US1552691A - Gradometer - Google Patents

Description

Sept 8, 1925.

GRADOMETEIR C. W.'GIRVIN Filed Aug. 16. 1925 Patented sept. 8, 1925 7 I i I i V UNITED STATES PATEN OFFICE CIARLES elm-Ni i T E Put-K, CALIFORINIA. I l v 8 v i I GRA OMETE'RQ Applicant filed August 2 Serial 7N0- 57,66 1.

To all whom it may concern: Figure 4 is a view ofthe type of Fig.1 1,-

Be it known thatI, CHARLES WV; GInvrN, the parts being in the positions assumed I a citizen of the vUnited States, residing at when the vehicle is traveling on a downward Buena Park, in the county of Orange and grade of acertain angle. i c v 5 State of California, have invented certain Figure 5 is a perspective fviewshow'ing a new and useful Improvements in Gradomeportion of the operating mechanism.

ters, of which the following is a specifica- Figure 6 is aside elevation of parts shown tion, reference being'had therein to the ac- Fig; 5, the same presenting a slightly 6O companying drawings. V a modified form} Y f V 1 This invention relates to improvements in As in devices, of this general, type, the

gradient meters, pertaining more p-articupresent invention is designed-to setup the .larly todevices designed to indicate the vaconditions of relative lmovement. between ,riations in grades, etc., automatically; 7 two coacting parts of the mechanism,one of I The invention may be employed in various these parts being practically held constant lines of service, asfor instance, in subma relative to a horizontal plane, the other part 7 rines, in motor vehicles, or in airplanes, shifting relative thereto in such manner as these uses being to ascertain the variation .to indicate, in some form .or another, the from a normal horizontal plane, but,-for;tl1e angular relation of the line thatirepresents purposes of illustration, the device is shown theroad over which the vehicle is travelling 20 as employed in connection with a motor vebearstosuch horizontal plane.

hicle, to indicate the grade over which the In the present. invention the maintenance vehicle may be travelling. v s of the conditions of the horizontal plane is The objects of the invention are to .prodependent upon a suitable liquid, preferably vide a device of this general character which mercury, the specific gravity of this liquid 25 is simple and efficient in operation, durable aiding in securing efliciency,}altho-ugh other in construction, readily installed, andwhich liquids may be used to provide forservicecan be manufactured at a relativelylow cost; a able results. .The shiftable part is carried In addition, the'object is to provide a'dein a fixed position by some part of the vevice that is accurate in itsindications, and hielewhich changes its angle. as the vehicle 30 which is sufiiciently sensitive to changes in follows the contour variation of the road.

conditions and responsiveito such changes The device itself, in the particular. em-

as will provide for efliciency in use, and at bodiment' shown in the drawings, is in. the

the same time prevent temporary and ab- 7. form of a cylindrical casing 10, having its normal conditions from materially affecting axis extending in a horizontal direction and th general tio I transversetothe direction of travel of'the To these and other ends, the nature of vehicle, the casing carrying a wall 11 of ma which will be readily understood, the inventerially smaller external diameter than the tion consists in the improved construction I, internal wall of the casing, and concentric and combination of parts hereinafter more therewith, the twowalls thus forming an an- 40 particularly described, illustrated in the aclnular chamber 12, the axial length-of the companying drawings, and particularly cylinder being as desired, being sufli'cient pointed out in the appended claims. to permit of the carrying of a suflicient In the accompanying drawings,'in which amount ofmercuryv within such chamber as similar reference characters indicate cone to provide foreflicient operation, the mer-- 45 sponding parts in the several views cury, beingindicated at 13. r

c Figure 1' is a vertical sectional view taken The two concentric walls are connected by through the device, theparts being shown 'a partition 1 L, which may, if desired, be in position when the vehicle is travelingin formed integral with either Jor bothv walls, a truly horizontal plane. this partition extending throughout the 50 Figure'Q is a top plan view, partly in sece axial length ofthechamber and preferably tion, ofthe same. I extends radially. It is preferred that this Figure 3 is aface view of thesame. partition be positioned-within the chamber in such manner that when the device as a whole is indicating that the vehicle is travelling on a truly horizontal plane, the partition will extend in a truly vertical plane. This is not actually essential, however, and may be varied, if desired, the purpose being to divide the mercury into two b0d1es the partition being at the bottom of the chamber-and then connect these mercury bodies by a small port 1 1 in the partition, the port being adjacent the bottom of the chamber. The two mercury bodies are thus in direct communication through the port,

and transference of mercury from one side to the other of the partition can and will take place as the instrument is being used.

Casing 10 mayhave its ends formed in any suitable manner, on form being that of having one end integral with the casmg cylindrical wall, the opposite end .being closed by a cap threaded to the casing; this form is shown in the drawing, the cap being indicated at 10 Other ways of producing a closed chamber 12 may be employed, the arrangement being such that the partition will properly fit the end walls-or possibly formed integral withone or bothso that transferenc of mercury around the ends of the partition is practically prevented.

The opposing end walls carry suitcble bearings for a shaft 15 which extends in the axis of theconcentric walls of the chamber, one of the ends of the shaft, indicated at 15 extending beyond the end wall .to receive an arm 16, presently referred to. The other end of the shaft may be stepped in or extend through the opposite end wall,

as may be desired.

The portion of shaft 15 located between the end walls is provided with an upwardly extending arm 17 which forms art of a frame 17 formed of the arm 1'7 projecting normal to the direction of length of arm 17 and having its ends 17 extending clownwardly, preferably parallel to arm 17 but spaced therefrom a distance suflicient to pen mit the free ends of "the arms 17 to be located approximately midway of the distance between the circular walls of the chamber. Arms 17 carry floats 18, of suitable formation, arms 17 being of the same length so that the Jfloats, when arm 17 is in a truly vertical .position, will lie in a horizontal plane. Arm 17 extends upwardly from shaft 15, and has a length such as to locate arm 17 wholly within .the chamber, wall 11 having an opening 11 to permit the passage of arm 1F, and of an angular length sufficient to cover the angular distancesth'at may be included within the .metering limits of the device. 1

Since the surfaceofjthe mercury normally remains on a horizontal plane, it will be readily understood that 'floats 18, when resting on that surface, will retain arm 17* in the vertical plane when the mercury is in equilibrium, even though the casing 10 should be shifted rotatively on its axis. If the shift of the casing be gradual and at low speed, the mercury will remain in practical equilibrium due to the transference of mercury through .port 14-it being understood that shifting of the casing will shift the position of partition 14. Where the shifting of the casing is sudden or with rapidity, there may be a small tendency to lag in responsiveness, since the amount of mercury transferrable per unit of time is limited by the size of the port 1 1 Under these latter conditions, the surface of the mercury in the chamber on opposite sides of partition 14 will momentarily vary from the single horizontal plane, due to the pushing action of the partition on one of the bodies to elevate its surface and the lowering of the surface of the other body due to the increase in space available at the bottom to receive the mercury of the body; but equilibrium is quickly restored by the transfer of mercury from the high surface side of the mercury through port 14. As the surface of the mercury changes the position of arm 17 will change correspondingly due tothe action of the floats.

Owing to the possibility of a splashing of the mercury, wall 11 may have a port 11 leading to the chamber at one side of partition 14, this port permitting escape of any mercury that may .pass throughopening 11 As will be understood, splashing confined to shifting mercury within the chamber provides no material damage, since it simply returns to the body of mercury. In this respect, the curvature of the walls is of advantage in that any abnormal splashing ef fect would tend to throw the mercury drops inward away from the floats and on to the wall 11. A greater advantage however, in

the concentric cylindrical wall formation is e found in the fact that while the walls may move relative to the floats, the latter always maintain the same relative position with respect to the walls, due to the fact that the walls have their movement on the same axis as th frame 17, and being concentric with such axis the floats will have the same spac ing relative to the walls regardless of the position of the casing in its rotative movement.

As will be understood the casing'lO, wall 11 and partition 1 1 move in unison relative to shaft 15 and the parts carried by the lat ter. To support the casing to permit this result to be obtained any suitable support which will hold the casing rigid with the part of the vehicle on which the device isv mounted, is employed. A simple arrange ment shown 'in the drawing is thataof a bracket '19 connecting cap 10* with "a part llii of theindicatorportion of the device, and a pair of brackets 19"" connecting the op-posite end wall of the casing to such part, thus permanently fixing the relation between the indicator part and the casing. Brackets 19 are spaced from the casing end Wall a distancesufficient'to permit the location of arm 16 within such space and outside of the casing; V

Arm. 16 carries, at its outer orfree end, a segmental rack 20, the teeth of which are adapted to engage a pinion of the indicating mechanism which will now be described. In the embodiment of the drawing, .21

indicates the part to which brackets 19 and- 19? are secured, this part being that shown as the dial plate of the indicator. This plate 21 is carried by a suitable casing 22, which may, desiredfhave an annular flange 22* by which the device can be secured on theinstrument board, (not shown) 'ofa motor vehicle, the board having an opening of proper dimensions to permit the passage of the casing, etc, therethrougln so that thelatterwillextend forward .of' the flange 22*, obviously, the conditions may be reversed so thatthe casing may extend'rean wardly instead of forwardly, the essential being that the generahdirection of length of arm 16 shall extend in the direction of general movement of the vehicle, a direction that'is generally that of front to rear of the vehicle itself. Where the face of the instrument board is truly normal to the surface on which thevehicle is travelling, plate 21 can be secured within casing 22 in the siinple manner shown in Fig. 1; where the face of the instrumentboard is inclined, flange22 may befarranged to compensate, or any other suitable arrangement employed so as to arrange plate 21 normal to'a horizontal'plane, asinQFir 1. I-IoWever, it will 0 be understood that. plate 21 need not, in service, beInoi'mal to such horizontal plane, Fig. ft indicating the positions of parts when said plate is out of the position normal to the horizontal plane. Fig. 4' is intended primarily to represent the position of the device of Fig. 1 when the-vehicle is traveling down grade, theindicating mechanism indicating the angle of variance from the horizontal of Figure 1; obviously, the in- ,dicating inechanismunay'be set so that'in the position of Fig. l, the indicator may be at the neutralor horizontal plane indicating point. This is referred to simply to indicate that the device can be readily placed. in position for proper indicating without special preparation offparts,;if necessary or desirable. v 1 I Assuming the. the v m'ou nting of the indicator mechanism is as in Fig. 1,-with-the supporting face of the boardnormal to the vertical, the axis of plate 21 is practically in the horizontal plane'of the axis of shaft 15,and the indications are provided by the movement of a pointer 23,over a calibrated scale 24 shown as carried by plate 21.

Pointer 23 is carried by a shaft 25extend ingv in the axis of plate 21, and supported by a bracket 26 carried'by the plate and by the plate itself. pinion 27 mountedbetween the bracket and Shaft 25 carries a,

plate and in position to mesh with the teeth of they segment rack 20. As shown in Fig. 3, the pointer is in the neutral position, this being the position of Fig. 1] under the as sumed conditions. Obviously, if the position of the pinion be changed to the position Of'Flg. twhile the pointerfremains as iii'Fig/3, or the pointer be shifted on shaft 25, thejposition of Fig. 4 may become the neutralposition of the instrument.

It will be readily understood thatif the flange 22% of Fig. lrbe shifted to an inclined position, the line which would "extend through shaft 25 and the axis of shaft 15 would shift correspondingly, such line being normal to the plane of plate21. This will be understood froni Fig. 4in which flange 22? is shown in, such inclined position. Diir' ingthechange in position, it. willbejun'derstood that the casing 10. will also' have shifted somewha'tindicated by the change in'position of partitionl l relative to-a vci tical plane. As the shifting takes place, the movement of the partition has tended to change the surface 'levelof the mercury on the opposite sides of the partition, thus shifting floats 18 androcking shaft 15, so

that the initial tendency of the segment 16 wouldfbe to maintain its relation to the pinion as shown in Fig. l.

However, this disturbance of the normal equilibrium of the mercury produces the transfer of mercury through portl l to again bring the surfaces of the mercury bodies to the same level, and this movement of the surfaces causes movements of the floats 18 to return frame 17 tothe'position of Fig. 1, this movement of the frame being effective on shaft 15 and hence on arm 16 to shift the position of the segment rack 20. This shift- 'ing of the segment-rotates pinion 27 and pointer will move in the opposite direction.

The responsiveness of the instrument thus far described, will depend upon the size of port 149.", Should theport be sufiiciently large to permit instant response, the sensit-iveness of the instrument will be such'as to make it diflicult'to gain an accurate reading of the scale, since any slight or short variationas for instance the striking of a stone or the running into a road depression, would cause corresponding movement of the pointer. I prefer, therefore, to employ a comparatively small port 14?; this will permit a fairly close response, and at the same time tend to prevent unsteadiness of the pointer in travelling over rough roads.

In the drawings, I have shown a weight portion 28 on one of the arms 17 for the purpose of acting as a counterbalance to the arm 16 and rack 20.

The structure so far described provides for efficient service and produces accurate readings, and for general usage is satisfactory. However, there are certain conditions of service that tend to set up a false indication, this being true in meters of this type generally; the conditions referred to are those of acceleration and deceleration of the vehicle. With either condition, the factor of the inertia of the mercury in the chambers becomes active.

For instance, if the device be mounted in .the car as in Fig. 1 with the casing in ad vance of the indicator, and the car traveling toward the left, acceleration of the vehicle moves the instrument forward at a corresponding increase of speed, but there is a momentary tendency of the mercury bodies to lag; since the position of the partition is not changed there is some transfer of mercury, from one side of the partition to the other, causing a difference in level, the result being that there is a tendency to shift the position of the floats and thus set up motion of arm 16 to actuate the pointer; should the driver scan the indicator at this moment he may be given a false indication. A similar condition exists during deceleration.

The action is due to the mobility of the mercury as compared with that of the easing, it being necessary for the mercury to overcome the conditions of inertia before the surface is restored. The condition rapidly vchanges to the normal, but during the period the indication made is more or less false, due to the fact that the disturbance of the surfaces has affected the positions of the floats 18.

To overcome this tendency, I preferably employ a body, such as a weight, for in stance, also subject to the conditions of in ertia and which is positioned to be active in opposition to the conditions of inertia of the mercury. For instance, in Fig. 5, I have shown an arm 30 extending vertically from shaft 15, the upper end of the arm carrying a weight 31. Since shaft 15 is capable of rotating, it will be understood-that weight 31is subject to the laws of inertia, and since theldirection of lag of the weight is:the-. sa'me as that of the mercury, and the weight and the mercury are located on opposite sides of shaft 15, it will be understood that the movement of the floats necessary to shift arm 16 must first overcome the resistance of weight 31. As a result, the opposing forces tend to neutralize the effect of each to shift arm 16, so that the latter is less likely to shift position during this period. When the change is in the direction of .deceleration, the reverse action takes place and again the arm 16 is held in a more or less stable position. As will be understood the action is temporary, and hence the mercury quickly returns to normal position.

Instead of employing a separate arm or weight, it will be understood that the same action can be provided by placing the proper weight 31 on frame 17, as indicated, for instance, in Fig. 6.

In either case it will be understood that when the surface of the mercury is on the single plane, the weight 31 is in a state of balance and ready for action when needed whether for acceleration or deceleration con- .ditions.

While the movement of frame 17 in presence of a change in grade will tend to shift arm and move weight 31 in the direction which would seemingly tend .to increase the amount of movement of frame 17 to set up a false indication, the weight has a different action, as will be understood from the following:

Assuming the vehicle to be travelling toward the left in Fig. 1, and a sudden change in grade equal to that shown in Fig. 4 is .encountered, the initial tendency would be to raise the float on the right through the rise in the level of the mercury, and to lower the float on the left, the level of its supporting mercury being lowered; this action would swing the weight 31 toward the left to add its value toward tilting the frame still farther. When this action is present, the added weight would tend to cause the float at the left to submerge to a greater extent than normal, at the same time tending to decrease the amount of submergence of the float at the right. Obviously, an increase of submergenceof the float at the left would act to displace mercury and thus increase the depth of submergence.

Under these conditions the variation thus provided in the buoyancy of the two floats produces a power factor active on the float at the left to raise the latter, this being continued by the mercury being transferred through port 1?, the result being that the The moment effect of weight 31 is of greatest value when its distance from its balancing point is greatest, and it is at this point that the maximum buoyancy value is present; as the:

' I shaft 15, so that thefloats are practically intheir normal conditions of-submergence.

value of the buoyancy factor decreases the moment effect also decreases since the weight is returning toward its position of equilibrium. As the mercury is approaching its position of equilibrium the weight is approacningits vertical position where the weight is being exerted mainly on the From this it will be understood that the buoyancy factor inherently opposes the weight factor in the attempt to set up false indications. But the presence of the weight tends to dampen the action of, the device 5 tra'lize minor tendencies to change, without,

however, disturbing the accuracy of the meter. \Vith the weight present, port 1 F may be comparatively small.

' To balance frame 17 I preferably placea weight 28 on the arm 17 opposite the direction of extension of arm 16, the weight counterbalancing the arm andsegment.

As shown-in Fig. 3, I prefer to calibrate the indicating face insuch manner as to indicate the-grade on each side of the neutral. I employ the usualbezel glass to protect the pointer and indication face.

Obviously, the calibrations can be et trolled as to distance in various ways, as by changing the size of the pinion, by varying the length of arm 16, or both. 7

From the above description it is believed that the advantages will be more or less obvious. The mercury is within a closed chamber but under no restraint as to splashing effects, the latter not affecting the oper-' ations of the device. The wall of the chamber 12 is concentric with the axisofthe shaft 15 and is cylindrical in shape so that regardless of the position of the instrument, the level of fluid in the chamber will remain the same. The device is simple and efficient in operation and is of a'constr'uction that will withstand the conditions of service.

I prefer to arrange the dimensions such that the level of the mercury is normally somewhat below the axis of shaft 15, thus tending to prevent leakage of mercury through the bearings, which can, if desired, be comparatively loose, thus decreasing the cost of manufacture.

While I have herein shown one or more ways in which the invention may be pro ice, and I therefore desire to be understood as reserving the right to make any and all such changes or modificatlons as may be found desirable or necessary, in so far as the same may fall within the spirt and scope of the invention asv expressed in the accompanying claims when broadly construed.

. Havingthus described my invention, what I-claim as new is:

:1. In grade meters and thelike, a cylindrical casing havingan annularchamber of uniform cross-section on radii of the casing,"a 'perforated member extending substantially radially of the, chamber to divide the" chamber below the axis of the chamber, said chambercarryinga liquidon opposite sides of and in communication through the perforated member, a rigid frame pivotally mounted in such axis, floats carried by the frame and located within said chamber on opposite sides of such member, indicating mechanism" including a movable indicator, and means 'operatively connecting the frame and said indicator for translating relative movements of frame and casing into move- I ment of the indicating mechanism.

2. In grade meters and the like, a casing having an annular chamber. of uniform' cross-section on radiiof the casing, the

chamber walls including inner and outer concentric walls spaced fro'm'thej axis of the chamber, a perforated member connecting said walls below such axis to divide the lower portion of said chamber, said chamber carrying a liquid on opposite sides of and incommunication through the perforations of such member, a rigid frame pivotally mounted. in such axis, floats carried by said frame and located within said chamber on opposite sides of such member, indicating mechanism including a movable indicator, and means operatively connecting the frame and said indicator for translating relative movements of frame and casing into movement of the indicating mechanism.

f 8. A meter as in claim 2 characterized in that the frame extends through the. innerv ,wall of the chamber, vsaid wall having an upwardly from the axis ofthe chamber and an arm carried thereby and extending transversely thereof, said latter arm carrying members extending downwardly within the chamber substantially parallel with the upstanding arm, each of such members carrying a float.

5. A meter as in claim 1 characterized in that the rigid frame member carries an arm rigid therewith and outside the casing, said arm extending in the direction of the indicating mechanism and carrying a gear element co-operative with a companion gear element ofthe indicating mechanism to 0peratively connect the frame with the indicator. p Y

6. A meter as in clannl characterized in that the frame includes a pivot portion which projects beyond the casing and carries an arm rigid therewith extending in the direction of the indicating mechanism and forming a part of the means operatively connecting the frame and indicator, a counterpoise carried by the frame within the chamber for balancing said arm.

7. In grade meters and the like, wherein variation in levels of liquid surfaces is operative to produce movements of an indicator, a casing for the liquid, a rigid frame pivoted in the casing floats carried by the casing adapted to be supported by the liquid to provide relative movement between frame and easing during variations in level of the liquid surfaces, means o-peratively connecting the frame and indicator, and means operatively connected with the frame for opposing float movement tending to be caused by inertia of the liquid.

8. In grade meters and the like, wherein variation in levels of liquid surfaces is operative to produce movements of an indicator, a casing for the liquid, a rigid frame pivoted in the casing, floats carried by the casing adapted to be supported by the liquid to produce relative movement between frame and casing during variations in level of the liquid surfaces, means operatively connecting the frame and indicator, and a weight element carried by the frame above the axis of frame movement and operative to oppose float movement tending to be caused by inertia of the liquid.

9. A meter as in claim 1 characterized in that the frame carries means operative to oppose float movement tending to be caused by inertia of the liquid within the chamber.

10. In a grade meter and the like, a casing, a body of liquid therein, a rigid frame pivotally mounted in the casing and having depending arms equidistant from and on opposite sides of the pivot axis of said frame, floats carried by said arms respectively so as to be buoyed by said liquid, an indicator, means operatively connecting the frame and indicator, and means carried by the frame adapted to oppose movement thereof tending to be caused by inertia of said liquid upon acceleration or deceleration of said meter. v

In testimony whereof I affix my signature.

CHAS. W. GIRVIN.

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