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Patent Searching and Data


Title:
LINEAR ACTUATOR AND DRIVE ROD
Document Type and Number:
WIPO Patent Application WO/2017/155404
Kind Code:
A1
Abstract:
A linear actuator comprises an actuator housing (10) with a body cavity (5) in which a drive body (15) is received for axial movement. A drive rod (20,30) extends from the drive body (15). The drive rod comprises a form-retaining core (30) which is covered all around with a flexible and sealed lining (20). The lining (20) seals a surface of the core (30) covered therewith.

Inventors:
HENDRIKS, Hessel Gerardus Martinus (Kuluutsheuvel 74, 5825 BG Overloon, 5825 BG, NL)
Application Number:
NL2017/050150
Publication Date:
September 14, 2017
Filing Date:
March 10, 2017
Export Citation:
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Assignee:
HENDRIKS BEHEER B.V. (Van Galenweg 17, 5431 LG Cuijk, 5431 LG, NL)
International Classes:
F15B15/14
Foreign References:
DE102011121198A12013-06-20
US4211151A1980-07-08
Attorney, Agent or Firm:
JILDERDA, Anne Ayolt (Lioc Patents and Trademarks, P.O. Box 97, 5700 AB Helmond, 5700 AB, NL)
Download PDF:
Claims:
Claims

1. Linear actuator comprising an actuator housing with a body cavity in which a drive body is received for axial movement, wherein a drive rod extends from the drive body and the drive rod comprises a form-retaining core which is covered all around with a flexible and sealed lining which seals a surface of the core covered therewith, characterized in that the lining is formed from an elastomer plastic, which elastomer plastic comprises a synthetic rubber from a group comprising nitrile rubber (NB ), Ethylene Propylene Diene Monomer (EPDM) and polyurethane rubber (PUR).

2. Linear actuator as claimed in claim 1, characterized in that the lining is formed from nitrile rubber (NBR).

3. Linear actuator as claimed in claim 1 or 2, characterized in that the rubber is vulcanized after the lining has been arranged on the core.

4. Linear actuator as claimed in one or more of the foregoing claims, characterized in that the lining has a dynamic hardness of between about 80 and about 100 Shore. 5. Linear actuator as claimed in one or more of the foregoing claims, characterized in that the lining has a thickness of between about 50 micron and 10 millimetres.

6. Linear actuator as claimed in one or more of the foregoing claims, characterized in that the body cavity comprises a cylinder cavity of a pressure cylinder in which the drive body is driven by a fluid under pressure, and that the lining and a wall of the actuator housing connect directly or indirectly in at least substantially seamless manner in order to form a seal therebetween.

7. Linear actuator as claimed in claim 6, characterized in that the lining connects in at least substantially leakage-free manner to an edge provided on an outer end of the body cavity.

8. Linear actuator as claimed in claim 7, characterized in that the edge is form- retaining, and particularly that the edge comprises a shoulder extending from the wall of the actuator housing.

9. Linear actuator as claimed in claim 7, characterized in that the edge is resilient, and particularly that the edge comprises a plastic gasket provided between the lining and the wall of the actuator housing.

10. Linear actuator as claimed in one or more of the foregoing claims, characterized in that the lining is covered with a coating impermeable to ultraviolet (UV) radiation.

11. Linear actuator as claimed in one or more of the foregoing claims, characterized in that the core of the piston rod comprises a metal body, in particular of steel, stainless steel or a carbon fibre-reinforced plastic body.

12. Drive rod of the type as applied in the linear actuator as claimed in one or more of the foregoing claims.

Description:
Linear actuator and drive rod

The present invention relates to a linear actuator comprising an actuator housing with a body cavity in which a drive body is received for axial movement, wherein a drive rod extends from the drive body and the drive rod comprises a form-retaining core which is covered all around with a flexible and sealed lining which seals a surface of the core covered therewith.

Linear actuators are applied on a large scale in tools and machines for the purpose of effecting therewith a linear movement (translation) or rotation of a component driven thereby. In the latter case an outer end of the drive rod will usually engage on the component eccentrically relative to a rotation axis in order to urge the component into rotation. The thus applied actuators have in practice a wide range of dimensions and embodiments depending on the specific application for which they will be utilized.

Meriting special attention here are actuators which will be applied in a highly corrosive environment, particularly in the case of heavy duty applications. Envisaged here are applications in the open air wherein the actuator, and in particular the drive rod thereof, is exposed to weather influences. Particularly in offshore and other maritime applications a drive rod is required here which, in addition to having great strength, also has a high resistance to corrosion so as to ensure a sufficient lifespan.

An approach usually opted for in practice in order to provide for great strength as well as high corrosion resistance is the use of a corrosion-resistant metal or metal alloy for the drive rod. A drawback here however is that such metals and metal alloys are generally relatively expensive, and moreover relatively susceptible to mechanical damage resulting from impact, for instance due to an object or body falling thereon. Known on the other hand from American patent USP 4,211,151 is a linear actuator of the type described in the preamble with a drive rod which is covered with a soft lining which will deform in the case of ballistic impact, and thereby absorb the force exerted thereby. It is however important for durable operation here that the plastic is able to fully absorb such an outside influence and subsequently return undamaged to its original state again afterward. Otherwise, while the core of the drive rod is safeguarded against damage, the drive rod as a whole is not.

The present invention has for its object, among others, to provide an actuator with a drive rod which, as well as being corrosion-resistant, can withstand undamaged to large extent sudden mechanical impacts thereon, such as strikes, and which moreover has a long lifespan.

In order to achieve the stated object a linear actuator of the type described in the preamble has the feature according to the invention that the lining is formed from an elastomer plastic, which elastomer plastic comprises a synthetic rubber from a group comprising nitrile rubber (NBR), Ethylene Propylene Diene Monomer (EPDM) and polyurethane rubber (PUR). A preferred embodiment of the linear actuator according to the invention has the feature here that the lining is formed from nitrile rubber (NBR).

According to the invention the drive rod is thus covered with a flexible lining of a synthetic rubber which is highly suitable for heavy duty use and in diverse environments to which linear actuators are frequently exposed in practice. This lining protects the core of the drive rod against corrosion as well as an external mechanical impact. The lining hereby provides for both mechanical and chemical protection of the core which in turn imparts the required strength to the drive rod. Although many plastics have a certain measure of resilience and can moreover fulfil a corrosion-resisting function, the above-mentioned synthetic rubbers from a group of nitrile rubber (NBR), Ethylene Propylene Diene Monomer (EPDM) and polyurethane rubber (PUR), and pre-eminently nitrile rubber (NBR), are particularly suitable within the scope of the invention.

Although with a view to this required strength use will as a rule nevertheless be made of a suitable metal or suitable metal alloy for the core, less strict requirements will thus need to be imposed thereon in respect of corrosion resistance. Metals and metal alloys which are usually considerably less expensive will hereby be suitable for the drive rod, whereby a significant cost price reduction can be realized.

With a view to an exceptionally good adhesion and close fit of the lining to the core, a further preferred embodiment of the linear actuator according to the invention has the feature that the rubber is vulcanized after the lining has been arranged on the core. The rubber is thus arranged in as yet non-vulcanized, relatively flexible state and only then subjected to a vulcanization process. The rubber acquires its final strength and wear resistance because of this vulcanization step, while the rubber is still optimally deformable during arranging of the rubber layer, this enhancing the production process.

The linear actuator can be driven per se in diverse ways, in particular by a mechanical transmission to the drive body. A preferred embodiment of the actuator according to the invention has the feature however that the body cavity comprises a cylinder cavity of a pressure cylinder in which the drive body is driven by a fluid under pressure, and that the lining and a wall of the actuator housing connect directly or indirectly in at least substantially seamless manner in order to form a seal therebetween. The actuator can thus be utilized directly for a hydraulic or pneumatic drive such as is frequently applied in practice in machines, tools and work vehicles. In a particular embodiment the actuator according to the invention has the feature that the lining connects in at least substantially leakage-free manner to an edge provided on an outer end of the body cavity. Grateful use is made here of the resilience which is characteristic of the lining according to the invention by thereby also providing a gasket to the actuator housing, in this case the body cavity. The actuator is more particularly characterized for this purpose in that either the edge is form-retaining, and particularly that the edge comprises a shoulder extending from the wall of the actuator housing, or the edge is resilient, and particularly that the edge comprises a plastic gasket provided between the lining and the wall of the actuator housing. In addition to protection against corrosion, the lining also provides an effective protection particularly against a sudden mechanical impact because of the elastic capability of the lining. Good results have been achieved in this respect with a further particular embodiment of the actuator according to the invention which is characterized in that the lining has a dynamic hardness of between about 80 and about 100 Shore. Such a dynamic hardness, or rebound hardness, is found sufficient in practice to adequately absorb impacts which occur without permanent damage. A thickness of the lining is also a significant factor here. A further particular embodiment of the actuator according to the invention has in this respect the feature that the lining has a thickness of between about 50 micron and 10 millimetres.

Although many plastics are highly chemically resistant and in addition also relatively resilient, many polymer chains are less well able to withstand radiation. Particularly in open-air applications the effect of ultraviolet radiation is a known cause of premature deterioration of plastics. In order to protect the actuator according to the invention against this a further particular embodiment of the actuator according to the invention has the feature that the lining is covered with a coating impermeable to ultraviolet (UV) radiation.

In order to provide a sufficient strength, particularly in respect of the drive force to be exerted by the actuator, a further particular embodiment of the actuator according to the invention has the feature that the core of the piston rod comprises a metal body, in particular of steel, stainless steel or a carbon fibre-reinforced plastic body.

The invention also relates to a drive rod as applied or for application in the above described actuator according to the invention, and will be further elucidated with reference to several exemplary embodiments and an accompanying drawing. In the drawing

figure 1 shows a longitudinal section of a first exemplary embodiment of an actuator according to the invention;

ure 1A is a detail drawing of a part of the section of figure 1;

ure 2 shows a longitudinal section of a second exemplary embodiment of an

actuator according to the invention; figure 2A is a detail drawing of a part of the section of figure 2; and figure 3 shows a cross-section of the drive rod as applied in the actuator of figures 1 and 2.

The figures are purely schematic and not drawn to scale. Some dimensions in particular may be exaggerated to greater or lesser extent for the sake of clarity. Corresponding parts are generally designated in the figures with the same reference numeral.

Shown in figure 1 is a longitudinal section of an exemplary embodiment of an actuator according to the invention. This is a hydraulic pressure cylinder in which a piston body 15 is drivable under the influence of a fluid (oil) at increased pressure. For mechanically lighter applications use can also be made here of a pneumatic pressure cylinder wherein the fluid is formed by compressed air. The actuator comprises a cylinder housing 10 having therein a body cavity 5 in which piston body 15 is received fittingly for axial movement, optionally via a suitable gasket. The body cavity comprises one or more connections 12,13 to which hydraulic conduits leading to a hydraulic pump can be connected by means of standard hydraulic couplings. Such a hydraulic (or pneumatic) system is assumed sufficiently known to a person with ordinary skill in the art and therefore not further shown in the figures. In this example the components of actuator housing 10 and piston body 15 are formed at least substantially from steel.

Extending from piston body 15 is a drive rod 20, 30 with which a component of a machine, tool, work vehicle or the like will be driven. Although not essential, the drive rod can be provided for this purpose at a distal end with an engaging member 35 which is adapted to the eventual mechanical coupling to the component. According to the invention the drive rod comprises a core 30 which is covered with a lining 20, see also figure 3. The core comprises in this example a rod body of steel having at a proximal end a threaded hole for a connection to a threaded end extending from piston body 15. The outer end with engaging member 35 is formed from the same material. Applied by contrast for lining 20 is a plastic which thereby protects core 30 of the drive rod against corrosion and mechanical damage. Use is particularly made here of an elastomer plastic, such as a synthetic rubber in particular. In this context a layer of nitrile rubber (NB ) is applied in this example. Nitrile rubber is a copolymer of butadiene and acrylonitrile and is characterized by a very good resistance to light and oxygen, and so to ageing. Nitrile rubber can moreover withstand oil, salts and diverse organic solvents, and is therefore highly suitable for demanding applications, such as in the outside air and particularly in offshore and maritime applications.

In this example lining 20 is arranged by covering the core with a layer of nitrile rubber and subsequently vulcanizing the layer onto the core until it has a dynamic hardness of between 80 and 100 Shore. This hardness imparts sufficient resilience that mechanical impacts which occur can be absorbed without leaving any traces whatsoever. Depending on the anticipated impact, a thicker layer can be applied or a thinner layer can suffice. Lining 20 will as a rule have a thickness of between 50 micron and typically in the order of 10 millimetres. In addition to providing mechanical protection, the lining also provides in all these cases a protection against corrosion of core 30 of the drive rod. An extremely strong adhesion is moreover obtained by vulcanizing the lining onto the drive rod.

Many other plastics, and particularly synthetic rubbers, are also suitable for the lining instead of nitrile rubber, so that depending on a specific application a skilled person can have recourse to a plastic with specific chemical and/or mechanical properties. If the lining to be manufactured therefrom has a lesser resistance to UV radiation, it is recommended to apply a UV-proof coating thereover. A UV-resistant lacquer layer can normally be applied for this purpose, which is applied over the lining by transfer, spraying or immersion and which, after curing, absorbs UV radiation without itself ageing. As well as being vulcanized, lining 20 can be arranged close-fittingly and durably on the core by adhesion or by crimping.

Provided between lining 20 and cylinder housing 10 is a leak-tight gasket 37 of a suitable elastomer plastic such as a synthetic rubber or polytetrafluoroethylene (PTFE), normally referred to under the brand name Teflon. Gasket 37 comprises a hydraulic sealing ring, usually referred to as seal or gasket, and is clampingly enclosed between lining 20 and an edge of cylinder housing 10 in order to ensure a leak-tight liquid barrier, see also figure 1A.

For the purpose of such a sealing use can advantageously also be made however of the resilient properties of the lining 20 itself. Use is made hereof in a second embodiment of the actuator according to the invention which is further shown in figures 2 and 2A. This actuator is substantially the same as that of the first exemplary embodiment, although the sealing of the body cavity (cylinder cavity) is provided here directly between lining 20 and a shoulder 36 extending from the cylinder housing, i.e. without interposing a separate gasket, see also figure 2A.

Although the invention has been further elucidated above on the basis of only several exemplary embodiments, it will be apparent that the invention is by no means limited thereto. On the contrary, many variations and embodiments are still possible within the scope of the invention for a person with ordinary skill in the art.