A printing apparatus

Abstract: A printing apparatus employing a shock absorbing tension spring (36), the tension spring (36) having first and second "U"-shaped portions (40,42) formed on one end thereof with the remaining end of the spring (36) being attached to a frame (16) of the apparatus. The first "U"-shaped portion (40) of the spring (36) is positioned around a stud (38) on a beam (12) of the apparatus, and the second "U"-shaped portion (42) engages a portion (12-6) of the beam (12). An actuator (28) is used to move a hammer (26) on the beam (12) to an impact position, and the tension spring (36) is used to return the beam (12) to a home position. As the beam (12) is moved toward the impact position, there is an increase in the area of contact between the stud (38) and the first "U"-shaped portion (40) to thereby minimize movement therebetween. When the spring (36) returns to the home position, the body portion (36-3) of the spring (36) assumes an "arched" position which minimizes "bounce" of the beam (12) in returning to the home position.

Description: The present invention relates to a printing apparatus and more particularly to a printing apparatus employing a shock absorbing tension spring. Most fly encoders (see for instance US-A-4 522 122) which are used in printing tend to deteriorate after they have been in operation for a while. A typical application for a fly encoder relates to printing or encoding MICR (magnetic ink character recognition) data on a document as the document is moved along a track or channel. In general, after processing about 200,000 documents in this.manner, the encoder may require some adjustment in order to meet the rather strict specifications required for the encoding of MICR data. The adjustment is usually made by technical personnel via a service call. Several such adjustments and readjustments may be necessary during the life of the fly encoder. Another problem with the fly encoders of the type mentioned is that the individual parts of the encoders tend to wear out after about 100 million cycles of operation or after processing about 5 million documents. Aside from the parts becoming "loose fitting", some of the parts actually wear through contacting parts. For example, a coiled tension spring which is used to return the associated print hammer or beam to a home position may actually cut through the beam. Naturally, this results in "down time" for the machine in which the encoder is used, and it also requires another service call. An object of the present invention is to provide a printing apparatus having a design in which there is less wearing of individual parts of the encoder, and consequently, there are fewer service calls to be made when compared to prior art encoders of the type mentioned. Accordingly, the present invention provides a printing apparatus including a beam mounted on pivot means for pivotal movement of said beam about a pivot axis enabling a first beam end portion of said beam to move in a reciprocal manner between first and second positions, a tension spring having first and second spring end portions respectively attached to first and second mounting means, said second mounting means being mounted on said beam, for resiliently biasing said first beam end portion towards said first position, characterized in that said second spring end portion includes a first generally U-shaped portion having first and second legs to partially surround said second mounting means and a second portion for engaging a portion of said beam whereby when said first beam end portion is in said first position said spring assumes an arched configuration with said first and second legs diverging away from each other at a first acute angle, and whereby when said first beam end portion moves to said second position said spring becomes straighter with said first and second legs diverging away from each other at a second acute angle less than said first acute angle thereby increasing the area of contact between said first generally U-shaped portion and said second mounting means. An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which:- Fig. 1 is a side view of a preferred embodiment of the invention, showing an encoder in a home or first position; Fig. 2 is a view similar to Fig. 1, showing the encoder in a second or an active position in which the associated hammer strikes an impact area; Fig. 3 shows an enlarged view of a spring shown in Figs. 1 and 2, with the spring being shown in a relaxed state in Figs. 3 4, and 5; Fig. 4 is a side view of the spring shown in Fig. 3, with the view being taken from the direction of arrow A in Fig. 2; Fig. 5 is a side view of the spring shown in Fig. 3, with the view being taken from the direction of arrow B in Fig. 2; and Fig. 6 is an exploded view, in perspective, of the encoder shown in Figs. 1-5, with this figure also showing some elements not included in Figs. 1-5. Fig. 1 shows a preferred embodiment of an apparatus like an encoder 10 made in accordance with this invention. The encoder 10 includes a generally planar hammer or beam 12 having the shape shown in Figs. 1 and 2. The beam 12 has a first beam end portion 12-1 and a second beam end portion 12-2, with the beam 12 being pivotally mounted between these end portions on a pivot member 14. The pivot member 14 is part of a means for mounting the beam 12 for pivotal movement between a first or home position shown in Fig. 1 and a second or an impact position shown in Fig. 2. The mounting means also includes a frame 16, with the frame 16 being secured to a support 18 by a fastener 20. The frame 16 is adjustably mounted on the support 18 (via a slot in the frame 16) to provide flexibility in mounting the encoder 10 relative to an impact area 24. The impact area 24 represents or includes a typewheel 24-1, a ribbon 24-2, a document 24-3, and indexing means 24-4 for indexing the typewheel 24-1 to present a preselected character or characters on the typewheel for encoding. The first beam end portion 12-1 has a hammer 26 which impacts against the impact area 24 (Fig. 1) to effect the printing or encoding when an actuator 28 is energized. The actuator 28 and the indexing means 24-4 are controlled by a controller 30 (Figs. 1 and 2) which may be part of a machine (not shown) like an encoding and proof machine, for example. The encoder 10 also includes a beam stop 32 which is formed of a flange portion 32-1 of the frame 16 and a resilient member 32-2 which is secured to the flange portion 32-1. When the beam 12 is in the first position shown in Fig. 1, the beam 12 is resiliently biased against the beam stop 32 by a tension spring 36. The design of the tension spring 36 increases the life of the encoder 10 as will be explained hereinafter. Figs. 3, 4, and 5 show additional details of the tension spring 36 when this spring is in a relaxed state. The dimensions given in these figures for tension spring 36 are stated in millimeters; however, this spring is shown enlarged in these figures. The spring 36 is made of #8 Gauge music wire (0.5 mm in diameter). The size of the beam 12 and the tension spring 36 are shown in approximately the correct size relative to each other in Figs. 1 and 2. Spring 36 has first and second spring end portions 36-1 and 36-2, respectively, which extend in opposed directions from a body portion 36-3 of the spring 36. The first spring end portion 36-1 has a generally "C"-shaped hook thereon which is secured to a mounting stud 37 which extends from the frame 16 as seen in Fig. 1. The second spring end 36-2 is coupled to the beam 12 (via a second stud 38 and a portion 12-6 of the beam 12) to bias the first beam end portion 12-1 to the first or home position as shown in Fig. 1. In this regard, the second spring end 36-2 of the tension spring 36 is formed to cause the body portion 36-3 to assume an "arched" shape when the spring 36 is mounted on the beam 12 and the first beam end portion 12-1 is positioned against the beam stop 32 as shown in Fig. 1. The shape of the body portion 36-3 is generally convex as viewed from the beam stop 32 in Fig. 1. The function of the arching will become clearer as the explanation proceeds. The second spring end 36-2 has a first generally "U"-shaped portion 40 (Fig. 3) which includes first and second legs 40-1 and 40-2 and a joining portion 40-3, with the first leg 40-1 being connected to the body portion 36-3 of the spring 36. The second spring end 36-2 also has a second "U"-shaped portion 42 (Fig. 4) which includes a first leg 42-1 and the second leg 40-2 which is shared in common with the first "U"-shaped portion 40. A joining portion 42-3 connects the first leg 42-1 and the second leg 40-2 as shown best in Fig. 4. The portion 12-6 of the beam 12 is received in the second "U"-shaped portion 42 when the spring 36 and the beam 12 are assembled as shown in Fig. 1. When in the relaxed state shown in Fig. 3, the leg portions 40-1 and 40-2 diverge away from each other at an angle of about 30 degrees. When the spring 36 is "arched" as shown in Fig. 1, the leg portions 40-1 and 40-2 diverge away from each other at an angle of about ten degrees which is about one third of the relaxed state angle. Fig. 6 is an exploded view, in perspective, of the encoder 10 and its associated elements shown in Figs. 1-5. The support 18 (shown only schematically in Figs. 1 and 2) is shown in more detail in Fig. 6. The support 18 includes a lower support member 18-1 and an upper support member 18-2. The lower support 18-1 has a Vespel (Trademark of E.I. Dupont De Nemours) tubular bearing 44 which is press fitted into a mating opening therein so as to leave a short portion 44-1 of the bearing 44 extending above the lower support 18-1. The lower support 18-1 also has two threaded pins 46 and 48 upstanding therefrom as shown in Fig. 6. The pins 46 and 48 are shown in their approximate positions and in dashed outlines in Figs. 1 and 2 to orient the reader. The Vespel material for bearing 44 is plastic which is as tough as steel. The frame 16 is positioned on the lower support 18-1 so that an opening 50 in the frame 16 is positioned around the short portion 44-1 of the bearing 44, and the fastener 20 is secured to the lower support 18-1 to secure the frame 16 thereto. As best seen in Fig. 6, the beam 12 has several ferrous laminations 12-3 and 12-4 which are positioned on opposed sides of the beam 12 and secured thereto by a fastener 12-5. The laminations 12-3 and 12-4 cooperate with the actuator 28 to move the hammer 26 to the impact area 24 whenever the actuator 28 is energized by the controller 30. The beam 12 is mounted on the frame 16 by inserting the lower end of the pivot member 14 (as viewed in Fig. 6) into the bearing 44. The tension spring 36 is then coupled to the beam 12 and the stud 37 as previously described. Continuing with a discussion of Fig. 6, the actuator 28 (Fig. 1) is made up of a laminated "U"-shaped core 52, a winding 54, and a "T"-shaped element 56 which is made of the same material as is the bearing 44. The "T"-shaped element 56 is positioned in a receiving recess 58 on the core 52, and thereafter, winding 54 is pushed over the leg 52-1 of the core 52. Because the laminations in the core 52 are uneven, the "T"-shaped element 56 provides a straight and durable stop for the second beam end portion 12-2 to keep the beam 12 from rocking when the hammer 26 impacts against the impact area 24 and the beam end 12-2 comes to a stop against the "T"-shaped element 56. After assembly, the actuator 28 is then positioned on the threaded pins 46 and 48 via holes 60 and 62, respectively, in the core 52. Continuing with a discussion of Fig. 6, the encoder 10 includes the upper support 18-2 which has a Vespel tubular bearing 64 press fitted therein. This bearing 64 has a short portion 64-1 which extends below the bottom surface of the upper support 18-2 as viewed in Fig. 6. The short portion 64-1 (Fig. 1) faces the beam 12. There is an exaggerated clearance 15 shown in Fig. 1 between the pivot member 14 and the short portion 64-1 of bearing 64. The actual clearance 15 is about .025 mm in the embodiment described. The bearing 64 receives the upper end of the pivot member 14 (as viewed in Fig. 6) when the upper support 18-2 is mounted on the threaded pins 46 and 48. A thin tubular sleeve 14-1, passing through the laminations 12-3, the beam 12, and the laminations 12-4 and having the ends thereof flattened, functions as a fastener to hold these elements together. The pin 14 is retained in the tubular sleeve 14-1 by press fitting. Holes 66 and 68 in the upper support 18-2 are provided for receiving the threaded pins 46 and 48, respectively, and suitable washers 70 and nuts 72 and 74 are used to secure the encoder 10 in assembled relationship. A dust cover 76, which is coupled to a box 54-1 in which the winding 54 is located, is used to keep dust out of the encoder 10. in certain prior art encoders, when a spring end like the "C"-shaped end 36-1 (Fig. 1) was placed around a stud on a hammer or beam like the stud 38 on beam 12, the "C"-shaped end would actually cut through the stud 38 after about 48 million cycles of operation. Or alternatively, the "C"-shaped end 36-1 of the spring would be cut through by the stud 38, resulting in down time and a service call to repair the associated encoder. The present invention obviates these problems. The tension spring 36 has been redesigned to bring about three different kinds of activities, namely: 1. To distribute the load on the beam by directing some of the load to the area 12-6 of the beam 12 which is received by the second "U"-shaped member 42 of the spring 36. 2. To increase the area of contact between the first "U"-shaped portion 40 of the spring 36 and the stud 38 as the beam 12 is moved from the home or first position shown in Fig. 1 to the impact or second position shown in Fig. 2; and 3. To "arch" the body 36-3 of the spring 36 as the beam 12 returns to the first position shown in Fig. 1. Notice that when the beam 12 is in the first position shown in Fig. 1, the first and second legs 40-1 and 40-2 of the tension spring 36 diverge away from each other at an acute angle of about 10 degrees, and as the beam approaches the impact position shown in Fig. 2, these same legs approach being parallel to each other. The significance of this observation means that the area of contact between the first "U"-shaped portion 40 of the spring 36 and the stud 38 is increasing. This increased contact area means that the spring 36 is gripping more tightly and moving less on the stud 38 (compared to prior art devices), with the result that there is less wear on the spring 36 or the stud 38. Notice that when the beam 12 is in the impact or second position shown in Fig. 2, the tension spring 36 is subjected to almost pure tension, and the body portion 36-3 thereof is straight. After deenergization of the encoder 10, the beam 12 returns from the position shown in Fig. 2 to the position shown in Fig. 1. In this process, the body portion 36-3 of the spring tends to assume the arched position shown in Fig. 1. The arching of the body portion of the spring 36-1 tends to minimize the "bounce" of the first end portion 12-1 from the beam stop 32 because it appears to take up some rebound energy to bend the body portion 36-3. The "bounce" in prior art devices tended to cause wear on the stud 38 and the spring 36. As the beam 12 returns to the home position shown in Fig. 1, the first and second leg portions 40-1 and 40-2 of the spring 36 tend to diverge away from each other to the position shown, and thereby "arch" the body portion 36-3 of the spring 36.

Claims: A printing apparatus including a beam (12) mounted on pivot means (14) for pivotal movement of said beam (12) about a pivot axis enabling a first beam end portion (12-1) of said beam (12) to move in a reciprocal manner between first and second positions, a tension spring (36) having first and second spring end portions (36-1, 36-2) respectively attached to first and second mounting means (37,38), said second mounting means (38) being mounted on said beam (12), for resiliently biasing said first beam end portion (12-1) towards said first position, characterized in that said second spring end portion (36-2) includes a first generally U-shaped portion (40) having first and second legs (40-1,40-2) to partially surround said second mounting means (38) and a second portion (42) for engaging a portion of said beam (12) whereby when said first beam end portion (12-1) is in said first position said spring (36) assumes an arched configuration with said first and second legs (40-1,40-2) diverging away from each other at a first acute angle, and whereby when said first beam end portion (12-1) moves to said second position said spring (36) becomes straighter with said first and second legs (40-1,40-2) diverging away from each other at a second acute angle less than said first acute angle thereby increasing the area of contact between said first generally U-shaped portion (40) and said second mounting means (38). A printing apparatus as claimed in claim 1, characterized in that said first and second legs (40-1,40-2) diverge away from each other at a third acute angle greater than said first acute angle when said tension spring (36) is in a relaxed state. 3. A printing apparatus as claimed in claim 1 or claim 2, characterized in that said second portion (42) is of a generally U-shaped configuration and extends from said first generally U-shaped portion (40). A printing apparatus as claimed in any one of claims 1 to 3, characterized in that said second mounting means (38) is a cylindrical stud (38) which extends from said beam (12). A printing apparatus as claimed in any one of claims 1 to 4, characterized in that said second mounting means (38) is positioned between said pivot means (14) and said first beam end portion (12-1). A printing apparatus as claimed in any one of claims 1 to 5, characterized by an actuator (28) for pivoting said beam (12) to move said first beam end portion (12-1) from said first position to said second position against the bias of said tension spring (36). A printing apparatus as claimed in claim 3, characterized in that said first acute angle is approximately one third of said third acute angle. A printing apparatus as claimed in claim 6 in which said apparatus also includes: a typewheel (24-1) located at an impact area, positioning means (24-4) for positioning a selected character on said typewheel (24-1) at said impact area, and a controller (30) for controlling said actuator (28) and said positioning means (24-4).

Inventors: TRIBERT JOHN, TRIBERT, JOHN
Applicants: NCR INT INC, NCR INTERNATIONAL INC.
Application year: 1990
Main classification: B41J9
IPC codes: F16F15, B41J9, F16F1, G01D5