Adjustable Side For Slip Form

Abstract

Automatically adjustable side skirts for the working tool such as a slip form or mule shoe of curb laying machines are disclosed to mitigate or prevent edge slump as the tool traverses grade deviations along the path of travel. One or a pair of vertically adjustable support means control the elevation of the side skirt through one or a pair of grade sensing shoes that contact the grade as the machine progresses. Means responsive to the movement of the grade sensing shoes cause the support means to extend or retract and thus form a retaining sidewall passing through the grade deviation which holds the concrete in place across the deviation. In one embodiment a single skirt is controlled by a single extensible member that is pivotally attached to the skirt at an approximate point of balance. In another embodiment a single skirt is controlled by a pair of longitudinaly spaced extensible members that are pivotally attached at spaced points on the skirt.

Parent Case Text

RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No. 103,423, filed on Jan. 4, 1971, which is a continuation-in-part of application Ser. No. 774,014, filed Nov. 7, 1968, now U.S. Pat. No. 3,606,827, all by the instant inventors.

Description

BACKGROUND OF THE INVENTION

The foregoing related patent application and U.S. patent described a construction machine that travels on four crawler tractors. Although the adjustable sided concrete extrusion tool of this invention can be used with any mobile curb, gutter or sidewalk laying machine, it will be described in relation to the curb machines of said patent and patent application which are used on rough grades.

These machines, which vary in certain of their steering capabilities, are capable of traversing a prepared grade, following a single grade line, and depositing the concrete in the form of a curbing, gutter, or sidewalk therealong with close control of the grade and slope of the finished product. Because of the level and grade control system, operating as it does through two independent tractors controlling the grade and through another pair of tractors carrying the frame central of a walking beam on the other side of slope control, the finished product can be laid as fast as concrete trucks can supply the concrete and with grade and slope tolerances that exceed present road or curb-building specifications.

A particular advantage of the machine is its ability to negotiate cul-de-sacs and large deviations in the grade without affecting the accuracy of the poured product. This means that the grade over which the machine travels need not be prepared to the exact standards required by other curb or sidewalk laying machines. It also means that little attention need be paid to the paths over which the tractors will travel and only the grade upon which the curb or sidewalk is laid needs any particular attention. However, because of the extremely accurate leveling, slope control and steering capabilities of the machine it is sometimes used on very poorly prepared grades wherein the deviations are so large that considerable amounts of concrete may be lost through edge slump or incomplete compaction of the concrete therein. Some of the advantages gained from the speed and extremely accurate grade and slope control characteristics of the machines may be lost where through intent, neglect, error or natural causes the prepared grade presents undulations or washouts in the path of the working tool which are large enough to cause slump of the concrete. The instant invention increases the versatility of machines of this type, prevents undue loss of concrete and eliminates the necessity of additional labor or loss of time required to repair such deviations in the grade before the work can continue or to repair the slumped edges of the formed work product.

SUMMARY OF THE INVENTION

In accordance with this invention one or more flat side skirt elements are pivotally suspended adjacent to and substantially flat against an outer sidewall of the slip form from one or a pair of extensible members capable of raising and lowering the side skirt elements in accordance with macro changes in the grade. The side skirt elements operate within guide means to hold them in sliding parallel relationship with the sidewall of the slip form during oscillation as the machine progresses over the deviation. The side skirt elements are allowed a degree of movement fore and aft within the guide means. The pivot axis of the side skirt is preferably above the center of gravity of the skirt. A grade sensing shoe is pivotally attached at its midpoint to a control rod carried by the side skirt for contact with the grade immediately adjacent and substantially parallel to the bottom edge of the side skirt.

The control rod is moved up and down by the sensing shoe to operate a power means controlling the extensible member. The axis of the control rod and its pivotal attachment to the sensing shoe are in line with the pivotal axis of the side skirt. Accordingly, the bottom edge of the side skirt follows and is maintained substantially coplanar with the transverse plane of the bottom of the grade sensing shoe.

Where a single side skirt is suspended from a pair of extensible members the foregoing arrangement is provided at spaced fore and aft positions along the side skirt. By these means the bottom edge of the side skirt can be oscillated on two axes and follows the contour of the depression in the grade to retain the concrete long enough so that slump is prevented after the machine passes the depression. The length of the grade sensing shoe controls the magnitude of correction and oscillation of the skirt.

DESCRIPTION OF THE DRAWINGS

The invention is illustrated, without limitation, by the drawings showing a curb-laying machine wherein:

FIG. 1 is a perspective view showing the front and outboard or curb side of a curb and gutter machine including the adjustable-sided slip form of this invention;

FIG. 2 is a side elevational view of the machine illustrated in FIG. 1 showing the outboard or curb side and showing some details of the adjustable side skirt;

FIG. 3 is a fragmentary perspective view of the mule shoe showing one form of elevation adjustment for one or more adjustable side skirts therealong therefor;

FIG. 4 is a cross-sectional view taken along the lines 10--10 of FIG. 3;

FIG. 5 is a cross-sectional view taken along the lines 11--11 of FIG. 4;

FIG. 6 is a detailed end view partially in section of a slip form with an adjustable side skirt or plate on each of its sides.

THE PREFERRED EMBODIMENT

Briefly, FIGS. 1 and 2 show the curb-forming machine 10 as described in more detail in said copending application, having the supply hopper 12 adapted to receive concrete 14 from the chute 16 of a concrete truck (not shown), convey the concrete upwardly through the screw conveyor 18, operated by the hydraulic motor and drive unit 20 and deposit the concrete from the opening 22 into the feed hopper 24. Vibrators are positioned within the hopper 24 and adjustably mounted so as to affect the required compaction of the concrete, eliminate air bubbles and facilitate the flow through the hopper. The consistency of the concrete is maintained so as to prevent slump of the finished curb under normal conditions of compaction.

The feed hopper 24 is shaped to facilitate compaction and has an open bottom communicating with the slip form or mule shoe 30. A continuous source of formable material is thus supplied to the mule shoe 30.

The forces acting on the machine are constantly changing as the machine progresses along the sub-grade 34 in the direction of the arrow 26. The suspension and controls of the invention described in said relation application and patent are adapted to maintain the mule shoe 30 at the desired slope, grade and path of curvature irrespective of these additional forces acting on the machine, without impairment of the compaction (density) of the finished curbing, illustrated at 38, and regardless of most macro deviations in the sub-grade. There is an upward pressure of the mule shoe upon its mounting with frame due to the compacting forces upon the curbing being laid. This compacting pressure at times causes side slump and loss of concrete under the bottom edge 38 of the mule shoe 30 where the length of the mule shoe is longer than the width or depression in the grade along the path of travel or the depression has an irregular or a V-bottom.

The slip form or mule shoe 30 is open at the bottom and rear and is closed at the front end by the transverse wall member 40 through which extend the guide tubes 42 having open flared ends to easily receive the reinforcing rods (not shown). The slip form or mule shoe 30 is elongated and has an inner shaped contour 46 (see FIG. 4) throughout its length to lay any desired curb or gutter design to specifications including the so-called battered form illustrated and such other contours such as drive over, roll and vertical curbs. The slip form 30 can be any desired length and can be widened so that sidewalks can be laid.

The hopper 24 is attached to and in communication with the mule shoe 30 at the forward end, just behind the plate 40. The reinforcing girder plates 48 are provided at spaced points along the length of the mule shoe, same being contoured to fit over the outer contoured surfaces of the mule shoe and affixed thereto by welding. The longitudinal reinforcing channels 50 are affixed at or near the lower outer edge of the mule shoe at selected locations. The mule shoe has the spaced uprights on each side such as illustrated at 52 attached to the rectilinear personnel platform 54 carried at the outboard side of the main frame 56.

The machine is self-contained with the prime mover 60 supplying the power necessary to drive the hydraulic pumps, hydraulic motors and generators that are required. All functions of the machine can be controlled by one man from the control console 62. The top part of the panel of the console contains the controls and instruments for the prime mover and elevation and slope control system, while the lower part of the panel contains the controls for the travel system.

For this latter purpose the main frame 56 carries the forward outboard support cylinder housing 66 in a vertical position at one corner and the rearward outboard support cylinder 68 in a vertical position at the other corner, as two spaced adjustable suspension points for grade control of the main frame and slip form. Affixed to an intermediate position on the inboard side of the main frame 56 is a pair of support cylinder housings 70 and 72 for slope control. These cylinders are oriented fore and aft of the main frame at these suspension points. The cylinder supports 66, 68, 70 and 72 each house double-acting rams which are connected by means of the pairs of hydraulic hoses 74, 76 and 78 to a source of hydraulic power. The flow of hydraulic fluid therein is reversible and controlled by the sensor-actuated valve system described in related U.S. Pat. No. 3,606,827.

These dual-acting rams are telescopically housed in the support cylinders and are journalled at the top and bottom by clevis pins to provide slight axial resilience and alignment for the working cylinders during reciprocation and leveling at each suspension point. Each of the rams is attached through a bottom clevis pin to a base plate seated in the bottom of its inner guide cylinders such as the cylinder 80.

On the outboard side of the machine each adjustable suspension means has a saddle mount that is pivoted to a self-propelled crawler type tractor unit 82. Each of these crawler tractor units 82 is pivotally mounted on a vertical axis from the cylinder supports and also adapted to extend and retract independently on a vertical guided axis by means of the rams to raise and lower that corner of the frame. The tractors are pivotally attached on a horizontal axis to the saddles by means of saddle pins located substantially in the center of their frame supports.

On the inboard side (see FIG. 2) the pair of inner guide cylinders 80 is rigidly mounted to a saddle 84 which is pivotally attached on a horizontal axis intermediate the ends of the walking beam 86 by means of the saddle pin 88 which extends through the saddle mount and the beam forming a central pivot for the walking beam. At each end of the walking beam, the inboard tractor units 82 are carried on their respective saddles through saddle pins. The vertical steering axes of this assembly are coincident with the rams on the inboard side and located at each end of the walking beam 86 on the outboard side.

The tractors each have individual hydraulic drive motors same being two-way or reversible hydraulic motors such as Charlyn Orbit motors. The motors on each side are connected in series to each other by means of suitable hydraulic lines so that they can be operated in unison.

In order to steer universally the front pair of tractor units is tied together, fore and aft of the saddle pins, by means of the paired steering linkages 87 and the rear pair of crawlers is tied together by similar steering linkages. By this arrangement the two fore tractors are turned in unison and the two aft tractors turned in unison. Steering of the front pair of tractors is controlled by a double-acting hydraulic steering ram 88 cross-connected between the steering linkages 87. The steering of the rear tractors is controlled by a separate ram cross-connected between the rear steering linkages.

In accordance with said copending application the respective pairs of steering linkages are simultaneously extended or retracted by the same amount as the tractor suspension negotiates uneven grades or the level of the grade on which the two tractors on one side of the machine navigates is lower than or higher than the level of the grade on which the other pair of fore and aft tractors navigates. This is accomplished by including a pair of cross-connected rams in these linkages which extend and retract in unison to accommodate the changing geometry transverse the machine and forms no part of this invention.

From the description thus far, it is seen that five saddle mounts are included in the suspension, with means to control the level (slope and grade), direction and horizontal attitude of the machine as it negotiates changes in the grade. The machine travels on the established and prepared grade 34 under the guidance of the grade reference or string line 90 which is supported from the horizontal arms of suitably spaced posts. The string line 90 is placed outside of the edge of the grade 34 at any desired predetermined elevation in relation to the grade and held therealong in a manner known in the art to define the path of the working tool.

The machine is accurately guided along the string line 90 by means to detect the direction of the line and by means to detect the elevation of the line. The former variable is detected by the steering sensor 92, for the forward tractors, and the steering sensor 94 for the rear tractors. The latter variable is detected by the elevation sensors 96 and 98 which are mounted for passage along the string line directly ahead of the respective steering sensors. The steering sensors each have a gimbal-mounted sensing arm 100 which contacts the string line 90 on the machine side thereof, while the elevation sensors have the sensor shoes 102 which contact the underside of the string line 90.

As described in detail in said copending application means are provided to move the front steering sensor arm 100 as it calls for a correction in the steering, a distance proportional to the amount of steer and in the direction of steer. This movement is a linear distance which is equal to or an increment of the steering correction. This action reduces each steering correction by a fraction so that the total amount of steer is approached in increments and over steering is reduced.

The rear steering sensor 94 functions in the same manner to retract or extend with respect to the string line as it controls the rear tractors 82. The machine 10, with which the features of this invention are incorporated, is self-powered, self-steering and self-leveling for fully automatic operation.

In accordance with this invention the slip form 30 has been modified to provide the vertically slidably apron plate or skirt 110 mounted on a sidewall 112 of the slip form. The lower edge 114 of the skirt 110 extends longitudinally of the side of the slip form 30. This plate is slidably mounted on a vertical axis by means of the support 116 which is carried by the frame of the slip form or may be affixed to the top wall thereof and also carries the double-acting ram 118, the operating piston thereof being illustrated at 120 by broken lines. The connecting rod 122 has the journal 124 at the lower end that is pivotally attached to the pin 126 carried by the guide plate 128. The guide plate is attached to the pair of U-shaped brackets 130 as at the weldments 132 and the ends of the brackets are welded to the apron plate or skirt 110 as at 134. This provides a space 136 between the guide plate 128 and the sidewall 112 to receive the vertical T-beam 138 supported at the end of the horizontal support 140 carried by the frame or the top of the slip form 30. The juncture of the bottom bracket 130 and the plate 128 has the brace member 142 welded therein to which is attached the journal 144. The actuating rod 146 is carried in reciprocating relationship within the journal 144. The journal has a pair of bearing gland members 148 and 149 which slidably receive the rod 146 in sealed relationship.

The hydraulic line 150, from a source of hydraulic pressure supplied by the machine 10, leads to the pilot valve member 152 carried at the top of the support sleeve 154 through which the rod 146 extends in operative reciprocating relationship with the valve 152. The hydraulic line 156 is a return line for the valve 152.

The support sleeve 154 extends from the adjusting nut 158 which engages internal threads in the lower gland member 149 and also encompasses the rod 146 in slidable relationship. The pair of hydraulic lines indicated at 160 and 162 lead from the valve 152 to respective sides of the piston 120 in the ram 118. The rod 146 is pivotally mounted from the pin 164 at its bottom end carried by suitable spaced cleats 166 extending from the sensing ski or shoe 168 having the upturned front end 170.

The shoe 168 is adapted to slide along the grade surface and detect macro deviations of the grade along the side of the mule shoe into which concrete may spill and be wasted. When the shoe detects such a depression, for example, it lowers following the contour of the depression and actuates the valve 152 to open same to introduce pressure fluid in line 160 and move the piston 120 downwardly. This moves the skirt or apron plate 110 downward along the T-beam 138, guided by the plate 128. Only the top end of the T-beam 138 is supported and the lower end 172 of the T-beam is unsupported for easy detachment of the assembly and to allow the apron plate 110 to extend therebelow. The inside of the plate 128 rides against the outer part of the T-beam 138 at the sliding juncture 174 and the back flat side 176 of the T-beam rides against the outside of the apron plate 110. The apron plate 110 in turn is held in sliding or spaced relationship with the mule shoe 30 as indicated at 180, depending on the spacing provided by the side 176 from the sidewall 112. Since the apron plate 110 is pivotally mounted on the pin 126, it can also swing to either side within the limits of the space 136 about the T-beam 138.

This arrangement of the apron plate 110 and its oscillatable support shown in FIGS. 3, 4 and 5 can be applied to either or both sides of slip form or mule shoe 30. The use of aprom plates 110 in single or multiple units in tandem along a side of the mule shoe provides the means for extending the effective edge of the slip form along the profile of the depression in the grade. In practice this arrangement of one or more apron plates is only necessary along the areas of where the greatest compression and vibration forces are acting on the concrete and the tendency to squeeze into depressions in the grade is greatest. This would place the apron plates or skirts under and to the rear of the hopper 24 with the type of concrete feed unit disclosed.

The lower edge 114 of the apron plate is thus maintained in a position along the compaction zone to prevent concrete from spilling out into any depressions that may be encountered along the grade without disturbing the attitude of the mule shoe. The apron plate 110 and associated sensing ski or shoe for a single unit as shown in FIG. 3 are about the same length and both of these members can be as long as is necessary to accomplish this purpose. If desired the leading corner of the apron plate 110 can be rounded, as indicated by the broken lines 182 in FIG. 3.

Referring to FIG. 6 there is shown a slip form 30 with a pair of apron plates 110, one on each of the outsides of the sides thereof and having their respective vertically adjustable support means represented by the double-acting rams 118 and associated connecting rods 122 and pivot pins 126. The support member 116 for the rams 118 as well as the support member 116 for the rams 118 as well as the support member 140 can be suitably attached to the outer and inner uprights 184 which carry the slip form from the main frame 56. Here also the T-bars 138 function to maintain the apron plate 110 in a parallel sliding or oscillating position with the respective outside wall 112 and inside wall 186 of the slip form through the guide plates 128.

Each of the apron plates or skirt members 110 has its sensor means represented by the shoes 168 and the associated connecting rods 146 and means responsive to the vertical undulations of the sensor represented by the hydraulic or mechanical servo valves 152. One form of this type of valve found to be suitable is manufactured by Fairey Hydraulics, Ltd.

It is apparent from FIG. 6 that the right hand shoe 168 is lowered into the depression 34a of the grade 34 and has caused a corresponding lowering of the apron plate 110 on that side of the slip form. The compressed and suitably de-aerated concrete in the area 188 is prevented from spilling into the depression and is held there long enough as the machine progresses to retain a rigid sidewall that will set without further attention.

Referring to FIGS. 1 and 2 the invention is further illustrated by the longer apron plate 110a which is positioned along the sidewall of the slip form 30 from the front wall 40 to a point rearward of the discharbge area of the compaction hopper 24. This apron plate 110a is suspended by a pair of vertical adjustment support means represented by the pair of rams and associated parts whose reference numbers correspond to those described in FIG. 3. The action of the skirt 110a as it oscillates on two suspension points is a combination of averaging and profiling of the contour of any depression encountered along that side of the slip form. The arrangement shown in FIG. 2 can be duplicated on the inside wall of the slip form in which event FIG. 6 would represent an end view thereof.

The distance between the pair of pivot points 121 can be different from that shown in FIG. 2 and their arrangement does not have to be symmetrical of the ends or center of the apron plate. Under some circumstances a longer apron plate would be used than that shown in FIGS. 1 and 2. Also depending on the condition of the grade 34, the slump characteristics of the concrete as well as the speed of pouring it may be desirable to have a second apron plate on one or the other or both sides of the slip form to the rear of the one shown.

To accommodate these different conditions including the tendency to slump stemming from the shape or height of the slip form contour 46, the cylinders 118 can be made detachable at the juncture 190 with the support 116 and the juncture 192 of the T-bar 138 with the support 140 can also be both detachable and adjustable in elevation. These members can be suitably flanged and bolts registering with one or more bore holes in the parts can be used for this purpose. More than one T-bar can be used within the space 136 for added stability where desired. The T-bars can be reversed from the positions shown so that their wider flanges are on the outside. An I-beam piece can be used for these members or any other shape of vertical guide can be used. Since the entire slip form can be readily raised by the machine 10 to a vertical position well above the grade, removal or replacement of an apron plate is simplified. The inclusion of apron plates on both sides of the slip form as shown in FIG. 6 that extend in closely spaced tandem relationship increases the versatility of the machine in that larger differences in the elevation of the grade on which the tractors traverse from the elevation of the grade on which the curbing or other continuous structure is to be laid can now be accommodated, provided any lack of planar continuity in the sidewalls of the formed product can be tolerated. The machine can thus be used to lay footings along deeply offset grades.

The curb laying machine of this invention with the adjustable side skirts one or both sidewalls of the slip form can use most standard mixes of concrete. The unavoidable slump of the finished curb along its length, depending on the curb design, should not exceed 2.5 inches and not less than 0.75 inch. The air in the concrete should not exceed 10 percent for good curb laying. The sub-grade 34 on which the curb is laid can be graded to one-fourth to one-half inch below the grade on which the machine travels to assure that the mule shoe will not strike on high material and cause inaccurate final grade of the finished product. The foregoing limitations do not apply to the same extent for larger material handling machines.

It is also apparent that the apron or skirt members need not be under the control of a sensor means and that mechanically manipulated means or valves can be used by the operator or his assistant to control the adjustable vertical support members while visual observation is used to detect the undulations in the grade being traversed. Preferably the apron structure shown in FIGS. 1 and 2 will extend as a unit or as multiple units along the entire length of the slip form. Each of the rams 118 shown need not be actuated to make a correction, that is one of the pivot points 126, preferably the rear one can be fixed in relation to the frame of the machine and not be vertically adjustable, while the other pivot point 126 (forward) and its adjustable support 118 can be under the control of a sensor or manipulated manually. This relationship can be reversed with the front pivot point being fixed in relation to the frame or slip form while the rear one is raised up and down.

In another embodiment the movable skirt can be a portion of the sidewall 112 of the slip form, that is, the slip form can be split longitudinally along the top wall to form two separate elongated wall members defining the contour 46 and having adjoining surfaces that define a sliding juncture with guide means such as lugs riding in vertical parallel slots therebetween to maintain the sliding relationship of one wall member to the other. This split wall arrangement can include the walls of the hopper 24. The same arrangement of adjustable vertical support means disclosed heretofore would be used with this embodiment with or without the sensing shoes.

Claims

What is claimed is:

1. A slip form for transport by a machine over a grade to lay a continuous layer of formable material therealong comprising:

an elongated form member adapted to be supported from said machine with its longitudinal axis extending along the path of travel;

said form member having laterally spaced sidewalls depending from an enclosing top wall;

said sidewalls having bottom edge portions defining the lateral limits of said continuous layer;

a skirt member associated with and contiguous to the outside bottom edge portion of one of said sidewalls;

vertically adjustable support means extending from said machine and carrying said skirt member for vertical movement independent of said one side wall of said form member;

power means provided by said machine for actuating said support means; and

sensor means carried by said machine and operatively controlling said power means to raise and lower said skirt member;

said sensor means being slideably engageable with said grade along and contiguous to said skirt member;

said sensor means being responsive to the depressions in said grade and operative to provide a control signal to actuate said power means and move said skirt member along the contours of said depressions.

2. A slip form in accordance with claim 1 in which,

said vertically adjustable support means includes means pivotally supporting said skirt member on an axis transverse the longitudinal axis of said slip form.

3. A slip form in accordance with claim 1 including,

a pair of said vertically adjustable support means each pivotally supporting said skirt member on spaced axes transverse the longitudinal axes of said slip form.

4. A slip form in accordance with claim 1 including,

guide means cooperating with said vertically adjustable support means,

said guide means comprising a bracket member supporting a vertical guide post parallel to and spaced from said bottom edge portion of said one sidewall, and

said skirt member being positioned in sliding relationship between said guide post and said bottom edge portion.

5. A slip form in accordance with claim 1 including:

a second skirt member associated with and contiguous to the outside bottom edge portion of the other of said sidewalls;

vertically adjustable support means extending from said machine and carrying said second skirt member for vertical movement independent of said side wall;

power means provided by said machine for actuating said second support member;

and sensor means carried by said machine and operatively controlling said power means to raise and lower said second skirt member;

said sensor means being slideably engageable with said grade along and contiguous to said second skirt member and being repsonsive to the depressions in the grade on said other side of said sidewall to actuate said power means and move said second skirt member along the contours of said depressions.

6. A slip form for transport by a concrete laying machine over a grade to lay a continuous layer of formed concrete therealong comprising:

an elongated form member adapted to be supported from said machine with its longitudinal axis extending along the path of travel;

said form member having laterally spaced vertical sidewalls depending from an enclosing top wall;

said sidewalls having bottom edge portions defining the lateral limits of said formed continuous layer;

a skirt member operably associated with the outside bottom edge of one of said sidewalls;

vertically operable support means extending from said machine and carrying said skirt member on a transverse pivotal axis;

power means provided by said machine for actuating said support means;

a grade sensing shoe member carried by said skirt member and controlling said power means to raise and lower said skirt member;

said grade sensing shoe member being pivotally mounted on a transverse axis from said skirt member in the plane of the transverse axes of said support means; and

said grade sensing shoe member having a length substantially equal to the length of said skirt member.

7. A slip form in accordance with claim 6 in which the pivotal axis of said skirt member and the pivotal axis of said vertically adjustable support means are coplanar.

8. A slip form in accordance with claim 6 in which,

said support means comprises a hydraulic ram and said power means comprises a source of hydraulic pressure connected thereto,

a two-way valve controlling said source of hydraulic pressure having a plunger member depending therefrom, and

said grade sensing shoe is pivotally attached to the lower end of said plunger.

9. A slip form for transport by a concrete laying machine over a grade to lay a continuous layer of formed concrete therealong comprising:

an elongated form member adatped to be supported from said machine with its longitudinal axis extending along the path of travel,

said form member having laterally spaced vertical sidewalls depending from an enclosing top wall,

said sidewalls having bottom edges defining the lateral limits of said formed continuous layer,

a skirt member operably associated with the outside bottom edge of one of said sidewalls,

a pair of vertically adjustable support means carrying said skirt member on longitudinally spaced transverse pivotal axes,

power means for individually actuating said support means, and

a grade sensing shoe controlling said power means to independently actuate said respective support means,

said grade sensing shoes being pivotally mounted on transverse axes in the plane of the respective transverse axes from said skirt member of said support means,

the combined lengths of said grade sensing shoes being less than the length of said skirt member.

10. A slip form in accordance with claim 9 in which,

guide means are included cooperating with each of said vertically adjustable support means to maintain said skirt members in parallel sliding relationship with said sidewalls.

11. A slip form for transport by a machine over a grade to lay a continuous layer of formable material therealong comprising:

an elongated form member adapted to be supported from said machine with its longitudinal axis extending along the path of travel;

said form member having laterally spaced sidewalls;

a skirt member associated with and contiguous to a bottom edge portion of one of said sidewalls;

vertically adjustable support means extending from said machine and carrying said skirt member for vertical movement independent of said one sidewall of said form member;

power means provided by said machine for actuating said support means; and

sensor means carried by said skirt member and controlling said power means to raise and lower said skirt member;

said sensor means being operatively engageable with a grade reference to provide a control signal to actuate said power means.

12. A slip form in accordance with claim 11 in which,

said vertically adjustable support means includes means pivotally supporting said skirt member on an axis transverse the longitudinal axis of said slip form.

13. A slip form in accordance with claim 11 including,

a pair of said vertically adjustable support means each pivotally supporting said skirt member on spaced axes transverse the longitudinal axes of said slip form.

14. A slip form in accordance with claim 11 including,

a second skirt member associated with and contiguous to the outside bottom edge portion of the other of said sidewalls,

vertically adjustable support means carrying said second skirt member, and

power means for actuating said second support member.