As techniques according to a related art relating to a manufacturing apparatus of a fiber-reinforced resin strand, for example, configurations described below are known.  To begin with, a manufacturing apparatus of a fiber-reinforced resin strand according to a first related art example will be described with reference to FIG.  4 which is a schematic view to explain the configuration of this apparatus.  The manufacturing apparatus of a fiber-reinforced resin strand according to the first related art example is configured to efficiently manufacture a fiber-reinforced resin strand having high adhesion between a reinforcing fiber and resin. 
To be more specific, spreaders 8 that spread a reinforcing fiber bundle are provided inside a crosshead 5 into which a molten resin material 2 is continuously supplied from an extruding machine 6 by driving of a screw 7.  In addition, at the exist side of the crosshead 5, a forming die 9, a cooler 10, twisting rollers (also referred to as cross roller capstans) 11 and 12, and pultruding rollers 13 are provided sequentially in this order from the exist side.  According to the manufacturing apparatus of a fiber-reinforced resin strand thus configured, after reinforcing fibers 1, 1, . . .  and so forth fed from bobbins 4, are soaked in a molten resin material 2 inside the crosshead 5 to be impregnated with resin, the sectional shape is determined by the forming die 9, after which they are cooled to harden by the cooler 10. 
The twisting rollers 11 and 12 are rubber rollers and configured to be driven to rotate in directions opposite to each other.  These twisting rollers 11 and 12 are provided so as to incline in directions opposite to each other on a horizontal plane.  A fiber-reinforced resin strand 3 being pinched in the crossed portion of the twisting rollers 11 and 12 is pultruded in the direction indicated by an arrow so that the fiber-reinforced resin strand 3 can rotate about the shaft center in the longitudinal direction.  The fiber-reinforced resin strand 3 is twisted on the way to the cooler 10 from the spreader 8 on the lowermost stream side owing to such rotations.  The fiber-reinforced resin strand 3 thus twisted is cut into a predetermined length to manufacture pellets by a pelletizer 14 located remote from the pultruding rollers 13 in the crosshead 5 (see, for example, Patent Document 1). 
A manufacturing apparatus of a continuous fiber-reinforced thermoplastic resin strand (hereinafter, referred to as a fiber-reinforced resin strand) according to a second related art example will be described briefly.  In short, the manufacturing apparatus of a fiber-reinforced resin strand according to the second related art example is configured to be able to perform the manufacturing continuously over a long period when manufacturing the fiber-reinforced resin strand. 
More specifically, it is an apparatus configured in such a manner that a reinforcing fiber bundle is introduced into molten thermoplastic resin inside a thermoplastic resin bath container (corresponding to the crosshead of the first related art example) to let the reinforcing fiber bundle be impregnated with the thermoplastic resin and a continuous fiber-reinforced thermoplastic resin strand is manufactured by pultruding a resin-impregnated fiber bundle from an exit nozzle of the thermoplastic resin bath container.  Rollers that come into contact with a reinforcing fiber bundle are disposed inside the thermoplastic resin bath container so as to cross a traveling track of the reinforcing fiber bundle.  Each roller is formed of a shaft and a tube, and the tube is supported around the shaft in a rotatable manner.  In addition, means for retaining the twists of the fiber-reinforced resin strand imparted from twisting rollers that twist the fiber-reinforced resin strand is provided between the twisting rollers and a pelletizer (see, for example, Patent Document 2). 
In the manufacturing apparatus of a fiber-reinforced resin strand according to related art, a pair of twisting rollers is inclined in different directions, that is, offset angles are imparted thereto, and the strand is pulled while twisting the strand between opposed outer peripheries of the pair of twisting rollers.  But in certain operating conditions, it is necessary to adjust the offset angle of each of the paired twisting rollers.  A roller offset angle adjusting device for adjusting offset angles of a pair of twisting rollers in such manufacturing apparatus of a fiber-reinforced resin strand according to a related art is configured for example as follows.  Two examples of roller offset angle adjusting devices in the manufacturing apparatus of a fiber-reinforced resin strand will be explained below while taking, as an example, a case of adjusting offset angles of the twisting rollers 11 and 12 in the manufacturing apparatus of a fiber-reinforced resin strand according to the foregoing first related art example, with reference to a schematic view for explaining the configuration which shows the main part of the roller offset angle adjusting device. 
First, the roller offset angle adjusting device in the manufacturing apparatus of a fiber-reinforced resin strand according to a first example will be described while making reference successively to FIG.  5(a) as seen from a strand moving direction side and FIG.  5(b) as seen in the direction of arrow B in FIG.  5(a).  In the roller offset angle adjusting device according to the first example, the first twisting roller 11 is configured so that an angle θ1 between a rotational center Rc1 of the first twisting roller 11 and a horizontal line LH is adjusted by first offset angle adjusting means (not shown) together with a first motor 71 with reduction gear which drives the first twisting roller 11 to rotate.  The second twisting roller 12 is configured so that an angle θ2 between a rotational center Rc2 of the second twisting roller 12 and the horizontal line LH is adjusted by second offset angle adjusting means (not shown) together with a second motor 72 with reduction gear which drives the second twisting roller 12 to rotate.  The reference numeral 73 denotes a strand and the numeral 74 denotes a strand pass line. 
Next, the roller offset angle adjusting device in the manufacturing apparatus of a fiber-reinforced resin strand according to the second example will be described while making reference successively to FIG.  6(a) as seen from a strand moving direction, and FIG.  6(b) as seen in the direction of arrow C in FIG.  6(a).  In the roller offset angle adjusting device according to this second example, an expansion joint 81b whose length can be adjusted axially, is connected to an opposite side of a roller shaft 81a of a first twisting roller 11 with respect to the roller 11, the shaft 81a being inclined at an angle of θ1 relative to a horizontal line LH.  A universal joint 81c is connected to the expansion joint 81b.  And the universal joint 81c is also connected to an expansion joint 81d, the expansion joint 81d being adjustable in length and connected to an end portion of a first driving shaft 81e which is rotated by a motor 83 via a belt 84 and a pulley 81f.  
On the other hand, an expansion joint 82b whose length can be adjusted axially, is connected to an opposite side of a roller shaft 82a of a second twisting roller 12 facing the first twisting roller 11, with respect to the roller 12.  The roller shaft 82a is inclined at an angle of θ2 relative to the horizontal line LH.  A universal joint 82c is connected to the expansion joint 82b.  And the universal joint 82c is also connected to an expansion joint 82d, the expansion joint being adjustable in length and connected to an end portion of a second driving shaft 82e which is rotated by the motor 83 via the belt 84 and a pulley 82f.  Further, an idler pulley (not shown), whose rotational center position is changed as necessary, is provided for the belt 84 to cope with a change in spacing between the pulleys 81f and 82f.  
Thus, according to the roller offset angle adjusting device of the second example, the offset angle θ1 of the first twisting roller 11 is adjusted by an expanding/contracting operation of the length-adjustable expansion joints 81b and 81d, while the offset angle θ2 of the second twisting roller 12 is adjusted by an expanding/contracting operation of the length-adjustable expansion joints 82b and 82d.  The reference numeral 85 denotes a strand, and the numeral 86 denotes a strand pass line. 
According to the general roller offset angle adjusting devices of the above two examples in the manufacturing apparatus of a fiber-reinforced resin strand according to related art, the offset angle adjusting operations for the twisting rollers are very complicated, the roller spacing adjusting operations for the twisting rollers performed in response to a change in strand diameter are also complicated, and the devices' structures are complicated.  Besides, an increase in size is unavoidable.  There have been such problems to be solved.  More particularly, in the roller offset angle adjusting device of the first example, in addition to the necessity of synchronized driving of two motors with reduction gear, the motors with reduction gear must be moved during roller offset angle adjustment and roller spacing adjustment.  As a result, it is inevitable for the angle adjusting means to become large-sized and complicated in configuration.  In the roller offset angle adjusting device of the second example, it is necessary to use universal joints, thus inevitably resulting in that the driving shaft system for driving the first and second twisting rollers become long.  In addition, the roller spacing adjustment for the twisting rollers requires movement of each driving shaft system.  Consequently, the angle adjusting means become large-sized and complicated, and the roller offset angle adjustment and the roller spacing adjustment for the twisting rollers also become complicated. 
[Patent Literature 1]    Japanese Patent Laid-Open Publication No.  Hei 5 (1993)-169445
[Patent Literature 2]    Japanese Patent Laid-Open Publication No.  2003-175512