GB2145831A - Self-aligning weighing platform - Google Patents

Abstract

A weighing platform is supported by a plurality of force- transmitting assemblies. Upon sideways movement of the platform, the force-transmitting assemblies and platform interact to align and center the platform. In one embodiment, each force transmitting assembly includes a slider 86 which is movable along a base surface 120. A rocker pin 102 transmits force between the slider and a load cell beam 76 connected with the platform. When the platform is moved the rocker pin is tilted to a maximum offset condition in which horizontally offset vertical force components are applied to the rocker pin. Continued movement results in movement of the slider relative to the base. When movement of the platform is interrupted by engagement with a bumper 64. the horizontally offset vertical force components applied to the rocker pin cause it to tilt to an aligned condition in which only vertically aligned force components are applied to the rocker pin. In another embodiment the slider and a spherical force transmitting member are connected with the base and the platform moves relative to the slider when the force transmitting assembly is in a maximum offset condition. <IMAGE>

Description

SPECIFICATION Self-aligning scale assembly and method Background of the Invention The present invention relates to a new and improved scale assembly and method by which it is aligned.

A known scale assembly is disclosed in U.S. Patent No. 4,258,810. This known scale assembly includes a platform having load transmitting assemblies at each of four corners of the platform. The load transmitting assemblies include load cells having floating pins which engage a support surface and are movable along the support surface. In order to accurately center the platform relative to an enclosing framework, the floating pins must be accurately positioned relative to the support surface. In addition, the application of sideward or horizontal loads to the platform can result in abutting engagement and the transmission of horizontal forces between side surfaces of the floating pins and side surfaces of openings in the load cells.

Although a scale constructed in the manner shown in U.S. Patent No. 4,258,810 is satisfactory in its operation, it has been found that the application of sideward or horizontal force components to a load cell tends to be detrimental to the accuracy of the scale. In addition, the time required to install the scale is increased due to the necessity of accurately positioning the platform relative to an enclosing framework.

In an effort to minimize horizontal or sideward force components in scales, rocker pins of the type shown in U.S. Patent Nos.

2,666,634 and 3,997,014 have been used.

Other scales have used spherical balls in an effort to tend to minimize horizontal force components in a manner similar to that shown in U.S. Patent Nos. 3,915,248 and 2,430,702.

Although the use of rocker pin or ball type force transmitting members may tend to reduce the magnitude of sideward force components to which a load cell is subjected, the force transmitting members of these known scales have been associated with stationary receivers which must be accurately located.

The necessity of accurately locating the stationary receivers for the rocker pins or balls of known scale assemblies increases the difficulty of installing the scale assemblies. If the receiver is to be subsequently removed for maintenance purposes, the location of the receiver must be accurately noted so that the receiver can be put back in its original position.

If stationary receivers for the rocker pins or balls of known scales are not properly located, sideward restoring forces may be permanently locked into the scales. Thus, mislocation of the receivers can cause the balls or pins to be permanently retained in an orientation which is offset or skewed relative to their intended orientation. This results in the application of sideward force components to parts of the scale. These sideward force components are detrimental to the accuracy of the scale.

Brief Summary of the Invention A new and improved scale assembly includes a platform which is supported by a plurality of force transmitting assemblies. The force transmitting assemblies and platform cooperate to automatically center the platform relative to an enclosing structure and to align the force transmitting assemblies and platform. The automatic centering of the platform and aligning of the force transmitting assemblies is accomplished by moving the platform back and forth in sideways directions against stops which limit motion of the platform.

Centering the platform and aligning the force transmitting assemblies is effective to eliminate sideward force components on load cells in the force transmitting assemblies.

Each force transmitting assembly includes an upper member, a lower member, and a force transmitting member which is disposed between the upper and lower members. The upper, lower and force transmitting members are movable relative to each other from a maximum offset condition through a range of offset conditions to an aligned condition.

When the upper and lower members are aligned, they are effective to apply only vertically aligned force components to the force transmitting member.

Brief Description of the Drawings The foregoing and other objects and features of the present invention will become more apparent upon consideration of the following description taken in connection with the accompanying drawings wherein: Fig. 1 is a fragmentary, pictorial illustration of the installation of a scale assembly constructed in accordance with the present invention; Fig. 2 is an exaggerated fragmentary schematic illustration of the scale assembly of Fig.

1 as initially installed with the platform in a noncentered relationship relative to a surrounding frame and with force transmitting assemblies in nonaligned relationships with the platform; Fig. 3 is an enlarged fragmentary sectional view of one of the force transmitting assemblies of Fig. 2, the components of the force transmitting assembly being shown in a maximum offset condition with the extent of offset being exaggerated for purposes of clarity of illustration; Fig. 4 is a fragmentary sectional view, illustrating the force transmitting assembly of Fig.

3 after the platform has moved sideways; Fig. 5 is a fragmentary sectional view of the force assembly of Figs. 3 and 4 in an aligned condition; Fig. 6 is a schematic illustration depicting the relationship between the platform and force transmitting assemblies, the force transmitting assemblies being indicated in dashed lines in a nonaligned relationship with the platform and in solid lines in an aligned relationship with the platform; Fig. 7 is a fragmentary sectional view of an embodiment of the invention in which a spherical ball is a force transmitting member; Fig. 8 is a fragmentary sectional view illustrating the components of the force transmitting assembly of Fig. 7 in a maximum offset condition; Fig. 9 is a fragmentary sectional view of an embodiment of the invention in which a platform is movable relative to a load cell and a ball type force transmitting member;; Fig. 10 is a fragmentary sectional view of an embodiment of the invention generally similar to that of Fig. 9 with a rocker pin as a force transmitting member; and Fig. 11 is a fragmentary sectional view of a presently preferred embodiment of the invention.

Description of Specific Preferred Embodiments of the Invention Scale Assembly-General The installation of a scale assembly 14 constructed in accordance with the present invention is illustrated in Fig. 1. The scale assembly 14 includes a rectangular platform 1 6 which receives a load to be weighed. The platform 16 is shown in Fig. 1 being lowered by chains 1 8 and 20 into a rectangular frame 22 disposed in a shallow pit 24 in a floor 26.

When the platform 1 6 is disposed in the frame 22, a flat upper surface 30 of the platform is level with an upper surface of the floor 26. Although the platform 16 has been shown as having a flat upper surface, the platform could have any desired configuration suitable for receiving a load.

A force transmitting assembly constructed in accordance with the present invention is provided at each of the four corners of the rectangular platform 1 6. Thus, a force transmitting assembly 34 is disposed at a corner 36, a force transmitting assembly 38 is disposed at a corner 40, a force transmitting assembly 42 is disposed at a corner 44 and a force transmitting assembly 45 (shown only in Fig. 6) is disposed at a corner 46 of the platform 1 6. Each of the four identical force transmiting assemblies is securely connected with the platform 1 6 in a manner similar to that disclosed in U.S. Patent No. 4,258,814.

When the platform 16 is lowered into the somewhat larger frame 22 (Fig. 1), the platform will not be precisely centered relative to the frame and there will probably be unequal distances between the sides of the platform and the frame; In addition, the force transmitting assemblies 34, 38, 42 and 45 will probably be in a nonaligned relationship with the platform 16. The nonaligned force transmitting assemblies will be effective to transmit sideward or horizontal force components which tend to impair the accuracy of the scale assembly 14.

In accordance with a feature of the present invention, the platform is automatically centered and the force transmitting assemblies are automatically aligned with the platform by merely moving the platform sideways relative to a base or floor 50 of the pit 24. If the force transmitting assemblies 34, 38, 42 and 45 are subsequently moved from an aligned condition (Fig. 5) to a nonaligned condition (Fig.

4), they are self-restoring to the aligned condition. This self-restoring feature of the force transmitting assemblies prevents them from being actuated to a misaligned condition by the application of operating loads to the scale assembly 14.

Centering of the platform 16 relative to the frame 22 provides a space between the platform and frame so that the platform does not abut or rub against the frame. Aligning the force transmitting assemblies 34, 38, 42 and 45 with the platform 1 6 results in the transmission of only vertically aligned force components which can be accurately measured by load cells. Therefore, there are no locked-in sideward force components on parts of the scale. The automatic centering of the platform and alignment of the force transmitting assemblies 34, 38, 42 and 45 facilitates the installation and subsequent maintenance of the scale assembly 14.

When the scale assembly 14 is installed, one of the platform sides, for example, the side 54 (Fig. 2), may be too close to the frame 22. In addition, the components of the force transmitting assemblies 34, 38, 42 and 45 may not be aligned properly with the platform 16. It should be noted that the extent of misalignment of the platform and force transmitting assemblies illustrated in Fig: 2 will only occur during installation and has been exaggerated in Fig. 2 for purposes of illustration.

In order to center the platform 1 6 in the frame 22 and align the force transmitting assemblies 34, 38, 42 and 45 with the platform 16, the platform is moved sideways toward and away from each of the four sides of the frame 22. Thus, the platform 1 6 is moved toward the right (as viewed in Fig. 2) toward a side 62 of the frame 22. The rightward movement of the platform is interrupted when a bumper or stop member 64 engages a stop surface 66 connected with the platform.

Once the bumper 64 has been engaged and the rightward (as viewed in Fig. 2) force on the platform 1 6 has been removed, restoring forces in the load transmitting assemblies 34, 38, 42 and 45 cause the platform to move toward the left (as viewed in Fig. 2) away from the bumper 64 toward a centered position. The platform 1 6 is then moved toward and away from each of the other three sides 68, 70 and 72 (Figs. 1 and 6) of the frame 22. Of course the platform 1 6 could be moved sideways toward the corners of the rectangular frame 22 rather than toward the sides of the frame if desired.

After this has been done, the frame 1 6 will be disposed in a centered position and the force transmitting assemblies 34, 38, 42 and 45 will be in an aligned relationship with the platform 1 6. The aligned force transmitting assemblies 34, 38, 42 and 45 will then transmit only vertical force components between the platform 1 6 and base 50. These vertical force components can be accurately measured by load cells or other types of force transducers in the force transmitting assemblies.

Force Transmitting Assembly -Embodiment of Figs. 3-5 The force transmitting assembly 34 (Fig. 3) includes a shear beam load cell or force transducer 70 the type disclosed in U.S.

Patent No. 4,258,814 and made by Hottinger, Baldwin Measurements, Inc., Natick, Massachusetts. The load cell 70 provides an output signal which is indicative of the magnitude of the vertical force applied to the load cell and, therefore, the weight of a load on the platform 16. Although it is preferred to use the shear beam load cell 70, other types of force transducers could be used if desired.

The load cell or force transducer 70 has a metal body portion 74 which is connected to the platform 1 6 and an outwardly projecting horizontal metal beam portion 76. Adjacent to the outer end of the beam 76 is formed a downwardly opening cylindrical recess 78.

The recess 78 has a flat bottom surface 80 and a cylindrical side surface 82.

The force transmitting assembly 34 also includes a metal slider or base pad 86 disposed immediately beneath the outer end portion of the load cell beam 76. The slider 86 has an upwardly opening cylindrical recess 88 of the same size as the recess 78 in the load cell beam 76. The slider recess 88 has a flat bottom surface 92 and a cylindrical sidewall 94. During installation of the scale assembly 14, the slider 86 is retained in position beneath the beam 76 by a retainer plate or member 98 in a manner similar to that disclosed in U.S. Patent No. 4,258,810.

A metal force transmitting member 102 extends into the recesses 78 and 88 and is effective to transmit load forces from the beam 76 to the slider 86. In the embodiment of Fig. 3, the force transmitting member 102 is a rocker pin having a cylindrical side surface 104 and end surfaces 106 and 108 which are polar portions of spheres. The arcuate end surfaces 106 and 108 abut the flat end surfaces 80 and 92 of the cylindrical recesses 78 and 88.

The cylindrical side surface 104 of the rocker pin 102 has an outside diameter which is smaller than the inside diameter of the recesses 78 and 88. Therefore, the rocker pin 102 is free to tilt from an aligned or vertical position (Fig. 5) through a plurality of offset positions to the maximum offset position shown in Fig. 3. However, it is preferred to use O-rings or other resilient elements (not shown) to urge the rocker pin 102 toward the vertical position with a force which can be easily overcome. For purposes of clarity of illustration, the extent of the tilting movement of the rocker pin has been exagerated somewhat in Fig. 3.

When the force transmitting assembly 34 is to be aligned with the platform 16, the platform is moved toward the right (as viewed in Figs. 2 and 3) until the stop surface 66 at one end of the load cell beam 76 abuts a bumper 64. If the components of the force transmitting assembly 34 are not in the maximum offset condition shown in Fig. 3, the initial rightward movement of the platform 1 6 moves the load cell beam 76 relative to the slider 86 and causes the rocker pin 102 to tilt in the maximum offset position. At this time, the vertical central axis of the upper recess 78 is offset from the vertical central axis of the lower recess 88.

When the force transmitting assembly 34 is in the maximum offset condition of Fig. 3, the rocker pin 102 is held against further tilting movement by engagement of the side surface 104 of the rocker pin with a circular edge portion 11 2 of the recess 78 and with a circular edge portion 114 the recess 88.

Therefore, once the force transmitting assembly 34 has moved to the maximum offset condition shown in Fig. 3, the spatial relationship between the load cell 76, rocker pin 102 and slider 86 remains constant as the platform continues to move toward the right. This results in sliding movement of a Teflon (RTM)covered circular bottom surface 11 8 of the slider 86 along a slider plate 1 20 preferably of stainless steel which is connected to a stationary base plate 1 22.

The coefficient of friction between the Teflon coated bottom surface 11 8 of the slider 86 and the upper surface of the metal base plate 1 20 is substantially less than the coefficient of friction between the ends 106 and 108 of the metal pin and the surfaces 80 and 92 on the load cell beam 76 and slider 86. Therefore, sliding movement occurs between the bottom surface 11 8 and the base plate 102 before sliding movement can occur between the rocker pin 40 and either the load cell beam 76 or between the rocker pin and the slider 86. It should be noted that the coefficient of friction between the lower end of the rocker pin 40 and the slider 86 must be greater than the coefficient of friction between the slider and the base plate 102.The commonly accepted coefficient of friction between the metal rocker pin 40 and base 86 is approximately 0.7. The commonly accepted coefficient of friction between the Teflon bottom surface 11 8 of the slider 86 and the base plate 102 is approximately 0.06.

Upon engagement of the stop surface 66 with the bumper 64 (see Fig. 4), rightward movement of the platform 1 6 movement is interrupted. When the force urging the platform 1 6 toward the right is removed, the restoring forces in the force transmitting assembly 34 cause the force transmitting assembly to move from the maximum offset condition in Fig. 4 to the aligned condition shown in Fig. 5. When the force transmitting assembly 34 is in the aligned condition, the vertical central axis of the upper recess 78 is aligned with the vertical central axis of the lower recess 88.

As the force transmitting assembly 34 moves from the maximum offset condition of Fig. 4 to the aligned condition of Fig. 5, the rocker pin 102 is effective to cause the load cell beam 76 and platform 1 6 to move toward the left away from the bumper 64. Thus, when the force transmitting assembly 34 is in a maximum offset condition shown in Fig. 4, the bottom surface 80 of the recess 78 is effective to apply a downward load force component, indicated at 1 30 in Fig. 4, to the left side of the dome shaped upper surface 106 on the rocker pin 102. The stationary slider 86 applies an upwardly directed reaction force, indicated at 1 32 in Fig. 4, against the right side of the dome shaped lower surface 108 on the rocker pin 102.

The vertical force components 1 30 and 1 32 are of equal magnitude and are horizontally offset. Therefore, the force components 1 30 and 1 32 apply a counterclockwise (as seen in Fig. 4) torque to the rocker pin 102.

The counterclockwise torque applied to the rocker pin 102 by the horizontally offset force components 1 30 and 1 32 is transmitted to the load cell beam 76 and is urges the load cell beam and platform 1 6 toward the left (as viewed in Fig. 4).

Although only force transmitting assembly 34 has been shown in Fig. 4, it should be understood that the force transmitting assemblies 38, 42 and 45 at the other corners of the platform 1 6 are in similar orientations and are effective to apply force to the platform urging it towards the left (as viewed in Fig. 4).

This results in movement of the platform 1 6 and load cell beam 76 leftward from the position shown in Fig. 4 to the aligned position shown in Fig. 5. As the load cell beam 76 and platform 1 6 move toward the left away from the bumper 64, the slider 86 remains stationary and the rocker pin 102 pivots to an upright orientation.

When the force transmitting assembly 34 is in the aligned condition, the bottom surface 80 of the load cell beam 76 applies a vertical downwardly directed load force component, indicated at 1 36 in Fig. 5, against the upper surface 106 of the rocker pin 1 2. Similarly, the bottom surface 92 of the recess 88 in the slider 86 is effective to apply an upwardly directed vertical reaction force component 1 38 against the lower side surface 108 of the rocker pin 102. The force components 1 36 and 1 38 are coincident with the central axis of the rocker pin 102 and the central axes of the cylindrical recesses 78 and 88.The axially aligned vertical force components 1 36 and 1 38 did not apply any moments to the rocker pin 102. Therefore, sideward or horizontal forces are not applied to the load cell beam 76.

Each of the force transmitting assemblies at the four corners of the platform 1 6 may be out of alignment with the platform 1 6 in a different direction. Therefore, it is necessary to move the platform 1 6 back and forth along horizontal X and Y axes in order to be certain that all four of the force transmitting assemblies are aligned with the platform and that the platform is centered relative to the frame 22. Thus it is necessary to move the platform 1 6 horizontally back and forth, in the manner indicated by the arrow 144 in Fig. 6, to align the force transmitting assemblies 34, 38, 42 and 45 along the X axis and to position the sides 54 and 148 of the platform 1 6 relative to the sides 62 and 70 of the frame 22.In addition, it is necessary to move the platform 1 6 horizontally back and forth along the Y axis in the manner indicated by the arrow 1 58 in Fig. 6. This aligns the force transmitting assemblies 34, 38, 42 and 45 along the Y axis and centers the sides 1 60 and 1 62 of the platform 1 6 relative to the sides 68 and 72 of the frame 22.

As the platform 1 6 is moved horizontally back and forth along the X and Y axes in the manner indicated by the arrows 144 and 1 58 in Fig. 6, the force transmitting assemblies 34, 38, 42 and 45 move from the nonaligned conditions indicated in dashed lines in Fig. 6 to the aligned conditions indicated in solid lines in Fig. 6. Suitable bumpers 170 are provided along the frame 22 to limit the sideways movement of the platform 1 6 in the same manner as previously explained in connection with the bumper 64. When the force transmitting assemblies 34, 38, 42 and 45 are in the aligned condition shown in solid lines in Fig. 6, the upwardly facing recesses 88 in the sliders 86 are aligned with the downwardly facing recesses 78 in the load cells 70.

If the distance between each of the stop surfaces connected to the platform 1 6 and each of the bumpers connected to the frame 22 is equal to or slightly less than the distance which the components of the force transmitting assembly 34 move from the maximum offset condition of Fig. 4 to the aligned condition of Fig. 5, the centered position of the platform will not change during use of the scale assembly. This allows vehicles to be driven onto and off of the platform without permanently changing the centered condition of the platform.

If a dynamic load is applied to the platform 1 6 and moves the platform toward the right, as seen in Fig. 6, the load cell beam 76 will move into an abutting engagement with the bumper 64 as the force transmitting assembly 34 is actuated to the maximum offset condition (see Fig. 4). This occurs while the slider 86 remains stationary. Therefore, the restoring forces in the force transmitting assembly 34 will return the force transmitting assembly to the aligned condition shown in Fig. 5.

Simultaneously therewith, the platform 1 6 will be returned to its previous centered position.

A dynamic load could be applied to the platform 1 6 in many different ways, for example, a vehicle could be driven onto the platform or a conveyor extending onto the platform could be started or stopped.

It is contemplated that the distance between bumpers on opposite sides of the frame 22 may be such as to allow the platform to move slightly toward either the left or the right (as viewed in Fig. 6) between centered positions. Thus, the space in between the bumpers could be increased slightly so that each time a vehicle moves onto and off of the platform, the force transmitting assemblies 34, 38, 42 and 45 move to the maximum offset condition (shown in Fig. 4) and then continue to move through a short distance into engagement with the bumpers. This would result in realignment of the force transmitting assemblies 34, 38, 42 and 45 with the platform 1 6 each time a vehicle is driven onto or off of the platform. Of course, the platform would also be centered in the frame 22 each time a vehicle was driven onto or off of the platform 16.

Although the construction of only the force transmitting assembly 34 is illustrated in Figs.

3-5, it should be understood that the force transmitting assemblies 38, 42 and 45 have the same construction and mode of operation as the force transmitting assembly 34. It should also be understood that the scale assembly 1 4 can be used for purposes other than weighing vehicles. Thus, other types of loads could be placed on the platform 1 6 and weighed by the load cells in the force transmitting assemblies. Of course, the platform could be shaped differently than shown in the drawings in order to receive a particular load.

If it becomes necessary to remove one of the load cells for maintenance, it is merely necessary to raise the platform 16, replace the load cell, and then return the platform to its position in the frame 22. The platform 1 6 would then be moved along the X and Y axes to align the force transmitting assemblies 34, 38, 42 and 45 and to center the platform in the frame 22 in the manner previously explained.

Force Transmitting Assembly -Embodiment of Figs. 7 and 8 It is contemplated that a force transmitting member other than a rocker pin may be used between a slider and a load cell beam. Thus in the embodiment of the invention shown in Figs. 7 and 8, a spherical ball 1 76 is used as a force transmitting member. Since the construction of the force transmitting assembly shown in Figs. 7 and 8 is generally similar to the construction of the force transmitting assembly shown in Figs. 3-5, similar numerals will be utilized to designate similar components, the suffex letter "a" being associated with the embodiment of the invention shown in Figs. 7 and 8 to avoid confusion.

The spherical load transmitting member or ball 1 76 is disposed in a downwardly opening recess 78a formed in the load cell beam 76a and in an upwardly opening recess 88a formed in the slider 86a. The recesses 78a and 88a have bottom surfaces 1 80 and 1 82 which form polar portions of spheres having larger radii than the spherical ball 1 76.

When the force transmitting assembly 34a is in the maximum offset condition illustrated in Fig. 8, the lower portion of the ball 1 76 is in engagement with a cy!indrical rim 1 90 of the recess 88a. Similarly, the ball 1 76 engages a cylindrical rim 1 92 of the recess 78a.

At this time, the recess 78a is offset to the left of the recess 88a.

Further leftward (as viewed in Fig. 8) movement of the platform and load cell beam 76a results in movement of the slider 86a along a stainless steel base plate or shim 120a. During this leftward movement of the load cell beam 76a, the relationship between the slider 86a, spherical ball 1 76 and load cell beam remains constant in the maximum offset condition shown in Fig. 8.

When the leftward movement of the load cell beam 76a is interrupted and the sideways force applied to the platform is withdrawn, the restoring forces on the ball 1 76 cause it to return the force transmitting assembly 34a to the aligned condition of Fig. 7. The restoring forces on the ball 1 76 include a downward vertical force component applied against the upper right (as viewed in Fig. 8) portion of the ball by the load cell beam 76a and an upward vertical reaction force component applied against the lower left portion of the ball by the slider 86a. The horizontally offset vertical force components on the ball 1 76 apply a clockwise moment to the ball. This moment urges the load cell beam 76a and platform toward the right as viewed in Fig. 8.

When the ball 1 76 has moved the load cell beam 76a to the aligned condition shown in Fig. 7, the recesses 78a and 88a are vertically aligned. The vertical downward load force component on the upper portion of the ball extends through the center of the ball and is aligned with a vertical upward reaction force component at the bottom portion of the ball. Therefore, there are no horizontal or sideward force components transmitted between the slider 86a and load cell beam 76a.

Force Transmitting Assembly -Embodiment of Fig. 9 In the embodiment of the force transmitting assembly shown in Figs. 3-5, the slider 86, rocker pin 102 and load cell beam 76 move together relative to the the base plate 1 22 when the platform 1 6 is moved to the right with the load transmitting assembly in the maximum offset condition shown in Fig. 3.

This results in sliding movement of the bottom surface 118 of the slider 86 along the top surface of the stainless steel shim 1 20. In the embodiment of the invention shown in Fig. 9, the slider engages a surface connected to the platform.

Once the force transmitting assembly shown illustrated in Fig. 9 has been actuated to a maximum offset condition, the slider and ball-type force transmitting member remain stationary while the platform moves relative to the slider. In addition, in the embodiment of the invention shown in Fig. 9, a stop surface is fixedly connected with the platform and moves into engagement with a bumper surface on a stationary load cell housing when the platform has reached a limit of movement in one direction. Since the embodiment of the invention shown in Fig. 9 is generally similar to the embodiments of the invention shown in Fig. 3-5, similar numerals will be utilized to designate similar components, the suffix letter "b" being associated with the numerals of Fig. 9 to avoid confusion.

Load forces are transmitted from the platform 1 6b through a force transmitting assembly 34b to a base 50b. The force transmitting assembly 34b includes a slider 86b having a downwardly opening recess 88b. The upper portion of an force transmitting member or spherical ball 200 extends into the recess 88b. A lower portion of the ball 200 extends into an upwardly opening recess 78b formed in the upper end portion of a stationary column 202 of the load cell 70b. Suitable strain gages 204 are connected with the load cell column 202 to provide an output indicative of the load applied to the column.

When the platform 1 6b move toward the left (as viewed in Fig. 9) the slider 86b moves with the platform until the ball 200, slider 86b and column 202 have reached a maximum offset condition corresponding to the maximum offset condition shown in Fig. 8.

The leftside of the ball 200 then engages a cylindrical rim 206 of the opening 78b in the load cell column 202. The cylindrical rim 204 on the recess 88b in the slider 86b engages the right side of the ball.

Continued leftward movement (as viewed in Fig. 9) of the platform 1 6b results in the stainless steel shim plate moving leftwardly relative to the stationary slider 86b. The stop surface 66b engages the bumper surface 64b when the platform 1 6b has moved to the limit of its leftward travel. After the force urging the platform 1 6b toward the left is removed, the restoring forces on the ball 200 cause the ball to move the slider 86b and platform 1 6b to the right until the slider 86b, ball 200 and column 202 have returned to the aligned condition shown in Fig. 9. During this rightward restoring movement of the platform 16b, the slider 86b does not move relative to the platform 16b.

Force Transmitting Assembly -Embodiment of Figure 10 It is contemplated that a rocker pin could be used in association with a force transmitting assembly having a construction similar to the construction shown in Fig. 9. Thus, in the embodiment of the invention shown in Fig.

10, a rocker pin is associated with a stationary load cell and a slider engages a movable surface on the platform. Since the embodiment of the invention shown in Fig. 10 is generally similar to the embodiment of the invention shown in Figs. 3-5, similar numerals will be utilized to designate similar components, the suffix letter "c" being associated with the embodiment of the invention shown in Fig. 10 to avoid confusion.

The force transmitting assembly 34c transmits load forces from the platform 1 6c to a base 50c. The force transmitting assembly 34c includes a slider 86c, a rocker pin 106c, and a load cell 70c. The upper portion of the rocker pin 1 02c is received in a cylindrical recess 88c in the slider 86c. The lower portion of the rocker pin 1 02c is received in a recess 78c in a load carrying end portion 210 of the load cell 70c.

The force transmitting assembly 34c has been shown in Fig. 10 in an aligned condition. Upon movement of the platform 1 6c toward ihe right, the rocker pin 1 02c tilts from the vertical or upright orientation shown in Fig. 10 through a plurality of offset positions to a maximum offset position corresponding to a position of the rocker pin 102 in Fig. 3. As the components of the force transmitting assembly 34c move to the maximum offset condition, the slider 86c does not move relative to the plate 120c on the platform 16c. Thus, the slider 86c moves with the platform 16c.

When the force transmitting assembly 36c reaches the maximum offset condition, further rightward movement of the platform 1 6c results in a sliding action between a tefloncovered upper side surface 11 8c of the slider 86c and the plate 120c. Thus, the slider 86c remains stationary while the platform 1 6c continues to move towards the right.

Rightward movement of the platform 1 6c is interrupted when the stop surface 66c engages a bumper 64c. When the force urging the platform 1 6c toward the right is removed, the restoring forces on the rocker pin 1 02c move the slider 86c and platform 1 6c together toward the left to the aligned condition of Fig. 10.

Force Transmitting Assembly -Embodiment of Fig. ii The embodiment of the invention shown in Fig. 11 is similar to the embodiment of the invention shown in Figs. 3-5. However, it is believed that the embodiment of the invention shown in Fig. 11 may be preferred. Since the embodiment of the invention shown in Fig.

11 is similar to the embodiment of the invention shown in Figs. 3-5, similar numerals will be used to designate similar components, the suffix letter "d" being associated with the components of the invention shown in Fig. 11 in order to avoid confusion.

In the embodiment of the invention shown in Fig. 11, a force transmitting assembly 34d includes a load cell 70d having a beam 76d with a cylindrical opening 78d in which the upper end portion of a rocker pin 102d is received. The lower end portion of the rocker pin 102d extends into a cylindrical opening 88d in a slider 86d. The slider 86d engages a stainless steel shim or plate 1 20d fixedly connected with a base plate 1 22d on a base 50d. A bumper 64d is engageable with an end surface 66d of the load cell beam 76d to limit rightward (as viewed in Fig. 11) movement of the load cell beam 76d and a platform connected to the load cell beam 76d.

In accordance with a feature of the embodiment of the invention shown in Fig. 11, the load cell beam 76d is provided with a cylindrical recess 21 6 which is co-axial with the cylindrical recess 78d. The recess 216 circumscribes a circular collar 21 8 on the slider 86d.

When the force transmitting assembly 34d is in a maximum offset condition, corresponding to the condition illustrated in Figs. 3 and 4 for the force transmitting assembly 34, the collar 218 engages a cylindrical sidewall 220 of the recess 216. The cylindrical side surface 1 04d of the rocker pin 1 02d is at all times spaced from the rims 11 2d and 11 4d of the openings 76d and 88d. Therefore, the forces which restrain the components of the force transmitting assembly 34d against further movement once they have reached a maximum offset condition are transmitted directly from the slider 86d to the load cell beam 76d. This reduces stresses on the rocker pin 102d.

A pair of annular O-rings 226 and 228 are disposed in annular slots 232 and 234 in the upper and lower end portions of the rocker pin 102d. The O-rings 226 and 228 urge the rocker pin back to the aligned condition shown in Fig. 11. The annular slots 232 and 234 have rectangular radial cross sectional configurations.

Summary A new and improved scale assembly 14 includes a platform 1 6 which is supported by a plurality of force transmitting assemblies 34, 38, 42 and 45. The force transmitting assemblies 34, 38, 42 and 45 and the platform 1 6 cooperate to automatically center the platform relative to an enclosing structure 22 and to align the force transmitting assemblies and platform. The automatic centering of the platform 1 6 and aligning of the force transmitting assemblies 34, 38, 42 and 45 is accomplished by moving the platform back and forth in sideways directions against stops 64, 1 70 which limit motion of the platform.Centering the platform and aligning the force transmitting asemblies 34, 38, 42 and 45 is effective to eliminate sideward force components on the load cells 70 in the force transmitting assemblies.

Each force transmitting assembly 34, 38, 42 and 45 includes an upper member 76, a lower member 86, and a force transmitting member 102 which is disposed between the upper and lower members. The upper, lower and force transmitting members 76, 86 and 102 are movable relative to each other from a maximum offset condition (Fig. 3) through a range of offset conditions to an aligned condition (Fig. 5).

When the upper and lower members 76 and 86 are aligned, they are effective to apply vertically aligned force components 1 36 and 1 38 (Fig. 5) to the force transmitting member 102. When the upper and lower members 76 and 86 are offset, they are effective to apply horizontally offset vertical force components 1 20 and 1 30 (Fig. 4) to the force transmitting member.

In order to enhance the accuracy of the scale assembly, it is desirable to have the platform 1 6 centered relative to a surrounding framework 22 and to have openings 78 and 88 in the upper and lower members 76 and 86 aligned so that vertically aligned force components 1 36 and 1 38 are applied to the force transmitting member 102. To obtain these ends, the platform 1 6 is moved back and forth in a sideways directions indicated by the arrows 144 and 158 in Fig. 6.

As the platform moves sideways in one direction, the upper, lower and force transmitting members 76, 86 and 102 move to a maximum offset condition (Fig. 3). Continued sideways movement of the platform 1 6 from the position shown in Fig. 3 to the position shown in Fig. 4 causes sliding movement between the slider 86 and a slider plate 1 20. During movement from the position shown in Fig. 3 to the position shown in Fig.

4, the upper, lower and force transmitting members 76, 86 and 102 are maintained in a maximum offset condition. Upon interruption of the sideways movement by engagement with the bumper 64, the force transmitting member 102 interacts with the upper and lower members 76 and 86 to effect relative movement between the members from the maximum offset condition (Fig. 4) to an aligned condition (Fig. 5). As the upper, lower, and force transmitting members 76, 86 and 102 move to the aligned condition, the platform 1 6 is moved to a centered position.

When the upper, lower and force transmitting members 76, 86 and 102 are in an aligned relationship with the platform 16, the recess 78 in the upper member is aligned with the recess 88 in the lower member 86.

Claims (15)

1. An assembly comprising a load receiving means for receiving a load to be weighed, a plurality of force-transmitting assemblies for transmitting the load to a base, each of said force transmitting assemblies including a force measuring transducer, a slider member slidable relative to said load receiving means or base, and a self-restoring force-transmitting member for vertically transmitting a force component between said slider and force measuring transducer when said slider and force measuring transducer are aligned, and means for effecting relative sliding movement between said slider and load receiving means or base to align said force measuring transducer and slider member in response to sideways movement of said load receiving means.

2. An assembly as set forth in claim 1 wherein said means for effecting relative sliding movement between said slider and load receiving means or base includes surface means connected with said slider for engaging a portion of said force transmitting member and preventing relative movement between said slider and said force transmitting member as said load receiving means moves in a sideways direction.

3. An assembly as set forth in claim 1 wherein said means for effecting relative sliding movement between said slider and said load receiving means or base includes means for maintaining the spatial relationship between said slider and force transmitting member constant during at least a portion of the sideways movement of said load receiving means.

4. An assembly as set forth in claim 3 wherein said means for effecting relative sliding movement further includes means for changing the spatial relationship between said slider and force transmitting member during a first portion of the sideways movement of said load receiving means and for maintaining the spatial relationship between said slider and surface constant during the second portion of the sideways movement of said load receiving means.

5. An assembly as set forth in claim 1 wherein said means for effecting relative sliding movement between said slider and said load receiving means or base includes means for maintaining a spatial relationship between said slider and force transmitting member constant during at least a portion of the movement of said load receiving means in a first sideways direction, said force transmitting member moving said load receiving means in a second sideways direction under the influence of horizontally offset vertical force components applied to said force transmitting member upon interruption of movement of said load receiving means in the first sideways direction.

6. An assembly as set forth in claim 1 wherein said slider includes first surface means for applying force against a lower portion of said force transmitting member, and further including second surface means connected with said load receiving means for applying force against an upper portion of said force transmitting member, said upper and lower portions of said force transmitting member having surface means for cooperating with said first and second surface means to effect movement of said force transmitting member and second surface means relative to said slider upon interruption of movement of said load receiving means in a sideways direction with said slider and load receiving means in the nonaligned relationship.

7. An assembly as set forth in claim 1 wherein said slider includes first surface means for applying force against an upper portion of said force transmitting member, said force transmitting means further including second surface means connected with the base for applying force against a lower portion of said force transmitting member, said upper and lower portions of said force transmitting member having surface means for cooperating with said first and scond surface means to effect movement of said force transmitting member and slider relative to said second surface means upon interruption of movement of said load receiving means in a sideways direction.

8. An assembly as set forth in claim 1 wherein said force transmitting member has a spherical configuration.

9. An assembly as set forth in claim 1 wherein said force transmitting member is a pin having arcuate upper and lower end portions interconnected by a cylindrical body portion.

10. An assembly as set forth in claim 1 wherein said means for effecting relative sliding movement between said slider and said load receiving means or base includes means for moving said slider along with said load receiving means relative to the base during movement of said load receiving means in a sideways direction.

11. An assembly as set forth in claim 1 wherein said means for effecting relative sliding movement between said slider and said load receiving means or base includes means for enabling said load receiving means to move relative to said base and slider.

1 2. An assembly as set forth in claim 1 wherein said force measuring transducer includes surface means for defining a downwardly opening recess having a vertical central axis, said slider including surface means for defining an upwardly opening recess having a vertical central axis, an upper portion of said force transmitting member being disposed in the downwardly opening recess in said force measuring transducer and a lower portion force transmitting member being disposed in the upwardly opening recess in said slider, said force measuring transducer and slider being positioned with the vertical axes of the recesses horizontally offset when said force measuring transducer, slider and force transmitting member are out of alignment, said force measuring transducer and slider being positioned with the vertical axes of the recesses coincident when said force measuring transducer, slider and force transmitting member are aligned.

1 3. An assembly as set forth in claim 1 further including a first stop surface connected with said load receiving means, and a second stop surface connected with said slider, said first and second stop surfaces being engageable to limit relative movement between said slider and load receiving means or base.

14. An assembly as set forth in claim 1 3 wherein said first stop surface is disposed in a recess connected with said force measuring transducer, said slider and force-transmitting member extending into said recess with said force transmitting member spaced from said first stop surface.

15. An assembly as set forth in claim 14 wherein said second stop surface is disposed on an outer side of said slider, said second stop surface being spaced from said first stop surface when said slider and force measuring transducer are aligned.