GB1578390A

GB1578390A - Drive mechanism for an endless band

Info

Publication number: GB1578390A
Application number: GB5436777A
Authority: GB
Original assignee: Computer Peripherals Inc
Current assignee: Computer Peripherals Inc
Priority date: 1977-01-24
Filing date: 1977-12-30
Publication date: 1980-11-05
Also published as: DE2802644A1; CA1104874A; JPS5393924A; FR2377956A1

Description

(54) DRIVE MECHANISM FOR AN ENDLESS BAND (71) We, COMPUTER PERIPHERALS INC., of 1480 N. Rochester Road, Rochester, Michigan 48063, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a drive mechanism for an endless band, in particular a print band, for use in a high-speed printer.

In the field of high speed printers, the drum printer has proved to be very successful in providing a rotating surface against which print hammers impact the characters carried on such surface. However, the need for a reduction in weight along with compactness in size and decrease in cost has brought about the endless print band which carries the type characters in a line along the print station and past the print hammers. Such print hammers are constructed in a bank which includes hammer drive solenoids for causing the hammers to be driven against the type characters on the band in a sequence dictated by the desired printing program.

The print band is trained around a drive pulley and a driven or idler pulley normally in horizontal manner, such pulleys being crowned to provide a tracking surface for the band.

A requirement in such arrangements is that the drive pulley and idler pulley should be movable relative to one another to provide uniform band tension during operation while permitting simple changing of the print band and allowing for variations in band length.

Thus according to one aspect of to the invention, there is provided a drive mechanism for an endless band including a drive member for rotation about a fixed axis mounted and a rotatable idler member which is spaced from said drive member and which has an axis of rotation parallel to that of said drive member, said endless band being trained around said drive member and idler member, wherein said idler member is mounted on a frame supported by resilient means which may be flexed so as to enable movement of said idler member in directious towards and away from said drive member, said resilient means being so arranged that the axes of rotation of said drive member and said idler member remain parallel to one another during such movement.

In the preferred embodiment of the invention, a drive pulley, which is driven by a motor, is in a fixed position. An idler pulley is spaced from the drive pulley and is supported in a cradle carried on resilient members which permit the idler pulley to be moved toward and away from the drive pulley. The cradle is U-shaped and is urged in a direction away from the drive pulley by a spring which cooperates with a cam member in positioning the idler pulley in a first or a second position when changing the type character endless band. The assembly of drive and driven pulleys, the print band, and associated supporting members are carried in a gate structure which is swingable at one end thereof from an operating position wherein the print band is adjacent the bank of hammers to an open position for loading paper into the printer or for loading a print band on the pulleys.The gate structure also includes a pair of guide rollers and a pair of flexible levers which are contacted by one edge of the print band when loading the band on the pulleys to properly position the band along a line cooperable with the line of impact of the print hammers against the type characters on the print band.

According to another aspect of the present invention there is provided support means for an idler member of a drive system having a drive member supported for rotation about a fixed axis and spaced from said idler member, and an endless band trained around said idler member and said drive member, said support means including a cradle frame member rotatably supporting said idler member; parallel spaced apart leaf springs of substantially equal length resiliently supporting said cradle frame member enabling movement of said idler member in a direction toward and away from said drive member; rotatable camming means operably connected with said cradle frame member for causing movement of said idler member a predetermined distance in the direction toward said drive member; and spring means aligned with said idler member and with said drive member and engageable with said rotatable camming means and with said cradle frame member for biasing said idler member in the direction away from said drive member.

According to yet another aspect of the present invention there is provided a printer having a gate structure, a drive member supported for rotation about an axis fixed with respect to said gate structure, an idler member spaced from said drive member, an endless type character carrier trained around said drive member and said idler member, and means supporting said idler member including a cradle frame member supporting said idler member for rotation about an idler axis; leaf spring resilient means connected with said gate structure and supporting said cradle frame member enabling movement of said idler member in a direction toward and away from said drive member whereby the orientation of said idler axis remains substantially constant throughout said movement; camming means connected with said gate structure and with said cradle frame member for moving said idler member in the direction toward said drive member upon rotation of said camming means; and spring means positioned between said drive member and said idler member and engageable with said camming means and with said cradle frame member for biasing said idler member in a direction away from said drive member.

According to a further aspect of the present invention there is provided a printer having a type character carrying structure pivotally supported therefrom and including a drive pulley and a driven pulley with a type character band trained around the pulleys, a plurality of hammers adapted to impact against the type characters in printing operations; a guide means for supporting said type character band; cradle means for journaling said driven pulley for rotation about an axis; first spring means connected with said type character carrying structure and with said cradle means for resiliently supporting said cradle means to enable linear movement of said driven pulley substantially in a direction toward and away from said drive pulley while maintaining the orientation of said axis substantially constant through us said movement; camming means connected with said type character carrying structure and with said cradle means for moving said driven pulley in the direction toward said drive pulley, and second spring means linearly positioned between said drive pulley and said driven pulley and engageable with said cradle means and with said camming means for biasing said driven pulley in a direction away from said drive pulley.

In order that the invention be better understood, an embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a portion of a printer incorporating the drive mechanism of the present invention; Fig. 2 is a plan view of a print band gate structure including drive and driven pulleys with a print band trained therearound; Fig. 3 is an elevational view of the print band gate structure shown in Fig. 2, with portions removed therefrom and showing resilient support members for the driven pulley; Fig. 4 is an enlarged view of the driven pulley support members; Fig. 5 is a side view, partly in section, of the print band and associated apparatus, taken along the line of printing; and Fig. 6 is an enlarged, exploded view of a cam structure for positioning the driven pulley.

As seen in Fig. 1, a printer 10 incorporating the drive mechanism of the present invention includes the framework of vertical side plates 12 and 14, which support a print band gate structure 16, a hammer bank 18, paper forms tractors 20, 22 carried on shafts 24, 26, a power supply and servo drive 28, and other major parts which will be explained in further detail hereinafter. An on-off switch 30 is located at the lower right front of the printer, a start-stop switch 32 and a forms feed switch 34 are positioned on the top right front of the printer, and a forms handling control mechanism 36 is located on the left side of the printer. A transformer 38 and a blower unit 40 are disposed under the gate structure 16, the blower unit providing cooling to the various areas and parts of the printer.

Form paper or like record media 41 is caused to be driven or pulled by the tractors 20, 22 from a forms stack below the gate structure 16, upwardly past the printing station between a type band 54 and the hammer bank 18, and out an exit slot at the rear of the printer. A ribbon (not shown in Fig. 1) is caused to be driven from a ribbon spool rotatable on the spindle 42 which is supported on a frame member 44 and driven by a motor 46 located at the left side of the gate structure 16, the ribbon being guided in a path rearward of the gate structure and onto a ribbon spool rotatable on a further spindle 48 which is supported on a frame member 50 and driven by a motor 52 at the right side of the gate structure.

The print or type band 54 is caused to be driven in a counter-clockwise direction by the drive pulley 56, at the left side of the gate structure 16, and around a driven or idler pulley 58 located at the right side of the structure 16, the band 54 being directed in a path adjacent a platen (not shown in Fig. 1) and past a print station and positioned to be impacted by print hammers aligned in a horizontal manner forward of the hammer bank 18. A hammer bank drive motor 60 is provided for driving or moving the hammer bank in a horizontal direction for purposes not relevant to the subject matter of the present invention.

In Fig. 2 is shown a plan view of the print band gate structure 16 with certain portions removed, and in Fig. 3 is an elevational view of the gate structure, partly in cross section, to better show the parts of the invention, such structure including an enclosed framework 70 supporting a motor 72 having a drive shaft 74 for rotating a pulley 76 about which a belt 78 is trained for driving a pulley 80 on a shaft 82 supported from and journaled in suitable bearings in the framework 70 and in an upper frame member 84 and causing rotation of the drive pulley 56 about which the print band 54 is trained. The print band 54 is of the endless belt type and, as mentioned above, follows a path adjacent the platen and past the print station where the hammers 86 impact against the characters on the band.

The axis of rotation of the drive pulley 56 is fixed in location but the driven or idler pulley 58 is supported in a manner to be movable in a direction toward and away from the drive pulley 56 as explained hereinafter. As illustrated in Fig. 3, pulley 56 is supported on a light spring 88 so as to assume a floating position axially with respect to the shaft 82, the pulley 56 being also crowned to provide proper tracking of the band in relation to the supports and guiding devices therefor.

The idler pulley 58 is carried on a shaft 90 which is journaled in suitable bearings 89 and 91 in a U-shaped frame member or cradle 92 which is secured to a pair of flexible supporting members, such as leaf springs 94 and 96, which extend upwardly from a lower portion of the gate structure framework 70, the upwardly extending leaf springs 94 and 96 being joined by suitable means to a base member 98 secured to the lower portion of the structure 70 and the upper ends of the leaf springs 94 and 96 being secured to opposite ends of the cradle 92 which is open at one side thereof to permit loading and unloading of the print band 54. The leaf springs 94 and 96 are spaced from each other and provide the sole support for the cradle 92 and hence the idler pulley 58, and allow the cradle 92 to move in the direction of the phantom lines as shown in Fig. 4.The axis of the idler pulley shaft 90 remains parallel to its original position (that shown by the solid line illustration of the cradle 92 and the leaf springs 94 and 96 in Fig. 4) while being subjected to horizontal motion or displaced from the original position as shown in expanded form by the phantom lines. The small vertical displacement of the cradle 92 resulting from the horizontal motion has no vertical effect on the pulley system since the pulley 56 is, in effect, floating and is dependent upon certain guide means for retaining the band 54 in a vertical position during its travel past the print hammers 86. In this manner, the idler pulley 58 remains aligned with the drive pulley 56.

In Fig. 5 is shown a side view of the associated parts at the printing station wherein a platen 110 is supported from the gate structure framework 70. A tape 112 is located adjacent the platen 110 to provide a bearing surface for the print band 54 as it travels past the platen 110, the print band having type characters 114 thereon in raised surface manner. An ink ribbon 116 is caused to be driven in a path adjacent the print band 54 and a ribbon shield 118 is supported between the ribbon 116 and the form paper 120, the shield having an elongated slot therein corresponding to the position of the line of print hammers 86. The ribbon shield 118 provides protection for the paper 120 from the ink ribbon 116 upon impact of the hammers 86 against the type characters 114.

Means is also provided to facilitate the changing of the print band 54 wherein the tension on the band is released and the idler pulley 58 is moved in a direction toward the drive pulley 56. Assuming that a bard 54 is to be installed or loaded on the machine, the gate structure framework 70 is swung into an open position (as shown by the phantom lines in Fig. 2) by means of a pivot 122 in which the print station is freely accessible therefor as well as for loading the forms paper 120 on the drive tractors 20, 22. With the gate structure framework 70 in the open position, a release lever 124 (Figs. 2 and 3) is swung ninety degrees about a pivot pin 126 supported from a sub-structure 128 of the gate structure framework 70.As seen more clearly in Fig. 6, the pivot pin 126 isjournaled in the substructure 128 and includes an extended cam surface 130 on one side thereof for engagement with and operating in a bore 131 of a T-shaped bushing member 132 which includes an adjusting screw member 134 about which a spring 136 is placed for exerting compression between an end portion 133 of the cradle 92, and a side portion of the bushing member 132, thereby urging the idler pulley 58 in a direction away from the drive pulley 56 (to the left in Fig. 3). A bearing plate 135 for one end of the spring 136 is secured to the end portion 133 of the cradle 92 by suitable means and has an aperture therein for passage of the screw member 134.When the release lever 124 is turned or rotated 90 degrees (Fig. 2), the bushing member 132 is caused to be moved to the right (Fig. 3) by reason of the camming action of the surface 130 in the bore 131 and the cradle 92 is caused to be moved to the right on its supporting leaf springs 94 and 96.

The slight displacement of the cradle 92 to the phantom line position of Fig. 4, along with the idler pulley 58 carried thereby, permits the opertor to easily load the print band 54 on the drive pulley 56 and on the idler pulley 58.

The screw member 124 also provides for adjusting the precise position of the cradle 92 in relation to the pivot pin 126 to allow for slight variations in length of different print bands.

Means is also provided for assuring that the print band 54 is properly placed or positioned when loading such band on the pulleys 56 and 58. As illustrated in Figs. 2 and 3, a pair of edge guide rollers 140 and 142 are journaled in one side of the gate structure framework 70 (opposite from the print station) to provide a support and guide for the print band edge along one side of the gate structure. A pair of resilient levers 144, 146 are secured to the gate structure frameowrk 70 on the print station side thereof (Fig. 2), the levers being formed so as to be normally bowed into an open position (see the phantom lines in Fig. 2), such position of the levers providing a support or limit for the edge of the print band 54 when loading therof.With the lower edge of the print band 54 in contact with the edge guide rollers 140, 142, and in contact with the top surface of the levers 144, 146 along the print station side of the gate structure, the release lever 124 is rotated 90 degrees to move the cradle 92 and the idler pulley 58 toward the left to tension the print band 54 for the operating condition. Frame members 148, 150 of the printer are engaged by the levers 144, 146 when the gate structure 16 is swung to the closed position, thereby causing the levers to be straightened, as shown in full lines in Fig. 2, to a position free and clear of engagement with the print band 54. When the printer 10 is operating, there is a slight clearance between the lower edge of the print band 54 and the top surface of the levers 144 and 146, as seen in Fig. 5.

WHAT WE CLAIM IS: 1. A drive mechanism for an endless band including a drive member mounted for rotation about a fixed axis and a rotatable idler member which is spaced from said drive member and which has an axis of rotation parallel to that of said drive member, said endless band being trained around said drive member and idler member, wherein said idler member is mounted on a frame supported by resilient means which may be flexed so as to enable movement of said idler member in directions toward and away from said drive member, said resilient means being so arranged that the axes of rotation of said drive member and said idler member remain parallel to one another during such movement.

2. A mechanism according to Claim 1, wherein said flexible means comprises two spaced leaf springs.

3. A mechanism according to Claim 2, wherein said two leaf springs are mounted on, and extend upwards from a base member, and support said frame at opposite ends thereof.

4. A mechanism according to any one of Claims 1 to 3, wherein said frame is U-shaped and said idler member is mounted between the two arms thereof permitting removal of said endless band from said idler member at the open end of the U-shaped frame.

5. A mechanism according to any one of the preceding Claims, including rotatable means operably connected with said frame for causing movement of said idler member in the direction toward said drive member.

6. A mechanism according to Claim 5, wherein said rotatable means includes a cam member for displacing said frame a predetermined distance from said drive member.

7. A mechanism according to either Claim 5 or 6, including spring means mounted between said rotatable means and said frame for biasing said idler member in the direction away from said drive member.

8. A mechanism according to any one of the preceding Claims, wherein said drive member and said idler member are pulleys.

9. A mechanism according to Claim 8, wherein the drive pulley is axially movable on a shaft.

10. A mechanism according to any one of the preceding Claims, wherein said endless band is a print band.

11. Support means for an idler member of a drive system having a drive member supported for rotation about a fixed axis and spaced from said idler member, and an endless band trained around said idler member and said drive member, said support means including a cradle frame member rotatably supporting said idler member; parallel spaced apart leaf springs of substantially equal length resiliently supporting said cradle frame member enabling movement of said idler member in a direction toward and away from said drive member; rotatable camming means operably connected with said cradle frame member for causing movement of said idler member a predetermined distance in the direction toward said drive member; and spring means aligned with said idler member and with said drive member and engageable with said rotatable camming means and with said cradle frame member for biasing said idler member in the direction away from said drive member.

12. A support means as claimed in claim 11 wherein said cradle frame member is Ushaped to define an opening permitting removal of said band from said idler member.

13. A printer having a gate structure, a drive member supported for rotation about an axis fixed with respect to said gate structure, an idler member spaced from said drive member, an endless type character carrier

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

The slight displacement of the cradle 92 to the phantom line position of Fig. 4, along with the idler pulley 58 carried thereby, permits the opertor to easily load the print band 54 on the drive pulley 56 and on the idler pulley 58.

The screw member 124 also provides for adjusting the precise position of the cradle 92 in relation to the pivot pin 126 to allow for slight variations in length of different print bands.

Means is also provided for assuring that the print band 54 is properly placed or positioned when loading such band on the pulleys 56 and 58. As illustrated in Figs. 2 and 3, a pair of edge guide rollers 140 and 142 are journaled in one side of the gate structure framework 70 (opposite from the print station) to provide a support and guide for the print band edge along one side of the gate structure. A pair of resilient levers 144, 146 are secured to the gate structure frameowrk 70 on the print station side thereof (Fig. 2), the levers being formed so as to be normally bowed into an open position (see the phantom lines in Fig. 2), such position of the levers providing a support or limit for the edge of the print band 54 when loading therof.With the lower edge of the print band 54 in contact with the edge guide rollers 140, 142, and in contact with the top surface of the levers 144, 146 along the print station side of the gate structure, the release lever 124 is rotated 90 degrees to move the cradle 92 and the idler pulley 58 toward the left to tension the print band 54 for the operating condition. Frame members 148,

150 of the printer are engaged by the levers 144,

146 when the gate structure 16 is swung to the closed position, thereby causing the levers to be straightened, as shown in full lines in Fig. 2, to a position free and clear of engagement with the print band 54. When the printer 10 is operating, there is a slight clearance between the lower edge of the print band 54 and the top surface of the levers 144 and 146, as seen in Fig. 5.

WHAT WE CLAIM IS: 1. A drive mechanism for an endless band including a drive member mounted for rotation about a fixed axis and a rotatable idler member which is spaced from said drive member and which has an axis of rotation parallel to that of said drive member, said endless band being trained around said drive member and idler member, wherein said idler member is mounted on a frame supported by resilient means which may be flexed so as to enable movement of said idler member in directions toward and away from said drive member, said resilient means being so arranged that the axes of rotation of said drive member and said idler member remain parallel to one another during such movement.
2. A mechanism according to Claim 1, wherein said flexible means comprises two spaced leaf springs.
3. A mechanism according to Claim 2, wherein said two leaf springs are mounted on, and extend upwards from a base member, and support said frame at opposite ends thereof.
4. A mechanism according to any one of Claims 1 to 3, wherein said frame is U-shaped and said idler member is mounted between the two arms thereof permitting removal of said endless band from said idler member at the open end of the U-shaped frame.
5. A mechanism according to any one of the preceding Claims, including rotatable means operably connected with said frame for causing movement of said idler member in the direction toward said drive member.
6. A mechanism according to Claim 5, wherein said rotatable means includes a cam member for displacing said frame a predetermined distance from said drive member.
7. A mechanism according to either Claim 5 or 6, including spring means mounted between said rotatable means and said frame for biasing said idler member in the direction away from said drive member.
8. A mechanism according to any one of the preceding Claims, wherein said drive member and said idler member are pulleys.
9. A mechanism according to Claim 8, wherein the drive pulley is axially movable on a shaft.
10. A mechanism according to any one of the preceding Claims, wherein said endless band is a print band.
11. Support means for an idler member of a drive system having a drive member supported for rotation about a fixed axis and spaced from said idler member, and an endless band trained around said idler member and said drive member, said support means including a cradle frame member rotatably supporting said idler member; parallel spaced apart leaf springs of substantially equal length resiliently supporting said cradle frame member enabling movement of said idler member in a direction toward and away from said drive member; rotatable camming means operably connected with said cradle frame member for causing movement of said idler member a predetermined distance in the direction toward said drive member; and spring means aligned with said idler member and with said drive member and engageable with said rotatable camming means and with said cradle frame member for biasing said idler member in the direction away from said drive member.
12. A support means as claimed in claim 11 wherein said cradle frame member is Ushaped to define an opening permitting removal of said band from said idler member.
13. A printer having a gate structure, a drive member supported for rotation about an axis fixed with respect to said gate structure, an idler member spaced from said drive member, an endless type character carrier

trained around said drive member and said idler member, and means supporting said idler member including a cradle frame member supporting said idler member for rotation about an idler axis; leaf spring resilient means connected with said gate structure and supporting said cradle frame member enabling movement of said idler member in a direction toward and away from said drive member whereby the orientation of said idler axis remains substantially constant throughout said movement; camming means connected with said gate structure and with said cradle frame member for moving said idler member in the direction toward said drive member upon rotation of said camming means; and spring means positioned between said drive member and said idler member and engageable with said camming means and with said cradle frame member for biasing said idler member in a direction away from said drive member.
14. A printer as claimed in claim 13 wherein said drive and idler members are pulleys and said carrier is a band having type characters thereon.
15. A printer having a type character carrying structure pivotally supported therefrom and including a drive pulley and a driven pulley with a type character band trained around the pulleys, a plurality of hammers adapted to impact against the type characters in printing operations; a guide means for supporting said type character band; cradle means for journaling said driven pulley for rotation about an axis; first spring means connected with said type character carrying structure and with said cradle means for resiliently supporting said cradle means to enable linear movement of said driven pulley substantially in a direction toward and away from said drive pulley while maintaining the orientation of said axis substantially constant throughout said movement; camming means connected with said type character carrying structure and with said cradle means for moving said driven pulley in the direction toward said drive pulley, and second spring means linearly positioned between said drive pulley and said driven pulley and engageable with said cradle means and with said camming means for biasing said driven pulley in a direction away from said drive pulley.
16. A printer as claimed in claim 15 wherein said cradle means includes a U-shaped frame member connected with said type character carrying structure permitting removal of said band from said driven pulley and said first spring means comprises a pair of leaf spring members spaced apart and supporting said frame member.
17. A printer as claimed in claim 15 or 16 wherein said camming means includes a shaft member having a cam portion thereon and a bushing member connected with said type character carrying structure and with said cradle means, the rotation of said shaft member can portion in said bushing member causing movement of said driven pulley toward said drive pulley.
18. A printer as claimed in any of claims 15 to 17 wherein said first spring means comprises a pair of upstanding leaf springlike members and said camming means includes a bushing member connected with said type character carrying structure and a shaft member rotatable in said bushing member for causing movement of said driven pulley in a direction toward said drive pulley upon rotation of said shaft member.
19. A printer as claimed in any of claims 15 to 18 wherein said camming means further includes an adjusting member connected with said bushing member and with said cradle means for permitting moving of said driven pulley a predetermined distance toward said drive pulley upon rotation of said shaft member.
20. A printer as claimed in claim 17 or claim 18 or 19 when dependent thereon wherein said second spring means is a coil spring engageable with said bushing member and with said cradle means for biasing said driven pulley in the direction from said drive pulley.
21. A drive mechanism for an endless band, substantially as hereinbefore described with reference to Figures 2 to 6 of the accompanying drawings.