JPH1054374A - Gear for gear pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate strong pressure formation in a remaining volume by forming at least one hole, one groove, or one notch on at least one part of gear, due to reduce compressive pressure in the remaining volume which is gradually reduced when a gear is deeply engaged with the inside of the gear groove of an opposing gear. SOLUTION: Two gears 1, 5 of a gear pump are engaged with each other, and rotated in narrows A, A' directions respectively. In this case, in respective gears 1, 5, holes 13, 23 which extend to the inside of a tooth are formed in respective teeth 9, 10 and in the region of tooth to parts 11, 21, and also side surface holes opened to the side of the rear side of the tooth in relation to a rotational direction are formed. In the case where, for example, a viscous polymer material are delivered to arrows B, B' directions, high compressive pressure is generated when the tooth 9 of one gear 1 is engaged into the tooth grove of the other gear 5, high compressive pressure by pushing-away of a residual oil material is escaped through holes 13, 23, 31, 33 so as to reduce pressure thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to gears, especially for gear pumps.

[0002]

2. Description of the Related Art A gear pump as a so-called displacement device is generally known. In this case, the displacement process in the gear pump is effected in such a way that one tooth respectively penetrates into the corresponding tooth space of the opposing gear. At a slight angle before the tooth position, where the tooth center line bisecting the tooth end face is exactly on the connecting line of both gear centers of the rotor,
A significant pressure rise in the gradually decreasing residual volume closed by the teeth and tooth space is initiated. Displacement of a liquid ejection medium such as, for example, a polymer melt, takes place axially from this residual volume via a progressively decreasing tooth-to-flank spacing and a progressively decreasing residual volume cross-section. Depending on the viscosity of the ejection medium, a very significant pressure is created, which applies a projection area limited by the smallest tooth-to-flank spacing. This leads to additional load peaks that occur every revolution by a multiple of the number of teeth, which can lead to overloading of the bearings or to a reduction in the bearing load used as differential pressure. In high viscosity polymer melts, furthermore, very high pressures can cause local destruction or damage of the polymer structure, which is unacceptable, especially for polymers to be processed transparently.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide at least one gear with structural means which can reduce or prevent a remarkably strong pressure build-up in a tapering residual volume. It is in.

[0004]

SUMMARY OF THE INVENTION According to the present invention, there is provided, in accordance with the present invention, a method for reducing the remaining volume of a gear which gradually decreases as the gear gradually dips into the tooth space of an opposite gear. The problem is solved by providing at least a part of the gear with at least one hole and / or at least one groove or notch in order to reduce the compression pressure in the gear.

In general, the material to be discharged in the remaining volume is discharged via the play on the tooth side and mainly through the remaining volume cross section perpendicular to the axial direction towards the bearing in the axial direction. In order to reduce the total flow resistance and thus the compression pressure peak, it is proposed according to the invention to advantageously create an additional hydraulic communication between the residual volume and the region having a relatively low pressure level. You. For manufacturing and process technical reasons, a chamber is provided which is loaded by the pressure on the discharge side.

According to another aspect of the invention, it is proposed to provide one or more holes in the tooth, starting from the tooth tip in a substantially radial direction, and in communication therewith, each tooth is provided with a respective hole. It is proposed to provide a plurality of holes axially in the posterior tooth flank in relation to the direction of rotation, in which case, advantageously,
These holes on the tooth side are located approximately within the pitch circle diameter area.

Another solution to the problem posed by the invention is that in order to reduce the compressive pressure, grooves or notches are provided on the respective tooth side in the direction of rotation rearward in the direction of rotation, which are advantageously provided. Starting from the tooth tip, it extends to approximately the pitch circle diameter.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the two gears 1, 5 of the gear pump in cross section in the region of their mutual engagement. Both gears 1 and 5 rotate about the central shaft 3 or 7, respectively, in the direction indicated by the arrow A or A '. Both gears 1, 5 are provided with holes 13 or 23, which extend into the teeth, respectively, in the teeth 9, 19, also in the region of their tips 11 or 21. In addition, side holes or tooth side holes 31 or 33 are provided, which open in the tooth side 16 or 26 behind the respective tooth in the direction of rotation.

If, for example, a viscous polymer material is dispensed in the direction indicated by the arrow B or B ', the two gears mesh with each other and a high compression occurs when the teeth of one gear enter the tooth space of the other gear. Pressure develops. By providing the holes, high compressive pressures due to displacement of the residual material are reduced through the respective holes of the intermeshing teeth.

[0011] During the process of retraction of the tooth of one gear into the tooth space of the other tooth, the aforementioned tooth side holes 31 or 3 are additionally provided.
3 is opened to handle the ejection of a part of the volume flow of the object to be displaced from the tooth space involved in the ejection. This reduces the compression pressure peak as expected. At the neutral position where the center line between the tooth space and the opposing tooth coincides,
Most of the tooth side holes 31 or 33 are already closed. The object to be discharged existing in the tooth hole 13 or 23 engaged with the discharge is a residual volume that gradually increases during the subsequent movement because the tooth side hole directed to the discharge side is not airtightly closed. Replenishes into the inside.

On the other side, tooth side holes 31 or 33
Is increasingly closer to the root of the tooth of the opposite gear, which then meshes and temporarily limits the tooth space involved in the discharge, so that this tooth space is better for the discharge chamber. Will be closed. This avoids pressure shorts and does not significantly reduce volumetric efficiency.

The material to be replenished flowing through the hole into the increasing residual volume causes a direct filling, which effectively mitigates the cavitation problem.

FIG. 2 partially shows the gear 5 shown in FIG. 1 in a perspective view. In this case, the holes 23 axially spaced along the tooth tip 21 can be clearly seen, and corresponding to these holes, the lateral tooth side holes or the hole addition portions 33 respectively. Are arranged in the tooth side surface 26. As can be clearly seen from FIG. 2, when the gear 5 rotates in the direction indicated by the arrow A 'and the remaining volume decreases, the remaining volume is airtightly closed in the discharge direction. Pressure compensation can take place via the holes 33 into the next tooth space.

FIG. 3 shows the gear 5 like FIG. 2 partially in a perspective view, but in this case an optional alternative for producing pressure compensation in the next tooth space. Is provided. Instead of the holes according to FIGS. 1 and 2, in this case, grooves or notches 35 are arranged in the tooth 19 on the rear side of the tooth with respect to the direction of rotation indicated by arrow A ′, which start from the tooth tip. And extends almost up to the pitch circle diameter C. These grooves or cutouts 35 preferably have a semicircular or semielliptical cross-section, so that the formation of so-called useless corners is avoided.

FIG. 4, like FIG. 1, shows the two gears 1, 5 of the gear pump in cross section in the region of their engagement. In this case, both gears 1 and 5 rotate about the central shaft 3 or 7 respectively in the direction indicated by the arrow A or A '. Instead of the holes, notches or grooves 15 or 35 are shown, similar to the teeth shown in FIG. 3, which have the same function as the holes according to FIG. Also in this case, by arranging the groove or the notch, the high compression pressure due to the displacement of the residual material can be reduced by the groove or the notch provided in the teeth meshing with each other.

The function and operation of the gear pump shown in FIGS. 3 and 4 will be described with reference to FIG.
Since the function is similar to that of the hole shown in FIG.

The gears shown in FIGS. 1 to 4 are merely examples and can be changed or changed in any manner. The structure shown in FIGS. 1 and 2 is only for explaining the basic idea of the present invention in detail. Other structural possibilities are also conceivable in order to achieve a pressure reduction in the tapering between the tip and the tooth space, in which the pressure compensation advantageously avoids pressure short circuits. In the discharge direction of the gear pump.

[Brief description of the drawings]

FIG. 1 shows, in cross section, the meshing area of two gears with teeth formed according to the invention of a gear pump.

FIG. 2 is a partial perspective view of one of the gears of FIG.

FIG. 3 is a partial perspective view of a gear according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view similar to the gear of the gear pump shown in FIG. 3, showing a meshing region of two gears formed according to the present invention;

[Explanation of symbols]

1 gear, 3 axes, 5 gears, 7 axes, 9
Teeth, 11 tooth tips, 13 holes, 15 grooves or notches, 16, 26 tooth side surfaces, 19 teeth, 21 tooth tips, 23 holes, 31, 33 tooth side holes, 35 grooves or notches, A, A 'gear rotation Arrow indicating direction

Claims (9)

[Claims] 1. A gear for a gear pump, wherein a gear (9) is provided to reduce the compressive pressure in the remaining volume that gradually decreases as the teeth of the gear progressively sink deeper into the tooth spaces of the opposing gear. , 19) is provided with at least one hole (13, 23, 31, 33) and / or at least one groove or notch (15, 35) for a gear pump. Gears. 2. The gear according to claim 1, wherein one of the holes is provided in the region of the tip (11). 3. The gear according to claim 1, wherein the hole additionally has a tooth-side hole addition on one lateral side of the tooth. 4. A bore (13, 23) extending radially within each tooth is axially spaced apart at the tip (11, 23).
The gear according to any one of claims 1 to 3, wherein the gear is arranged in (21). 5. A hole (13, 2) in a tooth tip (11, 21).
5. The gear according to claim 3, wherein 3) extends at least until it positively mates with the respective tooth side hole so as to communicate with the tooth side hole. 6. A tooth surface hole (31, 33) in each tooth (9, 19) is provided on a rear tooth surface (1) in the direction of rotation.
6, 6), and wherein the tooth-side bore additions on the respective tooth-sides are located approximately in the pitch-diameter region. gear. 7. Gear according to claim 1, wherein the grooves or notches (15, 35) are arranged on the tooth flanks behind the respective teeth (9, 19) of the gear. 8. The groove or notch (15, 35) has a semi-circular or semi-elliptical cross section and a tip (12, 35).
The gear according to claim 1 or 7, wherein the gear extends from the starting point (21) to approximately the pitch circle diameter (C). 9. A gear pump comprising at least two gears according to claim 1, wherein a pressure short circuit between the suction side and the discharge side of the gear pump is prevented. Wherein the additional portion, groove or notch of the tooth hole and the tooth side hole is arranged.