TITLE

BAND SAWING MACHINE WITH MOBILE GANTRY FRAME FOR AXIAL CUTTING OF METAL TUBES OR BARS

DESCRIPTION Field of the Invention

The present invention relates to the field of machine tools for cutting articles, more particularly metal articles, and relates more specifically to a band sawing machine for the axial cutting of bars or tubes, for example in stainless steel or aluminium, and more specifically for making axial diameterical cuts. Background Art

In the field of metal structural work there is a greatly felt need for bars with a semicircular section or semi-tubular bars, particularly in ground stainless steel. The bars with semicircular section can be produced by casting and rolling, although their surface remains rough and would require a laborious and costly surface finishing treatment for many applications. In the case of semi- tubular bars production by roller leveling is problematical and does not provide satisfactory results as it is not possible to maintain the circular profile at the longitudinal edges .

The object of the present invention is to provide a band sawing machine for the axial cutting of bars or tubes, more particularly in a metal material, which allows the requirements and needs indicated above to be met and which can also be used for the production of articles, taken from solid metal bar, which can normally be obtained, at significantly higher costs, by milling or turning.

A particular object of the present invention is to provide a sawing machine of the type mentioned above whose

working overall dimensions do not exceed its maximum overall dimensions .

Summary of the invention

These objects are achieved with the band sawing machine according to the present invention whose basic features are disclosed in claim 1.

The band sawing machine according to the invention comprises a support structure provided with longitudinally aligned supports for a piece to be machined and a first gantry frame mounted transversely thereon and holding a pair of coplanar motorized flywheels with horizontal axes, on which a continuous band cutting blade is wound, said gantry frame being mounted slidingly on said support structure and motor means being provided for transmitting a forward motion to said gantry frame in a longitudinal direction, during which the axial cutting of the piece is performed, and motion of return to a starting position at the end of the cutting operation.

Brief description of the drawings The features and advantages of the band sawing machine according to the present invention will be made clearer by the following description of one of its embodiments, given by way of a non-limiting example with reference to the accompanying drawings, in which: - Figure 1 is a side elevation view of the sawing machine according to the present invention;

Figure 2 is a plan view from above of the sawing machine of Figure 1 ;

Figure 3 is a front view of the sawing machine of the previous figures, with parts removed for the sake of simplicity of illustration;

- Figure 4 is a rear view of the band sawing machine

showing a first variation of the invention;

- Figure 5 is a front view of a second variation of the band sawing machine of the invention;

- Figure 6 is a side view of the band sawing machine of Figure 5.

Detailed description of the invention

Referring to the figures 1-3, 1 denotes generically a support structure or stand formed by two rows of columns or uprights 2 which support two longitudinal members 3 connected one to the other by crosspieces 4 placed at the columns 2. On each of the crosspieces 4 a table 5 is placed, holding a support housing 6, advantageously notched in a V shape to support the piece P to be processed on the machine, as mentioned herein below. The support bases 6 of each table 5 -are aligned longitudinally.

On the two longitudinal members 3 two respective hardened longitudinal guides 7 are mounted and two pairs of sliding blocks 8 for supporting a mobile bridge frame denoted generically by 9 rest on the guides 7. On the longitudinal members 3 two opposite racks 10 are also placed and pinions 11 with a vertical axis and fixedly connected to bridge frame 9 mesh on the racks 10.

The bridge frame 9 is made up of a first frame 12 placed transversely to the stand with two parallel side panels 13 extending from one of its sides and mounted on the sliding blocks 8. On the frame 12 a geared motor unit 30 is mounted which, thanks to shafting 31, transmits rotary motion to the pinions 11 for the movement of the bridge frame 9. On the side opposite to that from which the two side panels 13 extend, the first frame 12 supports a second frame 20 having hardened vertical guides 22 in which

sliding blocks 21 are arranged slidingly and are formed on the front of the first frame 12 at the side panels 13. The second frame 20 supports frontally two coplanar flywheels 14 with horizontal axes and a continuous band cutting blade 15 extending transversely in relation to the support 1 is wound on the flywheels 14. One of the two flywheels 14 is keyed on a shaft 16 made to rotate by a motor 17 via gearmotor 18. For reasons of safety the flywheels 14 and the blade 15 are enclosed in a casing 19 fixedly connected to the second frame 20 and shown in Figure 1 only. The vertical sliding of the second frame 20 is controlled by a pair of ball bearing screws 23 actuated by a geared motor unit 32.

The piece P (for example a cylindrical bar or a tube) to be cut axially into two halves is placed on the support housings 6 and blocked against horizontal sliding by means of a temporary weld or a counter bracket (not shown) at one of its ends, and against vertical sliding by a workpiece holder arm 24 ending with a grooved wheel 25 urged on the piece to be cut via elastic, hydraulic or pneumatic means. The arm 24 extends forwards from the casing 19 to which it is hinged, for example, in an elastic manner.

A blade tensioning device 26 with relative adjustment handwheel 27 is associated with one of the two flywheels 14, while the blade, near the piece to be cut, is guided in a pair of blade guide arms 28. Clearly, a motorized device can be provided as an alternative for adjusting of the tension of the blade. In a particularly advantageous embodiment of the invention the blade guide arms 28 are connected to the casing 19 so as to be able to perform axial rotation

through 90°, which allows the working section of the blade to be rotated through 90°, bringing it from a horizontal position to a vertical position. In this way it is possible to perform the cutting of the piece also into sections of predefined length, when this is necessary. In this case the second frame 20, which supports the flywheels 14, lowers at a controlled speed thanks to the ball bearing screws 23 actuated by the motor 32.

The arrangement of the motors is purely an example and a single motor may be provided as an alternative. In this case the single motor transmits both the motion of vertical sliding of the second frame 20 and translation of the gantry 9 via suitable transmissions. In other versions actuation means of a different type may be provided, for example of the hydraulic type, and the pinion-rack system which transmits the motion of translation to the gantry 9 can be replaced with a ball bearing system.

Advantageously, the band sawing machine according to the invention may be adapted to mount a removable milling unit shown in figure 4 and indicated at 33. The milling unit is supported by a plate 34 that can be temporarily attached, e.g. by screws, to the second frame 20. The milling unit is used to shape the housing 6 for the piece P according to its size so as to ensure a better positioning thereof. The milling unit is equipped with a milling tool 35 that can be displaced angularly with respect to the vertical position, shown in figure 4, and translates horizontally for a proper positioning in case a multiple-seat support housing has to be shaped. In the embodiment shown in figures 5 and 6, a band sawing machine according to the invention is shown in which a band sawing unit 36 is mounted laterally to permit

sawing of metal sheets, such as that indicated at S, supported by a worktable 41 in figure 5. The band sawing unit 36 comprises a pair of arms 37 extending from one side of the first frame 12 and lying on a vertical plane. Each arm 37 supports pivotally a flywheel 38 and a continuous band saw blade 39 is wound around them. Rotation of flywheels 38 is provided by motor means 40. Means for tensioning the blade, of the known type, are provided. In figure 5 there is also shown a cooling water tank 42 and relevant circulation pump 43 sucking from the tank 42. Cooling water facility of this type or other equivalent type although not shown, are obviously provided also for the embodiments shown in figures 1-3 and 4. In the above embodiment of the invention metal chips are collected in the water tank 42 and must be periodically removed. As an alternative, a metal chips conveyor of the commercial type may be installed in the water tank. A multiple-seat support housing 6 (in particular two-seat) is also shown in figure 5 to allow two pieces P to be axially cut at the same time. This feature may also be provided in the embodiments shown in figures 1-3 and 4.

Tests performed have shown that, using a blade 0.8 mm thick, it is possible to cut axially bars with a circular section in stainless steel starting with a minimum section of 4 mm. The typical length of the bars which it is possible to cut is 6 meters, although bars of different length, both greater and smaller, can be cut. Naturally with the band saw according to the invention it is possible to obtain articles other than the semicircular bar. For example it is possible to obtain

bars with a polygonal section from a cylindrical bar by removal of corresponding circular segments. It is also possible to produce parts with a special shape, obtained by means of successive vertical and horizontal cuts, parts that are normally obtained by milling or turning at significantly higher costs.

Various modifications and alterations to the invention may be appreciated based on a review of the disclosure. These changes and addictions are intended to be within the scope and spirit of the invention as defined in the following claims.