EP0018232A1

EP0018232A1 - Apparatus for inverting a sand mold

Info

Publication number: EP0018232A1
Application number: EP80301293A
Authority: EP
Inventors: Earl W. Powers
Original assignee: DEPENDABLE-FORDATH Inc; Dependable Fordath Inc
Current assignee: DEPENDABLE-FORDATH Inc; Dependable Fordath Inc
Priority date: 1979-04-23
Filing date: 1980-04-22
Publication date: 1980-10-29
Also published as: JPS55144361A

Abstract

Apparatus for and methods of inverting a sand mold wherein the apparatus comprises opposing upper and lower jaws (104 and 106) each having a plurality of rollers (48). The jaws are supported in a vertical frame (108) rotatably mounted on a stand (102). A rotary actuator (110) is provided to rotate the vertical frame about a horizontal axis and thus invert a sand mold clamped between hydraulically actuated arms (192) of the jaw (106). The rotation of the frame (108) and thus the jaws is controlled by means of a counterbalance valve which regulates the rate of delivery of hydraulic fluid from a pressure compensated pump to the rotary actuator (110). The rate of rotation of the jaws can therefore be adjusted so that even when a load is substantially off centre rotation starts and stops gradually preventing fracture of the mold. The apparatus is electrically controlled to enable a continuous sequence of operations to be performed.

Description

The present invention relates to apparatus for inverting sand molds. More particularly it concerns roll over draw and close apparatuses adapted to be incorporated into a multi-station assembly line apparatus for producing a continuous succession of joined cope and drag sand mold portions for foundry use.
Multi-station sand mold making apparatuses have been known heretofore. It is desirable that such apparatuses be capable of simultaneously producing the cope (upper half) and drag (lower half) portions of a composite sand mold, the two portions being complete and assembled upon each other and ready for the molten metal pouring operation at the time they leave the apparatus. Typically, a plurality of mold boxes, each containing a mold pattern, are circulated around a closed pathway through a succession of stations at which different mold making operations are performed. Each mold box forms either a cope half or a drag half of a completed sand mold.
At one station a predetermined amount of sand containing a binder and a catalyst is poured into an open-top mold box containing a pattern. The mold box is simultaneously vibrated to eliminate voids and produce some compaction of the sand. The amount of sand which is poured into the mold box is sufficient to form a mound which extends above the upper edges of the box.
At a succeeding strike off station the sand is distributed, levelled, and slightly compacted before the binder hardens. This may be done by hand tamping, by using a ramming apparatus, by using revolving rollers, or by some other known technique.
At the next station a bottom board is either manually placed or automatically fed onto the top of the mold box. Thereafter at the same station or at a succeeding station the mold box and bottom board are clamped together from above and below and inverted. The mold box is then vibrated and the now hardened cope or drag mold portion is stripped or "drawn" from the mold box and then removed from the bottom board.
Cope and drag halves produced in this manner may be joined or "closed" manually to form a composite sand mold which is then sent to a molten metal pouring station. However, due to their relatively great weight mechanical lifting devices often need to be employed. An efficient automated system capable of realizing the potential mold production rates made possible by the no-bake sand/resin binder process requires the ultilization of automatic, relatively rapid draw and close apparatuses. Such apparatuses must operate with precision and must be designed to minimize the scrap rate attributable to mold breakage.
According to the present invention, there is provided apparatus for inverting a sand mold comprising: means for receiving the mold and supporting the same for rotational movement; means for rotating the receiving and supporting means to invert the mold during a predetermined time interval; and means for regulating the rate of the rotation to substantially minimize the forces exerted on the internal structure of the mold and prevent fracturing of the same.
The main advantages provided by the present invention are that the sand mould inverting apparatus, for example an in-line roll over draw or close apparatus, receives the mold from and discharges it onto the same conveying line into which the apparatus is installed and the rotating means which control the rotation of the sand mould cause the mold to be smoothly inverted thus minimizing the frequency of breakages. Also, automatic control means enable the rapid production of a continous succession of joined cope and drag sand mold halves ready for a molten metal pouring operation. Moreover, the inverting apparatus is capable of accommodating a wide range of loads.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which :

FIGURE 1 is a simplified plan view of a multi-station assembly line sand mold making apparatus which utilizes one embodiment of the roll over draw apparatus of the present invention at one station and one embodiment of the roll over close apparatus of the present invention at a succeeding station;
FIGURE 2A is a functional diagram illustrating the manner in which the multi-station apparatus of Figure 1 forms a cope portion of a composite sand mold;
FIGURE 2B is a functional diagram illustrating the manner in which the multi-station apparatus of Figure 1 joins a cope portion and a drag portion to form a composite sand mold;
FIGURE 3 is a perspective view of one embodiment of the roll over draw apparatus of the present invention showing a portion of a main conveying line in phantom lines;
FIGURE 4 is an enlarged front elevational view of the roll over draw apparatus of Figure 3 taken along line 4-4 of Figure 3 with hidden portions shown in phantom lines;
FIGURE 5 is an enlarged side elevational view of the roll over draw apparatus of Figure 4 taken along line 5-5 of Figure 4 with hidden portions shown in phantom lines;
FIGURE 6 is an enlarged fragmentary horizontal sectional view of the roll over draw apparatus of Figure 5 taken along line 6-6 of Figure 5;
FIGURE 7 is a schematic diagram of the pneumatic circuit forming a part of the control circuit of the roll over draw apparatus shown in Figures 3-6;
FIGURE 8 is a schematic diagram of the hydraulic circuit forming a part of the respective control circuits of the embodiments of the roll over draw and close apparatuses described herein;
FIGURE 9 is a schematic diagram of the electric circuit forming a part of the control circuit of the roll over draw apparatus shown in Figures 3_"6;
FIGURE 10 is a fragmentary elevational view showing structural details of a portion of the lower jaw of one embodiment of the roll over close apparatus of the present invention, a sand mold and a bottom board being supported on the lower jaw;
FIGURE 11 is an enlarged view of Figure 10 taken along line 11-11 of Figure 10;
FIGURE 12 is a schematic diagram of the pneumatic circuit forming a part of the control circuit of the embodiment of the roll over close apparatus described herein; and
FIGURE 13 is a schematic diagram of the electric circuit forming a part of the control circuit of the embodiment of the roll over close apparatus described herein.

1. Overall Description of a Multi-Station Sand Mold Making Apparatus Incoroporating the Roll Over Draw and Close Apparatuses

Referring to Figures 1, 2A and 2B, a mixer apparatus 10, a strike off apparatus 12,- a bottom board feeder apparatus 14, a roll over draw apparatus 16 constructed in accordance with the present invention, and a roll over close apparatus 18 constructed in accordance with the present invention are stationed successively along a pathway or main conveying line 20 of intermittently powered conveying rollers. A plurality of open-top mold boxes of varying heights such as 22, being alternately cope and drag boxes, travel in a clockwise direction around the main conveying line 20. Each mold box contains a pattern such as indicated at 24.
The formation of a cope portion of a mold will first be described. When the mold box 22 reaches the corner 26 of the main conveying line 20 a pneumatic cylinder 28 pushes the mold box beneath the discharge end 30 of the mixer 10. A predetermined amount of sand 32 containing a resin binder and a catalyst is automatically poured into the mold box (Figure 2A, step A). The mold box is simultaneously vibrated to eliminate voids and produce some compaction of the sand. The amount of sand which is poured into the mold box is sufficient to form a mound which extends above the upper edges of the box. One suitable mixer is disclosed in co-pending U.S. Patent Application Serial No. 22,609 filed March 21, 1979.
Each mold box may have a metal strip affixed to its underside. The location of the strip serves as an indicator of the volume of the mold box. When the mold box is underneath the discharge end of the mixer apparatus the location of the strip is sensed by a proximity sensor in order to determine the quantity of sand which is to be poured into the mold box.
Next, the mold box 22 containing the mound of sand 32 is conveyed to a corner 34 of the main conveying line 20 where it momentarily stops. After a time delay, the mold box 22 leaves the corner 34 and travels toward the strike off apparatus 12. An infrared proximity sensor 36, mounted on an assembly supporting a pair of rollers 38, is activated. At this point the rollers 38 are at their upper limit of movement and an elevating mechanism lowers the roller assembly, and the sensor 36 until its horizontal scanning beam is intercepted by the mound of sand 32 in the mold box. This is done before the box reaches the rollers. The rollers 38 stop at a height so that they ride over the sand in the mold box as the box passes thereunder (Figure 2A, step B). The sand is levelled and slightly compacted by the rollers. After the mold box has passed under the rollers they are raised to their original positions and the strike off apparatus awaits the next succeeding box. The details of the strike off apparatus 12 are disclosed in co-pending U.S. Patent Application Serial No. 967,110 filed December 6, 1978.
Next, the mold box 22 is conveyed along the pathway 20 to the bottom board feeder apparatus 14 where it momentarily stops in position for receiving a bottom board such as 40. An infrared proximity sensor 42 mounted on the board elevating mechanism of the bottom board feeder apparatus senses the presence of the mold box 22. The bottom board 40 has already been conveyed along a return conveying line 44 of intermittently powered conveying onto the bottom board feeder apparatus 14. The elevating mechanism of the bottom board feeder apparatus raises the bottom board 40 until the horizontal scanning beam of the sensor 42 is above the upper surface of the mold box 22. Thereafter, a shuttle mechanism 46 of the bottom board feeder apparatus feeds the bottom board laterally onto the top of the mold box (Figure 2A, step C). The details of the bottom board feeder apparatus 14 are disclosed in co-pending U.S. Patent Application Serial No. 966,254 filed December 4, 1978.
Next, the mold box 22, now covered with a bottom board 40, is conveyed along the main conveying line 20 to the roll over draw apparatus 16. The mold box 22 and the bottom board 40 are clamped between jaws of rollers 48 and arms 50 grip the bottom flange of the mold box (Figure 2A, step D). The mold box 22 and the bottom board 40 are inverted, i.e. rolled over 180 degrees (Figure 2A, step E). The now hardened cope portion 52 of the sand mold is lowered out of the mold box 22 with the aid of vibrating mechanisms by unclamping the jaws of rollers 48 (Figure 2A, step F). The cope portion 52 and the bottom board 40 upon which it now rests are conveyed out of the roll over draw apparatus 16 and along the main conveying line 20 to the roll over close apparatus 18.
After the cope portion 52 and the bottom board 40 are conveyed out of the roll over draw apparatus 16, the mold box 22 is clamped between the rollers 48 and re-inverted, i.e. rolled over 180 degrees. The mold box 22 is then conveyed out of the roll over draw apparatus 16 to a box return mechanism 54 positioned between the roll over draw apparatus 16 and the roll over close apparatus 18. The mechanism 54 ejects the mold box 22 laterally and the mold box is returned along the main conveying line 20 to its original starting place.
Arms 56 of the roll over close apparatus 18 clamp the cope portion 52 and raise it off the bottom board 40 (Figure 2A, steps G and H). The bottom board 40 is conveyed out of the roll over close apparatus 18 to a position adjacent a pneumatic cylinder 58 which pushes the board laterally to a position adjacent a pneumatic cylinder 60. After the bottom board 40 is conveyed out of the roll over close apparatus 18, the cope portion 52 is inverted, i.e. rolled over 180 degrees (Figure 2A, step I). The cope portion 52 is maintained in an elevated position above the level of the main conveying line 20 awaiting the arrival of a drag portion.
In a similar fashion, the multi-station sand mold making apparatus shown in Figure 1 produces the drag portion 62 of the composite sand mold (Figure 2B, step J), the steps being the same as steps A through F (Figure 2A). The drag portion 62 and the bottom board 64 upon which it rests are then conveyed into the roll over close apparatus 1.8 directly underneath the waiting cope portion 52 (Figure 2B, step K). The cope and drag portions 52 and 62 are joined (Figure 2B, step L) and they are conveyed, resting on top of the bottom board 64, out of the roll over close apparatus 18 to a position adjacent the pneumatic cylinder 58. The pneumatic cylinder 58 pushes the bottom board 64, and the cope and drag portions 52 and 62 carried thereby, laterally to a position adjacent the pneumatic cylinder 60. The bottom board 64 pushes the bottom board 40 onto the return conveying line 44 and the powered conveying rollers thereof convey the bottom board 40 back to the bottom board feeder apparatus 14. An infrared proximity sensor 66 senses the presence of the completed sand mold and actuates the pneumatic cylinder 60 which pushes the joined cope and drag portions 52 and 62 . down a chute 68 which leads to a metal pouring station (Figure 2B, step M). The next succeeding bottom board that is pushed laterally by the pneumatic cylinder 58 will push the bottom board 64 laterally onto the return conveying line 44 which will return it to the bottom board feeder apparatus 14.
In actual operation a plurality of mold boxes and bottom boards are simultaneously circulated about the apparatus shown in Figure 1. A continuous succession of composite sand molds assembled and ready for the molten metal pouring operation is produced.

2. Description of the Mechanical Structure of the Roll Over Draw Apparatus

Referring to Figure 3, the roll over draw apparatus 16 includes a base or stand l02 made of steel box beams which are welded together to form a rigid supporting structure. Upper and lower jaws l04 and 106 each having a plurality of rollers 48 are supported in opposing relationship by a generally rectangular vertical frame 108 rotatably mounted on the stand 102. A hydraulic engine in the form of a rotary actuator 110 rotates the vertical frame 108 and the jaws 104 and 106 about a horizontal axis as indicated by the arrows.
The roll over draw apparatus 16 is designed to be inserted into a gap in the main conveying line 20 so that the rollers 48 of either its upper jaw 104 or its lower jaw 106 will form a continuation of the main conveying line. The axis of rotation of the vertical frame 108 and of the upper and lower jaws 104 and 106 extends transverse to the main conveying line 20. The term "transverse" as used herein refers to the direction perpendicular to the line of travel of the mold boxes down the main conveying line 20. The term "longitudinal" refers to the direction of extension of the main conveying line. The forward end of the roll over draw apparatus is that portion viewed along the line 4-4 of Figure 3. The rearward end of the apparatus is that portion which includes the stand 102.
A sand mold which is transported toward the roll over draw apparatus 16 by powered conveying rollers of the main conveying line 20 will be received on the rollers 48 of the lower jaw 106 of the apparatus. After being inverted by 180 degree rotation of the vertical frame 108 the mold will be discharged from the rollers 48 of the upper jaw 104 back onto the main conveying line 20. The roll over draw apparatus in thus an "in-line" apparatus in the sense that it receives from and discharges onto the same conveying line into which it is installed. It is thus more compact than other roll over draw apparatuses which rotate in a plane transverse to the main conveying line.
The stand 102 has a pair of legs 112 (Figures 3, 4 and 5) which rest on the floor and extend transversely underneath the main conveying line 20. The legs 112 are connected by a cross beam 114 (Figure 4). A pair of vertically extending beams 116 (Figure 3) are welded at their lower ends to the cross beam 114 and are supported from the side by inclined beams 118 (Figure 4). Front and back steel mounting plates 120 and 122 (Figure 3) are welded to opposite sides of the upper portions of the vertical beams 116. A pair of rearwardly extending inclined beams 116. A pair of rearwardly extending inclined beams 124 are welded at their upper ends to the back mounting plate 122 and at their lower ends to a pair of rearwardly extending horizontal legs 126 welded to the cross beam 114 of the stand 102. Triangular braces such as 128 are welded to adjoining beams in various locations to further strengthen the stand 102.
By constructing the stand 102 in the above described manner a rigid supporting structure is provided to support the jaws 104 and 106 and the frame 108 for rotational movement. The stand 102 must be capable of supporting loads of several thousand pounds. The legs 112 must be spaced far enough apart to prevent the stand 102 from tipping about the axis of rotation of the jaws when the rotational load is substantially off centre and unbalanced. In addition, the legs 112 and 126 must extend a sufficient distance in a transverse direction. Otherwise, the stand 102 may tip forwardly or backwardly when relatively heavy sand molds are conveyed onto the lower jaw 106 and thereafter off of the upper jaw 104.
Referring to Figure 4, the vertical frame 108 which supports the upper and lower jaws 104 and 106 includes a pair of vertically extending, inwardly facing channel beams 130. These beams are welded at their upper and lower ends to a pair of horizontally extending outwardly facing channel beams 132. Referring to Figure 3, a relatively large, vertically extending bearing plate 134 is welded to the rearward flanges 136 of the vertical channel beams 130. A large ring-type bearing 138 is bolted to the bearing plate 134 and to the front mounting plate 120 of the stand 102. It supports the vertical frame 108 and the upper and lower jaws 104 and 106 for rotational movement about a horizontal axis X (Figure 4) which extends transversely to the main conveying line 20. One suitable ring-type bearing is sold under the registered trademark ROTEK.
Referring still to Figure 3, the hydraulic rotary actuator 110 is rigidly secured to the back mounting plate 122 of the stand 102. One suitable hydraulic rotary actuator is manufactured by FLO-TORK, INC. Orville, Ohio, 44667 and is sold under the registered trademark FLO-TORK. It is manufactured under U.S. Patent Nos. 2,844,127; 2,844,128; and 3,246,581. This actuator has two pairs of opposing hydraulic cylinders. They move upper and lower rack gears which engage a pinion gear on its output shaft to rotate the same. This actuator is available with a wide range of operating pressures and torques. It is a positive displacement hydraulic engine capable of precise positioning of substantial loads. The cylinder heads serve as positive internal stops and may be provided with cushions to absorb some of the shock at each end of the rotation when the pistons contact the cylinder heads.
Referring still to Figure 3, the output shaft of the rotary actuator 110 extends through a hole in the back mounting plate 122 and is coupled to the rearward end of a drive shaft (not visible in the drawings). The drive shaft extends through a coupling 140 and through the bearing 138. Its forward end is rigidly secured to the bearing plate 134. Not shown in the drawings are the various hydraulic hoses, pneumatic hoses, and electrical cables which supply power to the various actuating components mounted on the jaws. Hydraulic fluid, pressurized air, and electrical current must be supplied to these "on board" actuating components. Preferably rotatable connections are made through or near the centre of rotation of the vertical fram 108 via the coupling 140. One suitable coupling includes manifold and slip-ring assemblies.
Referring to Figure 4, the hydraulic rotary actuator 110 shown in phantom lines rotates the vertical fram 108 180 degrees in a counter-clockwise direction indicated by the arrow to invert a mold contained within a mold box. In this inverted position the lower jaw 106 will be at the top of the apparatus and the upper jaw 104 will be at the bottom thereof. After the sand mold is drawn from the mold box and discharged from the jaw 104, the vertical frame 108 will be re-inverted, i.e. rotated back to its original position in a clockwise direction. Thus, the vertical frame 108 and the upper and lower jaws 104 and 106 do not rotate through a complete revolution.
The base or lower portion of the stand 102 has a stop assembly 150 welded thereto. It includes a rubber air bag 152 which is filled with air ambient- pressure. When the vertical frame 108 and the jaws are re-inverted a resilient pad 154 overlying the lower portion of one of the vertical channel beams 130 of the frame 108 will strike the air bag 152. The air bag 152 has an orifice through which air is expelled when it is compressed.
The air bag 152 serves as an auxiliary cushion to prevent rotation of the vertical frame 108 past its _" upright starting position. As will be described later on in greater detail, the roll over draw apparatus 16 includes hydraulic circuit elements which cause the vertical frame 108 and the upper and lower jaws 104 and 106 to start and stop their rotation smoothly. When a sand mold inside a mold box is being inverted the gradual starting and stopping of rotational movement prevents fracturing of the mold. While the hardened sand molds have considerable compressive strength, their flexure strength is relatively small. These sand molds will crack or fracture as a result of their own inertia if they are accelerated or stopped too quickly. A sand mold which has been fractured or cracked is unsuitable for the molten metal pouring operation since it will produce unacceptable castings.
Referring still to Figure 4, the lower jaw 106 is rigidly secured to the vertical frame 108. The upper jaw 104 is supported on the frame 108 for vertical movement toward and away from the lower jaw 106. After a sand mold has been conveyed onto the rollers 48 of the lower jaw 106, the upper jaw will automatically be lowered so that the mold is clamped between the rollers 48 of the upper and lower jaws. A lowered position of the upper jaw 104 is shown in phantom lines in Figure 4.
Referring to Figure 3, each jaw includes a generally square horizontal frame made of a pair of longitudinally extending beams 156 which are welded to the opposite ends of a pair of transversely extending cross pieces 158. Triangular braces 159 are welded at the junctions between the beams 156 and the cross pieces 158 to further strengthen the square frames. The cross pieces 158 and the rearward beam 156 of the lower jaw 106 are rigidly welded to the lower portions of the vertical channel beams 130 of the vertical frame 108 (See Figures 4 and 5).
The upper jaw 104 is mounted to a carriage generally designated 160 (Figure 4) which is adapted to travel upwardly and downwardly between the vertical channel beams 130 of the vertical frame 108 for raising and lowering the upper jaw. Referring to Figure 4, the carriage 160 includes a vertical panel 162. The side edges of the panel 162 are welded to transversely extending brackets 163. As shown in Figure 6, the forward edges of the brackets 163 are welded to the cross pieces 158 of the upper jaw 104. The brackets 163 have an assembly of wheels and rollers which are adapted to travel in the channels of the channel beams 130.
Referring to Figure 6, each of the vertical channel beams 130 is provided with an inwardly projecting rail 164 which extends intermediate the channel along the entire length thereof. Secured to the inner bottom surface of the channel beam 130 on opposite sides of the rail 164 are a pair of wear strips 166.
Referring still to Figure 6, mounted to each bracket 163 on either side of the carriage 160 are a plurality of pairs of wheels 168 and a plurality of pairs of rollers 170. The axis of rotation of the wheels 168 is perpendicular to that of the rollers 170. As shown in Figure 5, each of the brackets 163 of the carriage 160 has three vertically spaced pairs of wheels 168 and four vertically spaced pairs of rollers 170. As best shown in Figure 6, the wheels 168 engage and roll along the wear strips 166 mounted in the channel beams 130. The rollers 170 engage and roll along opposite sides of the rail 164 secured to the channel beams 130. The wheels 168 are rotatably supported by U-shaped housings 172 secured to the brackets 163. The rollers 170 are each rotatably journalled on pins (not visible in the drawings) eccentrically positioned on the heads of bolts 174 secured through corresponding holes in the brackets 163.
In this manner, the upper jaw 104 is movably supported on the vertical frame 108 and may be acted upon by relatively great forces without inhibiting the ability of the upper jaw to travel upwardly and downwardly along the vertical frame. Preferably the rail 164 and the wear strips 166 are made of case hardened steel and are secured at their ends to the channel beams 130 by bolt assemblies so that they can be readily replaced when worn. Preferably the wheels 168 and the rollers 170 are also made of case hardened steel so that they can resist wear. The wheels and rollers are mounted so that they can be readily replaced when worn. By rotating the eccentric pin/bolts 174 the clearance between the rollers 170 and the rail 164 can be adjusted.
Referring to Figure 4, the lower periphery of the panel 162 of the carriage 160 has a V-shaped cut out portion 176. The piston rod 178 of a vertically extending hydraulic cylinder 180 (see Figures 4 and 5) is connected to the lower periphery of the panel 162 intermediate its width. The base of the hydraulic cylinder 180 is secured to the lower channel beam 132 of the vertical frame 108. The hydraulic cylinder 180 can be actuated to raise and lower the upper jaw 104 as illustrated in phantom lines in Figures 4 and 5.
As previously noted, the upper and lower jaws 104 and 106 support a plurality of transversely extending powered rollers 48. As shown in Figure 3, the forward ends of the rollers 48 are rotatably journalled in longitudinally extending angle beams 182 secured to the inwardly facing surfaces of the beams 156 of the square frames of the upper and lower jaws.
The rearward ends of the rollers 48 are rotatably journalled inside rectangular housings 184 secured to the inwardly facing surfaces of the rearward beams 156 of the r upper and lower jaws. See also Figure 5. The rollers 48 of the upper and lower jaws are simultaneously rotated in the same direction by a drive mechanism not fully illustrated in the drawings. The rearward ends of the rollers 48 are each provided with a pair of sprockets and a series of endless chains are trained around adjacent sprockets so that the rollers 48 can be simultaneously driven by rotating one of the intermediate rollers.
As shown in Figure 5, hydraulic motors 186 and 188 shown in phantom lines are mounted to the upper and lower jaws, respectively, and are each drivingly coupled with an intermediate rollers 48. Suitable driven roller assemblies are manufactured by American Manufacturing Company, Inc., 2119 Pacific Avenue, P 0 Box 1237, Tacoma, Washington, 98401. They have variable speed hydraulically driven rollers which are designed to provide maximum torque throughout their speed range.
The lower jaw 106 is provided with means for gripping the bottom flange of a mold box. This permits a mold box to be held rigidly in position on the lower jaw 106 so that the same can be inverted and re-inverted through rotation of the vertical frame 108. Typically a mold box consists of four side walls and a bottom wall which extends beyond each of the side edges to provide a flange which can be readily gripped by a mechanical arm.
Referring to Figures 4 and 5, the lower jaw 106 has forward and rearward spaced apart pairs of vertical arms 190 and 192 which are adapted to grip the flange of a mold box. As best illustrated in Figure 4, the vertical arms 190 and 192 extend between adjacent rollers 48 of the lower jaw 106 and they are spaced relatively closely to the midpoint of the jaw. Referring to Figure 5, each vertical arm 190, 192 extends slightly above the upper peripheries of the rollers 48 and has a detent 194 for receiving the flange of the mold box. The lower ends of the rearward vertical arms 192 are welded to a longitundi- nally extending support member 196 whose opposite ends are welded to the cross pieces 158. The forward vertical arms 190 are mounted for reciprocal movement toward and away from the rearward vertical arms 192 so that mold boxes of different sizes can be accommodated.
The lower ends of the forward vertical arms 190 (Figure 5) are welded to the top of a dolly 198. The dolly has side wheels 200 which travel along the lower flanges of a pair of transversely extending, inwardly facing channel beams 202. These beams are welded to the inner surfaces of the cross pieces 158 of the lower jaw 106.
The dolly 198 carrying the vertical arms 190 is moved toward and away from the rearward vertical arms 192 by the piston rod 204 (Figure 5) of a horizontally extending pneumatic cylinder 206. The base of the cylinder 206 is secured to a support member 208 welded at its opposite ends to the cross pieces 158 of the lower jaw. The vertical arms 190 can be rapidly moved into gripping relationship with the flange of a mold box resting on the lower jaw 106 by actuation of the pneumatic cylinder 206. Thereafter, the mold box containing the sand mold is inverted. When the upper jaw 104 (now underneath the mold box) is lowered to draw the sand mold out of the mold box, the mold box will remain suspended from the lower jaw 106 as a result of the gripping action of the vertical arms 190 and 192.
Next, the sand mold, resting on the bottom board, is conveyed off the rollers of the lower jaw 104 onto the main conveying line 20 toward the roll over close apparatus 18. Thereafter, the vertical frame 108 and the jaws 104 and 106 are re-inverted. The pneumatic cylinder 206 is then actuated to cause the piston rod 204 thereof to extend so that the flange of the mold box will no longer be held in gripping relationship between the forward and rearward vertical arms 190 and 192. When the rollers 48 of the lower jaw 106 are thereafter rotated the mold box will be conveyed back onto the main conveying line 20.
The lower jaw 106 further includes means for ` imparting vibratory movement to the mold box to facilitate the drawing of the sand mold therefrom. Referring to Figures 3, 4 and 5, a pair of vertical, inverted U-shaped vibrating frames 210 extend vertically between pairs of the rollers 48. The vibrating frame 210 are welded at their lower ends to a horizontal plate 211 which is in turn supported at its four corners by four rubber air bags 212. The air bags are mounted on a pair of spaced apart longitudinally extending channel beams 214 which are welded at their opposite ends to the cross pieces 158 of the lower jaw 106. Bolted to the underside of the plate 211 is a hammer-style, linear air driven vibrator 216 (Figure 5).
When the mold box is initially conveyed onto the lower jaw 106, the air bags 212 are in their deflated condition. The upper surfaces of the vibrating frames 210 are below the upper peripheries of the rollers 48 and the vibrating frames 210 are not in contact with the bottom wall of the mold box. T_he vibrator 216 is not in operation at this time.
After the vertical frame 108 and the jaws 104 and 106 have been rotated to invert the mold box and the sand mold contained therein, the air bags 212 are inflated to move the frames 210 into engagement with the bottom wall of the mold box. At the same time the vibrator 216 is actuated so that rapid vibratory movement is imparted to the mold box. When the jaw 104 is lowered the vibratory motion facilitates the drawing of the sand mold out of the mold box. It eliminates any adhesion between the hardened sand mold and the walls of the mold box. It also reduces the friction of the sliding engagement between the sand mold and the walls of the mold box.
After the sand mold has been completely removed from the mold box, the vibrator 216 is de-energized, and the air bags 212 are deflated. When the vertical frame 108 and the jaws 104 and 106 are re-inverted to bring the mold box back to its original position, the vibrating frames 210 will no longer be in engagement with the bottom wall of the mold box so that the same can be freely ejected from the lower jaw 106.

3. The Pneumatic Circuit of the Roll Over Draw Apparatus

Referring to Figure 7, pressurized air is supplied through the rotary coupling 140 to a manifold 218 mounted on the lower jaw 106. The pneumatic cylinder 206, the air bags 212, and the vibrator 216, are each operatively coupled through hoses and through solenoid actuated valves to the manifold 118 for receiving pressurized air from the same upon demand.
The pneumatic cylinder 206 is connected to the manifold 218 through a spring biased, solenoid actuated flow reversing valve 220. When the valve 220 is in the position shown, pressurized air will flow into the pneumatic cylinder 206 to cause its piston rod 204 to extend. This maintains the forward vertical flange gripping arms 190 in their forwardmost positions shown in sold lines in Figure 5. Referring again to Figure 7, when the valve 220 is shifted to its flow reversing position the piston rod 204 of the pneumatic cylinder 206 will retract. This will cause the vertical flange gripping arms 190 to move in the direction indicated by the arrow in Figure 5. Continued pressurization of the pneumatic cylinder 206 when the valve 220 is in this mode will cause the vertical arms 190 to be forced against the flange of the mold box resting on the rollers 48 of the lower jaw 106. Thus, the mold box will be clamped between the arms 190 and 192.
The air bags 212 are operatively connected through hoses and through a solenoid actuated on-off valve 222 to the manifold 218. When the valve 222 is de-energized, pressurized air will not flow into the air bags 212 and the vibrating frames 210 will remain in their lowered positions. When the valve 222 is energized, it will shift to its on position causing pressurized air to be delivered to the air bags 212. This will inflate the air bags and move the vibrating frames 210 so that they will engage the bottom wall of the mold box.
The vibrator 216 is operatively connected to the manifold 218 through a solenoid actuated on-off valve 224. The valve 224 is shown in its de-energized off position in which pressurized air is not delivered to the vibrator 216. When the valve 224 is energized, it will shift to its on position and pressurized air will be delivered to the vibrator 216 causing the same to impart vibratory motion to the mold box gripped between the vertical arms 190 and 192.

4. The Hydraulic Circuit for the Roll Over Draw and Close Apparatuses

The roll over draw apparatus 16 of the present invention includes means for controlling the rate of rotation of the upper and lower jaws and the vertical frame which supports the same. Mold boxes of various sizes are conveyed onto the lower jaw 106. For example, one mold box may measure forty inches by fifty inches by seventeen inches, while the mold box following the same may measure ten inches by ten inches by twelve inches. The combined weight of a mold box and the hardened sand mold contained therein may range from less than one hundred pounds to several thousand pounds. Referring to Figure 4, it can be seen that the centre of mass of a mold box and sand mold clamped between the upper and lower jaws will in most cases be offset from the axis X of rotation of the vertical frame 108 and the upper and lower jaws 104 and 106. Thus frequently the rotational load of the roll over draw apparatus is subtantially off centre and unbalanced. One example of this would be when a mold box is clamped between the upper and lower jaws which has a height of vertical dimension such that the upper jaw 104 must be lowered to the position shown on phantom lines in Figure 4 in order for the mold box to be clamped between the upper and lower jaws.
In most instances, the centre of mass of the rotational load of the roll over draw apparatus will be below the axis of rotation X. Under these circumstances the rotational forces required to rotate the vertical frame lOR, the upper and lower jaws 104 and 106, the mold box, and the hardened sand mold will gradually increase throughout the first ninety degrees of counter-clockwise rotation and thereafter will gradually decrease. If a constant rotational force were to be applied to invert the sand mold and mold box, the rate of rotation would increase and the vertical frame 108 would overshoot the 180 degree position unless it engaged some kind of a stop. If there were a stop to prevent rotation past the 180 degree position under these circumstances the rapid deceleration would result in relatively great forces being exerted upon the internal structure of the sand mold which would greatly increase the probably of fracturing of the mold.
It should be noted here that the air bag 152 only operates when the vertical frame 108 is re-inverted, and even then it is only an auxiliary cushion which does not perform a significant amount of deceleration. It should also be noted at this point that the outer corners of the vertical frame 108 are angled or bevelled so that they will clear the air bag 152 on the stop 150 during the upswing or inversion of the frame 108. Likewise, the outer corners of the upper and lower jaws 104 and 106 are bevelled or angled so that they will clear the adjacent portions of the main conveying line 20.
After the sand mold has been drawn from the mold box and ejected from the roll over draw apparatus 16, the mold box must be re-inverted. Without the rotation controlling means of the present invention as soon as the vertical frame began to swing clockwise the off centre weight of the mold box would combine with the forces imparted by the rotary actuator. This would cause the vertical frame and jaws to rotate faster and faster as they approached their initial starting positions. Therefore, some means must be * incorporated into the apparatus to prevent the re-inversion or swinging down from taking place too rapidly. Without some adequate mechanism for gradually bringing the vertical frame and the jaws to rest again in their initial positions, the mold box may be jarred loose or damaged. In any case, damage to the machine itself may occur if the roll up or roll down rotational movement does not start and stop smoothly.
The problem of inverting heavy sand molds may also be viewed as a problem involving inertia. If the rotating jaws come to a stop too quickly, then the inertia of the relatively heavy sand mold supported therebetween will exert forces on the internal structure of the mold which can result in fracturing of the same. In theory at least, the jaws could be rotated very slowly and the likelihood of fracturing of the sand mold or of any damage occurring to the machine itself, or of the jaws rotating past their desired stop points, would be virtually eliminated. However, as a practical matter, in order for the roll over machines to function in a multi-station assembly line apparatus the inversion and re-inversion must be performed within a relatively short time interval, e.g. ten seconds. Therefore, the objective is to control the rate of rotation so as to substantially minimize the forces exerted on the internal structure of a mold for a given time interval in which the inversion must take place. The optimum way in which to achieve this would be to rotate the jaws so that they accelerate at a constant positive rate through their first ninety degrees of revolution and thereafter decelerate through the remaining ninety degrees at a constant rate which is the negative of the initial acceleration. As previously noted, in most instances the centre of mass of the sand mold will be below the axis X of rotation of the vertical frame and the upper and lower jaws. Therefore, the sand mold will travel through an arcuate path. It would be difficult to maintain an exact constant acceleration for the first ninety degrees of travel and an exact constant deceleration for the last ninety degrees of travel.
The present invention includes rotating means and means for controlling the rotating means which will cause the mold to move along an arcuate path so that its velocity increases at a substantially uniform rate along a first portion of the path and decreases at a substantially uniform rate along the remainder of the path. For a given time interval in which the inversion is to take place the forces that are exerted on the internal structure of the sand mold are substantially minimized.
Both the roll over draw and close apparatuses of the present invention utilize the hydraulic circuit shown in Figure 8. A hydraulic pump 230 driven by an electric motor 232 pumps hydraulic fluid from a source or reservoir 234. The fluid is pumped through an infeed line 235 and through valves 236 and 238 to the hydraulic rotary actuator 110. Hydraulic fluid can be supplied through a solenoid actuated on-off valve 240 to the hydraulic motor 188 which rotates the rollers 48 of the lower jaw 106. Likewise, hydraulic fluid can be supplied through a solenoid actuated on-off valve 242 to the hydraulic motor 186 which drives the rollers 48 of the upper jaw 104. Hydraulic fluid can be supplied through solenoid actuated valves 244 and 246 for actuating the hydraulic cylinder 180 to raise or lower the upper jaw 104.
Referring still to Figure 8, the hydraulic pump 230 is a positive displacement, variable flow-type pump. A compensator 248 is associated with the pump 230. It varies the flow or rate of displacement of the pump so that its output pressure is more or less constant. A hydraulic pump suitable for this purpose is known as a variable displacement axial piston pump. It may be readily utilized with a pressure compensating control. One suitable axial piston pump having a pressure compensating control is manufactured by Cessna Corp., Fluid. Plower Division, Hutchinson, Kansas.
The valve 238 controls the delivery of hydraulic fluid to and from the hydraulic rotary actuator 110. It is a commercially available block-type valve known in the hydraulic field as a counterbalance valve. Incorporated in this block-type valve are check valves 250 and 252 and graduated flow, pressure controlled sub-valves 254 and 256. These components are interconnected by conduits as indicated.
The manner in which the hydraulic circuit of Figure 8 controls the rotation of the vertical frame 108 and the upper and lower jaws 104 and 106 so that they will start and stop their rotational movement gradually and smoothly even when the rotational load is substantially off centre and unbalanced will now be described. First described will be the inversion or upswing (first 180 degree counter-clockwise rotation). In a response to a signal hereafter described, the solenoid actuated valve 236 is shifted to its flow reversing position and hydraulic fluid flows through a conduit or hose 258 into the counterbalance valve 238. At this time no weight or force is being exerted on the pistons of the hydraulic rotary actuator 110 which is viewed from the front in Figure 8. The cylinders of the actuator extend horizontally.
Hydraulic fluid can only flow downwardly through the sub-valves 254 and 256 in the direction indicated by the arrows. The amount of hydraulic fluid which can flow downwardly through these sub-valves is varied according to the hydraulic fluid pressure in the criss-cross diagonal conduits 260 and 262.
When the hydraulic fluid from the conduit 258 reaches a junction 265 in the counterbalance valve 238 some of it flows through the diagonal conduit 260 to the sub-valve 254 and the remainder flows upwardly through the check valve 252 and into the cylinders 264 and 266 of the hydraulic rotary actuator 110. Since the frame 108 is vertically oriented at this time, the hydraulic fluid pressure initially required to move the pistons of the cylinders 264 and 266 in order to initiate rotation of the frame 108, the upper and lower jaws 104 and 106, and the mold box and sand mold clamped therebetween is relatively small. The pressure sensed by the sub-valve 254 through the diagonal conduit 260 is therefore relatively low. As a result, the flow controlling orifice of the sub-valve 254 is relatively small or constricted. Hydraulic fluid from the cylinders 268 and 270 of the rotary actuator 110, can flow only very slowly through the sub-valve 254.
As the vertical frame 108 is rotated on its upswing from its initial at-rest position, the work which must be done by the hydraulic rotary actuator 110 increases. During the first ninety degrees of rotation, the pressure on the pistons in the cylinders 264 and 266 will gradually increase causing an increase in pressure at the junction 265. The increase in pressure at the junction 265 will in turn be sensed by the sub-valve 254 through the diagonal conduit 260 which will cause the orifice of the valve 254 to be enlarged. The rate of flow of hydraulic fluid from the cylinders 268 and 270 through the sub-valve 254 will be increased. This hydraulic fluid will flow out of the check valve 252 through a hose or conduit 272, and through the valve 236. From the valve 236 the hydraulic fluid will return to the reservoir 234 through a return line 273.
The compensator 248 will sense the higher of the pressures in the conduits 272 and 258 through check valves 274 and 276. Thus, during the first ninety degrees of counter-clockwise rotation on the upswing, the gradual increase in pressure at the junction 265 and in the conduit 258 will be sensed. The compensator 248 senses the difference between the hydraulic fluid pressure in the infeed line 235 and in the conduit 258 to vary the rate of displacement of the pump 230. Since the hydraulic rotary actuator 110 is a positive displacement device the rate of rotational movement imparted thereby is directly related to the rate at which hydraulic fluid flows into and out of the same.
When the vertical frame 108 moves through its first few degrees of revolution on the upswing almost all the force required to produce this initial motion is utilized in overcoming the static inertia of the mass rotated. As the vertical frame 108 swings through thirty degrees rotation, forty degrees rotation, etc., greater forces are required to impart the rotational movement because the relatively heavy sand mold and mold box are being lifted. As the pressure builds at the junction 265 and in the conduit 258 the sub-valve 254 is opened gradually to permit a greater amount of hydraulic fluid from the cylinders 268 and 270 to flow therethrough. The hydraulic pump 230 pumps just that quantity of oil which will flow through the system and as a result of the opening of the sub-valve 254 it delivers a greater quantity of hydraulic fluid.
As the vertical frame 108 approaches the ninety degree position on the upswing a condition is approached in which the hydraulic rotary actuator 110 will have to perform the greatest amount of work. The pressure on the pistons within the cylinders of the actuator approaches a maximum. The sub-valve 254 is opened widest when the vertical frame is at its ninety degree position. At this time, the pump 230 is delivering the maximum amount of hydraulic fluid which it will deliver during the inversion of the sand mold.
Once the vertical frame 108 swings past the ninety degree position on its upswing, the amount of work required of the actuator 110 will begin to decrease and accordingly the pressure on the pistons within the actuator will begin to decrease. This results in a gradual pressure drop at the junction 265 and in the conduit 258, resulting in a gradual closing of the sub-valve 254. The pump 230 will deliver a gradually decreasing quantity of hydraulic fluid and the vertical frame will gradually and smoothly come to a stop at the 180 degree inverted position. The last fifteen degrees of rotation of the vertical frame is accomplished very slowly. Thus, the hydraulic circuit is load sensitive. The greater the load or the work that must be done by the actuator 110, the faster the vertical frame 108 and the jaws mounted thereon will be rotated.
During the re-inversion or downswing of the vertical frame 108 the sub-valve 256 will restrict the amount of hydraulic fluid which can flow into the return line 273 from the cylinders 264 and 266 of the actuator 110. In order to accomplish the downswing, the hydraulic valve 236 is shifted to its direct flow position in which hydraulic fluid from the main infeed line 235 flows through the valve, through the conduit 272 and into the left side æthe counter-balance valve 238. At a junction 278 adjacent the sub-valve 254 some of the hydraulicftuid will flow into the cylinders 268 and 270 of the actuator 110 and some of the hydraulic fluid will flow through the diagonal conduit 262 to slightly open the sub-valve 256. Since on the downswing the apparatus is no longer carrying the sand mold, but merely the mold box, the off centre load is not as great. However, as the vertical frame 108 begins to rotate the weight of the mold box will urge clockwise rotation of the frame 108. The load on the pistons of the cylinders 268 and 270 will not be very great during the downswing and, thus, the pressure at the junction 278 and in the conduit 272 will remain relatively low. A relatively small quantity of hydraulic fluid will be delivered by the pump 230. The back pressure in the cylinders 264 and 266 will prevent the frame 108 from swinging downwardly too rapidly.
The time interval during which the roll over operation is performed may be controlled by adjusting a flow control valve 280. The speed of rotation of the rollers 48 of the upper and lower jaws may be independently controlled by adjusting flow control valves 282 and 284 respectively. The speed at which the upper jaw 104 is moved toward and away from the lower jaw 106 may be controlled by adjusting a flow control valve 286. A bleed line 287 with a flow control valve may be utilized to bleed off some of the pressure in the line which extends to the compensator 248.
It should be noted that the hydraulic rotary actuator 110, the hydraulic motor 186, the hydraulic motor 188, and the hydraulic cylinder 180 are each energized independently. That is to say, when one of them is receiving hydraulic fluid under pressure none of the others is. The compensator 248 senses the pressure of hydraulic fluid which is delivered to the motor 188, the motor 186, and the cylinder 180 through check valves 288, 290 and 292, respectively. Hydraulic fluid drawn from the reservoir 234 by the pump 230 passes through a filter 294. Hydraulic fluid returned to the reservoir 234 through the return line 273 passes through a filter 296.

5. The Electrical Circuit of the Roll Over Draw Apparatus

The automatic operation of the roll over draw apparatus 16 will now be described in detail in connection with an explanation of its electrical control circuit shown in Figure 9. This electrical circuit operates in conjunction with the pneumatic and hydraulic circuits shown in Figures 7 and 8 and previously described above.
Referring to Figure 9, a circuit breaker switch 300 is manually thrown to connect the circuit to a 230/460 Volt, three phase, sixty Hertz electrical power source. The electric motor 232 which drives the hydraulic fluid pump 230 (Figure 8) is connected through relay contacts 302 and a fuse 304 to the terminals of the breaker switch 300. The primary winding of a step down transformer 306 is connected to the electric power source through a fuse 308. One lead of the second winding of the transformer 306 is connected through a fuse 310 to a hot line 312. Another lead of the secondary winding of the transformer 306 is grounded and is connected to a line 314. The remaining components of the electrical circuit are connected between the lines 312 and 314.
The roll over draw apparatus 14 is started by depressing a momentary switch 316 which causes a master control relay winding 318 to be energized. This in turn, causes relay contacts 320 and 322 associated with the master control relay winding 318 to close.
As soon as the momentary switch 316 is depressed an indicator lamp 324 lights up to indicate that the roll : over draw apparatus is in its "power on" mode. If the lamp 324 does not light up when the momentary switch 316 is depressed, a tester switch 326 can be manually thrown. If the lamp 324 then lights up, the relay winding 318 and tlv relay contacts 322 should be checked for defects.
Next, a momentary switch 328 is manually depressed to energize a relay winding 330. This closes relay contacts 332 and 302 associated with the relay winding. The electric motor 232 is energized and begins to drive the hydraulic pump 230. As soon as the momentary switch 328 is depressed an indicator lamp 334 lights up to indicate that the hydraulic pump unit is on. If the lamp 334 does not light then a manual tester switch 336 can be thrown to determine if the relay 330 or the relay contacts 332 are defective.
The power to the circuit may be shut off by depressing a momentary switch 338 when it is desired to turn off the roll over draw apparatus. In the event of an emergency, a momentary switch 340 can be depressed to shut down the apparatus. When the circuit is energized the hydraulic pump motor can be de-energized by depressing a momentary switch 342.
Referring to Figure 4, a limit switch 344 is mounted between an adjacent pair of the rollers 48 of the lower jaw 106 adjacent the discharge end thereof. The limit switch 344 has a pivoting spring biased actuating arm 346 which normally extends above the upper peripheries of the rollers 48. The limit switch 344 includes two ganged switches 344a and 344b (Figure 9). The switch 344a is normally closed and the switch 344b is normally open. When a mold box is conveyed onto the lower jaw 106 the bottom wall thereof will depress the actuating arm 346 of the switch 344, opening switch 344a and closing switch 344_b.
Referring still to Figure 9, before a mold box is conveyed onto the lower jaw 106 the switch 344a is closed. Solenoids 348 and 350 protected by fuses 352 and 354, respectively, are in an energized state. Referring to Figure 8, when the solenoid 348 is energized the valve 240 is shifted so that hydraulic fluid flows into the hydraulic motor 188 to rotate the rollers 48 of the lower jaw 106. Referring to Figure 7, when the solenoid 350 is energized, the valve 220 is shifted so that the pneumatic cylinder 206 holds the forward vertical flange gripping arms 190 in the outer most position shown in solid lines in Figure 5.
Thus, when a mold box containing a hardened sand mold approaches the roll over draw apparatus 16 on the main conveying line 20 the rollers 48 of the lower jaw 106 are rotating. In addition, the forward vertical flange gripping arms 190 are in their forwardmost positions (adjacent the front edge of the lower jaw). When the mold box reaches the lower jaw 106 the powered conveying rollers 48 thereof carry the mold box onto the lower jaw until the bottom wall of the mold box trips the actuating arm 346 of the limit switch 344..As soon as this occurs, the limit switch 344a is opened (Figure 9) de-energizing the solenoids 348 and 350. This in turn causes the rollers 48 of the lower jaw to stop rotating. It also causes the forward vertical arms 190 to move inwardly so that the flange of the mold box is gripped between the arms 190 and 192. The limit switch 344 is positioned so that the rollers 48 will stop rotating when the mold box is roughly centred on the lower jaw 106.
At the same time the mold box depresses the actuating arm 346, the switch 344b is closed. This energizes a solenoid 358 protected by a fuse 360, and a relay winding 362. The energization of the relay winding 362 closes relay contacts 364 which energizes a solenoid 366 protected by a fuse 368. The energization of the solenoids 358 and 366 shifts the hydraulic valves 246 and 244, respectively, so that hydraulic fluid flows into the hydraulic cylinder 180 and causes the upper jaw 104 to be lowered.
Referring to Figure 4, a limit switch 370 is mounted between a pair of adjacent rollers 48 of the upper jaw 104. The limit switch 370 has a pivoting actuating arm 372 which is depressed by the bottom board resting on top of the mold box. The switch 370 is positioned so that its actuating arm 372 will be depressed when the upper jaw 104 has descended far enough so that the mold box and bottom board are firmly clamped between the upper and lower jaws. Referring again to Figure 9, the limit switch 370 includes a pair of ganged switches 370a and 370b which are normally closed and open, respectively. When the actuating arm 372 is depressed (after the mold box and bottom board have been clamped between the upper and lower jaws) the switch 370a will open and switch 370b will close. The opening of the switch 370a de-energizes the solenoids 358 and 366 and causes the upper jaw 104 to stop descending.
The closing of the switch 370b will energize a solenoid 374 protected by a fuse 376. The energization of the solenoid 374 shifts the hydraulic valve 236 (Figure 8) so that hydraulic fluid flows in to the hydraulic rotary actuator 110 and inverts the vertical frame 108 and the mold box and sand mold, i.e. rotates the upper and lower jaws counter-clockwise 180 degrees. As previously described in detail, this rotational movement starts and stops very smoothly and, thus, reducing the likelihood of fracturing of the sand mold.
As soon as the vertical frame reaches the 180 degree inverted position an actuating lever 378 (Figure 3) rigidly secured to one of the vertical channel beams 130 trips a limit switch 380 (Figure 5). The switch 380 is mounted to the inclined beam 118 on the other side of the stand 102. The limit switch 380 includes a pair of ganged switches 380a and 380b (Figure 9) which are normally closed and open, respectively.
When the switch 380 is tripped by the lever 378 the switch 380a opens and the switch 380b closes. The opening of switch 380a de-energizes the solenoid 374 and the spring biased hydraulic valve 236 (Figure 8) shifts back to its neutral (no-flow) position terminating the flow of hydraulic fluid to the rotary actuator 110 and stopping the vertical frame 108 in the inverted position. The closing of the switch 380b energizes time delay relays 382 and 384.
The energization of the time delay relay 382 closes relay contacts 385 which contacts 385 which causes solenoids 386 and 388 protected by fuses 390 and 392, respectively, to be energized. Referring to Figure 7, the energization of the solenoid 386 shifts the pneumatic valve 222 to inflate the air bags 212. This moves the vibrating frames 210 (Figure 5) into contact with the bottom wall of the mold box. The energization of the solenoid 388 shifts the pneumatic valve 224 (Figure 7) so that the vibrator 216 begins to impart vibratory movement to the mold box through the frames 210.
The energization of the time delay relay 384 closes relay contacts 394 causing a solenoid 396 protected by a fuse 398 to be energized. The solenoid 396 shifts the hydraulic valve 246 (Figure 8) to its flow reversing position. The energization of the time delay relay 384 also energizes a relay winding 400 which in turn closes relay contacts 402. The closing of the relay contacts 402 energizes the solenoid 366 and moves the hydraulic valve 244 (Figure 8) to its on position. Hydraulic fluid begins to flow into the cylinder 180 to cause its piston rod 178 to extend. The jaw 104 begins to descend (note the jaw 104 is now underneath the mold box). The sand mold starts to be drawn from the mold box, the vibratory movements imparted to such box by the vibrator 216 facilitating the stripping of the mold from the box.
After an interval of time sufficient for the jaw 104 to have descended several inches, the time delay relay 382 opens a switch 404 which de-energizes the solenoids 386 and 388. This causes the vibrating frames 210 to move out of engagement with the mold box and causes the ₌ vibrator 216 to cease vibrating. At the same time, the time delay relay 384 opens a switch 406. This de-energizes the solenoids 396 and 366 and causes the jaw 104 to stop descending momentarily.
If desired, a proximity sensing device, e.g. an infrared sensor, can be mounted on the jaw 104 so that its scanning beam extends horizontally across the jaw an inch or so above the upper peripheries of the rollers 48 thereof, If, after the jaw 104 has descended several inches, the sand mold is stuck within the mold box and is not being stripped there from there will be a gap of several inches between the mold box and the bottom board supported on the rollers 48 of the jaw 104. The proximity sensing device can be operatively connected to the circuitry to terminate the automatic operation of the roll over draw apparatus 16 and cause the illumination of a warning light under these circumstances. An operator can then override the apparatus manually and remove the mold box containing the sand mold which cannot be drawn from the mold box by the apparatus. The circuitry for accomplishing the above is not shown in Figure 9.
Continuing now with the description of the automatic operation and referring to Figure 9, after a further small time interval the time delay relay 382 closes a switch 408 which again energizes the solenoids 396 and 366. The jaw 104 starts to descend again and keeps descending until the sand mold, resting on top of the bottom board, has been completely drawn or stripped from the mold box. Referring to Figure 5, when the lower jaw 104 nears the end of the vertical frame 108 it trips a limit switch 410.
Referring to Figure 9, the limit switch 410 includes a pair of ganged switches 410a and 410b which are normally closed and open, respectively. When the jaw 104 trips the limit switch 410, the switch 4l0a is opened and the switch 410b is closed. The opening of the switch 410a de-energizes the solenoids 396 and 366 which causes the jaw 104 to stop descending.
The closing of the switch 410b energizes a solenoid 412 protected by a fuse 414. The solenoid 412 shifts the hydraulic valve 242 (Figure 8) causing the rollers 48 of the jaw 104 to rotate. The bottom board and the sand mold supported thereon are discharged from the jaw 104 onto the main conveying line 20.
The bottom board which has been discharged from the jaw 104 closes a limit switch 416 (Figure 9) mounted in the main conveying line 20 adjacent the box return mechanism 54 (Figure 1, switch not indicated in the drawing). This energizes a relay winding 418 which closes relay contacts 420. A solenoid 422 protected by a fuse 424 is energized. The solenoid 422 shifts the hydraulic valve 236 (Figure 8) so that hydraulic fluid flows into the rotary actuator 110 and causes the same to re-invert the frame 108 and the jaws 104 and 106 in smooth, gradual fashion.
The frame 108 swings clockwise (Figure 4) until the lever 378 (Figure 3) secured to the side thereof trips a limit switch 424. This switch is mounted on the inclined beam 118 on the other side of the stand 102 from the limit switch 380 (Figure 5). The limit switch 424 includes ganged switches 424a and 424b (Figure 9) which are normally closed and open, respectively.
The tripping of the limit switch 424 by the lever 378 opens the switch 424a and closes the switch 424b. The opening of the switch 424a de-energizes the relay winding 418 which inturn opens the contacts 420 and de-energizes the solenoid 422. The de-energization of the solenoid 422 results in the hydraulic valve 236 (Figure 8) shifting back to its middle or neutral position. This terminates the delivery of hydraulic fluid to and from the actuator 110 and the frame 108 stops rotating.
The closing of the switch 424b energizes a time delay relay 426. This closes relay contacts 428 and energizes another time delay relay 430. The energization of the time delay relay 430 closes relay contacts 432. After a short interval of time the switch 432 controlled by the time delay relay 426 opens.
Thereafter, a switch 434 controlled by the time delay relay 430 closes. This energizes the solenoid 350 which shifts the pneumatic valve 220 (Figure 7). Pressurized air is delivered to the pneumatic cylinder 206 to cause the vertical flange gripping arms 190 (Figure 5) to move forwardly. The mold box is thus no longer held between the vertical arms 190 and 192. At the same time the switch 434 is closed by the time delay relay 430, the same relay also opens relay contacts 436 and 438.
The closing of the switch 434 (Figure 9) also energizes the solenoid 348. The energization of the solenoid 348 shifts the hydraulic valve 240 (Figure 8) so that hydraulic fluid flows into the hydraulic motor 188. The rollers 48 of the lower jaw 106 begin to rotate. The mold box is discharged off of the lower jaw back onto the main conveying line 20.
As soon as the mold box travels off of the lower jaw 106; the actuating arm 346 of the limit switch 344 (Figure 4) springs up above the rollers 48. Referring to Figure 9, the switch 344a doses and the switch 344b opens. Thereafter, the time delay relay 430 times out completely. At this point, the time delay relay 426 is also completely timed out. The rollers 48 of the lower jaw 106 keep rotating awaiting the arrival of the next succeeding mold box. This completes the cycle of operation.

6. Description of the Mechanical Structure of the Roll Over Close Apparatus

As previously discussed in conjunction with an explanation of Figure 1, the roll over close apparatus 18 of the present invention receives a cope portion 52 (Figure 2A) of a sand mold conveyed thereto on a bottom board 40 by the main conveying line 20. Arms 56 of the roll over close apparatus clamp the cope portion 52 and raise it off of the bottom board 40 (Figure 2A, steps G and H). The bottom board 40 is discharged out of the roll over close apparatus 18. Thereafter, the cope portion 52 is inverted, i.e. rolled over 180 degrees (Figure 2A, step I). The cope portion 52 is maintained in an elevated position above the level of the main conveying line 20 awaiting the arrival of a drag portion 62 (Figure 2B).
The drag portion 62 and the bottom board 64, upon which it rests, are conveyed into the roll over close apparatus 18 directly underneath the awaiting cope portion 52 (Figure 2B, step K). The cope and drag portions 52 and 62 are joined (Figure 2B, step L) and they are conveyed, resting on top of the bottom board 64, out of the roll over close apparatus 18 back onto the main conveying line 20.
The mechanical structure of the roll over close apparatus 18 is similar in all respects to that of the roll over draw apparatus 16 except for certain structural details of its upper and lower jaws which are hereafter described.
In the case of the roll over close apparatus 18, it is also highly desirable that the rotational movement of the vertical frame and the jaws start and stop smoothly both on the upswing and on the downswing. When a cope portion of a mold such as 52 (see Figure 2A) is inverted in the roll over close apparatus the centre of mass of the mold portion is spaced downwardly from the axis X of rotation of the vertical frame and the jaws. When the cope portion is inverted in the roll over close apparatus 18 it is held in position by arms 56 (see Figure 2A, steps G, H and I). It is not held clamped between the upper and lower jaws. As with the roll over draw apparatus, the rotational load of the roll over close apparatus is frequently substantially off centre and unbalanced. Therefore, the roll over close apparatus must also have a means for controlling the rotational movement so that it starts up and slows down smoothly. After the joined cope and drag mold portion are ejected from the roll over close apparatus, the empty jaws are re-inverted and in order to avoid damage to the machine, it is also desirable during the roll down that the rotation start and stop smoothly.
The roll over close apparatus utilizes the same means for rotating the jaws and the sand mold supported therebetween smoothly and gradually as previously described in conjunction with the roll over draw apparatus. It is even more critical that the vertical frame and jaws of the roll over close apparatus start and stop their rotational movement gradually. This is because the sand mold which is inverted by the roll over close apparatus is not contained and supported by a surrounding mold box. Therefore, the sand mold is even more susceptible to fracturing during the inversion. Preferably the rotational velocity increases and thereafter decreases at a substantially uniform rate.
The roll over close apparatus incorporates the same hydraulic circuit (Figure 8) as the roll over draw apparatus. In addition, the roll over close apparatus incorporates a pneumatic circuit (Figure 12). Finally, the roll over close apparatus includes an electrical control circuit (Figure 13) which enables it to automatically perform the sequence of operations described above.
Figures 10 and 11 show structural details of the lower jaw 106' of one embodiment of the roll over close apparatus 18 of the present invention. In Figure 10, a cope portion 52 of a sand mold resting on a bottom board 40 is shown supported on the rollers 48 of the lower jaw 106'. A pair of vertical arms 56a are rigidly welded in position at their lower ends. The arms 56a extend vertically between the rollers 48 of the lower jaw. A second pair of vertical arms 56b are welded at their lower ends to the forward part of a carriage 500. The arms 56b also extend upwardly between the rollers 48. The carriage 500 has wheels 501 which travel along transversely extending tracks 501a.
Pivotably secured to the upper ends of the respective pairs of arms 56a and 56b are transversely extending gripping members 502. These members have teeth on their inner surfaces 504 for firmly holding the sand mold 52. A pneumatic cylinder 506 can be actuated to move the carriage 500 inwardly. When this occurs, the sand mold 52 will be firmly held between the gripping members 502.
The tracks 501a are held in position by four upper air bags 508 and four lower air bags 510. When the upper air bags 508 are not inflated the lower air bags 510 can be inflated to move the carriage 500 and the elements supported thereby upwardly (Figure 11). When the air bags 510 are not inflated, the air bags 508 can be inflated to move the carriage 500 and the el^pments supported thereby downwardly.

7. General Description of the Operationcf the Roll Over Close Apparatus

In actual operation, a cope portion of a sand mold, resting on top of a bottom board is conveyed into the roll over close apparatus 18. The cope portion of the sand mold comes to a stop intermediate the length of the lower jaw 106'. Next, the sand mold is clamped between the gripping members 502. The lower air bags 510 are inflated to raise the sand mold 52 off of the bottom board 40. Thereafter, the rollers 48 are momentarily rotated to discharge the bottom board off of the lower jaw 106' onto the main conveying line 20.
Next, the vertical frame 108 and the upper and lower jaws of the roll over close apparatus 18 are rotated (counter-clockwise in Figure 4) 180 degrees to invert the cope portion 52. The cope portion is maintained in an elevated position above the level of the main conveying line 20 awaiting the arrival of a drag portion 62 (Figure 2B) on a bottom board 64. Preferably, the jaw 104 has guides (not shown) mounted above the rollers 48. The guides align the drag portion transversely with the cope portion suspended above the same as the drag is conveyed onto the jaw 104.
Next, the jaw 104 is raised until the drag portion and the cope portion are joined. The pneumatic cylinder 506 is actuated to release the cope portion from between the gripping members 502. The jaw 104 and the joined cope and drag mold portions are lowered to the level of the main conveying line 20. Thereafter, the rollers 48 of the jaw 104 are rotated to power the joined cope and drag portions off of the jaw 104 onto the main conveying line 20. Finally, the vertical frame 108 and the jaws 104 and 106' are re-inverted back to their original position.

8. The Pneumatic Circuit of the Roll Over Close Apparatus

Referring to Figure 12, pressurized air is supplied through the rotary coupling 140 to a manifold 550 mounted on the lower jaw 106^t. The pneumatic cylinder 506, which moves the vertical mold gripping arms 56b, is coupled to the manifold 550 through a flow reversing valve 552. The air bags 508 and 510 are connected to the manifold 550 through a two position valve 554. The valves 552 and 554 are solenoid actuated spring biased valves. When the valve 554 is in the position shown, the upper air bags 508 (Figure 11) are inflated and the lower air bags 510 are deflated. When the solenoid of the valve 554 is energized it shifts the valve so that the upper air bags 508 are deflated and the lower air bags 510 are inflated.

9. The Electrical Circuit of the Roll Over Close Apparatus

The automatic operation of the roll over close apparatus 18 will now be described in detail in connection with an explanation of its electrical control circuit shown in Figure 13. This electrical circuit operates in conjunction with the pneumatic and hydraulic circuits shown in Figures 12 and 8, respectively, and previously described above.
Referring to Figure 13, the roll over close apparatus is placed in a power on mode by throwing a manual circuit breaker switch 600 and by pulling on a ganged start switch. 602a and 602b. The closing of the switches 602a and 602b energizes a relay winding 604. The energization of the relay winding 604 closes relay contacts 606 which causes the electric motor 232 (Figure 8) to be energized. The motor 232 drives the hydraulic pump 230. The energization of the relay winding 604 also closes relay contacts 608 and 610 (Figure 13).
A limit switch 612 is mounted between the rollers 48 of the lower jaw 106' in the same fashion as the limit switch 344 of the roll over draw apparatus (Figure 4). The limit switch 612 is normally open and is closed when its actuating arm is depressed by a cope portion conveyed onto the lower jaw 106' .
Before a cope portion reaches the roll over close apparatus 18 a solenoid 348 is in its energized state. In this condition the solenoid 348 hold the on-off hydraulic valve 240 (Figure 8) in its on position so that the rollers 48 of the lower jaw 106' are rotated. When the cope portion reaches the lower jaw 106' it will be conveyed longitudinally thereon until it is positioned intermediate the longitudinal length of the jaw. When the cope portion reaches this position on the lower jaw 106' it closes the limit switch 612 (Figure 13). This energizes a relay winding 614 which closes contacts 616 and 618. The closing of the relay contacts 616 energizes a time delay relay 620. The relay 620 closes contacts 622 to hold the relay energized. The relay 620 opens relay contacts 624, de-energizing the solenoid 348 and stopping the rotation of the rollers 48 of the lower jaw 106'.
The relay winding 620 further opens contacts 626 which de-energizes a solenoid 628 causing the pneumatic valve 552 (Figure 12) to shift to its flow reversing position. Pressurized air flows into the pneumatic cylinder 506 causing the arms 56b (Figure 10) to move inwardly. The cope portion 52 is firmly held between the gripping members 502.
The energization of the time delay relay 620 also opens relay contacts 630 which has no effect at this time. Finally, the energization of the relay winding 620 closes a switch 632. This energizes a solenoid 634 which shifts the pneumatic valve 554 (Figure 12) causing the lower four air bags 510 (Figure 11) to be inflated &nd the upper four air bags 508 to be deflated. This'raises the cope portion off of the rollers 48 of the lower jaw 106'.
The closing of the switch 632 also energizes a time delay relay 636 which closes a switch 638 so that the solenoid 348 is energized. The lower rollers 48 rotates long enough to eject the bottom board while the cope portion is elevated thereabove.
The energization of the time delay relay 636 also closes a switch 640 which energizes another time delay relay 642. Finally, the energization of tle relay winding 636 closes contacts 644 which has no effect at this time since a limit switch 646, which senses the presence of a drag portion, is open at this time.
Next, the time delay relay 642 opens a switch 648 which de-energizes the solenoid 348 and terminates the rotation of the rollers 48 of the lower jaw 106'. The time delay relay 642 also closes a switch 650 which energizes the solenoid 374. The energization of the solenoid 374 shifts the hydraulic valve 236 (Figure 8) so that the vertical frame 108 of the roll over close apparatus rotates counter clockwise 180 degrees to invert the cope portion. The lever 378 on the side of the vertical frame 108 (see Figure 3) trips the limit switch 380 (Figure 5) mounted to the stand 102 of the apparatus. The switch 380 includes a pair of ganged switches 380a and 380b (Figure 13) which are normally closed and open respectively. The tripping of the limit switch 380 opens the limit switch 380a and closes the limit switch 380b.
The opening of the switch 380a de-energizes the solenoid 374 which in turn causes the hydraulic valve 236 (Figure 8) to shift back to its neutral (no flow) position. This terminates the rotation of the vertical frame 108 of the roll over close apparatus. The closing of the limit switch 380b (Figure 13) energizes the solenoid 412. The energization of the solenoid 412 shifts the hydraulic valve 242 (Figure 8) to its on position causing the rollers 48 of the upper jaw 104 to rotate.
Thereafter, a drag portion 62 (Figure 2B) is conveyed on the main conveying line 20 onto the rollers 48 of the jaw 104 now positioned at the level of the main conveying line 20. The drag portion closes the limit switch 646. This switch is mounted between the rollers 48 of the jaw 104.
The closing of the limit switch 646 energizes a relay winding 652. The energization of the relay winding 652 opens relay contacts 654, de-energizing the solenoid 412 and terminating the rotation of the rollers 48 of the jaw 104. The energization of the relay winding 652 also closes relay contacts 656 which has no effect at this time. The energization of the relay winding 652 also closes relay contacts 658.
The closing of the drag present limit switch 646 also _I energizes the solenoid 358, the contacts 644 having previously been closed by the time delay relay 636. The closing of the relay contacts 658 by the relay winding 652 energizes the solenoid 366. The energization of the solenoids 358 and 366 causes hydraulic fluid to flow into ; the cylinder 180 (Figure 8) which raises the jaw 104 toward the jaw 106' thereabove. The drag portion is mated with the cope portion.
The cope portion is still held between the gripping members 502 of the arms 56a and 56b (Figure 10) at this time. The air bags 510 (Figure 11) are still inflated ao that the cope portion 52, resting on top of the drag portion, is held spaced from the rollers 48 of the jaw 106'. Therefore, at this time the limit switch 612 (Figure 13) mounted between the rollers 48 of the jaw 106' is open. The rising jaw 104 lifts the cope portion into engagement with the switch 612 closing the same.
The closing of the limit switch 612 re-energizes the relay winding 614. The energization of the relay winding 614 closes relay contacts 616 and 618. The closing of the relay contacts 618 causes a time delay relay 660 to be energized, the relay contacts 656 having previously been closed by the energization of the relay 652.
The energization of the time delay relay 660 opens contacts 662 and de-energizes the time delay relay 620. The de-energization of the relay winding 620 also opens the switch 632, de-energizing the solenoid 634 and the time delay relay 636. The de-energization of the solenoid 634 inflates the air bags 508 and deflates the air bags 510 lifting the sub-frame 500 (Figure 11) and the arms 56a and 56b carried thereby. The de-energization of the time delay relay 636 opens relay contacts 644 and 638. Opening of the contacts 644 de-energizes solenoid 358 and the jaw 104 stops rising. It also opens switch 640, de-energizing the time delay relay 642. The energization of the time delay relay 660 also opens relay contacts 664 which has no effect at this point. The energization of the time delay relay 660 further closes relay contacts 666 and closes relay contacts 668.
The de-energization of the time delay relay 620 opens the relay contacts 622 which has no effect at this time. It further closes the relay contacts 624 which also has no effect at this time. Finally, the de-energization of the time delay relay 620 closes the relay contacts 626, energizing the solenoid 628. The energization of the solenoid 628 shifts the pneumatic valve 552 (Figure 12) so that the cope portion is released by the gripping arms 56a and 56b (Figure 10). The de-energization of the time delay relay 620 further closes the relay contacts 630. The solenoid 396 is energized and since the solenoid 366 has been previously energized hydraulic fluid flows into the cylinder 180 cuasing the jaw 104 and the joined cope and drag portions supported thereon to descend.
The jaw 104 carrying the joined cope and drag portions continues to descend until the limit switch 410 (see Figure 5) is actuated. The limit switch 410 includes ganged switches 410a and 410b which are normally closed and open, respectively. When the limit switch 410 is engaged by the jaw 104 the switch 410a is opened and the switch 410b is closed. The opening of the switch 410a de-energizes the solenoid 396 and the jaw 104 stops descending. The closing of the switch 410b energizes a time delay relay 672.
The energization of the time delay relay 672 closes contacts 674, energizing the solenoid 412 and causing the rollers of the jaw 104 to rotate. The joined cope and drag portions 52 and 62, resting on top of the bottom board 64, are discharged out of the roll over close apparatus 18 onto the main conveying line 20. Thereafter, the time delay relay 672 opens a switch 676, de-energizing the solenoid 412 and terminating the rotation of the rollers 48 of the jaw 104.
Next, the time delay relay 672 closes a switch 678, energizing the solenoid 422. The energization of the solenoid 422 shifts the hydraulic valve 236 (Figure 8) cuasing the vertical frame 108 of the roll over close apparatus to swing counter-clockwise 180 degrees. When the vertical frame 108 reaches its initial starting position the lever 378 (Figure 3), on the side of the vertical frame 108, trips the limit switch 424, opening the same and de-energizing the solenoid 422 (Figure 13). The de-energization of the solenoid 422 allows the hydraulic valve 236 (Figure 8) to shift back to its middle position, thus terminating the rotation of the vertical frame 108. This completes the cycle of operation.

Claims

1. Apparatus for inverting a sand mold comprising: means for receiving the mold and supporting the same for rotational movement; means for rotating the receiving and supporting means to invert the mold during a predetermined time interval; and means for controlling the rate of the rotation to substantially minimize the forces exerted on the internal structure of the mold and prevent fracturing of the same.

2. Apparatus according to claim 1, wherein the receiving and supporting means supports the mold for movement along an arcuate path and the controlling means causes the mold to move along the path so that its velocity increases at a substantially uniform rate along a first portion of the path and decreases at a substantially uniform rate along a last portion of the path.

3. Apparatus according to claim 1 or 2, wherein the receiving and supporting means includes a pair of jaws for clamping the mold therebetween and a frame for supporting the jaws in opposing relationship for rotation about a horizontal axis.

4. Apparatus according to claim 3, and further comprising: means for moving one of the jaws toward and away from the other jaw; and gripping means on one of the jaws for holding a sand mold in position thereon.

5. Apparatus according to claim 3 or 4, wherein: each jaw has a plurality of rollers; mean are provided to drive the rollers; one jaw is fixedly mounted on the frame; the other jaw is mounted on the frame for vertical movement with respect to the frame; and movable arm means are provided on said one jaw for gripping engagement with a sand mold.

6. Apparatus according to claim 5, wherein the sand mold is contained within a mold box and the apparatus further comprises means for imparting vibrations to a mold box gripped by the movable arm means and means for moving the vibration imparting means into and out of engagement with a mold box gripped by the movable arm means.

7. Apparatus according to claim 5, and further comprising moving means for vertically moving the arm means to remove a mdd gripped by the same from a bottom board supported by the rollers of the one jaw.

8. Apparatus according to any preceding claim, wherein the rotating means includes a hydraulic engine, and means for drivingly connecting the engine with the receiving and supporting means.

9. Apparatus according to anyone of claims 3 to 7, wherein the means for rotating the frame and the jaws includes: a positive displacement hydraulic engine; means for drivingly connecting the engine and the frame so that when the engine is energized it will rotate the frame and the jaws about the horizontal axis; a source of hydraulic fluid; a flow regulated pressure compensated hydraulic pump; means for driving the pump; conduit means for connecting the source of hydraulic fluid, the pump and the engine so that hydraulic fluid can circulate between the pump and the engine; and a counterbalance valve for controlling the delivery of hydraulic fluid to and from the engine so that when the rotational load is substantially off centre and unbalanced the frame and the jaws will start and stop their rotational movement gradually to prevent fracturing of the mold.

10. A roll over draw apparatus for automatically drawing a sand mold from a mold box conveyed thereto, the top of the mold box being covered with a bottom board and the bottom wall of the mold box defining a flange, the apparatus comprising: upper and lower jaws each including a plurality of rollers; means for driving the rollers; a frame for supporting the jaws in opposing relationship, including means for rigidly mounting the lower jaw to the frame and a carriage for mounting the upper jaw to the frame for vertical movement toward and away from the lower jaw; first means for moving the upper jaw on the frame; movable arm means on the lower jaw for gripping the flange of a mold box engaged by the rollers thereof; second means for moving the arm means mounted on the lower jaw to grip a mold box engaged by the rollers of the lower jaw; means for imparting vibrations to a mold box gripped by the movable arm means; third means for moving the vibration imparting means into and out of engagement with a mold box gripped by the movable arm means; means for supporting the frame for rotating the frame and the jaws about a horizontal axis; means for rotating the frame and the jaws to invert a mold box gripped by the movable arm means and for thereafter re-inverting the frame and the jaws; and control means for automatically causing the driving means to rotate the rollers of the lower jaw to convey a mold box containing a sand mold and covered by a bottom board onto the lower jaw, for thereafter causing the driving means to cease rotating the rollers of the lower jaw, for thereafter causing the second moving means to move the arm means to grip the flange of the mold box and for causing the first moving means to move the upper jaw downwardly to clamp the mold box and bottom board between the upper and lower jaws, for thereafter causing the rotating means to rotate the frame and the jaws to invert the mold box, for thereafter causing the third moving means to move the vibration imparting means into engagement with the mold box for vibrating the same, for thereafter causing the first moving means to move the upper jaw downwardly away from the lower jaw situated thereabove to draw the sand mold, resting on top of the bottom board, from the mold box, for thereafter causing the third moving means to move the vibration imparting means out of engagement with the mold box, for thereafter causing the driving means to rotate the rollers of the upper jaw to discharge the bottom board and the sand mold _s resting thereon from the upper jaw, for thereafter causing the driving means to cease rotating the rollers of the upper jaw, for thereafter causing the rotating means to re-invert the frame and the jaws, for thereafter causing the second moving means to move the arm means out of gripping relationship with the flange of the mold box, and finally for causing the driving means to rotate the rollers of the lower jaw to discharge the mold box from the lower jaw.

11. A roll over close apparatus for automatically joining a cope portion of a sand mold with a drag portion of a sand mold, the cope and drag sand mold portions being supplied to the apparatus in succession, each resting on top of a bottom board, the apparatus comprising: upper and lower jaws each including a plurality of rollers; means for driving the rollers; a frame for supporting the jaws in opposing relationship, including means for rigidly mounting the lower jaw to the frame and a carriage for mounting the upper jaw to the frame for vertical movement toward and away from the lower jaw; first means for moving the upper jaw on the frame; movable arm means on the lower jaw for gripping a sand mold resting on a bottom board supported by the rollers of the lower jaw; second means for moving the arm means into gripping relationship with a sand mold resting on a bottom board supported by the rollers of the lower jaw; third moving means for vertically moving the arm means to lift a mold gripped by the same off of a bottom board supported by the rollers of the lower jaw; means for supporting the frame for rotating the frame and the jaws about a horizontal axis; means for rotating the frame and the jaws to invert a sand mold gripped by the movable arm means and for thereafter re-inverting the frame and the jaws; and control means for automatically causing the drive means to rotate the rollers of the lower jaw to convey a cope portion of a sand mold resting on a first bottom board onto the lower jaw, for thereafter causing the second moving means to move the arm means into gripping relationship with the cope portion, for thereafter causing the third moving means to vertically move the arm means and raise the cope portion off of the first bottom board, for thereafter causing the driving means to rotate the rollers of the lower jaw to discharge the first bottom board from the lower jaw, for therafter causing the rotating means to rotate the frame and the jaws to invert the cope portion, for thereafter causing the driving means to rotate the rollers of the upper jaw, now underneath the lower jaw, to convey a drag portion resting on a second bottom board onto the upper jaw, for thereafter causing the first moving means to raise the lower jaw to join the cope and drag mold portions, for thereafter causing the second moving means to move the arm means to ungrip the cope portion, for thereafter causing the first moving means to lower the upper jaw and the joined cope and drag mold portions resting on top of the second bottom board, for thereafter causing the driving means to rotate the rollers of the upper jaw to discharge the second bottom board and the joined cope and drag sand mold portions resting thereon from the upper jaw, and for thereafter causing the rotating means to rotate the frame and the jaws to re-invert the same.

12. Apparatus according to claims 10 or 11, wherein the means for rotating the frame and the jaws includes: a positive displacement hydraulic engine, means for drivingly connecting the engine and the frame so that when the engine is energized it will rotate the frame and the jaws about the horizontal axis; a source of hydraulic fluid; a flow regulated pressure compensated hydraulic pump; means for driving the pump; conduit means for connecting the source of hydraulic fluid, the pump and the engine so that hydraulic fluid can circulate between the pump and the engine; and a counterbalance valve for controlling the delivery of hydraulic fluid to and from the engine; whereby when the rotational load is substantially off centre and unbalanced the frame and the jaws will start and stop their rotational movement gradually to prevent fracturing of the mold.