GB2120997A - Gripping device - Google Patents

Abstract

A gripping device, for manipulating for example sand moulds, comprises a pair of arms (6,8) pivotally connected and operable by clamping means (22) comprising an extensible shaft (30) operated by an electric motor (28) to effect a clamping movement. The arms have gripper pads (18,20) designed to engage a mould, the pads being pivotal and rotatable and having protrusions on their faces. Automatic control means control the amount of pressure exerted by the pads in the clamping motion. <IMAGE>

Description

SPECIFICATION Article manipulating device This application relates to improvements in equip ment for handling and manipulating articles such as heavy sand molds as used in the metal casting industry.

The metal casting orfoundryindustryhasfor many years used molds made of chemically-bonded sand to form castings in metal. These sand molds are commonly, depending on the size ofthe casting, heavy and awkward to handle and require mechanical assistance for lifting and positioning. Where two halves of a mold are employed, it is necessary to position one half over the other with considerable care and precision.

Because of theirsize and weightand because the sand molds are somewhat destructible by compressive or shear force, it is necessaryto handle them carefully for reason of safety and economy.

Various devices have been developed designed to grip molds and allow them to be lifted and overturned or otherwise manipulate it into position, but all of these prior devices have shown some shortcomings.

For instance, some rely on mold frames, bars, lugs or other devices with which to grip the mold. Others are designed to grip the mold but their control ofthe applied force is precise and therefore there is danger that the mold will not be held firmly, orthat it will be held too firmly and crushed or damaged bythe mechanism.

Some devicesforthis purpose are heavy, bulky and expensive, and are awkward or inefficient to operate because their mechanism requires that the device move between two alternative positions, closed or fully opened. As a result, they are heavy to handle and difficultto operate.

It is therefore the purpose of this application to provide a mold handling and manipulating device which will grip the body ofthe mold without auxiliary attaching devices, will exert a smooth and controlled clamping force with which to maintain a secure and positive grip, and allow easy and convenient movement, manipulation and placementofthe mold by the operator.

Furthermore, it is the purpose of the present invention to provide a device which can be easily installed and connected to commonly available power and control services in industrial buildings.

These objects and other advantages are sought to be achieved by the present invention which provides a mold manipulating device comprising a pair of arms pivotally connected relative to one another attheir upper ends, said arms being spaced apartattheir lower ends, and means to supportthe device from the upper end of said connected arms, clamping means spanning between said arms adapted to move said arms apart ortowards each other in response to control means, means atthe lower ends of said arms adapted to grippingly engage an article. The clamping means comprises an extensible shaft connected at respective ends to the respective arms of the device and operable by means of an electric motorto extend or retract said shaft in response to control means to effect relative movement ofthe lower end ofthe arms.The lower end ofthe arms has gripping means comprising pads facing each otherwith pointed protrusions adapted to grip the article. The pads are pivotable about an axial line perpendicularthereto by means of ball and socket means. The gripping means are adapted to exert a preset pressure by means of a spring and means operable to shut off the powerto the clamping means when the preset pressure is achieved. The pads are rotatable aboutthe axis of their sockets to effect manipulation and the preferred embodiment may be equiped with vibratory means to assist in removing molds from mold boxesorpatterns.

The invention may be better understood by the following description of a preferred embodiment thereofwith reference to the drawings in which: Figure lisa perspective view of a preferred embodimentofthe present invention; Figure 2 is an exploded view of a portion of the mechanism ofthe device in Figure 1; Figure 3 is a cross-sectional view of a portion of the mechanism ofthedevice in Figure 1; and Figure 4 illustrates a modified version ofthe invention.

Molds used in the casting orfoundry industry commonly take the form of a large rectangular block of chemcially-bonded sand often in two parts which form the cavity in which the metal is cast. As a result it is commonly necessary to lift and position and manipulate these heavy mold pieces and to place one on top of the other in preparation for casting.

Figure 1 illustrates a mold handling and manipulating device in accordance with the present invention which may be suspended from an overhead travelling crane or similar device and used to lift and manipulate molds. The embodiment ofthe invention illustrated in Figure 1 comprises a ring 2, by which the device may be lifted or suspended from an overhead travelling crane orthe like, connected to a pin 4from which two diagonal upper arms 6 and 8 respectively are pivotally suspended to extend downwardly and outwardly.

Atthe ends ofthe upper arms 6 and 8 are a pair of lower arms 10 and 12 respectivelywhich extend downwardly substantially vertically and substantially parallel to each other.

At the lower end of the arms are a pair of mounting assemblies 14and 16 respectively on which a pair of gripper pads 18and 20 aresupported. Aswill be explained in greater detail herein, these gripper pads are inwardly facing and opposed and designed to engage and hold the sides of a mold between them.

Spaced above the gripper pads and connecting the two arms 10 and 12 neartheirupperends is a clamping mechanism 22 attached to the arms respectively at 24 and 26 by pivot pins and operable to draw the arms towards each other or push them apart in responseto an electric motor28 mechanically connected to operate a telescopic arm 30. The electric motor 28 is electrically connected by a cable 32 to a control panel 34 near the lower end of the arms.

In summary, a device ofthetype illustrated, can be used by suspending it from a support, such as an overhead travelling crane, by the ring 2sothatthe device hangs downwardly. An operator can then position the device by means of the handle 36, and usingthe controls on the panel 34, can operatethe electric motor28 so as to open or close the arms of the manipulator and by closing them can cause the gripper pads 18 and 20to engage and clamp onto the sides of a mold or similar object.

By use of an electric motor which is geared to drive the telescopic arm 30 by means of a screwthread, a relatively smooth and gentle opening and closing movement can be effected in a mannerwhich is not readily provided in a pneumatic cylinder or other mechanical mechanism.

Ideally, the control panel might incorporate dual buttons to effect both the clamping and the un-clamping mechanismssoastoavoidthe possibility of accidental activation ofthe device in the interests of safety.

This inventor has found that the operation of such a device can be made more effective and efficient by the design of the mounting and support structures of the gripper pads.

A preferred embodiment of this apparatus is shown in greaterdetail in Figures 2 and 3 in which the gripper pad 20 has a series of pointed protrusions 40 designed to engagethe surface ofthe mold to effect a more secure grip thereon.

The pad itself is mounted, by means of bolts such as 42, to a collar44which is formed in the nature of a socket and pivotal on a spherical member 46 so as to allowthe pad to pivot aboutthe axial direction, as defined bythe shaft 48 on which the ball 46 is mounted. The shaft 48 is supported by the lower end ofthe arm or mounting structure 16 by means of a sleeve 50 engaged bya bolt 52 which extendsthrough the opposite side of the arm.

As seen in Figure 3,the shaft48 and sleeve 50 are mounted in the wall of the hollow arm 12atthe mounting 16 and the shaft 48 is axially movable relative to the arm, its position being determined by (at least when it is not in use) the outward urging ofthe spring 54 and the relative positioning or adjustment of the bolt 52 which puts a limit on the outward expension ofthe spring 54.

An upwardly projecting plate 56 is attached to and moves with the shaft 48 and is designed at its upper end to engage the trigger 58 of an electrical switch 60 adjustably mounted by means of bolt 62 and springs 64 in the internal cavity of the arm 12 and adjustable by a threaded bolt 66.

In the foregoing description is will be appreciated that the gripper pad 20 is free to pivot, within certain limits aboutthe ball and socket 46 and 44so as to engagetheflatside of a mold evenly, whether its sides are parallel to not.

Itwill also be seen that as the arms close to engage the mold with the gripper pads, the shaft48will be forced against the urging ofthe spring 54 in an outward direction. As it does sothe plate 46 will eventually trip the switch 60 which is designed to open the electrical circuit and cut off power to the motor 28 thereby stopping the closing motion of the arms. The adjustment ofthe position ofthe switch 60 by the bolt 66 will determine the amountofmotion againstthe spring 54 which will be required before the closing mechanism ofthe device is halted and therefore will determine the amount of force, provided by the spring 54,which will be exerted bythe gripper pads 18and20 on the sides of the mold.

Thus, the present device provides a clamping mechanism which is adjustable to the shape and configurationofthe mold and which isadjustableto control the force exerted depending on the weight and strength ofthe mold being handled, which adjustment is independent of the judgement or skill orthe operator. In other words, it is automatic and predetermined.

In Figure 2 there is also illustrated a collapsible and flexible cover 38 designed to keep pads substantially parallel to the arm and protectthe ball and socket and the adjustable shaft mechanism while allowing the pivoting and thrusting movements to operate unhindered.

In use, this preferred embodiment can be suspended from an overhead crane or chain block by means ofthe ring 2 and the operator can locate it over the mold or similar deviceto be handled by engaging the appropriate buttons on the/control panel 34 which cancausethearmstoopento a dimension large enough to place the gripper pads 18 and 20 adjacentto the opposite sides ofthe mold.

Once in position the appropriate control buttons can be engaged to operate the motor 28 so as to close the arms until the pads 18 and 20 engage the sides ofthe mold. As the pads 18 and 20 engage the side of the mold, the increased pressure of the arms closing will causethe shaft48to compress the spring 54 until the switch 60 opens a circuit cutting off power to the motor28, atwhich timethe closing orclampingwill stop. Preferablythe motor 28 is equiped with brake means to thatthe clamping motion will stop substantially instantaneouslywhen the power to the motor is cut off. Notwithstanding that fact, the spring 54 determinesthe amountof pressure exerted on the mold bythe pads of the arms.

Because it is often desirable to pick up a mold and turn it over, the ball and socket 46 and 44will allowthe pads, and therefore the article held within their grip, to be rotated afull 360 degrees aboutthe axis ofthe shaft 48 (or approximately aboutthe axis depending on the pivotal position ofthe pad).

Becauseitisundesirableto havethe pads and the articles held thereby free to rotate orflip upside down unexpectedly, the device is provided with a locking mechanism illustrated at70 in Figure 1 in which a protrusion 72 is designed to engage a socket 74so as to held the pad 20 from rotation. A spring 76 is employed between the ring 78 and the collar80 which is mounted to the arm and serves to hold the protrusion mounted thereto. The handle 82 may be used to position the locking mechanism in the disengaged position, as illustrated in Figure 1, orto release it and engage the ring 74to holdthe device against undesired rotation.

With an article engaged as described above, the overhead support or crane can be used to liftthe device and the article and move it to the desired location.The mold can then be rotated to its proper upright or inverted position and lowered into place, usually on top ofthe mating portion ofthe restofthe mold. By reversing the motor 28 by means ofthe control on the panel 34 (which operation is not de-energized bythe switch 60) the arms can be opened and the pads disengaged from the mold.

Thus, by means of the present invention a simple, safe,convenient, and efficient device is provided for the handling of heavy and awkward items such as foundry molds.

The manipulator may also be used to separate moldsfrom fhe mold boxes and/orpatterns.The manipulatorcan be clamped onto the outside of mold or core boxes and when inverted gravity tends to separate the mold from the mold box pattern. (This is often aided bvtappingthe mold box).

Since it is sometimes difficult to disengage the chemically-bonded sand mold and/or cores from the sides ofthe pattern and mold box, especially where there are deep narrow sections on the pattern, it has been discovered that removal of the mold or cores can be more easily effected by applying vibration through the gripper pads to the mold box hanging inverted in the manipulator.

The vibration destroys the bond between the mold and the pattern allowing for a simple stripping operation.

To this is end, a modified version of the preferred embodimnt is illustrated in Figure 4 in which the vibrator90 is mounted on the pad 18. Vibratorsof various types are available and may be of piston or eccentric rotary mechanism and may be powered by electricity or air power as desired.

Afurther manual control on the panel will allowthe operator to exert somevibratory energy to the pads so as to effect release when stripping the molds.

Unlike previous devices,the mechanism ofthe present invention is smooth, controlled and precise and the device is adjustable to automatically deter mineandapplythedesired amount of pressure as may be dictated bythestrength ofthe material orthe weight of the article being handled. The pressure is determined automatically and controlled without guess work and the article can be manipulated by means ofthe ball and socket which allows rotation through 360 degrees in a vertical plane and by means of the single support or suspension atthe ring 2 which allows rotation in 360 degrees in the horizontal plane.

Because the device is electrically powered, it is easily installed and powered even in small plants where hydraulic or compressed air systems may not be available. Ideally, most of the electrical wiring can be located within the hollow arms or the device and if necessarythecontrol panel at34andthe preferred embodiment could be a remote portable hand-held unit.

Whitetheforegoing illustrates the preferred embodiment as conceived by the inventor, it will be appreciated that numerous variations and modifications in the details of such a device might be employed without departing from the inventive concept herein.

Claims (10)

1. An article manipulating device comprising: a pair of arms connected and pivotal relative to one another attheirupper ends; said arms being spaced apart at their lower ends; means to support said device from the upper end of said connected arms; clamping means spanning between said arms adapted to move said arms apartortowards each other in responseto control means; means on the lower end of said arms adapted to gripping engage an article.

2. A device as claimed in claim 1 in which said clamping means comprises an extensible shaft connected at the respective ends thereof to respective arms of the said device, said shaft being operable by means of an electrical motorto extend and retract said shaft in response to control means to effect relative movement ofthe lower end of said arms.

3. A device as claimed in claim 2 in which said gripping means comprising padsfacing each other mounted on the lower end of said arms, said pads being adapted to grip the article therebetween.

4. A device as claimed in claim 3 in which said pads are pivotable relative to a line mutually perpendicularthereto.

5. A device as claimed in claim 4 in which said pivotal means includes a ball and socket mounting said pads to said lower arms.

6. A device as claimed in claim 3 in which the pressure exerted by said pads are automatically limited.

7. A device as claimed in claim 6 in which said limiting means comprises a spring urging said pads against retraction and a switch operable by movement of said pads against said spring control said clamping means.

8. A device as claimed in claim 3 in which said pads are rotatable about an axis mutually perpendicu largo said pads.

9. A device as claimed in claim 3 and having meansadaptedtoexertvibratoryenergytoat least one of said pads.

10. A device as claimed in claim 3 in which said pads are adapted to grip the article therebetween by means pointed protrusions on the face of said pads.