Metal working – Means to assemble or disassemble – Means to assemble electrical device
Reexamination Certificate
2000-05-15
2001-12-04
Young, Lee (Department: 3729)
Metal working
Means to assemble or disassemble
Means to assemble electrical device
C029S743000, C029S832000, C029S564000
Reexamination Certificate
active
06324752
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a component placement machine with a frame and a transport device for transporting printed circuit boards in an X-direction, which transport device comprises a transport beam which extends in the X-direction and is capable of being driven in a reciprocating movement in the X-direction.
Such a placement machine is known from U.S. Pat. No. 5,680,699. The transport beam in this machine is provided with transport pins and positioning pins for the printed circuit boards. Said pins are present in openings of the printed circuit boards. The transport beam transports the printed circuit boards in an indexed manner in the positive X-direction, i.e. the transport beam with the printed circuit boards makes an intermittent movement each time over a predetermined distance which corresponds to a given position of the printed circuit board with respect to a placement head. Such a movement is necessary for bringing the printed circuit board in a desired position below the placement head so as to enable a placement of the components in the correct positions by means of the placement head. After a number of intermittent movements, the transport beam will be at the end of its stroke and is to be returned to its starting position. The pins are removed from the holes of the printed circuit boards in that the entire transport beam is moved down, i.e. in a Z-direction perpendicular to the X-direction, whereupon the transport beam is returned to its starting position in the negative X-direction. A new printed circuit board may then be placed on the transport beam and the printed circuit board at the other end can be removed from the row present on the transport beam. In view of the high accuracy with which components must be placed, and taking into account that the dimensions of the components themselves and the interspacings between the components on the printed circuit boards become smaller and smaller, it is necessary for the above movements to be carried out with a very high accuracy. A disadvantage of this manner of transport is that the tooling set present in the machine for the positioning and transport pins must be replaced by a different tooling set whenever a different type of printed circuit board is to be provided with components. In addition, a renewed calibration must take place. All this takes much time.
SUMMARY OF THE INVENTION
It is an object of the invention to avoid the disadvantage mentioned above.
The component placement machine as described in the opening paragraph is for this purpose characterized in that the transport device is provided with a transport belt which is at least partly supported by the transport beam, which is displaceable in the X-direction by means of the transport beam, and which has an outer surface on which printed circuit boards lie during operation, in that the frame is provided with a contact surface which extends in the X-direction such that an edge portion of the printed circuit board extending in the X-direction lies enclosed between the outer surface of the transport belt and the contact surface of the frame both during transport of the printed circuit board and during the placement of components on the printed circuit board, and in that said outer surface of the transport belt has a comparatively high friction coefficient with respect to the edge portion of the printed circuit board, while said contact surface of the frame has a comparatively low friction coefficient with respect to the edge portion of the printed circuit board. The combination of the comparatively high friction between the edge portion of the printed circuit board and the outer surface of the transport belt on the one hand and the comparatively low friction between the edge portion of the printed circuit board and the contact surface of the frame on the other hand ensures that the printed circuit board retains its position on the transport belt both during the placement of components on the printed circuit board and during transport of the printed circuit board, while the edge portion can easily slide along the contact surface of the frame during transport of the printed circuit board. Transporting and positioning pins are no longer necessary. The conversion of the machine to other types of printed circuit boards, such as an adaptation of the transport beam to the width of the printed circuit board, can take place in a simple manner and very fast. A renewed calibration is not necessary.
In practice, two mutually opposed edge portions of a printed circuit board can be supported and transported in the manner described above. In other words, the construction is a two-sided one. It is also possible for only one edge portion of the printed circuit board to be supported and transported in the manner described above, while the edge portion on the other side of the printed circuit board is exclusively supported by a support beam.
A preferred embodiment of the placement machine is characterized in that the contact surface of the frame is a surface of a pressure beam which is movable relative to the frame in the direction of the transport belt, and in that means are present for moving the pressure beam to the transport belt so as to press the contact surface with pre-stress against the edge portion of the printed circuit board. The force with which the edge portion of the printed circuit board is retained between the contact surface and the outer surface of the transport belt can be set for a desired value with these pressure means.
Preferably, said means comprise an inflatable air hose. The air pressure in the air hose can be controlled in a simple manner. The additional use of resilient means, such as a blade spring, also leads to an even force and an increase in the stiffness of the pressure beam.
A further embodiment of the placement machine is characterized in that the frame is provided with a clamping mechanism for preventing that portion of the transport belt on which the printed circuit boards will lie from moving relative to the frame. The transport of the printed circuit boards is obtained through a movement of the transport beam in the negative X-direction followed by a movement in the positive X-direction. It is possible in a comparatively simple manner by means of a clamping mechanism to block the transport belt during one of these movements.
An embodiment of the clamping mechanism is characterized in that the clamping mechanism comprises two clamping jaws and means for moving said clamping jaws with respect to one another for the purpose of clamping the transport belt between the clamping jaws or releasing the transport belt. The means for moving the clamping jaws relative to one another preferably comprise an inflatable air hose. The clamping force can be set for the desired value by means of this hose in a simple manner.
In a further embodiment, the transport beam is provided with air supply means for creating an air bearing between the transport beam and the transport belt while the transport belt is being clamped by the clamping mechanism and the transport beam is being displaced in the X-direction. The friction between the transport beam and the transport belt is eliminated thereby, or at least rendered as small as possible.
A yet further embodiment is characterized in that an inlet and an outlet device are present for feeding printed circuit boards onto the transport belt and removing printed circuit boards from the transport belt, which two devices each comprise a transport belt running over transport wheels, at least one transport wheel being movable in the X-direction under the influence of the reciprocating movement of the transport beam. The supply and delivery of printed circuit boards thus take place simultaneously and in a simple manner.
REFERENCES:
patent: Re. 29206 (1977-05-01), Jaffa
patent: 3638564 (1972-02-01), Prange et al.
patent: 4631812 (1986-12-01), Young
patent: 5259496 (1993-11-01), Common
patent: 5553536 (1996-09-01), Van Os
patent: 5680699 (1997-10-01), Vos
patent: 5692292 (1997-12-01), Asai et a
Reuvers Gerardus L. J.
Wesseling Wessel J.
Biren Steven R.
Trinh Minh
U.S. Philips Corporation
Young Lee
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