DE2921977A1 - SHAFT DRIVE ELEMENT - Google Patents

Description

The invention relates to a shaft drive element.

According to the state of the art, there is quick-change pellet mills and other applications, there has long been a need for a drive element that transmits high torques that is self-centering and self-releasing and that has maximum surface contact between the driving force and the driven element.

Previous attempts to connect the drive elements were based in this field and other cases of high loads on wedged cone connections, adapter sleeves or bolt connections. None of these arrangements turned out to be under the difficult conditions of a pellet mill as completely satisfactory, because of the point or Line contact, accelerated corrosion and / or tight tolerances leading to manufacturing difficulties and / or difficulty assembling or disassembling the drive elements. The invention addresses these problems fixed while maintaining the self-centering properties of a taper fit.

The invention relates to power drive elements, in particular elements for coupling a drive element to a driven element for transmitting a drive force. In particular, the invention relates to rotating shaft drive elements having a male and a female drive element. More particularly, the invention relates to the formation of the male and female driving and driven elements, respectively. According to the invention, a non-circular interference fit is provided which, in the exemplary embodiment described, is characterized by a multi-vane drive element, the contact surfaces of which are derived from a logarithmic spiral. This coupling is

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self-centering and can be designed such that it either locking or releasing properties when a torque is applied.

The aim of the invention is to provide a quick release drive element to accomplish. Another object of the invention is to provide a self-centering drive element create. The invention is also intended to provide a drive element whose solution properties are from can be predetermined by the designer.

Another object of the invention is to provide a drive element which has a maximum drive contact area has a minimum of force concentration points. The invention is also intended to provide a drive element can be created, the fit can be selected in a wide range, but still the full surface drive contact is retained «,

Another object of the invention is to provide an extremely strong shaft drive element that is economical can be manufactured, has a long service life and requires little maintenance »

These and other objects are achieved according to the invention by a drive element which is characterized by the following features: a penetrating drive element, the cross section of which is limited by segments of a logarithmic spiral connected to one another at their ends _? a female drive member, whose cross section is defined by interconnected at their ends segments of the same spiral having larger radius _$ wherein in the male and the female drive member, the one half of the segments of a clockwise spiral and the other half

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of the segments of a spiral counterclockwise.

The invention is explained in more detail below, for example with reference to the drawing; it shows:

1 shows the development of the underlying logarithmic spiral;

2 shows the application of the logarithmic spiral to a segment of the drive element;

3 is a partial sectional view of a pellet mill showing an application of the drive element; and

FIG. 4 is a sectional view along the line 4-4 of FIG. wherein the drive engagement of the drive element is shown.

For a better understanding, the application of the invention to the drive shaft of a pellet mill will first be described « According to the prior art, quick-change die-roll arrangements for pellet mills are known. Such a one The arrangement is described in US Pat. No. 5,911,550. The way of working and function of the quick-change pellet mill are therefore not described in detail but only to the extent that than is essential to the practice of the invention. For explanation, however, a part of a pellet mill is shown in FIG. 3, more precisely, the mill main shaft, the inner and outer hollow shafts and the gear box are shown. Of the Gearbox 1 carries the outer hollow shaft 2, the inner hollow shaft 3 and the main shaft 4, which are part of the drive for the pellet mill.

The inner and outer hollow shafts 2 and 3 stand together

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which is engaged by means of an intermediate drive element 5. The central or main shaft 4, which is within the two Hollow shaft is housed is fixed against rotation, but at the rear end of the main shaft 4- axially releasable and against axial or lateral movement by means of a nut and a washer or a similar device (not shown) held. On the yoke 6 of the working or front end of the main shaft are two or more rollers 7 (not shown in its entirety) attached. These rollers can rotate within the pellet mill die 8, whereby the Roller is driven by the die while it is rotating. The rollers rotate on the inner annular work surface 9 of the die, thereby extruding material outward through the holes radially formed in the die.

A support collar 11 surrounds the front end of the main shaft and holds the bearing 15 axially stationary on the roller shaft. The bearing sleeve 12 carries a bearing 15 for the rotary bearing of the main shaft 4- within the inner hollow shaft 3. Around the main shaft around a rotary seal 13 is also provided to prevent oil from the bearings in the feed material escapes and that supplied material penetrates from the extrusion area into the bearings.

A similar bearing 16 for the outer hollow shaft is attached between the outer hollow shaft and the gear box housing 1. A seal 17 prevents the oil from leaking out of the Gear box. In addition, a seal 18 is arranged between the inner and outer hollow shaft, so that the supplied Material does not penetrate to the intermediate drive element. A bearing 19 is provided at the rear end of the outer hollow shaft, to support the outer hollow shaft rotatably in the gear box housing. The camp is also for prevention

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an oil outlet sealed in a suitable manner. A centering bush 20 guides the rear end of the inner hollow shaft in the outer hollow shaft. The arrangement of the bearings and seals allows the inner hollow shaft 3 and the main shaft 4- to be thereby quickly separated from the gear box can that the retaining nut and the washer removed and the assembly slid axially to the right in FIG will.

The die 8 can be removed from the inner hollow shaft by removing the die clamp (not shown) which engages the flange of the inner hollow shaft 3 and the flange of the die 8. The person skilled in the art will recognize that the die, the rollers, the yoke, the main shaft and the inner hollow shaft for maintenance are easily removed from the Pellet mill can be removed.

The driving force for rotating the outer hollow shaft 2 is transmitted to the outer hollow shaft through the drive gear ΊΟ, which is wedged by means of the key 23 on the outer hollow shaft. The drive gear is by means of a no driven pinion gear shown, which in turn is driven by the power source, for example can be an electric motor not shown.

So that the inner hollow shaft is removed from the outer hollow shaft and the high drive torque required to rotate the die can still be transmitted, a coupling or drive element 5 is required, as will be evident to the person skilled in the art. This drive element must on the one hand can transmit the occurring high torque and on the other hand to facilitate the disassembly be easily solvable without further ado.

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In Fig. 4- is a sectional view along the section line 4-4 of Fig. 3, in which the inventive Drive element is shown which meets the requirements of this mode of operation. The drive element is a special design of a non-circular interlocking drive with a penetrating driven one Element 30, which is arranged on the inner hollow shaft, and a receiving drive element 40, which is effective is assigned to the surrounding outer hollow shaft. The special drive element comprises six segments of a logarithmic one Spirals connected to each other at their ends; three segments are from a spiral clockwise shaped and three segments from a spiral counterclockwise with the same radius. The receiving drive element is shaped in the same way from the same logarithmic spiral, but with a slight one larger radius.

Fig. 1 shows the development of the underlying logarithmic spiral.

Fig. 2 shows the application of the logarithmic spiral to a segment of a drive element. For further explanation of the invention and to aid understanding of the invention, the following specific example of a typical pellet mill drive element continued. In the described preferred embodiment, has the drive element takes the form of a three-leaf drive on, which is referred to below as a multi-vane or multi-cam drive. As mentioned earlier, the multi-cam surface is constructed from a part of a logarithmic spiral.

According to FIG. 1, the underlying logarithmic spiral can be defined by the equation R = e, where

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e is the base of the natural logarithm and has a value of approximately 2.3025851; a can be defined by the following equation: a = Λ / taxi'Y . θ is the angle of rotation from the beginning of the spiral and R is the radius of the spiral at angle Θ.

Ύ is defined as the angle at which the logarithmic spiral crosses a radial projection from the center of the spiral with respect to the radial projection. The complementary angle of * P , ie 90 minus Ύ, can be identified as the locking angle or the release or release angle of the spiral.

The particularly desirable property of that depicted in FIG logarithmic spiral is that the angle "* f" for each radial line or projection from the center point of the curve is constant for any given logarithmic spiral. The angle "V" can be changed, but this leads to a new spiral that has different physical properties in the multi-vane drive element will.

For the purposes of the pellet mill multi-vane drive, an angle * ¥ of 75 was selected due to the fact that cone fits with an angle of greater than 8 ° with respect to the center line are to be referred to as self-releasing cones. The locking angle of 15 ° therefore leads to a self-releasing drive. It is contemplated that the useful angle for high power drives can be varied within the range of 5 to 20 ° (Ύ + 70 to 85 °) depending on the materials of construction and the degree of interlocking desired between the mating parts . The angle 6 is measured in radians and determines which section of the

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logarithmic spiral is defined. This, on the other hand, makes the distance from the center of the spiral to the surface of the curve certainly.

The physical size of the parts and the torque to be transferred from one part to the other determine the application of the above equations. To explain the preferred exemplary embodiment, it is assumed, for example, that that the pellet mill has various size limits into which the multi-vane drive element fits have to be. The range of R is therefore known and the equation can be solved for θ in the extreme conditions d. H. for the smallest and largest radius of the drive. For example, the minimum radius in the The embodiment shown in Fig. 3 is 14.2875 cm (5 5/8 inches). It was also known that a segment with a curve length of 60 ° (560 ° divided by 6) was required.

Thus, R = 5 5/8 = e ^aÖ

5 5/8 = e ⁰ ' ^{2679 θ} or In 5 5/8 = 0.2679 θ

θ = 6.4461 RAD

^a - ΪΞΓψ - ΈΖΗ75 = ° '^2679;

when converting to degrees one gets 369.3330 °.

This means that in this example the section of the Curve at "Z" begins after the spiral has developed around the axis more than once. To determine the radius at the larger end of the curve, 60 ° are added to the above value and the solution for R is then determined again.

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So: 369.5350 ° + 60 ° = 429.3330 ° = 7.4933 RAD R = e ^a0 = e 0.2679 (7.4933) R = 7.4443 inches = 18.908522 cm;

Now that the end points of the curve section have been found, enough intermediate points are determined to start a program for to be able to write a numerically controlled milling machine. This process was performed with 2 intervals starting with 369.3 carried out. A series of values for θ and R resulted for a 60 ° segment of the curve. Using three Segments in the counterclockwise direction of the curve and three segments in the clockwise direction of the curve resulted in the total cross-section the shaft or the hub. In Fig. 2:

A = 60 ° counterclockwise segment of the logarithmic

spiral
-Segment
Spiral.

B = 60 ° clockwise segment of the logarithmic

The most essential property of the multi-wing shape is that the penetrating part is made appreciably smaller can be used as the female part for every fitting, and that nevertheless no high compressive stresses are generated, when two parts are locked together. To achieve just this, a slightly different section is used of the same spiral used. In the embodiment, for the surface of the penetrating part a segment of the curve from 369.3 ° to 429.3 ° is used. A section was made for the surface of the female part used between 370.9 ° and 430.9 °. This resulted in a clearance of approximately 0.2032 cm between the penetrating one and the receiving part. When the male part is inserted into the female part and a torque is applied was, there was a touch over almost the entire

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Length of the drive segment of the multi-vane element (see Pig. 4). In the pig. 4 the state is shown at which the female drive element is the penetrating drive element drives clockwise. As can be seen, about half of the circumferential surface is used for transfer of the torque used.

Another feature of this design is that the shaft moves into the hub when torque is applied or self-centered when rotated. In addition, the multi-vane element, which is made up of clockwise and counterclockwise spirals in both directions work. If only one direction of rotation is required, one group of the spirals can be omitted.

Although above the invention with reference to a three-winged Drive has been explained, it should be noted that a suitable drive with two or more wings or cams can be formed.

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Claims (7)

PAVdNTANWAt-VE HELMUT SCHROETER KLAUS LEHMANN DIPL.-PHYS. DIPL.-ING. CALIFORNIA PELLET MILL COMPANY ir-75 U / w May 30, 1979 Shaft drive element Claim e Shaft drive element, characterized by a penetrating coupling element (30), the cross section of which is bounded by segments of a logarithmic spiral, the ends of which are connected by a receiving coupling member (4-0), the cross section of which is through segments connected to one another at their ends same spiral with a larger radius is limited, and in that both with the penetrating as well as with the female coupling element half of the segments of a spiral clockwise and the other half corresponds to the segments of a spiral in a counterclockwise direction. 9098S0 / 0725 D-7070 SCHWABISCH GMOND COMMON ACCOUNTS: D-βΟΟΟ MUNICH 70 Telephone: (07171) 56 90 Deutsche Bank AG PustsActkkomo Telephone: (089) 725 2071 H. SCHROETER telegrams: Sdiroepac Munich 70/37 369 Munich K.LEHMANN telegrams: Schroep « Bodugasse49 Telex: 72 «868 pagdeä (BLZ 700 700 10) 1679 41-80 * Lipowskystraße 10 Telex: 5212248 pawe d 2. Drive element according to claim 1, characterized in that the penetrating coupling element (30) is defined by six segments of a logarithmic spiral connected to one another at their ends and that the cross section of the female coupling element (40) is limited by six segments of the same spiral is. 3. Drive element according to claim 1, characterized in that the logarithmic spiral through the equation R = e
is defined. 4. Drive element according to claim 3 »characterized in that a as the reciprocal of the Tangent of the complementary angle of the locking angle is defined. 5. Drive element according to claim 4, characterized in that the locking angle in the range between 5 and 20 degrees. 6.Antriebselement according to claim 3 »characterized by g ek e η η that the locking angle is approximately 15 degrees. 7. Drive element according to claim 1, characterized in that the penetrating coupling element (30) is in driving engagement with the inner hollow shaft (3) of a pellet mill that the receiving drive element (40) is in driving engagement with the outer hollow 909850/0725 shaft (2) of a pellet mill stands, and that the penetrating drive element (30) and the receiving drive element (4-0) cooperate to form a power transmission drive between the inner and outer hollow shaft. 9098BO / 072S-