Abstract:
A tube cutoff apparatus includes a parallelogram link assembly and a rotary arc ram which orbits 360° to maximize the vertical workstroke of the ram relative to the apparatus and has a lower inertia whereby to cut tubes of increased diameter, increase the ram length while decreasing the power required to drive the ram, and increase the driving response. The ram includes separated guide tracks with each track including a slide member that is disposed for sliding movement therein, the guide tracks defining wear plates and the slide members being connected to pairs of links. In one embodiment, two slide members are interconnected by a link plate, preferably by connecting to the individual pivot pins.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     This invention relates to improved apparatus of the rotary arc type for severing elongated material, such as round tubing, moving continuously of its length. 
     Rotary arc cutoff apparatus for severing metal tubing, roll-formed shapes and elongated extruded workpieces typically comprises a cutoff die set mounted for substantially linear reciprocating movement along tracks on the flat bed of a mechanical pres with a long, relatively heavy, ram moving with and causing a clamping and cutoff blade assembly associated with the die set to engage and sever the workpiece. A plurality of links are pivotably connected at their opposite respective ends to the press and the ram such that driving rotation of an eccentric crank connecting the ram to the press imparts swinging oscillatory motion to the ram whereby when the die set is accelerated up to that of the tube the cutoff blade reciprocates vertically relative to the die set. 
     In Borzym &#34;Flying Cutoff Machine with Swinging Ram&#34; U.S. Pat. No. 3,288,011 issued Nov. 29, 1966 the crank is pivotally connected to only one of the four links which connection limits the vertical rise of the ram. In general, the vertical rise of the ram correlates into longer strokes and greater tube diameters that can be cut. The length of the links would have to be increased to increase the tube diameters which can be cut. However, the driving connection between the crank and ram places a limit on the upward vertical movement of the ram and this limits the work that can be done. A ram which has greater vertical stroke and decreased inertia to allow for faster response in its stroke would be desirable. 
     In Riera et al. &#34;Flying Cutoff Machine&#34; U.S. Pat. No. 4,354,409 issued Oct. 19, 1982, specifically incorporated herein by reference, the ram is driven by a central crank assembly to impart an orbital movement to the ram and includes a slide member mounted thereto for sliding movement relative to the ram. Orbital movement of the ram permits cutting of heavier metals at higher speeds because the ram is traveling in the direction of the moving material during the cutting operation. Sliding contact between the metal surfaces over the entire stroke of the press causes high friction and inertia. Turning of the crank at very high RPM imposes a turning moment on the ram which can result in chattering effect wherein the ram experiences slight angular displacements along the ram longitudinal axis. As a result, available power to drive the ram may be consumed. It would be desirable to have a sliding connection between the link and ram which minimizes movement and friction which would correlate in a lower power required to move the ram in the orbital path. It would also be desirable to reduce the weight of the ram and its support apparatus whereby to further reduce the power required to drive the ram. The invention provides a ram assembly which has a faster response to its orbiting motion, and reduces power required to orbit the ram in parallel planes relative to a tube cutoff die set. The ram is constrained by a slide assembly for horizontal swinging movement without introducing wear on the ram. Without increase in link length, the present invention increases the vertical workstroke of the ram, to allow the severing of tubing having larger diameter and to increase the linear speed of th die relative to the longer bed. 
     Advantageously such a ram assembly would retrofit the prior cutoff machine of Riera et al. U.S. Pat. No. 4,354,409 without substantially redesigning same. 
     Other features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiment of the invention taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevation view of a rotary arc ram tube cutoff machine embodying the invention with the die set therefor removed in the interests of clarity. 
     FIG. 2 is a side elevation view of the cutoff machine shown in FIG. 1. 
     FIG. 3 is a view taken generally along line 3--3 in FIG. 1 with portions broken away and removed. 
     FIG. 4 is a view taken along line 4--4 in FIG. 1. 
     FIGS. 5 and 6 show alternate embodiments in accordance with this invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now the drawings, a cutoff machine embodying the present invention is of the type disclosed in the Riera et al. patent and is for severing round tubing extending longitudinally of its axis and delivered continuously from a source such as a tubing machine, not shown, which would be located to the left of the machine as viewed in FIG. 1. Such tubing can have various shaped cross-sections such as a channel, a T-section or the like. 
     The machine is generally designated at 10 and includes a frame 12 having a flat bed 14 extending longitudinally and parallel of the path of the tubing to be cut and beneath the workpath thereof and a head 16 spacedly overhanging the bed and tube path, a ram 18 extending parallel to the path and above the bed, and a parallelogram linkage 20 including a plurality of links 22 for supporting the ram from the head and for translatory swinging movement toward and from the tube path about axes perpendicular to the path. An eccentric crank 24 connects the ram to the frame for rotary movement, the crank being driven by a motor 26 whereby the crank rotates the ram 360° about its connection to the head. FIG. 1 shows orbiting path of the ram with portions designated &#34;A&#34; and &#34;B&#34; showing the locations of the ram. 
     A die set (shown and described in the above patents) for clamping onto the tube and severing the tube is mounted to the frame for sliding movement by a pair of transversely spaced rails 28 forming part of the bed and a pair of transversely spaced flange bars 30 forming part of the ram. The die set slides relative to both the bed and the ram and at the same time the tube severing blade severs the tube into sections as the ram undergoes its orbital movement. The distance the die set moves is determined by the speed of movement of the tube and the time to reciprocate the blade. 
     The head 16 includes a pair of transversely, spaced head plates 32 and 34 that superpose bed 14. The head plates are spaced apart a distance sufficient to receive the parallelogram linkage 20 and the driving connection afforded by the eccentric crank. The ram 18 is connected to the linkage for swinging movement between the head plates. When the crank rotates 360°, this causes the ram to orbit 360° between and relative to the head plates. 
     The parallelogram linkage 20 is formed by a plurality of separate links 22 with a like set of links being connected to each side of the ram. Each link has an upper end and a lower end with the upper end portions being provided with an opening sized to pass a pivot pin 36 and be suitably connected to one of the head plates and the lower end portions being provided with an opening sized to pass a pivot pin 38 and be suitably connected to the ram. The pivot axes of the pivot pins 36 and 38 for the upper and lower ends of the links define, respectively, planes above the bed which are parallel and horizontal to one another and to a horizontal plane including the bed. An imaginary line drawn between the pivot axes of a link is always parallel to a like line drawn through each other link. That is, when the ram rotates the lines drawn through the pivot axes of each respective link are maintained at an acute angle to the bed. As shown in FIG. 1, the links move the ram upwardly to the left in oscillating between the first and second positions. 
     In accordance with this invention, ram 18 is longitudinally extending, symmetrical in cross-section about a central longitudinal axis, and is primarily comprised of a single material having a density substantially less than that of steel. Preferably the material would be nonferrous, and have a density about one third that of steel, aluminum being found to be suitable in one application. The ram is generally in the form of an I-beam 40 having a vertical web 42 connecting upper and lower flanges 44 and 46 A pair of oval, laterally spaced, longitudinally extending slots 48 pass through the web. 
     A plurality of C-shaped guide tracks 50 are fixedly mounted by fasteners 52 to the side channels of the I-beam. Each guide track has a flat body 54 and upper and lower track portions 56 and 58, the track portions of the &#34;C&#34; defining both a guide and a bearing surface Shown best in FIG. 3 body 54 has an oval slot 60 therethrough which is coextensive with and in register with one of the slots 48 in the I-beam web. Preferably, guide tracks 50 are comprised of a wear resistant material such as steel. 
     A generally flat, rectangular, longitudinally extending slide member 62 is slidably received in each guide track 50 with the opposite end portions of each slide member having an opening therethrough sized to pass a respective pivot pin 38 connected to the lower end of a respective link. The pivot pins 38 pass through the registered slots 60 and 48, are free to slide longitudinally of the ram 18 in the slots, and interconnect a pair of slide members 62, one slide member being on each opposite side of the ram. The slide members 62 are free to slide within the C-shaped guide tracks 50 with wear on the ram being obviated by the upper and lower track portions 56 and 58 thereof. 
     Shown best in FIG. 4, links 22 on each side of the ram 18 suspend the ram to the respective head plates 32 and 34 with rotation and vertical rise of the ram therebetween being shown by the dotted lines and corresponding to the ram locations &#34;A&#34; and &#34;B&#34; shown in FIG. 1. It can be seen that no structure impedes the vertical rise, and thus the workstroke, of the ram. The upper pivot pins 36 allow the upper ends of the respective links to pivot relative to the head plates. The lower pivot pin 38 is tubular and has its opposite end portions nonrotatably secured to a respective link 22 at each of its opposite sides by threaded fasteners 64 and mounting plates 66. 
     The ram in accordance with this invention is such that while the mass of the ram, including the guide tracks and slide members, can be generally numerically equal to the mass of the ram described in the Riera et al. patent, the mass moment inertia of the ram herein is much lower. As such, the torque needed to initiate rotation, and thus the associated power required to swing the ram is lower. As a further benefit, the ram can be made longer in length. Generally an axis through the mass center of the ram, in the long direction, is parallel to the geometrical axis through the cross-section. 
     The links 22 oscillate between first and second positions but because of the slide members 62 and their connection of the lower ends to the ram, the links do not undergo a 360° rotation. Driving movement of ram 18 causes the slide members 62 to have a horizontal vector of movement in a direction opposite to the horizontal vector of movement of the ram. At least two links 22 connect to each slide member 62 with multiple slide members acting to assure that the ram orbits in vertical planes relative to the bed. 
     FIG. 5 illustrates an embodiment in accordance with this invention including a pair of slide assemblies being disposed on opposite side of the driving connection afforded by the crank. The assemblies include the C-shaped guide track, the slide member and the connection to a pair of parallel links. 
     Further, in accordance with this invention and as shown in FIGS. 1 and 6, a link plate 68 is provided to connect the slide members together. When the ram is long and utilizes several laterally spaced parallelogram linkages 20, such link plate 68 connection will assure that the ram orbits smoothly in parallel planes without chattering, can reduce mass over that required by the single slide member of the hereinabove referenced Riera et al. patent, and reduces wear and/or friction. This construction also would help assure that when a ram has many links that the crank can operate to drive the ram. While a pin-like connection permitting rotation between the members is shown, a box-like connection which inhibits relative rotation between the connected members may be desirable. 
     In FIG. 6 embodiment, relative to the driving crank connection, the slide member 50A and associated guide track 62A shown to the right are longer than the slide member 50 and guide track 62 shown to the left. 
     While the above description constitutes the preferred embodiment of the invention, it will be appreciated that the invention is susceptible to modification, variation, and change without departing form the proper scope or fair meaning of the accompanying claims.