A crosshead in combination with a connecting rod assembly and a piston rod

Abstract: The crosshead (14) has a body (18) formed of solid, metal plate, and of substantially U-shape. It comprises a pair of spaced-apart parallel limbs (20) which are bridged between by an integral transverse member (22), and the latter is bored (as at 24) through to receive a piston rod (16) therein. Shoe plates (26) are joined to the limbs (20) to guide the body (18) in reciprocation. In the combination with a connecting rod assembly (12) and the piston rod (16), the end of the piston rod (16) is directly fastened to the connecting rod assembly (12), and the crosshead (18) is coupled to an intermediate portion (50) of the piston rod.

Description: This invention pertains to crossheads, such as are used in reciprocating machinery, viz. pumps, gas compressors, engines, and the like, and in particular to a crosshead, per se, and in combination with a connecting rod assembly and a piston rod. Crossheads (such as those described in US-A-3,179,451) known in the prior art are commonly a principal source of machine failure, unwarranted inertia, excessive friction, and undue weight. Accordingly, it is an object of this invention to set forth an improved cross head, per se, and an improved crosshead in combination with a connecting rod assembly and a piston rod. The present invention provides a crosshead comprising a body formed of solid, flat metal plate of uniform thickness. said body having a pair of spaced-apart, substantially parallel limbs and a single transverse member integral with, and bridging between said limbs, said limbs having shoe plates joined thereto, wherein said transverse member has a borehole formed therethrough in which to slidably receive a piston rod and a connecting rod wherein said connecting rod has a hollow end formed of a substantially cylindrically shaped wall characterized in that said wall has an opening formed in a sector thereof, said transverse member is set in said opening, and further including a crosshead pin disposed within said wall, having a tapped hole formed therein, and a piston rod in penetration of said borehole and having a threaded end threadedly engaged with said tapped hole. One way of carrying out the present invention will now be described in detail by way of example with reference to a drawing which shows one specific embodiment. The drawing is an exploded view and a perspective illustration of a crosshead in accordance with the present invention in a combination of a crosshead, a connecting rod assembly and a piston rod in accordance with the present invention. As shown in the drawing, the combination 10 comprises a connecting rod assembly 12, a crosshead 14, and a piston rod 16. The crosshead 14 has a body 18, formed of solid, metal plate, having a pair of spaced-apart, substantially parallel limbs 20 (only one being visible, but the other being a mirror image thereof), and a single, transverse member 22 integral with, and bridging between the limbs 20. Member 22 has a borehole 24 formed therethrough in which to accommodate a portion of the piston rod 16. Shoe plates 26 have rectilinear grooves 28 formed therein, in flat, innermost surfaces thereof, in which, as keyways, to receive portions of the limbs 20. Too, the shoe plates 26, provided for guiding the crosshead 14 in its reciprocation, have lubrication grooves 30 in the outermost, arcuate surfaces thereof. Bolts (not shown) secure the shoe plates 26 to the limbs 20. The connecting rod 32 has a hollow end 34 formed of a substantially barrel-shaped wall 36, and the wall has an opening 38 formed in a sector thereof. A crosshead pin 40 is received in end 34 and is journalled, in interpositioned sleeve bearings 42, at opposite ends thereof. Pin 40 has a slot 44 formed through a sector thereof, which aligns with the opening 38 in wall 36. Too, a tapped hole 46 is formed in the pin 40 in the center of the slot. The transverse member 22 enters the opening 38 and sets into the slot 44, in turn, a threaded end 48 of the piston rod 16 is threadedly received in the tapped hole 46 in the pin 40. An intermediate portion of piston rod 16 has a threaded shoulder 50 to receive a lock nut 52 for snubbing the crosshead 14 up tight against the slot 44. In a manner well known, and not relevant to the instant invention, the connecting rod 32 is fastened to a crank 54 of a crankshaft 56 which has crankthrows 58 integral therewith. Use of this combination provides for a more direct load transfer between the connecting rod 32 and the piston rod 16. The basic mechanical efficiency of frame and running gear is improved due to the reduction in weight of the crosshead 14 and, therefore, a reduction in friction arising thereform. The combination can be used to retrofit existing engines and compressors with minimal changes, and its serviceability is enhanced due to a reduction of parts required therefor and reduction in the overall weight of the combination. The combination allows for an increase in operating speed of machines which are currently inertia limited, due to the reduction of inertia normally attributed to the crosshead. Too, clearly, the use of the crosshead body 18 formed of solid, metal plate, will eliminate problems associated with prior art crosshead castings, (i.e. material quality, cracking and sand inclusions). There has been described with reference to the drawing a combination of crosshead, connecting rod assembly and piston rod which is (a) of simple manufacture, greater service life, and exhibiting less inertia, weight and friction, and (b) which accommodates for direct coupling, hence direct load transfer, between the piston rod and the connecting rod assembly.

Claims: A crosshead (14) comprising: a body (18) formed of solid, flat metal plate of uniform thickness, said body (18) having a pair of spaced-apart, substantially parallel limbs (20), and a single transverse member (22) integral with, and bridging between said limbs (20), said limbs (20) having shoe plates (26) joined thereto, wherein said transverse member (22) has a borehole (24) formed therethrough in which to slidably receive a piston rod (16) and a connecting rod (32) wherein said connecting rod (32) has a hollow end (34) formed of a substantially cylindrically shaped wall (36), characterized in that said wall (36) has an opening (38) formed in a sector thereof, said transverse member (22) is set in said opening (38), and further including a crosshead pin (40) disposed within said wall (36), having a tapped hole (46) formed therein, and a piston rod (16) in penetration of said borehole (24) and having a threaded end (48) threadedly engaged with said tapped hole (46). A crosshead, according to claim 1, wherein said shoe plates (26) have rectilinear grooves (28) formed therein, and portions of said limbs (20) are set in said grooves. A crosshead, according to claim 1, wherein said shoe plates (26) have arcuate surfaces, and said arcuate surfaces are interrupted by lubrication channels (30). A crosshead, according to claim 1, wherein said body (18) has a given width, and said shoe plates (26) have a width considerably greater than said given width. The crosshead, according to claim 1, wherein said pin (40) has a recess (44) formed in a surface thereof, and said transverse member (22) is set in said recess. The crosshead, according to claim 5, wherein said tapped hole (46) opens onto said recess (44).

Inventors: ANDERSON ALAN C, BENNITT ROBERT A, ANDERSON, ALAN C., BENNITT, ROBERT A.
Applicants: DRESSER RAND CO, DRESSER-RAND COMPANY
Application year: 1988
Main classification: F16C5
IPC codes: F16C5, F16J1