WO2011007214A1

WO2011007214A1 - Pressure foot device for a drilling head for printed circuit boards

Info

Publication number: WO2011007214A1
Application number: PCT/IB2010/000010
Authority: WO
Inventors: Angelo Raiteri
Original assignee: MECHATRONIC SA
Current assignee: MECHATRONIC SA
Priority date: 2009-07-14
Filing date: 2010-01-04
Publication date: 2011-01-20
Anticipated expiration: 2012-01-14
Also published as: EP2454048A1; CN102497954A; CH701429A2; TW201102194A

Abstract

Pressure foot device (11) for a drilling head for printed circuit boards including a body (19) that defines an axial seat (21) where the drilling spindle (15) can slide, closed by a base (23) with an opening (25) for the passage of the drilling tool (17), in which at least two revolving shafts (35,37) are associated with corresponding drilling inserts (43, 45) can move from a working configuration, in which a drilling insert is brought into the opening (25) to a rest configuration in which said opening (25) is not associated with any drilling insert and vice versa.

Description

Pressure foot device for a drilling head for printed circuit boards

DESCRIPTION Field of the invention

The present invention relates to a pressure foot device for a drilling head for printed circuit boards.

More particularly, the invention concerns a pressure foot device for a drilling head which may be installed on a drilling machine for printed circuit boards.

Background information and Prior Art

As known in this particular technical sector, printed circuit boards can be made of layers of epoxy resin reinforced with fibers of glass, interspersed with sheets of copper, where each inner layer is made by photochemical processes.

Board drilling is performed in a plurality of positions allowing subsequent connection between the electrical circuits of the various layers and assembly of electronic components.

Nowadays, printed circuit boards processing demands machines which can operate with higher flexibility and productivity. For this purpose a range of drilling heads has been proposed in the past on drilling machines, typically equipped with six drilling heads, designed to simultaneously drill a corresponding stack of circuit boards.

The stack of boards is usually obtained by stacking a number of identical boards on a backup panel in Bakelite or cardboard and covering the stack with a thin aluminum foil or similar entry material. The stack is held together and placed on the tooling plate of the machine by means of two reference pins and tape.

The current drilling machine for printed circuit boards generally comprise a table translating along a first direction (Y axis), a cart translating along a second direction (X axis) orthogonal to the first which bears several drilling heads which can move along a third direction (Z axis) perpendicular to the first two.

In general, a drilling head of prior art comprises a linear or rotary motor that gives motion to the head along the Z axis, a flexible coupling, a linear guide or pneumostatic bushing, guiding the drilling head along the Z axis, a spindle carrying a drilling tool, usually driven by asynchronous motor and a pressure foot, usually consisting of a pneumatic system that applies a force to the stack of circuit boards, as close as possible to the point where the drilling takes place.

The optimal characteristics that the pressure foot must have are mainly:

ability to exercise pressure on the stack, as near as possible to the point where the drilling takes place;

ability to adjust the compression pressure of the stack;

— ability to evacuate the drilling debris, especially in the case of microdrilling; possibility to have at least two different inserts for drilling and, more specifically, a first insert of normal size, for example with hole diameter of 7.0 mm, suitable to drill up to 6.35 mm diameter drill bits and a second insert dedicated to smaller diameters, for example with hole diameter of 2.0-3.0 mm, to drill with tool diameter less than 1.0 mm.

A first purpose of the invention is therefore to provide a pressure foot, which satisfies the above conditions in an optimal way, more reliability compared to prior art.

A further aim of the invention is to provide a pressure foot which can be associated with existing drilling heads.

Not the least purpose of the invention is to provide a pressure foot for a drilling head of that type, which is easy and economical and can therefore be produced industrially at a lower cost. Description of Invention

These and other aims are obtained with the pressure foot for a drilling head for printed circuit boards, as claimed in claims combined.

A first advantage of the invention comes from the possibility of incorporating in the pressure foot at least two different drilling inserts to be used as needed.

Another advantage of the invention comes from the ability to park these inserts in a upper position in respect of the base-plan of the pressure foot, thereby avoiding interference and the risk of collision with any protruding from the drilling plan, such as reference pins and systems for clamping the stack.

Another advantage of the invention comes from the possibility of having both inserts out of working range, thereby allowing automatic tool change and dimensional control of the tool, which are not possible with existing pressure foot.

Description of Figures

A preferred form of realization of the pressure foot device for a drilling head for printed circuit boards according to the invention will be described below, merely for example, with reference to the attached figures in which:

Figure 1 is a perspective view from the bottom of the device according to the invention;

• Figure 2 is a section along a vertical plane of the device of Figure 1 ;

• Figure 3 is a partially sectioned view from below of the device of Figure 1 , in a first operational configuration;

• Figure 4 is a view from above of the device of Figure 1 , in a second operational configuration;

• Figure 5 is a partially sectioned view from the back of the device of Figure 1. With reference to attached figures, the pressure foot according to the invention, which is indicated as a whole by reference 1 1, is illustrated as installed on a drilling head 13 for printed circuit boards.

The drilling head 13 includes a drilling spindle 15, with electric motor, preferably of the asynchronous type, moving along the direction "Z" with respect to fixed support structure of the head 13, bearing a tool 17, for example, a drilling tool.

The drilling head 13, as per known technique, is associated with a fixed support structure (not shown), part of a unit of drilling for printed circuit boards.

The pressure foot 1 1 includes a body 19 that defines an axial seat 21, substantially cylindrical, where the spindle 15 can slide and a vacuum system generates a negative pressure to evacuate machining debris. The body 19 has a base 23, bottom termination of the seat 21, with an opening 25 at its center which is a passage for the drilling tool 17 when the drilling spindle 15 gets near to the base 23.

The seat 21 has also a radial hole 27 associated with a vacuum pipe 29 for machining debris removal.

In the body 19 of the pressure foot, axial guiding channels 31, 33 are defined in which rotating shafts 35, 37 are hosted free to rotate within their guiding channels 31, 33. A pair of oscillating blades 39,41, each bearing a respective drilling insert holes 43, 45, is installed on the base 23

In the example depicted the first insert 43 has a hole 43a, for example 7.0 mm in diameter, that is suitable for drilling with tools up to 6.35 mm, while the second insert 45 has a smaller hole 45a, for example 2.0-3.0 mm for drilling with tools with diameter smaller than 1.0 mm.

The edge of each oscillating blade 39, 41, on the opposite side of the drilling insert 43, 45, is connected to a corresponding revolving shaft 35, 37.

The base 23 also has side stops 47, 49 for the oscillating blades 39, 41.

The rotation of the shafts 35, 37 is actuated by a pair of pneumatic actuators 51 , 53 with two positions, one for each shaft, fixed to the structure of the drilling head 13 and provided with fittings 51a, 53a connecting it to the compressed air circuit.

A rotary piston 55, 57 is connected to the corresponding shaft in a chamber 59, 61 defined inside the body 19.

The pneumatic actuators 51,53 are advantageously equipped with male fittings 51b, 53b to transport the compressed air into the chambers 59, 61 and cooperating with female ducts 59a, 61a machined in the body 19 of the device.

A pulse of compressed air driven by the pneumatic actuator causes a corresponding rotation of approximately 180° of the respective rotary piston 55, 57 in the chamber 59, 61 (arrows F in Fig.5) and, consequently, its associated rotating shaft .

Radial levers 63, 65 are fixed at the edge of the shafts 35, 37 on the opposite side of the pistons 55, 57 to connect the edge of a spring element 67, 69, such as a coil spring, whose other edge is fixed to the body 19.

These elastic elements 67, 69 allow to keep the corresponding drilling insert 43, 45 in working or resting position associated with the respective piston 55, 57 even in the absence of compressed air in the circuit of the pneumatic actuator and also the arrangement of radial levers 63, 65 on the outside of the body 19 permits to rotate manually the shafts 35, 37 in case of need.

The work cycle of the pressure foot 1 1 will be described as follows:

a) when the cycle starts preferably both drilling inserts 43, 45 are out of range, which defines the opening position (Fig. 4);

b) the micro-drilling insert 45 is brought into working position with a rotational movement of the shaft 37 connected with this insert 45, said movement being impressed by the actuator 53 (Figs. 1, 2, 5);

c) the micro-drilling insert 45 is brought into out of range position using a rotational movement of the shaft 37 connected with this insert 45 for the tool 17 change, said movement being impressed by the actuator 53 (Fig. 4) ;

d) if it is necessary to operate with a drilling tool of larger diameter (typically a diameter bigger than 1.0 mm) the standard drilling insert 43 is brought into working position with a rotational movement of the shaft 35, said movement being impressed by the actuator 51 ;

e) repeating of the previous steps in reverse order to bring again the drilling insert 43 in out of range position.

Advantageously, according to the invention, the rotation of the shafts 35, 37 is actuated by mechanisms housed in the fixed part of the drilling head 13. In this way the use of mobile pipes connected to the pressure foot is avoided. This is advantageous because the pressure foot makes short movements in the order of hundreds of cycles per minute, which in time may deteriorate the air pipes, as in the actual solution on the market.

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Claims

1. Pressure foot device (1 1) for a drilling head for printed circuit boards including a body (19) that defines an axial seat (21) where the drilling spindle (15) can slide, closed by a base (23) with an opening (25) for the passage of the drilling tool (17), characterized by the fact to include at least one pair of revolving shafts (35.37) associated with corresponding drilling inserts (43, 45) can move from a working configuration, in which a drilling insert is brought into the opening (25) to a rest configuration in which said opening (25) is not associated with any drilling insert and vice versa.

2. Device according to claim 1, in which in the body (19) of the device, axial guiding channels 31, 33 are defined in which rotating shafts 35, 37 are hosted free to rotate within their guiding channels 31, 33.

3. Device according to claim 1 or 2, where at the base (23) a pair of oscillating blades 39, 41, each bearing a respective drilling insert holes 43, 45, is installed.

4. Device according to claim 3 in which a first drilling insert (43) has a hole (43a) with a diameter of about 7.0 mm, while a second drilling insert (45) has a hole (45a) with a diameter of about 2.0 - 3.0 mm for micro-drilling.

5. Device according to claim 3 in which the edges of the oscillating blades (39, 41), on the opposite side of the drilling insert (43, 45) is connected to a corresponding revolving shaft (35, 37).

6. Device according to any of the preceding claims, in which the base (23) is equipped with side stops (47, 49) for the oscillating blades (39, 41).

7. Device according to any of the preceding claims, in which the rotation of the shafts (35, 37) is actuated by a pair of pneumatic actuators (51, 53) with two positions, one for each shaft, fixed to the structure of the drilling head (13).

8. Device according to any of the preceding claims, in which a rotary piston (55, 57) is connected to the corresponding shaft in a chamber (59, 61) defined in the body (19) of the device, a pulse of compressed air controlled by a pneumatic actuator causing rotation of approximately 180 ° of the respective rotary piston (55, 57) in the chamber (59, 61) and, consequently, rotating the shaft connected to it.

9. A method of controlling a pressure foot (1 1) device for a drilling head for printed circuit boards realized according to any one of claims 1 to 8, including the steps of: - w - w _u I y a) to bring a first and a second insert (43, 45) out of range, i.e. in a opening position;

b) to bring a first insert into working position with a rotational movement of the shaft (37) connected to this insert (45);

c) to bring said first insert into out of range position with a rotary movement of the shaft (37) connected to this insert (45);

d) if it is necessary to operate with a different tool to bring a second drilling insert (43) into working position with a rotational movement of the shaft (35) connected to this insert (43);

c) Repeat steps of the previous cycle in reverse order to bring back said second insert into out of range position.