Abstract:
An interlocking chain type forward and backward actuating device is provided that does not increase workload involved in assembling the device, adjusting the rotation phase, and servicing and maintaining the device. The device is capable of smoothly actuating a driven body by advancing and retracting the body, and of preventing any pulsation or the like of the meshing chain. The interlocking chain type forward and backward actuating device includes chain-guide grooves formed so as to equalize an interlocked-state pin-to-pin distance (D 1 ) between a pair of connecting pins that face each other in a chain interlocking imaginary plane (S) and a rigid-state pin-to-pin distance (D 2 ) between a pair of connecting pins.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage Application under 35 U.S.C. 371 and claims the benefit of PCT Application No. PCT/JP2011/080166 having an international filing date of 27 Dec. 2011, which designated the United States, and which PCT application claimed the benefit of Japanese Patent Application No. 2011-015066 filed on 27 Jan. 2011, the entire disclosures of which is incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The present invention relates to a drive unit used in manufacturing facilities in various manufacturing fields, transportation facilities in the transportation field, nursing care facilities in medical and welfare fields, and stage facilities in art fields, and advancing and retreating a driven body such as a workpiece in parallel to an installation face, in particular, to an interlocking chain type forward and backward actuating device using interlocking chains as drive media for advancing/retreating movement. 
     BACKGROUND OF THE INVENTION 
     Conventionally, as a drive unit, an interlocking chain type lifting apparatus has been known that moves a workpiece such as a heavy material by using a pair of lifting interlocking chains interlocked with each other and integrally moved vertically (for example, refer to Patent Document 1). 
     The pair of lifting interlocking chains used in this conventional interlocking chain type lifting apparatus is designed to be driven by a pair of lifting sprockets, which are arranged to face the pair of lifting interlocking chains, respectively. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         Patent Document 1: Japanese Laid-Open Patent Publication No. 2009-255997 (Claims, FIG. 3) 
       
    
     SUMMARY OF THE INVENTION 
     However, the conventional interlocking chain type lifting apparatus  800  has problems in apparatus assembly and maintenance as shown in  FIG. 8 . Specifically, to engage a pair of lifting interlocking chains  810  with each other at a right timing by synchronizing rotation phases of a pair of lifting sprockets  820  with each other, an operation for adjusting the rotation phases involves an excessively heavy work burden. 
     Also, the conventional interlocking chain type lifting apparatus  800  is designed to rotate the pair of lifting sprockets  820  in a state where the lifting sprockets  820  are installed on both the left and right of the pair of lifting interlocking chains  810  arranged adjacent to each other to engage the pair of lifting interlocking chains  810  with each other and advance and retreat the chains in the same direction. The apparatus has problems in apparatus assembly and maintenance in that when the apparatus is entirely driven by a single drive source (not illustrated) such as an electric motor, the work burden to install a gear group  853  that interlocks rotary shafts  821  of the pair of lifting sprockets  820  with each other is increased. Further, the apparatus configuration becomes complicated, and this involves an excessively heavy work burden on apparatus assembly and maintenance. 
     Also, in the conventional interlocking chain type lifting apparatus  800 , when the above-described gear group  853  is composed of a pair of gears  853   a  attached to the respective rotary shafts  821  of the lifting sprockets  820 , as shown in  FIG. 8 , the diameter of the gears  853   a  are inevitably larger than the diameter of the lifting sprockets  820  because the lifting interlocking chains  810  are arranged between the pair of lifting sprockets  820 . Thus, the gear group  853  larger in diameter than the lifting sprockets  820  obstructs advancing/retreating movement of a driven body such as a workpiece near the installation surface of the interlocking chain type lifting apparatus  800 . 
     In addition, in the region in which the lifting interlocking chain  810  is driven from the chain bifurcating direction to the chain interlocking direction while being tilted by the lifting sprocket  820 , that is, in the region in which the lifting interlocking chain  810  is wound around the lifting sprocket  820 , known chordal action (polygonal action) occurs on the lifting interlocking chain  810 , so that a problem occurs in apparatus driving which causes the lifting interlocking chain  810  to pulsate (move up and down), vibrate, make noise, and fluctuate in speed. 
     Accordingly, a technical problem to be solved by the present invention, that is, an object of the present invention is to provide an interlocking chain type forward and backward actuating device that avoids an increase in work burden on apparatus assembly, adjustment of rotation phases, and maintenance, smoothly advances and retreats a driven body near an installation surface, and avoids pulsation (up-down movement), vibration, noise, and speed fluctuation of the interlocking chains. 
     The invention of claim  1  solves the above described problems by providing an interlocking chain type forward and backward actuating device comprising a pair of interlocking chains, a drive sprocket, and a chain guide. The interlocking chains are each composed by coupling, in the chain longitudinal direction, a great number of pairs of hook-shaped inner tooth plates spaced from each other in the chain width direction and a great number of pairs of hook-shaped outer tooth plates arranged adjacent to the outer sides of the hook-shaped inner tooth plates in the chain width direction by pairs of front and rear connecting pins. The interlocking chains are integrally made rigid to form a rigid chain part in a state where the interlocking chains are interlocked with each other and arranged to face each other. The interlocking chains are disengaged from each other to bifurcate. The drive sprocket engages with a first one of the pair of interlocking chains from a side position of the pair of interlocking chains to freely advance and retreat the pair of interlocking chains. The chain guide has chain guide grooves that interlock a second one of the interlocking chains with the first interlocking chain by a chain positioning guide portion provided in the fork region of the pair of interlocking chains to drive the second interlocking chain so as to follow the first interlocking chain. The connecting pins of the first interlocking chain include a first connecting pin. The first connecting pin is positioned on the drive sprocket side in a state where the first interlocking chain is engaged with sprocket teeth of the drive sprocket in a chain interlocking imaginary plane that is orthogonal to the driving direction of the rigid chain part and includes a drive shaft of the drive sprocket. The connecting pins of the second interlocking chain include a second connecting pin facing the first connecting pin along the chain interlocking imaginary plane. A distance that exists between the first connecting pin and the second connecting pin is defined as an interlocked-state pin-to-pin distance. The connecting pins in the rigid chain part include a pair of connecting pins facing each other while being parallel to the chain interlocking imaginary plane, a distance that exists between these pins being defined as a rigid-state pin-to-pin distance. The chain guide grooves are formed such that the interlocked-state pin-to-pin distance is equal to the rigid-state pin-to-pin distance. 
     The invention of claim  2  solves the above described problems by providing, in addition to the configuration of claim  1 , a configuration in which the chain positioning guide portion extends straight to a hollow region of the rigid chain part. 
     The invention of claim  3  solves the above described problems by providing, in addition to the configuration of claim  2 , a configuration in which the length of the straight extending portion extending to the hollow region from the chain engagement imaginary plane of the chain positioning guide portion is equal to or longer than a pin-to-pin distance between the pair of front and rear connecting pins. 
     The invention of claim  4  solves the above described problems by providing, in addition to the configuration of claim  3 , a configuration in which the length of the straight extending portion is twice or more as long as the pin-to-pin distance between the pair of front and rear connecting pins. 
     An interlocking chain type forward and backward actuating device according to claim  1  of the present invention includes a pair of interlocking chains, a drive sprocket, and a chain guide. The interlocking chains are each composed by coupling, in the chain longitudinal direction, a great number of pairs of hook-shaped inner tooth plates spaced from each other in the chain width direction and a great number of pairs of hook-shaped outer tooth plates arranged adjacent to the outer sides of the hook-shaped inner tooth plates in the chain width direction by pairs of front and rear connecting pins. The interlocking chains are integrally made rigid to form a rigid chain part in a state where the interlocking chains are interlocked with each other and arranged to face each other. The interlocking chains are disengaged from each other to bifurcate. The drive sprocket engages with a first one of the pair of interlocking chains from a side position of the pair of interlocking chains to freely advance and retreat the pair of interlocking chains. The chain guide has chain guide grooves that interlock a second one of the interlocking chains with the first interlocking chain by a chain positioning guide portion provided in the fork region of the pair of interlocking chains to drive the second interlocking chain so as to follow the first interlocking chain. Thus, not only can the driven body be advanced/retreated according to advancing/retreating movement of the pair of interlocking chains, but also particular effects corresponding to specific configurations as below can be exerted. 
     More specifically, in the interlocking chain type forward and backward actuating device according to claim  1 , the connecting pins of the first interlocking chain include a first connecting pin. The first connecting pin is positioned on the drive sprocket side in a state where the first interlocking chain is engaged with sprocket teeth of the drive sprocket in a chain interlocking imaginary plane that is orthogonal to the driving direction of the rigid chain part and includes a drive shaft of the drive sprocket. The connecting pins of the second interlocking chain include a second connecting pin facing the first connecting pin along the chain interlocking imaginary plane. A distance that exists between the first connecting pin and the second connecting pin is defined as an interlocked-state pin-to-pin distance. The connecting pins in the rigid chain part include a pair of connecting pins facing each other while being parallel to the chain interlocking imaginary plane. A distance that exists between these pins is defined as a rigid-state pin-to-pin distance. The chain guide grooves are formed such that the interlocked-state pin-to-pin distance is equal to the rigid-state pin-to-pin distance. Thus, the interlocking chains are driven by the drive sprocket engaging with the first interlocking chain. The hook-shaped inner tooth plates are meshed with each other, and the hook-shaped outer tooth plates are meshed with each other. The interlocking chains are driven in the rigid chain direction to smoothly complete the movement for meshing between the hook-shaped inner tooth plates and the movement for meshing between the hook-shaped outer tooth plates. Therefore, an increase in work burden on actuator assembly, adjustment of rotation phases, and maintenance is avoided. Also, the driven body is smoothly advanced and retreated near the installation surface, and occurrence of pulsation (up-down movement), vibration, noise, and speed fluctuation of the interlocking chains is avoided. 
     The interlocking chain type forward and backward actuating device according to claim  2  of the present invention is configured to have the following effects in addition to the effects exerted by the interlocking chain type forward and backward actuating device according to claim  1 . That is, the chain positioning guide portion extends straight to a hollow region of the rigid chain part, whereupon the chain positioning guide portion supports not only chain disengaged portions bifurcated by disengagement between the pair of interlocking chains, but also the rigid chain part in which the pair of interlocking chains are interlocked with each other and made rigid. Thus, occurrence of pulsation (up-down movement), vibration, noise, and speed fluctuation of the interlocking chains can be more reliably avoided by guiding the pair of interlocking chains until the pair of interlocking chains are made rigid from the state where the chains are disengaged from each other. 
     The interlocking chain type forward and backward actuating device according to claim  3  of the present invention is configured to have the following effects in addition to the effect exerted by the interlocking chain type forward and backward actuating device according to claim  2 . That is, the length of the straight extending portion extending to the hollow region from the chain engagement imaginary plane of the chain positioning guide portion is equal to or longer than a pin-to-pin distance between the pair of front and rear connecting pins. Thus, the straight extending portion guides the rigid chain part in the range of the pin-to-pin distance between the pair of front and rear connecting pins, so that the interlocking chains can be more smoothly driven. Also, occurrence of pulsation (up-down movement), vibration, noise, and speed fluctuation of the interlocking chains can be more reliably avoided as compared with the case where the pair of interlocking chains are guided only in the range until the pair of interlocking chains are interlocked with each other. 
     The interlocking chain type forward and backward actuating device according to claim  4  of the present invention is configured to have the following effects in addition to the effect exerted by the interlocking chain type forward and backward actuating device according to claim  3 . That is, the length of the straight extending portion is twice or more as long as the pin-to-pin distance between the pair of front and rear connecting pins. Thus, the side surface of the straight extending portion is made to face three or more connecting pins in the rigid chain direction to support these connecting pins directly or indirectly via bushings or rollers. Accordingly, the interlocking chains are more reliably and smoothly driven, and occurrence of pulsation (up-down movement), vibration, noise, and speed fluctuation of the interlocking chains is more reliably avoided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a general perspective view of an interlocking chain type forward and backward actuating device according to one embodiment of the present invention; 
         FIG. 2  is a partially enlarged view of the vicinity of a drive sprocket and interlocking chains shown in  FIG. 1 ; 
         FIG. 3  is a perspective view showing an exploded state and a disengaged state of the interlocking chains; 
         FIG. 4  is a partially enlarged view of the vicinity of the drive sprocket and the interlocking chains shown in  FIG. 1 ; 
         FIG. 5  is a partially enlarged view corresponding to  FIG. 4 , illustrating a first modification; 
         FIG. 6  is a partially enlarged view corresponding to  FIG. 4 , illustrating a second modification; 
         FIG. 7  is a partially enlarged view corresponding to  FIG. 4 , illustrating a third modification; and 
         FIG. 8  is a partially enlarged view of a conventional interlocking chain type lifting apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An interlocking chain type forward and backward actuating device according to the present invention includes a pair of interlocking chains, a drive sprocket, and a chain guide. The interlocking chains are each composed by coupling, in the chain longitudinal direction, a great number of pairs of hook-shaped inner tooth plates spaced from each other in the chain width direction and a great number of pairs of hook-shaped outer tooth plates arranged adjacent to the outer sides of the hook-shaped inner tooth plates in the chain width direction by pairs of front and rear connecting pins. The interlocking chains are integrally made rigid to form a rigid chain part in a state where the interlocking chains are interlocked with each other and arranged to face each other. The interlocking chains are disengaged from each other to bifurcate. The drive sprocket engages with a first one of the pair of interlocking chains from a side position of the pair of interlocking chains to freely advance and retreat the pair of interlocking chains. The chain guide has chain guide grooves that interlock a second one of the interlocking chains with the first interlocking chain by a chain positioning guide portion provided in the fork region of the pair of interlocking chains to drive the second interlocking chain so as to follow the first interlocking chain. The connecting pins of the first interlocking chain include a first connecting pin. The first connecting pin is positioned on the drive sprocket side in a state where the first interlocking chain is engaged with sprocket teeth of the drive sprocket in a chain interlocking imaginary plane that is orthogonal to the driving direction of the rigid chain part and includes a drive shaft of the drive sprocket. The connecting pins of the second interlocking chain include a second connecting pin facing the first connecting pin along the chain interlocking imaginary plane. A distance that exists between the first connecting pin and the second connecting pin is defined as an interlocked-state pin-to-pin distance. The connecting pins in the rigid chain part include a pair of connecting pins facing each other while being parallel to the chain interlocking imaginary plane, a distance that exists between these pins being defined as a rigid-state pin-to-pin distance. The chain guide grooves are formed such that the interlocked-state pin-to-pin distance is equal to the rigid-state pin-to-pin distance. Thus, an increase in work burden on actuator assembly, adjustment of rotation phases, and maintenance is avoided. Also, the driven body is smoothly advanced and retreated near the installation surface. Further, occurrence of pulsation (up-down movement), vibration, noise, and speed fluctuation of the interlocking chains is avoided. 
     For example, the pair of interlocking chains used in the interlocking chain type forward and backward actuating device according to the present invention may have any form as long as the interlocking chains are integrated by being interlocked with each other and bifurcate from each other by being disengaged from each other. For example, the interlocking chain may be composed of a single row in the chain width direction or two or more rows in the chain width direction. It is more preferable that the interlocking chain is composed of two or more rows in the chain width direction. The hook-shaped outer tooth plates and the hook-shaped inner tooth plates constituting a first one of the pair of interlocking chains are multiplexed and firmly interlocked in hook forms with the hook-shaped outer tooth plates and the hook-shaped inner tooth plates constituting a second one of the interlocking chain facing the first interlocking chain in a plurality of rows in the chain width direction. Thus, buckling frequently occurring in the chain width direction of the interlocking chains can be reliably restrained and excellent chain durability is realized. 
     The pair of interlocking chains used in the interlocking chain type forward and backward actuating device according to the present invention may be any of interlocking chains having no rollers, that is, having only bushings, or having rollers. When interlocking chains having only bushings are used, the number of chain components is reduced and the chain weight can be reduced. 
     As long as capable of smoothly guiding interlocking chains, the chain guide used in the interlocking chain type forward and backward actuating device according to the present invention may be formed to move a pair of left and right interlocking chains forward or backward along asymmetrical loci. If the chain guide has a chain guiding face having the same diameter as the root circle of the drive sprocket, the pair of the interlocking chains are moved forward and backward along symmetrical loci. Thus, smooth meshing and disengaging of the interlocking chains are achieved. 
     The interlocking chain type forward and backward actuating device according to the present invention has no trouble in vertical movements, with regard to an installation face, when the device is installed on a floor face as stationary installation or suspended from a ceiling face as suspended installation. Further, the device has no trouble in advancing and retreating movements corresponding to the above-described vertical movements when the device is installed on a vertical wall face as cantilever-supported installation. 
     EXAMPLE 
     Hereinafter, an interlocking chain type forward and backward actuating device of one embodiment of the present invention will be described based on the drawings. 
       FIG. 1  is a general perspective view of an interlocking chain type forward and backward actuating device according to one embodiment of the present invention.  FIG. 2  is a partially enlarged view of the vicinity of a drive sprocket and interlocking chains shown in  FIG. 1 .  FIG. 3  is a perspective view showing an exploded state and a disengaged state of the interlocking chains.  FIG. 4  is a partially enlarged view of the vicinity of the drive sprocket and the interlocking chains shown in  FIG. 1 .  FIG. 5  is a partially enlarged view corresponding to  FIG. 4 , illustrating a first modification.  FIG. 6  is a partially enlarged view corresponding to  FIG. 4 , illustrating a second modification.  FIG. 7  is a partially enlarged view corresponding to  FIG. 4 , illustrating a third modification. 
     First, an interlocking chain type forward and backward actuating device  100  according to one embodiment of the present invention vertically moves a driven body T, such as a lifting table on which a heavy material (not illustrated) as a workpiece is loaded, with respect to an installation face G as shown in  FIG. 1 . 
     The interlocking chain type forward and backward actuating device  100  according to the present embodiment includes, as shown in  FIG. 1  to  FIG. 3 , a pair of interlocking chains  110 ,  110 , a drive sprocket  120 , and a chain guide  130 . The interlocking chains  110 ,  110  are each composed by coupling, in the chain longitudinal direction, a great number of pairs of hook-shaped inner tooth plates  111  spaced from each other in the chain width direction and a great number of pairs of hook-shaped outer tooth plates  112  arranged adjacent to the outer sides of the hook-shaped inner tooth plates  111  in the chain width direction by pairs of front and rear connecting pins  113 . The interlocking chains  110 ,  110  are integrally made rigid to form a rigid chain part  110 G in a state where the interlocking chains  110 ,  110  are interlocked with each other and arranged to face each other. The interlocking chains  110 ,  110  are disengaged from each other to bifurcate. The drive sprocket  120  engages with a first one of the pair of interlocking chains  110 ,  110  from a side position of the pair of interlocking chains  110 ,  110  to freely advance and retreat the pair of interlocking chains  110 ,  110 . The chain guide  130  has chain guide grooves  131 ,  131  that interlock a second one of the interlocking chains  110 ,  110  with the first interlocking chain  110  by a chain positioning guide portion  132  provided in the fork region R 1  of the pair of interlocking chains  110 ,  110  to drive the second interlocking chain  110  so as to follow the first interlocking chain  110 . The interlocking chain type forward and backward actuating device  100  advances and retreats a driven body T according to advancing/retreating movement of the pair of interlocking chains  110  and  110  on the base plate  140 . 
     The interlocking chain type forward and backward actuating device  100  further includes a power transmission chain  151 , which transmits power to a driven side sprocket  152  for rotating the drive sprocket  120 , and a drive motor  150  as a drive source, which drives the power transmission chain  151 . Motor torque of the drive motor  150  is transmitted without waste by directly supporting and pushing up the driven body T on which the workpiece is loaded by the pair of interlocking chains  110  and  110 . 
     The drive sprocket  120  is designed to engage with bushings  114 , which are part of the interlocking chains  110 . 
     The pair of interlocking chains  110  and  110  used in the interlocking chain type forward and backward actuating device  100  are, as shown in  FIG. 3 , composed by coupling a great number of inner link units, which are each formed by press-fitting a pair of front and rear bushings  114  with the hook-shaped inner tooth plates  111  and  111  located in pairs and spaced from each other in the chain width direction W by pairs of front and rear connecting pins  113  press-fitted in pairs of front and rear pin holes of the hook-shaped outer tooth plates  112  located on the outermost side in the chain width direction W. 
     Next, the characteristic configuration of the interlocking chain type forward and backward actuating device  100  of the embodiment described above will be described in more detail with reference to  FIGS. 1 to 4 . 
     In the interlocking chain type forward and backward actuating device  100 , as shown in  FIG. 1  to  FIG. 4 , the connecting pins  113  of the first interlocking chain include a first connecting pin  113 . The first connecting pin  113  is positioned on the drive sprocket side in a state where the first interlocking chain  110  is engaged with sprocket teeth of the drive sprocket  120  in a chain interlocking imaginary plane S that is orthogonal to the driving direction A of the rigid chain part  110 G and includes a drive shaft  121  of the drive sprocket  120 . The connecting pins  113  of the second interlocking chain  110  include a second connecting pin  113  facing the first connecting pin  113  along the chain interlocking imaginary plane S. A distance that exists between the first connecting pin  113  and the second connecting pin  113  is defined as an interlocked-state pin-to-pin distance D 1 . The connecting pins  113  in the rigid chain part  110 G include a pair of connecting pins  113  facing each other while being parallel to the chain interlocking imaginary plane S. A distance that exists between these pins  113  is defined as a rigid-state pin-to-pin distance D 2 . The chain guide grooves  131  are formed such that the interlocked-state pin-to-pin distance D 1  is equal to the rigid-state pin-to-pin distance D 2 . The pair of interlocking chains  110  and  110  are driven by the drive sprocket  120  engaged with the first interlocking chain  110  to mesh the hook-shaped inner tooth plates  111  with each other and mesh the hook-shaped outer tooth plates  112  with each other, respectively, and the pair of interlocking chains  110  and  110  are driven as they are in the rigid chain direction A to smoothly complete the movement for meshing between the hook-shaped inner tooth plates  111  and the movement for meshing between the hook-shaped outer tooth plates  112 . Thus, an increase in work burden on actuator assembly, adjustment of rotation phases, and maintenance is avoided. Also, the driven body T is smoothly advanced and retreated near the installation surface. Further, occurrence of pulsation (up-down movement), vibration, noise, and speed fluctuation of the interlocking chains  110  is avoided. 
     In the interlocking chain type forward and backward actuating device  100 , the chain positioning guide portion  132  extends straight to a hollow region R 2  of the rigid chain part  110 G. Thus, the chain positioning guide portion  132  supports not only chain disengaged portions bifurcated by disengagement from each other between the pair of interlocking chains  110  and  110 , but also the rigid chain part  110 G in which the pair of interlocking chains  110  and  110  are interlocked with each other and made rigid. Accordingly, occurrence of pulsation (up-down movement), vibration, noise, and speed fluctuation of the interlocking chains  110  is more reliably avoided by guiding the pair of interlocking chains  110  and  110  until the pair of interlocking chains  110  and  110  are made rigid from the state where the chains are disengaged from each other. 
     In the interlocking chain type forward and backward actuating device  100 , the length L of the straight extending portion  132 A extending to the hollow region R 2  from the chain engagement imaginary plane S of the chain positioning guide portion  132  is equal to or longer than a pin-to-pin distance D between the pair of front and rear connecting pins  113 . Thus, the straight extending portion  132 A supports the rigid chain part  110 G in a range of the pin-to-pin distance D between the pair of front and rear connecting pins  113 . Accordingly the interlocking chains  110  are more smoothly driven. Also, occurrences of pulsation (up-down movement), vibration, noise, and speed fluctuation of the interlocking chains  110  are more reliably avoided as compared with the case where the pair of interlocking chains  110  and  110  are guided only in a range until the pair of interlocking chains  110  and  110  are interlocked with each other. 
     As described above, the pair of interlocking chains  110  and  110  are configured to have the following features. That is, the connecting pins  113  of the first interlocking chain include a first connecting pin  113 . The first connecting pin  113  is positioned on the drive sprocket side in a state where the first interlocking chain  110  is engaged with sprocket teeth of the drive sprocket  120  in a chain interlocking imaginary plane S that is orthogonal to the driving direction A of the rigid chain part  110 G and includes a drive shaft  121  of the drive sprocket  120 . The connecting pins  113  of the second interlocking chain  110  include a second connecting pin  113  facing the first connecting pin  113  along the chain interlocking imaginary plane S. A distance that exists between the first connecting pin  113  and the second connecting pin  113  is defined as an interlocked-state pin-to-pin distance D 1 . The connecting pins  113  in the rigid chain part  110 G include a pair of connecting pins  113  facing each other while being parallel to the chain interlocking imaginary plane S. A distance that exists between these pins  113  is defined as a rigid-state pin-to-pin distance D 2 . The chain guide grooves  131  are formed such that the interlocked-state pin-to-pin distance D 1  is equal to the rigid-state pin-to-pin distance D 2 . Therefore, the interlocking chain type forward and backward actuating device  100  according to the present embodiment achieves significant advantages. Specifically, an increase in work burden on actuator assembly, adjustment of rotation phases, and maintenance is avoided. Also, the driven body T is smoothly advanced and retreated near the installation surface. Further, occurrence of pulsation (up-down movement), vibration, noise, and speed fluctuation of the interlocking chains  110  is avoided. 
     Next, modifications of the above-described interlocking chain type forward and backward actuating device  100  will be described with reference to  FIGS. 5 to 7 . 
     In the following first to third modifications, components common to those of the above-described interlocking chain type forward and backward actuating device  100  are provided with common reference symbols, and detailed description thereof is omitted. 
     As shown in  FIG. 5 , in the interlocking chain type forward and backward actuating device according to a first modification, the length L 1  of the straight extending portion  132 A is twice or more as long as the pin-to-pin distance D between the pair of front and rear connecting pins  113 . Thus, the side surface of a straight extending portion  132 A is made to face three or more connecting pins  113  in the rigid chain direction A to support these connecting pins  113  directly or indirectly via bushings  114  or rollers. Accordingly, the interlocking chains  110  are more reliably and smoothly driven and occurrence of pulsation (up-down movement), vibration, noise, and speed fluctuation of the interlocking chains  110  is more reliably avoided. 
     Lubricant may be stored in recesses and grooves partially provided on the side surface, that is, the surface facing the bushings  114  of the straight extending portion  132 A to reduce noise during chain driving, and the wear resistance of the bushings may be improved. 
     As shown in  FIG. 6 , in the interlocking chain type forward and backward actuating device according to a second modification, the pair of interlocking chains  110  and  110  are formed such that the interlocked-state pin-to-pin distance D 1  and the rigid-state pin-to-pin distance D 2  are equal to each other. Thus, the drive sprocket  120  and a chain guide  230  forming a side wall facing the interlocking chain  110  on the side opposite to the drive sprocket  120  drive the rigid chain part  110 G in the rigid chain direction A without disengagement of the rigid chain part. Accordingly, the pair of interlocking chains  110  and  110  are smoothly driven, and occurrence of pulsation (up-down movement), vibration, noise, and speed fluctuation of the interlocking chains  110  is reliably avoided. 
     As shown in  FIG. 7 , in the interlocking chain type forward and backward actuating device according to a third modification, the pair of interlocking chains  110  and  110  are formed such that the interlocked-state pin-to-pin distance D 1  and the rigid-state pin-to-pin distance D 2  become equal to each other. Thus, the drive sprocket  120  and the chain guide groove  331  that forms a side wall facing the interlocking chain  110  on the side opposite to the drive sprocket  120  and has an opening edge  333  at the height equal to the height of the tip end of the straight extending portion  332 A guide the pair of interlocking chains  110  and  110  from both sides. Therefore, the pair of interlocking chains  110  and  110  are smoothly driven and occurrence of pulsation (up-down movement), vibration, noise, and speed fluctuation of the interlocking chains  110  is reliably avoided. 
     Description of the Reference Numerals 
     
         
           100  . . . interlocking chain type forward and backward actuating device 
           110  . . . interlocking chain 
           110 G . . . rigid chain part 
           111  . . . hook-shaped inner tooth plate 
           112  . . . hook-shaped outer tooth plate 
           113  . . . connecting pin 
           114  . . . bushing 
           120  . . . drive sprocket 
           121  . . . drive shaft 
           130 ,  230 ,  330  . . . chain guide 
           131 ,  231 ,  331  . . . chain guide groove 
           132 ,  232 ,  332  . . . chain positioning guide portion 
           132 A,  332 A . . . straight extending portion 
           140  . . . base plate 
           150  . . . drive motor 
           151  . . . power transmission chain 
           152  . . . driven side sprocket 
           800  . . . interlocking chain type lifting apparatus 
           810  . . . interlocking chain 
         A . . . rigid chain direction 
         D . . . pin-to-pin distance between pair of front and rear connecting pins 
         D 1  . . . Interlocked-state pin-to-pin distance 
         D 2  . . . Rigid-state pin-to-pin distance 
         G . . . installation surface 
         L, L 1 , L 3  . . . length of straight extending portion 
         R 1  . . . fork region of pair of interlocking chains 
         R 2  . . . hollow region of rigid chain part 
         S . . . chain engagement imaginary plane 
         T . . . driven body