Site News  |   Monitor Keywords  |   Monitor Archive  |   Organizer  |   Account Info  |

Axially driven piston-cylinder unit

Axially driven piston-cylinder unit description/claims

The invention relates to an axially-driven piston-cylinder unit.

A piston-cylinder unit is known, for example, from U.S. Pat. No. 5,525,845. In that, the piston rod is rigidly joined, both to the axially-movable drive element of the linear drive and also to the piston. During operation of the piston, which is driven by the linear motor, a state can arise in which the axial oscillation of the unit comprising the movable drive element, piston rod and piston, experiences an increase in the amplitude of the oscillations, so that the piston head of the piston can strike against the top of the cylinder bore. This can result in damage to the piston head or the top end face wall of the cylinder bore.

The object of the present invention is to design a generic axially-driven piston-cylinder unit in such a way that the danger of damage to the piston or the cylinder is reduced.

This object is achieved by the features specified in the claims.

In normal operation of the piston-cylinder unit, the piston rod is exactly located, both on the piston and on the drive element, and no relative movement occurs between the drive element, piston rod and piston. Only in the case of an overload, when the force applied by the drive element exceeds the pretensioning force of the elastic device does a relative movement occur between the drive element and the piston rod or between the piston rod and the piston.

By the decoupling of the mass of the drive element from the piston, by means of the elastic device, the drive element is braked by the elastic device if the piston lands on the top end face wall of the cylinder bore during a movement of the piston into the compression position. By this means, only the mass of the piston, possibly including the mass of the piston rod but not including the mass of the drive element, will strike the top end face wall of the cylinder bore. The shock pulse which arises from this is significantly less, compared to a rigid unit comprising the piston, piston rod and drive element, so that the danger of damage to the piston head or the top end face wall of the cylinder bore, is also greatly reduced.

In an advantageous embodiment, the piston head is provided with an opening through which the first end of the piston rod is passed, such that the piston rod can move relative to the piston in the axial direction of the piston, where the elastic device is provided between the piston rod and the piston and whereby the elastic device pretensions the piston rod from the piston towards the driver device, where the piston rod is provided with an end-stop which prevents the piston rod from coming out of the opening. With this form of embodiment, the mass striking against the top end face wall is yet further reduced, because the mass of the piston rod is also decoupled from the piston.

It is particularly advantageous here if the passage of the piston rod through the opening is sealed, for which purpose a seal which encircles the piston rod is preferably provided. With this form of embodiment, the compression efficiency is improved, because the medium which is compressed by the piston cannot leak through the annular gap around the piston rod.

Another advantageous form of embodiment is distinguished by the fact that the drive element is provided with an opening through which the second end of the piston rod is passed, that the piston rod can move relative to the drive element, in the axial direction of the drive element, that the elastic device is provided between the piston rod and the drive element and that the elastic device pre-tensions the piston rod from the drive element towards the piston, where the piston rod is provided with an end-stop which prevents the piston rod from coming out of the opening. With this variant, the decoupling is effected by means of the elastic device on the drive element side, so that a fixed joint can be provided between the piston and the piston rod and it is not necessary to provide an expensive seal on an opening in the piston head.

Preferably, the elastic device will have a spring or will be made of a spring. Particularly preferred here is the provision of a disk-spring arrangement or a spiral spring under compression or tension.

A realization of the present invention is especially effective in the case of a linear drive, for example a linear motor, where the piston is subject to the back and forward drive of a movable drive element of the linear drive.

A preferred application of the axially driven piston-cylinder unit in accordance with the invention is its use in a compressor for producing a pressurized fluid.

The invention is explained in more detail below using an example, with reference to the drawing. In this

FIG. 1 shows a first form of embodiment of the invention with a decoupling mechanism in the region of the piston, and

FIG. 2 shows an enlarged diagram of the passage of the piston rod through the piston head, in the form of embodiment shown in FIG. 1.

FIG. 1 shows a longitudinal section through a piston-cylinder unit 1 with a cylinder 2 and a piston 3. The cylinder 2 has a cylinder bore 10, in which the piston 3 is accommodated so that it is freely guided and can move back and forth along the direction of the longitudinal axis X of the cylinder bore 10. The piston 3 has a gas bearing in the cylinder 2. The top end face wall 12 of the cylinder bore 10, formed in a cylinder head 23, the internal circumferential wall 14 of the cylinder bore 10 and the piston head 16 delimit the cylinder chamber 18.

An inlet manifold 22 with a valve 20, which is shown schematically, opens out into the top end face wall 12 of the cylinder bore 10. Also provided in the top end face wall 12 is an exhaust manifold 24, which has a corresponding valve 26; this exhaust manifold also opens out into the cylinder bore 10.

• Provisional Patent
• Utility Patent

• What Is a Patent?
• What Is a Trademark or Servicemark?
• What Is a Copyright?
• Patent Laws