The Production of Small Worm Gears for Experimental Work

1947 ◽  
Vol 156 (1) ◽  
pp. 368-372
Author(s):  
A. M. Gunner

Small worm gear drives are a common feature in the design of many types of apparatus, and the following description of the methods used for producing them in an experimental establishment may be of interest. Quantities are small, one or two to each pattern being the general rule, but there is certainly no lack of variety. The worms and wheels most often called for range in size up to 1½ inches and 6 inches diameter respectively, while pitches vary from 10 to 60 d.p. (diametral pitch). Addendum and dedendum proportions of 1/ PN and 1·25/ PN have been standardized, and a pressure angle of 20 deg. is adopted throughout. The gears are designed as hollow-faced helical (spiral) gears, and all calculations are based on the normal pitch. This is to enable standard hobs and cutters to be used for the worms. The shaft angle is usually 90 deg., but the angle of crossing may be varied up to 10 deg. either way on the particular machine employed for cutting the wheels. For many applications, backlash must be reduced to the very minimum consistent with smooth running; and to avoid the extreme accuracy of workmanship which an exact centre distance would necessitate, provision is usually made for adjustment of the worm. Although the Reinecker tangential feed method of worm wheel generation by a single-point tool —representing one tooth of a hob—is generally known, very little information on cutter forming is available. The method outlined was developed at the Admiralty Research Laboratory. Given the use of a modern worm grinder (not available), it should be possible to profile-relief grind these cutters after hardening.

2021 ◽  
pp. 35-46
Author(s):  
S. Ryazanov ◽  
M. Reshetnikov

Spatial helical gears, worm gears with a cylindrical worm, globoid gears, etc., are widely used in most of modern engineering products [1-3; 37; 42]. Cylindrical worm gears are actively used in the creation of metalworking equipment (push mechanisms of rolling mills, presses, etc.), in lifting and transport machines, in drives and kinematic chains of various machine tool equipment where high kinematic accuracy is required (dividing machine tools, adjustment mechanisms), etc. In a worm gear a cylindrical worm or its cylindrical helical surface can be cut by various technological methods [49-51], but no matter how the shaping of the worm gear elements’ working surfaces is carried out, the worm wheel is cut with a gear cutting tool, whose producing surface coincides with the worm thread’s lateral surface [19; 22; 23]. In this regard, the working surface of the cylindrical worm wheel’s tooth, even with a non-orthogonal arrangement of axes, is an envelope of a one-parameter family of surfaces that gives a linear contact, which presence makes it possible to transfer a large load using a worm gear. For high-quality manufacturing of worm gears, it is necessary to design and manufacture a productive gear cutting tool - an accurate worm cutter, whose shaping (working) surface must be identical to the profiled worm’s shaping (working) surface [24-27; 54]. One of the most important tasks in the implementation of worm gearing is the problem of jamming of the cylindrical worm and the worm wheel’ contacting surfaces. This problem is excluded by relieving the contacting surfaces’ profile along the contact line. Considering that any violations of contacting surfaces’ geometric parameters affect the change in their geometric characteristics, the tasks of accurately determining the adjustment parameters of the technological equipment, used for shaping the worm and worm wheel, enter into in the foreground of the worm gearing elements production. In modern conditions of plant and equipment obsolescence, and in particular, of gear cutting machines used for worm gears manufacture, these machines physical wear, implies an inevitable decrease in the accuracy of their kinematic chains. Therefore, in order to maintain the produced gears’ quality at a sufficiently high level, it is necessary to use deliberate modification of contacting surfaces when calculating the worm gearing’s geometric parameters; such modification reduces the worm gear sensitivity to manufacturing and mounting errors of its elements [28-31].


Author(s):  
F Yang ◽  
D Su ◽  
C. R. Gentle

A new approach has been developed by the authors to estimate the load share of worm gear drives, and to calculate the instantaneous tooth meshing stiffness and loaded transmission errors. In the approach, the finite element (FE) modelling is based on the modified tooth geometry, which ensures that the worm gear teeth are in localized contact. The geometric modelling method for involute worm gears allows the tooth elastic deformation and tooth root stresses of worm gear drives under different load conditions to be investigated. On the basis of finite element analysis, the instantaneous meshing stiffness and loaded transmission errors are obtained and the load share is predicted. In comparison with existing methods, this approach applies loaded tooth contact analysis and provides more accurate load capacity rating of worm gear drives.


Author(s):  
M.Yu. KARELINA ◽  
N.V. ATAMANENKO ◽  
Т.Yu. CHEREPNINA

The article analyzes the prospects for the use of worm gears in the construction of vehicles. A review of the method of calculating the worm gear has been carried out, approaches to the selection of materials for the worm itself and the worm wheel have been analyzed. A comparative analysis of the characteristics of improved and normalized medium-carbon steels and cast irons has been carried out. The characteristics of materials characterized by the best antifriction and anti-seize properties, in particular, tin bronzes, are given. The methods for predicting the reliability of a worm pair as well as methods for increasing the resource have been considered. The choice of the material of the worm gear depending on the sliding speed has been justified. Calculations have been given to prevent failures in the worm pair: chipping of the working surfaces of the teeth, kinking of the worm wheel tooth, seizing and wear, breakage of the worm's body, overheating, jamming of the gear and others.


2020 ◽  
Vol 21 (4) ◽  
pp. 405
Author(s):  
Sándor Bodzás

The cylindrical worm gear drives are widely used in different mechanical construction such as in the vehicle industry, the robotics, the medical appliances etc. The main property of them is the perpendicular and space bypass axes arrangement. Quite high transmission ratio could be achieved because of the high number of teeth of the worm-wheel and a little number of threads of the worm. More teeth are connected on the worm-wheel at the same time that is why higher loads and power could be transferred. In this research an Archimedean type cylindrical worm gear drive was designed. After the determination of the geometric parameters the computer-aided models were created for the LTCA analysis. Knowing of the kinematic motions of the elements the contact points of the wrapping surfaces could be determined by mathematical way. The necessary coordinate system's arrangements and matrixes were also determined. Different torques were applied during the LTCA. The changing of the distribution of the normal stress and normal deformation into different directions was followed on each connecting tooth of the worm-wheel by the torques. Based on the results consequences were determined by the created diagrams which contain the torques and the analysed mechanical parameter for each tooth.


2019 ◽  
Vol 7 (2) ◽  
pp. 56-60 ◽  
Author(s):  
С. Рязанов ◽  
S. Ryazanov

Existing mathematical models for calculating worm gearing [34; 38] are quite complex and do not always provide an opportunity to quickly and accurately obtain the desired result [1; 3; 24–26]. A simpler way to find a suitable gearing option that satisfies the task is using computer simulation methods and computer graphics, and in particular solid modeling algorithms [4; 5; 30–33; 36; 37]. This information can be entered into the computer in order to simulate control of the movement of the cutting tool. Ultimately, this boils down to the problem of analytic description and computer representation of curves and surfaces in three-dimensional space [18–20]. Despite the diversity and good development of the calculation methods, and the analysis of the geometrical parameters of the worm gear, there is a lack of means and methods for displaying the process of forming the working surfaces of the worm gear elements [28; 29; 41]. There are no computer algorithms for obtaining the producing surfaces of a worm cutter, which are obtained by a tool with a modified producing surface. A change in the geometric shape of the tool producing surface will lead to a change in the working surfaces of the worm wheel and turns of the worm, which may lead to an improvement in their contact. This article shows the application of the developed methods and algorithms of geometric and computer modeling, which are designed to form the helical surface of the turns of the worm and the teeth of the worm wheel. Their use will speed up the process of calculating intermediate adjustments of machines used for cutting worm gears, bypassing complex mathematical calculations that, under conditions of aging of the gear-cutting machine fleet, their wear and inevitable reduction in the accuracy of their kinematic chains. This can be achieved only by applying a deliberate modification of the contacting surfaces, which reduces the sensitivity of the worm gear to the manufacturing errors of its elements, which allows to maintain the quality of the gears produced at a sufficiently high level.


Author(s):  
Eva-Maria Mautner ◽  
Werner Sigmund ◽  
Johann-Paul Stemplinger ◽  
Karsten Stahl

Within a research project, experimental investigations of large-sized worm gears (pairing steel worm with bronze worm wheel) with centre distance a = 315 mm are carried out. The primary aim is to gain verified knowledge regarding load-carrying capacity and efficiency for this worm gear size. The paper describes the conducted tests in detail and shows basic examples of experimental test results. In the course of these investigations, an overall worm gearbox efficiency of up to η = 96% is measured.


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