Star reducer

Abstract

The star reduction gear transmits torque via tappets performing reciprocating movements [Fig. 1]. The tappets are actuated by a system of cams fixed to the input shaft. By engaging with the fixed housing, they transmit the geared motion to the output shaft.

Description

Title of the invention: Star reducer

[0001] FIELD OF THE INVENTION TO WHICH THE INVENTION RELATES

[0002] The present invention relates to a mechanical assembly capable of transforming a high-speed, low-torque rotary motion into a low-speed, high-torque rotary motion. Assemblies of this type are called speed reducers. A typical use of a speed reducer is as an intermediary between a motor, which has a high rotational speed, and any slower-speed mechanism. EARLIER ART

[0003] The main types of speed reducers are: - Worm and wheel reducers. - Gear reducers. Motion transmission is achieved through gear trains. Examples include parallel shaft reducers, bevel gear reducers, and epicyclic reducers. - Reducers based on the cyclo principle of Lorenz Braren allow for a large reduction ratio, low weight, and small size. - Flexible gear reducers according to Walton Musser have equivalent performance.

[0004] The present invention relates to a new type of gearbox, called a star gearbox, with a high reduction ratio. For equivalent output torque, its weight and size are less than all other gearboxes. Its torsional rigidity is also high. This is due to the large number of active teeth, in contrast to all other types of gearboxes.

[0005] As an advantage of gear reducers, this type of reducer is absolutely homokinetic. BRIEF DESCRIPTION OF THE INVENTION

[0006] A reducer, regardless of the technology, comprises at least the following three elements: - The fixed housing that serves as a support for the torque transmission, - The input shaft, also called the high-speed shaft, - The output shaft, called the low-speed shaft,

[0007] In addition to these main parts, the reducer according to the invention comprises a minimum of two pushers arranged in a star pattern, each having a reciprocating motion. In the reciprocating motion in a rectangular cycle, four phases are distinguished: - The torque transmission phase: the tappet bears against the fixed housing via internal teeth. It is actuated by a cam on the input shaft in order to drive the output shaft. - The disengagement phase: when the pusher has completed a stroke, the cam on the input shaft allows it to disengage from the teeth. - In the return phase, the pusher makes a reverse movement of the torque transmission phase, to end up offset by one tooth from the initial position. - The dog engagement phase: the cam system of the input shaft pushes back the pusher to engage the teeth.

[0008] The cycles of the different tappets are staggered, so that at all times a minimum of one tappet is active for torque transmission. This also allows the same cam on the input shaft to act successively on each of the tappets.

[0009] Advantageously, the speed reducer comprises a minimum of five pushrods. Few pushrods induce a harsh pushrod return movement. Too many pushrods limit their travel, but this may be suitable for very high gear ratios. Brief description of the drawings

[0010] Other features and advantages of the invention will become apparent from the following detailed description, for an understanding of which reference should be made to the accompanying drawings in which: - Figure 1 is a diagram of the 4 operating phases of each push button - Figure 2 is a schematic representation of a push button - Figure [Fig. 3] is a cross-sectional view in the plane of the pushrods - Fig. 4 is an external view, parallel to the previous one - Figure 5 is a cross-sectional view in the plane of the axis of rotation. perpendicular to the previous ones.

[0011] DESCRIPTION OF A MODE OF EMBODIMENT OF THE INVENTION

[0012] According to various features of the invention, the described speed reducer comprises ([Fig.3]) a fixed housing (1), an input shaft (2), an output shaft and five pushrods (4). This number of pushrods can be increased or decreased according to the desired characteristics.

[0013] The set of pushers (4) is arranged in a star pattern ([Fig. 3]). The pushers engage with the gear teeth via articulated sectors (5). The pushers have a possible angular deflection relative to the articulated sectors.

[0014] The pushrods are clamp-shaped, for a double cam (6), so that the reducer can transmit torque in either direction. The double cam (6) is fixed to the input shaft (2). It should be noted that only one of the two cams will be loaded, depending on the direction of the torque.

[0015] During its rotation, the cam (6) angularly rotates the tappets (4). During the torque transmission phase, bearing against the fixed housing (1), they drive the output shaft (3) in rotation.

[0016] The pushrods are articulated on through shafts (7). At their ends, these shafts have radial translation guides ([Fig. 4]). These guides are engaged in radial grooves in the output shaft (3), thus transmitting torque and allowing radial freedom of the pushrods (4). The pushrods are constantly pulled towards the center by a spring system (8). The spring (8) is necessary for disengagement and for maintaining the pushrods in the return phase.

[0017] It is advantageous to have a minimum of 2 cam lobes, so that the radial forces on the shafts are symmetrical. Their resultant is thus canceled.

[0018] The angle formed by the center of the input shaft and the points of the two lever supports on the cams must not be too large to avoid jamming during the dog engagement phase. Industrial application

[0019] The present invention is in no way limited to the embodiments described and illustrated, but those skilled in the art will be able to make any variation in accordance with their intent. By way of example, the design shown in the figures is a reducer with 5 levers, 2 cam lobes, and 200 teeth. Depending on the application, other values ​​may be chosen. The pushers may have an oscillating movement as in the described model; in this case, they may be called levers.

[0020] Alternatively, the pushers can have a translational movement relative to the fixed housing, and act as a bias wedge system.

[0021] Alternatively, the pushers can be actuated by a single cam, with spring return. In this case, the reducer operates in only one direction of torque. If the torque is reversed, it operates like a freewheel.

[0022] Alternatively, the axes (7) do not have radial translation guides, but are linked to the output shaft (3) by small connecting rods.

[0023] The field of application of the star reducer is the search for low weight, or high torsional rigidity, or small size, or high regularity of movement, or low manufacturing cost.

[0024] The limit of use is at large reduction ratios.

[0025] If N is the number of teeth of the toothed ring, n the number of cam bosses, the reduction ratio is n / N.

[0026] They are particularly suitable in cases of low duty cycle: cam friction and weak external surfaces tend to cause a rise in temperature during movement.

[0027] The star reducer allows for very high reduction ratios. The higher the reduction ratio, the better the performance.

Claims

Demands

1. Mechanical assembly capable of transforming a rotational motion into a rotational motion at a lower speed and higher torque comprising a fixed housing (Figure 3:1), an input shaft (Figure 3:2), an output shaft (Figure 3:3), characterized in that the transmission of forces is done through several pushers (Figure 3:4) performing a sequential movement during the rotation of the main shafts.

2. Mechanical assembly according to claim 1, the pushers of which (Figure 3:4) are actuated by cams (Figure 3:6) fixed to the input shaft (Figure 3:2)

3. Mechanical assembly according to claim 1, wherein the pushers (Figure 3:4) are hooked to the fixed housing (Figure 3:1) during the torque transmission phase, and unhooked from the fixed housing during the return phase.

4. Mechanical assembly according to claim 3, wherein the pushers (Figure 3:4) are hooked to the fixed housing (Figure 3:1) by means of articulated toothed sectors (Figure 3:5)

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