Tool changing – With safety means – Guard
Reexamination Certificate
2000-05-04
2001-10-02
Briggs, William (Department: 3722)
Tool changing
With safety means
Guard
C409S134000, C409S219000, C451S451000
Reexamination Certificate
active
06296599
ABSTRACT:
The invention relates to a machining tool which includes a workpiece support displaceably guided on a machine bed, in accordance with the preamble of claim
1
.
Customarily, cooling lubricants are supplied during machining processing of workpieces to increase tool life by cooling and lubrication on the one hand, and to dissipate the heat introduced into the workpiece and into the tool as a result of the machining process, as well as remove the produced chips as promptly as possible from the location being processed, on the other hand.
In automotive industries it has become standard practice to use engine, running gear or body components of light metals, preferably of aluminum or magnesium alloys. Processing of such magnesium-containing alloys is, however, relatively problematic inasmuch as the chips produced in the process are easily flammable, so that a comparatively high expenditure is necessary in order to maintain the required production safety. Utilisation of cooling lubricants based on aqueous bases is not possible because magnesium reacts with such components, so that cooling lubricants containing oil must be employed. Such cooling lubricants containing oil do, however, frequently adhere to the workpieces being processed, which must then be cleaned with suitable cleaning agents after machining processing. The agents utilised for cooling and cleaning must be disposed of or separated following the processing/cleaning cycle, which involves relatively high expenditure.
In order to overcome these drawbacks, there is an increasing tendency to process the workpieces dry, i.e., without any cooling lubricants. What is essential in this processing is to carry the process chips away from the workpiece as promptly as possible during the machining process and keep them in a minimum space. In order to ensure this, the machine tools utilised for dry processing are equipped with a closed processing chamber wherein the workpiece to be processed is located, and into which the work spindle of the machining tool penetrates.
In special cases, machining in the processing chamber may furthermore be carried out under inert gas, whereby operational safety is improved.
FIG. 1
, which shall be referred to as early as now, shows a top view of a machining center
1
wherein a spindle carrier
2
movable in the X and Y directions (perpendicularly to the plane of drawing) is guided on a column
4
by means of a bidirecitonal guide mechanism. The spindle carrier
2
carries a horizontal work spindle
6
for receiving a machining tool.
The machining center
1
moreover includes a tool change which may, for example, be designed as a laterally arranged revolving hopper
8
in which the tools
10
to be supplied to the work spindle
6
are accommodated.
A workpiece support (table)
12
of the machining center
1
is mounted on a machine bed (not shown here) such as to be displaceable in the forward feed direction (Z). The workpiece support
12
and the work spindle
6
are surrounded by a processing chamber
14
so as to allow for dry processing. In order to shorten the periods between work cycles, a pallet changer
16
wherein two pallets
18
,
20
are mounted on pivoting means
22
is assigned to the workpiece support
12
.
The pallet changer
16
carries a pivoting door
26
, hereinafter referred to as a partition
26
, which is closed at the top and bottom sides (parallel with the plane of the drawing). Jointly with the side walls
15
and with the peripheral walls
24
having a circular arc curvature of the processing chamber
14
, the pivoting door
26
constitutes a complete encapsulation of the work range such as to allow for wet and dry processing. The pallet changer
16
moreover includes a circular arc shaped sliding door
25
which serves as an operator protection during pallet change and surrounds the pallets
18
,
20
jointly with the peripheral wall
24
.
As can be seen in
FIG. 1
, the processing chamber surrounds the entire workpiece support
12
together with the pallet
18
positioned thereon in the processing position, and also covers the linear guide mechanism
17
for the workpiece support
12
(workpiece table) formed on the machine bed.
As was already mentioned at the outset, the chips must be removed from the processing chamber as promptly as possible during dry processing of workpieces in order to avoid the risk of kindling and to also ensure proper functioning of the machining center because, e.g., the named linear guide members might be work by deposited chips. Particularly in the range of the linear guiding mechanism, chip removal is rendered difficult because the guide profiles having a comparatively complicated design —for example dovetail guides—may form dead spaces for chips to accumulate. During wet processing this problem is of minor importance because the cooling lubricant flushes the chips out of the processing range.
In contrast, the invention is based on the objective of furnishing a machining tool wherein chip removal is facilitated even during a dry processing.
This objective is attained by a machining tool having the features of claim
1
.
Thanks to the measure of arranging the guide members of the workpiece support externally of the processing chamber, undesired chip deposition inside the guiding range is prevented so that wear to the guide members due to such chip deposits can reliably be prevented. Another advantage residues in the fact that the guide members, being external of the processing chamber, are freely accessible and may thus be inspected and maintenanced in an easy manner. As both the means for driving the workpiece support as well as the guide members thereof may be arranged externally of the processing chamber in the machine according to the invention, suitable cover means serving to separate the drive means from the guide sections of the workpiece support need not be provided.
In a particularly preferred embodiment, the workpiece support is designed to have at least two brackets jutting out transversely with respect to the direction of guidance, to each one of which a respective guide member is associated for support on the machine bed.
Recesses allowing the brackets to pass through the wall of the processing chamber are formed in the latter, with these recesses being sealed by suitable movable covers during the feed movement, whereby complete encapsulation of the processing range is ensured.
These cover means may, e.g., be sliding metal sheets or other telescoping metal sheets or panels fasted on the workpiece support displaceable in the feed direction, and sealingly sliding on the adjacent walls of the processing chamber.
In a particularly preferred variant, the machine bed is formed of two bed members arranged at a distance from each other, with one of the above mentioned brackets each being guided on one of the bed members.
In the range between the two bed members a chip removal mechanism is formed, whereby the chips may be removed from the processing chamber located between the two guide members.
For reinforcement of the machine bed, the two bed members are advantageously coupled by means of suitable connecting or reinforcing webs and/or a common baseplate.
The wall areas of the processing chamber being impacted upon by chips are designed to have an inclination angle of at least 50° with the horizontal so that the chips slide off along the peripheral walls of the processing chamber towards the chip removal mechanism.
The latter is preferably designed as a chip conveyor (for example scraping panels drawn by chains).
In a case where the machining tool is to be used as a high-velocity machining center, a separate drive motor for the workpiece carrier is advantageously assigned to each guide member, with the drive motors advantageously being designed as linear drive means, so that no mechanical transmission elements are required for converting the rotary movement of a drive motor to a linear movement of the workpiece support.
Further advantageous developments of the invention are the subject matters of the further appended claims.
REFERENCES
Briggs William
Ex-Cell-O GmbH
Oliff & Berridg,e PLC
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