Patent Application
20100019428
The present invention relates to a clamping fixture.
Such clamping fixtures are put to use for chucking tools, workpieces or workpiece pallets positionally defined, the chuck usually being fixedly located on a work table of a machine tool or a press whilst the workpiece pallet is repeatedly releasably located precisely positioned at the chuck.
Known from EP 0 111 092 B2 is a coupling device for rotatably connecting replaceable a workpiece to a machining apparatus. The device comprises two coaxial centering members sandwiching a driving plate. The one coupling member is provided with a round centrically arranged driving pin as well as an elongated eccentrically arranged driving pin. The centrically arranged driving pin comprises a shell surface in the shape of a truncated cone whilst the eccentrically arranged driving pin features to each other side faces oriented radius parallel inclined to the axis of rotation of the coupling member. The driving plate features a centric circular opening as well as an eccentrically arranged substantially oval opening, each opening corresponding in shape and location to the corresponding driving pin. Arranged on one coupling member are three beads the surfaces of which protrude from the cross-section contacting the surface of the other coupling member when the coupling device is clamped. The driving plate is made of spring steel, the openings machined therein being oriented to correspond with the two driving pins such that the driving plate is axially elastically deformed in the region of the openings when the coupling device is clamped.
The invention is aimed at sophisticating a clamping fixture having a chuck and a clamping pallet releasably secured thereto such that the clamping fixture is practically immune to dirt, the clamping pallet permits repeated precision location at the chuck and the centering members are simple and cost-effective to make.
For this purpose a clamping fixture in accordance with one embodiment of the invention is characterized in that the clamping fixture comprises at least three centering openings and a corresponding number of centering pins, each of the centering pins featuring two conically tapered side faces and each centering opening being defined by two side walls oriented parallel to each other configured such that the conically tapered side faces of each centering pin come into contact therewith linearly.
Preferred embodiments and further aspects of the subject matter of the invention include: the clamping fixture including four centering openings and a corresponding number of centering pins; the centering openings are machined in a one-piece centering plate, the latter being flexible compliant at least in the region of the centering openings in the Z direction; the centering plate being secured by means of studs to a base body of the clamping pallet; the studs being screwed into the base body of the clamping pallet and the front end of each stud forming a Z stop for abutting the chuck; each centering opening being defined sideways by a side walls flexibly compliant in the Z direction; the centering plate being made of a stainless sheet metal; the centering plate being made of a softer material than that of the centering pins; the centering openings being cut out from the centering plate by precision stamping; the centering plate being maximally 2 mm, and particularly 0.8 to 1.5 mm thick; the side faces of the centering pins being machined, and particularly ground with high precision; the centering members being arranged uniformly distributed on a circle; the clamping pallet being spaced away from its front end with a centering plate and provided with four centering openings, each centering opening being enclosed on all sides by the centering plate; the chuck being provided with a base body featuring flats for abutting the studs; and the centering plate (8) being secured to a base body of the clamping pallet by means of four threaded studs, the front end of each stud forming a Z stop for abutting against the chuck.
To ensure that the clamping pallet is chucked positioned with high absolute repeatable accuracy at least three pairs of centering members are provided which cooperate such that the clamping pallet is positioned relative to the chuck in the X and Y direction as well as relative to the angular position about the Z axis, resulting in the line contact of the side faces of the centering pins with the sidewalls of each centering opening, rendering the fixture practically immune to becoming dirty.
To achieve high stability in the chucked clamping pallet four spacer pins are preferably provided, located relatively far outwardly.
In another aspect of the invention, a clamping pallet for use in a clamping fixture is configured such that the clamping pallet includes a base body to which a one-piece centering plate configured with at least three centering openings is secured such that it is flexible compliant in the Z direction in the region of the centering openings, and may be characterized in that the clamping pallet (6) is configured as a workpiece pallet.
In another aspect of the invention, a centering plate may be provided for use in the clamping fixture by being particularly preferred for attachment to a base body of a clamping pallet. Preferred further aspects of the centering plate include: the centering plate being provided with four centering openings arranged on a circle, each spaced away from the other by 90°, and each centering opening being defined sideways by two side walls oriented parallel to each other; a fastener drilling machined in the centering plate between each two adjacent centering openings; and the centering openings being produced by precision stamping.
A preferred example embodiment of the clamping fixture in accordance with the invention will now be described with reference to the drawings in which:
a is a detail on a magnified scale taken from
b is a view in perspective of two centering members;
Referring now to
In the present example the centering openings 9 are machined in a centering plate 8 the function of which is detained below. By means of studs 12 the centering plate 8 is located spaced away from the frontal face 6a of the base body 7 of the clamping pallet 6 such that the centering plate 8 is deflectable in the direction of the base body 7. The front end 13 of each stud 12 forms a Z stop for the clamping pallet 6. The base body 2 of the chuck 1 is provided with flats 4 for abutting the front end 13 of the studs 12. Each centering pin 3 is provided with two conically tapered side faces 3a, 3b contacting the side walls 9a, 9b of the centering plate 8 defining each centering opening 9 sideways. The centering pins 3 are made of a harder material than that of the centering plate 8. This has the advantage that wear of the side faces 3a, 3b of the centering pins 3 is minimized so that even after a high number of clamping actions the positioning accuracy is still not detrimented. Any wear of the side walls 9a, 9b of the centering plate 8 merely results in the face-line-contact with the centering pins 3 becoming somewhat wider which has no appreciable effect on the positioning accuracy.
Referring now to
In the condition as shown in which the two conically tapered side faces 3a, 3b of the centering pins 3 come into contact with the side walls 9a, 9b of the centering plate 8 defining the centering openings 9 sideways, line contact is achieved between each centering pin 3 and each side wall 9a, 9b. For this purpose the centering pins 3 are dimensioned so that the centering plate 8 is slightly deflected by each centering pin 3 in the direction of the base body of the clamping pallet 6 before the studs 12 abut the flats 4 of the chuck 1 by their front end 13. Referring now to
Referring now to
Referring now to
The clamping pallet 6 comprises a centering plate 8 secured to the base body 7 by means of spacers 15. The spacers 15 may be configured as separate elements secured to the base body 7. As an alternative they may be engineered integral with the base body 7. In a further alternative the base body 7 is provided with a substantially flat face machined recessed only in the region of each centering opening 9.
Actual fastening of the centering plate 8 is done by means of studs 12, the face end of which serves to stop the clamping pallet 6. The studs 12 are preferably provided with a rear thread by means of which they can be fixedly located in a female thread of each spacer 15 and base body 7 respectively. The studs 12 are located relatively far outwardly to attain high stability of the clamping pallet 6 clamped in the chuck 1. Preferably the studs 12 are arranged in the outer quarter of a virtual circle K3 located at the radially outermost points of the clamping pallet 6.
The longitudinal centerlines of the centering pins 3 as well as of the centering openings 9 are oriented radius parallel to the Z axis Z1 of the chuck 1 and clamping pallet 6 respectively. In any case, this arrangement of the centering members 3, 9 permits repeatedly precise positioning of the clamping pallet 6 relative to the chuck 1 in the X and Y direction as well as relative to the angular position about the Z axis. In addition to this, providing the studs 12 as described in contact with the flats 4 of the chuck 1 also achieves high precise positioning in the Z direction.
Referring now to
| Number | Date | Country | Kind |
|---|---|---|---|
| 01144/08 | Jul 2008 | CH | national |
