US2172368A

US2172368A - Recording pitchometer

Info

Publication number: US2172368A
Application number: US749518A
Authority: US
Inventors: Ivan D Eby
Original assignee: Individual
Current assignee: Individual
Priority date: 1934-10-23
Filing date: 1934-10-23
Publication date: 1939-09-12
Anticipated expiration: 1956-09-12
Also published as: GB534644A

Description

Sept. 12, 1939.

l. D. EBY

RECORDING PITCHOMETER 4 Sheets-Sheet 1 Filed Oct. 25, 1934 INVENTOR IVAN 0. EB) 75 M in ATTORNEY Sept. 12, 1939. 1. D. EBY 2,172,368

RECORDING PITCHOMETER Filed Oct. 23, 1954 4 Sheets-Sheet 2 :INVENTOR IVAN D. .EBIY

ATTORNEY Sept. 12, 1939. l. D. EBY

RECORDING PITCHOMETER 4 Sheets-Sheet 4 Filed Oct. 23, 1934 28 J2 .94. 4-0-2 w llllllllll lllllll INVENTOR IVAN 0. EB)

Patented Sept. 12, 1939 UNITED STATES PATENT OFFICE 20 Claims.

The present invention relates to recording pitchometers for determining the correctness of the surfaces of the blades of the propeller.

In designing propellers for the propulsion of ships, the propeller is designed to have helical surfaces to engage the fluid (water or air) in which the propeller operates. The pitch of the propeller is either what is known as true pitch or variable pitch. In the true pitch propeller the entire length of the propeller blade is designed to have a constant uniform pitch, while in the variable pitch propeller the pitch varies at different radii.

Propellers for water craft are made of cast metal, generally bronze. Either a built up propeller of cast hub and blades is employed, or the entire propeller is a single casting. The patterns from which the castings are made the prepared of wood to be as close as possible to the specific design laid on by the propeller designer, allowances being made in accordance with the experiences of foundry practice. The casting is done in sand molds and hence there is the likelihood of warping of the casting and distortion of the shape and surface contour of the casting.

It has heretofore been the practice, especially respecting propellers for large ships, to accept the propeller if a few measurements showed a sufiiciently close approximation to the specified pitch, the surface felt reasonably smooth, the balance was satisfactory, and the weight about what was calculated. There has been no satis: factory way of really checking the propeller made in the foundry to see whether it was of spaced about the circumference of the propeller and yet the propeller appear to be in static balance when tested in the usual way. Out of place blades cause uneven stresses and vibrations in the engine and shafting which are communicated to the ship. By carein the foundry and pattern shop the lock of proper blade distribution may be overcome. I 4 Owing to the ever curving character of the blade surface ordinary observation and scattered measurements of pitch between specified points is of no use in ascertaining how closely the surface conforms to the optimum surface. The 50 measurement of the overall pitch between two points on the surface is no indication of the uniformity of the pitch. If there is a high spot or a low spot between the points where the measurements would be taken, there is change of pitch above and below the overall or average the proper shape. The blades might be unevenly pitch. These high or low spots may be compared to the hills and valleys which exist in What appears to be a level plain.

Where a propeller of this irregular pitch is driven through the water wasteful turbulence 5 and eddies are unavoidable. The areas at excess pitch produce excessive frictional resistances, while the areas at insuficient pitch do not contribute the proper amount of thrust. This brings about a constant loss ofpower and necessitates greater power and fuel consumption for the same ship speed than would be the case if the entire surfaces were at exactly the designated pitch.

The present invention is directed toward the provision of a convenient apparatus by which the determinations of blade spacing and pitch may be accurately made. The machine for this purpose is designed so that these determinations may be made to a high degree of accuracy without laborious computation or different manipulation of delicate apparatus. According to the present invention this apparatus is capable of determining all the departures of the propeller surface from true, and it is so designed that it can be used on propellers of true or variable pitch, right or left handed blades, and a single apparatus may be used on propellers of a considerable range of outside diameters.

While the invention is more especially designed for use in connection with cast metal propellers for water craft, it may be used on the patterns for such propellers or on Wood or metal air screws.

The accompanying drawings, show for purposes of illustrating the present invention, two of the many possible embodiments in which the invention may take form, it being understood that the drawings are illustrative of the invention rather than limiting the same. In these drawings:

Fig. 1 is a top plan view of a recording pitchometer showing it in relation to a propeller blade; Y

Fig. 2 is a side elevational view of the same;

Figs. 3 and 4 are sectional views taken on line 3-3 and line 4-4 of Figure 1 and looking in the direction of the respective arrows;

Fig, 5 is a fragmentary view in plan showing parts in section along the line 5-5 of Figure 2;

Fig. 6 is a vertical sectional view taken along the line 6-6 of Figure 2;

Fig. '7 is a fragmentary sectional View taken along'the line 'l.'l of Figure 5;

' grees at its' outer. edge.'

Fig. 8 is an enlarged sectional view taken alon the line 8-8 of Figure 2;

Fig. 8a is a fragmentary view of a detail.

Fig. 9 illustrates a chart showing an ideal set of lines for the rear or working face of a true pitch propeller, and indicating a dotted irregular line (more or less exaggerated) which might be produced from a propeller surface having a distorted profile;

Fig. 9a is a fragmentary portion of an ideal chart at an enlarged scale, showing departures from the ideal in dotted lines;

Fig. 10 illustrates a chart similar to Figure 9 for the front face of the propeller blade;

Fig. 11 is an elevational view with parts insec- 7 Fig. 13 is a sectional view taken on the line.

I3I3 ofFigurell.

In Figures 1 to 10 of the'drawings aconventional form of propeller isindicate'd as being provided with the usual hub H and blades B. The

propeller hub has a machined hole It and machined faceshf and h". l A number of holes are tapped into the faces of the propeller hubas indicated at 10. In the formshown inthe drawings four cast iron legs II are employed to support a roundstiff disk". The legs llareprovided with slotted feet I3 adapted to receive capscrews I4 and with slotted upper flanges l5 adapted to receive through bolts I6. A centerlng device I1 is passed down through the center of the disk l2. With this arrangement of parts the plate l 2 may be moved so as to accurately center it over" the propeller axis.

As shown in the drawings the plate l2 has an upwardly extending hub l1. This hub revolvably supports a sector I8 shown here as somewhat larger than the plate l2 and isgraduated in de- The sector l8 may be adjustably secured to the plate l2 by clamp I! which engages the edge of the disk 12. An arm 20, preferably made of metal, is drilled as indi-. cated at2l to 'rotatably fitareduced portion of the hub I1 and is held in place by a nut 22. The metalarm 20 is provided with aclamping device 23 so that it may be secured to the disk in any desired position. Theouter .end 24.0f the metal arm'20 has a vertical flange 24' and a rear horizontal flange 24". A wooden arm 25 is secured of T-shaped cross section and has upper and lower bearingstrips. indicated at 21 and28, preferably made of mahogany, and stiffening braces29.

In the .constructionjust described, the swingable arm, as a whole comprises the

parts

20 and 25. This swingable arm'provides a radially ex tending guide for a movable carriage indicated;

generally at 30. a This carriage has" two front vertical parts 3| and 32, an' upper rearwardly extending member 33 and lower rearwardly extending member; shaped as shown in Figure 6,

'to embrace the'guide formed bythe radial am.

The front'm'einbers'fl and 32 are spaced to accomodate a vertical'slider or rod 35 preferably made'of wood. This'rod is held in placeby' the upper ends of these cylinders are coupled together by a strap indicated at 48. The cylinder 41 resembles to some extent an ordinary shade .roller. It is provided with a wind up spring 49 and a winding knob indicated at 50.

The cylinder 41 is adapted to receive a wrapping 5l of paper and act as a storage cylinder, the spring 49 (when tensioned) tending to wind the paper onto the cylinder. The end of the paper is indicated at 52. It is secured to the cylinder by suitable stickers indicated at 53. The paper may wrap around the cylinder 40 a sufficient number of times to provide the desired length of paper for the record to be made. The

cylinder 40 is rotatably driven by gear 42 in mesh. with a suitable form of rack 54 carried by the radial arm. This rack may conveniently be a length'of sprocket chain held taut by a tensioning device indicated at 55.

The lower end of the vertically movable rod member35 is provided with a sharp edged roller 56 adapted to bear on the upper surface of the propeller blade B so that the rod 35 will move up and downinaccordance withits profile in the plane in which the roller is moved. This roller may conveniently be a cutting roller such as used in a pipe cutter.

The contacting face of the roller 56 is preferably, though not necessarily, in the same plane as the front face of the cylinder- 40 and directly underneath the point where the cylinder is tangent to the radial plane through its surface. The slider 35 carries a marker in the form of a pencil51 which bears on the paper as is indicated in Figure 8. It is preferably held under.

formaking accurate readings of the position of the radial arm (20-25) relative to the fixed sector 18. In the form shownthe arm 60 is at 90 to the arm 20--25. The upper face of the fixed'disk I2 is provided with a circumferential groove'iil to receive. a

on a propeller and installing the recording paper 7 in place, is to ascertain'or determine the center lineCL of the propeller blade. This would ordinarily be done by bringing the radial or swinging arm and carriage 30 to such a position that the ro1ler'56 extends out to the extreme tip of the propeller." The radial arm may be clamped into position by the clamp 23 and then the adjustable ring 62 is moved about to bring the zero point 'ofthis ring directly underneath a center line or 40 as before,:-and the similar operations repeated of the other blades wire 55 carriedin the opening in the sector IS. The ring 62 may thenbe clamped in place and the arm 2025 released and'swun'g around to determine the center lines of the other blades of the propeller.

or not the blades are out of place. Shouldthey be out of place several measurements maybe 10" taken and an adjusted mean center position determined upon and the ring 62 moved to the proper position where it remainsduri'ng the tests. After the pro-per positions of the center lines are determined, the sector I8 is moved to bring its center exactly in line with the zero point of the ring 62.

To chart the profile of the blade surface along the center line, the carriage 30 is merely moved lengthwise of the radial arm. If the propeller is true and smooth, this will produce a straight line as indicated at the center of Figures 9 and 9a, but if the propeller is not true, there will be obtained instead of a straight line, a wavy line such as for example is-indicated in the dotted line of Figure 9. The radial arm is then moved through the desired angle (1 or 2") and another line drawn by shifting the carriage lengthwise of the radial arm. If the propeller surface were perfect and the lines drawn at even angular spacings there would be obtained a diagram composed of parallel evenly spaced lines as indicated in full lines in Figures 9 and 9a. These lines extend out to the dash line of Figure 9, indicating the shape of the propeller'blade as viewed in the horizontal plane. Should there, however, be humps, hollows, depressions or other irregularities, the lines drawn will no longer be straight, but will be wavy. At any place where the propeller is imperfect, the line will be displaced from the proper place as indicated in the dotted lines of Figure 9a. In

clamp it in position and shift the carriage along the radial arm. During the shifting ofthe car- .riage, roller 56 traverses the surface of the propeller blade and shifts the pencil 51- up and down accordingly; and the gear 42, in engagement with the stationary rack 54, turns the cylinder 40 so as to wind or unwind the paper from the cylinder. It Will be noted during this operation that the working surface of thepaper remains by the posiin a radial plane determined upon tion of the radial arm. v v

The radial arm is provided with graduations in feet and inches, marked as appears in Figure 2 and the carriage 30 is provided with a pointer 66 cooperable with these markings so as to determine the radius at which'the roller 56 is to engage the propeller surface. To make a vertical line on the record at points corresponding working face of one propeller blade, the paper bearing the chart is cut away from the storage cylinder andtaken off the, cylinder 40 for later The end of the paper remaining on the storage cylinder is then" secured tothe'cylinder use.

In this way one can determine the correctness of spacing of the 'centersofthe propeller blades and at once det'er'mine whether over the working face of each 0551 the propeller.

From the design of the propeller, it is easy'to construct a theoretically correct diagram or chart whichshould be that of each of the working surfaces, but in practice it is not necessary to construct such a diagram or chart as the one produced from the blade being tested is generally suifi'ciently near the ideal to permit the reconstructing of the ideal from the one made from theactual blade. The lines prepared on the diagram or chart should be a predeterminable shape and angle dependent upon the pitch of the propeller. In the true pitch type of propeller'they should be straight and parallel and at a uniform angle to the plane normal to the axis of the propeller. The ideal diagram or chart for such a propeller could therefore be deduced from the one made by the instrument by drawing straight, parallel, regularly spaced lines on the chart. Should the propeller be one having a variable pitch, the lines would diverge toward the tip for an increasing variable pitch and converge for a decreasing variable pitch. The inaccuracies of the propeller surface will be then represented by the departures of the actual lines drawn on thediagram or chart from the ideally placed lines;

The diagrams or charts obtained in the manner above described may be conveniently used as a guide'for'the machining or grinding opera-. tions necessary for correcting the surface ofthe propeller to bring it to the proper outline. Todo this the diagram or chart for the propeller blade may be left on the roller or maybe fastened to uprights 70' and H which may be secured to the radial arm as indicated in Figure 2. It is' held by these uprights and in the same position that it was when it was made on the revolving cylinder. The radial arm may then be clamped in the position in which it was when one of the lines was drawn on the chart and the place on the face of the propeller which should be ground down (or built up) could'be easily spotted or 10- cated by the roller 56 when the carriage 30 is shifted to bring a pointer (corresponding with the pencil 5'5) opposite the various points of the diagram or chart where correction is indicated. During these operations the diagram or chart may be readily referred to as a guide. After the surface has been ground (or built up) as indicated by the diagram or chart, a new diagram or chart can be prepared by repeating the operations above described, and this compared with the ideal for the blade. 1

In carrying out the operation of determining the pitch of the surfaces of the propeller blades at all points and the grinding and correcting of these blade surfaces, all the operations'can be carried on without' taking the device apart or removing it from the propeller.

After the working faced the propeller blade has'been plotted and correctedv the pitchometer is removed from the propeller, the propeller turned over and. the pitchometer attached to the. opposite face of the propeller hub, then a similar set of operations is carried out on the front-face of the propeller. In this case the diagram or chart obtained is somewhat like that shown in Figure 10 in which the parallel lines are closer on the.

leading edge of the blade and at an angle somewhat as shown.

It will be understood that the reference in the specification'to the position ofthe parts as being horizontal -'or vertica1'i'sonly for convenience in way in which the propeller is mounted or supported during the operations. In order to bal- 5: ance the weight of the radial arm, a rod 12 may be secured to the radial member 20 and a weight secured to this rod. If it is desired to determine tween selected lines on the diagram or chart. The lines more easily used are those 15 each side, of the center line. The portion of the propeller blade between these lines occupies 30 of are. or one twelfth of a circle and hence a measurement of the vertical distance in inches will give the pitch in feet. To facilitate these measurements, a slidable scale 68 is carried by the movable carriage 30 and is provided with suitable graduations opposite a pointer 69.

In the modified and simplified form of construction shown in Figures 11, 12, 13 the pitchometer is provided with a supporting shaft having a cone 8| adapted to bear on one end ofthe 255 hole in the propeller hub, a cone 82 adapted to bear in the other end of the hole in the propeller hub, and a wing nut 83 for securing the shaft in place in the propeller.

Adisk 84 provided withgraduations 85 is carried by the shaft 80 and may be clamped to it by a clamping device indicated at 86. This disk cor- V responds with the sector l8 of Figure 1.

A radial arm 81' is revolvably carried by the shaft. and corresponds in general with the ;radial arm of Figure 1.

the disk 84 by clamp indicated at 81 and is provided with a pointer 88 to move over the graduated scale. The radial arm carries a vertical drawing board 89 on which may be placed a sheet of. drawing paper 90. The slider or carriage. 9| is movable along the top and bottom of the drawing board in the same way that the slider or carriage 30 moves along the radial arm of Figure 1. The carriage 9| is provided with a vertically movablerod 92 having a roller 93 at the lower end and a marker 94 for cooperation with the paper. This device is operated substantially the same as that shown in the Figures 1 to 10 and a chart or diagram of the propeller surface secured. This arrangement is intended for use with smaller propellerswhere the size of the drawing board for'supporting the paper is not objectionable. It is obvious that the invention may be embodiedin many forms and constructions within the scope of the claimsgand' I wish it to be understoodthat the particular forms shown are but two of the many forms. Various modifications and changes being possible, I do not otherwise limit myself in any way with respect thereto.

What is claimed is: a r 1. A pitchometer for preparing a chart to show the departures of the surface of a screw propeller blade from an ideal blade surface whereby the pitch of the propeller may be recorded, comprising a radially extending swingable arm, means for rotatably supporting the arm coaxially of the propeller whereby the arm is adapted to be placed in various radial positions opposite. the sloping surface of the propeller blade, the arm being provided with a recording surface disposed in a radially extending plane, an arm-carried recording element co-operable with the recording surface, means for supporting, the recording element whereby it maybe moved radiallyv along I the actual overall. pitch of the, propeller at anyradius, it is merely mgnecessary-to measure thevertical distance be-' It may be clamped to theiarm and may be moved independently in;

directions parallel with the axis, and a-recording' element operating device bearing on. the blade surface and positionable thereby; whereby the position of the recording element at any radius is a function of the radial position of the arm and a chart comprising a series of spaced lines. on said recording surface may be prepared, each. line corresponding to one radial position oflthe 2. A pitchometer as claimed in claim 1, having an arm supported bodily. movable cylinder, a.

paper wrapping about said cylinder to provide said recording surface, means to rotate the cylinder in response to the radial movement of the. recording element, and a self winding storage cylinder to which the wrapping is secured.

3. A pitchometer as claimed in claim 1, having an arm supported bodily movable cylinder tangent to said radially extending plane, a paper wrapping about said cylinder to provide said' recording surface, and cylinder rotating means comprising a gear carried by the cylinder, a racksupported by the arm and with which the gear is engageable, and a self-winding storage cylin-" der to which the wrapping is secured.

4. Apitchometer as claimed in claim 1, wherein the operating device for the recording element 5 comprises a sharp edged roller and a rigid rod,

and wherein the recording element comprises a. pencil operated by the rod.

in the portion of the recording element in contact with the blade surface is in the plane of the recording surface. J

6. A pitchometer as claimed in claim 1, wherein the recording surface is in the form'of a flat. sheet fixedly secured to the movable arm.

'7. A pitchometer such as claimed in claim 1,

wherein the arm has graduations to indicate the radial position of the recording element whereby by manual movement of the recording element transverse lines may be made on the chart to provide a reference lineateach of the corresponding blade radii. 8'. A pitchometer such as claimed in claim 1, having a graduated sector for determining the angular spacings of the positions of the arm.

9. A pitchometer for preparing a chart to show the departures'of the surface of a screw propeller blade from an ideal blade surface whereby the pitch of the propeller may be recorded. comprising a radially extending swingable guide,

means for rotatably supporting the guide coaxially of the propeller whereby the guide is adapt -ed to be placed in various radial positions'opposite the sloping surface of the propeller blade,

a radially movable carriage on the guide, a carriage carried follower movable transversely thereof and held in contact with the blade surface being recorded whereby the position of the follower at any radius is a function of the radial position of the guide, a record holder. movable,

, so. 5. A pitchometer as claimed in claim 1, where with the swinging guide and having a recording 7 characterized in that the carriage is slidably car-, ried on the guide and in that the follower. is slidablycarried by the carriage. H

11. A pitchometer such as claimed in claim 9, having a graduated sector for determining the angular spacing of the positions of the arm.

12. A pitchometer for preparing a chart to show the departures of the surface of a screw propeller blade from an ideal blade surface whereby the pitch of the propeller may be recorded, comprising a radially extending swingable guide, means for rotatably supporting the guide coaxially of the propeller whereby the guide is adapted to be placed in various radial positions opposite the sloping surface of the propeller blade, a radially movable carriage on the guide, a carriage carried follower movable transversely thereof and held in contact with the blade surface being recorded whereby the position of the follower at any radius is a function of the radial position of the guide, a cylinder carried by the carriage and having thereon a paper wrapping, a follower actuated recording marker movable with the carriage and bearing on the paper wrapping, and means to turn the cylinder on its axis in response to movement of the cylinder along the radial guide so as to move the paper wrapping under the marker.

13. A pitchometer for preparing a chart to show the departures of the surface of a screw propeller blade from an ideal blade surface whereby the pitch of the propeller may be rerecorded, comprising a radially extending swingable guide, means for rotatably supporting the guide coaxially of the propeller whereby the guide is adapted to be placed in various radial positions opposite the sloping surface of the propeller blade, a radially movable carriage on the guide, a rotatable record carrying cylinder carried thereby, means to automatically rotate the record carrying cylinder as the carriage is shifted along the guide, a carriage supported marker movable parallel with the cylinder axis and bearing on the cylinder, and a follower engaging the surface of the propeller blade and operatively connected with the marker to move the latter, the records for the various radial positions being automatically spaced from one another on the recording medium by the relative change of elevation of the sloping blade surface with respect to the guide.

14. A pitchometer as claimed in claim 13, wherein the follower and the marker are in the plane of an element of the cylinder surface and the cylinder axis is parallel with the propeller axis.

15. A pitchometer as claimed in claim 13, wherein the cylinder rotating means includes a gear carried by the cylinder and a stationary rack carried by the swinging guide.

16. A pitchometer such as claimed in claim 13, having a self-winding storage cylinder to which the paper wrapping is secured.

17. A pitchometer for preparing a chart to show the departures of the surface of a screw propeller blade from an ideal blade surface whereby the pitch of the propeller may be recorded, comprising a radially extending swingable guide, means for rotatably supporting the guide coaxially of the propeller whereby the guide is adapted to be placed in various radial positions opposite the sloping surface of the propeller blade, a radially movable carriage on the guide, a rotatable record carrying cylinder carried thereby, the circumference of the cylinder being less than the length of the blade, a storage cylinder, a supply of paper Wound about the storage cylinder and having its end portion wrapped about and secured to the first cylinder, a wind up spring carried by the storage cylinder, means to automatically rotate the record carrying cylinder as the carriage is shifted along the guide, and a carriage supported marker movable parallel with the first cylinder axis and bearing on the paper winding thereon, and a follower engaging the surface of the propeller blade and operatively connected with the marker to move the latter, the records for the various radial positions being automatically spaced from one another on the recording medium by the relative change of elevation of the sloping blade surface with respect to the guide.

18. A recording pitchometer for propeller blades, said pitchometer having a radially extending chart receiving surface swingable past the blade and about the propeller axis, means to draw on said surface a series of lines each representing the profile of the propeller in the corresponding radial plane in which the surface then is, and means to space the lines apart a distance corresponding to the profile of the blade surface in tangential planes at corresponding radii.

19. A recording pitchometer for propeller blades, said pitchometer having a radially extending chart receiving surface swingable past the blade and about the propeller axis, means to draw on said surface a series of lines each representing the profile of the propeller in the corresponding radial plane in which the surface then is, means to space the lines apart a distance corresponding to the profile of the blade surface in tangential planes at corresponding radii, and fixed graduations to determine the angularity relations of the positions of said radial planes.

20. A pitchometer for preparing a chart to show the departures of the surface of a screw propeller blade from an ideal blade surface whereby the pitch of the propeller may be recorded, comprising a radially extending swingable arm, means for rotatably supporting the arm coaxially of the propeller whereby the arm is adapted to be placed in various radial positions opposite the sloping surface of the propeller blade, an arm supported radially-movable carriage, a cylinder rotatably mounted on the carriage, a rotatable storage cylinder parallel to the first cylinder, a paper wrapping on the storage cylinder and secured to the first cylinder, a wind up spring actuating the storage cylinder to wind the paper thereon, and means to rotate the first cylinder in response to the radial movement of the carriage, and a carriage supported recording element cooperable with the paper and positionable by the blade surface whereby the position of the recording element at any radius is a function of the radial position of the arm and a chart comprising a series of spaced lines on said recording surface may be prepared, each line corresponding to one radial position of the arm.