Pulley

About: Pulley is a research topic. Over the lifetime, 51636 publications have been published within this topic receiving 178220 citations. The topic is also known as: drum & block.

Rotational Response and Slip Prediction of Serpentine Belt Drive

Abstract: A nonlinear model is developed which describes the rotational response of automotive serpentine belt drive systems. Serpentine drives utilize a single {long) belt to drive all engine accessories from the crankshaft. An equilibrium analysis leads to a closed-form procedure for determining steady-state tensions in each belt span. The equations of motion are linearized about the equilibrium state and rotational mode vibration characteristics are determined from the eigenvalue problem governing free response. Numerical solutions of the nonlinear equations of motion indicate that, under certain engine operating conditions, the dynamic tension fluctuations may be sufficient to cause the belt to slip on particular accessory pulleys. Experimental measurements of dynamic response are in good agreement with theoretical results and confirm theoretical predictions of system vibration, tension fluctuations, and slip. 1 Introduction The trend in automotive accessory drives has been to replace multiple V-belt drives with a single flat belt drive to power all the accessories. Such systems are termed "serpentine" belt drives and include a spring loaded tensioner, as well as multiple accessory pulleys (see Fig. 1). These systems can exhibit com­plex dynamic behavior, including rotational vibrations of the pulleys with the belt spans serving as coupling springs, and transverse belt vibrations in the various spans. The transverse vibrations of translating belts [1, 2] belongs to the broad cat­egory of systems referred to as axially moving materials. Other examples of axially moving materials include chain drives [3, 4], band saws [5, 6, 7], V-belts [8], moving threadlines [9], translating cables [10], etc. The recent literature on axially moving materials is reviewed in [11]. Several recent studies have focused on serpentine belt drive systems (see Fig. 1). Gasper etal. [12] and Hawker [13] consider longitudinal deflection of the belt and rotational vibrations of the pulleys in the analysis of free and forced response. These studies, however, do not consider the effect of the tensioner on either the equilibrium state (steady-state tensions) or the dynamic response. The influence of the tensioner on longi­tudinal belt deflection is examined by Barker et al. [14] who focus on transient response due to drive pulley acceleration. Beikmann et al. [15] develop a prototypical model (two pulleys with a tensioner) to calculate the steady-state tensions and the tensioner position as functions of steady operating conditions. Ulsoy et al. [16] consider the coupling between the transverse

Pathomechanics of Closed Rupture of the Flexor Tendon Pulleys in Rock Climbers

Abstract: We performed a study on twenty-one cadaveric fingers (seven non-paired forearms) to determine the pathomechanics of closed traumatic rupture of the flexor tendon pulleys in rock climbers. The ages of the individuals at the time of death ranged from sixty-one to eighty-four years (mean, seventy-four years). The forearm was placed in a custom-made loading apparatus, and individual fingers were tested separately under simulated in vivo loading conditions. The flexor digitorum superficialis and profundus tendons of each digit were attached to computer-controlled linear stepper motors that were equipped with force transducers, and the force in the tendons was simultaneously increased until avulsion of the tendons or osseous failure occurred. The force in the tendons, the excursion of the tendons, and the force at the fingertip were measured. Damage to the pulleys and bowstringing of the tendons were visualized with a fiberoptic camera. Two fingers fractured before complete rupture of the pulleys. Seventeen of the remaining nineteen fingers sustained an isolated rupture of either the A2 or the A4 pulley as the initial failure event; the A4 pulley ruptured first in fourteen digits (p < 0.001). The A3 and A4 pulleys ruptured simultaneously in one finger, and the A2, A3, and A4 pulleys ruptured simultaneously in another. Subtle bowstringing of the flexor digitorum profundus tendon occurred only after two consecutive pulleys had ruptured (either the A2 and A3 pulleys or the A3 and A4 pulleys). Rupture of all three pulleys was required to produce obvious bowstringing. Isolated rupture of the A2 or A4 pulley did not result in detectable bowstringing of the flexor digitorum profundus tendon. The A1 pulley always remained intact. CLINICAL RELEVANCE: Bowstringing of the flexor digitorum profundus tendon across the proximal interphalangeal joint with resisted flexion of the fingertips has been considered diagnostic for isolated closed rupture of the A2 pulley. The results of the present study, however, suggest that isolated injury of the A2 pulley rarely occurs. On the basis of our findings, we believe that reliance on bowstringing of the tendon at the proximal interphalangeal joint as an indicator of an isolated rupture of the A2 or A4 pulley may be misleading.

Incomitant strabismus associated with instability of rectus pulleys.

Abstract: PURPOSE. Connective tissue pulleys serve as functional mechanical origins of the extraocular muscles (EOMs) and are normally stable relative to the orbit during gaze shifts. This study evaluated pulley stability in incomitant strabismus. METHODS. Contiguous 2- or 3-mm thick magnetic resonance images (MRIs) perpendicular to the orbital axis spanned the anteroposterior extents of 12 orbits of six patients with incomitant strabismus. Imaging was performed in central gaze, supraduction, infraduction, abduction, and adduction. Rectus EOM paths were defined by their area centroids and plotted in a normalized, oculocentric coordinate system. Paths of EOMs ran toward the pulleys. Sharp EOM path inflections in secondary gaze indicated pulley locations in three dimensions. RESULTS. MRI revealed substantial inferior shift of the lateral rectus (LR) pulley of up to 1 mm during vertical gaze shifts in patients with axial high myopia and a posterior shift from abduction to adduction in simulated Brown syndrome. There was substantial LR pulley shift opposite the direction of vertical gaze in a subject with X-pattern exotropia who had undergone repeated LR surgery. The medial rectus (MR) pulley shifted inferiorly with gaze elevation in Marfan syndrome. Pulley instability was associated with significantly increased globe translation during gaze shifts. CONCLUSIONS. Pulley instability, resulting in EOM sideslip during ductions, occurs in some cases of incomitant strabismus. Resultant patterns of strabismus may depend on static pulley positions, pulley instability, and coexisting globe translation that alters pulley locations relative to the globe. Translational instability of pulleys and the globe could produce abnormalities in actions of otherwise normal EOMs, and connective tissue disorders causing these instabilities should be considered as potential causes of strabismus. (Invest Ophthalmol Vis Sci. 2002;43:2169 ‐2178)

Compound archery bow

Abstract: A compound archery bow includes a bow handle having projecting limbs, and first and second pulleys mounted on the limbs for rotation around respective axes. A bow cable arrangement includes a bowstring cable extending from a bowstring anchor through a bowstring let-out groove on the first pulley and then toward the second pulley. A first power cable extends from a first power cable anchor through a power cable let-out arrangement on the first pulley toward the second pulley, and a second power cable extends from the second pulley through a power cable take-up arrangement on the first pulley to a second power cable anchor on the first pulley. Draw of the bowstring cable away from the handle lets out bowstring cable from the bowstring let-out groove and rotates the first pulley around the first axis, lets out the first power cable from the power cable let-out arrangement on the first pulley and takes up the second power cable into the second power cable take-up arrangement on the first pulley. A power cable stop is disposed on the first pulley at a position to be engaged by the first power cable as the first pulley is so rotated to inhibit further rotation of the first pulley and thereby inhibit further draw of the bowstring cable.

High fidelity mechanical transmission system and interface device

Abstract: A high-fidelity mechanical transmission system for transmitting forces which can be used in a human-computer force feedback interface device connected to a host computer. The transmission system includes multiple stages, including an actuator stage coupled to an actuator and one or more additional stages. The actuator stage includes a rotatable capstan pulley coupled to the actuator, a cylindrical capstan drum, and a flexible member, such as a cable, coupling the capstan pulley and drum. The cable is coupled to the capstan drum at both ends, and causes the capstan drum to rotate for multiple revolutions. The output stage is coupled to the driven object to rotate the driven object. The output stage can include a capstan pulley, capstan drum, and cable. An interface device can include the transmission system for inputting motion signals to a connected host computer and for providing force feedback to the user. The interface device includes a user manipulatable object, such a steering wheel, joystick, or the like, which is manipulated by the user to interact with the host computer.