US3274660A

US3274660A - Slump block producing machine

Info

Publication number: US3274660A
Application number: US63040A
Authority: US
Inventors: Bill L Mizer; Robert T Mizer; Donald E Whitehurst
Original assignee: Builders Equipment Co
Current assignee: Builders Equipment Co
Priority date: 1960-10-17
Filing date: 1960-10-17
Publication date: 1966-09-27
Anticipated expiration: 1983-09-27

Description

Sept. 27, 1966 B. 1.. MIZER ETAL 3,274,660

SLUMP BLOCK PRODUCING MACHINE Filed Oct. 17, 1960 2 Sheets-Sheet 1 IN VEN TORS B/AL L. M/ZEE 205E197 7f/W/ZEE-v4/Vfl- DOA/4A0 E. W/l/TEAZ/EST Sept. 27, 1966 Filed Oct. 17. 1960 B. L. MIZER ETAL SLUMP BLOCK PRODUCING MACHINE 2 Sheets-Sheet 2 United States Patent 3,274,660 SLUMP BLOIIK PRODUCING MACHINE Bill L. Mizer, Phoenix, Robert T. Mizer, Scottsdale, and Donald E. Whitehurst, Phoenix, Aria, assignors to Builders Equipment Company, a corporation of Arizona Filed Oct. 17, 1960, Ser. No. 63,040 4 tclaims. (Cl. 2541) This invention relates to a slump block producing machine and more particularly to a slump block producing machine capable of producing slump blocks of blocks formed by a conventional high production concrete production machine immediately after the conventionally formed blocks have been delivered therefrom.

The term, slump block, as used herein, defines a concrete block produced from mortor containing a slightly greater amount of moisture than is normally used in conventional concrete blocks and the term, slump bloc also defines a block, the side wall surfaces of which, are slightly bowed or slumped outwardly of flat vertical planes common to conventional high production concrete blocks.

Slump blocks are sometimes desirable from an architectural standpoint since they have uneven contoured surfaces and tend to break the monotony of conventional smooth flat surfaced block or wall construction.

It has heretofore been a problem to produce slump blocks on high production concrete block producing machines such as the well-known Besser machines. These machines normally produce very accurate smooth straight sided blocks at a very high rate, and most concrete block producing plant operators have recognized the desirability of utilizing such machines for producing slump blocks so that separate facilities may not be needed to produce these slump blocks. It has been a problem to provide means usable in connection with such high production machines which will convert the accurate blocks, thus produced, into slump blocks at a production rate approximating or normal to that of the high production machine.

Concrete block producing machines normally deliver several concrete blocks on rather extensive pallets and the blocks must be produced so that they have an excessive vertical dimension in order that they may subsequently be compressed into slump blocks. Considerable difliculty has been encountered in performing this operation and at the same time achieving uniform height of the slump blocks throughout the over-all area of the pallet on which the blocks are delivered. Additionally, great difiiculty has been encountered in forcing blocks, produced by a high production machine, into slump configuration within the time allowed during each cycle of operation of such a concrete block producing machine.

Accordingly, it is an object of the invention to provide a slump block producing machine which is located to compress blocks delivered by a conventional high production block machine into slump blocks at a rate compatible with the operation of the concrete block producing machine.

Another object of the invention is to provide a very simple slump block producing machine which may readily be located above and in adjacent relationship with the conventional delivery conveyor of a high production concrete block producing machine.

Another object of the invention is to provide a slump block producing machine having a novel means for suspending and vertically actuating a pressure plate which is utilized to compress conventional concrete blocks into slump blocks over the delivery conveyor of a high prodnction concrete block producing machine.

Another object of the invention is to provide a slump block producing machine having novel means for supporting a block laden pallet on the delivery conveyor of a high production concrete block machine while producing vibration of the pallet which supports blocks thereon, and while a pressure plate is concurrently vibrated and forced downwardly on the upper surfaces of blocks so that they are quickly converted from conventional high production concrete blocks into high production slump blocks.

Another object of the invention is to provide a slump block producing machine operable above and adjacent to the delivery conveyor of a high production concrete block producing machine and wherein novel means is provided for actuating and leveling a pressure plate, which engages the upper sunfaces of several blocks carried by a pallet on said conveyor whereby, engagement of said pressure plate with said blocks is accurately controlled evenly to apply vertical force on said blocks so that they are uniformly and accurately compressed into slump block configurations.

Further objects and advantages of the invention may be apparent from the following specification, appended claims and accompanying drawings in which:

FIG. 1 is a side elevational view of a slump block producing machine of the present invention shown supported on the delivery "conveyor frame structure of a conventional high production concrete block producing machine.

FIG. 2 is an enlarged fragmentary sectional view taken from the line 22 of FIG. 1.

FIG. 3 is a side elevational view of a slump block showing by broken lines, the relative outline and dimensions of an original high production concrete block from which the slump block is produced.

FIG. 4 is a fragmentary sectional View taken from the line 44 of FIG. 1.

FIG. 5 is an enlarged fragmentary sectional view taken from the line 55 of FIG. 4; and

FIG. 6 is a fragmentary sectional view taken from the line 66 of FIG. 4.

As shown in FIG. 1 of the drawings, the slump block producing machine of the invention is provided with a suspension frame 10 secured by bolts '12 to an output conveyor frame 14 of a conventional high production concrete block producing machine. Supported between the members '14 is a cross member 16 having upstanding members 18 which support rails 20.

Mounted on these rails 20 are rollers 22 which support conventional flexible pallet delivery belts 24. These belts 24- move pallets 26 away from the conventional high production concrete block machine and the belts are similar to those employed in connection with the conventional Besser concrete block producing machines.

The belts 24 are slightly resilient and also slightly compressible. According to the present invention, stop bars 28 are located at a level slightly below the lower surface of the pallet carried by the belts 24. As shown in FIG. 5 of the drawings, these bars 28- are provided with upper surfaces 30 which may be a small fraction of an inch below the normal upper surfaces 3-2 of the belts 24. The upper surfaces 30 of the bars 28 are adapted to support the pallet 26 when pressure is exerted on blocks carried by the pallet during the process of creating slump blocks. When such pressure is exerted on the pallet 26, the belt 24 is slightly compressed whereupon the lower surface 34 of the pallet 26 engages the upper surface 30 of the bars 28, all as will be hereinafter described in detail.

Mounted on the cross bar 16 is a vibrator assembly 36 comprising pivotally mounted vibrators 38 and 40. These vibrators 38 and 40 are pneumatically operated vibrators coupled to a compressed air supply tube 42. The assembly 36 is provided with a pair of

pivot pins

44 and 46 upon which the vibrators 38 and 40, respectively, are mounted. These vibrators are thus pivotally mounted so that they may move into broken line positions A when a laden pallet 26 moves thereover in a direction as indicated by the arrow B, all as shown in FIG. 2 of the drawings.

Coupled to the vibrators 38 and 40 are

pallet engaging members

48 and 50 disposed to engage the lower surface 34 of each pallet 26 as it passes thereover in the direction of the arrow B. These

pallet engaging members

48 and 50 are provided with curved surfaces 52, as shown in FIG. 2 of the drawings, whereby engagement of the pallet 26 therewith automatically pivots these members and the respective vibrators into the broken line position A, shown in FIG. 2 of the drawings. When pivoted into such position, the curved surface 52 continues to engage the lower surface 34 of the pallet 26 since gravity tends to act upon the vibrators 38 and 40 in a manner to maintain efficient contact of the

engaging members

48 and 50 with the lower surface 34 of the pallet 26. Thus, the vibrators 38 and 40 transmit vibration to each pallet 26 as it passes thereover and into position below a compression plate 54, shown in FIGS. 1 and 4 of the drawangs.

The pressure plate 54 is supported by a frame 56 and is coupled to a plunger 58 of a fluid cylinder 62 by means of a clevis pin 60. The fluid cylinder 62 is pivotally supported and suspended by a bolt 64 extending through cross member 66 of the suspension frame 10.

Thus, the pressure plate 54 is pivotally suspended from the bolt 64 and is thus capable of freely aligning with upper surfaces of concrete blocks carried by the pallet 26 supported on the belts 24, herein before described.

Cross arms 68 of the suspension frame 10 support coil springs 70 which are coupled to the frame 56 and resiliently lend support and suspension stability thereto.

Mounted on the frame 56 are

pneumatic vibrator motors

72 and 74 which are coupled to the compressed air conduit 42, as will be hereinafter described in detail.

The pressure plate frame 56 is provided with adjustable stop screws 76. Four of these screws 76 are provided and disposed to bear at their lower ends upon rails 78 and 80, carried by the members 14, shown best in FIG. 1 of the drawings. The lower ends of the stop screws 76 provide a fixed stop for the pressure plate 54 relative to the pallet 26 in order accurately to control the height of slump blocks produced in accordance with the present invention. These stop screws 76 are vertically adjustable to provide the precise parallel alignment of the pressure plate 54 relative to a pallet 26 therebelow.

Four springs 82 are carried by the pressure plate frame 56 and extend downwardly to a position slightly below the lower ends of the stop screws 76 whereby they provide initial leveling of the frame 56 as it moves downwardly. The lower ends of these springs 82 first engage the rails 78 and 80 in order to pivotally align the pressure plate frame 56 in substantially parallel relation with the upper surfaces of blocks carried by the pallet 26 before the pressure plate 54 engages these blocks. In operation, the springs 82 are compressed during the downward movement of the frame 56 until the lower ends of the adjusting screws 76 engage the rails 78 and 80.

Fixed to a bar member 84 of the frame 10 is a sleeve 86 having a rod 88 adjustably mounted therein. A set screw 90 screwthreadably connected to the sleeve 86 is disposed to fix the rod 88 in various adjusted positions therein, as desired.

Supported on the lower end of the rod 88 is a limit switch 92 having a contact roller 94 engageable with an arm 96 which is fixed to the plunger 58 by means of a jam nut 98. The arm 96 is provided with an end portion 100 adapted to contact the roller 94 for operating the switch 92, which is also shown schematically in FIG. 1 of the drawings.

The roller 94 is disposed to be engaged by the end portion 100 of the arm 96 when the pressure plate 54 has been extended downwardly to a predetermined position a few thousands of an inch above a location at which all of the stop screws 76 bear solidly upon the rails 78 and 80, all as will be hereinafter described relative to the operation of the slump block producing machine of the invention.

The cylinder 62 is operated by compressed air which communicates through a tube 102 with the upper end of the cylinder 62 and through a tube 104 connected to the lower end of the cylinder 62. The plunger 58 is provided with a double acting piston 114 so that it may be powered downwardly or upwardly according to operation of a solenoid valve 106.

This valve 106 communicates with a compressed air supply tube 108 and is a normally closed valve disposed to furnish a supply of air under pressure to the tube 102 and the tube 42 for energizing the cylinder 62 and the

vibrators

38, 40, 72 and 74. Thus, the solenoid valve 106, when energized, supplies compressed air to the upper end of a cylinder 62 tending to force the plunger downwardly and at the same time energizes all of the hereinbefore mentioned vibrators.

Interconnecting the tube 108 and the tube 104 is a pressure regulator 110. This pressure regulator reduces pressure of compressed air from the tube 108 to the tube 104 so that air acting on a lower surface 112 of the piston 114 is less than that acting on the upper surface 116 thereof. It will be understood that when the solenoid valve is in normally closed position, air pressure is exhausted from the upper side 116 of the piston 114 due to the fact that the air pressure acting on the lower side 112 causes the piston to move upwardly and to exhaust the remaining air in the cylinder outwardly through the tube 102, tube 42, and to the

vibrator motors

38, 40, 72 and 74. Further, it will be understood that when the solenoid valve 106 is open, air pressure in the tube 102 is greater than air pressure in the tube 104, the piston 114 is forced downwardly in the cylinder 62 thereby overcoming regulated air pressure acting on the side 112 of the piston 114, whereupon the frame 56 is moved a short distance downwardly in order to permit the pressure plate 54 to exert force on blocks carried by a pallet 26 to force them into 7 a slump condition.

In series with the switch 92, as shown schematically in FIG. 1 of the drawings, is a cam operated switch 118 which is operated by a rotary cam 120 driven in unison with the controls of the high production concrete producing machine which delivers concrete blocks on the pallet 26 and which is coupled to intermittently activate the conveyor belts 24 on the rollers 22.

This cam 120 is provided with a lobe 122 which is disposed to close the switch 118 and also a holding coil switch 124 which energizes a holding coil 125 so that the switch 118 is held closed until the switch 92 is opened.

A conductor 126 is provided to interconnect the solenoid valve 106 and the switch 118 when closed and another conductor 128 is coupled to one end of the holding coil 125 and is also coupled to the solenoid valve 106.

The slump block producing machine of the invention operates substantially as follows:

Concrete blocks of conventional shape are produced by the high production concrete block producing machine and are delivered on the conveyor belt 24 on the upper sides of pallets 26. The concrete blocks delivered by the machine are preferably made of a high slump material which includes slightly more moisture than the usual mix used to produce conventional concrete block.

The production machine is set so that its compression head stops at a position to produce blocks which are a fraction of an inch taller than the conventional blocks of a standard modulus. It is desirable that these blocks are, for example, three eighths of an inch taller than standard blocks to allow for compression and slumping thereof.

As shown in FIG. 3 of the drawings, the blocks delivered on the pallet 26 have an upper surface represented by the broken line C and side surfaces represented by broken lines D.

Several such concrete blocks are delivered on a pallet 26 by means of the belts 24 and when the pallet 26 approaches the

pallet engaging members

48 and 50, the cam lobe 122, as shown in FIG. 1 of the drawings, also approaches the actuating point in its cycle wherein the switch 118 is closed.

As the pallet 26 carrying the blocks moves over the engaging

members

48 and 50 of the vibrators 38 and 40, it also moves under the pressure plate 54.

When the lobe 122 of the cam 120 closes the switch 118, the solenoid valve 106 is energized to an open position and compressed air is furnished to the vibrators 38 and 40 and the

vibrators

72 and 74. Also, the piston 114 in the cylinder 62 is forced downwardly carrying the pressure plate frame 56 and the pressure plate 54. This pressure plate 54 is disposed in suspended swingable position by the pivotal bolt 64, as hereinbefore described, and the lower ends of the springs 82 engage the rails 78 and 80 as the pressure plate closely approaches the upper surfaces of the concrete blocks on the pallet 26. While the pressure plate is moved downwardly, it contacts the upper surfaces C of the blocks and gradually, with aid of vibra tion supplied by the vibrators, the block is compressed to a slump condition wherein its upper surface is disposed at F and its sides are caused unevenly to bow out into somewhat convex wall structures G and H as shown in FIG. 3 of the drawings. Thus, the slump block is formed by vibration and pressure in a free standing position on the pallet on which it was originally formed by the high production concrete block machine. It will be seen that this method may be carried out substantially in accordance with the cycle rate of the production machine and that the conventional conveyor belt 24 may be slightly compressed when pressure is applied to these blocks whereby compression of the belts permits the pallet 26 to rest on the bars 28 which solidly support the pallet during compression slumping of the blocks thereon.

When the pressure plate 54 has been forced downwardly to a predetermined position to locate the upper surface of the blocks at the level F, shown in FIG. 3 of the drawings, the roller 94 of the limit switch 92 is contacted by the end portion 100 of the arm 96 thereby opening the switch 92 and deenergizing the holding coil 125 which permits the switch 118 to open and deenergize the solenoid valve 106.

When the solenoid valve is deenergized, it closes and regulated pressure, acting on the lower side 112 of the piston 114, forces the piston upwardly which causes compressed air on the upper side 116 of the piston to be forced out of the cylinder 62 and through the tube 102 and tube 42 through the

vibrators

38, 40, 72 and 74. Thus, the plunger 58 is retracted together with the frame 56 'while the four coil springs 70 tend normally to hold the frame 56 in substantially level position so that it approaches the concrete blocks in a substantially level position as it moves downward to engage the upper surfaces thereof. It will be understood that the rails 28 provide a positive stop for downward movement of the pallet 26, when under pressure, while the ends of the adjustment screws 76 provide a positive stop for the downward movement of the pressure plate 54 whereby, a precise height of the slump block is con-trolled so that the distance between the upper surface F and the lower surface K is accurately controlled.

It will be appreciated that the present invention includes a method of producing slump blocks comprising; the production of conventional concrete blocks by a high production machine and permitting said high production machine to produce a block substantially taller than the ultimate elevation of the slump block. Then delivering the production concrete block from the machine and applying vertical pressure and vibration to said conventional block until it is compressed and externally bowed or deformed into a slump block configuration. Said 6 pressure and vibration is stopped when the elevation of the slump block is at a desired dimension which is substantially less than the original dimension, or height of the conventional concrete block originally produced by the high production concrete block machine.

The method also comprises the subjection of the blocks to vibration of the pallet as well as vibration of a pressure plate on the upper surfaces of the blocks while the pallet is supported or restrained vertically and while the pressure plate moves downwardly concurrently with vibration thereof.

It has been found that the pressure plate 54 may be made of various materials, however, plexiglass has been found most suitable since the usual concrete mix does not tend to adhere thereto as readily as it does to other known materials. Additionally, during the process of making the blocks, it has been found that intermittent swabbing of the lower surface of the pressure plate alleviates the tendency of the upper surfaces of the blocks to leave deposits on lower surface of the plate 54. The swabbing operation may include the application of a slight film or coat of oil by any suitable swabbing device.

Since the pressure plate 54 is only momentarily engaged with the upper surfaces of the concrete blocks, it will be recognized that the swabbing of this plate comprises a method step which is important in accordance with the foregoing method in high production of slump blocks when produced from conventional concrete blocks delivered from a high production machine. Thus, the method includes the application of pressure by a pressure plate on the upper surfaces of the blocks; the pressure plate being conditioned so that it does not adhere to the upper surfaces of the blocks.

It will be obvious to those skilled in the art that various modifications of the slump block producing machine and method of the invention may be resorted to in a manner limited only by a just interpretation of the following claims.

We claim:

1. In a slump block producing machine the combination of: a delivery'conveyor of a conventional high production concrete block machine; a vertically movable pressure plate disposed above said conveyor and adapted vertically to move into engagement with the upper surfaces of concrete blocks disposed on a pallet carried by said conveyor; actuating means coupled to said pressure plate and supporting the same; a frame for supporting said actuating means whereby said pressure plate is suspended thereby; said actuating means pivoted to said last mentioned frame so that the plane of said pressure plate is readily conformable to the planes of concrete blocks supported on a pallet therebelow; first vibrating means disposed to vibrate a pallet on said conveyor below said pressure plate; and second vibrating means coupled with said pressure plate for vibrating it; first means operable by a high production concrete block machine in connection with said conveyor said first means coupled to said actuating means and said first and second vibrating means for automatically initiating operation of said pressure plate actuating means and said first and second vibrating means; limit switch means disposed to be actuated in accordance with downward movement of said pressure plate for deenergizing said actuating means and said first and second vibrator means when said pressure plate reaches a predetermined vertical position; stop means in connection with said pressure plate; members stationarily disposed to be engaged by said stop means for mechanically limiting the downward travel of said pressure plate, said conveyor comprising compressible belts supporting a pallet thereon and bars slightly below the upper surfaces of said belts disposed to support the lower surface of a pallet when said pressure plate engages and compresses blocks on the upper surface thereof.

2. In a slump block producing machine the combination of: a delivery conveyor of a conventional high production concrete block machine; a vertically movable pres sure plate disposed above said conveyor and adapted vertically to move into engagement with the upper surfaces of concrete blocks disposed on a pallet carried by said conveyor; actuating means coupled to said pressure plate and supporting the same; a frame for supporting said actuating means whereby said pressure plate is suspended thereby; said actuating means pivoted to said last mentioned frame so that the plane of said pressure plate is readily conformable to the planes of concrete blocks supported on a pallet therebelow; first vibrating means disposed to vibrate a pallet on said conveyor below said pressure plate; and second vibrating means coupled with said pressure plate for vibrating it; first means operable by a high production concrete block machine in connection with said conveyor said first means coupled to said actuating means and said first and second vibrating means for automatically initiating operation of said pressure plate actuating means and said first and second vibrating means; limit switch means disposed to be actuated in accordance with downward movement of said pressure plate for deenergizing said actuating means and said first and second vibrator means when said pressure plate reaches a predetermined vertical position; stop means in connection with said pressure plate; members stationarily disposed to be engaged by said stop means for mechanically limiting the downward travel of said pressure plate, said conveyor comprising compressible belts supporting a pallet thereon and means slightly below the upper surfaces of said belts disposed to support the lower surface of a pallet when said pressure plate engages and compresses blocks on the upper surface thereof, said actuating means being a pneumatic cylinder having a plunger supporting said pressure plate; said vibrators also being pneumatically powered; solenoid valve means coupled to said first means for energizing said actuating means and said vibrators.

3. In a slump block producing machine, the combination of: a delivery conveyor of a conventional high production concrete block machine; a vertically movable pressure plate disposed above said conveyor and adapted vertically to move into engagement with upper surfaces of concrete blocks disposed on a pallet carried by said con veyor; actuating means coupled to said pressure plate for actuating the said pressure plate upwardly and downwardly; a frame for supporting said actuating means and said pressure plate; first vibrating means freely engageable with the bottom of a pallet on said conveyor and,

8 disposed to vibrate said pal-let on said conveyor; and second means coupled with said pressure plate for vibrating it; said first vibrating means pivotally mounted on a substantially horizontal axis adjacent said conveyor and having means norm-ally disposed above a lower surface of a pallet on said conveyor and, engageable with the lower surface of a pallet on said conveyor whereby said pallet when moved along on said conveyor pivots said last mentioned means downwardly about said horizontal axis and engages said last mentioned means with the bottom of said pallet.

'4. In a slump block producing machine, the combination of: a delivery conveyor of a conventional high production concrete block machine; a vertically movable pressure plate disposed above said conveyor and adapted vertically to move into engagement with upper surfaces of concrete blocks disposed on a pallet carried by said conveyor; actuating means coupled to said pressure plate for actuating the said pressure plate upwardly and downwardly; a frame for supporting said actuating means and said pressure plate; first vibrating means freely engageable with the bottom of a pallet on said conveyor and, disposed to vibrate said pallet on said conveyor; and second means coupled with said pressure plate for vibrating it; said conveyor having compressible belt means disposed to carry pallets thereon; and further means slightly below the upper surfaces of said belts disposed to provide supporting stops for the lower surfaces of a pallet when said pressure plate engages blocks on a pallet carried by said belt means and thereby causes compression thereof.

References Cited by the Examiner UNITED STATES PATENTS Re. 24,527 8/1958 Ripley 25155 288,240 11/1883 =Ittner 25-122 876,388 1/1908 Nieters.

1,787,449 1/1931 Jackson.

1,905,975 4/ 1933 Thomas.

2,431,034 11/ 1947 Gelbman.

2, 6=85,1 1'6 '8/ 1954 Schutt.

ROBERT F. WHITE, Primary Examiner.

MICHAEL V. BRINDI'SI, ALEXANDER H. BROD- MERKEL, Examiners.

R. B. MOFFITI, Assistant Examiner.

Claims

1. IN A SLUMP BLOCK PRODUCING MACHINE THE COMBINATION OF: A DELIVERY CONVEYOR OF A CONVENTIONAL HIGH PRODUCTION CONCRETE BLOCK MACHINE; A VERTICALLY MOVABLE PRESSURE PLATE DISPOSED ABOVE SAID CONVEYOR AND ADAPTED VERTICALLY TO MOVE INTO ENGAGEMENT WITH THE UPPER SURFACES OF CONCRETE BLOCKS DISPOSED ON A PALLET CARRIED BY SAID CONVEYOR; ACTUATING MEANS COUPLED TO SAID PRESSURE PLATE AND SUPPORTING THE SAME; A FRAME FOR SUPPORTING SAID ACTUATING MEANS WHEREBY SAID PRESSURE PLAT IS SUSPENDED THEREBY; SAID ACTUATING MEANS PIVOTED TO SAID LAST MEMTIONED FRAME SO THAT THE PLANE OF SAID PRESSURE PLATE IS READILY CONFORMABLE TO THE PLANES OF CONCRETE BLOCKS SUPPORTED ON A PALLET THEREBELOW; FIRST VIBRATING MEANS DISPOSED TO VIBRATE A PALLET ON SAID CONVEYOR BELOW SAID PRESSURE PLATE; AND SECOND VIBRATING MEANS COUPLED WITH SAID PRESSURE PLATE FOR VIBRATING IT; FIRST MEANS OPERABLE BY A HIGH PRODUCTION CONCRETE BLOCK MACHINE IN CONNECTION WITH SAID CONVEYOR SAID FIRST MEANS COUPLED TO SAID ACTUATING MEANS AND SAID FIRST AND SECOND VIBRATING MEANS FOR AUTOMATICALLY INITIATING OPERATION OF SAID PRESSURE PLATE ACTUATING MEANS AND SAID FIRST AND SECOND VIBRATING MEANS; LIMIT SWITCH MEANS DISPOSED TO BE ACTUATED IN ACCORDANCE WITH DOWNWARD MOVEMENT OF SAID PRESSURE PLATE FOR DEENERGIZING SAID ACTUATING MEANS AND SAID FIRST AND SECOND VIBRATOR MEANS WHEN SAID PRESSURE PLATE REACHES A PREDETERMINED VERTICAL POSITION; STOP MEANS IN CONNECTION WITH SAID PRESSURE PLATE; MEMBERS STAIONARILY DISPOSED TO THE ENGAGED BY SAID STOP MEANS FOR MECHANICALLY LIMITING THE DOWNWARD TRAVEL OF SAID PRESSURE PLATE, SAID CONVEYOR COMPRISING COMPRESSIBLE BELTS SUPPORTING A PALLET THEREON AND BARS SLIGHTLY BELOW THE UPPER SURFACES OF SAID BELTS DISPOSED TO SUPPORT THE LOWER SURFACE OF A PALLET WHEN SAID PRESSURE PLATE ENGAGES AND COMPRESSES BLOCKS ON THE UPPER SURFACE THEREOF.