BALANCING DEVICE FOR ROTARY CUTTING TOOLS

Abstract: Device intended to eliminate such unbalance and vibration occurring on unsymmetrical mounting of rotatable tools and tool holders at milling machines and the like such as arboring machines, drilling machines etc. According to the invention there is on the tool holder and in an appropriate place attached a weight support able to receive one or more weights appropriately sized and said weights being radially adjustably securable to the weight support means.

Description: Balancing device for rotary cutting tools. Technical field of the invention This invention relates to the area cutting and machining and more in detail to milling tools and the like intended to be fixed at a tool holder for example for inside machining of a work piece and preferably for cutting tools including a holder device displaceably arranged relatively- to the axis of rotation. Background of the invention Tools and arrangements of the kind mentioned above where the position of the tool or the tool holder is radially offset and thereby unbalanced exist in many connection whithin cutting technics and especially at milling or arboring machines and the like where a rotatable tool holder carries a tool and the tool is fastened in such a way that the center of gravity will be off- set from the axis of rotation. This is of minor importance at slowly turning machines as a relativly small weight of the tool in no negative way influences the machine as a whole. In the majority of cases two tools are used and allowed to balance each other. At high speed machines of the kind more and more used today and especially at machines having one single tool, problems will arise. Many machining tools are today placed on so called shoes or pads, i.e. fasteners having vibration dampings bodies of rubber or similar material and it has been revealed that if an unbalanced tool is used in such a machine the whole machine might start vibrating which is disturbing and negative for the result of the work. As a consequence you have to refrain from utilising the posiblity of allowing the machine work at high speed. Earlier revealed double or triple mounted tools can not be use on precision machining where it is intended to use cuttin inserts of the types mostly demanded today as it hardly would b practically possible to add to a production cycle suc complicated relative adjusting of diametrally opposite actin special tools or tool holders necessary. It is also not posibl to use standard inserts and tool holders for twin mounting an the result will be that the speed must be kept low if vibratio are to be avoided and standard parts to be used. One aspect with this invention is to bring about an arrangemen elimimating the above mentioned drawbacks resulting from un symmetrical mounting of rotating tools and tool holders a milling machines and the like as arboring machines, drillin machines and the like and making it possible to use in a rational way replaceble inserts of modern design which allow high yiel and simultaneuosly give a high quality result. Summary of the invention Vibration problems occur because the milling spindle or shaft of the milling head and tool holder as a hole are biassed by the unbalance occuring because the tool with its cutting insert are not correctly balanced in radial direction. Via bearing and the like the vibrations and unbalance bring the whole machine into a state of resonance vibration and this is a more tangible if the machine is carried by so called elastic pads. If the machine is firmly secured by bolts directly to the foundation or to a floor the vibrations might seem to be less intense but the machine nevertheless will be affected negativly. To this may be added the disconfort the operator has to accept. According to the invention the problem is solved by attaching to the tool holder in an appropriate position a carrier means adapted to receive one or more weights of appropriate sizes and by arranging the weight or weights to be radially adjustably attachable to the weight carrier means. Brief description of the drawing One embodiment of the device according to the invention will be described in the following with references to an attached drawing, in which Fig. 1 is a side view illustrating a portion of a tool holder to be attached to a milling machine shaft, said holder presenting the device according to the invention, Figs. 2 and 3 are a longitudinal sectional view and an end view, respectively and Fig. 4 is a longitudinal sectional view of a weight. The tool holder part designated 1 has an end face 2 presenting a recess 3 for a wedge adapted to fit into and be secured to corresponding details at the machine part, i.e. an end milling arbor or the like. The tool holder part 1 includes an inner portion 4 which is rigidly connectable with the part 1 and an outer portion 5 which by means of a slide guide 6 and by a screw device is radially displaceable relatively to the inner portion 4. At the outer portion 5 of the tool holder there are appropriately arranged abutments and clamping means for a tool holder, not shown. By using single tool holders projecting more of less in the one radial direction only there will occur a the outer portion 5 an unbalance which on rotation naturally also biasses the inner part 4 and the milling arbor 1. As different operations of work demand different radial setting and further, during the course of work, for example on internal turning, the insert holder with the insert will be displaced radially out- wardly different degrees of unbalance will be present within th arrangement as a hole. By attaching tools having differen weights in different radial positions the center of gravity wil be moved more or less away from the axis R of rotation. According to the invention there is at the tool holder at leas on one side thereof and preferably on the side opposite the sid towards any radial displacement is directed arranged a attachment seat for a weight holder and, this being arranged fo receiving and securing weights in different positions. More in detail there is at the outer part 5 of the tool holde a threaded bore 16 and in this bore 16 a threaded end portion 7 of a holed shaft 8 having a head 9 with a wrench attachment is mountable. On the shaft one or more weights 10 may be fastene according to the demand of balancing. One weight consists of body having a through bore 11 and also a lateral threaded bore for a stop screw 12. The size or weight of each weight 10 may be determined by the demand of balancing and you can instead of an one piece body 10 also use several thin washers or rings in sets which together can cover a widen range of weights. By making the weight or weights displaceable and affixable in different positions a very good adaptability is achieved for different demands. On the drawing the weight 10 is shown its inner most position and it is displaceable from this position to just any position as far as up to the head of the shaft 8 and each such position results in a given balancing value.

Claims: CLAIMS 1. Balancing device for rotatable holders for tools preferabl tool holders for milling machines and the like where a tool i attachable in different radial positions relatively to the axis (R) of rotation the tool holder and thereby causing an unbalanc in the combined holder (1) and tool unit, c h a r a c t e r i z e d in that at the tool holder (1) includes support means (8) positioned and localized in th predominent direction of radial displacement such support bein arranged to receie at least one weight (10) at an adjustable radial distance from the axis of rotation (R) in order t eliminate disturbing unbalance. 2. Device according to claim 1, c h a r a c t e r i z e d in that the suport means includes an elongated shaft (8) threaded into a bore at the tool holder body (2) preferably in an oute (5) part thereof radially movable relatively to an inner part (4) and that on such shaft (8) having an outer head, at least one preferably cylindrical weight body (10) is displaceably secured said weight body having a locking screw (12) to engage the shaft. 3. Device according to claim 1 or 2, c h a r a c t e r i z e d in that the weight body (10) includes a number of washer or ring like elements of which at least some have means for securing themself at predetermined radial positions on the shaft. AMENDED CLAIMS [received by the International Bureau on 16 October 1992 (16.10.92); original claims 1 and 2 replaced by amended claims 1 and 2 ( 1 page) ] 1. Balancing device for rotatable holders for tools preferabl tool holders for milling machines and the like where a tool i attachable in different radial positions relatively to the axis (R) of rotation of the tool holder thereby causing an unbalance in the combined holder (1) and tool unit, which too holder (1) includes support means (8) positioned and localize in the predominent direction of radial displacement of the tool and adapted to receive at least one radially adjustable weight (10) c h a r a c t e r i z e d in that the support means includes an elongated shaft (8) threaded into and extending from a radial bore at the tool holder body (2) in an outer (5) part thereof radially movable relatively to an inner part (4) and in that on such shaft (8) having an outer head, at least one preferably cylindrical weight (10) is radially adjustably securable. 2. Device according to claim 1, c h a r a c t e r i z e d in that the said weight (10) having a positioning and locking screw (12) to engage the shaft includes a number of washer or ring like elements of which at least some have means for securing themselves on the shaft.

Inventors: MIHIC WLAJKO, MIHIC, WLAJKO
Applicants: MIRCONA AB
Application year: 1992
Main classification: B23B29
IPC codes: B23B3, B23B29, B23Q11, G01M1