When the gap between the posterior medial tibia and the tibia exceeds the sputum, it should be given high priority. If necessary, the autologous bone graft should be taken to eliminate the defect. Only when the fracture sections are closely aligned, the stress at the fracture end can be evenly distributed, in order to effectively prevent the deformation and fracture of the internal fixation equipment, and promote the soft tissue injury of the fracture site of the bone. 2.3 The soft tissue injury of the fracture site is severe, and the incision skin is postoperative. Necrosis liquefaction, fracture and internal fixation equipment exposed to surgery failed a total of 12 cases, about 20 of the total number of missed sputum, of which 8 cases were tibiofibular fractures. Mostly direct impact and heavy weight injury, local skin and soft tissue contusion severe bone exposure, requiring emergency treatment. The operator was underestimated for soft tissue injury due to lack of experience. The skin tension increased due to soft tissue edema after internal fixation, and the suture was difficult to suture. In addition, the incision was not sufficient. The postoperative wound 1 skin necrotic liquefaction fracture was exposed. In addition, soft tissue damage destroys local blood circulation, directly affects the growth of the epiphysis, and makes the fracture heal slowly. If the weight is walking before the fracture is healed, the internal fixation equipment will bear the stress for a long time, and it is easy to see fatigue and fracture, and then the abnormal activity occurs at the broken end, which makes the operation fail. Therefore, the tibiofibular fracture with severe soft tissue injury should be fixed with an external fixator with less local circulatory disturbance. For open fractures with soft tissue contusion and skin defects after debridement, local rotation flaps should be used as much as possible. The free flaps can also be used to close the wounds. Improving the surgeon's wound handling ability and improving local blood circulation is the fundamental way to prevent such surgery failure. 2.4 Infection factors In this group, 9 cases of chronic osteomyelitis were caused by surgical infection. About the total number of failures, including one case of the femoral bone, one case of the ulna, the ulna and the phalanx. With the rapid development of antibiotics, people's fear of orthopedic surgery infection has gradually faded, and preoperative preparation for orthopedics tends to be simple and quick. Although orthopedic surgery is the most serious complication of internal fixation surgery. When the infection occurs, it will bring great pain and trouble to the patient, and the treatment is quite tricky. The infection course of this group is the shortest one year, the longest is 8 years, the average is 3 years, and the joint dysfunction of the affected limbs is left to varying degrees, which brings great harm to the patient's body and mind. Therefore, measures to prevent infection must be implemented. The surgeon should select appropriate fixation methods according to the age of the patient's injury, minimize the operation time, and wash and drain the wound after surgery. According to the patient's condition, the effective amount of 2.5 other factors were selected. In this group, there were 2 cases of stress shielding by the compression plate, bone absorption at the fracture end, and re-operation of bone grafting was needed. Two other cases were incorrectly moved too early and the bones were not connected. There are also 2 cases because the quality of the internal fixation material is inferior, resulting in fracture of the intramedullary needle splitting plate. Prevention is to correctly grasp the indications of compression plate, advocate elastic fixation; guide postoperative rehabilitation training, and strive to achieve step-by-step functional recovery; use internal fixators produced by regular manufacturers with quality assurance to prevent unqualified internal fixators In the clinic. 1 Xu Yuxiang, Liu, Li Changsheng and so on. The current basic treatment of the internal fixation of the internal fixation 4. Chinese Journal of Orthopaedics, 1996, 4204 edited by Song Hua homemade micro-spring embolization spermatic vein treatment of varicocele Song Huazhi Wang Ping Tian Jialin Xiaoxu Huang Weibing varicocele It is the cause of male infertility, accounting for 4 of infertility patients. The clinical symptoms include scrotal swelling and pain, which can affect work and life. In our hospital from 1999042000, in February, 25 cases of varicocele were treated with self-made micro-spring embolization of the internal spermatic vein, and the results were satisfactory. 1 Method and data received date 2000075 25 patients aged 2026 years, the median age of 21 years. All are left varicocele. One example is postoperative recurrence. 25 cases of clinical grade = grade 4 cases, grade 2.25 cases of all patients used 8 method, pulse puncture intubation, 22 cases of success, 3 cases of success, after the catheter was inserted into the left renal vein, push the ground plug Misong used 30 compound diatrizoate 1015,8, total 3, 虬 pressure 350 lbs, left renal vein angiography, to understand the position of the spermatic vein opening, the catheter tip close to the fine internal vein opening, inserted into the catheter The super-sliding guide wire is guided into the internal vein of the spermatic cord. Under the guidance of the super-sliding guide wire, the catheter is inserted into the internal vein of the spermatic cord at the level of the waist 3, and the internal spermatic vein is compared. Contrast condition 41 pressure below 150, total 161. According to the angiography, the catheter is placed in a suitable position. A tungsten wire microspring with a length of 2.5 and a diameter of 0.5, 1 is placed over the thin steel wire, fed into the 31-tube, and the thin steel wire is withdrawn, and the micro-spring is pushed out of the catheter with the hard end of the butt-shaped guide wire. The amount of micro springs was 23 times. After the embolization is completed, the catheter is withdrawn and the puncture site is pressurized and bandaged. Antibiotics were used for 3 days after surgery. Three patients had mild left-middle-abdominal pain after surgery, and were treated without treatment. No other discomfort or complications. 2 The results disappeared, and the scrotum was palpated without varicose veins. 9 cases were effective, that is, the symptoms were alleviated and the degree of varicocele was lightened. No recurrence and ineffective cases. Seven patients were treated with spermatic vein venography at the distal end of the resection of the varicocele, and no new collaterals were found. 3 Discussion 3.1 Physicochemical properties and characteristics of homemade tungsten filament microsprings The treatment of varicocele by internal veins of sputum spermatic cord has been widely used in clinical practice. Commonly used embolic materials are spring steel detachable ball, 31 and hardener. In 199904, we used self-made tungsten wire as the spring embolization spermatic vein for the treatment of varicocele. In addition to the same embolization effect as the above materials, the main advantages It is easy to obtain and low in price. Tungsten wire has stable spring performance and no obvious toxic side effects on the tissue. 5 Tungsten wire microspring has been used for embolization of intracranial aneurysms and venous leakage. 7. No complications were found by embolization with tungsten wire microsprings. 3.2 The treatment of spermatic vein embolization for the treatment of varicocele, there are many mature experiences. Some authors have suggested that the internal spermatic vein and the lumbar vein have traffic branches or traffic veins with the vena cava, and can not be embolized. 8. Some people have suggested that the contrast agent from the venous vein to the renal vein is not suitable for embolization. 9. We think Embedding with a micro-spring, as long as avoiding the traffic branch, will not cause embolization of the lumbar vein and vena cava. When the micro-spring is plugged, the effect of complete embolization can be achieved without the need to add a hardener, and it is not necessary to consider the reflux problem. In order to prevent recurrence after embolization, it is necessary to master the site of embolization. In each case, the location of the embolization was determined according to the venous angiography of the spermatic cord. It was suggested that if the proximal end of the spermatic vein was changed, the embolization site should be below. For example, there are 23 branches at the distal end of the internal spermatic vein, which should be embolized above all branch points. Our experience is basically the same as above, but if there is a side branch, it is best to give the embolism up and down separately. The intubation procedure must be light and avoid rough movements to avoid damage to the renal veins or to cause varicocele. When the catheter is close to the opening of the internal vein of the spermatic cord, the surgeon fixes the catheter and the assistant inserts the super-sliding guide wire through the catheter. After the super-sliding guide wire is inserted into the internal spermatic vein, the catheter is then sent to the internal spermatic vein to reach the level of 123, and the guide wire is withdrawn. An anatomical variation should be considered if the catheter is close to the internal spermatic vein opening, but the superslip guide wire cannot be inserted into the internal spermatic vein. This group has this case. After careful analysis of the contrast and smoke observation, it is found that the spermatic vein opening is above the renal vein. Therefore, the tip of the catheter is turned upside down to the internal vein of the spermatic vein, and guided by the super-sliding guide wire. The intubation was successful. In the case of embolization, if a spring is used, it is not necessary to use a hardener or gelatin sponge. The embolization can be achieved by the spring plug. When gelatin sponge or hardener is added, gelatin sponge and hardener can enter the scrotum. After surgery, the patient's scrotum is red and swollen, the pain is obvious, and there is obvious left lower abdomen pain. This phenomenon was first seen in 2 patients in this group. The gelatin sponge and hardener were not used in the future, and the above situation did not occur. In addition, the intubation time should not be too long, otherwise it may cause vasospasm and the intubation fails. If the intubation is unsuccessful, you don't have to be stubborn. You can intubate the tube for the next week or so, so as to avoid vascular damage caused by impatience. Although it has been reported that renal vein perforation has no adverse consequences, the value is best not to occur. The self-made tungsten wire micro-spring embolization of the spermatic vein for the treatment of varicocele, the patient has little pain, good effect, easy to take, low price, easy to promote and apply. 2 Li Baochi, Mu Lianbi, Luo Zemin and so on. Intravenous venous embolization for the treatment of varicocele in 20 cases reported to the Chinese Journal of Urology, 988, 9 5 brother Zuoquan, Ma Lianting, Zhang Lun and so on. The development of tungsten filament micro-coil and its observation of embolization effect. Chinese Journal of Experimental Surgery, 1994, 6369 6 Wu Xue. Wang Zhongcheng, Zhang Youping. Self-made micro-coil to embolize intracranial posterior circulation aneurysms. Chinese Journal of Radiology, 1996.309587 7 Song Huazhi, He Jiangang, Liu Qinzhen and so on. Treatment of 40 cases of venous leakage and impotence through deep penile vein embolization. Chinese Journal of Urology, 1996, 17 of Urology, 1984, 56739 Li Shenqin, Ge Hongfa, Cheng Jiyi and so on. Treatment of varicocele with spermatic vein embolization. Chinese Journal of Urology, 1988, 94243, edited by Song Hua's small incision for the treatment of 22 cases of middle-aged and elderly pituitary adenomas Luo Chaowei Tian Yingde, Quyou straight pituitary adenoma is the most common tumor in the sellar region, accounting for about the intracranial tumor year, but in the middle There are also many elderly patients, and the clinical treatment is mainly surgery. There are two types of traditional surgical methods: transcranial surgery and transsphenoidal surgery. The former is divided into the forehead and the pterional approach. In the transurethral approach, the incision is usually located in the hairline. The wound has a large wound. Since December 1993, we have used 22 patients with middle-aged and elderly patients with pituitary adenoma to remove the tumor with a small frontal craniotomy, which has achieved satisfactory results. The report is as follows. 1 Materials and Methods 1.1 General Information This group of 22 patients, 13 males and 9 females, aged 4769 years, mean 61.2 years old. The course of disease is as short as 4 months and the longest is 5 years, with an average of 2.7 years. Clinically, there were 22 cases of visual field changes, 16 cases of increased intracranial pressure such as headache and vomiting, and 7 cases of endocrine changes such as acromegaly and cardiac dysfunction. Imaging features and or 1 saddle tumor developed to the saddle, tumor position internal view cross-type or retrograde posterior type. In the skull, the sphenoidal saddle is enlarged, the double saddle is changed, the saddle bone is not damaged, and the frontal sinus is relatively small. 1.2 + method before the operation of Du Leng Ding and stability of the static pain, the operation of the middle of the static drop stability, if necessary, add a small amount of Du Lengding, in order to maintain a light sleep state for routine oxygen, monitor blood oxygen saturation. The patient was placed in the supine position, and the incision was made in the direction of the frontal line of the right eyebrow. The length of about 4, if the tumor is obviously to the left, the left incision can also be taken. After local anesthesia, the skin subcutaneous tissue and periosteum were completely cut, the periosteum was slightly peeled off, the skull was drilled and the bone window was enlarged about 3,7!3, the lower edge reached the upper edge of the iliac crest, and the bone window edge was coated with bone wax to stop bleeding. Open the dura mater in the arc, tear the frontal arachnoid membrane in the sulcus, slowly suck out the cerebrospinal fluid, and after the brain tissue collapses, gently lift the frontal lobe into the saddle area, and open the visual cross-cell to release the cerebrospinal fluid to facilitate the tumor. Exposure and surgical procedures. After the tumor is revealed, the tumor is puncture and aspiration is taken before the optic chiasm, the vascular tumor is excluded, the tumor capsule is electrocoagulated and the tumor is incision, and the tumor is resected; for the tumor capsule, it is not necessary to peel off, and the electrocoagulation can be made back. Shrink, to achieve adequate decompression of the optic nerve. After careful hemostasis, the dura mater is tightly sutured. The skull defect was repaired with plexiglass, and the incision skin was sutured. 2 treatment results 22 patients were removed 7 days after surgery, except for 2 cases of incision subcutaneous hemorrhage, physical therapy for blood absorption, the other patients without any complications, and the visual field began to gradually recover from the first day after surgery . There were no deaths in this group. 3 Discussion 3.1 The advantages of this procedure through the amount of the pituitary adenoma surgery in order to make the patient's appearance unacceptable date 2000 Department of Military Medical University Affiliated Hospital Neurosurgery Engine valves are mechanical components used in internal combustion engines to allow or restrict the flow of fluid or gas to and from the combustion chambers or cylinders during engine operation. Functionally, they perform similarly to many other types of valves in that they block or pass flow, however, they are a purely mechanical device that interfaces with other engine components such as rocker arms in order to open and close in the correct sequence and with the correct timing. Auto Engine Valve,Car Engine Valve,Engine Valve For Land Rover,Intake And Exhaust Valves Shijiazhuang Longshu Mechanical & Electrical Equipment Trading Co., Ltd. , https://www.lsjgbearing.com
The term engine valve may also refer to a type of check valve that is used for air injection as part of the emission control and exhaust gas recirculation systems in vehicles. This type of engine valve will not be addressed in this article.
Engine valves are common to many types of combustion engines, whether they run off a fuel such as gasoline, diesel, kerosene, natural gas (LNG), or propane (LP). Engine types vary by the number of cylinders which are the combustion chambers that generate power from the ignition of fuel. They also vary by the type of operation (2-cycle or 4-cycle), and by the design placement of the valves within the engine [overhead valve (OHV), overhead cam (OHC), or valve in block (VIB)].
This article will briefly describe the operation of engine valves in typical combustion engines, as well as present information on the types of valves and their design and materials. More information concerning other about other valve types may be found in our related guide Understanding Valves.
Engine Valve Nomenclature
Most engine valves are designed as poppet style valves because of their up and down popping motion and feature a conical profile valve head that fits against a machined valve seat to seal off the passage of fluids or gases. They are also called mushroom valves because of the distinctive shape of the valve head. Figure 1 shows the nomenclature for the different elements in a typical engine valve.
Diagram showing the nomenclature of a poppet valve.
Figure 1 - Nomenclature for a standard poppet style engine valve.
Image credit: https://dieselnet.com
The two primary elements are the valve stem and the valve head. The head contains a fillet that leads into a seat face that is machined at a specified angle to match the machining of the valve seat to which it will match. The seating of the valve face to the valve seat is what provides the seal for the valve against combustion pressure.
The valve stem connects the valve to the mechanical elements in the engine that operate the valve by creating a force to move the stem against the seating pressure provided by a valve spring. The keeper groove is used to hold the spring in position, and the tip of the valve stem is repeatedly contacted by a rocker arm, tappet, or lifter that actuates the valve.
Engine Operation
Four stoke or four-cycle internal combustion engines make use of two primary types of valves – the intake valve and the exhaust valve. Intake valves are opened to allow the flow of an air/fuel mixture into the engine`s cylinders prior to compression and ignition, while exhaust valves open to permit the expulsion of exhaust gases from the combustion process after ignition has occurred.
In normal operation, a crankshaft in the engine to which the pistons are attached is tied to a camshaft as part of a valve train arrangement for the engine. The movement of the crankshaft transfers motion to the camshaft through a timing chain, timing belt, or other geared mechanism. The timing and alignment between the position of the crankshaft (which establishes the position of the piston in the cylinder) and the position of the camshaft (which determines the position of the valves for the cylinder) is critical not only for peak engine performance but also to preclude interference between pistons and valves in high compression engines.
In the intake cycle, the intake cylinder piston cycles downwards as the intake valve opens. The piston movement creates negative pressure that helps draw the air/fuel mixture into the cylinder. Just after the piston reaches the lowest position in the cylinder (known as bottom dead center), the intake valve closes. In the compression cycle, the intake valve is closed to seal off the cylinder as the piston rises in the cylinder to the highest position (known as top dead center), which compresses the air/fuel mixture to a small volume. This compression action serves to provide a higher pressure against the piston when the fuel is ignited as well as pre-heating the mixture to assist with an efficient burning of the fuel. In the power cycle, the air/fuel mixture is ignited which creates an explosion that forces the piston back down to the lowest position and transfers the chemical energy released by burning the air/fuel mixture into the rotational motion of the crankshaft. The exhaust cycle has the piston again rising upward in the cylinder while the intake valve remains closed and the exhaust valve is now open. The pressure created by the piston helps force the exhaust gases out of the cylinder through the exhaust valve and into the exhaust manifold. Connected to the exhaust manifold are the exhaust system, a set of pipes that includes a muffler to reduce acoustical noise, and a catalytic converter system to manage emissions from the engine combustion. Once the piston reaches the top of the cylinder in the exhaust cycle, the exhaust valve begins to close and the intake valve starts to open, beginning the process over again. Note that the cylinder pressure on intake helps to keep the intake valve opened and the high pressure in the compression cycle helps to keep both valves closed.
In engines that have multiple cylinders, the same four cycles repeat in each one of the cylinders but sequenced so that the engine proves smooth power and minimizes noise and vibration. The sequencing of piston movement, valve movement, and ignition is accomplished through the precise mechanical design and electrical timing of ignition signals to the spark plugs that ignite the air/fuel mixture.
Engine Valve Motion
The motion of the engine valves is driven by the camshaft of the engine, which contains a series of lobes or cams that serve to create linear motion of the valve from the rotation of the camshaft. The number of cam lobes on the camshaft is equal to the number of valves in the engine. When the camshaft is in the cylinder head, the engine is called an overhead cam (OHC) design; when the camshaft is in the engine block, the engine is called an overhead valve (OHV) design. Regardless of the engine design, the basic movement of the engine valves occurs by the cam riding against a lifter or a tappet that provides a force that presses against the valve stem and compresses the valve spring, thereby removing the spring tension that keeps the valve in the closed position. This movement of the valve stem lifts the valve off the seat in the cylinder head and opens the valve. Once the camshaft rotates further and the cam lobe moves so that the eccentric portion is no longer directly in contact with the lifter or tappet, the spring pressure closes the valve as the valve stem rides on the centric portion of the cam lobe.
Maintaining the proper valve clearance between the valve stem and the rocker arm or cam is extremely important for the proper operation of the valves. Some minimal clearance is needed to allow for the expansion of metal parts as the engine temperature rises during operation. Specific clearance values vary from engine to engine, and failure to maintain proper clearance can have serious consequences to engine operation and performance. If the valve clearance is too large, then the valves will open later than optimally and will close sooner, which can reduce engine performance and increase engine noise. If the valve clearance is too small, valves will not close fully, which can result in a loss of compression. Hydraulic valve lifters are self-compensating and can eliminate the need for valve clearance adjustments.
Modern combustion engines can use a different number of valves per cylinder depending on the design and the application. Smaller engines such as those used in lawnmowers may have only a single intake valve and one exhaust valve. Larger vehicle engines such as 4-, 6- or 8-cylinder engines may use four valves per cylinder or sometimes five.
Engine Valve Materials
Engine valves are one of the components in internal combustion engines that are highly stressed. The need for reliable engine operation dictates that engine valves be capable of exhibiting resistance to repeated and continuous exposure to high temperature, high pressure from the combustion chamber, and mechanical loads and stresses from the engine dynamics.
The intake valves on internal combustion engines are subjected to less thermal stress because of the cooling effects of the incoming air/fuel mixture that passes by the valve during the intake cycle. Exhaust valves, by contrast, are exposed to higher levels of thermal stress by being in the pathway of the exhaust gases during the exhaust cycle of the engine. In addition, the fact that the exhaust valve is open during the exhaust cycle and not in contact with the cylinder head means the smaller thermal mass of the combustion face and valve head has a greater potential for a rapid temperature change.
Intake valves, because of their lower operating temperatures, are typically made of materials such as chrome, nickel, or tungsten steel. The higher temperature exhaust valves may use more heat resistant metals such as nichrome, silicon‑chromium, or cobalt-chromium alloys.
Valve faces that are exposed to higher temperatures are sometimes made more durable by the welding of Stellite, which is an alloy of cobalt and chromium, to the valve face.
Other types of material used for the fabrication of engine valves include stainless steel, titanium, and tribaloy alloys.
In addition, coatings and surface finishes can be applied to improve the mechanical properties and wear characteristics of the engine valves. Examples of this include chromium plating, phosphate plating, nitride coating, and swirl finishing.
Types of Engine Valves
Besides the characterization of engine valves by function (intake versus exhaust), there are several specific types of engine valves that exist based on design and materials. The primary types of engine valves include:
Monometallic engine valves
Bimetallic engine valves
Hollow engine valves
Monometallic engine valves, as their name implies, are fabricated from a single material that forms both the valve stem and valve head. These types of engine valves provide both high heat resistance and exhibit good anti-friction capabilities.
Bimetallic engine valves, also known as bimetal engine valves, are made by joining two different materials together using a friction welding process to create a valve that has austenitic steel on the valve head and martensitic steel for the valve stem. The properties of each of these steels serve an optimal purpose, wherein the austenitic steel on the valve head provides high-temperature resistance and corrosion resistance, and the martensitic steel for the valve stem offers high tensile strength and abrasive wear resistance.
Hollow engine valves are a special bimetallic valve that contains a hollow cavity that is filled with sodium. The sodium liquifies as the valve temperature rises and is circulated by the motion of the valve, which helps dissipate heat from the hotter valve head. The hollow design facilitates greater heat transfer through the stem than with solid valves because the martensitic stem material is a better conductor of heat than the austenitic head material. Hollow valves are especially suited for use in modern engines that are delivering more power out of smaller, denser engine designs that have higher exhaust gas temperatures which solid valves are not capable of handling. These higher exhaust temperatures are the result of several conditions, including:
A desire for a lean-burn combustion process that reduces greenhouse gas emissions
Engine designs with higher compression ratios and higher combustion pressures which offer greater efficiency
Integrated manifold designs that support turbochargers for more engine performance from smaller engines
There are several other types of engine valve designs. So-called sleeve valves consist of a tube or sleeve that sits between the cylinder wall and the piston, and which slide or rotate driven off a camshaft as with other engine valves. The movement of the sleeve valve causes ports that are cut into the sleeve to align with corresponding ports in the cylinder wall at different points in the engine cycle, thus functioning as a simple engine intake and exhaust valve without the complexities of rocker arms and lifters.
Engine Valve Specifications
Typical engine valves are specified by the parameters outlined below. Note that this data is intended for information purposes and be aware that variations in the parameters used for specifying engine valves may exist from manufacturer to manufacturer. By understanding the specifications, buyers are better equipped to engage in discussions of their specific needs with suppliers of engine valves.