Abstract:
A device in which the gripping action is achieved by a compliant membrane that adapts itself to the object to be lifted and then maintains such shape throughout the displacement of the object. The gripping force provided by the present invention is best suited for delicate objects, as it gently applies the gripping force necessary for displacement. This is accomplished through a chamber, a deformable membrane delimiting the chamber partially or entirely, and a means for changing the volume or shape of the chamber determined by the deformation of the membrane.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/947,039, filed on Mar. 3, 2014, and incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     Not Applicable. 
     FIELD OF THE INVENTION 
     This invention relates generally to a gripping device, and more particularly, to a passive-active gripping and releasing apparatus. 
     DISCUSSION OF RELATED ART 
     Generally, robotics can be described as automating laborious and repetitive activities, typically replacing those of a human laborer. Robotic gripping devices can generally be described as devices adapted to grip, lift, and otherwise displace a variety of target objects having different sizes and shapes. An active robotic gripping device typically has two or more parts adapted to apply a controlled pressure sufficient to lift a target object, much like a human arm. The main disadvantage of traditional active robotic gripping devices is that the moving parts needs to be carefully adjusted to adapt to the specific shape and size of each target object. 
     Other robotic gripping devices utilize negative pressure to lift their target objects. For example, suction cup solutions or vacuum end effectors are both widely used in the automation industry. The rigidity of the above robotic gripping devices are often problematic when dealing with soft and delicate target objects, such as horticultural products. 
     US 2013/0106127 describes a passive universal jamming gripping device, where a membrane is filled with a granular material such as sand, pushed onto the object, and then hardened by applying vacuum within the chamber. While this is one possible solution for working with target objects, the need of a granular material and a pumping mechanism to create depression inside the chamber adds complexity and cost to the apparatus. 
     While several robotic gripping devices exist in the prior art, none are adapted to simply and efficiently work with delicate objects. The complexity needed to render such devices suitable for delicate operations determines substantial increase in costs and operation times. As such, there is a continued need for a device in which the gripping action is achieved by a compliant membrane that adapts itself to the object to be lifted and then maintains such shape throughout the displacement of the object. Furthermore, there is a continued need for a device which is simple and effective in its operation and implementation. The present invention satisfies these needs. 
     SUMMARY OF THE INVENTION 
     The present invention will provide a device in which the gripping action is achieved by a compliant membrane that adapts itself to the object to be lifted and then maintains such shape throughout the displacement of the object. The gripping force provided by the present invention is best suited for delicate objects, as it gently applies the gripping force necessary for displacement. This is accomplished through a chamber, a deformable membrane delimiting the chamber partially or entirely, and a means for changing the volume or shape of the chamber determined by the deformation of the membrane. 
     The present invention comprises a chamber, a deformable membrane delimiting the chamber partially or entirely, and a means for changing the volume or shape of the chamber determined by the deformation of the membrane. The means for changing the volume or shape of the chamber include a piston and/or a phase-changing material. These elements work in conjunction to provide grip onto an object, or more specifically, by deforming the membrane such that it provides the grip necessary to lift and displace the object. The shape of the membrane will be maintained throughout the displacement of the object. 
     These and other objectives of the present invention will become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiments. It is to be understood that the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of the present invention; 
         FIG. 2  is a front perspective view of the present invention; 
         FIG. 3  is a front perspective view of the present invention; 
         FIG. 4  is a front perspective view of the present invention; 
         FIG. 5  is a front perspective view of the present invention; 
         FIG. 6  is a front perspective view of the present invention; 
         FIG. 7  is a front perspective view of the present invention; 
         FIG. 8  is a front perspective view of the present invention; 
         FIG. 9  is a front perspective view of the present invention; 
         FIG. 10  is a front perspective view of the present invention; 
         FIG. 11  is a front perspective view of the present invention; and 
         FIG. 12  is a front perspective view of various objects to be displaced. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Illustrative embodiments of the invention are described below. The following explanation provides specific details for a thorough understanding of and enabling description for these embodiments. One skilled in the art will understand that the invention may be practiced without such details. In other instances, well-known structures and functions have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments. 
     Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to.” Words using the singular or plural number also include the plural or singular number respectively. Additionally, the words “herein,” “above,” “below” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. When the claims use the word “or” in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list and any combination of the items in the list. 
     In the preferred embodiment, the present invention comprises a chamber  20 , a deformable membrane  30  delimiting the chamber  20  partially or entirely, and a means for changing the volume or shape of the chamber  20  determined by the deformation of the membrane  30 . The means for changing the volume or shape of the chamber  20  include a piston  40  and/or a phase-changing material  41 . These elements work in conjunction to provide grip onto an object, or more specifically, by deforming the membrane  30  such that it provides the grip necessary to lift and displace the object. The shape of the membrane  30  will be maintained throughout the displacement of the object. 
     The chamber  20  further comprises a void which may contain a gas, liquid, or phase-changing material  41 . In the preferred embodiment, the chamber  20  will have an open end  22  and a closed end  21 , sealed by the deformable membrane  30 . As such, the chamber  20  will have a fixed volume, wherein the deformation of the membrane  30  does not cause a change in this volume. In an alternative embodiment, the chamber  20  can be open. In this embodiment, the deformation of the membrane  30  does cause a change in volume of the chamber  20 . In a further alternative embodiment, the chamber  20  may further comprise a valve  23 . 
     The membrane  30  will come into direct contact with the object, providing the necessary grip to displace the object. Furthermore, the membrane  30  will seal the chamber  20  and maintain a fixed volume even when deformed. As such, the membrane  30  must be a stretchable, yet resistant, material that is capable of providing substantial grip (static friction). Suitable materials include latex, silicones, polyurethanes, and other types of stretchable polymers or materials. The surface of the membrane  30  can be smooth to better comply with smooth objects, or structured for objects with a rougher surface. The adhesion between the membrane  30  and the object to be displaced is partially due to the pressure acted by the membrane  30  as a result of its deformation in proximity of the object and partially due to dry adhesion mechanisms. Dry adhesion is based on van der Waals forces created at the surface of the membrane  30 . These van der Waals forces, based on electric dipole interactions, can be enhanced by means of electro dry adhesion. As such, electro dry adhesion can increase the preload of the membrane by exerting an electric force toward the object to be lifted. For this purpose, electrodes can be embedded into the membrane  30  and charged accordingly to increase the preload and to reduce the pressure applied on the object by the membrane. 
     More specifically, the membrane  30  may be specifically designed to provide attractive and/or repellant forces independent of its deformation. Here, the membrane  30  will further comprise a micro-featured surface adapted to provide dry adhesion, and at least one conductive material adapted to provide electrostatic adhesion. A voltage is applied to the conductive material(s), providing an attractive force to self-preload said micro-featured surface, a resistive force to self-peel said micro-featured surface, or alternating said voltage to self-clean said micro-featured surface. The membrane may comprise a conductive polymer, rubber or silicone rubber or a composite polymer, rubber, or silicone rubber material with embedded conductive particles such as carbon black, carbon nanotubes, silver particles, or other conductive materials, and one electrode. 
     In the preferred embodiment, the means for changing the volume or shape of the chamber  20  comprises a piston  40 . The piston  40  will be positioned on the closed end  21  of the chamber  20  and will change the volume within the chamber  20 . More specifically, the piston  40  will create either a positive or negative pressure within the chamber  20 , thereby deforming the membrane  30 . The piston  40  may or may not be attached to the membrane  30 . The deformation of the membrane  30  will be maintained as the object is displaced through the controlled position of the piston  40 . The piston  40  may further include piston seals to prevent any gas, liquid, or phase-changing material  41  from escaping. The piston  40  will move linearly and can also be positioned on the sides of the chamber  20 . The piston  40  may further comprise a positioning sensor  142  at its distal end  42  for detecting and positioning the device relative to the designated object. 
     In an alternative embodiment, the means for changing the volume or shape of the chamber  20  comprises a phase-changing material  41 . Here, the chamber  20  will be filled with the phase-changing material  41 , which will have a gaseous state and a liquid state. A flux of the phase-changing material  41  will deform the membrane. Just as before, the deformation of the membrane is maintained through the controlled flux of the phase-changing material. In a further alternative embodiment, both the piston  40  and the phase-changing material  41  may be used in conjunction to deform the membrane and maintain this deformation. 
       FIGS. 1-5  illustrates an embodiment where the piston  40  is attached to the membrane  30  directly. In  FIG. 1 , the deformation of the membrane  30  is maintained by the piston  40  itself.  FIG. 2  further comprises concentric chambers  20  such that the area of the membrane  30  in contact with the object can be better controlled.  FIGS. 3 and 4  illustrate the chamber  20  having a conical shape for better engaging the object to be displaced. More specifically,  FIG. 3  illustrates the device where the piston  40  is projected outward as it approaches to the object to be displaced.  FIG. 4  represents the same embodiment with the piston  40  withdrawn, engaging the object and providing the necessary grip for displacement. 
     In  FIG. 4 , the bulging of the membrane  30  determines that a positive pressure is being applied, and as such, the gripping force can be measured and adjusted by monitoring the pressure within the chamber  20 . Alternatively, when the object to be lifted presents a surface of contact which is much larger that the size of the membrane  30 , the same mechanism of action might determine grip through a mechanism similar to a suction cup, determined by the decreased pressure in the region immediately below the piston  40  between the membrane  30  and the designated object.  FIG. 5  represents a more complex embodiment in which the open end  22  of the chamber  20  is determined by a ring with an adjustable diameter. 
       FIGS. 6-10  illustrate the valve  23  which will control the flux of a gas or a phase-changing material  41 . In these embodiments, the piston  40  is not attached directly to the membrane  30 . Here, the deformation of the chamber  20  is maintained through the flux of the gas or the phase-changing material  41  in and out of the chamber  20 , but can also include additional deformation from the movement of the piston  40 . 
     While  FIGS. 1-5  illustrate embodiments where the piston  40  is directly attached to the membrane  30 , thereby directly deforming the membrane  30 ,  FIGS. 6-10  illustrate embodiments where the piston  40  is not directly attached to the membrane  30 . Here, the deformation of the membrane  30  is maintained through the pressure exerted on it by a gas (such as air) or by a phase-changing material  41  within the chamber  20 . As such, all embodiments, including  FIGS. 1-5 , may operate with or without the piston  40  directly attached to the membrane  30 . Conversely, embodiments illustrated in  FIGS. 1-5  may also include a valve  23 . 
       FIGS. 6-7  illustrates just such an embodiment, where the embodiment illustrated in  FIG. 5  further includes a valve  23 . The presence of a piston  40  and a valve  23  to regulate the pressure inside the chamber  20  is one of the most advantageous configurations, as it allows the device to have a more precise control over the deformation of the membrane  30  and the pressure exerted on the object to be displaced.  FIG. 6  illustrates the piston  40  projected outward toward the designated object, while  FIG. 7  illustrates the piston  40  withdrawn.  FIG. 8  illustrates a second valve for introducing and/or releasing gas or phase-changing material  41  into the chamber  20 .  FIGS. 9-10  illustrate embodiments without a piston  40 , relying only on gas or phase-changing material  41  for deforming the membrane  30 . 
       FIG. 11  illustrates an embodiment where there is no need of solid walls within the chamber  20 . This embodiment can also be mirrored in  FIGS. 6-10 . Here, the chamber  20  will be first filled with the phase-change material  41  in its fluid state so that the membrane  30  can passively comply with the object to be displaced. During this phase, the valve  23  can be opened to allow the flux of phase-change material  41  into or out of the chamber  20 , if a volume change of the membrane  30  is needed. Once the maximum area of contact has been established, the phase-changing material  41  will be converted to its solid form in order to maintain the deformation and position of the membrane  30  throughout the displacement of the object. Finally once the destination has been reached, in order to disengage the object, the phase-changing material  41  would be again converted to its fluid phase and the membrane  30  allowed detaching from the object. 
     The adaptability of the membrane  30  allows for the displacement of objects of different sizes with the same size of membrane and apparatus. However, an increased range of application is reached by employing an adaptable open end  22  of the chamber  20 . To achieve such adaptability, several alternative embodiments may be used. First, as illustrated in  FIG. 2 , a series of concentric cylinders  20  can be used, which allow handling a larger size distribution of objects. However, they might constitute an obstacle if the objects to be displaced are close to each other, especially in the configuration utilizing the smaller cylinder  20 . 
     Alternatively, and as illustrated in  FIGS. 5-11 , the perimeter of the open end  22  may have a variable diameter. This is achieved with a ring made of a circular cylinder which is able to slide into itself or around itself. The control of the ring&#39;s size can be achieve through extensible pods, through which the ring is attached to the chamber  20  or in any other way that would uniformly modulate the ring&#39;s size. As the membrane  30  is in contact with the chamber  20 , it is possible to facilitate its extension by placing wheels or ball bearings along the ring such that the increase or decrease in size of the ring does not cause the membrane  30  to stretch or shrink non-uniformly, thus causing unwanted stress on it or undesirable regions where the membrane  30  responds differently. 
     In a further alternative embodiment, the ring may be made of a uniformly deformable material such as an inflatable tube or rubber ring. This embodiment is illustrated in  FIGS. 8, 10 , &amp;  11 . In this embodiment, the increase in diameter of the ring is constant at every point, and as such, no further system is needed to maintain a constant strain of the membrane  30 . The inflatable tube is designed in such a way that the flux of air into or from it regulates the diameter of the ring formed by the tube. 
     In yet a further alternative embodiment, a conical shape of the open end  22  of the chamber  20  can be used, as shown in  FIGS. 3-4 . Here, an object can be approached without disturbing the neighboring objects. In this particular scenario, the shape of the cone trunk can be interchangeable to be able to adapt to a wide variety of objects maintaining the same apparatus. In this embodiment, however, the membrane  30  is secured to the outside edges of the open end  22  to avoid its bulging outward, potentially interfering with neighboring objects. 
     While the above description contains specific details regarding certain elements, sizes, and other teachings, it is understood that embodiments of the invention or any combination of them may be practiced without these specific details. Specifically, although certain materials are designated in the above embodiments, any suitable materials may be used. These details should not be construed as limitations on the scope of any embodiment, but merely as exemplifications of the presently preferred embodiments. In other instances, well known structures, elements, and techniques have not been shown to clearly explain the details of the invention. 
     The above detailed description of the embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed above or to the particular field of usage mentioned in this disclosure. While specific embodiments of, and examples for, the invention are described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. Also, the teachings of the invention provided herein can be applied to other systems, not necessarily the system described above. The elements and acts of the various embodiments described above can be combined to provide further embodiments. 
     Changes can be made to the invention in light of the above “Detailed Description.” While the above description details certain embodiments of the invention and describes the best mode contemplated, no matter how detailed the above appears in text, the invention can be practiced in many ways. Therefore, implementation details may vary considerably while still being encompassed by the invention disclosed herein. As noted above, particular terminology used when describing certain features or aspects of the invention should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the invention with which that terminology is associated. 
     While certain aspects of the invention are presented below in certain claim forms, the inventor contemplates the various aspects of the invention in any number of claim forms. Accordingly, the inventor reserves the right to add additional claims after filing the application to pursue such additional claim forms for other aspects of the invention.