Safety brake for vertical lift

• US 4,697,977 A
• Filed: 10/30/1986
• Issued: 10/06/1987
• Est. Priority Date: 06/15/1983
• Status: Expired due to Term

• Current Assignee: HK Systems Incorporated (KION GROUP AG)
• Original Assignee: Litton Systems Incorporated
• Inventors: Loomer, Weston R., Coons, Randall P.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/926,809
• Time in Patent Office: 341 Days
• Field of Search: 187/83, 187/85, 187/86, 414/282, 414/674, 414/662
• US Class Current: 414/662
• CPC Class Codes: B66F 9/07 Floor-to-roof stacking devices, e.g. "stacker cranes", "retrievers"

Abstract

A stacker-retriever lift carriage is disposed to be raised, lowered and positioned, in selected positions with respect to a pair of spaced support masts, by a flexible wire cable one end of which is connected to a lift carriage drive and the other end of which is connected to the lift carriage through a pair of four bar linkages pivotally connected together in spaced parallel relationship to form a safety brake operating mechanism. The upward pull by the cable upon the brake operating mechanism retracts a pair of opposed brake arms, pivotally carried by the brake operating mechanism, to a brake deactivated position with the back ends of each brake arm abutting each other. Loss of the pull of the cable on the lift carriage, as would occur if the cable severed or if the lift carriage hung up, permits a spring housed between the brake arms to move the brake operating mechanism and the brake arms to a braking position with brake pads carried by the brake arms in friction engagement with the support masts.

Claims

1. Safety brake mechanism for a vertical lift having a lift carriage disposed for movement with respect to a lift carriage support, and which is raised, lowered, and positioned during such movement by a lift carriage drive and a flexible member connecting the lift carriage to the lift carriage drive so that the flexible member is normally under tension and exerts at least a predetermined pull upon the lift carriage while the lift carriage is being raised, lowered, and positioned;

said safety brake mechanism, comprising;

(a) brake operating means connecting the lift carriage to the flexible member to transmit to the lift carriage at least the predetermined pull exerted by the lift carriage drive on the flexible member to raise, lower, and position the lift carriage;

(b) said brake operating means including at least four links of substantially equal size connected together proximate their respective ends into a linkage rectangle by pivot pins;

(c) brake means connected to said brake operating means and movable thereby between braking position in engagement with the lift carriage support and a brake unactuated position removed therefrom;

(d) said brake means including a first brake arm and a second brake arm;

(e) a first one of said pivot pins connecting said brake operating means to said lift carriage, a second one of said pivot pins connecting said brake operating means to said flexible member, a third one of said pivot pins connecting said brake operating means to said first brake arm and the fourth one of said pivot pins connecting said brake operating means to said second brake arm;

(f) a brake spring urging said first brake arm and said second brake arm towards said braking position in engagement with the lift carriage support;

(g) said brake means being moved to said brake unactuated position by said brake operating means and against the urging of said brake spring, by at least the predetermined pull exerted upon the brake operating means when connecting the flexible member to the lift carriage;

(h) said brake spring moving said brake operating means into a brake operating condition and said brake spring and brake operating means moving said brake means to said braking position when less than the predetermined pull is exerted by the flexible member upon the brake operating means; and

(i) mounting means mounting said first brake arm and said second brake arm each for combined pivoting and sliding movement towards and away from the lift carriage support and for coaction therewith, and in such a way that said coaction, between said respective brake arm and the lift carriage support, through said brake operating means facilitates the operation of said brake operating means into said brake operating condition and thereby the coaction between said brake means and the lift carriage support to increase braking forces of one upon the other.

2. The safety brake mechanism of claim 1, wherein said mounting means coact to assist the movement of said brake means into engagement with the lift carriage support following initial engagement of said brake means with the lift carriage support under urging of said brake spring.

3. The safety brake mechanism of claim 2, wherein power means are provided to power the lift carriage drive and power cut-off means are connected to said power means to cut-off power therefrom to the lift carriage drive and power cut-off operating means are connected to said brake operating means to be operated thereby to cut-off power to the lift carriage drive upon movement of said brake means towards said braking position.

4. The safety brake mechanism of claim 2, wherein each brake arm is mounted by a pivot, spaced from said pivot pin connecting the brake arm to said operating means and disposed within a slot, to provide said combined pivoting and sliding movement such that following said initial engagement moments are developed in each of said brake arms about its respective pivot which facilitates movement of said brake operating means into said brake operating condition and of said brake arms into said brake operating condition and of said brake arms into said braking position.

5. The safety brake of claim 4, wherein said mounting means includes a bracket within which said slot is formed.

6. The safety brake mechanism of claim 5, wherein said first brake arm and said second brake arm are disposed in an aligned relationship each with a back end disposed in spaced relationship one with the other and each such back end includes spring receiving means for said brake spring.

7. The safety brake mechanism of claim 6, wherein said back end of each of said brake arms are formed into a predetermined beveled configuration and said brake arms are further formed so that in the unactuated position thereof said back ends engage each other.

8. The safety brake mechanism of claim 7, wherein each brake arm includes a friction pad affixed to a front end thereof and positioned thereon for engagement with the lift carriage support when its brake arm is in engagement therewith.

9. The safety brake mechanism of claim 8, including shim means disposed between each of said friction pads and its respective brake arm.

10. The safety brake mechanism of claim 9, wherein said brake operating means includes a pair of linkage rectangles arranged in aligned and spaced and parallel relationship one with the other and said pivot pins extend between said linkage rectangles.

11. A stacker-retriever comprising:

(a) a lift carriage;

(b) shuttle means carried by said lift carriage;

(c) a pair of spaced support masts supporting said lift carriage to be raised, lowered, and positioned with respect to said support masts;

(d) a lift carriage drive;

(e) a flexible cable connected to said lift carriage drive and to said lift carriage so that said flexible cable is normally under tension and exerts at least a predetermined pull upon the lift carriage while the lift carriage is being so raised, lowered, and positioned.

(f) brake operating means connecting said lift carriage to said flexible cable to transmit to said lift carriage at least the predetermined pull exerted by said lift carriage drive on said flexible cable to raise, lower, and position said lift carriage;

(g) said brake operating means including at least four links of substantially equal size connected together proximate their respective ends into a linkage rectangle by pivot pins;

(h) brake means connected to said brake operating means and movable thereby between a braking position in engagement with said support masts and a brake unactuated position removed therefrom;

(i) said brake means including a first brake arm and a second brake arm;

(j) a first one of said pivot pins connecting said brake operating means of said lift carriage, a second one of said pivot pins connecting said brake operating means to said flexible cable, a third one of said pivot pins connecting said brake operating means to said first brake arm and the fourth one of said pivot pins connecting said brake operating means to said second brake arm;

(k) a brake spring urging said first brake arm and said second brake arms towards said braking position in engagement with said support masts;

(l) said brake means being moved to said brake unactuated position by said brake operating means and against the urging of said brake spring, by at least the predetermined pull exerted upon said brake operating means when connecting said flexible cable to said lift carriage;

(m) said brake spring moving said brake operating means into a brake operating condition and said brake spring and brake operating means moving said brake means to said braking position when less than said predetermined pull is exerted by said flexible cable upon said brake operating means; and

(n) mounting means mounting said first brake arm and said second brake arm each for combined pivoting and sliding movement towards and away from said support masts and for coaction therewith, and in such a way that said coaction, between said respective brake arms and said support masts, through said brake operating means, facilitates the operation of said brake operating means into said brake operating condition and thereby the coaction between said brake means and said support masts to increase braking forces of one upon the other.

12. The stacker-retriever of claim 11, wherein said mounting means coact to assist the movement of said brake means into engagement with said support masts following initial engagement of said brake means with said support masts under urging of said spring means.

13. The stacker-retriever of claim 12, wherein power means are provided to power said lift carriage drive and power cut-off means are connected to said power means to cut-off power therefrom to said lift carriage drive and power cut-off operating means are connected to said brake operating means to be operated thereby to cut-off power to said lift carriage drive upon movement of said brake means towards said braking position.

14. The stacker-retriever of claim 13, wherein said power means provide electrical power to an electrically operated lift carriage drive and said power cut-off means is an electrical switch.

15. The stacker-retriever of claim 12, wherein each brake arm is mounted by a pivot, spaced from said pivot pin connecting the brake arm to said operating means and disposed within a slot, to provide said combined pivoting and sliding movement such that following said initial engagement moments are developed in each of said brake arms about its respective pivot which facilitates movement of said brake operating means into said brake operating condition and of said brake arms into said braking position.

16. The stacker-retriever of claim 15, wherein said first brake arm and said second brake arm are disposed in an aligned relationship each with a back end disposed in spaced relationship one with the other and each such back end includes spring receiving means for said brake spring.

17. The stacker-retriever of claim 16, wherein said back end of each of said brake arms are formed into a predetermined beveled configuration and said brake arms are further formed so that in the unactuated position thereof said back ends engage each other.

18. The stacker-retriever of claim 17, wherein each brake arm includes a friction pad affixed to a front end thereof and positioned thereon for engagement with one of said support masts when its brake arm is in engagement therewith.

19. The stacker-retriever of claim 18, including shim means disposed between each of said friction pads and its respective brake arm.

20. The stacker-retriever of claim 19, wherein said brake operating means includes a pair of linkage rectangles arranged in aligned and spaced and parallel relationship one with the other and said pivot pins extend between said linkage rectangles.

21. The safety brake of claim 15, wherein said mounting means includes a bracket within which said slot is formed.