Subject of Invention

The subject of the invention is a dual column band saw preferably intended for the sawing of a variety of workpieces, preferably of long profiles into smaller pieces or for a rough cutting of a workpiece prior to precision and other treatment.

Technical Problem

The technical problem solved by the present invention is how to conceive such guides on a pair of columns to assure an even shift of a band saw along them without friction or deceleration of the saw in all shifts and loads of a band saw assembly, without having to take the limitations of guides in conceiving a sliding assembly into account.

Prior Art

Known dual column saws are designed in a way that on both their columns an axially movable band saw is arranged and can be driven in various ways, preferably hydraulically or pneumatically driven. The current variation of a sawing area position has to be observed, because it varies as a function of a workpiece being fixed in a vice and of its shape. Thus the point of force, with which a saw presses against a workpiece during sawing varies. Due to changing points of said force, not only axial forces appear in band saw guides, but also forces causing torques in the guides, said torques causing irregular movement of a band saw along guides.

In order to diminish this damaging influence of torques in band saw guides on columns, several hydraulic cylinders for the movement of a band saw are used or even a band saw can be fixed in its mass centre of gravity. Yet said problem is only alleviated, not done away with.

Several hydraulic cylinders, preferably two, are difficult to control that precisely to attain the desired smooth band saw shift. When a saw is fixed in its centre of gravity, only the influence of its weight is annulled, the influence of the force of sawing shift remains.

Said forces can cause damaging forces on the saw band, which consequently gets bent thus causing displacement of the sawing surface from the intended surface. Additionally, momentaneous overload or unload of individual sawing teeth may appear, causing a less than optimal speed of sawing and a too quick wear out of a saw band. Individual teeth or even the band may get broken.

Said constructions also render it impossible to precisely control the sawing force, which should be adapted to the workpiece material and to its changing surface of sawing.

Solution to the Technical Problem

The described technical problem is solved by the invention, characterised in that on the columns, on which a band saw is axially movable, there are two axially arranged racks, on which two mutually stiffly linked pinions run. Simultaneous and precise parallel shift of a band saw along the racks is thus guaranteed regardless of a changing point of force produced during sawing.

The invention will now be described in more detail in the continuation with a description of an embodiment and the enclosed drawing, in which

Fig. 1 shows a front view of a dual column band saw of the invention.

Fig. 2 shows a front view of a dual column band saw of the second embodiment.

A dual column band saw consists of a base frame 1 of an optional concept, on which there are two in parallel running columns 2, along which a band saw 3 is guided, whereas a workpiece, not shown in figures, is fixed in a vice 4. The band saw 3 is shifted by at least one means 5, for instance by a hydraulic cylinder or in another known way. Additionally, the saw has one control unit 6 and a terminal 7 for power source for the means 5, preferably a terminal for a hydraulic pump and a terminal 8, preferably for the electric motor of the saw 3.

An essential characteristic of the device of the invention is in that with each column 2 there is a coaxially positioned rack 21, along which a pinion 31 runs, said pinion being mounted on the band saw 3, whereby both pinions 31 are mutually stiffly linked by an axle 32. The racks 21 are preferably positioned on columns 2.

A parallel shift of the band saw 3 with respect to the columns 2 is thus always guaranteed, without any fear of appearance of damaging positions as indicated in the prior art.

In order to diminish or entirely do away with the clearance between the rack 21 and the belonging pinion 31, they have helical teeth. The pinion 31 is axially adaptable to the belonging rack 21 with known means 7, for instance with a nut positioned on a thread 8 on the axle 32, whereby the nut can be additionally secured against unscrewing, when the pinion 31 is fastened to the rack 21. The helical gearing on various columns or both pairs of the rack and the pinion is preferably symmetric.

To do away with the above disadvantages, there is an option to manually set the automatic force control of sawing, which can be adjusted during sawing, with respect to the workpiece material, the changing shape of the sawing surface as a function of the selected saw, i.e. the size, the number and quality of teeth and the speed of sawing.