A pushing tool adapted to grip a joist and exert pushing force on a board located immediately above the joist. The tool comprises a block having a threaded bore, a screw which threads into the bore, and a clamp fixed to the block. Four arms forming dual parallelogram linkages are pivotally mounted to the block and to the jaws of the clamp such that when the block is drawn along the screw by screw action, the arms fold in the direction of parallel orientation relative to the screw. This draws the jaws of the clamp towards one another such that they engage and grip the joist. The jaws of the clamp have cleats preventing the jaws from slipping ineffectually along the joist. Continued rotation of the screw advances the screw against the board located above the joist. Pitch of the threading of the bore and the screw enable great pressure to be exerted on the board when the screw is turned by a wrench.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to pushing tools, and more particularly to a
 tool which automatically clamps itself to one environmental object while
 simultaneously exerts a pushing force on a second environmental object. An
 illustrative application is in the field of carpentry. The tool anchors
 itself to, for example, a joist, while exerting a pushing force on a board
 which is to be nailed to that joist. Fields other than carpentry can
 benefit from the invention. Wherever there is an object requiring force to
 move beyond that which a person can reasonably exert, and that object is
 in close proximity to a fixed point of anchorage, the present invention
 can profitably be brought to bear on the object being moved.
 2. Description of the Prior Art
 Professional carpenters, home owners, hobbyists, and others engaging in
 carpentry from time to time encounter situations wherein rough and
 semi-finished lumber pieces such as planks and boards are warped to the
 point that they are barely if at all acceptable for being installed in a
 construction project. It is usually desired that buildings and other
 projects have straight, flat surfaces and perpendicular angles between
 boards. Warped boards and planks degrade suitability of the completed
 project. However, economics dictate that commercial supplies of rough and
 semi-finished lumber usually include warped pieces. The craftsman must
 deal with less than ideal lumber as best he or she can.
 Lumber for constructing buildings and related structures such as exterior
 decks, porches, garages, and the like must be sufficiently strong to bear
 considerable weight. Therefore, lumber is too strong for a carpenter or
 other craftsman to bend into an acceptable configuration by hand. A manual
 tool to perform such bending is desirable when poor quality lumber is to
 be incorporated into a structure. The prior art has proposed jacks and
 similar devices for exerting pushing forces considerably greater than
 those which can be developed by human strength.
 An example is seen in U.S. Pat. No. 5,087,019, issued to Dennis J. Peabody
 et al. on Feb. 11, 1992. Peabody et al. illustrates a spreader which can
 expand to exert a pushing force, but in which the device is arranged and
 acts linearly. That is, the point of anchorage is located colinearly with
 the axis of the device. This requires that the object receiving the
 pushing force be moved away from the point of anchorage. In the field of
 carpentry, it is frequently the case that a board being nailed into the
 structure being built is not suitably located for a linearly spreader to
 be effective. In contrast to linear spreaders, the present invention has
 an automatic clamp which grips a board as it expands to exert force on the
 board receiving force. The clamp is able to grasp a board not colinearly
 located with respect to the direction of expansion.
 U.S. Pat. No. 5,501,754, issued to Hiroaki Hiraguri on Mar. 26, 1996, shows
 a device for lifting floor panels. The device of Hiraguri is essentially a
 linear spreader having structure for engaging floor panels. The engaging
 structure is located at the point receiving the pushing force. By
 contrast, the present invention incorporates a clamp which can grasp a
 supporting object located out of line with the direction of expansion.
 U.S. Pat. No. 5,875,606, issued to Lars Dean Jensen on Mar. 2, 1999,
 describes a wall jack which expands between two opposing wall surfaces
 when a central screw member is turned. This device lacks a clamp found in
 the present invention, and cannot grasp one structural member from two
 sides, as can the device of the present invention.
 None of the above inventions and patents, taken either singly or in
 combination, is seen to describe the instant invention as claimed.
 SUMMARY OF THE INVENTION
 The present invention provides a device which grasps one structural member
 of a building, and exerts a pushing force on another member of the
 building. The novel device includes a clamp for clamping and has a
 threaded rod anchored to the clamp for exerting the pushing force. The
 axis of rotation of the threaded rod is located relative to the clamp such
 that the clamp grasps a joist while enabling the rod to press against a
 cross member laid over the joist. The threaded rod first tightens the
 clamp onto the joist, then exerts pushing force against the cross member.
 The invention is typically employed to straighten flooring and decking
 lumber such as planks and boards being nailed to joists. The flooring or
 decking lumber is oriented such that it is perpendicular to and above the
 joist. This requires a device which can anchor to the joist while exerting
 a pushing force parallel to but above the joist. The self-clamping pusher
 of the present invention includes a base block having a threaded bore
 through which is passed an elongated threaded rod. Clamp jaws are
 connected to the base block by arms acting in scissors fashion. The clamp
 jaws close over the joist responsive to rotation of the threaded rod as
 the base block rides along the threaded rod. When the clamp jaws bear
 against the joist such that no further closing motion is possible, the
 base block can no longer ride along the rod. The clamp is secured to the
 joist and prevented from sliding ineffectually along the joist by cleats
 formed in the jaws which cleats penetrate the surfaces of the joist.
 Instead, continued turning of the rod urges the rod to move helically
 through the base block. Alternatively stated, at first, the threaded rod
 does not move axially after its forward end contacts the board or plank.
 Instead, the base block moves relative to the joist and board or plank
 until the clamp has fully squeezed the joist. After this, the clamp
 prevents the base block from moving, and the rod is forced to move
 relative to the board or plank. The forward end of the rod thus advances,
 imposing pushing force against the board or plank. Thread pitch
 characteristics give the rod leverage such that force developed by the
 device will force most boards and planks to yield to this force, and
 thereby straighten. In summary, the threaded rod both operates the clamp
 and also subsequently brings force to bear against a board or plank being
 straightened.
 Accordingly, it is a principal object of the invention to provide a device
 capable of anchoring to a joist and also exerting a pushing force on
 lumber located above the joist.
 It is another object of the invention that the device operate by rotating a
 single member.
 It is a further object of the invention that clamping and pushing be
 performed sequentially such that rotation of one member first engage the
 joist and subsequently apply pressure to the lumber located above the
 joist.
 Still another object of the invention is to assure secure grip of the
 joist.
 It is an object of the invention to provide improved elements and
 arrangements thereof in an apparatus for the purposes described which is
 inexpensive, dependable and fully effective in accomplishing its intended
 purposes.
 These and other objects of the present invention will become readily
 apparent upon further review of the following specification and drawings.
 dr
 BRIEF DESCRIPTION OF THE DRAWINGS
 Various other objects, features, and attendant advantages of the present
 invention will become more fully appreciated as the same becomes better
 understood when considered in conjunction with the accompanying drawings,
 in which like reference characters designate the same or similar parts
 throughout the several views, and wherein:
 FIG. 1 is an exaggerated, environmental top plan view of an embodiment of
 the invention shown in an initial position engaging a workpiece.
 FIG. 2 is an environmental top plan view similar to FIG. 1, but showing
 adjustment of the novel apparatus to apply force against the workpiece.
 FIG. 3 is a diagrammatic detail view of the embodiment of FIG. 1 showing
 range of motion of components shown at the center of FIG. 1, but which
 components are somewhat obscured in the view of FIG. 1.
 FIG. 4 is an environmental, end elevational view of the embodiment of FIG.
 1, shown partially in cross section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Turning now to FIG. 1 of the drawings, self-clamping pusher 10 is shown in
 an initial position it would typically assume as it is placed over an
 elongate supporting environmental element for anchorage. Pusher 10
 includes a base block 12 and an elongate projecting member held within and
 guided by base block 12 such that the projecting member is disposed to
 project linearly from base block 12 so that it can exert a pushing force
 against a second environmental element located in close proximity to the
 elongate environmental element.
 A principal application of the invention is that of straightening boards
 and planks being joined to a joist 2, and further description will proceed
 with this task in mind. A board or plank (hereinafter referred to
 representatively as board 4) is typically laid upon joist 2 for subsequent
 nailing thereto. The two ends of board 4 are nailed at their two ends (not
 shown) to other joists (not shown). Board 4 is curved, and the center of
 the curve or warpage is located over joist 2 after the ends of board 4 are
 nailed down. Therefore, for purposes of discussion, joist 2 is the
 elongate supporting environmental element and board 4 is the second
 environmental object receiving the pushing force.
 Base block 12 is a structural element which supports the projecting member,
 which in the preferred embodiment is a threaded rod or screw 14 and also a
 clamp which will be described hereinafter. Block 12 may be a solid block
 of metal drilled and tapped to have a threaded bore 16 which receives and
 guides screw 14 such that distal end 18 of screw 14 advances in the
 direction indicated by arrow 20 to apply force against board 4. Screw 14
 has a polygonal head 15 and threads 17 matingly compatible with threads of
 bore 16. Alternatively, block 12 may be formed from square metallic tubing
 and have two threaded nuts (neither tubing nor nuts are separately shown)
 welded thereto at either end, thereby accomplishing a similar result as
 that had by drilling and tapping a solid metal block. Conventional nuts
 are highly suitable for the invention since they typically have thread
 pitch having slope characteristics such that one revolution of screw 14
 advances screw 14 by a distance less than half of the diameter of screw
 14. This characteristic affords leverage such that, when combined with
 that of a wrench (not shown) which is placed over head 15 of screw 14 for
 rotating or driving screw 14, considerable force is brought to bear on
 board 4. Still other constructions of block 12 may be employed if desired.
 The clamp of the invention is fixed to base block 12 in a location out of
 alignment with the direction of projection of screw 14, or alternatively
 stated, in a location wherein the axis 13 (see FIG. 4) of screw 14 will
 not intersect elements of the clamp. The clamp has two opposed jaws 22, 24
 disposed to move towards one another into a clamped position (see FIG. 2),
 thereby clamping joist 2 therebetween. Jaw 22 is held by arms 26, 28 which
 are pivotally connected and secured thereto by pins 30, 32 which penetrate
 arms 26, 28. Arms 26, 28 are pivotally connected and secured to base block
 12 by pins 34, 36 which penetrate arms 26, 28 and block 12.
 Jaw 24 is secured by a similar arrangement which is essentially a mirror
 image of that of jaw 22. The arrangement of jaw 24 includes arms 38, 40
 and pins 42, 44, 46, 48. Pin 44 passes through a boss 50 projecting from
 block 12. The arrangement of pin 44 and boss 50 is representative of
 remaining pins 42, 46, 48.
 Block 12 acts in conjunction with arms 26, 28, 38, 40 and with pins 30, 32,
 34, 36, 42, 44, 46, 48 to serve in the capacity of an actuator disposed to
 move jaws 22, 24 towards one another to effect clamping action. Block 12
 and its threaded bore 16 act as an actuator causing screw 14 to project
 from block 12 when screw 14 is rotated. The embodiment of FIG. 1 is
 advantageous because both actuation functions are performed simultaneously
 by one group of components. That is, two separate actuators are not
 required.
 In operation, self-clamping pusher 10 is lowered onto joist 2 with jaws 22,
 24 spread apart as seen in FIGS. 1 and 4 sufficiently such that cleats 52,
 54 do not obstruct placement of pusher 10 into position. Pusher 10 is then
 manually held against joist 2 such that at least one cleat 52 or 54
 engages the side of joist 2. When screw 14 is turned such that its distal
 end 18 advances in the direction of arrow 20 (see FIG. 1), screw 14 will
 come to abut board 4. At this point, board 4 acts as a resisting element
 resisting advancing motion of screw 14. Free, unfettered advance of screw
 14 will then be arrested. Continued rotation of screw 14 will draw block
 12 rearwardly, or in a direction opposite that of arrow 20. Ineffectual
 rearward travel of block 12 is prevented by engagement of cleats 52, 54
 with joist 2. Arms 26, 28 and 38, 40 move in parallelogram fashion
 responsive to continued rotation of screw 14 when block 12 is immobilized
 by cleats 52, 54 and additional cleats, shown in FIG. 1 but not designated
 by reference numerals. Additional cleats are provided both for assuring
 frictional engagement of joist 2 by jaws 22, 24, and also for symmetrical
 and stable loading of jaws 22, 24 when they are called upon to close over
 joist 2 and to maintain position of block 12 relative to joist 2.
 Parallelogram movement of arms 26, 28 and 38, 40 is shown diagrammatically
 in FIG. 3. In the depiction of FIG. 3, the fully open or spread position
 of jaws 22, 24 is shown in solid lines. A relatively closed or clamped
 position is shown in broken lines. It will be seen that arms 26, 28 remain
 parallel to one another and similarly arms 38, 40 remain parallel to one
 another. Jaws 22, 24 swing into the relatively clamped position as screw
 14 is turned, as indicated by arrows 56, 58.
 In practice, however, and referring now to FIG. 2, block 12 moves
 progressively towards head 15 of screw 14 after screw 14 abuts board 4.
 Correspondingly, a relatively greater length of the threaded shaft of
 screw 14 is visible to the right of block 12 than is visible in FIG. 1.
 When jaws 22, 24 have closed fully over joist 2, as shown in FIG. 2,
 further rotation of screw 14 causes screw 14 to continue to advance in the
 direction of arrow 20 of FIG. 1, thereby exerting great pressure against
 board 4. In FIG. 1, board 4 is depicted as being considerably bowed or
 warped. Application of pressure under the conditions shown in FIG. 2 will
 eventually force board 4 to yield to screw 14, thereby assuming the
 straightened condition depicted in FIG. 2. This may require nailing
 opposed ends (not shown) of board 4 to other joists (not shown) before
 applying pressure.
 In summary, operation proceeds in three stages. In the first stage, before
 screw 14 has contacted board 4, rotation of screw 14 advances screw 14
 relative to joist 2. Upon contact of screw 14 with board 4, a second stage
 commences wherein continued rotation of screw 14 draws block 12 rearwardly
 relative to joist 2, assuming that the cleats engage joist 2. In the
 second stage, screw 14 rotates but does not move axially with respect to
 joist 2. When the clamp is fully closed, thereby preventing block 12 from
 moving rearwardly along joist 2, a third stage commences. In the third
 stage, further rotation of screw 14 causes screw 14 to advance once more,
 overcoming the resistance of board 4 and forcing board 4 to deflect under
 pressure exerted by screw 14. Board 4, once straightened, can then be
 nailed to joist 2. Self-clamping pusher 10 is removed by reversing
 rotation of screw 14, prying jaws 22, 24 free from joist 2 if necessary,
 and lifting pusher 10 from joist 2.
 The present invention is susceptible to variations and modifications which
 may be introduced thereto without departing from the inventive concept.
 The actuator functions may be separated if desired and provided by
 separate elements. Screw actuation may be replaced by a hydraulic system
 or systems, or by another mechanical or electrically powered scheme, if
 desired.
 Block 12 may be modified to be stably and symmetrically loaded when
 tightening screw 14. Illustratively, the various pins may pass through the
 entire height of block 12 such that each pin is supported at both ends
 within block 12. Corresponding measures may be taken with respect to the
 arms and clamp jaws. Boss 50 and the remaining bosses may be replaced by
 other structure (not shown) if desired.
 Head 15 of screw 14 could be configured other than as described, provided
 it is keyed to accept a driving tool in close cooperation for the purposes
 of driving or rotating screw 14. Illustratively, head 15 could have a
 polygonal socket or any arrangement which assures rotation when the
 driving tool engages screw 14 and applies torque thereto.
 The applications of the invention may be expanded from the example
 illustrated herein. The invention may find utility as a spreader in the
 field of rescue in the event of motor vehicle collisions, building
 collapse, and in still other fields.
 It is to be understood that the present invention is not limited to the
 embodiments described above, but encompasses any and all embodiments
 within the scope of the following claims.