Tool changing – Including machine tool or component – Rotary spindle machine tool
Reexamination Certificate
1999-07-23
2001-03-20
Briggs, William (Department: 3722)
Tool changing
Including machine tool or component
Rotary spindle machine tool
C408S046000, C408S236000, C409S168000, C409S224000, C483S036000
Reexamination Certificate
active
06203478
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a flexible process and machine for drilling oil-holes in different positions in a range of various types of crankshaft, in medium- or high-capacity production, for combustion engines (cars, . . . ).
Oil-holes may be situated in various positions lengthways and widthways on the longitudinal axis of a crankshaft, as well as in different positions around the circumference described when turning on this longitudinal axis. They may also be perpendicular or with various angles of inclination with respect to this longitudinal axis of the crankshaft.
Until the automotive industry concerned itself with the concept of flexibility, the machining described was undertaken by transfer units (multi-station lines), with each station drilling one of various holes. This solution has been valid in times of few changes in the dimension and shape of crankshafts, when an automobile engine was certain to have an extended life on the market. But now that changes are frequent, both machine and process need to be flexible to adapt to crankshafts with dimensional and geometrical modifications, as well as variations in the position/inclination of the oil-holes and also in the number of such holes. This adaptation needs to be rapid, simple and low-cost, due to the frequency of such a need.
There is another factor that has been changing in recent years: when a new automobile engine is launched onto the market, there are always doubts about the demand and any initial forecast may be miscalculated, either above or below the mark. For this reason, automobile manufacturers nowadays prefer production methods that begin with low-scale investment and production and later, if there is a growing response from the market, to gradually add new productive units the same as at the beginning. If the first unit is enough for a production volume of up to 50,000 pieces/year, they will need to add a second unit when there is a demand for up to 100,000/year, a third unit if there is a further demand and so on.
These factors cannot be tackled with multi-station transfer units, because they are not very flexible, nor do they admit progressive investment in line with escalating production brought on by increasing demand, since these are high-cost and high-production machines from the outset.
Furthermore, the diversity of oil-hole placement, explained previously, is not possible in traditional machining centres, with their X, Y and Z axes, at least in mid-high production level. Also, there is the problem of the additional W axis which is needed to position independently the drill guide bushings, since this fourth axis does not exist in traditional machining centres. Neither is there a special device to enable occasional automatic changing of the tool+guide bushing, and at other times just the bushing, because the tool is being used for the next drilling, but the bushing needs to be changed because it requires a different plane on the front end, to adapt it to the plane of the zone of the crankshaft it is resting on.
Because of all this, there is a need for a machine for drilling oil-holes in different positions and in a varied range of crankshafts, it needs to be flexible and at the same time a productive unit capable of being included in a production line in a quantity that increases as production increases.
There has been a previous attempt to meet this ambitious objective, but it has not produced the expected results, as it has important drawbacks which in medium-high production are a great inconvenience for an industry as demanding as the automotive industry. Below are some of the known drawbacks of this previous attempt, which for simplicity's sake will be referred to as “I A” (U.S. Pat. No. 5,759,140):
a) The machine has to be capable of working with gun drills which have a collector for the chips produced during the drilling, as well as with twist drills with no collector, and then the chips are scattered over the working area. The second alternative requires the layout of the working area to be such that there is no piling up of the chips on the crankshaft-bearing tools and on adjoining mechanisms, making it essential for the chips to be eliminated by falling through cleared areas and without any obstacle.
In the “I A” machine, the crankshafts are supported on a box-shaped rectangular frame, almost closed in on one side and with an opening on the other side for loading and unloading the crankshafts. This box-frame pivots on a horizontal axis supported on two opposing bearings. The pivoting is so that the longitudinal axes of the crankshafts situated in the box-frame can take various positions:
1
st
position: horizontal during the loading/unloading of the crankshafts.
2
nd
position: vertical, when drilling the holes perpendicular to the longitudinal axis of the crankshafts.
3
rd
position: inclined upwards when drilling the holes which are inclined in one direction with respect to the longitudinal axis of the crankshafts.
4
th
position: inclined downwards when drilling holes with the opposite inclination to the previous one.
The box-frame is almost closed in on one side and also receives the crankshafts, as well as the positioning and fixture mechanisms, together with the turning mechanisms of the crankshafts on their longitudinal axis and other necessary mechanisms, piping etc. All these elements are piled up in the box-frame. And in the 3
rd
and 4
th
positions, which are inclined, the chips from drills with twist drills fall directly and in great quantity onto the box-frame and all the mechanisms contained therein, and as they have no free-fall, they start blocking up crevices and anywhere else they can find to settle. This is a serious drawback, and in subsequent loading/unloading of crankshafts, the piling up of chips will cause malfunctions which are inadmissible in mid-high production.
In the summary of the invention which is presented further on, point a
1
) describes its layout which is totally different to that of “I A”, the way in which the drawbacks of “A I” are avoided and the lack of comparison in layout and results between “I A” and this invention, both in this aspect and in those which are set out afterwards.
b). The problem of chips scattering all over the work area, when drilling with twist drills, is avoided when working with gun drills, because they have a chips collector in the shape of a collecting bin joined to the outlet pipe. But with “I A” there now arises another problem and serious at that. The collecting bin and the outlet pipe together are fairly bulky, and if the chips are of steel, they need to be very bulky, since steel chips are sizeable and difficult to evacuate. And the external configuration of this apparatus collides with the crankshaft-bearing box-frame and with its piled up mechanisms. This occurs in the 3
rd
and 4
th
positions, both inclined, as described in a). And to avoid this collision, one has to make do with combined collecting bin/outlet pipe apparatuses that are insufficient for their function, giving rise to obstructions in the evacuation of chips, continual stoppages and maintenance requirements that are unacceptable in mid-high production.
See b
1
) for the totally different layout of this invention that avoids this problem inherent in “I A”.
c). The pivoting on two bearings of the box-frame which supports the crankshafts in “I A” leaves this device supported only on its centrally-situated pivotal axis and the rest is hanging free. This is too much to be hanging free. Crankshafts are lengthy pieces, and at each end are the referencing and support elements, which make the sub-unit even longer and they can give some 500-600 mm to the right and to the left of the pivoting, with no additional support but for the pivotal axis. The other side of the rectangle of the box-frame is also rather large and the crankshafts, together with all the mechanisms in the box-frame make up a great weight, forming an enormous and heavy mobile sub-unit, which also bears the drilling forces. This situation is not helped by ju
Bierman, Muserlian and Lucas
Briggs William
Etxe-Tar, S.A.
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