MXPA05014022A - Rolling screw with smaller advance per turn than the pitch of the threading - Google Patents

Abstract

This invention concerns a rolling screw with smaller advance per turn than the pitch of the threading, characterised in that a threaded coupling is foreseen in which a screw (1) is turned inside one or more female screws inserted in a single body or sleeve (2) and where the pitch of the thread of said female screws is equal to that of the screw (1), whereas the nominal diameter is greater than that of the screw itself.

Description

- with amended claims and statement For two-letter codes and other abbreviations, rfr to the "Guid- (.8..8) D _at .e of .pu .bh..cap" on of .t..he..i. nt .ernap "ona, l search, report: anee N, otes, on Cod, is a nd Abbrevia" t-ions "" appearing attliebegin- r, _ "," nnr nlng ofeach regular tssue oj the PCI Gazette. 1 / March? Ü Date of publication of the amended claims and statement: 28 April 2005 TURN SCREW WITH SMALLER ADVANCEMENT RETURNING THAN THE STEP OF THE THREAD The present discovery refers to a turning screw that has application in the mechanical field, when it is necessary to move loads applying a torque of forces of limited value. They are known in the current state of the art: sliding screws: normally used in the so-called "female screw sockets", which have the disadvantage of low performance due to the substantial sliding friction which develops between the threaded surfaces of the screw and the female screw, in a mutual sliding position; with such type of threaded coupling the axial advance of the screw for each turn is equal to the length of the pitch of the thread; turning screws: they are characterized by a high performance because the friction present in such coupling types is the type of rotation, obtained with the use of bodies placed between the bolt and the female screw configured with rollers or balls; Thanks to the high performances, these screws are reversible and can be divided into three types: ball screws, where the axial feed per turn is equal to the thread pitch and the torque used is substantially proportional to the load and relationship between the pitch and the nominal circumference of the screw thread. threaded planetary roller screws, where the advance per turn is dependent on the pitch of the thread, the relationship between the pitch diameter of the screw and the pitch diameter of the planetary roller and the direction of rotation of the screw thread and the planetary roller . Such types of screws are applied when high load capacities associated with high travel speeds are required, made possible with the use of planetary rollers with a substantially smaller diameter with respect to the diameter of the screw (the advance per turn of the screw is greater than the pitch of the thread and for this reason these are reversible) and the torque used is substantially proportional to the load and the relationship between the feed and the circumference of pitch of the screw in the rollers; - roller screws, where the axial advance is equal to the pitch of the thread, the load capacity is very high, but the speed of rotation is of limited value; the torque that is used is substantially proportional to the load and to the ratio between the pitch and the circumference of pitch of the screw in the rollers. The purpose of the present discovery is to achieve that a turning screw does not have the drawbacks of similar known products; in particular, it must be able to move loads of substantial size, with the application of a minimum torque value, this must have a large number of turns and must be a reversible system. An additional purpose of the present discovery is to achieve a mechanism, with the functional characteristics of the main purpose, which is constructively simple and cost effective. An additional purpose of the present discovery is to achieve products and machines, such as mechanical screw plugs, linear actuators and the like, which use the rotating screw of the type described in the main purpose. The main purpose is carried out, according to claim 1, with a threaded coupling in which a screw is rotated inside one or more female screws (inserted in a single body or sleeve) and where the passage of the thread of said female screws is equal to that of the screw, while the nominal diameter is greater than that of the screw by itself. In a first embodiment, the female screws, all having the same nominal diameter, each consists of a support, of the type that is capable of simultaneously supporting both radial and axial charts, consisting of an inner ring having the threaded inner hole. In a second embodiment, the threaded inner hole is formed in a bearing which, in turn, fits into the inner ring of one or more supports. Constructively, the screw is inserted in one or more female screws, the axis of said female screws is parallel, but not coincident with the axis of the screw: in such a way the contact between the screw thread and the thread of each of the screws female is carried out, approximately on the generating line of the respective cylindrical surfaces; This can also be done when the female screws are not coaxial with each other. In a kinematic manner, it is also originated to make the screw turn to a corresponding rotation of the female screws in the supports, by sliding, not avoided by the antagonistic friction forces. To be specific, each turn of the screw corresponds to a rotation of the female screws of a value smaller than a complete revolution thereof; in particular, the axial advance of the screw in the sleeve is equal to the pitch of the thread multiplied by the difference between the number of turns completed by the screw and the number of turns completed by the female screw. From the operational point of view, given that the axis of relative rotation between the screw and each of the female screws roughly coincides with the line of contact points between the two threads, the resulting torque of friction is of reduced value, while, consequently, the performance is high; taking the advance by return of the screw to minimum values, the yield also decreases until the condition of irreversibility of the screw. In the practical mode, the command is carried out through the use of an engine reducer with low transmission ratio, therefore reversible and, in situations of failure or lack of power, even capable of being manually operated. Finally, the discovery foresees that the kinematism described above is completed with a mechanism that deals with the rotation block of the female screw in the sleeve, in the constructive solution with a turning screw or the screw itself, in the solution with a female screw, to bring back the aforementioned mechanism to the operation similar to that of a normal sliding screw, with advance equal to the pitch of the thread; this allows to be used for fast movements in the absence of load. The discovery will be better understood through the description of a possible modality thereof, provided only as a non-limiting example, with the help of the accompanying tables of the drawings, wherein: figs. 1 and 2 (Table I) represent, respectively, a plan view and a front elevated view, sectioned according to line ll-ll, of a device modality according to the discovery; - fig. 3 (Table ll) represents a perspective view of the device according to the discovery; fig. 4 (Table III) represents an exploded view of the device according to Figure 3; figs. 5 and 6 (Table IV) schematically represent a plan view and a detailed view, respectively, of the device according to the discovery. fig. 7 (Table V) represents a kinematic diagram of the device according to the discovery. As can be seen, in particular, in Figures 1 and 2, the screw 1 is inserted inside the sleeve 2, made of two half-shells 2 a and 2 b, which are held together by the screws 3. In the sleeve 2 , near the two bases, the guide supports are inserted, which are kept locked through the elastic rings 5. In the central zone of the sleeve 2, the support 6 is mounted, of the type suitable for supporting axial loads, which It has its inner ring 7 with a threaded hole. As can be seen, in particular, in figs. 1, 2 and 5, the support 6, with a threaded hole, is mounted eccentrically with respect to the axis of the screw 1 (value "e" of Fig. 5) and the axis of the two supports 4, to guide the screw through itself. In such a way, as can be seen in fig. 6, the threads of the screw 1 and the threads of the female screw, formed in the inner ring 7, are brought into contact with each other approximately along a generatrix of the threaded surface and not over the entire surface. Operationally, by causing the screw 1 to rotate about its axis, the threaded inner ring 7 of the central support 6 is also rotated in the same direction as that of the aforementioned screw. As can be seen in figs. 5, 6 and 7, the axis of mutual rotation between the screw and the threaded ring 7 coincides with the contact line (see point "C") of the two ideal cylinders, one with a smaller pitch diameter "Dpv" referring to the screw and the other with a larger pitch diameter "Dpm" referring to the female screw, said two cylinders rotating mutually, without generating a slip condition and wherein the above-mentioned pitch diameters "Dpv" and "Dpm" are they find in an intermediate position between the diameter of the crest and the diameter of the base of the threads of the two elements that match, the screw and the female screw. From the observation of the figures and keeping in mind the modality described above it can be seen that, in the rotation stage, the peripheral speed in the pitch diameter is identical for the screw and the female screw, while, due to the difference in diameter, the angular velocity of the screw is greater with respect to the angular velocity of the female screw; all this means that one turn of the screw corresponds to less than one complete angular rotation of the female screw equal to a given angle through the formula: aDpv / Dpm »360 ° where: Dpv = diameter of screw pitch; Dpm = pitch diameter of the female screw; Practically, in the two extreme operating conditions, if the screw is in the rotation stage and the female screw is at the same time, in the stopped stage, the advance of the screw for each turn of the same, will be equal to the step of the thread, while vice versa, if the female screw and the screw, at the same time, carry out the same number of turns, there would be no relative movement and, consequently, the advance of the screw by itself will be set to zero. Under normal operating conditions for the device, according to the discovery, the screw feed for each turn of the screw is provided through the formula: a = p • (1-Dpv / Dpm) where: p = thread pitch; In practice, the closer the relationship between the two diameters is to 1, the lower the screw feed for each complete revolution of the same. Again under normal operating conditions, the performance of the device according to the discovery depends on the friction that is generated and precisely based on: the sliding friction that is present in the contact zone between the screw and female screw threads; friction of rotation of supports of insignificant value. In the condition of normal application of the device according to the discovery, attributable to a lifting action of a load (see Fig. 7) one operates according to the formula: Ft = Fv + Fag where: Ft = load in the threads; Fv = external load; Fag = sliding friction, having the same direction, but orientation applied with respect to the advance of the screw, present between the screw and the wall of the hole of the supports of guide and a value, with greased surfaces, in the order of 0.15 Fv. Again in the condition of normal application of the device according to the discovery, the torque of friction present between the threads in mutual rotation is given by the formula: Maf = Ft »Ra« μ where: Ra = radius of the force of friction, of a value substantially equal to the pitch "p" of the thread; μ = coefficient of friction between the screw threads, of a value of approximately 0.10; Therefore, in the practical act, the moment to be applied to the screw 1 that causes it to advance is provided through the formula: Me = Ft »a / (2p) + Maf = Ft« a / (2μ) + Ft «p» μ where, when replacing the numerical values, it is: Me = 1 .15 »Fv» [a / (2μ) +0.10 »p] = 1 .15« Fv »[0.16« a + 0.1 0 »p] As can be seen from the last formula, since the advance value is less than the step value, friction can reach values which provide the reversibility of the system, and the value of the torque required to lift the load is very low, due to low advance value for each turn of the screw.

Finally, the load capacity and the correct operation of the device according to the discovery is dependent on numerous operative factors such as the number of threads in contact, the load capacity of the single or plurality of supports that hold the female screw and the presence of flexible radial loads of the screw, generated by the type of threading and by the eccentricity between the reaction direction Ft of the threads with respect to the direction of the load Fv of the screw. Within the general operating principle described above, the constructive solution for a practical embodiment of the rotating screw according to the discovery may be of the most different types; for example it is possible to foresee: that the screw 1 is in loco while the threaded ring 7, applied to the female screw is placed in rotation through a transmission system, which uses means known per se, such as belts and gears; that the screw 1 is fixed, while the whole sleeve 2 is placed in rotation through a transmission system, which uses known means per se, such as belts and gears; - the use of two or more female screws contained within the sleeve by itself; the absence of guide supports inside the sleeve; that the female screws consist of internally adjusted threaded bearings in the hole of at least one of the sliding or rotational supports contained in the sleeve; that the screw and the female screw are equipped with synchronized movement, made with any type of synchronization device known per se; - that a preload is applied on the screw to perform an extremely precise movement and the positioning of the rotation members to zero the space tolerance; the application of a system for locking / unlocking the rotation of the support or the supports of the female screw in order to obtain, when the previously mentioned supports are blocked, an advance for turning the screw equal to the value of the pitch of its thread; the application of a system for locking / unlocking the rotation of the screw so as to obtain, when it is locked, an advance per turn of the sleeve of a value equal to the pitch of the screw thread mentioned above; the use of a "freewheeling" type device, which prevents rotation of the female screw holder in one of the two directions; the use of a "freewheeling" type device, which prevents rotation of the screw in one of the two directions; a plurality of female screws having diameters of different values; that the female screws are capable of being placed in a non-contact condition with the screw independently of each other; that of the plurality of the female screws, with different diameters, only one selected can remain in contact with the screw, to obtain an advance per turn of the screw depending on the diameter of the specific female screw that is being used; that the diameters of each of the female screws has a value such that when all the aforementioned female screws are in the condition of separation of the screw it is possible to make the screw slide freely in the guide supports; that the female screw is equipped with circumferential grooves having the same pitch as the thread and with advance per turn equal to the pitch value of the screw thread; - that the screw is equipped with circumferential traps and with a return stroke equal to the thread of the female screw; that one or more female screws are replaced with externally threaded supports, said supports are capable of being placed in contact with the screw, to obtain advances by return of a higher value with respect to the pitch of the screw thread by itself.

Claims (23)

1. CLAIMS 1. Turn screw with smaller feed per turn than the thread pitch, characterized by a coupling threaded is provided in which a screw is rotated inside one or more female screws (inserted in a single body or sleeve) and where the pitch of the thread of said female screws is equal to that of the screw while the nominal diameter is greater than that of the screw by itself, each of the female screws consists of a support, capable of simultaneously supporting both radial and axial loads, with an inner ring having the threaded hole and where the axis of said female screws is parallel, but not coincident, with the axis of the screw; in such a way, the contact between the thread of the screw and the thread of each of the female screws is made, approximately in the generating line of the respective cylindrical surfaces, the device is characterized in that the screw and the female screw are equipped with synchronized movement, made with any type of synchronization device known per se. The turning screw according to claim 1, characterized in that the threaded inner bore of the female screw is formed in a bearing which, in turn, fits over the inner ring of at least one support. 3. The turning screw according to claims 1 and 2, characterized in that the female screws are not adjusted coaxially with each other. 4. The turning screw, according to claim 1, characterized in that the screw (1) is inserted inside the sleeve (2), made of two half liners (2a, 2b), held together by means of mobile connecting members (3) in the sleeve (2), near the two bases, with the guide supports (4) being inserted, kept blocked through the elastic rings (5); the screw by itself is inserted (but free of sliding) in said supports and in the central area of the sleeve (2) a support (6) is mounted, of the type suitable for axial support loads, which has its inner ring ( 7) with a threaded hole coupled with the screw itself, said support (6), with a threaded hole, being mounted eccentrically with respect to the axis of the screw (1) and with respect to the axis of the two guide supports (4). ) of the screw by itself, it being provided that the threads of the screw (1) and the threads of the female screw, formed on the inner ring (7), are brought into contact with each other approximately along a generatrix of the threaded surface and not on the whole surface of the thread itself, with the rotation of the screw (1) around its own axis, the threaded inner ring (7) of the central support (6) is also rotated in the same direction as that of the aforementioned screw. The turning screw, according to one or more of the previous claims, characterized in that the screw (1) is in loco, while the threaded ring (7), applied to the female screw, is placed in rotation through a system of transmission, which uses means known per se, such as belts and gears. The turning screw, according to one or more of the previous claims, characterized in that the screw (1) is fixed, while the whole sleeve (2) is placed in rotation, through a transmission system, which uses means known per se, such as belts and gears. The turning screw, according to one or more of the previous claims, characterized in that the use of two or more female screws contained within the sleeve is provided by itself. * 8. The turning screw, according to one or more of the previous claims, characterized in that it is provided that there is an absence of guide support inside the sleeve. The turning screw, according to one or more of the previous claims, characterized in that it is provided that the female screws consist of internally adjusted threaded bearings in the hole of at least one of the sliding or rotating supports contained in the sleeve. 10. The turning screw, according to one or more of the previous claims, characterized in that it is provided that a preload is applied to the screw to perform an extremely precise movement and the positioning of the rotation members to zero the space tolerance. eleven . The turning screw, according to one or more of the previous claims, characterized in that the application of a locking / unlocking system of the rotation of the support or of the supports of the female screw is envisaged to obtain, when the previously mentioned supports are blocked , one advance per turn of the screw equal to the value of the pitch of its thread. The turning screw, according to one or more of the previous claims, characterized in that the application of a system for locking / unlocking the rotation of the screw is envisaged to obtain, when it is locked, a forward movement of the sleeve of the screw. a value equal to the pitch of the aforementioned screw thread. The turning screw, according to one or more of the previous claims, characterized in that the use of a "free wheel" type device is provided, which prevents rotation of the female screw support in one of the two directions. The turning screw according to one or more of the previous claims, characterized in that the use of a "freewheeling" type device is provided, which prevents rotation of the screw in one of the two directions. The turning screw according to one or more of the previous claims, characterized in that a plurality of female screws having diameters of different values are provided. The turning screw, according to one or more of the previous claims, characterized in that it is provided that the female screws are capable of being placed in a non-contact condition with the screw independently of each other. 17. The turning screw, according to one or more of the previous claims, characterized in that it is provided that of the plurality of the female screws, with different diameters, only one selected can remain in contact with the screw, to obtain an advance per turn of the screw dependent on the diameter of the specific female screw that is being used. 18. The turning screw, according to one or more of the previous claims, characterized in that it is provided that the diameters of each of the female screws has a value such that when all the aforementioned female screws are in the condition of Separation of the screw is possible to make the screw slide freely on the guide supports. The turning screw, according to one or more of the previous claims, characterized in that it is provided that the female screw is equipped with circumferential traps and with a per revolution equal to the screw thread value. The turning screw according to one or more of the previous claims, characterized in that it is provided that the screw is equipped with circumferential traps and with a turn-forward equal to the thread pitch of the female screw. twenty-one . The turning screw, according to one or more of the previous claims, characterized in that it is provided that one or more female screws are replaced with externally threaded supports. 22. The spinning screw according to claim 21, characterized in that it is provided that the externally threaded supports are placed in contact with the screw, in order to obtain advances by turning a greater value with respect to the pitch of the screw itself. 23. The turning screw, according to one or more of the previous claims, characterized in that it is driven through the use of a motor reducer with low transmission ratio, therefore reversible and, in situations of failure or lack of power, even able to be manually operated.