Conveyors: power-driven – With means to facilitate working – treating – or inspecting... – Condition responsive control of conveyor or station apparatus
Utility Patent
1998-11-16
2001-01-02
Olszewski, Robert P. (Department: 3652)
Conveyors: power-driven
With means to facilitate working, treating, or inspecting...
Condition responsive control of conveyor or station apparatus
C198S345100, C198S810010
Utility Patent
active
06168003
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is directed to a method for linear positioning and for position recognition of a substrate within an onserting field of an automatic onserting unit and is also directed to an apparatus for the implementation of the method.
In the automatic equipping of substrates (for example, printed circuit boards or ceramic substrates) with components (for example, SMD components) (SMD=surface mounted device) or (Ball-Grad Arrays=BGA), the individual components are taken from a magazine or a delivery means with an onserting head and are then positioned on the substrate in a predetermined position. The substrates are also taken from a magazine, guided at two opposite sides and conveyed into the automatic onserting unit with the assistance of a linear transport. For precise onserting or equipping, it is required that the position of the printed circuit board along its conveying path be exactly known.
Ultrasound reflex sensors that recognize a conveyed printed circuit board have been used for the recognition of printed circuit boards. The linear transport is decelerated in response sensing of the substrate and the substrate is moved at low speed against an introduceable, mechanical stopper. Reflected light sensors are sometimes also employed instead of the ultrasound reflex sensor. Different circuit boards or ceramic substrates exhibit different transparencies for the light employed and, thus, exhibit different reflection properties.
EP 0 257 553, incorporated herein by reference, discloses an onserting unit with such sensors.
However, ultrasound reflex sensors, or, respectively, reflected light sensors are not suitable for all substrates. Over and above this, it is disadvantageous for all substrates to be moved against a permanently positioned mechanical stopper in this method, so that the onserting head must, in part, travel longer transport paths than would be necessary, given small substrates, for example, depending upon the position of the delivery devices. Moreover, the substrates can experience an acceleration given the abrupt deceleration by the mechanical stopper that can lead to sliding by components already put into place.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method and an apparatus for the implementation of the method for positioning substrates independently of their material and their spatial expanse in an automatic onserting unit such that optimally short travel paths with the equipping are obtained.
To this end in an embodiment, the invention provides a method for the linear positioning and for the position recognition of a substrate within an onserting field of an automatic onserting unit with a linear transport, comprising the steps of: directing a sensor field onto the substrate at a braking position along the conveying path of a substrate feature of the substrate within the equipping field; decelerating the linear transport after the substrate feature has passed through the braking position in a preselected way until it approximately achieves an onserting position; after the deceleration of the linear transport, setting the sensor field approximately to the onserting position of the substrate feature of the stopped substrate; and identifying the onserting position of the resting substrate feature for position recognition.
In an embodiment, the invention provides an apparatus for the linear positioning and for the position recognition of a substrate, comprising a linear transport for conveying the substrate, a sensor whose sensor field is set to a freely selectable braking position along the conveying path of a substrate feature of the substrate, and a control means connected to the linear transport and to the sensor for decelerating and stopping the linear transport, so that the substrate feature comes to rest in an onserting position.
In accordance with aspects of the invention, the position of a substrate in the entire onserting field can be determined by employing a sensor having a sensor field that essentially covers the onserting field of the automatic onserting unit. The sensor is first arranged such that a substrate conveyed into the onserting field is recognized by the sensor at a braking position. A predetermined substrate feature, for example the leading edge of the substrate, a bar code applied at a predetermined location of the substrate or terminals arranged on the substrate or other opaque locations of the substrate serve the purpose of recognition. The linear transport is decelerated after the sensor has recognized the substrate material, so that the substrate comes to rest at an onserting position. The sensor detects the position of a substrate feature at the equipping position, so that the position of the substrate is known.
According to an aspect of the invention, the position identification of the substrate feature at the onserting position is advantageously utilized to move an optical adjustment sensor into the region of adjustment marks applied on the substrate for an even more exact position identification.
To that end, in an embodiment, the invention provides a method for the linear positioning and for position recognition of a substrate, characterized in that an optical adjustment sensor is moved into the region of adjustment marks on the basis of the position data of the resting substrate feature.
According to another aspect of the invention, the front edge of the substrate is recognized as substrate material.
To that end, in an embodiment, the invention provides a method for the linear positioning and for the position recognition of a substrate, characterized in that the front edge of the substrate is acquired by the sensor as the substrate feature
Different substrate features, like the front edge or a bar code can be recognized in a simple way by employing an optical sensor.
To that end, in an embodiment, the invention provides that the sensor is an optical sensor.
According to a preferred aspect of the invention, the sensor is rigidly connected to an onserting head moveable above the substrate, so that the sensor and, thus, the sensor field can be adjusted in a simple way to the freely selectable braking position of the transport path.
To that end, in an embodiment, the invention provides that the sensor is rigidly connected to an onserting head of the automatic onserting unit moveable above the substrate
An especially advantageous aspect of the invention provides that the adjustment sensor normally arranged at the onserting head for the recognition of adjustment marks serves as a sensor for recognizing the substrate features, the cost for an additional sensor being eliminated as a result thereof.
To that end, in an embodiment, the invention provides that the adjustment sensor arranged at the onserting head serves as a sensor for the recognition of the substrate feature.
Finally, a simple optical sensor for the recognition of substrate features can be advantageously employed at the onserting head by providing an upwardly directed light source.
These and other features of the invention are discussed in greater detail below in the following detailed description of the presently preferred embodiments with reference to the accompanying drawings.
REFERENCES:
patent: 4463845 (1984-08-01), Harris
patent: 4643415 (1987-02-01), Kuehnert
patent: 36 30 178 A1 (1988-03-01), None
patent: 43 25 565 C2 (1994-02-01), None
patent: 43 25 565 A1 (1994-02-01), None
patent: 197 38 922 A1 (1998-11-01), None
patent: 0 257 553 A2 (1988-03-01), None
patent: 0 826 612 A1 (1998-03-01), None
patent: 2 150 098 (1985-06-01), None
Jaketic Bryan
Olszewski Robert P.
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
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