Machine tools abstract
The subject of the present invention is a pallet carrier for machine
tools, said carrier being mounted on an NC work table and comprising
profiled slideways as well as centering elements and hydraulic clamping
members. For thorough cleaning and improved adjustment the invention
provides pressure-fluid ducts within the pallet carrier coupled
to quick-action connectors in the front of the pallet carrier and
leading to spray nozzles which are disposed within the slide faces
of the said slideways.
Machine tools claims
I claim:
1. A pallet carrier for machine tools comprising:
an NC work table for mounting said carrier thereon;
profile slideways, centering elements and hydraulic clamping members;
pressure-fluid ducts formed within said carrier;
quick-action connectors located in the front of the pallet carrier
coupled to said ducts; and
spray nozzles disposed in slide faces of said slideways coupled
to said ducts.
2. The pallet carrier of claim 1 wherein said pressure-fluid ducts
are in fluid communication with branch ducts, said branch ducts
leading to the centering elements and the clamping members disposed
in said slideways.
3. The pallet carrier of claim 1 wherein the quick-action connectors
are configured as hollow cylinders for sealing accommodation of
a horizontally insertable fitting.
Machine tools description
FIELD OF THE INVENTION
The present invention is directed to a pallet carrier for machine
tools, said carrier being fixedly mounted on the work table and
comprising profiled slideways as well as centering bolts and hydraulic
clamping members for fixing a pallet in a precise position.
BACKGROUND OF THE INVENTION
Pallet carriers of the above-specified type are known in various
forms and are employed in program-controlled milling and drilling
machines as well as machining centers so as to permit rapid and
safe changing of the works loaded on pallets. One of the basic prerequisites
for the repeated performance of identical machining operations to
be carried out on the changed works is the automatic and high-precision
positioning of the switched pallets on the pallet carrier and their
firm mounting in the respective prescribed machining positions.
With known pallet carriers there arises the problem that the pallets
at the end of their transfer movement rest directly on the slideways
and upon insertion of the centering bolts still have to perform
some slight lateral adjusting movements in the transitional regions
between static friction and sliding friction before the hydraulic
clamping members become fully effective. This affects the precise
positioning of the pallet on the pallet carrier.
Further, it has been found that the operability of full automatic
machine tools is significantly reduced by deposits constituted of
solid particles, fine chips and the like on the slide faces of the
various slideways. When some object such as a pallet moves across
these slide faces, said deposits will be urged into the frequently
employed ductile slideway linings and will result in damage to the
fine-finished slide faces.
SUMMARY OF THE INVENTION
It is the objective of the present invention to provide a pallet
carrier for program-controlled cutting machine tools, said pallet
carrier permitting location of respective pallets in their predetermined
positions with increased precision and also providing for effective
cleaning of the critical components upon each pallet switching operation.
In accordance with the present invention the specified objective
is achieved in that pressure-fluid ducts are formed in the pallet
carrier and are connected to quick-acting closure means in the front
of the pallet carrier and lead to spray nozzles which are disposed
in the slide faces of the slideway.
In accordance with the present invention it is provided that upon
each switching operation, i.e. when a pallet is moved or placed
onto the slideways of the pallet carrier, a flushing liquid is introduced
at a high pressure of approximately 40 bars into the pressure-fluid
ducts of the pallet carrier. This pressure-fluid is jetted against
the advancing guide faces of the respective pallet and flows sideways
under high pressure through the gap formed between the two guide
faces of the pallet carrier and the pallet. Due to the high kinetic
energy of said fluid stream, dirt particles are loosened from one
or other of the slide faces and become entrained in the fluid. Moreover,
upon operation of the clamping members, i.e. while the pallet is
clamped on the pallet carrier, said pressure fluid creates a practically
friction less sliding cushion of high hydraulic pressure which due
to the lack of friction aids in the slight lateral movements required
for adjusting the pallet. Consequently, the present invention offers
the advantages that the slide faces of the slideways are effectively
cleaned from deposits, on the one hand, and that a more exact positioning
of the pallet is achieved, on the other hand.
In order also to enable removal of deposits or other contaminants
from the clamping or adjusting members the invention provides in
a suitable further embodiment that branch ducts in communication
with the pressure-fluid ducts lead to the clamping members or centering
bolts located in the slideways, whereby proper operation of these
components is ensured.
In order to achieve an automatic supply of pressure fluid to the
ducts disposed in the pallet carrier it is provided in accordance
with another improvement of the present invention that the quick-action
connectors provided at the front face of the pallet carrier are
configured as hollow cylinders and are outwardly covered by a hood.
Fittings are provided on the associated end face of a pallet transfer
slide, said fittings being in communication with a flushing fluid
pump through corresponding pressure conduits. Upon an advancing
movement of the slide said fittings will automatically come into
fluid-tight engagement with the hollow-cylindrical quick-action
connectors in the pallet carrier. In this respect it may be useful
to control the supply of pressure-fluid to said fittings such that
a fluid jet is emitted from said fittings already prior to the making
of the coupling in order to remove any deposits from the outer surface
of the quick-action connectors.
DESCRIPTION OF THE DRAWINGS
Further particularities and advantages of the present invention
have been realized in the embodiment which will be described in
detail below with reference to the accompanying drawing, in which:
FIG. 1 is a perspective view of a pallet transfer station with
the work table of a milling machine;
FIG. 2 is an enlarged perspective view showing the pallet carrier
with a pallet loaded thereon; and
FIGS. 3a and 3b illustrate two phases of loading a pallet onto
a pallet carrier.
DETAILED DESCRIPTION
The transfer station illustrated in FIG. 1 comprises on a supporting
frame 1 a slide 2 mounted on said supporting frame 1 for movement
in the direction of the dual arrow 3 and adapted for rotation on
said supporting frame 1 about a vertical axis (not illustrated).
On a central web 4 of the slide 2 a chain 5 is mounted which has
secured thereto a driver 6 with a pin projecting therefrom. By means
of a drive motor, which is not illustrated, said driver may be moved
together with a chain 5 from a rearward position indicated in dashed
lines to the final forward position shown in FIG. 1.
On an NC table 7 of the machining center, which is illustrated
only in part and comprises a double column 8 and a work spindle
10 mounted in a horizontal headstock 9 a pallet 12 is clamped by
way of a turntable 11 said pallet having rectangular shape With
bevelled corners and being provided on one end face thereof with
a hook-like driver 13. The pallet 12 is mounted on a pallet carrier
20 which may be rotatably disposed on the top of the NC table 7.
As will be particularly apparent from FIG. 2 the pallet carrier
20 includes two slideways 14 15 the fine-finished surfaces of which
respectively constitute a slide face for the correspondingly finished
counter-faces of the pallet 12 to be loaded thereon. Two posts 21
22 are mounted on the end face of the slide, each of said posts
carrying at the front thereof a fitting 23 24. Moreover, the slide
2 has two pressure-fluid conduits 25 26 formed therein which open
into the fittings 23 24 and are in communication with a high-pressure
pump (not illustrated) for producing a fluid pressure of at least
40 bars. Check valves (not illustrated) adapted to be opened and
closed via control means are disposed within said high-pressure
conduits 25 26.
The plate-like pallet carrier has pressure-fluid ducts 30 31 formed
therein which open into quick-action connectors 32 33 closed by
stop plugs and lead to nozzle-like spray apertures 34a, 34b and
35a, 35b. The quick-action connectors 32 33 are disposed on the
forward end of the pallet carrier such that upon an advancing movement
of the slide 2 the fittings 23 24 thereof will come into liquid-tight
engagement with said quick-action connectors. In the position of
the slide 2 illustrated in FIG. 2 in which the fittings 23 24
are not yet in engagement with the quick-action connectors 32 33
opening of the check Valves (not illustrated) causes sharp jets
of pressure fluid to be sprayed against the quick-action connectors
32 33 outwardly covered by hoods so as to remove any deposits from
the end faces thereof.
As will be apparent from a consideration of FIGS. 2 3a and 3b,
the engagement between the two fittings 23 24 and the quick-action
connectors provided on the pallet carrier 20 results in fluid communication
between the pressure-fluid ducts 30 31 in the pallet carrier and
the high-pressure conduits 25 26 in the slide 2. This is when--as
illustrated in FIG. 3--the supply of pressure-fluid to the spray
nozzles 34 35 will be started, the pressure-fluid being jetted
from the nozzle 35b, which is not yet covered by the pallet 12
into the working space which is enclosed by the protective hood
of the machine tool. A strong lateral flow will result in the intermediate
gap between the surface of the slideway 14 15 and the bottom of
the pallet 12 at the mouth of the nozzle 35a, which is already covered
by the pallet, Whereby any deposits of chips or other particles
possibly adhering to one or other of the surfaces will be flushed
away with high kinetic energy. In the final phase shown in FIG.
3b, the pallet 12 is in its prescribed working position, in which
clamping bolts 40 engage in corresponding apertures at the bottom
of the pallet and draw the pallet 12 with a high compressive force
against the surface of the slideways. Branch ducts 41 42 branching
off each of the high-pressure ducts 30 31 lead to said clamping
bolts. As soon as the pallet has reached the final position illustrated
in FIG. 3b, adjusting pins (not illustrated) or other precise abutment
means will become effective. At the same time pressure cushions
43a, 43b, 44a, and 44b will be formed at the nozzles 34 35 on which
cushions the pallet 12 floats, so to speak, so that any slight lateral
adjusting movements of the pallet 12 are performed substantially
without any friction. It is only when the clamping bolts 40 are
tightened that in the final phase the entire fluid will be squeezed
from the gap-like pressure cushions so that the pallet 12 will rest
in closely fitting and large-area contact on the predetermined surfaces
of the slideways. The present invention is not limited to the above-described
embodiment thereof. Rather, it would also be conceivable to provide
pallet carriers of different types with the pressure-fluid ducts,
for example pallet carriers onto which the pallets are set from
above by a lowering movement. Of course, in that case the quick-action
connectors in the pallets for providing communication with the pressure-fluid
would have a different appropriate configuration. |