US3049256A - Refuse body loading and packing mechanisms - Google Patents

Description

Aug. 14, 1962 G. E. URBAN 3,049,256

REFUSE BODY LOADING AND PACKING MECHANISMS Filed March 25, 1960 3 Sheets-Sheet 1 .IIIIHH" 4 1 INVENIOR.

Aug. 14, 1962 G. E. URBAN 3,049,256

REFUSE BODY LOADING AND PACKING MECHANISMS Filed March 23, 1960 3 Sheets-Sheet 2 Mum" 0.9

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REFUSE BODY LOADING AND PACKING MECHANISMS Filed March 23. 1960 3 Sheets-Sheet '3 INVENTOR.

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. Patented Aug. 14, 1962 3,049,256 REFUSE BODY LOADING AND PACKING MECHANISMS George E. Urban, South Milwaukee, Wis., assignor to The Heil C0,, Milwaukee, Win, a corporation of Wiscousin Filed Mar. 23, 1959, Ser. No. 17,004 11 Claims. (Cl. 214-618) This invention relates to improvements in refuse body loading and packing mechanisms.

The present invention relates to a refuse body of the type disclosed in United States Patent No. 2,798,624, dated July 9, 1957. In the use of the type of loading mechanism shown in said patent it is necessary to have complicated mechanical linkage to time the packer plate and bucket. In order to eliminate the necessity of using such complicated linkage it has heretofore been considered necessary either to employ a twin hydraulic circuit arrangement of the type shown in Herterich Patent No.

2,837,230, one for the cylinder which operates the packer plate, and the other for the cylinder which operates the bucket, which arrangement does not produce a proper timing and coordination, or to try to get a split flow from a single pump to the two cylinders. In this latter type of loader, during part of the cycle of operation, the packer plate starts its movement independently of the bucket, and at a later stage the bucket moves with the packer. With this latter system it is difficult to get a split flow from the pump to the two cylinders in such a way as to properly control the ratio of fluid flow to one cylinder with respect to the other. Furthermore there is a certain loss of time in all of these prior systems.

It is a general object of the present invention to obviate the above mentioned difliculties by having an improved hydraulic circuit wherein fluid exhausted from the packer operating cylinder is caused to flow directly to the bucket operating cylinder, rather than back to the reservoir, after the packer has completed approximately half of its movement. With this arrangement, several seconds are saved in the operation, and there is perfect coordination between the packer plate and the bucket.

An additional problem in connection with prior rear loading refuse bodies is that when the operators are starting to fill the body, no compaction takes place until enough refuse has been loaded in the body so that it will react against the front end thereof.

An additional object of the present invention is, therefore, to provide means for effecting stage precompaction, such precompaction beginning immediately after filling of the body has started, said precompaction being preferably accomplished by means of a precompaction plate which can be progressively moved toward the front of the body as the body is progressively filled.

A still further object of the present invention is to provide mechanism as above described wherein the precompaction plate may also serve as an ejector for discharging the load at the dump.

A still further object is to provide, in one form of the invention, power means under the control of the operator for progressively moving the precompaction plate.

A still further object is to provide, as another form of the invention, means for automatically bringing about progressive movement of the precompaction plate after a predetermined amount of material has been packed against it.

With the above and other objectives in view, the invention consists of the improvements in refuse body loading and packing mechanisms, and all of its parts and combinations, as set forth in the claims, and all equivalents thereof.

In the accompanying drawings, illustrating several embodiments of the invention, in which the same reference numerals designate the same parts in all of the views:

FIG. 1 is a fragmentary side elevational view of a refuse body, part of the body being broken away and shown in longitudinal vertical section and the tail gate being shown in vertical longitudinal section;

FIG. 2 is a fragmentary transverse sectional view showing the guiding means for the precompacting plate;

FIG. 3 is a diagrammatic view showing the control system for the bucket and packer plate cylinders;

FIG. 4 is a fragmentary side elevational view showing the use of a precompactor plate which can be manually released, parts being broken away and shown in section;

FIG. 5 is a diagrammatic View showing one form of control for the precompactor plate of FIG. 1;

FIG. 6 is a diagrammatic view showing another form of control for the precompactor plate of FIG. 1;

FIG. 7 is a diagrammatic view of one of the control valves of FIG. 3; and

FIG. 8 is a diagrammatic view of the other control valve of FIG. 3.

Referring more particularly to the drawings, the numeral l5 designates a vehicle refuse body having a tail gate unit 16, the latter having inwardly extending pivot brackets 17 by means of which the tail gate is pivotally connected to the body as at 13 for upward and rearward swinging movement as is common in the art. If desired, the body may be mounted on the vehicle frame 19 as at 2%) for upward and rearward swinging movement to provide for gravity dumping when the tail gate is elevated, all of which is well known in the art.

The tail gate unit includes spaced side members 21 connected by a transverse member 22 at the lower rear, the latter being flanged inwardly as at 23 to form a bucket stop. The spaced side plates 21 are also connected at the top and upper rear by a curved sheet metal plate 24. Above the stop 23 is a space which forms a rear loading opening which may be closed in any suitable manner if desired, this forming no part of the present invention. Rigidly mounted on a rotatable shaft 25 which extends transversely of the tail gate is a refuse bucket or hopper 26, the latter including a bottom 27 and \a front wall 28. The hopper is adapted to be moved from the full line position of FIG. 1 to the dot and dash line positions therein. The upper portion of the front wall 28 of the hopper is provided with an external stop member 29 for cooperation with the stop 23 when the bucket is in its lowermost full line position of FIG. 1.

Pivoted as at 30 to :an ear 31 on the bottom of the bucket is an hydraulic bucket cylinder 32 having an extensible ram 33. The outer end of the latter is piv-otably connected to the tail gate as at 34. The ram is preferably formed of multiple telescopic sections as illustrated.

Rigidly mounted on a rotatable shaft 35 which extends transversely of the tail gate is a swingable packer plate 36. The packer plate is adapted to be moved from the full line position of FIG. 1 to the dot and dash line positions therein. A packer plate operating cylinder 37 is pivoted as at 38 to the tail gate. It has an hydraulically actuated ram 39 which is pivoted as at 40 to an car 41 on the packer plate.

Suitably mounted for longitudinal movement in the body 15 is a precompa'cting plate 42 which will hereinafter be referred to as a precompactor. The plate has a base flange 43, and near each end of said flange there may be any suitable means for guiding the precompactor in sliding movement. As shown in FIG. 2, this may comprise shoes 44 which ride in grooves or guideways 45 in the upper surface of the floor '46 of the body. An angular skirt of metal or other suitable material 47 may be attached as at 48 to the rear face of the compactor plate to extend angularly rearwardly therefrom and provide a chamber 49. Secured within the chamber '49 is an hydraulic cylinder 50 having telescopic ram portions 51 projecting forwardly therefrom through a hole 52 near the bottom of the precompactor. The forward end of the ram is connected to or reacts against the front wall 14 of the body.

Any suitable means may be provided for swinging the tail gate to an open position for discharge of the load. The hydraulic cylinder 46 and ram 47 of Brown et al. Patent No. 2,798,624 is a satisfactory mechanism. In addition, there may be a cylinder such as the cylinders 151 of the 'beforementioned Brown patent for hoisting the body 15 on the pivots to dumping position when this is desired. Inasmuch as these mechanisms are common in the art, they have not been shown or described in the present case, as they have no direct bearing upon the features of the present invention.

FIG. 1 illustrates power actuated preeompactors. If desired, manually movable precompaetors may be employed as shown in FIG. 4. In FIG. 4 corresponding parts are designated 'by the same numerals used in FIG. 1 except that they are preceded by a 1. In the form of the invention of FIG. 4, the precompactor 142 is mounted for longitudinal sliding movement in the body 115. Pivoted to the body frame at longitudinally spaced intervals is a series of hooks 150, 151 and 152. Actuating levers 156, 157 and 158 for said hooks are mounted rigidly on pivot shafts 153, 154 and 155. The pivot shafts extend externally and are equipped with handles 159, 160 and 161. By swinging the handle 159 from the position illustrated in FIG. 4 to an upright position, the hook will be engaged with the lower edge of the precompactor 142 to lock it against forward movement. The engaging portion of the hook may move upwardly through a slot 162 in the bottom of the body. With thehook 150 released, the precompactor 142 may be permitted to move with the load to the intermediate position shown in FIG. 4 where it can be maintained by the hook 151. At a later stage in the loading the hook 151 may be released and the precompactor 142 allowed to move into engagement with the hook 152. Eventually the hook 152 may be released to allow the precompactor to move against the forward end of the body 115 as shown by.

dot and dash lines in the extreme left position. The precompactor plate may be maintained in upright position by any suitable means such as guides 164 on opposite sides of the plate which ride in guiding slots 163 in the sides of the body. It is desirable to use the construction of FIG. 4 only with a pivoted hydraulically actuated dump body as shown in FIG. 1 which pivots for dumping on pivots 20. With such a construction the precompactor plate 142 will return by gravity to the full line position of FIG. 4 during dumping to be ready for the next loading operation. When the power actuators 51 of FIG. 1 are used with the precompactor plate, then the use of a pivoted dump body is not essential as power ejection will take care of the unloading.

Operation Referring now to the form of the invention of FIG. 1 and to the diagrammatic hydraulic circuit of FIG. 3, at the start of a packing cycle and after the collectors have filled the hopper 26 with refuse, the valves 54 and 63 of FIG. 3 are operated either manually or electrically to positions 1 and 2 respectively, FIGS. 7 and 8, to provide communication between the line 55 and line 56 leading to the packer plate operating cylinder 37 and also communication between the exhaust line 59 and line 61, through valve 54, line 62 and valve 63. This causes hydraulic fluid to be pumped from a reservoir 57 by pump 58 through the lines 55 and 56. During this first phase, the packer plate 36 of FIG. 1 is retracted approximately half way from the full line position to the intermediate dot and dash line position of FIG. 1. While this takes place,

fluid exhausted from the cylinder 37 flows through the lines 59, valve 54, line 62, valve 63, and line 61 back to the reservoir 57.

The valve 63 is then moved either manually or automatically to position 1, FIG. 8, to switch the flow of exhausted oil from the line 59, which flows through line 62 leading to the valve 63, and line 64 leading into an end of the cylinder 32 which operates the hopper, with ex hausted oil from the cylinder 32 flowing back through the valve 63 to the reservoir. This causes the ram 33 to be extended with the result that there is upward movement of the hopper 26 approximately half Way. Thus oil from the low pressure side of cylinder 37 is conducted directly (without going through the reservoir or pump) into a hopper operating cylinder 32. By having the cylinders 37 and 32 sized correctly relative to one another, the motion of the hopper will be synchronized as desired so that it is moved from the lowermost full line position of FIG. 1 to a predetermined intermediate dot and dash line position therein.

At this point, valve 54 is returned to position 2, FIG. 7, either manually or automatically and valve 63 is left in its former position 1 so that the oil flow from the pump 58 will pass through valves 54 and 63 into the cylinder 32 for the rest of the movement of the hopper causing it to be elevated the rest of the way from the intermediate dot and dash line position of FIG. 1 to the uppermost dot and dash line position therein, oil exhausted from cylinder 32 flowing through the valve 63 back to the reservoir. While the bucket 26 was moving from its lowermost full line position to its intermediate position, the packer plate 36 moved from its intermediate position to its rearmost dot and dash line position to be held there until the bucket reached its uppermost position.

At this point, valve 63 is returned to its neutral position 2 (FIG. 8) and valve 54 is actuated to position 3 either manually or automatically to cause oil to flow from the pump into line 59 and into the base of cylinder 37.

This will move the packer plate 36 from its rearmost posi tion to its full line forwardmost position to sweep refuse from the hopper into the body proper. Thereafter valve 54 is returned to its neutral position 2 to hold the packer forwardly and valve 63 is operated to position 3 to cause oil from the pump to flow through the valves 54 and 63 to the top of the bucket cylinder 32 to cause lowering of the bucket back to its lowermost position, oil being exhausted from the base of cylinder 32 back through valve 63 to the reservoir. The valve diagrams to permit the above operations are shown in FIGS. 7 and 8.

At the start of a body loading operation the precompactor 42 is in the rearmost position (a) and is maintained in this position by the extended rams 51. Therefore, even at the stait of a body filling operation the refuse which is swept out of the hopper by the packing plate 36 is immediately precompacted against the plate 42 in the position (a). Heretofore, without the novel precompacting plate 42, no compaction took place until the body was nearly filled.

After -a predetermined amount of material has been packed against the precompactor 42, the hydraulic cylinder 50 may be actuated to move the precompactor forwardly such as from position (a) FIG. 1, to position (b). Loadingof the body is then continued until it will take no more while the plate is in position (b). The precornpactor is then moved forwardly a predetermined distance and the loading is continued. When the body has been completely filled, the precompactor 42 will be in the extreme left hand position of FIG. 1 against the forward wall of the body.

The manually operable precompactor 142 of FIG. 4 may be used similarly to cause precompaction as the body is being filled.

The hydraulically actuated precompactor 42 of FIG. 1 can also be used as a combination ejector and precompactor. That is, after the body has been filled, and with the plate 42 in the extreme left hand position of FIG. 1,

it can he forced rearwardly to eject the load from the body, the tail gate 16 being open. This eliminates the necessity of raising the body to dump by gravity. The precompactor can also be used with a gravity dump type of body and be returned to starting position automatically, through suitable valve actuation which is responsive to raising the body to dump the load.

The hydraulic cylinder 50 for the precompactor ejector of FIG. 1 may be either automatically controlled or manually controlled. FIG. 5 shows a diagram of an automatic control which may be employed. Referring to this figure, oil from a tank 66 is pumped by the pump 67 through a line 68 to a valve 69. From the valve 69 the fluid flows under pressure through a line 70 into the high pressure side of the cylinder 5% to extend the rams 51 and cause the precompactor ejector to move rearwardly in the body to forcibly eject the load, or to return the precompactor plate to starting position. During such movement fluid is exhausted from the cylinder through lines 71 and 71' back to the tank 66.

It is a feature of the control arrangement of FIG. 5 to provide for automatic movement of the precompactor plate from a rear position to a more forward position, such as from position (a) FIG. 1 to position (b). With this arrangement, after a predetermined amount of refuse has been packed against the plate when in position (a) FIG. 1, for example, the relief valve 73 of FIG. 5 will open at a predetermined setting allowing fluid to flow 'back into the tank 66 and allowing the load to move the 'precompaction plate 42 from the position (a) to the position (b), or to any other intermediate position. This movement relieves the pressure sufficiently to allow the relief valve to close and hold the precompaction plate 42 in a new position.

In FIG. 6 the exhaust line 71 leads back to the control valve and there is another line 73 from the control valve to the tank which does not directly communicate with the line 71. The check valve 72 of FIG. 5 and the relief valve 73 are omitted. Here the control valve 69 is operated manually when it is desired to allow the load to move the precompactor plate from one position, such as from position (a), to a more forwardly position such as position (b). With either the arrangement of FIG. 5 or the arrangement of FIG. 6, the plate 42 may be used as a combination precompactor and ejector if it is desired to eject the load from the body without tilting the body for gravity dumping.

Another important advantage of the present invention is that with the constructions shown in FIGS. 1 and 3, there is coordination between the second half of the movement of the packer plate and the movement of the bucket from its lowermost position to its intermediate position.

This is accomplished by having fluid which is exhausted from the packer operating cylinder led directly to the bucket operating cylinder after the packer plate 36 has completed a predetermined part of its movement forwardly. With this arrangement, two or three seconds time is saved during each cycle, and perfect coordination between the operation of the packer plate 36 and the hopper .26 is assured. The coordinated movement of the packer plate with respect to the bucket as shown in FIG. 1 is particularly effective when employed in connection with the .stage compacting obtained by use of the novel precompactor.

It is to be understood that the present invention is not to be limited to the exact details of construction shown and described, for obvious modifications will occur to persons skilled in the art.

What I claim is:

1. In a device for loading refuse into a truck body having a rear opening, said device being of the type having a pivotally mounted bucket and having a pivotally mounted packer plate for transferring refuse from the bucket into said rear opening when the bucket has been swung to elevated position on its pivot, said bucket and packer plate being in the tailgate, the first part of said bucket movement being simultaneous with the final part of retraction movement of said packer plate during the cycle of operation, a fluid pressure operated cylinder having a ram and pivotally connected at one end to said tailgate and at the other end to said packer plate for actuating the latter, a fluid pressure operated cylinder having a ram and pivotally connected at one end to said tailgate and at its other end to said bucket for operating the bucket, a source of fluid under pressure, an hydraulic circuit connected with said source and with both cylinders and means in said hydraulic circuit for causing exhausted fluid from the packer cylinder to flow directly to said bucket operating cylinder only during that part of the cycle of operation when the bucket is moving simultaneously with the packer plate to furnish the sole motive power for said bucket operating cylinder during said part of the cycle.

2. In a device for loading refuse into a truck body having a rear opening, said device being of the type having a pivotally mounted bucket and having a pivotally mounted packer plate for transferring refuse from the bucket into said rear opening when the bucket has been swung to elevated position on its pivot, said bucket and packer plate being in the tailgate, a fluid pressure operated cylinder having a ram and pivotally connected at one end to said tailgate and at the other end to said packer plate for actuating the latter, a fluid pressure operated cylinder having a ram and pivotally connected at one end to said tailgate and at its other end to said bucket for operating the bucket, an hydraulic circuit connected with both cylinders, a pump and a reservoir in said circuit, and control valve means providing first for part retraction of the packer plate, then for exhaustion of hydraulic fluid from the packer plate cylinder directly to the bucket cylinder to furnish the sole motive power for said bucket operating cylinder and to cause accurately coordinated part raising of the bucket simultaneously with the completion of retraction movement of the packer plate, and then for completion of raising of the bucket by means of power from said pump while the packer plate is held in completely retracted position.

3. In a device for loading refuse into a truck body having a rear opening, said device being of the type having a pivotally mounted bucket and having a pivotally mounted packer plate for transferring refuse from the bucket into said rear opening when the bucket has been swung to elevated position on its pivot, said bucket and packer plate being in the tail ate, a fluid pressure operated cylinder having a ram and pivotally connected at one end to said tailgate and at the other end to said packer plate for actuating the latter, a fluid pressure operated cylinder having a ram and pivotally connected at one end to said tailgate and at its other end to said bucket for operating the bucket, an hydraulic circuit connected with said cylinders, a pump and a reservoir in said circuit, means including first and second control valves in said circuit for directing hydraulic fluid exhausted from said packer plate cylinder either back to the reservoir or to the cylinder for said bucket, said second control valve being so connected in the circuit as to provide for selectively directing fluid from the pump directly to the cylinder for said bucket ram or for operation of said bucket ram cylinder solely by the fluid exhausted from said packer plate cylinder.

4. In a device for loading refuse into a truck body having a rear opening, said device being of the type having a pivotally mounted bucket and having a pivotally mounted packer plate for transferring refuse from the bucket'into said rear opening when the bucket has been swung to elevated position on its pivot, said bucket and packer plate being in the tailgate; a fluid pressure operated cylinder having a ram pivotally connected at one end to said tailgate and at the other end to said packer plate for actuating the latter; a fluid pressure operated cylinder having a ram pivotally connected at one end to said tailgate and at its other end to said bucket for operating the bucket; a reservoir; a pump; first and second control valve; fluid lines connecting said first valve to said pump, reservoir, packer plate cylinder and second valve; fluid lines connecting said second valve to said reservoir, first valve and bucket operating cylinder, said valves and fluid lines providing for the following alternatives: flow from the pump through the first valve to the packer plate cylinder to first partially retract said packer plate independently of bucket movement, with exhaust from said cylinder through said second valve back to the reservoir; flow of exhaust from said packer cylinder through said second valve to said bucket cylinder to cause partial raising of the bucket which is coordinated with the final retraction movement of the packer plate, with exhaust from said bucket cylinder back through said second valve to the reservoir; and holding of the packer plate while fluid from the pump flows through the first and second valves to the bucket cylinder for the final raising of the bucket, with exhaust from the bucket cylinder going back through the second valve to the reservoir.

5. In a device for loading refuse into a truck body 9 having a storage chamber and having a rear opening and having a tailgate, said device being of the type having a pivotally mounted bucket and having a pivotally mounted packer plate for transferring refuse from the bucket into said rear opening each time the bucket has been swung to elevated position on its pivot, said bucket and packer plate being in the tailgate, a precompacting plate having a rear face extending transversely of said body and mounted for longitudinal adjustment movement therein to form a movable front for said storage chamber, an hydraulic ram, an hydraulic circuit for said ram, and means in said circuit responsive to a predetermined pressure on the rear face of said precompacting plate caused by operation of said packer plate for allowing forward movement of the precompacting plate in response to pressure of the load to increase the effective size of said storage chamber from the rear to the front.

6. In a device for loading refuse into a truck body having a storage chamber and having a rear opening and having a tailgate, said device being of the type having a pivotally mounted bucket and having a pivotally mounted packer plate for transferring refuse from the bucket into said rear opening each time the bucket has been swung to elevated position on its pivot, said bucket and packer plate being in the tailgate, a precompacting plate having a rear face extending transversely of said body and mounted for longitudinal adjustable movement therein to form a movable front for said storage chamber, an hydraulic ram, an hydraulic circuit for said ram, and means in said circuit responsive to a predetermined pressure on the rear face of said precompacting plate caused by operation of said packer plate for causing said ram to move said plate to a new forward position of longitu dinal adjustment whereby the effective size of said storage chamber may be progressively increased from the rear to the front as the packer plate continues to deliver batches of refuse toward said rear face of the precompacting plate.

7. In a device for loading refuse into a truck body having a storage chamber and having a rear opening and having a tail gate, said device being of the type having a hopper and having a packer plate for transferring successive batches of refuse from the hopper into said rear opening, said hopper and packer plate being in the tail gate, a precompacting plate having a rear face and extending transversely of said body and mounted for longitudinal adjustment therein to form a movable front for said storage chamber, an hydraulic ram, an hydraulic circuit for said ram, and means in said circuit responsive to a predetermined pressure on the rear face of said precompacting plate caused by action of said packer plate for allowing forward movement of the precompacting plate in response to pressure of the load to thereby increase the effective size of said storage chamber from the rear to the front.

8. In a device for loading refuse into a truck body having a storage chamber and having a rear opening, said device being of the type having packer means adjacent said rear opening for delivering successive batches into said storage chamber, a precompacting plate having a rear face extending transversely of said body and mounted for longitudinal adjustable movement therein to form a movable front for said storage chamber, means for releasably holding said plate in a selected position of longitudinal adjustment while said packer means packs a batch toward its rear face, and mechanism associated with said releasable holding means which is responsive to a predetermined pressure on the rear face of said precompacting plate caused by operation of said packer means for allowing progressive forward movement of the recompacting plate to progressively increase the effective size of said storage chamber from the rear to the front.

9. In a device for loading refuse into a truck body having a storage chamber and having a rear opening and having a tailgate, said device being of the type having a hopper and having a packer plate for transferring refuse from the hopper into said rear opening, said hopper and packer plate being in the tailgate, a precompacting plate having a rear face extending transversely of said body and mounted for longitudinal adjustable movement therein to form a movable front for said storage chamber, power-operated means for releasably holding said precompacting plate in a selected position of longitudinal adjustment while said packer plate packs successive batches against its rear face, and mechanism associated with said power-operated means which is responsive to a predetermined pressure on the rear face of said precompacting plate caused by operation of said packer plate for allowing progressive forward movement of said precompacting plate to progressively increase the effective size of said storage chamber from the rear to the front.

10. In a device for loading refuse into a truck body having a storage chamber and having a rear opening and having a tailgate, said device being of the type having a pivotally mounted :bucket and having a pivotally mounted packer plate for transferring refuse from the bucket into said rear opening each time the bucket has been swung to elevated position on its pivot, said bucket and packer plate being in the tailgate, a precompacting and ejector plate having a rear face extending transversely of said body and mounted for longitudinal adjusta-ble movement therein to form a movable front for said storage chamber, power-operated means for releasably holding said precompacting plate in a selected position of longitudinal adjustment while said packer plate packs batches toward its rear face, said power-operated means also being operable to move said precom pacting plate to eject the load, and mechanism associated with said power-operated means which is responsive to a predetermined pressure on the rear face of said precompacting plate caused by operation of said packer plate for allowing forward movement of the precompacting plate in response to pressure of the load to increase the effective size of said storage chamber from the rear to the front.

11. In a device for loading refuse into a truck body having a storage chamber and having a rear opening and having a tailgate, said device being of the type having a hopper and having a packer plate for transferring successive batches of refuse from the hopper into said rear opening, said hopper and packer plate being in the tailgate, a precompacting plate having a rear face and extending transversely of said body and mounted for longitudinal adjustable movement therein to form a movable front for said storage chamber, power-operated means for releasably holding said precompacting plate in a selected position of longitudinal adjustment while said packer plate packs batches against its rear face, and mechanism associated with said power-operated means which is responsive to a predetermined pressure on the rear face of said precompacting plate caused by opera- References Cited in the file of this patent UNITED STATES PATENTS 2,456,320 Repke Dec. 14, 1948 2,793,769 Weber May 28, 1957 2,795,346 Farmer June 11, 1957 2,837,230 Herterich June 3, 1958

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