Abstract:
A method of preventing a nozzle or nozzles from dropping in a component mounting apparatus include gripping the nozzle structures with pivotal levers that are biased to a closed position. The pivotal levers are released after activation of the nozzles to permit appropriate movement for picking up, inspecting, orientating and locating electronic components on a substrate with the nozzles. During the operation of the mounting head, the levers are maintained in a release position against a biasing force and at the end of the operation, the biasing force can then cause the levers to close and support the nozzles in a gripping manner.

Description:
This is a division of 09/161,334 filed Sep. 25, 1998, now U.S. Pat. No. 6,240,628. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a component mounting apparatus which is applied to the mounting of an electronic component onto an electronic circuit substrate, and more particularly, to a nozzle drop prevention device, which is installed in a mounting head equipped with a nozzle for picking up a component. 
     2. Description of Related Art 
     With the propagation of leadless electronic components (chip component) in recent years, the shape and size of components have been diversified, and in an electronic component mounting apparatus for mounting these electronic components, there have been demands for high-speed operation, high precision, high productivity, and high reliability. 
     A conventional electronic component mounting apparatus will be hereinafter described with reference to FIG.  7 . In FIG. 7, the electronic component mounting apparatus comprises a mounting head  51  equipped with a nozzle for picking up an electronic component, a suction device  52  for attracting the electronic component with the nozzle, an XY robot  53  for moving the mounting head  51  in the X and Y directions, and a control device  54  which controls actions of the mounting head  51 , the suction device  52 , and the XY robot  53 . It is noted that FIG. 7 shows only the main elements of the mounting head  51 , and illustration of, for example, a body part is omitted. 
     Reference numeral  55  represents a spline shaft, to which two nuts  56 ,  57  are coupled such as to be movable in a direction of its axis. These nuts  56 ,  57  are supported in the body part (not shown) of the mounting head  51  via bearings  58 ,  59 , respectively. By this construction, the spline shaft  55  is movable in the direction of its axis as well as rotatable around its axis, and it is driven to rotate by a motor  60  mounted on the mounting head  51  via a pulley  61 , belt  62 , and another pulley  63 . 
     At the distal end  55   a  of the spline shaft  55  is mounted a nozzle  65  for picking up the electronic component  64 . Inside the nozzle  65 , a filter  66  is provided for preventing dust from entering into the nozzle when a suctional force is applied. The spline shaft  55  is pushed upwards by a compression spring  68  via a bearing  67  which is to be slidable in a circumferential direction, and by applying a pressing force from a voice coil motor  69 , the spline shaft  55  or the nozzle  65  is lowered to perform pick up and mounting actions of the electronic component  64 . 
     The actions of the component mounting apparatus with the above described construction will be explained. The control device  54  activates the XY robot  53  to move the mounting head  51  to a component pick-up position where the electronic component is picked up. Then, by the control of the control device  54 , the voice coil motor  69  is driven so as to compress the compression spring  68 , by which the nozzle  65  is lowered via the spline shaft  55 , and at the same time the suction device  52  is driven so that the nozzle  65  picks up the electronic component  64  by suctional force. Next, the nozzle  65  is lifted by means of the voice coil motor  69 . The XY robot  53  is then driven to move the mounting head  51  to a component mounting position above the circuit substrate, after which the nozzle  65  is lowered by means of the voice coil motor  69  so that the electronic component  64  is mounted on the circuit substrate. When the power source is off or at the time of a power failure, the pressing force is not applied from the voice coil motor  69 , and thus the spline shaft  55  or nozzle  65  is prevented from dropping due to the force of the compression spring  68  which is pushing the bearing  67  upwards. 
     However, in the above described construction, since the spline shaft  55  is urged upwards by the force of the compression spring  68 , the voice coil motor  69  needs to have a pressing force greater than the force of the compression spring  68 , alone wherefore there is a problem that precise control of pressing force for the mounting purpose cannot be achieved. Also, the voice coil motor  69  needs to have a capacity greater than necessary, thus causing the size of the voice coil motor or the mounting head  51  to become bulky. Furthermore, in order for minimizing the change of the compression spring  68  due to compression, it is necessary to make enough room for the compression spring  68 , whereby the mounting head  51  becomes elongated in a vertical direction. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the above problems in the prior art, an object of the present invention is to provide a nozzle drop prevention device in a component mounting apparatus by which, without using a compression spring for pushing the nozzle upwards, the nozzle is prevented from falling when power is turned off or cut with a simple and compact construction, and by which a pressing force applied to the nozzle can be precisely controlled with a compact voice coil motor. 
     The nozzle drop prevention device according to the present invention is used in a component mounting apparatus including a mounting head in which a nozzle is disposed at a distal end of a shaft which is movable upwards and downwards for picking up and mounting a component, and comprises: a shaft driving means for driving the shaft upwards and downwards; a pair of first levers which is swingable in an open and a close directions and is forced in the close direction by a compression spring to hold the shaft in a gripping manner; a release pin for opening the first levers opposite the pivotally connected end by engaging with an open/close end of the first levers; a second lever for driving, the release pin toward the open/close end of the first levers; by a driving means and a tension spring for forcing the second lever in a reverse direction with respect to a direction in which the release pin is driven; wherein during an operation of the mounting head the shaft driving means is activated the first levers are opened via the second lever by driving the release pin, only after the shaft and at the end of the operation, the driving of the release pin by the second lever is released, so that the shaft is vertically supported by the first levers. Since the shaft can move upwards and downwards freely when the mounting head is in operation, pressure application control can be precisely made with a compact shaft driving means, and the nozzle can be prevented from dropping since the shaft is supported by the first lever at the end of the operation, and even when there is a power failure where controlling actions are not effectuated, nozzle drop can be prevented by the action of the spring, by which mechanical damages can be avoided and high reliability is realized. 
     Instead of providing a spring for forcing the second lever in a reverse direction with respect to a direction in which the release pin is driven, a reciprocating moving means for moving the second lever in a release pin driving direction and in a reverse direction with respect to the driving direction can be provided, with which, when the mounting head is in operation, only after the shaft driving means is activated are the first levers opened via the second lever by driving the release pin in driving direction and at the end of the operation, the driving of the release pin by the second lever is released, so that the shaft is vertically supported by the first levers. In this case, since the second lever is not forced by the spring in the direction opposite to the driving direction, the speed of response when the second lever is driven in the release pin driving direction is increased, i.e., the response of actions in both directions is enhanced, by which a high-speed mounting operation is realized. By employing a double-acting air cylinder device as the reciprocating moving means, high-speed operation of the second lever is possible by a simple construction with an air source and a solenoid valve. 
     In the case where the mounting head is equipped with a plurality of nozzles, the release pin is also provided in plurality so as to correspond to each of the nozzles, and the release pins are driven in synchronism by the second lever, by which a plurality of shafts can be collectively supported in a vertical direction and the nozzles can be prevented from dropping. 
     The component mounting method of the present invention, in which a component is picked up and mounted by a nozzle attached to a lower end of a shaft which is movable upwards and downwards, is characterized in that the shaft is kept fixed in a grasping manner, and only when a component is picked up or mounted is the grip of the shaft released, and the shaft is moved upwards and downwards by a vertical moving means. According to this method, since the shaft is freely movable when mounting a component, pressure application control can be precisely made with a compact vertical moving means. 
     Furthermore, the component mounting apparatus of the present invention comprises a shaft which is movable upwards and downwards; a nozzle mounted at a lower end of the shaft for carrying out component pick up and mounting operations; a gripping means for fixedly gripping the shaft at a predetermined position; a shaft driving means for moving the shaft upwards and downwards; and a grip release means for releasing the grip of the shaft by the gripping means only when picking up and mounting a component, by which the above method of mounting a component can be carried out and the above effects can be achieved. 
     By constructing a component mounting apparatus such that the gripping means comprises a pair of first levers pivotally connected at one end such that the first levers can swing in an open and close direction and is forced in the close direction by a spring to grip the shaft, and the grip release means comprises a release pin which causes the first levers to open by engaging releases grooves at an open/close end of the first levers and a means for driving the release pin toward the open/close end of the first levers only when picking up and mounting a component, the grip and the release of the grip of the shaft can be effected with a simple arrangement. 
    
    
     Other objects and features of the invention will become clear through the detailed description of the invention and the drawings provided below. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing the schematic overall construction of a component mounting apparatus in one embodiment of the present invention; 
     FIG. 2 is a partial longitudinal section view showing a schematic construction of a mounting head in the embodiment; 
     FIG. 3 is a plan view showing the primary construction of the embodiment; 
     FIG. 4 is a side elevation view showing the primary construction of the embodiment; 
     FIGS. 5A-5C are diagrams showing timing of actions of a pin cylinder for locking a spline shaft in the embodiment; 
     FIG. 6A is a perspective view, FIG. 6B is a side elevation view of the part A in FIG. 6A, FIG. 6C is a view taken along the line B—B of FIG. 6B, all illustrating the primary construction of the nozzle drop prevention device in the component mounting apparatus of the present invention in another embodiment; and 
     FIG. 7 is a partial longitudinal section view showing the schematic construction of a mounting head in a conventional component mounting apparatus. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One embodiment of the component mounting apparatus and its nozzle drop prevention device will be hereinafter described with reference to FIGS. 1 to  5 . 
     Referring to FIG. 1, a circuit substrate  1  is loaded and unloaded by a transfer section  2 , and retained at a predetermined position during production. Reference numerals  3  and  4  both represent component feeding sections which accommodate and supply electronic components to be mounted on the circuit substrate  1 ; the component feeding section  3  is a reel type feeder in which components are accommodated in the form of a reel, and the component feeding section  4  is a tray type feeder in which components are housed on a tray. 
     Reference numeral  5  is a mounting head which effects upward, downward, and rotating movements of a nozzle  6  for picking up the electronic component, and this mounting head  5  is mounted on an XY robot  7  for movements in X and Y directions. When picking up the electronic component, the mounting head  5 , i.e., the nozzle  6  is moved by the XY robot  7  to a component supplying position at the component feeding section  3  or  4 , and lowered for attracting the component, after which the nozzle is lifted upward. 
     The state of the electronic component held by the nozzle  6  is imaged by a component recognition camera  8 , and it is judged whether correction of the angle of the component is required or not before mounting it on the circuit substrate  1  based on the image information. The electronic component held by the nozzle  6  is moved in the X and Y directions to a prescribed position above the circuit substrate  1  by the movements of the mounting head  5  which are effected by the XY robot  7 . Then, by the action of the mounting head  5 , the nozzle  6  is lowered, so that the electronic component is mounted on the prescribed component mounting position on the circuit substrate  1 , where the holding of the electronic component is released. By repeating the above described actions, each of the electronic components supplied from the component feeding section  3  or  4  is mounted on the circuit substrate  1 . 
     FIG. 2 shows a detailed construction of the mounting head  5 , together with the XY robot  7 , a suction device  9  for attracting the electronic component with the nozzle  6 , and a control device  10  for controlling the actions of the mounting head  5 , the XY robot  7 , and the suction device  9 . It is noted that the XY robot  7  actually drives the mounting head  5 , although it is illustrated in FIG. 2 for the sake of convenience such that the XY robot  7  directly drives the spline shaft  11 . 
     In the mounting head  5 , a pair of nuts  12 ,  13  are coupled to the spline shaft  11  such as to be movable along an axial direction of the shaft, and these nuts  12 ,  13  are supported on a body part (not shown) of the mounting head  5  via bearings  14 ,  15 . By this structure, the spline shaft  11  is supported such as to be movable in an axial direction thereof as well as rotatable around its axis, and is driven to rotate by a motor  16  mounted on the mounting head  5  via a pulley  17 , a belt  18 , and a pulley  19 . 
     The spline shaft  11  has at its distal end  11   a  nozzle  6  for picking up an electronic component  20  by a suctional force. There is a filter  21  provided inside the nozzle  6  for preventing dust from entering thereinto when suction is effected. A voice coil motor  22  is provided for driving the spline shaft  11  upwards and downwards, by which the spline shaft  11 , i.e., the nozzle  6  is moved upwards and downwards for carrying out electronic component pick up and mounting operations. 
     Furthermore, as shown in FIGS. 2 and 3, a pair of first levers  23  which lock and release the spline shaft  11  is provided above the voice coil motor  22 . The pair of first levers  23  are pivotally supported at its one end around a pivotal pin  24  such as to swing in open and close directions; urethane rubber  25  is provided in the middle part of the first levers  23  with which the spline shaft  11  is gripped; at the other end of the first levers  23  are a spring shaft  26  and a compression spring  27  for forcing the first levers  23  in the close direction so as to lock the spline shaft  11  in a grasping manner; and a release groove  28  is formed at opposing corners on the edge at the other end of the first levers  23 . 
     As shown through FIGS. 2 to  4 , a second lever  32  which extends along a direction of arrangement of the plurality of spline shafts  11  is activated by operating a bracket  31  to swing by means of a pin cylinder  29  and a ball plunger  30 . Release pins  33  are fixed to the second lever  32 , each of them corresponding to the respective pair of first levers  23  disposed on each of the spline shafts  11 , and these release pins  33  are inserted into the respective opposing release grooves  28  by the action of the second lever  32  so as to cause the first levers  23  to open, thus allowing the spline shaft  11  to be driven by the voice coil motor  22  upwards and downwards. The bracket  31  is forced by a tension spring  34  in a direction to move the release pins  33  away from the release grooves  28 . 
     In FIG. 2, reference numeral  22   a  is a casing of the voice coil motor  22 ,  35  is a voice coil, and  36  is a magnet. The suction device  9  and a hollow part  37  of the spline shaft  11  which is formed so as to communicate with the nozzle  6  are communicated with each other through an air joint  38 , a through hole  39  formed in the casing  22   a  of the voice coil motor  22 , and a through hole  40  provided in the spline shaft  11 . Further, a magnetic scale  41  is provided at the uppermost end  11   b  of the spline shaft  11 , where the vertical position of the spline shaft  11  is detected by a magnetic sensor  42 , as well as an original position of the spline shaft  11  is detected by the detection of the uppermost end of the magnetic scale  41  by means of a transmission sensor  43 . 
     Actions of the component mounting apparatus with the above described construction will be explained. Referring to FIG. 5A, the apparatus is constructed such that, when power source is turned on to activate the servo control of the voice coil motor  22 , only after a certain period of delay is the pin cylinder  29  switched on. After that, component pick up and mounting operations are started. 
     First, the XY robot  7  is activated by the control of the control device  10  to move the mounting head  5  to a component pick-up position where an electronic component is to be picked up. Then, the pin cylinder  29  is driven by the control of the control device  10  so as to push down the ball plunger  30  fixed to the bracket  31  downwards, so that the plurality of release pins  33  attached to the second lever  32  are inserted into and engaged with the release grooves  28  of the first levers  23 , thereby causing the first levers  23  open opened against the force of the compression spring  27 , bringing the urethane rubber  25  of the first levers  23  apart from the spline shaft  11 . Then, the spline shaft  11  is lowered by the voice coil motor  22  to bring down the nozzle  6 , and at the same time the suction device  9  is driven to allow the nozzle  6  to pick up the electronic component  20 . 
     Next, the nozzle  6  is moved upward by means of the voice coil motor  22 . Then, the XY robot  7  is driven to move the mounting head  5  to the component mounting position on the electronic circuit substrate, where the nozzle  6  is lowered by the voice coil motor  22 , so as to mount the electronic component  20  on the circuit substrate. 
     After the series of these actions has been completed, the pin cylinder  29  is driven by the control of the control device  10  for causing the ball plunger  30  which has been pressed downwards to return upwards so as to allow the plurality of release pins  33  mounted on the second lever  32  to be released from the release grooves  28  of the first levers  23 , by which the first levers  23  are closed by the function of the compression spring  27 , and the spline shaft  11  is locked by the first levers  23  in a grasping manner through the urethane rubber  25 . 
     When the power source is turned off, the pin cylinder  29  is switched off prior to the switching off of the servo control of the voice coil motor  22  as shown in FIG.  5 B. At the time of power failure in an emergency, since the control actions by the control device  10  are not effectuated, which means the voice coil motor  22  cannot support the spline shaft  11 , the spline shaft  11 , i.e., the nozzle  6  will fall by its own weight, but since the tension spring  34  mounted to the bracket  31  instantly causes the ball plunger  30  fixed to the bracket  31  to return upwards, the plurality of release pins  33  attached to the second lever  32  are released from the release grooves  28  of the first levers  23 , which causes the first levers  23  which have been opened to be closed by the function of the compression spring  27 , and the spline shaft  11  is locked in a grasping manner with the urethane rubber  25 . Since the tension force of the tension spring  34  is stronger than the force with which the pin cylinder  29  presses down the ball plunger  30  when power supply is cut, the spline shaft  11  can be grasped instantaneously even when there is an unexpected power failure. 
     Next, another embodiment of the present invention will be explained. In the above described embodiment, the pin cylinder  29  is used for moving the bracket  31  in a direction of driving the release pins  33 , and the tension spring  34  is used for effecting a returning action thereof in a reverse direction, while in this embodiment, as shown in FIG. 6, a double-acting cylinder  45  is employed. The double-acting cylinder  45  is constructed such that a solenoid valve  46  is turned on upon receiving signals from the control device  10 , by which cylinder chambers into which compression air supplied from an air source  49  through an air tube  50  is introduced are switched over, so that a cylinder shaft  45   a  is extended, while, when signals from the control device  10  stop, the solenoid valve  46  is turned off, upon which the cylinder chambers into which the compression air supplied from the air source  49  through the air tube  50  is introduced are switched over, so that the cylinder shaft  45   a  is retracted. 
     At the distal end of the cylinder shaft  45   a , a connecting block  47  is fixedly attached in contact with a lateral side of the bracket  31 . An elongated hole  47   a  is formed in the connecting block  47  in a direction orthogonal to its moving direction, into which a connecting pin  48  projected from the lateral side at the distal end of the bracket  31  is coupled. The end of the second lever  32  is fixedly inserted into a fixing hole  31   a  provided at the base end of the bracket  31 . Thus, when the cylinder shaft  45   a  is in the retracted position, the bracket  31  is swung upward to release the release pins  33  from the release grooves  28 , causing the spline shaft  11  to be locked in a grasping manner. On the other hand, when the cylinder shaft  45   a  is in the extended position, the bracket  31  is swung downward, allowing the release pins  33  to engage the release grooves  28  to open the first levers  23 , thus releasing the lock of the spline shaft  11 . 
     In the first embodiment which was previously described, if the force of the tension spring  34  were set strong in a order to enhance the response in locking action of the spline shaft  11 , the speed of response would decrease when releasing the spline shaft  11  by moving the second lever  32  in the release pin  33  driving direction against the force of the tension spring  34 . On the other hand, since there is no need for moving the second lever  32  in the release pin  33  driving direction against the force of the tension spring  34  in this embodiment, the speed of response is increased, and since the action in the reverse direction is carried out with high response by the double-acting cylinder  45 , the speed of response in both actions can be enhanced, whereby it is possible to realize a high-speed mounting operation. 
     While a preferred embodiment of the invention has been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.