The screw shaft and the nut are directly moving against each other on Electric actuators are devices capable of creating motion of a load, or an action that requires a force like clamping, making use of an electric motor to create the force that is necessary A linear actuator is a means for converting rotational motion into push or pull linear motion, which can be used for lifting, dropping, sliding, or tilting of machines or materials. FIG. Still some applications require longer shaft lengths and high speeds. Thus, each deflector acts to provide a closed loop or circuit for each of the three passages in the nut. BEAVER AEROSPACE & DEFENSE, INC., MICHIGAN, Free format text: startxref 6). This clearance is unwanted because it causes backlash. In this type of return system, the ball is returned to the opposite end of the circuit through or along the nut wall, but below the outside diameter through a "V" cap. 0000004711 00000 n Assigned to BEAVER AEROSPACE & DEFENSE, INC. Assignors: BEAVER PRECISION PRODUCTS, INC. However, the improved deflector 50 incorporates pairs of adjustable locator bosses 60 situated at opposite ends of the body 52 and in close proximity to the ends 56. The upper and lower bodies 62 and 64 are symmetrically positioned with respect to each other. The spacer applies force on the adjacent sides of two ball nuts; this force is transmitted to the nut and the grooves. 10. (a) The External Ball Return System. The ball deflector of claim 1 wherein said deflector body comprises two pairs of said locator bosses fixed to opposite sides of, and at opposite ends of, said elongated body. 0000003690 00000 n Ball screws address the sliding friction generated by metal lead screws. document.write(new Date().getFullYear());. However, the surface produced is rough, which decreases the efficiency and wear resistance of the ball screw due to the higher friction it will encounter. Meanwhile, ball screws need braking mechanisms to eliminate back driving. 0000026934 00000 n Therefore, the number of turns is always equal to the number of circuits for internal ball return systems. Ball screws have a higher load capacity than lead screws. Screws typically have one, two, or four starts. The auxiliary components supporting the ball screw must be mounted precisely to improve accuracy. To benefit from the lead accuracy a ball screw offers, it must have an accurate mounting. Call today! The design of ball screws yields high accuracy during operation. Deflectors, return tubes, and end caps are devices used to feed the ball back to its original position. The contact points of the ball between the screw shaft and the nut are distinguished by the groove profile of the two components where the ball touches. An inherent problem in such fit-up relates to cumulative manufacturing tolerances. It preserves the efficiency of the ball screw by keeping contaminants and foreign materials from entering the clearance between the ball and the nut; it also retains the lubrication of the ball screw assembly. Referring initially to FIG. 0000000016 00000 n The two deflectors located at the opposite ends of the nut 18 each employs only one of its two bevelled ends 48, as will be appreciated by those skilled in the art. 0000024483 00000 n They require more frequent lubrication to stay in top condition. The common groove profiles are the gothic arc and the circular arc: This is the most common groove profile. trailer 0000025842 00000 n The relationship between the turn and the circuit depends on the recirculation method of a ball screw. The ratio of the number of threads in the ball nut circuit to the number of threads on the ball screw determines how much sooner the ball nut will reach fatigue failure (wear out) than the ball screw will. 0000008149 00000 n The large plastic deformation of the blank results in a high strength screw shaft. Backlash is the lost motion caused by the clearance between the ball and the nut and screw tracks. They also generate less noise and vibration than external systems because recirculation only occurs inside the nut housing. Ball screws are made from materials with high rigidity and stiffness such as stainless steel. The pitch refers to the distance of two consecutive threads, while the lead is the linear distance covered in one complete rotation. Ball screws are a type of mechanical linear actuator. 0000028484 00000 n Single start screws are the most common. When using, the screw shaft supported end may need additional machining in accordance with the conditions of use. 0000005994 00000 n Even more of a problem, however, is the fact that cumulative tolerance variations in deflector and nut groove sizing is such that rarely is there a satisfactory deflector fitment. Ball grooves are also present in the internals of the nut that match the grooves of the screw shaft. They are capable of carrying heavier loads than single circuit ball nuts. ;uYm]}C3t,eER"Fj6HJ ge^, 4Ff+;-tX^TgXq5&/T}LW_{=Y7&SPSDmo-_zu$(Ep8Lb@n,.^r%qKFT F/,~`90/..0xD%$h?T*;=~ Hr#C L+~|]k(.1s8}e.\\(PRx9^O:lyyO~rJ>&8U.uITa Tz]~G2 %w "H5T PJ>&3sCy:VuJ kESj,Z]V[# 6[wz0B$RjIzmK]%WK) 'W#_Ys ydm RU/E 20~~-*sA~#G PN| ]}p}+R$0Z@ bxR}S_ Root diameter is the distance between the bottommost section of the groove to the bottommost section of the opposite groove. 1. 0000017074 00000 n The groove surface produced is smoother than the rolled screw. Ball circle diameter (or pitch circle diameter) is the center-to-center distance of two opposite balls measured when the ball bearings are in contact with the grooves. The start is the number of independent threads that run around the screw shaft. This is where a rotating ball nut design is needed. A large preload requires more torque and can cause excessive heat generation. The deflector typically includes a threaded stem fixed to the deflector body for securement of the body within the groove. 0000005814 00000 n This system can support fine lead ball screw assemblies and a wide range of screw shaft diameters. During assembly, the bosses 60 are adjusted by an electric grinder or other metal removal means to assure satisfactory deflector alignment with the nut groove. %%EOF In an external ball recirculation system, the ball traverses outside the nut housing when it is recirculated. They are more customizable than ball screws. The improved ball deflector of the present invention provides at least one pair of adjustable locator bosses, each of the pair disposed on adjacent upper quadrants of the circumference of the deflector body. They are used in medical equipment, food processing equipment, and laboratory machinery. The purposes of preloading are to increase the rigidity and to eliminate the backlash of the ball screw assembly. A lead screw is a kind of mechanical linear actuator that converts rotational motion into linear motion. PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362. %`vQ@9Jy=,swSIue0'G%}'#s-GF\tde9NMJeU DpVXWq;@Mn>.}~q066#di(ZQ!agk3id:He.LS9b=o#`4eAPFM#cTgm I The power to rotate the shaft is supplied by a motor, which is situated on its end. 0000023739 00000 n 3, the body 32 of the prior art deflector 30 is more fully shown in its operative environment between nut and screw grooves 20 and 14, respectively. As Industry 4.0 and related initiatives continue to transform and advance the European market, NSK saw the need to develop and bring to market new deflector type ball screws, the most commonly used type in European machine tools. 2 is a cross sectional view along lines 2--2 of FIG. During securement of the stem to the nut by means of threaded fasteners, manufacturing tolerances tend to give rise to an objectionable amount of cocking or shifting (about the stem axis) of the deflector body within the groove. %PDF-1.7 The radius R1 of the lower body 64 is approximately 30 percent of the ball diameter, while the radius R2 of the upper body 62 may range from approximately 35 to 50 percent of the ball diameter. Another classification of ball screws is according to the fabrication method of producing the ball grooves: Ground screw threads are fabricated by an abrasion process. 1). +7W.~\c]0:8rA@'%uvi=(PGx1W(\9x6 W3l'g =]J+m`f3[ .tkbM }V:5x>[j(J4( 0T$f%a=@P97]DX,4)]2[O: To the extent that there is a slight offset between the two centers 68 and 70, the upper and lower body portions are symmetrically joined together by a portion having exterior contours which are tangent to the lower body 64. NSK Ltd.CSR Division HeadquartersPublic Relations Department, Contributes to improved productivity of machine tools. This invention relates to ball screw and nut assemblies. 0000034930 00000 n Ideally, the bosses are symmetrically positioned on the upper body in a manner such that the two equal angles A equal 10 to 25 degrees (FIG. The bosses are semi-spherical in their preferred form. FIG. 0000024760 00000 n A substantial improvement would result if there were provided a mechanical means to alleviate or minimize such movement during fit-up of the deflector body within the nut groove. Machine tools, robots, actuators, sensors, and other mechanical equipment often require moving components in a straight line in any of the three-dimensional axes A linear actuator actuates, moves, in a linear, straight, line to complete or start a process. The screw shaft is a long cylindrical shaft that has a continuous groove, called the ball groove, that runs helically around the length of its shaft, which is referred to as the thread of the screw. FIG. FIG. In a preferred form, the bosses are disposed in adjacent quadrants on an upper body portion of the elongated deflector body, and are arranged in pairs, each disposed at opposite ends of the deflector body and located adjacent the ends of the deflector. It has a compact size, which is suitable for small clearance assemblies. 0000013741 00000 n 0000026177 00000 n Since there are no external protrusions, ball nuts with this return system are more compact. Although the bosses may be applied to the elongate body 52 by spot weld techniques, the entire deflector 50, including the bosses, is ideally a solid precision cast part. Lubrication is necessary for ball screws to avoid thermal expansion and galling. The ball recirculation system in the nut allows the balls to be "recycled" in the operation by returning them to their starting point in the circuit. To summarize, ball screws are valued for their power efficiency, accuracy, precision, and load capacity. It can disrupt the accuracy and repeatability, which are required for precise positioning applications. 0000009469 00000 n The key difference between ball screws and lead screws lies in their manner of transmitting loads. The screw shaft fixed end is finished to the type recommended by KURODA. 432 0 obj <> endobj Consequently, upon tightening the threaded fastener 36 on the stem 34 during assembly, the elongate body 32 is often rotated about the axis a--a of the stem, resulting in deflector ends 48 which are not aligned with the nut groove. There are a variety of terms used to describe a linear actuator such as ram, piston, or activator IQS Directory As is typical of the latter construction, the lower body portion 40 is formed to provide greater clearance from the sides of the mating groove 14 of the screw for accommodating axial and radial movement or lash in the screw relative to the nut to avoid binding of the screw on the deflector member. The ball groove serves as the pathway for the rolling ball bearings. 0000005303 00000 n The ball deflector of claim 7 wherein said bosses are semi-spherical, each having an initial unadjusted radius of approximately 0.100 inch. Barnes Industries engineering department has developed various rotating ball nut designs. 0000009557 00000 n 0000010364 00000 n The deflector body 32 contains bevelled ends 48 adapted to deflect each of the circulating train of balls 22 which pass through the mating grooves, so that the balls pass out of the nut and into the transfer tube though the apertures 24. Disposed within the mating grooves 14, 20 of nut and screw, for providing relatively frictionless rolling contact therebetween, are a plurality of ball bearings 22 (hereinafter referred to as balls). 0000009360 00000 n 0000025342 00000 n 0000015877 00000 n 0000006142 00000 n Rolled screw threads are fabricated by a cold work deformation process. Please click here for KURODA Selection Guide for Ball Screws. To download data, CADENAS WEB2CAD,Inc. The unique element of ball screws is the rolling balls in the helical groove which reduces the mechanical contact inside the screw assembly and replaces sliding friction with rolling friction. The balls are usually made from steel. It is dependent on the manufacturing accuracy of the ball grooves, compactness, and set-up precision of the assembly. xref y|@Ot99Qm)C`fpN S3OuKl6bUma*so+?eh02e1#[A\+kwE $M^b q;nPaB5 51hA!IWS11 esA;x:qVb;scZ0C?oV _>}dW!cVA& . $yzr] % Xh@o?,zZf4DSPk2H 0'q:h=F K2"iCr"O jnG9qNJbB#*l5gMOk6. 0000023543 00000 n Typically, such prior art nut would also include a flange (not shown) for providing actuation of a rod or coupling assembly mechanically fastened to the flange. 9. This solves the consequences of using higher leads. The return tube directs the balls back to their starting point. 0000010032 00000 n Owner name: The ball is in contact with the screw shaft and the nut. FIG. With this profile, the ball has two contact points on the screw shaft and two contact points on the nut. 0000015939 00000 n ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:UNITRON INCORPORATED;REEL/FRAME:007251/0005, Owner name: Referring now to FIG. 2 0 obj Lead screws, like ball screws, serve a similar purpose to mechanical linear actuators that translate rotational motion to linear motion. 0000008936 00000 n The preloading mechanisms commonly utilized in ball screw assemblies are as follows: In spacer preloading, a spacer is inserted between two ball nuts to achieve the desired preload. 0000003896 00000 n The ball deflector of claim 6 wherein said radius of said upper body comprises approximately 35 to 50% of said ball diameter. The lead error is the difference between the theoretical and actual distance that the nut has traveled when the screw shaft has rotated. 6 which depicts a cross section of the body 52 taken through a pair of the bosses 60, those skilled in the art will appreciate that an upper body portion 62 is adapted to be seated in the prior art nut groove 20, while the lower body 64 is adapted to be received in the groove -4 of a conventional screw. Multiple start screws are used when a rapid linear movement is for a lesser number of rotations and high load capacity screws. xViPv%%iwE C] uQHRDl `LR7VqnJsrNX9?wF>^ ` ,f,7Q_>@ #@{*vY=A.s--tM7__=v}K}1u_bJIo65^{qS0[8K1$nxln|&=85X)t]Q}{[_7H`*@hegwO#3Q*o]&] NNnDP'5zp3,(w5hMZ}|'fsqQul6:xBF6FMnW$9N!=v=$I\" 3xYfat|p"s2F8('z!+{}?&#rK*8C@>H;wiQ"~sT\-w].[/Yyf^G>_Um A%O2A*2T'[j5uz]Sv|xj0=?s&lr2gy=+}AR2mI`J(~!&&QH!g]T)1FkXF@']l:vXp=KB A ball deflector for a recirculating ball screw and nut assembly provides a plurality of adjustable semi-spherical locator bosses along an elongated body portion thereof for enhancing fitment of said deflector within a segment of the nut groove during assembly. Ball screws generate more noise than lead screws. This provides a very smooth flow of balls at any speed in a limited amount of space. 0000023441 00000 n ASSIGNMENT OF ASSIGNORS INTEREST. HW]T9}_!BS40+"( =:~O4>=>RVoQ'R+nB OBOo? xuxc,Q,duh>Cm)Irzq&j[H4GC{q#Mu/mV[l&h]6 BS*7^'u^=zL+uk 8:L13!C [W:+Nfm\ayt#6;EQOWFY2qut" {6>gMTJWEZ3X[>)\V)7Sr Mp ,8TYSI"Ho8!NQ)1}8 1. Circuit refers to the closed path in the recirculating system of the ball nut. 4. This is known as a cross-over deflector type internal return system. The screw shaft is the component of the ball screw that receives rotational force for it to rotate about its axis; this is translated to linear motion. endstream endobj 433 0 obj<> endobj 434 0 obj<> endobj 435 0 obj<>/ColorSpace<>/Font<>/ProcSet[/PDF/Text]/ExtGState<>>> endobj 436 0 obj<> endobj 437 0 obj<> endobj 438 0 obj<> endobj 439 0 obj<> endobj 440 0 obj[/DeviceN[/DIC#202591p]/DeviceCMYK 491 0 R] endobj 441 0 obj[/Separation/DIC#202591p/DeviceCMYK 476 0 R] endobj 442 0 obj<> endobj 443 0 obj[/DeviceN[/DIC#202591p]/DeviceCMYK 494 0 R] endobj 444 0 obj[/DeviceN[/DIC#202591p]/DeviceCMYK 489 0 R] endobj 445 0 obj[/DeviceN[/DIC#202591p]/DeviceCMYK 484 0 R] endobj 446 0 obj[/DeviceN[/DIC#202591p]/DeviceCMYK 475 0 R] endobj 447 0 obj<> endobj 448 0 obj<> endobj 449 0 obj<> endobj 450 0 obj<> endobj 451 0 obj<> endobj 452 0 obj<>stream The accuracy of ball screws is improved by preloading, lubrication, and increasing the mounting accuracy. Although only one preferred embodiment has been detailed and described herewith, the following claims envision numerous additional embodiments which are not shown or described herein. DANA CORPORATION, OHIO, Free format text: It can be prevented by preloading the ball screw. The nut houses the ball bearings and their recirculation mechanism. The ball deflector of claim 2 wherein said deflector body comprises integral upper and lower body portions, each portion defining a generally semi-cylindrical member, wherein said bosses are located on the quadrants defined by said upper body portion. In a preferred form, the deflector body has two pairs of the locator bosses fixed to opposite sides of, and opposite ends of, the elongate deflector body. Linear Rails are ideal for moving items through a production process with great precision and as little friction as possible if creating, packing, and distributing products. Preloading is the application of force to compact the ball screw structure to avoid backlash. 4, 5, and 6, a total of two pairs, or four bosses, are utilized with the bosses situated in adjacent quadrants of the upper body 62. Referring now to both FIGS. Heat causes the thermal expansion of the components and negatively affects the accuracy of the ball screw. 8. Those skilled in the art will appreciate the long standing practice of attempting to fit an elongate body of a deflector into a nut groove so as to cause the latter to be symmetrically seated and aligned within the screw groove.
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