US2580299A - Pile driving measuring instrument - Google Patents

Description

Dec. 25 1951 A. "B. HUNICKE 2,580,299

- PILE DRIVING MEASURING INSTRUMENT Filed May 5, 1947 ZSHEETS-SHEET 1 'nd l anion Tape Recorder Zinnentor H. Byron f'l u n l'cke (Ittomeg Dec. 25, 195] u cK 2,580,299

- PILEDRIVING MEASURING INSTRUMENT Filed May 5, 1947 ZSHEETS-SHEET 2 I fl. Byrdn W W F Patented Dec. 25, 1951 UNITED STEAT PATENT OFFICE PILE-DRNING MEASURING-"INSTRUMENT August: fiYionHiinicke, Siiri iigvffil l, A.

Application-Mays, 1947, SeriaTNo:-745;897

(c1; ia-s' i')" v 6 clams; 1i i This invention relates. to the measuring. of the distance a load bearing. pile is to be driven into the ground. In particular, the invention is di vrected. to an instrument for i-ndicatingautomatically when a pile has beendriven'a-sufiicientdistance. 4 Piles for supporting: the weight-- oi buildings, bridges, piers, and other. structures are eachre-' quired to carry acertaincprec-alculated load; is a pile is driven downwardlmttheresistance to the driving force increasesrwitha the depth; Driving is continued until itw-isucalculatedthat this resistance to penetration is.greater-. than theflequi valentweight of the. load; to becarried ultimate'ly by thepiler Oneof the commonly, knownways of calculating. this resistance is by the empirically derived Engineering-News.Formula? expressed as L=2E/ S+C') wherein. L- is the bearing, capacity or load to Icelcarried; E isrt'he energy ex pended in drivingthe pile, S is the set orvpenetra tion gained and: Cris; aiconstanttof the value 1" for drophammers and 0.1. for. steam hammers.

Practical difiiculties are encounteredin-obt'ai'ning the valuesto he. usedin solving this formula for the unknown-S astheloadl? and the energy E appli'edhy thehammer. aredetermihahle, The usual practice is to mark oifiroughly equal iiite'rvals on the'pile with a piece of CHEtIl'Qafid-thn, while sighting the chalk niarlis across some 015- ject, count the number of hammer blows required to sink the .pile from .one mark to the nextl when theaverage penetiationsperhammer hltw used in solving: the formula gives a figurenot'le's's' than the required load bearingcanacity for thep'il'; driving isstopped, and" the pile is considered good'andsafeuptothatloading;

'Illii'smethod. has thefollowing disadvantages which" roduce inaccurateresults. Theintervails marked with" chalk on the pile are" not always equal duetecarelessness-in layingthem out; and it" is" substantially impossiblefoneven an ex'peri' encediman to" count the blows given by'a steam" hammer working-at" upto 1'50 blows per minute; while" trying: to sight accurately" the position of themarlis on' thepile'; orto'i make a quick decision as-tc which blowto call the last .whe'IT the-- marks have been made thick. with diillpoint ed chalk; Thepossi'loility of. Human error. increases Witlrtheoperatoi"s'inexperience arid inefliciency; and once the: pile is'driven thereisfscarcelyg any. way in which theaccuracy' ofthe work. can he checked? As'"a* precaution; iIes-are'cften'ovcr' drivenwith"- a consequential unnecessary expen= l diture oftime'and Taber; and even? destruction: of="the*pilebecause*ofBeing*overdi'iven.

The: objects of this? invention are to produce driven in a given time; make a-permanent rec- 0rd" oftheresult of: thed-riving of each pile, and automatically, and mechanically doing the observingv and indicating necessary to. determine whether a pile has been drivensu-lficiently.

Generally, these: objects are accomplished by constructing a mechanismincl-uding an electrical circuit: in. which the'electrical equivalents of the hammer blows and penetration of the pile are madedependent upon the actual driving of a pile,andthe-actual loadbearing capacity of the pile indicatedat-any time by'the-mechanism in calibrated termsas'a function of the changing electrical values in the circuit therein.

The means" by'wliich-theobjects of the inven-- tion are obtained may be more fully understood with reference to the-accompanying drawings in which:'

Figure: l is: adiagrammatical' view illustratingthe application of the invention: to the driving of a'pile;

Figure 2 is" a diagr'amof: a modified form of the" inventionwhen: used in 4 connection with single'acting steam haifimer's Figure-34s amiagramof a modified forln of the invention when used with drop hammers: and

Figure 4 is 'a diagram of' ai -modified form of theinvention whenused with doubleacting steam hammers In Figure 1* apne Pis shown Being driven by a-h'ammer 4": Anarm'fi is-secured hy anyconvenient means'such asnails -8 tothe'pile; Mounted adjacent the pile is an endless belt I'O" which passes over-a headsheave l-2Z paralleltot-he pile 2, around a tail sheave l4? ovefttke-uprolls I6 and t8; at least once around adrum 20'; and thence" to "head sheave" [2'. Arm 8 is clamped to the-portion of belt Ilf whicheiiten'ds parallel to pile 2? As pile-2 is' driven downwardly under the includes in senesa resistance Q'Zlbatteries and 3E c'oupled parallehuammeter 3'8 'and switch-"40 A tape" recorder" 42 connected" to ammeter 38,

'3 and an indicator 44, which may be in the form of a horn, bell,.light or whistle, is likewise connected to the ammeter.

Switch 40 may be actuated by a solenoid 46 which in turn is energized by a time relay 48, said relay being set by movement of the shaft 24 through gears 50 and shaft 52.

The Engineering-News Formula" simply states that the bearing capacity is equal to a force E divided by a resistance S. This is the expression as in Ohms law in which amperes are equal to volts, a force, divided by ohms, a resistance. Therefore, the formula can be expressed as L=V/'S+C, and in the electrical circuit of Figure l, L is represented by the ammeter 38, V by the batteries 34 and 36, S by the rheostat 30 and C by the resistance 32.

When the pile is to be tested for the penetration being gained, arm 6 is coupled to belt I0, and the pile struck by hammer 4. The distance the pile is driven by each blow varies the setting of arm 28 in rheostat 30 and thus varies the resistance in the electrical circuit and the current flow registered by ammeter 38. This in turn actuates tape recorder 42 which may be calibrated to record in tons the load bearing capacity of the pile. A permanent record is thus obtained of the allowable load bearing capacity of the pile at the time driving is stopped. By testing the pile at regular intervals during the driving, it can be assured that the pile will not be overdriven, and that the driving can be stopped as soon as the proper readings are obtained, with a resulting saving of time. The indicator 44 is set to make a signal when a certain load value is reached and thereby calls attention to the fact that a pile has been driven sufiiciently. Recorder 42 can show the difierence between additive successive hammer blows, or alternatively means may be provided to return arm 28 of rheostat 3D to zero position following each hammer blow.

The switch 40 is held open by solenoid 43 until arm 28 has come to rest at the value determined by the set of the pile after each hammer blow. There is an increment of time between the instant of the hammer blow and the rest position of the pile in which the pile is moving, and this time is greater when the pile is driven in soft ground. Upon each impact, the pile moves downwardly, then bounces upwardly a fraction of the downward distance, and then settles to its final set. Consequently, each movement of the pile actuates the time delay relay 48 which in turn energizes solenoid 46, at the instant the pile stops moving and is at its final set, to close switch 40, and cause a recording to be made or signal given.

In Figure l, the batteries 34 and 36 indicate the voltage sources needed for measuring the force applied by either single acting or double acting steam hammers. For a single acting steam hammer the formula is L=2Wh/ (+0) wherein W is the weight of the hammer and h is height of the fall of the hammer. Figure 2 illustrates the modification of the circuit to include this value. Only a single current source 38 is included, its force, or voltage, being regulated to a constant value representing the value Wh by setting the rheostat 60. The setting on this resistance can be used to proportion the voltage from source 38 to suit a variety of hammer sizes.

When the device is used for drop hammers, it

is observed that the height the hammer is T 4 dropped varies, and consequently the value E in the formula becomes a variable. In Figure 3 the hammer 4 is actuated by a cable 1'0 passed over head pulley 12. This pulley is connected by a shaft 44 to speed and travel ratio gears i6 which are geared to the movable arm in rheostat 18. The force, or voltage, from battery 35 is thus adjusted by this variable resistance to the equivalent of the height to which the hammer 4 is pulled before it is dropped. Any mechanical means may be provided in the gear system connecting pulley 12 with rheostat i8 so that the setting of the rheostat is not changed as the hammer drops, and similarly means may be provided for returning the rheostat setting to zero after each recording has been made. Otherwise, the circuit and its operation are as in Figure 1.

In double acting steam hammers, the formula becomes L=2W+2aph/(S+C) wherein a is the piston area, 12 is the cylinder pressure and h is length of the piston stroke. Figure 4 shows the manner in which the electrical equivalents are achieved in this invention. The double acting hammer has its pressure cylinder in communication with a bellows 82 by means of the conduit 84. The bellows operates a rod 86 connected to an eccentric plate 88 which carries the arm 90 of the rheostat 92. The battery 34 represents the force applied to the hammer by the pressure cylinder, this force being modified by the rheostat 92. The rheostat and battery are coupled in parallel with battery 36, a switch 94 being provided to deactivate this coupling when desired. The system otherwise operates as described for Figure 1. It is evident that the source of pressure for the bellows 82 may be from the boiler, or air compressor, which furnishes the pressure for the pressure cylinder in the hammer 80, rather than the direct connection to the hammer as shown. Similarly other equivalent means may be used to vary the rheostat 92 in order to intro duce the value of Zaph into the circuit.

The invention is especially useful in the driving of piles under water as the attachment of the endless belt 18 to the pile presents no difilculties. The mechanism can be attached to any kind of pile, at any point along the length of a pile, and is easy to mount in the leads of the pile driver.

Having now described the means by which the objects of the invention are achieved,

I claim:

1. An apparatus for determining the load bearing capacity of a pile while driving said pile by successive impact forces, each of which causes the pile initially to move downwardly, followed immediately by an upward counter movement and then by a further downward movement to the final set of said pile, comprising means for completing an electrical circuit in which the current fiow is varied in response to movements of said pile under successive driving impact forces, means electrically connected to said circuit for visually showing said current variation as a function of the movement of said pile, and means actuated by said movements for delaying the variation in current until the pile reaches final set after each impact force.

2. An apparatus for determining the load bearing capacity of a pile while driving said pile by successive impact forces, each of which causes the pile initially to move downwardly, followed immediately by an upward counter movement and thenby a further downward movement to the final set of said pile, comprising means for producing an electrical current, means for varying the current'so produced in response to movements of said pile under successive driving impact forces, means actuated by said movements for delaying the start of current flow through said varying means until the pile reaches final set after each impact force, and means for visually showing said current variation as a function of the movement of said pile.

3. An apparatus for determining the load hearing capacity of a pile comprising in-series circuit a rheostat, a resistance, a voltage source, and an ammeter, means actuable by said pile for varying said rheostat in response to increments of movement of said pile during the driving of the same, and time delay switch means actuable by each initial movement of said rheostat varying means for completing said circuit after the pile has reached final set under a hammer blow.

4. An apparatus as in claim 3, in which said rheostat varying means comprises an endless belt a portion of which is adapted to extend parallel to the length of the pile, means for securing said portion to a pile, and means for transmitting motion of said belt to said rheostat.

5. An apparatus as in claim 3, said time delay switch means comprising a switch in the electrical circuit including said ammeter, and a time relay for actuating said switch in response to movements of said pile.

6. An apparatus for determining the point at which a pile being hammer driven has reached a desired ioad bearing capacity, comprising an electrical circuit composed of voltage means, rheostat means actual-ole by said pile for varying the cur rent produced in said circuit as a iunction of the movement of said pile, time delay means for delaying energizing of said circuit until after the pile reaches final set, and means actuated by said current flow through said circuit for indicating the load bearing capacity of said pile as a functien of the distance said pile is moved to final set.

A. BYRON HUNICKE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,304,022 Cole May 20, 1919 1,476,289 Feder Dec. 4, 1923 2,033,424 Gieskieng Mar. 10, 1936 2,081,598 Peters May 25, 1937 2,130,751 Van Der Meer Sept.'20, 1938 2,280,592 Mieux Apr. 21, 1942 2,373,504 Schlieben Apr. 10, 1945

Images