An apparatus having a pivoted arm mounted on a base for seizing and releasing an article that is hinged at one end and which includes a control link that maintains a fixed length while the arm moves the article about its hinged end between preset positions, but changes its length and thereby provides a signal indicating that the arm has seized the article when the latter is moved in a direction opposite to the normal movement.

This invention, in general, concerns an apparatus for moving an article 
between preset positions and, more particularly, an apparatus which serves 
to open and close the door of a vehicle while the latter is conveyed 
through a paint booth. 
More specifically, the present invention contemplates an apparatus having 
an article gripper which is power-operated for seizing and releasing the 
door of a vehicle as the vehicle is transported along a path past the 
apparatus. In the preferred form of the invention, the apparatus includes 
a carriage that is movable in either direction along a rail located 
adjacent to and parallel to a track along which the vehicle is conveyed. 
The carriage supports one end of a primary arm for pivotal movement about 
a first vertically orientated pivot axis, and the other end of the primary 
arm, in turn, supports an intermediate portion of a secondary arm for 
pivotal movement about a second vertically orientated pivot axis. The 
carriage also supports one end of a control link for pivotal movement 
about a third vertically orientated pivot axis which is spaced from the 
first pivot axis. The other end of the control link is pivotally connected 
to the secondary arm adjacent the second pivot axis for movement about a 
fourth vertically orientated pivot axis. The article gripper is mounted to 
the free end of the secondary arm and, upon command, is adapted to seize 
or release a rod attached to the hinged door of the vehicle. A motor is 
connected to the primary arm for moving the latter about the first pivot 
axis so as to cause the article gripper to move toward or away from the 
carriage along a programmed path for opening and closing the hinged door. 
The control link is collapsible but normally maintains a preset length 
during the opening and closing movements of the door for controlling such 
movement. However, when a predetermined force is applied to the control 
link along its longitudinal axis, the length of the control link is 
shortened, causing an associated switch to be actuated for providing a 
signal that the article gripper has seized the hinged door. 
The objects of the present invention are: to provide a new and improved 
door-opener apparatus which works in conjunction with an automatic spray 
device for painting the inside of a vehicle door; to provide a new and 
improved apparatus for automatically opening and closing a vehicle door as 
the vehicle sheet metal body is being conveyed through a paint booth; to 
provide a new and improved apparatus for opening and closing a vehicle 
door and that is characterized in that the apparatus has an article 
gripper pivotally supported on a movable carriage for seizing and 
releasing the vehicle door and also includes means responsive to the 
movement of the carriage after the article gripper moves toward the 
carriage for indicating whether or not the article gripper has seized the 
door; and to provide a new and improved apparatus having an arm mounted on 
a carriage for seizing and releasing an article and which includes a 
control link that maintains a fixed length while the arm moves the 
article, but changes its length to indicate that the arm has seized the 
article when the latter is moved in a direction opposite to the normal 
movement.

Referring to the drawings, and more particularly to FIG. 1 thereof, a 
vehicle body 10 made of sheet metal is shown mounted on a carrier 12 and 
being conveyed along a track 14 through a conventional paint booth which, 
in this case, houses a door-opener apparatus 16 made in accordance with 
the present invention and that works in conjunction with a paint robot 18. 
Both the door-opener apparatus 16 and the paint robot 18 are supported on 
a horizontal guide rail 20 for movement in either direction along a path 
that is parallel to the path of travel of the vehicle body 10. The guide 
rail 20 is mounted on spaced stanchions, two of which are shown in FIG. 1 
and identified by the reference numerals 22 and 24. In addition, and as 
seen in FIG. 2, the guide rail 20 is formed with a rack 26 that is engaged 
by appropriate toothed gearing (not shown) which forms a part of both the 
door-opener apparatus 16 and the paint robot 18 for causing driving 
movement of each of these devices along the guide rail 20. As seen in FIG. 
1, the door-opener apparatus 16 is adapted to seize a vertical door rod 28 
which is part of a fixture removably mounted to the inner panel of a 
vehicle door 30 and to cause the door to be moved about its hinged 
connection 31 to an opened position so that the inside of the door 30 can 
be painted by the paint robot 18 during the painting operation of the 
vehicle body 10. Thereafter, and as will be more fully explained in the 
description of the the operation, the door 30 is closed by the door-opener 
apparatus 16 and the door rod 28 is released, after which the door-opener 
apparatus 16 returns to the "ready" position, awaiting the arrival of 
another vehicle body for repeating the door opening and closing operation. 
It will be noted that both the door-opener apparatus 16 and the paint 
robot 18 are intended to be program-controlled so that their movements and 
positions can be coordinated during the painting operation. 
Referring now to FIGS. 1 through 5, the door-opener apparatus 16 
constructed in accordance with the present invention comprises a carriage 
32 which is supported for sliding movement along the guide rail 20. The 
carriage 32 houses the aforementioned toothed gearing which meshes with 
the teeth of rack 26. A rotary hydraulic motor 34, mounted on the carriage 
32, serves to drive the toothed gearing and thereby causes the carriage 32 
to move in either direction along the guide rail 20. The door-opener 
apparatus 16 also includes a primary arm 36, a secondary arm 38, and a 
control link 40-all of which are connected to and supported by the 
carriage 32. In this regard, it will be noted that the primary arm 36 has 
its inner end 37 supported by the carriage 32 for rotary movement about a 
vertical axis 42 and is driven about the vertical axis 42 by a hydraulic 
vane motor 44. The outer end 46 of the primary arm 36 is connected by a 
pivotal connection 48 to an intermediate portion of the secondary arm 38, 
one end of which is formed with a gripper 50. The other end 52 of the 
secondary arm 38 is connected by a pivotal connection 54 to one end of the 
control link 40. The other end of the control link 40 is connected to the 
carriage 32 by a pivotal connection 56 which is spaced from the vertical 
axis 42. 
Both the primary arm 36 and the secondary arm 38 are formed as rigid 
members of predetermined lengths. The control link 40, on the other hand, 
comprises a cylindrical member 58 and a double-headed piston member 60 
which can move relative to each other in an axial direction. In this 
regard and as best seen in FIG. 4, the cylindrical member 58 and piston 
member 60 are normally held in fixed positions relative to each other by a 
coil spring 62 housed in one end of the cylindrical member 58. The spring 
62 engages the pointed inner end 64 of the piston member 60 and exerts a 
predetermined amount of biasing force therein so that the cylindrical 
member 58 and piston member 60 normally maintain the relative positions of 
FIG. 4. Under certain conditions to be explained, the biasing force of the 
spring 62 can be overcome so as to cause the control link 40 to shorten in 
length. When this occurs, a dog 66, rigidly connected to the piston member 
60, moves away from a button 68, which is part of a switch 70 fixed with 
the cylindrical member 58, so as to cause the contacts (not shown) of the 
switch 70 to be closed and thereby generate a signal which indicates that 
the door-opener apparatus 16 has in fact opened the vehicle door 30. This 
signal then allows the paint robot 18 to move in and paint the inside of 
the vehicle door 30. 
The gripper 50, which forms a part of the secondary arm 38, can best be 
seen in FIG. 5 and comprises a generally round housing 72 which includes a 
pair of side walls 74 and 76. A jaw 78 is supported in the housing 72 for 
rotation about a shaft 80, the opposite ends of which are fixed to the 
side walls 74 and 76. The jaw 78 is formed with a tab 82 which is 
connected by a pivotal connection 84 to one end of a link 86 which extends 
rearwardly and is connected by a pivotal connection 88 with the piston rod 
90 of an air cylinder 92. The air cylinder 92 is adapted to receive 
pressurized air from any suitable source (not shown) that can flow through 
passages 94 and 96 which respectively lead to ports 98 and 100 formed at 
opposite ends of the air cylinder 92. Thus, when pressurized air is 
directed through passages 94 and 96 to the port 98 while venting port 100, 
the piston rod 90 will move to the right causing the link 86 to rotate the 
jaw 78 from the full-line closed position to the phantom-line opened 
position shown in FIG. 5. It will be noted that when the jaw 78 is in the 
full-line position shown in FIG. 5, it cooperates with the housing 72 for 
seizing and maintaining the door rod 28 in a fixed position within a slot 
101 that is defined by the space between the jaw 78 and the outer edges 
102 of the housing side walls 74 and 76. When the jaw 78 moves to the 
phantom-line position, the door rod 28, of course, is released. 
The operation of the door-opener apparatus 16 described above is as 
follows. As seen in FIGS. 1 and 6, a traveling conveyor chain 103 is 
fastened to the carrier 12 and causes the latter to move in the direction 
of the arrow 104 into the paint booth. The sheet metal vehicle body 10, 
mounted on the carrier 12, arrives with the vehicle door 30 closed and 
with the door rod 28 fastened to the inner panel of the vehicle door 30. 
As the sheet metal vehicle body 10 enters the work station wherein the 
door-opener apparatus 16 and the paint robot 18 are located, it passes a 
model-recognition detector 106 which sends a signal to a controller 108. 
The moving vehicle body 10 then trips a limit switch 110 which tells the 
controller 108 to start reading the counts from a conveyor resolver 112 
which is attached to the chain 103 through a sprocket 114. A feedback 
signal is then sent to the controller 108 from the paint robot 18; the 
controller 108 then directs the power supply 116 to synchronize the 
position of the carriage 32 on the guide rail 20 by counting the pulses of 
a resolver 118, associated with the toothed gearing in the carriage 32 
which meshes with the rack 26, and comparing such pulses to the position 
of the rod 28 attached to the vehicle door 30, as indicated by the 
conveyor resolver 112. When the carriage 32 is properly positioned 
relative to the door rod 28, the controller 108 commands the hydraulic 
vane motor 44 to rotate in a clockwise direction moving the primary arm 36 
to the fully extended position shown in full lines in FIG. 2. After the 
primary arm 36 is fully extended, the controller 108 then causes the air 
cylinder 92 to extend, which then closes the jaw 78 of the gripper 50 on 
the door rod 28. The controller 108 then causes the hydraulic vane motor 
44 to rotate the primary arm 36 in a counterclockwise direction about the 
vertical axis 42. At the same time, the movement of the carriage 32 along 
the guide rail 20 is coordinated with the travelling movement of the 
vehicle body 10, permitting the vehicle door 30 to be moved to the opened 
position shown in phantom lines in FIG. 2. Once the vehicle door 30 is 
moved to the opened position shown in FIG. 2, the controller 108 then 
causes the carriage 32 to move a short distance in an opposite direction. 
This reverse movement is shown in FIG. 7 wherein the various parts of the 
door-opener apparatus 16 and the vehicle door 30, when located in the 
fully door-opened position, are shown schematically and are identified by 
the same reference numerals previously used herein for identifying the 
particular parts. Also, the same reference numerals (but primed) are used 
to schematically show the new position of the various parts of the 
door-opener apparatus 16 and the vehicle door 30 when the carriage 32 is 
moved the aforementioned short distance (indicated by the letter A in FIG. 
7), in the opposite direction after the vehicle door 30 is opened. At such 
time if the gripper 50 has in fact seized the door rod 28 and fully opened 
the vehicle door 30, then the movement of the carriage 32 causes the 
door-opener apparatus 16 and the vehicle door 30 to assume the new 
position indicated by primed reference numerals. Thus, the pivotal 
connection 56 and the vertical axis 42 about which the primary arm 36 
rotates move to the positions indicated by the reference numerals 56' and 
42'. At the same time, the door rod 28 moves to the point indicated by the 
reference numeral 28'. This movement, in turn, causes contraction of the 
control link 40 so as to cause the switch 70 associated therewith to be 
actuated and to signal the controller 108 that the vehicle door 30 has in 
fact been opened. The controller 108 then causes the paint robot 18 to 
move into position and paint the inside of the vehicle door 30. On the 
other hand, if the gripper 50 of the door-opener apparatus 16 has not 
seized the door rod 28, then the movement of the carriage 32 the distance 
A in the opposite direction causes the gripper 50 to move parallel to the 
guide rail 20 along a straight path indicated by the line B. The latter 
movement does not cause the control link 40 to contract and, consequently, 
the contacts of the switch 70 are not closed and the controller 108 does 
not activate the paint robot 18. Thus, it can be seen that the movement of 
the door-opener apparatus 16 in a direction opposite to that of normal 
travel provides for automatically determining whether or not the gripper 
50 has seized the door rod 28. 
From the above description it should be apparent that the spring 62 
incorporated in the control link 40 should be one that is capable of 
preventing any inadvertent contraction of the control link 40 during the 
normal door-opening movement. It has been found that using a spring having 
preload force between 60 and 70 pounds is sufficient to prevent the 
inertia of the vehicle door 30 from collapsing the control link 40 from 
the fully extended position shown in FIG. 4 during the door-opening 
operation. In addition, it has been found that having the carriage 32 move 
a distance as little as approximately 100 millimeters in the opposite 
direction is sufficient to cause the gripper 50 to move the door rod 28 to 
the point indicated by the reference numeral 28' in FIG. 7. The latter 
movement occurs, of course, in response to the angular movement of the 
vehicle door 30 about its hinged connection 31. 
After the inside of the vehicle door 30 has been painted, the paint robot 
18 moves away from the vehicle door 30 and a signal is then given to the 
door-opener apparatus 16 to close the vehicle door 30. During such time, 
the gripper 50 moves the door rod 28 and, accordingly, the vehicle door 
30, from the phantom-line position shown in FIG. 2 to the full-line 
position, returning the vehicle door 30 to the closed position. The 
gripper 50 then releases the door rod 28 and returns to the initial 
position, awaiting arrival of another sheet metal vehicle body which is to 
be painted. 
Various changes and modifications can be made in this apparatus without 
departing from the spirit of the invention. Such changes and modifications 
are contemplated by the inventors, and they do not wish to be limited 
except by the scope of the appended claims.