US3538843A

US3538843A - Truss forming apparatus

Info

Publication number: US3538843A
Application number: US767744A
Authority: US
Inventors: Adolph H Lubin
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-10-15
Filing date: 1968-10-15
Publication date: 1970-11-10
Anticipated expiration: 1987-11-10

Description

United States Patent [72] Inventor Adolph ll. Lubin 718 S. 7th St., Springfield, Illinois 62703 211 Appl. No. 767,744 [22] Filed Oct. 15, 1968 [45] Patented Nov. 10, 1970 [73] Assignee Rose and Robert L. Lubin, executers of said Adolph l-l. Lubin, deceased [54] TRUSS FORMING APPARATUS 13 Claims, 12 Drawing Figs.

[52] U.S. Cl 100/53, 100/100, I00/209. 100/210; l44/288: 27/152, 269/321 [51] Int. Cl B30b 15/14 [50] Field of Search 227/152; 269/321F; l44/288.6; 100/53, 100,209, 210

[56] References Cited UNITED STATES PATENTS 3,255,943 6/1966 Sanford 227/152 3,390,628 7/1968 Sanford 100/100 3,464.348 9/1969 McGlinchey 100/210 Primary Examiner-Billy J. Wilhite Attorney-Dawson, Tilton, Fallon and Lungmus ABSTRACT: A machine is described for securing together separate wood members by means of nail plates to form a completed truss in one step, The machine includes a large, elongated, flat bed of high strength concrete for supporting the individual members of the truss in a desired configuration.

Nail plates are placed above and beneath the abutting locations of each of the individual truss members to overlap adjacent edges. A carriage is mounted at the sides of the bed for travel along the bed; and it includes a first roller mounted for rotation about a horizontal axis extending transverse of the direction of travel of the machine for rolling over the wood members formed into the desired truss configuration and driving the nail plates to a first predetermined depth into the wood members. A second, similar roller is mounted to the carriage; and it follows the first roller for completely driving the top and bottom nail plates into the truss members to thereby firmly secure individual members together in the desired truss configuration. The carriage is power-driven; and the same source of power drives the rollers about their axes during operation, Electrical circuitry permits starting, stopping and reversing of the carriage.

Patented No 10, 1970 4 3,538,843

Sheet 2 of4 ii' iliiim fin.

B Y o awdmugzfl m 1,, 21

Patented No.10,1970 3,538,843

FIRST ROLLER SECOND ROLLER TRAVEL DIRECT/0N J/(MZK 061% 1/ TRUSS FORMING APPARATUS BACKGROUND AND SUMMARY The present invention relates to a truss-forming machine; more particularly, it relates to a system for forming completed trusses in a single operation.

Trusses have long been used as structural, weight supporting members in bridges and the like; but only comparatively recently have the advantages of wooden trusses in residential construction been fully appreciated. The principle use of trusses in residential construction is, of course, in the support of peaked roofs, in which case a number of spaced-apart trusses are supported by the walls. Trusses as used in residential construction are formed by cutting the individual, separate members from construction lumber of the size and shape required, and then securing abutting edges of the separate members together in the desired truss configuration by means of nail plates.

An early method of forming trusses of the type with which the present invention is concerned requires the use of metal horses equipped with clamping mechanisms for holding the individual members in the desired truss configuration; and an operator pulls a hydraulically powered press with flat, opposing jaws extending in horizontal planes to each location at which a nail plate is to be driven into the abutting truss members. The members; and he then moves the hydraulically-actuated press over the junction area. When the operator actuates the trigger, the jaws come together and drive the nail plate into the truss member. Thus, the operator is required to move the presses (which conventionally is suspended from a con-.

versely of the direction of travel of the gantry to form a support for the truss being formed. The tables are adjustably spaced along the direction of the rails; and each table includes a heel pad for supporting the truss at the particular location at which a junction of individual members is to be made. Thus, in setting up a truss configuration, the tables have to be adjusted along the direction of travel of the gantry to selected locations for supporting the individual members being joined; and heel pads on each table have to be moved to the correct lateral location to lie beneath the junction.

Each of the junctions are then clamped to the heel pad; the nail plates are placed above the separate truss members, and the gantry is driven over the truss to drive the nail plates partially into the wood members. After the first set of nail plates are partially embedded in the truss, the truss is moved from its setup and placed on a conveyor belt to a second location at which the nail plates were fully driven into the truss.

It will be realized that the total number of truss configurations is of great magnitude, and that it is desirable to have a truss machine capable of efficiently and economically producing small numbers of trusses without additional and lengthy setup procedures before a run can be made. Setup was complicated by the need to space the tables longitudinally of the truss and to separately locate the heel pads along the width of the table at the location at which junctions were to be made. Aside from the cumbersome setup procedure required of the prior machine, it had the further disadvantage that the trusses had to be conveyed to a separate location before the nail plates could be fully driven into the truss member.

The present invention provides a flat, integral bed of very high strength concrete for supporting the individual truss members in a desired configuration with nail plates located below and above each junction to be formed. The bed provides sufficient area to support a plurality of truss members to form anumber of trusses (of the same or different configurations) at the sarne time. A plurality of channels are formed longitudinally of the concrete bed in which lock members are received for locking the individual truss members in the desired configuration for formation.

A carriage is supported at each side of the bed for movement along the bed and over the formed truss. A first roller is mounted in the carriage to press both the top and bottom nail plates into the truss members to a predetermined depth (which is less than the height of the nail prong) to start the nail plates into the wood truss member. A second roller is located in the carriage behind the first roller to fully drive the nail plates into the truss members and thus complete the formation of the truss. A third roller is also housed in the carriage at the same height as the previously-described first roller so that the carriage may form trusses while being driven in either direction.

It will thus be appreciated that the present system does not require the spacing of separate tables for supporting the individual trusses in the direction of travel of rollers. Secondly, there is no. need for the heel pads of the previously-described commercialized machine for supporting the unsecured truss at the juncture and locking the same place.

The height of the pressing rollers above the bed is independently adjustable so that the system may be adapted for trusses of different depths. Further, the adjustability of the initial or lead roller has been found to be advantageous in adapting the machine to all makes and gauges of nail plates and to further accommodate differences in density, penetration resistance, etc. of the woods encountered. The inventive system accommodates trusses of any configurations without the need to make adjustment of the supporting member. The flexibility of the arrangement used to lock the separate truss members into the desired configuration permits a set up with a minimum of adjustment. Further, the size of the bed permits the formation of several truss configurations, not all of which need be of the. same configuration. The same apparatus could readily be adapted to form wall panel assemblies, both interior and exterior of various lengths.

Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.

THE DRAWING FIG. 1 is a perspective view of a truss-forming system according to the present invention;

FIG. 2 is a close-up view of a setup for the formation of the truss;

FIG. 3 is an exploded view of a junction of individual truss members together with a detailed view of the truss locking mechanism;

FIG. 4 is a detailed view of a nail plate as seen in FIG. 3;

FIG. 5 is a side elevation view of the carriage and roller assembly together with the drive mechanism;

FIG. 6 is a detailed plan view of the adjustable roller mountmg;

FIG. 7 is a detailed elevation view of the roller mounting and the drive shaft;

FIG. 8 is a longitudinal cross section view of a roller;

FIG. 9 is a transverse cross section view of the table;

FIG. 10 is a perspective view of the lock mechanism for securing the truss in place;

FIG. 11 illustrates the operation of the lead and follower roller to form a truss; and

FIG. 12 is a circuit schematic diagram of the electrical system for controlling the apparatus of FIG. 1.

DETAILED DESCRIPTION Referring now to FIG. I, there is in perspective view a system incorporating the present invention. The system of FIG. 1 includes a table having an elongated, flat bed generally designated by reference numeral which is integrally made with and carried by a supporting base 11 which rests on the ground. The bed or platform 10 is formed of high strength concrete, as disclosed in greater detail within.

Rails

12 and 13 are rigidly secured to the elongated side edges of the bed 10. A driven carriage, generally designated 15, is mounted on the side rails 12 and 13 for rolling along them, as presently discussed.

The frame for the carriage 15 includes a pair of

vertical side plates

18 and 19 which are secured together at their upper sections by

crossbars

20 and 21. The

side plates

18 and 19 are secured together at a lower location by means of

transverse crossbars

22 and 22a (FIGS. 1 and 5) to form a very rigid structure adapted for movement longitudinally of the bed 10.

As seen clearly in FIG. 9, the bed 10 rests on a base of concrete as indicated by reference numeral 25. The base 25 is made from a high strength concrete of the order of 4,000 psi. The bed 10 preferably includes a covering layer 10a of abrasion-resistant concrete such as is available under the tradename Metalicorn. The side rails 12 and 13 are C-shaped in cross section, having inwardly-extending upper and lower flanges as at 12a and 12b, and 13a and 13b, respectively, for providing steel surfaces along which the rollers are drive wheels (described later) supporting the carriage 15 may ride.

Embedded in the upper surface of the bed 10 are a plurality of longitudinal channels generally designated by reference numeral in FIG. 1. The channels 30 are located at equallyspaced increments along the width of the bed 10; and each of the channels 30 extend for the full length of the bed 10. Referring now to FIG. l0, one of the channels 30 is seen in greater detail to include a ll-shupcd conduit member 3| defining an open upper track 32. The upper, side edges of the channel member 3] are provided with downwardly-turned flanges 33. A rectangular-shaped nut 34 is provided with tapered, serrated grooves along opposite edges of its upper surface for receiving the downwardly-turned flanges 33 of the channel member 31 and locking the nut 34 to the channel member when an upward force is inserted on the nut 34. A spring 34a interposed between the bottom of the channel 31 and the nut 34 resiliently urges the nut 34 into the upper position and thereby facilitates access to nut 34. Preferably, in horizontal cross section, the nut 34 is rectangular having its longest dimension transverse of the grooves 35 so that when the nut 34 is turned at a right angle, it may be removed from the channel member 31 through the open track 32 while at the same time, the nut 34 may be adjusted longitudinally of the channel member 31 to any desired position.

The nut 34 defines a vertical, threaded aperture 38 for receiving a threaded bolt 39. Rotatably mounted on the neck of the bolt 39 is an L-shaped angle brace generally designated 40, and including a horizontal portion 41 and an upstanding portion 42 for engaging and holding a truss supported on the bed 10 of the machine.

Referring again to MG. 1, it will be appreciated that each of the ChIlllflClH 30 may be provided with a nurnher of similar nuts, bolts and angle lH'ttClwlN for locking a truss in pluc'e after initial setup and prior to driving the carriage over the truss. The locking system described including the channels and fittings is distributed by Unistrut Corporation, Wayne, Michigan.

It will be appreciated that various modifications of the lock member described as well as alternatives to the overall locking mechanism may be equally effectively employed for locking the truss in place. One such modification is shown in FIG. 3 wherein a flat bearing plate 45 having an integral handle 46 replaces the previously-described angle bracket 40. The bearing plate 45 defines a contact surface 47 for engaging the sides of the wood members of the truss; and the contact surface 47 may be curved and eccentrically formed about the pivotal connection between the bolt 39 and the bearing plate 45; so that as the handle 46 is rotated in a direction of the arrow in FIG. 3, the surface 47 is brought into engagement with the wood member 48 which is an individual member forming the final truss.

FIGS. 2 and 3 illustrate in greater detail a setup which might be employed for a typical truss configuration. The base member of the truss is designated 49; and the nail plates are designated 50. It will be appreciated from a full understanding of the invention that the dimensions or gauge of the nail plates employed is not critical, and that nail plates having different areas may simultaneously be employed. A detailed view of a nail plate 50 is seen in FIG. 4 to include a flat piece of sheet metal 51 from which a plurality of prongs 52 are cut and bent to assume a position perpendicular to the plane of the plate 51. The prongs 52, of course, form the nails; and the plate 51 serves to provide a brace uniting the individual truss members (such as the

members

48 and 49 of FIG. 3) at a junction where the two wood members abut. After the individual members of the truss are laid out in proper relation on the bed 10, nail plates 50 are placed above and beneath each of the junctions of separate members to overlap the abutting edges. The truss is then locked into place by means of the previously-described locking members, which, it will be remembered, are slidably adjustable along the channel members 31.

Referring now to FIGS. 57, three pressing rollers are designated 55, 56, and 57 respectively. A convention will be made that the forward direction of the rollers 5557 is to the right in FIG. 5; so that the roller 55 will be sometimes be referred to as the forward roller, the roller 56 as the center roller, and the roller 57 as the rear roller.

Each of the pressing rollers 55-57 is similar in construction; and, referring to FIG. 8, the roller 57 is seen to include a shaft 60 and a cylindrical sleeve 61 which provides the surface which drives the nail plates into the truss member. The sleeve 61 may be heavy-wall type pipe stock. A plurality of baffle plates 62 extend radially of the shaft 60 and are spaced longitudinally along it. The plates 62 are plug-welded as at 63 to the cylindrical pipe 61. The baffle plates 62 are also welded as at 64 to the shaft 60. End plates 65 secure the ends of the pipe or sleeve 61 to the shaft 60; and further reinforcement is provided by end blocks 66 of heavier stock which end blocks also serve as mounting members for sprockets (not shown in FIG. 8).

Referring in particular to FIG. 5, each of the pressing rollers 55-57 is secured to their

respective side plates

18 and 19 of the carriage 15 in a similar fashion, and hence, only one such mounting need be described in detail for a complete understanding of themachine. Toward this end, the mounting for the forward roller 55 will be more fully explained presently.

The plate 18 defines a slot 68 which is elongated in the vertical direction for receiving a shaft 69 of the roller 55. The shaft 69 extends through the side plate 18 and is received in a roller bearing 70, as best seen in FIG. 6. The bearing 70 includes a casing 71 which is received by means of side slots in two vertical hearing guides 73 and 74. The hearing guides 73 and 74. The bearing guides 73 and 74 are rigidly mounted to the plate [8 by mcnns of

angle irons

75 and 76 which are welded to the outer surface of the plate IS. The bearing housing 7] is vertically slidable along the

guides

73 and 74. Secured to the bottom of the angle irons.75 and 76 is an internally-threaded housing generally designated 77 which receives a threaded shaft 78 which is secured to the bearing housing 71 as at 79. The housing 77 includes a capstan which, when turned, withdraws or extends the threaded shaft 78 to move the bearing housing vertically to a predetermined location along the bearing guides 73 and 74. The means just described for permitting vertical adjustment of the shaft of the pressing roller while rigidly fixing that position relative to the bed 10 of the machine during operation is commonly used and referred to as a type C elevator boot takeup and it is known to have very great strength in tension so as to easily sustain the force encountered in driving the nail plates into the wood truss member.

The side plate 18 also defines slots 81 and 82, similarly elongated in the vertical direction for receiving the shafts of the center and rear

pressing rollers

56 and 57 respectively. Elevator boot takeups, generally designated 83 and 84 in FIG. 6 are also provided formounting the shafts of the

pressing rollers

56 and 57 to the side plate 18 while permitting vertical adjustment thereof. Similar mountings are provided (though not illustrated) for the other side of each of the shafts of the rollers 55-57 in securing them to the side plate 19.

A drive motor 90 including a conventional speed reducer,

coupling, and brake is mounted on the interior side of the plate 18 by means of a bracket 91 fastened to the bottom of supporting

braces

92 and 93. A sprocket 94 is mounted on the shaft of the motor 90; and it drives a chain 95. The chain 95 is wound around a second sprocket 96 which is connected to a main drive shaft 97. The drive shaft 97 is rotatably mounted by means of pillow blocks 97a to a bracket 98 which, in turn, is fastened to the side wall 18 by means of the mounting members 99. The other side of the drive shaft 97 is similarly fastened to the other side wall 19. A pair of sprockets, smaller than the sprocket 96 and identified by reference numerals 100 and 100a in FIG. 7, are mounted on the drive shaft 97. Second and third chains 101 and 102 are driven respectively by the sprockets 100 and 100a to drive the carriage and the pressing rollers. The chain 100 is fitted around a sprocket 104 which is mounted on the shaft 69 of the forward roller 55 by means of the end block 66, as mentioned. The chain 100 is also wound about a sprocket 105 which is rigidly connected to the shaft of the center roller 56 by means ofa similar end block. The chain 101 is also fitted about an idler sprocket 106 which is laterally adjustably mounted in a horizontal slot 107 in theside plate 18. Similarly, the chain 102 is wound around an idler sprocket 108 laterally adjustable mounted in a horizontal slot 109 in the side plate 18, a sprocket 110 connected tothe drive shaft of the rear roller 57, and a sprocket 111 which is secured to the side plate 18 by means of a bearing block 112 and a shaft 112a.

A drive wheel 113 (FIGS. 1 and 7) is also mounted to the shaft 112a so that by driving the sprocket 111, the drive wheel 113 is rotated. The drive wheel 113 engages the top flange 12a of the side rail 12 of the bed 10. Thus, all of the rollers 55-57 as well as the carriage 18 are driven by means of the motor 90. Since the drive shaft 97 extends between each of the

side plates

18 and 19, a similar device arrangement is provided (although not shown in detail) for driving the other side of the carriage l5.

Cam followers

115 and 116 are conventionally mounted to the inside of the side plate 18; and they are rotatable about a horizontal axis perpendicular to the plane of the page of FIG. 5 for engaging the lower flange 12a of the rail 12 and preventing lifting of the side plate 18 as the rollers press over the nail plates and wood truss members. A similar cam follower 117 is suitable mounted 'to engage the upper flange 12a of the side rail 12 directly above the forward lower cam follower 116 to achieve stabilitycAs seen in FIG. 7, a similar cam follower 118 is secured by means of the mounting plate 119 to the inside surface of the side plate 18 and rotatably mounted about a vertical axis to engage the vertical side surface of the side rail 12 and prevent lateral shifting of the carriage 15. There are two such cam rollers (the other one being designated 119a in FIG. 5) for each side plate of the carriage 15, although the two attached to the side plate 19 are not shown for brevity.

OPERATION The operation of the above-described mechanical portion of the machine is best illustrated in FIG. 11 which is a vertical cross section view taken from the left side of the machine; and it is apparent that the illustration is condensed, having a midsection deleted. The roller 55 is adjusted to a height whereby its lowest portion is at a predetermined height above the upper surface of the bed to drive the two opposing

nail plates

125 and 126 partially into the wood truss member 127. After the sufficient to press the plate portions of the nail plates and 126 into contact with the truss member 127, continues to drive the

nail plates

125 and 126 fully into the truss member 127. It is assumed, of course, that the

nail plates

125 and 126 overlap to join together abutting portions, although only one individual truss member is shown. 7

Referring now to FIGS. 1 and 5', a safety feature is incorporated in the system to automatically shut down the motor which drives the carriage should an object or obstruction'be encountered in front of the carriage. A first bumper 130 has a lead rail 131 which extends completely transverse of the carriage 15 and lies in front of it. A similar bumper generally designated 132 and including a lead rail 133 (seen in FIG. 1 in perspective) is attached to the rear of the carriage 15. The

bumpers

130 and 132 are suspended from the framing (

crossbars

22 and 22a) of the carriage by means of links 135 which are pivotally connected at 136 to the crossbars. Thus, when either of the

bumpers

130 or 132 engages an obstruction, it will pivot in the direction of the carriage 15. A first collision limit switch 138 having a contact arm engaging the rear of the bumper 32 is mounted to the crossbar 22 of the framing of the carriage 15 to be closed when the bumper 132 encounters an obstruction. Similarly, a collision limit switch 139 having a wiper arm engaging the rear rail of bumper 130 is connected to the transverse brace 22a to open when the same encounters an obstruction. As will also be observed in FIG. 1, there are a plurality of control boxes generally designated 140 which are spaced longitudinally of the table 10 to permit an operator to control the movement of the carriage 15 at any number of locations along the table. It is contemplated that for a bed length of 100 feet, six such stations would be provided.

Turning now to FIG. 12, three input lines 141 are connected to a conventional three-phase, 60-cycle source of electricity (not shown). A three-phase disconnect switch, generally designated by reference numeral 142, is interposed in the lines 141. A fuse 143 is inserted in each of the lines 141. Forward/reverse contacts (controlled by separate relays) include three normally open contacts 145 one of which is connected in each of the lines 141 for coupling the source to drive the motor 90 (shown schematically in FIG. 12) in a forward direction, and three normally open contacts 146 for reversing the phase in two of the source lines to reverse the direction of rotation of the motor 90. The previously-described

collision limit switches

138 and 139 are connected in series with the coil ofa relay 147 across two of the power lines. Three normally open contacts 147a are connected in the main power lines 141 between the forward/reverse contacts 145 and 146 and the three-phase drive motor which is the previously-described drive motor 90. 'The motor is protected from thermal overload as at 148. When either of the

collision limit switches

138 or 139 is opened by its associated bumper encountering an object, the relay 147 will be deenergized to open the contacts 147a and shut down the motor 90. A brake coil 90a for the motor 90 is connected across two of the power lines 141 as is conventional.

The control circuitry for the individual control stations 140 spaced along the table is energized by means of a transformer 150 having its primary connected across two of the power lines 141 and its secondary fused as at 151 and 152. For purposes of illustration, it will be assumed that there are six of the independent control stations 140 (identified by roman numerals I-VI in FIG. 12) spaced along the table, although only two such stations are shown in FIG. 1. In order to facilitate the association of the components with each station, each of the stations will be represented respectively by the numerals 161, 162, 163, 164, 165, and 166 with an accompanying letter to represent a circuit element at the station. Thus, a series of six

stop push buttons

161a, 162a, 163a, 164a, 165a, and 166a are connected in series, with one terminal of the switch 161a connected to the fuse 151. The switches 161a-I66a are emergency stop switches.

Each station is also equipped with an on/off switch; and these are designated respectively 161b, 1621), 163b, 164b, 165b, and 16612. The switches 161b166b are key-operated selector switches; and they have one terminal connected in common to a terminal of the switch 166a. The on/off switch for station 161 is illustrated as being closed while the others are illustrated as being open; and each of the switches 16llb 1661; may be manually set to an on" or an off position by means of the key. Each of the individual stations is not activated until the switch is set to an onposition. Each station is also equipped with a forward push switch (designated respectively 161c-166c) and a reverse switch (designated 161d-166d respectively). The forward and the reverse push switches are spring return selector switches biased to the off position; and they each have one terminal connected to their respective on/off key-operated switches. The other terminal of all of the forward switches is connected in common to a normally-closed, movable right limit switch 167. The reverse switches for each of the stations have their second terminal connected in common and coupled to one terminal of a normally-closed, movable left limit switch 168. The movable right and left limit switches may be located beneath the bed 10 so as to be contacted by the cam followers 115; and they may be placed at any location along the bed.

A right limit switch which is normally closed and designated by reference numeral 169 is connected in series with the normally-closed movable right limit switch 167 and a normallyclosed pair of contacts 170 controlled by the forward relay 171. A similar left limit switch which is normally-closed and designated 174 is connected in series with the movable left limit switch 168 and a pair of normally-closed contacts 175 which are actuated by a reverse relay 176. The other terminal of the relay coils 171 and 176 are coupled to the second terminal of the secondary winding of the transformer 150. The forward relay 171 also actuates the forward contacts 145 interposed in the power lines 141; and the reverse relay 176 also actuates the reverse contacts 146. Normally-closed contacts 177 and 178 are connected in series with the forward and reverse

relays

171 and 176 to deenergize them when the motor is overloaded, according to conventional technique.

A normally-open set of relay contacts 150 which are controlled by the forward relay 171, are connected between the common junction of the on/off switches 16111-166b and the common terminal of the station reverse" switches 161d 166d to short circuit all the individual station reverse actuators when the carriage is moving in a forward directiomA pair of normally-open contacts 181 which are controlled by the reverse relay 176 are connected between the common junction of the station on/off switches 161d-166d and the common junction of the station forward switches 161c- 166c to similarly short circuit the station forward switches when the carriage is traveling in a reverse direction. Thus the carriage must be fully stopped before its direction may be changed.

in operation, after the main disconnect switch 142 has been closed, at least one of the station on/off switches 161b-166b (for example, switch 16212) has been actuated to energize the appropriate'stations, when an operator desires to move the carriage in a forward direction, one of the station's forward push switches 161c 166c must be closed. When this occurs, current is coupled from the secondary of the transformer 151) through the series-connected stop switches 161a166a, through the station on switch 162b, the station forward" switch 1620, the normally-closed movable right limit switch 167, the normally-closed fixed right limit switch 169 and the normally-closed contacts 170 to the coil 171 of the forward relay. When the relay 171 is energized, the contacts 145 are closed and, providing the collision limits switches 138 and 139 are also closed, the contacts 147a will be closed by relay 1457 to energize the drive motor 90. During this time, the contacts 81) will also be closed to insure that the station reverse switches are shorted. At the same time, the normally-closed contacts 175 will be open by the relay 171 to insure that the relay 176 cannot be energized. Thus, the carriage will continue in a forward motion with either one of the stations stop push switches 161a- -166a is opened, or the movable right limit switch 167 is encountered, or the fixed right limit switch 169 is actuated.

The operation of the station reverse" switches 161d-li6td is similar but complementary; and it will be observed that when the reverse relay 176 is energized, it controls a pair of normally-closed contacts 170 inserted in series with the coil of the forward relay 171 to open thereby insuring that the forward relay 171 cannot be energized while the carriage is moving in a reverse direction. At the same time, the reverse" relay reverses the phase in two of the motor power leads 141 to reverse the stator current by means of the normally-open contacts 146.

Having thus described in detail a preferred embodiment of the present invention, it will be apparent to persons skilled in the art that various modifications and substitutions may be made for the structure and circuitry which have been illustrated; and it is, therefore, intended that all such modifications and equivalents be covered as they are embraced within the spirit and scope of the appended claims.

It is claimed:

1. Apparatus for securing together separate wood members by means of nail plates to form a truss comprising: a table providing a flat bed for supporting said separate members in a desired truss configuration with a first nail plate located above and a second nail plate located below abutting locations of said members and with the prongs of said nail plates in engagement with the upper and lower surfaces respectively of said members; carriage means mounted to said table for travel along said bed and including first roller means spaced from said bed at a distance to drive said top and bottom nail plates into said truss members to a first depth less than the height of said nail prongs, and second roller means on said carriage generally parallel with and behind said first roller means and spaced from said bed at a second predetermined distance for rolling over said top and bottom nail plates and said truss members after said first roller means to fully drive said top and bottom nail plates into said truss members; and power means for driving said carriage along said bed.

2. The apparatus of claim 1 further comprising lock means for locking said truss members in a predetermined truss configuration and securing.

3. The apparatus of claim 2 wherein said lock means is connected to said bed for securing said truss configuration thereto.

4. The apparatus of claim 3 wherein said lock means comprises a plurality of elongated tracks fixed in said bed at laterally-spaced apart locations and extending longitudinally thereof, at least one look member slidably received by each of said tracks for adjustment therealong and rigidly securable to said track at any selected location along said bed; and a contact member secured by each of said lock members in engagement with a truss member for limiting lateral movement thereof.

5. The apparatus of claim 1 wherein said power means includes an electrical motor on said carriage and drive means powered by said motor and in frictional contact with said bed to drive said carriage along said bed and further including control means for selectively driving said carriage in either direction and for stopping motion thereof.

6. The apparatus of claim 1 further comprising third roller means mounted on said carriage on the other side of a said second roller means than is said first roller means and parallel thereto, and spaced from said bed at approximately the same distance as said first roller means whereby said carriage may form trusses in one pass in either direction of travel along said bed.

7. The apparatus of claim 6 further comprising lock means connected to said bed and adjustable therealong for securing individual members of said truss to said bed in said desired configuration.

8. The apparatus of claim 7 wherein said bed includes a supporting surface of high strength concrete of the order of 4000p.s.i. and said lock members include track means embedded in said concrete of said bed for slidably receiving said lock means to facilitate adjustment of said lock means along said bed during set up of a truss configuration.

9. The apparatus of claim 8 wherein said bed further includes first and second side rails mounted respectively to opposite sides of said bed and extending in the direction of elongation of said bed, said carriage mounted for rolling along said rails.

10. The apparatus of claim 9 further comprising drive wheel means rotatably mounted on said carriage and for frictional engagement with said bed, and coupling means for coupling the power of said motor to drive said rollers and said drive wheel means.

11. The apparatus of claim 7 further comprising control means for selectively driving said carriage in either direction and for stopping the same.

12. The apparatus of claim 11 wherein said control means comprises a plurality of control stations mounted at spaced in tervals along said bed, each station including forward control means for driving said carriage in a first direction along said bed, interlocking circuit means for disengaging one of said forward drive means and said reverse drive means when the other is energized, and stopcircuit means for disengaging all of said forward andreverse drive means to thereby stop said carriage.

13. The apparatus of claim 1 further comprising adjustable means for mounting each of said roller means to said carriage while permitting independent adjustment of said distance between each roller and said bed.