-1-
Field of the Invention
The present invention relates to an interlocking device for rigidly holding
together the body and flange of a hydraulic machine using bean-shaped dowels. The
interlocking mechanism according to the present invention can also be employed for
hydraulic pumps, motors, valves, etc. where containment of pressurized fluid is
required with due consideration for minimal deflection of the load bearing elements.
The present invention comprises an improvement in the invention disclosed and
claimed in the co-pending application by the same applicant, viz., Indian Patent
Application No. /KOL/2005 filed on 28th September 2005 (hereinafter referred to as
the main invention) for an interlocking device for rigidly holding together the body and
flange of a hydraulic machine using oval-shaped dowels.
Background of the Invention
For the effective functioning of a hydraulic machine, it is essential that the
relative positional displacement amongst the various component parts, viz., body,
flange and cover are controlled within reasonable limits. This factor helps to maintain
reduced clearance between the gear tip circle diameter and the bore of the body, so
that the hydraulic machine's volumetric efficiency can be kept optimum at various
levels of oil pressure.
The desired performance is met by the hydraulic machine construction by
employing positive close fit dowel arrangement between the flange and the body.
Such a construction ensures that the relative movement amongst these two
components is minimal.
Presently, the design of hydraulic machines is such that they are provided with
dowels disposed on the body at the inlet side in case of two hollow dowels and at
both inlet and outlet sides in case of four hollow dowels. These hollow dowels
accommodate the mounting bolts of the hydraulic machine to pass through.

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Figure 1 of the drawings accompanying the specification depicts the profile of a
pump body used in a conventional gear pump. Gear pumps using such profile and having
two hollow dowels are, and can be, employed satisfactorily for applications requiring upto
3000 Ibs./in2 (207 bar) oil pressure. The hollow dowels used in the body of a conventional
gear pump is shown in Figure 2 of the drawings accompanying the specification.
Figure 3 of the drawings accompanying the specification shows the profile of a
gear pump body used in a conventional gear pump where the application pressure
required is high. Gear pumps using such profile and having four hollow dowels are, and
can be, employed satisfactorily for applications requiring upto 4000 Ibs./in2 (275 bar) oil
pressure.
It is known from GB-A-2247923 to provide one or both ends of the housing with a
non-circular inner rim which is received within a recess of matching non-circular shape
defined by a flange projecting from a peripheral region of a respective end cover in a
direction parallel to the axis of rotation of the meshing rotors. One or both open ends of
the housing is thus supported by its end cover against outward deflection under the
effect of fluid pressure in the chambers in a plane transverse to the axes of rotation of
the meshing rotors.
GB-A-2247923 further discloses that the non-circular inner rim and matching non-
circular recess are difficult to machine accurately and require complex CNC programming.
Also, although this arrangement provides good alignment and support in a direction
normal to the aforesaid plane (i.e. in the direction of the minor axis), no support is given
in the direction of the major axis. Under the influence of internal pressure, the major
sides of the housing deflect outwards to a small extent whilst the minor sides of the
housing contract away from the mating edges of the peripheral flange on the end cover.
The flange thus only limits body deflection in an outwards direction. Furthermore, there
has to be an axial clearance between the peripheral flange and the end face of the
housing in order to ensure that the end face of the inner rim seats against the base of the
recess. The end cover is secured to the housing by bolts and this axial clearance results
in a bolt load overhang which imposes a considerable bending load on the flange profile.

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It is also known from GB 2408070A to provide a rotary positive displacement
hydraulic machine in the form of a gear pump or motor comprising defining two mutually
intersecting parallel working chambers having a low pressure inlet side and a high
pressure outlet side, two meshing rotors mounted for rotation in the two chambers
respectively, and two bearing supports at opposite ends of the chambers and each
supporting bearings in which the two rotors are joumalled for rotation, wherein at least
one end of the housing is closed by a separate end cover and wherein the separate end
cover and an adjacent end of the housing each has at least one elongate recess on each
of the two major sides of the working chambers, the recesses in the end cover being
alignable with respective recesses in the adjacent end of the housing and there being at
least one keying element in each pair of aligned recesses so that the open end of the
housing is supported against outward deflection by differential fluid pressure in the
chambers in a direction transverse to a plane containing the axes of rotation of the
meshing rotors.
There was a long-felt need in the art for an interlocking device for hydraulic
machines, in particular, gear pumps operating at pressure in excess of 275 bar that
prevents the undue relative displacement and the undesirable orientation of the gear
pump body with respect to its flange and cover. A higher relative displacement between
the structural component parts of the gear pump will correspondingly lower the
performance of the pump, particularly its volumetric efficiency, as discussed above. A
crucial factor, and hence a matter of concern for gear pump designers, is the
effectiveness of the doweling arrangement to prevent relative displacement of the pump
body and the flange at the operating pressure.
Therefore, the strategy for improving the effectiveness of the interlocking
arrangement is considered as a major step towards achieving high pump performance
levels with increased volumetric efficiency.
With the above objective, the present invention is oriented towards optimizing the
configuration of the dowel, i.e., its shape and size and also its disposition on the body of
the hydraulic machine. This critical shape and size of the locating dowel and its optimal

-4-
positioning have been arrived in the present invention through in-depth estimation of the
hydraulic forces occurring inside the pump body, which significantly behaves like a close
knit pressure vessel, while being in high pressure operation.
In order to identify the optimum interlocking concept, pump interlocking
arrangement using four bean-shaped dowels (as depicted in Figure 4 of the
accompanying drawings) has been evaluated for gear pumps operating at higher
application pressure in the range of 330 bar, and compared for the relative strength and
optimality with respect to the conventional hollow dowel arrangement.
The location of occurrence for the maximum stress and deflection position can be
naturally different in the bean-shaped dowel arrangement according to the present
invention as compared to the oval-shaped dowel arrangement invention according to the
main invention, due to variation in the body profile and dowel profile and location. The
optimality in deflection and stress for the body of a hydraulic machine while being used
under extreme operating conditions makes it clear that the bean-shaped dowel
arrangement is an improvement upon the oval-shaped dowel arrangement, as elucidated
in further detail in the description hereinafter.
Summary of the Invention
Accordingly, the present invention provides an interlocking device for rigidly
holding together the body and flange of a hydraulic machine comprising a body, flange,
gears, sealing means acting as body seal and lobe seal adapted to effectively seal
pressurized oil pockets within the hydraulic machine with a back-up ring that prevents
squeezing of said lobe seal and to retain it in its original position, appropriately
dimensioned bush bearings adapted to act as load bearing journals, wherein said
interlocking device comprises a plurality of bean-shaped dowels located at both inlet and
outlet sides that hold the body and flange together with minimum relative displacement
to ensure high volumetric efficiency of said hydraulic machine even at high operating
pressures in excess of 275 bar.

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Preferably, the number of bean-shaped dowels used is four. The curvilinear major
axis of each of the bean-shaped dowels is aligned at right angle with the resultant force
direction and their minor axis at the axis of symmetricity is aligned with the resultant
force direction. The width of said body is proportional to the fluid flow capacity. Said body
is made from high grade specially alloyed cast iron or aluminium materials depending
upon the application and pressure ratings. Said gears are made from special steels. Said
flange is made from cast iron castings. The profiles of said body and the flange are such
that adequate reinforcing is maintained at appropriate zones to enhance its load bearing
capacity and its rigidity.
Both said body and said flange are equipped with a provision for accommodating
said bean-shaped interlocking dowels. The profile of the lobe seal material matches with
that of the corresponding pressure plate. Said bush bearings, which are used as a load
bearing journal, are PTFE lined.
It would appear clear to persons skilled in the art that numerous developments and
modifications are possible without departing from the scope and spirit of the invention,
which has been described for illustrative purposes only, by way of example of an
interlocking device for rigidly holding together the body and flange of a hydraulic
machine, wherein said hydraulic machine is a gear pump.
Brief Description of the Accompanying Drawings
Embodiments of the invention for use with a hydraulic gear pump, will now be
described by way of example only, with reference to the accompanying drawings
wherein:
Figure 1 shows the profile of a pump body used in a conventional gear pump.
Figure 2 shows the hollow dowels used in the body of a conventional gear pump.
Figure 3 shows the profile of a gear pump body used in a conventional gear pump
where the application pressure required is high.

-6-
Figure 4 shows pump interlocking arrangement using four bean-shaped dowels
according to the present invention.
Figure 5 depicts the optimized profile of a body of a pump body using bean-shaped
dowel.
Figure 6 shows a bean-shaped dowel for a pump body.
Figure 7 is a free body diagram for a conventional pump body with oil pressure
loading.
Figure 8 is a linear representation of force diagram within a conventional pump
body.
Figure 9 is a free body diagram for a pump body according to the present invention
with oil pressure loading.
Figure 10 is a linear representation of force diagram within a pump body according
to the present invention.
Figure 11 shows an overall pump assembly.
Figure 12 is an exploded view of the pump assembly having an interlocking
mechanism using bean-shaped dowels according to the present invention.
Description of the Preferred Embodiments
Finite element analysis (FEA) was carried out for the conventional interlocking
mechanism and for the interlocking mechanism according to the present invention for a
pressure range of 207 bar which the conventional interlocking devices are able to
withstand, while applying to similar pump body profile. The FEA results are given in
Table-1.

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Table-1
Summary of Deflection and Stress Analysis

SI. Type of Interlocking
Between Pump
Body and Flange Maximum Deflection Maximum Stress

Value
in
Micron Location Value in
N/mm2 Location
1 2 Hollow Dowels
(Conventional) 45 Inlet Porting 355 Inlet Side Dowel
Holes
2 4 Hollow Dowels
(Conventional) 30 Outlet Porting 516 Outlet Side Dowel
Holes
3 4 Bean-Shaped Dowels
(according to the
invention) 28 Inlet and Outlet
Porting 345 Inlet Bolt Holes
The FEA results indicate that although the bean-shaped dowels with built-in bolt
hole results in near equal magnitude of deflection with respect to the four hollow dowel
configuration, it guarantees a better performance level since the maximum principle
stress magnitude is less which satisfies the requisite criteria from fatigue life
considerations. The above table thus provides an indication of the resilience of bean-
shaped dowels to withstand a higher pressure range, in view of low values of both
deflection and stress for the configuration.
Having identified that a bean-shaped doweling arrangement is the optimum
solution for a gear pump-flange interlocking arrangement, effort was channelized to
arrive at an ideal pump body profile.
The preferred embodiments of the invention is described below with reference to
the drawings.
Figure 5 represents the optimized profile of the pump body according to the
present invention using bean-shaped dowel.
Figure 6 shows a bean-shaped dowel for a pump body according to the present
invention.

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In order to account for the benefits accruing out of an interlocking mechanism
using bean-shaped dowel over conventional hollow dowel, both conventional and a pump
body profile according to the present invention having body width proportional to similar
flow capacity are taken into consideration. The profile of the pump body according to the
present invention must necessarily be different from that of the conventional body profile
in order to attain optimality from the strength point of view.
The force and maximum stress for a conventional pump body using hollow dowel
construction was estimated and Figure 7 represents the free body diagram for a
conventional pump body profile with indication of oil pressure from the suction side at "A"
to maximum outlet pressure at position Bl (or B2). The maximum pressure is assumed to
be as 250 bar. As can be seen from Figure 7, the resultant force "F" can be resolved into
coplanar force "F" acting at the hollow dowel at the location PI (or P2) along with a
turning couple of magnitude F x L. The couple tends to cause bending of the body halves
about the hollow dowel axis PI (or P2). This phenomenon is detrimental since it tends to
increase the tip circle clearance at the gear outer diameter cum body bore interface at the
high pressure outlet side.
Also, the 3466 kgf force acts on a slender hollow dowel projected area of [{(3.142
x 13)/2} x 11] sq. mm. = 224.6 sq. mm (Refer Figure 2 with D and L as 13 mm and 11
mm respectively) and the net compressive stress on each of the hollow dowel amounts to
3466/224.6 = 15.4 kgf/sq. mm. The maximum bearing pressure for the dowel made of
EN 8 material specification is allowed between 10 to 12 kgf/sq. mm. Hence, this clearly
indicates that the maximum compressive stress is on the higher side.
Figure 8 details the linear representation of force diagram as occurring within a
conventional pump body. The total resultant force amounts to 3466 kgf and occurring at
the position Cl (or C2) oriented at an angle of 38 degrees with respect to the vertical axis
(as shown in Figure 7). The values of resultant force and its angular location are specific
to the profile of the body bore geometry.
The force and maximum stress for the pump body with bean-shaped dowel
construction according to the invention was estimated. While making a comparative

-9-
analysis for the pump body using the bean-shaped dowel according to the invention, the
body profile was correspondingly modified to accommodate the bean-shaped dowel.
The stress induced in the dowels is computed using the following mathematical
relationship:
For hollow dowel:
D = Dowel outer diameter
T = Dowel thickness
F = Resultant force acting on the dowel
Projected dowel area, A = (n*D)/2*T
Net Compressive Stress on Dowel, S = F/A
For Bean-Shaped Dowe :
L = projected length of the dowel
T = Dowel thickness
F = Resultant force acting on the dowel
Projected dowel area, A = L * T
Net Compressive Stress on Dowel, S = F/A
Figure 9 represents the free body diagram for the pump body profile according to
the present invention with indication of oil pressure variation from the suction side at Al
(or A2) to the maximum outlet pressure at position Bl (or B2). The maximum pressure
was assumed to be 250 bar.
Figure 10 details the linear representation of force diagram as occurring within a
pump body according to the present invention. The total resultant force amounts to 4953
kgf and occurring at the position Cl (or C2) oriented at an angle of 38 degrees with
respect to the vertical axis (as shown in Figure 9).
As can be seen from Figure 9, the major curvilinear axis of the bean-shaped dowel
is located directly perpendicular to the line of resultant force "F", while the minor axis at

-10-
the line of symmetricity aligns with the line of force. The effect of positioning the bean
dowel in this manner eventually eliminates any possible chance of occurrence of turning
moment, and thus reduces the possibilities of increased gear tip circle clearance.
The resultant force of 4953 kgf acts on the bean-shaped dowel cross-section of
44.2 x 15 = 663 sq. mm. (see Figure 6 with T as 15 mm and length of curvilinear major
axis as 44.2 mm) and the net compressive stress on each of the bean-shaped dowel
amounts to 4953/663 = 7.47 kgf/sq. mm. The maximum bearing pressure for the dowel
made of EN 8 material specification is allowed between 10 to 12 kgf/sq. mm. Hence, this
clearly indicates that the maximum compressive stress is within the permissible limit and
the design of the bean-shaped dowel is satisfactory from the strength point of view.
It is also noted that the compressive stress acting on the bean-shaped dowel is 2.06
times less compared to the hollow dowel for gear pumps having similar flow and pressure
ratings.
The overall pump assembly and the exploded view of the gear pump assembly
having an interlocking mechanism using bean-shaped dowels according to the invention is
depicted in Figures 11 and 12 respectively. The structural components parts of the pump
are illustrated with the help of reference numerals.
The pump body (1) is made from high grade specially alloyed cast iron or
aluminium materials depending upon the application and pressure ratings, whereas the
flanges (2) are made from cast iron castings. The pump body and flange profiles are such
that adequate reinforcing is maintained at appropriate zones to enhance its load bearing
capacity and its rigidity, which in turn directly increases the pump pressure holding
capacity. Both the pump body and flange are suitably adapted to accommodate bean-
shaped interlocking dowels.
The pump gears (12, 13) are made from special steels with strict adherence to the
heat treatment requirements arising from its operational requirements. While designing
the gears, special attention has been paid to the load bearing property, particularly while
catering to high pressure and high flow requirements. The optimum sizing of the journal
diameter is one of the important parameters in this regard.

-11-
The specially designed oil seals (7, 10) known as body seal and lobe seal have
been developed with a view to successfully cater to efficient sealing of pressurized oil
pockets inside the pump. Along with lobe seal material, its profile which has to match
with the corresponding pressure plate profile, is of crucial importance for the successful
operation of the pump. Back-up rings (9) are used to prevent squeezing of lobe seal and
to retain the lobe seal in its original position.
Pressure plates (11) are a very important component of a hydraulic gear pump
having an interlocking mechanism according to the invention. It can be regarded as a sole
functionary responsible for the efficient functioning of the pump. The intricately machined
profile of the plate and its material composition are of immense importance, since it has
to optimally match with various other mating elements and operating conditions.
Optimally designed and appropriately dimensioned PTFE lined bush bearings (8)
are used as a load bearing journal.
The bean-shaped dowels (3) {4 nos.} enables clamping both pump body and
flange together resulting in a definitive near single unit for the pump assembly. This
singular item is responsible for imparting the various advantages.
The present invention offers the following distinct advantages:
(a) Higher volumetric efficiency of the gear pump
(b) Reduced heat loss due to lower internal oil leakage
(c) Longer life of the pump since low internal heat generation results in higher
performance and longevity of all the sealing materials
(d) Suitable for design of hydraulic machine applicable for high pressure and
unfavorable operating conditions.
With reference to the pump assembly shown in Figure 11, during operation of the
gear pump, a high pressure profile within the pump body (1) is generated with pressure
varying from the suction to the outlet as shown in Figure 9. The resultant of the hydraulic

-12-
load "F" acts on the gear pump body. This force which has a magnitude proportional to
the outlet oil pressure tends to cause spatial displacement for the pump body (1) with
respect to the pump flange (2), thereby increasing the gear tip circle cutting into the
pump body bore, and increasing the gear tip-body bore clearance. This phenomenon has
a negative bearing on the volumetric efficiency of the pump as already discussed and
hence, needs to be minimized.
The interlocking device acts in opposition with this disturbing hydraulic force "F",
and assists in maintaining the dimensional rigidity between the pump body and the
flange, and thus ensures reduced gear tip circle cutting into the pump body, resulting in
maximization of volumetric efficiency.
Various alternatives of the possible modes of combining the pump body and flange
using the conventional 2 hollow dowels and the proposed 4 bean-shaped dowels have
been considered. Finite element analysis was carried out for both maximum deflection
and principle stress values while employing gear pumps with the alternative interlocking
arrangements mentioned above with a maximum pressure of 250 bar. The detailed
analysis reveals the optimum suitability and superiority of the bean-shaped dowel
mechanism over conventional techniques.
The salient features of the interlocking mechanism for gear pump using bean-
shaped dowels according to the present invention can be appreciated by comparing the
finite element method (FEM) analysis outputs for both conventional and the interlocking
mechanism as per the invention.
Finite element analysis (FEA) was carried out in detail for both the conventional
interlocking mechanism and for the interlocking mechanism according to the present
invention. The summary of the deflection and stress analysis is given in Table-2. This FEA
is based on an optimized body profile that can withstand pressure upto 275 bar and also
intermittent pressure upto 330 bar.

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Table-2
Summary of Deflection and Stress Analysis

SI. Type of Interlocking
Between Pump
Body and Flange Maximum Deflection Maximum Stress

Value
in
Micron Location Value in
N/mnv Location
1 2 Hollow Dowels
(Conventional) 72 Outlet Porting 831 Inlet Side Bolt
Holes
2 4 Bean-Shaped Dowels 45 Rear Portion of
Pump Body 260 Inlet Side Bolt
Holes
The comparison as detailed above clearly indicates the superiority of the bean-
shaped dowel over the conventional hollow dowel concept. The use of bean-shaped
dowel as pump body-flange interlocking mechanism according to the present invention
helps to achieve higher volumetric efficiency of the gear pump during operation at high
pressure due to the fact that the relative deflection at the pump body-flange interface is
minimized owing to higher rigidity in dowel mounting, as evidenced in the computation of
bearing stress at the dowel.
Further, the use of four bean-shaped dowels (instead of two hollow dowels in the
conventional technique) establishes an all around rigidity factor at the separating joint
face.
The optimum location of the bean-shaped dowel having the curvilinear major axis
aligned at right angle with the resultant force direction and the minor axis at the axis of
symmetricity aligning with the resultant force direction ensures total avoidance of the
turning couple while using the bean-shaped dowel. This mechanism assists in maintaining
the oil tight chamber at the gear tip-body bore, thus ensuring higher pump volumetric
efficiency.

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The substantial variation in the volumetric efficiency during the operation of the
gear pump at a wide range of varying pressure compared to the initial running-in
pressure is considerably reduced since the pump gear deflection is minimized owing to
the more rigid interface joint through four bean-shaped dowels.
As stated hereinabove, the location of occurrence for the maximum stress and
deflection position can naturally be different in the bean-shaped dowel arrangement
according to the present invention as compared to the oval-shaped dowel arrangement
according to the main invention. The bean-shaped dwoel according to the present
invention is an improvement upon the oval-shaped dowel arrangement because of the
following:
(a) Optimality on deflection and stress for hydraulic machine body while being
used under extreme operating conditions, as would be clear from the figures in the Table
below:

Operating
Pressure (bar) Maximum Deflection in Micron Stress in N/sq. mm.
Bean-shaped Oval-shaped Bean-shaped Oval-shaped
207 28 25 345 246
275 45 45 260 522
(b) The maximum bearing pressure on the bean-shaped dowel is less compared
to oval-shaped dowel, viz., for oval-shaped dowel it is 9.1 Kgf/sq. mm. whereas for bean-
shaped dowel it is 7.47 Kgf/sq. mm.
With the advent of CNC machining technology, the machining of the bean-shaped
dowels and the corresponding dowel slots on the gear pump body and flange becomes
highly reproducible and complimentary to their respective slots and dowels because of
identical program being deployed for the machining.
The foregoing is to be considered as illustrative only of the principles of the
present invention. Further, since numerous modifications and changes will readily occur
to those skilled in the art, it is not desired to limit the invention to the exact construction

-15-
and applications shown and described, and accordingly, all suitable modifications,
developments and equivalents may be resorted to, falling within the scope of the
invention in the appended claims and their equivalents. Although the invention has been
described above with reference to a hydraulic gear pump, the scope of the invention is
not limited to hydraulic gear pump alone and it can be employed by all hydraulic
machines or devices including hydraulic pumps, motors, valves, etc. where containment
of pressurized fluid is required with due consideration for minimal deflection of the load
bearing elements.
*
-16-
WE CLAIM :
1. An interlocking device for rigidly holding together the body (1) and flange (2) of a
hydraulic machine comprising a body (1), flange (2), gears (12, 13), sealing means (7,
10) acting as a body seal and lobe seal adapted to effectively seal pressurized oil pockets
within said hydraulic machine with a back-up ring (9) that prevents squeezing of said lobe
seal and to retain it in its original position, appropriately dimensioned bush bearings (8)
adapted to act as load bearing journals, wherein said interlocking device comprises a
plurality of bean-shaped dowels located at both inlet and outlet sides that hold the body
and flange together with minimum relative displacement to ensure high volumetric
efficiency of said hydraulic machine even at high operating pressures of 275 bar or
higher.
2. An interlocking device for a hydraulic machine using bean-shaped dowels as
claimed in claim 1, wherein the number of bean-shaped dowels used is four, which
enables clamping of the body and the flange together resulting in a definitive near single
unit for the hydraulic machine assembly.
3. An interlocking device for a hydraulic machine using bean-shaped dowels as
claimed in claim 1, wherein the curvilinear major axis of each of the bean-shaped dowels
is aligned at right angle with the resultant force direction and their minor axis at the axis
of symmetricity is aligned with the resultant force direction.
4. An interlocking device for a hydraulic machine using bean-shaped dowels as
claimed in claim 1, wherein the width of said body is proportional to the fluid flow
capacity.
5. An interlocking device for a hydraulic machine using bean-shaped dowels as
claimed in claim 1, wherein said body (1) is made from high grade specially alloyed cast
iron or aluminium materials depending upon the application and pressure ratings.

-17-
6. An interlocking device for a hydraulic machine using bean-shaped dowels as
claimed in claim 1, wherein said gears (12, 13) are made from special steels.
7. An interlocking device for a hydraulic machine using bean-shaped dowels as
claimed in claim 1, wherein said flange is made from cast iron castings.
8. An interlocking device for a hydraulic machine using bean-shaped dowels as
claimed in claim 1, wherein the profiles of said body and the flange are such that
adequate reinforcing is maintained at appropriate zones to enhance its load bearing
capacity and its rigidity.
9. An interlocking device for a hydraulic machine using bean-shaped dowels as
claimed in claim 1, wherein both said body and said flange are provided with
corresponding recesses for accommodating said bean-shaped interlocking dowels.
10. An interlocking device for a hydraulic machine using bean-shaped dowels as
claimed in claim 1, wherein the profile of the lobe seal material matches with that of the
corresponding pressure plate.
11. An interlocking device for a hydraulic machine using bean-shaped dowels as
claimed in claim 1, wherein said bush bearings (8), which are used as a load bearing
journal, are PTFE lined.
12. An interlocking device for a hydraulic machine using bean-shaped dowels as
claimed in claim 1, wherein said oil seals (7, 10) are body seal and lobe seal, and a back-
up ring (9) prevents squeezing of said lobe seal and retain it in its original position.

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13. An interlocking device for rigidly holding together the body (1) and flange (2) of
a hydraulic machine, wherein said hydraulic machine is a gear pump.
14. An interlocking device as claimed in any preceding claim, wherein the machine
or pump body is designed to withstand a pressure upto 330 bar.
15. A hydraulic machine incorporating an interlocking device as claimed in any one
or more of the preceding claims.
16. An interlocking device for rigidly holding together the body and flange of a
hydraulic machine using bean-shaped dowel, substantially as herein described,
particularly with reference to and as illustrated in the Figures 4-6 and 9-12 of the
accompanying drawings.
Dated this 28l day of September, 2005.

(S. D. AHUJA)
of D.P. AHUJA&CO.
APPLICANTS' AGENT

An interlocking device for rigidly holding together the body (1) and flange (2) of a
hydraulic machine comprises a body (1), flange (2), gears (12, 13), sealing means (7, 10)
acting as a body seal and lobe seal adapted to effectively seal pressurized oil pockets
within the hydraulic machine with a back-up ring (9) that prevents squeezing of said lobe
seal and to retain it in its original position, appropriately dimensioned bush bearings (8)
adapted to act as load bearing journals, wherein said interlocking device comprises 3
plurality of bean-shaped dowels located at both inlet and outlet sides that hold the body
and flange together with minimum relative displacement to ensure high volumetric
efficiency of said hydraulic machine even at high operating pressures in excess of 275 bar
or higher.