EP2572156A1

EP2572156A1 - Mechanical trimming device and trimming method

Info

Publication number: EP2572156A1
Application number: EP11720093A
Authority: EP
Inventors: Göran Cewers
Original assignee: Mindray Medical Sweden AB
Current assignee: Shenzhen Mindray Bio Medical Electronics Co Ltd
Priority date: 2010-05-17
Filing date: 2011-05-16
Publication date: 2013-03-27
Also published as: WO2011144581A1

Abstract

The invention pertains to a device for trimming the thickness of a mechanical body. The trimming is performed by screwing a screw through a threaded hole and having the end of the screw pressing against the centre of a disk element, which by deformation, acts as a lever against an adjacent body. This reduces the influence of the lead of the screw to the transmission determined by the abovementioned lever.

Description

I LE: MECHANICAL TRIMMING DEVICE AND TRIMMING METHOD Related Applications

The present application relates to the following applications of the same inventor as the present

application with the following titles: "VALVE AND METHOD TO CONTROL A FLOW THROUGH THE VALVE" (US61/345, 623) ;

"MECHANICAL AMPLIFIER, SYSTEM OF SAID AMPLIFIERS AND METHOD FOR MECHANICALLY AMPLIFICATION OF A MOTION" (US61/345, 625) ; "VALVE AND METHOD TO CONTROL A FLOW" (US 61 /345 , 628 ) ;

"MECHANICAL TRIMMING DEVICE AND TRIMMING METHOD"

(US61/345, 733) ; "MECHANICAL TEMPERATURE COMPENSATION

MEANS, METHOD FOR ASSEMBLY SAID MEANS AND METHOD FOR

MECHANICALLY TEMPERATURE COMPENSATING" (US61/345, 756) ;

which all are incorporated herein by reference in their entirety for all purposes.

Background of the invention

Field of the Invention

The invention pertains to adjusting mechanical tolerances, and more precisely to a device and method for compensating or trimming mechanical tolerances in

tolerance critical systems. The invention also pertains to a device for carrying out said method.

Related Prior Art

When designing mechanical systems it is common for components of different materials to be used in the

construction. The reasons may be special requirements for the parts used such as hardness, exhaustion properties, corrosion resistance, surface roughness, transparency, colour, electrical properties, melting point, cost etc.

When parts with different materials are combined in a mechanical system, it is common for the parts to have different mechanical tolerances. These tolerances may include dimensional tolerances or tolerances in rigidity of the parts used.

The tolerances in rigidity of a spring are usually quite large, resulting in mechanical dimension tolerances for a specific force when a spring is included in a

mechanical system.

In many cases the tolerances may be improved by mechanical adjustment. Thus this is not always possible, e.g. if the parts used may be destroyed by adjustment or if the process is too costly.

A better alternative may than be to keep the

tolerances on the parts used and add a mechanical trimming device .

Examples of tolerance critical structures may be devices for micro-positioning, control of laser beams, microscope focusing - atomic, optical and ultrasound - semiconductor manufacture, sensors for micro-positioning, spectroscopy and optical benches.

In micro-positioning it is common for positioning to be controlled by an actuator in the form of a piezoelectric crystal stack. A piezoelectric crystal stack has an

actuation range of approximately 0.1% of the length of the stack. At the same time, the stack may also have a length tolerance of 0.5%. This results in a need of mechanical trimming .

The piezoelectric crystal stack may be arranged in a medical ventilator valve to control a gas flow, as e.g. described in US61/345, 623.

A simple method of mechanical trimming is to use an ordinary screw through a threaded hole and through a mechanical anchoring. The lead of normal threads, even down to M2 may be as much as 400 ym/turn. Trimming of a few ym would hardly be possible with such a screw and solution. One way of improving a trimming screw is to give it two opposing threads with a small difference in pitch between them. This principle is described in US patent 1,532,702. However, the disadvantages of this principle are that it is relatively costly, requires low surface roughness in the threads and is space requiring.

One object of the invention is thus to provide a device and/or method for mechanical trimming of tolerances in a system. In particular, such system should

advantageously have a simple design with low manufacturing costs and small dimensions. Summary of the Invention

These objects are met by means of the device and the method in accordance with in the appended independent claims, while particular embodiments are dealt with in the dependent claims.

Accordingly, embodiments of the present invention seek primarily to mitigate, alleviate or eliminate one or more of the above-identified deficiencies or disadvantages in the art, singly or in any combination, and solve at least partly the abovementioned issues by providing a device and method according to the appended patent claims.

The invention relates to a device and a method for trimming the thickness of a mechanical body. The trimming is performed by screwing a screw through a threaded hole. The end of the screw pressing against a centre of a disk member or washer, which by deformation acts as a lever against an adjacent body. This reduces the effect of the lead of the screw to the transmission determined by the abovementioned lever and the adjacent body is moved a substantially shorter distance than the screw.

In one aspect of the invention, a mechanical trimming device is provided comprising an adjustable; a first body having at least one threaded through hole that rotatable partly enclosing said adjustable screw; a movable second body, that is movable relative to the first body, and has a cavity into the second body. The cavity accommodates a proximal end of said screw. When the second body is laid against said first body; at least one disc member having a centre and an outer-edge and is positioned between the first and the second bodies. The cavity is facing the disc member and has an edge lying inside of the outer-edge of the disc member so that the outer edge of the disc member lies between the first and the second body.

The screw, when is adjusted, can raise the centre of the disc member in that the disc member works as a lever having a first distributed contact point against the cavity edge of the second body and a second distributed contact point along the outer-edge of the disc member against the surface of the first body, wherein the first body is moved in the axial direction of the screw with a substantially smaller motion than the screw.

This device provides the possibility of using a screw to adjust the second, relative to the first body movable, body, e.g. orthogonally relative to the surface of the first body. The orthogonal adjustment of the second body, occurring when the screwing the screw, is due to the design of the device extremely small in relation to the motion of the screw. Preferably the adjustment is in the micrometre range. The adjustment using the abovementioned device may be performed either vertically or horizontally depending on the positioning of the device. When trimming, the second body is moved along the axial direction of the screw with a movement substantially less than the screw.

When the trimming has been completed the disc member locks the adjustment screw in its position provided there is a counter force through the second body keeping the disc member in a pre-stressed position. Thus the trimming cannot come undone .

This provides a cost effective and simple way to obtain a device usable for trimming by micro-positioning, such as controlling laser beams, microscope focusing; atomic, optical and ultrasound, semiconductor manufacturing, sensors for micro-positioning, spectroscopy and optical benches.

For example, the device may be used for mechanical trimming of the stroke length of a piezoelectric crystal stack, but also for other types of actuator units.

In some embodiments, the mechanical trimming device has disc member slits running towards the centre. In some embodiments may the disc member also including towards the centre running sectioned elements. The disc member may be circular in shape but may also be polygonal. However, the geometry is not restrained to these shapes, but may also be ellipsoids or similar.

The disc member may be designed in many ways as long as the general principles described here within are

complied with. For example, the disc member may have a hole in the centre where the slits meet. It may also be large sections. The disc member may also be designed with a solid centre, where the screw presses, with outwards directing sections or arms.

In some embodiments of the mechanical trimming device, the mechanical trimming device is connected in series to a mechanical temperature compensation element. This configuration of the device also provides, if

required, compensation for changes in the ambient

temperature, e.g. the stroke length of an actuator unit, preferably a piezoactuator .

In yet another embodiment, the mechanical trimming device may be connected in series to an actuator unit and to a mechanical temperature compensation element, if necessary.

In another aspect, the invention comprises a method for trimming in an orthogonal direction relative to the surface of the mechanical trimming device. The method comprises adjusting a screw for raising a centre of a disc member so that the disc member acting as a lever having a first distributed contact point against a second body' s cavity edge and a second distributed contact point along the outer edge of the disc member against a surface of the first body. Wherein the second body is movable relative to the first body.

The advantages of this method are the same as for the above described equipment, comprising a simple and

inexpensive way of trimming the position.

Further embodiments of the invention are defined in the dependent claims, wherein features for the second and subsequent aspects of the invention are as for the first aspect mutatis mutandis.

It should be emphasized that the term

"comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

Brief Description of the Drawings

These and other aspects, features and advantages of which the invention at least is capable of will be apparent and elucidated from the following description of

embodiments of the present invention, reference being made to the accompanying drawings, in which

Figure 1 is a schematic view showing an exemplary embodiment using a disc member;

Figure 2 shows a detailed view of the disc member in

Figure 1 ;

Figure 3 shows an exemplary embodiment where a mechanical trimming device is combined with a temperature compensation element; and

Figure 4 is a flowchart of a method 200. Description of the Preferred Embodiments

Specific embodiments of the invention will now be described with reference to the accompanying drawings.

This invention may, however, be embodied in many different forms and should not be construed as limited to the

embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements.

Fig. 1 shows a mechanical trimming device according to an embodiment of the invention. The device is obtained by a disc element 11 being installed between a chassis 10 and a movable circular body 13. The chassis 10 comprises an adjustment screw 12 positioned under the centre of disc member 11, such as a washer. When the adjustment screw 12 is screwed into the chassis 10, the centre of disc member

11 is raised.

Segment 22, as shown in Fig. 2, may be formed by slits 20 in disc member 11, running towards the centre,

There slits may then bend upwards when the adjustment screw

12 is screwed into the chassis 10 . Thus each segment may be regarded as a lever acting on the outer edge of the disc member 11 against the chassis 10 and at the radius

according to the arrow 15 on the movable body 13. The motion of the screw may then easily be reduced to less than 50 ym per turn. The underside of the movable body 13 has a cavity to allow disc member 11 to be bent upwards

underneath it.

Additionally, the disc member 11 may have a hole in the centre with a diameter less than the diameter of the screw .

Additionally and/or alternatively, in some

embodiments, the mechanical trimming device includes towards the centre running sectioned elements fixed at the centre, for example may the centre be a solid centre, where the screw presses. The sections 22 will than be outwards directing sections or arms. The disc member may be designed in many ways as long as the general principles described here within are complied with.

This bending also exerts a locking force on the screw 12 so that it does not rotate unintentionally.

Additionally, a sealing member 14 may be integrated into the head of the adjustment screw to seal the inside of the chassis 10 from the outside. This may be advantageous in environments where there is a risk of explosion since it will avoid fluid to get into contact with the actuator.

Figure 3 shows an exemplary embodiment where a temperature compensation element 30 is positioned in series with the trimming device. Here the temperature compensation element 30 replaces the movable circular body 13 in Fig. 1. In the present exemplary embodiment are the parts circular, the geometry of the device is however not restricted to these shapes, but may also be polygons, ellipses etc.

For example, a piezoelectric crystal stack may be arranged inside the chassis 10 and a top of or above the circular body 13 to provide mechanical trimming of the stroke length of the crystal stack.

Other embodiments may also comprising the uses of extremely small adjustment lengths are needed, e.g. for other types of actuator unit.

Details on suitable mechanical temperature

compensation means, method for assembly the means and method for mechanically temperature compensating can be found in US patent applications numbers US61/345,756 and US13/106,644 of the same inventor, which is incorporated herein by reference in its entirety for all purposes. In US13/106,644 a mechanical temperature compensation means and method are disclosed for compensating for heat

expansion effects in solid materials, and a method for manufacturing the device.

The mechanical temperature compensation means and methods are well suitable for the present embodiments of mechanically trimming device, in accordance with the following reasoning. The temperature compensation is performed by mechanically working together with the device for which the temperature is to be compensated. The

temperature compensation element comprising an enclosed disc, which via an inclined link device is connected to a housing whose heat expansion coefficient is different compared to the enclosed disc. Compensation for both negative and positive temperatures can be conducted. The manufacturing method comprising heating up or cooling down the components, achieving a pressure fit when the parts have been assembled and the temperature of the components has been controlled to the intended temperature

compensation range.

In one aspect, the US61/345,756 disclosure includes a mechanical temperature compensation element intended to be used as a compensation element for heat expansion. The element comprises a flat element with a first heat

expansion coefficient, a housing with a second heat

expansion coefficient different from the first heat

expansion coefficient, a, in relation to the flat element, inclined linkage device which mechanically connecting the flat element and the housing; when the temperature changing the flat element expands radially and the linkage device is moved radially, wherein the radial expansion from the flat element is converted to an, relative to the flat element, orthogonal movement, which raises or lowers the housing depending on the temperature of the temperature

compensation element.

This configuration provides a mechanical device which may be used to mechanically compensate for changes

depending on temperature changes. The device may be used for temperature critical structures such as for micro- positioning, controlling of laser beams, microscope

focusing - atomic, optical and ultrasound - semiconductor manufacturing, sensors for micro-positioning, spectroscopy and optical benches.

Additionally and/or alternatively, the device could also be used to compensate for the temperature dependent stroke length of a piezo element such as an actuator.

The temperature compensating is obtained by the flat material having a heat coefficient being higher or lower than an upper laying housing or a housing made of two opposed halves. When a temperature change occurs, the flat element is expanded radially, which results in, a to the housing connected, mechanical device executing a lever-like movement and raising and lowering the housing orthogonally relative to the flat element.

The flat element and the housing may have varying shapes in various embodiments. For example, they can either be circular shaped, polygonal shaped or ellipsoid shaped.

Additionally and/or alternatively, in one embodiment of the mechanical temperature compensation element, the link device comprising a disk element, such as a washer, with a rhomboidal cross-section, radial slits and/or separate segments with rhomboidal cross-section.

It is through this design, of the mechanically linked device between the flat element and the housing that results in the lever-like movement which is caused by the flat element's temperature dependent radial change.

Additionally and/or alternatively, in one embodiment of the mechanical temperature compensation element, the flat element has a heat expansion coefficient higher than that of the housing.

This provides positive temperature compensation, which provides a raising effect when the temperature increases. Examples of a material that may be used for the flat element is Zinc.

Additionally and/or alternatively, in one embodiment of the mechanical temperature compensation element, the flat element has a heat expansion coefficient lower than that of the housing.

This provides negative temperature compensation, which causes the mechanical temperature compensation element to lowers when the temperature increases.

Additionally and/or alternatively, in one embodiment of the mechanical temperature compensation element, it may be connected in series to a piezo element.

In a connection of this kind, the mechanical

temperature compensation element is used to compensate for temperature dependent changes in the stroke length of the piezo element. But as already mentioned, the invention may be used to temperature compensate in other temperature critical structures.

Figure 4 shows a flowchart of a method for trimming 200 in an orthogonal direction relative to the surface of the herein-mentioned mechanical trimming device. The method comprises adjusting a screw 210 for raising a centre of a disc member so that the disc member acting as a lever 220. The disc has a first distributed contact point against a second body' s cavity edge and a second distributed contact point along the outer edge of said disc member against a surface of said first body. The second body is movable 230 relative to said first body.

Additionally and/or alternatively, the method may comprise usage of the mechanical trimming device for a mechanical trimming of a stroke length of a piezoelectric crystal stack .

Additionally and/or alternatively, the transmission of the lever is moving along the axial direction of the screw with a movement substantially less than the screw.

Additionally and/or alternatively, the method may comprise connecting the mechanical trimming device in series with a mechanical temperature compensating element.

This provides the advantage of being able to,

independently, both trimming the system for differences in dimension tolerances and being able to compensate for changes in the temperature.

Additionally and/or alternatively, the method may comprise connecting an actuator unit in series to the mechanical trimming device and when required a mechanical temperature compensating element.

The method is related to the presented trimming device, thus provides the same advantages as for the equipment described above.

The present invention has been described above with reference to specific embodiments. However, other

embodiments than the above described are equally possible within the scope of the invention. Different method steps than those described above, performing the method by hardware or software, may be provided within the scope of the invention. The different features and steps of the invention may be combined in other combinations than those described. The scope of the invention is only limited by the appended patent claims.

Claims

CLAIMS 1. A mechanical trimming device comprising:

an adjustable screw (12);

a first body (10) that has at least one threaded through hole at least partly enclosing said

adjustable screw for rotatable motion therein;

a movable second body (13), that is movable relative to said first body (10), and has a cavity into said second body, wherein said cavity

accommodates a proximal end of said screw, when said second body is laid against said first body;

at least one disc member (11) that has a centre and an outer-edge and is positioned between said first and said second bodies, wherein said cavity is facing said disc member (11) and has an edge lying inside of said outer-edge of said disc member so that said outer edge of said disc member lies between said first and said second body; and

wherein said screw, when adjusted, is arranged to raise said centre of said disc member in such a manner that said disc member works as a lever having a first distributed contact point against said cavity edge of said second body and a second distributed contact point along said outer-edge of said disc member against said surface of said first body,

whereby said first body is movable in an axial direction of said screw with a substantially smaller motion than said screw for said trimming.

2. The mechanical trimming device according to claim 1, wherein said disc member has slits running towards said centre.

The mechanical trimming device according to claim 1, wherein said disc member comprises sectioned elements directed towards the centre directed.

The mechanical trimming device according to any of claims 1-3, wherein said disc member is circular shaped.

The mechanical trimming device according to any of claims 1-3, wherein said disc member is polygonal shaped.

The mechanical trimming device according to any of claims 1-5, wherein said mechanical trimming device is connected in series to a mechanical temperature compensating element.

The mechanical trimming device according to any of claims 1-6, wherein an actuator unit is connected in series to said mechanical trimming device and when required a mechanical temperature compensating element.

The mechanical trimming device according to any of claims 1-7, wherein said mechanical trimming device is arranged in series to a piezoelectric crystal stack for trimming a stroke length of said piezoelectric crystal stack.

The mechanical trimming device according to claim 8, comprising said piezoelectric crystal stack arranged in a medical ventilator valve to control a gas flow.

10. A method for mechanically trimming (200) in an orthogonal direction relative to the surface of a mechanical trimming device, wherein the method comprises

adjusting a screw (210) for raising a centre of a disc member so that said disc member acting as a lever (220) having a first distributed contact point against a second body' s cavity edge and a second distributed contact point along the outer edge of said disc member against a surface of said first body; and

wherein said second body is movable (230) relative to said first body.

11. The method according to claim 10, comprising

usage of said mechanical trimming device according to any of claims 1-7, for a mechanical trimming of a stroke length of a piezoelectric crystal stack.

12. The method according to claim 10 or 11, wherein said transmission of said lever is moving along the axial direction of said screw with a movement substantially less than said screw