U.S. patent application number 15/763463 was filed with the patent office on 2018-10-04 for double-piston compressor of a compressed air supply device.
The applicant listed for this patent is WABCO GmbH. Invention is credited to Frank Meissner, Marco Seeger.
Application Number | 20180283366 15/763463 |
Document ID | / |
Family ID | 57758554 |
Filed Date | 2018-10-04 |
United States Patent
Application |
20180283366 |
Kind Code |
A1 |
Meissner; Frank ; et
al. |
October 4, 2018 |
DOUBLE-PISTON COMPRESSOR OF A COMPRESSED AIR SUPPLY DEVICE
Abstract
A double-piston compressor of a compressed air supply device.
The double-piston compressor includes a low pressure stage and a
high pressure stage, each of the low pressure stage and the high
pressure stage having a cylinder with a piston guided in an axially
movable manner therein. A piston of the cylinder of the low
pressure stage and a piston of the cylinder of the high pressure
stage are drivingly connected to the drive shaft via a sliding
block guide. Sliding block tracks of the sliding block guide are
constructed and arranged such that, during operation of the
double-piston compressor, a movement of the pistons follows a
stroke curve that deviates from a regular sinusoidal stroke curve,
which has an amplitude corresponding to an eccentricity of the
drive element.
Inventors: |
Meissner; Frank; (Hannover,
DE) ; Seeger; Marco; (Langenhagen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WABCO GmbH |
Hannover |
|
DE |
|
|
Family ID: |
57758554 |
Appl. No.: |
15/763463 |
Filed: |
November 14, 2016 |
PCT Filed: |
November 14, 2016 |
PCT NO: |
PCT/EP2016/001895 |
371 Date: |
March 27, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04B 27/02 20130101;
F04B 25/02 20130101; F04B 25/005 20130101; F04D 25/062 20130101;
F04B 53/147 20130101; F04B 27/0428 20130101 |
International
Class: |
F04B 25/00 20060101
F04B025/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 8, 2015 |
DE |
10 2015 015 946.1 |
Claims
1. A double-piston compressor of a compressed air supply device,
comprising: a low pressure stage and a high pressure stage, each of
the low pressure stage and the high pressure stage having a
cylinder with a piston guided in an axially movable manner therein,
wherein the cylinder of the low pressure stage and the cylinder of
the high pressure stage are arranged radially opposite with respect
to an axis of rotation of a drive shaft, wherein the piston of the
cylinder of the low pressure stage and the piston of the cylinder
of the high pressure stage are rigidly connected to one another by
a piston rod, wherein the piston of the cylinder of the low
pressure stage and the piston of the cylinder of the high pressure
stage are drivingly connected to the drive shaft via a sliding
block guide, wherein the sliding block guide has a recess which is
arranged in the piston rod, is provided with two parallel sliding
block tracks, and is aligned perpendicularly to the axis of
rotation of the drive shaft, wherein the sliding block guide has a
drive element in engagement with the recess, arranged axially
parallel with respect to the axis of rotation of the drive shaft,
and secured on the drive shaft with an eccentricity, wherein, the
sliding block tracks of the sliding block guide are constructed and
arranged such that, during operation of the double-piston
compressor, a movement of the pistons follows a stroke curve that
deviates from a regular sinusoidal stroke curve, which has an
amplitude corresponding to the eccentricity of the drive
element.
2. The double-piston compressor as claimed in claim 1, wherein the
sliding block tracks of the sliding block guide are arranged at an
inclination in a direction of rotation of the drive shaft relative
to a perpendicular on a longitudinal axis of the piston rod.
3. The double-piston compressor as claimed in claim 1, wherein the
sliding block tracks of the sliding block guide are arranged at an
inclination in opposition to the a direction of rotation of the
drive shaft relative to a perpendicular on the longitudinal axis of
the piston rod.
4. The double-piston compressor as claimed in claim 2, wherein an
angle of inclination of the sliding block tracks relative to a
perpendicular on a longitudinal axis of the piston rod is less than
or equal to 45.degree..
5. The double-piston compressor as claimed in claim 1, wherein at
least one of the sliding block tracks of the sliding block guide
has a circular-arc-shaped indentation in a central portion.
6. The double-piston compressor as claimed in claim 5, wherein a
radius and a depth of the circular-arc-shaped indentation of the at
least one sliding block track are dimensioned such that a stroke
height of the piston rod when the drive element passes through the
indentation is kept constant.
7. The double-piston compressor as claimed in claim 1, wherein the
sliding block tracks of the sliding block guide are curved in a
shape of a circular arc in a direction of one of the piston of the
cylinder of the low pressure stage and the piston of the cylinder
of the high pressure stages.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a U.S. National Stage Application under
35 U.S.C. .sctn. 371 of International Application No.
PCT/EP2016/001895 filed on Nov. 14, 2016, and claims benefit to
German Patent Application No. DE 10 2015 015 946.1 filed on Dec. 8,
2015. The International Application was published in German on Jun.
15, 2017 as WO 2017/097393 A1 under PCT Article 21(2).
FIELD
[0002] The invention relates to a double-piston compressor of a
compressed air supply device.
BACKGROUND
[0003] Double-piston compressors having two pistons which are
rigidly connected to one another via a piston rod and are guided in
an axially movable manner in cylinders arranged radially opposite
with respect to the axis of rotation of a drive shaft have long
been known in embodiments which differ in terms of their drive
technology.
[0004] In one type of double-piston compressor which is known for
example from DE 103 21 771 B4, the piston rod is drivingly
connected to the drive shaft via a con rod. The con rod is
connected in an articulated manner to the drive shaft and the
piston rod, on the one hand via a crank pin, which engages in a
first end-side bore and is secured eccentrically on the drive
shaft, and on the other hand via a drive pin which engages in a
second end-side bore and is secured off-center on the piston
rod.
[0005] In contrast, in a substantially simpler and more
space-saving design of a double-piston compressor, the piston rod
is drivingly connected to the drive shaft merely via a sliding
block guide. The sliding block guide comprises a recess, which is
constructed in the piston rod, is provided with two parallel
sliding block tracks and is aligned perpendicularly to the axis of
rotation of the drive shaft, and a drive element, which is in
engagement with the recess and is eccentrically secured on the
drive shaft such that it is axially parallel with respect to the
axis of rotation of the drive shaft. Depending on the resultant
force direction of the pressure forces acting on the two pistons,
the drive element abuts against one of the two sliding block tracks
and, bridging the clearance which is inevitably present in the
sliding block guide, moves to abut against the other sliding block
track when the resultant force direction is reversed. The recess in
the piston rod can be constructed in a U shape, as is known for
example from DE 918 042 B. In this case, the side walls of the
recess form the parallel sliding block tracks and the two parts of
the piston rod are connected to one another via the base wall of
the recess.
[0006] As an alternative to this, the recess can be constructed as
a slot-shaped through opening, as is known for example from FIG. 8
of DE 44 33 068 C2 and DE 10 2012 223 114 A1. In this case, the
side walls of the recess form the parallel sliding block tracks. To
connect the two parts of the piston rod, end-side webs are required
in this embodiment of the sliding block guide, which are usually
designed in the shape of a circular arc but, with an appropriate
spacing, can also be designed linearly. The drive element can be a
crank pin, which is eccentrically secured on the drive shaft such
that it is axially parallel with respect to the axis of rotation of
the drive shaft and which, as is known for example from FIG. 8 of
DE 44 33 068 C2, is guided in a directly slideable manner on the
parallel sliding block tracks of the sliding block guide.
[0007] To reduce the driving resistance and the wear on the sliding
block tracks, the driving element can, as is known for example from
DE 918 042 B, DE 1 932 737 U and DE 197 15 291 C2, also be
constructed as the outer ring of a rolling bearing, which is
arranged on a crank pin eccentrically secured on the drive shaft
and whereof the outer ring is guided in a rollable manner on the
sliding block tracks of the sliding block guide.
[0008] In contrast, EP 0 389 414 B1 describes a relatively large
reciprocating compressor provided for stationary use, having four
cylinders which are radially opposite in pairs and pistons which
are connected to one another, in which an externally substantially
rectangular sliding body in each case is mounted on a crank pin,
which is eccentrically secured on the drive shaft, such that it is
rotatable with relatively low resistance via a rolling bearing, and
is guided in a rollingly displaceable manner between sliding block
tracks of the sliding block guide via a linear guide having a
rolling body.
[0009] Common to the known types of double-piston compressors
having sliding block guides is that the two parallel sliding block
tracks are of a planar design and are aligned perpendicularly to
the longitudinal axis of the piston rod. This construction and
arrangement of the sliding block tracks inevitably results in a
regular sinusoidal stroke curve of the pistons with an amplitude
corresponding to the eccentricity of the crank pin.
SUMMARY
[0010] In an embodiment, the present invention provides a
double-piston compressor of a compressed air supply device. The
double-piston compressor includes a low pressure stage and a high
pressure stage, each of the low pressure stage and the high
pressure stage having a cylinder with a piston guided in an axially
movable manner therein. The cylinder of the low pressure stage and
the cylinder of the high pressure stage are arranged radially
opposite with respect to an axis of rotation of a drive shaft. The
piston of the cylinder of the low pressure stage and the piston of
the cylinder of the high pressure stage are rigidly connected to
one another by a piston rod. The piston of the cylinder of the low
pressure stage and the piston of the cylinder of the high pressure
stage are drivingly connected to the drive shaft via a sliding
block guide. The sliding block guide has a recess which is arranged
in the piston rod, is provided with two parallel sliding block
tracks, and is aligned perpendicularly to the axis of rotation of
the drive shaft. The sliding block guide has a drive element in
engagement with the recess, arranged axially parallel with respect
to the axis of rotation of the drive shaft, and secured on the
drive shaft with an eccentricity. The sliding block tracks of the
sliding block guide are constructed and arranged such that, during
operation of the double-piston compressor, a movement of the
pistons follows a stroke curve that deviates from a regular
sinusoidal stroke curve, which has an amplitude corresponding to
the eccentricity of the drive element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present invention will be described in even greater
detail below based on the exemplary figures. The invention is not
limited to the exemplary embodiments. All features described and/or
illustrated herein can be used alone or combined in different
combinations in embodiments of the invention. The features and
advantages of various embodiments of the present invention will
become apparent by reading the following detailed description with
reference to the attached drawings which illustrate the
following:
[0012] FIG. 1 illustrates a double-piston compressor according to
an embodiment of the invention in a schematic cross-sectional
view;
[0013] FIG. 1a is a graph of the stroke curve of the pistons of the
double-piston compressor according to FIG. 1 in a graph;
[0014] FIG. 2 illustrates a double-piston compressor according to a
second embodiment of the invention in a schematic cross-sectional
view;
[0015] FIG. 2a is a graph of the stroke curve of the pistons of the
double-piston compressor according to FIG. 2;
[0016] FIG. 3 illustrates a double-piston compressor according to a
third embodiment of the invention in a schematic cross-sectional
view;
[0017] FIG. 3a is a graph of the stroke curve of the pistons of the
double-piston compressor according to FIG. 3;
[0018] FIG. 4 illustrates a double-piston compressor according to a
fourth embodiment of the invention in a schematic cross-sectional
view;
[0019] FIG. 4a is a graph of the stroke curve of the pistons of the
double-piston compressor according to FIG. 4;
[0020] FIG. 5 illustrates a known embodiment of a double-piston
compressor in a schematic cross-sectional view;
[0021] FIG. 5a is a graph of the stroke curve of the pistons of the
double-piston compressor according to FIG. 5;
[0022] FIG. 6a is a detailed cross-sectional view of a first
embodiment of a drive element of a sliding block guide of the
double-piston compressors according to FIGS. 1 to 5;
[0023] FIG. 6b is a detailed cross-sectional view of a second
embodiment of the drive element of a sliding block guide of the
double-piston compressors according to FIGS. 1 to 5;
[0024] FIG. 6c is a detailed cross-sectional view of a third
embodiment of the drive element of a sliding block guide of the
double-piston compressors according to FIGS. 1 to 5; and
[0025] FIG. 6d is a detailed cross-sectional view of a fourth
embodiment of the drive element of a sliding block guide of the
double-piston compressors according to FIGS. 1 to 5.
DETAILED DESCRIPTION
[0026] Embodiments of the present invention provide a double-piston
compressor of a compressed air supply device, having a low pressure
stage and a high pressure stage, which each have a cylinder with a
piston guided in an axially movable manner therein, wherein the two
cylinders are arranged radially opposite with respect to an axis of
rotation of a drive shaft, wherein the two pistons are rigidly
connected to one another by means of a piston rod, wherein the two
pistons are drivingly connected to the drive shaft via a sliding
block guide, wherein the sliding block guide has a recess which is
arranged in the piston rod, is provided with two parallel sliding
block tracks and is aligned perpendicularly to the axis of rotation
of the drive shaft, and in which the sliding block guide has a
drive element which is in engagement with the recess, is arranged
axially parallel with respect to the axis of rotation of the drive
shaft and is secured on the drive shaft with an eccentricity.
[0027] Embodiments of the present invention provide a double-piston
compressor having a sliding block guide of the type mentioned at
the outset, which has two parallel sliding block tracks.
[0028] A regular sinusoidal stroke curve of pistons can be modified
in a desired manner by a suitable alteration to the alignment
and/or the contour of the parallel sliding block tracks of the
sliding block guide.
[0029] Embodiments of the invention therefore provide a
double-piston compressor of a compressed air supply device, which
has a low pressure stage and a high pressure stage. The two
pressure stages each have a cylinder with a piston guided in an
axially movable manner therein, wherein the two cylinders are
arranged radially opposite with respect to an axis of rotation of a
drive shaft. The two pistons are rigidly connected to one another
by means of a piston rod and are drivingly connected to the drive
shaft via a sliding block guide. The sliding block guide has a
recess which is arranged in the piston rod, is provided with two
parallel sliding block tracks and is aligned perpendicularly to the
axis of rotation of the drive shaft. Moreover, the sliding block
guide has a drive element which is in engagement with the recess in
the piston rod, is arranged axially parallel with respect to the
axis of rotation of the drive shaft and is secured on the drive
shaft with an eccentricity.
[0030] According to embodiments of the invention, the sliding block
tracks of the sliding block guide are constructed and arranged such
that, during operation of the double-piston compressor, the
movement of the pistons follows a stroke curve which deviates from
a regular sinusoidal stroke curve, which has an amplitude
corresponding to the eccentricity of the drive element.
[0031] A first modification of the sliding block guide provides
that the sliding block tracks of the sliding block guide are
arranged at an inclination in the direction of rotation of the
drive shaft relative to a perpendicular on a longitudinal axis of
the piston rod. It is thus achieved that the stroke curve of the
pistons is phase-shifted towards late and that the amplitude of the
stroke curve is increased beyond the eccentricity of the drive
element. In contrast, the stroke width, i.e. the angle of rotation
range of the intake and pressure strokes of the pistons, remains
unaltered.
[0032] An alternative second modification of the sliding block
guide provides that the sliding block tracks of the sliding block
guide are arranged at an inclination in opposition to the direction
of rotation of the drive shaft relative to the perpendicular on the
longitudinal axis of the piston rod. It is thus achieved that the
stroke curve of the pistons is phase-shifted towards early and that
the amplitude of the stroke curve is increased beyond the
eccentricity of the drive element. The stroke width of the intake
and pressure strokes of the pistons also remains unaltered in this
case.
[0033] For functional reasons, the angle of inclination of the
sliding block tracks relative to the perpendicular on the
longitudinal axis of the piston rod, should be a maximum of
45.degree..
[0034] A third modification of the sliding block guide, which can
be applied both to a perpendicular and an inclined alignment of the
sliding block tracks, provides that at least one of the sliding
block tracks of the sliding block guide has a circular-arc-shaped
indentation in a central portion. As a result of the indentation,
the peak of the stroke curve is capped, or the maximum amplitude is
reduced, and the pressure stroke of the piston facing the
indentation and the intake stroke of the piston facing away from
the indentation are therefore reduced accordingly.
[0035] The radius and the depth of the circular-arc-shaped
indentation of the at least one sliding block track are dimensioned
such that the stroke height of the piston rod when the drive
element passes through the indentation is kept constant. With such
a geometry of the indentation, it is ensured that the piston rod is
not displaced when the drive element passes through the
indentation, so that the progression of the stroke curve of the
pistons in the relevant portion is linear and not wavy.
[0036] A fourth modification of the sliding block guide, which can
be applied both to a perpendicular alignment of the sliding block
tracks and in combination with the above-mentioned modifications of
the sliding block guide, provides that the sliding block tracks of
the sliding block guide are curved in the shape of a circular arc
in the direction of one of the two pistons. As a result of this
modification of the sliding block guide, the stroke width, i.e. the
angle of rotation range of the piston rod, during the stroke
movement is increased in the direction of the cylinder facing the
curvature of the sliding block tracks and the stroke width of the
piston rod during the stroke movement is reduced by the same amount
in the direction of the cylinder facing away from the curvature of
the sliding block tracks.
[0037] An embodiment, known per se, of a double-piston compressor
1.5 of a compressed air supply device is shown in FIG. 5 in a
schematic cross-sectional view. The double-piston compressor 1.5
has a low pressure stage 2 and a high pressure stage 3 which each
comprise a cylinder 4, 6 with a piston 5, 7 guided in an axially
movable manner therein. The two cylinders 4, 6 are arranged
radially opposite in a housing with respect to an axis of rotation
11 of a drive shaft 10. The two pistons 5, 7 are rigidly connected
to one another via a piston rod 8 and are drivingly connected to
the drive shaft 10 via a sliding block guide 14.5. The sliding
block guide 14. 5 comprises a recess 15, which is constructed in
the piston rod 8, is provided with two parallel sliding block
tracks 16, 17 and is aligned perpendicularly to the axis of
rotation 11 of the drive shaft 10, and a drive element 12 which is
in engagement with the recess 15 and is eccentrically secured on
the drive shaft 10 such that it is axially parallel with respect to
the axis of rotation 11 of the drive shaft 10. The two sliding
block guides 16, 17 here are aligned perpendicularly to a
longitudinal axis 9 of the piston rod 8. By way of example, the
drive element 12 is formed by a crank pin 13 which is secured on
the drive shaft 10 such that it is radially spaced from the axis of
rotation 11 by the amount of an eccentricity e and is guided in a
directly slideable manner on the parallel sliding block tracks 16,
17 of the sliding block guide 14.5.
[0038] In FIG. 5a, a stroke curve Z.sub.H(.PHI.)_1.5 illustrates
the movement of the pistons 5, 7 or the piston rod 8 of the known
double-piston compressor 1.5 during a revolution of the drive shaft
10. The angle of rotation of the drive shaft 10 here is denoted by
.PHI., the direction of rotation of the drive shaft 10 is assumed
to be clockwise according to the direction of rotation arrow 18
shown in FIG. 5, the 0.degree. position of the drive shaft 10 or
the crank pin 13 corresponds to the position shown in FIG. 5, the
stroke height of the pistons 5, 7 is denoted by Z.sub.H and the
stroke direction of the pistons 5, 7 is assumed to be positive
according to the stroke direction arrow 19, shown in FIG. 5, in the
direction of the cylinder 6 of the high pressure stage 3. The
stroke curve Z.sub.H(.PHI.) of the pistons 5, 7, which is shown in
the graph of FIG. 5a, has a regular sinusoidal progression with the
amplitude which corresponds to the eccentricity e of the crank pin
13. The progression of this stroke curve can then be expressed as
Z.sub.H(.PHI.)=e*sin(.PHI.).
[0039] FIG. 1 illustrates a double-piston compressor 1.1 of a
compressed air supply device according to a first embodiment in a
schematic cross-sectional view, which differs from the embodiment
of the double-piston compressor 1.5 according to FIG. 5 due to an
altered arrangement of the sliding block guide 14.1. In this case,
the recess 15 with the two parallel sliding block tracks 16, 17 is
arranged pivoted relative to a perpendicular 20 located on the
longitudinal axis 9 of the piston rod 8 through an angle of
inclination of .alpha.=25.degree. here in the direction of rotation
18 of the drive shaft 10.
[0040] The stroke curve Z.sub.H(.PHI.)_1.1, shown in the graph of
FIG. 1a, of the pistons 5, 7 or the piston rod 8 of the
double-piston compressor 1.1 likewise has a regular sinusoidal
progression. However, owing to the inclined arrangement of the
sliding block tracks 16, 17 in the direction of rotation 18 of the
drive shaft 10, the stroke curve Z.sub.H(.PHI.)_1.1 has a phase
shift towards late and a stroke height exceeding the eccentricity e
of the crank pin 13. The progression of the stroke curve
Z.sub.H(.PHI.)_1.1 of the pistons 5, 7 of the double-piston
compressor 1.1 can be expressed by the formula
Z.sub.H(.PHI.)=e*(sin(.PHI.)-cos(.PHI.)*tan(.varies.)). For
comparison, in FIG. 1, the stroke curve Z.sub.H(.PHI.)_1.5 of the
pistons 5, 7 of the double-piston compressor 1.5 according to FIG.
5 is also shown as a dot-and-dash curve.
[0041] FIG. 2 illustrates a double-piston compressor 1.2 of a
compressed air supply device according to a second embodiment of
the invention in a schematic cross-sectional view, which differs
from the embodiment of the double-piston compressor 1.5 according
to FIG. 5 due to a differently altered arrangement of the sliding
block guide 14.2. The recess 15 with the two parallel sliding block
tracks 16, 17 is now arranged pivoted relative to the perpendicular
20 located on the longitudinal axis 9 of the piston rod 8 through
an angle of inclination of .alpha.=-25.degree. here in opposition
to the direction of rotation 18 of the drive shaft 10.
[0042] The stroke curve Z.sub.H(.PHI.)_1.2, shown in the graph of
FIG. 2a, of the pistons 5, 7 or the piston rod 8 of the
double-piston compressor 1.2 in turn has a regular sinusoidal
progression which, owing to the inclined arrangement of the sliding
block tracks 16, 17 in opposition to the direction of rotation 18
of the drive shaft 10, now has a phase shift towards early and
likewise a stroke height exceeding the eccentricity e of the crank
pin 13. Taking the minus sign of the angle of inclination a into
account, the progression of the stroke curve Z.sub.H(.PHI.)_1.2 of
the pistons 5, 7 of the double-piston compressor 1.2 can likewise
be expressed by the formula
Z.sub.H(.PHI.)=e*(sin(.PHI.)-cos(.PHI.)*tan(.varies.)), For
comparison, in FIG. 2, the stroke curve Z.sub.H(.PHI.)_1.5 of the
pistons 5, 7 of the double-piston compressor 1.5 according to FIG.
5 is also shown as a dot-and-dash curve.
[0043] FIG. 3 illustrates a double-piston compressor 1.3 of a
compressed air supply device according to a third embodiment of the
invention in a schematic cross-sectional view, which differs from
the embodiment of the double-piston compressor 1.5 according to
FIG. 5 due to a geometrically altered construction of the sliding
block guide 14.3. By way of example, the sliding block track 16' of
the sliding block guide 14.3 which faces the piston 5 of the lower
pressure stage 2 now has, in the region of the recess 15', a
circular-arc-shaped indentation 21 in a central portion. The radius
and the depth of the circular-arc-shaped indentation 21 are
dimensioned such that the stroke height Z.sub.H of the piston rod 8
when the crank pin 13 passes through the indentation 21 is held
constant.
[0044] In the first half-section of 0.degree. to 180.degree., which
forms the intake stroke of the piston 5 of the low pressure stage 2
and the pressure stroke of the piston 7 of the high pressure stage
3, the stroke curve Z.sub.H(.PHI.)_1.3, shown in the graph of FIG.
3a, of the pistons 5, 7 or the piston rod 8 is identical to the
stroke curve Z.sub.H(.PHI.)_1.5 of the pistons 5, 7 of the
double-piston compressor 1.5 according to FIG. 5. In contrast, in
the second half-section of the stroke curve Z.sub.H(.PHI.)_1.3 of
>180.degree. to <360.degree. , which forms the pressure
stroke of the piston 5 of the low pressure stage 2 and the intake
stroke of the piston 7 of the high pressure stage 3, the peak of
the stroke curve Z.sub.H(.PHI.)_1.3 is capped, so that the pressure
stroke of the piston 5 of the low pressure stage 2 and the intake
stroke of the piston 7 of the high pressure stage 3 are reduced in
relation to the stroke height produced by the eccentricity 3 of the
crank pin in the double-piston compressor 1.5 according to FIG. 5.
For comparison, in FIG. 3, the stroke curve Z.sub.H(.PHI.)_1.5 of
the pistons 5, 7 of the double-piston compressor 1.5 according to
FIG. 5 is likewise shown as a dot-and-dash curve.
[0045] FIG. 4 illustrates a double-piston compressor 1.4 of a
compressed air supply device according to a fourth embodiment of
the invention in a schematic cross-sectional view, which differs
from the embodiment of the double-piston compressor 1.5 according
to FIG. 5 due to a different geometrically altered construction of
the sliding block guide 14.4. By way of example, in the region of
the recess 15'', the two sliding block tracks 16'', 17'' of the
sliding block guide 14.4 are now designed to be curved in the shape
of a circular arc in the direction of the piston 7 of the high
pressure stage 3.
[0046] As can be seen from the stroke curve Z.sub.H(.PHI.)_1.4,
shown in the graph of FIG. 4a, of the pistons 5, 7 or the piston
rod 8 of the double-piston compressor 1.4, this modification of the
sliding block guide 14.4 results in the stroke width, i.e. the
angle of rotation range of the piston rod 8, during the stroke
movement increasing in the direction of the cylinder 6 of the high
pressure stage 3, which faces the curvature of the sliding block
tracks 16'', 17'', and the stroke width of the piston rod 8 during
the stroke movement reducing by the same amount in the direction of
the cylinder 5 of the low pressure stage 2, which faces away from
the curvature of the sliding block tracks 16'', 17''. In contrast,
the phase position and the stroke height of the stroke curve
Z.sub.H(.PHI.)_1.4 of the pistons 5, 7 of the double-piston
compressor 1.4 remain unaltered. For comparison, in FIG. 4, the
stroke curve Z.sub.H(.PHI.)_1.5 of the pistons 5, 7 of the
double-piston compressor 1.5 according to FIG. 5 is in turn shown
as a dot-and-dash curve.
[0047] With reference to the example of the known sliding block
guide 14. 5 of the double-piston compressor 1.5 according to FIG.
5, FIGS. 6a to 6d, described below, show a detailed cross-sectional
view of possible embodiments of the drive element 12.
[0048] In the first embodiment shown in FIG. 6a, the drive element
12 is constructed as a crank pin 13 which is secured on the drive
shaft 10 such that it is radially spaced form the axis of rotation
11 by the eccentricity e and is guided in a directly slideable
manner on the parallel sliding block tracks 16, 17 of the sliding
block guide 14.5. This embodiment of the drive element 12 has been
used by way of example in the drawings of the embodiments of the
double-piston compressor 1.1-1.5 in FIGS. 1 to 5. The crank pin 13
is clearly arranged with play in the recess 15 of the piston rod
8.
[0049] According to the second embodiment shown in FIG. 6b, the
drive element 12' is formed by the outer ring 24 of a rolling
bearing 22. The rolling bearing 22 is arranged with its inner ring
23 on a crank pin 13' which is secured on the drive shaft 10 such
that it is radially spaced from the axis of rotation 11 by
eccentricity e. The outer ring 24 of the rolling bearing 22 is
rollably guided on the parallel sliding block tracks 16, 17 of the
sliding block guide 14.5. With this embodiment of the drive element
12', the resistance and wear of the sliding block guide 14.5 is
clearly lower than with the embodiment of the drive element 12
according to FIG. 6a.
[0050] In a third embodiment shown in FIG. 6c, the drive element
12'' is formed by a slide bearing ring 25 which is slide-mounted on
the outer ring 24' of a rolling bearing 22'. The rolling bearing
22' is arranged with its inner ring 23' on a crank pin 13', which
is secured on the drive shaft 10 such that it is radially spaced
from the axis of rotation 11 by the eccentricity e. The slide
bearing ring 25 is rollably guided on the parallel sliding block
tracks 16, 17 of the sliding block guide 14.5. With this embodiment
of the drive element 12'', the resistance and wear of the sliding
block guide 14.5 is again lower than with the embodiment of the
drive element 12' according to FIG. 6b.
[0051] In a fourth embodiment shown in FIG. 6d, the drive element
12* is formed by an externally substantially rectangular slide body
27, which is rotatably mounted on a crank pin 13' via a rolling
bearing 26. The crank pin 13' is secured on the drive shaft 10 such
that it is radially spaced from the axis of rotation 11 by the
eccentricity e. The slide body 27 is slideably guided on the
parallel sliding block tracks 16, 17 of the sliding block guide
14.5. Owing to the low surface pressure between the slide body 27
and the sliding block tracks 16, 17, the resistance and wear of the
sliding block guide 14.5 in this embodiment of the drive element
12* is also relatively low.
[0052] While the invention has been illustrated and described in
detail in the drawings and foregoing description, such illustration
and description are to be considered illustrative or exemplary and
not restrictive. It will be understood that changes and
modifications may be made by those of ordinary skill within the
scope of the following claims. In particular, the present invention
covers further embodiments with any combination of features from
different embodiments described above and below.
[0053] The terms used in the claims should be construed to have the
broadest reasonable interpretation consistent with the foregoing
description. For example, the use of the article "a" or "the" in
introducing an element should not be interpreted as being exclusive
of a plurality of elements. Likewise, the recitation of "or" should
be interpreted as being inclusive, such that the recitation of "A
or B" is not exclusive of "A and B," unless it is clear from the
context or the foregoing description that only one of A and B is
intended. Further, the recitation of "at least one of A, B and C"
should be interpreted as one or more of a group of elements
consisting of A, B and C, and should not be interpreted as
requiring at least one of each of the listed elements A, B and C,
regardless of whether A, B and C are related as categories or
otherwise. Moreover, the recitation of "A, B and/or C" or "at least
one of A, B or C" should be interpreted as including any singular
entity from the listed elements, e.g., A, any subset from the
listed elements, e.g., A and B, or the entire list of elements A, B
and C.
LIST OF REFERENCE NUMERALS
[0054] 1.1 Double-piston compressor, first embodiment [0055] 1.2
Double-piston compressor, second embodiment [0056] 1.3
Double-piston compressor, third embodiment [0057] 1.4 Double-piston
compressor, fourth embodiment [0058] 1.5 Double-piston compressor,
known embodiment [0059] 2 Low pressure stage [0060] 3 High pressure
stage [0061] 4 Cylinder [0062] 5 Piston [0063] 6 Cylinder [0064] 7
Piston [0065] 8 Piston rod [0066] 9 Longitudinal axis of the piston
rod [0067] 10 Drive shaft [0068] 11 Axis of rotation of the drive
shaft [0069] 12 Drive element [0070] 12', 12'' Drive element [0071]
12* Drive element [0072] 13 Crank pin [0073] 13', 13'' Crank pin
[0074] 14.1 Sliding block guide, first embodiment [0075] 14.2
Sliding block guide, second embodiment [0076] 14.3 Sliding block
guide, third embodiment [0077] 14.4 Sliding block guide, fourth
embodiment [0078] 14.5 Sliding block guide, known embodiment [0079]
15 Recess [0080] 15' Recess [0081] 15'' Recess [0082] 16 First
sliding block track [0083] 16' First sliding block track [0084]
16'' First sliding block track [0085] 17 Second sliding block track
[0086] 17'' Second sliding block track [0087] 18
Direction-of-rotation arrow, direction of rotation [0088] 19
Stroke-direction arrow, stroke direction [0089] 20 Perpendicular
[0090] 21 Indentation of the first sliding block track 16' [0091]
22, 22' Rolling bearing [0092] 23, 23' Inner ring [0093] 24, 24'
Outer ring [0094] 25 Slide bearing ring [0095] 26 Rolling bearing
[0096] 27 Slide body [0097] e Eccentricity [0098] Z.sub.H Stroke
height [0099] Z.sub.H(.PHI.)_1.1 Stroke curve [0100]
Z.sub.H(.PHI.)_1.2 Stroke curve [0101] Z.sub.H(.PHI.)_1.3 Stroke
curve [0102] Z.sub.H(.PHI.)_1.4 Stroke curve [0103]
Z.sub.H(.PHI.)_1.5 Stroke curve [0104] .varies. Angle of
inclination [0105] tan(.varies.) Tangent of the angle of
inclination [0106] .PHI. Angle of rotation [0107] sin(.PHI.) Sinus
of the angle of rotation [0108] cos(.PHI.) Cosine of the angle of
rotation
* * * * *