Handling: hand and hoist-line implements – Utilizing fluid pressure – Venturi effect
Reexamination Certificate
2000-07-24
2001-12-11
Lillis, Eileen D (Department: 3652)
Handling: hand and hoist-line implements
Utilizing fluid pressure
Venturi effect
C029S740000, C414S752100, C901S040000
Reexamination Certificate
active
06328362
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of Invention
The present invention relates to an electric-component mounting head which is employed in an electric-component mounting apparatus and particularly to the art of controlling a mounting load as a pressing load with which an electric component (e.g., an electronic component) is pressed against an object (e.g., a printed wiring board) when the electric component is mounted on the object.
2. Related Art Statement
FIG. 8
schematically shows a conventional electric-component (“EC”) mounting head
100
. The EC mounting head
100
includes (a) a support member
102
, (b) a suction nozzle
104
which applies a suction to an EC and thereby holds the EC, (c) a ball spline
106
which connects the suction nozzle
104
to the support member
102
such that the nozzle
104
is movable relative to the support member
102
in a direction parallel to an axis line of the nozzle
104
, and (d) a coil spring
108
which biases the suction nozzle
104
in a downward direction. The ball spline
106
includes a ball-spline axis member
110
fixed to the support member
102
, and a ball-spline nut
112
fitted on the axis member
110
via balls. The suction nozzle
104
is held by the nut
112
, and is biased by the coil spring
108
via the nut
112
. The support member
102
is elevated and lowered by an elevating and lowing device (not shown).
Before the EC mounting head
100
starts an EC mounting operation, a relationship between the position of the suction nozzle
104
relative to the support member
102
and the downward force applied to the nozzle
104
is determined and, based on the thus determined relationship, a desired position to which the support member
102
is moved downward by the elevating and lowering device is determined. More specifically described, a contact sensor
114
detects a “contact” position of the support member
102
where the EC held by the suction nozzle
104
contacts an object (e.g., a printed wiring board, “PWB”), and a control device (not shown) controls, according to the determined relationship, an amount of downward movement (i.e., a downward stroke) of the support member
102
from the detected “contact” position, so that a desired downward force may be applied to the suction nozzle
104
and accordingly the EC held by the nozzle
104
may be mounted on the object with a desired mounting load. Thus, the conventional EC mounting head
100
essentially needs, for pressing an EC against an object with an appropriate load, the determination of a relationship between the position of the suction nozzle
104
relative to the support member
102
and the downward force applied to the nozzle
104
, and an accurate control of downward stroke of the support member
102
.
In addition, a minimal mounting load of the conventional EC mounting head
100
mainly depends on (1) the total weight of the suction nozzle
104
and one or more members which is or are moved as a unit with the nozzle
104
, (2) an elastic force of the coil spring
108
when the support member is moved downward to, and stopped at, the desired position, and (3) a resistance to the relative movement between the ball-spline axis member
110
and the ball-spline nut
112
. Thus, it has been difficult to sufficiently decrease the minimal mounting load.
SUMMARY OF INVENTION
The present invention provides an electric-component mounting head which has one or more of the following technical features that are described in below in respective paragraphs given parenthesized sequential numbers (1) to (8). Any technical feature which includes another technical feature shall do so by referring, at the beginning, to the parenthesized sequential number given to the latter feature. Thus, two or more of the following technical features may be combined, if appropriate. Each technical feature may be accompanied by a supplemental explanation, as needed. However, the following technical features and the appropriate combinations thereof are just examples to which the present invention is by no means limited. In addition, in the case where one technical feature recites a plurality of items, it is not essentially required that all of those items be simultaneously employed. That is, it is possible to select and employ only a portion (one, two, but not all) of those items.
(1) According to a first feature of the present invention, there is provided an electric-component mounting head, comprising a support member; a suction nozzle which applies a suction to an electric component and thereby holds the electric component; and a nozzle holder which is supported by the support member, which holds the suction nozzle such that the suction nozzle is movable relative to the support member in a direction parallel to an axis line of the suction nozzle, and which comprises a housing and a piston fitted in the housing such that one of the housing and the piston that is connected to the suction nozzle is movable relative to the other of the housing and the piston that is connected to the support member, the nozzle holder having at least one pressure chamber which is defined by at least one of axially opposite end surfaces of the piston and the housing, at least one communication opening which communicates with the at least one pressure chamber, two guide surfaces which are supported by the housing and the piston, respectively, and cooperate with each other to guide the relative movement of the housing and the piston, and a gas-supply passage which opens in a space provided between the two guide surfaces, at at least two positions axis-symmetric with each other with respect to an axis line of the piston, and supplies a pressurized gas to the space.
In the above EC mounting head, the two guide surfaces may be formed on the piston and the housing, respectively, or on a piston rod connected to the piston, and the housing, respectively. Since the space provided between the two guide surfaces is supplied with the pressurized gas, the two guide surfaces cooperate with each other to provide a gas bearing. Therefore, the resistance to the relative movement between the piston and/or the piston rod and the housing can be decreased to a negligibly small value. The suction holder may have either one or two pressure chambers. In the case where a pressure controller which controls a pressure of a gas supplied to the one air chamber is connected to the communication opening and a gas supplying device is connected to the air-supply passage, the present EC mounting head is readable on the following EC mounting head including the mounting-load control device in accordance the second feature (2).
(2) According to a second feature of the present invention, there is provided an electric-component mounting head, comprising a support member, a suction nozzle which applies a suction to an electric component and thereby holds the electric component, and a mounting-load control device which controls a mounting load with which the suction nozzle presses the electric component against an object when the suction nozzle mounts the electric component on the object, the mounting-load control device including a nozzle holder which connects the suction nozzle to the support member such that the suction nozzle is movable relative to the support member in a direction parallel to an axis line of the suction nozzle, and which comprises a housing and a piston fitted in the housing such that one of the housing and the piston that is connected to the suction nozzle is movable relative to the other of the housing and the piston that is connected to the support member, the nozzle holder having at least one pressure chamber which is defined by at least one of axially opposite end surfaces of the piston and the housing, and having two guide surfaces which are supported by the housing and the piston, respectively, and cooperate with each other to guide the relative movement of the housing and the piston, and a pressure controller which controls a pressure of a gas which is supplied to the one pressure chamber of the nozzle holder.
The present
Isogai Takeyoshi
Iwaki Noriaki
Katsumi Hiroshi
Chin Paul T.
Fuji Machine Mfg. Co. Ltd.
Lillis Eileen D
Oliff & Berridg,e PLC
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