1,720,964 research outputs found
Analysis and design of hollow helical springs for shape memory actuators
No full textThe shape memory alloys (SMAs) can be exploited successfully to reduce the complexity and the weight of actuators, but the main drawbacks that limit the use of SMAs are the low bandwidth, the poor energetic efficiency and the unsatisfactory stroke. This paper contributes to enhancing the mechanical, the thermal and the electric performances of SMA actuators by providing analysis and design equations for helical springs with hollow round section. Emptied of the inefficient material from its centre, the hollow section features a lower mass, a lower cooling time and a lower heating energy than its solid counterpart for given strength, stiffness and deflection. The advantages of the hollow construction over solid springs are presented and discussed by means of dimensionless functions. A step by step procedure leading to the optimal design of hollow springs with minimum energy consumption is finally proposed
Attuatore a memoria di forma
No full textL’attuatore lineare telescopico basato su molle cave a memoria di forma unisce i pregi dei fili e delle molle SMA (Shape Memory Alloy). Le prestazioni del sistema risultano ottime se comparate con attuatori lineari a memoria di forma, ma ancora non sono sufficienti per far competere l’attuazione SMA con quella elettrica convenzionale in campi differenti dalla microattuazione
Design equations for binary shape memory actuators under dissipative forces
No full textAn analytical procedure to design binary shape memory actuators is described. Ageneric actuator is considered where a cursor is moved against dissipative forces using an elasticsystem containing a primary shape memory spring and a bias (backup) element. Three typicalcases are analysed and differentiated in the way the bias force is applied to the primary shapememory spring, using a constant force, a conventional spring, or a second shape memory spring.Dimensionless, closed-form relationships are developed, which form the basis of a step-by-stepprocedure for an optimal design of the whole actuator (primary active spring and bias element).Specific formulas regarding the detailed design of the shape memory elements of the actuator inthe formof straight wires and wire helical springs are also presented
Molle elicoidali a memoria di forma a sezione cava
No full textIl presente trovato si riferisce al campo delle molle elicoidali a memoria di forma.Le molle elicoidali a memoria di forma oggetto del presente trovato sono caratterizzate da un filo a sezione cava, in grado di incrementare l’efficienza delle molle stesse, in termini di energia elastica accumulabile per unità di peso, in termini di risparmio energetico per l’attivazione della molla ed in termini di risposta dinamica della stessa.Le molle elicoidali a memoria di forma a sezione piena attualmente utilizzate sono caratterizzate da un’efficienza minore rispetto all’invenzione oggetto del presente trovato.In tutti i casi l’invenzione si basa sull’utilizzo di molle elicoidali a memoria di forma caratterizzate da un filo a sezione cava
A SYSTEM FOR ELECTRICAL SUPPLY TO ELECTRICAL AND/OR ELECTRONIC DEVICES
No full textAn embodiment of the present invention provides a module (50) for electrical connection of electrical and/or electronic devices to a supply base (10), in which the module (50) comprises a casing (51 ) containing winding means of an extractable electric cable (52), which exhibits an end that exits from the casing (51 ) and to which a connector (53) is associated, which connector (53) is destined to couple with a supply socket of an electrical and/or electronic device; the casing (51 ) being conformed such as to removably insert in a housing (18) of the supply base (10), and in which the casing (51 ) comprises an electrical contact (55) connected to the extractable electric cable (52), which is destined to contact a corresponding electrical contact (19) of the supply base (10), when the casing (51 ) is inserted in the housing (18)
Design equations for binary shape memory actuators under arbitrary external forces
No full textThis article presents the design equations for an on–off shape memory alloy actuator working against an external system of arbitrary constant forces. A binary shape memory alloy actuator is considered where a cursor is moved against both conservative and dissipative forces, which may be different during the push or pull phase. Three cases are analysed and differentiated in the way the bias force is applied to the primary shape memory alloy spring: using a constant force, a conventional spring or a second shape memory alloy spring. Closed-form dimensionless design equations are developed, which form the basis of a step-by-step procedure for an optimal design of the whole actuator
Conceptual design and simulation of a compact shape memory actuator for rotary motion
No full textThis work describes the conceptual design, the modelling, the optimization, the detail design and the virtual testing of a shape memory actuator purposely conceived to maximize torque and angular stroke while limiting overall size and electric consumption. The chosen design, achieved by means of a Quality Function Deployment approach, features a fully modular concept in which an arbitrary number of identical modules are assembled to produce the desired angular stroke and output torque. The basic module contains shape memory springs that actuate the device and also a conventional spring that reduces the torque ripple. Following the concept generation stage, a thermo-electromechanical model is developed and a numerical optimization performed, aimed at minimizing the electrical consumption of the actuator. Finally, the device is designed in detail and the actuator is tested virtually. Thanks to the proposed modular construction and the use of a conventional balancing spring, the device shows better performances than known rotary shape memory actuators in terms of rotation, torque and customization
Contact force distribution in the interference fit between a helical spring and a cylindrical shaft
No full textThis paper deals with the analysis of the contact forces developed by a helical spring shrink fitted on acircular shaft. This interference fit is an effective, fast to apply, reversible and inexpensive fastener. An analyticalsolution able to predict the contact forces distribution and the maximum thrust which the system can withstand hasbeen developed. The analytical results have been compared with a finite element analysis confirming theeffectiveness of the developed formulas
Metodo e dispositivo per controllare la posizione della lancetta di un indicatore
No full textLa presente invenzione è relativa a un metodo e a un dispositivo per controllare la posizione della lancetta di un indicatore, e a un indicatore comprendente tale dispositivo.In particolare, la presente invenzione trova vantaggiosa, ma non esclusiva applicazione negli indicatori che si trovano nei pannelli di controllo di veicoli o strumentazioni industriali e che impiegano uno o più fili di materiale e memoria di forma (Shape Memory Alloy - SMA) come attuatori per la movimentazione della lancetta dell'indicatore, cui la descrizione che segue farà esplicito riferimento senza per questo perdere in generalità
Design of a Telescopic Linear Actuator Based on Hollow Shape Memory Springs
No full textShape memory alloys (SMAs) are smart materials exploited in many applications to build actuators with high power to mass ratio. Typical SMA drawbacks are: wires show poor stroke and excessive length, helical springs have limited mechanical bandwidth and high power consumption. This work is focused on the design of a large-scale linear SMA actuator conceived to maximize the stroke while limiting the overall size and the electric consumption. This result is achieved by adopting for the actuator a telescopic multi-stage architecture and using SMA helical springs with hollow cross-section to power the stages. The hollow geometry leads to reduced axial size and mass of the actuator and to enhanced working frequency while the telescopic design confers to the actuator an indexable motion, with a number of different displacements being achieved through simple on-off control strategies. An analytical thermo-electro-mechanical model is developed to optimize the device. Output stroke and force are maximized while total size and power consumption are simultaneously minimized. Finally, the optimized actuator, showing good performance from all these points of view, is designed in detail
- …
