US3315595A

US3315595A - Suspension for press or the like

Info

Publication number: US3315595A
Application number: US496473A
Authority: US
Inventors: Walter G Moehlenpah; Jr George E Pallme
Original assignee: Hydro Air Engineering Inc
Current assignee: Hydro Air Engineering Inc
Priority date: 1965-10-15
Filing date: 1965-10-15
Publication date: 1967-04-25
Anticipated expiration: 1984-04-25
Also published as: GB1141476A

Description

April 25, 1967 w. G. MQEHLENPAH ETAL SUSPENSION FOR PRESS OR THE LIKE 5 Sheets-Sheet l Filed Oct. 15, 1965 FIG. I.

April 25, 1967 w. cs. MOEHLENPAH ETAL 3,315,595

SUSPENSION FOR PRESS OR THE LIKE.

Filed Oct. 15, 1965 5 Sheets-Sheet 2 April 25, 1967 v w. G. MOEHLENPAH ETAL 3,315,595

SUSPENSION FQR PRESS OR THE LIKE 3 Sheets-Sheet 3 Filed Oct. 15, 1965 FIG. 3.

SOL

United States Patent 3,315,595 SUSPENSION FOR PRESS OR THE LIKE Walter G. Moehlenpah, Ladue, and George E. Pallme, Jr., St. Louis County, Mo., assignors to Hydro-Air Engi: nearing, Inc., St. Louis, M0., a corporation of Missouri Fiied Oct. 15, 1965, Ser. No. 496,473 17 Claims. (Cl. 100-214) This invention relates to a suspension for a press or the like and more particularly to truss fabricating apparatus which includes a heavy fluid-operated press and means for suspending the press so that it is easily moved relative to the truss during its manufacture.

In one widely used system for manufacturing wood trusses a press is suspended from an overhead carriage and moved to various locations for driving nailing or connector plates into assembled precut wood truss members where they intersect or abut each other. Such a system is disclosed in the Moehlenpah and Pallme United States Patents 3,068,484 and 3,069,684. In such apparatus a press is hung from one end of a beam and hydraulic apparatus for actuating the press is mounted on the other end of the beam. The beam is pivotally suspended from a movable overhead carriage and thus the press is supported for universal movement to the various locations I when nailing plates are to be forced into the wood members to form the truss joints. This system has proved quite satisfactory for press installations where the trusses are manufactured from lighter sizes of lumber, such as 2 X 4s. However, there has been .a growing demand for larger, heavier trusses using large sizes of lumber (such as 2 X 12s) and this requires a proportionally larger capacity press, e.g., in the order of 50 tons instead of about 20 tons. Presses of this large capacity are quite heavy (e.g., 800 lbs. or more) and the hydraulic apparatus to power these presses is also massive. The great inertia and weight of such presses and associated hydraulic apparatus render it quite impractical to mount these components on opposite ends of a suspended pivoted beam and still permit an operator to effectively and quickly move from station to station and properly press the nailing plates into the wood to form the truss joints.

suspending the press from a movable carriage for universal movement to the various nailing plate locations is also impractical. This is due to the fact that the usual press for manufacturing wood trusses has a lower platen fixed relative to the press frame and an upper platen movable toward the first platen as the hydraulic power unit actuates the press. With these platens positioned above and below the opposed prepositioned connector plates bridging the upper and lower surfaces of abutting or intersecting wood members, actuation of the .hydraulic power unit will cause the upper platen to move downwardly and contact the upper nailing plate. Continued application of a downward force by the upper platen is accompanied by an equal upward force which tends to lift the press. This will cause the suspension for the press to become slack and then to cock over or tilt and thereby apply uneven forces on the nailing plates. Such action will in turn cause nails struck from the plate to collapse and buckle rather than be driven into the truss members.

Accordingly among the several objects of the invention may be noted the provision of improved means for suspending a fluid-operated press which prevents tilting or cocking of the press during operation of the press; the provision of a suspension for a press which is suificiently long and stiff to limit swinging of the press but is still sufliciently flexible to permit self-aligning of the press as its platens close; the provision of a suspension system for a press which during operation effects a smooth upward movement of the press as a whole at a substantially constant controlled rate; the provision of improved suspension means for a fluid-operated press or the like wherein the length of the suspension supporting the press varies with operation of the press; the provision of apparatus for fabricating wood trusses or the like using a heavy fluid-operated press for driving nailing plates wherein the weight of the press is suspended in such a manner that cocking or tilting of the press and the resulting collapse of nails of nailing plates is avoided. Other objects and features will be in part apparent and in part pointed out hereinafter.

In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated,

FIG. 1 is a perspective of apparatus of the invention showing a press for fabricating wood trusses or the like suspended from an overhead rail;

FIG. 2 is an elevation showing a portion of the press positioned for driving nailing plates into truss members;

FIG. 3 is a hydraulic circuit diagram; and

FIG. 4 is a modified hydraulic circuit diagram.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawmgs.

Referring now to the drawings, a hydraulic press suitable for use in manufacturing wood trusses or the like is generally designated 1 and comprises a lower platen 3 fixed relative to the press frame and an upper press platen 5 which is movable toward and away from the lower press platen 3 under control of a hydraulic press power means 7. Press 1 is suspended from an overhead carrier 9 by means shown generally to include a linkage 11 and a fluid lifter or expansible chamber 13 for counterbalancing the weight of the press and for varying the distance between the press and the carrier. Carrier 9 travels along an elevated I-beam or rail 15 to various positions where nailing together of truss members is to take place. In operation fluid under pressure is provided to the power means 7 of press 1 .and to the eXpansible chamber 13 by hydraulic control apparatus generally designated 17 in FIGS. 1 and 3.

Referring to FIG. 2 of the drawings,

be spliced together. The truss members are carried by a pedestal P which may, for example, be of the type shown in the beforementioned Moehlenpah et al. patents. The truss members T1 and T2 are held in abutting engagement on pedestal P by suitable clamping apparatus, a portion of which is designated 21 in FIG. 2. There is a vertically movable locator tray 23 immediately beneath the joint between truss members T1 and T2 on which a lower nailing plate N1 rests. A similar nailing plate N2 is positioned above the interesection of truss members T1 and T2.

Nailing plates N1 and N2 are driven into the truss members T1 and T2 by operation of the hydraulic power means 7 closing platens 3 and 5 relative to each other. Since platen 3 is fixed relative to the press frame, operation of power means 7 causes the upper platen 5 to be lower until it engages the top of nailing plate N2. Then application of additional force by upper platen 5 on nailing plate N2 lifts the lower platen 3 into engagement with locator plate 23 because there is less resistance to this upward movement of platen 3 than there is to driving nailing plates N2 into the truss members. Further operation of the hydraulic power means 7 causes the upper platen 5 to be forced downwardly for driving the upper nailing plate N2 into the truss members T1 and T2 and at the same time the lower platen 3 is forced upwardly against the locator plate 23 for driving the lower nailing plate N1 into the bottom of the press members T1 and T2. The lifting of the platen 3 occurs without the press cocking or tilting due to the operation of expansible chamber 13 which keeps the suspension for press 1 taut throughout the nailing operation.

Assuming the nailing plates both encounter equal resistance, they will be simultaneously driven into the truss members T1 and T2. However, should the nailing plates encounter unequal resistances to entering the wood members (e.g., one nailing plate might strike a hard knot) then the nailing plates may be alternately driven into the truss member. After the nailing plates have been driven into the truss members, hydraulic pressure is provided to power means 7 for separating platen from platen 3 so that the press may be moved from one of the pedestals P of the truss fabricating apparatus to another pedestal.

. More specifically, press 1 includes a generally C-shaped frame 27, the upper portion thereof being attached to the cylinder 29 of power means 7 and the lower portion thereof supporting the lower platen 3. Power means 7 has a piston 31 (FIG. 3) which sweeps through cylinder 29. A ram 33 attached to piston 31 projects fromthe lower end of cylinder 29 and is secured to upper platen 5. Hydraulic fluid under pressure is provided to the upper and lower ends of cylinder 29 by

fluid lines

35 and 37, respectively, for extending and retracting ram 33, thereby moving platen 5 toward and away from platen 3.

The carrier 9 comprises a center body portion 41 supported at each end by two pairs of flanged wheels or rollers 43 which engage and roll along the lower flange of the I-beam or rail 15. Rail 15 is supported at its ends by two spaced overhead beams (not shown) which are parallel to each other and to the lower chord of a truss on pedestals P. Rail 15 is generally perpendicular to these beams and to the lower chord of the truss. Rail 15 is preferably driven along these beams by a fluid motor 45 (FIG. 3) under control of the hydraulic apparatus described. later. The carrier 9 is easily moved along rail 15 by applying a force directly to press 1.

The expansible chamber 13 is attached to the lower center portion of carrier body 41 by a pin and clevis connection generally designated 47. The pin of this connection is parallel to rail 15. As shown in the drawings, chamber 13 includes a generally vertical cylinder 49 through which a piston 51 (FIG. 3) sweeps. Attached to the lower side of piston 51 and projecting through the lower end of cylinder 49 is a piston rod 53.

The outer end of rod 53 is attached by a pin and clevis connection 55 to a rod or pipe 57. The pin of connection 55 is parallel with truss chords between platens 3 and 5 and is perpendicular to the pin of connection 47 when the press is along the lower chord of a truss. The lower end of rod or pipe 57 is rigidly connected to a fork 59 which is rigidly secured to the upper portion ofthe press frame 27.

The full weight of press 1 on linkage 11 and cham- 7 her 13 makes the suspension stiff so that the suspension resists bending or flexing movement. The pivotal connections 47 and are as high as possible and near carrier 9 so that a pushing or pulling force on the press parallel to rail 15 is applied to the carrier 9 near rollers 43 and it easily moves the carrier along the rail. Therefore, the carrier closely follows movement of the press, and the press can be moved toward and away from pedestals P without tilting or cocking the press to any significant extent. The semi-stiff suspension provided reduces the tendency for the press to swing as it is moved and this permits more rapid positioning of the press than otherwise could be obtained. The suspension can flex or pivot at

connections

47, 55 for self-alignment of the platens during the pressing operation.

Hydarulic fluid is provided to and removed from cylinder 49 through a hydraulic line 61. A breather cap 63 at the upper end of cylinder 49 permits air to pass freely into or out of the upper end of cylinder 49 above piston 51. Thus extension and retraction of piston rod 53 and the lifting and lowering of press 1 is under control of piston 51 which is moved in response to fluid conditions 4 in line 61. When press 1 is rotated, piston 51 and rod 53 rotate with it in cylinder 49.

The hydraulic system 17 used for providing fluid under pressure to press means 7, motor 45 of the carrier and cylinder 49 of the expansible chamber 13 is illustrated in FIG. 3 of the drawings. The hydraulic system 17 comprises a motor 65 which drives a pair of variable displacement pressure compensated

pumps

67 and 69.

Pumps

67 and 69 draw hydraulic fluid from a reservoir 71 through

filters

73 and 75. Fluid under pressure discharged by pump 67 flows through a check valve 77 and is provided via

fluid lines

78, 80 to a three position control valve generally designated 79. A portion of the fluid from pump 69 is provided to fluid line 80 for delivery to control valve 79 through a fluid line 82. There are two check valves 81 and 83 in fluid line 82 and a two position control valve 85 is located between the check valves. Control valve 85 is biased to the position illustrated in FIG. 3 by a spring 87 and is moved to its other open position by a solenoid 89. When solenoid 89 is energized fluid is provided from pump 69 through valve 85 and a hydraulic line 91 to a three-position control valve 93 having four fluid-line connections.

Hydraulic lines

95 and 97 are in communication with two of the connections of valve 93 and another of the connections to the valves provides a drain to reservoir 71 as diagrammatically illustrated in FIG. 3. When valve 93 is in its neutral or closed position as shown in FIG. 3 hydraulic fluid in

lines

95 and 97 is drained through valve 93 to the reservoir. Valve 93 has two

solenoids

99 and 101 for shifting valve 93 to its two open positions so that line 91 can be placed in communication with either line 95 or line 97. In this manner fluid under pressure can be provided to motor 45 to move rail 15 and the press in a direction parallel to the lower'chord of a truss on pedestal P. Adjustable fluid restrictors 1G3 and 105 in

lines

95 and 97 control the rate at which fluid is delivered to motor 45 and thus the maximum speed of travel of the rail. When both

solenoids

99 and 101 are electrically deenergized, the valve 93 is returned to its neutral or closed position by

springs

107 and 109. When rail 15 is located at the desired position, the solenoid 89 for control valve 85 is deenergizedand spring 87 returns valve 85 to the to control valve 79.

Fluid is provided from

pumps

67 and 69 to the fluid line 80 which communicates with one of the four fluidline connections of the valve 79. The

hydraulic lines

35 and 37 attached to the upper and lower ends of cylinder 29 of power means 7 are in communication with the valve through two of its other connections. The fourth connection of valve 79 communicates with reservoir 71.

Valve 79 has

solenoids

113 and 115 for movingcontrol valve 79 to its two open positions and valve 79 is biased to the neutral or closed position by springs 1 17 and 119.'

With the valve 79 in. the position shown in FIG. 3, the upper end of cylinder 29 through fluid line 35 communicates with the reservoir 71. Also,

fluid from'pumps

67 and 69 is returned through valve 79 to the reservoir 71.

Fluid lines

35 and 80 are in communication through valve 79 and there is a small back pressure in line 35 and in the upper end of cylinder 29; However, this does not lower piston 31 since fluid line 37 communicate ing with the bottom of cylinder 29 is closed at valve 79 the line 80 communicates through the valve with line' 37 and hydraulic fluid is provided to the bottom of' position shownin FIG. 3 where pump 69 may provide fluid through it" cylinder 29 for raising the piston 31 in cylinder 29 and simultaneously forcing fluid out the top of the cylinder through line 35 to the reservoir. When valve 79 is shifted the other way, hydraulic fluid from line 80 is provided through line 35 to the top of cylinder 29 to force piston 31 down and thereby lower platen 5 toward platen 3. Fluid in the lower portion of cylinder 29 at this time passes through line 37 and valve 79 for return to the reservoir.

In order to prevent excessively high pressures in cylinder 29 (which might occur if the piston 31 was in its uppermost position and fluid continued to be applied to the lower end of cylinder 29) the circuit is provided with a relief valve 121 which is in communication with line 37 between cylinder 29 and valve 79. Relief valve 121 functions in a conventional manner and it opens at a predetermined pressure in line 37 to pass fluid from line 37 through the relief valve to the reservoir. Valve 121 prevents damage (due to excessive pressure) on the packings (not shown) which sealingly engage ram 33 in the lower end of cylinder 29.

Pumps

67, 69 are adjusted so that the downward pressure exerted by ram 33 is the maximum required for driving the nailing plates into the truss members, thereby preventing overloading of the upper end of cylinder 29.

The system for controlling delivery of fluid to the expansible chamber 13 includes a pressure reducing valve 125 which receives fluid from pump 69 through a line 127 connected to line 82 between check valve 81 and control valve 85. Thus fluid is available to valve 125 whenever pump 69 is operating. Valve 12-5 is preferably adjustable so that the pressure downstream of the valve may be varied over a range of values, e.g., 753000 psi. The reducing valve 125 includes a pressure-sensing line 129 which senses fluid pressure at the outlet side of the valve and regulates operation of the valve in response to the pressure sensed. Any incipient pressure increase at the downstream side of valve 125 beyond the preselected pressure setting causes the valve automatically to throttle down and discharge fluid from line 134 through a bleed line 131 to the reservoir. Any tendency for the pressure downstream of valve 125 to drop below the preset pressure setting of the valve is compensated by the biasing action of a spring 133 which increases the valve opening and permits increase passage of fluid to the line downstream of the valve.

Fluid from valve 125 is provided through a line 134 to the inlet connection of a two-position control valve 135. The outlet connection of valve 135 communicates with hydraulic line 61. Valve 135 is moved from its closed position (shown in FIG. 3) to its open position by a solenoid 137. Preferably, solenoid 137 is energized at the same time as the solenoid of valve 79 which opens that valve to supply fluid to line 35 and the top of cylinder 29. This may be accomplished by wiring them in the same electrical circuit for simultaneous energization. When solenoid 137 is deenergized the valve is returned to its closed position by a spring 139. When pump 69 is operating and valve 135 is open, fluid at a pressure determined by the pressure reducing valve 125 is supplied to the lower end of cylinder 49 through the hydraulic line 61.

There is an adjustable restrictor 141 in line 61 between valve 135 and the cylinder 49. Restrictor 141 regulates the rate at which fluid under pressure may enter or leave the cylinder 49 through line 61. The purpose of restrictor 141 is to provide a predetermined substantially constant rate of rise and descent of piston 41 and thus provide a smooth, substantially constant upward or downward movement of press frame 27 and platen 3 of press 1.

There is an adjustable restrictor or bleed orifice designated 143 which communicates with the reservoir and with line 61 between the variable restrictor 141 and the valve 135. Restrictor 143 provides a return path to the reservoir for hydraulic fluid vented from cylinder 49 and passing through line 61 and the variable restrictor 141. This occurs when the valve 135 is in its closed position after having previously provided fluid to cylinder 49 for lifting piston 51 and fluid is being forced from cylinder by the weight of press 1 pulling downwardly on piston 51. This hydraulic fluid cannot be bled through valve 135 since it is at that time closed. The opening of bleed orifice 143 is smaller than the opening in restrictor 141. the bottom of cylinder 49 and thus the time it takes press 1 to settle is regulated by adjustment of the opening in bleed 143. Even when valve 135 is open there is some fluid bled from line 61 through restrictor 143 but it is not a significant amount compared to the amount of fluid available to line 61 and therefore has no substantial effect on the raising of piston 51.

Fluid from the various portions of the hydraulic apparatus is returned to reservoir 71 through a fluid line 145 and filter 147.

Operation of the apparatus is as follows:

A truss comprising a plurality of precut wood truss members is assembled and clamped in position on a plurality of pedestals P. Nailing plates N1, N2 are then placed on the truss members T1, T2 below and above the intersections of the truss members.

The motor 65 is energized and pumps 67, 69 deliver fluid under pressure to

lines

78 and 82. The hydraulic press is moved into position for driving the upper and lower nailing plates into the truss members by first opening valve to place

hydraulic fluid lines

82 and 91 in communication through the valve and then energizing

solenoid

99 or 101 of valve 93 to direct fluid to the fluid motor 45 for moving rail 15 in the desired direction. By appropriate operation of valve 93 the press can be accurately located in front of one of the pedestals. Then press 1 is moved along rail 15 (by pushing on the press) until the press is positioned with the upper platen immediately above the upper nailing plate and with the lower platen immediately beneath the locator plate 23. If the pedestal does not have a locator plate, then the lower nailing plate is carried on the lower platen beneath the intersection of the truss members.

After the press has been accurately located, the solenoid S9 is deenergized and spring 87 moves valve 85 to the position illustrated in the drawings so that fluid is available to valve '79 from pump 69 as well as pump 67. Fluid from pump 59 is also available through the reducing valve to the control valve downstream from it and, when valve 135 is open, to the adjustable restrictor or needle valve 141 and the rod end of the counterbalance hydraulic cylinder 49. It will be understood that the setting on the reducing valve 125 is adjusted so that the fluid allowed to pass through it to cylinder 49 is at a pressure which, when applied to the rod end of cylinder 49 and against the lower surface of piston 51, Will be enough to counterbalance the weight of the hydraulic 'press and the linkage connecting it to the piston rod 53.

Thus assuming that the hydraulic press and associated linkage weigh approximately 1000 lbs, then the setting of the reducing valve 125 is such that there is about 1000 lbs. of pressure acting on the bottom of piston 51 in the cylinder 49.

The control switch is depressed to open valve 79 to provide hydraulic fluid from line 80 through line 35 to the top of cylinder 29 of the press hydraulic power means. This simultaneously operates the solenoid of the control valve 135 to open valve 135 and permit the hydraulic fluid under pressure to pass through it into the line 61 leading to the rod end of cylinder 49. Thus simultaneously the upper platen of the hydraulic press begins to travel downwardly toward the lower platen and the hydraulic fluid at a pressure controlled by the reducing Valve 125 is provided to the lower end of cylinder 49. At this time both platen 3 and 5 are spaced from the nailing plates and there is no upward movement of the press or The time required for piston 51 to reach has by the lower pl-aten.

the linkage connecting it to the counterbalancing cylinder since the fluid pressure on the bottom of the piston in the counterbalancing cylinder is not quite suflicient to lift this weight, only support it.

When the upper platen reaches the upper nailing plate it continues to push downwardly but since there is no equal and opposite force against which it may exert a force, it does not (at this time) drive the nailing plate into the truss members. Instead the downward force exerted by the power unit 29 through platen begins to lift the press since it takes less force to lift the press than to drive the upper nailing plate into the truss members. The net result is that a portion of the weight of the hydraulic press is then momentarily borne by the upper nailing plate and by the truss members immediately therebeneath. This reduces the load carried by the piston rod 53 of cylinder 49. Fluid from line 61 now enters the lower end of cylinder 49 and lifts piston 51 and piston rod 53. Restrictor 141 controls the rate at which fluid enters cylinder 49 and it may be adjusted to provide smooth upward movement of the press. Since the response of the expansible chamber 13 to the changing load conditions is almost instantaneous, linkage 11 remains vertical and there is no opportunity for the press to cock or tilt and bend the nails of the nailing plates.

This lifting of the press while the upper platen is in contact with the upper nailing plate continues until the lower nailing plate is being pushed against the truss mem- At this time both the upper and lower platens are engaging the nailing plates and are encountering substantially the same load. Then continued operation of the hydraulic power means will cause the upper and lower nailing plates to be substantially simultaneously driven into the truss members, assuming no significant wood irregularities. If one of the nailing plates encounters more resistance to entering the truss members than the other nailing plate (such as by contacting a knot in the wood) then the other nailing plate may be partially or completely driven into the truss members before the first nailing plate overcomes this greater resistance. Thus each of the nailing plates is fully driven into the truss members to splice them together. It will be understood that when the lower platen rises piston 51 rises at substantially the sme rate so that throughout the entire operation the expansible chamber 13 supports the weight of the hydraulic press and the linkage connecting it to the piston rod.

Some hydraulic fluid 'will bleed through the bleed orifice 143 and be returned to the reservoir whenever valve 135 is .open. However, the volume of fluid thus returned to the reservoir is relatively small and does not significantly affect the ability of the expansible chamber to substantially fully support the weight of the hydraulic press;

' After the nailing plates have been completely driven into the truss members, valves 79 and 135 are returned to the positions shown in FIG. 3. Hydraulic fluid cannot bleed from the lower endof press cylinder 297since it is blocked by valve 79. Valve 79 is then opened to supply hydraulic fluid to the bottom of cylinder 29 through line 37 to raise the upper platen until the platens are separated a distance sufii-cient to permit the press to be removed and taken to another pedestal. Relief valve 121 prevents cylinder 29 from being over-loaded since excessive perssure could damage the packings (not shown) at the bottom of cylinder '29. e V

5 As soon as the valve 135 is closed hydraulic fluid will begin bleeding from cylinder 49 through the adjustable needle valve 141and the bleed orifice 143 to the reservoir. Bleed 1'43 determines the rate at which fluid leaves cylinder 49 and it is adjusted to regulate the rate at which piston 51 and rod 5-3 of the counter-balancing cylinder (and press 1 suspended by them) are lowered. In the event the bleed from cylinder 49 is accomplished without opening the control valve 79 to lift the upper platen, then the pressure of the fluid above piston 31 in the hydraulic power unit is increased (because part of the weight of the press is carried by the upper platen causing it to exert an upward force on the fluid) and this forces hydraulic fluid out the top of the power means through valve 79 and back to the reservoir.

FIG. 4 illustrates a modification of the portion of the FIG. 3 circuit which controls flow of fluid to and from cylinder 49. The FIG. 4 circuit comprises a control valve 151 having an inlet port connected to the line 134 which connects reducing valve and control valve 135 in FIG. 3. Two ports of valve 151 communicate with line 61 and restrictor 143. The other port of valve 151 is blocked. The arrangement is such that when valve 151 is in its normal position (shown in FIG. 4) it blocks passage of fluid from line 134 to the hydraulic cylinder 49. When solenoid 153 of valve 151 is energized, it' moves the valve to its other position to place line 134 in com munication with line 61. Hydraulic fluid can then pass through the adjustable restrictor 141 and into the cylinder 49 in the manner previously described.

When solenoid 153 is deenergized, the valve 151 is returned to its FIG. 4 position by a spring 155 constituting part of the valve 151 and the fluid beneath piston 51 in cylinder 49 is then bled to reservoir 71 through line 61, adjustable restrictor 141, valve 151 and bleed orifice 143. With this arrangement all of the fluid passing from line 134 through valve 151 to'line 61 is available for lifting piston 51 whereas in the embodiment shown in FIG. 3 a portion of this fluid is lost through the bleed orifice 143.

In the foregoing description the fluid pressure against the bottom of piston 51 has been described as being yapequal to the weight of the press and linkage proximately it supports. It will be understood that this pressure is preferably slightly less (20-60 lbs. for example) than that necessary to exactly equal the press and linkage weight to avoid premature lifting of the press by a workman applying slight upward force on the press as it is moved into position straddling the truss joint. Also, while hydraulic fluid is preferred for presses that must exert very.

gaseous high forces, it will be understood that air or other fluids may be used with lower capacity presses. Where hydraulic fluid is required for. the press, then a separate air operated system may be used for expansible chamber In view of the above, it will be seen that the several objects of the invention are achieved and other adva'ntageous results attained. 7

As various changes could'be made in the above constructions without departing from the scope of the inven-.: tion, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. What is claimed is:

1. A suspension for a'fluid operated press which has' a first platen movable toward and away from a second platen under control of fluid power means of the press, the suspension comprising a carrier, means for suspending'the press from the carrier includingan expansible chamber,

7 means for providing fluid under pressure to't'he expansible chamber, and'means for regulating the pressure of the fluid delivered to the expansible chamber so that the V expansible chamber exerts a substantially constant upward force approximately equal to the weight of the press.

2. A suspension as set forth in claim 1 further comprising a restrictorbetween the pressure regulator means and the expansible chamber for limiting the rate at which fluid is supplied to the chamber.

3. A suspension as set forth in claim 2 further comprising a bleed orifice communicating with the chamber for venting fluid from the chamber. 7

4. Apparatus for fabricating wood trusses and the like comprising a fluid-operated press for driving nailing plates into opposing surfaces of substantially fixed abutting wood' members, said press having an upper and a lower platen relatively movable toward and away from one another 9 and hydraulic power means for moving the platens together, an overhead carrier, means for suspending said press from said carrier for movement to a position wherein the platens are located respectively above and below nailing plates to be driven into said wood members, the press suspending means including means for varying the distance between the press and the carrier in response to the load carried by the press suspending means, and means for supplying fluid under pressure to said power means and simultaneously actuating the distance varying means.

5. Apparatus as set forth in claim 4 wherein the means for varying the distance between the press and the carrier comprises a fluid operated lifter, and means for supplying fluid under pressure to the fluid lifter at a pressure sufficient to exert an upward force on the suspended press substantially equal to the weight thereof whereby the weight of the press is substantially counterbalanced.

6. Apparatus for fabricating wood trusses and the like comprising a fluid-operated press for driving nailing plates into opposing surfaces of substantially fixed abutting wood members, said press having an upper and a lower platen relatively movable toward and away from one another and hydraulic power means for moving the platens together, an overhead carrier, means for suspending said press from said carrier for movement to a position wherein the platens are located respectively above and below nailing plates to be driven into said Wood memhen, the press suspending means including an expansible chamber, means for simultaneously supplying fluid under pressure to said power means and to said expansible chamber, and means for regulating the pressure of the fluid supplied to the expansible chamber to exert an up ward force on the suspended press substantially equal to the weight thereof whereby as the platens are moved toward each other to drive the nailing plates into the abutting wood members, the weight of the press is substantially counterbalanced.

7. Apparatus as set forth in claim 6 wherein the fluid supplying means comprises a fluid pump adapted to supply a fluid under pressure to the power means and to the chamber, a first valve for controlling delivery of fluid from the pump to the power means, and a second valve for controlling delivery of fluid to the chamber, and means for opening the second control valve when the first control valve is opened to supply fluid to the power means for moving the platens together.

8. Apparatus as set forth in claim 7 wherein the pressure regulating means comprises a reducing valve between the pump and the second control valve.

9. Apparatus as set forth in claim 6 further comprising means for regulating the rate at which fluid is provided to the chamber, and means for bleeding fluid from the chamber.

10. Apparatus for suspending the weight of a hydraulic press having hydraulic power means for driving upper and lower nailing plates into truss members positioned between a lower platen fixed on the press and an upper press platen movable on the press toward and away from the lower platen under control of the hydraulic power means, the apparatus comprising a carrier, means suspending the press from the carrier including an expansible chamber comprising a piston movable vertically in a hydraulic cylinder and a piston rod attached to the piston and projecting from one end of the cylinder, a linkage connected to the press and to the expansible chamber, a reservoir for hydraulic fluid, means for supplying hydraulic fluid under pressure from the reservoir to the hydraulic power means of the press and to said one end of said cylinder, a reducing valve for regulating the pressure of fluid supplied to said cylinder so that the upward force for lifting the hydraulic press is substantially equal to the weight of the hydraulic press and the linkage connecting it to the expansible chamber whereby the weight of the press is substantially balanced by the fluid provided to said one end of the cylinder and the piston rod is retractable into said cylinder for lifting the press and the linkage when the relation between the platens is such that the upper platen is pressing downwardly on the upper nailing plate and lifting upwardly on the lower platen, and means for bleeding fluid from the cylinder to the reservoir.

11. Apparatus as set forth in claim 10 wherein the fluid supplying means comprises a fluid pump communicating with the reservoir, a first control valve having a first open position for delivering fluid from the pump to the power means for lowering the upper platen and having a second open position for delivering fluid from the pump to the power means for raising the upper platen, and a second control valve having an open position for delivering fluid to the chamber and having a closed position for blocking delivery of fluid to the chamber, and means for opening the second control valve when the first control valve is opened to its first open position to supply fluid to the power means for lowering the upper platen.

12. Apparatus as set forth in claim 11 further comprising a restrictor for regulating the rate at which fluid is delivered to the chamber, the restrictor being located between the chamber and the second control valve.

13. Apparatus as set forth in claim 11 further comprising a relief valve between the pump and said power pump means for limiting the pressure of fluid provided to said power means.

14. Apparatus as set forth in claim 11 wherein the means for bleeding fluid from the cylinder to the reservoir comprises a bleed orifice communicating with the reservoir and communicating with the chamber through the second control valve when it is in said closed position.

15. Apparatus as set forth in claim 11 wherein the means for bleeding fluid from the cylinder to the reservoir comprises an adjustable bleed orifice between the second control valve and said chamber, the bleed orifice communicating with the chamber and the reservoir.

16. Apparatus as set forth in claim 10 further comprising a rail, the carrier being adapted for travel along said rail, a fluid motor for moving said rail relative to truss members, and a valve for controlling delivery of fluid from the fluid supplying means to the fluid motor.

17. Apparatus as set forth in claim 10 wherein the upper end of the expansible chamber is pivoted to the carrier, the linkage is rigid and the upper end thereof is pivotally connected to the lower end of the expansible chamber, and the press is rigidly connected to the lower end of the linkage whereby the press has a high resistance to rotational movement in any direction.

References Cited by the Examiner UNITED STATES PATENTS 3,068,484 12/1962 Moehlenpah et al. 227l52 3,069,684 12/ 1962 Moehlenpah et al. 227152 3,207,406 9/1965 Bowman 227-4 52 BILLY J. WILHITE, Primary Examiner.

Claims

4. APPARATUS FOR FABRICATING WOOD TRUSSES AND THE LIKE COMPRISING A FLUID-OPERATED PRESS FOR DRIVING NAILING PLATES INTO OPPOSING SURFACES OF SUBSTANTIALLY FIXED ABUTTING WOOD MEMBERS, SAID PRESS HAVING AN UPPER AND A LOWER PLATEN RELATIVELY MOVABLE TOWARD AND AWAY FROM ONE ANOTHER AND HYDRAULIC POWER MEANS FOR MOVING THE PLATENS TOGETHER, AN OVERHEAD CARRIER, MEANS FOR SUSPENDING SAID PRESS FROM SAID CARRIER FOR MOVEMENT TO A POSITION WHEREIN THE PLATENS ARE LOCATED RESPECTIVELY ABOVE AND BELOW NAILING PLATES TO BE DRIVEN INTO SAID WOOD MEMBERS, THE PRESS SUSPENDING MEANS INCLUDING MEANS FOR VARYING THE DISTANCE BETWEEN THE PRESS AND THE CARRIER IN RESPONSE TO THE LOAD CARRIED BY THE PRESS SUSPENDING MEANS, AND MEANS FOR SUPPLYING FLUID UNDER PRESSURE TO SAID POWER MEANS AND SIMULTANEOUSLY ACTUATING THE DISTANCE VARYING MEANS.