Crescentless internal gear pump

A crescentless internal gear pump includes a housing with an intake connection and a pressure connection. An internally toothed internal gear has an outside surface and is disposed for rotation within the housing. Each tooth includes a head and a base, the internal gear having radial openings that form a conducting connection between a tooth base and the outside surface. A pinion, which is rotatably disposed within the housing and meshing with the internal gear, has teeth with each tooth including a head. The teeth of one of the internal gear and pinion, includes a profile groove with a base provided in the heads into which a sealing element is disposed and which slides on an opposing tooth head. The sealing element has a sealing surface and includes a channel that produces a conducting connection between the profile groove base and the sealing surface. The sealing element is slightly movable in the profile groove in the radial direction to form a controlled gap.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention concerns a crescentless internal gear pump with an internally 
toothed internal gear, a pinion that meshes with the internal gear and a 
housing that accommodates the internal gear and pinion. 
2. Description of the Related Art 
This type of internal gear pump is known, for example, from EP 0 607 497 
B1. The tooth heads of the hollow gear and the tooth heads of the pinion 
are each provided with a profile groove. A sealing element is inserted 
into the individual profile groove, which slides on the opposite tooth 
head of the pinion and internal gear during operation of the internal gear 
pump. The sealing element is provided with a channel that extends through 
the sealing element and makes a conducting connection between the base of 
the profile groove and the sealing surface of the sealing element. This 
ensures that the sealing element acquires the pressure necessary to force 
the sealing element against the opposite tooth head before the dead point 
is reached. After passing the dead point, however, the entire working 
pressure generated by the pump is not on the sealing element, but only a 
partial pressure. 
Internal gear pumps with such sealing elements have proven themselves in 
principle. 
The cited sealing elements are slightly moveable in the profile groove in 
the radial direction. The outer surface of each sealing element 
necessarily forms a gap with the inner surface of the profile groove. 
Control oil reaches this gap from the pressure side of a tooth head with 
the inserted sealing element in the internal space of the profile groove, 
i.e., the profile groove base. There the control oil enters the channel 
that passes through the sealing element in order to emerge again on the 
sealing surface of the sealing element in the region of the opposite tooth 
of the pinion or internal gear. 
It has been shown that, despite the channel that passes through the sealing 
element, control of oil flow and thus the pressure with which the sealing 
element is forced against the opposite tooth head is not optimal. 
Especially at high pressures, for example at pressures of 250 bar, 
fluctuations in pressure force occur. These fluctuations are 
disadvantageous, especially with reference to the sealing effect between 
the sealing element, on the one hand, and the opposite tooth, on the 
other, and thus the efficiency and operating method of the entire internal 
gear pump is less than optimal. 
SUMMARY OF THE INVENTION 
The underlying task of the invention is to configure a crescentless 
internal gear pump so that the pressure force of the sealing element 
against the head of the opposite tooth remains essentially the same, 
especially at high system pressures. 
The present invention comprises, a crescentless internal gear pump, 
including a housing with an intake connection and a pressure connection. 
The cresentless internal gear pump also includes an internally toothed 
internal gear comprising an outside surface, the internal gear disposed 
for rotation within the housing, each tooth including a head and a base, 
and the internal gear having radial openings that form a conducting 
connection between a tooth base and the outside surface. A pinion, which 
is rotatably disposed within the housing and meshing with the internal 
gear, having teeth with each tooth including a head is also included. The 
teeth of one of the internal gear and pinion include a profile groove with 
a base provided in the heads, into which a sealing element is disposed and 
which can slide on an opposing the tooth head. The sealing element 
includes a sealing surface and a channel that produces a conducting 
connection between the profile groove base and the sealing surface, the 
channel enclosed by the body of the sealing element as viewed in the 
rotation direction of the pinion. The sealing element slightly movable in 
the profile groove in the radial direction to form a gap between the 
sealing element and an inner surface of the profile groove so that the 
profile groove base is in a conducting connection with the pressure 
connection. One of the sealing element and profile groove is configured so 
that the width of the gap in any radial position of the sealing element is 
substantially the same. 
The present invention also comprises, inform thereof, a crescentless 
internal gear pump in which, viewed in an axial section, each sealing 
element includes a dovetail shaped part includes at least one groove is 
made in one of an outer surface of the sealing element or in the inner 
surface of the profile groove. 
The inventors have recognized that the width of the gap between the outer 
surface of the sealing elements and the inner surface of the profile 
groove changes during operation, especially during radial displacement of 
the sealing element. The amount of control oil that flows from the 
pressure side through the cited gap to the profile groove base is changed 
on this account. Accordingly, the inventor proposes that the width of the 
gap situated on the pressure side remain unchanged, regardless of the 
prevailing operating parameters. 
Numerous variants are possible. For example, the sealing element can be 
provided with appropriately configured grooves.

Corresponding reference characters indicate corresponding parts throughout 
the several views. The exemplification set out herein illustrates one 
preferred embodiment of the invention, in one form, and such 
exemplification is not to be construed as limiting the scope of the 
invention in any manner. 
DETAILED DESCRIPTION OF THE INVENTION 
The internal gear pump depicted in FIG. 1 is a crescentless, head-sealing 
and backlash-encumbered pump. It includes as essential elements an 
internal gear 1, a pinion 2, as well as a housing 3. The internal gear 1 
is provided with holes or Radial Openings 1.1. These produce a conducting 
connection between the surroundings and outside surface of the internal 
gear 1, on the one hand, and the intermediate space between internal gear 
1 and pinion 2, on the other. Sealing elements 4 are inserted into profile 
groups in the teeth of the internal gear. 
Pinion 2 is wedged on a pinion shaft 2.1 that rotates in the direction of 
arrow X within internal gear 1. 
The housing 3 has an intake connection 3.1 and a pressure connection 3.2. 
The teeth 1.3 of the internal gear and the teeth 2.2 of the pinion have a 
certain axial width. Internal gear 1 and pinion 2 are mounted 
eccentrically to each other. Moreover, the number of teeth 2.2 of pinion 2 
is one less than the number of teeth 1.3 of internal gear 1. 
The following are apparent in particular from FIG. 2. Each tooth 1.3 of the 
internal gear 1 has a profile groove 1.4. A sealing element 4 is inserted 
into each profile groove 1.4. This element 4 is configured in dovetail 
fashion on part of its cross section. Each sealing element 4 has a 
continuous channel 4.1. This produces a conducting connection between the 
internal space or profile base 1.5 and the sealing surface 4.2 of the 
sealing element 4. 
As is apparent from the double arrow Y, the sealing element 4 during 
operation of the internal gear pump can execute a radial movement. The 
other arrows shown on the center sealing element indicate the trend of the 
control oil flow. As is apparent, the control oil stream coming from the 
pressure side initially enters a gap 5 formed between the outer surface of 
the sealing element 4 and the inner surface of the profile groove 1.4. A 
groove 6 is made in the sealing element in the dovetail-shaped part of the 
sealing element. In the center part of the sealing element 4 a continuous 
groove 7 is provided. Groove 6 is configured and arranged so that the 
control oil flow is not throttled from the continuous groove 7 to the 
groove base 1.5. The width of the entire channel is also always the same 
during a radial displacement of the sealing element 4. The first section 
of this flow channel, namely gap 5, is parallel to the contact surface 8 
and thus independent in gap height of the radial movements Y. 
While this invention has been described as having a preferred design, the 
present invention can be further modified within the spirit and scope of 
this disclosure. This application is therefore intended to cover any 
variations, uses, or adaptations of the invention using its general 
principles. Further, this application is intended to cover such departures 
from the present disclosure as come within known or customary practice in 
the art to which this invention pertains and which fall within the limits 
of the appended claims.