US2836899A

US2836899A - Gauges

Info

Publication number: US2836899A
Application number: US364888A
Authority: US
Inventors: Boosey Frederick Robert
Original assignee: SIGMA INSTR CO Ltd
Current assignee: SIGMA INSTR CO Ltd; SIGMA INSTRUMENT Co Ltd
Priority date: 1952-07-01
Filing date: 1953-06-29
Publication date: 1958-06-03
Anticipated expiration: 1975-06-03

Description

F. R. BOOSEY June 3, 1958 GAUGES 2 Sheets-Sheet l Filed June 29 .1955

June 3, 1958 R. BOOSEY 2,836,399

GAUGES Filed June 29, 1953 2 Sheets-Sheet 2 2,836,899 Patented 'June 3, 1958 GAUGES Frederick Robert Eoosey, Letchworth, England, assignor to The Sigma Instrument Company Limited, Latchworth, England, a British company Application June 29, 1953, Serial No. 364,888

Claims priority, application Great Britain July 1, 1952 Claims. (Cl. 33-169) This invention relates to gauges and is concerned with the measuring head of a pneumatic gauge.

According to the present invention there is provided a measuring head for a pneumatic gauge, said head comprising a measuring anvil and a needle valve, the needle valve being connected to the measuring anvil so that measuring movement of the anvil causes movement of the valve, the needle part of the valve being located in a jet and being shaped so that when the anvil is moved the annular escape area between the needle part and the jet varies directly with the movement of the anvil.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made to the accompanying drawings, in which:

Figure 1 is a side elevational view of a measuring head and its support,

Figure 2 is a longitudinal section through the measuring head, with the support removed, and

Figure 3 is a perspective view of a detail of the head.

In Figure 1 the measuring head is shown as possessing a body 1 which completely encases the working parts of the head. The head has a measuring anvil 3 that cooperates with a second measuring anvil 4. The body 1 is rigidly attached to a base member 54 and this in turn is clamped to a base plate 50, which is used as the medium for securing the measuring head to the machine or mechanism to which it is desired to attach the head.

In the example cited, the base plate 50 is attached by means of a fixing screw 14 to a block 15, this in turn is fixed to a rail 16, which is attached to the body of the machine, as is also a rail 17 which supports the bottom or fixed measuring anvil 4.

The plate 50 (Figure 2) is formed with cavities 51 and slots 52 which permit machine screws 53 to pass through the plate 50 and secure the base member 54 thereto. The heads of the machine screws 53 are sunk into the plate 50 so that the latter shall present an uninterrupted surface for secure attachment within the block 15 (see Figure 1). Blade springs 55 are securely fixed to the base member 54, and are similarly anchored to a floating member 56. Cheeks 57 of a U-shaped bracket 57A carried by the base member 54 have ball races indicated at 58 which carry a transverse shaft 59 extending between the cheeks 57 and supporting a lever 60. The U-shaped bracket 57A is shown in Figure 3 and is secured to the member 54 by a screw 61 and pins 62. A block 87A extending horizontally from the base member 54 limits clockwise movement of the lever 60.

The free ends of the cheeks 57 are connected by a transverse bar 63 carrying an anchorage 64 for one end of a tension spring 66 the other end of which is hooked upon an arm 67 secured to the floating member 56. The effect of the tension spring 66 is to tend to hold the floating member 56 in a lower position. The member 56 has a laterally extending block 5 that carries an adjusting screw 6 lockable thereto by a nut 7. The lower end 8 of the screw 6 co-operates with a block 9 extending laterally from the base member 54 and serves as an adjustable stop for limiting downward movement of the floating member 56. The blade springs 55 are parallel and are employed in pairs at the top and bottom of the floating member 56, the blocks 5 and 9 being located between the two parallel blade springs 55 of the lower pair. The lower end of the floating member 56 has a block 68 attached to it, such block being adapted for removable engagement with the anvil 3.

The lever 60 has sapphire platens 69, 70 at the ends thereof. The knife-edge 71 of a knife element 72 carried by a spring strip 73 that is clamped to the floating member 56 bears on the platen 69. Flexing of the spring strip 73 permits the distance between the lever pivot 59 and the point of contact between the knife-edge 71 and the platen 69 to be varied. A screw 74 is carried by the floating member 56 for adjusting the position of the knife-edge 71, the strip 73 spring urging the knife element 72 against the tip of the screw 74. The screw 74 is passed through a tapped hole in a spring strip 75 that is secured to the member 56, the strip 75 serving for restraining adjusting movement of the screw 74. The body 1 is provided with a removable cover 76 to provide easy access to the screw 74 for adjustment purposes.

The lower end 77 of a needle valve 78 bears on the platen 70 carried by the lever 60. This needle valve 78 is vertically disposed and is carried by its untapered spindle portion in a body member 79 that is fixed to the base member 54 by screws 80. A vertical adjusting screw 81 is passed through a tapped hole in the body member 79, the tip of the screw 81 abutting against the top of the U-shaped bracket 57A. The screw 81 serves for adjusting the body member 79 vertically by an amount of the order of a few thousandths of an inch. The needle valve 78 is urged downwardly by a spring 82'. An open-ended air pipe 83 is passed through the top of the body 1 and the lower end portion of the pipe 83 is secured in a recess 84 in the body member 79. The recess 84 leads to a circular orifice or jet 85 in which the needle part 86 of the valve 78 operates. The needle part 86 of the valve is formed as a paraboloid or has part of its surface of paraboloid form.

it will now be appreciated that upon upward displacement of the anvil 3 from the position shown in Figure 2 the floating member 56 will be upwardly displaced against the action of the tension spring 66 and will cause the knife edge 71 to rise.

The base member 54 together with the body 1 and the floating member '56, are as a whole adjustable in the direction of movement of the floating member 56, with respect to the supporting plate 50. This adjustment is achieved by means of a hollow rod '87, one end of which carries a control head 88. The rod 87 is a turning fit in the base member 54 and has an eccentric portion 89 which is a turning fit in the plate 50. A shaft 90 passes through the hollow of the rod 87 and has at one end a control head 91 fitting within the control head 88 of the rod. The shaft 90 has a collar 94 thereon, the collar bottoming in a recess 95 formed in the control head 88. At the other end, the shaft 90 has a screw-threaded portion 92 which receives a nut 93. It will now be understood that when the control head 91 is turned to slacken the nut 93, the control head 88 may then also be turned to cause the base member 54 with associated parts, to be slidingly adjusted relative to its supporting plate 50. The degree of adjustment obtainable in way will be limited by the degree of eccentricity of the portion '89 with respect to the rod 87. A suitable clearance is allowed between the floating member 56 and the rod 87 toallow the floating member to move without'fouling the rod. When. the head 88 has been turned to secure a desired position of adjustment, the head 91 may be tightened whereby the shaft 9! draws down onto the supporting plate fiflby virtue ofthe nut 93, andicauses :the, base "plate :54 tob'e immobilised-with respect-to the supportingpla'te SO. i j 1 V i The upper endlof thegbody Ilis closedby a plate 96 through which J the upper .end of the pipe 83. projects. The body 1 has .a'n'aperture97 that is masked by a. grill 93.

The measuring head described above operates'as follows. Air is "fed'to the upper end of the pipe 83,:via

the pneumaticg-gauge'systeni described in our co-pending patent application. No. 353,744; A workpiece to be measured is introduced :between .the fixed anvil 4 and the;measuring;a nvil .3, whereby 'the latter is caused to move upwardly. Upward :rnovement of the measuring 78, which'is spring-urged downwardly, causes the lever 60 to {rot-ate "so that the platen 69 remains in contact with the knife-edge 71, The extent of movement of the needle valve 78 is proportional to the movement of the measuring anvil 3. Movement of the needle valve 73 causes a change in the annularescape area between the needle part 36 and the jet 8S and hence changes the rate of flow of air through the pipe 83 and alters the pressure of the air in thispipe. Airescaping from the jet 85 passes from the body 1 by way and the grill 98. 7

Since the needle part 86'is of paraboloid form it will be understood that movement of the valve 73 causes a of the aperture'9l V proportional alteration in the escape area, hence'the exa tent {of movement of the float in the glass manometer tube of said pneumatic gauge system varies directly with the movementlof the measuring anvil 3.

a 'By adjusting thepositionat which the knife-edge 71 encounters ;.the.platen 69, it is possible to vary the degree of mechanical magnification of the measuring head. In the --c-onstructional form of the measuring head as shown'it is possibleto adjust the position of the knifeedge to give ,a leverratio between knife-edge movement and needle valve movement of between 2: 1 and;1:l.

, When it is desired to measure a number of dimensions of a work-piece simultaneously a plurality of the measuring head-s can be employed, each measuring head being usedin conjunction with an associated pneumatic gauge system. The glass tubes of the pneumatic gauge systems are mounted 'side-by-side in front of a sheet having two horizontal tolerance lines ruled thereon. Although the permitted tolerances of the'dimensions of the work-piece to be measured may difier, it is possible by selecting valves 78 having differently shaped paraboloid portions and/or by suitably adjusting the lever ratio, to have all the floats between the two horizontal lines when the dimensions of the Work-piece are all within the permitted tolerance-s.

For example, one needle valve 78 may be designed to operateover a total movement of .005 inch and using the 2:1 ratio referred to, the maximum range for a measuring head using this needle valve will therefore sociated pneumatic gauge system. By virtue of this ar- 1. A measuring head for pneumatic gauges, said head comprising a displaceable measuring anvil for contacting a Work-piece to be gauged, there being a jet of circular section for connection to a source of air, a needle, a parabolic surface portion on said needle and entered in said jet sothat the annular escape area between said. surface portion and the periphery of the jet varies linearly with displacemnet of the needle into and out of the jet, and connecting means between the anvil and the needle to move the needle in direct proportionality to themovement of the anvil.

2. A measuring head'accor'ding'to claim 1, and further comprising a spindle portion on the needle, and a' body member in which the spindle portion'is slidably carried. 3. A measuring head according to claim 2, wherein the connecting means includes a lever pivoted between its ends, said spindle portion contacting one end portion of said lever, a knife element connected to move with the measuring anvil and contacting the other end portion of, said lever, and means for adjusting the point of contact between said knife element and said lever, in a direction towards and away from the pivot of the lever, thereby to adjust the ratio of movement of the needle to the move ment of the anvil.

4. A measuring headfor a pneumatic gauge, said head comprising a displaceable'measuring' anvil for contacting avvork-piece tobe gauged, a valvebodyhaving a passageway for connection to asource of air and a jet to which the passageway leads, the. jet being of circular section, a needle slidably carried in said valve body, a parabolic surface portion on said needle'and entered-in said ljet so that thefannular escape areabetween said surface portion and the peripheryiof the jet varies linearly .withdisplacement of theineedleinto'and out'of thejet, a'base memben means securing the valve body to the base mem-lher, an element on which the measuring anvil iscarried, parallel flexible spring strips supporting said element 7 from the base member, and means transmitting'motion from the element to the needle, I I

5. A measuring head according'to claim 4, wherein the means transmitting motion includes a lever pivoted between its ends onto said base member, a first jewelled platen on one end of the lever and a second jewelled platen on the other'end of the lever, aspindle portionlon said needle, spring means urgingthe spindle portion into,

contact .Wtih the first platen, a knife element carried by.

the first-mentioned element and contacting the second platen at a point spaced from the pivot of the lever, and

means for adjusting said point towards and'away from a 7 said pivot, whereby the ratio of movement of the needle to the movement of the anvil can be varied.

References Cited in the-file of this patent UNITEDSTATES PATENTS 699,779 N Great Britain Nov. 18, 1953