WO2020060398A2

WO2020060398A2 - Lattice comprising multiple branches and joints connecting the branches

Info

Publication number: WO2020060398A2
Application number: PCT/NL2019/050609
Authority: WO
Inventors: Marius Alexander LEEFLANG; Amir Abbas ZADPOOR
Original assignee: Technische Universiteit Delft
Current assignee: Technische Universiteit Delft
Priority date: 2018-09-18
Filing date: 2019-09-17
Publication date: 2020-03-26
Anticipated expiration: 2021-03-18
Also published as: WO2020060398A3; NL2021660B1

Abstract

Lattice (1) comprising multiple branches (2) and joints (3) connecting the branches (2), wherein characterized in that the lattice (1) is formable into a desired shape and exhibits at least two positions, a first position wherein the joints (3) enable that an outer circumference of the lattice (1) conforms and is moved to the desired shape, and a second position wherein the lattice (1) is locked into said desired shape, wherein the lattice (1) exhibits multiple degrees of freedom enabling the lattice (1) to assume an arbitrary external shape, said shape de- fining a boundary with an internal volume, and wherein said lattice (1) is present inside said internal volume so as to provide the boundary with structural rigidity when in the second position wherein the lattice (1) is locked.

Description

Lattice comprising multiple branches and joints connecting the branches

The invention relates to a lattice comprising multiple branches and joints connecting the branches.

Such a lattice is known and used in large-scale con structions such as bridges, but is not yet notably applied in micro scale applications as are the subject of the invention, examples of which will be provided hereinafter.

EP 1 897 470 A1 discloses a flexible sheet structure having improved conformability yet remaining strong and robust. The structure is made up of a plurality of modules that allow relative rotation in both an axis parallel to the plane and per pendicular to the plane of the sheet when laid flat. This allows the density of the sheet to be locally or globally changed so that improved conformability around complex shapes is provided. There is also disclosed a means for locking and unlocking the modules of the sheet using a locking material in each connection that is activated by the external addition of energy (e.g. heat energy) . A possible application is in the medical field.

According to the state-of-the-art many applications re quire that an object is provided with a dedicated shape. To this end it is common that the object is tailored to the needs of the specific application, which is of course costly and time- consuming. For instance in orthopaedics, 3-D printing has been used to provide patient specific implants (PSIs) to provide the implants with the desired shape matching the patient's needs. Despite their advantages, the clinical applications of PSIs have been limited so far partially because they are usually labour- intensive, time-consuming, and expensive. That is due to the pa tient-specific nature of the design process, which requires many steps including image acquisition and processing, image-guided implant design, evaluation of (alternative) patient-specific de sign (s) in consultation with the surgeon, and a dedicated pro duction process.

The high costs, which often are not reimbursed by health insurance companies, are not the only problem; in some cases, (e.g. traumas), it is not possible to wait several weeks to have the implant available. Moreover, medical images do not necessarily yield sufficiently accurate dimensions for the de sign of the PSIs. Even mildly inaccurate PSI geometries may cause problems during surgery and result in sub-optimal implan tations and accelerated wear and tear.

Also in other areas, such as robotic applications, the conventional design process is cumbersome and costly. Robotic grips for organic shapes are currently constructed out of sever al pistons to match the shape it should lift.

It is therefore an object of the invention to avoid the conventional design method and dedicated construction and shap ing of objects, and to avoid the high cost and large amount of time associated with the conventional design procedure.

Accordingly the invention proposes an entirely new ap proach that is based on a lattice comprising multiple branches and joints connecting the branches, and which is provided with the features of one or more of the appended claims.

First and foremost the lattice of the invention is formable into a desired shape and exhibits at least two posi tions, a first position wherein the joints enable that an outer circumference of the lattice conforms and is moved to the de sired shape, and a second position wherein the lattice is locked into said desired shape, wherein the joints are non-assembly joints and the lattice exhibits multiple degrees of freedom ena bling the lattice to assume an arbitrary external shape, said shape defining a boundary with an internal volume inside said boundary, and wherein said lattice is present inside said inter nal volume so as to provide the volume with structural rigidity when in the second position. The invention enables that the lat tice can simply be attuned to the desired shape which is re quired for the intended application, whereafter this shape can be frozen by the mentioned locking into the desired shape. Fur ther the lattice being present within the volume at the inside of the external shape, is an important feature to provide rigid ity to the volume when the lattice is being locked. This feature is important in particular for medical applications.

Considering the microscale applications in which the lattice of the invention is to be used, it is preferable that the lattice is manufactured with an additive manufacturing tech nique or 3-D printing, which enables non-assembly manufacturing of the lattice. Suitably the joints are selected from the group com prising a kinematic type and a compliant type. The kinematic type joints are for instance selected from the group comprising a hinge and a ball and socket joint, whereas the compliant type joints are operative by deformation of constituent elements of the joints .

The locking of the lattice in the second position to freeze the desired shape can be done with alternative means.

One option is that the lattice is lockable into the second position with external means. Another option is that the lattice comprises a locking mechanism for locking the lattice into the second position.

The locking mechanism is suitably embodied in one or more of the joints and selected from the group comprising an ac tuator, an air-canal in the lattice that can be pressurized for locking said one or more joints, and a pre-stressed element act ing as locking switch upon exposure to one of mechanical vibra tions or magnetic fields. The actuator can for instance comprise a network of fixed stops.

The lattice of the invention is preferably used for im plant fixation in orthopedics or as a grip that can be shaped for use in a robotic application.

The invention will hereinafter be further elucidated with reference to the drawing of an exemplary embodiment of an apparatus according to the invention that is not limiting as to the appended claims .

In the drawing:

-figures 1 - 10 shows various embodiments of a lattice according to the invention.

Whenever in the figures the same reference numerals are applied, these numerals refer to the same parts.

Figure 1 shows two examples of lattice 1 configurations comprising multiple branches 2 and in plane revolute joints 3 connecting the branches 2. In the top part of this figure 1 the joints 3 are located at the crossing 4 of the branches 2, and in the bottom part of this figure 1 the branches 2 join at the crossing 4.

Figure 2 shows two other examples of lattice 1 configu rations. In the top part on the left of figure 2 a 2D and on the right a 3D configuration of a lattice 1 is shown comprising com- pliant joints 3, wherein the branches 2 join at the crossings 4. At the bottom of figure 2 a lattice 1 is shown with kinematic joints 3 at the crossings 4.

Figure 3 shows on in figure 3A a lattice 1 with multi ple branches 2 and in plane revolute joints 3 connecting the branches 2. Further the figure shows in figures 3 B - E how this lattice 1 can conform to four different shapes depicting that the lattice 1 exhibits multiple degrees of freedom enabling the lattice 1 to assume an arbitrary external shape. The figures 3B - 3E also depict that the shape defines a boundary with an in ternal volume inside said boundary, wherein said lattice 1 is present inside said internal volume so as to provide the volume with structural rigidity when in the second (locked) position.

Figures 4A - 4D show four examples of non-assembly kin ematic joint configurations. Figure 4A shows in plane revolute joints 3. Figure 4B shows joints 3 enabling an out of plane rev olution. Figure 4C shows chain mail joints 3. Figure 4D shows sphereoid joints 3.

Figures 5A - 5C show three examples of non-assembly compliant joint configurations. Figure 5A shows S-joints. Figure 5B shows chicane joints. Figure 5C shows double u-notch joints. Each of these joints can be tailored to a desired stiffness and deformation behaviour.

In figure 6 an example is shown of how a lattice can be locked when it is brought into a desired shape. Figure 6A shows that the lattice is provided with air canals 5. In figure 6B the lattice is brought into a desired shape and the air canals 5 are pressurized which forces the lattice on to maintain its shape conforming to the inner boundaries 6 of the outer object 7. Fig ure 6B also illustrates that the lattice 1 exhibits multiple de grees of freedom enabling the lattice 1 to assume an arbitrary external shape, and that this shape defines a boundary with an internal volume inside said boundary, wherein the lattice 1 is present inside said internal volume so as to provide the volume with structural rigidity when in the second (locked) position.

Figure 7A - 7C show an example of a lattice 1 provided with a kinematic locking mechanism. At the right hand side of the figures detailed views are provided. In figure 7A the lock ing mechanism 5 is shown which comprises two out of plane revo lute joints 5' connecting to the components of an in plane revo- lute joint 5' ' . In this position the in plane revolute joint 5'' can move freely. In figure 7B the lattice 1 conforms to a de sired shape and the out of plane joints 5' of the locking mecha nism 5 are aligned. Subsequently it is shown that in figure 7C locking is accomplished by rotating the in plane revolute joint 5'' over 90° which locks the lattice 1 in the shape it has reached .

Figures 8A - 8C shows three examples of lattices 1 wherein the locking mechanism is embodied as a compliant mecha nism which are shown in a detail view at the right hand side of the respective figures. Locking is accomplished by first com pressing the lattice 1 which deforms the compliant members 5' ,

5' ' , 5' ' ' of the lattice 1 until the lattice 1 has reached its desired shape. Subsequently the lattice 1 is released which al lows the compliant members 5' , 5' ' , 5' ' ' of the lattice 1 to spring back and provide an outward driving force pressing the lattice 1 against the boundaries of the object to the shape of which the lattice 1 conforms.

Figures 9A - 9C shows an example of a lattice 1 which is convertible from a flat shape as shown in figure 9A into a folded shape as shown in figure 9C or vice versa, with an inter mediate shape shown in figure 9B. For this purpose the lattice 1 is embodied with out of plane revolute joints 3.

Figures 10A - 10C shows stacking of flat lattices 1 ac cording to the invention. Figure 10A shows three lattices 1 which are disconnected. In figure 10B the three lattices 1 are stacked and connected to each other using spheroid joints 3. Figure 10C shows the stacked lattices 1 of figure 10B in a per spective view. By the act of stacking also locking of the lat tices 1 is accomplished.

Although the invention has been discussed in the fore going with reference to exemplary embodiments of lattices of the invention, the invention is not restricted to these particular embodiments which can be varied in many ways without departing from the invention. The discussed exemplary embodiments shall therefore not be used to construe the appended claims strictly in accordance therewith. On the contrary the embodiments are merely intended to explain the wording of the appended claims without intent to limit the claims to these exemplary embodi ment. The scope of protection of the invention shall therefore be construed in accordance with the appended claims only, where in a possible ambiguity in the wording of the claims shall be resolved using these exemplary embodiments.

Claims

1. Lattice (1) comprising multiple branches (2) and joints (3) connecting the branches (2), wherein the lattice (1) is formable into a desired shape and exhibits at least two posi tions, a first position wherein the joints (3) enable that an outer circumference of the lattice (1) conforms and is moved to the desired shape, and a second position wherein the lattice (1) is locked into said desired shape, characterized in that the joints (3) are non-assembly joints and the lattice (1) exhibits multiple degrees of freedom enabling the lattice (1) to assume an arbitrary external shape, said shape defining a boundary with an internal volume inside the boundary, and wherein said lattice (1) is present inside said internal volume so as to provide the volume with structural rigidity when in the second position.

2. Lattice according to claim 1, characterized in that lattice (1) is provided with an additive manufacturing tech nique .

3. Lattice according to claim 1 or 2, characterized in that the joints (3) are selected from the group comprising a kinematic type and a compliant type.

4. Lattice according to claim 3, characterized in that the kinematic type joints (3) are selected from the group com prising a hinge, a ball and socket joint.

5. Lattice according to claim 3, characterized in that the compliant type joints (3) are operative by deformation of constituent elements of the joints.

6. Lattice according to any one of claims 1 - 5, characterized in that the lattice (1) is lockable into the second position with external means.

7. Lattice according to any one of claims 1 - 5, characterized in that the lattice (1) comprises a locking mechanism (5) for locking the lattice (1) into the second position.

8. Lattice according to claim 7, characterized in that the locking mechanism (5) is embodied in one or more of the joints (3) and selected from the group comprising an actuator, an air-canal in the lattice that can be pressurized for locking said one or more joints, and a pre-stressed element acting as locking switch upon exposure to one of mechanical vibrations and magnetic fields.

9. Lattice according to claim 8, characterized in that the actuator comprises a network of fixed stops.

10. Lattice according to any one of claims 1 - 9, char- acterized in that the lattice (1) is used for implant fixation in orthopedics or as a grip that can be shaped for use in a ro botic application.