System, method and apparatus for a single axis load cell module

Abstract

An apparatus, system and method of providing a single access load cell module. The embodiments include: first and second flexures, each having therethrough a plurality of circumferentially parallel cutouts to impart targeted compliance of each of the first and the second flexures; and a core sandwiched between the first and second flexures. The core may include: a travel lock cage that at least partially limits compliance of the first and second flexures; and a load cell element that measures forces exerted by a load.

Description

SYSTEM, METHOD AND APPARATUS FOR A SINGLE AXIS LOAD CELL MODULECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. provisional application No. 63 / 569,769, filed March 26, 2024, incorporated herein by reference in its entirety.BACKGROUNDField of the Disclosure

[0002] The disclosure relates to manufacturing processes, and, more particularly, to a system, method and apparatus for a single axis load cell module.Description of the Background

[0003] A load cell is an electro-mechanical sensor that is used to measure force or weight. A load cell generally relies upon transference between an applied force, material deformation and the flow of electricity.

[0004] Load cells are essential to many industrial and commercial processes, from automating car manufacturing to weighing items at a grocery store checkout. One key area in which load cells are often employed is in association with manufacturing processes, such as to monitor the load on a robotic end effector that carries a work item through process tasks.

[0005] A robotic end effector is a peripheral device that attaches to a robot’s wrist, allowing the robot to interact with the process task. End effectors are generally mechanical or electromechanical, and may serve as grippers, process tools, or sensors, by way of example.

[0006] Grippers may be vacuum grippers, magnetic grippers, needle grippers, or the like. Process tools may include robot welding tools, robot machining tools, robot painting tools, 3D printing tools, and the like. Sensors may be, by way of example, ultrasonic sensors, laser scanners, 2D and 3D cameras, or infrared sensors.

[0007] Robotic end effectors may be tasked with providing telemetry data, such as data on forces in specific vectors, while positioning parts during the aforementioned processes. Typically, the load cell measures these forces while a separate housing guides the forces and protects the load cell. However, numerous sources of data contamination are inherent in this prior art load cell system design, particularly due to the load cell housing that limits the distribution of forces outside of the acceptable directions.

[0008] For instance, a housing that uses bearings of various types incurs parasitic drag and hysteresis as well as presenting disadvantages due to large size, excess weight, and instability of the axis to be isolated for measurement. Industry has addressed these issues with force-torque sensors, but these devices have limited resolution in the lower force ranges and can become oversaturated and damaging, particularly in a fast-moving application on a robot.

[0009] Therefore, the need exists for an improved single axis load cell module.SUMMARY

[0010] The disclosure is directed to and includes an apparatus, system and method of providing a single access load cell module. The embodiments include: first and second flexures, each having therethrough a plurality of circumferentially parallel cutouts to impart targeted compliance of each of the first and the second flexures; and a core sandwiched between the first and second flexures.

[0011] The core may include: a travel lock cage that at least partially limits compliance of the first and second flexures; and a load cell element that measures forces exerted by a load on at least the first flexure based on at least compliance of the first flexure. The travel lock cage may comprise at least one locking piston and a flange against which the at least one locking piston presses. Pressure may be applied by elements of the core upon a periphery of each of the first and the second flexures, thereby substantially preventing compliance of the peripheries.

[0012] The load cell element may comprise a S-beam type load cell. The first and the second flexures may be formed of sheet or spring temper steel. The first and the second flexures may alternatively be formed of laminated fiberglass.

[0013] Also included may be a robot connection flange capable of connecting the module to a robotic end effector. The robot connection may enclose at least one of the first and the second flexures.

[0014] Moreover, ones of the disclosed single-axis load cell modules may be stacked or staggered, in series or in parallel. Accordingly, multiple single-axis load cells may provide a multi-axis load cell.

[0015] Therefore, the disclosure provides an improved single axis load cell module.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The disclosure provided herein describes and includes the accompanying drawings, in which like numerals may represent like elements, and wherein:

[0017] FIGs. 1A, IB and 1C illustrate flexures and a core for a single axis load cell module;

[0018] FIG. 2 illustrates aspects of an exemplary core of a single axis load cell module;

[0019] FIG. 3 illustrates aspects of an exemplary single axis load cell module;

[0020] FIG. 4 illustrates an exemplary load cell module; and

[0021] FIGs. 5 A and 5B illustrate an exemplary load cell module.DETAILED DESCRIPTION

[0022] The figures and descriptions provided herein may have been simplified to illustrate aspects that are relevant for a clear understanding of the herein described devices, systems, and methods, while eliminating, for the purpose of clarity, other aspects that may be found in typical similar devices, systems, and methods. Those of ordinary skill may thus recognize that other elements and / or operations may be desirable and / or necessary to implement the devices, systems, and methods described herein. But because such elements and operations are well known in the art, and because they do not facilitate a better understanding of the present disclosure, a discussion of such elements and operations is not provided herein. However, the present disclosure is deemed to inherently include all such elements, variations, and modifications to the described aspects that would be known to those of ordinary skill in the art.

[0023] Description is provided throughout so that this disclosure is sufficiently thorough and fully conveys the scope of the disclosed embodiments to those who are skilled in the art. Numerous specific details are set forth, such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. Nevertheless, it will be apparent to those skilled in the art that certain specific disclosed details need not be employed, and that embodiments may be embodied in different forms. As such, the embodiments described are exemplary in nature, and should not be construed to limit the scope of the disclosure.

[0024] The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. For example, as used herein, the singular forms "a", "an" and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having," are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

[0025] When an element or layer is referred to as being "on", "engaged to", "connected to" or "coupled to" another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly engaged to", "directlyconnected to" or "directly coupled to" another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0026] Although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. That is, terms such as "first," "second," and other numerical terms, when used herein, do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the exemplary embodiments.

[0027] To overcome the limitations of the conventional paradigm for load cell systems that uses bearings and bearing supports, which have associated therewith the aforementioned series of disadvantages, the embodiments use flexure plates to enforce the axis being measured. The flexure travel axis and the load cell measurement axis are aligned and isolated to operate in one uniform direction. The use of these diaphragm flexure plates, and particularly dual flexure plates, in the embodiments provides this isolation of the travel axis in one axis and prevents travel in other axes. The disclosed solution thus provides a short travel stroke due to the use of flexures, in conjunction with a dedicated load path, all in a toughened casing that protects the disclosed load cell module from errant vectors and loads.

[0028] It will be appreciated that the embodiments provide a flexure-based load cell module capable of deflection responsive to even a minute load, such as on the order of 25 to 50 microns, and including down to the sub-micron scale. The flexure-based design provides high accuracy and repeatability. Of course, due to this high accuracy and repeatability, the disclosed embodiments may be suitable to not only sense loads on the order of microns, but can also capably sense to instrument size loads or even larger payloads. In the embodiments, providing a flexure-centric load cell module prevents the formation of an indentation or, eventually, a hole responsive to repeated placement of even minute loads, but such wear does typically occur in the load cells of the known art.

[0029] A further advantage provided by the use of flexures in the embodiments is the non-use of bearings, which prevents bearing lash. In bearing lash, the bearings of prior art load systems wear out over time. Indeed, due to the extremely short stroke of movement of the flexures in the disclosed embodiments, the embodiments may provide a significant if not nearly unlimited lifetime for use of the disclosed load cell module. Needless to say, this contribution to improvements in up-cycle time for processes using the disclosed load cell is a significant advantage over the known art, in which lack of available sensing, such as due to load cell damage, frequently causes down-cycle time.

[0030] Moreover, the use of ball bearings and / or linear bearing bushings in the known art takes up significant physical space in a typical load cell system. Consequently, the use of these elements in the known art prevents a thin and compact footprint for the load cell module, which is particularly disadvantageous in use-contexts in which a robotic end effector must maneuver and / or support the weight and size of the load cell module.

[0031] Yet further, the use of bearings and bushings in the known art leads to significant data contamination of sensing performed by the load cell. This is particularly the case as the bearings and bushings begin to wear, and is further exacerbated by the wear into and through the load cell that often occurs after repeated loading, as referenced above.

[0032] Of particular note, by using flexures in a two-stack configuration, for example, minimal compliance in solely the z-axis responsive to even a minute load can be readily measured, while the x, y and theta axis stay locked in an orthogonal correct plane. Further, the flexure design is inexpensive to fabricate, as it can be laser or waterjet cut from sheet and / or spring temper steel, or from laminated fiber glass for non-magnetic applications, by way of nonlimiting example. The paired flexure plates in the load cell module replace instrument grade or preloaded bearings, and thus eliminate the typical limitations of prior art bearing-based systems, such as the need for lubrication and the production of particulate.

[0033] The flexure design provides a compact and lighter device compared to the known art, at least due to the reasons discussed herein. This is highly advantageous during use of the load cell module with robotic end effectors, as integration is greatly simplified, and performance enhanced, by placement of the disclosed compact, light load cell module as a compact puck between the end effector and a robotic wrist.

[0034] To protect the load cell module, such as while in transit between points, the load cell module may be equipped with a lockout actuator, i.e., a travel lock cage, that prevents travel of the sensing components while the measurement function is not required, such as at a pick position. This lockout mode protects the load cell module from overloads, general wear and processing of random data.

[0035] Multiple ones of the disclosed load cell modules can also be stacked to support measuring in additional axes, such as the theta or the x axis. This can be done by nesting one module within or on top of a second one, by way of non-limiting example. Flexure designs that permit only radial motion, such as when used in conjunction with a linear axial flexure, may also provide a multi-axis and blended axis load module.

[0036] Now with particular reference to the exemplary embodiment of FIGs. 1A, IB and 1C, illustrated are the flexure components 19 to the embodiments. As shown, the load cell module 100 disclosed comprises multiple flexures 19. These flexures 19 may be placed “atop” and “on bottom” of a core 110 of the disclosed load cell module 100.

[0037] The outer portions 19a of the flexure components 19 may be connected to a housing, or an outer ring, as discussed further below, of the core 110 of the load cell module. The inner portion 19b of the flexures then are free to provide sensitivity to the load correspondent to the compliance of the flexures and the effects thereof on the load cell element, and to thereby effect load measuring capabilities in conjunction with the load cell. Simply put, the core components 110 of the load cell module 100 are “sandwiched” between the top and bottom flexures 19, the peripheral portions 19a of which remain stationary in the embodiments.

[0038] By mounting the outer flexure portions 19a to a housing or core component(s), deflection is isolated to solely to the axial travel direction, i.e., the z axis. Deflection is thereby prevented in the x, y or theta axis. This not only enhances the robustness of the components disclosed, but further prevents misdetection and individual component failure, both of which are frequent occurrences in the load cells of the known art, as referenced above.

[0039] As is made more clearly evident in relation to FIG. 2 in conjunction with FIG. 1 , the flexures 19 may act as a pair of circular leaf springs atop and below the load cell core 110.The circular leaf springs 19 may include a series of circumferentially parallel cutouts 119 to impart the specifically desired flexing for a given load to be sensed. This cutout design 119 may also be particularly resistant to unwanted movement outside of the z-axis for given load levels. Further, limiting movement solely to the z-axis not only maintains alignment, but also improves measurement sensitivity and protects components from damage.

[0040] The two flexure design allows solely vertical compliance responsive to deflection and loading. Of course, those of skill in the pertinent arts will appreciate, in light of the discussion herein, that axial compliance limitations may be defined based on the use-context of the embodiments. That is, although the discussion herein focuses on limiting compliance to a single axis, namely the z axis as illustrated, the axis of compliance may vary by directionally varying the placement of the load cell, such as on an end effector, and / or such as by staggering and / or stacking the load cell modules.

[0041] In short, multiple flexures and cores may be stacked or staggered, in series or in parallel, in order to provide multiple axes, or multiple lines along an axis, of compliance. The stacking or staggering of multiple load cell modules can provide two or more guided axes coupled or nested to allow movement in a specific axis or axes, with a load measurement in each axis. Accordingly, stacked and staggered embodiments may provide scalability for a range of applications.

[0042] With particular reference now to FIGs. 1 and 2, the deflection and loading of the flexures is sensed particularly by inclusion of several different components in the load cell core 110. By way of example, an internal flange or flanges 324 may be provided to prevent extensionof the load cell module or its components, and particularly of the flexures, in unwanted directions. Further, an internal travel lock cage 220, effectuated, in part, by the flange or flanges 324, and in part by pistons 222, may be provided to prevent movement of components and deflection when the load cell module 100 is not in use. Similarly, the use of travel locking components may prevent overtravel of the flexures, which in turn prevents damage to the load cell module.

[0043] For example, a travel stop cage 220 may immediately surround the load cell 302, and may be effectuated by a travel stop flange 324 and travel lock pistons 222. Travel lock pistons 222 may serve as travel cage 220 actuators, for example, with actuation thereof preventing movement of the travel cage in relation to the robot flange. The travel stop flange 324, in conjunction with actuation of pistons 222, also prevents flexing of the flexures 19 and / or responsiveness of the load cell 302. That is, the travel stop flange may particularly prevent unwanted movement by the travel cage 220 toward the robot flange 321, in that actuation of the travel stop pistons 222 prevents movement of the travel cage 220 against the flange 324 in the z- axis beyond that which is desirable for the load cell module.

[0044] The travel lock pistons 222 may be, by way of non-limiting example, single action pistons having wound springs / disc springs to provide the retracting action. As the travel stop flange 324 prevents movement of the load cell components beyond the acceptable travel range of the load cell towards from the robot flange direction upon actuation of pistons 322, so too do the spring pistons 222 prevent movement of the other flexure and travel cage 220 beyond the acceptable range towards the load, at least in that the travel lock pistons 222 will, upon actuation, bottom out on the second travel flange 250 to prevent further motion away from the robot flange direction and toward the load. As such, the embodiments may provide a travel lock“cage” 220 of sorts, with the travel stop flange 324 bounding movement on one side, and the second flange 250 bounding movement on the other side, upon actuation of travel pistons 222 sandwiched therebetween. Of course, other manner of providing a travel lock may be evident to the skilled artisan based upon an understanding gained from the present disclosure.

[0045] Travel locking may occur at various points throughout processes employing the disclosed load cell module. By way of non-limiting example, the load cell core may be locked, such as to avoid noise measurements and / or to avoid damage, when approaching the pick position to pick a load, or while a load is in transit, such as upon an end effector, to a process position. This lock and / or breakaway functionality may be sensed so as to halt a work cell recipe and prevent tooling damage.

[0046] Also as illustrated, the load cell core may include a center pin 254 in the component body between flexures 19. The center pin 254 may reside at the center of the component body, such as adjacent the load cell element 302, and from that position may link the elements in the component body such that separation is impeded but breakaway is allowed. This not only prevents malfunction and mis-measurement, but also precludes catastrophic failure.

[0047] At the center of the load cell core 110 on the load cell flexure side is the load cell 302, i.e., the sensing element. The load cell element 302 makes the sensor measurements provided by the load cell module, i.e., the load cell element senses deflection of the flexure(s). The load cell may be an S-bridge type load cell element, or any suitable load cell type known to those skilled in the art in light of the discussion herein. The load cell element may be insulated and / or encased 260, such as to provide protection from damage to the sensitive element.

[0048] FIG. 3 illustrates a breakout view of aspects of an embodiment of the disclosed load cell module 100. Included in the illustration are the referenced load cell core 110, placed between upper and lower flexures 19.

[0049] More specifically, load cell adapter 301 may serve to allow a precise fitting of load cell 302 into the load cell module 100. As referenced, load cell 302 may be a S-beam type load cell, or may be any other suitable load cell element known to those skilled in the art. The load cell may reside within the housing in association with insulators 307, such as o-rings, to maintain core alignment, for example.

[0050] Top and bottom flexures 19 may be provided on either side of the core 110. Space between the flexures, and the alignment of the core therebetween, including of the load cell 302 within the core 110, may be maintained by, for example, a flexure spacer 324 and spacer ring 320. In some embodiments, spacer ring 320 may, for example, be flexible.

[0051] A top cover 323 may enclose the flexures 19 and core 110. This top cover may further include adaptors, such as band clamps 312 and / or plates 321, to further maintain alignment and location of the elements of module 100, and / or to provide an interface to, for example, an end effector.

[0052] Referring now to FIGs. 1-3, the travel stop 324 may be tied to the spacer ring 320. One flexure 19 may abut spacer ring 320 and plate / flange 324, and may thus be flexed until spacer ring 320 is pressed to plate 324. Likewise, the other flexure 19 may flex “downward” until it abuts spacer ring 320, The travel stop pistons 222 in conjunction with second flange / plate250 may prevent overtravel compression of the core 110 about the load cell itself.

[0053] FIG. 4 illustrates the full load cell module 100, including the flexures and the core enclosed between the top cover 323 under the robot connection flange 321 and the lower plate 250. That is, the spacer ring 320 at least partially provides the aforementioned housing that encloses the full load cell module 100 between the top cover 323 and lower plate 250.

[0054] FIGs. 5 A and 5B illustrates the load cell module 100 coupled to a robotic end effector 502. Of note, the robotic end effector 502 may connect to the top cover 323 or the lower plate 250, and the connectivity location and manner may depend on the application in which the load cell module 100 is used.

[0055] In the foregoing detailed description, it may be that various features are grouped together in individual embodiments for the purpose of brevity in the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that any subsequently claimed embodiments require more features than are expressly recited.

[0056] Further, the descriptions of the disclosure are provided to enable any person skilled in the art to make or use the disclosed embodiments. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein, but rather is to be accorded the widest scope consistent with the principles and novel features claimed as follows.

Claims

CLAIMSWhat is claimed is:

1. A load cell module, comprising: first and second flexures, each having therethrough a plurality of circumferentially parallel cutouts to impart targeted compliance of each of the first and the second flexures; a core sandwiched between the first and second flexures, the core comprising: a travel lock cage that at least partially limits compliance of the first and second flexures; a load cell element that measures forces exerted by a load on at least the first flexure based on at least compliance of the first flexure.

2. The module of claim 1, the travel lock cage comprising at least one locking piston and a flange against which the at least one locking piston presses.

3. The module of claim 1, the core further comprising a spacer ring that at least partially encloses the core.

4. The module of claim 3, the spacer ring pressing upon a periphery of each of the first and the second flexures, thereby substantially preventing compliance of the peripheries.

5. The module of claim 1, the load cell element comprising a S-beam type load cell.

6. The module of claim 1, at least one of the first and the second flexures being formed of steel.

7. The module of claim 6, wherein the steel is sheet steel.

8. The module of claim 6, wherein the steel is spring temper steel.

9. The module of claim 6, wherein both the first and the second flexures are formed of steel.

10. The module of claim 1, at least one of the first and the second flexures being formed of fiberglass.

11. The module of claim 10, wherein the fiberglass is laminated.

12. The module of claim 10, wherein both the first and the second flexures are formed of laminated fiberglass.

13. The module of claim 1, wherein the plurality of circumferentially parallel cutouts is laser cut.

14. The module of claim 1, wherein the plurality of circumferentially parallel cutouts is wateijet cut.

15. The module of claim 1, further comprising a robot connection flange capable of connecting to a robotic end effector, the robot connection flange enclosing at least one of the first and the second flexures.

16. The module of claim 15, further comprising a top cover that at least partially encloses at least one of the first and the second flexures, the top cover being capable of interfacing to the robot connection flange.

17. The module of claim 16, wherein the top cover comprises band clamps capable of sealing the top cover over the at least one of the first and the second flexures.

18. The module of claim 1 , further comprising insulation to maintain an alignment of the load cell element within the core.

19. The module of claim 18, wherein the insulation comprises a plurality of o-rings.

20. The module of claim 1, wherein the core further comprises a center linking pin proximate to the load cell element and capable of impeding misalignment of elements within the core.

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