CA1048122A - Tilt responsive device for setting and retaining a fixed direction - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An apparatus for sensing and and indicating the orientation of an object, such as a machine part, in a generally horizontal plane comprises two interconnected tilt sensing devices whose resistances vary responsive to the tilt of the devices. At least one of said sensing devices is mounted rotatably and via a mechanism connected to the object.

Description

The present inYention relates to a dev~ce for setting and retaining a fixed direction in an essentially horizontal plane. The m,ain field of application of such a device is the alignment, and particularly the repeated alignment, of a tool such as a drill or the like. Alignment problems of this kind arise when drill-ing rock when operating earth working or road building machines, in workshop practice, etc.
When working e.g. with a rock drill it may be necessary to drill a series of holes which are to be as parallel with one another as possible. The holes can extend either in an essen-tially horizontal or in an essentially vertical plane or at a spec-ified inclinatlon to one of these two planes, depending on - whether the drilling is made e.g. in a wall, in a bottom or in a ~eiling. It is often required, e.g. 9 in tunnel driving ~r the like that the bore holes be parallel one with another according to two coordinates, i.e., so that they not only be coincident with a single plane, but also extend at a constant mutual distance. This re~uirement mea~s in effect that the drills be located both in a single plane, and parallel one with another.
These requlrements are difficult to meet in practice, mainly because at the transfer of the rock drill from the place where one hole or one series of holes has been made to the place of another hole or hole series, the slope of the ground often changes. I~ is therefore not possible simply to retain the re- !
lati~e position between the drill ~eeder and the machine stand, as adjusted at the ~irst drilling.
It has therefore been necessary to readjust the drill fe~der after such move with the aid of a water lev~l~ which is a rather time-consuming operation. Besides, the achieved re-I sult depends on wh~r~, again~t what 50rt of a face and in which ~` ~

way the watçr level was applied to the respective machine part.
An automatic levelling control and clinometer has beenproposed in the U.S. patent 2,893,13~ for holding the scraper blade of a road grader at a predete~nined angle of inclination, which clinometer in one embodiment has a tilt-responsive posi-tion sensor in the form of a V-shaped tube of non-conductive material, partially filled with electrically conductive fluid such as mercury. ~hrough the tube extends lengthwise a resis-tance wire which is thus partially immersed in the volume of mercury. The mercury volume is at its lowest point with the aid of an intermediate contact and via an amplifier connected to an amperemeter, while the resistance wire is at both its ends outside the tube connected to a pair of resistors in a bridge circuit of the Wheatstone type. The other pair of re-sistors in this bridge circuit is formed by those legs of the resistance wire, which are not shunted by immersion in the mer-cury in the tube. A sensor element of this kind in order to ~ -be sufficiently sensitive and not unduly damped, must have vacuum over the mercury levels in both legs of the V-shaped tube. A gas-tight construction, necessary to keep the vacuum, is however more expensive than a construction where no regard has been paid to the ambient pre~sure. The vacuum also brings about the disadvantage that the mercury level can hardly be pro-vided with a layer of glidin~ o~ or overcoming the adhesion of mercury to a glass tu~e. T~e yacuum can also c~uSe undue ten-sion in a glass tu~e. A V-shaped sensor can be used only within a relatively limited deviation to sides of the zero position (in which the bendiny poin~ of the t~e lies lowest~ and can never be used when the deviation is 90 or more, An object of the present inventionisto provide a se~ting device o~
the above t~pe wl~ich can be used for position measurement or adjustment in or near a horizontal plane, with compensation for any vertical inclina-tion that may occur.

:;~ 2-- ' ~ ., .

According to the present invention, an apparatus is provided for sensing and indica ing the orientatio~ and relatively movable part of an object, such as palrts of a machine, in an .
approximately horizontal plane, comprising first and sec~nd electri~al sensors having an electrical resistance varying responsive to their tilt with respect to the vertical force of gravity, said sensors being arranged in approxLmately parallel mounting planes and adapted ~or being mounted on the measured ob]ect in such a manner that their said mounting planes are approximately vertical; electrical power supply means for pro-viding powar to the sensors; circuit means for interconnecting the sensors electrically in such a manner that tilt-responsive resistance variations in the first and in the second sensors caused by shared motion of the sensors ~ith re~pect to the :
vertical force of gravity are equal and cancel aach other and in such a manner that tilt~responsive .
resistance variations caused by relative motion of the sensors with respect to each other produce an indicia of said relative motion; and, first mechanical means, including a rotatable sensor mount play-~ree for tilting the first snesor in its mounting plane, independently o~ the second sensor and respensive to the movement of a part of the measured object in the approxi-mately horizontal plane.
Preferably, ~he second seneor is fixedly mounted on another part o~ the measured ob~e~t than a part by which the first sen~or is influenced. The apparatus according to the pre-sent invention ~ay co~prise second ~echanical mea~s, includi~g a rotatable.sensor mount and a pl~y-free mechanism allowing the tilt inq of the second snesor ln its mounting plane indapendently of the first sensor and rQsponsive to ~he movement in the said a~ least approxLmately horizont~l plane o~ ~nother part o~ ~he measur~d object than that by ~h~c~ ~he ~ t ~en~o~ is in~luQnced~ Pr~erably, saiA first and/or second play-fr~ mechanical mean~ includes ;~ bevel gear.

G_- The inv~ntion will.no~ be described by way of axample !' ~L~4~ :

with reference to the accompanying diagrammatic drawings, in which: .
': ~
FIG. 1 is a schematic representation of a sensing .
tube according to the state of axt; :
FIG. 2 is a view of one preferred embodiment of a sensing tube for use in an apparatus according to the invention;
FIG. 3 shows an embodi~ent o~-t~e ~en~ng :tu~e alternative to that of Fig. 2;

FIG. 4 is a schematic representation of one embodiment .
of the apparatus according to the invention; .
FIG. 5 shows schematically a further ~mbodiment of the apparatus according to the invention;
FIG. 6 shows schematLcally yet another embodiment of the apparatus according to the invention. lOn the sheet of Fig. 4).
FIG. 7 shows the arrangement of an apparatus accordîng to Fig. 5 on a rock drilling machine shown ~n a schematical plan .
view; and FIG. 8 is a simplified cirauit diag~am of ~he embodi~
ments according to Figs. A to 7. - : -Referring now t~ Fig. 1, a V-s~aped measuring tube of electrically non-conductive material such as glass or plastic is, according to the state of art, located in a housing 10 and partially filled with conductive liquid such as a volume of mercury 21. A screw 11 serves for fastening the housing 10 to an object (not shown) the vertical direction of which is to be measured. In the measuring tube 20 extends lengthwise a resis-. . .
i tance wire 30 the two end points 31, 32 o~ which are connectedto resistor elements 41, 42 which form a resistor pair in a Wheatstone bridge circuit. The end points 31, 32 are also con-nected to terminals 51, 52 for ~onnecting a source of electrical energy (battery) 50. The midpoint between the ends 31, 32 of the resistance wire 30 is connected to an ammeter 22 which, in turn, is further connected to junct:ion 43 between the two resis-tor elements 41 and 42.
The liquid levels 23 and 24 in the left and in the right leg of the measuring tube 20 lie in the example shown in ~he drawing at the same height over the intermediate contact point 33, with the result that the parts 34 and 35 of the resistance' wire 30, which are not immersed in and thus shunted by the mer-cury volume 21 are equally long and ~hus have equal resistance.
Th~ pointer 25 of the ammeter 22 therefore indicates zero or some other selected reference value. When the device is tilted to one side this state of electrical equilibrium is disturbed, and the pointer 25 indicates the de~iation.
In Fig. 2 where corresponding components have re-ceived identical or similar reference characters as in Fig. 1, the sensing tube 20a according to the present invention is made of glass, has an annular shape and is fully enclosed. The re-sistance wire 30 disposed in the sensing tube 20a bas two sep-arate end points 31 and 32 and an intermediate contact point 33.

The points 31, 32, 33 are connected ~ conductors~, ~ and d corresponding ~n turn to terminals 52, 51 and 43 in the embodiment of Fig. 1.

,. . .

8~2;~
Fig. 3 shows the embodi~ent of the sensing tube with a multiple intermediate contaci:. Tube 20ta is shown in a position turned by 90 relative to t:ube 20a in Fig. 2. T~be 20a would not be operable in such a position becau~e the contact point 33 would lie outside the mercury column 21 or the dis-proportion between the two legs of this column would be so ex-treme that accurate measurement were not possible. The housing - lOa is for simplicity not shown in Fig. 3. Along the periphery of t~be 20'a are disposed several contact points 33a in the form of metal pins penetrating through and fused into the wall of the glass tube 20'a. These pins 33a are outside the tube 20'a electrically connected one to another by a conductor 36, forming a part of or connected to the earlier named connection d to the indicator means (Fig. 2~. The contact pins 33a have such mutual distances, that at least one of them always is immersed in the mercury volume 21, i.e. a distance which is -shorter than the length of this mercury volume or column. Ir- -respective to which position the tube 20'a is tilted, some of the pins 33a will always via the mercury volume 21 be in con-tact with the resistance wire 30. Because all pins 33a are, with the exception of the connection via the mercury volume, -~ independent of the resistance wire 30, the mercury volume 21 forms a movable but permanent electrical connection between ~ --6--.; _ . . .

~41~1ZZ 11 some of the pins and the resistance wire. It is ~bYiously also possible to place the connecting wire 36 inside the sensor tube 20'a, parallel with but isolated (with the exception of the mer-cury volume of coursel, from the resistance wire 30, instead of ; the individual con~act points or pins 33a, fused into the wall of the sensor tube thus creati~.g an infinite ~umber of contact points.
In Fig~ 4, an apparatus according to the present invention is shown for indicating the orientation of an object in a horizontal plane. Two sensing tubes 20, 20b, disposed in generally vertical planes, are arranged generally parallel with one another and tube 20b is mounted on a mount 44 which is rotatably arranged in a housing lOb, as is symbolized by a dashed circular ~
line. ~he mount 44 is mechanically connected to the respective :
object by a bevel gear drive 45 which terminates at an arrow 15a symbolizing the said object, The housing lOb is shown with the front and upper walls removed to show that tube 20 is fixedly secured to the housing lOb. A power sour~e is connected b~tween both tubes 20, 20b essentially in the same way as in FigO 8, the connection no~ being sho~n in the dra~ing for clar~t~. It will be readily understood from the Figures that tilt responsive resistance variations in the first sensor 20 and in the second sensor 20~
caused by sh~red motion of the sensors with respect to the vertical force of gravity will be approximately equal and will compensate ; each other. For example, if ~he housing lOb tilts with respect to the vertical, the sensors will experience shared motions and ~he resistances detected by the indicator 22 will increase or decrease simultaneously and to the same extent, so that indicator ; 22.remains balancecl, If, ho~.ever, the.~ensor 20b ~otates ~ith respect to the housing while the sensor 20 remains fixed with respect ~ the housing, the indicator 22 will indicate the extent of this relative motionl i.e., motion which i8 not shared by both sensors.

Fig. 5 shows another em~odLment of the present invention wherein sensing tubes 20 and 20b are influenced by different parts (obj~cts) of a greater entity such as a boring machine, etc. Two sens-or units (housings~ and one indicator unit (hou~ing) or one complex unit ~housing incorporating one sensing tube and the indicator) and one additional sensor unit are examples of possible configurations of this arrangement, shown in Fig. 7, which will now be discussed.
A drilling machine has an undercarriage or a truck 55, the front part of which is shown in plan view ~ FigO 7. The truck 55 runs on caterpillar tracks 58 which are driven by wheels (not shown~ having a wheel axis 58a. Pivotally arranged on the truck 55 is an arm 56 which in turn bears, also pivotally~ a feeder 57 for a drill or the like ~not shown). Fixed to the arm ~ 56 is a sensor unit lOc with the first, ~otatable sensing tube - 20b (Fig. 5 or 6). This tube 20b is connected ~ia the bevel gear drive 45 to the feeder 57 and can thus together with the said ~ -feeder be set relative to a line 58b (Fig. 5) which represents the longitudinal axis of the truck 55, perpendicular to the wheel axis 58a. Both lines 58a and 58b lie in the horizontal plane, which also is the drawing plane of Fig. 7. The arrows 15a and 15'a in the later more fully explained Fig. 6 represent symboli~
cal-ly the machine parts by which the rotatable sensors are influenced, i.e., the feeder 57 and the t~uck 55 of Fig. 7, re-spectively which axe to be set in a selected direction in the horizontal plane.
The indicator means 22 indicates a compensated value, ; ~ecause there is al~ays another sensor unit or a ~ombined unit (SeI150r plUS indicator) ~uch~as 10lc with sensing bube 20 ~Fig.-5) arranged on the arm 56. The ~alue indicated by the inaicator is comp~nsated in that i~ reflects ~he relati~e po~ition of the respective machine part ~ith re~pect t~ ~ r~ference line such as , , , ;

~4~
58b regardless of the orientation of the truck with respect to the direction of the force of gravity, i.e., the true vertical direction. The connection 53a (Fig. 7) symbolizes, in general, the-electrical connection of parts lOc and 10~c, shown in detail -in Figs 5 and 6.
~ he disposition according to Fig. 6 differs from that according to Fig. 5 in ~hat the sensor unit lO'c on thc arm 56 (Fig. 7) is replaced by a sensor unit which is identical with the sensor unit lOc, i.e., has also a rotatable sensing tube ~OIb, its bevel gear 45' being connected to the truck 55. Components of the sensor unit 20'b are identified by the same reference charac-ters as in unit 20b, complemented with a dash. In operation, both sensor units lOc, lO'c are zeroed parallel with the longitudinal axis 58b.
A power source 50 (Fig. 8) is always connected to the junction between the two sensing tubes 20 and 20b (or 20b and 201b) which is not shown for clarity in Figs. 5 and 6.
The wiring diagram according to Fig. 8 represents the circuit for measuring horizontal directions with compensation for vertical inclinations, according to the present invention, and the same reference characters a~ in the previous ~igures are used;
20d represents any of the sensing tubes ~0, 20b or 201b. It will be apparent from ~he diagram that all components are connected to an addition--~nd~or sabtraction unit 40 of any known conventional design.

Those skilled in the art will appreciate that the tubé or ~ubes according to the l~resent specification and accompanying claims also can be realized, e. g., as a groove in a first body such as a plate. covered by a second body ~ith or without a corresponding groove. It is further evident 30 ~ that in all embodiments one or both of the two sensing tubes may have a multiple intermediate contact according to F`IG. 3. It i~ also obvious that _g_ the novel functional combination of two sensi~ s, exposed in the present specitication ~or the measurement of horizontal directions with corrlp~nsation of vertical inclinations, is :in principle also realizable wit,h the aid of previously known tilt-responsive~-electrical elements, such as the conventional V-s~aped sensing tubes according to Fig.
1 or, for that matter, any tilt-responsive sensor having an electrical resistance varying responsive to ~he tilt, and are therefore included with the scope of the claLms.
The principles, preferred embodiments and modes o~
operation, of the present invention have been described in the foregoing specification. The inven~ion which is intended to be protected is not, however, to be construed as limited to the particular forms disclosed since these are to be regarded as illustrative rather than restrictive. Variations and changes may be made by those skilled in th~ art without departing from the spirit and scope of the present invention.

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Claims (11)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An apparatus for sensing and indicating the orientation of relatively movable parts of an object, such as parts of a machine, in an approximately horizontal plane, com-prising first and second electrical sensors having an electrical resistance varying responsive to their tilt with respect to the vertical force of gravity, said sensors being arranged in approxi-mately parallel mounting planes and adapted for being mounted on the the measured object in such a manner that their said mounting planes are approximately vertical; electrical power supply means for providing power to the sensors; circuit means for interconnect-ing the sensors electrically in such a manner that tilt-responsive resistance variations in the first and in the second sensors caused by shared motion of the sensors with respect to the vertical force of gavity are equal and cancel each other and in such a manner that tilt-responsive resistance variations caused by relative motion of the sensors with respect to each other produce an indicia of said relative motion; and, first mechanical means, including a rotatable sensor mount a play-free mechanism for tilting the first sensor in its mounting plane, independently of the second sensor and responsive to the movement of a part of the measured object in the approximately horizontal plane.

2. The apparatus of claim 1 wherein the second sensor is fixedly mounted on another part of the measured object than a part by which the first sensor is influenced.

3. The apparatus of claim 1 comprising second mechan-ical means, including a rotatable sensor mount a play-free mechanism allowing the tilting of the second sensor in is mounting plane independently of the first sensor and responsive to the movement in the said at least approximately horizontal plane of another part of the measured object than that by which the first sensor is influenced.

4. The apparatus of claim 1 wherein at least one of the sensor via its mount is connected to a drill feeder of a rock boring machine for setting the drill feeder.

5. The apparatus of claim 4 wherein the first sensor is influenced by the drill feeder and the second sensor is influenced by a base means for pivotally supporting a connecting arm which in its turn pivotally supports the drill feeder of the rock boring machine, both sensors being seated on the connecting arm.

6. The apparatus of claim 1 wherein the first and second sensors each include:
a vessel;
a resistance wire disposed within the vessel;
at least one intermediate electrical contact point on said wire; and a flowable, electrically conductive material contacting said resistance wire and said electrical contact point for pro-viding a varying resistance between said contact and wire depen-dent upon the orientation of the sensor in a substantially verti cal plane.

7. The apparatus of claim 6 in which at least one of the sensors is arranged in a sensing unit separate form the rest of the apparatus.

8. The apparatus of claim 6 wherein the resistance wire is provided with a plurality of intermediate contact points for making electrical connection with conductive material 9 said contact points being spaced apart distances which are shorter than the length of a column of the conductive material in the vessel.

9. The apparatus of claim 6 wherein the vessel is configured in the form of a closed curve.

10. The apparatus of claim 1 wherein the second sensor is fixedly mounted in the same housing as the first sensor.

11. The apparatus of claim 7, wherein the said first mechanical means includes a bevel gear mechanism.