US2683368A - Sand agitator for variable duration, medium impact, shock machines - Google Patents

Description

w. MCDOWELL 2 ,683,368

C. SAND'AGITATOR FOR VARIABLE DURATION. MEDIUM IMPACT, SHOCK MACHINES 4 Sheets-Sheet 1 July 13, 1954 Filed March 5, 1953 LE Z CHHELIEE W. N 00 HTTOE/YE Y5 IN V EN TOR. LL

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SAND AGITATOR FOR VARIABLE DURATION. MEDIUM IMPACT, SHOCK MACHINES 4 Sheets-Sheet 2 Filed March 5, 1953 l I I I I I I I I I I l I l I I I I I I I I I I l I I l I I I l I I l M I H M I P I I I I H M UHWIMI M I I a 4 4 T L F h IM UH P HDHI I H M UH I MEn O I A 1 d 4 8 T I u 3 HI I I h h IM kHM MUI I= I Z u "z" M I I o HMI W IMUI WIMIUHI IHH I I I a 4 E 3 4 Z Z 5 h o d w u r u fl q c n d q 3 n IIIIIIIIIIIIIIII 4 v V T R. CHHELES W. IAQELL WW n/vn C. W. M DOWELL SAND AGITATOR FOR VARIABLE DURATION. MEDIUM IMPACT, SHOCK MACHINES July 13, 1954 4 Shets-Sheet 5 Filed March 5, 1953 INVENTOR.

CI /HELEJ M /75'00WEL w I 9ND muannwwm HTTOENEYS M mq . c. W.'MODOWELL 2,683,368 SAND AGITATOR FOR VARIABLE DURATION. MEDIUM IMPACT, SHOCK MACHINES July 13, 1954 Filed March 5, 1953 4 Sheets-Sheet 4 BY -4.; MW.6% m

HTTOENEYS Patented July 13, 1954 SAND AGITATOR FOR VARIABLE DURATION, MEDIUM IMPACT, SHOCK MACHINES Charles W. McDowell, Dayton, Ohio, assignor to the United States of America as represented by the Secretary of the Air Force Application March 5, 1953, Serial No. 340,647

7 Claims. (CI. 73-12) (Granted under Title 35, U. S. Code (1952),

sec. 266) l 2 The invention described herein may be manu- Fig. 3 is a horizontal section taken at 3--3 of factured and used by or for the United States Fig. 1. Government for governmental purposes without Fig. 4 is a vertical cross section taken at 34 payment to me of any royalty thereon. of Fig. 3.

This invention relates to shock testing machines 5 Fig. 5 is a small scale front elevation of the comof the type shown in Patent 2,645,931 dated July plete machine.

21, 1953, and has special reference to machines in which the extent of the shock and the intensity thereof are controllable.

The invention'may be further identified with that class of shock testing machines in which the intensity of theshock is determined by the speed at which the tested materialis moving when deceleration begins, and the time duration of the shock is controlled by the area over which the shock is distributed, the larger the area, the shorter the deceleration period.

As a setting for my improvement I adopt that type of testing apparatus which includes a free falling table or platform upon which the material to be testedis placed, means being provided to drop the platform onto a bed of sand from a height determined by the desired intensity and means to vary the area on the underside of the table by adding or removing part of the area Which contacts the decelerating sand when the platform is dropped.

Since, with machines of this class. a drop of the table on the sand may compact the sand more vin one area than in another; it is necessary in order to duplicate results obtained by succesive drops of the table, to prepare the sand after each shock by deep raking and careful leveling. This has heretofore been accomplished manually but not without considerable danger to the. workman since in carrying out the operation he quite free quentlyreaches under the table.

It is therefore an object of this invention to provide pneumatically controlled means to recondition the sand or other decelerating material after each shock.

Another object of the invention is to provide a machine which may be set up to simulate shock conditions rapidly and repeatedly and which are comparable to those to which the equipmentis subjected. in actual practice.

Other objects and meritorious features will become evident as the invention. is described in detail and reference has been had to the drawings,

wherein: J M

Fig. l is a'fragmentary front elevation, partly in section, showing the inflatable rubber diaphragm in its deflated-condition.

,"Fig. 2 is aviewlikeFig. 1v but with the device inflated.

' several views.

In the drawing, a box-like base I ii is formed of four side panels I2 and a bottom welded at the corners at [-4, leaving the top open. A plywood bottom It of the same size and contour as the outer outline of the base is placed on a floor of concrete or other suitable material and the metal base It placed upon it.

Into two diagonally oppositecorners of the base Iii a pair of columns I8 are secured by any suitable means such as riveting, bolting, welding, etc. A header 2!) extends across and is fastened to the upper ends of the columns. This header carries pulleys 23 over which'one end of the lifting cable 22 extends. The other end of the lifting cable extends downwardly and around the pulley or drum of an electrically operated winch 2%. An electric motor 25 with a reversing switch 21 supplies the necessary power for raising or lowering the table.

A sheet rubber. diaphragm 26 of the same outside dimensions as the plywood bottom it is spread on top of the plywood bottom, and a series of eight battens 28 are parallelly spaced on top of the diaphragm and cemented and fastened thereto with screws, with two additional battens, one at each end of the first said eight. laid normal thereto.

A series of seven air pressure pipes 38 are substantially equally spacedmidway of the battens 28 in parallel lines under the sheet rubber diaphragm. These pipes are perforated throughout their length and at the front end are brought together in a manifold 32 through which they are supplied with air under pressure.

In order that the pressure pipes 39- may, after assembly, lie in the space between the plywood bottom and the rubber diaphragm, and yet be brought together for entry into the manifold midway of the manifolds vertical thickness, each pressure pipe 36 is offset vertically at the forward end at 44, Fig. 4:, and entered through a transfer block .6, Fig. 4, having an opening corresponding to the vertical offset in the pressure pipe 30. An exhaust pipe 35 extends from the manifold 32 upwardly inside the front panel I! of the base iii, curves outwardly and'downwardly on the outside of the said front panel ill to a foot pedal operated control valve 29.

A. free falling table 38 fits into the base it with a substantial clearance around it. The table is provided with uprights ll at the ends which are supported by the outer ends of a cross beam at, the cross beam being attached to a releasable solenoid actuated grappling device 42 carried by the end of the lifting cable 22. Means are provided whereby the material which is to be shock tested may be bolted or similarly secured to the top of the table 38.

The base or box it is filled and leveled at a depth of fifteen inches with No. 40 sand blast sand and the underside of the table carries a series of readily detachable metal sheathed wooden striker blocks 59 which penetrate the sand when the table 3% falls. The time duration of the shock is controlled by the number and arrangement of striker blocks which are attached to the bottom of the table, the greater the number of blocks the larger the contact surface, and the larger the contact surface, the shorter the deceleration time. The nature and severity of the shock is adjusted by varying the height from which the table falls.

The valving mechanism which controls the operation of the hereinbefore described testing machine is shown in Fig. 4 where it is shown schematically. It comprises a floor bracket 48 to which is pivoted, at 59, a foot pedal 52. The shorter end of the foot pedal 52 is pivoted at 5% to the valve stem 56 which carries the stop collar 62 and the valve disc t l. Disc M is faced with rubber at 66 for engagement with the open end of the exhaust pipe 34. Valve stem 56 is concentrically supported by the valve stem guides 58 in the exhaust pipes 3 The valve stem guides 58 are perforated at 633 to permit air flow through the exhaust pipe 34. The stop collar 62 is fast on the valve stem 56 to limit downward movement of the stem by the spring 65. A pedal return spring it returns the pedal to the home position and moves the exhaust valve to open position. The several detail parts of the foot operated valving mechanism above described may be collectively referred to by the numeral 29.

Cooperating with the foot operated valve 29 just described is a solenoid Valve 3i which coinprises a valve casing 33, connected by pipe to a pump or source of air under pressure 551. Casing 33 has a valve seat 39 upon which a valve disc 4! is guided by a valve stem 43. A seating spring 45 holds the valve on its seat 39 and a solenoid ll is energized to open the valve whenever the foot pedal is depressed. This may be accomplished as follows:

Electrically separated contacts 49 and 5? are yieldably secured in spaced apart relation on the machine. A conductor 53 extends from a contact 49 through a solenoid coil, 47, through a source of supply of electric current 55 and back to the other contact 5 i.

When the pedal 52 is depressed, so as to engage contact 49 with 5!, the solenoid 4'5 operates to open the valve 35, whereby air under pressure will flow from the source 371 through the valve 3! and through a pipe 5'? and into the exhaust pipe 3%.

Since the rubber facing 52 is now being pressed by the disc against the open end of the pipe the air under pressure will pass through the manifold 32 into the pressure pipes 39 Which will expand the sections of he diaphragm which lie 4 between the battens 28 so that they will form waves 58 in the underside of the sand mass as in Fig. 2.

Substantially at the instant the foot pedal is released, the solenoid operated valve 3| closes, and the compressed air discharges backwardly from the perforated pressure pipes 30 into the manifold 32, then into the exhaust pipe and out to atmosphere via valve 2Q.

The mechanism for elevating or lowering the table 38 comp-rises a reversible motor 25 equipped with a standard reversing switch and suitable speed reducing gearing connecting the motor to the winch pulley whereby the table 38 may be elevated or lowered until the desired drop is set The motor and its switches, the pump or equivalent source of air under pressure, the solenoid valve and similar parts, being standard equipment, is not shown in detail since they may be purchased on the open market. The operation of the machine may be briefly recapitulated as follows:

When setting up a machine. of the character described for making a shock test, the sand box Ill is first filled to a depth of approximately fifteen inches with No. sand blast sand which should be raked or otherwise loosened and leveled manually.

The desired striking surface is now attached to the underside of the table 38 by securing thereto a number of detachable striker blocks 59 preferably in a symmetrical pattern. The article to be shock tested is bolted or similarly fastened to the top of the table 38. The machine is now ready for operation.

The reversing switch 2? is first used to control the motor 25 and to bring the table 38 to the proper height to produce the desired shock. The grappling hook solenoid is now actuated to release the table and allow it to fall on the levelled sand.

The table is next raised, and as the striking blocks clear the sand, the foot treadle is depressed to close a circuit through the solenoid 4'7 which will open the valve 39 to connect the exhaust pipe 34 to the source of compressed air and coincidentally close the exhaust valve 29, whereby the diaphragm is inflated in waves as seen in Fig. 2. This accomplishes a shifting and consequent breaking up of the hard columns formed by packing due to the impact of the previous drop. It likewise reproduces the surface of the sand, i. e., the surface is not disturbed. The surface is therefore identical with what it was on the preceding drop, whereby leveling and rakin is rendered unnecessary.

It is therefore obvious that, with the apparatus and the method herein disclosed, any number of like pieces may be drop tested one after the other without having to manually rake and level the surface of the sand in the sand box after each drop test.

Having described an embodiment of my invention, I claim:

1. In a shock testing machine having a sand box, a table adapted, on the top, for attaching the articles to be tested and adapted on the bottom for attaching a plurality of striker blocks, means for raising the table and dropping it on the sand in said boxes to cause said striker blocks to penetrate said sand, the improvement which comprises a plurality of flexible diaphragms in the bottom of the sand box under the sand, perforated high pressure air pipes under said dianected to said manifold and the other end connected to the atmosphere, a source of air under pressure, a passageway connecting said source to the exhaust pipe, a valve in said passageway, a second valve for closing the open end of said exhaust pipe, and means to coincidentally open the first said valve and close the second said valve.

2. In a shock testing machine of the type which includes a sand box, a table adapted for attaching the articles to be tested to the upper side thereof and a plurality of striker blocks to the under side thereof and means for raising the table and dropping it on the sand in said box to cause said striker blocks to penetrate said sand, the improvement which comprises a flexible diaphragm in the bottomof the sand box under the sand, means to divide said diaphragm into a series of small diaphragms, perforated high pressure air pipes spaced apart under said diaphragms to inflate said diaphragms, a manifold connecting one end of the spaced apart high pressure air pipes together, an exhaust pipe having one end connected to said manifold and the other end connected to the atmosphere, 2. source of air under pressure, a passageway connecting said source to the exhaust pipe, a valve in said passageway, a second valve for closing the open end of said exhaust pipe, and means to coincidentally open the first said valve and close the second said valve.

3. In a shock testing machine of the class wherein there is a sand box and a free falling table within the sand box with means for attaching articles to be tested to the top of the table and means on the bottom of said table for attaching a plurality of striker blocks and means for raising and dropping said table on to said sand to cause said striker blocks to penetrate said sand, the improvement which comprises a source of compressed air, inflatable means in the bottom of the box under the sand, a passageway connecting said source to said inflatable means, a valve in said passageway, a second valve connecting said inflatable means to atmosphere, and means for simultaneously opening the first valve and closing the second.

4. In a shock testing machine of the class wherein there is a sand box and a free falling table Within the sand box with means for attaching articles to be tested to the top of the table and means on the bottom of said table for attaching a plurality of striker blocks and means for raising and dropping said table on to said sand to cause said striker blocks to penetrate said sand, the improvement which comprises a source of compressed air, inflatable means in the bottom of the box under the sand, conduit means having a control valve therein for connecting or disconnecting said source to or from said inflatable means, an exhaust conduit from said conduit means open to atmosphere, a second valve means in said exhaust conduit for connecting or disconnecting said inflatable means to or from the atmosphere, and means for simultaneously opening said control valve means and closing the second valve means.

5. In a sand conditioning apparatus for impact shock testing machines of the class described having a vertically movable supporting platform formed with said impact member on its bottom for impact with the sand and means to raise the platform above the said sand and drop the same, said conditioning apparatus comprising an open container for receiving the sand and said impact member upon dropping of the platform, a plurality of flexible inflatable and expandable members carried within the container at the bottom thereof to support the sand, a manifold header member connected to the inflatable members for introducin a pressure fluid into said expandable members, a source of fluid pressure connected to said manifold header member for supplying fluid pressure into said header, and valve means connected for admitting the pressure fluid from the pressure source into the manifold, and exhausting the pressure fluid from said manifold.

6. In a sand conditioning apparatus for shock testing machines having a vertically movable supporting platform formed with sand impact means on its bottom for impact with the sand comprising an open top sand container for receiving the sand therein and receiving the platform when dropped vertically from above into container, plural elongated sand elevating and lowering agitating means disposed on top of the bottom of the container in spaced side-by-side spaced parallel relation adapted to be disposed under sand when placed within the container under the supporting platform impact means, and actuating means selectively actuating said sand agitating means to raise and lower the sand below the platform to condition the same prior to the impact of the impact means therewith.

7 Apparatus as claimed in claim 6 wherein said sand supporting and agitating means comprises a plurality of vertically expandable flexible diaphragm chambers facing upwardly and extending across the bottom of the container in sideby-side parallel relation, and the actuating means comprises means for selectively inflating and deflating the chambers to raise and lower the sand in the container to agitate the same in a general vertical direction to break up compactness of the sand, and includes conduit means adapted to be connected to a pressure fluid source and manually operable valve means connected in said conduit means for alternately connecting said chambers to the said conduit means to inflate and expand said diaphragm chambers and to vent and deflate said diaphragm chambers.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,971,852 Goebels Aug. 28, 1934 2,620,894 Peterson et al Dec. 9, 1952 2,645,931 Johnson July 21, 1953

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