Chapter 6 Analysis
6.4 Action Analysis
The key part in present design is section 2 of gear train, the mechanism for power switch and step change. Generally gear is used for transmitting power. But here the function of power switch is applied by the engagement or disengagement of planet gear. In this mechanism, because both the rotating arm and planet gear can rotate freely, it is hard to ensure which component will rotate so that here discuss the cases.
There are one force and two resistances that will effect the movement of these components,
1. F: rotating force
2. Rp: resistance of planet gear rotating 3. Ra: resistance of rotating arm rotating
Case 1: If Rp < Ra
As shown in Fig. 6.4 (a), while F is larger than Rp, the planet gear starts rotating but the rotating arm does not.
planet gear does not.
In the present design, it only needs case 2 because Ra will become larger than Rp after the planet gear engages the step-change cam gear or power transmitting gear. Therefore, here the way to ensure that the mechanism always working in case 2 is to increase the resistance of planet gear rotating.
There are two ways to increase the resistance. First one is to increase the friction between the gear bore for axis and the axis. Second is to increase the friction between the planet gear and the rotating arm. But first way is more difficult than second one so that here uses second way. As shown in Fig. 6.5, a spring is added between rotating arm plate and gear axis to supply a lateral force to planet gear so that the friction between gear and rotating arm will increase.
6.5 Remarks
1. The weight of present design is about 308g.
2. The maximum torque is 39.23 gf-cm while the pulse rate is 500 PPS and the minimum is 0.769 gf-cm while the pulse rate is 2061 PPS. One more gear must be added into the gear train to change the rotating direction of print head cam.
3. In order to ensure the movement of section 2, increasing the resistance on the planet gear
Table 6.1 The weights of print module
Component Weight
Printer frame 89g
upper cover 70g
motor support plate 5g
Frame
Axis support plate 16g
Ribbon cassette 19g
Thermal print head module(with spring,
frame and cam) 35g
Motor 15g
Platen roller 25g
Capstan roller 8g
Passive paper roller 7g
Gear train(including axis) 14.94g
Others 4.06g
Total 308g
Table 6.2 Specification of thermal print head
Model No. KPC-54-8PAO1-LO
Effective print width 54 ± 0.2mm Number of heater elements 432 dots/HEAD
Dot density 8.0 dot/mm
Subsequent scanning density 8.0 line/mm
Dot pitch 0.125mm
Table 6.3 Simulation result of rotation angle after deceleration
Fig. 6.1 The position of print head module
Print head cam
Pressure plate
Print head
Fig. 6.3 Simulation result of print head module A
B
(a) (b)
Fig. 6.4 The two cases of planet gear
Spring
Gear axis
Planet gear
Chapter 7 Conclusions
7.1 Conclusions
1. TRIZ provides principles to designers, and these principles are related to design parameters. Therefore, these principles are usually suitable to solve the problem. It is different from designer’s checklist method that developed by themselves. Therefore, using checklist method needs more creativity.
2. Compare these concepts in this study, concept 5 uses only one motor and need not any other electrical device to support the action. For the requirement of power saving, design of concept 5 can print more pages than other concepts with the same power.
3. The size of the present print module design is 107.4mm* 81.6mm* 26.8mm and its weight is about 308g. For the mobile requirement, it is lighter and smaller than general printers and near to ALPS products.
4. Compared with the design of ALPS, as shown in Table 7.1, there are two advantages, first, the design of ALPS needs to detect paper first, and then draw the paper back for printing.
Therefore, it needs 4 steps to complete the whole printing process. Second, while step
Therefore, the present design will save more time than ALPS products while printing.
7.2 Future Works
1. Search more related information. Patent is one of the important sources for the product design. Read more patents to make the database more complete. Other production related to printer can also be searched, such as the borderless printing, to increase the functions of printer.
2. Reduce the size of the present design. Here the study uses TRIZ to generate concepts about motor reduction. TRIZ or other optimum methods may be used to improve the size or weight of the present design.
3. Propose more new concepts. Use TRIZ or other innovative tools to find other better concept which can also use only one motor and the size is smaller.
4. Real size prototype. In the study, the size of prototype is twice to the embodiment design. Fabricate the whole mobile print module with real size to see if there is any other problem in the design.
Table 7.1 Comparison
ALPS Present design
Size 96.6 x 17.4 x 61.1 mm3 107.4 x 26.8 x 81.6 mm3
Motor 1 1
Steps 4 3
Gear 17 26
Rotating angle > 270° 120° & 240°
Rotation 1 Paper change & change Power output
Rotation 2 Paper out Change
References
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http://www.howstuffworks.com/inkjet-printer.htm, last visited on May, 30, 2005.
[6] Harris, T., “How Laser Printers Work” [On-line], Available:
http://computer.howstuffworks.com/laser-printer.htm, last visited on May, 30, 2005.
[7] Hi-Touch Imaging Technologies Co., Ltd, Available: http://www.hi-ti.com.tw, last visited on May, 30, 2005.
[8] Moroney, N. M. and Viggiano, J. A., “Color Imaging Using Variable Dot Thermal Wax Transfer”, RIT Research Corporation, Rochester, New York, 1994.
[9] Mohammad, H. S. and Nezafati, N., “A New Method for Creating the Non-Technologic Principles of TRIZ.” TRIZ-Journal, Oct. 2003.
[10] Altshuller, G., “40 Principles: TRIZ Keys to Technical Innovation”, 1997.
[11] Terninko, J., Zusman, A., and Zlotin, B., “STEP-by STEP TRIZ: Creating Innovative Solution Concepts”, St. Lucie Press, 1996.
[12] Unite States Patent Number: 6,392,682, May 21, 2002.