Explaining CAM And Its Followers

Explaining CAM And Its Followers BASIC DEFINITION OF CAM A cam is a mechanical component of a machine that is used to transmit motion to another component, called the follower, through a prescribed motion program by direct contact. INTRODUCTION TO CAM AND FOLLOWERS A cam follower, also known as a track follower,[1] is a specialized type of roller or needle bearing designed to follow cams. Cam followers come in a vast array of different configurations, however the most defining characteristic is how the cam follower mounts to its mating part; stud style cam followers use a stud while the yoke style has a hole through the middle.[2] The first cam follower was invented and patented in 1937 by Thomas L. Robinson of the McGill Manufacturing Company.[3] It replaced using just a standard bearing and bolt. The new cam followers were easier to use because the stud was already included and they could also handle higher loads.[ CAM AND MECHANISMS A cam mechanism consists of three elements: the cam, the follower (or follower system), and the frame. The follower is in direct contact with the cam. The cam may be of various shapes. The follower system includes all of the elements to which motion is imparted by the cam. This may be connected directly to the follower, or connected through linkages and gearing. The frame of the machine supports the bearing surfaces for the cam and for the follower. A CAM changes the input motion, which is usually rotary motion (a rotating motion), to a reciprocating motion of the follower. They are found in many machines and toys WHAT IS THE CONCEPT BEHIND CAM? A CAM is a rotating machine element which gives reciprocating or oscillating motion to another element known as follower. The cam and follower has a point or line contact constitute a higher pair or you can say that it is the mechanicl component of a machine that is used to transmit the motion to the another component of the machine called the follower, through a prescribed program by direct contact.The contact between them is maintained by an external force which is generally provided by the spring or sometimes by the weight of the follower itself ,when it is sufficient. Cam is the driver member and the follower is the driven member. The follower is in direct contact with the cam. CAM MECHANISM CONSIST OF THREE MECHANISMS CAM:It may be of many shapes FOLLOWER: It includes all the elements to which motion is imparted by the cam.This may be connected directly by the cam.This may be connected directly to the follower, or connected through linkages and gearing. FRAME: The frame of the machine supports the bearing surfaces for the cam and for the follower. APPLICATIONS OF CAM AND FOLLOWERS Cam and follower are widely used for operating inlet and exhaust valve of I C engine. These are used in wall clock. These are used in feed mechanism of automatic lathe Machine. These are used in paper cutting machine. Used in weaving textile machineries. The cam mechanism is a versatile one. It can be designed to produce almost unlimited types of motioning the follower. It is used to transform a rotary motion into a translating or oscillating motion. On certain occasions, it is also used to transform one translating or oscillating motion into a different translating or oscillating motion. Cams are used in a wide variety of automatic machines and instruments. The certain usuages of cam and followers that includes textile machineries, computers, printing presses, food processing machines, internal combustion engines, and countless other automatic machines, control systems and devices. The cam mechanism is indeed a very important component in modern mechanization. CLASSIFICATION OF CAMS Based on the physical shape Disk or plate cams Working of the disc cam with reciprocating follower. Working of the disc cam with oscillating follower. Cylindrical cam Translating cam CLASSIFICATION OF FOLLOWES (i) Based on surface in contact (a) Knife edge follower (b) Roller follower (c) Flat faced follower (d) Spherical follower (ii) Based on type of motion Oscillating followe Translating follower (iii) Based on line of action Radial (in line) follower (b) Off-set follower Cams can be conveniently classified into two main groups Group a: Cams that impart motion to the follower in a plane in line with the axis of rotation of the cam (as does a cylindrical cam). Group b: Cams that impart motion to the follower in a plane at 90 degrees to the axis of rotation, as with face or edge cams.Most cams fall into this category. TYPES OF CAMS Eccentric cam: A circular cam is often called an eccentric cam because the axis of rotation of the cam is offset from the geometric center of the circular disc. Concentric disc: A concentric disc attached to a rotating shaft would have its axis of rotation coinciding with its geometric center. PROFILE SHAPES OF SOME CAMS: PEAR-SHAPED CAMS: These type cams are often used for controlling valves. For example, they are used on motor car camshafts to operate the engine valves. A follower controlled by a pear-shaped cam remains motionless for about half a revolution of the cam. During the time that the follower is stationary, the cam is in a dwell period. During the other half revolution of the cam, the follower rises and then falls. As the pearshaped cam is symmetrical, the rise motion is the same as the fall motion. Edge cams It must be appreciated that this type of cam, where the follower is in contact with the edge of the cam disc, is only capable of imparting positive motion to its follower in one direction, that is, during the rise portion of the cam movement. During the fall portion of the cam movement the follower must be maintained in contact with the cam either by the mass of the follower and its mechanism or, more usually, by a spring. Both methods have their advantages. Box cams A groove can be milled in the face of cam discs. As the cam rotates, a follower located in the groove has its motion guided by the groove. This type of cam is called a box cam. Cylindrical cams: Cylindrical cams are used when motion has to be transmitted parallel to the axis of rotation of the cam. The cylindrical or barrel cam consists of a rotating cylinder with a helical (screw shaped) groove in its curvedsurface. A follower with a tapered roller end is located in the groove. As the cylinder turns, the follower moves in a straight line parallel to the axis of the rotation barrel cam. This type of cam is often used to guide thread on sewing machines, looms and fabric making machines. CIRCULAR CAMS: These cams are sometimes called eccentric cams. The cam profile is a circle. The center of rotation of the cam is often from the geometric center of the circle. The circular cam produces a smooth form of motion called a simple harmonic motion. These cams are often used to produce motion in pumps. Circular cams are often used to operate steam engine valves. As the cam is symmetrical, the rise and fall motions are the same. HEART SHAPED CAMS: This cam causes the follower to move with a uniform velocity. Heart-shaped cams are essential when the follower motion needs to be uniform or steady as, for example, in the mechanism that winds thread evenly on the bobbin of a sewing machine. A heart-shaped cam can be used for winding wire evenly on the former of a solenoid. UNIFORM ACCELERATION AND RETARDATION CAMS: A cam shaped as shown controls the motion of the follower so that it moves with uniform acceleration and retardation. The follower gains and looses velocity at a constant rate. Uniform acceleration and retardation cams are used to controls the motion of linkages in complex machinery. Types of Cam Followers There are three types of cam followers, and since the type of follower influences the profile of the cam it is worthwhile considering the advantages and disadvantages of each type. The three types are the knife-edge, the roller follower and the flatfoot or mushroom follower. The Knife Edge Follower: This is the simplest type, is not often used due to the rapid rate of wear. When it is adopted, it is usually for reciprocating motion, running in slides and there is considerable side thrust, this being a component of the thrust from the cam. The Roller Follower: This eliminates the problem of rapid wear since the sliding effect is largely replaced by a roller action. Some sliding will still take place due to the varying peripheral speed of the cam profile, due to the changing radius of the point of contact. Note also that the radial position of the contact between the cam and the roller, relative to the follower center, will change according to whether a rise or fall motion is taken place: this fact has to be considered when constructing the cam profile. Again,with the roller follower, considerable side thrusts are present, a disadvantage when dealing with reciprocating motions. This side thrust will be increased when using small rollers. The Flat Foot or Mushroom Follower: This has the advantage that the only side thrust present is that due to the friction between the follower and the cam. The problem of wear is not so great as with the knife-edge follower, since the point of contact between the cam and follower will move across the face of the follower according to the change of shape of the cam. A trick to lessen further the effect of wear is to design the follower to be capable of axial rotation and arrange the axis of the follower to lie to one side of the cam. Thus the contact with the cam will tend to cause rotation of the follower. The cam profile, to work with a flatfoot follower, must be convex at all parts, in order to prevent the corners of the follower digging into the cam profile. The minimum cam radius should be as small as possible to minimize sliding velocity and friction. All three types of cam followers can be mounted in the following ways: 1) In-line with the cam center line, 2) Offset from the cam center line, or 3) Mounted on a swinging radial arm. CAM-VALVE CAM TERMINOLOGY Trace point: A theoretical point on the follower, corresponding to the point of a fictitious knife-edge follower. It is used to generate the pitch curve. In the case of a roller follower, the trace point is at the center of the roller. 2.Pitch curve: The path generated by the trace point at the follower is rotated about a stationary cam. 3. Working curve: The working surface of a cam in contact with the follower. For the knife-edge follower of the plate cam, the pitch curve and the working curves coincide. In a close or grooved cam there is an inner profile and an outer working curve. 4. Pitch circle: A circle from the cam center through the pitch point. The pitch circle radius is used to calculate a cam of minimum size for a given pressure angle. 5. Prime circle (reference circle): The smallest circle from the cam center through the pitch curve. 6. Base circle: The smallest circle from the cam center through the cam profile curve. 7. Stroke or throw: The greatest distance or angle through which the follower moves or rotates. 8. Follower displacement: The position of the follower from a specific zero or rest position (usually its the position when the follower contacts with the base circle of the cam) in relation to time or the rotary angle of the cam. 9. Pressure angle: The angle at any point between the normal to the pitch curve and the instantaneous direction of the follower motion. This angle is important in cam design because it represents the steepness of the cam profile. Some question arises regarding cam and followers: When is a flat faced follower preferred as compared to roller followers and why? Flat faced followers are preferred to roller followers where space is limited for eg: cams with flat followers are used to operate valves of an automobile engine but in case of stationary and oil engines, roller followers are preferred because more space is available. What data is plotted on displacement diagram of cam and follower motion? Ans:Plot of linear displacement i.e. lift or stroke (s) of follower (on Y axis direction) versus angular displacement (ÃŽÂ ¸) of the cam for one rotation (on X axis direction) REFERENCES: WIKIPEDIA. McGILL CAMROLL bearings. Robinson, Thomas L., Bearing, US

Ethics for End of Life Care Essay -- Ethics, Arguments, History

In the article Ethics for End of Life Care, Jos V.M Welie introduces the case of Terri Schiavo. Schiavo has a medical condition called PVS or â€Å"persistent vegetative state.† The main question imposed is whether or not treatment for her should be continued with a bleak chance of recovery. This directly leads into the next issue of the role that medical treatment and technology have in the final days of life. How do we decide what treatments should be used for which patients? Today, the majority of physicians agree that treatment must be â€Å"medically indicated† before it is commenced or continued. A majority of us would be skeptical of a treatment that is experimental and potentially dangerous. The second key point the article makes involves the Catholic medical ethics known as â€Å"ordinary vs. extraordinary.† Ordinary and extraordinary treatment must always be based on the patient’s current situation. Before the treatment is initiated, there must be scientific evidence that the treatment will benefit the patient. The treatment should be discontinued if it does not improve the patient’s health. Only the patient is allowed to make the decision. If they are not competent enough too, a legally authorized person is required to decide. If there is no hope left for the patient, letting go is a better alternative than euthanasia. Euthanasia conflicts with God’s view of the human body. Gula explains in his work Reason Informed by Faith, that there has been a significant renewal in Roman Catholic moral theology. There has been a shift from the idea of human nature to that of the human person. The human body is seen as an image of God and therefore, is considered sacred. The human body must abide by the laws of the material world around it. Be... ...s. Although it was questionable if he was able to even make a decision, he was rarely, if at all approached by the doctor about it. Death is inevitable from a Christian perspective, but it is not the end. People struggle with death I believe because they are afraid of the unknown. What comes after death? Is there really an afterlife? Will I be rewarded or punished for my time on Earth? I consider that the best way to die is to be surrounded and comforted by my family and friends. The idea of a planned death just seems so unnatural. That is why I believe that euthanasia should not be legal. The hospital should perform the treatments that will actually help the patients recover. If no treatment is appropriate enough, the physician should not have to resort to assisting the patient in death. God intended death to be a natural cause, and it should remain that way.

AIU Human Resources Essay

To the head of AIU: In this message I would like to inform you about the relationship between job satisfaction and the age, this relationship will help in providing a clear indication of the best workers to employ in a company depending on satisfaction, the more satisfied the workers are then the higher is their productivity level and therefore companies should employ more satisfied workers. Summary of the survey participants: Gender: The following is a survey on some workers in a company and this email reports on the findings about the overall satisfaction of workers, the study included a total of 29 participants where 19 of them were male and 10 were female, the following chart summarizes the distribution of male and female in percentage: From the above chart it is evident that the probability of picking a male from the sample is 64.52% while the probability of picking a female from the sample is 34.48%. Tenure: Regarding tenure it was evident that 21.05% of males and 10% of female had worked at the company for less than two years, 57.89% of males and 50% of females have worked with the company for 2 to 5 years, finally 21.05% of males and 40% of females have worked with the company for over 5 years. The following table summarizes the results: MALE FEMALE Less than 2 years 21.05% 10.00% 2 to 5 years 57.89% 50.00% Over 5 Years 21.05% 40.00% From the table it is evident that majority of both males and females have worked with the company for 2 to 5 years, however the less females have worked with the company for less than two years. Department: There are three departments namely Human Resources, Information Technology and Administration, in this case the following was the distribution of participants in each department: From the chart it is evident that most of the participants were from the administration department, the least number of participants were from the information technology department. Satisfaction: The participants were asked to identify the level of intrinsic satisfaction, extrinsic satisfaction and overall satisfaction; the following tables summarize the mean values of satisfaction: MEAN MALE OVERALL 4.65 INTRINSIC 4.78 EXTRINSIC 4.81 MEAN FEMALE OVERALL 5.39 INTRINSIC 5.62 EXTRINSIC 4.62 From the table the mean value for overall and intrinsic satisfaction for female is greater than the mean value for the male; however the mean value of extrinsic satisfaction for males is greater than that for the females. Therefore from the above we can conclude that females are more satisfied than males. Age: The participants by age were categorized into three groups, this include those aged below 21, those aged between 22 and 49 and those above 50 years, the table below summarizes the results: participants percentage 21 and under 5 17.24% 22-49 17 58.62% 50 and over 7 24.14% From the table more participants were aged between the age of 22 and 49 years and that less participants were aged 21 years and below. Position: There are those participants that are hourly employees and the salaried employees, from the survey it was evident that more employees were salaried and this comprised of 58.62% of the participant; the table below summarizes the results. Hourly Employee (Overtime Eligible) 12 41.38% Salaried Employee (No Overtime) 17 58.62% Relationship between satisfaction and age: The following table below represents the mean level of satisfaction for the age groups OVERALL INTRINSIC EXTRINSIC 21 and under 4.34 4.02 5.78 22-49 4.69411765 5.317647059 4.8294118 50 and over 5.81428571 5.228571429 3.8 Overall satisfaction: There is an increase in the mean level of overall satisfaction as the age increases, from this reason those aged 50 and above years have the highest level of overall satisfaction, therefore these individuals will tend to be more productive in the company, for this reason the company should employ older people in the organization to realize the advantage of satisfied workers. Regarding intrinsic satisfaction it is clear that those aged below 21 years have the lowest intrinsic satisfaction while those aged 22 to 49 years have the highest mean level of intrinsic satisfaction, finally regarding extrinsic satisfaction those aged 50 years and above have the lowest extrinsic satisfaction. Conclusion: From the above discussion it is evident that age is an important factor to consider when employing individuals, a company should employ individuals aged between 22 years and 49 years this is due to the simple reason that they will work in the company for many years and also will have higher levels of intrinsic, extrinsic and overall satisfaction. Surveys: A survey is a study on all the individuals in a given population or a chosen number of participants using the sampling techniques, example of a survey is a country census that involves all individuals in the country. A census is used by the government to determine the population size and therefore decision on provision of social amenities is made easier. In a survey there is need to include the names of the individuals involved in order to keep the information private, to ensure that the information is unbiased there is a need to have a standard data collection tool, there is also a need to ensure that there are ways in which the consistence of information by a participant is checked. Time is an important factor to consider, there is need to have ample time for preparation of a survey, this is because if one wants to use questionnaires then one has to prepare the questionnaire and then pretest it. References: Robert Mason and Douglas Lind (1997) Statistics: An Introduction, Duxbury Press, New York

J.R.R. Tolkien Essay - 895 Words

J.R.R. Tolkien J.R.R. Tolkien (1892-1973) gained a reputation during the 1960’s and 1970’s as a cult figure among youths disillusioned with war and the technological age. His continuing popularity evidences his ability to evoke the oppressive realities of modern life while drawing audiences into a fantasy world. John Ronald Reuel was born on the third of January, 1892, at Bloemfontein, South Africa, where his father, Arthur, had taken a position with the Bank of Africa. In 1895 Tolkien’s mother, Mabel Suffield, moved back to England with her children, because Tolkien‘s health was affected by the climate. Arthur Tolkien hoped to return to England soon, but he contracted rheumatic fever the following autumn and died early in 1896.†¦show more content†¦After returning to Britain in 1917, he began writing The book of Lost Tales which ultimately became The Silmarillion and laid the groundwork for his stores about Middle-earth. Tolkien returned to Oxford, where he joined the staff of the Oxford English Dictionary and began work as a self-employed tutor. In 1920 he was appointed Reader in English Language at Leeds University, where he collaborated with E. V Gordon on an highly praised translation of Sir Gawain and the Green Knight, published in 1925. The following year Tolki en returned to Oxford and became friends with C.S. Lewis. They both attended meetings of The Coalbiters, a club founded by Tolkien, where Icelandic sagas were read aloud(Byers 259). Almost all of Tolkien’s work was never published. But in 1936 he was persuaded by friends to let the firm of Allen an Unwin to take a look at his typescript of The Hobbit. This story was said to delight all who read. Allen an Unwin decided to publish the book and it sold so well that they asked Tolkien to write a sequel. Tolkien wanted to, but it took him fifteen years to complete it(Kroeber 520). After thirty years of being a professor Tolkien finally began being recognized and rewarded for his academic achievements. In 1945 he was named an honorary Doctor of Letters by the University college in Dublin, Ireland and the University of Liege in Belgium. It wasn’t until the 1950’s that Tolkien started to be known out side his own field. InShow MoreRelatedEssay J.R.R. Tolkien1127 Words   |  5 PagesJohn Ronald Reuel Tolkien, creator of a world. When someone who knows Tolkien is asked about his works, one thought comes to mind, Middle Earth. This was the playground in his mind that such vivid descriptions of fantasylands came from. It is the base of his most well known stories, where dreams are just the norm. br brJ.R.R. may owe much of his success to his diverse beginnings. On April 16, 1891, Mabel Suffield and Arthur Reuel Tolkien were married in Bloemfontein, South Africa. They soon gaveRead MoreEssay on The Hobbit by J.R.R. Tolkien530 Words   |  3 PagesThe Hobbit by J.R.R. 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