原文：
CONVEYOR SYSTEMS
Conveyors are ud when material must be moved in relatively large quantities between specific locations over affixed path. The fixed path is implemented by a track system, which may be in-the-floor, above-the-floor, or overhead. Conveyors divide into two ba sic categories: (1) powered and (2) no-powered. In powered conveyors, the power mech anism is contained in the fixed path, using chains, belts, rotating rolls, or other devices to propel loads along the path. Powered conveyors are commonly ud in automated material transport systems in manufacturing plants, warehous, and distribution centers. In non-powered conveyors, materials are moved either manually by human workers wh o push the loads along the fixed path or by gravity from one elevation to a lower ele vation.
Types of Conveyors估算的方法小学三年级
A variety of conveyor equipment is commercially available. In the following paragr aphs, we describe the major types of powered conveyors, organized according to the ty pe of mechanical power provided in the fixed path.
Roller and Skate Wheel Conveyors. The conveyors have rolls or wheels on whic h the loads ride. Loads must posss a flat bottom surface of sufficient area to span veral adjacent rollers. Pallets, tote pans, or cartons rve this purpo well. The two m ain entries in this category are roller conveyors and skate wheel conveyors, pictured in Figure 10.6.
In roller conveyors, the pathway consists of a ries of tubes (rollers) that are per pendicular to the direction of travel. The rollers are contained in a fixed frame that ele vates the pathway above floor level from veral inches to veral feet. Flat pallets or tote pans carrying unit loads are moved forward as the rollers rotate. Roller conveyors can either be powered or non-powered. Powered roller conveyor are driven be belts or chains. Non-powered roller conveyors are often driven by gravity so than the pathway has a downward slope sufficient to overcome rolling friction. Roller conveyors are ud in a wide variety of applications, including manufacturing, asmbly, packaging, sortati on and distribution.
Skate-wheel conveyors are similar in operation to roller conveyors. Instead of rolle rs, they u skate wheels rotating on shafts connected to a frame to roll pallets or tote pans or other containers along the pathway. This provides the skate wheel conveyor w
ith a lighter weight construction than the roller conveyor. Applications of skate-wheel c onveyors are similar to tho of roller conveyors, except that the loads must generally be lighter since the contacts between the loads and the conveyor are must more concen trated. Becau of their light weight, skate wheel conveyors are sometimes built as port able equipment that can be ud for loading and unloading truck trailers at shipping an d receiving docks at factories and warehous.
浮游植物Belt Conveyors. Belt conveyors consist of a continuous loop: Half its length is u d for delivering materials, and the other half is the return run. The belt is made of rei nforced elastomer (rubber), so that it posss high flexibility but low extensibility. At one end of the conveyor is a drive roll that powers the belt. The flexible belt is supp orted by a frame that has rollers or support sliders along its forward loop. Belt convey ors are available in two common forms: (1) flat belts for pallets, individual parts, or e ven certain types of bulk materials; and (2) trough of belts for bulk materials. Material s placed on the belt surface travel along the moving pathway. In the ca of trough of belt conveyors, the rollers and supports give the flexible belt a V-shape on the forwar d (delivery) loop to contain bulk materials such as coal, gravel, grain, or similar partic ulate materials.
Conveyors Driven by Chains and Cables. The conveyors in this group are driven by a powered chain or cable that forms an endless loop. In some cas, the loop form s a straight line, with a pulley at ea
ch end. This is usually in an over-and-under confi guration. In other conveyors, the loop has a more-complex path, with more than two p ulleys needed to define the shape of the path. We discuss the following conveyors in t his category: (1) chain, (2) slat, (3) in –floor towline, (4) overhead trolley, and (5)pow er-and-free over-head trolley.
Chain conveyors consist of chain loops in an over-and-under configuration around powered sprockets at the ends of the pathway. One or more chains operating in paralle l may be ud to form the conveyor. The chains travel along channels in the floor that provide support for the flexible chain ctions. Either the chains slide along the chann el or they ride on rollers in the channel. The loads are generally dragged along the pat hway using bars that project up from the moving chain.
The slat conveyor sues individual platforms, called slats, connected to a continuously m oving chain. Although the drive mechanism is a powered chain, it operates much like a belt conveyor. Loads are placed on the slats and are transported along with them. Str aight line flows are common in slat conveyors systems. However, becau of the chain
drive and the capability to alter the chain direction using sprockets, the conveyor path way can have turns in its continuous loop.
Another variation of the chain conveyor is the in-floor towline conveyor. The co nveyors make u of four-wheel carts powered by moving chains or cables located in t renches in the floor, as in Figure 10.8. The chain or cable is called a towline; hence, t he name of the conveyor. Pathways for the conveyor system are defined by the trench and cable, and the cable is driven as a powered pulley system. Switching between pow ered pathways is possible in a towline system to achieve flexibility in routing. The cart s u steel pins that project below floor level into the trench to engage the chain for t owing. (Gripper devices are substituted for pins when cable is ud as the pulley syste m, similar to the San Francisco trolley.) The pin can be pulled out of the chain (or th e gripper releas the cable ) to dingage the cart for loading, unloading, switching, a ccumulation of parts, and manually pushing a cart the main pathway. Towline conveyor s systems are ud in manufacturing plants and warehous.
机器人画法
All of the preceding chain and cable drive conveyors operate at floor level or slig htly above. Chain-driven conveyors can also be designed to operate overhead, suspende d from the ceiling of the facility so as not to consume floorspace. The most common types are overhead trolley conveyors. The are available either as constant speed (sync hronous) or as power-and-free (asynchronous) systems.
A trolley in material handling is a wheeled carriage running on an overhead rail fr om which loads can be suspended. An overhead trolley conveyor, Figure 10.9, consists of multiple trolleys, usually equally spaced along a fixed track. The trolleys are conne cted together and moved along the track by means of a chain or cable that forms a co mplete loop. Suspended from the trolleys are hooks, baskets, or other receptacles to car ry loads. The chain (or cable) is attached to a drive wheel that supplies power to mov e the chain at a constant velocity. The conveyor path is determined by the configuratio n of the track system, which has turns and possible changes in elevation. Overhead tro lley conveyors are often ud in factories to move parts and asmblies between major production departments. They can be ud for both delivery and storage.
A power-and-free overhead trolley conveyor is similar to the overhead trolley conv eyor, except that the trolleys are capable of being disconnected from the drive chain, p roviding this conveyor with an asynchronous capability. This is usually accomplished by using two tracks, one just above the other. The upper track contains the continuously moving endless chain, and the trolleys that carry loads ride on the lower track. Each tr
olley includes a mechanism by which it can be connected to the drive chain and disco nnected from it. When connected, the trolley is pulled along its track by the moving c hain in the upper track. When
disconnected, the trolley is idle.
包拯墓Other Conveyor Types. Other powered conveyors include cart-on-track, screw, vibra tion-bad systems, and vertical lift conveyors. Cart-on-track conveyors consist of indivi dual carts riding on a track a few feet above floor level. The carts are driven by mea ns of a rotating shaft. A drive wheel, attached to the bottom of the cart and t at an angle to the rotating tube, rests against it and drives the cart forward. The cart speed is controlled by regulating the angle of contact between the drive wheel and the spinn ing tube. When the axis of the drive wheel is 45°, the cart is propelled forward. When the axis of the drive wheel is parallel to the tube, the cart does not move. Thus, cont rol of the drive wheel angle on the cart allows power-and-free operation of the convey or. One of the advantages of cart-on-track systems relative to many other conveyors is that the carts can be positioned with high accuracy. This permits their u for positioni ng work during production. Applications of cart-on-track systems include robotic spot w elding lines in automobile body plants and mechanical asmbly systems.
Screw conveyors are bad on the Archimedes screw, the water-raising device devi d in ancient times (circa 236 B.C.), consisting of a large screw inside a cylinder, tur ned by hand to pump water up-hill for irrigation purpos. Vibration-bad conveyors u a flat track connected to an electroma
gnet that imparts an angular vibratory motion t o the track to propel items in the desired direction. This same principle is ud in vibr atory bowl feeders to deliver components in automated asmbly systems . V ertical lift conveyors include a variety of mechanical elevators designed to provide vertical motion, such as between floors or to link floor-bad conveyors with overhead conveyors. Oth er conveyor types include non powered chutes, ramps, and tubes, which are driven by gravity.
搜索不到蓝牙耳机怎么办
Conveyor Operations and Features
丁细牙痛As indicated by our preceding discussion, conveyor equipment covers a wide variet y of operations and features. Let us restrict our discussion here to powered conveyors, excluding non powered types. Conveyor systems divide into two basic types in terms o
f the characteristic motion of the materials moved by the system: (1) continuous and
情景作文(2) asynchronous. Continuous motion conveyors move at a constant velocity V along th
e path. They include belt, roller, skate-wheel, overhead trolley, and slat conveyors.
Asynchronous conveyors operate with a stop-and-go motion in which loads, usually
小学科学实验报告contained in carriers (e.g., hooks, baskets, carts), move between stations and then stop and remain at the station until relead. Asynchronous handling allows independent mo vement of each carrier in the system. Examples of this type include overhead power-an d-free trolley, in-floor towline, and cart-on-track conveyors. Some roller and skate-wheel conveyors can also be operated asynchronously. Reasons for using asynchronous conve yors include: (1) to accumulate loads, (2) temporary storage, (3) to allow for differe nce s in production rates between adjacent processing areas, (4)to smooth production when cycle times vary at stations along the conveyor, and (5) to accommodate different conv eyor speeds along the pathway.
Conveyors can also be classified as: (1) single direction, (2) continuous loop, and
(3) recirculating. In the following paragraphs, we describe the operating features of thes
e categories. In Section 10.6.3, we prent equations and techniques with which to anal yze the conveyor systems. Single direction conveyors are ud to transport loads one way from origination point to destination point. The systems are appropriate when the re is no need to move loads in both directions or to return containers or carriers from the unloading stations back to the loading stations. Single direction powered conveyors include roller, skate wheel, belt, and chain-in-floor types. In addition, all gravity conve yors operate in one direction.
Continuous loop conveyors form a complete circuit. An overhead trolley conveyor is an example of this conveyor type. However, any conveyor type can be configured as a loop, even tho previously defined as single direction conveyors, simply by connect ing veral single direction conveyor ctions into a clod loop. A continuous loop sys tem slows materials to be moved between any two stations along the pathway. Continu ous loop conveyors are ud when loads are moved in carriers (e.g., hooks, baskets) be tween load and unload stations and the carriers are affixed to the conveyor loop. In thi s design, the empty carriers are automatically returned from the unload station back to the load station.
The preceding description of a continuous loop conveyor assumes that items loade d at the load station are unloaded at the unload station. There are no loads in the retu rn loop; the purpo of the return loop is simply to nd the empty carriers back for r eloading. This method of operation overlooks an important opportunity offered by a clo d loop conveyor: to store as well as deliver parts. Conveyor systems that allow parts to remain on the return loop for one or more revolutions are called recirculating conv eyors. In providing a storage function, the conveyor system can be ud to accumulate
