Patent Application
20090179445
Conventional grippers are typically comprised of intricate, highly machined parts that render the assembly expensive and difficult to manufacture.
Current commercial designs come from the heavy machinery markets and have been scaled down to be used on small parts. As these designs were scaled down they retained the machine design features and are not designed for instrument applications.
Known commercial grippers require high pneumatic pressures or servo motor drives to operate the gripping action. These actions are full open and full closed positions, or require position sensors integrated into the servomotors which increases the complexity of the gripper assembly.
High pneumatic pressures can pose serious safety risks. Furthermore, pneumatic systems add to the complexity and cost of an assembly and require periodic maintenance (e.g., to replace seals, valves, compressors, regulators, filters etc).
The general size of most gripper assemblies makes them undesirable for smaller applications. Moreover, custom designing, revisions or implementing modifications to a standard gripper are cost prohibitive.
Accordingly, there remains a need for an improved gripper assembly that is relatively simple, inexpensively constructed, versatile, and suitable for smaller applications.
The present invention provides a gripper assembly including a rotary motor and a linear motor disposed within the rotary motor. The linear motor includes a longitudinally slidable driven push rod and a pair of oppositely moving fingers. Each of the fingers is pivotally attached adjacent an end of the longitudinally slidable push rod. The push rod is moveable upon actuation of the linear motor to cause the fingers to move symmetrically toward and away from each other. This motion may be pivoting action about the pins or along linear guides via linkages. Upon actuation of the rotary stepper motor, rotational movement of the gripper fingers either on or about the center axis of the rotary motor.
The present invention further provides a gripper assembly having a motor end, a gripper end, and a longitudinal axis, the gripper assembly including a gripper body, a linear motor at least partially disposed within the gripper body, and a longitudinally slidable motor push rod substantially disposed within the gripper body.
The linear drive is mounted within the rotary motor, with its' body part mounted within the rotor of the rotating drive and utilizing the bearings of the rotary drive as design elements.
The push rod has a motor end in communication with the linear motor and a gripper end. The gripper assembly further includes a pair of oppositely moving fingers, each of the fingers having a pivot end and a mid-section, the pivot end of each finger being pivotally attached to the flange of the gripper body. The gripper assembly also has a pair of oppositely moving linkages, each of the linkages having one end pivotally attached to the longitudinally screw driven push rod adjacent the gripper end and another end pivotally attached to the mid-section of the respective finger.
The gripper element has several methods of translating the linear action of the linear motor to a gripping action.
This linkage design may attach between the pivot pin and the fingers (3rd class lever assembly) or be attached behind the pivot pin to provide different mechanical advantages (2nd class lever assembly). The arm may also be a bell-crank design to vary the clamping characteristics.
A parallel gripping head design where the grippers travel along guides is an option for gripping and processing larger sized items.
The push rod is moveable upon actuation of the linear motor in a first direction toward the motor end of the assembly so that the fingers move symmetrically toward each other and in a second direction toward the gripper end of the assembly so that the fingers move symmetrically away from each other. This allows for internal and external gripping action.
The present invention also provides a gripper assembly having a motor end, a gripper end, and a longitudinal axis, the gripper assembly including an annular gripper body having, a linear slidable motor at least partially disposed within the gripper body, and a rotary motor encasing the linear motor. A longitudinally slidable push rod is substantially disposed within the gripper body, the push rod including a motor end in communication with the linear motor and a gripper end. The gripper assembly further includes a pair of oppositely moving fingers, each of the fingers including a pivot end and a mid-section, the pivot end of each finger being pivotally attached to the flange of the gripper body. The gripper assembly also has a pair of oppositely moving linkages, each of the linkages having one end pivotally attached to the longitudinally slidable push rod adjacent the gripper end and another end pivotally attached to the mid-section of the respective finger. Upon actuation of the linear motor, linear movement of the longitudinally slidable push rod in a direction toward the motor end of the assembly causes the fingers to move symmetrically toward each other, and linear movement of the longitudinally slidable push rod in a direction toward the gripper end of the assembly causes the fingers to move symmetrically away from each other. Upon actuation of the rotary motor, rotational movement of the gripper body causes the fingers to synchronously rotate.
In yet another embodiment of the present invention, a gripper assembly may be provided as described above in the previous paragraph with a rotary motor encasing a linear motor.
The foregoing summary, as well as the following detailed description, will be readily understood in conjunction with the appended drawings which illustrate the preferred embodiments of the invention in the drawings.
Certain terminology is used in the following description for convenience only and is not considered limiting. Words such as “front,” “back,” “top,” and “bottom” designate directions in the drawings to which reference is made. This terminology includes the words specifically noted above, derivatives thereof, and words of similar import. Additionally, the terms “a” and “one” are defined as including one or more of the referenced item unless specifically noted. The phrase “at least one of” followed by a list of two or more items, such as A, B, or C, means any individual one of A, B, or C, as well as any combination thereof.
The preferred embodiments of the present invention are described below with reference to the drawing figures where like numerals represent like elements throughout.
Referring to
The gripper assembly 10 further includes a pair of oppositely moving fingers 34, each of the fingers 34 having a pivot end 36. The pivot end 36 of each finger 34 is pivotally attached to the gripper head 16 with, for example, respective pivot pins 40. The gripper assembly 10 also has a pair of oppositely moving linkages 42, each of the linkages 42 has one end that is pivotally attached to the longitudinally screw driven push rod 24 adjacent its gripper end 28 and another end pivotally attached to the mid-section of the respective finger 34 with, for example, respective pivot pins 44. The securing devices of the pivotal attachments of the present invention, however, are not limited to pivot pins 40, 44, and may include any type of rotational or hinge-like device suitable to adequately achieve the desired pivotal functions having kinematic design features such as paring links designed to increase motion or increase strength or reverse the direction of the drive element.
As represented in
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As represented in
In use, the push rod 24 is moveable upon actuation of the motors 22, 30. More specifically, upon actuation of the linear motor 22 linear movement of the longitudinally screw driven push rod 24 in a direction toward the motor end 12 of the assembly 10 causes the fingers 34 (through their respective pivotal connections to the gripper head connecting flange 18 and to the push rod 24 through the linkages 42) to move symmetrically toward each other. Such movement enables the fingers 34 to grip an object. Conversely, linear movement of the longitudinally screw driven push rod 24 in a direction toward the gripper end 14 of the assembly 10 causes the fingers 34 (through their respective pivotal connections to the gripper head connecting flange 18 and to the push rod 24 through the linkages 42) to move symmetrically away from each other. Such movement causes the fingers 34 to release the object (not shown).
Generally, the clamping force of the fingers 34 of the gripping assembly 10 may range from about 18 ounces per square inch to 150 pounds per square inch, but the gripping assembly 10 of the present invention may be configured to achieve clamping forces outside this range if necessary. The gripping force ranges may be varied by varying the length of the fingers 34 and the locations of their respective pivot points and the size of the linear motor.
Actuation of the rotary motor 30 causes rotational movement of the housing 20, mounted in bearings 32A, 32B and the gripper head 16 which, in turn causes the fingers 34 to synchronously rotate. Thus, once an object is gripped by the fingers 34, it can be rotated as desired, for example, to invert a component or mix a specimen in a container. The rotational accuracy of the gripper assembly 10 of the present invention is about 0.5 degrees.
The configuration of the fingers 34 may vary depending upon the application, as illustrated by the partial side schematic views of the gripper assembly 10 represented in
The linear and rotary motors are controlled by a microprocessor and drive circuitry located on a remote printed circuit board (not shown). Each motor has a distinct drive circuitry that is instructed by the microprocessor software to incrementally pulse the stepper motor coils to rotate the rotor magnets and index the rotary or linear position of the motors to a defined location to perform an operation of gripping or rotating an object. These actions are monitored by the microprocessor through additional circuitry to monitor the electrical current, amperage, consumed for each pulse which indicated the mechanical resistance to the movement. This resistance indicated when the gripper has contacted the object or when the rotary motion has contacted a physical stop, i.e. fingers open or closed, rotation at either end of its rotation. This sensing circuit replaces the more complex encoder electrical mechanical assemblies used for positional sensing.
The object, can be any object of any shape The application defines the shape and size of the fingers 34, and may utilized to grip a variety of objects in a variety of settings, for example, in the clinical laboratory automation industry, the computer board component placement industry, and various other automated industries.
The size of the gripper assembly 10 of the present invention is relatively small as compared to known grippers. At a gripping force of 18 ounces per square inch, the size of the assembly 10 (without fingers 34) is about 2.38 inches long by 1.66 inches square. At a gripping force of 150 pounds per square inch, the size of the assembly 10 (without fingers 34) is about 4.0 inches long by 3.39 inches square.
While the preferred embodiments of the invention have been described in detail above, the invention is not limited to the specific embodiments described which should be considered as merely exemplary. Further modifications and extensions of the present invention may be developed and all such modifications are deemed to be within the scope of the present invention as defined by the appended claims.
