Weighing apparatus comprising self-erecting rocker pin load cell with restricted rotation

Abstract: Load cells (32) incorporating rocker pin configured columnar central structures within a weighing system (10) have the attribute of self-­ erecting upon being displaced from a vertical orientation due to dynamic transverse loading effects, as may be occasioned by vehicle movements onto a scale. The resultant transient vector forces thus developed have been observed to cause a rotational phenomenon in the rocker pin configured cells (32) which causes unacceptable damage to the instrumentation control communication components of the load cell system. A mounting technique for such load cells (32) is developed wherein only these rotation inducing forces are restrained, while the vertical force vectors representing valid load data are maintained in an unrestricted or uncompromised manner. In one aspect of the invention, a hexagonal form of mounting between a rocker pin neck-contact surface region and a corresponding receiver cavity achieves a fully pivoting and freely abutting contact geometry while effecting the noted restriction of rotation. In another aspect, a resilient device such as spring is loaded during restricted rotational movement of the load cell and released at the termination of the transient rotational forces to return the load cells to their initial orientation while the load cells remain under load induced compression.

Description: The present invention relates to a weighing apparatus comprising a base, a load receiving surface, at least one self-erecting rocker pin load cell having a vertically aligned longitudinal axis and upper and lower end portions formed with upper and lower contact surfaces positioned between said base and said load receiving surface, respectively, for freely pivotal supporting contact with said load receiving surface, at least one of said upper and lower end portions being received in a rocker pin receiving cavity having a peripheral side wall of a receiver, said load cell being subject to both vertical and temporary transverse force vectors creating transient rotational force vectors urging said rocker pin to rotate about said longitudinal axis, said load cell further comprising restrainer means for providing a rotationally stable reference isolated from said rocker pin, and rotation limit means in contact with said load cell and coupled with said restrainer means so as to restrict said rotation of said load cell within predetermined limits by counteracting only said rotational force vectors while not affecting the reaction of said load cell to said vertical force vector and not substantially affecting said freely pivotal supporting contact. A weighing system having at least one self-erecting rocker pin load cell being subject to both vertical and temporary transverse force vectors creating transient rotational force vectors which act to rotate said rocker pin load cell about the longitudinal axis thereof is described in EP-A2-0 315 846. An important advantage involved in these systems stems from the self-erecting characteristic of the rocker pin load cell configuration. When the normally upright rocker pin is deflected by the transverse force vector experienced within the weighing system, it will return to its upright position when the deflecting force terms are removed. A detailed description of rocker pin load cells is also provided in US-A-4,815,547. In these weighing systems, generally a number of rocker pin load cells are supported in freely pivotal abutting fashion at their lower end by the base through the medium of a receiver component or the like. From this lower contact, the cells extend in vertical columnar fashion to the upper contact surface which, again, is in freely abutting contact with the downwardly disposed surface of a platform or frame which forms the load receiving surface adopted to carry the load to be weighed. The self -erecting feature is developed by configuring the cell or pin component thereof so that the radius of curvature of each end or contact surface is greater than one-half of the total height of the pin. Supported upon such load cell structures, the scale platform and associated horizontal loading surface exhibit several degrees of freedom of movement. Thus it is necessary to accommodate for temporary transverse forces or side loads or lateral forces induced by eccentric loading. For example, when weighing vehicles such as trucks, forward movement and braking, as well as maneuvering during scale entry will be the occasion of acceleration, deceleration, and induced turning moments and the like imposed through the platform in addition to vertical weight force vectors. Typically the extent of lateral travel of the platform is restricted to within small tolerances by bumper structures. Instrumentation of the rocker pin configured load cells is provided through the media of strain gauges coupled with the columnar or rocker pin components of the structure. This instrumentation may, for example, be protected by employing conventional circuit potting procedures or, may be contained within a protective, sealed, can-like enclosure suspended about the central portion of the rocker pin configured counterforce. Necessary power source inputs to and signal outputs from the enclosed circuitry typically extends through a port or connector connected at the side of the enclosure. Requisite cabling or wiring extends from that connector to power and data gathering systems and the like. Field experience with these weighing systems has revealed that the temporary transverse or side forces associated by the noted dynamic loads will engender a turning movement in the load cells about the longitudinal or columnar axes of the rocker pin structures. This rotational movement is developed by the somewhat rolling interaction of the contact surfaces of the load cells with an associated support or platform surface. While rocker pin structuring provides for a return to vertical upon removal of transverse loads, the point of contact of such surfaces may vary to evoke a point-to-point progression, the motion of the cells being observed to be somewhat precessional in nature. Particularly where the temporary lateral forces at the weighing platform are bidirectional or, in effect, rotational, this progression of contact point positions induces turning force vectors within the load cells to promote this rotation. Such rotation can be destructive to any appurtenances extending from the load cells. In this regard, the rotation tends to stress or "wind up" cabling or wiring extending to the load cell instrumentation, causing its breakage with resultant operational loss. Necessary repair to the load cells typically involves a substantial labor investment associated, for example, with the jacking up of the platform, the correction of an affected cell and a recalibration of the weighing system. US-A-3,284-749 discloses a load cell of a different type, in which a load receiving pin is forcedly supported in a casing with its longitudinal axis forcedly maintained in parallel to the vertical direction without permitting any pivotal movement of the pin. The vertical direction of the pin is maintained by bearings fitted between the pin and the casing and by a diaphragm radially disposed between the inner circumference of the casing and the upper end of the pin. Because of the diaphragm being rigidly connected to both the pin and the casing, the pin apart from being forcedly guided in the vertical direction is also prevented from rotation relative to the casing. This type of rotational motion prevention could not be made use of in weighing apparatus having self-erecting rocker pin load cells since it would encumber the self-erecting characteristics. A weighing apparatus with a self-erecting rocker pin load cell of the above referenced type is described in US-A-2 901 235 with reference to Fig. 3 thereof. In this known embodiment a long screw radially projecting from a stationary base portion supporting the rocker pin load cell has the function of rotational stable reference while said rotation limit means is formed by an axially extending bar-shaped member fixedly mounted to the rocker pin load cell at one end thereof while the other end thereof extends down to the long screw and has a long slot formed therein accommodating the radial shaft of the long screw. With the shaft of the long screw being caught in the long slot, the rocker pin load cell is prevented from rotation while permitting pivotal movement as a result of free play of the long screw within the slot. This arrangement is, however, disadvantageous in that pivotal movement in any axial plane other than the one containing the axis of the long screw necessarily results in frictional and possibly even jamming contact between the inner wall of the long slot and the shaft of the long screw thereby exerting undesirable forces which counteract the free pivotal movement of the load cell. Moreover, the arrangement of long slot and long screw accommodated therein requires comparatively large space thereby increasing the dimensions in the heightwise direction. A further embodiment disclosed in US-A-2 901 235 with reference to Figs 6 to 12 is based on a columnar load cell which is forcibly kept in its vertical upright position without allowance for sidewise pivotal movement. In this embodiment, rotation of the columnar load cell is prevented by engagement between vertically upstanding stationary ribs with correspondingly formed notches in a downwardly cup-shaped retainer fixed to the lower end portion of the columnar load cell. This arrangement while preventing rotation of the columnar load cell is, however, not designed or appropriate for pivotal movement since such movement would cause the notches to become inclined thereby causing friction or jam with the upstanding ribs. It is an object of the present invention to further improve a weighing apparatus of the above-referenced type as to optimize the ability to allow for free pivotal movement while restricting the rotation of the rocker pin load cell within acceptable tolerances thereby not affecting the dynamic performance of the load cells themselves. According to a first aspect of the present invention, this object is attained in that said restrainer means is formed by said receiver having a lateral portion of the peripheral side wall formed of non-circular configuration and extent and configured for effecting freely pivotal abutting support of said rocker pin load cell; and said rotation limit means is formed by the lower end portion of said rocker pin load cell received within said cavity and having a peripherally disposed positioning surface with a non-circular portion corresponding with and of lesser extent than said lateral portion. Thereby, freely abutting contact between the rocker pin positioning surface and the receiving cavity side surfaces non-circular portion is permitted thereby restricting rotation of the rocker pin load cell about the longitudinal axis during the freely pivotal movement. According to a second aspect of the invention, this object is attained in that said rotation limit means comprises spring means mounted between said restrainer means and said load cell along an axis substantially transverse to said longitudinal axis for resiliently returning said load cell to an initial position subsequent to the induced rotation thereof. Here, the resiliency of the spring means is used to become resiliently loaded only by the transient rotational force vectors. As these rotational forces subside, the rotationally induced but stored energy of the spring means returns the load cell to its initial orientation, even though the load cell remains under a load-induced compressive state. This return rotational motion is achieved inasmuch as, upon removal of the vector-induced rotational forces, it has been discovered that the cells are readily rotated by relatively small spring-developed forces. According to a third aspect of the invention, the above object is attained in that said rotation limit means comprises an engaging component extending from said rocker pin load cell generally normally to said longitudinal axis; and said restrainer means comprises first and second bumper components mutually spaced apart a distance representing a predetermined limit and located for freely abutting contact with said engaging component upon rotation of said load cell. In this approach the rotation of the rocker pin containing load cell is abuttably restricted while a requisite freely abutting and freely pivoting mounting of the cells is maintained. A property of resiliency is again made use of in accordance with a fourth aspect of the invention being characterized in that said rotation limit means comprises first and second oppositely disposed resiliently deformable springs fixed to and extending outwardly from said load cell generally normally to said longitudinal axis to respective first and second bumper surfaces of said restrainer means, said first and second bumper surfaces being mutually spaced apart and positioned for freely abutting engagement with one of said first and second resiliently deformable springs upon rotational movement of said load cell toward a predetermined limit. Irrespective of the particulars of embodying the invention, the transient nature of the rotation inducing transverse force vectors allows to carry out the evaluation of the vertical force vectors representing the weight subsequent to the termination of the transient rotational vector forces. Thereby the accuracy of the weighing apparatus is not degraded by any transient effect of cell rotation. For a fuller understanding of the nature, objects and advantages of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings. Brief Description of the Drawings Fig. 1 is a perspective view of a weighing facility incorporating the features of the invention with portions broken away to reveal internal structure; Fig. 2 is a partial sectional view taken through the plane 2-2 of Fig. 1; Fig. 3 is a top partial view of a portion of the facility of Fig. 1 at the location represented by Fig. 2; Fig. 4 is a sectional view taken through the plane 4-4 in Fig. 2; Fig. 5 is a sectional view of a receiver utilized in conjunction with Fig. 4; Fig. 6 is a partial front view of a rocker pin component employed with the load cell configuration of Fig. 4; Fig. 7 is a partial sectional view taken through the plane 7-7 in Fig. 4; Fig. 8 is a sectional view of an alternate embodiment for the invention represented in Fig. 4; Fig. 9 is a partial side view of another configuration of the instant invention; Fig. 10 is a partial front view of the load cell configuration shown in Fig. 9; Fig. 11 is a partial top view of the load cell mounting configuration shown in Figs. 9 and 10; Fig. 12 is a top schematic view of another embodiment of a load cell mounting configuration according to the invention; Fig. 13 is a schematic partial top view of another load cell mounting configuration according to the invention; and Fig. 14 is a schematic and partial sectional view of still another configuration of the load cell mounting assemblage according to the invention. Detailed Description of the Invention Referring to Fig. 1, a platform weighing facility structured in accordance with the invention is revealed generally at 10. The facility 10 is configured, for example, for the purpose of weighing elongate loads such as trucks or the like. Consequently, the facility 10 is seen to be positioned such that the load receiving surface 12 is located to facilitate the entrance of trucks upon and exit therefrom. While the instant representation shows receiving surface 12 to be at ground surface, other structures may be employed. For example, surface 12 may be elevated above ground surface 14 and accessed by entrance and exit ramps. For any such design, the positioning of a truck or the like upon the surface 12 will result in the generation of both vertically imposed load vectors as well as temporary or very short term dynamic transverse loads which will be manifested as horizontal or transverse force vectors. Upon occasion, these transverse vectors of force will be of such diverse horizontal directions as to impose essentially a circular movement into the surface 12. Surface 12 is seen supported by and represents a component of a load platform represented generally at 16 which typically is provided as a rigid structure formed of steel members, one of which is shown at 18. Load platform 16 and its associated load receiving surface 12 additionally are seen to be located within a rectangularly shaped peripherally disposed rigid edge or frame 20 which extends to a horizontal surface ground base support 22. Load platform 16 and its associated load receiving surface 12 are supported above the ground base 22 by a plurality of load cell structures positionally represented in Fig. 1 at 30a-30j. These load cells at positions 30a-30j essentially are structured in identical fashion, one being revealed in perspective at position 30a as having a load cell body portion 32 disposed in vertical fashion intermediate a bracket structure 34 coupled, in turn, to load platform 18 and a lower base plate 36. Referring to Fig. 2, a side sectional view of the load cell at position 30j is revealed. In the figure, a load cell represented generally at 38 is seen to be structured having a centrally disposed rocker pin component serving as a counterforce and representing, in effect, a short vertical column, portions of which are revealed at 40. The centrally disposed portion of rocker pin component 40 contains load cell instrumentation which, in turn, is protectively sealed within a can-like enclosure 42. Of course, other instrumentation protecting techniques not involving such enclosures may be utilized. A port 44, which may be configured as an electrical connector is formed at the surface of container 42 to provide access for cabling 46 which, in turn, carries power supplies, instrumentation data lines and the like. Cabling 46 extends from the load cells at each location 30a-30j to a data collection and control facility (not shown). Load forces are transferred to the load cell 38 from the platform 16 by a bracket structure 48 which, in turn, supports an annular upper receiver 50. Correspondingly, the lower portion of rocker pin 40 is supported from a lower annularly shaped receiver 52 which is retained, in turn, within a base plate 54 coupled to ground base support 22. Thus, the given central axis of the rocker pin 40 is essentially vertical and compressively supports the load represented by the platform 16 and the load supported upon the surface 12 thereof. To assure the integrity of load transfer into each of the load cells as at 30, no transverse oriented support of the platform 16 is provided. In effect, it enjoys a freedom of movement. However, to retain essentially a vertical orientation for the axes of the rocker pin counterforce components of the load cells as at 38, transversely oriented bumper structures are provided with the facility 10. These structures will limit transverse motion in either of the major horizontal axes to a select small value, for example 1/16 inch (1.6 mm). One degree or axial orientation of such restraint is provided by the bumper structure represented generally at 56. Figs. 2 and 3 show this structure to be comprised of an angle bracket 58 secured by bolts 60 to the platform 16 in a vertical orientation. Bracket 58 carries a carefully shimmed contact bolt 62. Contact face of Bolt 62 is so shimmed that the contact face thereof is spaced the noted preselected distance from a contact surface of a stud 64 fixed in upstanding fashion to plate 54. In similar manner, a bumper structure 66 is provided for limiting movement of platform 16 along the normally disposed major transverse axis. This bumper structure, as represented at 66 is comprised of a shimmed contact bolt 68 coupled to a bracket 70 which is fixed, in turn, to one of the beams of platform 16. The contact surface of bolt 68 is thus spaced a predetermined limiting distance from a contact surface associated with edge structure 20. Several such bumper structures as at 56 and 68 may be incorporated within a facility as at 10 depending upon the desires of the designer. Notwithstanding the very limited degree of horizontal or transverse movement thus acceded to the platform structure 16, it has been observed that a rotational force vector will be imparted to the rocker arm configured counterforce component 40 occasioned by induced transverse and temporary dynamics generally occurring with the movement of loads such as trucks onto the platform load receiving surface 12. In effect, a precessional form of movement is imparted into the columnar rocker pin counterforce components. The latter type movement occurs as these transverse load induced forces evoke a somewhat circular movement in the platform 16. While this movement is imparted into the load cells which, themselves, are unrestrained from any such movement, it is the nature of the rocker pin structure to self-erect or self-restore to a vertical orientation. However, as this return to vertical columnar orientation occurs, the positions of contact at the radiused surfaces of the rocker pin counterforce components will alter very slightly to the extent that, upon being restored to vertical, the points of contact between the platform and rocker pin and conversely between the lower receiver and the rocker pin may alter very slightly. This attribute of repositioning the contact point is discovered to induce a rotational vector into the load cells which, albeit transient in nature, represents a cumulative rotational effect. While such rotation may be bidirectional, it is statistically non-cancelling to the extent that the cabling as at 46 may commence to be stressed to breakage and/or to wind about enclosures 42 to effect a disruption of communication with control features of the weighing facility 10. Notwithstanding the presence of such implements as enclosure 42, the rotation of the load cell counterforce components occurs to cause such breakage and instrumentation damage. Because such induced rotational vectors are transient in nature, as they cease to occur the load cells return to a purely compressive state wherein no rotation is induced. It has been observed that, in view of the point contact support at hand, rotation of of the load cells, for example by hand, is quite simply carried out notwithstanding a vertically oriented imposition of very high loads upon them. The approach of the instant invention is to restrict only the rotational movement of the load cells while retaining all of their attributes for self-erecting and purely compressive load evaluation response. This may be carried out by restricting only the vertically imposed vectors, either, in a preferred approach utilizing a restricting geometry at one side of the load cells or by resiliently and compliantly returning the load cells to an acceptable rotational orientation under conditions wherein the transient rotational vectors are not present. Turning to Fig. 4, a partial sectional view of the load cell 38 is shown at an enhanced level of detail. The figure reveals that horizontal plate 72 of bracket 48 is configured having a circular opening 74 and serves as a support for the upper receiver 50. In this regard, a flange portion 76 of receiver 50 extends over the lower disposed surface of support plate 72 and the assembly 50 is adjusted in terms of vertical support position by a selection of annular shims as at 78. Receiver 50 additionally is configured having a centrally disposed rocker pin receiving cavity 80 of circular configuration and which flares at 82 outwardly from about the mid-point of the side surfaces thereof in conical profile to extend to its entrance opening at 84. Thus configured, the cavity 80 receives the curved or radiused contact surface 86 of the rocker pin 40 in freely abutting fashion and in a manner permitting freely pivotal movement thereof. To promote this freely pivotal movement, the side surfaces 88 of rocker pin 40 adjacent contact surface 86 are radiused and a radiused recessed portion 90 is formed adjacent the side surface 88. In similar fashion, the lower receiver 52 is configured having an annular outwardly extending flange 96 and a central body portion which is mounted within an annular opening 98 within the support or baseplate 54. As before, a rocker pin receiving cavity 100 is formed within receiver 52. The elevation of the receiver 52 is adjusted by selection of appropriate annular shims as are revealed at 102. Looking additionally to Fig. 5, a cross-sectional view of the receiver 52 is provided. In the latter figure, receiver cavity 100 is seen extending to a substantially flat, integrally disposed surface 104 intended for freely-abutting contact with the radiused lower disposed contact surface 106 of rocker pin configured component 40 (see Fig. 6). The upstanding sidewall 108 of cavity 100 extends upwardly from surface 104 and is configured having substantially flat lateral portions of equal length to define a hexagonal profile. Looking additionally to Fig. 7, these lateral portions or "flats" are revealed at 110a-110f. The figures further reveal that the lateral portions 110a-110f extend upwardly for a distance representing slightly greater than one-half the height of the cavity 100, whereupon the sidewalls 108 of the cavity are flared outwardly in 90° conical fashion to define an entrance opening 112. Fig. 7 additionally reveals that, for the embodiment disclosed, the receiver 52 is restrained from rotational movement by virtue of a slot 114 formed within flange 96 which abuttably engages a rigid pin 116 mounted within baseplate 54. Referring to Fig. 6, the lower portion of rocker pin 40 extending upwardly from lower contact surface 106 is seen to be configured in correspondence with the configuration of the lateral portions 110a-110f of cavity 100. In this regard, the rocker pin 40 is configured such that the side portions as revealed at 120a-120f are configured having six equally dimensioned "flats" or positioning surfaces of corresponding hexagonal profile as the lateral portions 110a-110f of cavity 100. However, these side portions 120a-120f are of slightly lesser extent permitting a freely pivotal movement of the rocker pin 40 within the receiver 52. In general, the side portions are radiused in the manner of a right cylinder in the lateral direction to promote this freely pivotal movement. Additionally, an annular taper 122 is seen formed between the contact surface 106 periphery and the commencement of side portions 120a-120f. As before, a recess as at 124 is formed in rocker pin component 40 above side portions 120a-120f. To further promote the freely pivotal interaction of the rocker pin 40 with receiver 52, the positions of intersection of adjacent side portions 120a-120f are rounded or radiused. Correspondingly, such rounding or radiusing is provided at the mutual intersections of the ends of lateral portions 110a-110f in cavity 100. Not essential to the noted freely pivotal performance, such rounding is found to facilitate the process of manufacture. Two of these rounded regions are represented in Figs. 6 and 7 at 126 and 128, the remaining such curved regions being unmarked in the interest of clarity. With the arrangement shown, transient force vectors imposed upon the load cell 38 will, from time-to-time induce a corresponding transient rotation about its axis of very short duration. This rotation is restrained by the structuring of side portions 120a-120f of the lower portion of rocker pin component 40 as associated with the corresponding lateral portions 110a-110f of the cavity 100 of receiver 52. Imposed transient rotational vectors are opposed by the non-circular corresponding components to impart a transient torsional term into the load cell which essentially disappears following a very short interval of time of occurrence of rotational vector forces. Generally, load measurements are made following the imposition of the term as the load cell 38 assumes a purely compressive status under a vertically imposed load induced force vector. As is apparent, the rotation limiting approach described hereinabove may be developed with either or both the upper or lower contact surfaces 86 or 106 of the rocker pin component 40 at the desire of the designer. Referring to Fig. 8, an adaptation to the rotation limiting arrangement heretofore described is revealed generally at 132. With this arrangement, the receiver 52 is rotationally mounted upon baseplate 54 by virtue of its being positioned upon an annular flat bearing 134 interposed between the upwardly disposed surface of base 54 and the lower disposed surface of flange portion 96. This bearing may be provided, for example, as a self-lubricating polymeric sheet material. Additionally, shims (not shown) as earlier described at 102 may be provided for height adjustment purposes. With this arrangement, however, a rigid pin as earlier described at 116 (Figs. 4 and 7) is replaced by a resilient motion restrictor extending in cantilever fashion from an upstanding stud 138 welded or otherwise fixed, in turn, to baseplate 54. Restrictor 136 may be provided, for example, as a rectangular piece of spring steel. By so resilently restraining the retainer 52, thus permitting its restricted rotation, peak, transient rotational vector forces are compliantly accommodated to reduce wear between the rocker pin 40 and receiver 52. Non-circular configurations other than the hexagonal profile described above may be provided in conjunction with the motion restraining approach above described. For example, only one or less than six non-circular side surface region may be provided for the receiver and rocker pin assemblage and, conversely, corresponding profiles having greater than six surfaces may be developed. Of importance, the freely pivotal association between rocker pin receiver must be retained to achieve proper load cell performance. Referring to Figs. 9-11, another embodiment of the invention is revealed. With this embodiment, the transient rotational vectors of force induced into the load cell assembly are permitted to evoke a corresponding rotation of the load cell in whichever rotational direction as might occur. However, as such rotation occurs on this transient basis, it is resiliently opposed by ever increasing oppositely directed and resiliently or spring derived return force vectors. Consequently, as the load induced transient rotational vectors of force cease or disappear, then the developed resilient countering force vectors of force return the load cell to its initial position. Thus, the load cell is returned to its initial position or orientation immediately following the imposition of any load induced rotational phenomena. Looking to Fig. 9, a load cell represented generally at 150 is seen supporting load platform 16 from ground base 22. The load platform 16 is supported from a bracket structure represented generally at 152 and having a horizontally disposed support plate 154. Plate 154 is, in turn, supported from two vertical plates 156 and 158 attached, in turn, to platform 16 (Fig. 10). An upper receiver 160 is attached to support plate 154 and, in turn, serves to provide a surface for freely abuttable contact with the corresponding curved contact surface of a rocker pin counterforce component 162. Correspondingly, the lower contact surface (not shown) of rocker pin component 162 engages a corresponding contact surface of lower receiver 164 which, in turn, is coupled to baseplate 166 positioned upon ground base 22. Fig. 10 shows that shims 170 and 172 are provided in conjunction with respective receivers 160 and 164 to adjust the vertical height of the load cell 150. A port as at 174 provides for input of cabling 176 as described hereinbefore. Positioned about the container or enclosure 178 is a clamping band 180 which is tightened against the container 178 by a tightening assembly 182 including a machine screw as shown. This band 180 serves to retain a rotation limiter represented generally at 184 which is formed of resilient sheet material such as stainless steel and includes a cylindrically formed support portion 186 retained by band 180 and from which are formed two oppositely disposed resiliently deformable spring members or wings 188 and 190. As revealed in Figs. 10 and 11, as the load cell 150 is subjected to rotational force vectors, one or the other of spring members 188 or 190 will be urged into abutting contact with a respective bumper surface of upstanding plates 158 and 156. Being connected to platform 16, the bumper surfaces of plates 156 and 158 essentially provide a stable reference which is dynamically isolated from the rocker pin 162 counterforce component function. Of course, such a bumpering function can be supported, for example, from the ground base 22. With the arrangement shown, upon rotation of load cell 150, abutting contact is made, for example, between resilient component 188 and the bumper surface of plate 158 to resiliently store energy until such time as the transient rotation inducing force vectors are removed, whereupon, the thus-deformed component 188 resiliently returns or rotates the load cell 150 to its original position. As is apparent, compressively deformable helical springs and the like may be employed to achieve the function of component 184. Looking to Fig. 12, another positional restoration assemblage is revealed in general at 194. Assemblage 194 operates in conjunction with a load cell represented generally at 196 which is configured and mounted in the same manner as represented in conjunction with Figs. 9 and 10. In this regard, the load cell 196 is configured having a centrally-disposed rocker pin configured counterforce component 198 which extends between two retainers (not shown). The upper one of the latter retainers is supported by a bracket which includes vertical plates 200 and 202 configured in the same manner as respective plates 156 and 158 shown in Fig. 10. An output port extending from instrumentation container 206 provides for the connection of cabling as at 208 for providing a power supply to the instrumentation contained therein, as well as control and data retrieval information. With the instant embodiment shown, the load cell 196 is constrained within a preferred rotational orentation through the utilization of two helical springs pre-loaded in tension schematically represented at 210 and 212 which are coupled to the container 206 of load cell 196 at a connector 214 extending from the surface thereof and fixed thereto. The opposite side of spring 210 is seen coupled at 216 to vertical plate 200, while the opposite side of spring 212 is coupled to plate 202 at 218. With the arrangement shown, any rotational inducing transient force vector imposed upon load cell 196 is countered by one or the other of springs 210 or 212 until such time as the transient rotational input force is removed. At such time, the oppositely acting springs restore load cell 196 to its initial orientation. A singular preloaded spring can be employed in place of springs 210 and 212 extending between points 216 and 218. Further, a single spring deformable in both tension and compression may be coupled between the load cell and either one of the points 216 or 218. Looking to Fig. 13, still another arrangement for restraining the rotational movement of a load cell while not affecting its performance as a counterforce component is revealed. As before, the load cell represented generally at 224 is mounted in the manner described in conjunction with Figs. 9 and 10. In this regard, the centrally disposed rocking pin configured component 226 is in freely abutting contact at its upper contact surface with a receiver (not shown) supported by a bracket assembly coupled to load platform 16. Two side plates of this bracket are represented at 226 and 228 which correspond with respective brackes 156 and 158 shown in Fig. 10. An instrumentation access port is represented at 230 which is coupled to the external surface of container 232 of load cell 224. The port 230 provides coupling to such instrumentation with an appropriate cabling 234. In accordance with the instant arrangement, a rod-like engaging component 236 is fixed to and extends outwardly from container 232 in an orientation essentially perpendicular to the central axis of rocker pin component 226. The resilient engaging component 236 is shown protruding between two resilient bumper components 238 and 240 of a U-shaped bracket represented generally at 242 fixed to and extending from platform 16. As before, the platform 16 functions, for the topology, shown as a restrainer providing a stable reference which is dynamically isolated from the load cell 224. Turning to Fig. 14, a symmetrical arrangement corresponding with the embodiment of Fig. 13 but which may be machined into the rocker pin counterforce component of a load cell is revealed. In this arrangement, the lower side portion or neck of the rocker pin component as represented at 250 may be machined or bored to receive two oppositely-disposed checking pins 252 and 254. These pins optionally may be formed of resilient or rigid material. Pins 252 and 254 are so positioned so as to be engageable with the machined surfaces of respective cavities 256 and 258 formed within an associated receiver, the surface of which is represented at 260. Thus, pin 252 will move into a resilient, freely abutting association with one surface 262 or 264 of cavity 256, while corresponding pin 254 will move into freely abutting but resilient contact with a corresponding surface 266 or 268 of cavity 258. A convenient structuring for the instant embodiment is achieved by forming pins 252 and 254 as a single, rod-like component, the opposite ends of which are tapered. This single component is inserted within a transverse bore extending through the neck of the rocker pin component. Since certain changes may be made in the above system, apparatus, and method without departing from the invention as claimed, it is intended that all matter contained in the description thereof or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims: Weighing apparatus comprising a base (22), a load receiving surface (12), at least one self-erecting rocker pin load cell (38) having a vertically aligned longitudinal axis and upper and lower end portions formed with upper (86) and lower (106) contact surfaces positioned between said base (22) and said load receiving surface, respectively, for freely pivotal supporting contact with said load receiving surface, at least one of said upper and lower end portions being received in a rocker pin receiving cavity (100) having a peripheral side wall (108) of a receiver (52), said load cell being subject to both vertical and temporary transverse force vectors creating transient rotational force vectors urging said rocker pin (40) to rotate about said longitudinal axis, said load cell further comprising restrainer means for providing a rotationally stable reference isolated from said rocker pin, and rotation limit means in contact with said load cell (38) and coupled with said restrainer means so as to restrict said rotation of said load cell (38) within predetermined limits by counteracting only said rotational force vectors while not affecting the reaction of said load cell to said vertical force vector and not substantially affecting said freely pivotal supporting contact, characterized in that said restrainer means is formed by said receiver (52) having a lateral portion (110a - 110f) of the peripheral side wall (108) formed of non-circular configuration and extent and configured for effecting freely pivotal abutting support of said rocker pin load cell (38); and said rotation limit means is formed by the lower end portion of said rocker pin load cell received within said cavity (100) and having a peripherally disposed positioning surface with a non-circular portion (120a - 120f) corresponding with and of lesser extent than said lateral portion (110a - 110f). Weighing apparatus as claimed in Claim 1, in which said receiver (52) is mounted in limited rotatable relationship with said apparatus. Weighing apparatus as claimed in Claim 2, in which said receiver (52) includes a bearing (134) mounted therewith for effecting said rotatable relationship; and resilient restrictor means (136) for resiliently restricting the extent of rotation of said receiver (52). Weighing apparatus as claimed in anyone of Claims 1 to 3, in which said rocker pin non-circular portion (120a - 120f) is configured as a segment of a right cylinder. Weighing apparatus as claimed in anyone of Claims 1 to 3, in which said receiver cavity (100) is formed having six said peripheral side wall lateral portions (110a - 110f) of substantially linear configuration and of generally hexagonal profile; and said rocker pin non-circular portion (120a - 120f) is configured having a corresponding said hexagonal profile. Weighing apparatus as claimed in Claim 1, in which said non-circular portion of said positioning surface of said rotation limit means comprises first and second checking pins (252, 254), fixed to and extending symmetrically outwardly from said end portion of said load cell (250); and said non-circular configuration of said side wall of said restrainer means has first and second cavity defining surfaces (262, 264; 266, 268) formed there, positioned to receive respective said first and second checking pins (252, 254) and dimensioned for restricting said rocker pin rotation within predetermined limits. Weighing apparatus comprising a base (22), a load receiving surface (12), at least one self-erecting rocker pin load cell (196) having a vertically aligned longitudinal axis and upper (86) and lower (106) contact surfaces positioned between said base (22) and said load receiving surface for freely pivotal supporting contact with said load receiving surface, said load cell being subject to both vertical and temporary transverse force vectors creating transient rotational force vectors urging said rocker pin (40) to rotate about said longitudinal axis, said load cell further comprising restrainer means for providing a rotationally stable reference isolated from said rocker pin, and rotation limit means in contact with said load cell (150) and coupled with said restrainer means so as to restrict said rotation of said load cell (196) within predetermined limits by counteracting only said rotational force vectors while not affecting the reaction of said load cell to said vertical force vector and not substantially affecting said freely pivotal supporting contact, characterized in that said rotation limit means comprises spring means (210, 212) mounted between said restrainer means (200, 202) and said load cell (196) along an axis substantially transverse to said longitudinal axis for resiliently returning said load cell (196) to an initial position subsequent to the induced rotation thereof. Weighing apparatus comprising a base (22), a load receiving surface (12), at least one self-erecting rocker pin load cell (224) having a vertically aligned longitudinal axis and upper (86) and lower (106) contact surfaces positioned between said base (22) and said load receiving surface for freely pivotal supporting contact with said load receiving surface, said load cell being subject to both vertical and temporary transverse force vectors creating transient rotational force vectors urging said rocker pin (40) to rotate about said longitudinal axis, said load cell further comprising restrainer means for providing a rotationally stable reference isolated from said rocker pin, and rotation limit means in contact with said load cell (150) and coupled with said restrainer means so as to restrict said rotation of said load cell (224) within predetermined limits by counteracting only said rotational force vectors while not affecting the reaction of said load cell to said vertical force vector and not substantially affecting said freely pivotal supporting contact, characterized in that said rotation limit means comprises an engaging component (236) extending from said rocker pin load cell (224) generally normally to said longitudinal axis; and said restrainer means comprises first and second bumper components (238, 240) mutually spaced apart a distance representing a predetermined limit and located for freely abutting contact with said engaging component (236) upon rotation of said load cell (224). Weighing apparatus as claimed in Claim 8, in which said first and second bumper components (238, 240) are resilient. Weighing apparatus comprising a base (22), a load receiving surface (12), at least one self-erecting rocker pin load cell (150) having a vertically aligned longitudinal axis and upper (86) and lower (106) contact surfaces positioned between said base (22) and said load receiving surface for freely pivotal supporting contact with said load receiving surface, said load cell being subject to both vertical and temporary transverse force vectors creating transient rotational force vectors urging said rocker pin (40) to rotate about said longitudinal axis, said load cell further comprising restrainer means for providing a rotationally stable reference isolated from said rocker pin, and rotation limit means in contact with said load cell (150) and coupled with said restrainer means so as to restrict said rotation of said load cell (150) within predetermined limits by counteracting only said rotational force vectors while not affecting the reaction of said load cell to said vertical force vector and not substantially affecting said freely pivotal supporting contact, characterized in that said rotation limit means comprises first and second oppositely disposed resiliently deformable springs (188, 190) fixed to and extending outwardly from said load cell (150) generally normally to said longitudinal axis to respective first and second bumper surfaces (156, 158) of said restrainer means, said first and second bumper surfaces (156, 158) being mutually spaced apart and positioned for freely abutting engagement with one of said first and second resiliently deformable springs (188, 190) upon rotational movement of said load cell (150) toward a predetermined limit.

Inventors: HECKENDORN LARRY C, LONG CURTIS W, MILLS NIGEL G, SMIGEL RICHARD T, HECKENDORN, LARRY C., LONG, CURTIS W., MILLS, NIGEL G., SMIGEL, RICHARD T.
Applicants: METTLER TOLEDO INC, METTLER-TOLEDO, INC.
Application year: 1990
Main classification: G01G19
IPC codes: G01G21, G01G3, G01G19