2) The saws disclosed in U.S. Pat. No. 2,072,590, U.S. Pat. No. 1,958,132, and U.S. Pat. No. 2,771,102 are saws strained by spring.
The saw rods of the above two kinas of saws are rigid and can not realize supple transmission, so that they all have the problems of inconstant tension or non-vertical movement.
(3) Though the saws disclosed in UK2205274 has supple transmission material, the whole transmission system is not independent, and the drive devices are connected in series. Therefore, the tension of the saw blade is still varied rather than constant.
When rollers reach the locations of points C and F, the length of AC is equal to that of GF. When rollers reach the locations of points D and E after turning 90°, point C has moved leftward a raduis-long distance, and have moved downward a radius-long distance as well. Point F has moved rightward a radius, and at the same time moved upward a radius. Though the respective leftward and rightward movement of points C and F does not cause length variation of the whole supple material, the vertical movement of points C and F makes both sides of the supple material become longer simultaneously. Consequently, the tension is increased. When the saw blade is being strained tightly, it will suffer a great variation in tension even as the supple material only has a tiny change in length. From the attached figure, we can understand that the length variation of supple material is very large when rollers are running, so that the resultant tension variation of the saw blade is enormous.
(4) Though the saw disclosed in UK2082114 has supple transmission material, the whole transmission system is not independent, and the drive devices are linked in series. So the tension of its saw blade is still inconstant rather than fixed.
When rod AB swings to the location of line CD, point A has not only a leftward movement but also a downward movement. Point B moves rightward and upward at the same time. The right-and-left movement of points A and B willnot cause the length variation of supple material. However, their up-and-down movement will cause the same so that the tension of the saw blade is increased sharply. When the mechanism is operating, the tension of the saw blade is not constant. Furthermore, the larger the amplitude is, the larger the tension variation that the saw blade has.
Though the above two patents have been issued, the schemes still have not been converted into practical products into market because of their poor practicability and low sawing quality. Curvilinear sawing cannot realize by both of the schemes. The reason is that their transmission and tension systems are not independent but are connected with a drive machine in series instead. They still have not resolved the two difficult problems existing in curvilinear sawing.
Although Swiss Patent No. 654.241 discloses a sweep saw, a great deal of difficulty will be encountered in the realization process of the i
Kong Fantong
Lin Lin
Zhang Weidong
Ashley Boyer
Westman Champlin & Kelly
Zhang Weidong
LandOfFree
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