Patent Document

TECHNICAL FIELD 
   The present invention relates to a turning device for a heavy object which is applied to a probe device and the like for measuring electrical characteristics of a body to be examined, such as a semiconductor device, and which turns a heavy object, such as a test head. 
   BACKGROUND ART 
   Conventional examination equipment, for example, a probe device is provided with a loader section having a conveyance mechanism for conveying semiconductor wafers one by one and a prober section for continuously electrically inspecting the semiconductor wafers. The prober section is provided with a mounting block for delivering and receiving the semiconductor wafers to/from the conveyance mechanism one by one, a probe card disposed above the mounting block, and a test head for electrically interrupting a section between the probe card and a tester. The test head is fixed on a rotating shaft through a test head frame and a hinge and is structured so as to obtain, for example, a 180-degree turn between the probe device body and a maintenance area around the rotating shaft. Recently, the test head has become larger in size to weigh 600 to 800 kg. In many cases, a motor is used to turn such a test head as a heavy object. Japanese Patent Laid-Open Publication No. Hei 9-298224 discloses almost the same prior art as the foregoing conventional one. 
   However, in the case of such a structure where a motor and a gear support the weight of a test head as seen in conventional examination equipment such as a probe device, the gear for transmitting a driving force of the motor unavoidably becomes larger in size and the gear is apt to have a multi-stage structure, thus causing the equipment to be complicated and expensive. Furthermore, there are also the following problems: turning the test head around the enlarged gear makes it difficult to reduce the turning radius and requires an increase in an installation space for the probe device. 
   DISCLOSURE OF THE INVENTION 
   In view of the above-described problems, it is an object of the present invention to provide a turning device for a heavy object with a minimum number of parts to be used without need for use of a large gear. 
   To achieve the above-mentioned object, according to a first aspect of the present invention, there is provided a turning device for a heavy object comprising: a turning arm joined to the heavy object and turning around a turning pivot on the axial line and a drive device for driving turning operations of the turning arm wherein: the drive device is composed of: a fixing section, a turning input section, a turning output section having an orthogonal plane orthogonal to the axial line of the turning pivot, a planetary gear type speed reducer with a pair of ball bearings disposed between the fixing section and the turning output section and a motor including a rotor shaft coaxially connected to a stator having a coil and the turning input section of the planetary gear type speed reducer; the turning arm has a first plane connected to the plane of the turning output section and a second plane connected to the heavy object, positioned nearer to the heavy object from the axial line of the turning pivot and orthogonal to the first plane; and the turning arm and the drive device are disposed within a width of the heavy object in the axial direction of the turning pivot. 
   According to a second aspect of the present invention, in the turning device of the first aspect, the center position in the axial line direction of the turning pivot of the heavy object is positioned within a distance between one of the pair of main bearings and an intersection obtained by crossing the axial line of the turning pivot with a line at a bearing contact angle to the perpendicular line of the main bearing as one ball bearing positioned on the orthogonal plane side of the rotation output section of the ball bearings. 
   According to a third aspect of the present invention, in the turning device of the first aspect, a previous-stage speed reducer as a previous-stage reduction gear mechanism is disposed between the planetary gear type speed reducer and the motor; an input rotation section of the previous-stage speed reducer and the rotor shaft of the motor are coaxially coupled to each other; and the output rotation section of the previous-stage reducer and the input rotation section of the planetary gear type speed reducer are coaxially coupled to each other. 
   According to a fourth aspect of the present invention, in the turning device of the first aspect, a supporting block for fixing the planetary gear type speed reducer and a frame for mounting the supporting block are provided; the fixing section of the planetary gear type speed reducer has a circular outside-diameter section and a mounting flat surface parallel to the plane of the rotation output section; the supporting block includes a first mounting surface for mounting the mounting flat surface of the fixing section of the planetary gear type speed reducer, a second mounting surface for mounting the frame and orthogonal to the first mounting surface and a pair of rib sections for connecting both ends of the first mounting surface in the outward direction with both ends of the second mounting surface in the outward direction; and the outside-diameter section of the mounting flat surface of the fixing section of the planetary gear type speed reducer is cut so that the pair of ribs may be shorter than the circular outside diameter. 
   According to a fifth aspect of the present invention, in a turning device comprising: a turning arm joined to a heavy object and turning around a turning pivot on the axial line and a drive device for driving turning operations of the turning arm wherein: the drive device includes a fixing section, a rotation input section, a rotation output section having an orthogonal plane orthogonal to the axial line of the turning pivot, a planetary gear type reducer having a pair of ball bearings disposed between the fixing section and the rotation output section, and a motor disposed coaxially to the rotation input section of the planetary gear type speed reducer; the turning arm has a first plane joined to the plane of the rotation output section and a second plane orthogonal to the first plane; and the turning arm and the drive device are disposed within a width of the heavy object in the axial direction of the turning pivot. 
   The turning device for a heavy object according to the present invention, being structured as described above, has the following advantages: 
   The first aspect of the present invention provides a turning device for a heavy object comprising: a turning arm joined to the heavy object and turning around a turning pivot on the axial line and a drive device for driving turning operations of the turning arm wherein: the drive device is composed of: a fixing section, a turning input section, a turning output section having an orthogonal plane orthogonal to the axial line of the turning pivot, a planetary gear type speed reducer with a pair of ball bearings disposed between the fixing section and the turning output section and a motor including a rotor shaft coaxially connected to a stator having a coil and the turning input section of the planetary gear type speed reducer; the turning arm has a first plane connected to the plane of the turning output section and a second plane connected to the heavy object, positioned nearer to the heavy object from the axial line of the turning pivot and orthogonal to the first plane; and the turning arm and the drive device are disposed within a width of the turning pivot of the heavy object in the axial direction. 
   Such a configuration provides a compact turning device for a heavy object which permits the turning arm and the drive device to be positioned within a width of the heavy object in the axial direction of the turning pivot by reducing a distance between the center of gravity of the heavy object and the axial line A of the turning pivot. 
   The second aspect of the present invention provides a turning device for a heavy object of the first aspect wherein: the center position in the axial line direction of the turning pivot of the heavy object is positioned within a distance between one of the pair of main bearings and an intersection obtained by crossing the axial line of the turning pivot with a line at a bearing contact angle to the perpendicular line of the main bearing as one ball bearing positioned on the orthogonal plane side of the rotation output section of the ball bearings. 
   Such a configuration provides a turning device for a heavy object capable of stably turning the heavy object without excessive swinging by supporting the heavy object in a cantilever manner. 
   The third aspect of the present invention provides a turning device for a heavy object of the first aspect wherein: a previous-stage speed reducer as a previous-stage reduction gear mechanism is disposed between the planetary gear type speed reducer and the motor; an input rotation section of the previous-stage speed reducer and the rotor shaft of the motor are coaxially coupled to each other; and the output rotation section of the previous-stage reducer and the input rotation section of the planetary gear type speed reducer are coaxially coupled to each other. 
   Such a configuration provides a turning device for a heavy object capable of further reducing a turning radius by reducing the outside diameters of the reducer and the motor because of a high reduction ratio by use of a double speed reduction mechanism. 
   The fourth aspect of the present invention provides a turning device for a heavy object of the first aspect wherein: a supporting block for fixing the planetary gear type speed reducer and a frame for mounting the supporting block are provided; the fixing section of the planetary gear type speed reducer has a circular outside-diameter section and a mounting flat surface parallel to the plane of the rotation output section; the supporting block includes a first mounting surface for mounting the mounting flat surface of the fixing section of the planetary gear type speed reducer, a second mounting surface orthogonal to the first mounting surface for mounting the frame and a pair of rib sections for connecting both ends of the first mounting surface in the outward direction with both ends of the second mounting surface in the outward direction; and the outside-diameter section of the mounting flat surface of the fixing section of the planetary gear type speed reducer is cut so that the pair of ribs may be shorter than the circular outside diameter. 
   Such a configuration provides a turning device for a heavy object capable of reinforcing the first mounting surface and the second mounting surface of the supporting block by the pair of rib sections to make the supporting block robust, without lengthening a section between the second plane of the turning arm and the axial line of the turning pivot, or without increasing the turning radius of the heavy weight because the pair of rib sections at the mounting flat surface outside diameter section of the fixing section of the planetary gear type speed reducer are cut short. 
   The fifth aspect of the present invention provides a turning device comprising: a turning arm joined to a heavy object and turning around a turning pivot on the axial line and a drive device for driving turning operations of the turning arm wherein: the drive device includes a fixing section, a rotation input section, a rotation output section having an orthogonal plane orthogonal to the axial line of the turning pivot, a planetary gear type reducer having a pair of ball bearings disposed between the fixing section and the rotation output section, and a motor disposed coaxially to the rotation input section of the planetary gear type speed reducer; the turning arm has a first plane joined to the plane of the rotation output section and a second plane orthogonal to the first plane; and the turning arm and the drive device are disposed within a width in the axial direction of the turning pivot of the heavy object. 
   Such a configuration provides a compact turning device for a heavy object which permits the turning arm and the drive device to be positioned within the width of the turning pivot of the heavy object. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is an elevation view showing an example of a turning device for a heavy object according to the present invention; 
       FIG. 2  is a plan view showing an example of the turning device for a heavy object according to the present invention, taken from  FIG. 1 ; 
       FIG. 3  is a side view showing a frame and a drive device of the turning device for a heavy object according to the present invention, as viewed in an arrow E direction shown in  FIG. 2 ; 
       FIG. 4  is a side view showing an example of the turning device for a heavy object according to the present invention, taken from an arrow F direction shown in  FIG. 1 ; 
       FIG. 5  is a side view illustrating the frame and the drive device of the turning device for a heavy object according to the present invention, as viewed in an arrow G direction shown in  FIG. 3 ; and 
       FIG. 6  is a vertical sectional view showing an example of the drive device in the turning device for a heavy object according to the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The embodiment of a turning device for a heavy object according to the present invention will be more particularly described with reference to the accompanying drawings. 
   A probe device  1 , for example, as shown in  FIG. 1 , is composed of a probe device body constituting a prober section which performs electrical examination for a body  2  to be examined, such as a semiconductor wafer, hereinafter referred to as a “device body”, a frame  3  disposed adjacent to the left side of the device body  2 , a test head  5  as a heavy object turned by approximately 180 degrees between the device body  2  and a maintenance area  4  by the frame  3 , a coupling ring  7  and a probe card  8 . To the immediate right of the device body  2 , there is disposed a semiconductor wafer transfer apparatus  9  which stores semiconductor wafers by cassette and loads and unloads the semiconductors into/from the prober section one by one from the cassette. 
   A central hole (not shown) in a head plate  10  constituting a top face of the device body  2  is attached with a probe cover  8 . The test head  5  is structured so as to be electrically connected to a coupling terminal on the top of the probe card  8  through the coupling ring  7  when the test head  5  turns and is positioned on the device body  2 . Therefore, for example, the probe device  1  receives a test signal from a tester at an electrode of the semiconductor wafer on a mounting block through the test head  5  and a probe pin of the probe card  8  to electrically examine respective IC chips of the semiconductor wafers. 
   The test head  5  is fixed onto a rotating shaft of a drive device  12  through a turning arm  11  having a first plane  11   a  and a second plane  11   b  orthogonal to the first plane  11   a  as shown in  FIG. 2 , and is structured so as to turn through the rotating shaft. The turning arm  11  is connected to the test head  5  as a heavy object and turns around a turning fulcrum on the axial line A of the rotating shaft of the drive device  12 . The drive device  12  drives a turning operation of the turning arm  11  and is installed on the top of the frame  3  through a supporting block  13 . The supporting block  13  has a fixing section of the drive device  12  or a planetary gear type speed reducer stored in the drive device  12 , that is, a first mounting surface  13   a  mounted on a mounting flat surface of a stationary case  28 , a second mounting surface  13   b  orthogonal to the first mounting surface  13   a , and a pair of rib sections  13   c ,  13   c  for connecting both ends of the first mounting surface  13   a  in the outward direction with both ends of the second mounting surface  13   b  in the outward direction. 
   The fixing section of the drive device  12  or the planetary gear type speed reducer stored in the drive device  12 , that is, the outside diameter section of the mounting flat surface of the stationary case  28  is formed with cut sections  28   a ,  28   a  on the pair of rib sections  13   c ,  13   c . As a result, the fixed section of the planetary gear type speed reducer, that is, the pair of rib sections  13   c ,  13   c  of the mounting flat surface outside diameter section of the stationary case  28  are cut, so that the first mounting surface  13   a  and the second mounting surface  13   b  of the supporting block  13  can be reinforced by the pair of rib sections  13   c ,  13   c , thus making the supporting block  13  robust, without lengthening a section between the second plane  11   b  of the turning arm  11  and the axial line A of a turning pivot, or without increasing a turning radius of a heavy weight such as the test head  5 . 
   A reference numeral  14  used in the figure denotes an installation block for installing the frame  3  storing a controller therein. Reference numerals  15 ,  15  denote bolts, which are inserted into slightly elongated clearance holes  15   a ,  15   a  in  FIGS. 2 and 3  formed in the second mounting surface  13   b  to locate the second mounting surface  13   b  from front to back and from side to side and fix the supporting block  13  on the frame  3 . A reference numeral  16  denotes a cover disposed on the front of an encoder for detecting the rotational position and speed of a motor  17  described later. 
   As shown in  FIGS. 4 and 5 , a rotation output section of the drive device  12  is formed with the first plane  11   a  of the turning arm  11 . The second plane  11   b  of the turning arm  11  is drilled with slots  11   c ,  11   c , . . . , for example, in four rows, into which bolts (not shown) are screwed, and the turning arm is fixed on the test head  5  with its vertical position adjusted to the position of the test head  5 . 
   Referring next to the drawings, and particularly to  FIG. 6 , the drive device  12  will be described below in detail. 
   The drive device  12  is roughly composed of: the motor  17 , reduction gear mechanisms for performing decelerating rotation by driving the motor  17  and an encoder  19  for detecting the rotational position and speed of the motor  17 . As the reduction gear mechanism, a single reduction gear mechanism may be used. The drive device includes a previous-stage reduction gear mechanism for firstly decelerating the rotational speed of the motor  17  and a subsequent-stage reduction gear mechanism for further secondly decelerating the rotational speed by the previous stage reduction gear mechanism. 
   The drive device  12  shown in  FIG. 6  is a structural example which includes two reduction gear mechanisms, which are two planetary gear type speed reducers for previous-stage speed reduction and subsequent-stage speed reduction. 
   A reference numeral  17  denotes a motor, which includes: a cylindrical stator  17   b  having a coil section  17   a , a rotor  17   d  having a rotatably supported rotor shaft  17   c  and disposed inside the stator; and a motor case  17   e  housing the stator  17   b  from the outside. The motor case  17   e  is composed of a first, a second and a third cases  17   e   1 ,  17   e   2  and  17   e   3 , which are connected to each other. The front section of the first case  17   e   1  is firmly covered by fixing bottom ends of the box-shaped cover  16  with bolts  18 ,  18 . A rotor shaft of the encoder  19  is connected directly to the other side of the rotor  17   d . A reference numeral  22  is a front wall of the first case  17   e   1 . 
   A reference numeral  20  denotes a front-stage speed reducer, which mainly consists of; a cylindrical inner teeth gear body  21  serving as a fixed section having a plurality of internal teeth pins  24   c   2  as internal teeth on an inner-periphery section; a pair of external teeth gear  24   c  of which external teeth of peritrochoide tooth profile mesh with the internal teeth pins  24   c   2  of the internal teeth gear body  21  for eccentric oscillation; a pinion gear  17   f  formed on the rotor shaft  17   c  as an input section; a shaft  23  as a rotation output section; and a planetary gear type speed reducer  24  having main bearings  24   a ,  24   b  as a pair of ball bearings at the previous and subsequent stages disposed between the internal teeth gear body  21  and the shaft  23 . 
   The shaft  23  is composed of a first end plate  23   a  whose outer-periphery surface engages with the pair of main bearings  24   a  at the previous stage and a second end plate  23   c  having a column section  23   b  loosely fitted into the internal teeth gear body  21 , whose outer-periphery surface engages with the pair of main bearings  24   b  at the subsequent stage. 
   The first end plate  23   a , the second end plate  23   c  having the column section  23   b  and a rotor shaft  26   a  described later are connected adjacent to each other by a taper pin  23   e  and a bolt  25  penetrated into a shaft hole  23   d  formed therein. A spur gear  23   g  provided at a crank shaft  23   f  meshes with a previous-stage pinion gear  17   f . The crank shaft  23   f  is rotatably supported on the first end plate  23   a  and the second end plate  23   c  and engages with the external teeth gear  24   c  through a needle bearing  24   c   1 . Rotation of the rotor shaft  17   c  is decelerated between the pinion gear  17   f  and the spur gear  23   g  and is transmitted to the crank shaft  23   f . Rotation of the crank shaft  23   f  eccentrically oscillates the external teeth gear  24   c , and decelerates and rotates the shaft  23 . 
   The upper front of the internal teeth gear body  21  is connected adjacent to a third case  17   e   3  of the motor case  17   e  and the upper rear of the internal teeth gear body  21  is connected adjacent to a cylindrical connection member  27  in which an outer surface joined to a subsequent-stage speed reducer  26  described later is formed into a stepped shape, by a bolt  20   a  respectively. 
   Next, the subsequent-stage speed reducer  26  will be described below: 
   The subsequent-stage speed reducer  26  consists of: a cylindrical internal teeth gear body  28  as a fixed section having a plurality of internal teeth pins  30   c   2  as internal teeth mainly on the inner-periphery section; a pair of external teeth gear  30   c  in which external teeth of peritrochoid tooth profile mesh with the internal teeth pins  30   c   2  of the inner teeth gear body  28  for eccentric oscillation; a pinion gear  26   b  formed on the rotor shaft  26   a  as a rotation input section; a shaft  29  as a rotation output section; and planetary gear type speed reducer  31  having main bearings  30   a ,  30   b  as a pair of ball bearings at the previous and subsequent stages disposed between the inner teeth gear body  28  and the shaft  29 . The rotor shaft  26   a  is connected to the second end plate  23   c.    
   The shaft  29  is composed of a first end plate  29   a  engaging the pair of main bearings  30   a  at the previous stage with an outer-periphery surface thereof and a second end plate  29   c  having a column  29   b  loosely fitted into the inner teeth gear body  28  and engaging the pair of main bearings  30   b  at the subsequent stage with an outer-periphery surface thereof. 
   The first end plate  29   a  and a second end plate  29   c  having the column section  29   b  are connected adjacent to each other by a taper pin (not shown) penetrated into shaft holes  29   d  formed therein and a bolt  32 . The previous-stage pinion gear  26   b  is meshed with a spur gear  29   g  provided on a crank shaft  29   f . The crank shaft  29   f  is rotatably supported on the first end plate  29   a  and the second end plate  29   c  and is engaged with the external teeth gear  30   c  through a needle bearing  30   c   1 . Rotation of the rotor shaft  26   a  is decelerated between a pinion gear  26   b  and the spur gear  29   g  and transmitted to the crank shaft  29   f . Rotation of the crank shaft  29   f  eccentrically oscillates the external teeth gear  30   c  and decelerates and rotates the shaft  29 . A reduction ratio of the previous-stage speed reducer  26  is set at, for example, approximately 1/100. 
   Accordingly, to an orthogonal plane  29   i  orthogonal to the axial line A of the turning pivot of the turning arm  11  of the second end plate  29   c , the turning arm  11  is connected by a bolt (not shown). 
   The turning arm  11  includes a first plane  11   a  connected to the plane of the shaft  29  as a rotation output section, namely, the second end plate  29   c  and a second plane  11   b  which is connected to a heavy object formed out of the test head  5  and so on and which is orthogonal to the first plane  11   a  positioned nearer to the heavy object than the axial line A of the turning pivot. As shown in  FIG. 2 , the turning arm  11  and the drive device  12  are disposed within a width D of the heavy object  5  in the axial direction of the turning pivot of the turning arm  11 . A dashed line C indicates the center position of the test head  5  as a heavy object in the direction of the axial line A. This can constitute a compact turning device for a heavy object which can reduce a distance between the center of gravity and the turning pivot of the heavy object such as the test head  5  on the axial line A and which allows the turning arm  11  and the drive device  12  to be positioned within the width D of the turning pivot of the heavy object in the direction of the axial line A. 
   The center position C along the direction of the axial line A of the turning pivot of the turning arm  11  of the heavy object, such as the test head  5 , is set within a distance L between the main bearing  30   b  as a ball bearing positioned on the orthogonal plane side of a rotation output section, out of the pair of ball bearings, and an intersection P obtained by crossing the axial line A of the turning pivot with a line B which forms a bearing contact angle a (°) to the perpendicular line of the main bearing  30   b . Preferably, the contact angle a (°) is to be set within the range from) 35(°) to 45(°). Such a configuration can support a heavy object such as the test head  5  in a cantilever manner and stably turn the heavy object. 
   On the first plane  11   a  side of the turning arm  11 , bolt insertion holes  11   d ,  11   d , . . . having slightly longer diameter are circumferentially arranged at desired intervals as shown in  FIG. 5 . By screwing bolts  11   e ,  11   e  . . . shown in  FIG. 4  into the bolt insertion holes  11   d ,  11   d  . . . , to engage shaft holes  29   e  (see  FIG. 6 ), vertical or horizontal positioning movement of the drive device  12  in the rotational direction is adjusted to fix it to the turning arm  11 . 
   Next, there is illustrated the operation of the turning device for a heavy object according to the present invention. 
   The motor  17  rotates at a high speed so that a turning operation of a heavy object such as the test head  5  may be driven between a position indicated by a solid line and a position indicated by a virtual line as shown in  FIG. 1 . Thus, the rotor  17   d  rotates at a high speed inside the cylindrical stator  17   b  to rotate the rotor shaft  17   c  connected directly to the rotor  17   d  and supported by a bearing  26   c . A rotational force is transmitted to the spur gear  23   g  engaged with the pinion gear  17   f  formed on the rear end of the rotor shaft  17   c  and, by the rotation of the spur gear  23   g , the crank shaft  23   f  having a crank section in the rough center rotates while being supported by a pair of bearings disposed on the shaft  23 . 
   A rotational force of the crank shaft  23   f  is transmitted to the external teeth gears  24   c ,  24   c  configured in two rows adjacent to each other, and the rotation action of the external teeth gears  24   c ,  24   c  decelerates the first end plate  23   a  and the second end plate  23   c  having the column section  23   b  of the shaft  23  as a rotation output section. The second end plate  23   c  transmits the rotational force to the subsequent-stage speed reducer  26  by the bolt  25 . Hence, the previous-stage speed reducer  20  decelerates the rotational speed of the motor  17 , for example, to approximately 1/60 by the planetary gear type speed reducer  24 . 
   Next, a rotational force of the shaft  23  decelerated to the first stage as described above is transmitted to the rotor shaft  26   a  as a rotation input section, and the rotor shaft  26   a  rotates at a speed decelerated by the previous-stage speed reducer  20 . A rotational force is transmitted to the spur gear  29   g  engaged with a pinion gear  26   b  formed on the rear end of the rotor shaft  26   a . By the rotation of the spur gear  29   g , the crank shaft  29   f  having a crank section  29   h  in the rough center rotates while being supported by main bearings  30   d ,  30   e  disposed adjacent to each other in front of the spur gear  29   g . A rotational force of the crank shaft  29   f  is transmitted to the external teeth gears  30   c ,  30   c  configured in two rows adjacent to each other. The rotation action of the external teeth gears  30   c ,  30   c  further decelerates the rotation of the first end plate  29   a  and the second end plate  29   c  having the column  29   b  of the shaft  29  as a rotation output section. The second end plate  29   c  is connected to the first plane  11   a  of the turning arm  11  so as to be adjacent to each other by the bolts  11   e ,  11   e , . . . to decelerate the driving force of the turning arm  11 . 
   Accordingly, a heavy object such as the test head  5  is adjusted while the rotational position or speed of the motor  17  is detected by the encoder  19  to be rotationally driven with an angle of approximately 180° from a position indicated by a virtual line to a position indicated by a solid line shown in  FIG. 1 . The test head  5  is electrically connected to a contact on the top of the probe card  8  through an adjacent ring. The probe device  1  receives a test signal from a tester by an electrode of a semiconductor wafer on a mounting block through the test head  5  and a probe pin of the probe card  8  for electrical examination of respective IC chips of the semiconductor wafers. 
   Hence, the subsequent-stage speed reducer  26  decelerates the rotational speed of the previous-stage speed reducer  20 , for example, to approximately 1/100, and decelerates the rotational speed of the motor  17 , for example, to approximately 1/6000. The high reduction ratio obtained by the two-stage reduction gear mechanism can reduce the outside diameter of each of the previous-stage and subsequent-stage speed reducers  20 ,  26  and the motor  17 , which can further reduce the turning radius of a heavy object such as the test head  5 . A value of the reduction ratio can be selected by setting design dimensions and shapes of internal components or members of the planetary gear type speed reducer  31  as appropriate. 
   The present invention can constitute a turning device for a heavy object of a single speed reducer only for previous stage by fixing the shaft  23  having the said second end plate  29   c  to the said turning arm  11 . 
   INDUSTRIAL APPLICABILITY 
   As described above, the turning device for a heavy object according to the present invention is applied to a probe device and the like for measuring the electric characteristics of an object to be examined, such as a semiconductor device.

Technology Category: 2