This invention relates to a pipe shearing device or, more particularly, to a device which is adapted to shear a pipe fed to the device at a constant speed precisely into predetermined lengths.
There are several types of pipe shearing devices of conventional design. One of them is comprised of a lower blade fixed on a carriage and an upper blade adapted to be moved up and down freely by a crank mechanism, while the carriage is designed to be moved reciprocally along the pipe and a pipe carrier by a rack-and-pinion mechanism.
As the carriage and the pipe fed by the pipe carrier move in the same direction at the same speed (while their speeds are synchronized with each other), the upper blade comes down and cooperates with the lower blade successively to cut the pipe fed by the pipe carrier into pieces of a predetermined length successively.
A device of this type requires two sources of power: one is to be provided for operating the upper blade and the other for driving the rack-and-pinion mechanism. Thus, operation of such a device involves much power consumption in proportion to the number and capacity of the power sources required. Moreover, the pipes cut by such a device have end faces distorted by the shearing force of the upper blade and, when viewed facing to the end face of each a dimple is seen formed at the upper part of the end face.
Another conventional device is provided with a carriage having a vertical square slit in which a slidable member having the upper blade fixed is set so that it will move up and down freely and at the lower end of which the lower blade is arranged firmly. The vertical movement of the upper blade and reciprocal movement of the carriage are actuated by a motor which drives a crank mechanism and which is controlled by a motor controller. However, in order for such device to be operated exactly and in a smooth manner, an additional controller is required besides the main controller.
The end faces of pipes cut by this type of device are also distorted and, when viewed facing their end faces, dimples are seen formed at about their upper parts.
One pipe shearing device free of the main shortcomings of the conventional devices is disclosed in patent applications filed in Japan (Patent Application No. SHO 54-131219), U.S. Ser. (No. 192,835), Canada (No. 361,429) and West Germany (P3038043.9). The Japanese application published on May 18, 1981 with Patent Publication No. SHO 56-56321.
This prior device comprises a holder means, and a pair of rotary blades and a clamp means mounted on the holder means, the rotary blades consisting of a first blade and a second blade, the clamp means gripping and holding a pipe while the blades shear the pipe. The holder means has fixed at its lower part a cam follower which is engaged with the cam groove of a drum cam installed thereunder so that it makes a reciprocal movement as the drum cam revolves. The pair of rotary blades are driven by torque conveyed across a pair of spline shafts in opposite directions while being movable freely in the shaft direction to permit cutting of a pipe free from the formation of a dimple by giving an incision at a predetermined position of the pipe with the first blade and cutting the pipe at such position with the second blade. Further, the clamp means is composed of two pairs of wall blocks. Each pair consists of a movable block and a fixed block each having a respective semicircular lower blade provided on a side end face, these lower blades forming a true circle when both blocks join. As the movable block moves, it comes into contact with, and separates from, the fixed block on the side end face. The pipe, when the pair of rotary blades shear it, is gripped or held by the lower blades as the movable blocks come into contact with the fixed blocks on their respective side end faces. The pair of rotary blades perform shearing as they pass a clearance provided between two pairs of wall blocks. Pipe shearing is, of course, performed when the holder means is driven forwardly by the drum cam at the same speed with the pipe.
This device has the advantage that when used to sheer a pipe no dimple is produced on the pipe end face. However, this device does create a problem in that the reciprocal movement of the holder means is effected by a combination of the drum cam having a cam groove and the cam follower engaged with the cam groove of the drum cam so that when the holder means changes its direction of travel, the surface of engagement of the cam follower changes in the cam groove, resulting in chattering and great vibration. The device has other problems as well. The drum cam is not constructed to be light in weight and the drum cam has to be located beneath the holder means and is, therefore, subject to impingement by chips from the pipe. Further, the clamp means including its drive mechanism is rather complicated in structure so that it takes much time to maintain or change the diameter of the lower blades, when such is required.
The present invention provides a solution to the problems found in the conventional pipe shearing devices, and has a structure comprising the following components:
(1) a carriage supported for free movement by a pair of spline shafts and coupled to a pair of follower rollers connected in a holding condition to a cam rail on a drum cam which is disposed in parallel with the carriage and is separated from the carrier by a partitioning curtain, the drum cam being driven to rotate by a motor across a gear train so that the carriage makes a reciprocal movement as the drum cam revolves;
(2) a pair of rotary blades mounted rotatably on the carriage and provided in a pair of spline bosses respectively enmeshed with the pair of spline shafts, the spline shafts being supported by a box and adapted to revolve in opposite directions, so that one of the rotary blades cuts the surface of the pipe being fed by a pipe carrier to form a slit in the pipe as the blade revolves, while the other rotary blade cutting the pipe successively at the slit into predetermined lengths as it revolves in a reverse direction, this operation being performed in one revolution of the respective blades; and
(3) a chuck mechanism disposed on the carrier and comprising a pair of arms adapted to open or close freely, chucks provided to counter the arms and a lower blade provided in each of the chucks so that when the arms are operated to close by an arm drive mechanism, the grip or hold of the pipe by the lower blades is continued until the rotary blades perform pipe incision and cut through clearances formed in the arms.
It is an object of the present invention to provide means for cutting a pipe with ease and without deformation of the end face by providing a pair of rotary blades revolving in opposite directions and having one of the rotary blades form a slit at a predetermined position of the pipe and the other cut the pipe through the slit.
Another object of the invention is to provide a compact pipe shearing device which cuts a running pipe exactly into predetermined lengths at a high speed and with a small power source.
A further object of the invention is to provide a pipe shearing device which is controllable with ease by a numerical control system of the prior art.
A still further object of the invention is to provide a pipe shearing device having less vibration in operation and involving less failure than pipe shearing devices of the prior art, and permitting the device to be easily maintained.
The above and novel features of the invention will be more fully understood from the following description when the same is read in connection with the accompanying drawings. It should be noted, however, that the drawings are for the purpose of illustration only and are not intended to define the limits of the invention in any way.