Successive sheet feed mechanism

Abstract: Mechanism which is able to set a sheet in a simple operation and is also able to provide a positive sheet feed operation. A first tractor (100) is slidably mounted onto a drive shaft (14) and a guide shaft (15) respectively disposed between first and second frames (11 and 12), and a wire (20) passing through the first tractor (100) is stretched between the first and second frames (11 and 12) by use of a tension spring (30). In the first tractor (100), there are provided fixing means (110) for fixing the first tractor (100) to the wire (20) and loosening means (120) which, simultaneously when or after the wire is fixed, produces a loosened portion in the wire (20) at a position thereof nearer to the second frame (12) than the fixed portion of the first tractor (100) and wire (20).

Description: The present invention relates to a successive sheet feed mechanism for use in a printing device such as a printer or the like and, more particularly, to a successive sheet feed mechanism which is able positively to feed successive sheets when the widths of the successive sheets are increased or reduced due to change in temperature, humidity and the like. In general, a conventional successive sheet feed mechanism includes a pair of tractors each having a pin belt and is adapted to bring holes, respectively formed in the two side portions of successive sheets, into engagement with pins provided in the pin belts thereby to feed the successive sheets. In this structure, when the positions of the pair of tractors (that is, pin belts) are fixed, if the widths of the successive sheets are increased or reduced because of change in temperature, humidity and the like, then holes in the successive sheets cannot be engaged with the pins correctly, with the result that the successive sheets cannot be fed positively. In order to solve the above problem, there have been already proposed sheet feed mechanisms in Japanese Patent Laid-Open Publications No. 1-271344 of Heisei and No. 3-216447 of Heisei, respectively. Figure 13 is an explanatory view of the principle of the sheet feed mechanism 1 designates a drive shaft, 2 designates a guide shaft, and 3 is a frame member which is slidably mounted onto the drive shaft 1 and guide shaft 2. Reference 4 designates a tractor which is installed in the frame member 3 and is slidably mounted onto the drive shaft 1 and guide shaft 2. The tractor 4 is energised in a direction of X1 shown in figure 13 by a spring 5 provided between the frame member 3 and the tractor 4. Reference 6 stands for successive sheets and 6a points out holes respectively formed in the two side portions of the successive sheets 6. Reference 4a designates pins provided on a pin belt to be engaged with the holes 6a, 4b stands for a cover plate for guiding the successive sheet 6 in such a manner that it loosely holds the two side portions of the successive sheet between the pin belt and itself, and 4c points out an elongated hole formed in the cover plate 4b for escape of the pin 4a. Reference 7 designates a lock mechanism which is used to fix the frame member 3 to the guide shaft 2 in an unslidable manner. In figure 13, only the left one of the pair of tractors is shown and the other tractor does not include the frame member but is fixed to the drive shaft 1 and guide shaft 2. To set the successive sheet 6 to this sheet feed mechanism, at first, one set of side holes (the right side holes in figure 13) in the successive sheet is set to one tractor (not shown) which is fixed. Then, as shown in figure 14(a), with the lock mechanism 7 unlocked, the frame member 3 and tractor 4 are slid along the shafts 1 and 2 thereby to bring the pins 4a of the tractor 4 into engagement with the holes 6a of the successive sheet 6, and then the cover plate 4b is closed. After that, as shown in figure 14(b), the frame member 3 is pulled in a direction of an arrow c, to produce a clearance S between the frame member 3 and tractor 4. In this state, the frame member 3 is locked by the lock mechanism 7 and then the successive sheet is set. The successive sheet 6 set in this manner always receives a tensile force given by the spring 5 for spreading the width W of the sheet. Therefore, even if the width W of the successive sheet 6 is extended or contracted due to change in temperature, humidity and the like, the extension or contraction is absorbed by the sliding of the tractor 1, so that the successive sheet 6 can be fed positively. However, in the above-mentioned conventional sheet feed mechanism, it is necessary to provide the frame member 3, which makes the mechanism complicated. Now, the sheet feed mechanism disclosed in Japanese Patent Laid-Open Publication No. 3-216447 of Heisei aims at eliminating the above-mentioned problem. As shown in figure 15, in this mechanism, a tractor 8 includes a tractor main body 8a and a pin belt 8b. In particular, the tractor main body 8a is used as the above-mentioned frame member 3 and the pin belt 8b is arranged such that it is movable with respect to the tractor main body 8a. Also, a spring 8c is interposed between the tractor main body 8a and a pulley over which the pin belt 8b is extended. Any of the above-mentioned conventional sheet feed mechanisms has a problem that, when a proper clearance S is not formed between the tractor 4 and frame member 3 or between the pin belt 8b and main body 8a, the desired operation cannot be obtained. For example, when the clearance S is set small in figure 14(b), then the tractor 4 is not able to follow an increase in width of the successive sheet 6 if the extension is greater than the clearance S. On the other hand, when the clearance S is set large, then the tractor is not able to follow sufficiently a reduction in width of the successive sheet 6. Also, as shown in figure 14(a), when the clearance S is zero because of operator error, the tractor 4 cannot possibly follow an increase in width of the successive sheet 6. When the tractor cannot follow the change in width of the successive sheet, then the sheet cannot be fed positively, as discussed before. That is, in any of the conventional sheet feed mechanisms, if the sheet is not set properly, then the clearance S is caused to vary, which makes it impossible to obtain a desired operation. In other words, to obtain a desired operation, it is necessary to set the sheet so carefully that a proper clearance S can be formed, which means that the sheet setting operation is complicated. Also, while the frame member 3 is being pulled by one hand in a direction of the arrow c against the force of the spring, the lock mechanism 7 must be operated by the other hand, which further complicates the sheet setting operation. In view of the above, the present invention seeks to obviate or mitigate the drawbacks found in the above-mentioned conventional mechanisms. Accordingly, it is an object of the invention to provide a successive sheet feed mechanism which is able to set a sheet by a simple operation and is also able to obtain a positive feed operation. The present invention is a successive sheet feed mechanism, comprising: a drive shaft extending between first and second spaced frames; first and second tractors each including a pin belt supported by said drive shaft and, when driven by said drive shaft, engageable with holes respectively formed in the two side portions of each of successive sheets to thereby be able to feed said successive sheets; a guide member for supporting at least said first tractor of said first and second tractors slidably with respect to said drive shaft; a linear member stretched between said first and second frames and passing through at least said first tractor; tensioning means disposed nearer to said first frame than said first tractor for applying a tension force to said linear member; fixing means disposed in said first tractor for fixing said first tractor to said linear member; and loosening means for producing when or after said linear member and first tractor are fixed to each other by said fixing means, a loosened portion in said linear member at a position thereof nearer to said second frame than the fixed portion of said linear member and first tractor. In an embodiment of the present invention the linear member comprises a wire, thereby improving its durability. One end of the linear member may be fixed to the second frame and the other end may be fixed to the first frame through a tension spring serving as the tensioning means, thus permitting a simple setting operation. One end of the linear member may be fixed to the second frame and the other end thereof is extended through the first frame and is fixed through a tension spring serving as the tensioning means to a third frame disposed at a distance from the first frame, so that the sliding range of the first tractor can be set large. The tension spring interposed between the first and third frames may be covered with a cover member, thus reducing the risk of accidental damage to the tension spring during normal use of the mechanism or during maintenance thereof. A stopper may be provided in the linear member between the tension spring and first frame, which stopper is allowed to come into contact with the first frame to thereby restrict the extension of the tension spring when the linear member is pulled toward the second frame, and thereby prevent over-extension of the tension spring. Preferably one end of the linear member is fixed to the second frame, the other end thereof is extended through the first frame and is fixed to a weight serving as the tensioning means, and the weight is suspended by the linear member. Preferably, the fixing means includes a lock lever rotatably mounted on the first tractor and capable of taking a lock position and an unlock position, and a holding portion, when the lock lever is rotated to the lock position, for holding and fixing the linear member between the tractor and the fixing means, whereby fixing of the first tractor to the linear member can be achieved more simply by means of the lock lever. Preferably, the loosening means consists of a loosening member which is arranged such that it displaces forcibly the linear member into a projecting shape against the tension force given by the tensioning means at a position nearer to the second frame than the fixing position of the linear member and first tractor when the linear member and first tractor are not fixed to each other by the fixing means, and that, simultaneously with or after the linear member and first tractor are fixed to each other, it removes the forced displacement of the linear member to thereby produce a loosened portion in the linear member. The loosening means may be disposed on the first tractor. The loosening producing means may be formed integrally with the lock lever. In a successive sheet feed mechanism according to the present invention, the successive sheets are fed by the pin belts of the first and second tractors respectively supported by the drive shaft which is extended between the first and second frames. At least the first tractor of the first and second tractors is supported by the guide member in such a manner that it is slidable with respect to the drive shaft and, therefore, by sliding the first tractor, successive sheets of various widths can be set. In the first tractor, there is provided fixing means with the linear member which is extended through the first tractor and between the first and second frames and is used to fix the first tractor to the linear member to which the tension force is given by the tensioning means provided at a position nearer to the first frame than the first tractor. Thanks to this structure, if the first tractor is fixed to the linear member by the fixing means, then the tension force given by the tensioning means acts on the first tractor through the linear member. Even when the tension force acts on the first tractor, if it is assumed that the linear member is not loosened at all between the fixed position of the linear member and first tractor and the second frame, then the first tractor cannot be slid in the direction of the first frame, as the extension of the linear member itself can be ignored. However, according to the present invention, there is provided loosening means which can produce a loosened portion in the linear member on the side thereof nearer to the second frame than the fixed position of the linear member and first tractor simultaneously when or after the linear member and first tractor are fixed to each other by the fixing means. That is, in the present invention, the first tractor can be slid toward the first frame by an amount corresponding to the loosened portion in the linear member produced by the loosening means. Therefore, at first, before the first tractor is fixed to the linear member, if the successive sheet is set to the first and second tractors and then the first tractor is fixed to the linear member by the fixing means, then the tension force given by the tensioning means acts on the first tractor through the linear member and the above-mentioned loosened portion is produced in the linear member thereby to allow the first tractor to be slid toward the first frame and, at the same time, the tensile force by the tensioning means is balanced with the tensile force that is produced in the successive sheet as the reaction force against the former tensile force. In this state, if the width of the sheet is increased due to change in temperature, humidity and the like, then the action of the tensioning means causes the first tractor to slide by an amount corresponding to the increase of the sheet width. On the other hand, if the width of the sheet is reduced, then the tensile force of the sheet causes the first tractor to slide by an amount corresponding to the reduction in width of the successive sheet. As described above, according to the successive sheet feed mechanism of the invention, since the first tractor can be slid according to the increase or reduction in width of the successive sheet, there can be executed a positive sheet feed operation. Also, the setting of successive sheet to the sheet feed mechanism can be achieved by setting the successive sheet to the tractors and after that by executing the operation of the fixing means and the loosening means without requiring a careful operation with respect to the clearance S as in the before-described conventional mechanisms. That is, according to the invention, the setting of the successive sheet can be executed by a simple operation. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a plan view of a first embodiment of a successive sheet feed mechanism according to the invention; Figures 2A and 2B are sectional front views of a first tractor employed in the first embodiment in locked and unlocked positions respectively; Figure 2C is across section on A1 to A1' of figure 2A; Figure 2D is a cross section along A2 to A2' of figure 2A; Figure 2E is a cross section along A1 to A1'of figure 2B; Figure 2F is a cross section along A2 to A2' of figure 2B; Figure 3A is a plan view to explain a sheet setting operation in the first embodiment; Figure 3B is an explanatory view of the operation of the first embodiment; Figure 4 a plan view of a second embodiment of a successive sheet feed mechanism according to the invention; Figure 5 is an enlarged plan view of a first tractor employed in the second embodiment; Figure 6A is a sectional view taken along line a-a of figure 5, showing a view of a lock lever employed in the second embodiment, with the lock lever set in its unlocked position; Figure 6B is a sectional view along line b-b of figure 5, showing the lock lever employed in the second embodiment; Figure 6C is a sectional view along lines c-c of figure 5, showing a view of a lock lever of the second embodiment, with a side frame omitted; Figure 7 is an explanatory view of the operation of the second embodiment; Figure 8 is a partially enlarged view of figure 7; Figure 9A is a sectional view taken along line a-a of figure 5, showing the lock lever set in its lock position; Figure 9B is a sectional view along line b-b of figure 5, showing the lock lever in its locked position; Figure 9C is a sectional view along line c-c of figure 5, showing the lock lever in its locked position with the side frame omitted; Figure 9D is a partially enlarged view of the lock lever shown in figure 9B; Figure 10 is a schematic partial front view of a third embodiment of a successive sheet feed mechanism according to the invention; Figure 11 is a schematic partial front view of a fourth embodiment of a successive sheet feed mechanism according to the invention; Figure 12 is a plan view of a modification of a loosening producing means employed in the invention; Figure 13 is a plan view of a conventional successive sheet feed mechanism; Figures 14A and Figure 14B are explanatory views of a sheet setting operation, to be performed in a conventional mechanism; and Figure 15 is a plan view of another conventional successive sheet feed mechanism. As shown in figures 1 and 2A the successive sheet feed mechanism according to the first embodiment of the invention includes first and second frames 11, 12 disposed at a distance from each other, a drive shaft 14 and a guide shaft 15 respectively provided between the first and second frames 11, 12, first and second tractors 100, 200, a linear member 20 stretched between the first and second frames 11, 12, tensioning means 30, and fixing means 110 and loosening means 120 respectively disposed on the first tractor 100. The first and second frames are respectively formed of the side frames of a printer or a similar device. The drive shaft 14 is rotatably mounted to the first and second frames 11, 12 and can be rotationally driven by a drive mechanism (not shown). The guide shaft 15 is fixed to the first and second frames 11, 12 and serves as a guide member for supporting the first and second tractors 100, 200 in such a manner that they are slidable. The first tractor 100 includes a main body 130 and a side frame 140 fixed to the side portion of the main body 130. The main body 130 incorporates therein a drive pulley (see reference character 132 shown in figure 6A), a driven pulley (not shown), and a pin belt 150 laid over the drive and driven pulleys omitted in Figure 6A and Figure 9A. The drive shaft 14 is inserted through the drive pulley and side frame 140 and the guide shaft 15 is inserted through the driven pulley and side frame 140, so that the first tractor 100 can be slid with respect to the drive shaft 14 and guide shaft 15. The pin belt 150 includes a plurality of pins 151 provided at regular intervals and the pins 151 are engageable with holes (see 6a shown in figure 3) respectively formed in the successive sheet thereby to be able to feed the successive sheet. The pin belt 150 is driven through the drive pulley by the drive shaft 14. Also, in the main body 130, there is provided a sheet holding plate 160 in such a manner that the holding plate 160 can be opened or closed. When closed, the hold plate 160 lightly presses down the sheet from above by means of a spring 161 interposed between the main body 130 and the holding plate 160. Reference character 162 designates an elongated hole which is used to allow the pins 151 to escape. The second tractor 200 is constructed similarly to a general tractor and, in particular, includes a main body 230, drive and driven pulleys, a pin belt 250, and a sheet holding plate 260 which are similar to those in the first tractor 100. Reference character 270 designates a slide lock lever which is used to fix the tractor 200 to the guide shaft 15. The linear member 20 is made of a wire and is inserted through the first tractor 100 and second tractor 200. One end 20b of the linear member 20 is fixed to the second frame 12, while the other end 20a thereof is fixed to the first frame 11 through a tension spring 30 serving as tensioning means. That is, the linear member 20 is stretched between the first and second frames by the tensile force of the tension spring 30. The fixing means 110 provided in the tractor 100, as shown in Figure 2, includes a lock lever 111 rotatably mounted on the side frame 140 and a hold portion 112 formed integrally with the lock lever 111. The lock lever 111 is arranged such that it can take a lock position (a position shown in Figure 2B) and an unlock position (Figure 2A). The hold portion 112, as shown in Figure 2B, is arranged such that it can hold and fix the linear member 20 between a hold portion 141 of the side frame 140 and itself when the lock lever 111 is rotated to its lock position. The loosening means 120 is composed of a loosening member 122 having an eccentric cam shape which is rotatably mounted between the main body 130 and side frame 140 by a shaft 121. The loosening member 122 is linked to the lock lever 111 by a shaft 121 and, as shown in Figure 2A, when the lock lever 111 is set at its unlock position, a larger diameter portion 122a thereof goes in deeply between the main body 130 and side frame 140 to displace the linear member 20 forcibly into a projecting shape against the tensile force of the tension spring 30 (the displaced portion of the linear member 20 is designated by reference character 21). On the other hand, as shown in Figure 2B, when the lock lever 111 is set at its lock position, the larger diameter portion 122a is caused to escape upwardly (see Figure 1) and thus removes the forced displacement of the linear member 20 to thereby produce a loosened portion 22 in the linear member 20. Next, the operation of setting the successive sheet in the above structured successive sheet feed mechanism will be described with reference to Figure 3 as well. The hold plate 260 of the second tractor 200 is opened, the holes 6a respectively formed on the right side of the sheet 6 are fitted with the pins 251 respectively provided on the pin belt 250, and then the hold plate 260 is closed. If necessary, the locking by the slide lock lever 270 may be removed to allow adjustment of the position of the second tractor 200. Similarly, the holes 6a respectively formed on the left side of the sheet are fitted over the pins 151 respectively provided on the pin belt 150 and then the hold plate 160 is closed (see Figure 3A). During this operation, if the lock lever 111 is set at its unlock position (see Figure 2A), then the first tractor 100 can be freely slid in the directions of arrows X1, X2 according to the width of the sheet 6. When the first tractor 100 is slid, then the linear member 20, as shown in Figure 2A, passes through the first tractor 100 bypassing the larger diameter portion 122a of the loosening member 122. At this stage, since the first tractor 100 is not fixed to the linear member 20, the tensile force of the tension spring 30 does not act on the first tractor 100. The lock lever 111 is rotated to its lock position, as shown in Figures 2B and 3B. As a result of this, the linear member 20 is held between the hold portion 112 of the lock lever 111 and the hold portion 141 of the side frame, the first tractor 100 is fixed to the linear member 20 by these hold portions, and the larger diameter portion 122a of the loosening member 122 is caused to escape upwardly to thereby produce a loosened portion 22 in the linear member 20. When the first tractor 100 is fixed to the linear member 20 in this manner, then the tensile force T1 of the tension spring 30 acts on the first tractor 100 through the linear member 20. However, even when the tensile force T1 acts, if it is assumed that the loosened portion 22 is not present in the linear member 20 on the side thereof nearer to the second frame 12 than the fixed portion (that is, the hold portion) of the linear member 20 and first tractor 100, the first tractor 100 cannot be slid toward the first frame, that is, in the direction of the arrow X1, if the extension of the linear member itself is neglected. However, in the successive sheet feed mechanism according to the present embodiment, due to the fact that the loosened portion 22 is produced in the linear member 20 at a position thereof nearer to the second frame 12 than the fixed portion (that is, hold portion), the first tractor 100 can be slid in the direction of the arrow X1 by an amount corresponding to the loosened portion 22. In other words, by rotating the lock lever 111 to its lock position, the tensile force T1 given by the tension spring 30 acts on the first tractor 100, the loosened portion 22 is produced in the linear member 20 thereby to allow the first tractor 100 to slide in the arrow X1 direction, and at the same time the tensile force T1 by the tension spring 30 is balanced with a tensile force (see an arrow T2) produced in the successive sheet 6 as a reaction against the tensile force T1. In this state, if the width of the successive sheet 6 is increased due to change in temperature, humidity and the like, then the first tractor 100, due to the action of the tension spring 30, is slid in the arrow X1 direction by an amount corresponding to the width increase of the successive sheet 6. On the other hand, if the width of the successive sheet 6 is reduced, then the first tractor, due to the action of the tensile force T2 of the successive sheet 6, is slid in the arrow X2 direction by an amount corresponding to the width reduction of the successive sheet 6. As described above, in the successive sheet feed mechanism according to the present embodiment, since the first tractor 100 is slid according to the width increase or reduction of the successive sheet 6, there can be obtained a positive sheet feed operation. And, setting of the successive sheet 6 can be achieved simply by setting the successive sheet 6 to the tractors 100, 200 and after then by operating the lock lever 111, which eliminates the need for such a careful operation with respect to the clearance S using two hands as has been required in the conventional successive sheet feed mechanism. That is, the successive sheet 6 can be set in a simple operation. Figure 4 is a plan view of a second embodiment of a successive sheet feed mechanism according to the invention, Figure 5 is an enlarged plan view of a first tractor employed in the second embodiment, Figure 6A is a section view taken along the arrow line a-a in Figure 5 with the pin belt 150 omitted, Figure 6B is a section view taken along the arrow line b-b in Figure 5, and Figure 6C is a section view taken along the arrow line c-c in Figure 5 (with a side frame omitted). The second embodiment is characterized by its fixing means and loosening means and the remaining portions thereof are similar in structure to those in the first embodiment. Therefore, in Figures 4 to 6, the parts of the second embodiment similar in structure to those in the first embodiment are respectively given the same reference characters and the description thereof is omitted here. In the present embodiment, fixing means 170 provided in a first tractor 100, as shown mainly in Figure 6, includes a lock lever 171 mounted rotatably between the main body 130 and side frame 140, and a hold portion 172 (see Figure 9) formed concentrically and integrally with a cylindrical base portion 171a of the lock lever 171. The lock lever 171 is arranged such that it can take a lock position (a position shown in Figure 9) and an unlock position (a position shown in Figure 6). The hold portion 172 includes a flat portion 172a and an inclined portion 172b adjoining the flat portion 172a. As shown in Figure 9, the hold portion 172 is adapted such that, when the lock lever 171 is rotated to its lock position, it holds and fixes a linear member 20 between the side frame 140 and hold portion 172. The portion of the linear member held by the hold portion 172 is designated by reference character 25 in Figures 9B and D. Figures 7 and 8 are respectively views of a process in which the linear member is held. As shown in Figure 6C, when the lock lever 171 is set at its unlock position, a part 25' of the linear member 20 hangs on the inclined portion 172b of the hold portion 172 and, therefore, if the lock lever 171 is rotated in the locking direction, than the part 25', as shown in Figure 8, is pushed down by the inclined portion 172b and is thus pushed in the direction of the hold portion 145 of the side frame 140. And, when the lock lever 171 is rotated to its lock position, then the part 25' is held by and between the flat portion 172a of the hold portion 172 of the lock lever 171 and the hold portion 145 of the side frame 140, as described above. Here, in Figures 6 and 9, reference character 173 designates an elastic piece formed integrally with the cylindrical base portion 171a of the lock lever 171 to fix the lock lever 171 provisionally at the lock or unlock position with a clicking feeling. In particular, a recessed portion 173a formed in the elastic piece 173 is fitted with a pin 174 formed integrally with the main body 130 or side frame, whereby the lock lever 171 can be provisionally fixed at the unlock or lock position with a clicking feeling. The loosening means employed in the present embodiment is composed of a hook-shaped loosening member (which will be hereinafter referred to as a hook portion) 175 which is formed integrally with and extended from the cylindrical base portion 171a of the lock lever 171. The hook portion 175 is also formed integrally with the above-mentioned hold portion 172. The hook portion 175 includes a hook groove 176 on which the linear member 20 is placed. When the lock lever 171 is set at its unlock position, as shown in Figures 5 and 6, the hook portion 175 hangs up the linear member 20 to forcibly displace the linear member 20 into a projecting shape against the tensile force of the tension spring 30 (the displaced portion is shown by reference character 23). Also, as shown in Figure 9, when the lock lever 171 is set at its lock position, the hook portion 175 moves down to remove the forced displacement of the linear member 20, thereby producing a loosened portion 24 in the linear member 20. Therefore, in the second embodiment as well, simply by rotating the lock lever 171 to the lock position, the linear member 20 can be held between the hold portion 172 of the lock lever 171 and the hold portion 145 of the side frame 140 and, by means of these hold portions, the first tractor 100 can be fixed to the linear member 20 and the loosened portion 24 can be produced in the linear member 20. Also, according to the present embodiment, since the fixing means 170 and loosening means 175 are respectively formed thin between the main body 130 and side frame 140, the first tractor can be made compact. As shown in Figure 6, if the first tractor 100 is slid with the lock lever 171 set at the unlock position, then the linear member 20 is passed within the first tractor 100 via the hook groove 176. In Figure 6B, 131 designates a hole formed in the main body 130 through which the linear member is passed, and 142 stands for a hole formed in the side frame 140 through which the linear member is passed. Figure 10 is a schematic partial front view of a third embodiment of a successive sheet feed mechanism according to the invention. The third embodiment is characterised by the structure of the end portions of the tension spring 30, and the remaining portions of the third embodiment are structured similarly to the first and second embodiments. In the third embodiment, the left end 20a of the linear member 20 is extended through the first frame 11 and is fixed through the tension spring 30 to a third frame 13 provided at a distance from the first frame 11. Also, the periphery of the tension spring 30 is covered with a cover member 16. Reference numeral 26 designates a stopper which is securely fixed to the linear member 20 and also which is adapted to come in contact with the first frame to thereby restrict the extension of the tension spring 30 when the linear member 20 is pulled in the direction of X2. A distance L between the stopper 26 and first frame 11 is set greater than the amount of expected reduction of the successive sheet width due to change in humidity and the like. However, the distance L is also set smaller than the amount of extension that destroys the function of the tension spring 30. According to the above-mentioned structure, the sliding range of the first tractor between the first and second frames 11 and 12 can be set large. Also, the present structure eliminates the possibility that, when the present sheet feed mechanism is in use or is under the maintenance operation, the tension spring can be slipped off or destroyed in error. Further, even when, due to a misoperation, the first tractor 100 is slid in the X2 direction with the lock lever set at the lock position, the stopper 26 comes in contact with the first frame 11 to restrict the sliding movement of the first tractor 100, thereby eliminating the danger that the tension spring can be extended excessively to impair the function thereof. Referring now to Figure 11, there is shown a schematic partial front view of a fourth embodiment of a successive sheet feed mechanism according to the invention. The fourth embodiment is characterised in that a weight 31 is used as tensioning means and the remaining portions of the fourth embodiment are structured similarly to the above-mentioned first and second embodiments. In the present embodiment, the left end 20a of the linear member 20 passes through the first frame 11 and over a pulley 32 and is then fixed to the weight 31, so that the weight 31 is suspended by the linear member 20. According to the structure of the fourth embodiment, a similar effect can be obtained to the first embodiment of the invention, that is, a sheet can be set simply and also a positive sheet feed operation can be executed by a more simplified structure. While the invention has been described heretofore in its preferred embodiments, modification may be made thereto. For example, the loosening means, as shown in Figure 12, may be composed of a lever 180 rotatably mounted onto the side frame 140 and a disk portion 181 formed integrally with the lever 180, whereby when the lever 180 is rotated in a direction of an arrow D, then the disk portion 181 displaces the linear member 20 forcibly into a projecting shape and, when the lever 180 is rotated in a direction of an arrow E, then the disk portion 181 removes the forced displacement of the linear member 20 to thereby produce a loosened portion in the linear member 20. In this case, means for fixing the linear member 20 is provided in the rotational support portion 182 of the lever 180. According to the successive sheet feed mechanism of the invention, the sheet can be set in a simple operation and a positive sheet feed operation can be executed.

Claims: A successive sheet feed mechanism, comprising: a drive shaft (14) extending between first and second spaced frames (11, 12), first (100) and second (200) tractors each including a pill belt (150, 250) supported by said drive shaft (14) and, when driven by said drive shaft, engageable with holes respectively formed in the two side portions of each of successive sheets to thereby be able to feed said successive sheets; a guide member (15) for supporting at least said first tractor (100) of said first and second tractors slidably with respect to said drive shaft (14); a linear member (20) stretched between said first and second frames (11, 12) and passing through at least said first tractor (100); tensioning means (30) disposed nearer to said first frame (11) than said first tractor (100) for applying a tension force to said linear member (20); fixing means (110) disposed in said first tractor (100) for fixing said first tractor to said linear member; and loosening means (120) for producing when or after said linear member and first tractor are fixed to each other by said fixing means, a loosened portion (22) in said linear member at a position thereof nearer to said second frame (12) than the fixed portion of said linear member and first tractor (100). A successive sheet feed mechanism as claimed in claim 1, wherein said linear member is formed of a wire (20). A successive sheet feed mechanism as claimed in claim 1 or claim 2, wherein one end of said linear member is fixed to said second frame (12) and the other end thereof is fixed to said first frame (11) through a tension spring (30) serving as tensioning means. A successive sheet feed mechanism as claimed in claim 1 or claim 2, wherein one end of said linear member is fixed to said second frame (12) and the other end thereof is extended through said first frame (11) and is fixed to a third frame (13) spaced apart from said first frame through a tension spring (30) serving as tensioning means. A successive sheet feed mechanism as set forth in claim 4, wherein said tension spring (30) interposed between said first (11) and third (13) frames is covered with a cover member (16). A successive sheet feed mechanism as claimed in claim 4 or claim 5, wherein a stopper (26) is provided in said linear member (20) between said tension spring and said first frame, for coming into contact with said first frame to restrict the extension of said tension spring when said linear member is pulled towards the second frame. A successive sheet feed mechanism as claimed in claim 1 or claim 2, wherein one end of said linear member (20) is fixed to said second frame (12), the other end thereof is extended through said first frame (11) and is fixed to a weight (31) serving as tensioning means, and said weight is suspended by said linear member. A successive sheet feed mechanism as claimed in any preceding claim, wherein said fixing means (110) includes a lock lever (111) rotatably mounted on said first tractor and capable of taking a lock position and an unlock position, and a hold portion (112) formed integrally with said lock lever for holding and fixing said linear member between said first tractor (100) and said hold portion (112) when said lock lever is rotated to said lock position. A successive sheet feed mechanism as claimed in any preceding claim, wherein said loosening means is composed of a loosening member (122) which is arranged such that it displaces said linear member forcibly into a projecting shape at a position thereof nearer to said second frame than said fixed portion of said linear member and first tractor against the tension force of said tensioning means when said linear member and first tractor are not fixed by said fixing means and also that, simultaneously when or after said linear member and first tractor are fixed, it removes said forced displacement of said linear member to thereby produce a loosened portion in said linear member. A successive sheet feed mechanism as claimed in any one of claims 1 to 9, wherein said loosening means is disposed on said first tractor (100). A successive sheet feed mechanism as claimed in claim 9 when dependent on claim 8, wherein said loosening means is formed integrally with said lock lever.

Inventors: KISHIDA TAKEO C O SEIKO EPSON, KISHIDA, TAKEO, C/O SEIKO EPSON CORPORATION
Applicants: SEIKO EPSON CORP, SEIKO EPSON CORPORATION
Application year: 1993
Main classification: B65H20
IPC codes: B41J11, B65H20