GB2070733A - Flexible couplings - Google Patents

Abstract

A coupling between a power source and a rotating or oscillating working element comprises a flexible power storing and transmitting mechanism, constituted by a V-belt pulley 1 whose crown 5 is connected to spokes 4 by springs 15 and is circumferentially guided by the spokes which engage between pairs of plates 6 fixed to the crown. <IMAGE>

Description

SPECIFICATION Gear unit for power-saving drive of working elements of rotary or oscillatory motion, especially of agricultural cutter drums and peg drums The subject matter of the invention is a gear unit for power-saving drive of working ele ments of rotary or oscillatory motion, espe cially of agricultural cutter drums and peg drums, which is built in into the driving chain between the power source and working ele ment of the given equipment.

It is proved both by the experiments and the practical experience that if blades carrying out chipping operation are driven, in addition to the main motion vertical to the edge, also with an auxiliary motion along the edge, the chipping occurs not by shearing but by so called slicing, whereby the power demand is considerably reduced.

In the agricultural machine industry this recognition is utilized among others in such a manner that on the cutter drum the blades are fastened somewhat upturned as compared to the generatrices of the drum mantle, i.e. the generatrices and the blades include acute angles.

The drawback of this widely-used solution consists in that the auxiliary motion is but a relative displacement as compared to the ma terial to be chopped and therefore the blades -up to the occurrence of the slicing--exclu- sively compact the material to be chopped by consuming about 30 to 40 % of the entire power.

While compacting, the load of edges natu rally increases, which as an additional drawback, reduces the useful life of blades.

In order to eliminate these drawbacks it wouid be self-evident to realize the auxiliary motion as an absolute motion, namely as an oscillatory motion. The constructions based on this conclusion are, however, all provided with independent vibrating devices requiring exter nal power. These implements do not meet, however, the practical requirernents due to their high purchase and operational costs, as well as to their uncertain operation, so that they are not widely used.

The reduction of power consumption was observed in the experiments carried out with threshing machines in which an oscillatory motion was superimposed to the uniform cir cular motion of the rasp bars, but even these solutions are not used in the practice.

The task of the invention is the develop ment of a solution applicable in the working practice, in which an oscillatory motion, as an auxiliary motion, can be superimposed to the working main motion without any surplus power.

This task is accomplished according to the invention in such a manner that the gear unit is a flexible, power-storing and transmitting device excited by the momentary changes of the technological power demand of the material fed in the equipment.

The invention is based on the recognition that the momentary technological power demand, in the present case the chipping power demand, of the material fed in the equipment, e.g. of the produce to be chopped is constantly changing and the current deviation is utilized for producing the auxiliary motion.

Under flexible device, in the present description such a mechanical part built in into the driving chain is to be understood, as compared to which the other elements of the driving chain are rigid in statical sense, independently of the fact that they are produced of elastic structural material.

The elastic properties of the construction to be applied in the given equipment shall be determined when projecting, and rating, respectively, in such a way that the mechanism could be excited but cannot considerably modify the equilibration of the working element, e.g. of the cutter drum, further cannot cause any quality change in the produce, so that e.g. the longitudinal size of the chopped produce should remain within the required dimensional limits.

The attribute "power-storing and transmitting", however, defines a mechanism of a behaviour contrary to the known spring member, on the one hand, i.e. which is characterized not at all by the as perfect damping as possible of the excitation, that is by the consumption of potential energy and it manifests that the mechanism operates without external power, i.e. without a separate power source, on the other hand.

The invention will be now introduced in details by means of the accompanying drawings of an embodiment developed to a selfpropelled straw chopper. In the drawings Figure 1 is a partly broken side view, Figure 2 shows the section taken along the line ll-ll of Fig. 1, Figure 3 is the section taken along the line Ill-Ill of Fig. 1.

The embodiment shown in the drawing has been developed to the self-propelled straw chopper or type E 280, made in the German Democratic Republic, in which the flexible, power-storing and transmitting device according to the invention is a V-belt pulley 1 driving the cutter drum as the last element of the driving chain, and this V-belt pulley 1 is wedged to the shaft 2 of the cutter drum. The distinctive particularity of the V-belt pulley 1 consists in that its hub 3 and the spoke 4 are developed in one piece, its crown 5, however, independently. The flexible elements-in a narrow sense are built in between the spokes 4 and the crown 5.It should be noted that the power source, and the driving chain of the straw chopper, and the V-belts built in into the driving chain and driving the V-belt pulley 1, respectively, are not shown in the drawing, on the one hand, and the V-belt operating with a definitive prestress act as a rigid body as compared to the flexible mechanism according to the invention, as mentioned above, on the other hand.

The spokes 4 of the V-belt pulley 1 according to the present invention are positively guided one by one in a sliding manner between the one pair each of guide rails 6 fastened on the inner mantle of the crown 5, in a plane vertical to the axle 2, along the periphery.

According to Fig. 1, to the left from the guide rails 4 in a given distance, a shoe 7 is fixed through the boring of which a threaded bolt 8 is led. The threaded bolt 8 is fixed in the shoe 7 by means of a tab washer 9 and of a nut 1 0. On the threaded bolt 8 between the jaws of the shoe 7, the head of a pilot pin 11 is tiltingle supported which is led through the open-end longitudinal hole 1 2 developed in the spoke 4. Between the shoulder 1 3 formed on the pilot pin 11 and the washer 14 bearing against the spoke 4, a spring 1 5 is arranged. On the part overhanging the spoke 4 of the threaded bolt 8 a flexible washer 1 6 is pulled on.The clearance between the crown 5 and the spoke 4, as well as the calculated prestress of the spring 1 5 can be adjusted by means of a nut 17 and a counternut 18.

It should be noted that another variant of the embodiment shown here is also conceivable in which the V-belt pulley 1 is not provided with spokes but is "solid", i.e. the crown 5 is positively guided on the hub 3 directly or at least with the intermediation of a spring 15.

In the course of the experiments such a variant was also examined in which the spoke 4 is clamped between two springs 1 5 pulled up on the pilot pin 11. The investigations have proved, however, that the introduced variant is also fully capable of working.

When dimensioning the spring 15, we started from two postulations; we stated, on the one hand, that with cutter drums working with a revolution number of 600-1500 rev/ min, having a diameter of 600 mm and a blade position of 1 5-20ç, the amplitude of the superimposed oscillatory motion should be rated between the values of 3-3.5 mm measured on the periphery. With the observation of the permissible amplitude, the equilibrium condition of the working element and the meeting of quality demands of the produce can be ensured. According to our experiments, between the diameter of the cutter drum and the permissible amplitude a linear or nearly linear relationship exists. The amplitude is decisive for the maximum compression of the spring 1 5.

On the other hand, the moment variation measured on the cutter drum was determined by experimental measurements, wherefrom the load, and working range, respectively, of the spring 1 5 can be calculated.

As a result of the calculations, a spring rigidity of S = 200 N/mm was obtained with the introduced embodiment.

In the self-propelled straw chopper equipped with the device according to the invention the V-belt pulley 1 according to Fig.

1 was driven in clockwise direction. The structural length of the spring 1 5 varied always in accordance with the variation of the current cutting power demand of the fed material flow, i.e., as compared to the uniform rotary motion of the crown, the shaft and the cutter drum were always in advance or in delay, that is an oscillatory motion was superimposed to the main motion.

According to our measurements the excitation frequency of the V-belt pulley 1 was 20-40 Hz, on the basis of the assumed moment curve.

The most significant advantage of the introduced embodiment consists therefore in the power saving of about 1 5 %. An advantageous property with respect to the practical realization consists in that the existing equipment, in the present case the self-propelled straw chopper, can be modified by replacing one single part, namely the V-belt pulley and the operation and working of the modified implement remain unchanged, i.e. a skilled worker can operate it without any special qualification, on the one hand, and that the Vbelt pulley according to the invention is simple and safe, on the other hand, i.e. the reliability of the modified implement is not deteriorated.

In other embodiments of the solution according to the invention the above advantages manifest themselves in our opinion with more or less deviation.

Numerous other variants of the solution according to the invention are conceivable within the scope of protection, thus, from among the elements to be built in into the driving chain the elastic couplings of type Bibby, Forst, Elcard, as well as those equipped with various rubber blocks or rubber hoses, further the toothed belt are mentioned only by way of example. Their spring rigidity and spring constant shall be determined, as a matter of course, according to the demands of the given equipment and of the given field of application, on the basis of our recognition.

As a possible field of application, in addition to the agricultural processing machines, the classing operation is mentioned by way of example, for power-saving driving of e.g. reciprocating sieves or swinging sieves.

Claims (3)

1. A gear unit for driving a working element in rotary or oscillatory motion, which is installed between a power source and the working element, the unit comprising a flexible, power storing and transmitting mechanism excited by the momentary variations of the power demand of the working element.

2. A unit as claimed in claim 1, in which the said mechanism comprises a split V-belt pulley having a crown which is positively guided along the periphery in a slidable man ner on spokes, with the intermediation of springs.

3. A unit as claimed in claim 1, substantially as described with reference to the accompanying drawings.