US3418902A

US3418902A - Concrete surface finishing apparatus

Info

Publication number: US3418902A
Application number: US543273A
Authority: US
Inventors: Herbert W Wilson
Original assignee: Individual
Current assignee: Individual
Priority date: 1966-04-18
Filing date: 1966-04-18
Publication date: 1968-12-31
Anticipated expiration: 1985-12-31

Description

Dec. 31, 1968 H. w. WILSON CONCRETE SURFACE FINISHING APPARATUS Sheet of 5 Filed vApril 13. 1966 Herbert W. Wilson BY/W ATTORNEY Dec. 31, 1968 H. w. WILSON 3,418,902

CONCRETE SURFACE FINISHING APPARATUS Filed April 18, 1966 Sheet 2 of 5 Fig.2

INVENTOR Herbert W. Wilson ATTORNEY Dec. 31, 1968 w, wlLSON 3,418,902

CONCRETE SURFACE FINISHING APPARATUS Filed April 18, 1966 Sheet 3 of5 Fig.5 INVENTOR Herbert W. Wilson ATTORNEY United States Patent 3,418,992 CONCRETE SURFACE FlNlSl-HNG APPARATUS Herbert W. Wilson, Rte. 1, Box 457, Abilene, Tex. 79691 Filed Apr. 18, 1966, Ser. No. 543,273 Claims. (Cl. 9445) ABSTRACT OF THE DISCLOSURE A concrete surface finishing apparatus includes a pair of wheeled carriages which move along a preselected path on opposite sides of a concrete surface. A pair of spaced apart truss frameworks span the concrete surface and are slida'bly supported in rolling engagement at the opposite ends by rollers on each of the wheeled carriages. A screed member is carried on the bottom of each of the truss frameworks for engaging and working the concrete surface. A driving motor supported by one of the truss frameworks includes a lever arm connected to the other of the truss frameworks for relatively reciprocating the truss frameworks to cause the screed members to finish the concrete surface.

This invention relates to an apparatus for finishing a concrete surface, and more particularly to a concrete surface finishing apparatus which spans the surface of the concrete to be finished and has reciprocating screed members which engage and work the concrete surface.

There are various types of concrete finishing apparatuses which employ screed members for finishing the surface of the concrete immediately after the concrete is poured. Some of these apparatuses are adapted to oscillate or reciprocate the screed members in various manners for finishing the concrete surface, and in addition to which some are adapted to vary the contour of the screed members to effect selected crown configurations of the concrete surface. Such an apparatus has particular application to the finishing of a bridge deck, wherein the portability and mobility of the apparatus is of prime importance. For bridge deck applications, the weight of the apparatus becomes a factor so as not to subject the elevated bridge structure to an excessive load during construction. Although these apparatuses have a particular utility for finishing bridge decks, they are also useful in the finishing of concrete surfaces of road beds.

It is with respect to this particular type of apparatus that the present invention is directed as an improvement thereof. In one aspect, the present invention is directed to the provision of an apparatus very light in weight which is particularly suitable for finishing concrete surfaces of a bridge deck. The invention is also directed to the provision of an apparatus which is highly portable as a result of its light weight. Another consideration is the provision of such an apparatus that is simple in construction and adequately powered to provide an effective finishing action for a concrete surface, yet which is able to withstand the various stresses and strains to which such an apparatus is subjected during operation. These particular objects are accomplished as the result of the novel structural arrangement of the apparatus employing a minimum number of parts and structural elements. As a result, another object of the invention is achieved, which is the provision of such an apparatus that is economical to manufacture.

In accordance with the above objects, the apparatus of the invention includes a pair of spaced apart, wheeled carriages adapted to run on a pair of tracks situated on opposite sides of the concrete surface to be finished and running parallel therewith. A pair of truss frameworks which span the concrete surface to be finished are supported at their opposite ends by the carriages, wherein each truss framework includes a screed member along the bottom thereof for engaging and working the concrete surface. The truss frameworks are supported at their 0pposite ends by the respective carriages in parallel and spaced apart relation, wherein the truss frameworks include support members which project through housings in the carriages and are supported therein on roller means, the latter of which allow the truss frameworks to be reciprocated back and forth within the housings of the carriages laterally with respect to the line of travel of the apparatus. A driving means, such as a gasoline motor, is structurally supported on one of the truss frameworks for movement therewith and is coupled by a crank arm to the other truss framework. Actuation of the driving means causes the truss framework which is coupled to the driving means by a crank arm to be reciprocated, whereby the other truss framework is caused to be reciprocated relative or oppositely to the first truss framework as a result of the equal and opposite reaction of the crank arm. Thus it will be seen that a very simple driving means is employed for reciprocating both truss frameworks in opposite manners, and that the main structure of the apparatus, which comprises the two truss frameworks, is reciprocated with the screed members. This obviates the necessity of large structural frameworks for supporting additional frameworks which are reciprocable. The apparatus of the invention is also adjustable in height from the tracks on which the carriages roll in order to adjust the screed members to the proper elevation. Moreover, very simple means are provided for varying the contour of the screed members to provide selected crown configurations of the concrete surface. To provide this, the truss frameworks of the apparatus are constructed in separate segments along the top, and between adjacent segments there are provided simple manual adjustment means for adjusting the separations between the sections. All of the truss sections are rigidly secured at the lower ends thereof to the screed members so that variations of the separations between the adjacent truss sections cause the screed members to be bowed accordingly to adjust the contour thereof.

There are many other objects, features and advantages of the present invention that will become readily apparent from the following detailed description of a preferred embodiment thereof when taken in conjunction with the appended claims and the attached drawing wherein like reference numerals refer to like parts throughout the several figures, and in which:

FIGURE 1 is a front elevational view, partly broken away, of the apparatus of the invention;

FIGURE 2 is a top plan view of the apparatus;

FIGURE 3 is an elevational view in section of the two truss frameworks of the apparatus taken through section lines 3-3 of FIGURE 1;

FIGURE 4 is an end elevational view of the apparatus, with some of the components of the apparatus shown in phantom;

FIGURE 5 is an elevational view in section of the apparatus taken through section lines 55 of FIGURE 1;

FIGURE 6 is a rear elevational view of one end of the apparatus, shown partly in section; and

FIGURE 7, is a fragmentary, elevational view in section of a manual screed contour adjustment means.

Referring now to the front elevational view of the apparatus shown in FIGURE 1, the apparatus includes a 7 pair of spaced apart, wheeled carriages generally designated at

numerals

10 and 12 which are adapted to roll along a pair of tracks. 11 and 13, respectively, the latter of which are situated on opposite sides of a bridge deck, or road surface as the case may be, and running parallel therewith. The purpose of the carriages is to support truss frameworks which carry screed members for working a concrete surface, and are adjustable to adjust the height of the screed members to the proper elevation. A pair of

vertical truss frameworks

14 and 16, shown in FIGURES 1-3, span the width of the concrete surface or deck to be worked and are supported at their opposite ends in carriages and 12. These truss frameworks are spaced apart in substantially parallel relationship with each other, whereby the truss frameworks are adapted to be reciprocated relative to each other as will be described hereinafter. A pair of spaced apart screed members 18 and form the lower part of the two

truss frameworks

14 and 16, respectively, whereby the screed members are relatively flexible for being bowed to provide selected crown configurations of the concrete surface. Truss framework 14 includes a pair of support members 54 and 56 which are supported with

carriages

10 and 12, respectively, in rolling engagement therewith, so that truss framework .14 can be reciprocated laterally with respect to the movement of the apparatus. The members 54 and 56 support the truss framework 14,

carriages

10 and 12 support the truss framework 14 through members 54 and 56, respectively, and the tracks 11 and 13

support carriages

10 and 12, respectively.

Similar support members

55 and 57 are included in truss framework 16 and are supported in rolling engagement with

carriages

10 and 12, respectively, for the same purpose. A more detailed description of the truss frameworks will be set forth below, wherein a more general description of the apparatus in its function will now be given.

A suitable driving means 22, such as a gasoline motor, for example, is rigidly supported from one of the truss frameworks .16 for movement therewith by means of a motor base 24 secured to the bottom of support members 57 of truss framework 16. The driving means is situated between the two

truss frameworks

14 and 16 and is connected to truss framework 14 only by a coupling means as will be described. A sprocket 26 is driven by the motor and drives a larger sprocket 28 through a chain 30. Sprocket 28 is connected to a drive wheel 34 through a suitably supported shaft 27, and a crank arm 32 is pivotally connected at one end to the wheel 34 eccentric of the axis of rotation thereof and is pivotally connected at its other end to a structural member 36 forming a part of support member 56. Actuation of the driving means 22 causes truss framework 14 to be reciprocated by means of crank arm 32 laterally with respect to the line of movement of the apparatus on the rails, and the equal and opposite reaction of the driving means in response thereto causes truss framework 16 to be oppositely reciprocated as a result of the driving means being rigidly connected to truss framework 16. Because of this structural arrangement and driving means, the apparatus is greatly simplified and requires only a single crank arm. It will be apparent that as the truss frameworks are reciprocated, the support members associated therewith move relative to the carriages.

To provide additional support for the truss frameworks, a plurality of spaced apart, connecting truss frameworks are provided for interconnecting

truss frameworks

14 and 16 in hinged relation, as shown in the elevational view in section of FIGURE 3 taken through section lines 33 of FIGURE 1, and as shown in FIGURE 1. The interconnecting truss frameworks comprise

horizontal members

40 and 44 hingedly connected at their opposite ends, respectively, to the

truss framework

14 and 16. It will be seen that a plurality of these interconnecting truss frameworks are provided in spaced apart relation along the lengths of the

main truss frameworks

14 and 16. Horizontal member 40 is connected at One end to the upper end of truss framework 14 by means of a hinge 41, and is connected at its other end 'to the top of truss framework 16 by means of another hinge 42. Similarly, horizontal member 44 is connected at one end to the lower end of truss framework 14 by means of a hinge 45 and at its other end to the lower end of truss framework 16 by means of another hinge 46. Members 48 rigidly interconnect horizontal'members 40 and 44 to provide additional strength therefor. It will be obvious that as the

truss frameworks

14 and 16 reciprocate relative to each other, the interconnecting truss frameworks are caused to swing in accordance therewith. As a result of the interconnecting truss frameworks, the two

main truss frameworks

14 and 16 will be brought closer together when they are disposed at relatively reciprocated positions with each other. However, the lateral limits of movements of the truss frameworks and screed members are small as compared to the overall length of the truss frameworks, and consequently, the distance of separation between

truss frameworks

14 and 16 varies only slightly.

The

main truss frameworks

14 and 16 are comprised of vertical

structural members

50 and 52, respectively, connected at the lower ends thereof to the

screed members

18 and 20, respectively. A plurality of these vertical members are provided along the lengths of the truss frameworks. The upper parts of the truss frameworks are comprised of a plurality of horizontal members providing the upper support for the vertical members. In particular, truss framework 14 comprises a plurality of

separate members

15 and 15 which are spaced apart but connected by a manual adjustment means 60. Similarly, truss frameworks 16 includes a plurality of separated section 17 and 17' which are spaced apart but connected by manual adjustment means 62. The manual adjustment means, which will be described in more detail below, comprises a screw means with oppositely threaded ends screwed into the adjacent truss members. Rotation of the member in one direction causes the two adjacent truss sections to be brought closer together and rotation of the member in an opposite direction causes the separation of the two adjacent truss sections to be increased. This results in the section of the screed member which corresponds to the truss section including the manual adjustment means to be bowed accordingly to provide selected crown configurations of the concrete surface. To provide further structural support for the main truss sections, additional structural member 66 is provided between selected vertical bars 50 in truss framework 14, and similar members are provided for truss framework 16. It will be noted that a plurality of the manual adjustment means 60 are provided along the top of truss framework 14 at selected intervals, and that these manual adjustment means are provided between only some of the vertical members. It will be apparent that the additional structural members 66 cannot be provided between adjacent vertical members 50 between which there is provided a manual adjustment means, since this would prevent the spreading between the two vertical members thereof. Thus the additional structural members 66 are provided only between those adjacent vertical members which do not include a manual adjustment means.

Reference will now be had to all of FIGURES 1, 2, and 4-6, with particular reference to FIGURES 46, for a description of the wheeled carriages which support the vertical truss frameworks. Referring particular to FIG- URE 4, which is a view of the end of the apparatus which includes the driving means for the reciprocating the screed members, a channel 70 through which support members 56 passes is provided adjacent one end of the carriage and includes roller means therein on which support member 56 rides in rolling engagement. The roller means comprises a pair of spaced apart

rollers

71 and 72 rotatably mounted within the housing or channel as more clearly seen in phantom in FIGURE 1. A corresponding channel is provided in carriage 10 for support ing member 54 in rolling engagement. The two channels of the two

carriages

10 and 12 are aligned with truss framework 14 and the respective support members associated therewith. Another channel 74 is provided adjacent the other end of carriage 12 and includes another pair of roller means, only one of which is shown at 76 in FIG- URE 4. A corresponding channel is provided in carriage 10, with these two channels being aligned with truss framework 16. Carriage 12 comprises a main horizontal structural member 68 for supporting the channels. Each of the channels has an inside width slightly greater than the width of the support members which pass therethrough, so that as the truss frameworks and the corresponding screed members are reciprocated, the support members engaging the roller means within the channels can move sideways within the limits required by the bringing of the

truss frameworks

14 and 16 closer together. It will be recalled that this occurs because of the hinged interconnection of the truss frameworks by the interconnecting truss structures spaced along the lengths thereof. Connecting bars 40 and 44' are connected by hinges at their ends to

frameworks

14 and 16 above and below the driving means to provide additional strength on this end of the apparatus.

The structural arrangement of the motor mounting base 24 is seen more clearly in the elevation view in section of FIGURE 5, taken through section lines 5-5 of FIG- URE 6. Motor 22 is supported on a motor base 24, and the latter is rigidly secured, as by welding, at one end 24a to the underside of support member 57, wherein an adequate clearance is left between the motor base 24 and support member 56. The base 24 is thus rigidly supported from support member 57 in a cantilever relationship, with no connection between end 24b and support member 56. It will thus be seen that the motor is rigidly supported solely from truss framework 16 by means of the support member 57, and that the only connection between the motor and truss framework 14 is by means of the crank arm 32. The relative reciprocation of the two screed members and associated truss frameworks as a result of the driving means is therefore apparent.

From the foregoing description, it will be seen that both

truss frameworks

14 and 16 and the driving means associated therewith are free to move laterally with respect to the line of travel of the apparatus along the rails and with respect to the two carriages, it being understood that any motion of the truss frameworks parallel with the line of travel of the apparatus will be within the limits of the carriage housings through which the support members pass. Unless the truss frameworks are anchored to a part of the apparatus that is fixed against any lateral movement, the truss frameworks and associated screed members will have a tendency to work closer to one carriage than the other as they are reciprocated. To maintain the screed members and truss frameworks centered between the pair of carriages, an anchor means is provided which maintains the mean or average position of the screed members and truss frameworks fixed relative to one of the carriages, but which in no way hinders the reciprocation of the screed members and truss frameworks. Referring particularly to FIGURE 6, which is an elevational view, partly in section, of the end of the apparatus that supports the driving means, a bar 90 is pivotally attached by a collar 91 to a bolt means 92, the latter of which is secured to the main body 68 of carriage 12 with a suitable spacer or collar 93 between the carriage 68 and collar 91 of rod 90. This rod is anchored to the carriage midway between the two

channels

70 and 74 and extends laterally between

truss frameworks

14 and 16 to a point along a line between the ends of

support members

56 and 57, as shown more clearly in FIGURE 2. Referring to FIGURES 2, 4 and 6, bar 90 is pivotally attached to a cross bar 96 by means of a fork 94 and cross bar 96 extends laterally with respect to bar 90 adjacent the inside surfaces of

support member

56 and 57. Another bolt means 103 is secured to the inside wall of support member 56 by means of a collar 100, and includes shoulders or

washers

101 and 102 at the lower end thereof. Cross bar 96 is pivotally attached at one end to bolt means 103 by a collar 106 disposed about the bolt between the washers. Similarly, another bolt means 113 is secured to the inside wall of support member 57 by means of a collar 110 and includes washers 111 and 112 between which the other end of cross bar 96 is pivotally attached by a collar 116. One of the bolt means 103, for example, is seen attached to support member 56 more clearly in FIGURE 6, whereas the attachment of the cross bar to both of these bolt means is more clearly seen in FIGURES 2 and 4. As the screed members and truss frameworks are caused to be reciprocated relatively to each other, cross bar 96 will swing back and forth accordingly as do the interconnecting truss frameworks that are hingedly connected between the

main truss frameworks

14 and 16. However, bar 90 maintains the position of the center of cross bar 96 essentially fixed so that the average or mean position of the screed members and truss frameworks remain fixed.

The elevation of the screed members can be adjusted to the proper height for working the concrete surface, whereby the carriages that support the main truss frameworks and screed members provide this function. Referring again to FIGURE 4, carriage 12 includes a generally U- shaped housing (also seen in FIGURE 1) attached to the main body 68 of the carriage through channel 70. A wheel assembly 132, including a Wheel 134 mounted on an axle therein, is pivotally attached within the housing adjacent the channel 70 by means of a bolt 133. A threaded member 136 is threaded through housing 130 and engages the top of the wheel assembly at its lower end, whereby the end of the threaded member below the housing 130 can be varied by rotation through a crank handle 138. By so doing, this end of the carriage can be raised or lowered with respect to track 13. A suitable electric motor 140 is secured to the outside of the wheel assembly and coupled directly to the axle on which wheel 134 rotates so that the entire apparatus can be moved along the track as desired. The corresponding end of the other car riage on the other side of the apparatus is similarly constructed and also includes an electric motor for driving this end of the apparatus or the other rail.

The other end of carriage 12 is similarly constructed and includes a generally U-shaped housing secured to the main body 68 of the carriage through channel 74, with a wheel assembly 152 pivotally secured adjacent channel 74 by means of a bolt 153. The wheel assembly includes a wheel 154 mounted on an axle within the wheel assembly for riding on the track. Another threaded member 156 is threaded through housing 150 to engage the wheel assembly, and can be driven in and out of the housing by means of a crank handle 158.

The track 13 is preferably supported above the ground surface by means of any suitable spacer members that are variable to adjust the elevation of the track. As shown in FIGURE 4, jack members comprising a housing 158, with a suitable base thereon, and a threaded member 159 for supporting the track is positioned at one point under the track for support. Similarly, a plurality of other spaced apart jack members are employed, such as housing 160 and threaded member 161 for supporting another section of the track. The elevation of these jack members can be varied as desired to adjust the elevation of the track 13.

A fragmentary, elevational view in section of the manual adjustment means for varying the contour of the screened members is shown in FIGURE 7. The manual adjustment means 60 comprises a double shank bolt means having a shoulder 182 which can be rotated with any suitable wrench, and first and second oppositely extending shanks and 181 which are oppositely threaded. One shank 180 is secured to one of the upper truss members 15 in threaded engagement therewith, and the other shank 181 is secured to an adjacent upper truss member 115' in threaded engagement therewith. As the bolt is turned in one direction, adjacent truss members and 15 are caused to be brought closer together, whereas rotation of the bolt means in the opposite direction causes the separation between the truss members 15 and 15' to be increased. This causes a corresponding moment or torque to be applied to the part of the screed member which corresponds vertically with the manual adjustment means through the vertical truss members 50. As a result, the contour of the screed member is varied accordingly. By providing a plurality of the manual adjustment means along the length of each of the

truss frameworks

14 and 16, a smooth contour of the screed member can be effected, which contour can be varied or adjusted to provide the desired crown configuration of the concrete surface.

Although the foregoing description has had reference to a preferred embodiment of the invention, there are certain modifications and substitutions that do not depart from the true scope of the invention that will undoubtedly occur to those skilled in the art. Therefore, it is intended that the invention be limited only as defined in the appended claims.

What is claimed is:

1. Apparatus for finishing a concrete surface comprising:

(a) a first truss framework including a first screed member carried along the bottom thereof for engaging said concrete surface,

(b) a second truss framework spaced from said first truss framework in parallel relation therewith and including a second screed member carried along the bottom thereof for engaging said concrete surface,

(c) first and second carriages disposed adjacent opposite ends of said first and said second truss frameworks including first and second roller means, respectively, aligned with said first truss framework and third and fourth roller means, respectively, aligned with said second truss framework,

(d) said first truss framework including first and second support members slidably supported by said first and second roller means, respectively, in rolling engagement therewith for freely supporting said first truss framework for reciprocation along a path between said first and second roller means,

(c) said second truss framework including third and fourth support members slidably supported by said third and said fourth roller means, respectively, in rolling engagement therewith for freely supporting said second truss framework for reciprocation along a path between said third and said fourth roller means,

(f) means disposed adjacent each of said roller means for constraining said truss frameworks for reciprocation along said paths,

(g) driving means supported by said first truss framework for movement therewith and including crank means coupled to said second truss framework for systematically reciprocating said second truss framework and for reactively reciprocating said first truss framework oppositely in response to the thrust of the crank means reciprocating said second truss framework, and

(h) hinge means interconnecting said first and second truss frameworks in hinged relation so that said first and second truss frameworks are relatively reciprocable.

2. Apparatus according to claim 1 wherein said hinge means comprises a plurality of spaced apart connecting truss structures connected in hinged relation to said first and said second truss frameworks along the lengths thereof.

3. Apparatus according to claim 1 wherein each of said first and said second truss frameworks include adjustable means for adjusting the length along the top thereof, and said first and said second screed members are relatively flexible in response to the adjustment of said first and said second truss frameworks, respectively, to take on selected are configurations along the lower surfaces thereof to produce selected crown configurations of said concrete surface.

4. Apparatus according to claim 1 wherein said first and said second carriages include first and second channels through which said first and said second support members pass, respectively, for confining the movement of said first and said second support members laterally in relation to the reciprocating movement thereof within the limits of said first and said second channels; and said first and said second carriages include third and fourth channels through which said third and said fourth support members pass, respectively, for confining the movement of said third and said fourth support members laterally in relation to the reciprocating movement thereof within the limits of said third and said fourth channels.

5. Apparatus according to claim 1 wherein each of said first and said second carriages include wheels for riding along parallel tracks, respectively, for supporting said first and said second carriages and for movement of said apparatus in a direction substantially perpendicular to the line of reciprocation of said first and said second truss frameworks.

6. Apparatus according to claim 5 wherein said first and said second carriages include means for driving said apparatus along said parallel tracks.

7. Apparatus according to claim 1 wherein said first and said second carriages include wheels pivotally attached thereto for riding along parallel tracks for supporting said first and said second carriages and for movement of said apparatus in a direction substantially perpendicular to the line of reciprocation of said first and said second truss frameworks, and means for pivotally adjusting said wheels to adjust the height of said first and said second truss frameworks in relation to said wheels.

8. Apparatus according to claim 1 including a first bar pivotally connected at its two ends to said first and said second truss frameworks, and a second bar pivotally connected at one end to said first bar intermediate said two ends thereof and connected at the other end to one of said first and said second carriages to constrain the average reciprocal positions of said first and said second truss frameworks.

9. Apparatus for finishing a concrete surface adapted for movement along a preselected path over the concrete surface, comprising:

(a) a pair of wheeled carriages adapted to run on a pair of tracks disposed along opposite sides of said concrete surface parallel with said preselected path,

('b) said pair of carriages including corresponding pairs of spaced apart roller means which are freely rotatable about axesparallel to said path,

(c) a pair of spaced apart truss frameworks spanning said concrete surface and supported in free rolling engagement at their opposite ends by corresponding roller means of said pair of carriages so as to be freely reciprocable laterally with respect to said path,

((1) means disposed adjacent each of said roller means for constraining said truss frameworks for reciprocation laterally with respect to said path,

(e) each of said pair of truss frameworks including a screed member for reciprocation therewith carried along the bottom thereof for engaging said concrete surface,

(f) driving means supported by one of said pair of truss frameworks for reciprocation therewith and having crank means coupled to the other of said pair of truss frameworks for reciprocating said other of said pair of truss frameworks laterally with respect to said path and causing an opposite reciprocation of said one of said pair of truss frameworks, and

(g) hinge means connecting said first and second truss frameworks in hinged relation so that said truss frameworks are relatively reciprocable.

10. Apparatus as set forth in claim 9 wherein each of said pair of truss frameworks comprises a plurality of vertical sections spaced apart along a plane extending transversely of said path and attached at the lower ends thereof along said screed member, and a plurality of adjustment means interconnecting the upper ends of adjacent sections of said plurality of sections for adjusting the spacial separations therebetween so as to adjust the contour of said screed member in said plane.

11. Apparatus as set forth in claim 10 including a plurality of spaced apart connecting truss structures interconnecting said pair of truss frameworks in parallel, hinged relation along the lengths thereof laterally with respect to said path.

12. Apparatus as set forth in claim 11 including a first member pivotally connected at its opposite ends to said pair of truss frameworks, and a second member pivotally connected at one end to said first member intermediate said opposite ends and at the other end to one of said pair of carriages.

13. Apparatus as set forth in claim 12 wherein each of said pair of truss frameworks include support members at the opposite ends thereof for engaging said corresponding roller means of said pair of carriages for supporting said truss frameworks.

14. Apparatus as set forth in claim 13 wherein said pair of carriages include corresponding pairs of spaced apart channels through which said truss framework support members pass and engage said roller means.

15. Apparatus as set forth in claim 14 wherein each of said pair of carriages includes a generally horizontal framework supporting said channels and said roller means, a wheel assembly for engaging said tracks pivotally attached at each end thereof, and wheel adjust ment means for adjusting said wheel assembly in pivotal relationship with respect to said horizontal framework to adjust the elevation of said corresponding screed member.

References Cited UNITED STATES PATENTS 1,945,145 1/1934 Gordon 9448 2,054,263 9/1936 McCrery 9445 2,248,247 9/1941 NiChOlS 9445 2,372,163 3/1945 Whiteman 9445 2,951,426' 9/ 1960 POllitZ 9445 XR FOREIGN PATENTS 854,941 11/1960 Great Britain.

JACOB L. NACKENOFF, Primary Examiner.