PISTON RETAINING RING

Description

[0001] Piston retaining rings for securing the piston against the piston rod are known from the prior art. Particularly well-known are spring-loaded O-rings or rings with a rectangular cross-section, which, due to their spring tension, spring either outwardly or conversely in a concentric direction.The document DE 20 2012 008999 U1, which is regarded as the closest prior art, discloses a piston retaining ring of a piston unit, having a flattened radial cross-section, wherein the flattened radial cross-section has a cross-sectional longitudinal axis and a cross-sectional transverse axis, wherein the cross-section extends longer along the cross-sectional longitudinal axis than along the cross-sectional transverse axis, wherein the cross-section along the cross-sectional longitudinal axis has opposite flat boundaries which form a first and a second annular surface, wherein the piston retaining ring is designed to be elastically resilient, wherein the piston retaining ring is designed to assume a stress position under the action of a force and a relaxation position without the action of a force, wherein in a relaxation position the cross-sectional longitudinal axis is inclined by an angle α with respect to a ring plane.

[0002] The piston retaining rings known in the prior art have the disadvantage that their insertion position must either be directly radially accessible or that, in the case of axial access, a comparatively large radial installation space must be provided for covered assembly.

[0003] The object of the invention is to provide a piston retaining ring for a piston unit with which a piston and a piston rod can be coupled to form a piston unit, which is easy to assemble, enables a space-saving arrangement and enables a high strength of the coupling of piston and piston rod.

[0004] This object is achieved by the features listed in claim 1. Preferred developments are set forth in the subclaims. According to the invention, the piston retaining ring has an annular gap and a flattened radial cross-section.

[0005] The annular gap radially interrupts the piston retaining ring. It enables a resilient expansion of the piston retaining ring, widening the annular gap. This is referred to below as radial expansion. Depending on the width of the annular gap, the piston retaining ring can also be resiliently compressed, whereby the width of the annular gap is then reduced. This is referred to below as radial compression. Preferably, the piston retaining ring can be compressed until the width of the annular gap is reduced to zero. The design of a piston retaining ring with a radial annular gap is known in the art.

[0006] According to the invention, the piston retaining ring further has a flattened radial cross-section. The flattened radial cross-section has a longitudinal cross-sectional axis and a transverse cross-sectional axis.

[0007] The longitudinal axis of the cross-section and the transverse axis of the cross-section are orthogonal to each other. The two axes can be inscribed in the flattened radial cross-section. According to the invention, the cross-section extends longer along the longitudinal axis of the cross-section than along the transverse axis of the cross-section.

[0008] According to the invention, the cross section has opposing planar boundaries along the longitudinal axis of the cross section, which form a first and a second annular surface. The boundaries of the cross section are essentially parallel and inclined relative to a main longitudinal axis. The annular surfaces are arranged on an inner and outer side of the piston retaining ring. In a geometric sense, the annular surfaces preferably correspond essentially to the surface of a truncated cone.

[0009] According to the invention, the piston retaining ring is designed to be elastically resilient. For this purpose, the piston retaining ring is made of a flexible and resilient material, preferably spring steel. The piston retaining ring is thus capable of responding to a loading force by elastically deforming.

[0010] According to the invention, the piston retaining ring is designed to assume a tension position under the action of a force and a relaxation position without the action of a force.

[0011] In the tensioned position, the piston retaining ring is elastically deformed by the applied force and thus becomes tensioned. When the force is removed, the piston retaining ring returns to its relaxed position.

[0012] According to the invention, in a relaxed position, the cross-sectional longitudinal axis is inclined by an angle alpha relative to a ring plane.

[0013] The ring plane is defined as the plane orthogonal to the main longitudinal axis of the piston retaining ring. Furthermore, the circumferential ring axis is defined as the circular intersection of the respective cross-sectional transverse axis with the cross-sectional longitudinal axis in all cross sections. The ring plane and the circumferential ring axis are parallel to each other.

[0014] The angle alpha is preferably between 20 and 70 degrees, particularly preferably between 45 and 60 degrees. This results in a conical shape for the piston retaining ring.

[0015] According to the invention, the piston retaining ring can be tensioned to a stress level by deformation with a change in the cross-sectional longitudinal axis around the circumferential ring axis, wherein in the stress level the cross-sectional longitudinal axis is inclined by an angle beta and the angle beta is greater than the angle alpha. When the piston retaining ring is tensioned by means of an applied force, the piston retaining ring deforms such that the cross-sectional longitudinal axis is aligned towards the ring plane. Thus, the angle between the cross-sectional longitudinal axis and the ring plane is greater than in the relaxed position. The difference between the angle alpha and the angle beta is preferably more than 20 degrees. Furthermore, the inner diameter preferably increases while the outer diameter decreases. However, it is also possible for the deformation due to rotation around the circumferential ring axis to be superimposed with a radial expansion or radial compression.For example, it is possible for both the inner and outer diameters to decrease in the stressed area, with the outer diameter then decreasing more than the inner diameter. In any case, however, the difference between the inner and outer diameters decreases in the stressed area. If the inner and outer diameters are projected onto the ring plane or onto a plane parallel to the ring plane, a projection surface of the piston retaining ring is created. This projection surface can also be referred to as the axial overlap surface.

[0016] The axial overlap area decreases in the stress position.

[0017] According to the invention, the piston unit comprises a piston and a piston rod. The piston unit itself is not part of the piston retaining ring according to the invention.

[0018] The piston and piston rod can be secured against axial displacement by means of the piston retaining ring. For this purpose, the piston and piston rod each have a circumferential annular groove. Both grooves are designed to form an annular groove space into which the piston retaining ring can be inserted.

[0019] The piston retaining ring is designed so that it can be inserted into the annular space in the tensioned position through a gap between the piston and piston rod. As a particular advantage, the gap can be made so narrow that the piston retaining ring can only be inserted into the gap in the tensioned position and can then be inserted into the annular groove space. After being positioned in the annular groove space, the piston retaining ring returns to the unstressed position. This allows the gap to be made narrower than the unstressed position of the piston retaining ring. The larger projection area in the unstressed position could not be inscribed in the gap.

[0020] After the piston retaining ring has been inserted, it returns to its relaxed position in the ring groove and from then on blocks the axial movement between the piston and the piston rod.

[0021] A key advantage of the piston retaining ring is that it can be inserted through the small gaps between the piston and piston rod and inserted into the ring groove. This allows for a very simple design for the piston retaining ring, as well as for the piston and piston rod, with only two corresponding ring grooves, which can be produced cost-effectively.

[0022] A further advantage is that the piston retaining ring can counteract higher forces compared to the elastic deformation caused by rotation around the rotating ring axis with the same dimensions than, for example, with a mere radial expansion or radial compression.

[0023] According to an advantageous further development, the piston retaining ring has a larger outer diameter in the relaxed position than in the stressed position.

[0024] By increasing the outer diameter in the unloaded position, the positive coupling between the piston and piston rod is improved. In particular, this allows the piston retaining ring to enter the annular space of an undercut.

[0025] According to an advantageous refinement, the cross-section is rectangular. A rectangular cross-section allows for a very effective reduction in the axial contact area when changing to the stress state. By varying the size of the ring surfaces and the spring constant, the locking effect in the ring groove can be adjusted after the piston retaining ring has been released.

[0026] According to an advantageous development, the cross-section is rounded at least at a first transition contour, which forms an inner diameter, and at a second transition contour, which forms the outer diameter. Rounding the essential contours further simplifies the insertion of the piston retaining ring, as the ring can slide into the ring groove without jamming, thus preventing damage.

[0027] The two transition contours also serve to determine the inner and outer diameters.

[0028] The invention is illustrated by way of example with reference to Fig. 1 Top and sectional view of the piston retaining ring (schematic) Fig. 2 Functional diagram of the stress and tension position of the piston retaining ring Fig. 3 Piston unit with inserted piston retaining ring (schematic) Fig. 4 Piston retaining ring (isometric) Fig. 5 Piston retaining ring in stress and tension position for comparison (isometric) Fig. 6 Piston unit with inserted piston retaining ring (sectional view) explained in more detail.

[0029] The Figuren 1 bis 3 show schematic representations and the Figuren 4 bis 6 isometric drawings and a sectional drawing.

[0030] Fig. 1 (a) shows a top view of the piston retaining ring 1. The piston retaining ring 1 has an annular gap 2.

[0031] In Fig. 1 (b) A sectional view along the section plane (AA) of the piston retaining ring is shown. This view shows the flattened radial cross-section 3 of the piston retaining ring 1 in an enlarged scale. The cross-sectional longitudinal axis 5 and the cross-sectional transverse axis 6 are inscribed in this cross-section 3. The ring plane 12 runs through their intersection points. The inner diameter 1.1 is formed here by the first transition contour 10. The outer diameter 1.2 is defined by the second transition contour 11. The two transition contours 10, 11 are rounded in this design.

[0032] The two boundaries 7 parallel to the cross-sectional longitudinal axis 5 form the two annular surfaces, which represent the inside as the first annular surface 7.1 and the outside as the second annular surface 7.2 of the piston retaining ring 1.

[0033] The angle α is enclosed between the cross-sectional longitudinal axis 5 and the ring plane 12. The vertex of the inscribed angle α, which is Fig. 1 (b) at the same time the intersection point between the cross-sectional longitudinal axis 5 and the cross-sectional transverse axis 6, simultaneously forms the circumferential ring axis 14 when projected along the piston retaining ring 1.

[0034] In Fig. 2 A functional diagram of the tensioned piston retaining ring 1 is shown. The top shows the unloaded position and the bottom shows the tensioned position (dashed). The illustration is analogous to Fig. 1 (b) .

[0035] In the stress situation, the angle between the longitudinal axis of the cross section and the ring plane 12 increases and is referred to as angle β to clarify the situation.

[0036] The axial overlap surface 13 is limited by the inner and outer diameter of the piston retaining ring 1, which in Fig. 2 is projected onto the ring plane 12. In this illustration, the axial overlap surface 13 is shown outside the actual ring plane 12 by two vertical auxiliary lines at the first transition contour 10 and second transition contour 11 for better overview.

[0037] By increasing the angle, the axial contact area 13 is reduced in the stressed position. The axial contact area 13 is shown as a dashed line in the stressed position and as a solid line in the relaxed position.

[0038] Fig. 3 shows the piston unit 4 with inserted piston retaining ring 1 in partial section in a schematic representation.

[0039] The piston retaining ring is inserted in its tensioned position into the annular groove formed by the opposing grooves of the piston 8 and the piston rod 9. The annular gap 2 in the piston retaining ring allows it to be placed on the piston rod 8. Here, too, the tensioned position is shown in dashed lines.

[0040] In the ring groove, the piston retaining ring 1 relaxes and blocks the displacement between the piston 9 and the piston rod 8 due to the axial form fit that is created.

[0041] Fig. 4 shows the piston retaining ring 1 in an isometric view. It shows the spatial configuration. In particular, the inclined cross-sectional area of ​​the flattened radial cross section 3, the annular gap 2, and the body of the piston retaining ring 1 are shown.

[0042] The first ring surface 7.1, the second ring surface 7.2 and the two transition contours 10, 11, which form the inner diameter 1.1 and the outer diameter 1.2, can also be seen.

[0043] Fig. 5 shows the piston retaining ring 1 in the relaxed position and in the tensioned position in an isometric view.

[0044] The tensioned form (left), i.e., piston retaining ring 1 in the tensioned position, exhibits the inclination angle β of the flattened radial cross-section 3, an annular gap 2 closed by the tension, and changed diameters 1.1, 1.2 compared to the unstressed form (right). The unstressed form (right), i.e., piston retaining ring 1 in the unstressed position, exhibits the smaller inclination angle α.

[0045] This isometric view illustrates the Fig. 2 shown springy deformation additionally.

[0046] Fig. 6 shows the piston unit with inserted piston retaining ring 1 in a sectional drawing. Fig. 6 supplements the functional scheme according to Fig. 3 .

[0047] Also in Fig. 6 The piston retaining ring 1 is shown both tensioned, i.e. in the tensioned position, and untensioned, i.e. in the relaxed position.

[0048] The piston retaining ring 1 in the tensioned position represents the position and deformation during the assembly process. For this purpose, the piston retaining ring 1 is pushed into the circumferential space between the piston 9 and the piston rod 8, whereby it deforms elastically under the action of force and thus tensions. Only when it reaches the ring groove can it assume its relaxed position by elastically recovering. The relaxed piston retaining ring 1 has the smaller angle of inclination α and secures in the piston unit 4 according to Fig. 6a coupling ring 15, which is not part of the invention, in its position in an annular groove in the piston unit 4. Reference symbols used

[0049] 1Piston retaining ring 1.1Inner diameter 1.2Outer diameter 2Annular gap 3Flattened radial cross-section 4Piston unit 5Cross-sectional longitudinal axis 6Cross-sectional transverse axis 7Limitations 7.1First ring surface 7.2Second ring surface 8Piston rod 9Piston 10First transition contour 11Second transition contour 12Ring plane 13Axial overlap surface 14Circumferential ring axis 15Coupling ring αAngle alpha βAngle beta

Claims

1. A piston retaining ring (1) of a piston unit (4), comprising an annular gap (2), a flattened radial cross-section (3), wherein the flattened radial cross-section (3) has a cross-sectional longitudinal axis (5) and a cross-sectional transverse axis (6), wherein the cross-section (3) extends more longitudinally along the cross-sectional longitudinal axis (5) than along the cross-sectional transverse axis (6), wherein the cross-section (3) along the cross-sectional longitudinal axis (5) has opposing even boundaries (7), which form a first and a second ring surface (7.1; 7.2), wherein the piston retaining ring (1) is designed as an elastically resilient element, wherein the piston retaining ring (1) is designed to assume a tensioned position under the action of a force and a relaxed position without the action of a force, wherein in a relaxed position, the cross-sectional longitudinal axis (5) is inclined at an angle α with respect to a ring plane (12), wherein the piston retaining ring (1) can be tensioned by means of a change in the cross-sectional longitudinal axis (5) round a circumferential ring axis to a tensioned position, wherein in the tensioned position the cross-sectional longitudinal axis (5) is inclined by an angle β and wherein the angle β is greater than the angle α, wherein the piston unit (4) comprises a piston rod (8) and a piston (9) which are coupled one to the other by means of the piston retaining ring (1).

2. The piston retaining ring (1) of a piston unit according to claim 1, characterized in that it has a larger external diameter in the relaxed position than in the tensioned position.

3. The piston retaining ring of a piston unit according to claims 1 and 2, characterized in that the cross section (3) has a rectangular design.

4. The piston retaining ring of a piston unit according to one of the preceding claims, characterized in that the cross-section (3) is rounded at least at a first transition contour (10), which forms an internal diameter, and at a second transition contour (11), which forms the external diameter.