Abstract:
A sheet conveyor for conveying a sheet by engaging an engaging member with openings formed in a sheet and conveying the sheet by displacement of the engaging member. The conveyor includes a holding device for holding the engaging member so as to be movable between an operative position and a retracted position retracted from the operative position, a device deformable to move the engaging member provided on the holding device between the operative position and the retracted position, and a drive device for driving the holding device to displace the engaging member.

Description:
This application is a continuation of application Ser. No. 07/555,809, filed Jul. 23, 1990, which is a continuation of application Ser. No. 07/328,815, filed Mar. 24, 1989, which is a continuation of application Ser. No. 06/883,748, filed Jul. 9, 1986, all now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 1. Field of the Invention 
     This invention relates to a sheet conveyor applied to an image recording apparatus such as a printer, a typewriter, a laser beam printer or an electrophotographic copying apparatus. More particularly, the present invention relates to a sheet conveyor for engaging an engaging member with openings formed in a sheet and conveying the sheet by displacing the engaging member. 
     2. Related Background Art 
     Various structures have been proposed as paper feeding mechanisms used, for example, in printers, and one of them is a pin feed mechanism. 
     This pin feed mechanism has a structure in which a pin wheel rotatable with a platen is provided near the platen and pins projecting from the pin wheel are fitted in through-holes formed along the opposite side edges of recording paper at the same pitch as the interval between the pins, thereby effecting paper feed. 
     This pin feed mechanism is generally classified into two types, i.e., the pull type as shown in FIG. 1 of the accompanying drawings and the push-in type as shown in FIG. 2 of the accompanying drawings. 
     In a pull type mechanism recording paper 1 is guided along a paper guide 2 and between a platen 3 and a recording head 4, the recording paper 1 is urged against the platen 3 by a bail roller 6, the pins 5aof a pin wheel 5 are fitted into the feed holes of the recording paper and the recording paper is pulled and thereby fed. Designated by 4a is a recording portion which effects recording on the recording paper 1. 
     Denoted by 7 in FIG. 1 is a carriage carrying the recording head 4 thereon, and recording is effected while the carriage 7 is moved along a guide shaft 8. When recording of one line is completed, the pin wheel 5 is rotated by a predetermined angle by the drive force from a drive source (not shown), and the recording paper is fed by an amount corresponding to one line. Where such a pull type pin wheel mechanism is used, if an attempt is made to feed the recording paper in reverse, there is the possibility of the feeding of the recording paper becoming unstable. 
     Also, the distance from the upper end of the recording paper to the recording starting position is required to be equal to at least the distance from the recording portion to the pin wheel, and this leads to the problem that the recording paper cannot be used effectively. 
     In such a pull type pin feed mechanism, the pin wheel is situated on the outlet side of the recording paper, whereas in the push-in type pin feed mechanism, the pin wheel is situated on the recording paper side as shown in FIG. 2. 
     In FIG. 2, portions identical or corresponding to those in FIG. 1 are given similar reference characters and need not be described. 
     In a push-in type pin feed mechanism, the pin wheel is situated on the inlet side of the recording paper and therefore, the recording starting position of the recording paper is at a very short distance from the upper end of the recording paper and thus, the recording paper can be used effectively. However, in a push-in type pin feed mechanism, the recording paper is pushed in and paper feed is effected by resorting to the rigidity of the recording paper and therefore, if the distance from the pin wheel to the recording position is long, there is the possibility of the conveyance of the recording paper becoming unstable. 
     Also, in the push-in type pin feed mechanism, the recording paper 1 is urged against the platen 3 by the bail roller 6, and the friction feed of the platen 3 rotated for the conveyance of the recording paper is combined with the friction of the conveyance force of the push-in by the pin wheel 5, but adjustment of the strengths of the two conveying forces is difficult and also is liable to be affected by the kind, temperature, etc. of the recording paper, and this also leads to the possibility of the conveyance of the recording paper becoming unstable. 
     Also, both the pull type pin feed mechanism and the push-in type pin feed mechanism require a considerable installation space, and this hinders to the compactness of the recording apparatus. 
     To solve such problems, a structure as shown in FIGS. 3 and 4 of the accompanying drawings has been proposed. 
     Designated by 9 in these Figures is a pin wheel to which a rotational force is transmitted by a drive source, not shown, through a feed shaft 10. A plurality of through-holes 9a are formed in the pin wheel 9 at predetermined angular intervals circumferentially thereof, and a pin 11 is slidably fitted in each of the through-holes 9a. A fixed cam 12 is disposed on the outer side of the pin wheel 9, as shown in FIG. 4, and a rail portion 12a is provided on the inner side of the fixed cam 12. 
     Two projections 11a and 11a provided on the sides of each pin 11 sandwich the rail portion 12a therebetween, and with rotation of the pin wheel 9, the pins 11 move into and out of the pin wheel 9. 
     This reciprocation of pins 11 is determined by the shape of the rail portion 12a. 
     In the example shown, when the pins come to the recording head 4 side, the pins move into the pin wheel 9. Also, the pins are adapted to protrude from the pin wheel when they are at a position far from the recording head 4. Thus, under the pin wheel 9, the recording paper 1 is nipped between the pin wheel 9 and the paper guide 2 so that the feed holes do not come off the pins 11. Above the pin wheel 9, the recording paper 1 is nipped between a paper keeper 13 and the pin wheel 9 so that the feed holes do not come off the pins 11. It is for the purpose of avoiding the interference with the recording head 4 that on the recording head side, the pins 11 move into the pin wheel. 
     As shown in FIG. 4, a pin feed body 14 is disposed on the inner side of the pin wheel 9, and with the aforementioned fixed cam 12, it is prevented from rotating by a pin feed guide shaft 15. 
     The pin wheel 9 is disposed at each end of the platen 3 and therefore, if such a structure is adopted, pin feed is effected near the recording position and the mating of the feed holes of the recording paper and the pins is possible upstream and downstream of the recording position. Also, both during forward rotation and during reverse rotation, stable conveyance of the recording paper can be realized, and the distance from the upper end of the recording paper to the recording starting position becomes shorter and the recording paper can be utilized effectively. 
     Also, the pin wheels can be disposed coaxially with the platen and therefore, the installation space can be reduced and compactness of the device can be realized. 
     However, in spite of the above-described advantages, the pin feed mechanism in which the pins move into and out of the pin wheel suffers from the following problem. 
     That is, the pins protruding under the pin wheel 9 are situated at a position which cannot be seen by the user. Therefore, the user must fit the pins into the feed holes when he or she sets recording paper, but it is difficult and cumbersome to do it at a position which cannot be seen. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a sheet conveyor in which the operability of sheet mounting is improved. 
     It is another object of the present invention to provide a sheet conveyor which can convey a sheet accurately to a predetermined position. 
     It is still another object of the present invention to provide a sheet conveyor which can easily mount a sheet thereon. 
     It is yet still another object of the present invention to provide a sheet conveyor in which the amount by which the pins protrude can be changed and when recording paper is to be set, the pins are retracted to accomplish reliable setting of the recording paper and after the recording paper has been set, the pins protrude to ensure the engagement of the pins with the recording paper and thereby enable reliable conveyance to be accomplished. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 and 2 are side views of pins feed mechanisms according to the prior art. 
     FIG. 3 is a longitudinal cross-sectional view of a pin feed mechanism according to the prior art. 
     FIG. 4 is a perspective view of the pin feed mechanism. 
     FIG. 5 is a longitudinal cross-sectional view showing recording paper as it is set. 
     FIG. 6 is a longitudinal cross-sectional view showing the recording paper as it is conveyed. 
     FIG. 7 is a perspective view of a cam portion. 
     FIG. 8 is a perspective view of a recording paper conveyor using an embodiment of the present invention. 
     FIG. 9 is a perspective view of a cam portion. 
     FIG. 10 illustrates a cam portion using another embodiment. 
     FIG. 11 is an enlarged transverse plan view of the cam portion. 
     FIG. 12 is a longitudinal cross-sectional side view showing the recording paper as it is set. 
     FIG. 13 is a longitudinal cross-sectional side view showing the recording paper as it is conveyed. 
     FIG. 14 is a longitudinal cross-sectional side view showing the recording paper as it is set. 
     FIG. 15 is a longitudinal cross-sectional side view showing the recording paper as it is conveyed. 
     FIG. 16 is a side view showing the recording paper as it is set. 
     FIG. 17 is a longitudinal cross-sectional side view showing the recording paper as it is set. 
     FIG. 18 is a side view showing the recording paper as it is conveyed. 
     FIG. 19 is a longitudinal cross-sectional side view showing the recording paper as it is conveyed. 
     FIGS. 20 and 21 are cross-sectional views showing the state of a pin feed type sheet conveyor during the insertion of a sheet thereinto. 
     FIGS. 22 and 23 are cross-sectional views showing the state of the conveyor during the setting of the sheet. 
     FIGS. 24 and 25 are cross-sectional views showing the state of a sheet conveyor according to another embodiment during the insertion of a sheet thereinto. 
     FIGS. 26 and 27 are cross-sectional views showing the state of the conveyor during the setting of the sheet. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will hereinafter be described in greater detail with respect to some embodiments thereof. 
     In a printer having pin wheels fixed to the opposite ends of a platen coaxially therewith, the embodiments described hereinafter are of a structure in which pins are slidably provided radially on the pin wheels and cam means capable of adjusting the amount of protrusion of these pins from the pin wheels is provided, which is extraneously operably. 
     If the structure as described above is adopted, the amount by which the pins protrude from the pin wheels can be adjusted simply by operating the cam means, and during the setting and conveyance of recording paper, the amount by which the pins protrude can be adjusted to thereby enable reliable setting and conveyance of the recording paper to be accomplished. 
     The details of the present invention will hereinafter be described with respect to the embodiments thereof shown in the drawings. 
     FIGS. 5 to 9 illustrate a first embodiment of the present invention. In these Figures, members similar or corresponding to those in FIGS. 1 to 4 are given the same reference characters and need not be described. 
     FIG. 5 is a longitudinal cross-sectional side view showing recording paper as it is set, FIG. 6 is a longitudinal cross-sectional side view showing the recording paper as it is conveyed, FIG. 7 is a perspective view of a cam, FIG. 8 is a perspective view of a sheet conveyor, and FIG. 9 is a perspective view of a cam according to another embodiment. FIGS. 5 and 6 show a state in which an outer wall 20a (shown in FIG. 8) has been removed, and in these Figures, a rail portion is additionally shown to make the invention easy to understand. Although not shown in FIG. 8, feed rollers are provided on the opposite ends of the platen. 
     Reference numeral 9 designates a pin wheel having a plurality of holes 9a provided radially. A cylinder-like pin 11 is slidably fitted in each of these holes 9a and can protrude from or retract into the hole 9a. Each of the pins 11 has a projection 11a provided on the peripheral surface thereof. In FIG. 5, pins a, b and h protrude from the holes 9a and pins c, d, e, f and g are retracted into the holes 9a. The pin wheel 9 is sandwiched between a pair of outer walls 20a and 20b and is rotatably mounted relative to the outer walls 20a and 20b. This pin wheel 9 is rotated by the drive force of a motor M transmitted thereto by a shaft 10. The drive force of the motor M is transmitted to the shaft 10 through a drive gear G1 and a feed gear G2. 
     On the other hand, cams 12 and 16 are provided inside the outer wall 20a. The cam 12 is fixed to the outer wall 20a, while the cam 16 is movable relative to the outer wall 20a. 
     In the present embodiment, the fixed cam 12 is semicircular and a side surface thereof is provided with a rail portion 12a, and the semicircular movable cam 16 is vertically movably and provided below the fixed cam 12, and the outer side surface thereof is provided with a semicircular rail portion 16a. 
     Cut-away portions 12b and 16b are provided in the opposite ends of the rail portions 12a and 16a, respectively, and by these cut-away portions overlapping each other, the two rail portions 12a and 16a are engageable with each other. 
     The cut-away portions 12b and 16b are formed in the straight portions 12c and 16c at the opposite ends of the rail portions 12a and 16a, and these straight portions 12c and 16c are situated on the side opposed to a recording head and the side opposite thereto. 
     Since the rail portions 12a and 16a are fitted between the projections 11a of the pins 11, the pins 11 are vertically movable in the holes 9a along the outer peripheries of the rail portions 12a and 16a. 
     When recording paper 1 is to be mounted on the sheet conveyor 21 under the above-described structure, the operator touches the movable cam 16 from the outside of the outer wall and raises the movable cam 16 upwardly as shown in FIG. 5, thereby making the cut-away portions 12b and 16b of the rail portions 12a and 16a overlap each other. 
     If this is done, the shape of the rail portions 12a and 16a will be varied into a shape in which the lengths of the straight portions 12c and 16c have been shortened as viewed in the general tracks of the rail portions. 
     In this state, as shown in FIG. 5, the rail portion 12a is situated upwardly and the rail portion 16a is also situated upwardly and as a whole, the rail portions are in their upwardly moved positions. As a result, the pins 11 protrude from the holes 9a only on the upper side of the pin wheel. In the Figure, the pins a, b and h protrude from the holes 9a and the pins c, d, e, f and g are retracted into the holes 9a. 
     Accordingly, even if the recording paper 1 is inserted between the paper guide 2 of the printer body and the pin wheel 9, there is no protrusion of the pins 11 below the pin wheel 9, thus permitting smooth passage of the recording paper. 
     If the recording paper 1 thus directed to between the guide 2 and the pin wheel 9 is placed above the pin wheel 9 and the pins 11 are fitted into feed holes 1a (provided at the opposite ends relative to the direction in which the recording paper 1 is conveyed) with a paper keeper 13 raised upwardly and then the paper keeper 13 is lowered, the setting of the recording paper 1 to the sheet conveyor 21 will be completed. 
     If subsequently, the movable cam 16 is lowered as shown in FIG. 6, the amount by which the rail portions 12a and 16a overlap each other will decrease and the entire rail portions will take a shape in which their straight portions have become longer. 
     As a result, the pins 11 will protrude also below the pin wheel 9 and will come to be fitted in the feed holes 1a of the recording paper. 
     Thus, above and below the pin wheel 9, the pins 11 are fitted in the feed holes, thereby permitting stable feeding of the recording paper 1. Thereupon, a clear corresponding to image information is formed on the recording paper 1 by the recording head 4. 
     Operation of the movable cam may be effected through a lever or the like provided integrally with the movable cam 16, although not shown, and the above-described setting of the recording paper may be accomplished by a very simple operation. 
     The movable cam is changed over to the recording paper setting position and the recording paper conveying position in this manner, whereby it becomes possible to accomplish reliable setting and conveyance of the recording paper. 
     Another embodiment of the cam will now be described with reference to FIG. 9. 
     This embodiment enables the vertical movement of the movable cam 16 relative to the fixed cam 12 to be accomplished more accurately at a predetermined position. 
     In the present embodiment, cut-aways 12d are provided in the opposite end portions of the fixed cam 12 and guides 16d fitting in the cut-aways 12d are provided at the upper ends of the movable cam 16. Thus, according to the present embodiment, the movable cam 16 can vertically move at a predetermined position without causing positional deviation relative to the fixed cam 12. 
     Further, in the present embodiment, a dowel 16e is provided at a side edge of the movable cam 16 and this dowel 16e projects from a slot 20c in the outer wall 20a so that the operator may grasp the dowel 16e and thereby vertically move the movable cam 16. Thereby, the operation of vertically moving the movable cam is improved. 
     The sheet conveyor 21 shown in FIG. 8 is an example in which such dowel 16e is provided. 
     FIG. 10 illustrates still another embodiment of the present invention. In this embodiment, parallel auxiliary rail portions 16f and 16f project and are provided at the left and right of the opposite ends of the rail portion 16a of the movable cam 16 (not shown). 
     These auxiliary rail portions 16f and 16f are provided in the portion where the rail portions 12a  and 16a overlap each other, and the spacing between the two is set so as to be capable of guiding the outer sides of two projections 11a and 11a provided on and projecting from the pin 11. 
     If such a structure is adopted, the rail portion 16a moves up as indicated by the dotted line during the setting of the recording paper and the orbit of the pin 11 is determined with the rail portions 12a and 16a being nipped between the two projections 11a and 11a of the pin; but the rail portion 16a moves down during the conveyance of the recording paper and the orbit of the pin 11 is determined by the auxiliary rail portions 16f and 16f nipping the projections 11a and 11a from the outside thereof. 
     Adoption of such a structure also leads to an effect similar to that of the aforedescribed embodiment. 
     The auxiliary rail portions may also be provided on the fixed cam side. 
     FIG. 11 illustrates yet still a further embodiment of the present invention. In this embodiment, the movable cam 16 and the fixed cam 12 are provided in parallel and overlapping relationship with each other, and the rail portions 12a and 16a are also provided in opposed relationship with each other. 
     Two projections 11a sandwiching the rail portions 12a and 16a therebetween are provided on each side of the pin 11. 
     Adoption of such a structure also enables the movable cam 16 to be vertically moved and the pin 11 to be reliably guided. 
     FIGS. 12 and 13 illustrate yet still a further embodiment of the present invention. In this embodiment, the rail portion 16a of the movable cam (not shown) is made pivotable about a shaft 16d relative to the rail portion 12a of the fixed cam (not shown), and the portions of the outer ends of the rail portions 12a and 16a which overlap each other are provided along a circular locus about the shaft 16d. 
     Where such a structure is adopted, the rail portion 16a is pivoted about the shaft 16d through a movable cam during the setting of recording paper so that the portion of one end of the rail portion 12a and the portion of one end of the rail portion 16a which overlap each other may be wider, as shown in FIG. 12. 
     Thereupon, the lower portion of the rail portion 16a moves upwardly and under the pin wheel 9, the pins 11 do not protrude. 
     Accordingly, the recording paper 1 can be set freely. 
     On the other hand, during the conveyance of the recording paper, if the rail portion 16a is pivoted counter-clockwise about the shaft 16d as shown in FIG. 13 to thereby reduce the length of the portion of the one end of the rail portion 12a and the portion of the one end of the rail portion 16a which overlap each other, the lower portion of the rail portion 16a will become situated at a low position and under the pin wheel 9 also, the pins 11 will protrude from wheel 9, and thus, in the upper and lower portions of the pin wheel 9, the pins 11 can be fitted into feed holes 1a, thereby enabling the recording paper to be fed reliably in either direction. 
     Adoption of such a structure also leads to an effect similar to that of the above-described embodiments. 
     FIGS. 14 and 15 illustrate another embodiment of the present invention. In this embodiment, a movable cam 30 is provided for rotation relative to a boss 10a fitted to a shaft 10. 
     Respective pins 11 are normally urged against the cam surface 30a of the movable cam 30 by a spring 17. 
     The present embodiment is constructed as described above and therefore, during the setting of recording paper, when the movable cam 30 is rotated so that the major axis thereof becomes horizontal, the lower portion of the movable cam 30 provides the minor axis and under the pin wheel 9, the pins 11 do not protrude from the pin wheel 9. 
     When the movable cam 30 is rotated counterclockwise by 90° as shown in FIG. 15 after the setting of the recording paper has been completed in this state, the major axis thereof becomes vertical and therefore, above and below the pin wheel 9, the pins 11 protrude to enable paper feed to be reliably accomplished. 
     In the embodiment shown in FIGS. 14 and 15, there is shown a structure in which the pins 11 are urged toward the movable cam 30 by the spring 17, but alternatively, a structure may be adopted in which a rail portion is provided on the movable cam 30 and the rail portion is sandwiched between two projections provided on each pin 11. 
     Now, each of the above-described embodiments have been shown by taking as an example a serial printer in which recording is effected while the carriage is moved in a direction orthogonal to the direction in which recording paper is fed, but the present invention is equally applicable to a line printer in which recording is effected in the direction in which recording paper is fed. 
     Also, the present invention is likewise applicable to a printer such as a wire dot printer, an ink jet printer or a thermal printer if they are provided with a pin feed mechanism. 
     Still another embodiment will hereinafter be described with reference to FIGS. 16 to 18. 
     The embodiment described hereinafter is one in which pins are slidably provided radially in the pin wheel and a cam member for adjusting the amount by which these pins protrude is provided and operatively associated with a bail roller. 
     Designated by 36a in the Figures is a bail roller shaft. The bail roller shaft 36a has its lower end journalled to the upper end of a bail roller arm 47 pivotally supported about a shaft 48. The shaft 48 can serve also as the guide shaft of the carriage. A plurality of bail rollers 36 are provided at intervals on the bail roller shaft 36a. The bail rollers 36 urge recording paper 1 against the platen 3. 
     One end of an arm gear 49 is pivotally connected to the bail roller shaft 36a. The arm gear 49 is in mesh engagement with the gear portion 50a of a cam gear 50 rotatably journalled to the round shaft portion 40a of a feed shaft 40 so that the cam gear 50 is rotated to the left and right through the arm gear 49 by the pressure contact and separation of the bail rollers 36 with respect to the platen 3. Also, in a portion of the cam gear 50, there is formed a cam slot 50b with a predetermined locus. In the embodiment illustrated, the cam slot 50b is voluted. 
     A movable cam 46 is formed in a U-shape and has one end thereof pivotally supported about a shaft 46c, and a projection 46d fitted in cam slot 50b is provided substantially at the center of the movable cam. A rail portion 46a is also provided on the movable cam 46, and the free end of the movable cam 46 and one end of the rail portion 42a of a fixed cam 42 overlap each other as shown, for example, in FIG. 7, and the rail portions 42a and 46a together form a predetermined track. 
     Operation of the present embodiment constructed as described above will now be described. 
     During the setting of recording paper 1, the bail rollers 36 are rotated clockwise about the shaft 48 as viewed in FIG. 16. As a result, the arm gear 49 is also rotated clockwise and the cam gear 50 is also rotated in the same direction. At this time, the projection 46d of the movable cam 46 comes to lie on that side of the cam slot 50b which is nearest to the feed shaft 40 and the lower portion of the movable cam 46 assumes its most elevated position. 
     Accordingly, as shown in FIG. 17, the pin 41 is in a state in which it does not protrude under the pin wheel 39. In this state, the recording paper may be inserted into the setting position. Designated by 42 is a fixed cam. 
     Subsequently, as shown in FIGS. 18 and 19, the bail rollers 36 are rotated in a direction in which they are urged against the platen, i.e., in a counterclockwise direction as viewed in FIG. 18. As a result arm gear 49 is moved forward and the cam gear 50 is rotated counter-clockwise and thus, the projection 46d of the movable cam 46 is guided to the position of the cam slot 50b which is remotest from the feed shaft 40. 
     As a result, the lower portion of the movable cam 45 is moved to its lowermost position as shown in FIG. 19, and under the pin wheel 39, the pins 41 protrude and are fitted into the feed holes of the recording paper 1. 
     In this manner, the amount of protrusion of the pins of the pin wheel is changed in conformity with the pressure contact and separation, respectively, of the bail rollers with respect to the platen to thereby enable reliable setting and conveyance of the recording paper to be accomplished. 
     Although the above-described embodiment has been shown with respect only to an example in which the present invention is applied to a so-called serial printer, the present invention can be applied to any of line printers and dot printers which adopt a pin feed system. 
     As is apparent from the foregoing description, the present embodiment adopts a structure in which cam means for adjusting the amount by which the pins of the pin wheel protrude is provided and operatively associated with the pressure contact state and the separated state of the bail rollers with respect to the platen. Therefore, the amount by which the pins of the pin wheel protrude can be automatically adjusted to the set state and the conveyance state of the recording paper simply by moving the bail rollers and thus, the operation of setting the recording paper is greatly simplified. 
     Still another embodiment of the present invention will hereinafter be described with reference to FIGS. 20 to 27. 
     The embodiment described hereinafter is a pin feed type sheet conveyor in a recording apparatus characterized in that the protrusion and retraction of pins engaged with the feed holes of a sheet are made variable and the protrusion and retraction of the pins are operatively associated with the opening-closing of the sheet keeper of a pin feed device. 
     The present embodiment will hereinafter be described more specifically with reference to FIGS. 20 to 27. 
     FIGS. 20 to 23 show the pin feed type sheet conveyor according to an embodiment of the present invention. 
     FIGS. 20 and 21 show cross-sections of the sheet conveyor when a sheet has been inserted thereinto. 
     A sheet keeper 58 rotates about a sheet keeper shaft (in the example shown, a pin feed guide shaft) 64 and assumes an opened position (FIG. 20) along the peripheral surface of a feed roller 51 and a closed position (FIG. 22) retracted from said opened position. An arm gear 67 is formed integrally with the sheet keeper 58, and a gear portion 67A, arcuately shaped about the sheet gear shaft 64, is formed on the arm gear 67. The sheet keeper 58 is adapted to cause a sheet 56 to travel along the peripheral surface of the feed roller 51. 
     A cam gear 68 is rotatably supported on the round shaft portion 52A of a feed shaft 52, and rotation is transmitted thereto by the arm gear 67 through the gear portion 68A of the cam gear 68. That is, the cam gear 68 is adapted to rotate to the left and right in conformity with the opening and closing of the sheet keeper 58. A cam slot 68B is formed in the cam gear 68 so that the distance of a cam projection 65B provided on a movable cam 65 (FIG. 21) from the center of the round shaft portion 52A of the feed shaft 52 is varied in accordance with the rotation of the cam gear 68. In FIG. 20, the cam gear 68 is rotated clockwise and the cam projection 65B is set to a position near the round shaft portion 52A of the feed shaft by the cam slot 68B. 
     The movable cam 65 provided with the cam projection 65B is rotatable about a center of movement 65C (FIG. 21). Designated by 63 is a pin feed body. 
     In FIGS. 20 and 21, the cam projection 65B is drawn toward the center of the round shaft portion 52A of the feed shaft by the cam slot 68B and the movable cam 65 is generally drawn up. Therefore, a movable cam rail portion 65A provided on the movable cam 65 is also drawn toward the center of the feed shaft and forms a generally pulled up track. Pins 53 generally revolve about the feed shaft 52 with the rotation of a pin feed roller 51. Also, the pins 53 are slidable radially along the concave pin guide portions 51A of the pin feed roller 51, and pin projections 53A are provided at the opposite sides of the rail portions 54A and 65A of fixed cam 54 and movable cam 65 and therefore, the orbits of the pins 53 (the protrusion from and retraction into the guide portions 51A) are determined by the fixed cam rail portion 54A and the movable cam rail portion 65A. 
     In FIGS. 20 and 21, the movable cam rail portion 65A is in its pulled up state and therefore, the orbits of the pins 53 are in their retracted state in the lower portion of the pin feed roller 51. 
     As described above, by the sheet keeper 58 being brought into its opened state, the movable cam 65 is brought into its pulled up state through the arm gear 67 and the cam gear 68, and the orbits of the pins 53 are in their retracted state in the lower portion of the pin feed roller. Accordingly, in the position of FIGS. 20 and 21, the insertion of the sheet 56 into a path 70 can be accomplished easily and smoothly. 
     FIGS. 22 and 23 show the state after the setting of the sheet 56 has been completed. 
     When the sheet keeper 58 is closed, the arm gear 67 rotates the cam gear 68 counterclockwise about the round shaft portion 52A of the feed shaft. Therefore, by the cam slot 68B formed in the cam gear 68, the cam projection 65B of the movable cam 65 is downwardly move away from the axis of the feed shaft 52. 
     Accordingly, the movable cam 65 rotates about the center of movement 65C and the movable cam rail portion 65A provided on the movable cam 65 is generally pulled down. 
     With the movable cam rail portion 65A being thus pulled down, the orbits of the pins 53 become protruded in the lower portion. 
     The orbits in the portion where the fixed cam rail portion 54A and the movable cam rail portion 65A overlap each other depict an arc about the center of rotation 65C of the movable cam, whereby the overlapping of the fixed cam rail portion 54A and the movable cam rail portion 65A may be accomplished by the change-over of the pulling-up and the pulling-down of the movable cam 65. 
     FIGS. 24 to 27 show a pin feed device according to a further embodiment of the present invention. 
     FIGS. 24 and 25 show cross-sections of the pin feed device when a sheet has been inserted thereinto. 
     A sheet keeper 58 is mounted relative to a pin feed body 63 for upward and downward movement along a guide 71, and the operator may raise the sheet keeper 58 to thereby open it, and may depress the sheet keeper 58 to thereby close it. 
     A movable cam 65 in the lower half portion is mounted for upward and downward movement in a manner similar to what has been described previously. 
     Cam projections 65B are provided at two left and right locations on the movable cam 65, and these cam projections 65B protrude toward the sheet keeper 58 through a slot 72 formed in the pin feed body 63. 
     Engaging portions 73A and 73B, engaging the respective cam projections 65B, are provided on the sheet keeper 58. Thus, by moving up and down (opening and closing) the sheet keeper 58, the movable cam 65 can be moved up and down by a predetermined amount. 
     In FIGS. 24 and 25, the cam projection 65B is raised by the engaging portion 73A and drawn toward the center of a feed shaft 52, and along therewith, a movable cam rail portion 65A provided on the movable cam 65 is also moved up, whereby the amount of overlap thereof with a fixed cam rail portion 54A is increased. 
     Pins 53 generally revolve about a feed shaft 52 with the rotation of a pin feed roller 51 and are slidable radially along the pin guide portions 51A of the pin feed roller 51, and pin projections 53A are provided at the opposite sides of a fixed cam rail portion 54A and a movable cam rail portion 65A. Therefore, the orbits (protrusion and retraction) of the pins 53 are determined by these rail portions 54A and 65A. 
     In FIGS. 24 and 25, the movable cam 65 is pulled up through the cam projections 65B and the movable cam rail portion 65A is also pulled up and therefore, the orbits of the pins 53 are retracted in the lower portion of the pin feed roller 51. 
     As described above, by opening the sheet keeper 58, the orbits of the pins can be retracted in the lower portion, whereby the insertion of a sheet 56 can be accomplished easily and smoothly. 
     FIGS. 26 and 27 show the state after the setting of the sheet 56 has been completed. 
     By closing (depressing) the sheet keeper 58, the cam projection 75B is depressed by the engaging portion 73B. Accordingly, the movable cam 65 is depressed and the movable cam rail portion 65A is also depressed and thus, the amount of overlap thereof with the fixed cam rail portion 54A is decreased as shown. 
     With this depression of the movable cam rail portion 65A, the pins 53 protrude in the lower portion of the pin feed roller 51. 
     According to each of the above-described embodiments, the pins 53 on the sheet insertion side (the lower portion of the pin feed roller 51) are retracted or extended in response to the movement of the sheet keeper 58, which is opened and closed during the insertion, removal and setting of the sheet 56. Therefore, in the pin feed device of the present invention in which the protrusion and retraction of the pins 53 engaged with the feed holes of the sheet 56 can be varied, the operation during the setting of the sheet can be mitigated and the setting of the sheet can be accomplished easily and stable conveyance of the sheet can be realized. 
     In the above-described embodiment, there has been shown the case of the serial type recording apparatus in which recording is effected while the recording head is moved by the carriage 60, but each of the above-described embodiments is equally applicable to a line type recording apparatus in which recording is effected line by line, to a a page print type recording apparatus in which recording is effected page by page, and to a color recording apparatus having a plurality of recording heads. 
     The above-described embodiments are also applicable to any recording apparatuses provided with a pin feed device, such as a wire dot type recording apparatus, a ink jet type recording apparatus and a thermal recording apparatus. Further, in the above-described embodiments, there has been shown an example in which feed holes are formed in the opposite side edge portions of the sheet, whereas the present invention is not restricted thereto, and can be applied to a device in which the feed holes may be formed, for example, in a row in the center of the sheet. 
     As is apparent from the foregoing description, according to the present invention, there is provided a pin feed device in a recording apparatus in which the operation during the sheet setting can be mitigated and the sheet setting can be accomplished easily and stable sheet conveyance can be realized. 
     In the above-described embodiments, cylinder-like pins have been described as an example of the members engaged with the feed holes of the sheet, but the present invention is not restricted thereto, the members may be, for example, of a rectangular parallelo-piped shape or the like. Also, in the above-described embodiments, a feed roller has been described as an example of the means for holding the feed pins, but the present invention is not restricted thereto said; the feed pins holding means may be, for example, an endless belt or the like. Further, in the above-described embodiments, the operating means for extraneously adjusting the amount by which the pins protrude has been shown as serving also as a bail roller arm or a sheet keeper, but the present invention is not restricted thereto; the operating means may be operatively associated with another member.