US3215402A

US3215402A - Jack

Info

Publication number: US3215402A
Application number: US81301A
Authority: US
Inventors: Ion V K Hott; Ii Warren E Webster
Original assignee: HOTT
Current assignee: HOTT
Priority date: 1961-01-09
Filing date: 1961-01-09
Publication date: 1965-11-02
Anticipated expiration: 1982-11-02

Description

1965 l. v. K. HOTT ETAL 3,

JACK

4 Sheets-Sheet 2 Filed Jan. 9, 1961 III-E; \vii l INVENTORS ION V. K. HDTT WARREN E. WEBSTER II.

THE/R 4TTOEN5V5 Nov. 2, 1965 l. v. K. HOTT ETAL 3,215,402

JACK

Filed Jan. 9, 1961 4 Sheets-Sheet 3 Z a /I INVENTORS I 4 l/K 0 f/OTT WA REE/V E. WEBSTE/{H 1965 v. K. HOTT ETAL 3 3 JACK Filed Jan. 9. 1961 4 Sheets-Sheet 4 IN VEN TOR. mm 1/ z H0 77' 3-15. 11 BY mqeea/a wzwrza United States Patent Ohio Filed Jan. 9, 1961, Ser. No. 81,301 7 Claims. (Cl. 254-7) This invention relates to a jack lift and more particularly to a portable electrically driven automobile jack lift.

In automobile lifts of the type having a vertically movable load lifting carriage, there are numerous ways to drive the carriage upwardly and downwardly. One of the simplest and most effective ways of driving a load lifting carriage is by electric motive power. However, electrically operated jacks have not been widely accepted. One reason for this is that the control of the jack may be quite complicated and require expensive structure. Necessarily, means must be provided to limit the vertical travel of the carriage since it would be destructive of the jack if the carriage were permitted to move too far upwardly or downwardly. Also, it is desirable to provide a safety lock mechanism to lock the carriage in its upper position to insure against accidental downward travel of the carriage beam and the load carried thereby.

One method of controlling the extent of vertical travel of the carriage and also of controlling a safety lock mechanism is to provide a plurality of limit switches which are engaged during the travel of the carriage. The switches are used to shut off the source of motive power. Provision of a plurality of switches, however, is not desirable due to the complexity of the circuit arrangement and the cost of providing several switches in the path of the carriage. Furthermore, if the electric power system should require repair, all of the switches would have to be removed along with the remainder of the power unit. This would be expensive and diflicult, if not impossible, since the switches and their circuit connections are desirably enclosed within a portion of the jack frame.

An object of this invention is to provide an improved electrically operated jack including improved means to control the operation of the electric motive unit.

A further object of this invention is to provide an improved electrically operated jack in which the electric motive unit may be simply and easily removed and replaced by a substitute unit. With this construction, the electric unit may be repaired while the jack is still in use.

Another object of this invention is to provide an improved electrically operated jack in which a single switch is used to control the electric motive unit so as to prevent the load lifting structure of the jack from operating accidentally.

Still a further object of this invention is the provision of a novel manual switch device including means preventing accidental operation thereof.

Oftentimes it is desired to use a pair of portable jacks to lift both ends of an automobile. By using a pair of portable jacks, it may be possible to raise an entire automobile in much the same manner as the larger, stationary automotive lifts. To perform work on the underside of an automobile, it is necessary to lift an automobile to a considerable height. For this purpose, jacks having a high lift are required. High lift jacks employing screw shafts tend to become heavy and bulky. There are several reasons for this. The screw usually must be quite large in diameter in order to tolerate the weight of the load to be lifted. Since the screw shaft itself must be large, the support for the base of the screw shaft usually must be comparatively heavy. In addition, there is oftentimes high friction between the screw shaft and the lifting carriage of the jack so that once the carriage is raised, the high friction holds the carriage in its elevated position. Therefore, a powerful motive source is required to operate the jack to overcome the friction when raising a load. If the power source is an electric motor, a large and heavy motor is required.

In recent years, a screw jack based on the ball hearing screw principle has been developed. The ball hearing screw jack utilizes a ball bearing connection between the screw shaft and the load lifting carriage. The friction resulting from this connection may be as low as 10%. Thus the weight and size of the electric motor may be reduced. We have also found it possible when using the ball bearing screw assembly to support the screw shaft and connect the screw shaft and motor in such a way as to further reduce the weight and size of the jack.

Accordingly, another object of this invention is the provision of an improved lightweight readily portable jack of the type employing a screw shaft.

Still another object of this invention is to provide an improved high lift portable jack employing a ball bearing screw assembly driven by a lightweight, comparatively small electric motor.

A further object of this invention is the provision of a novel base structure for a portable jack wherein the base is comparatively small for easy portability but sufliciently stable under all normal operating conditions.

Other objects and advantages reside in the construction of parts, the combination thereof, the method of manufacture and the mode of operation, as will become more apparent from the following description.

Referring to the drawings:

FIGURE 1 is a perspective view of the front of a novel jack made in accordance with this invention.

FIGURE 2 is a fragmentary perspective view of the top portion of the rear of the jack shown in FIGURE 1.

FIGURE 3 is a fragmentary sectional view of the jack structure taken along lines 33 of FIGURE 1.

FIGURE 4 is a sectional view of the lower portion of the jack structure taken along lines 44 of FIGURE 3.

FIGURE 5 is another sectional view of the jack structure taken along lines 55 of FIGURE 2.

FIGURE 6 is a front elevational view of the single switch used to limit the travel of the carriage and a portion of the control means therefor.

FIGURE 7 is an exploded perspective View of a safety lock mechanism made in accordance with this invention.

FIGURE 8 is a view of a portion of the jack mechanism illustrating an automatic control feature for the safety lock mechanism as viewed in the direction of the arrows 8-8 in FIGURE 1.

FIGURE 9 is a perspective view illustrating the manner in which a pair of jacks made in accordance with this invention may be utilized to lift an entire automobile.

FIGURE 10 is a perspective view of a control switch used in the system of FIGURE 9 enclosed within the circular line 10 of FIGURE 9.

FIGURE 11 is a cross sectional View of the electric drive motor, which is shown schematically, and the drive train between the motor and the screw shaft. FIGURE 11 also shows the connection between the screw shaft and the lifting carriage in cross section.

Referring more particularly to the drawings, a jack structure made in accordance with this invention is designated by the reference character 10 in FIGURE 1. The structure 10 includes a vertical frame 12 mounted upon a base structure 14 which will be described in detail later. The vertical frame 12 includes a pair of upright guide rails or posts 16 which are welded or otherwise afiixed to the base 14. A pair of side plates 18 are attached to the posts 16 and serve as a partial housing for the control elements of the jack. The rails 16 and the side plates 18 are interconnected at their bottom by a horizontal supporting plate 20 and at their top by a top plate 22, which are affixed thereto by welding or suitable fastening devices (not shown).

The jack or lifting mechanism is of the screw type and includes an elongate vertical screw shaft 24 extending substantially along the entire length of the jack. The screw shaft 24 extends through a central aperture (not shown) in the top plate 22 and a thrust bearing 26 supported on the top plate. A collar 28, which is larger than the apertures in the plate 22 and the bearing 26 is connected, as by a dowel pin 30, to the top of the screw shaft 24. Thus, the shaft 24 is suspended from the top plate 22 centrally of the vertical frame 12.

Referring to FIGURES 4 and 11, a flange or key 32 depends from the base of the shaft 24. The key 32 is received within a slot or keyway 33 in a stub shaft 34 which is rotatably mounted centrally of a gear housing 36. The stub shaft 34 is rotated by an electric motor 38, shown in FIGURES l and 11 which, along with the gear housing 36, is mounted on top of the horizontal plate 20. The shaft 38a (FIGURE 11) of the motor 38 is connected to the driven stub shaft 34 by spur gears located in the gear housing 36. The structure of the transmission of power between the motor shaft 38a and the screw shaft 24 through the stub shaft 34 will be described in greater detail below. To insure rotation of the screw shaft 24 along with rotation of the stub shaft 34, a sleeve 35 is slidably mounted on the shaft 24 in surrounding relationship to the key and

slot connection

32 and 33 between the shafts.

The screw shaft 24 is adapted to drive a vertically movable jack carrier or carriage 40. The carriage 40 is of a conventional type and includes a horizontal carriage beam 42 having a central aperture in surrounding relation to the screw shaft 24. The sides of the carriage beam 42 are connected to a pair of L-shaped or angled jack arms 44, the lower portions of which diverge outwardly to cradle a load lifting beam or channel 46 having a pair of telescopic end sections 48 which in turn support a pair of conventional load engaging saddles 50. The jack arms 44 may be reinforced and interconnected by a horizontal plate 52. The entire carriage 40 is guided in its vertical path by a guiding system including a pair of guide rollers 54 mounted on the upper portion of the jack arm 44 and a second pair of guide rollers 56 mounted on the lower portion of the jack arms 44. As shown most clearly in FIGURE 5, the upper rollers 54 are engaged behind the guide rails or posts 16 while the lower rollers 56 are engaged in front of the posts 16. This guiding system has proved quite effective in the past for guiding the vertical travel of load lifting carriages without danger of binding.

Referring to FIGURE 11, the screw shaft 24 is provided with a conventional ball bearing screw assembly including a traveling nut 200 which serves as a housing for a plurality of ball bearings (not shown) which are guided along the screw threads. That is, the threads of the screw shaft 24 are so cut as to form ball races for the ball bearings as is well known to those versed in the art. The nut 200 may be drivingly engaged with the carriage beam 42 in any suitable fashion. As illustrated, the nut 200 may be provided with a flange 202 which is engaged with the lower face of the top of the carriage beam 42. Similarly, the base of the nut 200 may abut against the upper face of the bottom of the carriage beam 42. Thus, as the screw shaft rotates in one direction to drive the nut 200 upwardly, the carriage beam 42 is likewise driven upwardly. Rotation of the screw shaft 24 in the opposite direction, of course, forces the carriage beam 42 downwardly.

In order to selectively drive the screw shaft in opposite directions to raise and lower the carriage 40, the motor shaft 38a is driven in either direction by the motor 38. Rotation of the motor shaft 38a is transmitted to the stub shaft 34 through a simple speed reducing gear train within the gear housing comprising four spur gears, 204, 206, 208 and 210. As is apparent from FIGURE 11, the gear 204 is a pinion which is mounted on the base of the motor shaft 381: and is drivingly engaged with the spur gear 206 mounted upon a spindle 212 rotatably held within the gear housing by a pair of roller bearings 214. The gear 208 is also mounted upon the spindle 212 and serves as a pinion to drive the gear 210 mounted upon the base of the stub shaft 34. The stub shaft 34 is held within the housing 36 by a pair of roller bearings 216.

Circuits capable of energizing the motor 38 so as to rotate its shaft 38a selectively in opposite directions are well known in the art, and therefore are not disclosed in detail herein. Briefly, such a circuit includes an up" circuit and a down circuit. When the up circuit is closed, the motor shaft is driven in One direction to in turn drive the screw shaft 24 in the direction in which the carriage is elevated. Similarly, when the down circuit is closed, the carriage is lowered. The up and down circuits may be closed by a suitable manual selec tor switch such as a toggle switch 60a mounted on the side of the box 60 or the remote control switch shown in FIGURE 10 which are connected to the circuit elements located in a circuit control boX 60. The switch in FIGURE 10 will be described in greater detail below. An electromagnetic brake 220 is mounted on top of the motor shaft 38a within the motor casing. The brake 220 is of the conventional type employing a braking plate 222 which is non-rotatably secured to the shaft 38a through a splined nut 224. A plurality of springs within the brake 220 urge a pair of pressure plates 226 into engagement with the plate 222 when the motor is deenergized. When the motor is energized, however, the pressure plates 226 are separated by a plurality of solenoids thus permitting the motor shaft 38a to be driven freely by the motor. Therefore, when the motor 38 is energized to rotate the screw shaft 24 such as to elevate the carriage 40, the brake does not interfere with the operation of the jack. However, when the desired elevation of the carriage is reached and the motor is deenergized, the brake 220 functions to prevent the shaft 38a, and accordingly the screw shaft 24 from rotating, whereupon the carriage 40 is held in its desired position. This construction differs from the usual construction of electrically driven jacks in that the combined efliciency of the ball bearing screw assembly and the spur gear train 204 through 210 is in the neighborhood of 70%. As such, the friction provided by the ball bearing screw assembly and the

gear train

204, 206, 208 and 210 is insufficient to hold the carriage 40 in an elevated position. However, in addition to providing speed reduction between the motor shaft 38a and the screw shaft 34a, the gear train provides a mechanical advantage for the electromagnetic brake 220 to resist rotation of the shaft 34 even when a heavy load is held in an elevated position by the carriage 40. Thus the brake, not the screw and gear train, holds the carriage in an elevated position. By utilizing the high elficiency transmission between the motor shaft 38a and the carriage beam 42, a relatively small power motor may be used. If, on the other hand, the friction of the screw and gear train alone were used to prevent the carriage from lowering, the size of the motor would be greatly increased. In a portable jack, the relative size of the motor becomes extremely important. If a large, high horsepower motor were required, the jack would become too heavy and cumbersome [for ready portability. When the motor 38 is energized to lower the carriage 40, the brake 220, of course, is released. Upon deenergization of the motor 38, the brake again is brought into operation whereupon it serves to prevent over-travel of the carriage 40. That is, while the momentum of the carriage 40 upon traveling downwardly is sutficient to cause continued rotation of the shaft 24 after the motor 38 is deenergize-d, such continued rotation of the shaft 24 is considerably reduced by operation of the brake 220.

The gear housing 36 and the motor 38 are mounted solely upon the lower horizontal supporting plate 20. Furthermore, the electrical control box 60 for the motor 38 may be supported entirely thereon. As shown in FIGURES 3 and 4, the gear housing 36 and the motor 38 may be connected to the plate 20 by a plurality of bolts 62. Accordingly, if the electrical system should require repair for any reason, the electrical unit may be very simply removed from the jack by removing the bolts 62, sliding the sleeve 35 upwardly on the screw shaft 24, and then sliding the electrical unit including the electric motor 38, gear housing 36 and electrical control box 60 off plate 20, thus breaking the

keyed connection

32, 33 between the

shafts

24, 34. The screw shaft 24 and carriage 40 retain their positions, since as described above, the screw shaft is suspended from the top plate 22. This construction is important. Not only may the entire electrical unit be removed rapidly, but perhaps more importantly, a substitute unit may replace the original electric unit so that the jack may be used while the original electric motor unit is being repaired. Further, since the screw shaft is suspended from the top plate 22 rather than supported from beneath, and is loaded in tension rather than in compression, a comparatively small diameter screw shaft may be used for a high lift.

While the jack unit as thus described is operable without further structure, it is obviously desirable to limit the extent of the upward and downward movement of the carriage 48 so that the jack could not accidentally be driven too far, thus damaging either the jack frame, the carriage or the drive unit. A preferred manner of limiting the travel of the carriage 40 is to provide switch means operative to cut off the source of electric current to the motor 38. Such switch means is located most desirably on some portion of the electric motive unit so that the switch means may be removed, if desired, along with the rest of the unit. In the presently preferred embodiment, the switch means is located in a switch housing 63 afiixed to the box 60 and includes a limit switch having a switch arm 64 pivotally mounted on the housing 63. The arm 64 lies horizontally transversely between the side plates 18 of the jack and in front of the box 60. Ordinarily, it would be expected that more than one limit would be required since it is desired to limit both the upward and downward travel of the carriage. However, in accordance with this invention, a novel switch control means which senses the position of the carriage 40 is utilized to control the limit switch arm 64.

Referring to FIGURES 1, 2 and 6, the novel control means comprises a control rod 66 which extends vertically parallel to the screw shaft 24. The major portion of the rod 66 is square or rectangular in cross section but is rounded at its lower portion so as to be rotatably journalled within the supporting plate 20. The upper portion of the rod 66 is likewise rounded for rotation in an aperture in a horizontal mounting plate 68 affixed to the top plate 22. For reasons which will be made more apparent later, the top of the rod 66 is provided with an enlarged head 70. A spring 72 encircles the top portion of the rod 66 and extends between the bottom face of the enlarged head 70 and the top face of the plate 68 so as to resiliently suspend the rod 66 from the plate 22. A switch actuator 74, shown most clearly in FIGURE 6, is fixedly attached to the rod 66, as by means of a pin 76. The switch actuator 7'4 comprises a lower switch engaging plate 78 having a horizontal top surface and an upper switch engaging plate 80 having a horizontal lower sur face. The upper and lower surfaces are connected by an arcuate bracket 82 which may be integral with the upper and

lower plates

78, 80. The side of the bracket 82 which mates with the lower face of the upper plate 80 slopes away from the lower face to provide a cam surface 84 for reasons which will be discussed below.

The construction of the limit switch is such that the switch arm 64 normally lies in a center or substantially horizontal position, as indicated in full lines in FIGURE 6. In this center position, the switch does not interfere with the transmission of electricity to the motor 38. However, if the lower plate 78 of the switch actuator should force the switch arm 64 to rotate in a counterclockwise direction to a first ofi-center position illustrated by dotted lines 64a in FIGURE 6, the up motor circuit is opened, thereby preventing further upward travel of the carriage 40. Similarly, if the upper plate 80 of the switch actuator should engage the switch arm 64 to rotate it in a clockwise direction to a second off-center position indicated by dotted lines 64b in FIGURE 6, the down motor circuit will be opened. The specific manner in which the switch controls the motor circuits may be conventional.

The spring 72 normally suspends the rod 66 such that the

plates

78, 80 lie respectively below and above the arm 64. When the carriage reaches certain predetermined positions, however, the structure described immediately below causes either the plate 78 or the plate to engage the arm 64, thus selectively opening the up or the down circuits.

A bracket 88 is mounted on top of the carriage beam 42. The bracket 88 supports a pair of horizontally rearwardly extending sensing elements or fingers 90 each of which, as shown in FIGURES 2 and 5, is provided with an aperture 92 receiving the control rod 66. It should be noted that the apertures 92 are sufficiently large that the sensing fingers 90 do not contact the control rod 66. The upper sensing finger 90 is adapted to strike an upper abutment or collar 94 which is fixedly pinned near one end of the control rod 66 below the upper plate 22. When the upper sensing finger 90 strikes the collar 94 upon upward movement of the carriage, the control rod 66 is raised whereupon the lower switch engaging plate 78 contacts the free end of the switch arm 64 whereby the up motor circuit is opened as discussed above. If desired, the spring 72 may be attached at its opposite ends to the plate 68 and the head 70 so that the upper finger 90 when it strikes the abutment 94, in addition to working against the weight of the rods, also works against the spring 72. In this way, the movement of the rod 66 will be dampened and there is no danger that it will bounce upwardly and thus injure the limit switch. It is seen then that the upper sensing finger 90 strikes the collar 94 to limit the extent of upward travel of the carriage 40. The downward travel of the carriage is limited in a similar fashion. In this case, however, the lower sensing finger 90 mounted on the bracket 88 strikes the top face of the lower plate 78 of the switch actuator 74. Accordingly, the control rod 66 is pushed downwardly against the bias of the spring 72 whereupon the arm 64 is moved to the position 6411 to open the down motor circuit. Thus, in accordance with this invention, only one limit switch is required to limit the extent of both upward and downward travel of the jack carriage 44.

In addition to the limit switch and control mechanism therefor already described, it is often desirable to provide a mechanical safety lock mechanism. The purpose of a lock mechanism is to mechanically lock the carriage at or near its uppermost position thereby preventing the carriage from accidentally lowering. In addition to a mechanical lock mechanism, with this invention, the down motor circuit is cut oif when the carriage is near its uppermost position. The structure for accomplishing this is as follows.

Referring to FIGURE 1, an aperture is located near 7 the top of one of the upright guide rails or posts 16. As shown in FIGURES Sand 7, a lock bar 102 adapted to enter the aperture 100 andthus interengage the guide post 16 with the carriage 40 is rotatably and slidably received within a hollow cylindrical socket 104 which in turn is fixedly mounted in an aperture in the jack arm 44 adjacent to the aforementioned guide post 16. The lock bar 102 is constrained outwardly, so that its front end engages the aforementioned guide post 16, by a spring 106 housed within the socket 104 behind the rear end of the bar 102. The movement of the bar 102 is limited by a radially projecting adjusting pin 110 which is received within an aperture 112 therein. The pin 110 projects through a slot 114 extending longitudinally of the bar 102 and the socket 104. Thus, the length of travel of the bar 102 is determined by the length of the slot 114. In operation, as the carriage travels upwardly, the front end of the bar 102 slides along the adjacent post 16. When the carriage nears the top of its travel, the bar 102 enters the aperture 100, whereupon the carriage is mechanically locked in its upper position. To unlock the carriage, the pin 110 is manually moved to the right against the bias of the spring 106. The bar 102 may then be held out of locking position by forcing the pin 110 into a latching .slot 116 which extends transversely of the slot 114. Consequently, the carriage may then be lowered by energization of the down circuit.

As an additional safety measure, a mechanism is provided further to limit the operation of the motor 38 when the bar 102 enters the aperture 100. As shown most clearly in FIGURES 2 and 5, a collar 118 non-rotatably but slidably mounted on the control rod 66 is confined between the sensing fingers 90 so as to slide along the rod 66 with the movement of the carriage 40. i The collar 118 is coupled with the safety mechanism through linkage comprising a transverse link 120 attached at one end to the collar 118 by a hinge 122 and at its other end by a pin 124 to a sleeve 126 which is slidably mounted on the socket 104. A transverse slot 128 is out within the sleeve 126 through which the pin 110 projects. Accordingly, the position of the sleeve 126 is determined by the position of the lock bar 102. Thus, when the bar 102 enters the aperture 100, the sleeve 126 moves toward the adjacent post 16, i.e., to the left as viewed in FIGURE 5. The link 120 likewise moves to the left thereby rotating the collar 118 and the rod 66 in a counterclockwise direction.

Referring to FIGURES 1 and 6, it is apparent that rotation ofthe rod 66 as the bar 102 enters the aperture 100 causes the cam surface 84 on the switch actuator 74 to engage and lower the end of the switch arm 64, thus opening the down circuit.

As the carriage 40 continues upwardly, the upper sensing element 90 engages the abutment 94 to raise the rod 66 and the lower plate 78 of the actuator 74 thereby closing the down circuit but opening the up circuit before the rod 102 strikes the top of the aperture 100. Thus, the abutment 94 and cam surface 84 are so positioned that when the bar 102 is within the aperture 100, the carriage 40 may be moved up and down within limits defined by the aperture 100 but the motor circuit is opened at the limits of the aperture 100 so that there is no danger of placing a strain on the motor or the rest of the jack mechanism.

As described before, the lock bar 102 may be withdrawn from the aperture 100 by moving the pin 110 to the right, as viewed in FIGURES 2 and 5, and then downwardly, as viewed in FIGURE 2, so that it occupies a position within the transverse latching slot 116 beneath the longitudinal slot 114. This causes the control rod 66 to be rotated back to its original position wherein the switch arm 64 occupies its normal position between the horizontal portions of the lower and

upper plates

78 and 80. The carriage 40 may then be lowered. As the carriage approaches its lowermost position, the safety lock mechanism is repositioned by means of an upwardly extending flange 130 mounted on the motor 38, as shown in FIGURE 8. Thus, the pin 110 engages the flange 130 as the carriage beam 42 lowers and is thereby pivoted back to a position within the longitudinal slot 114 in the socket 104. The position of the pin 110 when it is locked within the transverse slot 112 is shown in full lines in FIGURE 8 and in dotted lines after it has been pivoted to the position within the slot 114. Accordingly, when the carriage 40 is again moved upwardly, the locking bar 102 is free to enter the aperture in the adjacent post 16.

Other, or intermediate, apertures similar to the aperture 100 may be located in the post 16 in vertical alignment with the aperture 100 as indicated by dotted lines 1000. The additional apertures 100a function to pro- Vide a plurality of intermediate mechanically locked positions of the carriage 40. In operation, as the carriage travels upwardly, the lock bar 102 enters each successive aperture. As described above, each time the lock bar 102 enters an aperture, the switch arm 64 is moved downwardly to prevent unwanted operation of the down motor circuit. Thus, if the upward travel of the carriage 40 should be stopped while the lock bar 102 is within one of the intermediate apertures, accidental downward travel of the carriage is prevented, both by the lock bar 102 and by the operation of the switch arm 64. Even if the travel of the carriage 40 were stopped in a position wherein the lock bar 102 is above an intermediate aperture and the manual switch in FIGURE 10 energized, the carriage 40 could only move downwardly until such time as the lock bar entered the said intermediate aperture. Of course, when it is desired to lower the carriage With out interference, the lock bar 102 may be held out of position by latching the pin within the slot 116 as described previously. As shown in FIGURE 7, the upper forward portion of the lock bar 102 is bevelled to provide a cam surface 102a. Each time the lock bar 102 enters an intermediate aperture 100a during upward travel of the carriage 40, the cam surface 102a is engaged by the top of the aperture. The lock bar 102, then, is cammed or forced against the bias of the spring 106 out of the aperture 100a. By camming the lock bar 102 out of each of the intermediate apertures 100a, continued upward travel of the carriage 40 is permitted.

It is to be noted that the upright posts 16 and accordingly the screw shaft 24 are quite high as compared to ordinary jacks. As such, the jack may be termed a high lift jack and is ideally suited, as shown in FIGURE 9, to be used in conjunction with an identical jack to lift automobiles above the ground. Thus, as shown in FIG- URE 9, two jacks 10 may be rolled into position on opposite sides or ends of an automobile indicated at C. The respective control boxes 60 for each jack are connected by current carrying lead lines 132 through a common remote control switch housing 134 to an electric current source by a current supply line 135.

As shown in FIGURE 10, the switch housing 134, which may be cast or molded, comprises a cylindrical receptacle 134a having apertured ends for receiving the lines 132. The details of the circuit and the switch terminals within the receptacle 134a may be conventional and as such are not described herein. A separate switch actuating pin 136 is provided for each jack. The pins 136 extend through apertures in a raised panel 138 forming a portion of the receptacle 134a. For ease of operation, a handle 1341) extends normally outwardly from the receptacle. As illustrated, the handle 134b may be hollow to receive the supply line 135. In use, as shown in FIG- URE 9, the handle 134b may be grasped by one hand while the thumb of the same hand actuates one or both of the switch pins 136. For this reason, the handle 134b lies closely adjacent the panel 138. The panel 138 is also provided with a pair of guard plates 137, 139 which are designated UP and DOWN, respectively, to indicate the direction of throw of the pins 136 for proper 9 operation of the jacks. In addition, the plates 1'37, 139 provide a protective shield for the pins 136. In the event the switch housing is dropped, or stepped on accidentally, the plates 137 and 139 and not the pins 136 will be engaged.

In operation, the operator may first separately raise each carriage to properly engage the car by actuation of the toggle switches 66:: on each jack structure 10. Then, as shown in FIGURE 9, he may stand away from the jack structure 10 and the automobile C with the remote control switch 134 in his hand and move the carriages 40 associated with each jack structure 10 upwardly by simultaneously pushing the switch pins 136 toward the UP plate 137. The operator need not be concerned that the carriages 4%? will move too far upwardly because of the control mechanism including the limit switch and the safety lock mechanism described above. After the required work has been performed on the automobile C, it may be lowered by first moving the pins 110 associated with the safety lock mechanisms on each jack into their respective transverse slot portions 112, thereby removing the lock bars 102 from their associated apertures 100. The switch pins 136 are then pivoted toward the DOWN plate 139. While it may be possible to utilize only one switch pin 136 for the pair of jacks, it is preferable to provide two switch pins which control separate circuits to the electric motor unit. One reason for this is that the motors 38 may not operate in perfect synchronism so that one motor may lift its associated carriage faster than the other motor. In that event, all the operator need do is adjust the relative positions of the jack carriage 40 by selective control of one or the other switch pins 136.

To the end that the jacks 10 are easily portable and compact, a novel base structure 14 is used with the jack structure described above. Referring to FIGURES 1 and 9, the base structure 14 includes a pair of horizontal legs 140 extending forwardly and outwardly from the guide posts 16 and side plates 18. As shown most clearly in FIGURE 1, the legs 140 have an outwardly diverging portion 141 and then are angled so as to provide parallel forward portions 142. The base 14 rides on a pair of fixed rear wheels 144 mounted on the base of the side plates 18 and a pair of forward swivelly mounted caster wheels 146 mounted on the parallel portions 142 of the legs 140. Each caster wheel 146 is mounted beneath a spring housing 148 attached to a plate 150, which in turn is attached to the portion 142 of its associated leg 140. The purpose of the spring housing 148 is to elevate the legs 140 above the caster wheels 146. Therefore, as the jack is being rolled to the desired location, the rear wheels 144 and the caster wheels 146 are the only portions of the jack which engage the ground. However, when the carriage 40 engages the load, the weight of the load is such as to overcome the bias of the springs (not shown) located within the spring housing 148 whereupon the entire bottom face of the parallel portions 142 engage the ground, thus providing a stationary support for the jack and the load.

Desirably, the spacing between the legs 140 is as small as possible so that the jack may be stored in a small space. Even with a comparatively small spacing between the outermost portion of the legs 140, the legs provide sufficient balance for the jacks to lift smaller, narrower automobiles, such as those now commonly referred to as compact cars. However, the legs themselves are not sufficient to safely balance the jacks when raising larger automobiles. Accordingly, an extension arm 152 is pivoted to each of the arms 140 by means of a hinge 154. Normally, the extension arms 152 occupy a position in which the elongate sides of the extension arms 152 extend parallel to the divergent portions 141 of the legs 140, as indicated by dotted lines in FIGURE 1. When lifting larger loads, the extension arms 152 are pivoted so as to extend outwardly at right angles to the parallel portions of the legs 140, thus providing a wide base for the jack, as indicated in full lines in FIGURES 1 and 9. In this manner, the jack structures may be balanced for the widest automobiles. To aid in the portability of the jacks and also to provide reinforcement for the upright guide posts 16, the posts 16 are interconnected by a rearwardly extending U-shaped handle member 156.

Although the presently preferred embodiment of the device has been described, it will be understood that within the purview of this invention various changes may be made in the form, details, proportion and arrangement of parts, the combination thereof and mode of operation, which generally stated consist in a device capable of carrying out the objects set forth, as disclosed and defined in the appended claims.

Having thus described my invention, I claim:

1. In a jack of the type having a movable load lifting carriage driven along a vertical path on a jack frame, the combination comprising: drive means selective to move the carriage upwardly or downwardly along the vertical path; switch means operable to deenergize said drive means; control means engageable with said switch means; abutment means on said carriage adapted to actuate the control means during movement of the carriage to deenergize the drive means and thereby halt continued movement of the carriage; a safety lock mechanism carried by said carriage including a movable locking bar; means interconnecting said locking bar and said control means whereby said switch is operated to deenergize said drive means; and manually actuable means for releasing said lock mechanism.

2. In a jack of the type having a vertically movable load lifting carriage supported by a frame and motive means to drive the carriage, means to limit the vertical travel of the carriage upon the frame comprising: a switch operable to deenergize said motive means; a switch actuator engageable with said switch; control means responsive to vertical movement of said carriage to move said actuator thereby to actuate said switch to limit both upward and downward movement of the carriage; a safety lock mechanism including a locking member interengaging the carriage and frame when the carriage is in a raised position; and means interconnecting said locking member and said control means to further limit the downward travel of the carriage.

3. In a jack of the type having a vertically movable load lifting carriage supported by a frame and motive means to drive the carriage, means to limit the vertical travel of the carriage upon the frame comprising: a switch operable to deenergize said motive means; said switch including a switch arm adapted to occupy a central position, wherein the switch does not interfere with the motive means and two off-center positions wherein the switch deenergizes said motive means; a switch actuator having a pair of spaced surfaces engageable with said switch arm, said surface being joined by a sloping third surface; control means responsive to vertical movement of said carriage adapted to cause one of said pair of surfaces to engage and move said arm to one of the off-center positions at the upper limit of travel of the carriage and the other of said pair of surfaces to engage and move said arm to the other off-center position at the lower limit of travel of the carriage; a safety mechanism including a locking member interengaging the carriage and the frame when the carriage is in at least one raised position; and means interconnecting said locking member and said switch actuator including said control means whereby said sloping surface engages and actuates the switch arm when said locking member interengages the carriage and the frame, thereby further limiting travel of the carriage.

4. The apparatus of claim 3, wherein said control means comprises a vertical control rod having a sensing element fixedly mounted near its upper end and the switch actuator fixedly mounted near its lower end; wherein resilient means are provided to hold said rod in a position in which said surfaces on the switch actuator straddle said switch arm; and wherein abutment means are provided on said carriage which engage said sensing element during upward travel of the carriage thereby to lift the rod upwardly and which engage the switch actuator upon downward movement of the carriage thereby to lower the rod 5. The apparatus of claim 4, wherein the means interconnecting said locking member and said switch actuator includes means to rotate said control rod.

6. In a jack of the type having a vertically movable load lifting carriage and motive means to drive the carriage means to limit the vertical travel of the carriage comprising: a switch operable to deenergize said motive means; said switch including a switch arm adapted to occupy a central position wherein the switch does not interfere with the motive means and two off-center positions wherein the switch deenergizes said motive means; a switch actuator having a pair ofsurfaces engageable with said switch arm; control means comprising a vertical rod having a sensing element fixedly mounted near its upper end and the switch actuator fixedly mounted near its lower end; resilient means holding said rod in a position in which said surfaces on the switch actuator straddle said switch arm; and abutment means on said carriage engaging said sensing element during upward travel of the carriage thereby to lift the rod upwardly to cause one of said surfaces to engage and move said switch arm to one of the off-center positions, and said abutment means engaging the switch actuator upon downward movement of the carriage to cause the other of said surfaces to engage and move said arm to the other off-center position.

7. In a jack of the type having a vertically movable load lifting carriage supported by a frame and motive means to drive the carriage, means to limit the vertical travel of the carriage upon the frame including: a switch normally occupying a central position wherein it does not interfere with the motive means and having two off-center positions wherein the switch deenergizes said motive means; control means adapted to actuate said switch comprising a vertical rod having a pair of spaced fixed abutment members thereon, one adjacent each end of said rod, resilient means holding said rod in a predetermined position on said frame, abutment means supported by and movable with said carriage having a portion straddling said vertical rod and movable there-along as said carriage is raised and lowered, said abutment means supported by said carriage engaging the spaced abutment members on said vertical rod adjacent the upper and lower limits of movement of said carriage thereby to raise and lower said rod, and a switch actuator fixed to said rod engaging said switch and moving said switch to one of its off-center positions as the rod is lowered and moving said switch to the other of said olf-center positions as said rod is raised whereby said switch limits both the upper and the lower vertical travel of said carriage.

References Cited by the Examiner UNITED STATES PATENTS 1,324,851 12/19 Roos.

1,477,790 12/23 Townsend 254-7 2,479,679 8/49 Grime 254-93 X 2,550,801 5/51 Geerds 25486 X 2,742,257 4/56 Hott et al 254-7 2,792,913 5/57 Capgras l878.41 2,928,921 3/60 Cranmore 200157 2,975,257 3/61 Happe et a1. 200157 DONLEY I. STOCKING, Primary Examiner.

JOSEPH STRIZAK, HARRISON R. MOSELEY,

Examiners.

Claims

1. IN A JACK OF THE TYPE HAVING A MOVABLE LOAD LIFTING CARRIAGE DRIVEN ALONG A VERTICAL PATYH ON A JACK FRAME, THE COMBINATION COMPRISING: DRIVE MEANS SELECTIVE TO MOVE THE CARRIAGE UPWARDLY OR DOWNWARDLY ALONG THE VERTICAL PATH; SWITCH MEANS OPERABLE TO DEENERGIZE SAID DRIVE MEANS; CONTROL MEANS ENGAGEABLE WITH SAID SWITCH MEANS; ABUTMENT MEANS ON SAID CARRIAGE ADAPTED TO ACTUATE THE CONTROL MEANS DURING MOVEMENT OF TGHE CARRIAGE TO DEENERGIZE THE DRIVE MEANS AND THEREBY HALT CONTINUED MOVEMENT OF THE CARRIAGE; A SAFETY LOCK MECHANISM CARRIED BY SAID CARRIAGE INCLUDING A MOVABLE LOCKING BAR; MEANS INTERCONNECTING SAID LOCKING BAR AND SAID CONTROL MEANS WHEREBY SAID SWITCH IS OPERATED TO DEENERGIZE SAID DRIVE MEANS; AND MANUALLY ACTUABLE MEANS FOR RELEASING SAID LOCK MECHANISM.