# US 4,398,898 A · Shock sub > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,398,898 A - Document ID: US4398898A - Status: Granted - Kind: A - Application number: 06/239,442 - Filed: 1981-03-02 - Granted: 1983-08-16 - Earliest claimed: 1981-03-02 - Assignees: Texas Long Life Tool Co., Inc. - Inventors: Robert L. Odom - Web page: https://patentgrep.com/patent/US4398898A ## CPC - E21B 17/07: Telescoping joints for varying drill string lengths; Shock absorbers - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS ## Abstract A novel shock sub is disclosed for use in a drill string for absorbing longitudinal and impact loads. A tubular housing is provided for connection to one part of a drill string and a tubular mandrel extends into the housing for longitudinal sliding movement with an outer end portion for connection to the other part of the drill string. The mandrel and housing define an annular cavity when assembled. The mandrel has two slots, positioned 90.degree. apart circumferentially extending for length of the annular cavity. Annular spring washers positioned in the annular cavity are of a size having a sliding fit on the outside of the mandrel and inside the housing. The spring washers are each corrugated in a wave configuration and with a tab of a size fitting one of the mandrel slots and are placed on the mandrel with alternate ones having tabs fitting in one of the slots and the others having their tabs fitting another mandrel slot. This prevents nesting of the washers and provides a greater spring efficiency in absorbing longitudinal shock. An arrangement of slots and bearings interconnects the mandrel and housing to permit sliding movement and transmit rotary motion while absorbing longitudinal shocks. ## Claims ### Claim 1 A shock sub for use in a drill string for absorbing longitudinal and impact loads comprising a tubular housing adapted for connection to one part of a drill string, a tubular mandrel extending longitudinally into said housing for longitudinal sliding movement therein and having an end portion adapted for connection to another part of a drill string, said housing having a smooth cylindrical inner wall surface portion with an inner diameter larger than the outer diameter of said mandrel, said mandrel having a cylindrical surface portion defining an annular cavity inside said housing smooth cylindrical inner wall surface portion, said mandrel having two longitudinally extending slots, positioned 90.degree. apart circumferentially and extending substantially the entire length of said annular cavity, a plurality of annular spring washers positioned in said annular cavity of a size having a circular opening with a sliding fit on said mandrel and circular exterior with a sliding fit inside said housing smooth cylindrical inner wall surface portion, each of said spring washers being corrugated circumferentially in a wave configuration and having an internally extending tab of a size fitting said mandrel slots, said spring washers being assembled on said mandrel with alternate ones having the tabs thereof fitting in one of said mandrel slots and the remaining alternate ones having the tabs thereof fitting in another mandrel slot positioned 90.degree. from said one slot to secure said washers in circumferentially fixed relation with the troughs of one washer resting on the crests of the next adjacent washer, and means interconnecting said mandrel and said housing permitting longitudinal sliding movement therebetween and preventing relative rotary movement comprising a plurality of longitudinal grooves in the bore of said housing, a plurality of matching grooves in the surface of said mandrel, and a plurality of cylindrical bearing members positioned between said matching grooves in said housing and in said mandrel. ### Claim 2 (depends on 1) A shock sub according to claim 1 in which said washers each have wave corrugations with symmetrical alternating crests and troughs circumferentially thereof, and said assembly of alternate washers on said mandrel by said washer tabs and mandrel grooves being effective to align said washers with the troughs of one washer resting on the crests of an adjacent washer. ### Claim 3 (depends on 1) A shock sub according to claim 1 in which said housing has an enlarged bore comprising said smooth cylindrical inner wall surface portion with an internally extending circumferential shoulder, said mandrel has a portion of reduced diameter with a circumferential shoulder, said shoulders, said housing enlarged bore, and said mandrel portion of reduced diameter defining said cavity, and said washers being positioned in said cavity abutting said shoulders and extending the entire length of said cavity. ### Claim 4 (depends on 1) A shock sub according to claim 1 in which said housing has an enlarged bore adjacent to said smooth cylindrical inner wall surface portion and said mandrel has a portion of reduced diameter cooperating when assembled to define a second cavity adjacent said first-named cavity to contain lubricant for said shock sub, an annular bearing and sealing member positioned at one end of said second cavity to seal against leakage of lubricant and support said housing and mandrel for relative sliding movement, and bearing and sealing means positioned adjacent the end of said first-named cavity opposite said second cavity permitting lubricant to fill both cavities and supporting said housing and mandrel for relative sliding movement. ### Claim 5 (depends on 1) A shock sub according to claim 1 in which one end of said housing into which said mandrel extends includes an internal shoulder limiting downward movement of said mandrel when said housing is lifted. ### Claim 6 (depends on 5) A shock sub according to claim 5 in which said housing comprises a plurality of separate sections threadedly securable together for assembly and disassembly, said internal shoulder being on the lowermost housing section, and said mandrel comprising a plurality of separate sections threadedly securable together for assembly and disassembly.