US3704860A

US3704860A - Wedging and prying tool

Info

Publication number: US3704860A
Application number: US700512A
Authority: US
Inventors: John M Krapu
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-01-25
Filing date: 1968-01-25
Publication date: 1972-12-05
Anticipated expiration: 1989-12-05

Abstract

An apparatus for use a jack or pry tool with a U-shaped base member having a lifting bar or jaw disposed within the legs of the base. The bar is attached to a carriage which is moved by a ratchet actuated rack and pinion. The rack teeth are formed on a central post member which is attached perpendicular to the base and also serves as a guide means for the carriage.

Description

[451 Dec. 5, 1972 United States Patent Krapu r541 WEDGING AND PRYING TOOL 3,081,066 3/1963 Murawski...............................254/93 Primary Examiner-Othell M. Simpson Assistant Examiner-David R. Melton [22] Filed:

ABSTRACT An apparatus for use a jack or pry tool with a U U.S. 254/104 shaped base member having a lifting bar or jaw disposed within the legs of the base. The bar is atm we S m d Ld mm 11] Z OO 555 [ll tached to a carriage which is moved by a ratchet actuated rack and pinion. The rack teeth are formed on a central post member which is attached perpendicular [56] References Cited UNITED STATES PATENTS to the base and also serves as a guide means for the carriage.

2,668,569 2/1954 Fat 254/95 X 3,038,510 6/1962 Vorkoeper.......................254/104 X 5 Claims, 3 Drawing Figures I]. .ll

I'NVENTOR. JOAW 4/, 1664/ a B p 9 2 mu h Ea 6 J i951: H w %W@ PATENTEDuEc 5 i972 WEDGING AND PRYING TOOL This invention relates to a multi-purpose tool, that may serve carpenters, iron workers, electricians, as well as others, for use in reclaiming used lumber, nails, wire stretching and as an adjustable sleeper for shoring heavy building doors, or members, and more particularly to a tool having both a space operating, and mechanical advantage to that served by an conven-' tional crow-bar.

The invention residing in a jack that serves to provide a wedging tool when in a collapsed position, and as a pryingor load separating tool, when the jack is moved into a second position that superposes the first position.

The main object of my invention is to provide a jack actuated wedging and prying tool that may serve to both interpose and spana fixed and movable pair of releasably secured building members or the like, a distance sufficient to separate the members.

Another object of my invention is to provide a tool of the aforementioned characteristics that is adapted to withdraw a nail or a spike from a building member in a straight and uniform manner without marring the surface of the building member.

A further object of my invention is to provide a jack actuated wedging and prying tool that may be adapted for use in sustaining in an elevated position a vertically aligned building member from that of a transverse member.

A still further object of my invention is to provide a tool of this kind that is readily adaptable for tensioning barbed wire strands that maybe strung on fence posts.

Another important purpose of my invention is to provide a diminitive but powerful manually actuated tool that is adapted for use in a substantially limited working space.

Other objects and advantages of my invention reside in the details of construction and mode of operation as l have henceforth described and claimed, with reference being bad to the accompanying drawing wherein the several views thereof, form part hereof, and wherein like reference numerals are employed to designate similar components of construction, and in which:

FIG. 1 is an elevational view in perspective that substantially illustrates my invention.

FIG. 2 is a fragementary portion of FIG. 1 taken substantially on the line 4-4 thereof, in vertical section.

FIG. 3 is a second fragmentary portion of FIG. 1 taken substantially on the line 5--5 thereof, in vertical section.

Referring now in detail to the drawing, wherein I have illustrated a preferred embodiment of my invention, that is shown to embody a substantially flat and U- shaped base plate that is provided with forwardly tapered limb portions that constitute mole chisels II, II, a bight portion 12, having a centrally disposed rectangular slot 13, formed therethrough, and spaced equally from the opposite sides thereof there are provided a pair of

bores

14, 14, that may serve to detachably secure the base 10 onto either a planar surface, or a vertical surface, as by conventional means.

The base plate 10 serves to support a standard 15, that is provided with a rectangular cross section, having a reduced end portion- 18, that is adapted to be press fitted into the base slot 13, and further welded in secured relation therewith, the standard I5 is shown to included an integral rack I7 at the rearward face thereof, and a pair of opposed longitudinally disposed grooves that are provided in the side faces associated therewith, and which grooves constitute

guideways

16, 16, that serve to slidably secure a hollow frame onto the standard 15, and which frame constitutes a carriage 19, of box-like structure, having the rear wall 22 thereof spaced substantially from the rack 17, and serv-. ingas the means for slidably securing the carriage 19 with the standard 15, as'has been previously mentioned, and where by the endwise movement of the former in respect to the latter is obviated, there is for this purpose provided the integral

key members

23, 23,

that are disposed laterally and transversely with the respective inner faces of the. carriage

opposite side walls

21, 21, and which

key members

23, 23, are adapted to complement a frictional slidable fit with the

respective guideways

16, 16, as when the carriage 19 is adapted to gearingly ride the standard 15.

The carriage 19 further includes a depending nail clinching bifuricated member that constitutesa lifting bar 25 that is disposed in depending and lateral relation with the forward carriage wall 20, and so adapted that it will interpose the mole chisels II, II, as when the carriage 19 is disposed in a collapsed position in respect to the standard 15, and

furtherthe limbs

24, 24, of the lifting bar 25, are so shaped that they complement the forwardly tapered portions of the respective mole chisels II, II, thereby, the composite of both the mole chisels and the lifting bar, when disposed in interposed relation therewith may serve as the wedging tool of my invention, and which maybe readily forced within a crevice formed by a pair of secured and yieldable building members, as by a hammer blow applied upon the rearward or anvil side of the base plate 12, and serving as the means for spanning the building members in adjusted relation relative to each other, there is for this purpose provided in general, a pinion 40, shaft 42, spur gear 54, Y lever 59, plunger 60, and the ratchet mechanism35.

Referring best to FIG. 2 the pinion 40 is shown to be disposed in meshing relation with the rack 17 as when positioned adjacent the carriage rear wall 22 and in interposed relation with the

side walls

21, 21, thereof, and with reference being bad to both FIGS. 2 and 3, there is shown that the pinion 40 is provided with a keyhole 41 therethrough, that is adapted to slidably complement the keyed shaft portion 43 of the shaft 42, as when the keyed shaft portion 43 is passed selectively through the complementary keyholes 39, 39, that are provided co-axially in the

respective side walls

21, 21, of the carriage l9, and when the pinion 40 is disposed in surrounding and locking relation with the keyed shaft portion 43, it being apparent that the shaft 42 will be disposed in rotatable relation with the bores 38, 38, of the respective key-holes 39, 39, and with further reference to FIG. 3, there is shown that the extensible end portion 47 of the shaft 42 is provided with a second keyed shaft portion 49 that serves to slidably secure therewith the spur gear 54 that is disposed axially and inwardly the open ended annular housing 50, and serving to seal the spur gear 54 within the housing 50, there is provided in weldingly secured relation with the transverse peripheral surface of each rim thereof, a disc shaped closure wall 51. The

closure walls

51, 51, are

provided with co-axial keyholes 53, 53, respectively, that Complement the keyhole 55 provided in the spur gear 54 therethrough, and also the keyed shaft portion 49, whereby it being apparent that the spur gear 54 may be slidably mounted upon the shaft 42 and in slidable lock-in relation with the keyed shaft portion 49, as when the shaft 42 is passed through a selective side wall 51, of the housing 50, and in a similar manner as has been previously recited, the extensible end portion of the shaft 42 will be disposed in journaled relation with the bores 52, 52, of the respective keyholes 53, 53, as associated with the annular

housing side walls

51, 51, respectively.

In order to obviate the axial displacement of the shaft 42 in respect to both the carriage 19, and the annular housing 50 there is provided in slidable clamping relation therewith, a pair of collars 4s, and 56, each of which being adapted to complement slidably and selectively an

extensible end portion

44 or 47 of the shaft 42, and which collars 45 and 56, are brought to bear into contiguous relation with both the carriage l9 and the annular housing 50, in a manner whereby the interposed friction reducing washer 48 is slidably secured therebetween, as by the conventional

set screw fasteners

46, and 51, that are provided in screw threaded relation with both the collar 45 and 56, respectively, and in bearing relation with both the

extensible end portion

44, and 47, of the shaft 42, respectively.

Communicating with the interior of the annular housing 50 and extending laterally therefrom, there is provided an elongated open ended tubular member that constitutes a handle 59 of uniform diameter that is secured as what may be considered the, lower end thereof in telescopic relation with a complementary radial bore 58 provided in the housing 50 therethrough, and disposed in axially spaced relation and extensible therefrom, there is provided a rectangular shaft member that constitutes the plunger 60 that is adapted for automatic recall when alternately depressed inwardly the handle 59. The plunger 60 is shown to be provided with a V-shaped extremity that constitutes a clutch 61 that is adapted to slidably and fixedly engage with a selective pair of the spur gears 54 teeth, as when disposed in interposed relation therewith, when alternately depressed therein by a manually applied force rendered upon the opposite end of the plunger 60 that is surrounded by the thumb rest 69 as at 70, and which thumb rest 69 is fixedly secured with the plunger 60 by the conventional fastener 71 that is secured in transverse relation therewith, and serving to guide the plunger 60 in axial alignment with the spur gear 54 there is provided the collar 67 that is adapted to be press fitted telescopically in the upper end of the handle 59 by the reduced neck portion 68 thereof, and in order to recall the plunger 60 from the spur gear 54 as when the said force is removed from the thumb rest 69,, there is for this purpose provided a coil spring 64 that is formed helical in shape.

The coil spring 64 is adapted for both a complementary slidable fit upon the plunger 60 when disposed telescopically in the handle 59, and to interpose in abutting relation a pair of collars 62 and 65, whereas the collar 62 is secured in fixed relation with the inner side adjacent the lower end portion of the handle 59 by the conventional screw fasteners 63, and the collar 65 being in turn secured to the plunger 60 by the conventional transversing pin 66, it now being apparent that when the clutch 61 is released from the spur gear 54 that the handle 59 may be moved substantially in either a counter or clock-wise direction in respect thereto whereby the clutch 61 will be disposed adjacent a selective pair of teeth associated with the spur gear 54, and in order to advance the carriage 19 on the standard 15 through the medium of the said gearing, whereby the standard 15 will carry the carriage 19 in releasably secured relation therewith, which in turn will span the lifting bar 25 from the mole chisels II, II, there is for this purpose provided the ratchet assembly 35.

The ratchet assembly 35 in its entirety comprises an I open ended tubular barrel 27 of uniform'diameter having what may be considered the inner end portion thereof weldingly secured in telescopic relation with the bore 26 that is provided medially in the rear wall 22 of the carriage l9 therethrough, nd extending through the barrel 27 there is provided 'a pawl member 29 of circular cross section that is provided with an outwardly disposed finger gripping knob 36 that is secured in concentric relation with the outwardly disposed extensible end portion of the pawl 29, as by the conventional fastener 36a that transverses both the knob 36 and the pawl 29. The knob 36 further serves selectively as a latching member whereby the pawl 29 maybe releasably secured with the barrel 27 for restricting the rotatable movement of the former in respect to the latter, as when the V-shaped dog 37 that is radially and laterally disposed with the inner side face of the knob 36 is slidably disposed in the complementary groove 28 provided axially and radially in the outer end portion of the barrel 27, and which said combination correspond to positioning of the upwardly inclined transversing end portion of the pawl 29 that constitutes a planar cam surface 29a in abutting slidable relation with a transperposed tooth of the pinion 40 whereby the movement of the pinion 40 in a counter clockwise direction as when observed from the actuating end thereof is restricted by the aforementioned position of the pawl 29 in respect to-the pinion 40, and serving to resist resilently the outward movement of the pawl 29 in respect to the barrel 27 as when the pawl 29 is biased by the first said tooth of the pinion 40 when moved transversely and upwardly on the inclined face of the cam surface 29a whereby the pawl 29 will be adapted to ratchet automatically with a preceeding tooth of the pinion 40 when moved progressively in the last stated clockwise direction, there is for this purpose provided the coiled expansion spring 32 that is disposed both in telescopic relation with the bore of the barrel 27 and in surrounding relation with an intermediate portion of the pawl 29, and which spring 32 further interposes in abutting relation a pair of spaced collars 30 and 34a that are disposed inwardly the barrel 27 and in surrounding relation with the pawl 29, wherein the collar 30 is fixedly secured therewith by the transversely disposed fastener 31, and the collar 34a being f xedly secured to the inner-side wall of the barrel 27 by the pair of diametrically opposed screw threaded

fasteners

34,34, it now can be described as to how the carriage 19 may be advanced progressively on the standard and thereby span the lifting bar in selective adjusted relation with the mole chisels ll, Ii, whereby the action thereof provides the prying tool of my invention.

In the operation of theprying tool of my invention, as when the serving as a wedging device between a pair of releasably secured building members, as has been previously described; I move the handle 59 into an extreme left hand position as when the tool is observed from the actuating sidethereof, and by virtue of the clutching relation between the plunger 60 and the spur gear 54, I am thereby enabled to impart a rotatable motion on the pinion gear 40, in a manner whereby the pinion will meshingly engage and ride upwardly on a successive number of rack teeth, and correspondingly carry the carriage 19 therewith, as when the handle 59 is manually moved in a converse direction, and by virtue of the pawl 29 when disposed in ratched relation with the pinion 40, and when the handle 59 is disposed in fixed relation with the shaft 42, as when moved in the said right hand direction, it than being apparent by the repeated oscillator action applied on the handle 59 will serve to progress the carriage 19 on the standard 15, and thereby span the lifting bar 25 a selective distance from the mole chisels II, ll, whereby the building members will be influenced to part by the prying action of the tool, and further as the handle 59 is normally disengaged from the gearing of the tool, it therefore will not in turn react prematurely and possibly strike the operator if in the event the tool is accidentally collapsed when sustaining a load in an elevated position, by the swinging movement thereof.

From the aforegoing description, it will be observed that my invention provides a novel and improved wedging and prying device which if desired may be actuated to serve alternately as a tensioning and compressioning tool depending on certain required operations that may be remote from the building trades, and as the tool is actuated by a very short throw of the handle, it is then apparent that it may be used in a limited working space, wherein other similar devices would be hard to manipulate and sometimes prove to be useless. The invention also provides a means whereby nails may be extracted from wooden building members in both a uniform manner, and whereby injure to the wooden member by marring the surface thereof is obviated, and further the safety feature incorporated thereby will materially reduce the number of injuries, as has been known to me, to have occurred to journeymen when the use of prying tool is required during a certain operation. Further, the assemblage of the various parts recited possesses superior compactness and convience without in any way sacrificing simplicity. The structure which I have disclosed is merely given by way of example because in actual practice it attains the features of advantage enumerated as desirable in the description thereof, it will therefore be apparent that changes in details of construction, and in the combination and arrangement of certain parts may be resorted to without departing from either the spirit or scope thereof, as herein claimed.

lclaim:

1, The combination of a wedging and prying tool for use with releasably secured building members, comprising a flat U-shaped base having forwardly tapered limbs constituting mole chisels, agrectangular standard secured with said base and rising from a medial'portion of the web of said base, said standard including an integral rack disposed on the rearward face thereof adjacent the rearward side of said base, and a pair of diagonally disposed grooves each being provided in a respective side face of said standard, said grooves constituting guideways, said rack and said guides extending axially-the length of said standard, an open box-shaped frame constituting a carriage, said. carriage including a depending laterally disposed lifting bar, said bar being bifurcated and adapted to clinch the shank of a substantially driven nail, said carriage further including a a pair of rectangular integral key members, said key members adapted to slidably engage the said guideways, and said lifting bar adapted to interpose the said mole chisels, as when said carriage is disposed on saidstandard in collapsed relation in respect thereto, said lifting bar being further provided with forwardly tapered limbs complementary to the inclined plane of said mole chisels, thereby constituting a wedging tool, a shaft of circular cross section journaled extensible in the side walls of said carriage transversely and medially an opening afforded thereby at the rearward side of said standard, said shaft including a rectangular integral key disposed axially and radially therewith, and interposing said side walls, a pinion disposed in meshing relation with said rack, and in surrounding fixed relation with the keyed portion of said shaft, said shaft including a second and identical keyed portion disposed intermediate'one extensible end portion of said shaft, a spur gear disposed in surrounding fixed relation with the second keyed portion ofsaid shaft, a cylindrical housing disposed in axial surrounding relation with said spur gear, and adapted for journaled relation with said shaft at the opposite transverse sides of said spur gear, an elongated tubular member of circular cross section constituting a handle, said handle disposed in fixed radial relation with said housing, and in communication with the chamber thereof, said handle including a head member having a medial rectangular opening therethrough constituting a guideway, a shaft of rectangular cross section constituting a plunger said plunger adapted to complement slidably said guide-way and disposed extensible said handle, said plunger including a flat circular head member constituting a thumb rest, and a V-shaped lower extremity constituting a clutch member, said clutch member adapted to clutch with an axial groove of said spur gear when depressed therein by a manual force applied upon said thumb rest through the medium of said plunger, whereby said pinion may be moved rotatable by said handle in a direction for progressing upon a substantial number of successive teeth of said rack, whereby said lifting bar will be spanned from said mole chisels through the medium of said carriage thereby providing a prying tool, a flat washer disposed in surrounding relation with said shaft and interposing said carriage and said housing whereby the latter will be spaced from the former, adjustable clamping means, provided with the opposite terminal end portions of said shaft, whereby obviating the axial displacement of said shaft in respect to both the said pinion and said spur gear, recall means provided with said plunger and fixed with said handle whereby said handle may be oscillated on said shaft and thereby be moved to a substantially selective position in respect of said spur gear, a second plunger means provided with said carriage and adapted to ratched with the pinion teeth disposed diametrically from the pinion teeth that mesh with said rack, whereby said pinion will be adapted to progress successively on the teeth of said rack, and moving said carriage and said lifting bar correspondingly for selective adjustment on said standard, as when said handle is adapted to move said shaft in adirection resisted by the gravitational pull on said carriage, and means to instantly collapse said carriage from an elevated and fixed position on said standard for instant reuse of said tool, wherein said handle serves to stabilize the equilibrium thereof when divorced from said shaft.

2; As claimed in claim 1, wherein the said clamping meanscomprises a pair of collars, each being adapted for surrounding fixed relation with a respective end portion of said shaft, nd both being disposed in abutting clamping relation with both the said carriage and the said housing respectively, and in a manner whereby said washer will be free to move rotatably.

3. As claimed in claim 1, wherein the recall means for the said plunger comprises a pair of spaced collars that are adapted to both surround slidably said plunger and to transverse the inner side wall of said handle, with one lower collar being secured in fixed relation with an intermediate portion of said handle, and the opposite collar being both fixed with said plunger and disposed in abutting relation with a pretensioned compression spring that extends from the lower said collar in slidable surrounding relation with said plunger.

, 4. As claimed in claim 1, wherein the second plunger means that is adapted to ratchet with the teeth of said pinion, comprises a barrel of uniform diameter that is disposed laterally and in fixed relation with a medial portion of the rear wall of the carriage, in a manner whereby the barrel communicates with the opening thereof, and disposed axially and extensibly the barrel there is provided an elongated shaft of circular cross section that constitutes a pawl that is provided with a finger gripping knob that is disposed concentrically with the outer extensible end portion thereof and in abutting relation with the rim of said barrel as when biased thereon by a compression spring that is disposed both slidably within the confine of said barrel and in surrounding relation with said pawl, with one end of said spring being disposed inabutting relation with a first collar that is disposed both slidably in the said barrel and in fixed surrounding relation with an inner portion of said pawl, the opposite end of said spring being disposed in abutting relation with a second collar that is disposed slidably on said pawl and in fixed relation with the inner peripheral wall of said barrel, said pawl further including an upwardly inclined transverse face at the free opposite terminal portion thereof, said pawl face being adapted to both slidably abut a co-axially aligned pinion tooth and to intercept the under-side of a second superposed tooth at the apex thereof, whereby rotational movement of the pinion in a direction for progressing upwardly on the successive rack teeth will recip rogate said pawl in respect to said barre and permit t e ree movement of said pinion in the first said direction, and when said pawl is biased to move in a converse direction as when said carriage is resting in an elevated position on said standard said pinion will then be disposed in fixed supporting relation upon he apex portion of said pawl face, and thereby sustain the carriage in selective adjustment with said standard.

5. As claimed in claim 1, wherein the means to collapse said carriage on said standard for instant re-use of said tool comprises a V-shaped dog that is disposed in lateral relation with with said finger gripping knob of said pawl member, and which dog normally is disposed in slidable relation with a complementary slot formed inwardly the wall of said barrel and opening through said rim thereof, whereby said composite restricts the displacement of said pawl face in respect to a transverse tooth of said pinion as when the tool is adapted for a prying operation, and when said dog is withdrawn from said slot by the medium of said finger gripping knob, and rotatably disposed in abutting relation with the rim portion of said barrel, said pinion will then be released from said pawl and be biased to move in said converse direction by the gravitational pull on said carriage when sustained in an elevated position on said standard by the first said position of said pawl in respect to said pinion.

Claims

1. The combination of a wedging and prying tool for use with releasably secured building members, comprising a flat U-shaped base having forwardly tapered limbs constituting mole chisels, a rectangular standard secured with said base and rising from a medial portion of the web of said base, said standard including an integral rack disposed on the rearward face thereof adjacent the rearward side of said base, and a pair of diagonally disposed grooves each being provided in a respective side face of said standard, said grooves constituting guideways, said rack and said guides extending axially the length of said standard, an open box-shaped frame constituting a carriage, said carriage including a depending laterally disposed lifting bar, said bar being bifurcated and adapted to clinch the shank of a substantially driven nail, said carriage further including a pair of rectangular integral key members, said key members adapted to slidably engage the said guideways, and said lifting bar adapted to interpose the said mole chisels, as when said carriage is disposed on said standard in collapsed relation in respect thereto, said lifting bar being further provided with forwardly tapered limbs complementary to the inclined plane of said mole chisels, thereby constituting a wedging tool, a shaft of circular cross section journaled extensible in the side walls of said carriage transversely and medially an opening afforded thereby at the rearward side of said standard, said shaft including a rectangular integral key disposed axially and radially therewith, and interposing said side walls, a pinion disposed in meshing relation with said rack, and in surrounding fixed relation with the keyed portion of said shaft, said shaft including a second and identical keyed portion disposed intermediate one extensible end portion of said shaft, a spur gear disposed in surrounding fixed relation with the second keyed portion of said shaft, a cylindrical housing disposed in axial surrounding relation with said spur gear, and adapted for journaled relation with said shaft at the opposite transverse sides of said spur gear, an elongated tubular member of circular cross section constituting a handle, said handle disposed in fixed radial relation with said housing, and in communication with the chamber thereof, said handle including a head membeR having a medial rectangular opening therethrough constituting a guideway, a shaft of rectangular cross section constituting a plunger said plunger adapted to complement slidably said guide-way and disposed extensible said handle, said plunger including a flat circular head member constituting a thumb rest, and a V-shaped lower extremity constituting a clutch member, said clutch member adapted to clutch with an axial groove of said spur gear when depressed therein by a manual force applied upon said thumb rest through the medium of said plunger, whereby said pinion may be moved rotatable by said handle in a direction for progressing upon a substantial number of successive teeth of said rack, whereby said lifting bar will be spanned from said mole chisels through the medium of said carriage thereby providing a prying tool, a flat washer disposed in surrounding relation with said shaft and interposing said carriage and said housing whereby the latter will be spaced from the former, adjustable clamping means, provided with the opposite terminal end portions of said shaft, whereby obviating the axial displacement of said shaft in respect to both the said pinion and said spur gear, recall means provided with said plunger and fixed with said handle whereby said handle may be oscillated on said shaft and thereby be moved to a substantially selective position in respect of said spur gear, a second plunger means provided with said carriage and adapted to ratched with the pinion teeth disposed diametrically from the pinion teeth that mesh with said rack, whereby said pinion will be adapted to progress successively on the teeth of said rack, and moving said carriage and said lifting bar correspondingly for selective adjustment on said standard, as when said handle is adapted to move said shaft in a direction resisted by the gravitational pull on said carriage, and means to instantly collapse said carriage from an elevated and fixed position on said standard for instant reuse of said tool, wherein said handle serves to stabilize the equilibrium thereof when divorced from said shaft.

2. As claimed in claim 1, wherein the said clamping means comprises a pair of collars, each being adapted for surrounding fixed relation with a respective end portion of said shaft, nd both being disposed in abutting clamping relation with both the said carriage and the said housing respectively, and in a manner whereby said washer will be free to move rotatably.

4. As claimed in claim 1, wherein the second plunger means that is adapted to ratchet with the teeth of said pinion, comprises a barrel of uniform diameter that is disposed laterally and in fixed relation with a medial portion of the rear wall of the carriage, in a manner whereby the barrel communicates with the opening thereof, and disposed axially and extensibly the barrel there is provided an elongated shaft of circular cross section that constitutes a pawl that is provided with a finger gripping knob that is disposed concentrically with the outer extensible end portion thereof and in abutting relation with the rim of said barrel as when biased thereon by a compression spring that is disposed both slidably within the confine of said barrel and in surrounding relation with said pawl, with one end of said spring being disposed inabutting relation with a first collar that is disposed both slidably in the said barrel and in fixed surrounding relation with an inner portion of said pawl, the opposite end of said sprinG being disposed in abutting relation with a second collar that is disposed slidably on said pawl and in fixed relation with the inner peripheral wall of said barrel, said pawl further including an upwardly inclined transverse face at the free opposite terminal portion thereof, said pawl face being adapted to both slidably abut a co-axially aligned pinion tooth and to intercept the under-side of a second superposed tooth at the apex thereof, whereby rotational movement of the pinion in a direction for progressing upwardly on the successive rack teeth will reciprocate said pawl in respect to said barrel and permit the free movement of said pinion in the first said direction, and when said pawl is biased to move in a converse direction as when said carriage is resting in an elevated position on said standard said pinion will then be disposed in fixed supporting relation upon he apex portion of said pawl face, and thereby sustain the carriage in selective adjustment with said standard.