The first question, let me talk about the core. What are the advantages and disadvantages of the above general principles? Advantages: simple structure, large clamping force, reliable operation (large lead tolerance) and long service life; Disadvantages: the push-out force is large and it is impossible to adopt more advanced principles. So the core-pulling operation is more troublesome. It is necessary to change the posture of holding the pen with your fingers, and use your thumb to do axial movement to push out the lead.
There are hundreds of mechanical pencil's patented inventions in history, but I have studied some of them and found that they are all similar, and there are only a few real automatic principles. Other patents are the evolution of a certain principle. To sum up, the most advanced principle is a principle called "automatic" core pulling, which was first invented by the Germans and later improved and evolved by the Japanese, and developed into many different patents. Its principle is not complicated. There are two unidirectional chuck mechanisms in the pen body, so that the lead can only move in one direction, but not in the opposite direction. A chuck is connected with the sliding core protection tube, which is pushed forward by the spring and limited by the inner flange of the pen tip, and the rear chuck can move in the pen body, with a delay mechanism and a retaining spring. When writing, the lead is getting shorter and shorter. When the paper touches the core protection tube, it will retract, but the wire will be caught by the back chuck and will not follow. When the writer releases the pen, the core-protecting tube automatically returns under the action of the stop spring, and the front chuck pulls the lead out of the back chuck a little, thus achieving the effect of automatic core ejection. This principle also has the function of pushing out the lead core. When writing, although the lead is not worn flush with the core protection tube, the writer can still press the lead head to make the lead move backwards with the two clips, and then raise his hand. First, the lead core moves forward together with the core protection tube to pull the lead core out of the back clip. Then, after a period of delay, the previous clip has been reset, and the following clip begins to reset. At this point, the lead core will be pushed out of the core protection tube to complete.
For the most advanced automatic core-pulling mechanical pencil, the key point is that the chuck must have excellent unidirectional performance, or the greater the resistance difference between the two directions, the better. When the core protection tube is pushed in, the force is very small, and there is enough clamping resistance to drive the wire to move forward when it is reset. In order to achieve this effect, this kind of pencil often adopts inclined ball precision chuck. It is a copper bowl with an inner conical surface, and there are three balls in it. It is easy to insert the lead from one side, but it will be strongly blocked when moving in the opposite direction. Regarding the delay mechanism, the principle is also different. Some designs use real damping delay, such as using soft organic materials for damping, or using metal parts with damping oil to make the thick chuck reset later than the front chuck; However, some designs are different and adopt mechanical self-locking structure, so that the chuck will get stuck after moving in place. Only after the current chuck is reset, the rear chuck will be locked and released, just like the mechanical curtain shutter.
This all-mechanical pencil principle is very advanced, and looks excellent in performance, but the actual situation is not as perfect as expected. First of all, the spherical chuck is an extremely accurate accessory. A small change in the diameter of the lead core will lead to a large change in the axial position of the ball when it is clamped. If the diameter error of the lead is slightly larger, the clamping resistance will fail, so it is necessary to use high-precision lead, otherwise it is not suitable to use domestic lead. Secondly, when the 3-ball chuck clamps the lead, the ball will press on three points on the circumference of the lead. The greater the writing pressure, the greater the force of the ball pressing the lead, so that if the lead is slightly weak, it will break. Thirdly, the principle of automatic core jacking is based on the fact that when writing, the paper touches the core protection tube, which makes the core protection tube move and bring out the lead core. That is to say, when writing, the core protection tube should always contact the paper. Because the friction between the paper and it is horizontal, and the retraction of the core tube is axial, the friction between them will be great, which will not only affect the writing feel, but also cause the rapid wear of the core tube, which will have a great impact on the life of the pencil. Thirdly, the movement accuracy of this principle is extremely high, and the tolerance of parts cannot be greater than 1um or even smaller, which brings great trouble to processing and production and greatly increases the cost of products. Moreover, if the parts inside the chuck are slightly worn, its work will be abnormal, and the resistance of the chuck will be greatly reduced, so that the whole pen will be scrapped. Another problem is that the double-ended mechanical pencil surplus lead core should not be too short, which is a great waste.
There are several commonly used structures in Japanese patents. For example, there are two core-pulling principles for lateral pressure. One is to just move the tail cap to the side of the pencil, closer to the nib, so that the action of pushing out the lead does not need to change the writing posture, which does have a certain effect, but it does not belong to the real side chin movement type; Another real side chin style is that the buttons on the side chin are arranged at 90 degrees, which greatly improves the feel. However, this coring method is not ideal. Because of the wear of the refill when writing with a pencil, it is necessary to rotate the pen body continuously and change the contact angle between the refill and the paper when writing. In this way, when you plan to take out the core, the side button won't know where it is hidden! The principle of folding core is much better than the above two schemes. This pencil can be folded at any angle of 360 degrees. You can bend the pen anywhere, which is very convenient.
I also designed two very special automatic principles, which can also be patented. The first one is called the automatic principle of electric core pulling. The structure of the pen is not special, and the chuck is also a three-ball type, but the driving mechanism is an electromagnet. A miniaturized lithium battery charges the 1F supercapacitor. When the core needs to be ejected, press the electronic switch button, and the capacitor will discharge the powerful electromagnet, generating a large amount of thrust to push the core ejection mechanism. This scheme has a high degree of automation and complex structure, but it is cumbersome to operate because it needs to be recharged. If there is no conditional charge, there is nothing to do. Moreover, those batteries, electromagnets and large capacitors are not small in size and will occupy a lot of pen space. The second is called the automatic principle of inertia core pulling. A large heavy hammer is installed at the back of the pen to press out the refill. When you need a lead, shake the pencil and the lead will be pushed out for a while. This advanced design is very valuable.
The second question, I talk about practicality. At present, there are many common mechanical pencil designs, such as the German Red Ring Type 600 and the Shide Building Type 925-85/925-95. , are carefully designed, slender shape, slender core-protecting tube, all-metal high-grade pen body, high friction knurling front section, hexagonal or round rear section, with lead core hardness indicator, tail cap rubber, adjustable single core-pulling length, etc. , multi-functional, accurate processing. But this product can only be used in a fixed place, which is not convenient to carry. If it is put in a pocket, its core protection tube will pierce the pocket like a needle, so that the pocket will also scratch the core protection tube. If you accidentally drop the pencil on the ground, because its center of gravity is close to the end of the pen, the nib will definitely hit the ground first, and the core protection tube will bend beyond repair. In addition, the size of this pen body is also very long, about 145mm, which can't be put in a coat pocket, so it's really inconvenient to carry. The more feasible way to carry it is to put it in a portable pen container, then put it in your trouser pocket and take it out when you use it. It's quite troublesome!
I think a better portable design is to shorten the total length of the pen body and not to design the diameter of the pen holder too small. Panto in Japan and Lamy in Germany both have short and fat mechanical pencil, which looks very gratifying, silly and cute, but these products are all low-grade plastic, and the principle is very simple. Of course, to be portable, we should not only design such a shape, but also consider how to protect the precious core tube. Sunfeili and Parker in America have a large number of fashion products. I call it this. The tips of these pencils have no slender protective core tube. The nib is a conical metal similar to a ballpoint pen, which is very strong and won't break. But of course, this pen can't be used to draw, only to write. Some patents in Japan design the core protection tube to be movable, which can be put into the pen tube together with the core protection tube when the tail button is pressed to retract the core, thus playing a protective role. However, this design has some disadvantages. The core protection tube was originally small, and later it was designed as a sliding single piece. A slight matching error will cause the core protection tube to shake during normal use, and the feel is extremely poor! There are also some patents that design the structure that the whole nib can be retracted, and this principle can be better; An excellent design is to attach a slidable protective sleeve, which can slide out by rotating the front section after the proportion is used up, and cover the pen tip and refill protective sleeve to prevent them from being hurt.
An interesting design needs to be mentioned here. An American was the first to make a multi-core interchangeable composite pen like a revolver. The principle is that six sliding mechanisms with return springs are installed on the wheel, the end of each mechanism is connected with a pen core, the center of the wheel is a sliding push rod connected with a tail cap, and an iron plug suspended by gravity is installed in the push rod. When the pen body rotates downward to a sliding mechanism, the iron plug will fall into the notch of the sliding mechanism. At this time, the tail cap is pushed, and the sliding mechanism can be pushed out and self-locked, thus pushing the related pen core out of the pen tip. This design is ingenious. It is the first time to realize 1 pen 6 cores. These six refills can be four ballpoint pens, 1 ballpoint pen, 1 mechanical pencil. The application range is quite extensive. I once bought such a product and found that its most serious shortcoming was enough to destroy the patent value. Every refill it pushes out is inclined, from the outer edge of the pen tube to the axis, which has a great influence on writing, especially for pencils, especially when the angle of the refill needs to be rotated. At that time, I also began to design and improve the structure of this special revolver, and finally got a pretty good patent. Unfortunately, I have never published it, so there is no such product in the world.
My design is a seven-hole structure. There are six refills on the outer edge of the large-diameter pen tube. The inner circles of six refills are inserted into a semicircular thin-walled tube with a gap. The thin-walled tube is connected to the rotating ring at the end of the pen and can be rotated manually. A counterweight and a locking structure are installed at the end of each pen core, a spring and a locking mechanism are installed in the pen tip, and the locking mechanism is controlled to open through the rotating sleeve of the pen waist. When the pen core needs to be used, manually rotate the tail ring to align the notch of the semi-circular sleeve in the pen with the corresponding pen core, then rotate the pen body to make the notch face upwards, and the pen core will fall into the shaft cavity of the pen, then swing the pen body downwards, and under the action of the heavy hammer, the pen core will rush out of the pen tip, and then be locked, so that it can be used. After the pen is used up, it can be unlocked by rotating the waist of the pen, and the refills can be reset by the spring, and then by gravity, thus realizing the multi-core function, and each refill can be discharged absolutely vertically, so that the writing performance is excellent, and the pressing tail cover is omitted.
The third question, let me talk about the friction device. On the automatic principle of pencil, the friction device should be a one-way chuck, which is installed in the nib and exerts a clamping force on the lead, allowing only the lead to move forward and not backward. However, on the one hand, considering the centralized core, on the other hand, considering its function, it does not need good unidirectional performance, so the designer simplified it as a friction device and made it with cheap soft rubber and other materials. This kind of friction device is press-fitted in the inner hole of the pen head, and its problem is quite serious. On the one hand, the friction device is not firmly fixed, and when people pick up the pencil core, the lead will retreat, and the friction force can easily push the friction device to fall off from the pen tip, which is still useless, so that the pencil is useless and cannot be taken out; On the other hand, the life of rubber is quite short, and the friction device will fail in a few years, so it is impossible for such parts to be used in high-grade pens.
In order to improve the performance of the friction device, Japan began to weld some thin wires with radians in the inner hole of the nib instead of rubber parts. These highly elastic manganese alloy steel wires have excellent wear resistance, will not be worn off after being used for 10 years, and the friction force is also excellent. I have admired this design for many years.
The performance of this friction device is problematic, because it is not a one-way mechanism, but a two-way mechanism, and the friction forces in both directions are completely equal, which means that the push-out force of the lead core is too large and the anti-retraction ability is insufficient. For the commonly used automatic principle of using three-grasping chuck, core-pulling is realized by manually pressing the tail button, so the core-pulling force is great and the resistance of friction device is completely unnecessary; For those advanced and complicated core-pulling principles, it is required that the core-pulling action can be completed reliably under the action of a small core-pulling force, which requires the friction device to have a small positive force and a large enough reverse force. In fact, the friction device in mechanical pencil adopts a three-ball chuck with the same structure. Its performance is so good, except that it can't shrink the core, and the effect is very ideal. As you can imagine, this kind of pencil can't be retracted, so you must consider designing a protection scheme for the core protection tube and the lead, such as retracting the whole nib or pushing out a section of protection tube to cover the core protection tube and the lead.
I always pay attention to the high-end mechanical pencil market, and sometimes I search for many new products and designs online. I found that many high-end products actually belong to fashion rather than technology. For example, in the most common core-pulling principle, pen covers are made of special materials such as mahogany, nanmu and marble, and titanium or gold is plated on the metal to make elegant and fashionable shapes and countless fancy designs. In fact, these products have no use value, even the collection value is not great, and they have completely become commercial things, which means the same as gold-plated seats. Really high-performance mechanical pencil is rare. For example, the fully automatic products I described above are basically not seen in the China market. I think the market share of 3-ball chuck is less than 1/10000, which is the status quo.
Finally, I want to talk about my ideas and specific structural design in detail.
* About the 3-ball chuck: On an inclined plane, three balls with very small diameters are evenly distributed in the original 360-degree circumference. These balls are pushed to the small diameter end of the inclined cone by weak springs and collide with each other to form a 3-ball chuck. When a lead core is inserted from the small diameter end of the cone, it will push away three balls, pass through the chuck body and protrude from the other end. This kind of lead can only go forward, not backward. When it retreats, the three balls will roll on the inclined plane of the cone, resulting in the reduction of the diameter of the axis circle. As a result, the lead is clamped. The greater the retreating force, the greater the clamping force. Moreover, due to the inclination angle, the clamping force will always be greater than the retreating force. Therefore, the one-way action performance of this chuck is extremely high, and it is not necessary to clamp the core with the force of a strong spring like a common three-jaw chuck. This kind of 3-ball chuck is different. The forward force is extremely small, the reverse force is extremely strong, and the performance is quite ideal.
One design is simplified in structure. The small-diameter end of the bronze cone is equipped with a magnet end plate, and the three balls are attracted by the magnet to automatically gather at the small-diameter end, thus saving the spring. This design is good, but whether the performance of the magnet will affect the service life needs to be considered. Another improvement is to make the cone into three grooves and put a ball in each groove, which limits the random string movement of the ball and makes the performance more stable.
Three-ball jam also has its shortcomings. The first disadvantage is that the lead core is clamped by three-point contact, and the contact surface is small, which naturally clamps the lead core out of a hemispherical pit. If the strength of the lead core is not high enough, it is easy to pinch off the lead core. So this pen can only use resin lead, not carbon lead. If the ball diameter is properly increased, the problem of core breakage will be improved, but it still cannot be completely solved; The second disadvantage is that the inclination angle of the cone is difficult to design, and the angle is small, which greatly improves the clamping reliability and self-locking ability, but it requires high accuracy of the lead core diameter. If the lead core is too thin, the fixture will lose its function and cannot prevent the lead core from returning; If the angle is designed to be larger, the accuracy requirement of the lead core diameter can be reduced, but the reliability of clamping will be reduced, and sometimes it will lose its function without self-locking; The third disadvantage is that the diameter of the three balls is extremely small, the cone surface accuracy is extremely high, and the size error cannot be greater than 1 micron. Such high-precision machining will inevitably lead to a substantial increase in cost, so this chuck is very expensive; The fourth disadvantage, for the same reason, once the lead core is pinched off, some lead powder chips may adhere to the three balls or conical surfaces under high pressure, which leads to the dysfunction of the chuck, so the working reliability of the structure is not ideal; Fifth, for the same reason, the slight wear of chuck parts will obviously affect its performance. Although the inclined plane has the performance of automatically eliminating errors, the tolerance is still too small, so the service life of the design will not be long; The sixth disadvantage is that this chuck is not easy to open manually. Unlike the three-jaw chuck, the three-jaw chuck can be opened by pushing the tail cap connected with the chuck, so that the chuck can freely pass through the wire. It is difficult for this three-ball chuck to push away three balls and let the lead pass freely, so it is the most difficult to solve the problem of continuous core when designing pencils with it. My improvement scheme is to make the magnetic end plate into a movable tube, which can not only attract small balls but also push them away through the tail pressing cap, so that the lead core falls into and passes through the chuck under the action of gravity, and the problem of core continuation is solved.
* With regard to the core-pulling principle, I think the commonly used method of back chin tail cap is not ideal. When drawing and writing, the thumb should be changed frequently, and pushing the tail cap to push out the lead will delay the work and affect the creative idea. In this respect, the folding design is much more advanced, and there is no need to change the position of the hand. As long as you press the pen slightly hard, the lead will stick out, which is simple and quick. Unfortunately, this design will be structurally limited and difficult to manufacture. I deny the automatic paper wiping principle of core-protecting tube, but its pre-Qin core-pulling principle is not bad. You can use the period in writing as a core-pulling action, which is heavier than the general writing pressure; But what if you are drawing a picture? You can't add a point online or borrow a piece of toilet paper to do a core action, can you? So it can be seen that the pre-Qin style is not practical! The best core-pulling principle has puzzled people for decades, just like the ideal pistol automatic principle. There are few principles available, and people are at their wit's end and can't think of a more ideal scheme. My design is to use gravity to go to the core. As long as you shake your arm, lead will stretch for a while. The implementation of this scheme is very simple. Just add a heavy hammer big enough behind the pen body and it will be solved! Are the seniors too stupid?
There must be something wrong with the gravity core-pulling design. One is to use high-performance chucks, such as 3-ball chucks, and the other is to solve the problem of core continuity. The ball of the rear chuck must be pushed away by the tail cap, so that the lead can pass through the chuck and reach the ball hole of the front chuck, and the subsequent action can be operated by a heavy hammer.