US3754432A

US3754432A - Force unit for metal working

Info

Publication number: US3754432A
Application number: US00038406A
Authority: US
Inventors: W Hagerty
Original assignee: W Hagerty
Current assignee: Hein Werner Corp
Priority date: 1970-05-18
Filing date: 1970-05-18
Publication date: 1973-08-28
Anticipated expiration: 1990-08-28
Also published as: CA943819A; JPS5759209Y2; JPS5660523U

Abstract

A force unit that may be readily employed to develop a pulling force for physically shaping, or molding, a work piece by bending, is disclosed. The force unit includes a power member which is physically moved by a hydraulically operated ram for the purpose of retracting a load chain or cable that is attached at one end to a stabilized work piece to be shaped and at an opposite end to the force unit. The ram is vertically mounted on an appropriate support. A fulcrum pulley is mounted at any vertical position along the length of the ram or a support post to which it may be attached. An anchor is employed to secure the force unit from movement in the direction of the work piece.

Description

[4 Aug. 28, 1973 United States Patent m1 Hagerty [54] FORCE UNIT FOR METAL WORKING 3,583,203 6/1971 72/705 X Inventor: will. Kenneth g 605 E. 3,612,482 10/1971 72/705 X N d PL, A 3 hambra Calif Primary Examiner-Charles W. Lanham Assistant Examiner-E. M. Combs Attorney-Jackson and Jones [22] Filed: May 18, 1970 [21] Appl. No.: 38,406

[ ABSTRACT A force unit that may be readily employed to develop a pulling force for physically shaping, or molding, a work piece by bending, is disclosed. The force unit in- [52] U.S. 72/447, 72/705 [51] Int. B2ld 1/14 [58] Field of 72/705, 447;

254/93 R, DIG. l eludes a power member which is physically moved by a hydraulically operated ram for the purpose of retract- 56] References Cited UNITED STATES PAT ing a load chain or cable that is attached at one end to a stabilized work piece to be shaped and at an opposite nma n odrrH de on at he mnmcm uan a: m w m h y-m m m yd m 86 av hh W m 6 l P va F 8 n t m mm 8 .mm u& .m e w c m-Dec a l Y k r f mgamwp D A m k 6 h te T m m h w m hmm.we p h m h uunwu C e Wf fin n f flflm e c m m m 1 f m m WW 0 oi m. m wwm emasem XXXXJXXX s5 oowmmwwm HHHHDHH 2222 222 7777 777 m mm "m m Tm m o m m menk k Ba m .m nfl cmh cHswTBcM 7 7094 67671677 99999999 HHHHHHHH 932 .25.25 0795&46 2655 968 064 5 -07 46092 37 .3 333- 333 2 Sheets-Sheet 2 FORCE UNIT FOR METAL WORKING BACKGROUND OF THE INVENTION 1. Field of the Invention This invention generally relates to devices that may be employed to apply a pulling force to a work piece to be shaped or molded. More specifically, the present invention concerns a force unit that serves to develop pulling forces which are typically employed to bend metal work pieces such as portions of a damaged automobile to be restored to an original configuration.

2. Description of the Prior Art Ordinarily, the repair and/or restoration of damaged automobile bodies involves the application of physical force to deformed portions of the body or frame. Such physical force may be in the form of a pushing force such as may be applied by using a hammer or the like. More typically, however, devices employed in the repair of automobiles exert a pulling force which is applied to one or more selected points of a damaged work piece. The desired bending or shaping is generally accomplished by securing the automobile part in a fixed position relative to the pulling force.

Most of the prior art equipment that is designated to develop such pulling forces is bulky and awkward to use. As a consequence, the repair of automobile bodies is a time consuming and cumbersome process. Exemplary of the prior art equipment in the unit disclosed in the U.S. Pat. to Smith, No. 3,149,660, issued on Sept. 22, 1964, which unit is intended to be situated beneath an automobile and secured thereto at one or more pulling points and at least one retention point. When in operation, physical forces used to accomplish a desired bending are confined to the unit. Otherwise stated, the unit serves to develop both the desired action forces and the necessary reaction forces.

Devices having a design typified by the Smith unit have been found to have several attendant disadvantages. Firstly, the shear size of the unit makes the positioning thereof an awkward task and requires that a fairly large work area be available. Secondly, the use of more than one of the units to provide the oftentimes necessary multiple pulls of different force and/or travel is very inconvenient due to the need to avoid crossing the elongate platform included in a unit. Additionally, because the unit is intended tto provide both the action and reaction forces, the structure must have extreme strength to avoid self-destruction by the ordinary forces involved. Conventionally, these forces may range as high as l tons. Needless to say, the requirement for such extreme strength may involve the use of additional amounts of material, which use would contribute additional weight to the unit and may consequently increase manufacturing costs.

Accordingly, it is the intention of the present invention to provide a force unit that is readily potable, that is capable of being easily used in combination with other units, and which is not subject to self-destructive forces as are many prior art devices.

SUMMARY OF THE INVENTION Briefly described, the present invention involves a cured at one end to an appropriate support. A power member is adapted to be vertically extended or retracted by being attached to the piston of the ram. Pulling forces are applied to a work piece by a load chain or cable that is secured to the work piece and to the force unit at the respective ends thereof. A fulcrum pulley, which is secured to either the ram or a support post serves to feed the line from the work piece to the power member. An anchor is provided to restrain movement of the force unit in the direction of the work piece. The anchor and the fulcrum pulley are horizontally positioned with respect to each other such that resultant forces created during the operation of the force unit are substantially directed along the longitudinal axis of the ram. 7

The many attendant advantages of this invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description which is to be considered in connection with the accompanying drawings wherein like reference symbols designate like parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS tive view of a flat base employable with the force unit,

force unit that is readily employable to develop pulling forces useful in the repair and/or restoration of metal work pieces such as motor vehicle bodies and frames.

More particularly, the subject force unit includes a hydraulically operated ram having a sleeve that is sein accordance with the present invention.

FIG. 4 is an isometric diagram illustrating perspective view of an alternate base employable with the present invention.

FIG. 5 is an isometric diagram illustrating a perspective view of an alternate power member usable with the present invention.

FIG. 6 is a schematic diagram illustrating a partially fragmented side view of a force unit equipped with the alternate power member shown in FIG. 5 and adapted to have a removable collar for enabling secondary pulls to be made.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2 of the drawings, a force unit, in accordance with the present invention, essentially includes a hydraulically operated ram 12, a power member 14, a fulcrum pulley l6, and an anchor member 18.

The hydraulically operated ram 12 serves as the source of the desired pulling forces. A suitable ram includes an outer cylindrical sleeve 22 and an extensible or telescoping piston 24. The cylindrical sleeve 22 should be adapted to be securely mounted at a mounting end 26 to a supporting member, such as a base member 20. An input port 28, to which an appropriate source of power may be attached, is appropriately mounted on the sleeve 22 and serves to communicate with a hydraulic chamber formed by the sleeve 22. Any of the conventional sources of hydraulic power, such as a pressurized fluid container, may be employed to power the ram 12 and cause the piston 24 to be extended. A suitable fluid valve (not shown), of a type well known in the prior art, may be employed to control the application of pressurized fluid to the ram 12 through the input port 28. An exemplary ram that is suitable for use with the present invention is commercially available as Model RC] 59, manufactured by the Blackhawk Manufacturing Company.

The power member 14 serves to forcibly retract a load chain 30, by being urged upward by movement of the piston 24. The power member 14 may include a U- shaped yoke 32 having a pair of arms 34 and 36 and a cylindrical body portion 38. The body portion 38 is adapted to be secured to an end of the piston 24. Screw threads cut about the inner surface of the body portion 38 and matching a set of screw threads cut about the outer surface of the piston 24, at the end thereof, may be used to secure the yoke 32 to the ram 12.

A sprocket wheel 40 is rotatably mounted between the pair of arms 34 snd 36. A centrally located aperture through which an axle or pin 41 is extended may be employed to mount the wheel 40 on the yoke 32. As illustrated, the periphery of the sprocket wheel 40 is shaped to have a series of alternating flat portions 42 and pointed portions 44. The flat portions 42 are adapted to accommodate a link of the chain 30 when laid flat against the periphery of the wheel 40. The pointed portions 44 are adapted to extend between alternate links of the chain 30 so as to engage the chain 30 as the power member 14 is forced upward by extension of the piston 24. As shown in FIG. 2, each of the pointed portions 44 are slotted to accommodate the edge of alternate links of the load chain 30.

The fulcrum pulley 16 serves to redirect and feed the load chain 30 from a work piece towards the power member 14 as indicated by the arrow 48. The fulcrum pulley also includes a yoke formed by a pair of

arms

50 and 52 and a portion of an O-shaped bracket 54. A sprocket wheel 56, that may be identical in design to the sprocket wheel 40, is rotatably mounted between the

arms

50 and 52 which extend from the O-shaped bracket 54. Each of the

arms

50 and 52 may be shaped and sized to extend beyond the periphery of the sprocket wheel 56 for the purpose of guiding the load chain 30 onto the sprockets of the wheel 56 as the chain 30 is retracted in the direction indicated by the arrow 48. A leaf spring 58 is secured to the bracket 54 between the

arms

50 and 52 and serves to bias the individual links of the load chain 30 against the sprocket wheel 56 to prevent disengagement.

The O-shaped bracket 54 is sized to be fit about the cylindrical sleeve 22 of the ram 12 or about a support post 60 (FIG. 3), which is sized to have an outer diameter equal to the outer diameter of the sleeve 22 and which may be employed to elevate the ram 12 and the elements attached thereto. The support post 60 may be adapted to be secured to the cylindrical sleeve 22 and to the base member 20 in any conventional manner such as by having the respective elements to be joined properly sized and threaded to allow a threaded coupling of the type well known to any person of ordinary skill in the art. For the alternative, any other well known mechanical technique may be used. The O- shaped bracket 54 is adapted to have a gap (not shown), between the

arms

50 and 52, to enable the inner diameter of the bracket 54 to be reduced, by rotation of a threaded tightening bolt 62, for the purpose of clamping the fulcrum pulley 16 in a desired vertical position. It has been found that clamping the fulcrum pulley 16 in place effectively draws the

arms

50 and 52 together. However, such slight inward movement of the

arms

50 and 52 does not affect operation of the fulcrum pulley 16 when the bracket 54, the distance between the

arms

50 and 52, and the thickness of the sprocket wheel 56, are appropriately sized.

The bracket 54 is designed to have a vertically situated flange 64 extending from an outer surface of the bracket 54 at a position diametrically opposite the

arms

50 and 52. The anchor member 18 is appropriately secured to the flange and serves to restrain the force unit from movement in the direction of the work piece. This may be accomplished by coupling opposite ends of an anchor chain or cable to the anchor member 18 and to a relatively immovable body such as the floor of a work area.

In operation it is ordinarily desirable to attach the force unit to an appropriate support, such as a base plate, for purposes of maintaining the unit in a vertical position. Referring to FIG. 3, an acceptable base plate 66 may have a flat configuration. An attaching member 68, having an appropriate configuration, may be centrally located on the base plate 66.

As shown, a support post 60 may be attached to the base plate 66 for the purpose of elevating a force unit. The vertical support post 60 may be formed as a single cylindrical element of any desired length. In the ordinary use of a force unit for developing pulling forces for the repair of automobiles, a variety of lengths may be required to accommodate an assortment of different pull directions, Accordingly, a number of cylindrical elements may be serially connected to provide a support post 60 of desired height.

An auxiliary anchor 70 may be fastened to the base plate 66 by an appropriate ring 72 for the purpose of providing an additional restraining force for the force unit whenever necessary. As in the case with the anchor member 18, the anchor 70 may be secured to an immovable independent body by an anchor chain 74 to provide the desired restraining force. It has been found that the additional restraining force provided by the anchor 70 may be useful whenever the force unit is employed to make a downward pull, i.e., the load chain 30 (FIG. 1), is drawn away from a work piece in a downward direction.

As an alternative to using the flat base plate 66, a rail 76, as illustrated by FIG. 4, may be employed. The ram 12 may again be either directly secured to the rail 76 or through a support post of desired length. A hole 78, or a suitable attaching member, may be included for this purpose when a rail 76 is used. It may in some instances be desirable to anchor the force unit to the rail 76 instead of to an independent body. In such a case, an anchor chain 80, or the like, may be used to secure the force unit to the rail 76 by being fastened to a ring or loop 82 which may be provided for this purpose. It is to be noted that the use of the rail 76 enables the force unit to be employed in the fashion of conventional units wherein the rail 76 is also attached to the work piece. A loop 84 at the end 86 of the rail 76 is provided for such conventional attachment.

It is to be understood that as a further alternative to employing either the flat base 66 or the rail 76, the ram 12 of a force unit may be simply retained in a hole that has been suitably placed in the floor of a work shop.

Considering now the operation of a force unit, with reference to FIGS. 1 and 2, a load chain 30 is secured at one end thereof to a work piece, such as a portion of a damaged automobile. After the load chain 30 is engaged with the sprockets of the

wheels

56 and 40 of the fulcrum pulley l6 and the power member 14, respectively, the opposite end 88 of the load chain 30 may be secured to a forked member 90 having a pair of fingers through which the load chain 30 is inserted and retained. Any other suitable means of securing the end 88 of the load chain 30 to the force unit may be employed. For example, the loop 72 on the flat base 66 (FIG. 3) may be employed for this purpose. After the force unit has been anchored, application of pressurized fluid to the ram 12 through the input port 28 will then cause the piston 24 to be moved in an upward direction as indicated by the arrow 92. Such movement of the piston 24 will force the power member 14 upwards and thereby retract the load chain 30 to develop the desired pulling force. It is to be noted that the axis of the load chain 30, at the fulcrum pulley l6, and the connection point 93 of the anchor member 18 are aligned along a horizontal line. Consequently, resultant forces will be generally directed along the axis of the ram 12 and of any support post 60 that may be used. It has been found that when the load chain 30 is making a horizontal pull, only nominal resultant forces are developed. However, when an upward pull is being made, considerable resultant forces are directed downward through the axis of the ram 12. These forces are naturally directed downward towards a supporting surface such as a floor. A downward pull causes upwardly directed resultant forces to be developed.

It has been found that up to 5 tons of pulling force can be developed by the force unit, illustrated by FIGS. 1 and 2, when a ram 12 rated at tons force is employed.

In some instances, it maybe desirable to utilize the full 10 tons of force available. An alternate power member provided for this purpose, is illustrated by FIGS. 5 and 6. As shown, an alternate power member 94 may be cylindrical and have alower end 96 that is adapted to be attached to the piston 24 of the ram 12. The upper end 98 is adapted to have a slot 100 having a width and depth intended to accommodate a chain link 102, at the end of the load chain 30, as shown. A suspended chain link 104 will serve to retain the chain 30 in the slot 100 as the power member 94 is moved in an upward direction as indicated by the arrow 105. When employed, the power member 94 will serve to move the load chain 30 for a distance exactly equal to the distance through which the piston 24 is moved. By comparison, employment of the power member 14 (FIG. 1) will cause retraction of a length, of the load chain 30, equal to twice the distance moved by the piston 24.

As shown in FIG. 6, a removable collar 106 may be attached to the fulcrum pulley 16 with a pin 108. The pin 108 may also serve as the axle mounting the sprocket wheel 56 between the

arms

50 and 52 or may be an independent member. When the pin 1'08 is an independent member, the axle for the sprocket wheel 56 should have an axial bore to accommodate the pin 108. The collar 106 may serve to conveniently enable secondary pulls to be made with a second load chain 110 that is appropriately powered, such as by a block and tackle. The benefit of using th collar is that the pulling 6s forces may be generally directed through a common point on a force unit.

It should be noted that such secondary pulls normally involve the application of substantially lesser force relative to the primary pull. Consequently, a secondary pull will not upset the force balance of a force unit.

It may now be appreciated that a readily portable and easily employable force unit has been provided by the present invention, which force unit is not subject to extreme self-contained forces that may cause the destruction of a unit if compensating structural strength is not provided.

While a preferred embodiment of the present invention has been described hereinabove, it is intended that all matter contained in the above description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense and that all modifications, constructions and arrangements which fall within the scope and spirit of the invention may be made.

What is claimed is:

l. A force unit for applying a pulling force to a work piece through a flexible cable attached thereto, said force unit comprising:

a hydraulically operated ram including a cylindrical sleeve and an extensible piston, said ram being ver- ,tically positioned to enable said piston to be extended upwardly along an essentially vertical axis;

a power-member operatively connected to said piston to developsaid pulling force on said pulling chain by extension of said piston;

a fulcrum pulley secured to said cylindrical sleeve of said ram at a selected position along said vertical axis for directing said flexible cable from said work piece to said power member;

a support post having an elongate cylindrical configuration, said support post serving to elevate said ram, said fulcrum pulley being adapted to be secured at selected positions along said support post;

anchor means for restraining said force unit from movement in the direction of said work piece, said anchor means being connected to a stationary body independent of said work piece; and

support means for maintaining said ram in a vertical position, said support means being independent of any contact or connection with said work piece other than through said flexible cable.

2. The apparatus defined by claim 1 wherein said power member includes:

a yoke having a body portion and a pair of parallel arms extending from said body portion, said body portion being adapted for attachment to said extensible piston; and

a sprocket wheel rotatably mounted between said pair of parallel arms.

3. The apparatus defined by claim 2 further including means positioned on said ram for securing an end of said flexible cable to said force unit.

4. The apparatus defined by claim 1 wherein said power member includes a cylindrical element having a first end adapted for attachment to said extensible piston and a second end having a longitudinal slot for receiving an end of said flexible cable.

5. The apparatus defined by claim 1 wherein said fulcrum pulley includes:

a yoke having a pair of arms;

a sprocket wheel rotatably mounted between said pair of arms;

bracket means for securing said yoke at a selected position along said cylindrical sleeve; and

bias means for urging engagement of said flexible cable with said sprocket wheel, said bias means being secured to said yoke and extending between said pair of arms.

6. The apparatus defined by claim wherein said anchor means includes a coupling device attached to said bracket means at a point diametrically opposite said pair of arms and situated along an essentially horizontal line extending tangentially to a lowermost peripheral point of said sprocket wheel.

7. The apparatus defined by claim 1 wherein said support means comprises a flat plate having a centrally located mounting means for receiving said support post and ram.

8. The apparatus defined by claim 7 wherein said flat plate further includes means for securing said support means to an immovable independent body.

9. The apparatus defined by claim 1 wherein aid support means includes an elongate member having: 7

means for receiving said support post and ram, and

means situated at one end of said elongate member for enabling an anchor member to be coupled to said support means.

10. The apparatus defined by claim 1 wherein said power member includes:

a power yoke having a body portion and a pair of parallel arms extending from said body portion, said body portion being adapted for attachment to said extensible piston; and

a power sprocket wheel rotatably mounted between said pair of parallel arms included on said power yoke.

l l. The apparatus defined by claim 10 further including means positioned on said ram for securing an end of said flexible cable to said force unit.

12. The apparatus defined by claim 6 wherein said power member includes a cylindrical element having a first end adapted for attachment to said extensible piston and a second end having a longitudinal slot for receiving an end of said flexible cable.

13. The apparatus defined by claim 11 wherein said support means comprises a flat plate having a centrally located mounting means for receiving said support post and ram.

14. The apparatus defined by claim 13 wherein said flat plate further includes means for securing said support means to an immovable independent body.

15. The apparatus defined by claim 11 wherein said support means includes an elongate member having:

means for receiving said ram, and

16. A force unit for transmitting a pulling force to a work piece via a pulling chain, the force unit comprismg:

a hydraulically operated ram having an extensible member and a stationary member forming two ends of the ram, extension of the extensible member operating to separate said two ends along a longitudinal axis of the ram;

a power member secured to said extensible member to be moved and thereby apply a pulling force to said work piece via said pulling chain in response to extension of the extensible member;

a base for supporting the ram in a substantially vertical position atop a supporting surface, said base being operatively connected to said stationary member and aligned along said longitudinal axis, said base being independent of any contact or connection with the work piece other than via the pulling chain;

a cylindrical support post for elevating said ram by being interposed between, and connected, to said base and said stationary member of said ram;

a fulcrum pulley secured to said stationary member of said ram for directing the pulling chain from the work piece to the power member; and

anchor means for anchoring said force unit to said supporting surface to substantially restrain movement of said force unit towards said work piece.

17. The force unit defined by claim 16, said fulcrum pulley including:

a sprocket wheel; and

yoke means for securing said sprocket wheel to said force unit along said longitudinal axis, said yoke means including a pair of arms between which said sprocket wheel is rotatably mounted, the pulling chain engaging said sprocket wheel to direct said chain from the work piece to the power member.

18. The force unit defined by claim 17, said fulcrum pulley further including means for urging engagement of said chain with said sprocket wheel.

19. The force unit defined by claim 17, said anchor means including a coupling device attached to said yoke means at a point along said longitudinal axis and opposite said pair of arms, said anchor means adapted to receive an anchor chain for connection to said sup porting surface.

20. The force unit defined by claim 16 further including means positioned on said force unit along said longitudinal axis for securing an end of said pulling chain, said power member including:

a power yoke having a body portion and a pair of upstanding parallel arms extending therefrom, said body portion being adapted for attachment to said extensible member of said ram; and

a power sprocket wheel rotatably mounted between said pair of upstanding arms for receiving said power chain.

21. A force unit for applying a pulling force to a work piece through a flexible cable attached thereto, said force unit comprising:

a hydraulically operated ram including a cylindrical sleeve and an extensible piston, said piston being adapted to be housed by said sleeve and extended therefrom along a longitudinal axis mutual to said sleeve and said piston; power pulley operatively connected to an end of said piston to be moved by extension of said piston from said sleeve;

a fulcrum pulley secured to an exterior surface of said sleeve for receiving and directing said flexible cable from said work piece towards said power pulley, said extension of said piston and movement of said power pulley causing said flexible cable to exert a pulling force on a work piece attached to said flexible cable;

cable securing means secured to the exterior surface of said sleeve for securing an end of said flexible cable to the force unit such that resultant force on the power pulley resulting from said pulling force is directed along the longitudinal axis of the ram; ram to receive said flexible cable, said power pulley inanchor means for restraining said force unit from eluding:

movement in the direction of said work piece, said a yoke having a body portion and a pair of parallel anchor means being a flexible member operatively arms extending in a direction away from said end connected between said sleeve and a stationary of said piston and parallel to said longitudinal axis body that is independent of said work piece; and of said ram, said body portion attached to said end support means for supporting said ram in an upright of said piston; and

position, said support means being independent of a sprocket wheel rotatably mounted between said any contact or connection with said work piece pair of parallel arms, said sprocket wheel engaging other than through said flexible cable. said flexible cable to produce said pulling force by 22. The force unit defined by claim 21, said power the extension of said piston.

pulley being aligned along said longitudinal axis of said

Claims

1. A force unit for applying a pulling force to a work piece through a flexible cable attached thereto, said force unit comprising: a hydraulically operated ram including a cylindrical sleeve and an extensible piston, said ram being vertically positioned to enable said piston to be extended upwardly along an essentially vertical axis; a power member operatively connected to said piston to develop said pulling force on said pulling chain by extension of said piston; a fulcrum pulley secured to said cylindrical sleeve of said ram at a selected position along said vertical axis for directing said flexible cable from said work piece to said power member; a suppoRt post having an elongate cylindrical configuration, said support post serving to elevate said ram, said fulcrum pulley being adapted to be secured at selected positions along said support post; anchor means for restraining said force unit from movement in the direction of said work piece, said anchor means being connected to a stationary body independent of said work piece; and support means for maintaining said ram in a vertical position, said support means being independent of any contact or connection with said work piece other than through said flexible cable.

2. The apparatus defined by claim 1 wherein said power member includes: a yoke having a body portion and a pair of parallel arms extending from said body portion, said body portion being adapted for attachment to said extensible piston; and a sprocket wheel rotatably mounted between said pair of parallel arms.

5. The apparatus defined by claim 1 wherein said fulcrum pulley includes: a yoke having a pair of arms; a sprocket wheel rotatably mounted between said pair of arms; bracket means for securing said yoke at a selected position along said cylindrical sleeve; and bias means for urging engagement of said flexible cable with said sprocket wheel, said bias means being secured to said yoke and extending between said pair of arms.

6. The apparatus defined by claim 5 wherein said anchor means includes a coupling device attached to said bracket means at a point diametrically opposite said pair of arms and situated along an essentially horizontal line extending tangentially to a lowermost peripheral point of said sprocket wheel.

9. The apparatus defined by claim 1 wherein aid support means includes an elongate member having: means for receiving said support post and ram, and means situated at one end of said elongate member for enabling an anchor member to be coupled to said support means.

10. The apparatus defined by claim 1 wherein said power member includes: a power yoke having a body portion and a pair of parallel arms extending from said body portion, said body portion being adapted for attachment to said extensible piston; and a power sprocket wheel rotatably mounted between said pair of parallel arms included on said power yoke.

11. The apparatus defined by claim 10 further including means positioned on said ram for securing an end of said flexible cable to said force unit.

15. The apparatus defined by claim 11 wherein said support means includes an elongate member having: means for receiving said ram, and means situated at one end of said elongate member for enabling an anchor member to be coupled to said support means.

16. A force uniT for transmitting a pulling force to a work piece via a pulling chain, the force unit comprising: a hydraulically operated ram having an extensible member and a stationary member forming two ends of the ram, extension of the extensible member operating to separate said two ends along a longitudinal axis of the ram; a power member secured to said extensible member to be moved and thereby apply a pulling force to said work piece via said pulling chain in response to extension of the extensible member; a base for supporting the ram in a substantially vertical position atop a supporting surface, said base being operatively connected to said stationary member and aligned along said longitudinal axis, said base being independent of any contact or connection with the work piece other than via the pulling chain; a cylindrical support post for elevating said ram by being interposed between, and connected, to said base and said stationary member of said ram; a fulcrum pulley secured to said stationary member of said ram for directing the pulling chain from the work piece to the power member; and anchor means for anchoring said force unit to said supporting surface to substantially restrain movement of said force unit towards said work piece.

17. The force unit defined by claim 16, said fulcrum pulley including: a sprocket wheel; and yoke means for securing said sprocket wheel to said force unit along said longitudinal axis, said yoke means including a pair of arms between which said sprocket wheel is rotatably mounted, the pulling chain engaging said sprocket wheel to direct said chain from the work piece to the power member.

19. The force unit defined by claim 17, said anchor means including a coupling device attached to said yoke means at a point along said longitudinal axis and opposite said pair of arms, said anchor means adapted to receive an anchor chain for connection to said supporting surface.

20. The force unit defined by claim 16 further including means positioned on said force unit along said longitudinal axis for securing an end of said pulling chain, said power member including: a power yoke having a body portion and a pair of upstanding parallel arms extending therefrom, said body portion being adapted for attachment to said extensible member of said ram; and a power sprocket wheel rotatably mounted between said pair of upstanding arms for receiving said power chain.

21. A force unit for applying a pulling force to a work piece through a flexible cable attached thereto, said force unit comprising: a hydraulically operated ram including a cylindrical sleeve and an extensible piston, said piston being adapted to be housed by said sleeve and extended therefrom along a longitudinal axis mutual to said sleeve and said piston; a power pulley operatively connected to an end of said piston to be moved by extension of said piston from said sleeve; a fulcrum pulley secured to an exterior surface of said sleeve for receiving and directing said flexible cable from said work piece towards said power pulley, said extension of said piston and movement of said power pulley causing said flexible cable to exert a pulling force on a work piece attached to said flexible cable; cable securing means secured to the exterior surface of said sleeve for securing an end of said flexible cable to the force unit such that resultant force on the power pulley resulting from said pulling force is directed along the longitudinal axis of the ram; anchor means for restraining said force unit from movement in the direction of said work piece, said anchor means being a flexible member operatively connected between said sleeve and a stationary body that is independent of said work piece; and support means for supporting said ram in an upright position, said suppoRt means being independent of any contact or connection with said work piece other than through said flexible cable.

22. The force unit defined by claim 21, said power pulley being aligned along said longitudinal axis of said ram to receive said flexible cable, said power pulley including: a yoke having a body portion and a pair of parallel arms extending in a direction away from said end of said piston and parallel to said longitudinal axis of said ram, said body portion attached to said end of said piston; and a sprocket wheel rotatably mounted between said pair of parallel arms, said sprocket wheel engaging said flexible cable to produce said pulling force by the extension of said piston.